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 unsigned long ip_ct_tcp_timeout_established =   5 DAYS;
  92 unsigned long ip_ct_tcp_timeout_fin_wait =      2 MINS;
  93 unsigned long ip_ct_tcp_timeout_close_wait =   60 SECS;
  94 unsigned long ip_ct_tcp_timeout_last_ack =     30 SECS;
  95 unsigned long ip_ct_tcp_timeout_time_wait =     2 MINS;
  96 unsigned long ip_ct_tcp_timeout_close =        10 SECS;
  97
  98 /* RFC1122 says the R2 limit should be at least 100 seconds.
  99    Linux uses 15 packets as limit, which corresponds
 100    to ~13-30min depending on RTO. */
 101 unsigned long ip_ct_tcp_timeout_max_retrans =     5 MINS;
 102
 103 static unsigned long * tcp_timeouts[]
 104 = { NULL,                              /*      TCP_CONNTRACK_NONE */
 105     &ip_ct_tcp_timeout_syn_sent,       /*      TCP_CONNTRACK_SYN_SENT, */
 106     &ip_ct_tcp_timeout_syn_recv,       /*      TCP_CONNTRACK_SYN_RECV, */
 107     &ip_ct_tcp_timeout_established,    /*      TCP_CONNTRACK_ESTABLISHED,      */
 108     &ip_ct_tcp_timeout_fin_wait,       /*      TCP_CONNTRACK_FIN_WAIT, */
 109     &ip_ct_tcp_timeout_close_wait,     /*      TCP_CONNTRACK_CLOSE_WAIT,       */
 110     &ip_ct_tcp_timeout_last_ack,       /*      TCP_CONNTRACK_LAST_ACK, */
 111     &ip_ct_tcp_timeout_time_wait,      /*      TCP_CONNTRACK_TIME_WAIT,        */
 112     &ip_ct_tcp_timeout_close,          /*      TCP_CONNTRACK_CLOSE,    */
 113     NULL,                              /*      TCP_CONNTRACK_LISTEN */
 114  };
 115
 116 #define sNO TCP_CONNTRACK_NONE
 117 #define sSS TCP_CONNTRACK_SYN_SENT
 118 #define sSR TCP_CONNTRACK_SYN_RECV
 119 #define sES TCP_CONNTRACK_ESTABLISHED
 120 #define sFW TCP_CONNTRACK_FIN_WAIT
 121 #define sCW TCP_CONNTRACK_CLOSE_WAIT
 122 #define sLA TCP_CONNTRACK_LAST_ACK
 123 #define sTW TCP_CONNTRACK_TIME_WAIT
 124 #define sCL TCP_CONNTRACK_CLOSE
 125 #define sLI TCP_CONNTRACK_LISTEN
 126 #define sIV TCP_CONNTRACK_MAX
 127 #define sIG TCP_CONNTRACK_IGNORE
 128
 129 /* What TCP flags are set from RST/SYN/FIN/ACK. */
 130 enum tcp_bit_set {
 131         TCP_SYN_SET,
 132         TCP_SYNACK_SET,
 133         TCP_FIN_SET,
 134         TCP_ACK_SET,
 135         TCP_RST_SET,
 136         TCP_NONE_SET,
 137 };
 138
 139 /*
 140  * The TCP state transition table needs a few words...
 141  *
 142  * We are the man in the middle. All the packets go through us
 143  * but might get lost in transit to the destination.
 144  * It is assumed that the destinations can't receive segments
 145  * we haven't seen.
 146  *
 147  * The checked segment is in window, but our windows are *not*
 148  * equivalent with the ones of the sender/receiver. We always
 149  * try to guess the state of the current sender.
 150  *
 151  * The meaning of the states are:
 152  *
 153  * NONE:        initial state
 154  * SYN_SENT:    SYN-only packet seen
 155  * SYN_RECV:    SYN-ACK packet seen
 156  * ESTABLISHED: ACK packet seen
 157  * FIN_WAIT:    FIN packet seen
 158  * CLOSE_WAIT:  ACK seen (after FIN)
 159  * LAST_ACK:    FIN seen (after FIN)
 160  * TIME_WAIT:   last ACK seen
 161  * CLOSE:       closed connection
 162  *
 163  * LISTEN state is not used.
 164  *
 165  * Packets marked as IGNORED (sIG):
 166  *      if they may be either invalid or valid
 167  *      and the receiver may send back a connection
 168  *      closing RST or a SYN/ACK.
 169  *
 170  * Packets marked as INVALID (sIV):
 171  *      if they are invalid
 172  *      or we do not support the request (simultaneous open)
 173  */
 174 static enum tcp_conntrack tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = {
 175         {
 176 /* ORIGINAL */
 177 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 178 /*syn*/    { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sIV },
 179 /*
 180  *      sNO -> sSS      Initialize a new connection
 181  *      sSS -> sSS      Retransmitted SYN
 182  *      sSR -> sIG      Late retransmitted SYN?
 183  *      sES -> sIG      Error: SYNs in window outside the SYN_SENT state
 184  *                      are errors. Receiver will reply with RST
 185  *                      and close the connection.
 186  *                      Or we are not in sync and hold a dead connection.
 187  *      sFW -> sIG
 188  *      sCW -> sIG
 189  *      sLA -> sIG
 190  *      sTW -> sSS      Reopened connection (RFC 1122).
 191  *      sCL -> sSS
 192  */
 193 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 194 /*synack*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
 195 /*
 196  * A SYN/ACK from the client is always invalid:
 197  *      - either it tries to set up a simultaneous open, which is
 198  *        not supported;
 199  *      - or the firewall has just been inserted between the two hosts
 200  *        during the session set-up. The SYN will be retransmitted
 201  *        by the true client (or it'll time out).
 202  */
 203 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 204 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
 205 /*
 206  *      sNO -> sIV      Too late and no reason to do anything...
 207  *      sSS -> sIV      Client migth not send FIN in this state:
 208  *                      we enforce waiting for a SYN/ACK reply first.
 209  *      sSR -> sFW      Close started.
 210  *      sES -> sFW
 211  *      sFW -> sLA      FIN seen in both directions, waiting for
 212  *                      the last ACK.
 213  *                      Migth be a retransmitted FIN as well...
 214  *      sCW -> sLA
 215  *      sLA -> sLA      Retransmitted FIN. Remain in the same state.
 216  *      sTW -> sTW
 217  *      sCL -> sCL
 218  */
 219 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 220 /*ack*/    { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV },
 221 /*
 222  *      sNO -> sES      Assumed.
 223  *      sSS -> sIV      ACK is invalid: we haven't seen a SYN/ACK yet.
 224  *      sSR -> sES      Established state is reached.
 225  *      sES -> sES      :-)
 226  *      sFW -> sCW      Normal close request answered by ACK.
 227  *      sCW -> sCW
 228  *      sLA -> sTW      Last ACK detected.
 229  *      sTW -> sTW      Retransmitted last ACK. Remain in the same state.
 230  *      sCL -> sCL
 231  */
 232 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 233 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
 234 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
 235         },
 236         {
 237 /* REPLY */
 238 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 239 /*syn*/    { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
 240 /*
 241  *      sNO -> sIV      Never reached.
 242  *      sSS -> sIV      Simultaneous open, not supported
 243  *      sSR -> sIV      Simultaneous open, not supported.
 244  *      sES -> sIV      Server may not initiate a connection.
 245  *      sFW -> sIV
 246  *      sCW -> sIV
 247  *      sLA -> sIV
 248  *      sTW -> sIV      Reopened connection, but server may not do it.
 249  *      sCL -> sIV
 250  */
 251 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 252 /*synack*/ { sIV, sSR, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIV },
 253 /*
 254  *      sSS -> sSR      Standard open.
 255  *      sSR -> sSR      Retransmitted SYN/ACK.
 256  *      sES -> sIG      Late retransmitted SYN/ACK?
 257  *      sFW -> sIG      Might be SYN/ACK answering ignored SYN
 258  *      sCW -> sIG
 259  *      sLA -> sIG
 260  *      sTW -> sIG
 261  *      sCL -> sIG
 262  */
 263 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 264 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
 265 /*
 266  *      sSS -> sIV      Server might not send FIN in this state.
 267  *      sSR -> sFW      Close started.
 268  *      sES -> sFW
 269  *      sFW -> sLA      FIN seen in both directions.
 270  *      sCW -> sLA
 271  *      sLA -> sLA      Retransmitted FIN.
 272  *      sTW -> sTW
 273  *      sCL -> sCL
 274  */
 275 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 276 /*ack*/    { sIV, sIV, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIV },
 277 /*
 278  *      sSS -> sIV      Might be a half-open connection.
 279  *      sSR -> sSR      Might answer late resent SYN.
 280  *      sES -> sES      :-)
 281  *      sFW -> sCW      Normal close request answered by ACK.
 282  *      sCW -> sCW
 283  *      sLA -> sTW      Last ACK detected.
 284  *      sTW -> sTW      Retransmitted last ACK.
 285  *      sCL -> sCL
 286  */
 287 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 288 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
 289 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
 290         }
 291 };
 292
 293 static int tcp_pkt_to_tuple(const struct sk_buff *skb,
 294                             unsigned int dataoff,
 295                             struct ip_conntrack_tuple *tuple)
 296 {
 297         struct tcphdr _hdr, *hp;
 298
 299         /* Actually only need first 8 bytes. */
 300         hp = skb_header_pointer(skb, dataoff, 8, &_hdr);
 301         if (hp == NULL)
 302                 return 0;
 303
 304         tuple->src.u.tcp.port = hp->source;
 305         tuple->dst.u.tcp.port = hp->dest;
 306
 307         return 1;
 308 }
 309
 310 static int tcp_invert_tuple(struct ip_conntrack_tuple *tuple,
 311                             const struct ip_conntrack_tuple *orig)
 312 {
 313         tuple->src.u.tcp.port = orig->dst.u.tcp.port;
 314         tuple->dst.u.tcp.port = orig->src.u.tcp.port;
 315         return 1;
 316 }
 317
 318 /* Print out the per-protocol part of the tuple. */
 319 static int tcp_print_tuple(struct seq_file *s,
 320                            const struct ip_conntrack_tuple *tuple)
 321 {
 322         return seq_printf(s, "sport=%hu dport=%hu ",
 323                           ntohs(tuple->src.u.tcp.port),
 324                           ntohs(tuple->dst.u.tcp.port));
 325 }
 326
 327 /* Print out the private part of the conntrack. */
 328 static int tcp_print_conntrack(struct seq_file *s,
 329                                const struct ip_conntrack *conntrack)
 330 {
 331         enum tcp_conntrack state;
 332
 333         READ_LOCK(&tcp_lock);
 334         state = conntrack->proto.tcp.state;
 335         READ_UNLOCK(&tcp_lock);
 336
 337         return seq_printf(s, "%s ", tcp_conntrack_names[state]);
 338 }
 339
 340 static unsigned int get_conntrack_index(const struct tcphdr *tcph)
 341 {
 342         if (tcph->rst) return TCP_RST_SET;
 343         else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET);
 344         else if (tcph->fin) return TCP_FIN_SET;
 345         else if (tcph->ack) return TCP_ACK_SET;
 346         else return TCP_NONE_SET;
 347 }
 348
 349 /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering
 350    in IP Filter' by Guido van Rooij.
 351
 352    http://www.nluug.nl/events/sane2000/papers.html
 353    http://www.iae.nl/users/guido/papers/tcp_filtering.ps.gz
 354
 355    The boundaries and the conditions are changed according to RFC793:
 356    the packet must intersect the window (i.e. segments may be
 357    after the right or before the left edge) and thus receivers may ACK
 358    segments after the right edge of the window.
 359
 360         td_maxend = max(sack + max(win,1)) seen in reply packets
 361         td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets
 362         td_maxwin += seq + len - sender.td_maxend
 363                         if seq + len > sender.td_maxend
 364         td_end    = max(seq + len) seen in sent packets
 365
 366    I.   Upper bound for valid data:     seq <= sender.td_maxend
 367    II.  Lower bound for valid data:     seq + len >= sender.td_end - receiver.td_maxwin
 368    III. Upper bound for valid ack:      sack <= receiver.td_end
 369    IV.  Lower bound for valid ack:      ack >= receiver.td_end - MAXACKWINDOW
 370
 371    where sack is the highest right edge of sack block found in the packet.
 372
 373    The upper bound limit for a valid ack is not ignored -
 374    we doesn't have to deal with fragments.
 375 */
 376
 377 static inline __u32 segment_seq_plus_len(__u32 seq,
 378                                          size_t len,
 379                                          struct iphdr *iph,
 380                                          struct tcphdr *tcph)
 381 {
 382         return (seq + len - (iph->ihl + tcph->doff)*4
 383                 + (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0));
 384 }
 385
 386 /* Fixme: what about big packets? */
 387 #define MAXACKWINCONST                  66000
 388 #define MAXACKWINDOW(sender)                                            \
 389         ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin     \
 390                                               : MAXACKWINCONST)
 391
 392 /*
 393  * Simplified tcp_parse_options routine from tcp_input.c
 394  */
 395 static void tcp_options(const struct sk_buff *skb,
 396                         struct iphdr *iph,
 397                         struct tcphdr *tcph,
 398                         struct ip_ct_tcp_state *state)
 399 {
 400         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
 401         unsigned char *ptr;
 402         int length = (tcph->doff*4) - sizeof(struct tcphdr);
 403
 404         if (!length)
 405                 return;
 406
 407         ptr = skb_header_pointer(skb,
 408                                  (iph->ihl * 4) + sizeof(struct tcphdr),
 409                                  length, buff);
 410         BUG_ON(ptr == NULL);
 411
 412         state->td_scale =
 413         state->flags = 0;
 414
 415         while (length > 0) {
 416                 int opcode=*ptr++;
 417                 int opsize;
 418
 419                 switch (opcode) {
 420                 case TCPOPT_EOL:
 421                         return;
 422                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 423                         length--;
 424                         continue;
 425                 default:
 426                         opsize=*ptr++;
 427                         if (opsize < 2) /* "silly options" */
 428                                 return;
 429                         if (opsize > length)
 430                                 break;  /* don't parse partial options */
 431
 432                         if (opcode == TCPOPT_SACK_PERM
 433                             && opsize == TCPOLEN_SACK_PERM)
 434                                 state->flags |= IP_CT_TCP_FLAG_SACK_PERM;
 435                         else if (opcode == TCPOPT_WINDOW
 436                                  && opsize == TCPOLEN_WINDOW) {
 437                                 state->td_scale = *(u_int8_t *)ptr;
 438
 439                                 if (state->td_scale > 14) {
 440                                         /* See RFC1323 */
 441                                         state->td_scale = 14;
 442                                 }
 443                                 state->flags |=
 444                                         IP_CT_TCP_FLAG_WINDOW_SCALE;
 445                         }
 446                         ptr += opsize - 2;
 447                         length -= opsize;
 448                 }
 449         }
 450 }
 451
 452 static void tcp_sack(const struct sk_buff *skb,
 453                      struct iphdr *iph,
 454                      struct tcphdr *tcph,
 455                      __u32 *sack)
 456 {
 457         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
 458         unsigned char *ptr;
 459         int length = (tcph->doff*4) - sizeof(struct tcphdr);
 460         __u32 tmp;
 461
 462         if (!length)
 463                 return;
 464
 465         ptr = skb_header_pointer(skb,
 466                                  (iph->ihl * 4) + sizeof(struct tcphdr),
 467                                  length, buff);
 468         BUG_ON(ptr == NULL);
 469
 470         /* Fast path for timestamp-only option */
 471         if (length == TCPOLEN_TSTAMP_ALIGNED*4
 472             && *(__u32 *)ptr ==
 473                 __constant_ntohl((TCPOPT_NOP << 24)
 474                                  | (TCPOPT_NOP << 16)
 475                                  | (TCPOPT_TIMESTAMP << 8)
 476                                  | TCPOLEN_TIMESTAMP))
 477                 return;
 478
 479         while (length > 0) {
 480                 int opcode=*ptr++;
 481                 int opsize, i;
 482
 483                 switch (opcode) {
 484                 case TCPOPT_EOL:
 485                         return;
 486                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 487                         length--;
 488                         continue;
 489                 default:
 490                         opsize=*ptr++;
 491                         if (opsize < 2) /* "silly options" */
 492                                 return;
 493                         if (opsize > length)
 494                                 break;  /* don't parse partial options */
 495
 496                         if (opcode == TCPOPT_SACK
 497                             && opsize >= (TCPOLEN_SACK_BASE
 498                                           + TCPOLEN_SACK_PERBLOCK)
 499                             && !((opsize - TCPOLEN_SACK_BASE)
 500                                  % TCPOLEN_SACK_PERBLOCK)) {
 501                                 for (i = 0;
 502                                      i < (opsize - TCPOLEN_SACK_BASE);
 503                                      i += TCPOLEN_SACK_PERBLOCK) {
 504                                         tmp = ntohl(*((u_int32_t *)(ptr+i)+1));
 505
 506                                         if (after(tmp, *sack))
 507                                                 *sack = tmp;
 508                                 }
 509                                 return;
 510                         }
 511                         ptr += opsize - 2;
 512                         length -= opsize;
 513                 }
 514         }
 515 }
 516
 517 static int tcp_in_window(struct ip_ct_tcp *state,
 518                          enum ip_conntrack_dir dir,
 519                          unsigned int index,
 520                          const struct sk_buff *skb,
 521                          struct iphdr *iph,
 522                          struct tcphdr *tcph)
 523 {
 524         struct ip_ct_tcp_state *sender = &state->seen[dir];
 525         struct ip_ct_tcp_state *receiver = &state->seen[!dir];
 526         __u32 seq, ack, sack, end, win, swin;
 527         int res;
 528
 529         /*
 530          * Get the required data from the packet.
 531          */
 532         seq = ntohl(tcph->seq);
 533         ack = sack = ntohl(tcph->ack_seq);
 534         win = ntohs(tcph->window);
 535         end = segment_seq_plus_len(seq, skb->len, iph, tcph);
 536
 537         if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
 538                 tcp_sack(skb, iph, tcph, &sack);
 539
 540         DEBUGP("tcp_in_window: START\n");
 541         DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 542                "seq=%u ack=%u sack=%u win=%u end=%u\n",
 543                 NIPQUAD(iph->saddr), ntohs(tcph->source),
 544                 NIPQUAD(iph->daddr), ntohs(tcph->dest),
 545                 seq, ack, sack, win, end);
 546         DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
 547                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 548                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 549                 sender->td_scale,
 550                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 551                 receiver->td_scale);
 552
 553         if (sender->td_end == 0) {
 554                 /*
 555                  * Initialize sender data.
 556                  */
 557                 if (tcph->syn && tcph->ack) {
 558                         /*
 559                          * Outgoing SYN-ACK in reply to a SYN.
 560                          */
 561                         sender->td_end =
 562                         sender->td_maxend = end;
 563                         sender->td_maxwin = (win == 0 ? 1 : win);
 564
 565                         tcp_options(skb, iph, tcph, sender);
 566                         /*
 567                          * RFC 1323:
 568                          * Both sides must send the Window Scale option
 569                          * to enable window scaling in either direction.
 570                          */
 571                         if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE
 572                               && receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE))
 573                                 sender->td_scale =
 574                                 receiver->td_scale = 0;
 575                 } else {
 576                         /*
 577                          * We are in the middle of a connection,
 578                          * its history is lost for us.
 579                          * Let's try to use the data from the packet.
 580                          */
 581                         sender->td_end = end;
 582                         sender->td_maxwin = (win == 0 ? 1 : win);
 583                         sender->td_maxend = end + sender->td_maxwin;
 584                 }
 585         } else if (((state->state == TCP_CONNTRACK_SYN_SENT
 586                      && dir == IP_CT_DIR_ORIGINAL)
 587                     || (state->state == TCP_CONNTRACK_SYN_RECV
 588                         && dir == IP_CT_DIR_REPLY))
 589                     && after(end, sender->td_end)) {
 590                 /*
 591                  * RFC 793: "if a TCP is reinitialized ... then it need
 592                  * not wait at all; it must only be sure to use sequence
 593                  * numbers larger than those recently used."
 594                  */
 595                 sender->td_end =
 596                 sender->td_maxend = end;
 597                 sender->td_maxwin = (win == 0 ? 1 : win);
 598
 599                 tcp_options(skb, iph, tcph, sender);
 600         }
 601
 602         if (!(tcph->ack)) {
 603                 /*
 604                  * If there is no ACK, just pretend it was set and OK.
 605                  */
 606                 ack = sack = receiver->td_end;
 607         } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
 608                     (TCP_FLAG_ACK|TCP_FLAG_RST))
 609                    && (ack == 0)) {
 610                 /*
 611                  * Broken TCP stacks, that set ACK in RST packets as well
 612                  * with zero ack value.
 613                  */
 614                 ack = sack = receiver->td_end;
 615         }
 616
 617         if (seq == end
 618             && (!tcph->rst
 619                 || (seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)))
 620                 /*
 621                  * Packets contains no data: we assume it is valid
 622                  * and check the ack value only.
 623                  * However RST segments are always validated by their
 624                  * SEQ number, except when seq == 0 (reset sent answering
 625                  * SYN.
 626                  */
 627                 seq = end = sender->td_end;
 628
 629         DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 630                "seq=%u ack=%u sack =%u win=%u end=%u\n",
 631                 NIPQUAD(iph->saddr), ntohs(tcph->source),
 632                 NIPQUAD(iph->daddr), ntohs(tcph->dest),
 633                 seq, ack, sack, win, end);
 634         DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
 635                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 636                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 637                 sender->td_scale,
 638                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 639                 receiver->td_scale);
 640
 641         DEBUGP("tcp_in_window: I=%i II=%i III=%i IV=%i\n",
 642                 before(seq, sender->td_maxend + 1),
 643                 after(end, sender->td_end - receiver->td_maxwin - 1),
 644                 before(sack, receiver->td_end + 1),
 645                 after(ack, receiver->td_end - MAXACKWINDOW(sender)));
 646
 647         if (sender->loose || receiver->loose ||
 648             (before(seq, sender->td_maxend + 1) &&
 649              after(end, sender->td_end - receiver->td_maxwin - 1) &&
 650              before(sack, receiver->td_end + 1) &&
 651              after(ack, receiver->td_end - MAXACKWINDOW(sender)))) {
 652                 /*
 653                  * Take into account window scaling (RFC 1323).
 654                  */
 655                 if (!tcph->syn)
 656                         win <<= sender->td_scale;
 657
 658                 /*
 659                  * Update sender data.
 660                  */
 661                 swin = win + (sack - ack);
 662                 if (sender->td_maxwin < swin)
 663                         sender->td_maxwin = swin;
 664                 if (after(end, sender->td_end))
 665                         sender->td_end = end;
 666                 /*
 667                  * Update receiver data.
 668                  */
 669                 if (after(end, sender->td_maxend))
 670                         receiver->td_maxwin += end - sender->td_maxend;
 671                 if (after(sack + win, receiver->td_maxend - 1)) {
 672                         receiver->td_maxend = sack + win;
 673                         if (win == 0)
 674                                 receiver->td_maxend++;
 675                 }
 676
 677                 /*
 678                  * Check retransmissions.
 679                  */
 680                 if (index == TCP_ACK_SET) {
 681                         if (state->last_dir == dir
 682                             && state->last_seq == seq
 683                             && state->last_ack == ack
 684                             && state->last_end == end)
 685                                 state->retrans++;
 686                         else {
 687                                 state->last_dir = dir;
 688                                 state->last_seq = seq;
 689                                 state->last_ack = ack;
 690                                 state->last_end = end;
 691                                 state->retrans = 0;
 692                         }
 693                 }
 694                 /*
 695                  * Close the window of disabled window tracking :-)
 696                  */
 697                 if (sender->loose)
 698                         sender->loose--;
 699
 700                 res = 1;
 701         } else {
 702                 if (LOG_INVALID(IPPROTO_TCP))
 703                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 704                         "ip_ct_tcp: %s ",
 705                         before(seq, sender->td_maxend + 1) ?
 706                         after(end, sender->td_end - receiver->td_maxwin - 1) ?
 707                         before(sack, receiver->td_end + 1) ?
 708                         after(ack, receiver->td_end - MAXACKWINDOW(sender)) ? "BUG"
 709                         : "ACK is under the lower bound (possible overly delayed ACK)"
 710                         : "ACK is over the upper bound (ACKed data not seen yet)"
 711                         : "SEQ is under the lower bound (already ACKed data retransmitted)"
 712                         : "SEQ is over the upper bound (over the window of the receiver)");
 713
 714                 res = ip_ct_tcp_be_liberal;
 715         }
 716
 717         DEBUGP("tcp_in_window: res=%i sender end=%u maxend=%u maxwin=%u "
 718                "receiver end=%u maxend=%u maxwin=%u\n",
 719                 res, sender->td_end, sender->td_maxend, sender->td_maxwin,
 720                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin);
 721
 722         return res;
 723 }
 724
 725 #ifdef CONFIG_IP_NF_NAT_NEEDED
 726 /* Update sender->td_end after NAT successfully mangled the packet */
 727 void ip_conntrack_tcp_update(struct sk_buff *skb,
 728                              struct ip_conntrack *conntrack,
 729                              enum ip_conntrack_dir dir)
 730 {
 731         struct iphdr *iph = skb->nh.iph;
 732         struct tcphdr *tcph = (void *)skb->nh.iph + skb->nh.iph->ihl*4;
 733         __u32 end;
 734 #ifdef DEBUGP_VARS
 735         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[dir];
 736         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[!dir];
 737 #endif
 738
 739         end = segment_seq_plus_len(ntohl(tcph->seq), skb->len, iph, tcph);
 740
 741         WRITE_LOCK(&tcp_lock);
 742         /*
 743          * We have to worry for the ack in the reply packet only...
 744          */
 745         if (after(end, conntrack->proto.tcp.seen[dir].td_end))
 746                 conntrack->proto.tcp.seen[dir].td_end = end;
 747         conntrack->proto.tcp.last_end = end;
 748         WRITE_UNLOCK(&tcp_lock);
 749         DEBUGP("tcp_update: sender end=%u maxend=%u maxwin=%u scale=%i "
 750                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 751                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 752                 sender->td_scale,
 753                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 754                 receiver->td_scale);
 755 }
 756
 757 #endif
 758
 759 #define TH_FIN  0x01
 760 #define TH_SYN  0x02
 761 #define TH_RST  0x04
 762 #define TH_PUSH 0x08
 763 #define TH_ACK  0x10
 764 #define TH_URG  0x20
 765 #define TH_ECE  0x40
 766 #define TH_CWR  0x80
 767
 768 /* table of valid flag combinations - ECE and CWR are always valid */
 769 static u8 tcp_valid_flags[(TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG) + 1] =
 770 {
 771         [TH_SYN]                        = 1,
 772         [TH_SYN|TH_ACK]                 = 1,
 773         [TH_SYN|TH_ACK|TH_PUSH]         = 1,
 774         [TH_RST]                        = 1,
 775         [TH_RST|TH_ACK]                 = 1,
 776         [TH_RST|TH_ACK|TH_PUSH]         = 1,
 777         [TH_FIN|TH_ACK]                 = 1,
 778         [TH_ACK]                        = 1,
 779         [TH_ACK|TH_PUSH]                = 1,
 780         [TH_ACK|TH_URG]                 = 1,
 781         [TH_ACK|TH_URG|TH_PUSH]         = 1,
 782         [TH_FIN|TH_ACK|TH_PUSH]         = 1,
 783         [TH_FIN|TH_ACK|TH_URG]          = 1,
 784         [TH_FIN|TH_ACK|TH_URG|TH_PUSH]  = 1,
 785 };
 786
 787 /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c.  */
 788 static int tcp_error(struct sk_buff *skb,
 789                      enum ip_conntrack_info *ctinfo,
 790                      unsigned int hooknum)
 791 {
 792         struct iphdr *iph = skb->nh.iph;
 793         struct tcphdr _tcph, *th;
 794         unsigned int tcplen = skb->len - iph->ihl * 4;
 795         u_int8_t tcpflags;
 796
 797         /* Smaller that minimal TCP header? */
 798         th = skb_header_pointer(skb, iph->ihl * 4,
 799                                 sizeof(_tcph), &_tcph);
 800         if (th == NULL) {
 801                 if (LOG_INVALID(IPPROTO_TCP))
 802                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 803                                 "ip_ct_tcp: short packet ");
 804                 return -NF_ACCEPT;
 805         }
 806
 807         /* Not whole TCP header or malformed packet */
 808         if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {
 809                 if (LOG_INVALID(IPPROTO_TCP))
 810                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 811                                 "ip_ct_tcp: truncated/malformed packet ");
 812                 return -NF_ACCEPT;
 813         }
 814
 815         /* Checksum invalid? Ignore.
 816          * We skip checking packets on the outgoing path
 817          * because the semantic of CHECKSUM_HW is different there
 818          * and moreover root might send raw packets.
 819          */
 820         /* FIXME: Source route IP option packets --RR */
 821         if (hooknum == NF_IP_PRE_ROUTING
 822             && skb->ip_summed != CHECKSUM_UNNECESSARY
 823             && csum_tcpudp_magic(iph->saddr, iph->daddr, tcplen, IPPROTO_TCP,
 824                                  skb->ip_summed == CHECKSUM_HW ? skb->csum
 825                                  : skb_checksum(skb, iph->ihl*4, tcplen, 0))) {
 826                 if (LOG_INVALID(IPPROTO_TCP))
 827                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 828                                   "ip_ct_tcp: bad TCP checksum ");
 829                 return -NF_ACCEPT;
 830         }
 831
 832         /* Check TCP flags. */
 833         tcpflags = (((u_int8_t *)th)[13] & ~(TH_ECE|TH_CWR));
 834         if (!tcp_valid_flags[tcpflags]) {
 835                 if (LOG_INVALID(IPPROTO_TCP))
 836                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 837                                   "ip_ct_tcp: invalid TCP flag combination ");
 838                 return -NF_ACCEPT;
 839         }
 840
 841         return NF_ACCEPT;
 842 }
 843
 844 /* Returns verdict for packet, or -1 for invalid. */
 845 static int tcp_packet(struct ip_conntrack *conntrack,
 846                       const struct sk_buff *skb,
 847                       enum ip_conntrack_info ctinfo)
 848 {
 849         enum tcp_conntrack new_state, old_state;
 850         enum ip_conntrack_dir dir;
 851         struct iphdr *iph = skb->nh.iph;
 852         struct tcphdr *th, _tcph;
 853         unsigned long timeout;
 854         unsigned int index;
 855
 856         th = skb_header_pointer(skb, iph->ihl * 4,
 857                                 sizeof(_tcph), &_tcph);
 858         BUG_ON(th == NULL);
 859
 860         WRITE_LOCK(&tcp_lock);
 861         old_state = conntrack->proto.tcp.state;
 862         dir = CTINFO2DIR(ctinfo);
 863         index = get_conntrack_index(th);
 864         new_state = tcp_conntracks[dir][index][old_state];
 865
 866         switch (new_state) {
 867         case TCP_CONNTRACK_IGNORE:
 868                 /* Either SYN in ORIGINAL
 869                  * or SYN/ACK in REPLY. */
 870                 if (index == TCP_SYNACK_SET
 871                     && conntrack->proto.tcp.last_index == TCP_SYN_SET
 872                     && conntrack->proto.tcp.last_dir != dir
 873                     && ntohl(th->ack_seq) ==
 874                              conntrack->proto.tcp.last_end) {
 875                         /* This SYN/ACK acknowledges a SYN that we earlier
 876                          * ignored as invalid. This means that the client and
 877                          * the server are both in sync, while the firewall is
 878                          * not. We kill this session and block the SYN/ACK so
 879                          * that the client cannot but retransmit its SYN and
 880                          * thus initiate a clean new session.
 881                          */
 882                         WRITE_UNLOCK(&tcp_lock);
 883                         if (LOG_INVALID(IPPROTO_TCP))
 884                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 885                                           "ip_ct_tcp: killing out of sync session ");
 886                         if (del_timer(&conntrack->timeout))
 887                                 conntrack->timeout.function((unsigned long)
 888                                                             conntrack);
 889                         return -NF_DROP;
 890                 }
 891                 conntrack->proto.tcp.last_index = index;
 892                 conntrack->proto.tcp.last_dir = dir;
 893                 conntrack->proto.tcp.last_seq = ntohl(th->seq);
 894                 conntrack->proto.tcp.last_end =
 895                     segment_seq_plus_len(ntohl(th->seq), skb->len, iph, th);
 896
 897                 WRITE_UNLOCK(&tcp_lock);
 898                 if (LOG_INVALID(IPPROTO_TCP))
 899                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 900                                   "ip_ct_tcp: invalid packet ignored ");
 901                 return NF_ACCEPT;
 902         case TCP_CONNTRACK_MAX:
 903                 /* Invalid packet */
 904                 DEBUGP("ip_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
 905                        dir, get_conntrack_index(th),
 906                        old_state);
 907                 WRITE_UNLOCK(&tcp_lock);
 908                 if (LOG_INVALID(IPPROTO_TCP))
 909                         nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 910                                   "ip_ct_tcp: invalid state ");
 911                 return -NF_ACCEPT;
 912         case TCP_CONNTRACK_SYN_SENT:
 913                 if (old_state < TCP_CONNTRACK_TIME_WAIT)
 914                         break;
 915                 if ((conntrack->proto.tcp.seen[dir].flags &
 916                          IP_CT_TCP_FLAG_CLOSE_INIT)
 917                     || after(ntohl(th->seq),
 918                              conntrack->proto.tcp.seen[dir].td_end)) {
 919                         /* Attempt to reopen a closed connection.
 920                         * Delete this connection and look up again. */
 921                         WRITE_UNLOCK(&tcp_lock);
 922                         if (del_timer(&conntrack->timeout))
 923                                 conntrack->timeout.function((unsigned long)
 924                                                             conntrack);
 925                         return -NF_REPEAT;
 926                 } else {
 927                         WRITE_UNLOCK(&tcp_lock);
 928                         if (LOG_INVALID(IPPROTO_TCP))
 929                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 930                                               "ip_ct_tcp: invalid SYN");
 931                         return -NF_ACCEPT;
 932                 }
 933         case TCP_CONNTRACK_CLOSE:
 934                 if (index == TCP_RST_SET
 935                     && test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)
 936                     && conntrack->proto.tcp.last_index == TCP_SYN_SET
 937                     && ntohl(th->ack_seq) == conntrack->proto.tcp.last_end) {
 938                         /* RST sent to invalid SYN we had let trough
 939                          * SYN was in window then, tear down connection.
 940                          * We skip window checking, because packet might ACK
 941                          * segments we ignored in the SYN. */
 942                         goto in_window;
 943                 }
 944                 /* Just fall trough */
 945         default:
 946                 /* Keep compilers happy. */
 947                 break;
 948         }
 949
 950         if (!tcp_in_window(&conntrack->proto.tcp, dir, index,
 951                            skb, iph, th)) {
 952                 WRITE_UNLOCK(&tcp_lock);
 953                 return -NF_ACCEPT;
 954         }
 955     in_window:
 956         /* From now on we have got in-window packets */
 957         conntrack->proto.tcp.last_index = index;
 958
 959         DEBUGP("tcp_conntracks: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 960                "syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
 961                 NIPQUAD(iph->saddr), ntohs(th->source),
 962                 NIPQUAD(iph->daddr), ntohs(th->dest),
 963                 (th->syn ? 1 : 0), (th->ack ? 1 : 0),
 964                 (th->fin ? 1 : 0), (th->rst ? 1 : 0),
 965                 old_state, new_state);
 966
 967         conntrack->proto.tcp.state = new_state;
 968         if (old_state != new_state
 969             && (new_state == TCP_CONNTRACK_FIN_WAIT
 970                 || new_state == TCP_CONNTRACK_CLOSE))
 971                 conntrack->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
 972         timeout = conntrack->proto.tcp.retrans >= ip_ct_tcp_max_retrans
 973                   && *tcp_timeouts[new_state] > ip_ct_tcp_timeout_max_retrans
 974                   ? ip_ct_tcp_timeout_max_retrans : *tcp_timeouts[new_state];
 975         WRITE_UNLOCK(&tcp_lock);
 976
 977         if (!test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
 978                 /* If only reply is a RST, we can consider ourselves not to
 979                    have an established connection: this is a fairly common
 980                    problem case, so we can delete the conntrack
 981                    immediately.  --RR */
 982                 if (th->rst) {
 983                         if (del_timer(&conntrack->timeout))
 984                                 conntrack->timeout.function((unsigned long)
 985                                                             conntrack);
 986                         return NF_ACCEPT;
 987                 }
 988         } else if (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
 989                    && (old_state == TCP_CONNTRACK_SYN_RECV
 990                        || old_state == TCP_CONNTRACK_ESTABLISHED)
 991                    && new_state == TCP_CONNTRACK_ESTABLISHED) {
 992                 /* Set ASSURED if we see see valid ack in ESTABLISHED
 993                    after SYN_RECV or a valid answer for a picked up
 994                    connection. */
 995                         set_bit(IPS_ASSURED_BIT, &conntrack->status);
 996         }
 997         ip_ct_refresh_acct(conntrack, ctinfo, skb, timeout);
 998
 999         return NF_ACCEPT;
1000 }
1001
1002 /* Called when a new connection for this protocol found. */
1003 static int tcp_new(struct ip_conntrack *conntrack,
1004                    const struct sk_buff *skb)
1005 {
1006         enum tcp_conntrack new_state;
1007         struct iphdr *iph = skb->nh.iph;
1008         struct tcphdr *th, _tcph;
1009 #ifdef DEBUGP_VARS
1010         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[0];
1011         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[1];
1012 #endif
1013
1014         th = skb_header_pointer(skb, iph->ihl * 4,
1015                                 sizeof(_tcph), &_tcph);
1016         BUG_ON(th == NULL);
1017
1018         /* Don't need lock here: this conntrack not in circulation yet */
1019         new_state
1020                 = tcp_conntracks[0][get_conntrack_index(th)]
1021                 [TCP_CONNTRACK_NONE];
1022
1023         /* Invalid: delete conntrack */
1024         if (new_state >= TCP_CONNTRACK_MAX) {
1025                 DEBUGP("ip_ct_tcp: invalid new deleting.\n");
1026                 return 0;
1027         }
1028
1029         if (new_state == TCP_CONNTRACK_SYN_SENT) {
1030                 /* SYN packet */
1031                 conntrack->proto.tcp.seen[0].td_end =
1032                         segment_seq_plus_len(ntohl(th->seq), skb->len,
1033                                              iph, th);
1034                 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1035                 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1036                         conntrack->proto.tcp.seen[0].td_maxwin = 1;
1037                 conntrack->proto.tcp.seen[0].td_maxend =
1038                         conntrack->proto.tcp.seen[0].td_end;
1039
1040                 tcp_options(skb, iph, th, &conntrack->proto.tcp.seen[0]);
1041                 conntrack->proto.tcp.seen[1].flags = 0;
1042                 conntrack->proto.tcp.seen[0].loose =
1043                 conntrack->proto.tcp.seen[1].loose = 0;
1044         } else if (ip_ct_tcp_loose == 0) {
1045                 /* Don't try to pick up connections. */
1046                 return 0;
1047         } else {
1048                 /*
1049                  * We are in the middle of a connection,
1050                  * its history is lost for us.
1051                  * Let's try to use the data from the packet.
1052                  */
1053                 conntrack->proto.tcp.seen[0].td_end =
1054                         segment_seq_plus_len(ntohl(th->seq), skb->len,
1055                                              iph, th);
1056                 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1057                 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1058                         conntrack->proto.tcp.seen[0].td_maxwin = 1;
1059                 conntrack->proto.tcp.seen[0].td_maxend =
1060                         conntrack->proto.tcp.seen[0].td_end +
1061                         conntrack->proto.tcp.seen[0].td_maxwin;
1062                 conntrack->proto.tcp.seen[0].td_scale = 0;
1063
1064                 /* We assume SACK. Should we assume window scaling too? */
1065                 conntrack->proto.tcp.seen[0].flags =
1066                 conntrack->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM;
1067                 conntrack->proto.tcp.seen[0].loose =
1068                 conntrack->proto.tcp.seen[1].loose = ip_ct_tcp_loose;
1069         }
1070
1071         conntrack->proto.tcp.seen[1].td_end = 0;
1072         conntrack->proto.tcp.seen[1].td_maxend = 0;
1073         conntrack->proto.tcp.seen[1].td_maxwin = 1;
1074         conntrack->proto.tcp.seen[1].td_scale = 0;
1075
1076         /* tcp_packet will set them */
1077         conntrack->proto.tcp.state = TCP_CONNTRACK_NONE;
1078         conntrack->proto.tcp.last_index = TCP_NONE_SET;
1079
1080         DEBUGP("tcp_new: sender end=%u maxend=%u maxwin=%u scale=%i "
1081                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
1082                 sender->td_end, sender->td_maxend, sender->td_maxwin,
1083                 sender->td_scale,
1084                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
1085                 receiver->td_scale);
1086         return 1;
1087 }
1088
1089 struct ip_conntrack_protocol ip_conntrack_protocol_tcp =
1090 {
1091         .proto                  = IPPROTO_TCP,
1092         .name                   = "tcp",
1093         .pkt_to_tuple           = tcp_pkt_to_tuple,
1094         .invert_tuple           = tcp_invert_tuple,
1095         .print_tuple            = tcp_print_tuple,
1096         .print_conntrack        = tcp_print_conntrack,
1097         .packet                 = tcp_packet,
1098         .new                    = tcp_new,
1099         .error                  = tcp_error,
1100 };