SELinux: Return correct context for SO_PEERSEC
[linux-3.10.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
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 presence 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  */
65
66 #include <linux/mm.h>
67 #include <linux/module.h>
68 #include <linux/sysctl.h>
69 #include <net/tcp.h>
70 #include <net/inet_common.h>
71 #include <linux/ipsec.h>
72 #include <asm/unaligned.h>
73 #include <net/netdma.h>
74
75 int sysctl_tcp_timestamps __read_mostly = 1;
76 int sysctl_tcp_window_scaling __read_mostly = 1;
77 int sysctl_tcp_sack __read_mostly = 1;
78 int sysctl_tcp_fack __read_mostly = 1;
79 int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH;
80 int sysctl_tcp_ecn __read_mostly;
81 int sysctl_tcp_dsack __read_mostly = 1;
82 int sysctl_tcp_app_win __read_mostly = 31;
83 int sysctl_tcp_adv_win_scale __read_mostly = 2;
84
85 int sysctl_tcp_stdurg __read_mostly;
86 int sysctl_tcp_rfc1337 __read_mostly;
87 int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
88 int sysctl_tcp_frto __read_mostly;
89 int sysctl_tcp_nometrics_save __read_mostly;
90
91 int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
92 int sysctl_tcp_abc __read_mostly;
93
94 #define FLAG_DATA               0x01 /* Incoming frame contained data.          */
95 #define FLAG_WIN_UPDATE         0x02 /* Incoming ACK was a window update.       */
96 #define FLAG_DATA_ACKED         0x04 /* This ACK acknowledged new data.         */
97 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted.  */
98 #define FLAG_SYN_ACKED          0x10 /* This ACK acknowledged SYN.              */
99 #define FLAG_DATA_SACKED        0x20 /* New SACK.                               */
100 #define FLAG_ECE                0x40 /* ECE in this ACK                         */
101 #define FLAG_DATA_LOST          0x80 /* SACK detected data lossage.             */
102 #define FLAG_SLOWPATH           0x100 /* Do not skip RFC checks for window update.*/
103
104 #define FLAG_ACKED              (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
105 #define FLAG_NOT_DUP            (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
106 #define FLAG_CA_ALERT           (FLAG_DATA_SACKED|FLAG_ECE)
107 #define FLAG_FORWARD_PROGRESS   (FLAG_ACKED|FLAG_DATA_SACKED)
108
109 #define IsReno(tp) ((tp)->rx_opt.sack_ok == 0)
110 #define IsFack(tp) ((tp)->rx_opt.sack_ok & 2)
111 #define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4)
112
113 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
114
115 /* Adapt the MSS value used to make delayed ack decision to the 
116  * real world.
117  */ 
118 static void tcp_measure_rcv_mss(struct sock *sk,
119                                 const struct sk_buff *skb)
120 {
121         struct inet_connection_sock *icsk = inet_csk(sk);
122         const unsigned int lss = icsk->icsk_ack.last_seg_size; 
123         unsigned int len;
124
125         icsk->icsk_ack.last_seg_size = 0; 
126
127         /* skb->len may jitter because of SACKs, even if peer
128          * sends good full-sized frames.
129          */
130         len = skb_shinfo(skb)->gso_size ?: skb->len;
131         if (len >= icsk->icsk_ack.rcv_mss) {
132                 icsk->icsk_ack.rcv_mss = len;
133         } else {
134                 /* Otherwise, we make more careful check taking into account,
135                  * that SACKs block is variable.
136                  *
137                  * "len" is invariant segment length, including TCP header.
138                  */
139                 len += skb->data - skb->h.raw;
140                 if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) ||
141                     /* If PSH is not set, packet should be
142                      * full sized, provided peer TCP is not badly broken.
143                      * This observation (if it is correct 8)) allows
144                      * to handle super-low mtu links fairly.
145                      */
146                     (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
147                      !(tcp_flag_word(skb->h.th)&TCP_REMNANT))) {
148                         /* Subtract also invariant (if peer is RFC compliant),
149                          * tcp header plus fixed timestamp option length.
150                          * Resulting "len" is MSS free of SACK jitter.
151                          */
152                         len -= tcp_sk(sk)->tcp_header_len;
153                         icsk->icsk_ack.last_seg_size = len;
154                         if (len == lss) {
155                                 icsk->icsk_ack.rcv_mss = len;
156                                 return;
157                         }
158                 }
159                 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)
160                         icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2;
161                 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED;
162         }
163 }
164
165 static void tcp_incr_quickack(struct sock *sk)
166 {
167         struct inet_connection_sock *icsk = inet_csk(sk);
168         unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss);
169
170         if (quickacks==0)
171                 quickacks=2;
172         if (quickacks > icsk->icsk_ack.quick)
173                 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
174 }
175
176 void tcp_enter_quickack_mode(struct sock *sk)
177 {
178         struct inet_connection_sock *icsk = inet_csk(sk);
179         tcp_incr_quickack(sk);
180         icsk->icsk_ack.pingpong = 0;
181         icsk->icsk_ack.ato = TCP_ATO_MIN;
182 }
183
184 /* Send ACKs quickly, if "quick" count is not exhausted
185  * and the session is not interactive.
186  */
187
188 static inline int tcp_in_quickack_mode(const struct sock *sk)
189 {
190         const struct inet_connection_sock *icsk = inet_csk(sk);
191         return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong;
192 }
193
194 /* Buffer size and advertised window tuning.
195  *
196  * 1. Tuning sk->sk_sndbuf, when connection enters established state.
197  */
198
199 static void tcp_fixup_sndbuf(struct sock *sk)
200 {
201         int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 +
202                      sizeof(struct sk_buff);
203
204         if (sk->sk_sndbuf < 3 * sndmem)
205                 sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]);
206 }
207
208 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
209  *
210  * All tcp_full_space() is split to two parts: "network" buffer, allocated
211  * forward and advertised in receiver window (tp->rcv_wnd) and
212  * "application buffer", required to isolate scheduling/application
213  * latencies from network.
214  * window_clamp is maximal advertised window. It can be less than
215  * tcp_full_space(), in this case tcp_full_space() - window_clamp
216  * is reserved for "application" buffer. The less window_clamp is
217  * the smoother our behaviour from viewpoint of network, but the lower
218  * throughput and the higher sensitivity of the connection to losses. 8)
219  *
220  * rcv_ssthresh is more strict window_clamp used at "slow start"
221  * phase to predict further behaviour of this connection.
222  * It is used for two goals:
223  * - to enforce header prediction at sender, even when application
224  *   requires some significant "application buffer". It is check #1.
225  * - to prevent pruning of receive queue because of misprediction
226  *   of receiver window. Check #2.
227  *
228  * The scheme does not work when sender sends good segments opening
229  * window and then starts to feed us spaghetti. But it should work
230  * in common situations. Otherwise, we have to rely on queue collapsing.
231  */
232
233 /* Slow part of check#2. */
234 static int __tcp_grow_window(const struct sock *sk, struct tcp_sock *tp,
235                              const struct sk_buff *skb)
236 {
237         /* Optimize this! */
238         int truesize = tcp_win_from_space(skb->truesize)/2;
239         int window = tcp_win_from_space(sysctl_tcp_rmem[2])/2;
240
241         while (tp->rcv_ssthresh <= window) {
242                 if (truesize <= skb->len)
243                         return 2 * inet_csk(sk)->icsk_ack.rcv_mss;
244
245                 truesize >>= 1;
246                 window >>= 1;
247         }
248         return 0;
249 }
250
251 static void tcp_grow_window(struct sock *sk, struct tcp_sock *tp,
252                             struct sk_buff *skb)
253 {
254         /* Check #1 */
255         if (tp->rcv_ssthresh < tp->window_clamp &&
256             (int)tp->rcv_ssthresh < tcp_space(sk) &&
257             !tcp_memory_pressure) {
258                 int incr;
259
260                 /* Check #2. Increase window, if skb with such overhead
261                  * will fit to rcvbuf in future.
262                  */
263                 if (tcp_win_from_space(skb->truesize) <= skb->len)
264                         incr = 2*tp->advmss;
265                 else
266                         incr = __tcp_grow_window(sk, tp, skb);
267
268                 if (incr) {
269                         tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp);
270                         inet_csk(sk)->icsk_ack.quick |= 1;
271                 }
272         }
273 }
274
275 /* 3. Tuning rcvbuf, when connection enters established state. */
276
277 static void tcp_fixup_rcvbuf(struct sock *sk)
278 {
279         struct tcp_sock *tp = tcp_sk(sk);
280         int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
281
282         /* Try to select rcvbuf so that 4 mss-sized segments
283          * will fit to window and corresponding skbs will fit to our rcvbuf.
284          * (was 3; 4 is minimum to allow fast retransmit to work.)
285          */
286         while (tcp_win_from_space(rcvmem) < tp->advmss)
287                 rcvmem += 128;
288         if (sk->sk_rcvbuf < 4 * rcvmem)
289                 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]);
290 }
291
292 /* 4. Try to fixup all. It is made immediately after connection enters
293  *    established state.
294  */
295 static void tcp_init_buffer_space(struct sock *sk)
296 {
297         struct tcp_sock *tp = tcp_sk(sk);
298         int maxwin;
299
300         if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
301                 tcp_fixup_rcvbuf(sk);
302         if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
303                 tcp_fixup_sndbuf(sk);
304
305         tp->rcvq_space.space = tp->rcv_wnd;
306
307         maxwin = tcp_full_space(sk);
308
309         if (tp->window_clamp >= maxwin) {
310                 tp->window_clamp = maxwin;
311
312                 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
313                         tp->window_clamp = max(maxwin -
314                                                (maxwin >> sysctl_tcp_app_win),
315                                                4 * tp->advmss);
316         }
317
318         /* Force reservation of one segment. */
319         if (sysctl_tcp_app_win &&
320             tp->window_clamp > 2 * tp->advmss &&
321             tp->window_clamp + tp->advmss > maxwin)
322                 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
323
324         tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
325         tp->snd_cwnd_stamp = tcp_time_stamp;
326 }
327
328 /* 5. Recalculate window clamp after socket hit its memory bounds. */
329 static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp)
330 {
331         struct inet_connection_sock *icsk = inet_csk(sk);
332
333         icsk->icsk_ack.quick = 0;
334
335         if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
336             !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
337             !tcp_memory_pressure &&
338             atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
339                 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
340                                     sysctl_tcp_rmem[2]);
341         }
342         if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
343                 tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss);
344 }
345
346
347 /* Initialize RCV_MSS value.
348  * RCV_MSS is an our guess about MSS used by the peer.
349  * We haven't any direct information about the MSS.
350  * It's better to underestimate the RCV_MSS rather than overestimate.
351  * Overestimations make us ACKing less frequently than needed.
352  * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
353  */
354 void tcp_initialize_rcv_mss(struct sock *sk)
355 {
356         struct tcp_sock *tp = tcp_sk(sk);
357         unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache);
358
359         hint = min(hint, tp->rcv_wnd/2);
360         hint = min(hint, TCP_MIN_RCVMSS);
361         hint = max(hint, TCP_MIN_MSS);
362
363         inet_csk(sk)->icsk_ack.rcv_mss = hint;
364 }
365
366 /* Receiver "autotuning" code.
367  *
368  * The algorithm for RTT estimation w/o timestamps is based on
369  * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
370  * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
371  *
372  * More detail on this code can be found at
373  * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
374  * though this reference is out of date.  A new paper
375  * is pending.
376  */
377 static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
378 {
379         u32 new_sample = tp->rcv_rtt_est.rtt;
380         long m = sample;
381
382         if (m == 0)
383                 m = 1;
384
385         if (new_sample != 0) {
386                 /* If we sample in larger samples in the non-timestamp
387                  * case, we could grossly overestimate the RTT especially
388                  * with chatty applications or bulk transfer apps which
389                  * are stalled on filesystem I/O.
390                  *
391                  * Also, since we are only going for a minimum in the
392                  * non-timestamp case, we do not smooth things out
393                  * else with timestamps disabled convergence takes too
394                  * long.
395                  */
396                 if (!win_dep) {
397                         m -= (new_sample >> 3);
398                         new_sample += m;
399                 } else if (m < new_sample)
400                         new_sample = m << 3;
401         } else {
402                 /* No previous measure. */
403                 new_sample = m << 3;
404         }
405
406         if (tp->rcv_rtt_est.rtt != new_sample)
407                 tp->rcv_rtt_est.rtt = new_sample;
408 }
409
410 static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
411 {
412         if (tp->rcv_rtt_est.time == 0)
413                 goto new_measure;
414         if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
415                 return;
416         tcp_rcv_rtt_update(tp,
417                            jiffies - tp->rcv_rtt_est.time,
418                            1);
419
420 new_measure:
421         tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
422         tp->rcv_rtt_est.time = tcp_time_stamp;
423 }
424
425 static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, const struct sk_buff *skb)
426 {
427         struct tcp_sock *tp = tcp_sk(sk);
428         if (tp->rx_opt.rcv_tsecr &&
429             (TCP_SKB_CB(skb)->end_seq -
430              TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss))
431                 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
432 }
433
434 /*
435  * This function should be called every time data is copied to user space.
436  * It calculates the appropriate TCP receive buffer space.
437  */
438 void tcp_rcv_space_adjust(struct sock *sk)
439 {
440         struct tcp_sock *tp = tcp_sk(sk);
441         int time;
442         int space;
443         
444         if (tp->rcvq_space.time == 0)
445                 goto new_measure;
446         
447         time = tcp_time_stamp - tp->rcvq_space.time;
448         if (time < (tp->rcv_rtt_est.rtt >> 3) ||
449             tp->rcv_rtt_est.rtt == 0)
450                 return;
451         
452         space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
453
454         space = max(tp->rcvq_space.space, space);
455
456         if (tp->rcvq_space.space != space) {
457                 int rcvmem;
458
459                 tp->rcvq_space.space = space;
460
461                 if (sysctl_tcp_moderate_rcvbuf &&
462                     !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
463                         int new_clamp = space;
464
465                         /* Receive space grows, normalize in order to
466                          * take into account packet headers and sk_buff
467                          * structure overhead.
468                          */
469                         space /= tp->advmss;
470                         if (!space)
471                                 space = 1;
472                         rcvmem = (tp->advmss + MAX_TCP_HEADER +
473                                   16 + sizeof(struct sk_buff));
474                         while (tcp_win_from_space(rcvmem) < tp->advmss)
475                                 rcvmem += 128;
476                         space *= rcvmem;
477                         space = min(space, sysctl_tcp_rmem[2]);
478                         if (space > sk->sk_rcvbuf) {
479                                 sk->sk_rcvbuf = space;
480
481                                 /* Make the window clamp follow along.  */
482                                 tp->window_clamp = new_clamp;
483                         }
484                 }
485         }
486         
487 new_measure:
488         tp->rcvq_space.seq = tp->copied_seq;
489         tp->rcvq_space.time = tcp_time_stamp;
490 }
491
492 /* There is something which you must keep in mind when you analyze the
493  * behavior of the tp->ato delayed ack timeout interval.  When a
494  * connection starts up, we want to ack as quickly as possible.  The
495  * problem is that "good" TCP's do slow start at the beginning of data
496  * transmission.  The means that until we send the first few ACK's the
497  * sender will sit on his end and only queue most of his data, because
498  * he can only send snd_cwnd unacked packets at any given time.  For
499  * each ACK we send, he increments snd_cwnd and transmits more of his
500  * queue.  -DaveM
501  */
502 static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb)
503 {
504         struct inet_connection_sock *icsk = inet_csk(sk);
505         u32 now;
506
507         inet_csk_schedule_ack(sk);
508
509         tcp_measure_rcv_mss(sk, skb);
510
511         tcp_rcv_rtt_measure(tp);
512         
513         now = tcp_time_stamp;
514
515         if (!icsk->icsk_ack.ato) {
516                 /* The _first_ data packet received, initialize
517                  * delayed ACK engine.
518                  */
519                 tcp_incr_quickack(sk);
520                 icsk->icsk_ack.ato = TCP_ATO_MIN;
521         } else {
522                 int m = now - icsk->icsk_ack.lrcvtime;
523
524                 if (m <= TCP_ATO_MIN/2) {
525                         /* The fastest case is the first. */
526                         icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2;
527                 } else if (m < icsk->icsk_ack.ato) {
528                         icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m;
529                         if (icsk->icsk_ack.ato > icsk->icsk_rto)
530                                 icsk->icsk_ack.ato = icsk->icsk_rto;
531                 } else if (m > icsk->icsk_rto) {
532                         /* Too long gap. Apparently sender failed to
533                          * restart window, so that we send ACKs quickly.
534                          */
535                         tcp_incr_quickack(sk);
536                         sk_stream_mem_reclaim(sk);
537                 }
538         }
539         icsk->icsk_ack.lrcvtime = now;
540
541         TCP_ECN_check_ce(tp, skb);
542
543         if (skb->len >= 128)
544                 tcp_grow_window(sk, tp, skb);
545 }
546
547 /* Called to compute a smoothed rtt estimate. The data fed to this
548  * routine either comes from timestamps, or from segments that were
549  * known _not_ to have been retransmitted [see Karn/Partridge
550  * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
551  * piece by Van Jacobson.
552  * NOTE: the next three routines used to be one big routine.
553  * To save cycles in the RFC 1323 implementation it was better to break
554  * it up into three procedures. -- erics
555  */
556 static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt)
557 {
558         struct tcp_sock *tp = tcp_sk(sk);
559         long m = mrtt; /* RTT */
560
561         /*      The following amusing code comes from Jacobson's
562          *      article in SIGCOMM '88.  Note that rtt and mdev
563          *      are scaled versions of rtt and mean deviation.
564          *      This is designed to be as fast as possible 
565          *      m stands for "measurement".
566          *
567          *      On a 1990 paper the rto value is changed to:
568          *      RTO = rtt + 4 * mdev
569          *
570          * Funny. This algorithm seems to be very broken.
571          * These formulae increase RTO, when it should be decreased, increase
572          * too slowly, when it should be increased quickly, decrease too quickly
573          * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
574          * does not matter how to _calculate_ it. Seems, it was trap
575          * that VJ failed to avoid. 8)
576          */
577         if(m == 0)
578                 m = 1;
579         if (tp->srtt != 0) {
580                 m -= (tp->srtt >> 3);   /* m is now error in rtt est */
581                 tp->srtt += m;          /* rtt = 7/8 rtt + 1/8 new */
582                 if (m < 0) {
583                         m = -m;         /* m is now abs(error) */
584                         m -= (tp->mdev >> 2);   /* similar update on mdev */
585                         /* This is similar to one of Eifel findings.
586                          * Eifel blocks mdev updates when rtt decreases.
587                          * This solution is a bit different: we use finer gain
588                          * for mdev in this case (alpha*beta).
589                          * Like Eifel it also prevents growth of rto,
590                          * but also it limits too fast rto decreases,
591                          * happening in pure Eifel.
592                          */
593                         if (m > 0)
594                                 m >>= 3;
595                 } else {
596                         m -= (tp->mdev >> 2);   /* similar update on mdev */
597                 }
598                 tp->mdev += m;          /* mdev = 3/4 mdev + 1/4 new */
599                 if (tp->mdev > tp->mdev_max) {
600                         tp->mdev_max = tp->mdev;
601                         if (tp->mdev_max > tp->rttvar)
602                                 tp->rttvar = tp->mdev_max;
603                 }
604                 if (after(tp->snd_una, tp->rtt_seq)) {
605                         if (tp->mdev_max < tp->rttvar)
606                                 tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2;
607                         tp->rtt_seq = tp->snd_nxt;
608                         tp->mdev_max = TCP_RTO_MIN;
609                 }
610         } else {
611                 /* no previous measure. */
612                 tp->srtt = m<<3;        /* take the measured time to be rtt */
613                 tp->mdev = m<<1;        /* make sure rto = 3*rtt */
614                 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
615                 tp->rtt_seq = tp->snd_nxt;
616         }
617 }
618
619 /* Calculate rto without backoff.  This is the second half of Van Jacobson's
620  * routine referred to above.
621  */
622 static inline void tcp_set_rto(struct sock *sk)
623 {
624         const struct tcp_sock *tp = tcp_sk(sk);
625         /* Old crap is replaced with new one. 8)
626          *
627          * More seriously:
628          * 1. If rtt variance happened to be less 50msec, it is hallucination.
629          *    It cannot be less due to utterly erratic ACK generation made
630          *    at least by solaris and freebsd. "Erratic ACKs" has _nothing_
631          *    to do with delayed acks, because at cwnd>2 true delack timeout
632          *    is invisible. Actually, Linux-2.4 also generates erratic
633          *    ACKs in some circumstances.
634          */
635         inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar;
636
637         /* 2. Fixups made earlier cannot be right.
638          *    If we do not estimate RTO correctly without them,
639          *    all the algo is pure shit and should be replaced
640          *    with correct one. It is exactly, which we pretend to do.
641          */
642 }
643
644 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
645  * guarantees that rto is higher.
646  */
647 static inline void tcp_bound_rto(struct sock *sk)
648 {
649         if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
650                 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
651 }
652
653 /* Save metrics learned by this TCP session.
654    This function is called only, when TCP finishes successfully
655    i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
656  */
657 void tcp_update_metrics(struct sock *sk)
658 {
659         struct tcp_sock *tp = tcp_sk(sk);
660         struct dst_entry *dst = __sk_dst_get(sk);
661
662         if (sysctl_tcp_nometrics_save)
663                 return;
664
665         dst_confirm(dst);
666
667         if (dst && (dst->flags&DST_HOST)) {
668                 const struct inet_connection_sock *icsk = inet_csk(sk);
669                 int m;
670
671                 if (icsk->icsk_backoff || !tp->srtt) {
672                         /* This session failed to estimate rtt. Why?
673                          * Probably, no packets returned in time.
674                          * Reset our results.
675                          */
676                         if (!(dst_metric_locked(dst, RTAX_RTT)))
677                                 dst->metrics[RTAX_RTT-1] = 0;
678                         return;
679                 }
680
681                 m = dst_metric(dst, RTAX_RTT) - tp->srtt;
682
683                 /* If newly calculated rtt larger than stored one,
684                  * store new one. Otherwise, use EWMA. Remember,
685                  * rtt overestimation is always better than underestimation.
686                  */
687                 if (!(dst_metric_locked(dst, RTAX_RTT))) {
688                         if (m <= 0)
689                                 dst->metrics[RTAX_RTT-1] = tp->srtt;
690                         else
691                                 dst->metrics[RTAX_RTT-1] -= (m>>3);
692                 }
693
694                 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
695                         if (m < 0)
696                                 m = -m;
697
698                         /* Scale deviation to rttvar fixed point */
699                         m >>= 1;
700                         if (m < tp->mdev)
701                                 m = tp->mdev;
702
703                         if (m >= dst_metric(dst, RTAX_RTTVAR))
704                                 dst->metrics[RTAX_RTTVAR-1] = m;
705                         else
706                                 dst->metrics[RTAX_RTTVAR-1] -=
707                                         (dst->metrics[RTAX_RTTVAR-1] - m)>>2;
708                 }
709
710                 if (tp->snd_ssthresh >= 0xFFFF) {
711                         /* Slow start still did not finish. */
712                         if (dst_metric(dst, RTAX_SSTHRESH) &&
713                             !dst_metric_locked(dst, RTAX_SSTHRESH) &&
714                             (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
715                                 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
716                         if (!dst_metric_locked(dst, RTAX_CWND) &&
717                             tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
718                                 dst->metrics[RTAX_CWND-1] = tp->snd_cwnd;
719                 } else if (tp->snd_cwnd > tp->snd_ssthresh &&
720                            icsk->icsk_ca_state == TCP_CA_Open) {
721                         /* Cong. avoidance phase, cwnd is reliable. */
722                         if (!dst_metric_locked(dst, RTAX_SSTHRESH))
723                                 dst->metrics[RTAX_SSTHRESH-1] =
724                                         max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
725                         if (!dst_metric_locked(dst, RTAX_CWND))
726                                 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1;
727                 } else {
728                         /* Else slow start did not finish, cwnd is non-sense,
729                            ssthresh may be also invalid.
730                          */
731                         if (!dst_metric_locked(dst, RTAX_CWND))
732                                 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1;
733                         if (dst->metrics[RTAX_SSTHRESH-1] &&
734                             !dst_metric_locked(dst, RTAX_SSTHRESH) &&
735                             tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1])
736                                 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
737                 }
738
739                 if (!dst_metric_locked(dst, RTAX_REORDERING)) {
740                         if (dst->metrics[RTAX_REORDERING-1] < tp->reordering &&
741                             tp->reordering != sysctl_tcp_reordering)
742                                 dst->metrics[RTAX_REORDERING-1] = tp->reordering;
743                 }
744         }
745 }
746
747 /* Numbers are taken from RFC2414.  */
748 __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
749 {
750         __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
751
752         if (!cwnd) {
753                 if (tp->mss_cache > 1460)
754                         cwnd = 2;
755                 else
756                         cwnd = (tp->mss_cache > 1095) ? 3 : 4;
757         }
758         return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
759 }
760
761 /* Set slow start threshold and cwnd not falling to slow start */
762 void tcp_enter_cwr(struct sock *sk)
763 {
764         struct tcp_sock *tp = tcp_sk(sk);
765
766         tp->prior_ssthresh = 0;
767         tp->bytes_acked = 0;
768         if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
769                 tp->undo_marker = 0;
770                 tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk);
771                 tp->snd_cwnd = min(tp->snd_cwnd,
772                                    tcp_packets_in_flight(tp) + 1U);
773                 tp->snd_cwnd_cnt = 0;
774                 tp->high_seq = tp->snd_nxt;
775                 tp->snd_cwnd_stamp = tcp_time_stamp;
776                 TCP_ECN_queue_cwr(tp);
777
778                 tcp_set_ca_state(sk, TCP_CA_CWR);
779         }
780 }
781
782 /* Initialize metrics on socket. */
783
784 static void tcp_init_metrics(struct sock *sk)
785 {
786         struct tcp_sock *tp = tcp_sk(sk);
787         struct dst_entry *dst = __sk_dst_get(sk);
788
789         if (dst == NULL)
790                 goto reset;
791
792         dst_confirm(dst);
793
794         if (dst_metric_locked(dst, RTAX_CWND))
795                 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
796         if (dst_metric(dst, RTAX_SSTHRESH)) {
797                 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
798                 if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
799                         tp->snd_ssthresh = tp->snd_cwnd_clamp;
800         }
801         if (dst_metric(dst, RTAX_REORDERING) &&
802             tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
803                 tp->rx_opt.sack_ok &= ~2;
804                 tp->reordering = dst_metric(dst, RTAX_REORDERING);
805         }
806
807         if (dst_metric(dst, RTAX_RTT) == 0)
808                 goto reset;
809
810         if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
811                 goto reset;
812
813         /* Initial rtt is determined from SYN,SYN-ACK.
814          * The segment is small and rtt may appear much
815          * less than real one. Use per-dst memory
816          * to make it more realistic.
817          *
818          * A bit of theory. RTT is time passed after "normal" sized packet
819          * is sent until it is ACKed. In normal circumstances sending small
820          * packets force peer to delay ACKs and calculation is correct too.
821          * The algorithm is adaptive and, provided we follow specs, it
822          * NEVER underestimate RTT. BUT! If peer tries to make some clever
823          * tricks sort of "quick acks" for time long enough to decrease RTT
824          * to low value, and then abruptly stops to do it and starts to delay
825          * ACKs, wait for troubles.
826          */
827         if (dst_metric(dst, RTAX_RTT) > tp->srtt) {
828                 tp->srtt = dst_metric(dst, RTAX_RTT);
829                 tp->rtt_seq = tp->snd_nxt;
830         }
831         if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
832                 tp->mdev = dst_metric(dst, RTAX_RTTVAR);
833                 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
834         }
835         tcp_set_rto(sk);
836         tcp_bound_rto(sk);
837         if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
838                 goto reset;
839         tp->snd_cwnd = tcp_init_cwnd(tp, dst);
840         tp->snd_cwnd_stamp = tcp_time_stamp;
841         return;
842
843 reset:
844         /* Play conservative. If timestamps are not
845          * supported, TCP will fail to recalculate correct
846          * rtt, if initial rto is too small. FORGET ALL AND RESET!
847          */
848         if (!tp->rx_opt.saw_tstamp && tp->srtt) {
849                 tp->srtt = 0;
850                 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
851                 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
852         }
853 }
854
855 static void tcp_update_reordering(struct sock *sk, const int metric,
856                                   const int ts)
857 {
858         struct tcp_sock *tp = tcp_sk(sk);
859         if (metric > tp->reordering) {
860                 tp->reordering = min(TCP_MAX_REORDERING, metric);
861
862                 /* This exciting event is worth to be remembered. 8) */
863                 if (ts)
864                         NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER);
865                 else if (IsReno(tp))
866                         NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER);
867                 else if (IsFack(tp))
868                         NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER);
869                 else
870                         NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER);
871 #if FASTRETRANS_DEBUG > 1
872                 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
873                        tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state,
874                        tp->reordering,
875                        tp->fackets_out,
876                        tp->sacked_out,
877                        tp->undo_marker ? tp->undo_retrans : 0);
878 #endif
879                 /* Disable FACK yet. */
880                 tp->rx_opt.sack_ok &= ~2;
881         }
882 }
883
884 /* This procedure tags the retransmission queue when SACKs arrive.
885  *
886  * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
887  * Packets in queue with these bits set are counted in variables
888  * sacked_out, retrans_out and lost_out, correspondingly.
889  *
890  * Valid combinations are:
891  * Tag  InFlight        Description
892  * 0    1               - orig segment is in flight.
893  * S    0               - nothing flies, orig reached receiver.
894  * L    0               - nothing flies, orig lost by net.
895  * R    2               - both orig and retransmit are in flight.
896  * L|R  1               - orig is lost, retransmit is in flight.
897  * S|R  1               - orig reached receiver, retrans is still in flight.
898  * (L|S|R is logically valid, it could occur when L|R is sacked,
899  *  but it is equivalent to plain S and code short-curcuits it to S.
900  *  L|S is logically invalid, it would mean -1 packet in flight 8))
901  *
902  * These 6 states form finite state machine, controlled by the following events:
903  * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
904  * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
905  * 3. Loss detection event of one of three flavors:
906  *      A. Scoreboard estimator decided the packet is lost.
907  *         A'. Reno "three dupacks" marks head of queue lost.
908  *         A''. Its FACK modfication, head until snd.fack is lost.
909  *      B. SACK arrives sacking data transmitted after never retransmitted
910  *         hole was sent out.
911  *      C. SACK arrives sacking SND.NXT at the moment, when the
912  *         segment was retransmitted.
913  * 4. D-SACK added new rule: D-SACK changes any tag to S.
914  *
915  * It is pleasant to note, that state diagram turns out to be commutative,
916  * so that we are allowed not to be bothered by order of our actions,
917  * when multiple events arrive simultaneously. (see the function below).
918  *
919  * Reordering detection.
920  * --------------------
921  * Reordering metric is maximal distance, which a packet can be displaced
922  * in packet stream. With SACKs we can estimate it:
923  *
924  * 1. SACK fills old hole and the corresponding segment was not
925  *    ever retransmitted -> reordering. Alas, we cannot use it
926  *    when segment was retransmitted.
927  * 2. The last flaw is solved with D-SACK. D-SACK arrives
928  *    for retransmitted and already SACKed segment -> reordering..
929  * Both of these heuristics are not used in Loss state, when we cannot
930  * account for retransmits accurately.
931  */
932 static int
933 tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
934 {
935         const struct inet_connection_sock *icsk = inet_csk(sk);
936         struct tcp_sock *tp = tcp_sk(sk);
937         unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked;
938         struct tcp_sack_block_wire *sp = (struct tcp_sack_block_wire *)(ptr+2);
939         int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
940         int reord = tp->packets_out;
941         int prior_fackets;
942         u32 lost_retrans = 0;
943         int flag = 0;
944         int dup_sack = 0;
945         int i;
946
947         if (!tp->sacked_out)
948                 tp->fackets_out = 0;
949         prior_fackets = tp->fackets_out;
950
951         /* SACK fastpath:
952          * if the only SACK change is the increase of the end_seq of
953          * the first block then only apply that SACK block
954          * and use retrans queue hinting otherwise slowpath */
955         flag = 1;
956         for (i = 0; i< num_sacks; i++) {
957                 __u32 start_seq = ntohl(sp[i].start_seq);
958                 __u32 end_seq =  ntohl(sp[i].end_seq);
959
960                 if (i == 0){
961                         if (tp->recv_sack_cache[i].start_seq != start_seq)
962                                 flag = 0;
963                 } else {
964                         if ((tp->recv_sack_cache[i].start_seq != start_seq) ||
965                             (tp->recv_sack_cache[i].end_seq != end_seq))
966                                 flag = 0;
967                 }
968                 tp->recv_sack_cache[i].start_seq = start_seq;
969                 tp->recv_sack_cache[i].end_seq = end_seq;
970
971                 /* Check for D-SACK. */
972                 if (i == 0) {
973                         u32 ack = TCP_SKB_CB(ack_skb)->ack_seq;
974
975                         if (before(start_seq, ack)) {
976                                 dup_sack = 1;
977                                 tp->rx_opt.sack_ok |= 4;
978                                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
979                         } else if (num_sacks > 1 &&
980                                    !after(end_seq, ntohl(sp[1].end_seq)) &&
981                                    !before(start_seq, ntohl(sp[1].start_seq))) {
982                                 dup_sack = 1;
983                                 tp->rx_opt.sack_ok |= 4;
984                                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
985                         }
986
987                         /* D-SACK for already forgotten data...
988                          * Do dumb counting. */
989                         if (dup_sack &&
990                             !after(end_seq, prior_snd_una) &&
991                             after(end_seq, tp->undo_marker))
992                                 tp->undo_retrans--;
993
994                         /* Eliminate too old ACKs, but take into
995                          * account more or less fresh ones, they can
996                          * contain valid SACK info.
997                          */
998                         if (before(ack, prior_snd_una - tp->max_window))
999                                 return 0;
1000                 }
1001         }
1002
1003         if (flag)
1004                 num_sacks = 1;
1005         else {
1006                 int j;
1007                 tp->fastpath_skb_hint = NULL;
1008
1009                 /* order SACK blocks to allow in order walk of the retrans queue */
1010                 for (i = num_sacks-1; i > 0; i--) {
1011                         for (j = 0; j < i; j++){
1012                                 if (after(ntohl(sp[j].start_seq),
1013                                           ntohl(sp[j+1].start_seq))){
1014                                         sp[j].start_seq = htonl(tp->recv_sack_cache[j+1].start_seq);
1015                                         sp[j].end_seq = htonl(tp->recv_sack_cache[j+1].end_seq);
1016                                         sp[j+1].start_seq = htonl(tp->recv_sack_cache[j].start_seq);
1017                                         sp[j+1].end_seq = htonl(tp->recv_sack_cache[j].end_seq);
1018                                 }
1019
1020                         }
1021                 }
1022         }
1023
1024         /* clear flag as used for different purpose in following code */
1025         flag = 0;
1026
1027         for (i=0; i<num_sacks; i++, sp++) {
1028                 struct sk_buff *skb;
1029                 __u32 start_seq = ntohl(sp->start_seq);
1030                 __u32 end_seq = ntohl(sp->end_seq);
1031                 int fack_count;
1032
1033                 /* Use SACK fastpath hint if valid */
1034                 if (tp->fastpath_skb_hint) {
1035                         skb = tp->fastpath_skb_hint;
1036                         fack_count = tp->fastpath_cnt_hint;
1037                 } else {
1038                         skb = sk->sk_write_queue.next;
1039                         fack_count = 0;
1040                 }
1041
1042                 /* Event "B" in the comment above. */
1043                 if (after(end_seq, tp->high_seq))
1044                         flag |= FLAG_DATA_LOST;
1045
1046                 sk_stream_for_retrans_queue_from(skb, sk) {
1047                         int in_sack, pcount;
1048                         u8 sacked;
1049
1050                         tp->fastpath_skb_hint = skb;
1051                         tp->fastpath_cnt_hint = fack_count;
1052
1053                         /* The retransmission queue is always in order, so
1054                          * we can short-circuit the walk early.
1055                          */
1056                         if (!before(TCP_SKB_CB(skb)->seq, end_seq))
1057                                 break;
1058
1059                         in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1060                                 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1061
1062                         pcount = tcp_skb_pcount(skb);
1063
1064                         if (pcount > 1 && !in_sack &&
1065                             after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
1066                                 unsigned int pkt_len;
1067
1068                                 in_sack = !after(start_seq,
1069                                                  TCP_SKB_CB(skb)->seq);
1070
1071                                 if (!in_sack)
1072                                         pkt_len = (start_seq -
1073                                                    TCP_SKB_CB(skb)->seq);
1074                                 else
1075                                         pkt_len = (end_seq -
1076                                                    TCP_SKB_CB(skb)->seq);
1077                                 if (tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size))
1078                                         break;
1079                                 pcount = tcp_skb_pcount(skb);
1080                         }
1081
1082                         fack_count += pcount;
1083
1084                         sacked = TCP_SKB_CB(skb)->sacked;
1085
1086                         /* Account D-SACK for retransmitted packet. */
1087                         if ((dup_sack && in_sack) &&
1088                             (sacked & TCPCB_RETRANS) &&
1089                             after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
1090                                 tp->undo_retrans--;
1091
1092                         /* The frame is ACKed. */
1093                         if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
1094                                 if (sacked&TCPCB_RETRANS) {
1095                                         if ((dup_sack && in_sack) &&
1096                                             (sacked&TCPCB_SACKED_ACKED))
1097                                                 reord = min(fack_count, reord);
1098                                 } else {
1099                                         /* If it was in a hole, we detected reordering. */
1100                                         if (fack_count < prior_fackets &&
1101                                             !(sacked&TCPCB_SACKED_ACKED))
1102                                                 reord = min(fack_count, reord);
1103                                 }
1104
1105                                 /* Nothing to do; acked frame is about to be dropped. */
1106                                 continue;
1107                         }
1108
1109                         if ((sacked&TCPCB_SACKED_RETRANS) &&
1110                             after(end_seq, TCP_SKB_CB(skb)->ack_seq) &&
1111                             (!lost_retrans || after(end_seq, lost_retrans)))
1112                                 lost_retrans = end_seq;
1113
1114                         if (!in_sack)
1115                                 continue;
1116
1117                         if (!(sacked&TCPCB_SACKED_ACKED)) {
1118                                 if (sacked & TCPCB_SACKED_RETRANS) {
1119                                         /* If the segment is not tagged as lost,
1120                                          * we do not clear RETRANS, believing
1121                                          * that retransmission is still in flight.
1122                                          */
1123                                         if (sacked & TCPCB_LOST) {
1124                                                 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1125                                                 tp->lost_out -= tcp_skb_pcount(skb);
1126                                                 tp->retrans_out -= tcp_skb_pcount(skb);
1127
1128                                                 /* clear lost hint */
1129                                                 tp->retransmit_skb_hint = NULL;
1130                                         }
1131                                 } else {
1132                                         /* New sack for not retransmitted frame,
1133                                          * which was in hole. It is reordering.
1134                                          */
1135                                         if (!(sacked & TCPCB_RETRANS) &&
1136                                             fack_count < prior_fackets)
1137                                                 reord = min(fack_count, reord);
1138
1139                                         if (sacked & TCPCB_LOST) {
1140                                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1141                                                 tp->lost_out -= tcp_skb_pcount(skb);
1142
1143                                                 /* clear lost hint */
1144                                                 tp->retransmit_skb_hint = NULL;
1145                                         }
1146                                 }
1147
1148                                 TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
1149                                 flag |= FLAG_DATA_SACKED;
1150                                 tp->sacked_out += tcp_skb_pcount(skb);
1151
1152                                 if (fack_count > tp->fackets_out)
1153                                         tp->fackets_out = fack_count;
1154                         } else {
1155                                 if (dup_sack && (sacked&TCPCB_RETRANS))
1156                                         reord = min(fack_count, reord);
1157                         }
1158
1159                         /* D-SACK. We can detect redundant retransmission
1160                          * in S|R and plain R frames and clear it.
1161                          * undo_retrans is decreased above, L|R frames
1162                          * are accounted above as well.
1163                          */
1164                         if (dup_sack &&
1165                             (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
1166                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1167                                 tp->retrans_out -= tcp_skb_pcount(skb);
1168                                 tp->retransmit_skb_hint = NULL;
1169                         }
1170                 }
1171         }
1172
1173         /* Check for lost retransmit. This superb idea is
1174          * borrowed from "ratehalving". Event "C".
1175          * Later note: FACK people cheated me again 8),
1176          * we have to account for reordering! Ugly,
1177          * but should help.
1178          */
1179         if (lost_retrans && icsk->icsk_ca_state == TCP_CA_Recovery) {
1180                 struct sk_buff *skb;
1181
1182                 sk_stream_for_retrans_queue(skb, sk) {
1183                         if (after(TCP_SKB_CB(skb)->seq, lost_retrans))
1184                                 break;
1185                         if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1186                                 continue;
1187                         if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) &&
1188                             after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) &&
1189                             (IsFack(tp) ||
1190                              !before(lost_retrans,
1191                                      TCP_SKB_CB(skb)->ack_seq + tp->reordering *
1192                                      tp->mss_cache))) {
1193                                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1194                                 tp->retrans_out -= tcp_skb_pcount(skb);
1195
1196                                 /* clear lost hint */
1197                                 tp->retransmit_skb_hint = NULL;
1198
1199                                 if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) {
1200                                         tp->lost_out += tcp_skb_pcount(skb);
1201                                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1202                                         flag |= FLAG_DATA_SACKED;
1203                                         NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
1204                                 }
1205                         }
1206                 }
1207         }
1208
1209         tp->left_out = tp->sacked_out + tp->lost_out;
1210
1211         if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss)
1212                 tcp_update_reordering(sk, ((tp->fackets_out + 1) - reord), 0);
1213
1214 #if FASTRETRANS_DEBUG > 0
1215         BUG_TRAP((int)tp->sacked_out >= 0);
1216         BUG_TRAP((int)tp->lost_out >= 0);
1217         BUG_TRAP((int)tp->retrans_out >= 0);
1218         BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0);
1219 #endif
1220         return flag;
1221 }
1222
1223 /* RTO occurred, but do not yet enter loss state. Instead, transmit two new
1224  * segments to see from the next ACKs whether any data was really missing.
1225  * If the RTO was spurious, new ACKs should arrive.
1226  */
1227 void tcp_enter_frto(struct sock *sk)
1228 {
1229         const struct inet_connection_sock *icsk = inet_csk(sk);
1230         struct tcp_sock *tp = tcp_sk(sk);
1231         struct sk_buff *skb;
1232
1233         tp->frto_counter = 1;
1234
1235         if (icsk->icsk_ca_state <= TCP_CA_Disorder ||
1236             tp->snd_una == tp->high_seq ||
1237             (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1238                 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1239                 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1240                 tcp_ca_event(sk, CA_EVENT_FRTO);
1241         }
1242
1243         /* Have to clear retransmission markers here to keep the bookkeeping
1244          * in shape, even though we are not yet in Loss state.
1245          * If something was really lost, it is eventually caught up
1246          * in tcp_enter_frto_loss.
1247          */
1248         tp->retrans_out = 0;
1249         tp->undo_marker = tp->snd_una;
1250         tp->undo_retrans = 0;
1251
1252         sk_stream_for_retrans_queue(skb, sk) {
1253                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_RETRANS;
1254         }
1255         tcp_sync_left_out(tp);
1256
1257         tcp_set_ca_state(sk, TCP_CA_Open);
1258         tp->frto_highmark = tp->snd_nxt;
1259 }
1260
1261 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1262  * which indicates that we should follow the traditional RTO recovery,
1263  * i.e. mark everything lost and do go-back-N retransmission.
1264  */
1265 static void tcp_enter_frto_loss(struct sock *sk)
1266 {
1267         struct tcp_sock *tp = tcp_sk(sk);
1268         struct sk_buff *skb;
1269         int cnt = 0;
1270
1271         tp->sacked_out = 0;
1272         tp->lost_out = 0;
1273         tp->fackets_out = 0;
1274
1275         sk_stream_for_retrans_queue(skb, sk) {
1276                 cnt += tcp_skb_pcount(skb);
1277                 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1278                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
1279
1280                         /* Do not mark those segments lost that were
1281                          * forward transmitted after RTO
1282                          */
1283                         if (!after(TCP_SKB_CB(skb)->end_seq,
1284                                    tp->frto_highmark)) {
1285                                 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1286                                 tp->lost_out += tcp_skb_pcount(skb);
1287                         }
1288                 } else {
1289                         tp->sacked_out += tcp_skb_pcount(skb);
1290                         tp->fackets_out = cnt;
1291                 }
1292         }
1293         tcp_sync_left_out(tp);
1294
1295         tp->snd_cwnd = tp->frto_counter + tcp_packets_in_flight(tp)+1;
1296         tp->snd_cwnd_cnt = 0;
1297         tp->snd_cwnd_stamp = tcp_time_stamp;
1298         tp->undo_marker = 0;
1299         tp->frto_counter = 0;
1300
1301         tp->reordering = min_t(unsigned int, tp->reordering,
1302                                              sysctl_tcp_reordering);
1303         tcp_set_ca_state(sk, TCP_CA_Loss);
1304         tp->high_seq = tp->frto_highmark;
1305         TCP_ECN_queue_cwr(tp);
1306
1307         clear_all_retrans_hints(tp);
1308 }
1309
1310 void tcp_clear_retrans(struct tcp_sock *tp)
1311 {
1312         tp->left_out = 0;
1313         tp->retrans_out = 0;
1314
1315         tp->fackets_out = 0;
1316         tp->sacked_out = 0;
1317         tp->lost_out = 0;
1318
1319         tp->undo_marker = 0;
1320         tp->undo_retrans = 0;
1321 }
1322
1323 /* Enter Loss state. If "how" is not zero, forget all SACK information
1324  * and reset tags completely, otherwise preserve SACKs. If receiver
1325  * dropped its ofo queue, we will know this due to reneging detection.
1326  */
1327 void tcp_enter_loss(struct sock *sk, int how)
1328 {
1329         const struct inet_connection_sock *icsk = inet_csk(sk);
1330         struct tcp_sock *tp = tcp_sk(sk);
1331         struct sk_buff *skb;
1332         int cnt = 0;
1333
1334         /* Reduce ssthresh if it has not yet been made inside this window. */
1335         if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
1336             (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) {
1337                 tp->prior_ssthresh = tcp_current_ssthresh(sk);
1338                 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
1339                 tcp_ca_event(sk, CA_EVENT_LOSS);
1340         }
1341         tp->snd_cwnd       = 1;
1342         tp->snd_cwnd_cnt   = 0;
1343         tp->snd_cwnd_stamp = tcp_time_stamp;
1344
1345         tp->bytes_acked = 0;
1346         tcp_clear_retrans(tp);
1347
1348         /* Push undo marker, if it was plain RTO and nothing
1349          * was retransmitted. */
1350         if (!how)
1351                 tp->undo_marker = tp->snd_una;
1352
1353         sk_stream_for_retrans_queue(skb, sk) {
1354                 cnt += tcp_skb_pcount(skb);
1355                 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS)
1356                         tp->undo_marker = 0;
1357                 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
1358                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
1359                         TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
1360                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1361                         tp->lost_out += tcp_skb_pcount(skb);
1362                 } else {
1363                         tp->sacked_out += tcp_skb_pcount(skb);
1364                         tp->fackets_out = cnt;
1365                 }
1366         }
1367         tcp_sync_left_out(tp);
1368
1369         tp->reordering = min_t(unsigned int, tp->reordering,
1370                                              sysctl_tcp_reordering);
1371         tcp_set_ca_state(sk, TCP_CA_Loss);
1372         tp->high_seq = tp->snd_nxt;
1373         TCP_ECN_queue_cwr(tp);
1374
1375         clear_all_retrans_hints(tp);
1376 }
1377
1378 static int tcp_check_sack_reneging(struct sock *sk)
1379 {
1380         struct sk_buff *skb;
1381
1382         /* If ACK arrived pointing to a remembered SACK,
1383          * it means that our remembered SACKs do not reflect
1384          * real state of receiver i.e.
1385          * receiver _host_ is heavily congested (or buggy).
1386          * Do processing similar to RTO timeout.
1387          */
1388         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL &&
1389             (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
1390                 struct inet_connection_sock *icsk = inet_csk(sk);
1391                 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING);
1392
1393                 tcp_enter_loss(sk, 1);
1394                 icsk->icsk_retransmits++;
1395                 tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue));
1396                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
1397                                           icsk->icsk_rto, TCP_RTO_MAX);
1398                 return 1;
1399         }
1400         return 0;
1401 }
1402
1403 static inline int tcp_fackets_out(struct tcp_sock *tp)
1404 {
1405         return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out;
1406 }
1407
1408 static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb)
1409 {
1410         return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto);
1411 }
1412
1413 static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp)
1414 {
1415         return tp->packets_out &&
1416                tcp_skb_timedout(sk, skb_peek(&sk->sk_write_queue));
1417 }
1418
1419 /* Linux NewReno/SACK/FACK/ECN state machine.
1420  * --------------------------------------
1421  *
1422  * "Open"       Normal state, no dubious events, fast path.
1423  * "Disorder"   In all the respects it is "Open",
1424  *              but requires a bit more attention. It is entered when
1425  *              we see some SACKs or dupacks. It is split of "Open"
1426  *              mainly to move some processing from fast path to slow one.
1427  * "CWR"        CWND was reduced due to some Congestion Notification event.
1428  *              It can be ECN, ICMP source quench, local device congestion.
1429  * "Recovery"   CWND was reduced, we are fast-retransmitting.
1430  * "Loss"       CWND was reduced due to RTO timeout or SACK reneging.
1431  *
1432  * tcp_fastretrans_alert() is entered:
1433  * - each incoming ACK, if state is not "Open"
1434  * - when arrived ACK is unusual, namely:
1435  *      * SACK
1436  *      * Duplicate ACK.
1437  *      * ECN ECE.
1438  *
1439  * Counting packets in flight is pretty simple.
1440  *
1441  *      in_flight = packets_out - left_out + retrans_out
1442  *
1443  *      packets_out is SND.NXT-SND.UNA counted in packets.
1444  *
1445  *      retrans_out is number of retransmitted segments.
1446  *
1447  *      left_out is number of segments left network, but not ACKed yet.
1448  *
1449  *              left_out = sacked_out + lost_out
1450  *
1451  *     sacked_out: Packets, which arrived to receiver out of order
1452  *                 and hence not ACKed. With SACKs this number is simply
1453  *                 amount of SACKed data. Even without SACKs
1454  *                 it is easy to give pretty reliable estimate of this number,
1455  *                 counting duplicate ACKs.
1456  *
1457  *       lost_out: Packets lost by network. TCP has no explicit
1458  *                 "loss notification" feedback from network (for now).
1459  *                 It means that this number can be only _guessed_.
1460  *                 Actually, it is the heuristics to predict lossage that
1461  *                 distinguishes different algorithms.
1462  *
1463  *      F.e. after RTO, when all the queue is considered as lost,
1464  *      lost_out = packets_out and in_flight = retrans_out.
1465  *
1466  *              Essentially, we have now two algorithms counting
1467  *              lost packets.
1468  *
1469  *              FACK: It is the simplest heuristics. As soon as we decided
1470  *              that something is lost, we decide that _all_ not SACKed
1471  *              packets until the most forward SACK are lost. I.e.
1472  *              lost_out = fackets_out - sacked_out and left_out = fackets_out.
1473  *              It is absolutely correct estimate, if network does not reorder
1474  *              packets. And it loses any connection to reality when reordering
1475  *              takes place. We use FACK by default until reordering
1476  *              is suspected on the path to this destination.
1477  *
1478  *              NewReno: when Recovery is entered, we assume that one segment
1479  *              is lost (classic Reno). While we are in Recovery and
1480  *              a partial ACK arrives, we assume that one more packet
1481  *              is lost (NewReno). This heuristics are the same in NewReno
1482  *              and SACK.
1483  *
1484  *  Imagine, that's all! Forget about all this shamanism about CWND inflation
1485  *  deflation etc. CWND is real congestion window, never inflated, changes
1486  *  only according to classic VJ rules.
1487  *
1488  * Really tricky (and requiring careful tuning) part of algorithm
1489  * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1490  * The first determines the moment _when_ we should reduce CWND and,
1491  * hence, slow down forward transmission. In fact, it determines the moment
1492  * when we decide that hole is caused by loss, rather than by a reorder.
1493  *
1494  * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1495  * holes, caused by lost packets.
1496  *
1497  * And the most logically complicated part of algorithm is undo
1498  * heuristics. We detect false retransmits due to both too early
1499  * fast retransmit (reordering) and underestimated RTO, analyzing
1500  * timestamps and D-SACKs. When we detect that some segments were
1501  * retransmitted by mistake and CWND reduction was wrong, we undo
1502  * window reduction and abort recovery phase. This logic is hidden
1503  * inside several functions named tcp_try_undo_<something>.
1504  */
1505
1506 /* This function decides, when we should leave Disordered state
1507  * and enter Recovery phase, reducing congestion window.
1508  *
1509  * Main question: may we further continue forward transmission
1510  * with the same cwnd?
1511  */
1512 static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp)
1513 {
1514         __u32 packets_out;
1515
1516         /* Trick#1: The loss is proven. */
1517         if (tp->lost_out)
1518                 return 1;
1519
1520         /* Not-A-Trick#2 : Classic rule... */
1521         if (tcp_fackets_out(tp) > tp->reordering)
1522                 return 1;
1523
1524         /* Trick#3 : when we use RFC2988 timer restart, fast
1525          * retransmit can be triggered by timeout of queue head.
1526          */
1527         if (tcp_head_timedout(sk, tp))
1528                 return 1;
1529
1530         /* Trick#4: It is still not OK... But will it be useful to delay
1531          * recovery more?
1532          */
1533         packets_out = tp->packets_out;
1534         if (packets_out <= tp->reordering &&
1535             tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
1536             !tcp_may_send_now(sk, tp)) {
1537                 /* We have nothing to send. This connection is limited
1538                  * either by receiver window or by application.
1539                  */
1540                 return 1;
1541         }
1542
1543         return 0;
1544 }
1545
1546 /* If we receive more dupacks than we expected counting segments
1547  * in assumption of absent reordering, interpret this as reordering.
1548  * The only another reason could be bug in receiver TCP.
1549  */
1550 static void tcp_check_reno_reordering(struct sock *sk, const int addend)
1551 {
1552         struct tcp_sock *tp = tcp_sk(sk);
1553         u32 holes;
1554
1555         holes = max(tp->lost_out, 1U);
1556         holes = min(holes, tp->packets_out);
1557
1558         if ((tp->sacked_out + holes) > tp->packets_out) {
1559                 tp->sacked_out = tp->packets_out - holes;
1560                 tcp_update_reordering(sk, tp->packets_out + addend, 0);
1561         }
1562 }
1563
1564 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1565
1566 static void tcp_add_reno_sack(struct sock *sk)
1567 {
1568         struct tcp_sock *tp = tcp_sk(sk);
1569         tp->sacked_out++;
1570         tcp_check_reno_reordering(sk, 0);
1571         tcp_sync_left_out(tp);
1572 }
1573
1574 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1575
1576 static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked)
1577 {
1578         if (acked > 0) {
1579                 /* One ACK acked hole. The rest eat duplicate ACKs. */
1580                 if (acked-1 >= tp->sacked_out)
1581                         tp->sacked_out = 0;
1582                 else
1583                         tp->sacked_out -= acked-1;
1584         }
1585         tcp_check_reno_reordering(sk, acked);
1586         tcp_sync_left_out(tp);
1587 }
1588
1589 static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1590 {
1591         tp->sacked_out = 0;
1592         tp->left_out = tp->lost_out;
1593 }
1594
1595 /* Mark head of queue up as lost. */
1596 static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp,
1597                                int packets, u32 high_seq)
1598 {
1599         struct sk_buff *skb;
1600         int cnt;
1601
1602         BUG_TRAP(packets <= tp->packets_out);
1603         if (tp->lost_skb_hint) {
1604                 skb = tp->lost_skb_hint;
1605                 cnt = tp->lost_cnt_hint;
1606         } else {
1607                 skb = sk->sk_write_queue.next;
1608                 cnt = 0;
1609         }
1610
1611         sk_stream_for_retrans_queue_from(skb, sk) {
1612                 /* TODO: do this better */
1613                 /* this is not the most efficient way to do this... */
1614                 tp->lost_skb_hint = skb;
1615                 tp->lost_cnt_hint = cnt;
1616                 cnt += tcp_skb_pcount(skb);
1617                 if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, high_seq))
1618                         break;
1619                 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1620                         TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1621                         tp->lost_out += tcp_skb_pcount(skb);
1622
1623                         /* clear xmit_retransmit_queue hints
1624                          *  if this is beyond hint */
1625                         if(tp->retransmit_skb_hint != NULL &&
1626                            before(TCP_SKB_CB(skb)->seq,
1627                                   TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) {
1628
1629                                 tp->retransmit_skb_hint = NULL;
1630                         }
1631                 }
1632         }
1633         tcp_sync_left_out(tp);
1634 }
1635
1636 /* Account newly detected lost packet(s) */
1637
1638 static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp)
1639 {
1640         if (IsFack(tp)) {
1641                 int lost = tp->fackets_out - tp->reordering;
1642                 if (lost <= 0)
1643                         lost = 1;
1644                 tcp_mark_head_lost(sk, tp, lost, tp->high_seq);
1645         } else {
1646                 tcp_mark_head_lost(sk, tp, 1, tp->high_seq);
1647         }
1648
1649         /* New heuristics: it is possible only after we switched
1650          * to restart timer each time when something is ACKed.
1651          * Hence, we can detect timed out packets during fast
1652          * retransmit without falling to slow start.
1653          */
1654         if (!IsReno(tp) && tcp_head_timedout(sk, tp)) {
1655                 struct sk_buff *skb;
1656
1657                 skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint
1658                         : sk->sk_write_queue.next;
1659
1660                 sk_stream_for_retrans_queue_from(skb, sk) {
1661                         if (!tcp_skb_timedout(sk, skb))
1662                                 break;
1663
1664                         if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1665                                 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1666                                 tp->lost_out += tcp_skb_pcount(skb);
1667
1668                                 /* clear xmit_retrans hint */
1669                                 if (tp->retransmit_skb_hint &&
1670                                     before(TCP_SKB_CB(skb)->seq,
1671                                            TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
1672
1673                                         tp->retransmit_skb_hint = NULL;
1674                         }
1675                 }
1676
1677                 tp->scoreboard_skb_hint = skb;
1678
1679                 tcp_sync_left_out(tp);
1680         }
1681 }
1682
1683 /* CWND moderation, preventing bursts due to too big ACKs
1684  * in dubious situations.
1685  */
1686 static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
1687 {
1688         tp->snd_cwnd = min(tp->snd_cwnd,
1689                            tcp_packets_in_flight(tp)+tcp_max_burst(tp));
1690         tp->snd_cwnd_stamp = tcp_time_stamp;
1691 }
1692
1693 /* Lower bound on congestion window is slow start threshold
1694  * unless congestion avoidance choice decides to overide it.
1695  */
1696 static inline u32 tcp_cwnd_min(const struct sock *sk)
1697 {
1698         const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
1699
1700         return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh;
1701 }
1702
1703 /* Decrease cwnd each second ack. */
1704 static void tcp_cwnd_down(struct sock *sk)
1705 {
1706         struct tcp_sock *tp = tcp_sk(sk);
1707         int decr = tp->snd_cwnd_cnt + 1;
1708
1709         tp->snd_cwnd_cnt = decr&1;
1710         decr >>= 1;
1711
1712         if (decr && tp->snd_cwnd > tcp_cwnd_min(sk))
1713                 tp->snd_cwnd -= decr;
1714
1715         tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);
1716         tp->snd_cwnd_stamp = tcp_time_stamp;
1717 }
1718
1719 /* Nothing was retransmitted or returned timestamp is less
1720  * than timestamp of the first retransmission.
1721  */
1722 static inline int tcp_packet_delayed(struct tcp_sock *tp)
1723 {
1724         return !tp->retrans_stamp ||
1725                 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
1726                  (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0);
1727 }
1728
1729 /* Undo procedures. */
1730
1731 #if FASTRETRANS_DEBUG > 1
1732 static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg)
1733 {
1734         struct inet_sock *inet = inet_sk(sk);
1735         printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1736                msg,
1737                NIPQUAD(inet->daddr), ntohs(inet->dport),
1738                tp->snd_cwnd, tp->left_out,
1739                tp->snd_ssthresh, tp->prior_ssthresh,
1740                tp->packets_out);
1741 }
1742 #else
1743 #define DBGUNDO(x...) do { } while (0)
1744 #endif
1745
1746 static void tcp_undo_cwr(struct sock *sk, const int undo)
1747 {
1748         struct tcp_sock *tp = tcp_sk(sk);
1749
1750         if (tp->prior_ssthresh) {
1751                 const struct inet_connection_sock *icsk = inet_csk(sk);
1752
1753                 if (icsk->icsk_ca_ops->undo_cwnd)
1754                         tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk);
1755                 else
1756                         tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1);
1757
1758                 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
1759                         tp->snd_ssthresh = tp->prior_ssthresh;
1760                         TCP_ECN_withdraw_cwr(tp);
1761                 }
1762         } else {
1763                 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
1764         }
1765         tcp_moderate_cwnd(tp);
1766         tp->snd_cwnd_stamp = tcp_time_stamp;
1767
1768         /* There is something screwy going on with the retrans hints after
1769            an undo */
1770         clear_all_retrans_hints(tp);
1771 }
1772
1773 static inline int tcp_may_undo(struct tcp_sock *tp)
1774 {
1775         return tp->undo_marker &&
1776                 (!tp->undo_retrans || tcp_packet_delayed(tp));
1777 }
1778
1779 /* People celebrate: "We love our President!" */
1780 static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp)
1781 {
1782         if (tcp_may_undo(tp)) {
1783                 /* Happy end! We did not retransmit anything
1784                  * or our original transmission succeeded.
1785                  */
1786                 DBGUNDO(sk, tp, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans");
1787                 tcp_undo_cwr(sk, 1);
1788                 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss)
1789                         NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1790                 else
1791                         NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO);
1792                 tp->undo_marker = 0;
1793         }
1794         if (tp->snd_una == tp->high_seq && IsReno(tp)) {
1795                 /* Hold old state until something *above* high_seq
1796                  * is ACKed. For Reno it is MUST to prevent false
1797                  * fast retransmits (RFC2582). SACK TCP is safe. */
1798                 tcp_moderate_cwnd(tp);
1799                 return 1;
1800         }
1801         tcp_set_ca_state(sk, TCP_CA_Open);
1802         return 0;
1803 }
1804
1805 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1806 static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp)
1807 {
1808         if (tp->undo_marker && !tp->undo_retrans) {
1809                 DBGUNDO(sk, tp, "D-SACK");
1810                 tcp_undo_cwr(sk, 1);
1811                 tp->undo_marker = 0;
1812                 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO);
1813         }
1814 }
1815
1816 /* Undo during fast recovery after partial ACK. */
1817
1818 static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp,
1819                                 int acked)
1820 {
1821         /* Partial ACK arrived. Force Hoe's retransmit. */
1822         int failed = IsReno(tp) || tp->fackets_out>tp->reordering;
1823
1824         if (tcp_may_undo(tp)) {
1825                 /* Plain luck! Hole if filled with delayed
1826                  * packet, rather than with a retransmit.
1827                  */
1828                 if (tp->retrans_out == 0)
1829                         tp->retrans_stamp = 0;
1830
1831                 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1);
1832
1833                 DBGUNDO(sk, tp, "Hoe");
1834                 tcp_undo_cwr(sk, 0);
1835                 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO);
1836
1837                 /* So... Do not make Hoe's retransmit yet.
1838                  * If the first packet was delayed, the rest
1839                  * ones are most probably delayed as well.
1840                  */
1841                 failed = 0;
1842         }
1843         return failed;
1844 }
1845
1846 /* Undo during loss recovery after partial ACK. */
1847 static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp)
1848 {
1849         if (tcp_may_undo(tp)) {
1850                 struct sk_buff *skb;
1851                 sk_stream_for_retrans_queue(skb, sk) {
1852                         TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1853                 }
1854
1855                 clear_all_retrans_hints(tp);
1856
1857                 DBGUNDO(sk, tp, "partial loss");
1858                 tp->lost_out = 0;
1859                 tp->left_out = tp->sacked_out;
1860                 tcp_undo_cwr(sk, 1);
1861                 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1862                 inet_csk(sk)->icsk_retransmits = 0;
1863                 tp->undo_marker = 0;
1864                 if (!IsReno(tp))
1865                         tcp_set_ca_state(sk, TCP_CA_Open);
1866                 return 1;
1867         }
1868         return 0;
1869 }
1870
1871 static inline void tcp_complete_cwr(struct sock *sk)
1872 {
1873         struct tcp_sock *tp = tcp_sk(sk);
1874         tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
1875         tp->snd_cwnd_stamp = tcp_time_stamp;
1876         tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
1877 }
1878
1879 static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag)
1880 {
1881         tp->left_out = tp->sacked_out;
1882
1883         if (tp->retrans_out == 0)
1884                 tp->retrans_stamp = 0;
1885
1886         if (flag&FLAG_ECE)
1887                 tcp_enter_cwr(sk);
1888
1889         if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) {
1890                 int state = TCP_CA_Open;
1891
1892                 if (tp->left_out || tp->retrans_out || tp->undo_marker)
1893                         state = TCP_CA_Disorder;
1894
1895                 if (inet_csk(sk)->icsk_ca_state != state) {
1896                         tcp_set_ca_state(sk, state);
1897                         tp->high_seq = tp->snd_nxt;
1898                 }
1899                 tcp_moderate_cwnd(tp);
1900         } else {
1901                 tcp_cwnd_down(sk);
1902         }
1903 }
1904
1905 static void tcp_mtup_probe_failed(struct sock *sk)
1906 {
1907         struct inet_connection_sock *icsk = inet_csk(sk);
1908
1909         icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1;
1910         icsk->icsk_mtup.probe_size = 0;
1911 }
1912
1913 static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb)
1914 {
1915         struct tcp_sock *tp = tcp_sk(sk);
1916         struct inet_connection_sock *icsk = inet_csk(sk);
1917
1918         /* FIXME: breaks with very large cwnd */
1919         tp->prior_ssthresh = tcp_current_ssthresh(sk);
1920         tp->snd_cwnd = tp->snd_cwnd *
1921                        tcp_mss_to_mtu(sk, tp->mss_cache) /
1922                        icsk->icsk_mtup.probe_size;
1923         tp->snd_cwnd_cnt = 0;
1924         tp->snd_cwnd_stamp = tcp_time_stamp;
1925         tp->rcv_ssthresh = tcp_current_ssthresh(sk);
1926
1927         icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size;
1928         icsk->icsk_mtup.probe_size = 0;
1929         tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
1930 }
1931
1932
1933 /* Process an event, which can update packets-in-flight not trivially.
1934  * Main goal of this function is to calculate new estimate for left_out,
1935  * taking into account both packets sitting in receiver's buffer and
1936  * packets lost by network.
1937  *
1938  * Besides that it does CWND reduction, when packet loss is detected
1939  * and changes state of machine.
1940  *
1941  * It does _not_ decide what to send, it is made in function
1942  * tcp_xmit_retransmit_queue().
1943  */
1944 static void
1945 tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
1946                       int prior_packets, int flag)
1947 {
1948         struct inet_connection_sock *icsk = inet_csk(sk);
1949         struct tcp_sock *tp = tcp_sk(sk);
1950         int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP));
1951
1952         /* Some technical things:
1953          * 1. Reno does not count dupacks (sacked_out) automatically. */
1954         if (!tp->packets_out)
1955                 tp->sacked_out = 0;
1956         /* 2. SACK counts snd_fack in packets inaccurately. */
1957         if (tp->sacked_out == 0)
1958                 tp->fackets_out = 0;
1959
1960         /* Now state machine starts.
1961          * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
1962         if (flag&FLAG_ECE)
1963                 tp->prior_ssthresh = 0;
1964
1965         /* B. In all the states check for reneging SACKs. */
1966         if (tp->sacked_out && tcp_check_sack_reneging(sk))
1967                 return;
1968
1969         /* C. Process data loss notification, provided it is valid. */
1970         if ((flag&FLAG_DATA_LOST) &&
1971             before(tp->snd_una, tp->high_seq) &&
1972             icsk->icsk_ca_state != TCP_CA_Open &&
1973             tp->fackets_out > tp->reordering) {
1974                 tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq);
1975                 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
1976         }
1977
1978         /* D. Synchronize left_out to current state. */
1979         tcp_sync_left_out(tp);
1980
1981         /* E. Check state exit conditions. State can be terminated
1982          *    when high_seq is ACKed. */
1983         if (icsk->icsk_ca_state == TCP_CA_Open) {
1984                 if (!sysctl_tcp_frto)
1985                         BUG_TRAP(tp->retrans_out == 0);
1986                 tp->retrans_stamp = 0;
1987         } else if (!before(tp->snd_una, tp->high_seq)) {
1988                 switch (icsk->icsk_ca_state) {
1989                 case TCP_CA_Loss:
1990                         icsk->icsk_retransmits = 0;
1991                         if (tcp_try_undo_recovery(sk, tp))
1992                                 return;
1993                         break;
1994
1995                 case TCP_CA_CWR:
1996                         /* CWR is to be held something *above* high_seq
1997                          * is ACKed for CWR bit to reach receiver. */
1998                         if (tp->snd_una != tp->high_seq) {
1999                                 tcp_complete_cwr(sk);
2000                                 tcp_set_ca_state(sk, TCP_CA_Open);
2001                         }
2002                         break;
2003
2004                 case TCP_CA_Disorder:
2005                         tcp_try_undo_dsack(sk, tp);
2006                         if (!tp->undo_marker ||
2007                             /* For SACK case do not Open to allow to undo
2008                              * catching for all duplicate ACKs. */
2009                             IsReno(tp) || tp->snd_una != tp->high_seq) {
2010                                 tp->undo_marker = 0;
2011                                 tcp_set_ca_state(sk, TCP_CA_Open);
2012                         }
2013                         break;
2014
2015                 case TCP_CA_Recovery:
2016                         if (IsReno(tp))
2017                                 tcp_reset_reno_sack(tp);
2018                         if (tcp_try_undo_recovery(sk, tp))
2019                                 return;
2020                         tcp_complete_cwr(sk);
2021                         break;
2022                 }
2023         }
2024
2025         /* F. Process state. */
2026         switch (icsk->icsk_ca_state) {
2027         case TCP_CA_Recovery:
2028                 if (prior_snd_una == tp->snd_una) {
2029                         if (IsReno(tp) && is_dupack)
2030                                 tcp_add_reno_sack(sk);
2031                 } else {
2032                         int acked = prior_packets - tp->packets_out;
2033                         if (IsReno(tp))
2034                                 tcp_remove_reno_sacks(sk, tp, acked);
2035                         is_dupack = tcp_try_undo_partial(sk, tp, acked);
2036                 }
2037                 break;
2038         case TCP_CA_Loss:
2039                 if (flag&FLAG_DATA_ACKED)
2040                         icsk->icsk_retransmits = 0;
2041                 if (!tcp_try_undo_loss(sk, tp)) {
2042                         tcp_moderate_cwnd(tp);
2043                         tcp_xmit_retransmit_queue(sk);
2044                         return;
2045                 }
2046                 if (icsk->icsk_ca_state != TCP_CA_Open)
2047                         return;
2048                 /* Loss is undone; fall through to processing in Open state. */
2049         default:
2050                 if (IsReno(tp)) {
2051                         if (tp->snd_una != prior_snd_una)
2052                                 tcp_reset_reno_sack(tp);
2053                         if (is_dupack)
2054                                 tcp_add_reno_sack(sk);
2055                 }
2056
2057                 if (icsk->icsk_ca_state == TCP_CA_Disorder)
2058                         tcp_try_undo_dsack(sk, tp);
2059
2060                 if (!tcp_time_to_recover(sk, tp)) {
2061                         tcp_try_to_open(sk, tp, flag);
2062                         return;
2063                 }
2064
2065                 /* MTU probe failure: don't reduce cwnd */
2066                 if (icsk->icsk_ca_state < TCP_CA_CWR &&
2067                     icsk->icsk_mtup.probe_size &&
2068                     tp->snd_una == tp->mtu_probe.probe_seq_start) {
2069                         tcp_mtup_probe_failed(sk);
2070                         /* Restores the reduction we did in tcp_mtup_probe() */
2071                         tp->snd_cwnd++;
2072                         tcp_simple_retransmit(sk);
2073                         return;
2074                 }
2075
2076                 /* Otherwise enter Recovery state */
2077
2078                 if (IsReno(tp))
2079                         NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY);
2080                 else
2081                         NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY);
2082
2083                 tp->high_seq = tp->snd_nxt;
2084                 tp->prior_ssthresh = 0;
2085                 tp->undo_marker = tp->snd_una;
2086                 tp->undo_retrans = tp->retrans_out;
2087
2088                 if (icsk->icsk_ca_state < TCP_CA_CWR) {
2089                         if (!(flag&FLAG_ECE))
2090                                 tp->prior_ssthresh = tcp_current_ssthresh(sk);
2091                         tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk);
2092                         TCP_ECN_queue_cwr(tp);
2093                 }
2094
2095                 tp->bytes_acked = 0;
2096                 tp->snd_cwnd_cnt = 0;
2097                 tcp_set_ca_state(sk, TCP_CA_Recovery);
2098         }
2099
2100         if (is_dupack || tcp_head_timedout(sk, tp))
2101                 tcp_update_scoreboard(sk, tp);
2102         tcp_cwnd_down(sk);
2103         tcp_xmit_retransmit_queue(sk);
2104 }
2105
2106 /* Read draft-ietf-tcplw-high-performance before mucking
2107  * with this code. (Supersedes RFC1323)
2108  */
2109 static void tcp_ack_saw_tstamp(struct sock *sk, int flag)
2110 {
2111         /* RTTM Rule: A TSecr value received in a segment is used to
2112          * update the averaged RTT measurement only if the segment
2113          * acknowledges some new data, i.e., only if it advances the
2114          * left edge of the send window.
2115          *
2116          * See draft-ietf-tcplw-high-performance-00, section 3.3.
2117          * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2118          *
2119          * Changed: reset backoff as soon as we see the first valid sample.
2120          * If we do not, we get strongly overestimated rto. With timestamps
2121          * samples are accepted even from very old segments: f.e., when rtt=1
2122          * increases to 8, we retransmit 5 times and after 8 seconds delayed
2123          * answer arrives rto becomes 120 seconds! If at least one of segments
2124          * in window is lost... Voila.                          --ANK (010210)
2125          */
2126         struct tcp_sock *tp = tcp_sk(sk);
2127         const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
2128         tcp_rtt_estimator(sk, seq_rtt);
2129         tcp_set_rto(sk);
2130         inet_csk(sk)->icsk_backoff = 0;
2131         tcp_bound_rto(sk);
2132 }
2133
2134 static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag)
2135 {
2136         /* We don't have a timestamp. Can only use
2137          * packets that are not retransmitted to determine
2138          * rtt estimates. Also, we must not reset the
2139          * backoff for rto until we get a non-retransmitted
2140          * packet. This allows us to deal with a situation
2141          * where the network delay has increased suddenly.
2142          * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2143          */
2144
2145         if (flag & FLAG_RETRANS_DATA_ACKED)
2146                 return;
2147
2148         tcp_rtt_estimator(sk, seq_rtt);
2149         tcp_set_rto(sk);
2150         inet_csk(sk)->icsk_backoff = 0;
2151         tcp_bound_rto(sk);
2152 }
2153
2154 static inline void tcp_ack_update_rtt(struct sock *sk, const int flag,
2155                                       const s32 seq_rtt)
2156 {
2157         const struct tcp_sock *tp = tcp_sk(sk);
2158         /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2159         if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
2160                 tcp_ack_saw_tstamp(sk, flag);
2161         else if (seq_rtt >= 0)
2162                 tcp_ack_no_tstamp(sk, seq_rtt, flag);
2163 }
2164
2165 static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
2166                            u32 in_flight, int good)
2167 {
2168         const struct inet_connection_sock *icsk = inet_csk(sk);
2169         icsk->icsk_ca_ops->cong_avoid(sk, ack, rtt, in_flight, good);
2170         tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp;
2171 }
2172
2173 /* Restart timer after forward progress on connection.
2174  * RFC2988 recommends to restart timer to now+rto.
2175  */
2176
2177 static void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp)
2178 {
2179         if (!tp->packets_out) {
2180                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
2181         } else {
2182                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
2183         }
2184 }
2185
2186 static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb,
2187                          __u32 now, __s32 *seq_rtt)
2188 {
2189         struct tcp_sock *tp = tcp_sk(sk);
2190         struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 
2191         __u32 seq = tp->snd_una;
2192         __u32 packets_acked;
2193         int acked = 0;
2194
2195         /* If we get here, the whole TSO packet has not been
2196          * acked.
2197          */
2198         BUG_ON(!after(scb->end_seq, seq));
2199
2200         packets_acked = tcp_skb_pcount(skb);
2201         if (tcp_trim_head(sk, skb, seq - scb->seq))
2202                 return 0;
2203         packets_acked -= tcp_skb_pcount(skb);
2204
2205         if (packets_acked) {
2206                 __u8 sacked = scb->sacked;
2207
2208                 acked |= FLAG_DATA_ACKED;
2209                 if (sacked) {
2210                         if (sacked & TCPCB_RETRANS) {
2211                                 if (sacked & TCPCB_SACKED_RETRANS)
2212                                         tp->retrans_out -= packets_acked;
2213                                 acked |= FLAG_RETRANS_DATA_ACKED;
2214                                 *seq_rtt = -1;
2215                         } else if (*seq_rtt < 0)
2216                                 *seq_rtt = now - scb->when;
2217                         if (sacked & TCPCB_SACKED_ACKED)
2218                                 tp->sacked_out -= packets_acked;
2219                         if (sacked & TCPCB_LOST)
2220                                 tp->lost_out -= packets_acked;
2221                         if (sacked & TCPCB_URG) {
2222                                 if (tp->urg_mode &&
2223                                     !before(seq, tp->snd_up))
2224                                         tp->urg_mode = 0;
2225                         }
2226                 } else if (*seq_rtt < 0)
2227                         *seq_rtt = now - scb->when;
2228
2229                 if (tp->fackets_out) {
2230                         __u32 dval = min(tp->fackets_out, packets_acked);
2231                         tp->fackets_out -= dval;
2232                 }
2233                 tp->packets_out -= packets_acked;
2234
2235                 BUG_ON(tcp_skb_pcount(skb) == 0);
2236                 BUG_ON(!before(scb->seq, scb->end_seq));
2237         }
2238
2239         return acked;
2240 }
2241
2242 static u32 tcp_usrtt(struct timeval *tv)
2243 {
2244         struct timeval now;
2245
2246         do_gettimeofday(&now);
2247         return (now.tv_sec - tv->tv_sec) * 1000000 + (now.tv_usec - tv->tv_usec);
2248 }
2249
2250 /* Remove acknowledged frames from the retransmission queue. */
2251 static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
2252 {
2253         struct tcp_sock *tp = tcp_sk(sk);
2254         const struct inet_connection_sock *icsk = inet_csk(sk);
2255         struct sk_buff *skb;
2256         __u32 now = tcp_time_stamp;
2257         int acked = 0;
2258         __s32 seq_rtt = -1;
2259         u32 pkts_acked = 0;
2260         void (*rtt_sample)(struct sock *sk, u32 usrtt)
2261                 = icsk->icsk_ca_ops->rtt_sample;
2262         struct timeval tv = { .tv_sec = 0, .tv_usec = 0 };
2263
2264         while ((skb = skb_peek(&sk->sk_write_queue)) &&
2265                skb != sk->sk_send_head) {
2266                 struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 
2267                 __u8 sacked = scb->sacked;
2268
2269                 /* If our packet is before the ack sequence we can
2270                  * discard it as it's confirmed to have arrived at
2271                  * the other end.
2272                  */
2273                 if (after(scb->end_seq, tp->snd_una)) {
2274                         if (tcp_skb_pcount(skb) > 1 &&
2275                             after(tp->snd_una, scb->seq))
2276                                 acked |= tcp_tso_acked(sk, skb,
2277                                                        now, &seq_rtt);
2278                         break;
2279                 }
2280
2281                 /* Initial outgoing SYN's get put onto the write_queue
2282                  * just like anything else we transmit.  It is not
2283                  * true data, and if we misinform our callers that
2284                  * this ACK acks real data, we will erroneously exit
2285                  * connection startup slow start one packet too
2286                  * quickly.  This is severely frowned upon behavior.
2287                  */
2288                 if (!(scb->flags & TCPCB_FLAG_SYN)) {
2289                         acked |= FLAG_DATA_ACKED;
2290                         ++pkts_acked;
2291                 } else {
2292                         acked |= FLAG_SYN_ACKED;
2293                         tp->retrans_stamp = 0;
2294                 }
2295
2296                 /* MTU probing checks */
2297                 if (icsk->icsk_mtup.probe_size) {
2298                         if (!after(tp->mtu_probe.probe_seq_end, TCP_SKB_CB(skb)->end_seq)) {
2299                                 tcp_mtup_probe_success(sk, skb);
2300                         }
2301                 }
2302
2303                 if (sacked) {
2304                         if (sacked & TCPCB_RETRANS) {
2305                                 if(sacked & TCPCB_SACKED_RETRANS)
2306                                         tp->retrans_out -= tcp_skb_pcount(skb);
2307                                 acked |= FLAG_RETRANS_DATA_ACKED;
2308                                 seq_rtt = -1;
2309                         } else if (seq_rtt < 0) {
2310                                 seq_rtt = now - scb->when;
2311                                 skb_get_timestamp(skb, &tv);
2312                         }
2313                         if (sacked & TCPCB_SACKED_ACKED)
2314                                 tp->sacked_out -= tcp_skb_pcount(skb);
2315                         if (sacked & TCPCB_LOST)
2316                                 tp->lost_out -= tcp_skb_pcount(skb);
2317                         if (sacked & TCPCB_URG) {
2318                                 if (tp->urg_mode &&
2319                                     !before(scb->end_seq, tp->snd_up))
2320                                         tp->urg_mode = 0;
2321                         }
2322                 } else if (seq_rtt < 0) {
2323                         seq_rtt = now - scb->when;
2324                         skb_get_timestamp(skb, &tv);
2325                 }
2326                 tcp_dec_pcount_approx(&tp->fackets_out, skb);
2327                 tcp_packets_out_dec(tp, skb);
2328                 __skb_unlink(skb, &sk->sk_write_queue);
2329                 sk_stream_free_skb(sk, skb);
2330                 clear_all_retrans_hints(tp);
2331         }
2332
2333         if (acked&FLAG_ACKED) {
2334                 tcp_ack_update_rtt(sk, acked, seq_rtt);
2335                 tcp_ack_packets_out(sk, tp);
2336                 if (rtt_sample && !(acked & FLAG_RETRANS_DATA_ACKED))
2337                         (*rtt_sample)(sk, tcp_usrtt(&tv));
2338
2339                 if (icsk->icsk_ca_ops->pkts_acked)
2340                         icsk->icsk_ca_ops->pkts_acked(sk, pkts_acked);
2341         }
2342
2343 #if FASTRETRANS_DEBUG > 0
2344         BUG_TRAP((int)tp->sacked_out >= 0);
2345         BUG_TRAP((int)tp->lost_out >= 0);
2346         BUG_TRAP((int)tp->retrans_out >= 0);
2347         if (!tp->packets_out && tp->rx_opt.sack_ok) {
2348                 const struct inet_connection_sock *icsk = inet_csk(sk);
2349                 if (tp->lost_out) {
2350                         printk(KERN_DEBUG "Leak l=%u %d\n",
2351                                tp->lost_out, icsk->icsk_ca_state);
2352                         tp->lost_out = 0;
2353                 }
2354                 if (tp->sacked_out) {
2355                         printk(KERN_DEBUG "Leak s=%u %d\n",
2356                                tp->sacked_out, icsk->icsk_ca_state);
2357                         tp->sacked_out = 0;
2358                 }
2359                 if (tp->retrans_out) {
2360                         printk(KERN_DEBUG "Leak r=%u %d\n",
2361                                tp->retrans_out, icsk->icsk_ca_state);
2362                         tp->retrans_out = 0;
2363                 }
2364         }
2365 #endif
2366         *seq_rtt_p = seq_rtt;
2367         return acked;
2368 }
2369
2370 static void tcp_ack_probe(struct sock *sk)
2371 {
2372         const struct tcp_sock *tp = tcp_sk(sk);
2373         struct inet_connection_sock *icsk = inet_csk(sk);
2374
2375         /* Was it a usable window open? */
2376
2377         if (!after(TCP_SKB_CB(sk->sk_send_head)->end_seq,
2378                    tp->snd_una + tp->snd_wnd)) {
2379                 icsk->icsk_backoff = 0;
2380                 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0);
2381                 /* Socket must be waked up by subsequent tcp_data_snd_check().
2382                  * This function is not for random using!
2383                  */
2384         } else {
2385                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2386                                           min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
2387                                           TCP_RTO_MAX);
2388         }
2389 }
2390
2391 static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag)
2392 {
2393         return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
2394                 inet_csk(sk)->icsk_ca_state != TCP_CA_Open);
2395 }
2396
2397 static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag)
2398 {
2399         const struct tcp_sock *tp = tcp_sk(sk);
2400         return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
2401                 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR));
2402 }
2403
2404 /* Check that window update is acceptable.
2405  * The function assumes that snd_una<=ack<=snd_next.
2406  */
2407 static inline int tcp_may_update_window(const struct tcp_sock *tp, const u32 ack,
2408                                         const u32 ack_seq, const u32 nwin)
2409 {
2410         return (after(ack, tp->snd_una) ||
2411                 after(ack_seq, tp->snd_wl1) ||
2412                 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd));
2413 }
2414
2415 /* Update our send window.
2416  *
2417  * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2418  * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2419  */
2420 static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp,
2421                                  struct sk_buff *skb, u32 ack, u32 ack_seq)
2422 {
2423         int flag = 0;
2424         u32 nwin = ntohs(skb->h.th->window);
2425
2426         if (likely(!skb->h.th->syn))
2427                 nwin <<= tp->rx_opt.snd_wscale;
2428
2429         if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
2430                 flag |= FLAG_WIN_UPDATE;
2431                 tcp_update_wl(tp, ack, ack_seq);
2432
2433                 if (tp->snd_wnd != nwin) {
2434                         tp->snd_wnd = nwin;
2435
2436                         /* Note, it is the only place, where
2437                          * fast path is recovered for sending TCP.
2438                          */
2439                         tp->pred_flags = 0;
2440                         tcp_fast_path_check(sk, tp);
2441
2442                         if (nwin > tp->max_window) {
2443                                 tp->max_window = nwin;
2444                                 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie);
2445                         }
2446                 }
2447         }
2448
2449         tp->snd_una = ack;
2450
2451         return flag;
2452 }
2453
2454 static void tcp_process_frto(struct sock *sk, u32 prior_snd_una)
2455 {
2456         struct tcp_sock *tp = tcp_sk(sk);
2457         
2458         tcp_sync_left_out(tp);
2459         
2460         if (tp->snd_una == prior_snd_una ||
2461             !before(tp->snd_una, tp->frto_highmark)) {
2462                 /* RTO was caused by loss, start retransmitting in
2463                  * go-back-N slow start
2464                  */
2465                 tcp_enter_frto_loss(sk);
2466                 return;
2467         }
2468
2469         if (tp->frto_counter == 1) {
2470                 /* First ACK after RTO advances the window: allow two new
2471                  * segments out.
2472                  */
2473                 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
2474         } else {
2475                 /* Also the second ACK after RTO advances the window.
2476                  * The RTO was likely spurious. Reduce cwnd and continue
2477                  * in congestion avoidance
2478                  */
2479                 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
2480                 tcp_moderate_cwnd(tp);
2481         }
2482
2483         /* F-RTO affects on two new ACKs following RTO.
2484          * At latest on third ACK the TCP behavior is back to normal.
2485          */
2486         tp->frto_counter = (tp->frto_counter + 1) % 3;
2487 }
2488
2489 /* This routine deals with incoming acks, but not outgoing ones. */
2490 static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
2491 {
2492         struct inet_connection_sock *icsk = inet_csk(sk);
2493         struct tcp_sock *tp = tcp_sk(sk);
2494         u32 prior_snd_una = tp->snd_una;
2495         u32 ack_seq = TCP_SKB_CB(skb)->seq;
2496         u32 ack = TCP_SKB_CB(skb)->ack_seq;
2497         u32 prior_in_flight;
2498         s32 seq_rtt;
2499         int prior_packets;
2500
2501         /* If the ack is newer than sent or older than previous acks
2502          * then we can probably ignore it.
2503          */
2504         if (after(ack, tp->snd_nxt))
2505                 goto uninteresting_ack;
2506
2507         if (before(ack, prior_snd_una))
2508                 goto old_ack;
2509
2510         if (sysctl_tcp_abc) {
2511                 if (icsk->icsk_ca_state < TCP_CA_CWR)
2512                         tp->bytes_acked += ack - prior_snd_una;
2513                 else if (icsk->icsk_ca_state == TCP_CA_Loss)
2514                         /* we assume just one segment left network */
2515                         tp->bytes_acked += min(ack - prior_snd_una, tp->mss_cache);
2516         }
2517
2518         if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
2519                 /* Window is constant, pure forward advance.
2520                  * No more checks are required.
2521                  * Note, we use the fact that SND.UNA>=SND.WL2.
2522                  */
2523                 tcp_update_wl(tp, ack, ack_seq);
2524                 tp->snd_una = ack;
2525                 flag |= FLAG_WIN_UPDATE;
2526
2527                 tcp_ca_event(sk, CA_EVENT_FAST_ACK);
2528
2529                 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS);
2530         } else {
2531                 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
2532                         flag |= FLAG_DATA;
2533                 else
2534                         NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS);
2535
2536                 flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq);
2537
2538                 if (TCP_SKB_CB(skb)->sacked)
2539                         flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2540
2541                 if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th))
2542                         flag |= FLAG_ECE;
2543
2544                 tcp_ca_event(sk, CA_EVENT_SLOW_ACK);
2545         }
2546
2547         /* We passed data and got it acked, remove any soft error
2548          * log. Something worked...
2549          */
2550         sk->sk_err_soft = 0;
2551         tp->rcv_tstamp = tcp_time_stamp;
2552         prior_packets = tp->packets_out;
2553         if (!prior_packets)
2554                 goto no_queue;
2555
2556         prior_in_flight = tcp_packets_in_flight(tp);
2557
2558         /* See if we can take anything off of the retransmit queue. */
2559         flag |= tcp_clean_rtx_queue(sk, &seq_rtt);
2560
2561         if (tp->frto_counter)
2562                 tcp_process_frto(sk, prior_snd_una);
2563
2564         if (tcp_ack_is_dubious(sk, flag)) {
2565                 /* Advance CWND, if state allows this. */
2566                 if ((flag & FLAG_DATA_ACKED) && tcp_may_raise_cwnd(sk, flag))
2567                         tcp_cong_avoid(sk, ack,  seq_rtt, prior_in_flight, 0);
2568                 tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag);
2569         } else {
2570                 if ((flag & FLAG_DATA_ACKED))
2571                         tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 1);
2572         }
2573
2574         if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP))
2575                 dst_confirm(sk->sk_dst_cache);
2576
2577         return 1;
2578
2579 no_queue:
2580         icsk->icsk_probes_out = 0;
2581
2582         /* If this ack opens up a zero window, clear backoff.  It was
2583          * being used to time the probes, and is probably far higher than
2584          * it needs to be for normal retransmission.
2585          */
2586         if (sk->sk_send_head)
2587                 tcp_ack_probe(sk);
2588         return 1;
2589
2590 old_ack:
2591         if (TCP_SKB_CB(skb)->sacked)
2592                 tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2593
2594 uninteresting_ack:
2595         SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
2596         return 0;
2597 }
2598
2599
2600 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
2601  * But, this can also be called on packets in the established flow when
2602  * the fast version below fails.
2603  */
2604 void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab)
2605 {
2606         unsigned char *ptr;
2607         struct tcphdr *th = skb->h.th;
2608         int length=(th->doff*4)-sizeof(struct tcphdr);
2609
2610         ptr = (unsigned char *)(th + 1);
2611         opt_rx->saw_tstamp = 0;
2612
2613         while(length>0) {
2614                 int opcode=*ptr++;
2615                 int opsize;
2616
2617                 switch (opcode) {
2618                         case TCPOPT_EOL:
2619                                 return;
2620                         case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
2621                                 length--;
2622                                 continue;
2623                         default:
2624                                 opsize=*ptr++;
2625                                 if (opsize < 2) /* "silly options" */
2626                                         return;
2627                                 if (opsize > length)
2628                                         return; /* don't parse partial options */
2629                                 switch(opcode) {
2630                                 case TCPOPT_MSS:
2631                                         if(opsize==TCPOLEN_MSS && th->syn && !estab) {
2632                                                 u16 in_mss = ntohs(get_unaligned((__be16 *)ptr));
2633                                                 if (in_mss) {
2634                                                         if (opt_rx->user_mss && opt_rx->user_mss < in_mss)
2635                                                                 in_mss = opt_rx->user_mss;
2636                                                         opt_rx->mss_clamp = in_mss;
2637                                                 }
2638                                         }
2639                                         break;
2640                                 case TCPOPT_WINDOW:
2641                                         if(opsize==TCPOLEN_WINDOW && th->syn && !estab)
2642                                                 if (sysctl_tcp_window_scaling) {
2643                                                         __u8 snd_wscale = *(__u8 *) ptr;
2644                                                         opt_rx->wscale_ok = 1;
2645                                                         if (snd_wscale > 14) {
2646                                                                 if(net_ratelimit())
2647                                                                         printk(KERN_INFO "tcp_parse_options: Illegal window "
2648                                                                                "scaling value %d >14 received.\n",
2649                                                                                snd_wscale);
2650                                                                 snd_wscale = 14;
2651                                                         }
2652                                                         opt_rx->snd_wscale = snd_wscale;
2653                                                 }
2654                                         break;
2655                                 case TCPOPT_TIMESTAMP:
2656                                         if(opsize==TCPOLEN_TIMESTAMP) {
2657                                                 if ((estab && opt_rx->tstamp_ok) ||
2658                                                     (!estab && sysctl_tcp_timestamps)) {
2659                                                         opt_rx->saw_tstamp = 1;
2660                                                         opt_rx->rcv_tsval = ntohl(get_unaligned((__be32 *)ptr));
2661                                                         opt_rx->rcv_tsecr = ntohl(get_unaligned((__be32 *)(ptr+4)));
2662                                                 }
2663                                         }
2664                                         break;
2665                                 case TCPOPT_SACK_PERM:
2666                                         if(opsize==TCPOLEN_SACK_PERM && th->syn && !estab) {
2667                                                 if (sysctl_tcp_sack) {
2668                                                         opt_rx->sack_ok = 1;
2669                                                         tcp_sack_reset(opt_rx);
2670                                                 }
2671                                         }
2672                                         break;
2673
2674                                 case TCPOPT_SACK:
2675                                         if((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
2676                                            !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
2677                                            opt_rx->sack_ok) {
2678                                                 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
2679                                         }
2680                                 };
2681                                 ptr+=opsize-2;
2682                                 length-=opsize;
2683                 };
2684         }
2685 }
2686
2687 /* Fast parse options. This hopes to only see timestamps.
2688  * If it is wrong it falls back on tcp_parse_options().
2689  */
2690 static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
2691                                   struct tcp_sock *tp)
2692 {
2693         if (th->doff == sizeof(struct tcphdr)>>2) {
2694                 tp->rx_opt.saw_tstamp = 0;
2695                 return 0;
2696         } else if (tp->rx_opt.tstamp_ok &&
2697                    th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
2698                 __be32 *ptr = (__be32 *)(th + 1);
2699                 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
2700                                   | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
2701                         tp->rx_opt.saw_tstamp = 1;
2702                         ++ptr;
2703                         tp->rx_opt.rcv_tsval = ntohl(*ptr);
2704                         ++ptr;
2705                         tp->rx_opt.rcv_tsecr = ntohl(*ptr);
2706                         return 1;
2707                 }
2708         }
2709         tcp_parse_options(skb, &tp->rx_opt, 1);
2710         return 1;
2711 }
2712
2713 static inline void tcp_store_ts_recent(struct tcp_sock *tp)
2714 {
2715         tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
2716         tp->rx_opt.ts_recent_stamp = xtime.tv_sec;
2717 }
2718
2719 static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
2720 {
2721         if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
2722                 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
2723                  * extra check below makes sure this can only happen
2724                  * for pure ACK frames.  -DaveM
2725                  *
2726                  * Not only, also it occurs for expired timestamps.
2727                  */
2728
2729                 if((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 ||
2730                    xtime.tv_sec >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS)
2731                         tcp_store_ts_recent(tp);
2732         }
2733 }
2734
2735 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
2736  *
2737  * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
2738  * it can pass through stack. So, the following predicate verifies that
2739  * this segment is not used for anything but congestion avoidance or
2740  * fast retransmit. Moreover, we even are able to eliminate most of such
2741  * second order effects, if we apply some small "replay" window (~RTO)
2742  * to timestamp space.
2743  *
2744  * All these measures still do not guarantee that we reject wrapped ACKs
2745  * on networks with high bandwidth, when sequence space is recycled fastly,
2746  * but it guarantees that such events will be very rare and do not affect
2747  * connection seriously. This doesn't look nice, but alas, PAWS is really
2748  * buggy extension.
2749  *
2750  * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
2751  * states that events when retransmit arrives after original data are rare.
2752  * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
2753  * the biggest problem on large power networks even with minor reordering.
2754  * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
2755  * up to bandwidth of 18Gigabit/sec. 8) ]
2756  */
2757
2758 static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb)
2759 {
2760         struct tcp_sock *tp = tcp_sk(sk);
2761         struct tcphdr *th = skb->h.th;
2762         u32 seq = TCP_SKB_CB(skb)->seq;
2763         u32 ack = TCP_SKB_CB(skb)->ack_seq;
2764
2765         return (/* 1. Pure ACK with correct sequence number. */
2766                 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
2767
2768                 /* 2. ... and duplicate ACK. */
2769                 ack == tp->snd_una &&
2770
2771                 /* 3. ... and does not update window. */
2772                 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
2773
2774                 /* 4. ... and sits in replay window. */
2775                 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ);
2776 }
2777
2778 static inline int tcp_paws_discard(const struct sock *sk, const struct sk_buff *skb)
2779 {
2780         const struct tcp_sock *tp = tcp_sk(sk);
2781         return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW &&
2782                 xtime.tv_sec < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS &&
2783                 !tcp_disordered_ack(sk, skb));
2784 }
2785
2786 /* Check segment sequence number for validity.
2787  *
2788  * Segment controls are considered valid, if the segment
2789  * fits to the window after truncation to the window. Acceptability
2790  * of data (and SYN, FIN, of course) is checked separately.
2791  * See tcp_data_queue(), for example.
2792  *
2793  * Also, controls (RST is main one) are accepted using RCV.WUP instead
2794  * of RCV.NXT. Peer still did not advance his SND.UNA when we
2795  * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
2796  * (borrowed from freebsd)
2797  */
2798
2799 static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
2800 {
2801         return  !before(end_seq, tp->rcv_wup) &&
2802                 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
2803 }
2804
2805 /* When we get a reset we do this. */
2806 static void tcp_reset(struct sock *sk)
2807 {
2808         /* We want the right error as BSD sees it (and indeed as we do). */
2809         switch (sk->sk_state) {
2810                 case TCP_SYN_SENT:
2811                         sk->sk_err = ECONNREFUSED;
2812                         break;
2813                 case TCP_CLOSE_WAIT:
2814                         sk->sk_err = EPIPE;
2815                         break;
2816                 case TCP_CLOSE:
2817                         return;
2818                 default:
2819                         sk->sk_err = ECONNRESET;
2820         }
2821
2822         if (!sock_flag(sk, SOCK_DEAD))
2823                 sk->sk_error_report(sk);
2824
2825         tcp_done(sk);
2826 }
2827
2828 /*
2829  *      Process the FIN bit. This now behaves as it is supposed to work
2830  *      and the FIN takes effect when it is validly part of sequence
2831  *      space. Not before when we get holes.
2832  *
2833  *      If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
2834  *      (and thence onto LAST-ACK and finally, CLOSE, we never enter
2835  *      TIME-WAIT)
2836  *
2837  *      If we are in FINWAIT-1, a received FIN indicates simultaneous
2838  *      close and we go into CLOSING (and later onto TIME-WAIT)
2839  *
2840  *      If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
2841  */
2842 static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
2843 {
2844         struct tcp_sock *tp = tcp_sk(sk);
2845
2846         inet_csk_schedule_ack(sk);
2847
2848         sk->sk_shutdown |= RCV_SHUTDOWN;
2849         sock_set_flag(sk, SOCK_DONE);
2850
2851         switch (sk->sk_state) {
2852                 case TCP_SYN_RECV:
2853                 case TCP_ESTABLISHED:
2854                         /* Move to CLOSE_WAIT */
2855                         tcp_set_state(sk, TCP_CLOSE_WAIT);
2856                         inet_csk(sk)->icsk_ack.pingpong = 1;
2857                         break;
2858
2859                 case TCP_CLOSE_WAIT:
2860                 case TCP_CLOSING:
2861                         /* Received a retransmission of the FIN, do
2862                          * nothing.
2863                          */
2864                         break;
2865                 case TCP_LAST_ACK:
2866                         /* RFC793: Remain in the LAST-ACK state. */
2867                         break;
2868
2869                 case TCP_FIN_WAIT1:
2870                         /* This case occurs when a simultaneous close
2871                          * happens, we must ack the received FIN and
2872                          * enter the CLOSING state.
2873                          */
2874                         tcp_send_ack(sk);
2875                         tcp_set_state(sk, TCP_CLOSING);
2876                         break;
2877                 case TCP_FIN_WAIT2:
2878                         /* Received a FIN -- send ACK and enter TIME_WAIT. */
2879                         tcp_send_ack(sk);
2880                         tcp_time_wait(sk, TCP_TIME_WAIT, 0);
2881                         break;
2882                 default:
2883                         /* Only TCP_LISTEN and TCP_CLOSE are left, in these
2884                          * cases we should never reach this piece of code.
2885                          */
2886                         printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
2887                                __FUNCTION__, sk->sk_state);
2888                         break;
2889         };
2890
2891         /* It _is_ possible, that we have something out-of-order _after_ FIN.
2892          * Probably, we should reset in this case. For now drop them.
2893          */
2894         __skb_queue_purge(&tp->out_of_order_queue);
2895         if (tp->rx_opt.sack_ok)
2896                 tcp_sack_reset(&tp->rx_opt);
2897         sk_stream_mem_reclaim(sk);
2898
2899         if (!sock_flag(sk, SOCK_DEAD)) {
2900                 sk->sk_state_change(sk);
2901
2902                 /* Do not send POLL_HUP for half duplex close. */
2903                 if (sk->sk_shutdown == SHUTDOWN_MASK ||
2904                     sk->sk_state == TCP_CLOSE)
2905                         sk_wake_async(sk, 1, POLL_HUP);
2906                 else
2907                         sk_wake_async(sk, 1, POLL_IN);
2908         }
2909 }
2910
2911 static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq)
2912 {
2913         if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
2914                 if (before(seq, sp->start_seq))
2915                         sp->start_seq = seq;
2916                 if (after(end_seq, sp->end_seq))
2917                         sp->end_seq = end_seq;
2918                 return 1;
2919         }
2920         return 0;
2921 }
2922
2923 static void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq)
2924 {
2925         if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
2926                 if (before(seq, tp->rcv_nxt))
2927                         NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT);
2928                 else
2929                         NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT);
2930
2931                 tp->rx_opt.dsack = 1;
2932                 tp->duplicate_sack[0].start_seq = seq;
2933                 tp->duplicate_sack[0].end_seq = end_seq;
2934                 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok);
2935         }
2936 }
2937
2938 static void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq)
2939 {
2940         if (!tp->rx_opt.dsack)
2941                 tcp_dsack_set(tp, seq, end_seq);
2942         else
2943                 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
2944 }
2945
2946 static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
2947 {
2948         struct tcp_sock *tp = tcp_sk(sk);
2949
2950         if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
2951             before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
2952                 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
2953                 tcp_enter_quickack_mode(sk);
2954
2955                 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
2956                         u32 end_seq = TCP_SKB_CB(skb)->end_seq;
2957
2958                         if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
2959                                 end_seq = tp->rcv_nxt;
2960                         tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq);
2961                 }
2962         }
2963
2964         tcp_send_ack(sk);
2965 }
2966
2967 /* These routines update the SACK block as out-of-order packets arrive or
2968  * in-order packets close up the sequence space.
2969  */
2970 static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
2971 {
2972         int this_sack;
2973         struct tcp_sack_block *sp = &tp->selective_acks[0];
2974         struct tcp_sack_block *swalk = sp+1;
2975
2976         /* See if the recent change to the first SACK eats into
2977          * or hits the sequence space of other SACK blocks, if so coalesce.
2978          */
2979         for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) {
2980                 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
2981                         int i;
2982
2983                         /* Zap SWALK, by moving every further SACK up by one slot.
2984                          * Decrease num_sacks.
2985                          */
2986                         tp->rx_opt.num_sacks--;
2987                         tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
2988                         for(i=this_sack; i < tp->rx_opt.num_sacks; i++)
2989                                 sp[i] = sp[i+1];
2990                         continue;
2991                 }
2992                 this_sack++, swalk++;
2993         }
2994 }
2995
2996 static inline void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2)
2997 {
2998         __u32 tmp;
2999
3000         tmp = sack1->start_seq;
3001         sack1->start_seq = sack2->start_seq;
3002         sack2->start_seq = tmp;
3003
3004         tmp = sack1->end_seq;
3005         sack1->end_seq = sack2->end_seq;
3006         sack2->end_seq = tmp;
3007 }
3008
3009 static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
3010 {
3011         struct tcp_sock *tp = tcp_sk(sk);
3012         struct tcp_sack_block *sp = &tp->selective_acks[0];
3013         int cur_sacks = tp->rx_opt.num_sacks;
3014         int this_sack;
3015
3016         if (!cur_sacks)
3017                 goto new_sack;
3018
3019         for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) {
3020                 if (tcp_sack_extend(sp, seq, end_seq)) {
3021                         /* Rotate this_sack to the first one. */
3022                         for (; this_sack>0; this_sack--, sp--)
3023                                 tcp_sack_swap(sp, sp-1);
3024                         if (cur_sacks > 1)
3025                                 tcp_sack_maybe_coalesce(tp);
3026                         return;
3027                 }
3028         }
3029
3030         /* Could not find an adjacent existing SACK, build a new one,
3031          * put it at the front, and shift everyone else down.  We
3032          * always know there is at least one SACK present already here.
3033          *
3034          * If the sack array is full, forget about the last one.
3035          */
3036         if (this_sack >= 4) {
3037                 this_sack--;
3038                 tp->rx_opt.num_sacks--;
3039                 sp--;
3040         }
3041         for(; this_sack > 0; this_sack--, sp--)
3042                 *sp = *(sp-1);
3043
3044 new_sack:
3045         /* Build the new head SACK, and we're done. */
3046         sp->start_seq = seq;
3047         sp->end_seq = end_seq;
3048         tp->rx_opt.num_sacks++;
3049         tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3050 }
3051
3052 /* RCV.NXT advances, some SACKs should be eaten. */
3053
3054 static void tcp_sack_remove(struct tcp_sock *tp)
3055 {
3056         struct tcp_sack_block *sp = &tp->selective_acks[0];
3057         int num_sacks = tp->rx_opt.num_sacks;
3058         int this_sack;
3059
3060         /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
3061         if (skb_queue_empty(&tp->out_of_order_queue)) {
3062                 tp->rx_opt.num_sacks = 0;
3063                 tp->rx_opt.eff_sacks = tp->rx_opt.dsack;
3064                 return;
3065         }
3066
3067         for(this_sack = 0; this_sack < num_sacks; ) {
3068                 /* Check if the start of the sack is covered by RCV.NXT. */
3069                 if (!before(tp->rcv_nxt, sp->start_seq)) {
3070                         int i;
3071
3072                         /* RCV.NXT must cover all the block! */
3073                         BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq));
3074
3075                         /* Zap this SACK, by moving forward any other SACKS. */
3076                         for (i=this_sack+1; i < num_sacks; i++)
3077                                 tp->selective_acks[i-1] = tp->selective_acks[i];
3078                         num_sacks--;
3079                         continue;
3080                 }
3081                 this_sack++;
3082                 sp++;
3083         }
3084         if (num_sacks != tp->rx_opt.num_sacks) {
3085                 tp->rx_opt.num_sacks = num_sacks;
3086                 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3087         }
3088 }
3089
3090 /* This one checks to see if we can put data from the
3091  * out_of_order queue into the receive_queue.
3092  */
3093 static void tcp_ofo_queue(struct sock *sk)
3094 {
3095         struct tcp_sock *tp = tcp_sk(sk);
3096         __u32 dsack_high = tp->rcv_nxt;
3097         struct sk_buff *skb;
3098
3099         while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
3100                 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
3101                         break;
3102
3103                 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
3104                         __u32 dsack = dsack_high;
3105                         if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
3106                                 dsack_high = TCP_SKB_CB(skb)->end_seq;
3107                         tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack);
3108                 }
3109
3110                 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3111                         SOCK_DEBUG(sk, "ofo packet was already received \n");
3112                         __skb_unlink(skb, &tp->out_of_order_queue);
3113                         __kfree_skb(skb);
3114                         continue;
3115                 }
3116                 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
3117                            tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3118                            TCP_SKB_CB(skb)->end_seq);
3119
3120                 __skb_unlink(skb, &tp->out_of_order_queue);
3121                 __skb_queue_tail(&sk->sk_receive_queue, skb);
3122                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3123                 if(skb->h.th->fin)
3124                         tcp_fin(skb, sk, skb->h.th);
3125         }
3126 }
3127
3128 static int tcp_prune_queue(struct sock *sk);
3129
3130 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
3131 {
3132         struct tcphdr *th = skb->h.th;
3133         struct tcp_sock *tp = tcp_sk(sk);
3134         int eaten = -1;
3135
3136         if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
3137                 goto drop;
3138
3139         __skb_pull(skb, th->doff*4);
3140
3141         TCP_ECN_accept_cwr(tp, skb);
3142
3143         if (tp->rx_opt.dsack) {
3144                 tp->rx_opt.dsack = 0;
3145                 tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks,
3146                                                     4 - tp->rx_opt.tstamp_ok);
3147         }
3148
3149         /*  Queue data for delivery to the user.
3150          *  Packets in sequence go to the receive queue.
3151          *  Out of sequence packets to the out_of_order_queue.
3152          */
3153         if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3154                 if (tcp_receive_window(tp) == 0)
3155                         goto out_of_window;
3156
3157                 /* Ok. In sequence. In window. */
3158                 if (tp->ucopy.task == current &&
3159                     tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
3160                     sock_owned_by_user(sk) && !tp->urg_data) {
3161                         int chunk = min_t(unsigned int, skb->len,
3162                                                         tp->ucopy.len);
3163
3164                         __set_current_state(TASK_RUNNING);
3165
3166                         local_bh_enable();
3167                         if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
3168                                 tp->ucopy.len -= chunk;
3169                                 tp->copied_seq += chunk;
3170                                 eaten = (chunk == skb->len && !th->fin);
3171                                 tcp_rcv_space_adjust(sk);
3172                         }
3173                         local_bh_disable();
3174                 }
3175
3176                 if (eaten <= 0) {
3177 queue_and_out:
3178                         if (eaten < 0 &&
3179                             (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3180                              !sk_stream_rmem_schedule(sk, skb))) {
3181                                 if (tcp_prune_queue(sk) < 0 ||
3182                                     !sk_stream_rmem_schedule(sk, skb))
3183                                         goto drop;
3184                         }
3185                         sk_stream_set_owner_r(skb, sk);
3186                         __skb_queue_tail(&sk->sk_receive_queue, skb);
3187                 }
3188                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3189                 if(skb->len)
3190                         tcp_event_data_recv(sk, tp, skb);
3191                 if(th->fin)
3192                         tcp_fin(skb, sk, th);
3193
3194                 if (!skb_queue_empty(&tp->out_of_order_queue)) {
3195                         tcp_ofo_queue(sk);
3196
3197                         /* RFC2581. 4.2. SHOULD send immediate ACK, when
3198                          * gap in queue is filled.
3199                          */
3200                         if (skb_queue_empty(&tp->out_of_order_queue))
3201                                 inet_csk(sk)->icsk_ack.pingpong = 0;
3202                 }
3203
3204                 if (tp->rx_opt.num_sacks)
3205                         tcp_sack_remove(tp);
3206
3207                 tcp_fast_path_check(sk, tp);
3208
3209                 if (eaten > 0)
3210                         __kfree_skb(skb);
3211                 else if (!sock_flag(sk, SOCK_DEAD))
3212                         sk->sk_data_ready(sk, 0);
3213                 return;
3214         }
3215
3216         if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3217                 /* A retransmit, 2nd most common case.  Force an immediate ack. */
3218                 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
3219                 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3220
3221 out_of_window:
3222                 tcp_enter_quickack_mode(sk);
3223                 inet_csk_schedule_ack(sk);
3224 drop:
3225                 __kfree_skb(skb);
3226                 return;
3227         }
3228
3229         /* Out of window. F.e. zero window probe. */
3230         if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
3231                 goto out_of_window;
3232
3233         tcp_enter_quickack_mode(sk);
3234
3235         if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3236                 /* Partial packet, seq < rcv_next < end_seq */
3237                 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
3238                            tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3239                            TCP_SKB_CB(skb)->end_seq);
3240
3241                 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
3242                 
3243                 /* If window is closed, drop tail of packet. But after
3244                  * remembering D-SACK for its head made in previous line.
3245                  */
3246                 if (!tcp_receive_window(tp))
3247                         goto out_of_window;
3248                 goto queue_and_out;
3249         }
3250
3251         TCP_ECN_check_ce(tp, skb);
3252
3253         if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3254             !sk_stream_rmem_schedule(sk, skb)) {
3255                 if (tcp_prune_queue(sk) < 0 ||
3256                     !sk_stream_rmem_schedule(sk, skb))
3257                         goto drop;
3258         }
3259
3260         /* Disable header prediction. */
3261         tp->pred_flags = 0;
3262         inet_csk_schedule_ack(sk);
3263
3264         SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
3265                    tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3266
3267         sk_stream_set_owner_r(skb, sk);
3268
3269         if (!skb_peek(&tp->out_of_order_queue)) {
3270                 /* Initial out of order segment, build 1 SACK. */
3271                 if (tp->rx_opt.sack_ok) {
3272                         tp->rx_opt.num_sacks = 1;
3273                         tp->rx_opt.dsack     = 0;
3274                         tp->rx_opt.eff_sacks = 1;
3275                         tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
3276                         tp->selective_acks[0].end_seq =
3277                                                 TCP_SKB_CB(skb)->end_seq;
3278                 }
3279                 __skb_queue_head(&tp->out_of_order_queue,skb);
3280         } else {
3281                 struct sk_buff *skb1 = tp->out_of_order_queue.prev;
3282                 u32 seq = TCP_SKB_CB(skb)->seq;
3283                 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
3284
3285                 if (seq == TCP_SKB_CB(skb1)->end_seq) {
3286                         __skb_append(skb1, skb, &tp->out_of_order_queue);
3287
3288                         if (!tp->rx_opt.num_sacks ||
3289                             tp->selective_acks[0].end_seq != seq)
3290                                 goto add_sack;
3291
3292                         /* Common case: data arrive in order after hole. */
3293                         tp->selective_acks[0].end_seq = end_seq;
3294                         return;
3295                 }
3296
3297                 /* Find place to insert this segment. */
3298                 do {
3299                         if (!after(TCP_SKB_CB(skb1)->seq, seq))
3300                                 break;
3301                 } while ((skb1 = skb1->prev) !=
3302                          (struct sk_buff*)&tp->out_of_order_queue);
3303
3304                 /* Do skb overlap to previous one? */
3305                 if (skb1 != (struct sk_buff*)&tp->out_of_order_queue &&
3306                     before(seq, TCP_SKB_CB(skb1)->end_seq)) {
3307                         if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3308                                 /* All the bits are present. Drop. */
3309                                 __kfree_skb(skb);
3310                                 tcp_dsack_set(tp, seq, end_seq);
3311                                 goto add_sack;
3312                         }
3313                         if (after(seq, TCP_SKB_CB(skb1)->seq)) {
3314                                 /* Partial overlap. */
3315                                 tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq);
3316                         } else {
3317                                 skb1 = skb1->prev;
3318                         }
3319                 }
3320                 __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue);
3321                 
3322                 /* And clean segments covered by new one as whole. */
3323                 while ((skb1 = skb->next) !=
3324                        (struct sk_buff*)&tp->out_of_order_queue &&
3325                        after(end_seq, TCP_SKB_CB(skb1)->seq)) {
3326                        if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3327                                tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq);
3328                                break;
3329                        }
3330                        __skb_unlink(skb1, &tp->out_of_order_queue);
3331                        tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq);
3332                        __kfree_skb(skb1);
3333                 }
3334
3335 add_sack:
3336                 if (tp->rx_opt.sack_ok)
3337                         tcp_sack_new_ofo_skb(sk, seq, end_seq);
3338         }
3339 }
3340
3341 /* Collapse contiguous sequence of skbs head..tail with
3342  * sequence numbers start..end.
3343  * Segments with FIN/SYN are not collapsed (only because this
3344  * simplifies code)
3345  */
3346 static void
3347 tcp_collapse(struct sock *sk, struct sk_buff_head *list,
3348              struct sk_buff *head, struct sk_buff *tail,
3349              u32 start, u32 end)
3350 {
3351         struct sk_buff *skb;
3352
3353         /* First, check that queue is collapsible and find
3354          * the point where collapsing can be useful. */
3355         for (skb = head; skb != tail; ) {
3356                 /* No new bits? It is possible on ofo queue. */
3357                 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3358                         struct sk_buff *next = skb->next;
3359                         __skb_unlink(skb, list);
3360                         __kfree_skb(skb);
3361                         NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3362                         skb = next;
3363                         continue;
3364                 }
3365
3366                 /* The first skb to collapse is:
3367                  * - not SYN/FIN and
3368                  * - bloated or contains data before "start" or
3369                  *   overlaps to the next one.
3370                  */
3371                 if (!skb->h.th->syn && !skb->h.th->fin &&
3372                     (tcp_win_from_space(skb->truesize) > skb->len ||
3373                      before(TCP_SKB_CB(skb)->seq, start) ||
3374                      (skb->next != tail &&
3375                       TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq)))
3376                         break;
3377
3378                 /* Decided to skip this, advance start seq. */
3379                 start = TCP_SKB_CB(skb)->end_seq;
3380                 skb = skb->next;
3381         }
3382         if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3383                 return;
3384
3385         while (before(start, end)) {
3386                 struct sk_buff *nskb;
3387                 int header = skb_headroom(skb);
3388                 int copy = SKB_MAX_ORDER(header, 0);
3389
3390                 /* Too big header? This can happen with IPv6. */
3391                 if (copy < 0)
3392                         return;
3393                 if (end-start < copy)
3394                         copy = end-start;
3395                 nskb = alloc_skb(copy+header, GFP_ATOMIC);
3396                 if (!nskb)
3397                         return;
3398                 skb_reserve(nskb, header);
3399                 memcpy(nskb->head, skb->head, header);
3400                 nskb->nh.raw = nskb->head + (skb->nh.raw-skb->head);
3401                 nskb->h.raw = nskb->head + (skb->h.raw-skb->head);
3402                 nskb->mac.raw = nskb->head + (skb->mac.raw-skb->head);
3403                 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
3404                 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
3405                 __skb_insert(nskb, skb->prev, skb, list);
3406                 sk_stream_set_owner_r(nskb, sk);
3407
3408                 /* Copy data, releasing collapsed skbs. */
3409                 while (copy > 0) {
3410                         int offset = start - TCP_SKB_CB(skb)->seq;
3411                         int size = TCP_SKB_CB(skb)->end_seq - start;
3412
3413                         BUG_ON(offset < 0);
3414                         if (size > 0) {
3415                                 size = min(copy, size);
3416                                 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
3417                                         BUG();
3418                                 TCP_SKB_CB(nskb)->end_seq += size;
3419                                 copy -= size;
3420                                 start += size;
3421                         }
3422                         if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3423                                 struct sk_buff *next = skb->next;
3424                                 __skb_unlink(skb, list);
3425                                 __kfree_skb(skb);
3426                                 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3427                                 skb = next;
3428                                 if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3429                                         return;
3430                         }
3431                 }
3432         }
3433 }
3434
3435 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3436  * and tcp_collapse() them until all the queue is collapsed.
3437  */
3438 static void tcp_collapse_ofo_queue(struct sock *sk)
3439 {
3440         struct tcp_sock *tp = tcp_sk(sk);
3441         struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
3442         struct sk_buff *head;
3443         u32 start, end;
3444
3445         if (skb == NULL)
3446                 return;
3447
3448         start = TCP_SKB_CB(skb)->seq;
3449         end = TCP_SKB_CB(skb)->end_seq;
3450         head = skb;
3451
3452         for (;;) {
3453                 skb = skb->next;
3454
3455                 /* Segment is terminated when we see gap or when
3456                  * we are at the end of all the queue. */
3457                 if (skb == (struct sk_buff *)&tp->out_of_order_queue ||
3458                     after(TCP_SKB_CB(skb)->seq, end) ||
3459                     before(TCP_SKB_CB(skb)->end_seq, start)) {
3460                         tcp_collapse(sk, &tp->out_of_order_queue,
3461                                      head, skb, start, end);
3462                         head = skb;
3463                         if (skb == (struct sk_buff *)&tp->out_of_order_queue)
3464                                 break;
3465                         /* Start new segment */
3466                         start = TCP_SKB_CB(skb)->seq;
3467                         end = TCP_SKB_CB(skb)->end_seq;
3468                 } else {
3469                         if (before(TCP_SKB_CB(skb)->seq, start))
3470                                 start = TCP_SKB_CB(skb)->seq;
3471                         if (after(TCP_SKB_CB(skb)->end_seq, end))
3472                                 end = TCP_SKB_CB(skb)->end_seq;
3473                 }
3474         }
3475 }
3476
3477 /* Reduce allocated memory if we can, trying to get
3478  * the socket within its memory limits again.
3479  *
3480  * Return less than zero if we should start dropping frames
3481  * until the socket owning process reads some of the data
3482  * to stabilize the situation.
3483  */
3484 static int tcp_prune_queue(struct sock *sk)
3485 {
3486         struct tcp_sock *tp = tcp_sk(sk); 
3487
3488         SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
3489
3490         NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED);
3491
3492         if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
3493                 tcp_clamp_window(sk, tp);
3494         else if (tcp_memory_pressure)
3495                 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
3496
3497         tcp_collapse_ofo_queue(sk);
3498         tcp_collapse(sk, &sk->sk_receive_queue,
3499                      sk->sk_receive_queue.next,
3500                      (struct sk_buff*)&sk->sk_receive_queue,
3501                      tp->copied_seq, tp->rcv_nxt);
3502         sk_stream_mem_reclaim(sk);
3503
3504         if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3505                 return 0;
3506
3507         /* Collapsing did not help, destructive actions follow.
3508          * This must not ever occur. */
3509
3510         /* First, purge the out_of_order queue. */
3511         if (!skb_queue_empty(&tp->out_of_order_queue)) {
3512                 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED);
3513                 __skb_queue_purge(&tp->out_of_order_queue);
3514
3515                 /* Reset SACK state.  A conforming SACK implementation will
3516                  * do the same at a timeout based retransmit.  When a connection
3517                  * is in a sad state like this, we care only about integrity
3518                  * of the connection not performance.
3519                  */
3520                 if (tp->rx_opt.sack_ok)
3521                         tcp_sack_reset(&tp->rx_opt);
3522                 sk_stream_mem_reclaim(sk);
3523         }
3524
3525         if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3526                 return 0;
3527
3528         /* If we are really being abused, tell the caller to silently
3529          * drop receive data on the floor.  It will get retransmitted
3530          * and hopefully then we'll have sufficient space.
3531          */
3532         NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED);
3533
3534         /* Massive buffer overcommit. */
3535         tp->pred_flags = 0;
3536         return -1;
3537 }
3538
3539
3540 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3541  * As additional protections, we do not touch cwnd in retransmission phases,
3542  * and if application hit its sndbuf limit recently.
3543  */
3544 void tcp_cwnd_application_limited(struct sock *sk)
3545 {
3546         struct tcp_sock *tp = tcp_sk(sk);
3547
3548         if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
3549             sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
3550                 /* Limited by application or receiver window. */
3551                 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk));
3552                 u32 win_used = max(tp->snd_cwnd_used, init_win);
3553                 if (win_used < tp->snd_cwnd) {
3554                         tp->snd_ssthresh = tcp_current_ssthresh(sk);
3555                         tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
3556                 }
3557                 tp->snd_cwnd_used = 0;
3558         }
3559         tp->snd_cwnd_stamp = tcp_time_stamp;
3560 }
3561
3562 static int tcp_should_expand_sndbuf(struct sock *sk, struct tcp_sock *tp)
3563 {
3564         /* If the user specified a specific send buffer setting, do
3565          * not modify it.
3566          */
3567         if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
3568                 return 0;
3569
3570         /* If we are under global TCP memory pressure, do not expand.  */
3571         if (tcp_memory_pressure)
3572                 return 0;
3573
3574         /* If we are under soft global TCP memory pressure, do not expand.  */
3575         if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0])
3576                 return 0;
3577
3578         /* If we filled the congestion window, do not expand.  */
3579         if (tp->packets_out >= tp->snd_cwnd)
3580                 return 0;
3581
3582         return 1;
3583 }
3584
3585 /* When incoming ACK allowed to free some skb from write_queue,
3586  * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3587  * on the exit from tcp input handler.
3588  *
3589  * PROBLEM: sndbuf expansion does not work well with largesend.
3590  */
3591 static void tcp_new_space(struct sock *sk)
3592 {
3593         struct tcp_sock *tp = tcp_sk(sk);
3594
3595         if (tcp_should_expand_sndbuf(sk, tp)) {
3596                 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
3597                         MAX_TCP_HEADER + 16 + sizeof(struct sk_buff),
3598                     demanded = max_t(unsigned int, tp->snd_cwnd,
3599                                                    tp->reordering + 1);
3600                 sndmem *= 2*demanded;
3601                 if (sndmem > sk->sk_sndbuf)
3602                         sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
3603                 tp->snd_cwnd_stamp = tcp_time_stamp;
3604         }
3605
3606         sk->sk_write_space(sk);
3607 }
3608
3609 static void tcp_check_space(struct sock *sk)
3610 {
3611         if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
3612                 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
3613                 if (sk->sk_socket &&
3614                     test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
3615                         tcp_new_space(sk);
3616         }
3617 }
3618
3619 static inline void tcp_data_snd_check(struct sock *sk, struct tcp_sock *tp)
3620 {
3621         tcp_push_pending_frames(sk, tp);
3622         tcp_check_space(sk);
3623 }
3624
3625 /*
3626  * Check if sending an ack is needed.
3627  */
3628 static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
3629 {
3630         struct tcp_sock *tp = tcp_sk(sk);
3631
3632             /* More than one full frame received... */
3633         if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss
3634              /* ... and right edge of window advances far enough.
3635               * (tcp_recvmsg() will send ACK otherwise). Or...
3636               */
3637              && __tcp_select_window(sk) >= tp->rcv_wnd) ||
3638             /* We ACK each frame or... */
3639             tcp_in_quickack_mode(sk) ||
3640             /* We have out of order data. */
3641             (ofo_possible &&
3642              skb_peek(&tp->out_of_order_queue))) {
3643                 /* Then ack it now */
3644                 tcp_send_ack(sk);
3645         } else {
3646                 /* Else, send delayed ack. */
3647                 tcp_send_delayed_ack(sk);
3648         }
3649 }
3650
3651 static inline void tcp_ack_snd_check(struct sock *sk)
3652 {
3653         if (!inet_csk_ack_scheduled(sk)) {
3654                 /* We sent a data segment already. */
3655                 return;
3656         }
3657         __tcp_ack_snd_check(sk, 1);
3658 }
3659
3660 /*
3661  *      This routine is only called when we have urgent data
3662  *      signaled. Its the 'slow' part of tcp_urg. It could be
3663  *      moved inline now as tcp_urg is only called from one
3664  *      place. We handle URGent data wrong. We have to - as
3665  *      BSD still doesn't use the correction from RFC961.
3666  *      For 1003.1g we should support a new option TCP_STDURG to permit
3667  *      either form (or just set the sysctl tcp_stdurg).
3668  */
3669  
3670 static void tcp_check_urg(struct sock * sk, struct tcphdr * th)
3671 {
3672         struct tcp_sock *tp = tcp_sk(sk);
3673         u32 ptr = ntohs(th->urg_ptr);
3674
3675         if (ptr && !sysctl_tcp_stdurg)
3676                 ptr--;
3677         ptr += ntohl(th->seq);
3678
3679         /* Ignore urgent data that we've already seen and read. */
3680         if (after(tp->copied_seq, ptr))
3681                 return;
3682
3683         /* Do not replay urg ptr.
3684          *
3685          * NOTE: interesting situation not covered by specs.
3686          * Misbehaving sender may send urg ptr, pointing to segment,
3687          * which we already have in ofo queue. We are not able to fetch
3688          * such data and will stay in TCP_URG_NOTYET until will be eaten
3689          * by recvmsg(). Seems, we are not obliged to handle such wicked
3690          * situations. But it is worth to think about possibility of some
3691          * DoSes using some hypothetical application level deadlock.
3692          */
3693         if (before(ptr, tp->rcv_nxt))
3694                 return;
3695
3696         /* Do we already have a newer (or duplicate) urgent pointer? */
3697         if (tp->urg_data && !after(ptr, tp->urg_seq))
3698                 return;
3699
3700         /* Tell the world about our new urgent pointer. */
3701         sk_send_sigurg(sk);
3702
3703         /* We may be adding urgent data when the last byte read was
3704          * urgent. To do this requires some care. We cannot just ignore
3705          * tp->copied_seq since we would read the last urgent byte again
3706          * as data, nor can we alter copied_seq until this data arrives
3707          * or we break the semantics of SIOCATMARK (and thus sockatmark())
3708          *
3709          * NOTE. Double Dutch. Rendering to plain English: author of comment
3710          * above did something sort of  send("A", MSG_OOB); send("B", MSG_OOB);
3711          * and expect that both A and B disappear from stream. This is _wrong_.
3712          * Though this happens in BSD with high probability, this is occasional.
3713          * Any application relying on this is buggy. Note also, that fix "works"
3714          * only in this artificial test. Insert some normal data between A and B and we will
3715          * decline of BSD again. Verdict: it is better to remove to trap
3716          * buggy users.
3717          */
3718         if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
3719             !sock_flag(sk, SOCK_URGINLINE) &&
3720             tp->copied_seq != tp->rcv_nxt) {
3721                 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
3722                 tp->copied_seq++;
3723                 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
3724                         __skb_unlink(skb, &sk->sk_receive_queue);
3725                         __kfree_skb(skb);
3726                 }
3727         }
3728
3729         tp->urg_data   = TCP_URG_NOTYET;
3730         tp->urg_seq    = ptr;
3731
3732         /* Disable header prediction. */
3733         tp->pred_flags = 0;
3734 }
3735
3736 /* This is the 'fast' part of urgent handling. */
3737 static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
3738 {
3739         struct tcp_sock *tp = tcp_sk(sk);
3740
3741         /* Check if we get a new urgent pointer - normally not. */
3742         if (th->urg)
3743                 tcp_check_urg(sk,th);
3744
3745         /* Do we wait for any urgent data? - normally not... */
3746         if (tp->urg_data == TCP_URG_NOTYET) {
3747                 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
3748                           th->syn;
3749
3750                 /* Is the urgent pointer pointing into this packet? */   
3751                 if (ptr < skb->len) {
3752                         u8 tmp;
3753                         if (skb_copy_bits(skb, ptr, &tmp, 1))
3754                                 BUG();
3755                         tp->urg_data = TCP_URG_VALID | tmp;
3756                         if (!sock_flag(sk, SOCK_DEAD))
3757                                 sk->sk_data_ready(sk, 0);
3758                 }
3759         }
3760 }
3761
3762 static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
3763 {
3764         struct tcp_sock *tp = tcp_sk(sk);
3765         int chunk = skb->len - hlen;
3766         int err;
3767
3768         local_bh_enable();
3769         if (skb->ip_summed==CHECKSUM_UNNECESSARY)
3770                 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
3771         else
3772                 err = skb_copy_and_csum_datagram_iovec(skb, hlen,
3773                                                        tp->ucopy.iov);
3774
3775         if (!err) {
3776                 tp->ucopy.len -= chunk;
3777                 tp->copied_seq += chunk;
3778                 tcp_rcv_space_adjust(sk);
3779         }
3780
3781         local_bh_disable();
3782         return err;
3783 }
3784
3785 static int __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
3786 {
3787         int result;
3788
3789         if (sock_owned_by_user(sk)) {
3790                 local_bh_enable();
3791                 result = __tcp_checksum_complete(skb);
3792                 local_bh_disable();
3793         } else {
3794                 result = __tcp_checksum_complete(skb);
3795         }
3796         return result;
3797 }
3798
3799 static inline int tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
3800 {
3801         return skb->ip_summed != CHECKSUM_UNNECESSARY &&
3802                 __tcp_checksum_complete_user(sk, skb);
3803 }
3804
3805 #ifdef CONFIG_NET_DMA
3806 static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, int hlen)
3807 {
3808         struct tcp_sock *tp = tcp_sk(sk);
3809         int chunk = skb->len - hlen;
3810         int dma_cookie;
3811         int copied_early = 0;
3812
3813         if (tp->ucopy.wakeup)
3814                 return 0;
3815
3816         if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list)
3817                 tp->ucopy.dma_chan = get_softnet_dma();
3818
3819         if (tp->ucopy.dma_chan && skb->ip_summed == CHECKSUM_UNNECESSARY) {
3820
3821                 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan,
3822                         skb, hlen, tp->ucopy.iov, chunk, tp->ucopy.pinned_list);
3823
3824                 if (dma_cookie < 0)
3825                         goto out;
3826
3827                 tp->ucopy.dma_cookie = dma_cookie;
3828                 copied_early = 1;
3829
3830                 tp->ucopy.len -= chunk;
3831                 tp->copied_seq += chunk;
3832                 tcp_rcv_space_adjust(sk);
3833
3834                 if ((tp->ucopy.len == 0) ||
3835                     (tcp_flag_word(skb->h.th) & TCP_FLAG_PSH) ||
3836                     (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) {
3837                         tp->ucopy.wakeup = 1;
3838                         sk->sk_data_ready(sk, 0);
3839                 }
3840         } else if (chunk > 0) {
3841                 tp->ucopy.wakeup = 1;
3842                 sk->sk_data_ready(sk, 0);
3843         }
3844 out:
3845         return copied_early;
3846 }
3847 #endif /* CONFIG_NET_DMA */
3848
3849 /*
3850  *      TCP receive function for the ESTABLISHED state. 
3851  *
3852  *      It is split into a fast path and a slow path. The fast path is 
3853  *      disabled when:
3854  *      - A zero window was announced from us - zero window probing
3855  *        is only handled properly in the slow path. 
3856  *      - Out of order segments arrived.
3857  *      - Urgent data is expected.
3858  *      - There is no buffer space left
3859  *      - Unexpected TCP flags/window values/header lengths are received
3860  *        (detected by checking the TCP header against pred_flags) 
3861  *      - Data is sent in both directions. Fast path only supports pure senders
3862  *        or pure receivers (this means either the sequence number or the ack
3863  *        value must stay constant)
3864  *      - Unexpected TCP option.
3865  *
3866  *      When these conditions are not satisfied it drops into a standard 
3867  *      receive procedure patterned after RFC793 to handle all cases.
3868  *      The first three cases are guaranteed by proper pred_flags setting,
3869  *      the rest is checked inline. Fast processing is turned on in 
3870  *      tcp_data_queue when everything is OK.
3871  */
3872 int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
3873                         struct tcphdr *th, unsigned len)
3874 {
3875         struct tcp_sock *tp = tcp_sk(sk);
3876
3877         /*
3878          *      Header prediction.
3879          *      The code loosely follows the one in the famous 
3880          *      "30 instruction TCP receive" Van Jacobson mail.
3881          *      
3882          *      Van's trick is to deposit buffers into socket queue 
3883          *      on a device interrupt, to call tcp_recv function
3884          *      on the receive process context and checksum and copy
3885          *      the buffer to user space. smart...
3886          *
3887          *      Our current scheme is not silly either but we take the 
3888          *      extra cost of the net_bh soft interrupt processing...
3889          *      We do checksum and copy also but from device to kernel.
3890          */
3891
3892         tp->rx_opt.saw_tstamp = 0;
3893
3894         /*      pred_flags is 0xS?10 << 16 + snd_wnd
3895          *      if header_prediction is to be made
3896          *      'S' will always be tp->tcp_header_len >> 2
3897          *      '?' will be 0 for the fast path, otherwise pred_flags is 0 to
3898          *  turn it off (when there are holes in the receive 
3899          *       space for instance)
3900          *      PSH flag is ignored.
3901          */
3902
3903         if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
3904                 TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3905                 int tcp_header_len = tp->tcp_header_len;
3906
3907                 /* Timestamp header prediction: tcp_header_len
3908                  * is automatically equal to th->doff*4 due to pred_flags
3909                  * match.
3910                  */
3911
3912                 /* Check timestamp */
3913                 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
3914                         __be32 *ptr = (__be32 *)(th + 1);
3915
3916                         /* No? Slow path! */
3917                         if (*ptr != htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
3918                                           | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP))
3919                                 goto slow_path;
3920
3921                         tp->rx_opt.saw_tstamp = 1;
3922                         ++ptr; 
3923                         tp->rx_opt.rcv_tsval = ntohl(*ptr);
3924                         ++ptr;
3925                         tp->rx_opt.rcv_tsecr = ntohl(*ptr);
3926
3927                         /* If PAWS failed, check it more carefully in slow path */
3928                         if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
3929                                 goto slow_path;
3930
3931                         /* DO NOT update ts_recent here, if checksum fails
3932                          * and timestamp was corrupted part, it will result
3933                          * in a hung connection since we will drop all
3934                          * future packets due to the PAWS test.
3935                          */
3936                 }
3937
3938                 if (len <= tcp_header_len) {
3939                         /* Bulk data transfer: sender */
3940                         if (len == tcp_header_len) {
3941                                 /* Predicted packet is in window by definition.
3942                                  * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3943                                  * Hence, check seq<=rcv_wup reduces to:
3944                                  */
3945                                 if (tcp_header_len ==
3946                                     (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
3947                                     tp->rcv_nxt == tp->rcv_wup)
3948                                         tcp_store_ts_recent(tp);
3949
3950                                 /* We know that such packets are checksummed
3951                                  * on entry.
3952                                  */
3953                                 tcp_ack(sk, skb, 0);
3954                                 __kfree_skb(skb); 
3955                                 tcp_data_snd_check(sk, tp);
3956                                 return 0;
3957                         } else { /* Header too small */
3958                                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
3959                                 goto discard;
3960                         }
3961                 } else {
3962                         int eaten = 0;
3963                         int copied_early = 0;
3964
3965                         if (tp->copied_seq == tp->rcv_nxt &&
3966                             len - tcp_header_len <= tp->ucopy.len) {
3967 #ifdef CONFIG_NET_DMA
3968                                 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) {
3969                                         copied_early = 1;
3970                                         eaten = 1;
3971                                 }
3972 #endif
3973                                 if (tp->ucopy.task == current && sock_owned_by_user(sk) && !copied_early) {
3974                                         __set_current_state(TASK_RUNNING);
3975
3976                                         if (!tcp_copy_to_iovec(sk, skb, tcp_header_len))
3977                                                 eaten = 1;
3978                                 }
3979                                 if (eaten) {
3980                                         /* Predicted packet is in window by definition.
3981                                          * seq == rcv_nxt and rcv_wup <= rcv_nxt.
3982                                          * Hence, check seq<=rcv_wup reduces to:
3983                                          */
3984                                         if (tcp_header_len ==
3985                                             (sizeof(struct tcphdr) +
3986                                              TCPOLEN_TSTAMP_ALIGNED) &&
3987                                             tp->rcv_nxt == tp->rcv_wup)
3988                                                 tcp_store_ts_recent(tp);
3989
3990                                         tcp_rcv_rtt_measure_ts(sk, skb);
3991
3992                                         __skb_pull(skb, tcp_header_len);
3993                                         tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3994                                         NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER);
3995                                 }
3996                                 if (copied_early)
3997                                         tcp_cleanup_rbuf(sk, skb->len);
3998                         }
3999                         if (!eaten) {
4000                                 if (tcp_checksum_complete_user(sk, skb))
4001                                         goto csum_error;
4002
4003                                 /* Predicted packet is in window by definition.
4004                                  * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4005                                  * Hence, check seq<=rcv_wup reduces to:
4006                                  */
4007                                 if (tcp_header_len ==
4008                                     (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
4009                                     tp->rcv_nxt == tp->rcv_wup)
4010                                         tcp_store_ts_recent(tp);
4011
4012                                 tcp_rcv_rtt_measure_ts(sk, skb);
4013
4014                                 if ((int)skb->truesize > sk->sk_forward_alloc)
4015                                         goto step5;
4016
4017                                 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS);
4018
4019                                 /* Bulk data transfer: receiver */
4020                                 __skb_pull(skb,tcp_header_len);
4021                                 __skb_queue_tail(&sk->sk_receive_queue, skb);
4022                                 sk_stream_set_owner_r(skb, sk);
4023                                 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4024                         }
4025
4026                         tcp_event_data_recv(sk, tp, skb);
4027
4028                         if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
4029                                 /* Well, only one small jumplet in fast path... */
4030                                 tcp_ack(sk, skb, FLAG_DATA);
4031                                 tcp_data_snd_check(sk, tp);
4032                                 if (!inet_csk_ack_scheduled(sk))
4033                                         goto no_ack;
4034                         }
4035
4036                         __tcp_ack_snd_check(sk, 0);
4037 no_ack:
4038 #ifdef CONFIG_NET_DMA
4039                         if (copied_early)
4040                                 __skb_queue_tail(&sk->sk_async_wait_queue, skb);
4041                         else
4042 #endif
4043                         if (eaten)
4044                                 __kfree_skb(skb);
4045                         else
4046                                 sk->sk_data_ready(sk, 0);
4047                         return 0;
4048                 }
4049         }
4050
4051 slow_path:
4052         if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb))
4053                 goto csum_error;
4054
4055         /*
4056          * RFC1323: H1. Apply PAWS check first.
4057          */
4058         if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
4059             tcp_paws_discard(sk, skb)) {
4060                 if (!th->rst) {
4061                         NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4062                         tcp_send_dupack(sk, skb);
4063                         goto discard;
4064                 }
4065                 /* Resets are accepted even if PAWS failed.
4066
4067                    ts_recent update must be made after we are sure
4068                    that the packet is in window.
4069                  */
4070         }
4071
4072         /*
4073          *      Standard slow path.
4074          */
4075
4076         if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4077                 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4078                  * (RST) segments are validated by checking their SEQ-fields."
4079                  * And page 69: "If an incoming segment is not acceptable,
4080                  * an acknowledgment should be sent in reply (unless the RST bit
4081                  * is set, if so drop the segment and return)".
4082                  */
4083                 if (!th->rst)
4084                         tcp_send_dupack(sk, skb);
4085                 goto discard;
4086         }
4087
4088         if(th->rst) {
4089                 tcp_reset(sk);
4090                 goto discard;
4091         }
4092
4093         tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4094
4095         if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4096                 TCP_INC_STATS_BH(TCP_MIB_INERRS);
4097                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4098                 tcp_reset(sk);
4099                 return 1;
4100         }
4101
4102 step5:
4103         if(th->ack)
4104                 tcp_ack(sk, skb, FLAG_SLOWPATH);
4105
4106         tcp_rcv_rtt_measure_ts(sk, skb);
4107
4108         /* Process urgent data. */
4109         tcp_urg(sk, skb, th);
4110
4111         /* step 7: process the segment text */
4112         tcp_data_queue(sk, skb);
4113
4114         tcp_data_snd_check(sk, tp);
4115         tcp_ack_snd_check(sk);
4116         return 0;
4117
4118 csum_error:
4119         TCP_INC_STATS_BH(TCP_MIB_INERRS);
4120
4121 discard:
4122         __kfree_skb(skb);
4123         return 0;
4124 }
4125
4126 static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
4127                                          struct tcphdr *th, unsigned len)
4128 {
4129         struct tcp_sock *tp = tcp_sk(sk);
4130         struct inet_connection_sock *icsk = inet_csk(sk);
4131         int saved_clamp = tp->rx_opt.mss_clamp;
4132
4133         tcp_parse_options(skb, &tp->rx_opt, 0);
4134
4135         if (th->ack) {
4136                 /* rfc793:
4137                  * "If the state is SYN-SENT then
4138                  *    first check the ACK bit
4139                  *      If the ACK bit is set
4140                  *        If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4141                  *        a reset (unless the RST bit is set, if so drop
4142                  *        the segment and return)"
4143                  *
4144                  *  We do not send data with SYN, so that RFC-correct
4145                  *  test reduces to:
4146                  */
4147                 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
4148                         goto reset_and_undo;
4149
4150                 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4151                     !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
4152                              tcp_time_stamp)) {
4153                         NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED);
4154                         goto reset_and_undo;
4155                 }
4156
4157                 /* Now ACK is acceptable.
4158                  *
4159                  * "If the RST bit is set
4160                  *    If the ACK was acceptable then signal the user "error:
4161                  *    connection reset", drop the segment, enter CLOSED state,
4162                  *    delete TCB, and return."
4163                  */
4164
4165                 if (th->rst) {
4166                         tcp_reset(sk);
4167                         goto discard;
4168                 }
4169
4170                 /* rfc793:
4171                  *   "fifth, if neither of the SYN or RST bits is set then
4172                  *    drop the segment and return."
4173                  *
4174                  *    See note below!
4175                  *                                        --ANK(990513)
4176                  */
4177                 if (!th->syn)
4178                         goto discard_and_undo;
4179
4180                 /* rfc793:
4181                  *   "If the SYN bit is on ...
4182                  *    are acceptable then ...
4183                  *    (our SYN has been ACKed), change the connection
4184                  *    state to ESTABLISHED..."
4185                  */
4186
4187                 TCP_ECN_rcv_synack(tp, th);
4188
4189                 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4190                 tcp_ack(sk, skb, FLAG_SLOWPATH);
4191
4192                 /* Ok.. it's good. Set up sequence numbers and
4193                  * move to established.
4194                  */
4195                 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4196                 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4197
4198                 /* RFC1323: The window in SYN & SYN/ACK segments is
4199                  * never scaled.
4200                  */
4201                 tp->snd_wnd = ntohs(th->window);
4202                 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq);
4203
4204                 if (!tp->rx_opt.wscale_ok) {
4205                         tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
4206                         tp->window_clamp = min(tp->window_clamp, 65535U);
4207                 }
4208
4209                 if (tp->rx_opt.saw_tstamp) {
4210                         tp->rx_opt.tstamp_ok       = 1;
4211                         tp->tcp_header_len =
4212                                 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4213                         tp->advmss          -= TCPOLEN_TSTAMP_ALIGNED;
4214                         tcp_store_ts_recent(tp);
4215                 } else {
4216                         tp->tcp_header_len = sizeof(struct tcphdr);
4217                 }
4218
4219                 if (tp->rx_opt.sack_ok && sysctl_tcp_fack)
4220                         tp->rx_opt.sack_ok |= 2;
4221
4222                 tcp_mtup_init(sk);
4223                 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
4224                 tcp_initialize_rcv_mss(sk);
4225
4226                 /* Remember, tcp_poll() does not lock socket!
4227                  * Change state from SYN-SENT only after copied_seq
4228                  * is initialized. */
4229                 tp->copied_seq = tp->rcv_nxt;
4230                 mb();
4231                 tcp_set_state(sk, TCP_ESTABLISHED);
4232
4233                 security_inet_conn_established(sk, skb);
4234
4235                 /* Make sure socket is routed, for correct metrics.  */
4236                 icsk->icsk_af_ops->rebuild_header(sk);
4237
4238                 tcp_init_metrics(sk);
4239
4240                 tcp_init_congestion_control(sk);
4241
4242                 /* Prevent spurious tcp_cwnd_restart() on first data
4243                  * packet.
4244                  */
4245                 tp->lsndtime = tcp_time_stamp;
4246
4247                 tcp_init_buffer_space(sk);
4248
4249                 if (sock_flag(sk, SOCK_KEEPOPEN))
4250                         inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp));
4251
4252                 if (!tp->rx_opt.snd_wscale)
4253                         __tcp_fast_path_on(tp, tp->snd_wnd);
4254                 else
4255                         tp->pred_flags = 0;
4256
4257                 if (!sock_flag(sk, SOCK_DEAD)) {
4258                         sk->sk_state_change(sk);
4259                         sk_wake_async(sk, 0, POLL_OUT);
4260                 }
4261
4262                 if (sk->sk_write_pending ||
4263                     icsk->icsk_accept_queue.rskq_defer_accept ||
4264                     icsk->icsk_ack.pingpong) {
4265                         /* Save one ACK. Data will be ready after
4266                          * several ticks, if write_pending is set.
4267                          *
4268                          * It may be deleted, but with this feature tcpdumps
4269                          * look so _wonderfully_ clever, that I was not able
4270                          * to stand against the temptation 8)     --ANK
4271                          */
4272                         inet_csk_schedule_ack(sk);
4273                         icsk->icsk_ack.lrcvtime = tcp_time_stamp;
4274                         icsk->icsk_ack.ato       = TCP_ATO_MIN;
4275                         tcp_incr_quickack(sk);
4276                         tcp_enter_quickack_mode(sk);
4277                         inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
4278                                                   TCP_DELACK_MAX, TCP_RTO_MAX);
4279
4280 discard:
4281                         __kfree_skb(skb);
4282                         return 0;
4283                 } else {
4284                         tcp_send_ack(sk);
4285                 }
4286                 return -1;
4287         }
4288
4289         /* No ACK in the segment */
4290
4291         if (th->rst) {
4292                 /* rfc793:
4293                  * "If the RST bit is set
4294                  *
4295                  *      Otherwise (no ACK) drop the segment and return."
4296                  */
4297
4298                 goto discard_and_undo;
4299         }
4300
4301         /* PAWS check. */
4302         if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0))
4303                 goto discard_and_undo;
4304
4305         if (th->syn) {
4306                 /* We see SYN without ACK. It is attempt of
4307                  * simultaneous connect with crossed SYNs.
4308                  * Particularly, it can be connect to self.
4309                  */
4310                 tcp_set_state(sk, TCP_SYN_RECV);
4311
4312                 if (tp->rx_opt.saw_tstamp) {
4313                         tp->rx_opt.tstamp_ok = 1;
4314                         tcp_store_ts_recent(tp);
4315                         tp->tcp_header_len =
4316                                 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4317                 } else {
4318                         tp->tcp_header_len = sizeof(struct tcphdr);
4319                 }
4320
4321                 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4322                 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4323
4324                 /* RFC1323: The window in SYN & SYN/ACK segments is
4325                  * never scaled.
4326                  */
4327                 tp->snd_wnd    = ntohs(th->window);
4328                 tp->snd_wl1    = TCP_SKB_CB(skb)->seq;
4329                 tp->max_window = tp->snd_wnd;
4330
4331                 TCP_ECN_rcv_syn(tp, th);
4332
4333                 tcp_mtup_init(sk);
4334                 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
4335                 tcp_initialize_rcv_mss(sk);
4336
4337
4338                 tcp_send_synack(sk);
4339 #if 0
4340                 /* Note, we could accept data and URG from this segment.
4341                  * There are no obstacles to make this.
4342                  *
4343                  * However, if we ignore data in ACKless segments sometimes,
4344                  * we have no reasons to accept it sometimes.
4345                  * Also, seems the code doing it in step6 of tcp_rcv_state_process
4346                  * is not flawless. So, discard packet for sanity.
4347                  * Uncomment this return to process the data.
4348                  */
4349                 return -1;
4350 #else
4351                 goto discard;
4352 #endif
4353         }
4354         /* "fifth, if neither of the SYN or RST bits is set then
4355          * drop the segment and return."
4356          */
4357
4358 discard_and_undo:
4359         tcp_clear_options(&tp->rx_opt);
4360         tp->rx_opt.mss_clamp = saved_clamp;
4361         goto discard;
4362
4363 reset_and_undo:
4364         tcp_clear_options(&tp->rx_opt);
4365         tp->rx_opt.mss_clamp = saved_clamp;
4366         return 1;
4367 }
4368
4369
4370 /*
4371  *      This function implements the receiving procedure of RFC 793 for
4372  *      all states except ESTABLISHED and TIME_WAIT. 
4373  *      It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4374  *      address independent.
4375  */
4376         
4377 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
4378                           struct tcphdr *th, unsigned len)
4379 {
4380         struct tcp_sock *tp = tcp_sk(sk);
4381         struct inet_connection_sock *icsk = inet_csk(sk);
4382         int queued = 0;
4383
4384         tp->rx_opt.saw_tstamp = 0;
4385
4386         switch (sk->sk_state) {
4387         case TCP_CLOSE:
4388                 goto discard;
4389
4390         case TCP_LISTEN:
4391                 if(th->ack)
4392                         return 1;
4393
4394                 if(th->rst)
4395                         goto discard;
4396
4397                 if(th->syn) {
4398                         if (icsk->icsk_af_ops->conn_request(sk, skb) < 0)
4399                                 return 1;
4400
4401                         /* Now we have several options: In theory there is 
4402                          * nothing else in the frame. KA9Q has an option to 
4403                          * send data with the syn, BSD accepts data with the
4404                          * syn up to the [to be] advertised window and 
4405                          * Solaris 2.1 gives you a protocol error. For now 
4406                          * we just ignore it, that fits the spec precisely 
4407                          * and avoids incompatibilities. It would be nice in
4408                          * future to drop through and process the data.
4409                          *
4410                          * Now that TTCP is starting to be used we ought to 
4411                          * queue this data.
4412                          * But, this leaves one open to an easy denial of
4413                          * service attack, and SYN cookies can't defend
4414                          * against this problem. So, we drop the data
4415                          * in the interest of security over speed.
4416                          */
4417                         goto discard;
4418                 }
4419                 goto discard;
4420
4421         case TCP_SYN_SENT:
4422                 queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
4423                 if (queued >= 0)
4424                         return queued;
4425
4426                 /* Do step6 onward by hand. */
4427                 tcp_urg(sk, skb, th);
4428                 __kfree_skb(skb);
4429                 tcp_data_snd_check(sk, tp);
4430                 return 0;
4431         }
4432
4433         if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
4434             tcp_paws_discard(sk, skb)) {
4435                 if (!th->rst) {
4436                         NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4437                         tcp_send_dupack(sk, skb);
4438                         goto discard;
4439                 }
4440                 /* Reset is accepted even if it did not pass PAWS. */
4441         }
4442
4443         /* step 1: check sequence number */
4444         if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4445                 if (!th->rst)
4446                         tcp_send_dupack(sk, skb);
4447                 goto discard;
4448         }
4449
4450         /* step 2: check RST bit */
4451         if(th->rst) {
4452                 tcp_reset(sk);
4453                 goto discard;
4454         }
4455
4456         tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4457
4458         /* step 3: check security and precedence [ignored] */
4459
4460         /*      step 4:
4461          *
4462          *      Check for a SYN in window.
4463          */
4464         if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4465                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4466                 tcp_reset(sk);
4467                 return 1;
4468         }
4469
4470         /* step 5: check the ACK field */
4471         if (th->ack) {
4472                 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH);
4473
4474                 switch(sk->sk_state) {
4475                 case TCP_SYN_RECV:
4476                         if (acceptable) {
4477                                 tp->copied_seq = tp->rcv_nxt;
4478                                 mb();
4479                                 tcp_set_state(sk, TCP_ESTABLISHED);
4480                                 sk->sk_state_change(sk);
4481
4482                                 /* Note, that this wakeup is only for marginal
4483                                  * crossed SYN case. Passively open sockets
4484                                  * are not waked up, because sk->sk_sleep ==
4485                                  * NULL and sk->sk_socket == NULL.
4486                                  */
4487                                 if (sk->sk_socket) {
4488                                         sk_wake_async(sk,0,POLL_OUT);
4489                                 }
4490
4491                                 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
4492                                 tp->snd_wnd = ntohs(th->window) <<
4493                                               tp->rx_opt.snd_wscale;
4494                                 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq,
4495                                             TCP_SKB_CB(skb)->seq);
4496
4497                                 /* tcp_ack considers this ACK as duplicate
4498                                  * and does not calculate rtt.
4499                                  * Fix it at least with timestamps.
4500                                  */
4501                                 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4502                                     !tp->srtt)
4503                                         tcp_ack_saw_tstamp(sk, 0);
4504
4505                                 if (tp->rx_opt.tstamp_ok)
4506                                         tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
4507
4508                                 /* Make sure socket is routed, for
4509                                  * correct metrics.
4510                                  */
4511                                 icsk->icsk_af_ops->rebuild_header(sk);
4512
4513                                 tcp_init_metrics(sk);
4514
4515                                 tcp_init_congestion_control(sk);
4516
4517                                 /* Prevent spurious tcp_cwnd_restart() on
4518                                  * first data packet.
4519                                  */
4520                                 tp->lsndtime = tcp_time_stamp;
4521
4522                                 tcp_mtup_init(sk);
4523                                 tcp_initialize_rcv_mss(sk);
4524                                 tcp_init_buffer_space(sk);
4525                                 tcp_fast_path_on(tp);
4526                         } else {
4527                                 return 1;
4528                         }
4529                         break;
4530
4531                 case TCP_FIN_WAIT1:
4532                         if (tp->snd_una == tp->write_seq) {
4533                                 tcp_set_state(sk, TCP_FIN_WAIT2);
4534                                 sk->sk_shutdown |= SEND_SHUTDOWN;
4535                                 dst_confirm(sk->sk_dst_cache);
4536
4537                                 if (!sock_flag(sk, SOCK_DEAD))
4538                                         /* Wake up lingering close() */
4539                                         sk->sk_state_change(sk);
4540                                 else {
4541                                         int tmo;
4542
4543                                         if (tp->linger2 < 0 ||
4544                                             (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4545                                              after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
4546                                                 tcp_done(sk);
4547                                                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4548                                                 return 1;
4549                                         }
4550
4551                                         tmo = tcp_fin_time(sk);
4552                                         if (tmo > TCP_TIMEWAIT_LEN) {
4553                                                 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
4554                                         } else if (th->fin || sock_owned_by_user(sk)) {
4555                                                 /* Bad case. We could lose such FIN otherwise.
4556                                                  * It is not a big problem, but it looks confusing
4557                                                  * and not so rare event. We still can lose it now,
4558                                                  * if it spins in bh_lock_sock(), but it is really
4559                                                  * marginal case.
4560                                                  */
4561                                                 inet_csk_reset_keepalive_timer(sk, tmo);
4562                                         } else {
4563                                                 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
4564                                                 goto discard;
4565                                         }
4566                                 }
4567                         }
4568                         break;
4569
4570                 case TCP_CLOSING:
4571                         if (tp->snd_una == tp->write_seq) {
4572                                 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4573                                 goto discard;
4574                         }
4575                         break;
4576
4577                 case TCP_LAST_ACK:
4578                         if (tp->snd_una == tp->write_seq) {
4579                                 tcp_update_metrics(sk);
4580                                 tcp_done(sk);
4581                                 goto discard;
4582                         }
4583                         break;
4584                 }
4585         } else
4586                 goto discard;
4587
4588         /* step 6: check the URG bit */
4589         tcp_urg(sk, skb, th);
4590
4591         /* step 7: process the segment text */
4592         switch (sk->sk_state) {
4593         case TCP_CLOSE_WAIT:
4594         case TCP_CLOSING:
4595         case TCP_LAST_ACK:
4596                 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4597                         break;
4598         case TCP_FIN_WAIT1:
4599         case TCP_FIN_WAIT2:
4600                 /* RFC 793 says to queue data in these states,
4601                  * RFC 1122 says we MUST send a reset. 
4602                  * BSD 4.4 also does reset.
4603                  */
4604                 if (sk->sk_shutdown & RCV_SHUTDOWN) {
4605                         if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4606                             after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
4607                                 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4608                                 tcp_reset(sk);
4609                                 return 1;
4610                         }
4611                 }
4612                 /* Fall through */
4613         case TCP_ESTABLISHED: 
4614                 tcp_data_queue(sk, skb);
4615                 queued = 1;
4616                 break;
4617         }
4618
4619         /* tcp_data could move socket to TIME-WAIT */
4620         if (sk->sk_state != TCP_CLOSE) {
4621                 tcp_data_snd_check(sk, tp);
4622                 tcp_ack_snd_check(sk);
4623         }
4624
4625         if (!queued) { 
4626 discard:
4627                 __kfree_skb(skb);
4628         }
4629         return 0;
4630 }
4631
4632 EXPORT_SYMBOL(sysctl_tcp_ecn);
4633 EXPORT_SYMBOL(sysctl_tcp_reordering);
4634 EXPORT_SYMBOL(tcp_parse_options);
4635 EXPORT_SYMBOL(tcp_rcv_established);
4636 EXPORT_SYMBOL(tcp_rcv_state_process);
4637 EXPORT_SYMBOL(tcp_initialize_rcv_mss);