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
  40 #if 0
  41 #define DEBUGP printk
  42 #define DEBUGP_VARS
  43 #else
  44 #define DEBUGP(format, args...)
  45 #endif
  46
  47 /* Protects conntrack->proto.tcp */
  48 static DEFINE_RWLOCK(tcp_lock);
  49
  50 /* "Be conservative in what you do,
  51     be liberal in what you accept from others."
  52     If it's non-zero, we mark only out of window RST segments as INVALID. */
  53 int ip_ct_tcp_be_liberal = 0;
  54
  55 /* When connection is picked up from the middle, how many packets are required
  56    to pass in each direction when we assume we are in sync - if any side uses
  57    window scaling, we lost the game.
  58    If it is set to zero, we disable picking up already established
  59    connections. */
  60 int ip_ct_tcp_loose = 3;
  61
  62 /* Max number of the retransmitted packets without receiving an (acceptable)
  63    ACK from the destination. If this number is reached, a shorter timer
  64    will be started. */
  65 int ip_ct_tcp_max_retrans = 3;
  66
  67   /* FIXME: Examine ipfilter's timeouts and conntrack transitions more
  68      closely.  They're more complex. --RR */
  69
  70 static const char *tcp_conntrack_names[] = {
  71         "NONE",
  72         "SYN_SENT",
  73         "SYN_RECV",
  74         "ESTABLISHED",
  75         "FIN_WAIT",
  76         "CLOSE_WAIT",
  77         "LAST_ACK",
  78         "TIME_WAIT",
  79         "CLOSE",
  80         "LISTEN"
  81 };
  82
  83 #define SECS * HZ
  84 #define MINS * 60 SECS
  85 #define HOURS * 60 MINS
  86 #define DAYS * 24 HOURS
  87
  88 unsigned long ip_ct_tcp_timeout_syn_sent =      2 MINS;
  89 unsigned long ip_ct_tcp_timeout_syn_recv =     60 SECS;
  90 unsigned long ip_ct_tcp_timeout_established =   5 DAYS;
  91 unsigned long ip_ct_tcp_timeout_fin_wait =      2 MINS;
  92 unsigned long ip_ct_tcp_timeout_close_wait =   60 SECS;
  93 unsigned long ip_ct_tcp_timeout_last_ack =     30 SECS;
  94 unsigned long ip_ct_tcp_timeout_time_wait =     2 MINS;
  95 unsigned long ip_ct_tcp_timeout_close =        10 SECS;
  96
  97 /* RFC1122 says the R2 limit should be at least 100 seconds.
  98    Linux uses 15 packets as limit, which corresponds
  99    to ~13-30min depending on RTO. */
 100 unsigned long ip_ct_tcp_timeout_max_retrans =     5 MINS;
 101
 102 static unsigned long * tcp_timeouts[]
 103 = { NULL,                              /*      TCP_CONNTRACK_NONE */
 104     &ip_ct_tcp_timeout_syn_sent,       /*      TCP_CONNTRACK_SYN_SENT, */
 105     &ip_ct_tcp_timeout_syn_recv,       /*      TCP_CONNTRACK_SYN_RECV, */
 106     &ip_ct_tcp_timeout_established,    /*      TCP_CONNTRACK_ESTABLISHED,      */
 107     &ip_ct_tcp_timeout_fin_wait,       /*      TCP_CONNTRACK_FIN_WAIT, */
 108     &ip_ct_tcp_timeout_close_wait,     /*      TCP_CONNTRACK_CLOSE_WAIT,       */
 109     &ip_ct_tcp_timeout_last_ack,       /*      TCP_CONNTRACK_LAST_ACK, */
 110     &ip_ct_tcp_timeout_time_wait,      /*      TCP_CONNTRACK_TIME_WAIT,        */
 111     &ip_ct_tcp_timeout_close,          /*      TCP_CONNTRACK_CLOSE,    */
 112     NULL,                              /*      TCP_CONNTRACK_LISTEN */
 113  };
 114
 115 #define sNO TCP_CONNTRACK_NONE
 116 #define sSS TCP_CONNTRACK_SYN_SENT
 117 #define sSR TCP_CONNTRACK_SYN_RECV
 118 #define sES TCP_CONNTRACK_ESTABLISHED
 119 #define sFW TCP_CONNTRACK_FIN_WAIT
 120 #define sCW TCP_CONNTRACK_CLOSE_WAIT
 121 #define sLA TCP_CONNTRACK_LAST_ACK
 122 #define sTW TCP_CONNTRACK_TIME_WAIT
 123 #define sCL TCP_CONNTRACK_CLOSE
 124 #define sLI TCP_CONNTRACK_LISTEN
 125 #define sIV TCP_CONNTRACK_MAX
 126 #define sIG TCP_CONNTRACK_IGNORE
 127
 128 /* What TCP flags are set from RST/SYN/FIN/ACK. */
 129 enum tcp_bit_set {
 130         TCP_SYN_SET,
 131         TCP_SYNACK_SET,
 132         TCP_FIN_SET,
 133         TCP_ACK_SET,
 134         TCP_RST_SET,
 135         TCP_NONE_SET,
 136 };
 137
 138 /*
 139  * The TCP state transition table needs a few words...
 140  *
 141  * We are the man in the middle. All the packets go through us
 142  * but might get lost in transit to the destination.
 143  * It is assumed that the destinations can't receive segments
 144  * we haven't seen.
 145  *
 146  * The checked segment is in window, but our windows are *not*
 147  * equivalent with the ones of the sender/receiver. We always
 148  * try to guess the state of the current sender.
 149  *
 150  * The meaning of the states are:
 151  *
 152  * NONE:        initial state
 153  * SYN_SENT:    SYN-only packet seen
 154  * SYN_RECV:    SYN-ACK packet seen
 155  * ESTABLISHED: ACK packet seen
 156  * FIN_WAIT:    FIN packet seen
 157  * CLOSE_WAIT:  ACK seen (after FIN)
 158  * LAST_ACK:    FIN seen (after FIN)
 159  * TIME_WAIT:   last ACK seen
 160  * CLOSE:       closed connection
 161  *
 162  * LISTEN state is not used.
 163  *
 164  * Packets marked as IGNORED (sIG):
 165  *      if they may be either invalid or valid
 166  *      and the receiver may send back a connection
 167  *      closing RST or a SYN/ACK.
 168  *
 169  * Packets marked as INVALID (sIV):
 170  *      if they are invalid
 171  *      or we do not support the request (simultaneous open)
 172  */
 173 static enum tcp_conntrack tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = {
 174         {
 175 /* ORIGINAL */
 176 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 177 /*syn*/    { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sIV },
 178 /*
 179  *      sNO -> sSS      Initialize a new connection
 180  *      sSS -> sSS      Retransmitted SYN
 181  *      sSR -> sIG      Late retransmitted SYN?
 182  *      sES -> sIG      Error: SYNs in window outside the SYN_SENT state
 183  *                      are errors. Receiver will reply with RST
 184  *                      and close the connection.
 185  *                      Or we are not in sync and hold a dead connection.
 186  *      sFW -> sIG
 187  *      sCW -> sIG
 188  *      sLA -> sIG
 189  *      sTW -> sSS      Reopened connection (RFC 1122).
 190  *      sCL -> sSS
 191  */
 192 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 193 /*synack*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
 194 /*
 195  * A SYN/ACK from the client is always invalid:
 196  *      - either it tries to set up a simultaneous open, which is
 197  *        not supported;
 198  *      - or the firewall has just been inserted between the two hosts
 199  *        during the session set-up. The SYN will be retransmitted
 200  *        by the true client (or it'll time out).
 201  */
 202 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 203 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
 204 /*
 205  *      sNO -> sIV      Too late and no reason to do anything...
 206  *      sSS -> sIV      Client migth not send FIN in this state:
 207  *                      we enforce waiting for a SYN/ACK reply first.
 208  *      sSR -> sFW      Close started.
 209  *      sES -> sFW
 210  *      sFW -> sLA      FIN seen in both directions, waiting for
 211  *                      the last ACK.
 212  *                      Migth be a retransmitted FIN as well...
 213  *      sCW -> sLA
 214  *      sLA -> sLA      Retransmitted FIN. Remain in the same state.
 215  *      sTW -> sTW
 216  *      sCL -> sCL
 217  */
 218 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 219 /*ack*/    { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV },
 220 /*
 221  *      sNO -> sES      Assumed.
 222  *      sSS -> sIV      ACK is invalid: we haven't seen a SYN/ACK yet.
 223  *      sSR -> sES      Established state is reached.
 224  *      sES -> sES      :-)
 225  *      sFW -> sCW      Normal close request answered by ACK.
 226  *      sCW -> sCW
 227  *      sLA -> sTW      Last ACK detected.
 228  *      sTW -> sTW      Retransmitted last ACK. Remain in the same state.
 229  *      sCL -> sCL
 230  */
 231 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 232 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
 233 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
 234         },
 235         {
 236 /* REPLY */
 237 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 238 /*syn*/    { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
 239 /*
 240  *      sNO -> sIV      Never reached.
 241  *      sSS -> sIV      Simultaneous open, not supported
 242  *      sSR -> sIV      Simultaneous open, not supported.
 243  *      sES -> sIV      Server may not initiate a connection.
 244  *      sFW -> sIV
 245  *      sCW -> sIV
 246  *      sLA -> sIV
 247  *      sTW -> sIV      Reopened connection, but server may not do it.
 248  *      sCL -> sIV
 249  */
 250 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 251 /*synack*/ { sIV, sSR, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIV },
 252 /*
 253  *      sSS -> sSR      Standard open.
 254  *      sSR -> sSR      Retransmitted SYN/ACK.
 255  *      sES -> sIG      Late retransmitted SYN/ACK?
 256  *      sFW -> sIG      Might be SYN/ACK answering ignored SYN
 257  *      sCW -> sIG
 258  *      sLA -> sIG
 259  *      sTW -> sIG
 260  *      sCL -> sIG
 261  */
 262 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 263 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
 264 /*
 265  *      sSS -> sIV      Server might not send FIN in this state.
 266  *      sSR -> sFW      Close started.
 267  *      sES -> sFW
 268  *      sFW -> sLA      FIN seen in both directions.
 269  *      sCW -> sLA
 270  *      sLA -> sLA      Retransmitted FIN.
 271  *      sTW -> sTW
 272  *      sCL -> sCL
 273  */
 274 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 275 /*ack*/    { sIV, sIV, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIV },
 276 /*
 277  *      sSS -> sIV      Might be a half-open connection.
 278  *      sSR -> sSR      Might answer late resent SYN.
 279  *      sES -> sES      :-)
 280  *      sFW -> sCW      Normal close request answered by ACK.
 281  *      sCW -> sCW
 282  *      sLA -> sTW      Last ACK detected.
 283  *      sTW -> sTW      Retransmitted last ACK.
 284  *      sCL -> sCL
 285  */
 286 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 287 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
 288 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
 289         }
 290 };
 291
 292 static int tcp_pkt_to_tuple(const struct sk_buff *skb,
 293                             unsigned int dataoff,
 294                             struct ip_conntrack_tuple *tuple)
 295 {
 296         struct tcphdr _hdr, *hp;
 297
 298         /* Actually only need first 8 bytes. */
 299         hp = skb_header_pointer(skb, dataoff, 8, &_hdr);
 300         if (hp == NULL)
 301                 return 0;
 302
 303         tuple->src.u.tcp.port = hp->source;
 304         tuple->dst.u.tcp.port = hp->dest;
 305
 306         return 1;
 307 }
 308
 309 static int tcp_invert_tuple(struct ip_conntrack_tuple *tuple,
 310                             const struct ip_conntrack_tuple *orig)
 311 {
 312         tuple->src.u.tcp.port = orig->dst.u.tcp.port;
 313         tuple->dst.u.tcp.port = orig->src.u.tcp.port;
 314         return 1;
 315 }
 316
 317 /* Print out the per-protocol part of the tuple. */
 318 static int tcp_print_tuple(struct seq_file *s,
 319                            const struct ip_conntrack_tuple *tuple)
 320 {
 321         return seq_printf(s, "sport=%hu dport=%hu ",
 322                           ntohs(tuple->src.u.tcp.port),
 323                           ntohs(tuple->dst.u.tcp.port));
 324 }
 325
 326 /* Print out the private part of the conntrack. */
 327 static int tcp_print_conntrack(struct seq_file *s,
 328                                const struct ip_conntrack *conntrack)
 329 {
 330         enum tcp_conntrack state;
 331
 332         read_lock_bh(&tcp_lock);
 333         state = conntrack->proto.tcp.state;
 334         read_unlock_bh(&tcp_lock);
 335
 336         return seq_printf(s, "%s ", tcp_conntrack_names[state]);
 337 }
 338
 339 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
 340     defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
 341 static int tcp_to_nfattr(struct sk_buff *skb, struct nfattr *nfa,
 342                          const struct ip_conntrack *ct)
 343 {
 344         struct nfattr *nest_parms = NFA_NEST(skb, CTA_PROTOINFO_TCP);
 345
 346         read_lock_bh(&tcp_lock);
 347         NFA_PUT(skb, CTA_PROTOINFO_TCP_STATE, sizeof(u_int8_t),
 348                 &ct->proto.tcp.state);
 349         read_unlock_bh(&tcp_lock);
 350
 351         NFA_NEST_END(skb, nest_parms);
 352
 353         return 0;
 354
 355 nfattr_failure:
 356         read_unlock_bh(&tcp_lock);
 357         return -1;
 358 }
 359
 360 static int nfattr_to_tcp(struct nfattr *cda[], struct ip_conntrack *ct)
 361 {
 362         struct nfattr *attr = cda[CTA_PROTOINFO_TCP-1];
 363         struct nfattr *tb[CTA_PROTOINFO_TCP_MAX];
 364
 365         nfattr_parse_nested(tb, CTA_PROTOINFO_TCP_MAX, attr);
 366
 367         if (!tb[CTA_PROTOINFO_TCP_STATE-1])
 368                 return -EINVAL;
 369
 370         write_lock_bh(&tcp_lock);
 371         ct->proto.tcp.state =
 372                 *(u_int8_t *)NFA_DATA(tb[CTA_PROTOINFO_TCP_STATE-1]);
 373         write_unlock_bh(&tcp_lock);
 374
 375         return 0;
 376 }
 377 #endif
 378
 379 static unsigned int get_conntrack_index(const struct tcphdr *tcph)
 380 {
 381         if (tcph->rst) return TCP_RST_SET;
 382         else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET);
 383         else if (tcph->fin) return TCP_FIN_SET;
 384         else if (tcph->ack) return TCP_ACK_SET;
 385         else return TCP_NONE_SET;
 386 }
 387
 388 /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering
 389    in IP Filter' by Guido van Rooij.
 390
 391    http://www.nluug.nl/events/sane2000/papers.html
 392    http://www.iae.nl/users/guido/papers/tcp_filtering.ps.gz
 393
 394    The boundaries and the conditions are changed according to RFC793:
 395    the packet must intersect the window (i.e. segments may be
 396    after the right or before the left edge) and thus receivers may ACK
 397    segments after the right edge of the window.
 398
 399         td_maxend = max(sack + max(win,1)) seen in reply packets
 400         td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets
 401         td_maxwin += seq + len - sender.td_maxend
 402                         if seq + len > sender.td_maxend
 403         td_end    = max(seq + len) seen in sent packets
 404
 405    I.   Upper bound for valid data:     seq <= sender.td_maxend
 406    II.  Lower bound for valid data:     seq + len >= sender.td_end - receiver.td_maxwin
 407    III. Upper bound for valid ack:      sack <= receiver.td_end
 408    IV.  Lower bound for valid ack:      ack >= receiver.td_end - MAXACKWINDOW
 409
 410    where sack is the highest right edge of sack block found in the packet.
 411
 412    The upper bound limit for a valid ack is not ignored -
 413    we doesn't have to deal with fragments.
 414 */
 415
 416 static inline __u32 segment_seq_plus_len(__u32 seq,
 417                                          size_t len,
 418                                          struct iphdr *iph,
 419                                          struct tcphdr *tcph)
 420 {
 421         return (seq + len - (iph->ihl + tcph->doff)*4
 422                 + (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0));
 423 }
 424
 425 /* Fixme: what about big packets? */
 426 #define MAXACKWINCONST                  66000
 427 #define MAXACKWINDOW(sender)                                            \
 428         ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin     \
 429                                               : MAXACKWINCONST)
 430
 431 /*
 432  * Simplified tcp_parse_options routine from tcp_input.c
 433  */
 434 static void tcp_options(const struct sk_buff *skb,
 435                         struct iphdr *iph,
 436                         struct tcphdr *tcph,
 437                         struct ip_ct_tcp_state *state)
 438 {
 439         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
 440         unsigned char *ptr;
 441         int length = (tcph->doff*4) - sizeof(struct tcphdr);
 442
 443         if (!length)
 444                 return;
 445
 446         ptr = skb_header_pointer(skb,
 447                                  (iph->ihl * 4) + sizeof(struct tcphdr),
 448                                  length, buff);
 449         BUG_ON(ptr == NULL);
 450
 451         state->td_scale =
 452         state->flags = 0;
 453
 454         while (length > 0) {
 455                 int opcode=*ptr++;
 456                 int opsize;
 457
 458                 switch (opcode) {
 459                 case TCPOPT_EOL:
 460                         return;
 461                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 462                         length--;
 463                         continue;
 464                 default:
 465                         opsize=*ptr++;
 466                         if (opsize < 2) /* "silly options" */
 467                                 return;
 468                         if (opsize > length)
 469                                 break;  /* don't parse partial options */
 470
 471                         if (opcode == TCPOPT_SACK_PERM
 472                             && opsize == TCPOLEN_SACK_PERM)
 473                                 state->flags |= IP_CT_TCP_FLAG_SACK_PERM;
 474                         else if (opcode == TCPOPT_WINDOW
 475                                  && opsize == TCPOLEN_WINDOW) {
 476                                 state->td_scale = *(u_int8_t *)ptr;
 477
 478                                 if (state->td_scale > 14) {
 479                                         /* See RFC1323 */
 480                                         state->td_scale = 14;
 481                                 }
 482                                 state->flags |=
 483                                         IP_CT_TCP_FLAG_WINDOW_SCALE;
 484                         }
 485                         ptr += opsize - 2;
 486                         length -= opsize;
 487                 }
 488         }
 489 }
 490
 491 static void tcp_sack(const struct sk_buff *skb,
 492                      struct iphdr *iph,
 493                      struct tcphdr *tcph,
 494                      __u32 *sack)
 495 {
 496         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
 497         unsigned char *ptr;
 498         int length = (tcph->doff*4) - sizeof(struct tcphdr);
 499         __u32 tmp;
 500
 501         if (!length)
 502                 return;
 503
 504         ptr = skb_header_pointer(skb,
 505                                  (iph->ihl * 4) + sizeof(struct tcphdr),
 506                                  length, buff);
 507         BUG_ON(ptr == NULL);
 508
 509         /* Fast path for timestamp-only option */
 510         if (length == TCPOLEN_TSTAMP_ALIGNED*4
 511             && *(__u32 *)ptr ==
 512                 __constant_ntohl((TCPOPT_NOP << 24)
 513                                  | (TCPOPT_NOP << 16)
 514                                  | (TCPOPT_TIMESTAMP << 8)
 515                                  | TCPOLEN_TIMESTAMP))
 516                 return;
 517
 518         while (length > 0) {
 519                 int opcode=*ptr++;
 520                 int opsize, i;
 521
 522                 switch (opcode) {
 523                 case TCPOPT_EOL:
 524                         return;
 525                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 526                         length--;
 527                         continue;
 528                 default:
 529                         opsize=*ptr++;
 530                         if (opsize < 2) /* "silly options" */
 531                                 return;
 532                         if (opsize > length)
 533                                 break;  /* don't parse partial options */
 534
 535                         if (opcode == TCPOPT_SACK
 536                             && opsize >= (TCPOLEN_SACK_BASE
 537                                           + TCPOLEN_SACK_PERBLOCK)
 538                             && !((opsize - TCPOLEN_SACK_BASE)
 539                                  % TCPOLEN_SACK_PERBLOCK)) {
 540                                 for (i = 0;
 541                                      i < (opsize - TCPOLEN_SACK_BASE);
 542                                      i += TCPOLEN_SACK_PERBLOCK) {
 543                                         tmp = ntohl(*((u_int32_t *)(ptr+i)+1));
 544
 545                                         if (after(tmp, *sack))
 546                                                 *sack = tmp;
 547                                 }
 548                                 return;
 549                         }
 550                         ptr += opsize - 2;
 551                         length -= opsize;
 552                 }
 553         }
 554 }
 555
 556 static int tcp_in_window(struct ip_ct_tcp *state,
 557                          enum ip_conntrack_dir dir,
 558                          unsigned int index,
 559                          const struct sk_buff *skb,
 560                          struct iphdr *iph,
 561                          struct tcphdr *tcph)
 562 {
 563         struct ip_ct_tcp_state *sender = &state->seen[dir];
 564         struct ip_ct_tcp_state *receiver = &state->seen[!dir];
 565         __u32 seq, ack, sack, end, win, swin;
 566         int res;
 567
 568         /*
 569          * Get the required data from the packet.
 570          */
 571         seq = ntohl(tcph->seq);
 572         ack = sack = ntohl(tcph->ack_seq);
 573         win = ntohs(tcph->window);
 574         end = segment_seq_plus_len(seq, skb->len, iph, tcph);
 575
 576         if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
 577                 tcp_sack(skb, iph, tcph, &sack);
 578
 579         DEBUGP("tcp_in_window: START\n");
 580         DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 581                "seq=%u ack=%u sack=%u win=%u end=%u\n",
 582                 NIPQUAD(iph->saddr), ntohs(tcph->source),
 583                 NIPQUAD(iph->daddr), ntohs(tcph->dest),
 584                 seq, ack, sack, win, end);
 585         DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
 586                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 587                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 588                 sender->td_scale,
 589                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 590                 receiver->td_scale);
 591
 592         if (sender->td_end == 0) {
 593                 /*
 594                  * Initialize sender data.
 595                  */
 596                 if (tcph->syn && tcph->ack) {
 597                         /*
 598                          * Outgoing SYN-ACK in reply to a SYN.
 599                          */
 600                         sender->td_end =
 601                         sender->td_maxend = end;
 602                         sender->td_maxwin = (win == 0 ? 1 : win);
 603
 604                         tcp_options(skb, iph, tcph, sender);
 605                         /*
 606                          * RFC 1323:
 607                          * Both sides must send the Window Scale option
 608                          * to enable window scaling in either direction.
 609                          */
 610                         if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE
 611                               && receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE))
 612                                 sender->td_scale =
 613                                 receiver->td_scale = 0;
 614                 } else {
 615                         /*
 616                          * We are in the middle of a connection,
 617                          * its history is lost for us.
 618                          * Let's try to use the data from the packet.
 619                          */
 620                         sender->td_end = end;
 621                         sender->td_maxwin = (win == 0 ? 1 : win);
 622                         sender->td_maxend = end + sender->td_maxwin;
 623                 }
 624         } else if (((state->state == TCP_CONNTRACK_SYN_SENT
 625                      && dir == IP_CT_DIR_ORIGINAL)
 626                     || (state->state == TCP_CONNTRACK_SYN_RECV
 627                         && dir == IP_CT_DIR_REPLY))
 628                     && after(end, sender->td_end)) {
 629                 /*
 630                  * RFC 793: "if a TCP is reinitialized ... then it need
 631                  * not wait at all; it must only be sure to use sequence
 632                  * numbers larger than those recently used."
 633                  */
 634                 sender->td_end =
 635                 sender->td_maxend = end;
 636                 sender->td_maxwin = (win == 0 ? 1 : win);
 637
 638                 tcp_options(skb, iph, tcph, sender);
 639         }
 640
 641         if (!(tcph->ack)) {
 642                 /*
 643                  * If there is no ACK, just pretend it was set and OK.
 644                  */
 645                 ack = sack = receiver->td_end;
 646         } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
 647                     (TCP_FLAG_ACK|TCP_FLAG_RST))
 648                    && (ack == 0)) {
 649                 /*
 650                  * Broken TCP stacks, that set ACK in RST packets as well
 651                  * with zero ack value.
 652                  */
 653                 ack = sack = receiver->td_end;
 654         }
 655
 656         if (seq == end
 657             && (!tcph->rst
 658                 || (seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)))
 659                 /*
 660                  * Packets contains no data: we assume it is valid
 661                  * and check the ack value only.
 662                  * However RST segments are always validated by their
 663                  * SEQ number, except when seq == 0 (reset sent answering
 664                  * SYN.
 665                  */
 666                 seq = end = sender->td_end;
 667
 668         DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 669                "seq=%u ack=%u sack =%u win=%u end=%u\n",
 670                 NIPQUAD(iph->saddr), ntohs(tcph->source),
 671                 NIPQUAD(iph->daddr), ntohs(tcph->dest),
 672                 seq, ack, sack, win, end);
 673         DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
 674                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 675                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 676                 sender->td_scale,
 677                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 678                 receiver->td_scale);
 679
 680         DEBUGP("tcp_in_window: I=%i II=%i III=%i IV=%i\n",
 681                 before(seq, sender->td_maxend + 1),
 682                 after(end, sender->td_end - receiver->td_maxwin - 1),
 683                 before(sack, receiver->td_end + 1),
 684                 after(ack, receiver->td_end - MAXACKWINDOW(sender)));
 685
 686         if (sender->loose || receiver->loose ||
 687             (before(seq, sender->td_maxend + 1) &&
 688              after(end, sender->td_end - receiver->td_maxwin - 1) &&
 689              before(sack, receiver->td_end + 1) &&
 690              after(ack, receiver->td_end - MAXACKWINDOW(sender)))) {
 691                 /*
 692                  * Take into account window scaling (RFC 1323).
 693                  */
 694                 if (!tcph->syn)
 695                         win <<= sender->td_scale;
 696
 697                 /*
 698                  * Update sender data.
 699                  */
 700                 swin = win + (sack - ack);
 701                 if (sender->td_maxwin < swin)
 702                         sender->td_maxwin = swin;
 703                 if (after(end, sender->td_end))
 704                         sender->td_end = end;
 705                 /*
 706                  * Update receiver data.
 707                  */
 708                 if (after(end, sender->td_maxend))
 709                         receiver->td_maxwin += end - sender->td_maxend;
 710                 if (after(sack + win, receiver->td_maxend - 1)) {
 711                         receiver->td_maxend = sack + win;
 712                         if (win == 0)
 713                                 receiver->td_maxend++;
 714                 }
 715
 716                 /*
 717                  * Check retransmissions.
 718                  */
 719                 if (index == TCP_ACK_SET) {
 720                         if (state->last_dir == dir
 721                             && state->last_seq == seq
 722                             && state->last_ack == ack
 723                             && state->last_end == end)
 724                                 state->retrans++;
 725                         else {
 726                                 state->last_dir = dir;
 727                                 state->last_seq = seq;
 728                                 state->last_ack = ack;
 729                                 state->last_end = end;
 730                                 state->retrans = 0;
 731                         }
 732                 }
 733                 /*
 734                  * Close the window of disabled window tracking :-)
 735                  */
 736                 if (sender->loose)
 737                         sender->loose--;
 738
 739                 res = 1;
 740         } else {
 741                 if (LOG_INVALID(IPPROTO_TCP))
 742                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 743                         "ip_ct_tcp: %s ",
 744                         before(seq, sender->td_maxend + 1) ?
 745                         after(end, sender->td_end - receiver->td_maxwin - 1) ?
 746                         before(sack, receiver->td_end + 1) ?
 747                         after(ack, receiver->td_end - MAXACKWINDOW(sender)) ? "BUG"
 748                         : "ACK is under the lower bound (possible overly delayed ACK)"
 749                         : "ACK is over the upper bound (ACKed data not seen yet)"
 750                         : "SEQ is under the lower bound (already ACKed data retransmitted)"
 751                         : "SEQ is over the upper bound (over the window of the receiver)");
 752
 753                 res = ip_ct_tcp_be_liberal;
 754         }
 755
 756         DEBUGP("tcp_in_window: res=%i sender end=%u maxend=%u maxwin=%u "
 757                "receiver end=%u maxend=%u maxwin=%u\n",
 758                 res, sender->td_end, sender->td_maxend, sender->td_maxwin,
 759                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin);
 760
 761         return res;
 762 }
 763
 764 #ifdef CONFIG_IP_NF_NAT_NEEDED
 765 /* Update sender->td_end after NAT successfully mangled the packet */
 766 void ip_conntrack_tcp_update(struct sk_buff *skb,
 767                              struct ip_conntrack *conntrack,
 768                              enum ip_conntrack_dir dir)
 769 {
 770         struct iphdr *iph = skb->nh.iph;
 771         struct tcphdr *tcph = (void *)skb->nh.iph + skb->nh.iph->ihl*4;
 772         __u32 end;
 773 #ifdef DEBUGP_VARS
 774         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[dir];
 775         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[!dir];
 776 #endif
 777
 778         end = segment_seq_plus_len(ntohl(tcph->seq), skb->len, iph, tcph);
 779
 780         write_lock_bh(&tcp_lock);
 781         /*
 782          * We have to worry for the ack in the reply packet only...
 783          */
 784         if (after(end, conntrack->proto.tcp.seen[dir].td_end))
 785                 conntrack->proto.tcp.seen[dir].td_end = end;
 786         conntrack->proto.tcp.last_end = end;
 787         write_unlock_bh(&tcp_lock);
 788         DEBUGP("tcp_update: sender end=%u maxend=%u maxwin=%u scale=%i "
 789                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 790                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 791                 sender->td_scale,
 792                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 793                 receiver->td_scale);
 794 }
 795
 796 #endif
 797
 798 #define TH_FIN  0x01
 799 #define TH_SYN  0x02
 800 #define TH_RST  0x04
 801 #define TH_PUSH 0x08
 802 #define TH_ACK  0x10
 803 #define TH_URG  0x20
 804 #define TH_ECE  0x40
 805 #define TH_CWR  0x80
 806
 807 /* table of valid flag combinations - ECE and CWR are always valid */
 808 static u8 tcp_valid_flags[(TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG) + 1] =
 809 {
 810         [TH_SYN]                        = 1,
 811         [TH_SYN|TH_ACK]                 = 1,
 812         [TH_SYN|TH_ACK|TH_PUSH]         = 1,
 813         [TH_RST]                        = 1,
 814         [TH_RST|TH_ACK]                 = 1,
 815         [TH_RST|TH_ACK|TH_PUSH]         = 1,
 816         [TH_FIN|TH_ACK]                 = 1,
 817         [TH_ACK]                        = 1,
 818         [TH_ACK|TH_PUSH]                = 1,
 819         [TH_ACK|TH_URG]                 = 1,
 820         [TH_ACK|TH_URG|TH_PUSH]         = 1,
 821         [TH_FIN|TH_ACK|TH_PUSH]         = 1,
 822         [TH_FIN|TH_ACK|TH_URG]          = 1,
 823         [TH_FIN|TH_ACK|TH_URG|TH_PUSH]  = 1,
 824 };
 825
 826 /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c.  */
 827 static int tcp_error(struct sk_buff *skb,
 828                      enum ip_conntrack_info *ctinfo,
 829                      unsigned int hooknum)
 830 {
 831         struct iphdr *iph = skb->nh.iph;
 832         struct tcphdr _tcph, *th;
 833         unsigned int tcplen = skb->len - iph->ihl * 4;
 834         u_int8_t tcpflags;
 835
 836         /* Smaller that minimal TCP header? */
 837         th = skb_header_pointer(skb, iph->ihl * 4,
 838                                 sizeof(_tcph), &_tcph);
 839         if (th == NULL) {
 840                 if (LOG_INVALID(IPPROTO_TCP))
 841                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 842                                 "ip_ct_tcp: short packet ");
 843                 return -NF_ACCEPT;
 844         }
 845
 846         /* Not whole TCP header or malformed packet */
 847         if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {
 848                 if (LOG_INVALID(IPPROTO_TCP))
 849                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 850                                 "ip_ct_tcp: truncated/malformed packet ");
 851                 return -NF_ACCEPT;
 852         }
 853
 854         /* Checksum invalid? Ignore.
 855          * We skip checking packets on the outgoing path
 856          * because the semantic of CHECKSUM_HW is different there
 857          * and moreover root might send raw packets.
 858          */
 859         /* FIXME: Source route IP option packets --RR */
 860         if (hooknum == NF_IP_PRE_ROUTING
 861             && skb->ip_summed != CHECKSUM_UNNECESSARY
 862             && csum_tcpudp_magic(iph->saddr, iph->daddr, tcplen, IPPROTO_TCP,
 863                                  skb->ip_summed == CHECKSUM_HW ? skb->csum
 864                                  : skb_checksum(skb, iph->ihl*4, tcplen, 0))) {
 865                 if (LOG_INVALID(IPPROTO_TCP))
 866                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 867                                   "ip_ct_tcp: bad TCP checksum ");
 868                 return -NF_ACCEPT;
 869         }
 870
 871         /* Check TCP flags. */
 872         tcpflags = (((u_int8_t *)th)[13] & ~(TH_ECE|TH_CWR));
 873         if (!tcp_valid_flags[tcpflags]) {
 874                 if (LOG_INVALID(IPPROTO_TCP))
 875                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 876                                   "ip_ct_tcp: invalid TCP flag combination ");
 877                 return -NF_ACCEPT;
 878         }
 879
 880         return NF_ACCEPT;
 881 }
 882
 883 /* Returns verdict for packet, or -1 for invalid. */
 884 static int tcp_packet(struct ip_conntrack *conntrack,
 885                       const struct sk_buff *skb,
 886                       enum ip_conntrack_info ctinfo)
 887 {
 888         enum tcp_conntrack new_state, old_state;
 889         enum ip_conntrack_dir dir;
 890         struct iphdr *iph = skb->nh.iph;
 891         struct tcphdr *th, _tcph;
 892         unsigned long timeout;
 893         unsigned int index;
 894
 895         th = skb_header_pointer(skb, iph->ihl * 4,
 896                                 sizeof(_tcph), &_tcph);
 897         BUG_ON(th == NULL);
 898
 899         write_lock_bh(&tcp_lock);
 900         old_state = conntrack->proto.tcp.state;
 901         dir = CTINFO2DIR(ctinfo);
 902         index = get_conntrack_index(th);
 903         new_state = tcp_conntracks[dir][index][old_state];
 904
 905         switch (new_state) {
 906         case TCP_CONNTRACK_IGNORE:
 907                 /* Either SYN in ORIGINAL
 908                  * or SYN/ACK in REPLY. */
 909                 if (index == TCP_SYNACK_SET
 910                     && conntrack->proto.tcp.last_index == TCP_SYN_SET
 911                     && conntrack->proto.tcp.last_dir != dir
 912                     && ntohl(th->ack_seq) ==
 913                              conntrack->proto.tcp.last_end) {
 914                         /* This SYN/ACK acknowledges a SYN that we earlier
 915                          * ignored as invalid. This means that the client and
 916                          * the server are both in sync, while the firewall is
 917                          * not. We kill this session and block the SYN/ACK so
 918                          * that the client cannot but retransmit its SYN and
 919                          * thus initiate a clean new session.
 920                          */
 921                         write_unlock_bh(&tcp_lock);
 922                         if (LOG_INVALID(IPPROTO_TCP))
 923                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 924                                               NULL, "ip_ct_tcp: "
 925                                               "killing out of sync session ");
 926                         if (del_timer(&conntrack->timeout))
 927                                 conntrack->timeout.function((unsigned long)
 928                                                             conntrack);
 929                         return -NF_DROP;
 930                 }
 931                 conntrack->proto.tcp.last_index = index;
 932                 conntrack->proto.tcp.last_dir = dir;
 933                 conntrack->proto.tcp.last_seq = ntohl(th->seq);
 934                 conntrack->proto.tcp.last_end =
 935                     segment_seq_plus_len(ntohl(th->seq), skb->len, iph, th);
 936
 937                 write_unlock_bh(&tcp_lock);
 938                 if (LOG_INVALID(IPPROTO_TCP))
 939                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 940                                   "ip_ct_tcp: invalid packet ignored ");
 941                 return NF_ACCEPT;
 942         case TCP_CONNTRACK_MAX:
 943                 /* Invalid packet */
 944                 DEBUGP("ip_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
 945                        dir, get_conntrack_index(th),
 946                        old_state);
 947                 write_unlock_bh(&tcp_lock);
 948                 if (LOG_INVALID(IPPROTO_TCP))
 949                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 950                                   "ip_ct_tcp: invalid state ");
 951                 return -NF_ACCEPT;
 952         case TCP_CONNTRACK_SYN_SENT:
 953                 if (old_state < TCP_CONNTRACK_TIME_WAIT)
 954                         break;
 955                 if ((conntrack->proto.tcp.seen[dir].flags &
 956                          IP_CT_TCP_FLAG_CLOSE_INIT)
 957                     || after(ntohl(th->seq),
 958                              conntrack->proto.tcp.seen[dir].td_end)) {
 959                         /* Attempt to reopen a closed connection.
 960                         * Delete this connection and look up again. */
 961                         write_unlock_bh(&tcp_lock);
 962                         if (del_timer(&conntrack->timeout))
 963                                 conntrack->timeout.function((unsigned long)
 964                                                             conntrack);
 965                         return -NF_REPEAT;
 966                 } else {
 967                         write_unlock_bh(&tcp_lock);
 968                         if (LOG_INVALID(IPPROTO_TCP))
 969                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 970                                               NULL, "ip_ct_tcp: invalid SYN");
 971                         return -NF_ACCEPT;
 972                 }
 973         case TCP_CONNTRACK_CLOSE:
 974                 if (index == TCP_RST_SET
 975                     && test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)
 976                     && conntrack->proto.tcp.last_index == TCP_SYN_SET
 977                     && ntohl(th->ack_seq) == conntrack->proto.tcp.last_end) {
 978                         /* RST sent to invalid SYN we had let trough
 979                          * SYN was in window then, tear down connection.
 980                          * We skip window checking, because packet might ACK
 981                          * segments we ignored in the SYN. */
 982                         goto in_window;
 983                 }
 984                 /* Just fall trough */
 985         default:
 986                 /* Keep compilers happy. */
 987                 break;
 988         }
 989
 990         if (!tcp_in_window(&conntrack->proto.tcp, dir, index,
 991                            skb, iph, th)) {
 992                 write_unlock_bh(&tcp_lock);
 993                 return -NF_ACCEPT;
 994         }
 995     in_window:
 996         /* From now on we have got in-window packets */
 997         conntrack->proto.tcp.last_index = index;
 998
 999         DEBUGP("tcp_conntracks: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
1000                "syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
1001                 NIPQUAD(iph->saddr), ntohs(th->source),
1002                 NIPQUAD(iph->daddr), ntohs(th->dest),
1003                 (th->syn ? 1 : 0), (th->ack ? 1 : 0),
1004                 (th->fin ? 1 : 0), (th->rst ? 1 : 0),
1005                 old_state, new_state);
1006
1007         conntrack->proto.tcp.state = new_state;
1008         if (old_state != new_state
1009             && (new_state == TCP_CONNTRACK_FIN_WAIT
1010                 || new_state == TCP_CONNTRACK_CLOSE))
1011                 conntrack->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
1012         timeout = conntrack->proto.tcp.retrans >= ip_ct_tcp_max_retrans
1013                   && *tcp_timeouts[new_state] > ip_ct_tcp_timeout_max_retrans
1014                   ? ip_ct_tcp_timeout_max_retrans : *tcp_timeouts[new_state];
1015         write_unlock_bh(&tcp_lock);
1016
1017         ip_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
1018         if (new_state != old_state)
1019                 ip_conntrack_event_cache(IPCT_PROTOINFO, skb);
1020
1021         if (!test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
1022                 /* If only reply is a RST, we can consider ourselves not to
1023                    have an established connection: this is a fairly common
1024                    problem case, so we can delete the conntrack
1025                    immediately.  --RR */
1026                 if (th->rst) {
1027                         if (del_timer(&conntrack->timeout))
1028                                 conntrack->timeout.function((unsigned long)
1029                                                             conntrack);
1030                         return NF_ACCEPT;
1031                 }
1032         } else if (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
1033                    && (old_state == TCP_CONNTRACK_SYN_RECV
1034                        || old_state == TCP_CONNTRACK_ESTABLISHED)
1035                    && new_state == TCP_CONNTRACK_ESTABLISHED) {
1036                 /* Set ASSURED if we see see valid ack in ESTABLISHED
1037                    after SYN_RECV or a valid answer for a picked up
1038                    connection. */
1039                 set_bit(IPS_ASSURED_BIT, &conntrack->status);
1040                 ip_conntrack_event_cache(IPCT_STATUS, skb);
1041         }
1042         ip_ct_refresh_acct(conntrack, ctinfo, skb, timeout);
1043
1044         return NF_ACCEPT;
1045 }
1046
1047 /* Called when a new connection for this protocol found. */
1048 static int tcp_new(struct ip_conntrack *conntrack,
1049                    const struct sk_buff *skb)
1050 {
1051         enum tcp_conntrack new_state;
1052         struct iphdr *iph = skb->nh.iph;
1053         struct tcphdr *th, _tcph;
1054 #ifdef DEBUGP_VARS
1055         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[0];
1056         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[1];
1057 #endif
1058
1059         th = skb_header_pointer(skb, iph->ihl * 4,
1060                                 sizeof(_tcph), &_tcph);
1061         BUG_ON(th == NULL);
1062
1063         /* Don't need lock here: this conntrack not in circulation yet */
1064         new_state
1065                 = tcp_conntracks[0][get_conntrack_index(th)]
1066                 [TCP_CONNTRACK_NONE];
1067
1068         /* Invalid: delete conntrack */
1069         if (new_state >= TCP_CONNTRACK_MAX) {
1070                 DEBUGP("ip_ct_tcp: invalid new deleting.\n");
1071                 return 0;
1072         }
1073
1074         if (new_state == TCP_CONNTRACK_SYN_SENT) {
1075                 /* SYN packet */
1076                 conntrack->proto.tcp.seen[0].td_end =
1077                         segment_seq_plus_len(ntohl(th->seq), skb->len,
1078                                              iph, th);
1079                 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1080                 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1081                         conntrack->proto.tcp.seen[0].td_maxwin = 1;
1082                 conntrack->proto.tcp.seen[0].td_maxend =
1083                         conntrack->proto.tcp.seen[0].td_end;
1084
1085                 tcp_options(skb, iph, th, &conntrack->proto.tcp.seen[0]);
1086                 conntrack->proto.tcp.seen[1].flags = 0;
1087                 conntrack->proto.tcp.seen[0].loose =
1088                 conntrack->proto.tcp.seen[1].loose = 0;
1089         } else if (ip_ct_tcp_loose == 0) {
1090                 /* Don't try to pick up connections. */
1091                 return 0;
1092         } else {
1093                 /*
1094                  * We are in the middle of a connection,
1095                  * its history is lost for us.
1096                  * Let's try to use the data from the packet.
1097                  */
1098                 conntrack->proto.tcp.seen[0].td_end =
1099                         segment_seq_plus_len(ntohl(th->seq), skb->len,
1100                                              iph, th);
1101                 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1102                 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1103                         conntrack->proto.tcp.seen[0].td_maxwin = 1;
1104                 conntrack->proto.tcp.seen[0].td_maxend =
1105                         conntrack->proto.tcp.seen[0].td_end +
1106                         conntrack->proto.tcp.seen[0].td_maxwin;
1107                 conntrack->proto.tcp.seen[0].td_scale = 0;
1108
1109                 /* We assume SACK. Should we assume window scaling too? */
1110                 conntrack->proto.tcp.seen[0].flags =
1111                 conntrack->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM;
1112                 conntrack->proto.tcp.seen[0].loose =
1113                 conntrack->proto.tcp.seen[1].loose = ip_ct_tcp_loose;
1114         }
1115
1116         conntrack->proto.tcp.seen[1].td_end = 0;
1117         conntrack->proto.tcp.seen[1].td_maxend = 0;
1118         conntrack->proto.tcp.seen[1].td_maxwin = 1;
1119         conntrack->proto.tcp.seen[1].td_scale = 0;
1120
1121         /* tcp_packet will set them */
1122         conntrack->proto.tcp.state = TCP_CONNTRACK_NONE;
1123         conntrack->proto.tcp.last_index = TCP_NONE_SET;
1124
1125         DEBUGP("tcp_new: sender end=%u maxend=%u maxwin=%u scale=%i "
1126                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
1127                 sender->td_end, sender->td_maxend, sender->td_maxwin,
1128                 sender->td_scale,
1129                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
1130                 receiver->td_scale);
1131         return 1;
1132 }
1133
1134 struct ip_conntrack_protocol ip_conntrack_protocol_tcp =
1135 {
1136         .proto                  = IPPROTO_TCP,
1137         .name                   = "tcp",
1138         .pkt_to_tuple           = tcp_pkt_to_tuple,
1139         .invert_tuple           = tcp_invert_tuple,
1140         .print_tuple            = tcp_print_tuple,
1141         .print_conntrack        = tcp_print_conntrack,
1142         .packet                 = tcp_packet,
1143         .new                    = tcp_new,
1144         .error                  = tcp_error,
1145 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
1146     defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
1147         .to_nfattr              = tcp_to_nfattr,
1148         .from_nfattr            = nfattr_to_tcp,
1149         .tuple_to_nfattr        = ip_ct_port_tuple_to_nfattr,
1150         .nfattr_to_tuple        = ip_ct_port_nfattr_to_tuple,
1151 #endif
1152 };