Linux-2.6.12-rc2
[linux-2.6.git] / net / ipv4 / tcp_input.c
1 /*
2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
3  *              operating system.  INET is implemented using the  BSD Socket
4  *              interface as the means of communication with the user level.
5  *
6  *              Implementation of the Transmission Control Protocol(TCP).
7  *
8  * Version:     $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $
9  *
10  * Authors:     Ross Biro, <bir7@leland.Stanford.Edu>
11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12  *              Mark Evans, <evansmp@uhura.aston.ac.uk>
13  *              Corey Minyard <wf-rch!minyard@relay.EU.net>
14  *              Florian La Roche, <flla@stud.uni-sb.de>
15  *              Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
16  *              Linus Torvalds, <torvalds@cs.helsinki.fi>
17  *              Alan Cox, <gw4pts@gw4pts.ampr.org>
18  *              Matthew Dillon, <dillon@apollo.west.oic.com>
19  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
20  *              Jorge Cwik, <jorge@laser.satlink.net>
21  */
22
23 /*
24  * Changes:
25  *              Pedro Roque     :       Fast Retransmit/Recovery.
26  *                                      Two receive queues.
27  *                                      Retransmit queue handled by TCP.
28  *                                      Better retransmit timer handling.
29  *                                      New congestion avoidance.
30  *                                      Header prediction.
31  *                                      Variable renaming.
32  *
33  *              Eric            :       Fast Retransmit.
34  *              Randy Scott     :       MSS option defines.
35  *              Eric Schenk     :       Fixes to slow start algorithm.
36  *              Eric Schenk     :       Yet another double ACK bug.
37  *              Eric Schenk     :       Delayed ACK bug fixes.
38  *              Eric Schenk     :       Floyd style fast retrans war avoidance.
39  *              David S. Miller :       Don't allow zero congestion window.
40  *              Eric Schenk     :       Fix retransmitter so that it sends
41  *                                      next packet on ack of previous packet.
42  *              Andi Kleen      :       Moved open_request checking here
43  *                                      and process RSTs for open_requests.
44  *              Andi Kleen      :       Better prune_queue, and other fixes.
45  *              Andrey Savochkin:       Fix RTT measurements in the presnce of
46  *                                      timestamps.
47  *              Andrey Savochkin:       Check sequence numbers correctly when
48  *                                      removing SACKs due to in sequence incoming
49  *                                      data segments.
50  *              Andi Kleen:             Make sure we never ack data there is not
51  *                                      enough room for. Also make this condition
52  *                                      a fatal error if it might still happen.
53  *              Andi Kleen:             Add tcp_measure_rcv_mss to make 
54  *                                      connections with MSS<min(MTU,ann. MSS)
55  *                                      work without delayed acks. 
56  *              Andi Kleen:             Process packets with PSH set in the
57  *                                      fast path.
58  *              J Hadi Salim:           ECN support
59  *              Andrei Gurtov,
60  *              Pasi Sarolahti,
61  *              Panu Kuhlberg:          Experimental audit of TCP (re)transmission
62  *                                      engine. Lots of bugs are found.
63  *              Pasi Sarolahti:         F-RTO for dealing with spurious RTOs
64  *              Angelo Dell'Aera:       TCP Westwood+ support
65  */
66
67 #include <linux/config.h>
68 #include <linux/mm.h>
69 #include <linux/module.h>
70 #include <linux/sysctl.h>
71 #include <net/tcp.h>
72 #include <net/inet_common.h>
73 #include <linux/ipsec.h>
74 #include <asm/unaligned.h>
75
76 int sysctl_tcp_timestamps = 1;
77 int sysctl_tcp_window_scaling = 1;
78 int sysctl_tcp_sack = 1;
79 int sysctl_tcp_fack = 1;
80 int sysctl_tcp_reordering = TCP_FASTRETRANS_THRESH;
81 int sysctl_tcp_ecn;
82 int sysctl_tcp_dsack = 1;
83 int sysctl_tcp_app_win = 31;
84 int sysctl_tcp_adv_win_scale = 2;
85
86 int sysctl_tcp_stdurg;
87 int sysctl_tcp_rfc1337;
88 int sysctl_tcp_max_orphans = NR_FILE;
89 int sysctl_tcp_frto;
90 int sysctl_tcp_nometrics_save;
91 int sysctl_tcp_westwood;
92 int sysctl_tcp_vegas_cong_avoid;
93
94 int sysctl_tcp_moderate_rcvbuf = 1;
95
96 /* Default values of the Vegas variables, in fixed-point representation
97  * with V_PARAM_SHIFT bits to the right of the binary point.
98  */
99 #define V_PARAM_SHIFT 1
100 int sysctl_tcp_vegas_alpha = 1<<V_PARAM_SHIFT;
101 int sysctl_tcp_vegas_beta  = 3<<V_PARAM_SHIFT;
102 int sysctl_tcp_vegas_gamma = 1<<V_PARAM_SHIFT;
103 int sysctl_tcp_bic = 1;
104 int sysctl_tcp_bic_fast_convergence = 1;
105 int sysctl_tcp_bic_low_window = 14;
106 int sysctl_tcp_bic_beta = 819;          /* = 819/1024 (BICTCP_BETA_SCALE) */
107
108 #define FLAG_DATA               0x01 /* Incoming frame contained data.          */
109 #define FLAG_WIN_UPDATE         0x02 /* Incoming ACK was a window update.       */
110 #define FLAG_DATA_ACKED         0x04 /* This ACK acknowledged new data.         */
111 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted.  */
112 #define FLAG_SYN_ACKED          0x10 /* This ACK acknowledged SYN.              */
113 #define FLAG_DATA_SACKED        0x20 /* New SACK.                               */
114 #define FLAG_ECE                0x40 /* ECE in this ACK                         */
115 #define FLAG_DATA_LOST          0x80 /* SACK detected data lossage.             */
116 #define FLAG_SLOWPATH           0x100 /* Do not skip RFC checks for window update.*/
117
118 #define FLAG_ACKED              (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
119 #define FLAG_NOT_DUP            (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
120 #define FLAG_CA_ALERT           (FLAG_DATA_SACKED|FLAG_ECE)
121 #define FLAG_FORWARD_PROGRESS   (FLAG_ACKED|FLAG_DATA_SACKED)
122
123 #define IsReno(tp) ((tp)->rx_opt.sack_ok == 0)
124 #define IsFack(tp) ((tp)->rx_opt.sack_ok & 2)
125 #define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4)
126
127 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
128
129 /* Adapt the MSS value used to make delayed ack decision to the 
130  * real world.
131  */ 
132 static inline void tcp_measure_rcv_mss(struct tcp_sock *tp,
133                                        struct sk_buff *skb)
134 {
135         unsigned int len, lss;
136
137         lss = tp->ack.last_seg_size; 
138         tp->ack.last_seg_size = 0; 
139
140         /* skb->len may jitter because of SACKs, even if peer
141          * sends good full-sized frames.
142          */
143         len = skb->len;
144         if (len >= tp->ack.rcv_mss) {
145                 tp->ack.rcv_mss = len;
146         } else {
147                 /* Otherwise, we make more careful check taking into account,
148                  * that SACKs block is variable.
149                  *
150                  * "len" is invariant segment length, including TCP header.
151                  */
152                 len += skb->data - skb->h.raw;
153                 if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) ||
154                     /* If PSH is not set, packet should be
155                      * full sized, provided peer TCP is not badly broken.
156                      * This observation (if it is correct 8)) allows
157                      * to handle super-low mtu links fairly.
158                      */
159                     (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
160                      !(tcp_flag_word(skb->h.th)&TCP_REMNANT))) {
161                         /* Subtract also invariant (if peer is RFC compliant),
162                          * tcp header plus fixed timestamp option length.
163                          * Resulting "len" is MSS free of SACK jitter.
164                          */
165                         len -= tp->tcp_header_len;
166                         tp->ack.last_seg_size = len;
167                         if (len == lss) {
168                                 tp->ack.rcv_mss = len;
169                                 return;
170                         }
171                 }
172                 tp->ack.pending |= TCP_ACK_PUSHED;
173         }
174 }
175
176 static void tcp_incr_quickack(struct tcp_sock *tp)
177 {
178         unsigned quickacks = tp->rcv_wnd/(2*tp->ack.rcv_mss);
179
180         if (quickacks==0)
181                 quickacks=2;
182         if (quickacks > tp->ack.quick)
183                 tp->ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
184 }
185
186 void tcp_enter_quickack_mode(struct tcp_sock *tp)
187 {
188         tcp_incr_quickack(tp);
189         tp->ack.pingpong = 0;
190         tp->ack.ato = TCP_ATO_MIN;
191 }
192
193 /* Send ACKs quickly, if "quick" count is not exhausted
194  * and the session is not interactive.
195  */
196
197 static __inline__ int tcp_in_quickack_mode(struct tcp_sock *tp)
198 {
199         return (tp->ack.quick && !tp->ack.pingpong);
200 }
201
202 /* Buffer size and advertised window tuning.
203  *
204  * 1. Tuning sk->sk_sndbuf, when connection enters established state.
205  */
206
207 static void tcp_fixup_sndbuf(struct sock *sk)
208 {
209         int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 +
210                      sizeof(struct sk_buff);
211
212         if (sk->sk_sndbuf < 3 * sndmem)
213                 sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]);
214 }
215
216 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
217  *
218  * All tcp_full_space() is split to two parts: "network" buffer, allocated
219  * forward and advertised in receiver window (tp->rcv_wnd) and
220  * "application buffer", required to isolate scheduling/application
221  * latencies from network.
222  * window_clamp is maximal advertised window. It can be less than
223  * tcp_full_space(), in this case tcp_full_space() - window_clamp
224  * is reserved for "application" buffer. The less window_clamp is
225  * the smoother our behaviour from viewpoint of network, but the lower
226  * throughput and the higher sensitivity of the connection to losses. 8)
227  *
228  * rcv_ssthresh is more strict window_clamp used at "slow start"
229  * phase to predict further behaviour of this connection.
230  * It is used for two goals:
231  * - to enforce header prediction at sender, even when application
232  *   requires some significant "application buffer". It is check #1.
233  * - to prevent pruning of receive queue because of misprediction
234  *   of receiver window. Check #2.
235  *
236  * The scheme does not work when sender sends good segments opening
237  * window and then starts to feed us spagetti. But it should work
238  * in common situations. Otherwise, we have to rely on queue collapsing.
239  */
240
241 /* Slow part of check#2. */
242 static int __tcp_grow_window(struct sock *sk, struct tcp_sock *tp,
243                              struct sk_buff *skb)
244 {
245         /* Optimize this! */
246         int truesize = tcp_win_from_space(skb->truesize)/2;
247         int window = tcp_full_space(sk)/2;
248
249         while (tp->rcv_ssthresh <= window) {
250                 if (truesize <= skb->len)
251                         return 2*tp->ack.rcv_mss;
252
253                 truesize >>= 1;
254                 window >>= 1;
255         }
256         return 0;
257 }
258
259 static inline void tcp_grow_window(struct sock *sk, struct tcp_sock *tp,
260                                    struct sk_buff *skb)
261 {
262         /* Check #1 */
263         if (tp->rcv_ssthresh < tp->window_clamp &&
264             (int)tp->rcv_ssthresh < tcp_space(sk) &&
265             !tcp_memory_pressure) {
266                 int incr;
267
268                 /* Check #2. Increase window, if skb with such overhead
269                  * will fit to rcvbuf in future.
270                  */
271                 if (tcp_win_from_space(skb->truesize) <= skb->len)
272                         incr = 2*tp->advmss;
273                 else
274                         incr = __tcp_grow_window(sk, tp, skb);
275
276                 if (incr) {
277                         tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp);
278                         tp->ack.quick |= 1;
279                 }
280         }
281 }
282
283 /* 3. Tuning rcvbuf, when connection enters established state. */
284
285 static void tcp_fixup_rcvbuf(struct sock *sk)
286 {
287         struct tcp_sock *tp = tcp_sk(sk);
288         int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
289
290         /* Try to select rcvbuf so that 4 mss-sized segments
291          * will fit to window and correspoding skbs will fit to our rcvbuf.
292          * (was 3; 4 is minimum to allow fast retransmit to work.)
293          */
294         while (tcp_win_from_space(rcvmem) < tp->advmss)
295                 rcvmem += 128;
296         if (sk->sk_rcvbuf < 4 * rcvmem)
297                 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]);
298 }
299
300 /* 4. Try to fixup all. It is made iimediately after connection enters
301  *    established state.
302  */
303 static void tcp_init_buffer_space(struct sock *sk)
304 {
305         struct tcp_sock *tp = tcp_sk(sk);
306         int maxwin;
307
308         if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
309                 tcp_fixup_rcvbuf(sk);
310         if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
311                 tcp_fixup_sndbuf(sk);
312
313         tp->rcvq_space.space = tp->rcv_wnd;
314
315         maxwin = tcp_full_space(sk);
316
317         if (tp->window_clamp >= maxwin) {
318                 tp->window_clamp = maxwin;
319
320                 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
321                         tp->window_clamp = max(maxwin -
322                                                (maxwin >> sysctl_tcp_app_win),
323                                                4 * tp->advmss);
324         }
325
326         /* Force reservation of one segment. */
327         if (sysctl_tcp_app_win &&
328             tp->window_clamp > 2 * tp->advmss &&
329             tp->window_clamp + tp->advmss > maxwin)
330                 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
331
332         tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
333         tp->snd_cwnd_stamp = tcp_time_stamp;
334 }
335
336 static void init_bictcp(struct tcp_sock *tp)
337 {
338         tp->bictcp.cnt = 0;
339
340         tp->bictcp.last_max_cwnd = 0;
341         tp->bictcp.last_cwnd = 0;
342         tp->bictcp.last_stamp = 0;
343 }
344
345 /* 5. Recalculate window clamp after socket hit its memory bounds. */
346 static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp)
347 {
348         struct sk_buff *skb;
349         unsigned int app_win = tp->rcv_nxt - tp->copied_seq;
350         int ofo_win = 0;
351
352         tp->ack.quick = 0;
353
354         skb_queue_walk(&tp->out_of_order_queue, skb) {
355                 ofo_win += skb->len;
356         }
357
358         /* If overcommit is due to out of order segments,
359          * do not clamp window. Try to expand rcvbuf instead.
360          */
361         if (ofo_win) {
362                 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
363                     !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
364                     !tcp_memory_pressure &&
365                     atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0])
366                         sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
367                                             sysctl_tcp_rmem[2]);
368         }
369         if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) {
370                 app_win += ofo_win;
371                 if (atomic_read(&sk->sk_rmem_alloc) >= 2 * sk->sk_rcvbuf)
372                         app_win >>= 1;
373                 if (app_win > tp->ack.rcv_mss)
374                         app_win -= tp->ack.rcv_mss;
375                 app_win = max(app_win, 2U*tp->advmss);
376
377                 if (!ofo_win)
378                         tp->window_clamp = min(tp->window_clamp, app_win);
379                 tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss);
380         }
381 }
382
383 /* Receiver "autotuning" code.
384  *
385  * The algorithm for RTT estimation w/o timestamps is based on
386  * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
387  * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
388  *
389  * More detail on this code can be found at
390  * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
391  * though this reference is out of date.  A new paper
392  * is pending.
393  */
394 static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
395 {
396         u32 new_sample = tp->rcv_rtt_est.rtt;
397         long m = sample;
398
399         if (m == 0)
400                 m = 1;
401
402         if (new_sample != 0) {
403                 /* If we sample in larger samples in the non-timestamp
404                  * case, we could grossly overestimate the RTT especially
405                  * with chatty applications or bulk transfer apps which
406                  * are stalled on filesystem I/O.
407                  *
408                  * Also, since we are only going for a minimum in the
409                  * non-timestamp case, we do not smoothe things out
410                  * else with timestamps disabled convergance takes too
411                  * long.
412                  */
413                 if (!win_dep) {
414                         m -= (new_sample >> 3);
415                         new_sample += m;
416                 } else if (m < new_sample)
417                         new_sample = m << 3;
418         } else {
419                 /* No previous mesaure. */
420                 new_sample = m << 3;
421         }
422
423         if (tp->rcv_rtt_est.rtt != new_sample)
424                 tp->rcv_rtt_est.rtt = new_sample;
425 }
426
427 static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
428 {
429         if (tp->rcv_rtt_est.time == 0)
430                 goto new_measure;
431         if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
432                 return;
433         tcp_rcv_rtt_update(tp,
434                            jiffies - tp->rcv_rtt_est.time,
435                            1);
436
437 new_measure:
438         tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
439         tp->rcv_rtt_est.time = tcp_time_stamp;
440 }
441
442 static inline void tcp_rcv_rtt_measure_ts(struct tcp_sock *tp, struct sk_buff *skb)
443 {
444         if (tp->rx_opt.rcv_tsecr &&
445             (TCP_SKB_CB(skb)->end_seq -
446              TCP_SKB_CB(skb)->seq >= tp->ack.rcv_mss))
447                 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
448 }
449
450 /*
451  * This function should be called every time data is copied to user space.
452  * It calculates the appropriate TCP receive buffer space.
453  */
454 void tcp_rcv_space_adjust(struct sock *sk)
455 {
456         struct tcp_sock *tp = tcp_sk(sk);
457         int time;
458         int space;
459         
460         if (tp->rcvq_space.time == 0)
461                 goto new_measure;
462         
463         time = tcp_time_stamp - tp->rcvq_space.time;
464         if (time < (tp->rcv_rtt_est.rtt >> 3) ||
465             tp->rcv_rtt_est.rtt == 0)
466                 return;
467         
468         space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
469
470         space = max(tp->rcvq_space.space, space);
471
472         if (tp->rcvq_space.space != space) {
473                 int rcvmem;
474
475                 tp->rcvq_space.space = space;
476
477                 if (sysctl_tcp_moderate_rcvbuf) {
478                         int new_clamp = space;
479
480                         /* Receive space grows, normalize in order to
481                          * take into account packet headers and sk_buff
482                          * structure overhead.
483                          */
484                         space /= tp->advmss;
485                         if (!space)
486                                 space = 1;
487                         rcvmem = (tp->advmss + MAX_TCP_HEADER +
488                                   16 + sizeof(struct sk_buff));
489                         while (tcp_win_from_space(rcvmem) < tp->advmss)
490                                 rcvmem += 128;
491                         space *= rcvmem;
492                         space = min(space, sysctl_tcp_rmem[2]);
493                         if (space > sk->sk_rcvbuf) {
494                                 sk->sk_rcvbuf = space;
495
496                                 /* Make the window clamp follow along.  */
497                                 tp->window_clamp = new_clamp;
498                         }
499                 }
500         }
501         
502 new_measure:
503         tp->rcvq_space.seq = tp->copied_seq;
504         tp->rcvq_space.time = tcp_time_stamp;
505 }
506
507 /* There is something which you must keep in mind when you analyze the
508  * behavior of the tp->ato delayed ack timeout interval.  When a
509  * connection starts up, we want to ack as quickly as possible.  The
510  * problem is that "good" TCP's do slow start at the beginning of data
511  * transmission.  The means that until we send the first few ACK's the
512  * sender will sit on his end and only queue most of his data, because
513  * he can only send snd_cwnd unacked packets at any given time.  For
514  * each ACK we send, he increments snd_cwnd and transmits more of his
515  * queue.  -DaveM
516  */
517 static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb)
518 {
519         u32 now;
520
521         tcp_schedule_ack(tp);
522
523         tcp_measure_rcv_mss(tp, skb);
524
525         tcp_rcv_rtt_measure(tp);
526         
527         now = tcp_time_stamp;
528
529         if (!tp->ack.ato) {
530                 /* The _first_ data packet received, initialize
531                  * delayed ACK engine.
532                  */
533                 tcp_incr_quickack(tp);
534                 tp->ack.ato = TCP_ATO_MIN;
535         } else {
536                 int m = now - tp->ack.lrcvtime;
537
538                 if (m <= TCP_ATO_MIN/2) {
539                         /* The fastest case is the first. */
540                         tp->ack.ato = (tp->ack.ato>>1) + TCP_ATO_MIN/2;
541                 } else if (m < tp->ack.ato) {
542                         tp->ack.ato = (tp->ack.ato>>1) + m;
543                         if (tp->ack.ato > tp->rto)
544                                 tp->ack.ato = tp->rto;
545                 } else if (m > tp->rto) {
546                         /* Too long gap. Apparently sender falled to
547                          * restart window, so that we send ACKs quickly.
548                          */
549                         tcp_incr_quickack(tp);
550                         sk_stream_mem_reclaim(sk);
551                 }
552         }
553         tp->ack.lrcvtime = now;
554
555         TCP_ECN_check_ce(tp, skb);
556
557         if (skb->len >= 128)
558                 tcp_grow_window(sk, tp, skb);
559 }
560
561 /* When starting a new connection, pin down the current choice of 
562  * congestion algorithm.
563  */
564 void tcp_ca_init(struct tcp_sock *tp)
565 {
566         if (sysctl_tcp_westwood) 
567                 tp->adv_cong = TCP_WESTWOOD;
568         else if (sysctl_tcp_bic)
569                 tp->adv_cong = TCP_BIC;
570         else if (sysctl_tcp_vegas_cong_avoid) {
571                 tp->adv_cong = TCP_VEGAS;
572                 tp->vegas.baseRTT = 0x7fffffff;
573                 tcp_vegas_enable(tp);
574         } 
575 }
576
577 /* Do RTT sampling needed for Vegas.
578  * Basically we:
579  *   o min-filter RTT samples from within an RTT to get the current
580  *     propagation delay + queuing delay (we are min-filtering to try to
581  *     avoid the effects of delayed ACKs)
582  *   o min-filter RTT samples from a much longer window (forever for now)
583  *     to find the propagation delay (baseRTT)
584  */
585 static inline void vegas_rtt_calc(struct tcp_sock *tp, __u32 rtt)
586 {
587         __u32 vrtt = rtt + 1; /* Never allow zero rtt or baseRTT */
588
589         /* Filter to find propagation delay: */
590         if (vrtt < tp->vegas.baseRTT) 
591                 tp->vegas.baseRTT = vrtt;
592
593         /* Find the min RTT during the last RTT to find
594          * the current prop. delay + queuing delay:
595          */
596         tp->vegas.minRTT = min(tp->vegas.minRTT, vrtt);
597         tp->vegas.cntRTT++;
598 }
599
600 /* Called to compute a smoothed rtt estimate. The data fed to this
601  * routine either comes from timestamps, or from segments that were
602  * known _not_ to have been retransmitted [see Karn/Partridge
603  * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
604  * piece by Van Jacobson.
605  * NOTE: the next three routines used to be one big routine.
606  * To save cycles in the RFC 1323 implementation it was better to break
607  * it up into three procedures. -- erics
608  */
609 static void tcp_rtt_estimator(struct tcp_sock *tp, __u32 mrtt)
610 {
611         long m = mrtt; /* RTT */
612
613         if (tcp_vegas_enabled(tp))
614                 vegas_rtt_calc(tp, mrtt);
615
616         /*      The following amusing code comes from Jacobson's
617          *      article in SIGCOMM '88.  Note that rtt and mdev
618          *      are scaled versions of rtt and mean deviation.
619          *      This is designed to be as fast as possible 
620          *      m stands for "measurement".
621          *
622          *      On a 1990 paper the rto value is changed to:
623          *      RTO = rtt + 4 * mdev
624          *
625          * Funny. This algorithm seems to be very broken.
626          * These formulae increase RTO, when it should be decreased, increase
627          * too slowly, when it should be incresed fastly, decrease too fastly
628          * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
629          * does not matter how to _calculate_ it. Seems, it was trap
630          * that VJ failed to avoid. 8)
631          */
632         if(m == 0)
633                 m = 1;
634         if (tp->srtt != 0) {
635                 m -= (tp->srtt >> 3);   /* m is now error in rtt est */
636                 tp->srtt += m;          /* rtt = 7/8 rtt + 1/8 new */
637                 if (m < 0) {
638                         m = -m;         /* m is now abs(error) */
639                         m -= (tp->mdev >> 2);   /* similar update on mdev */
640                         /* This is similar to one of Eifel findings.
641                          * Eifel blocks mdev updates when rtt decreases.
642                          * This solution is a bit different: we use finer gain
643                          * for mdev in this case (alpha*beta).
644                          * Like Eifel it also prevents growth of rto,
645                          * but also it limits too fast rto decreases,
646                          * happening in pure Eifel.
647                          */
648                         if (m > 0)
649                                 m >>= 3;
650                 } else {
651                         m -= (tp->mdev >> 2);   /* similar update on mdev */
652                 }
653                 tp->mdev += m;          /* mdev = 3/4 mdev + 1/4 new */
654                 if (tp->mdev > tp->mdev_max) {
655                         tp->mdev_max = tp->mdev;
656                         if (tp->mdev_max > tp->rttvar)
657                                 tp->rttvar = tp->mdev_max;
658                 }
659                 if (after(tp->snd_una, tp->rtt_seq)) {
660                         if (tp->mdev_max < tp->rttvar)
661                                 tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2;
662                         tp->rtt_seq = tp->snd_nxt;
663                         tp->mdev_max = TCP_RTO_MIN;
664                 }
665         } else {
666                 /* no previous measure. */
667                 tp->srtt = m<<3;        /* take the measured time to be rtt */
668                 tp->mdev = m<<1;        /* make sure rto = 3*rtt */
669                 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
670                 tp->rtt_seq = tp->snd_nxt;
671         }
672
673         tcp_westwood_update_rtt(tp, tp->srtt >> 3);
674 }
675
676 /* Calculate rto without backoff.  This is the second half of Van Jacobson's
677  * routine referred to above.
678  */
679 static inline void tcp_set_rto(struct tcp_sock *tp)
680 {
681         /* Old crap is replaced with new one. 8)
682          *
683          * More seriously:
684          * 1. If rtt variance happened to be less 50msec, it is hallucination.
685          *    It cannot be less due to utterly erratic ACK generation made
686          *    at least by solaris and freebsd. "Erratic ACKs" has _nothing_
687          *    to do with delayed acks, because at cwnd>2 true delack timeout
688          *    is invisible. Actually, Linux-2.4 also generates erratic
689          *    ACKs in some curcumstances.
690          */
691         tp->rto = (tp->srtt >> 3) + tp->rttvar;
692
693         /* 2. Fixups made earlier cannot be right.
694          *    If we do not estimate RTO correctly without them,
695          *    all the algo is pure shit and should be replaced
696          *    with correct one. It is exaclty, which we pretend to do.
697          */
698 }
699
700 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
701  * guarantees that rto is higher.
702  */
703 static inline void tcp_bound_rto(struct tcp_sock *tp)
704 {
705         if (tp->rto > TCP_RTO_MAX)
706                 tp->rto = TCP_RTO_MAX;
707 }
708
709 /* Save metrics learned by this TCP session.
710    This function is called only, when TCP finishes successfully
711    i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
712  */
713 void tcp_update_metrics(struct sock *sk)
714 {
715         struct tcp_sock *tp = tcp_sk(sk);
716         struct dst_entry *dst = __sk_dst_get(sk);
717
718         if (sysctl_tcp_nometrics_save)
719                 return;
720
721         dst_confirm(dst);
722
723         if (dst && (dst->flags&DST_HOST)) {
724                 int m;
725
726                 if (tp->backoff || !tp->srtt) {
727                         /* This session failed to estimate rtt. Why?
728                          * Probably, no packets returned in time.
729                          * Reset our results.
730                          */
731                         if (!(dst_metric_locked(dst, RTAX_RTT)))
732                                 dst->metrics[RTAX_RTT-1] = 0;
733                         return;
734                 }
735
736                 m = dst_metric(dst, RTAX_RTT) - tp->srtt;
737
738                 /* If newly calculated rtt larger than stored one,
739                  * store new one. Otherwise, use EWMA. Remember,
740                  * rtt overestimation is always better than underestimation.
741                  */
742                 if (!(dst_metric_locked(dst, RTAX_RTT))) {
743                         if (m <= 0)
744                                 dst->metrics[RTAX_RTT-1] = tp->srtt;
745                         else
746                                 dst->metrics[RTAX_RTT-1] -= (m>>3);
747                 }
748
749                 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
750                         if (m < 0)
751                                 m = -m;
752
753                         /* Scale deviation to rttvar fixed point */
754                         m >>= 1;
755                         if (m < tp->mdev)
756                                 m = tp->mdev;
757
758                         if (m >= dst_metric(dst, RTAX_RTTVAR))
759                                 dst->metrics[RTAX_RTTVAR-1] = m;
760                         else
761                                 dst->metrics[RTAX_RTTVAR-1] -=
762                                         (dst->metrics[RTAX_RTTVAR-1] - m)>>2;
763                 }
764
765                 if (tp->snd_ssthresh >= 0xFFFF) {
766                         /* Slow start still did not finish. */
767                         if (dst_metric(dst, RTAX_SSTHRESH) &&
768                             !dst_metric_locked(dst, RTAX_SSTHRESH) &&
769                             (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
770                                 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
771                         if (!dst_metric_locked(dst, RTAX_CWND) &&
772                             tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
773                                 dst->metrics[RTAX_CWND-1] = tp->snd_cwnd;
774                 } else if (tp->snd_cwnd > tp->snd_ssthresh &&
775                            tp->ca_state == TCP_CA_Open) {
776                         /* Cong. avoidance phase, cwnd is reliable. */
777                         if (!dst_metric_locked(dst, RTAX_SSTHRESH))
778                                 dst->metrics[RTAX_SSTHRESH-1] =
779                                         max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
780                         if (!dst_metric_locked(dst, RTAX_CWND))
781                                 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1;
782                 } else {
783                         /* Else slow start did not finish, cwnd is non-sense,
784                            ssthresh may be also invalid.
785                          */
786                         if (!dst_metric_locked(dst, RTAX_CWND))
787                                 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1;
788                         if (dst->metrics[RTAX_SSTHRESH-1] &&
789                             !dst_metric_locked(dst, RTAX_SSTHRESH) &&
790                             tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1])
791                                 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
792                 }
793
794                 if (!dst_metric_locked(dst, RTAX_REORDERING)) {
795                         if (dst->metrics[RTAX_REORDERING-1] < tp->reordering &&
796                             tp->reordering != sysctl_tcp_reordering)
797                                 dst->metrics[RTAX_REORDERING-1] = tp->reordering;
798                 }
799         }
800 }
801
802 /* Numbers are taken from RFC2414.  */
803 __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
804 {
805         __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
806
807         if (!cwnd) {
808                 if (tp->mss_cache_std > 1460)
809                         cwnd = 2;
810                 else
811                         cwnd = (tp->mss_cache_std > 1095) ? 3 : 4;
812         }
813         return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
814 }
815
816 /* Initialize metrics on socket. */
817
818 static void tcp_init_metrics(struct sock *sk)
819 {
820         struct tcp_sock *tp = tcp_sk(sk);
821         struct dst_entry *dst = __sk_dst_get(sk);
822
823         if (dst == NULL)
824                 goto reset;
825
826         dst_confirm(dst);
827
828         if (dst_metric_locked(dst, RTAX_CWND))
829                 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
830         if (dst_metric(dst, RTAX_SSTHRESH)) {
831                 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
832                 if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
833                         tp->snd_ssthresh = tp->snd_cwnd_clamp;
834         }
835         if (dst_metric(dst, RTAX_REORDERING) &&
836             tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
837                 tp->rx_opt.sack_ok &= ~2;
838                 tp->reordering = dst_metric(dst, RTAX_REORDERING);
839         }
840
841         if (dst_metric(dst, RTAX_RTT) == 0)
842                 goto reset;
843
844         if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
845                 goto reset;
846
847         /* Initial rtt is determined from SYN,SYN-ACK.
848          * The segment is small and rtt may appear much
849          * less than real one. Use per-dst memory
850          * to make it more realistic.
851          *
852          * A bit of theory. RTT is time passed after "normal" sized packet
853          * is sent until it is ACKed. In normal curcumstances sending small
854          * packets force peer to delay ACKs and calculation is correct too.
855          * The algorithm is adaptive and, provided we follow specs, it
856          * NEVER underestimate RTT. BUT! If peer tries to make some clever
857          * tricks sort of "quick acks" for time long enough to decrease RTT
858          * to low value, and then abruptly stops to do it and starts to delay
859          * ACKs, wait for troubles.
860          */
861         if (dst_metric(dst, RTAX_RTT) > tp->srtt) {
862                 tp->srtt = dst_metric(dst, RTAX_RTT);
863                 tp->rtt_seq = tp->snd_nxt;
864         }
865         if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
866                 tp->mdev = dst_metric(dst, RTAX_RTTVAR);
867                 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
868         }
869         tcp_set_rto(tp);
870         tcp_bound_rto(tp);
871         if (tp->rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
872                 goto reset;
873         tp->snd_cwnd = tcp_init_cwnd(tp, dst);
874         tp->snd_cwnd_stamp = tcp_time_stamp;
875         return;
876
877 reset:
878         /* Play conservative. If timestamps are not
879          * supported, TCP will fail to recalculate correct
880          * rtt, if initial rto is too small. FORGET ALL AND RESET!
881          */
882         if (!tp->rx_opt.saw_tstamp && tp->srtt) {
883                 tp->srtt = 0;
884                 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
885                 tp->rto = TCP_TIMEOUT_INIT;
886         }
887 }
888
889 static void tcp_update_reordering(struct tcp_sock *tp, int metric, int ts)
890 {
891         if (metric > tp->reordering) {
892                 tp->reordering = min(TCP_MAX_REORDERING, metric);
893
894                 /* This exciting event is worth to be remembered. 8) */
895                 if (ts)
896                         NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER);
897                 else if (IsReno(tp))
898                         NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER);
899                 else if (IsFack(tp))
900                         NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER);
901                 else
902                         NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER);
903 #if FASTRETRANS_DEBUG > 1
904                 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
905                        tp->rx_opt.sack_ok, tp->ca_state,
906                        tp->reordering,
907                        tp->fackets_out,
908                        tp->sacked_out,
909                        tp->undo_marker ? tp->undo_retrans : 0);
910 #endif
911                 /* Disable FACK yet. */
912                 tp->rx_opt.sack_ok &= ~2;
913         }
914 }
915
916 /* This procedure tags the retransmission queue when SACKs arrive.
917  *
918  * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
919  * Packets in queue with these bits set are counted in variables
920  * sacked_out, retrans_out and lost_out, correspondingly.
921  *
922  * Valid combinations are:
923  * Tag  InFlight        Description
924  * 0    1               - orig segment is in flight.
925  * S    0               - nothing flies, orig reached receiver.
926  * L    0               - nothing flies, orig lost by net.
927  * R    2               - both orig and retransmit are in flight.
928  * L|R  1               - orig is lost, retransmit is in flight.
929  * S|R  1               - orig reached receiver, retrans is still in flight.
930  * (L|S|R is logically valid, it could occur when L|R is sacked,
931  *  but it is equivalent to plain S and code short-curcuits it to S.
932  *  L|S is logically invalid, it would mean -1 packet in flight 8))
933  *
934  * These 6 states form finite state machine, controlled by the following events:
935  * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
936  * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
937  * 3. Loss detection event of one of three flavors:
938  *      A. Scoreboard estimator decided the packet is lost.
939  *         A'. Reno "three dupacks" marks head of queue lost.
940  *         A''. Its FACK modfication, head until snd.fack is lost.
941  *      B. SACK arrives sacking data transmitted after never retransmitted
942  *         hole was sent out.
943  *      C. SACK arrives sacking SND.NXT at the moment, when the
944  *         segment was retransmitted.
945  * 4. D-SACK added new rule: D-SACK changes any tag to S.
946  *
947  * It is pleasant to note, that state diagram turns out to be commutative,
948  * so that we are allowed not to be bothered by order of our actions,
949  * when multiple events arrive simultaneously. (see the function below).
950  *
951  * Reordering detection.
952  * --------------------
953  * Reordering metric is maximal distance, which a packet can be displaced
954  * in packet stream. With SACKs we can estimate it:
955  *
956  * 1. SACK fills old hole and the corresponding segment was not
957  *    ever retransmitted -> reordering. Alas, we cannot use it
958  *    when segment was retransmitted.
959  * 2. The last flaw is solved with D-SACK. D-SACK arrives
960  *    for retransmitted and already SACKed segment -> reordering..
961  * Both of these heuristics are not used in Loss state, when we cannot
962  * account for retransmits accurately.
963  */
964 static int
965 tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
966 {
967         struct tcp_sock *tp = tcp_sk(sk);
968         unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked;
969         struct tcp_sack_block *sp = (struct tcp_sack_block *)(ptr+2);
970         int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
971         int reord = tp->packets_out;
972         int prior_fackets;
973         u32 lost_retrans = 0;
974         int flag = 0;
975         int i;
976
977         /* So, SACKs for already sent large segments will be lost.
978          * Not good, but alternative is to resegment the queue. */
979         if (sk->sk_route_caps & NETIF_F_TSO) {
980                 sk->sk_route_caps &= ~NETIF_F_TSO;
981                 sock_set_flag(sk, SOCK_NO_LARGESEND);
982                 tp->mss_cache = tp->mss_cache_std;
983         }
984
985         if (!tp->sacked_out)
986                 tp->fackets_out = 0;
987         prior_fackets = tp->fackets_out;
988
989         for (i=0; i<num_sacks; i++, sp++) {
990                 struct sk_buff *skb;
991                 __u32 start_seq = ntohl(sp->start_seq);
992                 __u32 end_seq = ntohl(sp->end_seq);
993                 int fack_count = 0;
994                 int dup_sack = 0;
995
996                 /* Check for D-SACK. */
997                 if (i == 0) {
998                         u32 ack = TCP_SKB_CB(ack_skb)->ack_seq;
999
1000                         if (before(start_seq, ack)) {
1001                                 dup_sack = 1;
1002                                 tp->rx_opt.sack_ok |= 4;
1003                                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
1004                         } else if (num_sacks > 1 &&
1005                                    !after(end_seq, ntohl(sp[1].end_seq)) &&
1006                                    !before(start_seq, ntohl(sp[1].start_seq))) {
1007                                 dup_sack = 1;
1008                                 tp->rx_opt.sack_ok |= 4;
1009                                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
1010                         }
1011
1012                         /* D-SACK for already forgotten data...
1013                          * Do dumb counting. */
1014                         if (dup_sack &&
1015                             !after(end_seq, prior_snd_una) &&
1016                             after(end_seq, tp->undo_marker))
1017                                 tp->undo_retrans--;
1018
1019                         /* Eliminate too old ACKs, but take into
1020                          * account more or less fresh ones, they can
1021                          * contain valid SACK info.
1022                          */
1023                         if (before(ack, prior_snd_una - tp->max_window))
1024                                 return 0;
1025                 }
1026
1027                 /* Event "B" in the comment above. */
1028                 if (after(end_seq, tp->high_seq))
1029                         flag |= FLAG_DATA_LOST;
1030
1031                 sk_stream_for_retrans_queue(skb, sk) {
1032                         u8 sacked = TCP_SKB_CB(skb)->sacked;
1033                         int in_sack;
1034
1035                         /* The retransmission queue is always in order, so
1036                          * we can short-circuit the walk early.
1037                          */
1038                         if(!before(TCP_SKB_CB(skb)->seq, end_seq))
1039                                 break;
1040
1041                         fack_count += tcp_skb_pcount(skb);
1042
1043                         in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1044                                 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1045
1046                         /* Account D-SACK for retransmitted packet. */
1047                         if ((dup_sack && in_sack) &&
1048                             (sacked & TCPCB_RETRANS) &&
1049                             after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
1050                                 tp->undo_retrans--;
1051
1052                         /* The frame is ACKed. */
1053                         if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
1054                                 if (sacked&TCPCB_RETRANS) {
1055                                         if ((dup_sack && in_sack) &&
1056                                             (sacked&TCPCB_SACKED_ACKED))
1057                                                 reord = min(fack_count, reord);
1058                                 } else {
1059                                         /* If it was in a hole, we detected reordering. */
1060                                         if (fack_count < prior_fackets &&
1061                                             !(sacked&TCPCB_SACKED_ACKED))
1062                                                 reord = min(fack_count, reord);
1063                                 }
1064
1065                                 /* Nothing to do; acked frame is about to be dropped. */
1066                                 continue;
1067                         }
1068
1069                         if ((sacked&TCPCB_SACKED_RETRANS) &&
1070                             after(end_seq, TCP_SKB_CB(skb)->ack_seq) &&
1071                             (!lost_retrans || after(end_seq, lost_retrans)))
1072                                 lost_retrans = end_seq;
1073
1074                         if (!in_sack)
1075                                 continue;
1076
1077                         if (!(sacked&TCPCB_SACKED_ACKED)) {
1078                                 if (sacked & TCPCB_SACKED_RETRANS) {
1079                                         /* If the segment is not tagged as lost,
1080                                          * we do not clear RETRANS, believing
1081                                          * that retransmission is still in flight.
1082                                          */
1083                                         if (sacked & TCPCB_LOST) {
1084                                                 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1085                                                 tp->lost_out -= tcp_skb_pcount(skb);
1086                                                 tp->retrans_out -= tcp_skb_pcount(skb);
1087                                         }
1088                                 } else {
1089                                         /* New sack for not retransmitted frame,
1090                                          * which was in hole. It is reordering.
1091                                          */
1092                                         if (!(sacked & TCPCB_RETRANS) &&
1093                                             fack_count < prior_fackets)
1094                                                 reord = min(fack_count, reord);
1095
1096                                         if (sacked & TCPCB_LOST) {
1097                                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1098                                                 tp->lost_out -= tcp_skb_pcount(skb);
1099                                         }
1100                                 }
1101
1102                                 TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
1103                                 flag |= FLAG_DATA_SACKED;
1104                                 tp->sacked_out += tcp_skb_pcount(skb);
1105
1106                                 if (fack_count > tp->fackets_out)
1107                                         tp->fackets_out = fack_count;
1108                         } else {
1109                                 if (dup_sack && (sacked&TCPCB_RETRANS))
1110                                         reord = min(fack_count, reord);
1111                         }
1112
1113                         /* D-SACK. We can detect redundant retransmission
1114                          * in S|R and plain R frames and clear it.
1115                          * undo_retrans is decreased above, L|R frames
1116                          * are accounted above as well.
1117                          */
1118                         if (dup_sack &&
1119                             (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
1120                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1121                                 tp->retrans_out -= tcp_skb_pcount(skb);
1122                         }
1123                 }
1124         }
1125
1126         /* Check for lost retransmit. This superb idea is
1127          * borrowed from "ratehalving". Event "C".
1128          * Later note: FACK people cheated me again 8),
1129          * we have to account for reordering! Ugly,
1130          * but should help.
1131          */
1132         if (lost_retrans && tp->ca_state == TCP_CA_Recovery) {
1133                 struct sk_buff *skb;
1134
1135                 sk_stream_for_retrans_queue(skb, sk) {
1136                         if (after(TCP_SKB_CB(skb)->seq, lost_retrans))
1137                                 break;
1138                         if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1139                                 continue;
1140                         if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) &&
1141                             after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) &&
1142                             (IsFack(tp) ||
1143                              !before(lost_retrans,
1144                                      TCP_SKB_CB(skb)->ack_seq + tp->reordering *
1145                                      tp->mss_cache_std))) {
1146                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1147                                 tp->retrans_out -= tcp_skb_pcount(skb);
1148
1149                                 if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) {
1150                                         tp->lost_out += tcp_skb_pcount(skb);
1151                                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1152                                         flag |= FLAG_DATA_SACKED;
1153                                         NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
1154                                 }
1155                         }
1156                 }
1157         }
1158
1159         tp->left_out = tp->sacked_out + tp->lost_out;
1160
1161         if ((reord < tp->fackets_out) && tp->ca_state != TCP_CA_Loss)
1162                 tcp_update_reordering(tp, ((tp->fackets_out + 1) - reord), 0);
1163
1164 #if FASTRETRANS_DEBUG > 0
1165         BUG_TRAP((int)tp->sacked_out >= 0);
1166         BUG_TRAP((int)tp->lost_out >= 0);
1167         BUG_TRAP((int)tp->retrans_out >= 0);
1168         BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0);
1169 #endif
1170         return flag;
1171 }
1172
1173 /* RTO occurred, but do not yet enter loss state. Instead, transmit two new
1174  * segments to see from the next ACKs whether any data was really missing.
1175  * If the RTO was spurious, new ACKs should arrive.
1176  */
1177 void tcp_enter_frto(struct sock *sk)
1178 {
1179         struct tcp_sock *tp = tcp_sk(sk);
1180         struct sk_buff *skb;
1181
1182         tp->frto_counter = 1;
1183
1184         if (tp->ca_state <= TCP_CA_Disorder ||
1185             tp->snd_una == tp->high_seq ||
1186             (tp->ca_state == TCP_CA_Loss && !tp->retransmits)) {
1187                 tp->prior_ssthresh = tcp_current_ssthresh(tp);
1188                 if (!tcp_westwood_ssthresh(tp))
1189                         tp->snd_ssthresh = tcp_recalc_ssthresh(tp);
1190         }
1191
1192         /* Have to clear retransmission markers here to keep the bookkeeping
1193          * in shape, even though we are not yet in Loss state.
1194          * If something was really lost, it is eventually caught up
1195          * in tcp_enter_frto_loss.
1196          */
1197         tp->retrans_out = 0;
1198         tp->undo_marker = tp->snd_una;
1199         tp->undo_retrans = 0;
1200
1201         sk_stream_for_retrans_queue(skb, sk) {
1202                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_RETRANS;
1203         }
1204         tcp_sync_left_out(tp);
1205
1206         tcp_set_ca_state(tp, TCP_CA_Open);
1207         tp->frto_highmark = tp->snd_nxt;
1208 }
1209
1210 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1211  * which indicates that we should follow the traditional RTO recovery,
1212  * i.e. mark everything lost and do go-back-N retransmission.
1213  */
1214 static void tcp_enter_frto_loss(struct sock *sk)
1215 {
1216         struct tcp_sock *tp = tcp_sk(sk);
1217         struct sk_buff *skb;
1218         int cnt = 0;
1219
1220         tp->sacked_out = 0;
1221         tp->lost_out = 0;
1222         tp->fackets_out = 0;
1223
1224         sk_stream_for_retrans_queue(skb, sk) {
1225                 cnt += tcp_skb_pcount(skb);
1226                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1227                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
1228
1229                         /* Do not mark those segments lost that were
1230                          * forward transmitted after RTO
1231                          */
1232                         if (!after(TCP_SKB_CB(skb)->end_seq,
1233                                    tp->frto_highmark)) {
1234                                 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1235                                 tp->lost_out += tcp_skb_pcount(skb);
1236                         }
1237                 } else {
1238                         tp->sacked_out += tcp_skb_pcount(skb);
1239                         tp->fackets_out = cnt;
1240                 }
1241         }
1242         tcp_sync_left_out(tp);
1243
1244         tp->snd_cwnd = tp->frto_counter + tcp_packets_in_flight(tp)+1;
1245         tp->snd_cwnd_cnt = 0;
1246         tp->snd_cwnd_stamp = tcp_time_stamp;
1247         tp->undo_marker = 0;
1248         tp->frto_counter = 0;
1249
1250         tp->reordering = min_t(unsigned int, tp->reordering,
1251                                              sysctl_tcp_reordering);
1252         tcp_set_ca_state(tp, TCP_CA_Loss);
1253         tp->high_seq = tp->frto_highmark;
1254         TCP_ECN_queue_cwr(tp);
1255
1256         init_bictcp(tp);
1257 }
1258
1259 void tcp_clear_retrans(struct tcp_sock *tp)
1260 {
1261         tp->left_out = 0;
1262         tp->retrans_out = 0;
1263
1264         tp->fackets_out = 0;
1265         tp->sacked_out = 0;
1266         tp->lost_out = 0;
1267
1268         tp->undo_marker = 0;
1269         tp->undo_retrans = 0;
1270 }
1271
1272 /* Enter Loss state. If "how" is not zero, forget all SACK information
1273  * and reset tags completely, otherwise preserve SACKs. If receiver
1274  * dropped its ofo queue, we will know this due to reneging detection.
1275  */
1276 void tcp_enter_loss(struct sock *sk, int how)
1277 {
1278         struct tcp_sock *tp = tcp_sk(sk);
1279         struct sk_buff *skb;
1280         int cnt = 0;
1281
1282         /* Reduce ssthresh if it has not yet been made inside this window. */
1283         if (tp->ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
1284             (tp->ca_state == TCP_CA_Loss && !tp->retransmits)) {
1285                 tp->prior_ssthresh = tcp_current_ssthresh(tp);
1286                 tp->snd_ssthresh = tcp_recalc_ssthresh(tp);
1287         }
1288         tp->snd_cwnd       = 1;
1289         tp->snd_cwnd_cnt   = 0;
1290         tp->snd_cwnd_stamp = tcp_time_stamp;
1291
1292         tcp_clear_retrans(tp);
1293
1294         /* Push undo marker, if it was plain RTO and nothing
1295          * was retransmitted. */
1296         if (!how)
1297                 tp->undo_marker = tp->snd_una;
1298
1299         sk_stream_for_retrans_queue(skb, sk) {
1300                 cnt += tcp_skb_pcount(skb);
1301                 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS)
1302                         tp->undo_marker = 0;
1303                 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
1304                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
1305                         TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
1306                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1307                         tp->lost_out += tcp_skb_pcount(skb);
1308                 } else {
1309                         tp->sacked_out += tcp_skb_pcount(skb);
1310                         tp->fackets_out = cnt;
1311                 }
1312         }
1313         tcp_sync_left_out(tp);
1314
1315         tp->reordering = min_t(unsigned int, tp->reordering,
1316                                              sysctl_tcp_reordering);
1317         tcp_set_ca_state(tp, TCP_CA_Loss);
1318         tp->high_seq = tp->snd_nxt;
1319         TCP_ECN_queue_cwr(tp);
1320 }
1321
1322 static int tcp_check_sack_reneging(struct sock *sk, struct tcp_sock *tp)
1323 {
1324         struct sk_buff *skb;
1325
1326         /* If ACK arrived pointing to a remembered SACK,
1327          * it means that our remembered SACKs do not reflect
1328          * real state of receiver i.e.
1329          * receiver _host_ is heavily congested (or buggy).
1330          * Do processing similar to RTO timeout.
1331          */
1332         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL &&
1333             (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
1334                 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING);
1335
1336                 tcp_enter_loss(sk, 1);
1337                 tp->retransmits++;
1338                 tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue));
1339                 tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto);
1340                 return 1;
1341         }
1342         return 0;
1343 }
1344
1345 static inline int tcp_fackets_out(struct tcp_sock *tp)
1346 {
1347         return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out;
1348 }
1349
1350 static inline int tcp_skb_timedout(struct tcp_sock *tp, struct sk_buff *skb)
1351 {
1352         return (tcp_time_stamp - TCP_SKB_CB(skb)->when > tp->rto);
1353 }
1354
1355 static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp)
1356 {
1357         return tp->packets_out &&
1358                tcp_skb_timedout(tp, skb_peek(&sk->sk_write_queue));
1359 }
1360
1361 /* Linux NewReno/SACK/FACK/ECN state machine.
1362  * --------------------------------------
1363  *
1364  * "Open"       Normal state, no dubious events, fast path.
1365  * "Disorder"   In all the respects it is "Open",
1366  *              but requires a bit more attention. It is entered when
1367  *              we see some SACKs or dupacks. It is split of "Open"
1368  *              mainly to move some processing from fast path to slow one.
1369  * "CWR"        CWND was reduced due to some Congestion Notification event.
1370  *              It can be ECN, ICMP source quench, local device congestion.
1371  * "Recovery"   CWND was reduced, we are fast-retransmitting.
1372  * "Loss"       CWND was reduced due to RTO timeout or SACK reneging.
1373  *
1374  * tcp_fastretrans_alert() is entered:
1375  * - each incoming ACK, if state is not "Open"
1376  * - when arrived ACK is unusual, namely:
1377  *      * SACK
1378  *      * Duplicate ACK.
1379  *      * ECN ECE.
1380  *
1381  * Counting packets in flight is pretty simple.
1382  *
1383  *      in_flight = packets_out - left_out + retrans_out
1384  *
1385  *      packets_out is SND.NXT-SND.UNA counted in packets.
1386  *
1387  *      retrans_out is number of retransmitted segments.
1388  *
1389  *      left_out is number of segments left network, but not ACKed yet.
1390  *
1391  *              left_out = sacked_out + lost_out
1392  *
1393  *     sacked_out: Packets, which arrived to receiver out of order
1394  *                 and hence not ACKed. With SACKs this number is simply
1395  *                 amount of SACKed data. Even without SACKs
1396  *                 it is easy to give pretty reliable estimate of this number,
1397  *                 counting duplicate ACKs.
1398  *
1399  *       lost_out: Packets lost by network. TCP has no explicit
1400  *                 "loss notification" feedback from network (for now).
1401  *                 It means that this number can be only _guessed_.
1402  *                 Actually, it is the heuristics to predict lossage that
1403  *                 distinguishes different algorithms.
1404  *
1405  *      F.e. after RTO, when all the queue is considered as lost,
1406  *      lost_out = packets_out and in_flight = retrans_out.
1407  *
1408  *              Essentially, we have now two algorithms counting
1409  *              lost packets.
1410  *
1411  *              FACK: It is the simplest heuristics. As soon as we decided
1412  *              that something is lost, we decide that _all_ not SACKed
1413  *              packets until the most forward SACK are lost. I.e.
1414  *              lost_out = fackets_out - sacked_out and left_out = fackets_out.
1415  *              It is absolutely correct estimate, if network does not reorder
1416  *              packets. And it loses any connection to reality when reordering
1417  *              takes place. We use FACK by default until reordering
1418  *              is suspected on the path to this destination.
1419  *
1420  *              NewReno: when Recovery is entered, we assume that one segment
1421  *              is lost (classic Reno). While we are in Recovery and
1422  *              a partial ACK arrives, we assume that one more packet
1423  *              is lost (NewReno). This heuristics are the same in NewReno
1424  *              and SACK.
1425  *
1426  *  Imagine, that's all! Forget about all this shamanism about CWND inflation
1427  *  deflation etc. CWND is real congestion window, never inflated, changes
1428  *  only according to classic VJ rules.
1429  *
1430  * Really tricky (and requiring careful tuning) part of algorithm
1431  * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1432  * The first determines the moment _when_ we should reduce CWND and,
1433  * hence, slow down forward transmission. In fact, it determines the moment
1434  * when we decide that hole is caused by loss, rather than by a reorder.
1435  *
1436  * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1437  * holes, caused by lost packets.
1438  *
1439  * And the most logically complicated part of algorithm is undo
1440  * heuristics. We detect false retransmits due to both too early
1441  * fast retransmit (reordering) and underestimated RTO, analyzing
1442  * timestamps and D-SACKs. When we detect that some segments were
1443  * retransmitted by mistake and CWND reduction was wrong, we undo
1444  * window reduction and abort recovery phase. This logic is hidden
1445  * inside several functions named tcp_try_undo_<something>.
1446  */
1447
1448 /* This function decides, when we should leave Disordered state
1449  * and enter Recovery phase, reducing congestion window.
1450  *
1451  * Main question: may we further continue forward transmission
1452  * with the same cwnd?
1453  */
1454 static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp)
1455 {
1456         __u32 packets_out;
1457
1458         /* Trick#1: The loss is proven. */
1459         if (tp->lost_out)
1460                 return 1;
1461
1462         /* Not-A-Trick#2 : Classic rule... */
1463         if (tcp_fackets_out(tp) > tp->reordering)
1464                 return 1;
1465
1466         /* Trick#3 : when we use RFC2988 timer restart, fast
1467          * retransmit can be triggered by timeout of queue head.
1468          */
1469         if (tcp_head_timedout(sk, tp))
1470                 return 1;
1471
1472         /* Trick#4: It is still not OK... But will it be useful to delay
1473          * recovery more?
1474          */
1475         packets_out = tp->packets_out;
1476         if (packets_out <= tp->reordering &&
1477             tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
1478             !tcp_may_send_now(sk, tp)) {
1479                 /* We have nothing to send. This connection is limited
1480                  * either by receiver window or by application.
1481                  */
1482                 return 1;
1483         }
1484
1485         return 0;
1486 }
1487
1488 /* If we receive more dupacks than we expected counting segments
1489  * in assumption of absent reordering, interpret this as reordering.
1490  * The only another reason could be bug in receiver TCP.
1491  */
1492 static void tcp_check_reno_reordering(struct tcp_sock *tp, int addend)
1493 {
1494         u32 holes;
1495
1496         holes = max(tp->lost_out, 1U);
1497         holes = min(holes, tp->packets_out);
1498
1499         if ((tp->sacked_out + holes) > tp->packets_out) {
1500                 tp->sacked_out = tp->packets_out - holes;
1501                 tcp_update_reordering(tp, tp->packets_out+addend, 0);
1502         }
1503 }
1504
1505 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1506
1507 static void tcp_add_reno_sack(struct tcp_sock *tp)
1508 {
1509         tp->sacked_out++;
1510         tcp_check_reno_reordering(tp, 0);
1511         tcp_sync_left_out(tp);
1512 }
1513
1514 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1515
1516 static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked)
1517 {
1518         if (acked > 0) {
1519                 /* One ACK acked hole. The rest eat duplicate ACKs. */
1520                 if (acked-1 >= tp->sacked_out)
1521                         tp->sacked_out = 0;
1522                 else
1523                         tp->sacked_out -= acked-1;
1524         }
1525         tcp_check_reno_reordering(tp, acked);
1526         tcp_sync_left_out(tp);
1527 }
1528
1529 static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1530 {
1531         tp->sacked_out = 0;
1532         tp->left_out = tp->lost_out;
1533 }
1534
1535 /* Mark head of queue up as lost. */
1536 static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp,
1537                                int packets, u32 high_seq)
1538 {
1539         struct sk_buff *skb;
1540         int cnt = packets;
1541
1542         BUG_TRAP(cnt <= tp->packets_out);
1543
1544         sk_stream_for_retrans_queue(skb, sk) {
1545                 cnt -= tcp_skb_pcount(skb);
1546                 if (cnt < 0 || after(TCP_SKB_CB(skb)->end_seq, high_seq))
1547                         break;
1548                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1549                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1550                         tp->lost_out += tcp_skb_pcount(skb);
1551                 }
1552         }
1553         tcp_sync_left_out(tp);
1554 }
1555
1556 /* Account newly detected lost packet(s) */
1557
1558 static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp)
1559 {
1560         if (IsFack(tp)) {
1561                 int lost = tp->fackets_out - tp->reordering;
1562                 if (lost <= 0)
1563                         lost = 1;
1564                 tcp_mark_head_lost(sk, tp, lost, tp->high_seq);
1565         } else {
1566                 tcp_mark_head_lost(sk, tp, 1, tp->high_seq);
1567         }
1568
1569         /* New heuristics: it is possible only after we switched
1570          * to restart timer each time when something is ACKed.
1571          * Hence, we can detect timed out packets during fast
1572          * retransmit without falling to slow start.
1573          */
1574         if (tcp_head_timedout(sk, tp)) {
1575                 struct sk_buff *skb;
1576
1577                 sk_stream_for_retrans_queue(skb, sk) {
1578                         if (tcp_skb_timedout(tp, skb) &&
1579                             !(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1580                                 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1581                                 tp->lost_out += tcp_skb_pcount(skb);
1582                         }
1583                 }
1584                 tcp_sync_left_out(tp);
1585         }
1586 }
1587
1588 /* CWND moderation, preventing bursts due to too big ACKs
1589  * in dubious situations.
1590  */
1591 static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
1592 {
1593         tp->snd_cwnd = min(tp->snd_cwnd,
1594                            tcp_packets_in_flight(tp)+tcp_max_burst(tp));
1595         tp->snd_cwnd_stamp = tcp_time_stamp;
1596 }
1597
1598 /* Decrease cwnd each second ack. */
1599
1600 static void tcp_cwnd_down(struct tcp_sock *tp)
1601 {
1602         int decr = tp->snd_cwnd_cnt + 1;
1603         __u32 limit;
1604
1605         /*
1606          * TCP Westwood
1607          * Here limit is evaluated as BWestimation*RTTmin (for obtaining it
1608          * in packets we use mss_cache). If sysctl_tcp_westwood is off
1609          * tcp_westwood_bw_rttmin() returns 0. In such case snd_ssthresh is
1610          * still used as usual. It prevents other strange cases in which
1611          * BWE*RTTmin could assume value 0. It should not happen but...
1612          */
1613
1614         if (!(limit = tcp_westwood_bw_rttmin(tp)))
1615                 limit = tp->snd_ssthresh/2;
1616
1617         tp->snd_cwnd_cnt = decr&1;
1618         decr >>= 1;
1619
1620         if (decr && tp->snd_cwnd > limit)
1621                 tp->snd_cwnd -= decr;
1622
1623         tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);
1624         tp->snd_cwnd_stamp = tcp_time_stamp;
1625 }
1626
1627 /* Nothing was retransmitted or returned timestamp is less
1628  * than timestamp of the first retransmission.
1629  */
1630 static inline int tcp_packet_delayed(struct tcp_sock *tp)
1631 {
1632         return !tp->retrans_stamp ||
1633                 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
1634                  (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0);
1635 }
1636
1637 /* Undo procedures. */
1638
1639 #if FASTRETRANS_DEBUG > 1
1640 static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg)
1641 {
1642         struct inet_sock *inet = inet_sk(sk);
1643         printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1644                msg,
1645                NIPQUAD(inet->daddr), ntohs(inet->dport),
1646                tp->snd_cwnd, tp->left_out,
1647                tp->snd_ssthresh, tp->prior_ssthresh,
1648                tp->packets_out);
1649 }
1650 #else
1651 #define DBGUNDO(x...) do { } while (0)
1652 #endif
1653
1654 static void tcp_undo_cwr(struct tcp_sock *tp, int undo)
1655 {
1656         if (tp->prior_ssthresh) {
1657                 if (tcp_is_bic(tp))
1658                         tp->snd_cwnd = max(tp->snd_cwnd, tp->bictcp.last_max_cwnd);
1659                 else
1660                         tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1);
1661
1662                 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
1663                         tp->snd_ssthresh = tp->prior_ssthresh;
1664                         TCP_ECN_withdraw_cwr(tp);
1665                 }
1666         } else {
1667                 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
1668         }
1669         tcp_moderate_cwnd(tp);
1670         tp->snd_cwnd_stamp = tcp_time_stamp;
1671 }
1672
1673 static inline int tcp_may_undo(struct tcp_sock *tp)
1674 {
1675         return tp->undo_marker &&
1676                 (!tp->undo_retrans || tcp_packet_delayed(tp));
1677 }
1678
1679 /* People celebrate: "We love our President!" */
1680 static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp)
1681 {
1682         if (tcp_may_undo(tp)) {
1683                 /* Happy end! We did not retransmit anything
1684                  * or our original transmission succeeded.
1685                  */
1686                 DBGUNDO(sk, tp, tp->ca_state == TCP_CA_Loss ? "loss" : "retrans");
1687                 tcp_undo_cwr(tp, 1);
1688                 if (tp->ca_state == TCP_CA_Loss)
1689                         NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1690                 else
1691                         NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO);
1692                 tp->undo_marker = 0;
1693         }
1694         if (tp->snd_una == tp->high_seq && IsReno(tp)) {
1695                 /* Hold old state until something *above* high_seq
1696                  * is ACKed. For Reno it is MUST to prevent false
1697                  * fast retransmits (RFC2582). SACK TCP is safe. */
1698                 tcp_moderate_cwnd(tp);
1699                 return 1;
1700         }
1701         tcp_set_ca_state(tp, TCP_CA_Open);
1702         return 0;
1703 }
1704
1705 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1706 static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp)
1707 {
1708         if (tp->undo_marker && !tp->undo_retrans) {
1709                 DBGUNDO(sk, tp, "D-SACK");
1710                 tcp_undo_cwr(tp, 1);
1711                 tp->undo_marker = 0;
1712                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO);
1713         }
1714 }
1715
1716 /* Undo during fast recovery after partial ACK. */
1717
1718 static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp,
1719                                 int acked)
1720 {
1721         /* Partial ACK arrived. Force Hoe's retransmit. */
1722         int failed = IsReno(tp) || tp->fackets_out>tp->reordering;
1723
1724         if (tcp_may_undo(tp)) {
1725                 /* Plain luck! Hole if filled with delayed
1726                  * packet, rather than with a retransmit.
1727                  */
1728                 if (tp->retrans_out == 0)
1729                         tp->retrans_stamp = 0;
1730
1731                 tcp_update_reordering(tp, tcp_fackets_out(tp)+acked, 1);
1732
1733                 DBGUNDO(sk, tp, "Hoe");
1734                 tcp_undo_cwr(tp, 0);
1735                 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO);
1736
1737                 /* So... Do not make Hoe's retransmit yet.
1738                  * If the first packet was delayed, the rest
1739                  * ones are most probably delayed as well.
1740                  */
1741                 failed = 0;
1742         }
1743         return failed;
1744 }
1745
1746 /* Undo during loss recovery after partial ACK. */
1747 static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp)
1748 {
1749         if (tcp_may_undo(tp)) {
1750                 struct sk_buff *skb;
1751                 sk_stream_for_retrans_queue(skb, sk) {
1752                         TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1753                 }
1754                 DBGUNDO(sk, tp, "partial loss");
1755                 tp->lost_out = 0;
1756                 tp->left_out = tp->sacked_out;
1757                 tcp_undo_cwr(tp, 1);
1758                 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1759                 tp->retransmits = 0;
1760                 tp->undo_marker = 0;
1761                 if (!IsReno(tp))
1762                         tcp_set_ca_state(tp, TCP_CA_Open);
1763                 return 1;
1764         }
1765         return 0;
1766 }
1767
1768 static inline void tcp_complete_cwr(struct tcp_sock *tp)
1769 {
1770         if (tcp_westwood_cwnd(tp)) 
1771                 tp->snd_ssthresh = tp->snd_cwnd;
1772         else
1773                 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
1774         tp->snd_cwnd_stamp = tcp_time_stamp;
1775 }
1776
1777 static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag)
1778 {
1779         tp->left_out = tp->sacked_out;
1780
1781         if (tp->retrans_out == 0)
1782                 tp->retrans_stamp = 0;
1783
1784         if (flag&FLAG_ECE)
1785                 tcp_enter_cwr(tp);
1786
1787         if (tp->ca_state != TCP_CA_CWR) {
1788                 int state = TCP_CA_Open;
1789
1790                 if (tp->left_out || tp->retrans_out || tp->undo_marker)
1791                         state = TCP_CA_Disorder;
1792
1793                 if (tp->ca_state != state) {
1794                         tcp_set_ca_state(tp, state);
1795                         tp->high_seq = tp->snd_nxt;
1796                 }
1797                 tcp_moderate_cwnd(tp);
1798         } else {
1799                 tcp_cwnd_down(tp);
1800         }
1801 }
1802
1803 /* Process an event, which can update packets-in-flight not trivially.
1804  * Main goal of this function is to calculate new estimate for left_out,
1805  * taking into account both packets sitting in receiver's buffer and
1806  * packets lost by network.
1807  *
1808  * Besides that it does CWND reduction, when packet loss is detected
1809  * and changes state of machine.
1810  *
1811  * It does _not_ decide what to send, it is made in function
1812  * tcp_xmit_retransmit_queue().
1813  */
1814 static void
1815 tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
1816                       int prior_packets, int flag)
1817 {
1818         struct tcp_sock *tp = tcp_sk(sk);
1819         int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP));
1820
1821         /* Some technical things:
1822          * 1. Reno does not count dupacks (sacked_out) automatically. */
1823         if (!tp->packets_out)
1824                 tp->sacked_out = 0;
1825         /* 2. SACK counts snd_fack in packets inaccurately. */
1826         if (tp->sacked_out == 0)
1827                 tp->fackets_out = 0;
1828
1829         /* Now state machine starts.
1830          * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
1831         if (flag&FLAG_ECE)
1832                 tp->prior_ssthresh = 0;
1833
1834         /* B. In all the states check for reneging SACKs. */
1835         if (tp->sacked_out && tcp_check_sack_reneging(sk, tp))
1836                 return;
1837
1838         /* C. Process data loss notification, provided it is valid. */
1839         if ((flag&FLAG_DATA_LOST) &&
1840             before(tp->snd_una, tp->high_seq) &&
1841             tp->ca_state != TCP_CA_Open &&
1842             tp->fackets_out > tp->reordering) {
1843                 tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq);
1844                 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
1845         }
1846
1847         /* D. Synchronize left_out to current state. */
1848         tcp_sync_left_out(tp);
1849
1850         /* E. Check state exit conditions. State can be terminated
1851          *    when high_seq is ACKed. */
1852         if (tp->ca_state == TCP_CA_Open) {
1853                 if (!sysctl_tcp_frto)
1854                         BUG_TRAP(tp->retrans_out == 0);
1855                 tp->retrans_stamp = 0;
1856         } else if (!before(tp->snd_una, tp->high_seq)) {
1857                 switch (tp->ca_state) {
1858                 case TCP_CA_Loss:
1859                         tp->retransmits = 0;
1860                         if (tcp_try_undo_recovery(sk, tp))
1861                                 return;
1862                         break;
1863
1864                 case TCP_CA_CWR:
1865                         /* CWR is to be held something *above* high_seq
1866                          * is ACKed for CWR bit to reach receiver. */
1867                         if (tp->snd_una != tp->high_seq) {
1868                                 tcp_complete_cwr(tp);
1869                                 tcp_set_ca_state(tp, TCP_CA_Open);
1870                         }
1871                         break;
1872
1873                 case TCP_CA_Disorder:
1874                         tcp_try_undo_dsack(sk, tp);
1875                         if (!tp->undo_marker ||
1876                             /* For SACK case do not Open to allow to undo
1877                              * catching for all duplicate ACKs. */
1878                             IsReno(tp) || tp->snd_una != tp->high_seq) {
1879                                 tp->undo_marker = 0;
1880                                 tcp_set_ca_state(tp, TCP_CA_Open);
1881                         }
1882                         break;
1883
1884                 case TCP_CA_Recovery:
1885                         if (IsReno(tp))
1886                                 tcp_reset_reno_sack(tp);
1887                         if (tcp_try_undo_recovery(sk, tp))
1888                                 return;
1889                         tcp_complete_cwr(tp);
1890                         break;
1891                 }
1892         }
1893
1894         /* F. Process state. */
1895         switch (tp->ca_state) {
1896         case TCP_CA_Recovery:
1897                 if (prior_snd_una == tp->snd_una) {
1898                         if (IsReno(tp) && is_dupack)
1899                                 tcp_add_reno_sack(tp);
1900                 } else {
1901                         int acked = prior_packets - tp->packets_out;
1902                         if (IsReno(tp))
1903                                 tcp_remove_reno_sacks(sk, tp, acked);
1904                         is_dupack = tcp_try_undo_partial(sk, tp, acked);
1905                 }
1906                 break;
1907         case TCP_CA_Loss:
1908                 if (flag&FLAG_DATA_ACKED)
1909                         tp->retransmits = 0;
1910                 if (!tcp_try_undo_loss(sk, tp)) {
1911                         tcp_moderate_cwnd(tp);
1912                         tcp_xmit_retransmit_queue(sk);
1913                         return;
1914                 }
1915                 if (tp->ca_state != TCP_CA_Open)
1916                         return;
1917                 /* Loss is undone; fall through to processing in Open state. */
1918         default:
1919                 if (IsReno(tp)) {
1920                         if (tp->snd_una != prior_snd_una)
1921                                 tcp_reset_reno_sack(tp);
1922                         if (is_dupack)
1923                                 tcp_add_reno_sack(tp);
1924                 }
1925
1926                 if (tp->ca_state == TCP_CA_Disorder)
1927                         tcp_try_undo_dsack(sk, tp);
1928
1929                 if (!tcp_time_to_recover(sk, tp)) {
1930                         tcp_try_to_open(sk, tp, flag);
1931                         return;
1932                 }
1933
1934                 /* Otherwise enter Recovery state */
1935
1936                 if (IsReno(tp))
1937                         NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY);
1938                 else
1939                         NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY);
1940
1941                 tp->high_seq = tp->snd_nxt;
1942                 tp->prior_ssthresh = 0;
1943                 tp->undo_marker = tp->snd_una;
1944                 tp->undo_retrans = tp->retrans_out;
1945
1946                 if (tp->ca_state < TCP_CA_CWR) {
1947                         if (!(flag&FLAG_ECE))
1948                                 tp->prior_ssthresh = tcp_current_ssthresh(tp);
1949                         tp->snd_ssthresh = tcp_recalc_ssthresh(tp);
1950                         TCP_ECN_queue_cwr(tp);
1951                 }
1952
1953                 tp->snd_cwnd_cnt = 0;
1954                 tcp_set_ca_state(tp, TCP_CA_Recovery);
1955         }
1956
1957         if (is_dupack || tcp_head_timedout(sk, tp))
1958                 tcp_update_scoreboard(sk, tp);
1959         tcp_cwnd_down(tp);
1960         tcp_xmit_retransmit_queue(sk);
1961 }
1962
1963 /* Read draft-ietf-tcplw-high-performance before mucking
1964  * with this code. (Superceeds RFC1323)
1965  */
1966 static void tcp_ack_saw_tstamp(struct tcp_sock *tp, int flag)
1967 {
1968         __u32 seq_rtt;
1969
1970         /* RTTM Rule: A TSecr value received in a segment is used to
1971          * update the averaged RTT measurement only if the segment
1972          * acknowledges some new data, i.e., only if it advances the
1973          * left edge of the send window.
1974          *
1975          * See draft-ietf-tcplw-high-performance-00, section 3.3.
1976          * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
1977          *
1978          * Changed: reset backoff as soon as we see the first valid sample.
1979          * If we do not, we get strongly overstimated rto. With timestamps
1980          * samples are accepted even from very old segments: f.e., when rtt=1
1981          * increases to 8, we retransmit 5 times and after 8 seconds delayed
1982          * answer arrives rto becomes 120 seconds! If at least one of segments
1983          * in window is lost... Voila.                          --ANK (010210)
1984          */
1985         seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
1986         tcp_rtt_estimator(tp, seq_rtt);
1987         tcp_set_rto(tp);
1988         tp->backoff = 0;
1989         tcp_bound_rto(tp);
1990 }
1991
1992 static void tcp_ack_no_tstamp(struct tcp_sock *tp, u32 seq_rtt, int flag)
1993 {
1994         /* We don't have a timestamp. Can only use
1995          * packets that are not retransmitted to determine
1996          * rtt estimates. Also, we must not reset the
1997          * backoff for rto until we get a non-retransmitted
1998          * packet. This allows us to deal with a situation
1999          * where the network delay has increased suddenly.
2000          * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2001          */
2002
2003         if (flag & FLAG_RETRANS_DATA_ACKED)
2004                 return;
2005
2006         tcp_rtt_estimator(tp, seq_rtt);
2007         tcp_set_rto(tp);
2008         tp->backoff = 0;
2009         tcp_bound_rto(tp);
2010 }
2011
2012 static inline void tcp_ack_update_rtt(struct tcp_sock *tp,
2013                                       int flag, s32 seq_rtt)
2014 {
2015         /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2016         if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
2017                 tcp_ack_saw_tstamp(tp, flag);
2018         else if (seq_rtt >= 0)
2019                 tcp_ack_no_tstamp(tp, seq_rtt, flag);
2020 }
2021
2022 /*
2023  * Compute congestion window to use.
2024  *
2025  * This is from the implementation of BICTCP in
2026  * Lison-Xu, Kahaled Harfoush, and Injog Rhee.
2027  *  "Binary Increase Congestion Control for Fast, Long Distance
2028  *  Networks" in InfoComm 2004
2029  * Available from:
2030  *  http://www.csc.ncsu.edu/faculty/rhee/export/bitcp.pdf
2031  *
2032  * Unless BIC is enabled and congestion window is large
2033  * this behaves the same as the original Reno.
2034  */
2035 static inline __u32 bictcp_cwnd(struct tcp_sock *tp)
2036 {
2037         /* orignal Reno behaviour */
2038         if (!tcp_is_bic(tp))
2039                 return tp->snd_cwnd;
2040
2041         if (tp->bictcp.last_cwnd == tp->snd_cwnd &&
2042            (s32)(tcp_time_stamp - tp->bictcp.last_stamp) <= (HZ>>5))
2043                 return tp->bictcp.cnt;
2044
2045         tp->bictcp.last_cwnd = tp->snd_cwnd;
2046         tp->bictcp.last_stamp = tcp_time_stamp;
2047       
2048         /* start off normal */
2049         if (tp->snd_cwnd <= sysctl_tcp_bic_low_window)
2050                 tp->bictcp.cnt = tp->snd_cwnd;
2051
2052         /* binary increase */
2053         else if (tp->snd_cwnd < tp->bictcp.last_max_cwnd) {
2054                 __u32   dist = (tp->bictcp.last_max_cwnd - tp->snd_cwnd)
2055                         / BICTCP_B;
2056
2057                 if (dist > BICTCP_MAX_INCREMENT)
2058                         /* linear increase */
2059                         tp->bictcp.cnt = tp->snd_cwnd / BICTCP_MAX_INCREMENT;
2060                 else if (dist <= 1U)
2061                         /* binary search increase */
2062                         tp->bictcp.cnt = tp->snd_cwnd * BICTCP_FUNC_OF_MIN_INCR
2063                                 / BICTCP_B;
2064                 else
2065                         /* binary search increase */
2066                         tp->bictcp.cnt = tp->snd_cwnd / dist;
2067         } else {
2068                 /* slow start amd linear increase */
2069                 if (tp->snd_cwnd < tp->bictcp.last_max_cwnd + BICTCP_B)
2070                         /* slow start */
2071                         tp->bictcp.cnt = tp->snd_cwnd * BICTCP_FUNC_OF_MIN_INCR
2072                                 / BICTCP_B;
2073                 else if (tp->snd_cwnd < tp->bictcp.last_max_cwnd
2074                                         + BICTCP_MAX_INCREMENT*(BICTCP_B-1))
2075                         /* slow start */
2076                         tp->bictcp.cnt = tp->snd_cwnd * (BICTCP_B-1)
2077                                 / (tp->snd_cwnd-tp->bictcp.last_max_cwnd);
2078                 else
2079                         /* linear increase */
2080                         tp->bictcp.cnt = tp->snd_cwnd / BICTCP_MAX_INCREMENT;
2081         }
2082         return tp->bictcp.cnt;
2083 }
2084
2085 /* This is Jacobson's slow start and congestion avoidance. 
2086  * SIGCOMM '88, p. 328.
2087  */
2088 static inline void reno_cong_avoid(struct tcp_sock *tp)
2089 {
2090         if (tp->snd_cwnd <= tp->snd_ssthresh) {
2091                 /* In "safe" area, increase. */
2092                 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
2093                         tp->snd_cwnd++;
2094         } else {
2095                 /* In dangerous area, increase slowly.
2096                  * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
2097                  */
2098                 if (tp->snd_cwnd_cnt >= bictcp_cwnd(tp)) {
2099                         if (tp->snd_cwnd < tp->snd_cwnd_clamp)
2100                                 tp->snd_cwnd++;
2101                         tp->snd_cwnd_cnt=0;
2102                 } else
2103                         tp->snd_cwnd_cnt++;
2104         }
2105         tp->snd_cwnd_stamp = tcp_time_stamp;
2106 }
2107
2108 /* This is based on the congestion detection/avoidance scheme described in
2109  *    Lawrence S. Brakmo and Larry L. Peterson.
2110  *    "TCP Vegas: End to end congestion avoidance on a global internet."
2111  *    IEEE Journal on Selected Areas in Communication, 13(8):1465--1480,
2112  *    October 1995. Available from:
2113  *      ftp://ftp.cs.arizona.edu/xkernel/Papers/jsac.ps
2114  *
2115  * See http://www.cs.arizona.edu/xkernel/ for their implementation.
2116  * The main aspects that distinguish this implementation from the
2117  * Arizona Vegas implementation are:
2118  *   o We do not change the loss detection or recovery mechanisms of
2119  *     Linux in any way. Linux already recovers from losses quite well,
2120  *     using fine-grained timers, NewReno, and FACK.
2121  *   o To avoid the performance penalty imposed by increasing cwnd
2122  *     only every-other RTT during slow start, we increase during
2123  *     every RTT during slow start, just like Reno.
2124  *   o Largely to allow continuous cwnd growth during slow start,
2125  *     we use the rate at which ACKs come back as the "actual"
2126  *     rate, rather than the rate at which data is sent.
2127  *   o To speed convergence to the right rate, we set the cwnd
2128  *     to achieve the right ("actual") rate when we exit slow start.
2129  *   o To filter out the noise caused by delayed ACKs, we use the
2130  *     minimum RTT sample observed during the last RTT to calculate
2131  *     the actual rate.
2132  *   o When the sender re-starts from idle, it waits until it has
2133  *     received ACKs for an entire flight of new data before making
2134  *     a cwnd adjustment decision. The original Vegas implementation
2135  *     assumed senders never went idle.
2136  */
2137 static void vegas_cong_avoid(struct tcp_sock *tp, u32 ack, u32 seq_rtt)
2138 {
2139         /* The key players are v_beg_snd_una and v_beg_snd_nxt.
2140          *
2141          * These are so named because they represent the approximate values
2142          * of snd_una and snd_nxt at the beginning of the current RTT. More
2143          * precisely, they represent the amount of data sent during the RTT.
2144          * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
2145          * we will calculate that (v_beg_snd_nxt - v_beg_snd_una) outstanding
2146          * bytes of data have been ACKed during the course of the RTT, giving
2147          * an "actual" rate of:
2148          *
2149          *     (v_beg_snd_nxt - v_beg_snd_una) / (rtt duration)
2150          *
2151          * Unfortunately, v_beg_snd_una is not exactly equal to snd_una,
2152          * because delayed ACKs can cover more than one segment, so they
2153          * don't line up nicely with the boundaries of RTTs.
2154          *
2155          * Another unfortunate fact of life is that delayed ACKs delay the
2156          * advance of the left edge of our send window, so that the number
2157          * of bytes we send in an RTT is often less than our cwnd will allow.
2158          * So we keep track of our cwnd separately, in v_beg_snd_cwnd.
2159          */
2160
2161         if (after(ack, tp->vegas.beg_snd_nxt)) {
2162                 /* Do the Vegas once-per-RTT cwnd adjustment. */
2163                 u32 old_wnd, old_snd_cwnd;
2164
2165                 
2166                 /* Here old_wnd is essentially the window of data that was
2167                  * sent during the previous RTT, and has all
2168                  * been acknowledged in the course of the RTT that ended
2169                  * with the ACK we just received. Likewise, old_snd_cwnd
2170                  * is the cwnd during the previous RTT.
2171                  */
2172                 old_wnd = (tp->vegas.beg_snd_nxt - tp->vegas.beg_snd_una) /
2173                         tp->mss_cache_std;
2174                 old_snd_cwnd = tp->vegas.beg_snd_cwnd;
2175
2176                 /* Save the extent of the current window so we can use this
2177                  * at the end of the next RTT.
2178                  */
2179                 tp->vegas.beg_snd_una  = tp->vegas.beg_snd_nxt;
2180                 tp->vegas.beg_snd_nxt  = tp->snd_nxt;
2181                 tp->vegas.beg_snd_cwnd = tp->snd_cwnd;
2182
2183                 /* Take into account the current RTT sample too, to
2184                  * decrease the impact of delayed acks. This double counts
2185                  * this sample since we count it for the next window as well,
2186                  * but that's not too awful, since we're taking the min,
2187                  * rather than averaging.
2188                  */
2189                 vegas_rtt_calc(tp, seq_rtt);
2190
2191                 /* We do the Vegas calculations only if we got enough RTT
2192                  * samples that we can be reasonably sure that we got
2193                  * at least one RTT sample that wasn't from a delayed ACK.
2194                  * If we only had 2 samples total,
2195                  * then that means we're getting only 1 ACK per RTT, which
2196                  * means they're almost certainly delayed ACKs.
2197                  * If  we have 3 samples, we should be OK.
2198                  */
2199
2200                 if (tp->vegas.cntRTT <= 2) {
2201                         /* We don't have enough RTT samples to do the Vegas
2202                          * calculation, so we'll behave like Reno.
2203                          */
2204                         if (tp->snd_cwnd > tp->snd_ssthresh)
2205                                 tp->snd_cwnd++;
2206                 } else {
2207                         u32 rtt, target_cwnd, diff;
2208
2209                         /* We have enough RTT samples, so, using the Vegas
2210                          * algorithm, we determine if we should increase or
2211                          * decrease cwnd, and by how much.
2212                          */
2213
2214                         /* Pluck out the RTT we are using for the Vegas
2215                          * calculations. This is the min RTT seen during the
2216                          * last RTT. Taking the min filters out the effects
2217                          * of delayed ACKs, at the cost of noticing congestion
2218                          * a bit later.
2219                          */
2220                         rtt = tp->vegas.minRTT;
2221
2222                         /* Calculate the cwnd we should have, if we weren't
2223                          * going too fast.
2224                          *
2225                          * This is:
2226                          *     (actual rate in segments) * baseRTT
2227                          * We keep it as a fixed point number with
2228                          * V_PARAM_SHIFT bits to the right of the binary point.
2229                          */
2230                         target_cwnd = ((old_wnd * tp->vegas.baseRTT)
2231                                        << V_PARAM_SHIFT) / rtt;
2232
2233                         /* Calculate the difference between the window we had,
2234                          * and the window we would like to have. This quantity
2235                          * is the "Diff" from the Arizona Vegas papers.
2236                          *
2237                          * Again, this is a fixed point number with
2238                          * V_PARAM_SHIFT bits to the right of the binary
2239                          * point.
2240                          */
2241                         diff = (old_wnd << V_PARAM_SHIFT) - target_cwnd;
2242
2243                         if (tp->snd_cwnd < tp->snd_ssthresh) {
2244                                 /* Slow start.  */
2245                                 if (diff > sysctl_tcp_vegas_gamma) {
2246                                         /* Going too fast. Time to slow down
2247                                          * and switch to congestion avoidance.
2248                                          */
2249                                         tp->snd_ssthresh = 2;
2250
2251                                         /* Set cwnd to match the actual rate
2252                                          * exactly:
2253                                          *   cwnd = (actual rate) * baseRTT
2254                                          * Then we add 1 because the integer
2255                                          * truncation robs us of full link
2256                                          * utilization.
2257                                          */
2258                                         tp->snd_cwnd = min(tp->snd_cwnd,
2259                                                            (target_cwnd >>
2260                                                             V_PARAM_SHIFT)+1);
2261
2262                                 }
2263                         } else {
2264                                 /* Congestion avoidance. */
2265                                 u32 next_snd_cwnd;
2266
2267                                 /* Figure out where we would like cwnd
2268                                  * to be.
2269                                  */
2270                                 if (diff > sysctl_tcp_vegas_beta) {
2271                                         /* The old window was too fast, so
2272                                          * we slow down.
2273                                          */
2274                                         next_snd_cwnd = old_snd_cwnd - 1;
2275                                 } else if (diff < sysctl_tcp_vegas_alpha) {
2276                                         /* We don't have enough extra packets
2277                                          * in the network, so speed up.
2278                                          */
2279                                         next_snd_cwnd = old_snd_cwnd + 1;
2280                                 } else {
2281                                         /* Sending just as fast as we
2282                                          * should be.
2283                                          */
2284                                         next_snd_cwnd = old_snd_cwnd;
2285                                 }
2286
2287                                 /* Adjust cwnd upward or downward, toward the
2288                                  * desired value.
2289                                  */
2290                                 if (next_snd_cwnd > tp->snd_cwnd)
2291                                         tp->snd_cwnd++;
2292                                 else if (next_snd_cwnd < tp->snd_cwnd)
2293                                         tp->snd_cwnd--;
2294                         }
2295                 }
2296
2297                 /* Wipe the slate clean for the next RTT. */
2298                 tp->vegas.cntRTT = 0;
2299                 tp->vegas.minRTT = 0x7fffffff;
2300         }
2301
2302         /* The following code is executed for every ack we receive,
2303          * except for conditions checked in should_advance_cwnd()
2304          * before the call to tcp_cong_avoid(). Mainly this means that
2305          * we only execute this code if the ack actually acked some
2306          * data.
2307          */
2308
2309         /* If we are in slow start, increase our cwnd in response to this ACK.
2310          * (If we are not in slow start then we are in congestion avoidance,
2311          * and adjust our congestion window only once per RTT. See the code
2312          * above.)
2313          */
2314         if (tp->snd_cwnd <= tp->snd_ssthresh) 
2315                 tp->snd_cwnd++;
2316
2317         /* to keep cwnd from growing without bound */
2318         tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
2319
2320         /* Make sure that we are never so timid as to reduce our cwnd below
2321          * 2 MSS.
2322          *
2323          * Going below 2 MSS would risk huge delayed ACKs from our receiver.
2324          */
2325         tp->snd_cwnd = max(tp->snd_cwnd, 2U);
2326
2327         tp->snd_cwnd_stamp = tcp_time_stamp;
2328 }
2329
2330 static inline void tcp_cong_avoid(struct tcp_sock *tp, u32 ack, u32 seq_rtt)
2331 {
2332         if (tcp_vegas_enabled(tp))
2333                 vegas_cong_avoid(tp, ack, seq_rtt);
2334         else
2335                 reno_cong_avoid(tp);
2336 }
2337
2338 /* Restart timer after forward progress on connection.
2339  * RFC2988 recommends to restart timer to now+rto.
2340  */
2341
2342 static inline void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp)
2343 {
2344         if (!tp->packets_out) {
2345                 tcp_clear_xmit_timer(sk, TCP_TIME_RETRANS);
2346         } else {
2347                 tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto);
2348         }
2349 }
2350
2351 /* There is one downside to this scheme.  Although we keep the
2352  * ACK clock ticking, adjusting packet counters and advancing
2353  * congestion window, we do not liberate socket send buffer
2354  * space.
2355  *
2356  * Mucking with skb->truesize and sk->sk_wmem_alloc et al.
2357  * then making a write space wakeup callback is a possible
2358  * future enhancement.  WARNING: it is not trivial to make.
2359  */
2360 static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb,
2361                          __u32 now, __s32 *seq_rtt)
2362 {
2363         struct tcp_sock *tp = tcp_sk(sk);
2364         struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 
2365         __u32 seq = tp->snd_una;
2366         __u32 packets_acked;
2367         int acked = 0;
2368
2369         /* If we get here, the whole TSO packet has not been
2370          * acked.
2371          */
2372         BUG_ON(!after(scb->end_seq, seq));
2373
2374         packets_acked = tcp_skb_pcount(skb);
2375         if (tcp_trim_head(sk, skb, seq - scb->seq))
2376                 return 0;
2377         packets_acked -= tcp_skb_pcount(skb);
2378
2379         if (packets_acked) {
2380                 __u8 sacked = scb->sacked;
2381
2382                 acked |= FLAG_DATA_ACKED;
2383                 if (sacked) {
2384                         if (sacked & TCPCB_RETRANS) {
2385                                 if (sacked & TCPCB_SACKED_RETRANS)
2386                                         tp->retrans_out -= packets_acked;
2387                                 acked |= FLAG_RETRANS_DATA_ACKED;
2388                                 *seq_rtt = -1;
2389                         } else if (*seq_rtt < 0)
2390                                 *seq_rtt = now - scb->when;
2391                         if (sacked & TCPCB_SACKED_ACKED)
2392                                 tp->sacked_out -= packets_acked;
2393                         if (sacked & TCPCB_LOST)
2394                                 tp->lost_out -= packets_acked;
2395                         if (sacked & TCPCB_URG) {
2396                                 if (tp->urg_mode &&
2397                                     !before(seq, tp->snd_up))
2398                                         tp->urg_mode = 0;
2399                         }
2400                 } else if (*seq_rtt < 0)
2401                         *seq_rtt = now - scb->when;
2402
2403                 if (tp->fackets_out) {
2404                         __u32 dval = min(tp->fackets_out, packets_acked);
2405                         tp->fackets_out -= dval;
2406                 }
2407                 tp->packets_out -= packets_acked;
2408
2409                 BUG_ON(tcp_skb_pcount(skb) == 0);
2410                 BUG_ON(!before(scb->seq, scb->end_seq));
2411         }
2412
2413         return acked;
2414 }
2415
2416
2417 /* Remove acknowledged frames from the retransmission queue. */
2418 static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
2419 {
2420         struct tcp_sock *tp = tcp_sk(sk);
2421         struct sk_buff *skb;
2422         __u32 now = tcp_time_stamp;
2423         int acked = 0;
2424         __s32 seq_rtt = -1;
2425
2426         while ((skb = skb_peek(&sk->sk_write_queue)) &&
2427                skb != sk->sk_send_head) {
2428                 struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 
2429                 __u8 sacked = scb->sacked;
2430
2431                 /* If our packet is before the ack sequence we can
2432                  * discard it as it's confirmed to have arrived at
2433                  * the other end.
2434                  */
2435                 if (after(scb->end_seq, tp->snd_una)) {
2436                         if (tcp_skb_pcount(skb) > 1)
2437                                 acked |= tcp_tso_acked(sk, skb,
2438                                                        now, &seq_rtt);
2439                         break;
2440                 }
2441
2442                 /* Initial outgoing SYN's get put onto the write_queue
2443                  * just like anything else we transmit.  It is not
2444                  * true data, and if we misinform our callers that
2445                  * this ACK acks real data, we will erroneously exit
2446                  * connection startup slow start one packet too
2447                  * quickly.  This is severely frowned upon behavior.
2448                  */
2449                 if (!(scb->flags & TCPCB_FLAG_SYN)) {
2450                         acked |= FLAG_DATA_ACKED;
2451                 } else {
2452                         acked |= FLAG_SYN_ACKED;
2453                         tp->retrans_stamp = 0;
2454                 }
2455
2456                 if (sacked) {
2457                         if (sacked & TCPCB_RETRANS) {
2458                                 if(sacked & TCPCB_SACKED_RETRANS)
2459                                         tp->retrans_out -= tcp_skb_pcount(skb);
2460                                 acked |= FLAG_RETRANS_DATA_ACKED;
2461                                 seq_rtt = -1;
2462                         } else if (seq_rtt < 0)
2463                                 seq_rtt = now - scb->when;
2464                         if (sacked & TCPCB_SACKED_ACKED)
2465                                 tp->sacked_out -= tcp_skb_pcount(skb);
2466                         if (sacked & TCPCB_LOST)
2467                                 tp->lost_out -= tcp_skb_pcount(skb);
2468                         if (sacked & TCPCB_URG) {
2469                                 if (tp->urg_mode &&
2470                                     !before(scb->end_seq, tp->snd_up))
2471                                         tp->urg_mode = 0;
2472                         }
2473                 } else if (seq_rtt < 0)
2474                         seq_rtt = now - scb->when;
2475                 tcp_dec_pcount_approx(&tp->fackets_out, skb);
2476                 tcp_packets_out_dec(tp, skb);
2477                 __skb_unlink(skb, skb->list);
2478                 sk_stream_free_skb(sk, skb);
2479         }
2480
2481         if (acked&FLAG_ACKED) {
2482                 tcp_ack_update_rtt(tp, acked, seq_rtt);
2483                 tcp_ack_packets_out(sk, tp);
2484         }
2485
2486 #if FASTRETRANS_DEBUG > 0
2487         BUG_TRAP((int)tp->sacked_out >= 0);
2488         BUG_TRAP((int)tp->lost_out >= 0);
2489         BUG_TRAP((int)tp->retrans_out >= 0);
2490         if (!tp->packets_out && tp->rx_opt.sack_ok) {
2491                 if (tp->lost_out) {
2492                         printk(KERN_DEBUG "Leak l=%u %d\n",
2493                                tp->lost_out, tp->ca_state);
2494                         tp->lost_out = 0;
2495                 }
2496                 if (tp->sacked_out) {
2497                         printk(KERN_DEBUG "Leak s=%u %d\n",
2498                                tp->sacked_out, tp->ca_state);
2499                         tp->sacked_out = 0;
2500                 }
2501                 if (tp->retrans_out) {
2502                         printk(KERN_DEBUG "Leak r=%u %d\n",
2503                                tp->retrans_out, tp->ca_state);
2504                         tp->retrans_out = 0;
2505                 }
2506         }
2507 #endif
2508         *seq_rtt_p = seq_rtt;
2509         return acked;
2510 }
2511
2512 static void tcp_ack_probe(struct sock *sk)
2513 {
2514         struct tcp_sock *tp = tcp_sk(sk);
2515
2516         /* Was it a usable window open? */
2517
2518         if (!after(TCP_SKB_CB(sk->sk_send_head)->end_seq,
2519                    tp->snd_una + tp->snd_wnd)) {
2520                 tp->backoff = 0;
2521                 tcp_clear_xmit_timer(sk, TCP_TIME_PROBE0);
2522                 /* Socket must be waked up by subsequent tcp_data_snd_check().
2523                  * This function is not for random using!
2524                  */
2525         } else {
2526                 tcp_reset_xmit_timer(sk, TCP_TIME_PROBE0,
2527                                      min(tp->rto << tp->backoff, TCP_RTO_MAX));
2528         }
2529 }
2530
2531 static inline int tcp_ack_is_dubious(struct tcp_sock *tp, int flag)
2532 {
2533         return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
2534                 tp->ca_state != TCP_CA_Open);
2535 }
2536
2537 static inline int tcp_may_raise_cwnd(struct tcp_sock *tp, int flag)
2538 {
2539         return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
2540                 !((1<<tp->ca_state)&(TCPF_CA_Recovery|TCPF_CA_CWR));
2541 }
2542
2543 /* Check that window update is acceptable.
2544  * The function assumes that snd_una<=ack<=snd_next.
2545  */
2546 static inline int tcp_may_update_window(struct tcp_sock *tp, u32 ack,
2547                                         u32 ack_seq, u32 nwin)
2548 {
2549         return (after(ack, tp->snd_una) ||
2550                 after(ack_seq, tp->snd_wl1) ||
2551                 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd));
2552 }
2553
2554 /* Update our send window.
2555  *
2556  * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2557  * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2558  */
2559 static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp,
2560                                  struct sk_buff *skb, u32 ack, u32 ack_seq)
2561 {
2562         int flag = 0;
2563         u32 nwin = ntohs(skb->h.th->window);
2564
2565         if (likely(!skb->h.th->syn))
2566                 nwin <<= tp->rx_opt.snd_wscale;
2567
2568         if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
2569                 flag |= FLAG_WIN_UPDATE;
2570                 tcp_update_wl(tp, ack, ack_seq);
2571
2572                 if (tp->snd_wnd != nwin) {
2573                         tp->snd_wnd = nwin;
2574
2575                         /* Note, it is the only place, where
2576                          * fast path is recovered for sending TCP.
2577                          */
2578                         tcp_fast_path_check(sk, tp);
2579
2580                         if (nwin > tp->max_window) {
2581                                 tp->max_window = nwin;
2582                                 tcp_sync_mss(sk, tp->pmtu_cookie);
2583                         }
2584                 }
2585         }
2586
2587         tp->snd_una = ack;
2588
2589         return flag;
2590 }
2591
2592 static void tcp_process_frto(struct sock *sk, u32 prior_snd_una)
2593 {
2594         struct tcp_sock *tp = tcp_sk(sk);
2595         
2596         tcp_sync_left_out(tp);
2597         
2598         if (tp->snd_una == prior_snd_una ||
2599             !before(tp->snd_una, tp->frto_highmark)) {
2600                 /* RTO was caused by loss, start retransmitting in
2601                  * go-back-N slow start
2602                  */
2603                 tcp_enter_frto_loss(sk);
2604                 return;
2605         }
2606
2607         if (tp->frto_counter == 1) {
2608                 /* First ACK after RTO advances the window: allow two new
2609                  * segments out.
2610                  */
2611                 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
2612         } else {
2613                 /* Also the second ACK after RTO advances the window.
2614                  * The RTO was likely spurious. Reduce cwnd and continue
2615                  * in congestion avoidance
2616                  */
2617                 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
2618                 tcp_moderate_cwnd(tp);
2619         }
2620
2621         /* F-RTO affects on two new ACKs following RTO.
2622          * At latest on third ACK the TCP behavor is back to normal.
2623          */
2624         tp->frto_counter = (tp->frto_counter + 1) % 3;
2625 }
2626
2627 /*
2628  * TCP Westwood+
2629  */
2630
2631 /*
2632  * @init_westwood
2633  * This function initializes fields used in TCP Westwood+. We can't
2634  * get no information about RTTmin at this time so we simply set it to
2635  * TCP_WESTWOOD_INIT_RTT. This value was chosen to be too conservative
2636  * since in this way we're sure it will be updated in a consistent
2637  * way as soon as possible. It will reasonably happen within the first
2638  * RTT period of the connection lifetime.
2639  */
2640
2641 static void init_westwood(struct sock *sk)
2642 {
2643         struct tcp_sock *tp = tcp_sk(sk);
2644
2645         tp->westwood.bw_ns_est = 0;
2646         tp->westwood.bw_est = 0;
2647         tp->westwood.accounted = 0;
2648         tp->westwood.cumul_ack = 0;
2649         tp->westwood.rtt_win_sx = tcp_time_stamp;
2650         tp->westwood.rtt = TCP_WESTWOOD_INIT_RTT;
2651         tp->westwood.rtt_min = TCP_WESTWOOD_INIT_RTT;
2652         tp->westwood.snd_una = tp->snd_una;
2653 }
2654
2655 /*
2656  * @westwood_do_filter
2657  * Low-pass filter. Implemented using constant coeffients.
2658  */
2659
2660 static inline __u32 westwood_do_filter(__u32 a, __u32 b)
2661 {
2662         return (((7 * a) + b) >> 3);
2663 }
2664
2665 static void westwood_filter(struct sock *sk, __u32 delta)
2666 {
2667         struct tcp_sock *tp = tcp_sk(sk);
2668
2669         tp->westwood.bw_ns_est =
2670                 westwood_do_filter(tp->westwood.bw_ns_est, 
2671                                    tp->westwood.bk / delta);
2672         tp->westwood.bw_est =
2673                 westwood_do_filter(tp->westwood.bw_est,
2674                                    tp->westwood.bw_ns_est);
2675 }
2676
2677 /* 
2678  * @westwood_update_rttmin
2679  * It is used to update RTTmin. In this case we MUST NOT use
2680  * WESTWOOD_RTT_MIN minimum bound since we could be on a LAN!
2681  */
2682
2683 static inline __u32 westwood_update_rttmin(const struct sock *sk)
2684 {
2685         const struct tcp_sock *tp = tcp_sk(sk);
2686         __u32 rttmin = tp->westwood.rtt_min;
2687
2688         if (tp->westwood.rtt != 0 &&
2689             (tp->westwood.rtt < tp->westwood.rtt_min || !rttmin))
2690                 rttmin = tp->westwood.rtt;
2691
2692         return rttmin;
2693 }
2694
2695 /*
2696  * @westwood_acked
2697  * Evaluate increases for dk. 
2698  */
2699
2700 static inline __u32 westwood_acked(const struct sock *sk)
2701 {
2702         const struct tcp_sock *tp = tcp_sk(sk);
2703
2704         return tp->snd_una - tp->westwood.snd_una;
2705 }
2706
2707 /*
2708  * @westwood_new_window
2709  * It evaluates if we are receiving data inside the same RTT window as
2710  * when we started.
2711  * Return value:
2712  * It returns 0 if we are still evaluating samples in the same RTT
2713  * window, 1 if the sample has to be considered in the next window.
2714  */
2715
2716 static int westwood_new_window(const struct sock *sk)
2717 {
2718         const struct tcp_sock *tp = tcp_sk(sk);
2719         __u32 left_bound;
2720         __u32 rtt;
2721         int ret = 0;
2722
2723         left_bound = tp->westwood.rtt_win_sx;
2724         rtt = max(tp->westwood.rtt, (u32) TCP_WESTWOOD_RTT_MIN);
2725
2726         /*
2727          * A RTT-window has passed. Be careful since if RTT is less than
2728          * 50ms we don't filter but we continue 'building the sample'.
2729          * This minimum limit was choosen since an estimation on small
2730          * time intervals is better to avoid...
2731          * Obvioulsy on a LAN we reasonably will always have
2732          * right_bound = left_bound + WESTWOOD_RTT_MIN
2733          */
2734
2735         if ((left_bound + rtt) < tcp_time_stamp)
2736                 ret = 1;
2737
2738         return ret;
2739 }
2740
2741 /*
2742  * @westwood_update_window
2743  * It updates RTT evaluation window if it is the right moment to do
2744  * it. If so it calls filter for evaluating bandwidth. 
2745  */
2746
2747 static void __westwood_update_window(struct sock *sk, __u32 now)
2748 {
2749         struct tcp_sock *tp = tcp_sk(sk);
2750         __u32 delta = now - tp->westwood.rtt_win_sx;
2751
2752         if (delta) {
2753                 if (tp->westwood.rtt)
2754                         westwood_filter(sk, delta);
2755
2756                 tp->westwood.bk = 0;
2757                 tp->westwood.rtt_win_sx = tcp_time_stamp;
2758         }
2759 }
2760
2761
2762 static void westwood_update_window(struct sock *sk, __u32 now)
2763 {
2764         if (westwood_new_window(sk)) 
2765                 __westwood_update_window(sk, now);
2766 }
2767
2768 /*
2769  * @__tcp_westwood_fast_bw
2770  * It is called when we are in fast path. In particular it is called when
2771  * header prediction is successfull. In such case infact update is
2772  * straight forward and doesn't need any particular care.
2773  */
2774
2775 static void __tcp_westwood_fast_bw(struct sock *sk, struct sk_buff *skb)
2776 {
2777         struct tcp_sock *tp = tcp_sk(sk);
2778
2779         westwood_update_window(sk, tcp_time_stamp);
2780
2781         tp->westwood.bk += westwood_acked(sk);
2782         tp->westwood.snd_una = tp->snd_una;
2783         tp->westwood.rtt_min = westwood_update_rttmin(sk);
2784 }
2785
2786 static inline void tcp_westwood_fast_bw(struct sock *sk, struct sk_buff *skb)
2787 {
2788         if (tcp_is_westwood(tcp_sk(sk)))
2789                 __tcp_westwood_fast_bw(sk, skb);
2790 }
2791
2792
2793 /*
2794  * @westwood_dupack_update
2795  * It updates accounted and cumul_ack when receiving a dupack.
2796  */
2797
2798 static void westwood_dupack_update(struct sock *sk)
2799 {
2800         struct tcp_sock *tp = tcp_sk(sk);
2801
2802         tp->westwood.accounted += tp->mss_cache_std;
2803         tp->westwood.cumul_ack = tp->mss_cache_std;
2804 }
2805
2806 static inline int westwood_may_change_cumul(struct tcp_sock *tp)
2807 {
2808         return (tp->westwood.cumul_ack > tp->mss_cache_std);
2809 }
2810
2811 static inline void westwood_partial_update(struct tcp_sock *tp)
2812 {
2813         tp->westwood.accounted -= tp->westwood.cumul_ack;
2814         tp->westwood.cumul_ack = tp->mss_cache_std;
2815 }
2816
2817 static inline void westwood_complete_update(struct tcp_sock *tp)
2818 {
2819         tp->westwood.cumul_ack -= tp->westwood.accounted;
2820         tp->westwood.accounted = 0;
2821 }
2822
2823 /*
2824  * @westwood_acked_count
2825  * This function evaluates cumul_ack for evaluating dk in case of
2826  * delayed or partial acks.
2827  */
2828
2829 static inline __u32 westwood_acked_count(struct sock *sk)
2830 {
2831         struct tcp_sock *tp = tcp_sk(sk);
2832
2833         tp->westwood.cumul_ack = westwood_acked(sk);
2834
2835         /* If cumul_ack is 0 this is a dupack since it's not moving
2836          * tp->snd_una.
2837          */
2838         if (!(tp->westwood.cumul_ack))
2839                 westwood_dupack_update(sk);
2840
2841         if (westwood_may_change_cumul(tp)) {
2842                 /* Partial or delayed ack */
2843                 if (tp->westwood.accounted >= tp->westwood.cumul_ack)
2844                         westwood_partial_update(tp);
2845                 else
2846                         westwood_complete_update(tp);
2847         }
2848
2849         tp->westwood.snd_una = tp->snd_una;
2850
2851         return tp->westwood.cumul_ack;
2852 }
2853
2854
2855 /*
2856  * @__tcp_westwood_slow_bw
2857  * It is called when something is going wrong..even if there could
2858  * be no problems! Infact a simple delayed packet may trigger a
2859  * dupack. But we need to be careful in such case.
2860  */
2861
2862 static void __tcp_westwood_slow_bw(struct sock *sk, struct sk_buff *skb)
2863 {
2864         struct tcp_sock *tp = tcp_sk(sk);
2865
2866         westwood_update_window(sk, tcp_time_stamp);
2867
2868         tp->westwood.bk += westwood_acked_count(sk);
2869         tp->westwood.rtt_min = westwood_update_rttmin(sk);
2870 }
2871
2872 static inline void tcp_westwood_slow_bw(struct sock *sk, struct sk_buff *skb)
2873 {
2874         if (tcp_is_westwood(tcp_sk(sk)))
2875                 __tcp_westwood_slow_bw(sk, skb);
2876 }
2877
2878 /* This routine deals with incoming acks, but not outgoing ones. */
2879 static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
2880 {
2881         struct tcp_sock *tp = tcp_sk(sk);
2882         u32 prior_snd_una = tp->snd_una;
2883         u32 ack_seq = TCP_SKB_CB(skb)->seq;
2884         u32 ack = TCP_SKB_CB(skb)->ack_seq;
2885         u32 prior_in_flight;
2886         s32 seq_rtt;
2887         int prior_packets;
2888
2889         /* If the ack is newer than sent or older than previous acks
2890          * then we can probably ignore it.
2891          */
2892         if (after(ack, tp->snd_nxt))
2893                 goto uninteresting_ack;
2894
2895         if (before(ack, prior_snd_una))
2896                 goto old_ack;
2897
2898         if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
2899                 /* Window is constant, pure forward advance.
2900                  * No more checks are required.
2901                  * Note, we use the fact that SND.UNA>=SND.WL2.
2902                  */
2903                 tcp_update_wl(tp, ack, ack_seq);
2904                 tp->snd_una = ack;
2905                 tcp_westwood_fast_bw(sk, skb);
2906                 flag |= FLAG_WIN_UPDATE;
2907
2908                 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS);
2909         } else {
2910                 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
2911                         flag |= FLAG_DATA;
2912                 else
2913                         NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS);
2914
2915                 flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq);
2916
2917                 if (TCP_SKB_CB(skb)->sacked)
2918                         flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2919
2920                 if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th))
2921                         flag |= FLAG_ECE;
2922
2923                 tcp_westwood_slow_bw(sk,skb);
2924         }
2925
2926         /* We passed data and got it acked, remove any soft error
2927          * log. Something worked...
2928          */
2929         sk->sk_err_soft = 0;
2930         tp->rcv_tstamp = tcp_time_stamp;
2931         prior_packets = tp->packets_out;
2932         if (!prior_packets)
2933                 goto no_queue;
2934
2935         prior_in_flight = tcp_packets_in_flight(tp);
2936
2937         /* See if we can take anything off of the retransmit queue. */
2938         flag |= tcp_clean_rtx_queue(sk, &seq_rtt);
2939
2940         if (tp->frto_counter)
2941                 tcp_process_frto(sk, prior_snd_una);
2942
2943         if (tcp_ack_is_dubious(tp, flag)) {
2944                 /* Advanve CWND, if state allows this. */
2945                 if ((flag & FLAG_DATA_ACKED) &&
2946                     (tcp_vegas_enabled(tp) || prior_in_flight >= tp->snd_cwnd) &&
2947                     tcp_may_raise_cwnd(tp, flag))
2948                         tcp_cong_avoid(tp, ack, seq_rtt);
2949                 tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag);
2950         } else {
2951                 if ((flag & FLAG_DATA_ACKED) && 
2952                     (tcp_vegas_enabled(tp) || prior_in_flight >= tp->snd_cwnd))
2953                         tcp_cong_avoid(tp, ack, seq_rtt);
2954         }
2955
2956         if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP))
2957                 dst_confirm(sk->sk_dst_cache);
2958
2959         return 1;
2960
2961 no_queue:
2962         tp->probes_out = 0;
2963
2964         /* If this ack opens up a zero window, clear backoff.  It was
2965          * being used to time the probes, and is probably far higher than
2966          * it needs to be for normal retransmission.
2967          */
2968         if (sk->sk_send_head)
2969                 tcp_ack_probe(sk);
2970         return 1;
2971
2972 old_ack:
2973         if (TCP_SKB_CB(skb)->sacked)
2974                 tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2975
2976 uninteresting_ack:
2977         SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
2978         return 0;
2979 }
2980
2981
2982 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
2983  * But, this can also be called on packets in the established flow when
2984  * the fast version below fails.
2985  */
2986 void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab)
2987 {
2988         unsigned char *ptr;
2989         struct tcphdr *th = skb->h.th;
2990         int length=(th->doff*4)-sizeof(struct tcphdr);
2991
2992         ptr = (unsigned char *)(th + 1);
2993         opt_rx->saw_tstamp = 0;
2994
2995         while(length>0) {
2996                 int opcode=*ptr++;
2997                 int opsize;
2998
2999                 switch (opcode) {
3000                         case TCPOPT_EOL:
3001                                 return;
3002                         case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
3003                                 length--;
3004                                 continue;
3005                         default:
3006                                 opsize=*ptr++;
3007                                 if (opsize < 2) /* "silly options" */
3008                                         return;
3009                                 if (opsize > length)
3010                                         return; /* don't parse partial options */
3011                                 switch(opcode) {
3012                                 case TCPOPT_MSS:
3013                                         if(opsize==TCPOLEN_MSS && th->syn && !estab) {
3014                                                 u16 in_mss = ntohs(get_unaligned((__u16 *)ptr));
3015                                                 if (in_mss) {
3016                                                         if (opt_rx->user_mss && opt_rx->user_mss < in_mss)
3017                                                                 in_mss = opt_rx->user_mss;
3018                                                         opt_rx->mss_clamp = in_mss;
3019                                                 }
3020                                         }
3021                                         break;
3022                                 case TCPOPT_WINDOW:
3023                                         if(opsize==TCPOLEN_WINDOW && th->syn && !estab)
3024                                                 if (sysctl_tcp_window_scaling) {
3025                                                         __u8 snd_wscale = *(__u8 *) ptr;
3026                                                         opt_rx->wscale_ok = 1;
3027                                                         if (snd_wscale > 14) {
3028                                                                 if(net_ratelimit())
3029                                                                         printk(KERN_INFO "tcp_parse_options: Illegal window "
3030                                                                                "scaling value %d >14 received.\n",
3031                                                                                snd_wscale);
3032                                                                 snd_wscale = 14;
3033                                                         }
3034                                                         opt_rx->snd_wscale = snd_wscale;
3035                                                 }
3036                                         break;
3037                                 case TCPOPT_TIMESTAMP:
3038                                         if(opsize==TCPOLEN_TIMESTAMP) {
3039                                                 if ((estab && opt_rx->tstamp_ok) ||
3040                                                     (!estab && sysctl_tcp_timestamps)) {
3041                                                         opt_rx->saw_tstamp = 1;
3042                                                         opt_rx->rcv_tsval = ntohl(get_unaligned((__u32 *)ptr));
3043                                                         opt_rx->rcv_tsecr = ntohl(get_unaligned((__u32 *)(ptr+4)));
3044                                                 }
3045                                         }
3046                                         break;
3047                                 case TCPOPT_SACK_PERM:
3048                                         if(opsize==TCPOLEN_SACK_PERM && th->syn && !estab) {
3049                                                 if (sysctl_tcp_sack) {
3050                                                         opt_rx->sack_ok = 1;
3051                                                         tcp_sack_reset(opt_rx);
3052                                                 }
3053                                         }
3054                                         break;
3055
3056                                 case TCPOPT_SACK:
3057                                         if((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
3058                                            !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
3059                                            opt_rx->sack_ok) {
3060                                                 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
3061                                         }
3062                                 };
3063                                 ptr+=opsize-2;
3064                                 length-=opsize;
3065                 };
3066         }
3067 }
3068
3069 /* Fast parse options. This hopes to only see timestamps.
3070  * If it is wrong it falls back on tcp_parse_options().
3071  */
3072 static inline int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
3073                                          struct tcp_sock *tp)
3074 {
3075         if (th->doff == sizeof(struct tcphdr)>>2) {
3076                 tp->rx_opt.saw_tstamp = 0;
3077                 return 0;
3078         } else if (tp->rx_opt.tstamp_ok &&
3079                    th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
3080                 __u32 *ptr = (__u32 *)(th + 1);
3081                 if (*ptr == ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
3082                                   | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
3083                         tp->rx_opt.saw_tstamp = 1;
3084                         ++ptr;
3085                         tp->rx_opt.rcv_tsval = ntohl(*ptr);
3086                         ++ptr;
3087                         tp->rx_opt.rcv_tsecr = ntohl(*ptr);
3088                         return 1;
3089                 }
3090         }
3091         tcp_parse_options(skb, &tp->rx_opt, 1);
3092         return 1;
3093 }
3094
3095 static inline void tcp_store_ts_recent(struct tcp_sock *tp)
3096 {
3097         tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
3098         tp->rx_opt.ts_recent_stamp = xtime.tv_sec;
3099 }
3100
3101 static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
3102 {
3103         if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
3104                 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3105                  * extra check below makes sure this can only happen
3106                  * for pure ACK frames.  -DaveM
3107                  *
3108                  * Not only, also it occurs for expired timestamps.
3109                  */
3110
3111                 if((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 ||
3112                    xtime.tv_sec >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS)
3113                         tcp_store_ts_recent(tp);
3114         }
3115 }
3116
3117 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3118  *
3119  * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3120  * it can pass through stack. So, the following predicate verifies that
3121  * this segment is not used for anything but congestion avoidance or
3122  * fast retransmit. Moreover, we even are able to eliminate most of such
3123  * second order effects, if we apply some small "replay" window (~RTO)
3124  * to timestamp space.
3125  *
3126  * All these measures still do not guarantee that we reject wrapped ACKs
3127  * on networks with high bandwidth, when sequence space is recycled fastly,
3128  * but it guarantees that such events will be very rare and do not affect
3129  * connection seriously. This doesn't look nice, but alas, PAWS is really
3130  * buggy extension.
3131  *
3132  * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3133  * states that events when retransmit arrives after original data are rare.
3134  * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3135  * the biggest problem on large power networks even with minor reordering.
3136  * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3137  * up to bandwidth of 18Gigabit/sec. 8) ]
3138  */
3139
3140 static int tcp_disordered_ack(struct tcp_sock *tp, struct sk_buff *skb)
3141 {
3142         struct tcphdr *th = skb->h.th;
3143         u32 seq = TCP_SKB_CB(skb)->seq;
3144         u32 ack = TCP_SKB_CB(skb)->ack_seq;
3145
3146         return (/* 1. Pure ACK with correct sequence number. */
3147                 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
3148
3149                 /* 2. ... and duplicate ACK. */
3150                 ack == tp->snd_una &&
3151
3152                 /* 3. ... and does not update window. */
3153                 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
3154
3155                 /* 4. ... and sits in replay window. */
3156                 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (tp->rto*1024)/HZ);
3157 }
3158
3159 static inline int tcp_paws_discard(struct tcp_sock *tp, struct sk_buff *skb)
3160 {
3161         return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW &&
3162                 xtime.tv_sec < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS &&
3163                 !tcp_disordered_ack(tp, skb));
3164 }
3165
3166 /* Check segment sequence number for validity.
3167  *
3168  * Segment controls are considered valid, if the segment
3169  * fits to the window after truncation to the window. Acceptability
3170  * of data (and SYN, FIN, of course) is checked separately.
3171  * See tcp_data_queue(), for example.
3172  *
3173  * Also, controls (RST is main one) are accepted using RCV.WUP instead
3174  * of RCV.NXT. Peer still did not advance his SND.UNA when we
3175  * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3176  * (borrowed from freebsd)
3177  */
3178
3179 static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
3180 {
3181         return  !before(end_seq, tp->rcv_wup) &&
3182                 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
3183 }
3184
3185 /* When we get a reset we do this. */
3186 static void tcp_reset(struct sock *sk)
3187 {
3188         /* We want the right error as BSD sees it (and indeed as we do). */
3189         switch (sk->sk_state) {
3190                 case TCP_SYN_SENT:
3191                         sk->sk_err = ECONNREFUSED;
3192                         break;
3193                 case TCP_CLOSE_WAIT:
3194                         sk->sk_err = EPIPE;
3195                         break;
3196                 case TCP_CLOSE:
3197                         return;
3198                 default:
3199                         sk->sk_err = ECONNRESET;
3200         }
3201
3202         if (!sock_flag(sk, SOCK_DEAD))
3203                 sk->sk_error_report(sk);
3204
3205         tcp_done(sk);
3206 }
3207
3208 /*
3209  *      Process the FIN bit. This now behaves as it is supposed to work
3210  *      and the FIN takes effect when it is validly part of sequence
3211  *      space. Not before when we get holes.
3212  *
3213  *      If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3214  *      (and thence onto LAST-ACK and finally, CLOSE, we never enter
3215  *      TIME-WAIT)
3216  *
3217  *      If we are in FINWAIT-1, a received FIN indicates simultaneous
3218  *      close and we go into CLOSING (and later onto TIME-WAIT)
3219  *
3220  *      If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3221  */
3222 static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
3223 {
3224         struct tcp_sock *tp = tcp_sk(sk);
3225
3226         tcp_schedule_ack(tp);
3227
3228         sk->sk_shutdown |= RCV_SHUTDOWN;
3229         sock_set_flag(sk, SOCK_DONE);
3230
3231         switch (sk->sk_state) {
3232                 case TCP_SYN_RECV:
3233                 case TCP_ESTABLISHED:
3234                         /* Move to CLOSE_WAIT */
3235                         tcp_set_state(sk, TCP_CLOSE_WAIT);
3236                         tp->ack.pingpong = 1;
3237                         break;
3238
3239                 case TCP_CLOSE_WAIT:
3240                 case TCP_CLOSING:
3241                         /* Received a retransmission of the FIN, do
3242                          * nothing.
3243                          */
3244                         break;
3245                 case TCP_LAST_ACK:
3246                         /* RFC793: Remain in the LAST-ACK state. */
3247                         break;
3248
3249                 case TCP_FIN_WAIT1:
3250                         /* This case occurs when a simultaneous close
3251                          * happens, we must ack the received FIN and
3252                          * enter the CLOSING state.
3253                          */
3254                         tcp_send_ack(sk);
3255                         tcp_set_state(sk, TCP_CLOSING);
3256                         break;
3257                 case TCP_FIN_WAIT2:
3258                         /* Received a FIN -- send ACK and enter TIME_WAIT. */
3259                         tcp_send_ack(sk);
3260                         tcp_time_wait(sk, TCP_TIME_WAIT, 0);
3261                         break;
3262                 default:
3263                         /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3264                          * cases we should never reach this piece of code.
3265                          */
3266                         printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
3267                                __FUNCTION__, sk->sk_state);
3268                         break;
3269         };
3270
3271         /* It _is_ possible, that we have something out-of-order _after_ FIN.
3272          * Probably, we should reset in this case. For now drop them.
3273          */
3274         __skb_queue_purge(&tp->out_of_order_queue);
3275         if (tp->rx_opt.sack_ok)
3276                 tcp_sack_reset(&tp->rx_opt);
3277         sk_stream_mem_reclaim(sk);
3278
3279         if (!sock_flag(sk, SOCK_DEAD)) {
3280                 sk->sk_state_change(sk);
3281
3282                 /* Do not send POLL_HUP for half duplex close. */
3283                 if (sk->sk_shutdown == SHUTDOWN_MASK ||
3284                     sk->sk_state == TCP_CLOSE)
3285                         sk_wake_async(sk, 1, POLL_HUP);
3286                 else
3287                         sk_wake_async(sk, 1, POLL_IN);
3288         }
3289 }
3290
3291 static __inline__ int
3292 tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq)
3293 {
3294         if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
3295                 if (before(seq, sp->start_seq))
3296                         sp->start_seq = seq;
3297                 if (after(end_seq, sp->end_seq))
3298                         sp->end_seq = end_seq;
3299                 return 1;
3300         }
3301         return 0;
3302 }
3303
3304 static inline void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq)
3305 {
3306         if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
3307                 if (before(seq, tp->rcv_nxt))
3308                         NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT);
3309                 else
3310                         NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT);
3311
3312                 tp->rx_opt.dsack = 1;
3313                 tp->duplicate_sack[0].start_seq = seq;
3314                 tp->duplicate_sack[0].end_seq = end_seq;
3315                 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok);
3316         }
3317 }
3318
3319 static inline void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq)
3320 {
3321         if (!tp->rx_opt.dsack)
3322                 tcp_dsack_set(tp, seq, end_seq);
3323         else
3324                 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
3325 }
3326
3327 static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
3328 {
3329         struct tcp_sock *tp = tcp_sk(sk);
3330
3331         if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
3332             before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3333                 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
3334                 tcp_enter_quickack_mode(tp);
3335
3336                 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
3337                         u32 end_seq = TCP_SKB_CB(skb)->end_seq;
3338
3339                         if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
3340                                 end_seq = tp->rcv_nxt;
3341                         tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq);
3342                 }
3343         }
3344
3345         tcp_send_ack(sk);
3346 }
3347
3348 /* These routines update the SACK block as out-of-order packets arrive or
3349  * in-order packets close up the sequence space.
3350  */
3351 static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
3352 {
3353         int this_sack;
3354         struct tcp_sack_block *sp = &tp->selective_acks[0];
3355         struct tcp_sack_block *swalk = sp+1;
3356
3357         /* See if the recent change to the first SACK eats into
3358          * or hits the sequence space of other SACK blocks, if so coalesce.
3359          */
3360         for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) {
3361                 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
3362                         int i;
3363
3364                         /* Zap SWALK, by moving every further SACK up by one slot.
3365                          * Decrease num_sacks.
3366                          */
3367                         tp->rx_opt.num_sacks--;
3368                         tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3369                         for(i=this_sack; i < tp->rx_opt.num_sacks; i++)
3370                                 sp[i] = sp[i+1];
3371                         continue;
3372                 }
3373                 this_sack++, swalk++;
3374         }
3375 }
3376
3377 static __inline__ void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2)
3378 {
3379         __u32 tmp;
3380
3381         tmp = sack1->start_seq;
3382         sack1->start_seq = sack2->start_seq;
3383         sack2->start_seq = tmp;
3384
3385         tmp = sack1->end_seq;
3386         sack1->end_seq = sack2->end_seq;
3387         sack2->end_seq = tmp;
3388 }
3389
3390 static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
3391 {
3392         struct tcp_sock *tp = tcp_sk(sk);
3393         struct tcp_sack_block *sp = &tp->selective_acks[0];
3394         int cur_sacks = tp->rx_opt.num_sacks;
3395         int this_sack;
3396
3397         if (!cur_sacks)
3398                 goto new_sack;
3399
3400         for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) {
3401                 if (tcp_sack_extend(sp, seq, end_seq)) {
3402                         /* Rotate this_sack to the first one. */
3403                         for (; this_sack>0; this_sack--, sp--)
3404                                 tcp_sack_swap(sp, sp-1);
3405                         if (cur_sacks > 1)
3406                                 tcp_sack_maybe_coalesce(tp);
3407                         return;
3408                 }
3409         }
3410
3411         /* Could not find an adjacent existing SACK, build a new one,
3412          * put it at the front, and shift everyone else down.  We
3413          * always know there is at least one SACK present already here.
3414          *
3415          * If the sack array is full, forget about the last one.
3416          */
3417         if (this_sack >= 4) {
3418                 this_sack--;
3419                 tp->rx_opt.num_sacks--;
3420                 sp--;
3421         }
3422         for(; this_sack > 0; this_sack--, sp--)
3423                 *sp = *(sp-1);
3424
3425 new_sack:
3426         /* Build the new head SACK, and we're done. */
3427         sp->start_seq = seq;
3428         sp->end_seq = end_seq;
3429         tp->rx_opt.num_sacks++;
3430         tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3431 }
3432
3433 /* RCV.NXT advances, some SACKs should be eaten. */
3434
3435 static void tcp_sack_remove(struct tcp_sock *tp)
3436 {
3437         struct tcp_sack_block *sp = &tp->selective_acks[0];
3438         int num_sacks = tp->rx_opt.num_sacks;
3439         int this_sack;
3440
3441         /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
3442         if (skb_queue_len(&tp->out_of_order_queue) == 0) {
3443                 tp->rx_opt.num_sacks = 0;
3444                 tp->rx_opt.eff_sacks = tp->rx_opt.dsack;
3445                 return;
3446         }
3447
3448         for(this_sack = 0; this_sack < num_sacks; ) {
3449                 /* Check if the start of the sack is covered by RCV.NXT. */
3450                 if (!before(tp->rcv_nxt, sp->start_seq)) {
3451                         int i;
3452
3453                         /* RCV.NXT must cover all the block! */
3454                         BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq));
3455
3456                         /* Zap this SACK, by moving forward any other SACKS. */
3457                         for (i=this_sack+1; i < num_sacks; i++)
3458                                 tp->selective_acks[i-1] = tp->selective_acks[i];
3459                         num_sacks--;
3460                         continue;
3461                 }
3462                 this_sack++;
3463                 sp++;
3464         }
3465         if (num_sacks != tp->rx_opt.num_sacks) {
3466                 tp->rx_opt.num_sacks = num_sacks;
3467                 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3468         }
3469 }
3470
3471 /* This one checks to see if we can put data from the
3472  * out_of_order queue into the receive_queue.
3473  */
3474 static void tcp_ofo_queue(struct sock *sk)
3475 {
3476         struct tcp_sock *tp = tcp_sk(sk);
3477         __u32 dsack_high = tp->rcv_nxt;
3478         struct sk_buff *skb;
3479
3480         while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
3481                 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
3482                         break;
3483
3484                 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
3485                         __u32 dsack = dsack_high;
3486                         if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
3487                                 dsack_high = TCP_SKB_CB(skb)->end_seq;
3488                         tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack);
3489                 }
3490
3491                 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3492                         SOCK_DEBUG(sk, "ofo packet was already received \n");
3493                         __skb_unlink(skb, skb->list);
3494                         __kfree_skb(skb);
3495                         continue;
3496                 }
3497                 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
3498                            tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3499                            TCP_SKB_CB(skb)->end_seq);
3500
3501                 __skb_unlink(skb, skb->list);
3502                 __skb_queue_tail(&sk->sk_receive_queue, skb);
3503                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3504                 if(skb->h.th->fin)
3505                         tcp_fin(skb, sk, skb->h.th);
3506         }
3507 }
3508
3509 static int tcp_prune_queue(struct sock *sk);
3510
3511 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
3512 {
3513         struct tcphdr *th = skb->h.th;
3514         struct tcp_sock *tp = tcp_sk(sk);
3515         int eaten = -1;
3516
3517         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
3518                 goto drop;
3519
3520         th = skb->h.th;
3521         __skb_pull(skb, th->doff*4);
3522
3523         TCP_ECN_accept_cwr(tp, skb);
3524
3525         if (tp->rx_opt.dsack) {
3526                 tp->rx_opt.dsack = 0;
3527                 tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks,
3528                                                     4 - tp->rx_opt.tstamp_ok);
3529         }
3530
3531         /*  Queue data for delivery to the user.
3532          *  Packets in sequence go to the receive queue.
3533          *  Out of sequence packets to the out_of_order_queue.
3534          */
3535         if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3536                 if (tcp_receive_window(tp) == 0)
3537                         goto out_of_window;
3538
3539                 /* Ok. In sequence. In window. */
3540                 if (tp->ucopy.task == current &&
3541                     tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
3542                     sock_owned_by_user(sk) && !tp->urg_data) {
3543                         int chunk = min_t(unsigned int, skb->len,
3544                                                         tp->ucopy.len);
3545
3546                         __set_current_state(TASK_RUNNING);
3547
3548                         local_bh_enable();
3549                         if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
3550                                 tp->ucopy.len -= chunk;
3551                                 tp->copied_seq += chunk;
3552                                 eaten = (chunk == skb->len && !th->fin);
3553                                 tcp_rcv_space_adjust(sk);
3554                         }
3555                         local_bh_disable();
3556                 }
3557
3558                 if (eaten <= 0) {
3559 queue_and_out:
3560                         if (eaten < 0 &&
3561                             (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3562                              !sk_stream_rmem_schedule(sk, skb))) {
3563                                 if (tcp_prune_queue(sk) < 0 ||
3564                                     !sk_stream_rmem_schedule(sk, skb))
3565                                         goto drop;
3566                         }
3567                         sk_stream_set_owner_r(skb, sk);
3568                         __skb_queue_tail(&sk->sk_receive_queue, skb);
3569                 }
3570                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3571                 if(skb->len)
3572                         tcp_event_data_recv(sk, tp, skb);
3573                 if(th->fin)
3574                         tcp_fin(skb, sk, th);
3575
3576                 if (skb_queue_len(&tp->out_of_order_queue)) {
3577                         tcp_ofo_queue(sk);
3578
3579                         /* RFC2581. 4.2. SHOULD send immediate ACK, when
3580                          * gap in queue is filled.
3581                          */
3582                         if (!skb_queue_len(&tp->out_of_order_queue))
3583                                 tp->ack.pingpong = 0;
3584                 }
3585
3586                 if (tp->rx_opt.num_sacks)
3587                         tcp_sack_remove(tp);
3588
3589                 tcp_fast_path_check(sk, tp);
3590
3591                 if (eaten > 0)
3592                         __kfree_skb(skb);
3593                 else if (!sock_flag(sk, SOCK_DEAD))
3594                         sk->sk_data_ready(sk, 0);
3595                 return;
3596         }
3597
3598         if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3599                 /* A retransmit, 2nd most common case.  Force an immediate ack. */
3600                 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
3601                 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3602
3603 out_of_window:
3604                 tcp_enter_quickack_mode(tp);
3605                 tcp_schedule_ack(tp);
3606 drop:
3607                 __kfree_skb(skb);
3608                 return;
3609         }
3610
3611         /* Out of window. F.e. zero window probe. */
3612         if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
3613                 goto out_of_window;
3614
3615         tcp_enter_quickack_mode(tp);
3616
3617         if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3618                 /* Partial packet, seq < rcv_next < end_seq */
3619                 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
3620                            tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3621                            TCP_SKB_CB(skb)->end_seq);
3622
3623                 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
3624                 
3625                 /* If window is closed, drop tail of packet. But after
3626                  * remembering D-SACK for its head made in previous line.
3627                  */
3628                 if (!tcp_receive_window(tp))
3629                         goto out_of_window;
3630                 goto queue_and_out;
3631         }
3632
3633         TCP_ECN_check_ce(tp, skb);
3634
3635         if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3636             !sk_stream_rmem_schedule(sk, skb)) {
3637                 if (tcp_prune_queue(sk) < 0 ||
3638                     !sk_stream_rmem_schedule(sk, skb))
3639                         goto drop;
3640         }
3641
3642         /* Disable header prediction. */
3643         tp->pred_flags = 0;
3644         tcp_schedule_ack(tp);
3645
3646         SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
3647                    tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3648
3649         sk_stream_set_owner_r(skb, sk);
3650
3651         if (!skb_peek(&tp->out_of_order_queue)) {
3652                 /* Initial out of order segment, build 1 SACK. */
3653                 if (tp->rx_opt.sack_ok) {
3654                         tp->rx_opt.num_sacks = 1;
3655                         tp->rx_opt.dsack     = 0;
3656                         tp->rx_opt.eff_sacks = 1;
3657                         tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
3658                         tp->selective_acks[0].end_seq =
3659                                                 TCP_SKB_CB(skb)->end_seq;
3660                 }
3661                 __skb_queue_head(&tp->out_of_order_queue,skb);
3662         } else {
3663                 struct sk_buff *skb1 = tp->out_of_order_queue.prev;
3664                 u32 seq = TCP_SKB_CB(skb)->seq;
3665                 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
3666
3667                 if (seq == TCP_SKB_CB(skb1)->end_seq) {
3668                         __skb_append(skb1, skb);
3669
3670                         if (!tp->rx_opt.num_sacks ||
3671                             tp->selective_acks[0].end_seq != seq)
3672                                 goto add_sack;
3673
3674                         /* Common case: data arrive in order after hole. */
3675                         tp->selective_acks[0].end_seq = end_seq;
3676                         return;
3677                 }
3678
3679                 /* Find place to insert this segment. */
3680                 do {
3681                         if (!after(TCP_SKB_CB(skb1)->seq, seq))
3682                                 break;
3683                 } while ((skb1 = skb1->prev) !=
3684                          (struct sk_buff*)&tp->out_of_order_queue);
3685
3686                 /* Do skb overlap to previous one? */
3687                 if (skb1 != (struct sk_buff*)&tp->out_of_order_queue &&
3688                     before(seq, TCP_SKB_CB(skb1)->end_seq)) {
3689                         if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3690                                 /* All the bits are present. Drop. */
3691                                 __kfree_skb(skb);
3692                                 tcp_dsack_set(tp, seq, end_seq);
3693                                 goto add_sack;
3694                         }
3695                         if (after(seq, TCP_SKB_CB(skb1)->seq)) {
3696                                 /* Partial overlap. */
3697                                 tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq);
3698                         } else {
3699                                 skb1 = skb1->prev;
3700                         }
3701                 }
3702                 __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue);
3703                 
3704                 /* And clean segments covered by new one as whole. */
3705                 while ((skb1 = skb->next) !=
3706                        (struct sk_buff*)&tp->out_of_order_queue &&
3707                        after(end_seq, TCP_SKB_CB(skb1)->seq)) {
3708                        if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3709                                tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq);
3710                                break;
3711                        }
3712                        __skb_unlink(skb1, skb1->list);
3713                        tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq);
3714                        __kfree_skb(skb1);
3715                 }
3716
3717 add_sack:
3718                 if (tp->rx_opt.sack_ok)
3719                         tcp_sack_new_ofo_skb(sk, seq, end_seq);
3720         }
3721 }
3722
3723 /* Collapse contiguous sequence of skbs head..tail with
3724  * sequence numbers start..end.
3725  * Segments with FIN/SYN are not collapsed (only because this
3726  * simplifies code)
3727  */
3728 static void
3729 tcp_collapse(struct sock *sk, struct sk_buff *head,
3730              struct sk_buff *tail, u32 start, u32 end)
3731 {
3732         struct sk_buff *skb;
3733
3734         /* First, check that queue is collapsable and find
3735          * the point where collapsing can be useful. */
3736         for (skb = head; skb != tail; ) {
3737                 /* No new bits? It is possible on ofo queue. */
3738                 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3739                         struct sk_buff *next = skb->next;
3740                         __skb_unlink(skb, skb->list);
3741                         __kfree_skb(skb);
3742                         NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3743                         skb = next;
3744                         continue;
3745                 }
3746
3747                 /* The first skb to collapse is:
3748                  * - not SYN/FIN and
3749                  * - bloated or contains data before "start" or
3750                  *   overlaps to the next one.
3751                  */
3752                 if (!skb->h.th->syn && !skb->h.th->fin &&
3753                     (tcp_win_from_space(skb->truesize) > skb->len ||
3754                      before(TCP_SKB_CB(skb)->seq, start) ||
3755                      (skb->next != tail &&
3756                       TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq)))
3757                         break;
3758
3759                 /* Decided to skip this, advance start seq. */
3760                 start = TCP_SKB_CB(skb)->end_seq;
3761                 skb = skb->next;
3762         }
3763         if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3764                 return;
3765
3766         while (before(start, end)) {
3767                 struct sk_buff *nskb;
3768                 int header = skb_headroom(skb);
3769                 int copy = SKB_MAX_ORDER(header, 0);
3770
3771                 /* Too big header? This can happen with IPv6. */
3772                 if (copy < 0)
3773                         return;
3774                 if (end-start < copy)
3775                         copy = end-start;
3776                 nskb = alloc_skb(copy+header, GFP_ATOMIC);
3777                 if (!nskb)
3778                         return;
3779                 skb_reserve(nskb, header);
3780                 memcpy(nskb->head, skb->head, header);
3781                 nskb->nh.raw = nskb->head + (skb->nh.raw-skb->head);
3782                 nskb->h.raw = nskb->head + (skb->h.raw-skb->head);
3783                 nskb->mac.raw = nskb->head + (skb->mac.raw-skb->head);
3784                 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
3785                 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
3786                 __skb_insert(nskb, skb->prev, skb, skb->list);
3787                 sk_stream_set_owner_r(nskb, sk);
3788
3789                 /* Copy data, releasing collapsed skbs. */
3790                 while (copy > 0) {
3791                         int offset = start - TCP_SKB_CB(skb)->seq;
3792                         int size = TCP_SKB_CB(skb)->end_seq - start;
3793
3794                         if (offset < 0) BUG();
3795                         if (size > 0) {
3796                                 size = min(copy, size);
3797                                 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
3798                                         BUG();
3799                                 TCP_SKB_CB(nskb)->end_seq += size;
3800                                 copy -= size;
3801                                 start += size;
3802                         }
3803                         if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3804                                 struct sk_buff *next = skb->next;
3805                                 __skb_unlink(skb, skb->list);
3806                                 __kfree_skb(skb);
3807                                 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3808                                 skb = next;
3809                                 if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3810                                         return;
3811                         }
3812                 }
3813         }
3814 }
3815
3816 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3817  * and tcp_collapse() them until all the queue is collapsed.
3818  */
3819 static void tcp_collapse_ofo_queue(struct sock *sk)
3820 {
3821         struct tcp_sock *tp = tcp_sk(sk);
3822         struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
3823         struct sk_buff *head;
3824         u32 start, end;
3825
3826         if (skb == NULL)
3827                 return;
3828
3829         start = TCP_SKB_CB(skb)->seq;
3830         end = TCP_SKB_CB(skb)->end_seq;
3831         head = skb;
3832
3833         for (;;) {
3834                 skb = skb->next;
3835
3836                 /* Segment is terminated when we see gap or when
3837                  * we are at the end of all the queue. */
3838                 if (skb == (struct sk_buff *)&tp->out_of_order_queue ||
3839                     after(TCP_SKB_CB(skb)->seq, end) ||
3840                     before(TCP_SKB_CB(skb)->end_seq, start)) {
3841                         tcp_collapse(sk, head, skb, start, end);
3842                         head = skb;
3843                         if (skb == (struct sk_buff *)&tp->out_of_order_queue)
3844                                 break;
3845                         /* Start new segment */
3846                         start = TCP_SKB_CB(skb)->seq;
3847                         end = TCP_SKB_CB(skb)->end_seq;
3848                 } else {
3849                         if (before(TCP_SKB_CB(skb)->seq, start))
3850                                 start = TCP_SKB_CB(skb)->seq;
3851                         if (after(TCP_SKB_CB(skb)->end_seq, end))
3852                                 end = TCP_SKB_CB(skb)->end_seq;
3853                 }
3854         }
3855 }
3856
3857 /* Reduce allocated memory if we can, trying to get
3858  * the socket within its memory limits again.
3859  *
3860  * Return less than zero if we should start dropping frames
3861  * until the socket owning process reads some of the data
3862  * to stabilize the situation.
3863  */
3864 static int tcp_prune_queue(struct sock *sk)
3865 {
3866         struct tcp_sock *tp = tcp_sk(sk); 
3867
3868         SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
3869
3870         NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED);
3871
3872         if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
3873                 tcp_clamp_window(sk, tp);
3874         else if (tcp_memory_pressure)
3875                 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
3876
3877         tcp_collapse_ofo_queue(sk);
3878         tcp_collapse(sk, sk->sk_receive_queue.next,
3879                      (struct sk_buff*)&sk->sk_receive_queue,
3880                      tp->copied_seq, tp->rcv_nxt);
3881         sk_stream_mem_reclaim(sk);
3882
3883         if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3884                 return 0;
3885
3886         /* Collapsing did not help, destructive actions follow.
3887          * This must not ever occur. */
3888
3889         /* First, purge the out_of_order queue. */
3890         if (skb_queue_len(&tp->out_of_order_queue)) {
3891                 NET_ADD_STATS_BH(LINUX_MIB_OFOPRUNED, 
3892                                  skb_queue_len(&tp->out_of_order_queue));
3893                 __skb_queue_purge(&tp->out_of_order_queue);
3894
3895                 /* Reset SACK state.  A conforming SACK implementation will
3896                  * do the same at a timeout based retransmit.  When a connection
3897                  * is in a sad state like this, we care only about integrity
3898                  * of the connection not performance.
3899                  */
3900                 if (tp->rx_opt.sack_ok)
3901                         tcp_sack_reset(&tp->rx_opt);
3902                 sk_stream_mem_reclaim(sk);
3903         }
3904
3905         if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3906                 return 0;
3907
3908         /* If we are really being abused, tell the caller to silently
3909          * drop receive data on the floor.  It will get retransmitted
3910          * and hopefully then we'll have sufficient space.
3911          */
3912         NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED);
3913
3914         /* Massive buffer overcommit. */
3915         tp->pred_flags = 0;
3916         return -1;
3917 }
3918
3919
3920 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3921  * As additional protections, we do not touch cwnd in retransmission phases,
3922  * and if application hit its sndbuf limit recently.
3923  */
3924 void tcp_cwnd_application_limited(struct sock *sk)
3925 {
3926         struct tcp_sock *tp = tcp_sk(sk);
3927
3928         if (tp->ca_state == TCP_CA_Open &&
3929             sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
3930                 /* Limited by application or receiver window. */
3931                 u32 win_used = max(tp->snd_cwnd_used, 2U);
3932                 if (win_used < tp->snd_cwnd) {
3933                         tp->snd_ssthresh = tcp_current_ssthresh(tp);
3934                         tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
3935                 }
3936                 tp->snd_cwnd_used = 0;
3937         }
3938         tp->snd_cwnd_stamp = tcp_time_stamp;
3939 }
3940
3941
3942 /* When incoming ACK allowed to free some skb from write_queue,
3943  * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3944  * on the exit from tcp input handler.
3945  *
3946  * PROBLEM: sndbuf expansion does not work well with largesend.
3947  */
3948 static void tcp_new_space(struct sock *sk)
3949 {
3950         struct tcp_sock *tp = tcp_sk(sk);
3951
3952         if (tp->packets_out < tp->snd_cwnd &&
3953             !(sk->sk_userlocks & SOCK_SNDBUF_LOCK) &&
3954             !tcp_memory_pressure &&
3955             atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
3956                 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache_std) +
3957                         MAX_TCP_HEADER + 16 + sizeof(struct sk_buff),
3958                     demanded = max_t(unsigned int, tp->snd_cwnd,
3959                                                    tp->reordering + 1);
3960                 sndmem *= 2*demanded;
3961                 if (sndmem > sk->sk_sndbuf)
3962                         sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
3963                 tp->snd_cwnd_stamp = tcp_time_stamp;
3964         }
3965
3966         sk->sk_write_space(sk);
3967 }
3968
3969 static inline void tcp_check_space(struct sock *sk)
3970 {
3971         if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
3972                 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
3973                 if (sk->sk_socket &&
3974                     test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
3975                         tcp_new_space(sk);
3976         }
3977 }
3978
3979 static void __tcp_data_snd_check(struct sock *sk, struct sk_buff *skb)
3980 {
3981         struct tcp_sock *tp = tcp_sk(sk);
3982
3983         if (after(TCP_SKB_CB(skb)->end_seq, tp->snd_una + tp->snd_wnd) ||
3984             tcp_packets_in_flight(tp) >= tp->snd_cwnd ||
3985             tcp_write_xmit(sk, tp->nonagle))
3986                 tcp_check_probe_timer(sk, tp);
3987 }
3988
3989 static __inline__ void tcp_data_snd_check(struct sock *sk)
3990 {
3991         struct sk_buff *skb = sk->sk_send_head;
3992
3993         if (skb != NULL)
3994                 __tcp_data_snd_check(sk, skb);
3995         tcp_check_space(sk);
3996 }
3997
3998 /*
3999  * Check if sending an ack is needed.
4000  */
4001 static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
4002 {
4003         struct tcp_sock *tp = tcp_sk(sk);
4004
4005             /* More than one full frame received... */
4006         if (((tp->rcv_nxt - tp->rcv_wup) > tp->ack.rcv_mss
4007              /* ... and right edge of window advances far enough.
4008               * (tcp_recvmsg() will send ACK otherwise). Or...
4009               */
4010              && __tcp_select_window(sk) >= tp->rcv_wnd) ||
4011             /* We ACK each frame or... */
4012             tcp_in_quickack_mode(tp) ||
4013             /* We have out of order data. */
4014             (ofo_possible &&
4015              skb_peek(&tp->out_of_order_queue))) {
4016                 /* Then ack it now */
4017                 tcp_send_ack(sk);
4018         } else {
4019                 /* Else, send delayed ack. */
4020                 tcp_send_delayed_ack(sk);
4021         }
4022 }
4023
4024 static __inline__ void tcp_ack_snd_check(struct sock *sk)
4025 {
4026         struct tcp_sock *tp = tcp_sk(sk);
4027         if (!tcp_ack_scheduled(tp)) {
4028                 /* We sent a data segment already. */
4029                 return;
4030         }
4031         __tcp_ack_snd_check(sk, 1);
4032 }
4033
4034 /*
4035  *      This routine is only called when we have urgent data
4036  *      signalled. Its the 'slow' part of tcp_urg. It could be
4037  *      moved inline now as tcp_urg is only called from one
4038  *      place. We handle URGent data wrong. We have to - as
4039  *      BSD still doesn't use the correction from RFC961.
4040  *      For 1003.1g we should support a new option TCP_STDURG to permit
4041  *      either form (or just set the sysctl tcp_stdurg).
4042  */
4043  
4044 static void tcp_check_urg(struct sock * sk, struct tcphdr * th)
4045 {
4046         struct tcp_sock *tp = tcp_sk(sk);
4047         u32 ptr = ntohs(th->urg_ptr);
4048
4049         if (ptr && !sysctl_tcp_stdurg)
4050                 ptr--;
4051         ptr += ntohl(th->seq);
4052
4053         /* Ignore urgent data that we've already seen and read. */
4054         if (after(tp->copied_seq, ptr))
4055                 return;
4056
4057         /* Do not replay urg ptr.
4058          *
4059          * NOTE: interesting situation not covered by specs.
4060          * Misbehaving sender may send urg ptr, pointing to segment,
4061          * which we already have in ofo queue. We are not able to fetch
4062          * such data and will stay in TCP_URG_NOTYET until will be eaten
4063          * by recvmsg(). Seems, we are not obliged to handle such wicked
4064          * situations. But it is worth to think about possibility of some
4065          * DoSes using some hypothetical application level deadlock.
4066          */
4067         if (before(ptr, tp->rcv_nxt))
4068                 return;
4069
4070         /* Do we already have a newer (or duplicate) urgent pointer? */
4071         if (tp->urg_data && !after(ptr, tp->urg_seq))
4072                 return;
4073
4074         /* Tell the world about our new urgent pointer. */
4075         sk_send_sigurg(sk);
4076
4077         /* We may be adding urgent data when the last byte read was
4078          * urgent. To do this requires some care. We cannot just ignore
4079          * tp->copied_seq since we would read the last urgent byte again
4080          * as data, nor can we alter copied_seq until this data arrives
4081          * or we break the sematics of SIOCATMARK (and thus sockatmark())
4082          *
4083          * NOTE. Double Dutch. Rendering to plain English: author of comment
4084          * above did something sort of  send("A", MSG_OOB); send("B", MSG_OOB);
4085          * and expect that both A and B disappear from stream. This is _wrong_.
4086          * Though this happens in BSD with high probability, this is occasional.
4087          * Any application relying on this is buggy. Note also, that fix "works"
4088          * only in this artificial test. Insert some normal data between A and B and we will
4089          * decline of BSD again. Verdict: it is better to remove to trap
4090          * buggy users.
4091          */
4092         if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
4093             !sock_flag(sk, SOCK_URGINLINE) &&
4094             tp->copied_seq != tp->rcv_nxt) {
4095                 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
4096                 tp->copied_seq++;
4097                 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
4098                         __skb_unlink(skb, skb->list);
4099                         __kfree_skb(skb);
4100                 }
4101         }
4102
4103         tp->urg_data   = TCP_URG_NOTYET;
4104         tp->urg_seq    = ptr;
4105
4106         /* Disable header prediction. */
4107         tp->pred_flags = 0;
4108 }
4109
4110 /* This is the 'fast' part of urgent handling. */
4111 static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
4112 {
4113         struct tcp_sock *tp = tcp_sk(sk);
4114
4115         /* Check if we get a new urgent pointer - normally not. */
4116         if (th->urg)
4117                 tcp_check_urg(sk,th);
4118
4119         /* Do we wait for any urgent data? - normally not... */
4120         if (tp->urg_data == TCP_URG_NOTYET) {
4121                 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
4122                           th->syn;
4123
4124                 /* Is the urgent pointer pointing into this packet? */   
4125                 if (ptr < skb->len) {
4126                         u8 tmp;
4127                         if (skb_copy_bits(skb, ptr, &tmp, 1))
4128                                 BUG();
4129                         tp->urg_data = TCP_URG_VALID | tmp;
4130                         if (!sock_flag(sk, SOCK_DEAD))
4131                                 sk->sk_data_ready(sk, 0);
4132                 }
4133         }
4134 }
4135
4136 static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
4137 {
4138         struct tcp_sock *tp = tcp_sk(sk);
4139         int chunk = skb->len - hlen;
4140         int err;
4141
4142         local_bh_enable();
4143         if (skb->ip_summed==CHECKSUM_UNNECESSARY)
4144                 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
4145         else
4146                 err = skb_copy_and_csum_datagram_iovec(skb, hlen,
4147                                                        tp->ucopy.iov);
4148
4149         if (!err) {
4150                 tp->ucopy.len -= chunk;
4151                 tp->copied_seq += chunk;
4152                 tcp_rcv_space_adjust(sk);
4153         }
4154
4155         local_bh_disable();
4156         return err;
4157 }
4158
4159 static int __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
4160 {
4161         int result;
4162
4163         if (sock_owned_by_user(sk)) {
4164                 local_bh_enable();
4165                 result = __tcp_checksum_complete(skb);
4166                 local_bh_disable();
4167         } else {
4168                 result = __tcp_checksum_complete(skb);
4169         }
4170         return result;
4171 }
4172
4173 static __inline__ int
4174 tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
4175 {
4176         return skb->ip_summed != CHECKSUM_UNNECESSARY &&
4177                 __tcp_checksum_complete_user(sk, skb);
4178 }
4179
4180 /*
4181  *      TCP receive function for the ESTABLISHED state. 
4182  *
4183  *      It is split into a fast path and a slow path. The fast path is 
4184  *      disabled when:
4185  *      - A zero window was announced from us - zero window probing
4186  *        is only handled properly in the slow path. 
4187  *      - Out of order segments arrived.
4188  *      - Urgent data is expected.
4189  *      - There is no buffer space left
4190  *      - Unexpected TCP flags/window values/header lengths are received
4191  *        (detected by checking the TCP header against pred_flags) 
4192  *      - Data is sent in both directions. Fast path only supports pure senders
4193  *        or pure receivers (this means either the sequence number or the ack
4194  *        value must stay constant)
4195  *      - Unexpected TCP option.
4196  *
4197  *      When these conditions are not satisfied it drops into a standard 
4198  *      receive procedure patterned after RFC793 to handle all cases.
4199  *      The first three cases are guaranteed by proper pred_flags setting,
4200  *      the rest is checked inline. Fast processing is turned on in 
4201  *      tcp_data_queue when everything is OK.
4202  */
4203 int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
4204                         struct tcphdr *th, unsigned len)
4205 {
4206         struct tcp_sock *tp = tcp_sk(sk);
4207
4208         /*
4209          *      Header prediction.
4210          *      The code loosely follows the one in the famous 
4211          *      "30 instruction TCP receive" Van Jacobson mail.
4212          *      
4213          *      Van's trick is to deposit buffers into socket queue 
4214          *      on a device interrupt, to call tcp_recv function
4215          *      on the receive process context and checksum and copy
4216          *      the buffer to user space. smart...
4217          *
4218          *      Our current scheme is not silly either but we take the 
4219          *      extra cost of the net_bh soft interrupt processing...
4220          *      We do checksum and copy also but from device to kernel.
4221          */
4222
4223         tp->rx_opt.saw_tstamp = 0;
4224
4225         /*      pred_flags is 0xS?10 << 16 + snd_wnd
4226          *      if header_predition is to be made
4227          *      'S' will always be tp->tcp_header_len >> 2
4228          *      '?' will be 0 for the fast path, otherwise pred_flags is 0 to
4229          *  turn it off (when there are holes in the receive 
4230          *       space for instance)
4231          *      PSH flag is ignored.
4232          */
4233
4234         if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
4235                 TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
4236                 int tcp_header_len = tp->tcp_header_len;
4237
4238                 /* Timestamp header prediction: tcp_header_len
4239                  * is automatically equal to th->doff*4 due to pred_flags
4240                  * match.
4241                  */
4242
4243                 /* Check timestamp */
4244                 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
4245                         __u32 *ptr = (__u32 *)(th + 1);
4246
4247                         /* No? Slow path! */
4248                         if (*ptr != ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
4249                                           | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP))
4250                                 goto slow_path;
4251
4252                         tp->rx_opt.saw_tstamp = 1;
4253                         ++ptr; 
4254                         tp->rx_opt.rcv_tsval = ntohl(*ptr);
4255                         ++ptr;
4256                         tp->rx_opt.rcv_tsecr = ntohl(*ptr);
4257
4258                         /* If PAWS failed, check it more carefully in slow path */
4259                         if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
4260                                 goto slow_path;
4261
4262                         /* DO NOT update ts_recent here, if checksum fails
4263                          * and timestamp was corrupted part, it will result
4264                          * in a hung connection since we will drop all
4265                          * future packets due to the PAWS test.
4266                          */
4267                 }
4268
4269                 if (len <= tcp_header_len) {
4270                         /* Bulk data transfer: sender */
4271                         if (len == tcp_header_len) {
4272                                 /* Predicted packet is in window by definition.
4273                                  * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4274                                  * Hence, check seq<=rcv_wup reduces to:
4275                                  */
4276                                 if (tcp_header_len ==
4277                                     (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
4278                                     tp->rcv_nxt == tp->rcv_wup)
4279                                         tcp_store_ts_recent(tp);
4280
4281                                 tcp_rcv_rtt_measure_ts(tp, skb);
4282
4283                                 /* We know that such packets are checksummed
4284                                  * on entry.
4285                                  */
4286                                 tcp_ack(sk, skb, 0);
4287                                 __kfree_skb(skb); 
4288                                 tcp_data_snd_check(sk);
4289                                 return 0;
4290                         } else { /* Header too small */
4291                                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
4292                                 goto discard;
4293                         }
4294                 } else {
4295                         int eaten = 0;
4296
4297                         if (tp->ucopy.task == current &&
4298                             tp->copied_seq == tp->rcv_nxt &&
4299                             len - tcp_header_len <= tp->ucopy.len &&
4300                             sock_owned_by_user(sk)) {
4301                                 __set_current_state(TASK_RUNNING);
4302
4303                                 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) {
4304                                         /* Predicted packet is in window by definition.
4305                                          * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4306                                          * Hence, check seq<=rcv_wup reduces to:
4307                                          */
4308                                         if (tcp_header_len ==
4309                                             (sizeof(struct tcphdr) +
4310                                              TCPOLEN_TSTAMP_ALIGNED) &&
4311                                             tp->rcv_nxt == tp->rcv_wup)
4312                                                 tcp_store_ts_recent(tp);
4313
4314                                         tcp_rcv_rtt_measure_ts(tp, skb);
4315
4316                                         __skb_pull(skb, tcp_header_len);
4317                                         tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4318                                         NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER);
4319                                         eaten = 1;
4320                                 }
4321                         }
4322                         if (!eaten) {
4323                                 if (tcp_checksum_complete_user(sk, skb))
4324                                         goto csum_error;
4325
4326                                 /* Predicted packet is in window by definition.
4327                                  * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4328                                  * Hence, check seq<=rcv_wup reduces to:
4329                                  */
4330                                 if (tcp_header_len ==
4331                                     (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
4332                                     tp->rcv_nxt == tp->rcv_wup)
4333                                         tcp_store_ts_recent(tp);
4334
4335                                 tcp_rcv_rtt_measure_ts(tp, skb);
4336
4337                                 if ((int)skb->truesize > sk->sk_forward_alloc)
4338                                         goto step5;
4339
4340                                 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS);
4341
4342                                 /* Bulk data transfer: receiver */
4343                                 __skb_pull(skb,tcp_header_len);
4344                                 __skb_queue_tail(&sk->sk_receive_queue, skb);
4345                                 sk_stream_set_owner_r(skb, sk);
4346                                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4347                         }
4348
4349                         tcp_event_data_recv(sk, tp, skb);
4350
4351                         if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
4352                                 /* Well, only one small jumplet in fast path... */
4353                                 tcp_ack(sk, skb, FLAG_DATA);
4354                                 tcp_data_snd_check(sk);
4355                                 if (!tcp_ack_scheduled(tp))
4356                                         goto no_ack;
4357                         }
4358
4359                         if (eaten) {
4360                                 if (tcp_in_quickack_mode(tp)) {
4361                                         tcp_send_ack(sk);
4362                                 } else {
4363                                         tcp_send_delayed_ack(sk);
4364                                 }
4365                         } else {
4366                                 __tcp_ack_snd_check(sk, 0);
4367                         }
4368
4369 no_ack:
4370                         if (eaten)
4371                                 __kfree_skb(skb);
4372                         else
4373                                 sk->sk_data_ready(sk, 0);
4374                         return 0;
4375                 }
4376         }
4377
4378 slow_path:
4379         if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb))
4380                 goto csum_error;
4381
4382         /*
4383          * RFC1323: H1. Apply PAWS check first.
4384          */
4385         if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
4386             tcp_paws_discard(tp, skb)) {
4387                 if (!th->rst) {
4388                         NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4389                         tcp_send_dupack(sk, skb);
4390                         goto discard;
4391                 }
4392                 /* Resets are accepted even if PAWS failed.
4393
4394                    ts_recent update must be made after we are sure
4395                    that the packet is in window.
4396                  */
4397         }
4398
4399         /*
4400          *      Standard slow path.
4401          */
4402
4403         if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4404                 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4405                  * (RST) segments are validated by checking their SEQ-fields."
4406                  * And page 69: "If an incoming segment is not acceptable,
4407                  * an acknowledgment should be sent in reply (unless the RST bit
4408                  * is set, if so drop the segment and return)".
4409                  */
4410                 if (!th->rst)
4411                         tcp_send_dupack(sk, skb);
4412                 goto discard;
4413         }
4414
4415         if(th->rst) {
4416                 tcp_reset(sk);
4417                 goto discard;
4418         }
4419
4420         tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4421
4422         if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4423                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
4424                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4425                 tcp_reset(sk);
4426                 return 1;
4427         }
4428
4429 step5:
4430         if(th->ack)
4431                 tcp_ack(sk, skb, FLAG_SLOWPATH);
4432
4433         tcp_rcv_rtt_measure_ts(tp, skb);
4434
4435         /* Process urgent data. */
4436         tcp_urg(sk, skb, th);
4437
4438         /* step 7: process the segment text */
4439         tcp_data_queue(sk, skb);
4440
4441         tcp_data_snd_check(sk);
4442         tcp_ack_snd_check(sk);
4443         return 0;
4444
4445 csum_error:
4446         TCP_INC_STATS_BH(TCP_MIB_INERRS);
4447
4448 discard:
4449         __kfree_skb(skb);
4450         return 0;
4451 }
4452
4453 static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
4454                                          struct tcphdr *th, unsigned len)
4455 {
4456         struct tcp_sock *tp = tcp_sk(sk);
4457         int saved_clamp = tp->rx_opt.mss_clamp;
4458
4459         tcp_parse_options(skb, &tp->rx_opt, 0);
4460
4461         if (th->ack) {
4462                 /* rfc793:
4463                  * "If the state is SYN-SENT then
4464                  *    first check the ACK bit
4465                  *      If the ACK bit is set
4466                  *        If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4467                  *        a reset (unless the RST bit is set, if so drop
4468                  *        the segment and return)"
4469                  *
4470                  *  We do not send data with SYN, so that RFC-correct
4471                  *  test reduces to:
4472                  */
4473                 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
4474                         goto reset_and_undo;
4475
4476                 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4477                     !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
4478                              tcp_time_stamp)) {
4479                         NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED);
4480                         goto reset_and_undo;
4481                 }
4482
4483                 /* Now ACK is acceptable.
4484                  *
4485                  * "If the RST bit is set
4486                  *    If the ACK was acceptable then signal the user "error:
4487                  *    connection reset", drop the segment, enter CLOSED state,
4488                  *    delete TCB, and return."
4489                  */
4490
4491                 if (th->rst) {
4492                         tcp_reset(sk);
4493                         goto discard;
4494                 }
4495
4496                 /* rfc793:
4497                  *   "fifth, if neither of the SYN or RST bits is set then
4498                  *    drop the segment and return."
4499                  *
4500                  *    See note below!
4501                  *                                        --ANK(990513)
4502                  */
4503                 if (!th->syn)
4504                         goto discard_and_undo;
4505
4506                 /* rfc793:
4507                  *   "If the SYN bit is on ...
4508                  *    are acceptable then ...
4509                  *    (our SYN has been ACKed), change the connection
4510                  *    state to ESTABLISHED..."
4511                  */
4512
4513                 TCP_ECN_rcv_synack(tp, th);
4514                 if (tp->ecn_flags&TCP_ECN_OK)
4515                         sock_set_flag(sk, SOCK_NO_LARGESEND);
4516
4517                 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4518                 tcp_ack(sk, skb, FLAG_SLOWPATH);
4519
4520                 /* Ok.. it's good. Set up sequence numbers and
4521                  * move to established.
4522                  */
4523                 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4524                 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4525
4526                 /* RFC1323: The window in SYN & SYN/ACK segments is
4527                  * never scaled.
4528                  */
4529                 tp->snd_wnd = ntohs(th->window);
4530                 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq);
4531
4532                 if (!tp->rx_opt.wscale_ok) {
4533                         tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
4534                         tp->window_clamp = min(tp->window_clamp, 65535U);
4535                 }
4536
4537                 if (tp->rx_opt.saw_tstamp) {
4538                         tp->rx_opt.tstamp_ok       = 1;
4539                         tp->tcp_header_len =
4540                                 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4541                         tp->advmss          -= TCPOLEN_TSTAMP_ALIGNED;
4542                         tcp_store_ts_recent(tp);
4543                 } else {
4544                         tp->tcp_header_len = sizeof(struct tcphdr);
4545                 }
4546
4547                 if (tp->rx_opt.sack_ok && sysctl_tcp_fack)
4548                         tp->rx_opt.sack_ok |= 2;
4549
4550                 tcp_sync_mss(sk, tp->pmtu_cookie);
4551                 tcp_initialize_rcv_mss(sk);
4552
4553                 /* Remember, tcp_poll() does not lock socket!
4554                  * Change state from SYN-SENT only after copied_seq
4555                  * is initialized. */
4556                 tp->copied_seq = tp->rcv_nxt;
4557                 mb();
4558                 tcp_set_state(sk, TCP_ESTABLISHED);
4559
4560                 /* Make sure socket is routed, for correct metrics.  */
4561                 tp->af_specific->rebuild_header(sk);
4562
4563                 tcp_init_metrics(sk);
4564
4565                 /* Prevent spurious tcp_cwnd_restart() on first data
4566                  * packet.
4567                  */
4568                 tp->lsndtime = tcp_time_stamp;
4569
4570                 tcp_init_buffer_space(sk);
4571
4572                 if (sock_flag(sk, SOCK_KEEPOPEN))
4573                         tcp_reset_keepalive_timer(sk, keepalive_time_when(tp));
4574
4575                 if (!tp->rx_opt.snd_wscale)
4576                         __tcp_fast_path_on(tp, tp->snd_wnd);
4577                 else
4578                         tp->pred_flags = 0;
4579
4580                 if (!sock_flag(sk, SOCK_DEAD)) {
4581                         sk->sk_state_change(sk);
4582                         sk_wake_async(sk, 0, POLL_OUT);
4583                 }
4584
4585                 if (sk->sk_write_pending || tp->defer_accept || tp->ack.pingpong) {
4586                         /* Save one ACK. Data will be ready after
4587                          * several ticks, if write_pending is set.
4588                          *
4589                          * It may be deleted, but with this feature tcpdumps
4590                          * look so _wonderfully_ clever, that I was not able
4591                          * to stand against the temptation 8)     --ANK
4592                          */
4593                         tcp_schedule_ack(tp);
4594                         tp->ack.lrcvtime = tcp_time_stamp;
4595                         tp->ack.ato      = TCP_ATO_MIN;
4596                         tcp_incr_quickack(tp);
4597                         tcp_enter_quickack_mode(tp);
4598                         tcp_reset_xmit_timer(sk, TCP_TIME_DACK, TCP_DELACK_MAX);
4599
4600 discard:
4601                         __kfree_skb(skb);
4602                         return 0;
4603                 } else {
4604                         tcp_send_ack(sk);
4605                 }
4606                 return -1;
4607         }
4608
4609         /* No ACK in the segment */
4610
4611         if (th->rst) {
4612                 /* rfc793:
4613                  * "If the RST bit is set
4614                  *
4615                  *      Otherwise (no ACK) drop the segment and return."
4616                  */
4617
4618                 goto discard_and_undo;
4619         }
4620
4621         /* PAWS check. */
4622         if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0))
4623                 goto discard_and_undo;
4624
4625         if (th->syn) {
4626                 /* We see SYN without ACK. It is attempt of
4627                  * simultaneous connect with crossed SYNs.
4628                  * Particularly, it can be connect to self.
4629                  */
4630                 tcp_set_state(sk, TCP_SYN_RECV);
4631
4632                 if (tp->rx_opt.saw_tstamp) {
4633                         tp->rx_opt.tstamp_ok = 1;
4634                         tcp_store_ts_recent(tp);
4635                         tp->tcp_header_len =
4636                                 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4637                 } else {
4638                         tp->tcp_header_len = sizeof(struct tcphdr);
4639                 }
4640
4641                 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4642                 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4643
4644                 /* RFC1323: The window in SYN & SYN/ACK segments is
4645                  * never scaled.
4646                  */
4647                 tp->snd_wnd    = ntohs(th->window);
4648                 tp->snd_wl1    = TCP_SKB_CB(skb)->seq;
4649                 tp->max_window = tp->snd_wnd;
4650
4651                 TCP_ECN_rcv_syn(tp, th);
4652                 if (tp->ecn_flags&TCP_ECN_OK)
4653                         sock_set_flag(sk, SOCK_NO_LARGESEND);
4654
4655                 tcp_sync_mss(sk, tp->pmtu_cookie);
4656                 tcp_initialize_rcv_mss(sk);
4657
4658
4659                 tcp_send_synack(sk);
4660 #if 0
4661                 /* Note, we could accept data and URG from this segment.
4662                  * There are no obstacles to make this.
4663                  *
4664                  * However, if we ignore data in ACKless segments sometimes,
4665                  * we have no reasons to accept it sometimes.
4666                  * Also, seems the code doing it in step6 of tcp_rcv_state_process
4667                  * is not flawless. So, discard packet for sanity.
4668                  * Uncomment this return to process the data.
4669                  */
4670                 return -1;
4671 #else
4672                 goto discard;
4673 #endif
4674         }
4675         /* "fifth, if neither of the SYN or RST bits is set then
4676          * drop the segment and return."
4677          */
4678
4679 discard_and_undo:
4680         tcp_clear_options(&tp->rx_opt);
4681         tp->rx_opt.mss_clamp = saved_clamp;
4682         goto discard;
4683
4684 reset_and_undo:
4685         tcp_clear_options(&tp->rx_opt);
4686         tp->rx_opt.mss_clamp = saved_clamp;
4687         return 1;
4688 }
4689
4690
4691 /*
4692  *      This function implements the receiving procedure of RFC 793 for
4693  *      all states except ESTABLISHED and TIME_WAIT. 
4694  *      It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4695  *      address independent.
4696  */
4697         
4698 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
4699                           struct tcphdr *th, unsigned len)
4700 {
4701         struct tcp_sock *tp = tcp_sk(sk);
4702         int queued = 0;
4703
4704         tp->rx_opt.saw_tstamp = 0;
4705
4706         switch (sk->sk_state) {
4707         case TCP_CLOSE:
4708                 goto discard;
4709
4710         case TCP_LISTEN:
4711                 if(th->ack)
4712                         return 1;
4713
4714                 if(th->rst)
4715                         goto discard;
4716
4717                 if(th->syn) {
4718                         if(tp->af_specific->conn_request(sk, skb) < 0)
4719                                 return 1;
4720
4721                         init_westwood(sk);
4722                         init_bictcp(tp);
4723
4724                         /* Now we have several options: In theory there is 
4725                          * nothing else in the frame. KA9Q has an option to 
4726                          * send data with the syn, BSD accepts data with the
4727                          * syn up to the [to be] advertised window and 
4728                          * Solaris 2.1 gives you a protocol error. For now 
4729                          * we just ignore it, that fits the spec precisely 
4730                          * and avoids incompatibilities. It would be nice in
4731                          * future to drop through and process the data.
4732                          *
4733                          * Now that TTCP is starting to be used we ought to 
4734                          * queue this data.
4735                          * But, this leaves one open to an easy denial of
4736                          * service attack, and SYN cookies can't defend
4737                          * against this problem. So, we drop the data
4738                          * in the interest of security over speed.
4739                          */
4740                         goto discard;
4741                 }
4742                 goto discard;
4743
4744         case TCP_SYN_SENT:
4745                 init_westwood(sk);
4746                 init_bictcp(tp);
4747
4748                 queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
4749                 if (queued >= 0)
4750                         return queued;
4751
4752                 /* Do step6 onward by hand. */
4753                 tcp_urg(sk, skb, th);
4754                 __kfree_skb(skb);
4755                 tcp_data_snd_check(sk);
4756                 return 0;
4757         }
4758
4759         if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
4760             tcp_paws_discard(tp, skb)) {
4761                 if (!th->rst) {
4762                         NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4763                         tcp_send_dupack(sk, skb);
4764                         goto discard;
4765                 }
4766                 /* Reset is accepted even if it did not pass PAWS. */
4767         }
4768
4769         /* step 1: check sequence number */
4770         if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4771                 if (!th->rst)
4772                         tcp_send_dupack(sk, skb);
4773                 goto discard;
4774         }
4775
4776         /* step 2: check RST bit */
4777         if(th->rst) {
4778                 tcp_reset(sk);
4779                 goto discard;
4780         }
4781
4782         tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4783
4784         /* step 3: check security and precedence [ignored] */
4785
4786         /*      step 4:
4787          *
4788          *      Check for a SYN in window.
4789          */
4790         if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4791                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4792                 tcp_reset(sk);
4793                 return 1;
4794         }
4795
4796         /* step 5: check the ACK field */
4797         if (th->ack) {
4798                 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH);
4799
4800                 switch(sk->sk_state) {
4801                 case TCP_SYN_RECV:
4802                         if (acceptable) {
4803                                 tp->copied_seq = tp->rcv_nxt;
4804                                 mb();
4805                                 tcp_set_state(sk, TCP_ESTABLISHED);
4806                                 sk->sk_state_change(sk);
4807
4808                                 /* Note, that this wakeup is only for marginal
4809                                  * crossed SYN case. Passively open sockets
4810                                  * are not waked up, because sk->sk_sleep ==
4811                                  * NULL and sk->sk_socket == NULL.
4812                                  */
4813                                 if (sk->sk_socket) {
4814                                         sk_wake_async(sk,0,POLL_OUT);
4815                                 }
4816
4817                                 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
4818                                 tp->snd_wnd = ntohs(th->window) <<
4819                                               tp->rx_opt.snd_wscale;
4820                                 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq,
4821                                             TCP_SKB_CB(skb)->seq);
4822
4823                                 /* tcp_ack considers this ACK as duplicate
4824                                  * and does not calculate rtt.
4825                                  * Fix it at least with timestamps.
4826                                  */
4827                                 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4828                                     !tp->srtt)
4829                                         tcp_ack_saw_tstamp(tp, 0);
4830
4831                                 if (tp->rx_opt.tstamp_ok)
4832                                         tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
4833
4834                                 /* Make sure socket is routed, for
4835                                  * correct metrics.
4836                                  */
4837                                 tp->af_specific->rebuild_header(sk);
4838
4839                                 tcp_init_metrics(sk);
4840
4841                                 /* Prevent spurious tcp_cwnd_restart() on
4842                                  * first data packet.
4843                                  */
4844                                 tp->lsndtime = tcp_time_stamp;
4845
4846                                 tcp_initialize_rcv_mss(sk);
4847                                 tcp_init_buffer_space(sk);
4848                                 tcp_fast_path_on(tp);
4849                         } else {
4850                                 return 1;
4851                         }
4852                         break;
4853
4854                 case TCP_FIN_WAIT1:
4855                         if (tp->snd_una == tp->write_seq) {
4856                                 tcp_set_state(sk, TCP_FIN_WAIT2);
4857                                 sk->sk_shutdown |= SEND_SHUTDOWN;
4858                                 dst_confirm(sk->sk_dst_cache);
4859
4860                                 if (!sock_flag(sk, SOCK_DEAD))
4861                                         /* Wake up lingering close() */
4862                                         sk->sk_state_change(sk);
4863                                 else {
4864                                         int tmo;
4865
4866                                         if (tp->linger2 < 0 ||
4867                                             (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4868                                              after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
4869                                                 tcp_done(sk);
4870                                                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4871                                                 return 1;
4872                                         }
4873
4874                                         tmo = tcp_fin_time(tp);
4875                                         if (tmo > TCP_TIMEWAIT_LEN) {
4876                                                 tcp_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
4877                                         } else if (th->fin || sock_owned_by_user(sk)) {
4878                                                 /* Bad case. We could lose such FIN otherwise.
4879                                                  * It is not a big problem, but it looks confusing
4880                                                  * and not so rare event. We still can lose it now,
4881                                                  * if it spins in bh_lock_sock(), but it is really
4882                                                  * marginal case.
4883                                                  */
4884                                                 tcp_reset_keepalive_timer(sk, tmo);
4885                                         } else {
4886                                                 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
4887                                                 goto discard;
4888                                         }
4889                                 }
4890                         }
4891                         break;
4892
4893                 case TCP_CLOSING:
4894                         if (tp->snd_una == tp->write_seq) {
4895                                 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4896                                 goto discard;
4897                         }
4898                         break;
4899
4900                 case TCP_LAST_ACK:
4901                         if (tp->snd_una == tp->write_seq) {
4902                                 tcp_update_metrics(sk);
4903                                 tcp_done(sk);
4904                                 goto discard;
4905                         }
4906                         break;
4907                 }
4908         } else
4909                 goto discard;
4910
4911         /* step 6: check the URG bit */
4912         tcp_urg(sk, skb, th);
4913
4914         /* step 7: process the segment text */
4915         switch (sk->sk_state) {
4916         case TCP_CLOSE_WAIT:
4917         case TCP_CLOSING:
4918         case TCP_LAST_ACK:
4919                 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4920                         break;
4921         case TCP_FIN_WAIT1:
4922         case TCP_FIN_WAIT2:
4923                 /* RFC 793 says to queue data in these states,
4924                  * RFC 1122 says we MUST send a reset. 
4925                  * BSD 4.4 also does reset.
4926                  */
4927                 if (sk->sk_shutdown & RCV_SHUTDOWN) {
4928                         if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4929                             after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
4930                                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4931                                 tcp_reset(sk);
4932                                 return 1;
4933                         }
4934                 }
4935                 /* Fall through */
4936         case TCP_ESTABLISHED: 
4937                 tcp_data_queue(sk, skb);
4938                 queued = 1;
4939                 break;
4940         }
4941
4942         /* tcp_data could move socket to TIME-WAIT */
4943         if (sk->sk_state != TCP_CLOSE) {
4944                 tcp_data_snd_check(sk);
4945                 tcp_ack_snd_check(sk);
4946         }
4947
4948         if (!queued) { 
4949 discard:
4950                 __kfree_skb(skb);
4951         }
4952         return 0;
4953 }
4954
4955 EXPORT_SYMBOL(sysctl_tcp_ecn);
4956 EXPORT_SYMBOL(sysctl_tcp_reordering);
4957 EXPORT_SYMBOL(tcp_parse_options);
4958 EXPORT_SYMBOL(tcp_rcv_established);
4959 EXPORT_SYMBOL(tcp_rcv_state_process);