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/config.h>
  23 #include <linux/types.h>
  24 #include <linux/sched.h>
  25 #include <linux/timer.h>
  26 #include <linux/netfilter.h>
  27 #include <linux/module.h>
  28 #include <linux/in.h>
  29 #include <linux/ip.h>
  30 #include <linux/tcp.h>
  31 #include <linux/spinlock.h>
  32
  33 #include <net/tcp.h>
  34
  35 #include <linux/netfilter.h>
  36 #include <linux/netfilter_ipv4.h>
  37 #include <linux/netfilter_ipv4/ip_conntrack.h>
  38 #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
  39 #include <linux/netfilter_ipv4/lockhelp.h>
  40
  41 #if 0
  42 #define DEBUGP printk
  43 #define DEBUGP_VARS
  44 #else
  45 #define DEBUGP(format, args...)
  46 #endif
  47
  48 /* Protects conntrack->proto.tcp */
  49 static DECLARE_RWLOCK(tcp_lock);
  50
  51 /* "Be conservative in what you do,
  52     be liberal in what you accept from others."
  53     If it's non-zero, we mark only out of window RST segments as INVALID. */
  54 int ip_ct_tcp_be_liberal = 0;
  55
  56 /* When connection is picked up from the middle, how many packets are required
  57    to pass in each direction when we assume we are in sync - if any side uses
  58    window scaling, we lost the game.
  59    If it is set to zero, we disable picking up already established
  60    connections. */
  61 int ip_ct_tcp_loose = 3;
  62
  63 /* Max number of the retransmitted packets without receiving an (acceptable)
  64    ACK from the destination. If this number is reached, a shorter timer
  65    will be started. */
  66 int ip_ct_tcp_max_retrans = 3;
  67
  68   /* FIXME: Examine ipfilter's timeouts and conntrack transitions more
  69      closely.  They're more complex. --RR */
  70
  71 static const char *tcp_conntrack_names[] = {
  72         "NONE",
  73         "SYN_SENT",
  74         "SYN_RECV",
  75         "ESTABLISHED",
  76         "FIN_WAIT",
  77         "CLOSE_WAIT",
  78         "LAST_ACK",
  79         "TIME_WAIT",
  80         "CLOSE",
  81         "LISTEN"
  82 };
  83
  84 #define SECS * HZ
  85 #define MINS * 60 SECS
  86 #define HOURS * 60 MINS
  87 #define DAYS * 24 HOURS
  88
  89 unsigned long ip_ct_tcp_timeout_syn_sent =      2 MINS;
  90 unsigned long ip_ct_tcp_timeout_syn_recv =     60 SECS;
  91 #if HZ < 9942
  92 unsigned long ip_ct_tcp_timeout_established =  5U DAYS;
  93 #else
  94 unsigned long ip_ct_tcp_timeout_established =  2U DAYS;
  95 #endif
  96 unsigned long ip_ct_tcp_timeout_fin_wait =      2 MINS;
  97 unsigned long ip_ct_tcp_timeout_close_wait =   60 SECS;
  98 unsigned long ip_ct_tcp_timeout_last_ack =     30 SECS;
  99 unsigned long ip_ct_tcp_timeout_time_wait =     2 MINS;
 100 unsigned long ip_ct_tcp_timeout_close =        10 SECS;
 101
 102 /* RFC1122 says the R2 limit should be at least 100 seconds.
 103    Linux uses 15 packets as limit, which corresponds
 104    to ~13-30min depending on RTO. */
 105 unsigned long ip_ct_tcp_timeout_max_retrans =     5 MINS;
 106
 107 static unsigned long * tcp_timeouts[]
 108 = { NULL,                              /*      TCP_CONNTRACK_NONE */
 109     &ip_ct_tcp_timeout_syn_sent,       /*      TCP_CONNTRACK_SYN_SENT, */
 110     &ip_ct_tcp_timeout_syn_recv,       /*      TCP_CONNTRACK_SYN_RECV, */
 111     &ip_ct_tcp_timeout_established,    /*      TCP_CONNTRACK_ESTABLISHED,      */
 112     &ip_ct_tcp_timeout_fin_wait,       /*      TCP_CONNTRACK_FIN_WAIT, */
 113     &ip_ct_tcp_timeout_close_wait,     /*      TCP_CONNTRACK_CLOSE_WAIT,       */
 114     &ip_ct_tcp_timeout_last_ack,       /*      TCP_CONNTRACK_LAST_ACK, */
 115     &ip_ct_tcp_timeout_time_wait,      /*      TCP_CONNTRACK_TIME_WAIT,        */
 116     &ip_ct_tcp_timeout_close,          /*      TCP_CONNTRACK_CLOSE,    */
 117     NULL,                              /*      TCP_CONNTRACK_LISTEN */
 118  };
 119
 120 #define sNO TCP_CONNTRACK_NONE
 121 #define sSS TCP_CONNTRACK_SYN_SENT
 122 #define sSR TCP_CONNTRACK_SYN_RECV
 123 #define sES TCP_CONNTRACK_ESTABLISHED
 124 #define sFW TCP_CONNTRACK_FIN_WAIT
 125 #define sCW TCP_CONNTRACK_CLOSE_WAIT
 126 #define sLA TCP_CONNTRACK_LAST_ACK
 127 #define sTW TCP_CONNTRACK_TIME_WAIT
 128 #define sCL TCP_CONNTRACK_CLOSE
 129 #define sLI TCP_CONNTRACK_LISTEN
 130 #define sIV TCP_CONNTRACK_MAX
 131 #define sIG TCP_CONNTRACK_IGNORE
 132
 133 /* What TCP flags are set from RST/SYN/FIN/ACK. */
 134 enum tcp_bit_set {
 135         TCP_SYN_SET,
 136         TCP_SYNACK_SET,
 137         TCP_FIN_SET,
 138         TCP_ACK_SET,
 139         TCP_RST_SET,
 140         TCP_NONE_SET,
 141 };
 142
 143 /*
 144  * The TCP state transition table needs a few words...
 145  *
 146  * We are the man in the middle. All the packets go through us
 147  * but might get lost in transit to the destination.
 148  * It is assumed that the destinations can't receive segments
 149  * we haven't seen.
 150  *
 151  * The checked segment is in window, but our windows are *not*
 152  * equivalent with the ones of the sender/receiver. We always
 153  * try to guess the state of the current sender.
 154  *
 155  * The meaning of the states are:
 156  *
 157  * NONE:        initial state
 158  * SYN_SENT:    SYN-only packet seen
 159  * SYN_RECV:    SYN-ACK packet seen
 160  * ESTABLISHED: ACK packet seen
 161  * FIN_WAIT:    FIN packet seen
 162  * CLOSE_WAIT:  ACK seen (after FIN)
 163  * LAST_ACK:    FIN seen (after FIN)
 164  * TIME_WAIT:   last ACK seen
 165  * CLOSE:       closed connection
 166  *
 167  * LISTEN state is not used.
 168  *
 169  * Packets marked as IGNORED (sIG):
 170  *      if they may be either invalid or valid
 171  *      and the receiver may send back a connection
 172  *      closing RST or a SYN/ACK.
 173  *
 174  * Packets marked as INVALID (sIV):
 175  *      if they are invalid
 176  *      or we do not support the request (simultaneous open)
 177  */
 178 static enum tcp_conntrack tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = {
 179         {
 180 /* ORIGINAL */
 181 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 182 /*syn*/    { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sIV },
 183 /*
 184  *      sNO -> sSS      Initialize a new connection
 185  *      sSS -> sSS      Retransmitted SYN
 186  *      sSR -> sIG      Late retransmitted SYN?
 187  *      sES -> sIG      Error: SYNs in window outside the SYN_SENT state
 188  *                      are errors. Receiver will reply with RST
 189  *                      and close the connection.
 190  *                      Or we are not in sync and hold a dead connection.
 191  *      sFW -> sIG
 192  *      sCW -> sIG
 193  *      sLA -> sIG
 194  *      sTW -> sSS      Reopened connection (RFC 1122).
 195  *      sCL -> sSS
 196  */
 197 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 198 /*synack*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
 199 /*
 200  * A SYN/ACK from the client is always invalid:
 201  *      - either it tries to set up a simultaneous open, which is
 202  *        not supported;
 203  *      - or the firewall has just been inserted between the two hosts
 204  *        during the session set-up. The SYN will be retransmitted
 205  *        by the true client (or it'll time out).
 206  */
 207 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 208 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
 209 /*
 210  *      sNO -> sIV      Too late and no reason to do anything...
 211  *      sSS -> sIV      Client migth not send FIN in this state:
 212  *                      we enforce waiting for a SYN/ACK reply first.
 213  *      sSR -> sFW      Close started.
 214  *      sES -> sFW
 215  *      sFW -> sLA      FIN seen in both directions, waiting for
 216  *                      the last ACK.
 217  *                      Migth be a retransmitted FIN as well...
 218  *      sCW -> sLA
 219  *      sLA -> sLA      Retransmitted FIN. Remain in the same state.
 220  *      sTW -> sTW
 221  *      sCL -> sCL
 222  */
 223 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 224 /*ack*/    { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV },
 225 /*
 226  *      sNO -> sES      Assumed.
 227  *      sSS -> sIV      ACK is invalid: we haven't seen a SYN/ACK yet.
 228  *      sSR -> sES      Established state is reached.
 229  *      sES -> sES      :-)
 230  *      sFW -> sCW      Normal close request answered by ACK.
 231  *      sCW -> sCW
 232  *      sLA -> sTW      Last ACK detected.
 233  *      sTW -> sTW      Retransmitted last ACK. Remain in the same state.
 234  *      sCL -> sCL
 235  */
 236 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 237 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
 238 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
 239         },
 240         {
 241 /* REPLY */
 242 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 243 /*syn*/    { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
 244 /*
 245  *      sNO -> sIV      Never reached.
 246  *      sSS -> sIV      Simultaneous open, not supported
 247  *      sSR -> sIV      Simultaneous open, not supported.
 248  *      sES -> sIV      Server may not initiate a connection.
 249  *      sFW -> sIV
 250  *      sCW -> sIV
 251  *      sLA -> sIV
 252  *      sTW -> sIV      Reopened connection, but server may not do it.
 253  *      sCL -> sIV
 254  */
 255 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 256 /*synack*/ { sIV, sSR, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIV },
 257 /*
 258  *      sSS -> sSR      Standard open.
 259  *      sSR -> sSR      Retransmitted SYN/ACK.
 260  *      sES -> sIG      Late retransmitted SYN/ACK?
 261  *      sFW -> sIG
 262  *      sCW -> sIG
 263  *      sLA -> sIG
 264  *      sTW -> sIG
 265  *      sCL -> sIG
 266  */
 267 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 268 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
 269 /*
 270  *      sSS -> sIV      Server might not send FIN in this state.
 271  *      sSR -> sFW      Close started.
 272  *      sES -> sFW
 273  *      sFW -> sLA      FIN seen in both directions.
 274  *      sCW -> sLA
 275  *      sLA -> sLA      Retransmitted FIN.
 276  *      sTW -> sTW
 277  *      sCL -> sCL
 278  */
 279 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 280 /*ack*/    { sIV, sIG, sIV, sES, sCW, sCW, sTW, sTW, sCL, sIV },
 281 /*
 282  *      sSS -> sIG      Might be a half-open connection.
 283  *      sSR -> sIV      Simultaneous open.
 284  *      sES -> sES      :-)
 285  *      sFW -> sCW      Normal close request answered by ACK.
 286  *      sCW -> sCW
 287  *      sLA -> sTW      Last ACK detected.
 288  *      sTW -> sTW      Retransmitted last ACK.
 289  *      sCL -> sCL
 290  */
 291 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 292 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
 293 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
 294         }
 295 };
 296
 297 static int tcp_pkt_to_tuple(const struct sk_buff *skb,
 298                             unsigned int dataoff,
 299                             struct ip_conntrack_tuple *tuple)
 300 {
 301         struct tcphdr _hdr, *hp;
 302
 303         /* Actually only need first 8 bytes. */
 304         hp = skb_header_pointer(skb, dataoff, 8, &_hdr);
 305         if (hp == NULL)
 306                 return 0;
 307
 308         tuple->src.u.tcp.port = hp->source;
 309         tuple->dst.u.tcp.port = hp->dest;
 310
 311         return 1;
 312 }
 313
 314 static int tcp_invert_tuple(struct ip_conntrack_tuple *tuple,
 315                             const struct ip_conntrack_tuple *orig)
 316 {
 317         tuple->src.u.tcp.port = orig->dst.u.tcp.port;
 318         tuple->dst.u.tcp.port = orig->src.u.tcp.port;
 319         return 1;
 320 }
 321
 322 /* Print out the per-protocol part of the tuple. */
 323 static int tcp_print_tuple(struct seq_file *s,
 324                            const struct ip_conntrack_tuple *tuple)
 325 {
 326         return seq_printf(s, "sport=%hu dport=%hu ",
 327                           ntohs(tuple->src.u.tcp.port),
 328                           ntohs(tuple->dst.u.tcp.port));
 329 }
 330
 331 /* Print out the private part of the conntrack. */
 332 static int tcp_print_conntrack(struct seq_file *s,
 333                                const struct ip_conntrack *conntrack)
 334 {
 335         enum tcp_conntrack state;
 336
 337         READ_LOCK(&tcp_lock);
 338         state = conntrack->proto.tcp.state;
 339         READ_UNLOCK(&tcp_lock);
 340
 341         return seq_printf(s, "%s ", tcp_conntrack_names[state]);
 342 }
 343
 344 static unsigned int get_conntrack_index(const struct tcphdr *tcph)
 345 {
 346         if (tcph->rst) return TCP_RST_SET;
 347         else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET);
 348         else if (tcph->fin) return TCP_FIN_SET;
 349         else if (tcph->ack) return TCP_ACK_SET;
 350         else return TCP_NONE_SET;
 351 }
 352
 353 /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering
 354    in IP Filter' by Guido van Rooij.
 355
 356    http://www.nluug.nl/events/sane2000/papers.html
 357    http://www.iae.nl/users/guido/papers/tcp_filtering.ps.gz
 358
 359    The boundaries and the conditions are slightly changed:
 360
 361         td_maxend = max(sack + max(win,1)) seen in reply packets
 362         td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets
 363         td_end    = max(seq + len) seen in sent packets
 364
 365    I.   Upper bound for valid data:     seq + len <= sender.td_maxend
 366    II.  Lower bound for valid data:     seq >= sender.td_end - receiver.td_maxwin
 367    III. Upper bound for valid ack:      sack <= receiver.td_end
 368    IV.  Lower bound for valid ack:      ack >= receiver.td_end - MAXACKWINDOW
 369
 370    where sack is the highest right edge of sack block found in the packet.
 371
 372    The upper bound limit for a valid ack is not ignored -
 373    we doesn't have to deal with fragments.
 374 */
 375
 376 static inline __u32 segment_seq_plus_len(__u32 seq,
 377                                          size_t len,
 378                                          struct iphdr *iph,
 379                                          struct tcphdr *tcph)
 380   {
 381         return (seq + len - (iph->ihl + tcph->doff)*4
 382                 + (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0));
 383 }
 384
 385 /* Fixme: what about big packets? */
 386 #define MAXACKWINCONST                  66000
 387 #define MAXACKWINDOW(sender)                                            \
 388         ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin     \
 389                                               : MAXACKWINCONST)
 390
 391 /*
 392  * Simplified tcp_parse_options routine from tcp_input.c
 393  */
 394 static void tcp_options(const struct sk_buff *skb,
 395                         struct iphdr *iph,
 396                         struct tcphdr *tcph,
 397                         struct ip_ct_tcp_state *state)
 398 {
 399         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
 400         unsigned char *ptr;
 401         int length = (tcph->doff*4) - sizeof(struct tcphdr);
 402
 403         if (!length)
 404                 return;
 405
 406         ptr = skb_header_pointer(skb,
 407                                  (iph->ihl * 4) + sizeof(struct tcphdr),
 408                                  length, buff);
 409         BUG_ON(ptr == NULL);
 410
 411         state->td_scale =
 412         state->flags = 0;
 413
 414         while (length > 0) {
 415                 int opcode=*ptr++;
 416                 int opsize;
 417
 418                 switch (opcode) {
 419                 case TCPOPT_EOL:
 420                         return;
 421                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 422                         length--;
 423                         continue;
 424                 default:
 425                         opsize=*ptr++;
 426                         if (opsize < 2) /* "silly options" */
 427                                 return;
 428                         if (opsize > length)
 429                                 break;  /* don't parse partial options */
 430
 431                         if (opcode == TCPOPT_SACK_PERM
 432                             && opsize == TCPOLEN_SACK_PERM)
 433                                 state->flags |= IP_CT_TCP_FLAG_SACK_PERM;
 434                         else if (opcode == TCPOPT_WINDOW
 435                                  && opsize == TCPOLEN_WINDOW) {
 436                                 state->td_scale = *(u_int8_t *)ptr;
 437
 438                                 if (state->td_scale > 14) {
 439                                         /* See RFC1323 */
 440                                         state->td_scale = 14;
 441                                 }
 442                                 state->flags |=
 443                                         IP_CT_TCP_FLAG_WINDOW_SCALE;
 444                         }
 445                         ptr += opsize - 2;
 446                         length -= opsize;
 447                 }
 448         }
 449 }
 450
 451 static void tcp_sack(struct tcphdr *tcph, __u32 *sack)
 452 {
 453         __u32 tmp;
 454         unsigned char *ptr;
 455         int length = (tcph->doff*4) - sizeof(struct tcphdr);
 456
 457         /* Fast path for timestamp-only option */
 458         if (length == TCPOLEN_TSTAMP_ALIGNED*4
 459             && *(__u32 *)(tcph + 1) ==
 460                 __constant_ntohl((TCPOPT_NOP << 24)
 461                                  | (TCPOPT_NOP << 16)
 462                                  | (TCPOPT_TIMESTAMP << 8)
 463                                  | TCPOLEN_TIMESTAMP))
 464                 return;
 465
 466         ptr = (unsigned char *)(tcph + 1);
 467         while (length > 0) {
 468                 int opcode=*ptr++;
 469                 int opsize, i;
 470
 471                 switch (opcode) {
 472                 case TCPOPT_EOL:
 473                         return;
 474                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 475                         length--;
 476                         continue;
 477                 default:
 478                         opsize=*ptr++;
 479                         if (opsize < 2) /* "silly options" */
 480                                 return;
 481                         if (opsize > length)
 482                                 break;  /* don't parse partial options */
 483
 484                         if (opcode == TCPOPT_SACK
 485                             && opsize >= (TCPOLEN_SACK_BASE
 486                                           + TCPOLEN_SACK_PERBLOCK)
 487                             && !((opsize - TCPOLEN_SACK_BASE)
 488                                  % TCPOLEN_SACK_PERBLOCK)) {
 489                                 for (i = 0;
 490                                      i < (opsize - TCPOLEN_SACK_BASE);
 491                                      i += TCPOLEN_SACK_PERBLOCK) {
 492                                         tmp = ntohl(*((u_int32_t *)(ptr+i)+1));
 493
 494                                         if (after(tmp, *sack))
 495                                                 *sack = tmp;
 496                                 }
 497                                 return;
 498                         }
 499                         ptr += opsize - 2;
 500                         length -= opsize;
 501                 }
 502         }
 503 }
 504
 505 static int tcp_in_window(struct ip_ct_tcp *state,
 506                          enum ip_conntrack_dir dir,
 507                          unsigned int *index,
 508                          const struct sk_buff *skb,
 509                          struct iphdr *iph,
 510                          struct tcphdr *tcph)
 511 {
 512         struct ip_ct_tcp_state *sender = &state->seen[dir];
 513         struct ip_ct_tcp_state *receiver = &state->seen[!dir];
 514         __u32 seq, ack, sack, end, win, swin;
 515         int res;
 516
 517         /*
 518          * Get the required data from the packet.
 519          */
 520         seq = ntohl(tcph->seq);
 521         ack = sack = ntohl(tcph->ack_seq);
 522         win = ntohs(tcph->window);
 523         end = segment_seq_plus_len(seq, skb->len, iph, tcph);
 524
 525         if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
 526                 tcp_sack(tcph, &sack);
 527
 528         DEBUGP("tcp_in_window: START\n");
 529         DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 530                "seq=%u ack=%u sack=%u win=%u end=%u\n",
 531                 NIPQUAD(iph->saddr), ntohs(tcph->source),
 532                 NIPQUAD(iph->daddr), ntohs(tcph->dest),
 533                 seq, ack, sack, win, end);
 534         DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
 535                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 536                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 537                 sender->td_scale,
 538                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 539                 receiver->td_scale);
 540
 541         if (sender->td_end == 0) {
 542                 /*
 543                  * Initialize sender data.
 544                  */
 545                 if (tcph->syn && tcph->ack) {
 546                         /*
 547                          * Outgoing SYN-ACK in reply to a SYN.
 548                          */
 549                         sender->td_end =
 550                         sender->td_maxend = end;
 551                         sender->td_maxwin = (win == 0 ? 1 : win);
 552
 553                         tcp_options(skb, iph, tcph, sender);
 554                         /*
 555                          * RFC 1323:
 556                          * Both sides must send the Window Scale option
 557                          * to enable window scaling in either direction.
 558                          */
 559                         if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE
 560                               && receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE))
 561                                 sender->td_scale =
 562                                 receiver->td_scale = 0;
 563                 } else {
 564                         /*
 565                          * We are in the middle of a connection,
 566                          * its history is lost for us.
 567                          * Let's try to use the data from the packet.
 568                          */
 569                         sender->td_end = end;
 570                         sender->td_maxwin = (win == 0 ? 1 : win);
 571                         sender->td_maxend = end + sender->td_maxwin;
 572                 }
 573         } else if (((state->state == TCP_CONNTRACK_SYN_SENT
 574                      && dir == IP_CT_DIR_ORIGINAL)
 575                     || (state->state == TCP_CONNTRACK_SYN_RECV
 576                         && dir == IP_CT_DIR_REPLY))
 577                     && after(end, sender->td_end)) {
 578                 /*
 579                  * RFC 793: "if a TCP is reinitialized ... then it need
 580                  * not wait at all; it must only be sure to use sequence
 581                  * numbers larger than those recently used."
 582                  */
 583                 sender->td_end =
 584                 sender->td_maxend = end;
 585                 sender->td_maxwin = (win == 0 ? 1 : win);
 586
 587                 tcp_options(skb, iph, tcph, sender);
 588         }
 589
 590         if (!(tcph->ack)) {
 591                 /*
 592                  * If there is no ACK, just pretend it was set and OK.
 593                  */
 594                 ack = sack = receiver->td_end;
 595         } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
 596                     (TCP_FLAG_ACK|TCP_FLAG_RST))
 597                    && (ack == 0)) {
 598                 /*
 599                  * Broken TCP stacks, that set ACK in RST packets as well
 600                  * with zero ack value.
 601                  */
 602                 ack = sack = receiver->td_end;
 603         }
 604
 605         if (seq == end)
 606                 /*
 607                  * Packets contains no data: we assume it is valid
 608                  * and check the ack value only.
 609                  */
 610                 seq = end = sender->td_end;
 611
 612         DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 613                "seq=%u ack=%u sack =%u win=%u end=%u trim=%u\n",
 614                 NIPQUAD(iph->saddr), ntohs(tcph->source),
 615                 NIPQUAD(iph->daddr), ntohs(tcph->dest),
 616                 seq, ack, sack, win, end,
 617                 after(end, sender->td_maxend) && before(seq, sender->td_maxend)
 618                 ? sender->td_maxend : end);
 619         DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
 620                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 621                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 622                 sender->td_scale,
 623                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 624                 receiver->td_scale);
 625
 626         /* Ignore data over the right edge of the receiver's window. */
 627         if (after(end, sender->td_maxend) &&
 628             before(seq, sender->td_maxend)) {
 629                 end = sender->td_maxend;
 630                 if (*index == TCP_FIN_SET)
 631                         *index = TCP_ACK_SET;
 632         }
 633         DEBUGP("tcp_in_window: I=%i II=%i III=%i IV=%i\n",
 634                 before(end, sender->td_maxend + 1)
 635                     || before(seq, sender->td_maxend + 1),
 636                 after(seq, sender->td_end - receiver->td_maxwin - 1)
 637                     || after(end, sender->td_end - receiver->td_maxwin - 1),
 638                 before(sack, receiver->td_end + 1),
 639                 after(ack, receiver->td_end - MAXACKWINDOW(sender)));
 640
 641         if (sender->loose || receiver->loose ||
 642             (before(end, sender->td_maxend + 1) &&
 643              after(seq, sender->td_end - receiver->td_maxwin - 1) &&
 644              before(sack, receiver->td_end + 1) &&
 645              after(ack, receiver->td_end - MAXACKWINDOW(sender)))) {
 646                 /*
 647                  * Take into account window scaling (RFC 1323).
 648                  */
 649                 if (!tcph->syn)
 650                         win <<= sender->td_scale;
 651
 652                 /*
 653                  * Update sender data.
 654                  */
 655                 swin = win + (sack - ack);
 656                 if (sender->td_maxwin < swin)
 657                         sender->td_maxwin = swin;
 658                 if (after(end, sender->td_end))
 659                         sender->td_end = end;
 660                 if (after(sack + win, receiver->td_maxend - 1)) {
 661                         receiver->td_maxend = sack + win;
 662                         if (win == 0)
 663                                 receiver->td_maxend++;
 664                 }
 665
 666                 /*
 667                  * Check retransmissions.
 668                  */
 669                 if (*index == TCP_ACK_SET) {
 670                         if (state->last_dir == dir
 671                             && state->last_seq == seq
 672                             && state->last_ack == ack
 673                             && state->last_end == end)
 674                                 state->retrans++;
 675                         else {
 676                                 state->last_dir = dir;
 677                                 state->last_seq = seq;
 678                                 state->last_ack = ack;
 679                                 state->last_end = end;
 680                                 state->retrans = 0;
 681                         }
 682                 }
 683                 /*
 684                  * Close the window of disabled window tracking :-)
 685                  */
 686                 if (sender->loose)
 687                         sender->loose--;
 688
 689                 res = 1;
 690         } else {
 691                 if (LOG_INVALID(IPPROTO_TCP))
 692                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 693                         "ip_ct_tcp: %s ",
 694                         before(end, sender->td_maxend + 1) ?
 695                         after(seq, sender->td_end - receiver->td_maxwin - 1) ?
 696                         before(sack, receiver->td_end + 1) ?
 697                         after(ack, receiver->td_end - MAXACKWINDOW(sender)) ? "BUG"
 698                         : "ACK is under the lower bound (possibly overly delayed ACK)"
 699                         : "ACK is over the upper bound (ACKed data has never seen yet)"
 700                         : "SEQ is under the lower bound (retransmitted already ACKed data)"
 701                         : "SEQ is over the upper bound (over the window of the receiver)");
 702
 703                 res = ip_ct_tcp_be_liberal && !tcph->rst;
 704         }
 705
 706         DEBUGP("tcp_in_window: res=%i sender end=%u maxend=%u maxwin=%u "
 707                "receiver end=%u maxend=%u maxwin=%u\n",
 708                 res, sender->td_end, sender->td_maxend, sender->td_maxwin,
 709                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin);
 710
 711         return res;
 712 }
 713
 714 #ifdef CONFIG_IP_NF_NAT_NEEDED
 715 /* Update sender->td_end after NAT successfully mangled the packet */
 716 void ip_conntrack_tcp_update(struct sk_buff *skb,
 717                              struct ip_conntrack *conntrack,
 718                              enum ip_conntrack_dir dir)
 719 {
 720         struct iphdr *iph = skb->nh.iph;
 721         struct tcphdr *tcph = (void *)skb->nh.iph + skb->nh.iph->ihl*4;
 722         __u32 end;
 723 #ifdef DEBUGP_VARS
 724         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[dir];
 725         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[!dir];
 726 #endif
 727
 728         end = segment_seq_plus_len(ntohl(tcph->seq), skb->len, iph, tcph);
 729
 730         WRITE_LOCK(&tcp_lock);
 731         /*
 732          * We have to worry for the ack in the reply packet only...
 733          */
 734         if (after(end, conntrack->proto.tcp.seen[dir].td_end))
 735                 conntrack->proto.tcp.seen[dir].td_end = end;
 736         conntrack->proto.tcp.last_end = end;
 737         WRITE_UNLOCK(&tcp_lock);
 738         DEBUGP("tcp_update: sender end=%u maxend=%u maxwin=%u scale=%i "
 739                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 740                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 741                 sender->td_scale,
 742                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 743                 receiver->td_scale);
 744 }
 745
 746 #endif
 747
 748 #define TH_FIN  0x01
 749 #define TH_SYN  0x02
 750 #define TH_RST  0x04
 751 #define TH_PUSH 0x08
 752 #define TH_ACK  0x10
 753 #define TH_URG  0x20
 754 #define TH_ECE  0x40
 755 #define TH_CWR  0x80
 756
 757 /* table of valid flag combinations - ECE and CWR are always valid */
 758 static u8 tcp_valid_flags[(TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG) + 1] =
 759 {
 760         [TH_SYN]                        = 1,
 761         [TH_SYN|TH_ACK]                 = 1,
 762         [TH_RST]                        = 1,
 763         [TH_RST|TH_ACK]                 = 1,
 764         [TH_RST|TH_ACK|TH_PUSH]         = 1,
 765         [TH_FIN|TH_ACK]                 = 1,
 766         [TH_ACK]                        = 1,
 767         [TH_ACK|TH_PUSH]                = 1,
 768         [TH_ACK|TH_URG]                 = 1,
 769         [TH_ACK|TH_URG|TH_PUSH]         = 1,
 770         [TH_FIN|TH_ACK|TH_PUSH]         = 1,
 771         [TH_FIN|TH_ACK|TH_URG]          = 1,
 772         [TH_FIN|TH_ACK|TH_URG|TH_PUSH]  = 1,
 773 };
 774
 775 /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c.  */
 776 static int tcp_error(struct sk_buff *skb,
 777                      enum ip_conntrack_info *ctinfo,
 778                      unsigned int hooknum)
 779 {
 780         struct iphdr *iph = skb->nh.iph;
 781         struct tcphdr _tcph, *th;
 782         unsigned int tcplen = skb->len - iph->ihl * 4;
 783         u_int8_t tcpflags;
 784
 785         /* Smaller that minimal TCP header? */
 786         th = skb_header_pointer(skb, iph->ihl * 4,
 787                                 sizeof(_tcph), &_tcph);
 788         if (th == NULL) {
 789                 if (LOG_INVALID(IPPROTO_TCP))
 790                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 791                                 "ip_ct_tcp: short packet ");
 792                 return -NF_ACCEPT;
 793         }
 794
 795         /* Not whole TCP header or malformed packet */
 796         if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {
 797                 if (LOG_INVALID(IPPROTO_TCP))
 798                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 799                                 "ip_ct_tcp: truncated/malformed packet ");
 800                 return -NF_ACCEPT;
 801         }
 802
 803         /* Checksum invalid? Ignore.
 804          * We skip checking packets on the outgoing path
 805          * because the semantic of CHECKSUM_HW is different there
 806          * and moreover root might send raw packets.
 807          */
 808         /* FIXME: Source route IP option packets --RR */
 809         if (hooknum == NF_IP_PRE_ROUTING
 810             && csum_tcpudp_magic(iph->saddr, iph->daddr, tcplen, IPPROTO_TCP,
 811                                  skb->ip_summed == CHECKSUM_HW ? skb->csum
 812                                  : skb_checksum(skb, iph->ihl*4, tcplen, 0))) {
 813                 if (LOG_INVALID(IPPROTO_TCP))
 814                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 815                                   "ip_ct_tcp: bad TCP checksum ");
 816                 return -NF_ACCEPT;
 817         }
 818
 819         /* Check TCP flags. */
 820         tcpflags = (((u_int8_t *)th)[13] & ~(TH_ECE|TH_CWR));
 821         if (!tcp_valid_flags[tcpflags]) {
 822                 if (LOG_INVALID(IPPROTO_TCP))
 823                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 824                                   "ip_ct_tcp: invalid TCP flag combination ");
 825                 return -NF_ACCEPT;
 826         }
 827
 828         return NF_ACCEPT;
 829 }
 830
 831 /* Returns verdict for packet, or -1 for invalid. */
 832 static int tcp_packet(struct ip_conntrack *conntrack,
 833                       const struct sk_buff *skb,
 834                       enum ip_conntrack_info ctinfo)
 835 {
 836         enum tcp_conntrack new_state, old_state;
 837         enum ip_conntrack_dir dir;
 838         struct iphdr *iph = skb->nh.iph;
 839         struct tcphdr *th, _tcph;
 840         unsigned long timeout;
 841         unsigned int index;
 842
 843         th = skb_header_pointer(skb, iph->ihl * 4,
 844                                 sizeof(_tcph), &_tcph);
 845         BUG_ON(th == NULL);
 846
 847         WRITE_LOCK(&tcp_lock);
 848         old_state = conntrack->proto.tcp.state;
 849         dir = CTINFO2DIR(ctinfo);
 850         index = get_conntrack_index(th);
 851         new_state = tcp_conntracks[dir][index][old_state];
 852
 853         switch (new_state) {
 854         case TCP_CONNTRACK_IGNORE:
 855                 /* Either SYN in ORIGINAL
 856                  * or SYN/ACK in REPLY
 857                  * or ACK in REPLY direction (half-open connection). */
 858                 if (index == TCP_SYNACK_SET
 859                     && conntrack->proto.tcp.last_index == TCP_SYN_SET
 860                     && conntrack->proto.tcp.last_dir != dir
 861                     && after(ntohl(th->ack_seq),
 862                              conntrack->proto.tcp.last_seq)) {
 863                         /* This SYN/ACK acknowledges a SYN that we earlier
 864                          * ignored as invalid. This means that the client and
 865                          * the server are both in sync, while the firewall is
 866                          * not. We kill this session and block the SYN/ACK so
 867                          * that the client cannot but retransmit its SYN and
 868                          * thus initiate a clean new session.
 869                          */
 870                         WRITE_UNLOCK(&tcp_lock);
 871                         if (LOG_INVALID(IPPROTO_TCP))
 872                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 873                                           "ip_ct_tcp: killing out of sync session ");
 874                         if (del_timer(&conntrack->timeout))
 875                                 conntrack->timeout.function((unsigned long)
 876                                                             conntrack);
 877                         return -NF_DROP;
 878                 }
 879                 conntrack->proto.tcp.last_index = index;
 880                 conntrack->proto.tcp.last_dir = dir;
 881                 conntrack->proto.tcp.last_seq = ntohl(th->seq);
 882
 883                 WRITE_UNLOCK(&tcp_lock);
 884                 if (LOG_INVALID(IPPROTO_TCP))
 885                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 886                                   "ip_ct_tcp: invalid packet ignored ");
 887                 return NF_ACCEPT;
 888         case TCP_CONNTRACK_MAX:
 889                 /* Invalid packet */
 890                 DEBUGP("ip_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
 891                        dir, get_conntrack_index(th),
 892                        old_state);
 893                 WRITE_UNLOCK(&tcp_lock);
 894                 if (LOG_INVALID(IPPROTO_TCP))
 895                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 896                                   "ip_ct_tcp: invalid state ");
 897                 return -NF_ACCEPT;
 898         case TCP_CONNTRACK_SYN_SENT:
 899                 if (old_state >= TCP_CONNTRACK_TIME_WAIT) {
 900                         /* Attempt to reopen a closed connection.
 901                         * Delete this connection and look up again. */
 902                         WRITE_UNLOCK(&tcp_lock);
 903                         if (del_timer(&conntrack->timeout))
 904                                 conntrack->timeout.function((unsigned long)
 905                                                             conntrack);
 906                         return -NF_REPEAT;
 907                 }
 908                 break;
 909         case TCP_CONNTRACK_CLOSE:
 910                 if (index == TCP_RST_SET
 911                     && ((test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)
 912                          && conntrack->proto.tcp.last_index <= TCP_SYNACK_SET)
 913                         || (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
 914                          && conntrack->proto.tcp.last_index == TCP_ACK_SET))
 915                     && after(ntohl(th->ack_seq),
 916                              conntrack->proto.tcp.last_seq)) {
 917                         /* Ignore RST closing down invalid SYN or ACK
 918                            we had let trough. */
 919                         WRITE_UNLOCK(&tcp_lock);
 920                         if (LOG_INVALID(IPPROTO_TCP))
 921                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 922                                           "ip_ct_tcp: invalid RST (ignored) ");
 923                         return NF_ACCEPT;
 924                 }
 925                 /* Just fall trough */
 926         default:
 927                 /* Keep compilers happy. */
 928                 break;
 929         }
 930
 931         if (!tcp_in_window(&conntrack->proto.tcp, dir, &index,
 932                            skb, iph, th)) {
 933                 WRITE_UNLOCK(&tcp_lock);
 934                 return -NF_ACCEPT;
 935         }
 936         /* From now on we have got in-window packets */
 937
 938         /* If FIN was trimmed off, we don't change state. */
 939         conntrack->proto.tcp.last_index = index;
 940         new_state = tcp_conntracks[dir][index][old_state];
 941
 942         DEBUGP("tcp_conntracks: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 943                "syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
 944                 NIPQUAD(iph->saddr), ntohs(th->source),
 945                 NIPQUAD(iph->daddr), ntohs(th->dest),
 946                 (th->syn ? 1 : 0), (th->ack ? 1 : 0),
 947                 (th->fin ? 1 : 0), (th->rst ? 1 : 0),
 948                 old_state, new_state);
 949
 950         conntrack->proto.tcp.state = new_state;
 951         timeout = conntrack->proto.tcp.retrans >= ip_ct_tcp_max_retrans
 952                   && *tcp_timeouts[new_state] > ip_ct_tcp_timeout_max_retrans
 953                   ? ip_ct_tcp_timeout_max_retrans : *tcp_timeouts[new_state];
 954         WRITE_UNLOCK(&tcp_lock);
 955
 956         if (!test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
 957                 /* If only reply is a RST, we can consider ourselves not to
 958                    have an established connection: this is a fairly common
 959                    problem case, so we can delete the conntrack
 960                    immediately.  --RR */
 961                 if (th->rst) {
 962                         if (del_timer(&conntrack->timeout))
 963                                 conntrack->timeout.function((unsigned long)
 964                                                             conntrack);
 965                         return NF_ACCEPT;
 966                 }
 967         } else if (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
 968                    && (old_state == TCP_CONNTRACK_SYN_RECV
 969                        || old_state == TCP_CONNTRACK_ESTABLISHED)
 970                    && new_state == TCP_CONNTRACK_ESTABLISHED) {
 971                 /* Set ASSURED if we see see valid ack in ESTABLISHED
 972                    after SYN_RECV or a valid answer for a picked up
 973                    connection. */
 974                         set_bit(IPS_ASSURED_BIT, &conntrack->status);
 975         }
 976         ip_ct_refresh_acct(conntrack, ctinfo, skb, timeout);
 977
 978         return NF_ACCEPT;
 979 }
 980
 981   /* Called when a new connection for this protocol found. */
 982 static int tcp_new(struct ip_conntrack *conntrack,
 983                    const struct sk_buff *skb)
 984 {
 985         enum tcp_conntrack new_state;
 986         struct iphdr *iph = skb->nh.iph;
 987         struct tcphdr *th, _tcph;
 988 #ifdef DEBUGP_VARS
 989         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[0];
 990         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[1];
 991 #endif
 992
 993         th = skb_header_pointer(skb, iph->ihl * 4,
 994                                 sizeof(_tcph), &_tcph);
 995         BUG_ON(th == NULL);
 996
 997         /* Don't need lock here: this conntrack not in circulation yet */
 998         new_state
 999                 = tcp_conntracks[0][get_conntrack_index(th)]
1000                 [TCP_CONNTRACK_NONE];
1001
1002         /* Invalid: delete conntrack */
1003         if (new_state >= TCP_CONNTRACK_MAX) {
1004                 DEBUGP("ip_ct_tcp: invalid new deleting.\n");
1005                 return 0;
1006         }
1007
1008         if (new_state == TCP_CONNTRACK_SYN_SENT) {
1009                 /* SYN packet */
1010                 conntrack->proto.tcp.seen[0].td_end =
1011                         segment_seq_plus_len(ntohl(th->seq), skb->len,
1012                                              iph, th);
1013                 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1014                 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1015                         conntrack->proto.tcp.seen[0].td_maxwin = 1;
1016                 conntrack->proto.tcp.seen[0].td_maxend =
1017                         conntrack->proto.tcp.seen[0].td_end;
1018
1019                 tcp_options(skb, iph, th, &conntrack->proto.tcp.seen[0]);
1020                 conntrack->proto.tcp.seen[1].flags = 0;
1021                 conntrack->proto.tcp.seen[0].loose =
1022                 conntrack->proto.tcp.seen[1].loose = 0;
1023         } else if (ip_ct_tcp_loose == 0) {
1024                 /* Don't try to pick up connections. */
1025                 return 0;
1026         } else {
1027                 /*
1028                  * We are in the middle of a connection,
1029                  * its history is lost for us.
1030                  * Let's try to use the data from the packet.
1031                  */
1032                 conntrack->proto.tcp.seen[0].td_end =
1033                         segment_seq_plus_len(ntohl(th->seq), skb->len,
1034                                              iph, th);
1035                 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1036                 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1037                         conntrack->proto.tcp.seen[0].td_maxwin = 1;
1038                 conntrack->proto.tcp.seen[0].td_maxend =
1039                         conntrack->proto.tcp.seen[0].td_end +
1040                         conntrack->proto.tcp.seen[0].td_maxwin;
1041                 conntrack->proto.tcp.seen[0].td_scale = 0;
1042
1043                 /* We assume SACK. Should we assume window scaling too? */
1044                 conntrack->proto.tcp.seen[0].flags =
1045                 conntrack->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM;
1046                 conntrack->proto.tcp.seen[0].loose =
1047                 conntrack->proto.tcp.seen[1].loose = ip_ct_tcp_loose;
1048         }
1049
1050         conntrack->proto.tcp.seen[1].td_end = 0;
1051         conntrack->proto.tcp.seen[1].td_maxend = 0;
1052         conntrack->proto.tcp.seen[1].td_maxwin = 1;
1053         conntrack->proto.tcp.seen[1].td_scale = 0;
1054
1055         /* tcp_packet will set them */
1056         conntrack->proto.tcp.state = TCP_CONNTRACK_NONE;
1057         conntrack->proto.tcp.last_index = TCP_NONE_SET;
1058
1059         DEBUGP("tcp_new: sender end=%u maxend=%u maxwin=%u scale=%i "
1060                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
1061                 sender->td_end, sender->td_maxend, sender->td_maxwin,
1062                 sender->td_scale,
1063                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
1064                 receiver->td_scale);
1065         return 1;
1066 }
1067
1068 struct ip_conntrack_protocol ip_conntrack_protocol_tcp =
1069 {
1070         .proto                  = IPPROTO_TCP,
1071         .name                   = "tcp",
1072         .pkt_to_tuple           = tcp_pkt_to_tuple,
1073         .invert_tuple           = tcp_invert_tuple,
1074         .print_tuple            = tcp_print_tuple,
1075         .print_conntrack        = tcp_print_conntrack,
1076         .packet                 = tcp_packet,
1077         .new                    = tcp_new,
1078         .error                  = tcp_error,
1079 };