[IP]: Introduce ip_hdrlen()
[linux-3.10.git] / net / ipv4 / netfilter / ip_conntrack_proto_tcp.c
1 /* (C) 1999-2001 Paul `Rusty' Russell
2  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation.
7  *
8  * Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>:
9  *      - Real stateful connection tracking
10  *      - Modified state transitions table
11  *      - Window scaling support added
12  *      - SACK support added
13  *
14  * Willy Tarreau:
15  *      - State table bugfixes
16  *      - More robust state changes
17  *      - Tuning timer parameters
18  *
19  * version 2.2
20  */
21
22 #include <linux/types.h>
23 #include <linux/timer.h>
24 #include <linux/netfilter.h>
25 #include <linux/module.h>
26 #include <linux/in.h>
27 #include <linux/ip.h>
28 #include <linux/tcp.h>
29 #include <linux/spinlock.h>
30
31 #include <net/tcp.h>
32
33 #include <linux/netfilter_ipv4.h>
34 #include <linux/netfilter_ipv4/ip_conntrack.h>
35 #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
36
37 #if 0
38 #define DEBUGP printk
39 #define DEBUGP_VARS
40 #else
41 #define DEBUGP(format, args...)
42 #endif
43
44 /* Protects conntrack->proto.tcp */
45 static DEFINE_RWLOCK(tcp_lock);
46
47 /* "Be conservative in what you do,
48     be liberal in what you accept from others."
49     If it's non-zero, we mark only out of window RST segments as INVALID. */
50 int ip_ct_tcp_be_liberal __read_mostly = 0;
51
52 /* If it is set to zero, we disable picking up already established
53    connections. */
54 int ip_ct_tcp_loose __read_mostly = 1;
55
56 /* Max number of the retransmitted packets without receiving an (acceptable)
57    ACK from the destination. If this number is reached, a shorter timer
58    will be started. */
59 int ip_ct_tcp_max_retrans __read_mostly = 3;
60
61   /* FIXME: Examine ipfilter's timeouts and conntrack transitions more
62      closely.  They're more complex. --RR */
63
64 static const char *tcp_conntrack_names[] = {
65         "NONE",
66         "SYN_SENT",
67         "SYN_RECV",
68         "ESTABLISHED",
69         "FIN_WAIT",
70         "CLOSE_WAIT",
71         "LAST_ACK",
72         "TIME_WAIT",
73         "CLOSE",
74         "LISTEN"
75 };
76
77 #define SECS * HZ
78 #define MINS * 60 SECS
79 #define HOURS * 60 MINS
80 #define DAYS * 24 HOURS
81
82 unsigned int ip_ct_tcp_timeout_syn_sent __read_mostly =      2 MINS;
83 unsigned int ip_ct_tcp_timeout_syn_recv __read_mostly =     60 SECS;
84 unsigned int ip_ct_tcp_timeout_established __read_mostly =   5 DAYS;
85 unsigned int ip_ct_tcp_timeout_fin_wait __read_mostly =      2 MINS;
86 unsigned int ip_ct_tcp_timeout_close_wait __read_mostly =   60 SECS;
87 unsigned int ip_ct_tcp_timeout_last_ack __read_mostly =     30 SECS;
88 unsigned int ip_ct_tcp_timeout_time_wait __read_mostly =     2 MINS;
89 unsigned int ip_ct_tcp_timeout_close __read_mostly =        10 SECS;
90
91 /* RFC1122 says the R2 limit should be at least 100 seconds.
92    Linux uses 15 packets as limit, which corresponds
93    to ~13-30min depending on RTO. */
94 unsigned int ip_ct_tcp_timeout_max_retrans __read_mostly =   5 MINS;
95
96 static const unsigned int * tcp_timeouts[]
97 = { NULL,                              /*      TCP_CONNTRACK_NONE */
98     &ip_ct_tcp_timeout_syn_sent,       /*      TCP_CONNTRACK_SYN_SENT, */
99     &ip_ct_tcp_timeout_syn_recv,       /*      TCP_CONNTRACK_SYN_RECV, */
100     &ip_ct_tcp_timeout_established,    /*      TCP_CONNTRACK_ESTABLISHED,      */
101     &ip_ct_tcp_timeout_fin_wait,       /*      TCP_CONNTRACK_FIN_WAIT, */
102     &ip_ct_tcp_timeout_close_wait,     /*      TCP_CONNTRACK_CLOSE_WAIT,       */
103     &ip_ct_tcp_timeout_last_ack,       /*      TCP_CONNTRACK_LAST_ACK, */
104     &ip_ct_tcp_timeout_time_wait,      /*      TCP_CONNTRACK_TIME_WAIT,        */
105     &ip_ct_tcp_timeout_close,          /*      TCP_CONNTRACK_CLOSE,    */
106     NULL,                              /*      TCP_CONNTRACK_LISTEN */
107  };
108
109 #define sNO TCP_CONNTRACK_NONE
110 #define sSS TCP_CONNTRACK_SYN_SENT
111 #define sSR TCP_CONNTRACK_SYN_RECV
112 #define sES TCP_CONNTRACK_ESTABLISHED
113 #define sFW TCP_CONNTRACK_FIN_WAIT
114 #define sCW TCP_CONNTRACK_CLOSE_WAIT
115 #define sLA TCP_CONNTRACK_LAST_ACK
116 #define sTW TCP_CONNTRACK_TIME_WAIT
117 #define sCL TCP_CONNTRACK_CLOSE
118 #define sLI TCP_CONNTRACK_LISTEN
119 #define sIV TCP_CONNTRACK_MAX
120 #define sIG TCP_CONNTRACK_IGNORE
121
122 /* What TCP flags are set from RST/SYN/FIN/ACK. */
123 enum tcp_bit_set {
124         TCP_SYN_SET,
125         TCP_SYNACK_SET,
126         TCP_FIN_SET,
127         TCP_ACK_SET,
128         TCP_RST_SET,
129         TCP_NONE_SET,
130 };
131
132 /*
133  * The TCP state transition table needs a few words...
134  *
135  * We are the man in the middle. All the packets go through us
136  * but might get lost in transit to the destination.
137  * It is assumed that the destinations can't receive segments
138  * we haven't seen.
139  *
140  * The checked segment is in window, but our windows are *not*
141  * equivalent with the ones of the sender/receiver. We always
142  * try to guess the state of the current sender.
143  *
144  * The meaning of the states are:
145  *
146  * NONE:        initial state
147  * SYN_SENT:    SYN-only packet seen
148  * SYN_RECV:    SYN-ACK packet seen
149  * ESTABLISHED: ACK packet seen
150  * FIN_WAIT:    FIN packet seen
151  * CLOSE_WAIT:  ACK seen (after FIN)
152  * LAST_ACK:    FIN seen (after FIN)
153  * TIME_WAIT:   last ACK seen
154  * CLOSE:       closed connection
155  *
156  * LISTEN state is not used.
157  *
158  * Packets marked as IGNORED (sIG):
159  *      if they may be either invalid or valid
160  *      and the receiver may send back a connection
161  *      closing RST or a SYN/ACK.
162  *
163  * Packets marked as INVALID (sIV):
164  *      if they are invalid
165  *      or we do not support the request (simultaneous open)
166  */
167 static const enum tcp_conntrack tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = {
168         {
169 /* ORIGINAL */
170 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
171 /*syn*/    { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sIV },
172 /*
173  *      sNO -> sSS      Initialize a new connection
174  *      sSS -> sSS      Retransmitted SYN
175  *      sSR -> sIG      Late retransmitted SYN?
176  *      sES -> sIG      Error: SYNs in window outside the SYN_SENT state
177  *                      are errors. Receiver will reply with RST
178  *                      and close the connection.
179  *                      Or we are not in sync and hold a dead connection.
180  *      sFW -> sIG
181  *      sCW -> sIG
182  *      sLA -> sIG
183  *      sTW -> sSS      Reopened connection (RFC 1122).
184  *      sCL -> sSS
185  */
186 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
187 /*synack*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
188 /*
189  * A SYN/ACK from the client is always invalid:
190  *      - either it tries to set up a simultaneous open, which is
191  *        not supported;
192  *      - or the firewall has just been inserted between the two hosts
193  *        during the session set-up. The SYN will be retransmitted
194  *        by the true client (or it'll time out).
195  */
196 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
197 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
198 /*
199  *      sNO -> sIV      Too late and no reason to do anything...
200  *      sSS -> sIV      Client migth not send FIN in this state:
201  *                      we enforce waiting for a SYN/ACK reply first.
202  *      sSR -> sFW      Close started.
203  *      sES -> sFW
204  *      sFW -> sLA      FIN seen in both directions, waiting for
205  *                      the last ACK.
206  *                      Migth be a retransmitted FIN as well...
207  *      sCW -> sLA
208  *      sLA -> sLA      Retransmitted FIN. Remain in the same state.
209  *      sTW -> sTW
210  *      sCL -> sCL
211  */
212 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
213 /*ack*/    { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV },
214 /*
215  *      sNO -> sES      Assumed.
216  *      sSS -> sIV      ACK is invalid: we haven't seen a SYN/ACK yet.
217  *      sSR -> sES      Established state is reached.
218  *      sES -> sES      :-)
219  *      sFW -> sCW      Normal close request answered by ACK.
220  *      sCW -> sCW
221  *      sLA -> sTW      Last ACK detected.
222  *      sTW -> sTW      Retransmitted last ACK. Remain in the same state.
223  *      sCL -> sCL
224  */
225 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
226 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
227 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
228         },
229         {
230 /* REPLY */
231 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
232 /*syn*/    { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
233 /*
234  *      sNO -> sIV      Never reached.
235  *      sSS -> sIV      Simultaneous open, not supported
236  *      sSR -> sIV      Simultaneous open, not supported.
237  *      sES -> sIV      Server may not initiate a connection.
238  *      sFW -> sIV
239  *      sCW -> sIV
240  *      sLA -> sIV
241  *      sTW -> sIV      Reopened connection, but server may not do it.
242  *      sCL -> sIV
243  */
244 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
245 /*synack*/ { sIV, sSR, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIV },
246 /*
247  *      sSS -> sSR      Standard open.
248  *      sSR -> sSR      Retransmitted SYN/ACK.
249  *      sES -> sIG      Late retransmitted SYN/ACK?
250  *      sFW -> sIG      Might be SYN/ACK answering ignored SYN
251  *      sCW -> sIG
252  *      sLA -> sIG
253  *      sTW -> sIG
254  *      sCL -> sIG
255  */
256 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
257 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
258 /*
259  *      sSS -> sIV      Server might not send FIN in this state.
260  *      sSR -> sFW      Close started.
261  *      sES -> sFW
262  *      sFW -> sLA      FIN seen in both directions.
263  *      sCW -> sLA
264  *      sLA -> sLA      Retransmitted FIN.
265  *      sTW -> sTW
266  *      sCL -> sCL
267  */
268 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
269 /*ack*/    { sIV, sIG, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIV },
270 /*
271  *      sSS -> sIG      Might be a half-open connection.
272  *      sSR -> sSR      Might answer late resent SYN.
273  *      sES -> sES      :-)
274  *      sFW -> sCW      Normal close request answered by ACK.
275  *      sCW -> sCW
276  *      sLA -> sTW      Last ACK detected.
277  *      sTW -> sTW      Retransmitted last ACK.
278  *      sCL -> sCL
279  */
280 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
281 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
282 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
283         }
284 };
285
286 static int tcp_pkt_to_tuple(const struct sk_buff *skb,
287                             unsigned int dataoff,
288                             struct ip_conntrack_tuple *tuple)
289 {
290         struct tcphdr _hdr, *hp;
291
292         /* Actually only need first 8 bytes. */
293         hp = skb_header_pointer(skb, dataoff, 8, &_hdr);
294         if (hp == NULL)
295                 return 0;
296
297         tuple->src.u.tcp.port = hp->source;
298         tuple->dst.u.tcp.port = hp->dest;
299
300         return 1;
301 }
302
303 static int tcp_invert_tuple(struct ip_conntrack_tuple *tuple,
304                             const struct ip_conntrack_tuple *orig)
305 {
306         tuple->src.u.tcp.port = orig->dst.u.tcp.port;
307         tuple->dst.u.tcp.port = orig->src.u.tcp.port;
308         return 1;
309 }
310
311 /* Print out the per-protocol part of the tuple. */
312 static int tcp_print_tuple(struct seq_file *s,
313                            const struct ip_conntrack_tuple *tuple)
314 {
315         return seq_printf(s, "sport=%hu dport=%hu ",
316                           ntohs(tuple->src.u.tcp.port),
317                           ntohs(tuple->dst.u.tcp.port));
318 }
319
320 /* Print out the private part of the conntrack. */
321 static int tcp_print_conntrack(struct seq_file *s,
322                                const struct ip_conntrack *conntrack)
323 {
324         enum tcp_conntrack state;
325
326         read_lock_bh(&tcp_lock);
327         state = conntrack->proto.tcp.state;
328         read_unlock_bh(&tcp_lock);
329
330         return seq_printf(s, "%s ", tcp_conntrack_names[state]);
331 }
332
333 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
334     defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
335 static int tcp_to_nfattr(struct sk_buff *skb, struct nfattr *nfa,
336                          const struct ip_conntrack *ct)
337 {
338         struct nfattr *nest_parms;
339
340         read_lock_bh(&tcp_lock);
341         nest_parms = NFA_NEST(skb, CTA_PROTOINFO_TCP);
342         NFA_PUT(skb, CTA_PROTOINFO_TCP_STATE, sizeof(u_int8_t),
343                 &ct->proto.tcp.state);
344         read_unlock_bh(&tcp_lock);
345
346         NFA_NEST_END(skb, nest_parms);
347
348         return 0;
349
350 nfattr_failure:
351         read_unlock_bh(&tcp_lock);
352         return -1;
353 }
354
355 static const size_t cta_min_tcp[CTA_PROTOINFO_TCP_MAX] = {
356         [CTA_PROTOINFO_TCP_STATE-1]     = sizeof(u_int8_t),
357 };
358
359 static int nfattr_to_tcp(struct nfattr *cda[], struct ip_conntrack *ct)
360 {
361         struct nfattr *attr = cda[CTA_PROTOINFO_TCP-1];
362         struct nfattr *tb[CTA_PROTOINFO_TCP_MAX];
363
364         /* updates could not contain anything about the private
365          * protocol info, in that case skip the parsing */
366         if (!attr)
367                 return 0;
368
369         nfattr_parse_nested(tb, CTA_PROTOINFO_TCP_MAX, attr);
370
371         if (nfattr_bad_size(tb, CTA_PROTOINFO_TCP_MAX, cta_min_tcp))
372                 return -EINVAL;
373
374         if (!tb[CTA_PROTOINFO_TCP_STATE-1])
375                 return -EINVAL;
376
377         write_lock_bh(&tcp_lock);
378         ct->proto.tcp.state =
379                 *(u_int8_t *)NFA_DATA(tb[CTA_PROTOINFO_TCP_STATE-1]);
380         write_unlock_bh(&tcp_lock);
381
382         return 0;
383 }
384 #endif
385
386 static unsigned int get_conntrack_index(const struct tcphdr *tcph)
387 {
388         if (tcph->rst) return TCP_RST_SET;
389         else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET);
390         else if (tcph->fin) return TCP_FIN_SET;
391         else if (tcph->ack) return TCP_ACK_SET;
392         else return TCP_NONE_SET;
393 }
394
395 /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering
396    in IP Filter' by Guido van Rooij.
397
398    http://www.nluug.nl/events/sane2000/papers.html
399    http://www.iae.nl/users/guido/papers/tcp_filtering.ps.gz
400
401    The boundaries and the conditions are changed according to RFC793:
402    the packet must intersect the window (i.e. segments may be
403    after the right or before the left edge) and thus receivers may ACK
404    segments after the right edge of the window.
405
406         td_maxend = max(sack + max(win,1)) seen in reply packets
407         td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets
408         td_maxwin += seq + len - sender.td_maxend
409                         if seq + len > sender.td_maxend
410         td_end    = max(seq + len) seen in sent packets
411
412    I.   Upper bound for valid data:     seq <= sender.td_maxend
413    II.  Lower bound for valid data:     seq + len >= sender.td_end - receiver.td_maxwin
414    III. Upper bound for valid ack:      sack <= receiver.td_end
415    IV.  Lower bound for valid ack:      ack >= receiver.td_end - MAXACKWINDOW
416
417    where sack is the highest right edge of sack block found in the packet.
418
419    The upper bound limit for a valid ack is not ignored -
420    we doesn't have to deal with fragments.
421 */
422
423 static inline __u32 segment_seq_plus_len(__u32 seq,
424                                          size_t len,
425                                          struct iphdr *iph,
426                                          struct tcphdr *tcph)
427 {
428         return (seq + len - (iph->ihl + tcph->doff)*4
429                 + (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0));
430 }
431
432 /* Fixme: what about big packets? */
433 #define MAXACKWINCONST                  66000
434 #define MAXACKWINDOW(sender)                                            \
435         ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin     \
436                                               : MAXACKWINCONST)
437
438 /*
439  * Simplified tcp_parse_options routine from tcp_input.c
440  */
441 static void tcp_options(const struct sk_buff *skb,
442                         struct iphdr *iph,
443                         struct tcphdr *tcph,
444                         struct ip_ct_tcp_state *state)
445 {
446         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
447         unsigned char *ptr;
448         int length = (tcph->doff*4) - sizeof(struct tcphdr);
449
450         if (!length)
451                 return;
452
453         ptr = skb_header_pointer(skb,
454                                  (iph->ihl * 4) + sizeof(struct tcphdr),
455                                  length, buff);
456         BUG_ON(ptr == NULL);
457
458         state->td_scale =
459         state->flags = 0;
460
461         while (length > 0) {
462                 int opcode=*ptr++;
463                 int opsize;
464
465                 switch (opcode) {
466                 case TCPOPT_EOL:
467                         return;
468                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
469                         length--;
470                         continue;
471                 default:
472                         opsize=*ptr++;
473                         if (opsize < 2) /* "silly options" */
474                                 return;
475                         if (opsize > length)
476                                 break;  /* don't parse partial options */
477
478                         if (opcode == TCPOPT_SACK_PERM
479                             && opsize == TCPOLEN_SACK_PERM)
480                                 state->flags |= IP_CT_TCP_FLAG_SACK_PERM;
481                         else if (opcode == TCPOPT_WINDOW
482                                  && opsize == TCPOLEN_WINDOW) {
483                                 state->td_scale = *(u_int8_t *)ptr;
484
485                                 if (state->td_scale > 14) {
486                                         /* See RFC1323 */
487                                         state->td_scale = 14;
488                                 }
489                                 state->flags |=
490                                         IP_CT_TCP_FLAG_WINDOW_SCALE;
491                         }
492                         ptr += opsize - 2;
493                         length -= opsize;
494                 }
495         }
496 }
497
498 static void tcp_sack(const struct sk_buff *skb,
499                      struct iphdr *iph,
500                      struct tcphdr *tcph,
501                      __u32 *sack)
502 {
503         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
504         unsigned char *ptr;
505         int length = (tcph->doff*4) - sizeof(struct tcphdr);
506         __u32 tmp;
507
508         if (!length)
509                 return;
510
511         ptr = skb_header_pointer(skb,
512                                  (iph->ihl * 4) + sizeof(struct tcphdr),
513                                  length, buff);
514         BUG_ON(ptr == NULL);
515
516         /* Fast path for timestamp-only option */
517         if (length == TCPOLEN_TSTAMP_ALIGNED*4
518             && *(__be32 *)ptr == htonl((TCPOPT_NOP << 24)
519                                        | (TCPOPT_NOP << 16)
520                                        | (TCPOPT_TIMESTAMP << 8)
521                                        | TCPOLEN_TIMESTAMP))
522                 return;
523
524         while (length > 0) {
525                 int opcode=*ptr++;
526                 int opsize, i;
527
528                 switch (opcode) {
529                 case TCPOPT_EOL:
530                         return;
531                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
532                         length--;
533                         continue;
534                 default:
535                         opsize=*ptr++;
536                         if (opsize < 2) /* "silly options" */
537                                 return;
538                         if (opsize > length)
539                                 break;  /* don't parse partial options */
540
541                         if (opcode == TCPOPT_SACK
542                             && opsize >= (TCPOLEN_SACK_BASE
543                                           + TCPOLEN_SACK_PERBLOCK)
544                             && !((opsize - TCPOLEN_SACK_BASE)
545                                  % TCPOLEN_SACK_PERBLOCK)) {
546                                 for (i = 0;
547                                      i < (opsize - TCPOLEN_SACK_BASE);
548                                      i += TCPOLEN_SACK_PERBLOCK) {
549                                         tmp = ntohl(*((__be32 *)(ptr+i)+1));
550
551                                         if (after(tmp, *sack))
552                                                 *sack = tmp;
553                                 }
554                                 return;
555                         }
556                         ptr += opsize - 2;
557                         length -= opsize;
558                 }
559         }
560 }
561
562 static int tcp_in_window(struct ip_ct_tcp *state,
563                          enum ip_conntrack_dir dir,
564                          unsigned int index,
565                          const struct sk_buff *skb,
566                          struct iphdr *iph,
567                          struct tcphdr *tcph)
568 {
569         struct ip_ct_tcp_state *sender = &state->seen[dir];
570         struct ip_ct_tcp_state *receiver = &state->seen[!dir];
571         __u32 seq, ack, sack, end, win, swin;
572         int res;
573
574         /*
575          * Get the required data from the packet.
576          */
577         seq = ntohl(tcph->seq);
578         ack = sack = ntohl(tcph->ack_seq);
579         win = ntohs(tcph->window);
580         end = segment_seq_plus_len(seq, skb->len, iph, tcph);
581
582         if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
583                 tcp_sack(skb, iph, tcph, &sack);
584
585         DEBUGP("tcp_in_window: START\n");
586         DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
587                "seq=%u ack=%u sack=%u win=%u end=%u\n",
588                 NIPQUAD(iph->saddr), ntohs(tcph->source),
589                 NIPQUAD(iph->daddr), ntohs(tcph->dest),
590                 seq, ack, sack, win, end);
591         DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
592                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
593                 sender->td_end, sender->td_maxend, sender->td_maxwin,
594                 sender->td_scale,
595                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
596                 receiver->td_scale);
597
598         if (sender->td_end == 0) {
599                 /*
600                  * Initialize sender data.
601                  */
602                 if (tcph->syn && tcph->ack) {
603                         /*
604                          * Outgoing SYN-ACK in reply to a SYN.
605                          */
606                         sender->td_end =
607                         sender->td_maxend = end;
608                         sender->td_maxwin = (win == 0 ? 1 : win);
609
610                         tcp_options(skb, iph, tcph, sender);
611                         /*
612                          * RFC 1323:
613                          * Both sides must send the Window Scale option
614                          * to enable window scaling in either direction.
615                          */
616                         if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE
617                               && receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE))
618                                 sender->td_scale =
619                                 receiver->td_scale = 0;
620                 } else {
621                         /*
622                          * We are in the middle of a connection,
623                          * its history is lost for us.
624                          * Let's try to use the data from the packet.
625                          */
626                         sender->td_end = end;
627                         sender->td_maxwin = (win == 0 ? 1 : win);
628                         sender->td_maxend = end + sender->td_maxwin;
629                 }
630         } else if (((state->state == TCP_CONNTRACK_SYN_SENT
631                      && dir == IP_CT_DIR_ORIGINAL)
632                     || (state->state == TCP_CONNTRACK_SYN_RECV
633                         && dir == IP_CT_DIR_REPLY))
634                     && after(end, sender->td_end)) {
635                 /*
636                  * RFC 793: "if a TCP is reinitialized ... then it need
637                  * not wait at all; it must only be sure to use sequence
638                  * numbers larger than those recently used."
639                  */
640                 sender->td_end =
641                 sender->td_maxend = end;
642                 sender->td_maxwin = (win == 0 ? 1 : win);
643
644                 tcp_options(skb, iph, tcph, sender);
645         }
646
647         if (!(tcph->ack)) {
648                 /*
649                  * If there is no ACK, just pretend it was set and OK.
650                  */
651                 ack = sack = receiver->td_end;
652         } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
653                     (TCP_FLAG_ACK|TCP_FLAG_RST))
654                    && (ack == 0)) {
655                 /*
656                  * Broken TCP stacks, that set ACK in RST packets as well
657                  * with zero ack value.
658                  */
659                 ack = sack = receiver->td_end;
660         }
661
662         if (seq == end
663             && (!tcph->rst
664                 || (seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)))
665                 /*
666                  * Packets contains no data: we assume it is valid
667                  * and check the ack value only.
668                  * However RST segments are always validated by their
669                  * SEQ number, except when seq == 0 (reset sent answering
670                  * SYN.
671                  */
672                 seq = end = sender->td_end;
673
674         DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
675                "seq=%u ack=%u sack =%u win=%u end=%u\n",
676                 NIPQUAD(iph->saddr), ntohs(tcph->source),
677                 NIPQUAD(iph->daddr), ntohs(tcph->dest),
678                 seq, ack, sack, win, end);
679         DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
680                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
681                 sender->td_end, sender->td_maxend, sender->td_maxwin,
682                 sender->td_scale,
683                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
684                 receiver->td_scale);
685
686         DEBUGP("tcp_in_window: I=%i II=%i III=%i IV=%i\n",
687                 before(seq, sender->td_maxend + 1),
688                 after(end, sender->td_end - receiver->td_maxwin - 1),
689                 before(sack, receiver->td_end + 1),
690                 after(ack, receiver->td_end - MAXACKWINDOW(sender)));
691
692         if (before(seq, sender->td_maxend + 1) &&
693             after(end, sender->td_end - receiver->td_maxwin - 1) &&
694             before(sack, receiver->td_end + 1) &&
695             after(ack, receiver->td_end - MAXACKWINDOW(sender))) {
696                 /*
697                  * Take into account window scaling (RFC 1323).
698                  */
699                 if (!tcph->syn)
700                         win <<= sender->td_scale;
701
702                 /*
703                  * Update sender data.
704                  */
705                 swin = win + (sack - ack);
706                 if (sender->td_maxwin < swin)
707                         sender->td_maxwin = swin;
708                 if (after(end, sender->td_end))
709                         sender->td_end = end;
710                 /*
711                  * Update receiver data.
712                  */
713                 if (after(end, sender->td_maxend))
714                         receiver->td_maxwin += end - sender->td_maxend;
715                 if (after(sack + win, receiver->td_maxend - 1)) {
716                         receiver->td_maxend = sack + win;
717                         if (win == 0)
718                                 receiver->td_maxend++;
719                 }
720
721                 /*
722                  * Check retransmissions.
723                  */
724                 if (index == TCP_ACK_SET) {
725                         if (state->last_dir == dir
726                             && state->last_seq == seq
727                             && state->last_ack == ack
728                             && state->last_end == end
729                             && state->last_win == win)
730                                 state->retrans++;
731                         else {
732                                 state->last_dir = dir;
733                                 state->last_seq = seq;
734                                 state->last_ack = ack;
735                                 state->last_end = end;
736                                 state->last_win = win;
737                                 state->retrans = 0;
738                         }
739                 }
740                 res = 1;
741         } else {
742                 res = 0;
743                 if (sender->flags & IP_CT_TCP_FLAG_BE_LIBERAL ||
744                     ip_ct_tcp_be_liberal)
745                         res = 1;
746                 if (!res && LOG_INVALID(IPPROTO_TCP))
747                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
748                         "ip_ct_tcp: %s ",
749                         before(seq, sender->td_maxend + 1) ?
750                         after(end, sender->td_end - receiver->td_maxwin - 1) ?
751                         before(sack, receiver->td_end + 1) ?
752                         after(ack, receiver->td_end - MAXACKWINDOW(sender)) ? "BUG"
753                         : "ACK is under the lower bound (possible overly delayed ACK)"
754                         : "ACK is over the upper bound (ACKed data not seen yet)"
755                         : "SEQ is under the lower bound (already ACKed data retransmitted)"
756                         : "SEQ is over the upper bound (over the window of the receiver)");
757         }
758
759         DEBUGP("tcp_in_window: res=%i sender end=%u maxend=%u maxwin=%u "
760                "receiver end=%u maxend=%u maxwin=%u\n",
761                 res, sender->td_end, sender->td_maxend, sender->td_maxwin,
762                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin);
763
764         return res;
765 }
766
767 #ifdef CONFIG_IP_NF_NAT_NEEDED
768 /* Update sender->td_end after NAT successfully mangled the packet */
769 void ip_conntrack_tcp_update(struct sk_buff *skb,
770                              struct ip_conntrack *conntrack,
771                              enum ip_conntrack_dir dir)
772 {
773         struct iphdr *iph = skb->nh.iph;
774         struct tcphdr *tcph = (void *)skb->nh.iph + ip_hdrlen(skb);
775         __u32 end;
776 #ifdef DEBUGP_VARS
777         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[dir];
778         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[!dir];
779 #endif
780
781         end = segment_seq_plus_len(ntohl(tcph->seq), skb->len, iph, tcph);
782
783         write_lock_bh(&tcp_lock);
784         /*
785          * We have to worry for the ack in the reply packet only...
786          */
787         if (after(end, conntrack->proto.tcp.seen[dir].td_end))
788                 conntrack->proto.tcp.seen[dir].td_end = end;
789         conntrack->proto.tcp.last_end = end;
790         write_unlock_bh(&tcp_lock);
791         DEBUGP("tcp_update: sender end=%u maxend=%u maxwin=%u scale=%i "
792                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
793                 sender->td_end, sender->td_maxend, sender->td_maxwin,
794                 sender->td_scale,
795                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
796                 receiver->td_scale);
797 }
798
799 #endif
800
801 #define TH_FIN  0x01
802 #define TH_SYN  0x02
803 #define TH_RST  0x04
804 #define TH_PUSH 0x08
805 #define TH_ACK  0x10
806 #define TH_URG  0x20
807 #define TH_ECE  0x40
808 #define TH_CWR  0x80
809
810 /* table of valid flag combinations - ECE and CWR are always valid */
811 static const u8 tcp_valid_flags[(TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG) + 1] =
812 {
813         [TH_SYN]                        = 1,
814         [TH_SYN|TH_PUSH]                = 1,
815         [TH_SYN|TH_URG]                 = 1,
816         [TH_SYN|TH_PUSH|TH_URG]         = 1,
817         [TH_SYN|TH_ACK]                 = 1,
818         [TH_SYN|TH_ACK|TH_PUSH]         = 1,
819         [TH_RST]                        = 1,
820         [TH_RST|TH_ACK]                 = 1,
821         [TH_RST|TH_ACK|TH_PUSH]         = 1,
822         [TH_FIN|TH_ACK]                 = 1,
823         [TH_ACK]                        = 1,
824         [TH_ACK|TH_PUSH]                = 1,
825         [TH_ACK|TH_URG]                 = 1,
826         [TH_ACK|TH_URG|TH_PUSH]         = 1,
827         [TH_FIN|TH_ACK|TH_PUSH]         = 1,
828         [TH_FIN|TH_ACK|TH_URG]          = 1,
829         [TH_FIN|TH_ACK|TH_URG|TH_PUSH]  = 1,
830 };
831
832 /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c.  */
833 static int tcp_error(struct sk_buff *skb,
834                      enum ip_conntrack_info *ctinfo,
835                      unsigned int hooknum)
836 {
837         struct iphdr *iph = skb->nh.iph;
838         struct tcphdr _tcph, *th;
839         unsigned int tcplen = skb->len - iph->ihl * 4;
840         u_int8_t tcpflags;
841
842         /* Smaller that minimal TCP header? */
843         th = skb_header_pointer(skb, iph->ihl * 4,
844                                 sizeof(_tcph), &_tcph);
845         if (th == NULL) {
846                 if (LOG_INVALID(IPPROTO_TCP))
847                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
848                                 "ip_ct_tcp: short packet ");
849                 return -NF_ACCEPT;
850         }
851
852         /* Not whole TCP header or malformed packet */
853         if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {
854                 if (LOG_INVALID(IPPROTO_TCP))
855                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
856                                 "ip_ct_tcp: truncated/malformed packet ");
857                 return -NF_ACCEPT;
858         }
859
860         /* Checksum invalid? Ignore.
861          * We skip checking packets on the outgoing path
862          * because it is assumed to be correct.
863          */
864         /* FIXME: Source route IP option packets --RR */
865         if (ip_conntrack_checksum && hooknum == NF_IP_PRE_ROUTING &&
866             nf_ip_checksum(skb, hooknum, iph->ihl * 4, IPPROTO_TCP)) {
867                 if (LOG_INVALID(IPPROTO_TCP))
868                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
869                                   "ip_ct_tcp: bad TCP checksum ");
870                 return -NF_ACCEPT;
871         }
872
873         /* Check TCP flags. */
874         tcpflags = (((u_int8_t *)th)[13] & ~(TH_ECE|TH_CWR));
875         if (!tcp_valid_flags[tcpflags]) {
876                 if (LOG_INVALID(IPPROTO_TCP))
877                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
878                                   "ip_ct_tcp: invalid TCP flag combination ");
879                 return -NF_ACCEPT;
880         }
881
882         return NF_ACCEPT;
883 }
884
885 /* Returns verdict for packet, or -1 for invalid. */
886 static int tcp_packet(struct ip_conntrack *conntrack,
887                       const struct sk_buff *skb,
888                       enum ip_conntrack_info ctinfo)
889 {
890         enum tcp_conntrack new_state, old_state;
891         enum ip_conntrack_dir dir;
892         struct iphdr *iph = skb->nh.iph;
893         struct tcphdr *th, _tcph;
894         unsigned long timeout;
895         unsigned int index;
896
897         th = skb_header_pointer(skb, iph->ihl * 4,
898                                 sizeof(_tcph), &_tcph);
899         BUG_ON(th == NULL);
900
901         write_lock_bh(&tcp_lock);
902         old_state = conntrack->proto.tcp.state;
903         dir = CTINFO2DIR(ctinfo);
904         index = get_conntrack_index(th);
905         new_state = tcp_conntracks[dir][index][old_state];
906
907         switch (new_state) {
908         case TCP_CONNTRACK_IGNORE:
909                 /* Ignored packets:
910                  *
911                  * a) SYN in ORIGINAL
912                  * b) SYN/ACK in REPLY
913                  * c) ACK in reply direction after initial SYN in original.
914                  */
915                 if (index == TCP_SYNACK_SET
916                     && conntrack->proto.tcp.last_index == TCP_SYN_SET
917                     && conntrack->proto.tcp.last_dir != dir
918                     && ntohl(th->ack_seq) ==
919                              conntrack->proto.tcp.last_end) {
920                         /* This SYN/ACK acknowledges a SYN that we earlier
921                          * ignored as invalid. This means that the client and
922                          * the server are both in sync, while the firewall is
923                          * not. We kill this session and block the SYN/ACK so
924                          * that the client cannot but retransmit its SYN and
925                          * thus initiate a clean new session.
926                          */
927                         write_unlock_bh(&tcp_lock);
928                         if (LOG_INVALID(IPPROTO_TCP))
929                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
930                                               NULL, "ip_ct_tcp: "
931                                               "killing out of sync session ");
932                         if (del_timer(&conntrack->timeout))
933                                 conntrack->timeout.function((unsigned long)
934                                                             conntrack);
935                         return -NF_DROP;
936                 }
937                 conntrack->proto.tcp.last_index = index;
938                 conntrack->proto.tcp.last_dir = dir;
939                 conntrack->proto.tcp.last_seq = ntohl(th->seq);
940                 conntrack->proto.tcp.last_end =
941                     segment_seq_plus_len(ntohl(th->seq), skb->len, iph, th);
942
943                 write_unlock_bh(&tcp_lock);
944                 if (LOG_INVALID(IPPROTO_TCP))
945                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
946                                   "ip_ct_tcp: invalid packet ignored ");
947                 return NF_ACCEPT;
948         case TCP_CONNTRACK_MAX:
949                 /* Invalid packet */
950                 DEBUGP("ip_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
951                        dir, get_conntrack_index(th),
952                        old_state);
953                 write_unlock_bh(&tcp_lock);
954                 if (LOG_INVALID(IPPROTO_TCP))
955                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
956                                   "ip_ct_tcp: invalid state ");
957                 return -NF_ACCEPT;
958         case TCP_CONNTRACK_SYN_SENT:
959                 if (old_state < TCP_CONNTRACK_TIME_WAIT)
960                         break;
961                 if ((conntrack->proto.tcp.seen[dir].flags &
962                          IP_CT_TCP_FLAG_CLOSE_INIT)
963                     || after(ntohl(th->seq),
964                              conntrack->proto.tcp.seen[dir].td_end)) {
965                         /* Attempt to reopen a closed connection.
966                         * Delete this connection and look up again. */
967                         write_unlock_bh(&tcp_lock);
968                         if (del_timer(&conntrack->timeout))
969                                 conntrack->timeout.function((unsigned long)
970                                                             conntrack);
971                         return -NF_REPEAT;
972                 } else {
973                         write_unlock_bh(&tcp_lock);
974                         if (LOG_INVALID(IPPROTO_TCP))
975                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
976                                               NULL, "ip_ct_tcp: invalid SYN");
977                         return -NF_ACCEPT;
978                 }
979         case TCP_CONNTRACK_CLOSE:
980                 if (index == TCP_RST_SET
981                     && ((test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)
982                          && conntrack->proto.tcp.last_index == TCP_SYN_SET)
983                         || (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
984                             && conntrack->proto.tcp.last_index == TCP_ACK_SET))
985                     && ntohl(th->ack_seq) == conntrack->proto.tcp.last_end) {
986                         /* RST sent to invalid SYN or ACK we had let through
987                          * at a) and c) above:
988                          *
989                          * a) SYN was in window then
990                          * c) we hold a half-open connection.
991                          *
992                          * Delete our connection entry.
993                          * We skip window checking, because packet might ACK
994                          * segments we ignored. */
995                         goto in_window;
996                 }
997                 /* Just fall through */
998         default:
999                 /* Keep compilers happy. */
1000                 break;
1001         }
1002
1003         if (!tcp_in_window(&conntrack->proto.tcp, dir, index,
1004                            skb, iph, th)) {
1005                 write_unlock_bh(&tcp_lock);
1006                 return -NF_ACCEPT;
1007         }
1008     in_window:
1009         /* From now on we have got in-window packets */
1010         conntrack->proto.tcp.last_index = index;
1011
1012         DEBUGP("tcp_conntracks: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
1013                "syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
1014                 NIPQUAD(iph->saddr), ntohs(th->source),
1015                 NIPQUAD(iph->daddr), ntohs(th->dest),
1016                 (th->syn ? 1 : 0), (th->ack ? 1 : 0),
1017                 (th->fin ? 1 : 0), (th->rst ? 1 : 0),
1018                 old_state, new_state);
1019
1020         conntrack->proto.tcp.state = new_state;
1021         if (old_state != new_state
1022             && (new_state == TCP_CONNTRACK_FIN_WAIT
1023                 || new_state == TCP_CONNTRACK_CLOSE))
1024                 conntrack->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
1025         timeout = conntrack->proto.tcp.retrans >= ip_ct_tcp_max_retrans
1026                   && *tcp_timeouts[new_state] > ip_ct_tcp_timeout_max_retrans
1027                   ? ip_ct_tcp_timeout_max_retrans : *tcp_timeouts[new_state];
1028         write_unlock_bh(&tcp_lock);
1029
1030         ip_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
1031         if (new_state != old_state)
1032                 ip_conntrack_event_cache(IPCT_PROTOINFO, skb);
1033
1034         if (!test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
1035                 /* If only reply is a RST, we can consider ourselves not to
1036                    have an established connection: this is a fairly common
1037                    problem case, so we can delete the conntrack
1038                    immediately.  --RR */
1039                 if (th->rst) {
1040                         if (del_timer(&conntrack->timeout))
1041                                 conntrack->timeout.function((unsigned long)
1042                                                             conntrack);
1043                         return NF_ACCEPT;
1044                 }
1045         } else if (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
1046                    && (old_state == TCP_CONNTRACK_SYN_RECV
1047                        || old_state == TCP_CONNTRACK_ESTABLISHED)
1048                    && new_state == TCP_CONNTRACK_ESTABLISHED) {
1049                 /* Set ASSURED if we see see valid ack in ESTABLISHED
1050                    after SYN_RECV or a valid answer for a picked up
1051                    connection. */
1052                 set_bit(IPS_ASSURED_BIT, &conntrack->status);
1053                 ip_conntrack_event_cache(IPCT_STATUS, skb);
1054         }
1055         ip_ct_refresh_acct(conntrack, ctinfo, skb, timeout);
1056
1057         return NF_ACCEPT;
1058 }
1059
1060 /* Called when a new connection for this protocol found. */
1061 static int tcp_new(struct ip_conntrack *conntrack,
1062                    const struct sk_buff *skb)
1063 {
1064         enum tcp_conntrack new_state;
1065         struct iphdr *iph = skb->nh.iph;
1066         struct tcphdr *th, _tcph;
1067 #ifdef DEBUGP_VARS
1068         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[0];
1069         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[1];
1070 #endif
1071
1072         th = skb_header_pointer(skb, iph->ihl * 4,
1073                                 sizeof(_tcph), &_tcph);
1074         BUG_ON(th == NULL);
1075
1076         /* Don't need lock here: this conntrack not in circulation yet */
1077         new_state
1078                 = tcp_conntracks[0][get_conntrack_index(th)]
1079                 [TCP_CONNTRACK_NONE];
1080
1081         /* Invalid: delete conntrack */
1082         if (new_state >= TCP_CONNTRACK_MAX) {
1083                 DEBUGP("ip_ct_tcp: invalid new deleting.\n");
1084                 return 0;
1085         }
1086
1087         if (new_state == TCP_CONNTRACK_SYN_SENT) {
1088                 /* SYN packet */
1089                 conntrack->proto.tcp.seen[0].td_end =
1090                         segment_seq_plus_len(ntohl(th->seq), skb->len,
1091                                              iph, th);
1092                 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1093                 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1094                         conntrack->proto.tcp.seen[0].td_maxwin = 1;
1095                 conntrack->proto.tcp.seen[0].td_maxend =
1096                         conntrack->proto.tcp.seen[0].td_end;
1097
1098                 tcp_options(skb, iph, th, &conntrack->proto.tcp.seen[0]);
1099                 conntrack->proto.tcp.seen[1].flags = 0;
1100         } else if (ip_ct_tcp_loose == 0) {
1101                 /* Don't try to pick up connections. */
1102                 return 0;
1103         } else {
1104                 /*
1105                  * We are in the middle of a connection,
1106                  * its history is lost for us.
1107                  * Let's try to use the data from the packet.
1108                  */
1109                 conntrack->proto.tcp.seen[0].td_end =
1110                         segment_seq_plus_len(ntohl(th->seq), skb->len,
1111                                              iph, th);
1112                 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1113                 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1114                         conntrack->proto.tcp.seen[0].td_maxwin = 1;
1115                 conntrack->proto.tcp.seen[0].td_maxend =
1116                         conntrack->proto.tcp.seen[0].td_end +
1117                         conntrack->proto.tcp.seen[0].td_maxwin;
1118                 conntrack->proto.tcp.seen[0].td_scale = 0;
1119
1120                 /* We assume SACK and liberal window checking to handle
1121                  * window scaling */
1122                 conntrack->proto.tcp.seen[0].flags =
1123                 conntrack->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM |
1124                                                      IP_CT_TCP_FLAG_BE_LIBERAL;
1125         }
1126
1127         conntrack->proto.tcp.seen[1].td_end = 0;
1128         conntrack->proto.tcp.seen[1].td_maxend = 0;
1129         conntrack->proto.tcp.seen[1].td_maxwin = 1;
1130         conntrack->proto.tcp.seen[1].td_scale = 0;
1131
1132         /* tcp_packet will set them */
1133         conntrack->proto.tcp.state = TCP_CONNTRACK_NONE;
1134         conntrack->proto.tcp.last_index = TCP_NONE_SET;
1135
1136         DEBUGP("tcp_new: sender end=%u maxend=%u maxwin=%u scale=%i "
1137                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
1138                 sender->td_end, sender->td_maxend, sender->td_maxwin,
1139                 sender->td_scale,
1140                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
1141                 receiver->td_scale);
1142         return 1;
1143 }
1144
1145 struct ip_conntrack_protocol ip_conntrack_protocol_tcp =
1146 {
1147         .proto                  = IPPROTO_TCP,
1148         .name                   = "tcp",
1149         .pkt_to_tuple           = tcp_pkt_to_tuple,
1150         .invert_tuple           = tcp_invert_tuple,
1151         .print_tuple            = tcp_print_tuple,
1152         .print_conntrack        = tcp_print_conntrack,
1153         .packet                 = tcp_packet,
1154         .new                    = tcp_new,
1155         .error                  = tcp_error,
1156 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
1157     defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
1158         .to_nfattr              = tcp_to_nfattr,
1159         .from_nfattr            = nfattr_to_tcp,
1160         .tuple_to_nfattr        = ip_ct_port_tuple_to_nfattr,
1161         .nfattr_to_tuple        = ip_ct_port_nfattr_to_tuple,
1162 #endif
1163 };