net/netfilter/nf_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  * 27 Oct 2004: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
  20  *      - genelized Layer 3 protocol part.
  21  *
  22  * Derived from net/ipv4/netfilter/ip_conntrack_proto_tcp.c
  23  *
  24  * version 2.2
  25  */
  26
  27 #include <linux/config.h>
  28 #include <linux/types.h>
  29 #include <linux/sched.h>
  30 #include <linux/timer.h>
  31 #include <linux/netfilter.h>
  32 #include <linux/module.h>
  33 #include <linux/in.h>
  34 #include <linux/tcp.h>
  35 #include <linux/spinlock.h>
  36 #include <linux/skbuff.h>
  37 #include <linux/ipv6.h>
  38 #include <net/ip6_checksum.h>
  39
  40 #include <net/tcp.h>
  41
  42 #include <linux/netfilter.h>
  43 #include <linux/netfilter_ipv4.h>
  44 #include <linux/netfilter_ipv6.h>
  45 #include <net/netfilter/nf_conntrack.h>
  46 #include <net/netfilter/nf_conntrack_protocol.h>
  47
  48 #if 0
  49 #define DEBUGP printk
  50 #define DEBUGP_VARS
  51 #else
  52 #define DEBUGP(format, args...)
  53 #endif
  54
  55 /* Protects conntrack->proto.tcp */
  56 static DEFINE_RWLOCK(tcp_lock);
  57
  58 /* "Be conservative in what you do,
  59     be liberal in what you accept from others."
  60     If it's non-zero, we mark only out of window RST segments as INVALID. */
  61 int nf_ct_tcp_be_liberal = 0;
  62
  63 /* When connection is picked up from the middle, how many packets are required
  64    to pass in each direction when we assume we are in sync - if any side uses
  65    window scaling, we lost the game.
  66    If it is set to zero, we disable picking up already established
  67    connections. */
  68 int nf_ct_tcp_loose = 3;
  69
  70 /* Max number of the retransmitted packets without receiving an (acceptable)
  71    ACK from the destination. If this number is reached, a shorter timer
  72    will be started. */
  73 int nf_ct_tcp_max_retrans = 3;
  74
  75   /* FIXME: Examine ipfilter's timeouts and conntrack transitions more
  76      closely.  They're more complex. --RR */
  77
  78 static const char *tcp_conntrack_names[] = {
  79         "NONE",
  80         "SYN_SENT",
  81         "SYN_RECV",
  82         "ESTABLISHED",
  83         "FIN_WAIT",
  84         "CLOSE_WAIT",
  85         "LAST_ACK",
  86         "TIME_WAIT",
  87         "CLOSE",
  88         "LISTEN"
  89 };
  90
  91 #define SECS * HZ
  92 #define MINS * 60 SECS
  93 #define HOURS * 60 MINS
  94 #define DAYS * 24 HOURS
  95
  96 unsigned long nf_ct_tcp_timeout_syn_sent =      2 MINS;
  97 unsigned long nf_ct_tcp_timeout_syn_recv =     60 SECS;
  98 unsigned long nf_ct_tcp_timeout_established =   5 DAYS;
  99 unsigned long nf_ct_tcp_timeout_fin_wait =      2 MINS;
 100 unsigned long nf_ct_tcp_timeout_close_wait =   60 SECS;
 101 unsigned long nf_ct_tcp_timeout_last_ack =     30 SECS;
 102 unsigned long nf_ct_tcp_timeout_time_wait =     2 MINS;
 103 unsigned long nf_ct_tcp_timeout_close =        10 SECS;
 104
 105 /* RFC1122 says the R2 limit should be at least 100 seconds.
 106    Linux uses 15 packets as limit, which corresponds
 107    to ~13-30min depending on RTO. */
 108 unsigned long nf_ct_tcp_timeout_max_retrans =     5 MINS;
 109
 110 static unsigned long * tcp_timeouts[]
 111 = { NULL,                              /* TCP_CONNTRACK_NONE */
 112     &nf_ct_tcp_timeout_syn_sent,       /* TCP_CONNTRACK_SYN_SENT, */
 113     &nf_ct_tcp_timeout_syn_recv,       /* TCP_CONNTRACK_SYN_RECV, */
 114     &nf_ct_tcp_timeout_established,    /* TCP_CONNTRACK_ESTABLISHED, */
 115     &nf_ct_tcp_timeout_fin_wait,       /* TCP_CONNTRACK_FIN_WAIT, */
 116     &nf_ct_tcp_timeout_close_wait,     /* TCP_CONNTRACK_CLOSE_WAIT, */
 117     &nf_ct_tcp_timeout_last_ack,       /* TCP_CONNTRACK_LAST_ACK, */
 118     &nf_ct_tcp_timeout_time_wait,      /* TCP_CONNTRACK_TIME_WAIT, */
 119     &nf_ct_tcp_timeout_close,          /* TCP_CONNTRACK_CLOSE, */
 120     NULL,                              /* TCP_CONNTRACK_LISTEN */
 121  };
 122
 123 #define sNO TCP_CONNTRACK_NONE
 124 #define sSS TCP_CONNTRACK_SYN_SENT
 125 #define sSR TCP_CONNTRACK_SYN_RECV
 126 #define sES TCP_CONNTRACK_ESTABLISHED
 127 #define sFW TCP_CONNTRACK_FIN_WAIT
 128 #define sCW TCP_CONNTRACK_CLOSE_WAIT
 129 #define sLA TCP_CONNTRACK_LAST_ACK
 130 #define sTW TCP_CONNTRACK_TIME_WAIT
 131 #define sCL TCP_CONNTRACK_CLOSE
 132 #define sLI TCP_CONNTRACK_LISTEN
 133 #define sIV TCP_CONNTRACK_MAX
 134 #define sIG TCP_CONNTRACK_IGNORE
 135
 136 /* What TCP flags are set from RST/SYN/FIN/ACK. */
 137 enum tcp_bit_set {
 138         TCP_SYN_SET,
 139         TCP_SYNACK_SET,
 140         TCP_FIN_SET,
 141         TCP_ACK_SET,
 142         TCP_RST_SET,
 143         TCP_NONE_SET,
 144 };
 145
 146 /*
 147  * The TCP state transition table needs a few words...
 148  *
 149  * We are the man in the middle. All the packets go through us
 150  * but might get lost in transit to the destination.
 151  * It is assumed that the destinations can't receive segments
 152  * we haven't seen.
 153  *
 154  * The checked segment is in window, but our windows are *not*
 155  * equivalent with the ones of the sender/receiver. We always
 156  * try to guess the state of the current sender.
 157  *
 158  * The meaning of the states are:
 159  *
 160  * NONE:        initial state
 161  * SYN_SENT:    SYN-only packet seen
 162  * SYN_RECV:    SYN-ACK packet seen
 163  * ESTABLISHED: ACK packet seen
 164  * FIN_WAIT:    FIN packet seen
 165  * CLOSE_WAIT:  ACK seen (after FIN)
 166  * LAST_ACK:    FIN seen (after FIN)
 167  * TIME_WAIT:   last ACK seen
 168  * CLOSE:       closed connection
 169  *
 170  * LISTEN state is not used.
 171  *
 172  * Packets marked as IGNORED (sIG):
 173  *      if they may be either invalid or valid
 174  *      and the receiver may send back a connection
 175  *      closing RST or a SYN/ACK.
 176  *
 177  * Packets marked as INVALID (sIV):
 178  *      if they are invalid
 179  *      or we do not support the request (simultaneous open)
 180  */
 181 static enum tcp_conntrack tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = {
 182         {
 183 /* ORIGINAL */
 184 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 185 /*syn*/    { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sIV },
 186 /*
 187  *      sNO -> sSS      Initialize a new connection
 188  *      sSS -> sSS      Retransmitted SYN
 189  *      sSR -> sIG      Late retransmitted SYN?
 190  *      sES -> sIG      Error: SYNs in window outside the SYN_SENT state
 191  *                      are errors. Receiver will reply with RST
 192  *                      and close the connection.
 193  *                      Or we are not in sync and hold a dead connection.
 194  *      sFW -> sIG
 195  *      sCW -> sIG
 196  *      sLA -> sIG
 197  *      sTW -> sSS      Reopened connection (RFC 1122).
 198  *      sCL -> sSS
 199  */
 200 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 201 /*synack*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
 202 /*
 203  * A SYN/ACK from the client is always invalid:
 204  *      - either it tries to set up a simultaneous open, which is
 205  *        not supported;
 206  *      - or the firewall has just been inserted between the two hosts
 207  *        during the session set-up. The SYN will be retransmitted
 208  *        by the true client (or it'll time out).
 209  */
 210 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 211 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
 212 /*
 213  *      sNO -> sIV      Too late and no reason to do anything...
 214  *      sSS -> sIV      Client migth not send FIN in this state:
 215  *                      we enforce waiting for a SYN/ACK reply first.
 216  *      sSR -> sFW      Close started.
 217  *      sES -> sFW
 218  *      sFW -> sLA      FIN seen in both directions, waiting for
 219  *                      the last ACK.
 220  *                      Migth be a retransmitted FIN as well...
 221  *      sCW -> sLA
 222  *      sLA -> sLA      Retransmitted FIN. Remain in the same state.
 223  *      sTW -> sTW
 224  *      sCL -> sCL
 225  */
 226 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 227 /*ack*/    { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV },
 228 /*
 229  *      sNO -> sES      Assumed.
 230  *      sSS -> sIV      ACK is invalid: we haven't seen a SYN/ACK yet.
 231  *      sSR -> sES      Established state is reached.
 232  *      sES -> sES      :-)
 233  *      sFW -> sCW      Normal close request answered by ACK.
 234  *      sCW -> sCW
 235  *      sLA -> sTW      Last ACK detected.
 236  *      sTW -> sTW      Retransmitted last ACK. Remain in the same state.
 237  *      sCL -> sCL
 238  */
 239 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 240 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
 241 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
 242         },
 243         {
 244 /* REPLY */
 245 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 246 /*syn*/    { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
 247 /*
 248  *      sNO -> sIV      Never reached.
 249  *      sSS -> sIV      Simultaneous open, not supported
 250  *      sSR -> sIV      Simultaneous open, not supported.
 251  *      sES -> sIV      Server may not initiate a connection.
 252  *      sFW -> sIV
 253  *      sCW -> sIV
 254  *      sLA -> sIV
 255  *      sTW -> sIV      Reopened connection, but server may not do it.
 256  *      sCL -> sIV
 257  */
 258 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 259 /*synack*/ { sIV, sSR, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIV },
 260 /*
 261  *      sSS -> sSR      Standard open.
 262  *      sSR -> sSR      Retransmitted SYN/ACK.
 263  *      sES -> sIG      Late retransmitted SYN/ACK?
 264  *      sFW -> sIG      Might be SYN/ACK answering ignored SYN
 265  *      sCW -> sIG
 266  *      sLA -> sIG
 267  *      sTW -> sIG
 268  *      sCL -> sIG
 269  */
 270 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 271 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
 272 /*
 273  *      sSS -> sIV      Server might not send FIN in this state.
 274  *      sSR -> sFW      Close started.
 275  *      sES -> sFW
 276  *      sFW -> sLA      FIN seen in both directions.
 277  *      sCW -> sLA
 278  *      sLA -> sLA      Retransmitted FIN.
 279  *      sTW -> sTW
 280  *      sCL -> sCL
 281  */
 282 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 283 /*ack*/    { sIV, sIV, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIV },
 284 /*
 285  *      sSS -> sIV      Might be a half-open connection.
 286  *      sSR -> sSR      Might answer late resent SYN.
 287  *      sES -> sES      :-)
 288  *      sFW -> sCW      Normal close request answered by ACK.
 289  *      sCW -> sCW
 290  *      sLA -> sTW      Last ACK detected.
 291  *      sTW -> sTW      Retransmitted last ACK.
 292  *      sCL -> sCL
 293  */
 294 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 295 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
 296 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
 297         }
 298 };
 299
 300 static int tcp_pkt_to_tuple(const struct sk_buff *skb,
 301                             unsigned int dataoff,
 302                             struct nf_conntrack_tuple *tuple)
 303 {
 304         struct tcphdr _hdr, *hp;
 305
 306         /* Actually only need first 8 bytes. */
 307         hp = skb_header_pointer(skb, dataoff, 8, &_hdr);
 308         if (hp == NULL)
 309                 return 0;
 310
 311         tuple->src.u.tcp.port = hp->source;
 312         tuple->dst.u.tcp.port = hp->dest;
 313
 314         return 1;
 315 }
 316
 317 static int tcp_invert_tuple(struct nf_conntrack_tuple *tuple,
 318                             const struct nf_conntrack_tuple *orig)
 319 {
 320         tuple->src.u.tcp.port = orig->dst.u.tcp.port;
 321         tuple->dst.u.tcp.port = orig->src.u.tcp.port;
 322         return 1;
 323 }
 324
 325 /* Print out the per-protocol part of the tuple. */
 326 static int tcp_print_tuple(struct seq_file *s,
 327                            const struct nf_conntrack_tuple *tuple)
 328 {
 329         return seq_printf(s, "sport=%hu dport=%hu ",
 330                           ntohs(tuple->src.u.tcp.port),
 331                           ntohs(tuple->dst.u.tcp.port));
 332 }
 333
 334 /* Print out the private part of the conntrack. */
 335 static int tcp_print_conntrack(struct seq_file *s,
 336                                const struct nf_conn *conntrack)
 337 {
 338         enum tcp_conntrack state;
 339
 340         read_lock_bh(&tcp_lock);
 341         state = conntrack->proto.tcp.state;
 342         read_unlock_bh(&tcp_lock);
 343
 344         return seq_printf(s, "%s ", tcp_conntrack_names[state]);
 345 }
 346
 347 static unsigned int get_conntrack_index(const struct tcphdr *tcph)
 348 {
 349         if (tcph->rst) return TCP_RST_SET;
 350         else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET);
 351         else if (tcph->fin) return TCP_FIN_SET;
 352         else if (tcph->ack) return TCP_ACK_SET;
 353         else return TCP_NONE_SET;
 354 }
 355
 356 /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering
 357    in IP Filter' by Guido van Rooij.
 358
 359    http://www.nluug.nl/events/sane2000/papers.html
 360    http://www.iae.nl/users/guido/papers/tcp_filtering.ps.gz
 361
 362    The boundaries and the conditions are changed according to RFC793:
 363    the packet must intersect the window (i.e. segments may be
 364    after the right or before the left edge) and thus receivers may ACK
 365    segments after the right edge of the window.
 366
 367         td_maxend = max(sack + max(win,1)) seen in reply packets
 368         td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets
 369         td_maxwin += seq + len - sender.td_maxend
 370                         if seq + len > sender.td_maxend
 371         td_end    = max(seq + len) seen in sent packets
 372
 373    I.   Upper bound for valid data:     seq <= sender.td_maxend
 374    II.  Lower bound for valid data:     seq + len >= sender.td_end - receiver.td_maxwin
 375    III. Upper bound for valid ack:      sack <= receiver.td_end
 376    IV.  Lower bound for valid ack:      ack >= receiver.td_end - MAXACKWINDOW
 377
 378    where sack is the highest right edge of sack block found in the packet.
 379
 380    The upper bound limit for a valid ack is not ignored -
 381    we doesn't have to deal with fragments.
 382 */
 383
 384 static inline __u32 segment_seq_plus_len(__u32 seq,
 385                                          size_t len,
 386                                          unsigned int dataoff,
 387                                          struct tcphdr *tcph)
 388 {
 389         /* XXX Should I use payload length field in IP/IPv6 header ?
 390          * - YK */
 391         return (seq + len - dataoff - tcph->doff*4
 392                 + (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0));
 393 }
 394
 395 /* Fixme: what about big packets? */
 396 #define MAXACKWINCONST                  66000
 397 #define MAXACKWINDOW(sender)                                            \
 398         ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin     \
 399                                               : MAXACKWINCONST)
 400
 401 /*
 402  * Simplified tcp_parse_options routine from tcp_input.c
 403  */
 404 static void tcp_options(const struct sk_buff *skb,
 405                         unsigned int dataoff,
 406                         struct tcphdr *tcph,
 407                         struct ip_ct_tcp_state *state)
 408 {
 409         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
 410         unsigned char *ptr;
 411         int length = (tcph->doff*4) - sizeof(struct tcphdr);
 412
 413         if (!length)
 414                 return;
 415
 416         ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr),
 417                                  length, buff);
 418         BUG_ON(ptr == NULL);
 419
 420         state->td_scale =
 421         state->flags = 0;
 422
 423         while (length > 0) {
 424                 int opcode=*ptr++;
 425                 int opsize;
 426
 427                 switch (opcode) {
 428                 case TCPOPT_EOL:
 429                         return;
 430                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 431                         length--;
 432                         continue;
 433                 default:
 434                         opsize=*ptr++;
 435                         if (opsize < 2) /* "silly options" */
 436                                 return;
 437                         if (opsize > length)
 438                                 break;  /* don't parse partial options */
 439
 440                         if (opcode == TCPOPT_SACK_PERM
 441                             && opsize == TCPOLEN_SACK_PERM)
 442                                 state->flags |= IP_CT_TCP_FLAG_SACK_PERM;
 443                         else if (opcode == TCPOPT_WINDOW
 444                                  && opsize == TCPOLEN_WINDOW) {
 445                                 state->td_scale = *(u_int8_t *)ptr;
 446
 447                                 if (state->td_scale > 14) {
 448                                         /* See RFC1323 */
 449                                         state->td_scale = 14;
 450                                 }
 451                                 state->flags |=
 452                                         IP_CT_TCP_FLAG_WINDOW_SCALE;
 453                         }
 454                         ptr += opsize - 2;
 455                         length -= opsize;
 456                 }
 457         }
 458 }
 459
 460 static void tcp_sack(const struct sk_buff *skb, unsigned int dataoff,
 461                      struct tcphdr *tcph, __u32 *sack)
 462 {
 463         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
 464         unsigned char *ptr;
 465         int length = (tcph->doff*4) - sizeof(struct tcphdr);
 466         __u32 tmp;
 467
 468         if (!length)
 469                 return;
 470
 471         ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr),
 472                                  length, buff);
 473         BUG_ON(ptr == NULL);
 474
 475         /* Fast path for timestamp-only option */
 476         if (length == TCPOLEN_TSTAMP_ALIGNED*4
 477             && *(__u32 *)ptr ==
 478                 __constant_ntohl((TCPOPT_NOP << 24)
 479                                  | (TCPOPT_NOP << 16)
 480                                  | (TCPOPT_TIMESTAMP << 8)
 481                                  | TCPOLEN_TIMESTAMP))
 482                 return;
 483
 484         while (length > 0) {
 485                 int opcode = *ptr++;
 486                 int opsize, i;
 487
 488                 switch (opcode) {
 489                 case TCPOPT_EOL:
 490                         return;
 491                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 492                         length--;
 493                         continue;
 494                 default:
 495                         opsize = *ptr++;
 496                         if (opsize < 2) /* "silly options" */
 497                                 return;
 498                         if (opsize > length)
 499                                 break;  /* don't parse partial options */
 500
 501                         if (opcode == TCPOPT_SACK
 502                             && opsize >= (TCPOLEN_SACK_BASE
 503                                           + TCPOLEN_SACK_PERBLOCK)
 504                             && !((opsize - TCPOLEN_SACK_BASE)
 505                                  % TCPOLEN_SACK_PERBLOCK)) {
 506                                 for (i = 0;
 507                                      i < (opsize - TCPOLEN_SACK_BASE);
 508                                      i += TCPOLEN_SACK_PERBLOCK) {
 509                                         memcpy(&tmp, (__u32 *)(ptr + i) + 1,
 510                                                sizeof(__u32));
 511                                         tmp = ntohl(tmp);
 512
 513                                         if (after(tmp, *sack))
 514                                                 *sack = tmp;
 515                                 }
 516                                 return;
 517                         }
 518                         ptr += opsize - 2;
 519                         length -= opsize;
 520                 }
 521         }
 522 }
 523
 524 static int tcp_in_window(struct ip_ct_tcp *state,
 525                          enum ip_conntrack_dir dir,
 526                          unsigned int index,
 527                          const struct sk_buff *skb,
 528                          unsigned int dataoff,
 529                          struct tcphdr *tcph,
 530                          int pf)
 531 {
 532         struct ip_ct_tcp_state *sender = &state->seen[dir];
 533         struct ip_ct_tcp_state *receiver = &state->seen[!dir];
 534         __u32 seq, ack, sack, end, win, swin;
 535         int res;
 536
 537         /*
 538          * Get the required data from the packet.
 539          */
 540         seq = ntohl(tcph->seq);
 541         ack = sack = ntohl(tcph->ack_seq);
 542         win = ntohs(tcph->window);
 543         end = segment_seq_plus_len(seq, skb->len, dataoff, tcph);
 544
 545         if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
 546                 tcp_sack(skb, dataoff, tcph, &sack);
 547
 548         DEBUGP("tcp_in_window: START\n");
 549         DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 550                "seq=%u ack=%u sack=%u win=%u end=%u\n",
 551                 NIPQUAD(iph->saddr), ntohs(tcph->source),
 552                 NIPQUAD(iph->daddr), ntohs(tcph->dest),
 553                 seq, ack, sack, win, end);
 554         DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
 555                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 556                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 557                 sender->td_scale,
 558                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 559                 receiver->td_scale);
 560
 561         if (sender->td_end == 0) {
 562                 /*
 563                  * Initialize sender data.
 564                  */
 565                 if (tcph->syn && tcph->ack) {
 566                         /*
 567                          * Outgoing SYN-ACK in reply to a SYN.
 568                          */
 569                         sender->td_end =
 570                         sender->td_maxend = end;
 571                         sender->td_maxwin = (win == 0 ? 1 : win);
 572
 573                         tcp_options(skb, dataoff, tcph, sender);
 574                         /*
 575                          * RFC 1323:
 576                          * Both sides must send the Window Scale option
 577                          * to enable window scaling in either direction.
 578                          */
 579                         if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE
 580                               && receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE))
 581                                 sender->td_scale =
 582                                 receiver->td_scale = 0;
 583                 } else {
 584                         /*
 585                          * We are in the middle of a connection,
 586                          * its history is lost for us.
 587                          * Let's try to use the data from the packet.
 588                          */
 589                         sender->td_end = end;
 590                         sender->td_maxwin = (win == 0 ? 1 : win);
 591                         sender->td_maxend = end + sender->td_maxwin;
 592                 }
 593         } else if (((state->state == TCP_CONNTRACK_SYN_SENT
 594                      && dir == IP_CT_DIR_ORIGINAL)
 595                    || (state->state == TCP_CONNTRACK_SYN_RECV
 596                      && dir == IP_CT_DIR_REPLY))
 597                    && after(end, sender->td_end)) {
 598                 /*
 599                  * RFC 793: "if a TCP is reinitialized ... then it need
 600                  * not wait at all; it must only be sure to use sequence
 601                  * numbers larger than those recently used."
 602                  */
 603                 sender->td_end =
 604                 sender->td_maxend = end;
 605                 sender->td_maxwin = (win == 0 ? 1 : win);
 606
 607                 tcp_options(skb, dataoff, tcph, sender);
 608         }
 609
 610         if (!(tcph->ack)) {
 611                 /*
 612                  * If there is no ACK, just pretend it was set and OK.
 613                  */
 614                 ack = sack = receiver->td_end;
 615         } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
 616                     (TCP_FLAG_ACK|TCP_FLAG_RST))
 617                    && (ack == 0)) {
 618                 /*
 619                  * Broken TCP stacks, that set ACK in RST packets as well
 620                  * with zero ack value.
 621                  */
 622                 ack = sack = receiver->td_end;
 623         }
 624
 625         if (seq == end
 626             && (!tcph->rst
 627                 || (seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)))
 628                 /*
 629                  * Packets contains no data: we assume it is valid
 630                  * and check the ack value only.
 631                  * However RST segments are always validated by their
 632                  * SEQ number, except when seq == 0 (reset sent answering
 633                  * SYN.
 634                  */
 635                 seq = end = sender->td_end;
 636
 637         DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 638                "seq=%u ack=%u sack =%u win=%u end=%u\n",
 639                 NIPQUAD(iph->saddr), ntohs(tcph->source),
 640                 NIPQUAD(iph->daddr), ntohs(tcph->dest),
 641                 seq, ack, sack, win, end);
 642         DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
 643                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 644                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 645                 sender->td_scale,
 646                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 647                 receiver->td_scale);
 648
 649         DEBUGP("tcp_in_window: I=%i II=%i III=%i IV=%i\n",
 650                 before(seq, sender->td_maxend + 1),
 651                 after(end, sender->td_end - receiver->td_maxwin - 1),
 652                 before(sack, receiver->td_end + 1),
 653                 after(ack, receiver->td_end - MAXACKWINDOW(sender)));
 654
 655         if (sender->loose || receiver->loose ||
 656             (before(seq, sender->td_maxend + 1) &&
 657              after(end, sender->td_end - receiver->td_maxwin - 1) &&
 658              before(sack, receiver->td_end + 1) &&
 659              after(ack, receiver->td_end - MAXACKWINDOW(sender)))) {
 660                 /*
 661                  * Take into account window scaling (RFC 1323).
 662                  */
 663                 if (!tcph->syn)
 664                         win <<= sender->td_scale;
 665
 666                 /*
 667                  * Update sender data.
 668                  */
 669                 swin = win + (sack - ack);
 670                 if (sender->td_maxwin < swin)
 671                         sender->td_maxwin = swin;
 672                 if (after(end, sender->td_end))
 673                         sender->td_end = end;
 674                 /*
 675                  * Update receiver data.
 676                  */
 677                 if (after(end, sender->td_maxend))
 678                         receiver->td_maxwin += end - sender->td_maxend;
 679                 if (after(sack + win, receiver->td_maxend - 1)) {
 680                         receiver->td_maxend = sack + win;
 681                         if (win == 0)
 682                                 receiver->td_maxend++;
 683                 }
 684
 685                 /*
 686                  * Check retransmissions.
 687                  */
 688                 if (index == TCP_ACK_SET) {
 689                         if (state->last_dir == dir
 690                             && state->last_seq == seq
 691                             && state->last_ack == ack
 692                             && state->last_end == end)
 693                                 state->retrans++;
 694                         else {
 695                                 state->last_dir = dir;
 696                                 state->last_seq = seq;
 697                                 state->last_ack = ack;
 698                                 state->last_end = end;
 699                                 state->retrans = 0;
 700                         }
 701                 }
 702                 /*
 703                  * Close the window of disabled window tracking :-)
 704                  */
 705                 if (sender->loose)
 706                         sender->loose--;
 707
 708                 res = 1;
 709         } else {
 710                 if (LOG_INVALID(IPPROTO_TCP))
 711                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 712                         "nf_ct_tcp: %s ",
 713                         before(seq, sender->td_maxend + 1) ?
 714                         after(end, sender->td_end - receiver->td_maxwin - 1) ?
 715                         before(sack, receiver->td_end + 1) ?
 716                         after(ack, receiver->td_end - MAXACKWINDOW(sender)) ? "BUG"
 717                         : "ACK is under the lower bound (possible overly delayed ACK)"
 718                         : "ACK is over the upper bound (ACKed data not seen yet)"
 719                         : "SEQ is under the lower bound (already ACKed data retransmitted)"
 720                         : "SEQ is over the upper bound (over the window of the receiver)");
 721
 722                 res = nf_ct_tcp_be_liberal;
 723         }
 724
 725         DEBUGP("tcp_in_window: res=%i sender end=%u maxend=%u maxwin=%u "
 726                "receiver end=%u maxend=%u maxwin=%u\n",
 727                 res, sender->td_end, sender->td_maxend, sender->td_maxwin,
 728                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin);
 729
 730         return res;
 731 }
 732
 733 #ifdef CONFIG_IP_NF_NAT_NEEDED
 734 /* Update sender->td_end after NAT successfully mangled the packet */
 735 /* Caller must linearize skb at tcp header. */
 736 void nf_conntrack_tcp_update(struct sk_buff *skb,
 737                              unsigned int dataoff,
 738                              struct nf_conn *conntrack,
 739                              int dir)
 740 {
 741         struct tcphdr *tcph = (void *)skb->data + dataoff;
 742         __u32 end;
 743 #ifdef DEBUGP_VARS
 744         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[dir];
 745         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[!dir];
 746 #endif
 747
 748         end = segment_seq_plus_len(ntohl(tcph->seq), skb->len, dataoff, tcph);
 749
 750         write_lock_bh(&tcp_lock);
 751         /*
 752          * We have to worry for the ack in the reply packet only...
 753          */
 754         if (after(end, conntrack->proto.tcp.seen[dir].td_end))
 755                 conntrack->proto.tcp.seen[dir].td_end = end;
 756         conntrack->proto.tcp.last_end = end;
 757         write_unlock_bh(&tcp_lock);
 758         DEBUGP("tcp_update: sender end=%u maxend=%u maxwin=%u scale=%i "
 759                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 760                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 761                 sender->td_scale,
 762                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 763                 receiver->td_scale);
 764 }
 765
 766 #endif
 767
 768 #define TH_FIN  0x01
 769 #define TH_SYN  0x02
 770 #define TH_RST  0x04
 771 #define TH_PUSH 0x08
 772 #define TH_ACK  0x10
 773 #define TH_URG  0x20
 774 #define TH_ECE  0x40
 775 #define TH_CWR  0x80
 776
 777 /* table of valid flag combinations - ECE and CWR are always valid */
 778 static u8 tcp_valid_flags[(TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG) + 1] =
 779 {
 780         [TH_SYN]                        = 1,
 781         [TH_SYN|TH_ACK]                 = 1,
 782         [TH_SYN|TH_PUSH]                = 1,
 783         [TH_SYN|TH_ACK|TH_PUSH]         = 1,
 784         [TH_RST]                        = 1,
 785         [TH_RST|TH_ACK]                 = 1,
 786         [TH_RST|TH_ACK|TH_PUSH]         = 1,
 787         [TH_FIN|TH_ACK]                 = 1,
 788         [TH_ACK]                        = 1,
 789         [TH_ACK|TH_PUSH]                = 1,
 790         [TH_ACK|TH_URG]                 = 1,
 791         [TH_ACK|TH_URG|TH_PUSH]         = 1,
 792         [TH_FIN|TH_ACK|TH_PUSH]         = 1,
 793         [TH_FIN|TH_ACK|TH_URG]          = 1,
 794         [TH_FIN|TH_ACK|TH_URG|TH_PUSH]  = 1,
 795 };
 796
 797 /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c.  */
 798 static int tcp_error(struct sk_buff *skb,
 799                      unsigned int dataoff,
 800                      enum ip_conntrack_info *ctinfo,
 801                      int pf,
 802                      unsigned int hooknum,
 803                      int(*csum)(const struct sk_buff *,unsigned int))
 804 {
 805         struct tcphdr _tcph, *th;
 806         unsigned int tcplen = skb->len - dataoff;
 807         u_int8_t tcpflags;
 808
 809         /* Smaller that minimal TCP header? */
 810         th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
 811         if (th == NULL) {
 812                 if (LOG_INVALID(IPPROTO_TCP))
 813                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 814                                 "nf_ct_tcp: short packet ");
 815                 return -NF_ACCEPT;
 816         }
 817
 818         /* Not whole TCP header or malformed packet */
 819         if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {
 820                 if (LOG_INVALID(IPPROTO_TCP))
 821                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 822                                 "nf_ct_tcp: truncated/malformed packet ");
 823                 return -NF_ACCEPT;
 824         }
 825
 826         /* Checksum invalid? Ignore.
 827          * We skip checking packets on the outgoing path
 828          * because the semantic of CHECKSUM_HW is different there
 829          * and moreover root might send raw packets.
 830          */
 831         /* FIXME: Source route IP option packets --RR */
 832         if (((pf == PF_INET && hooknum == NF_IP_PRE_ROUTING) ||
 833              (pf == PF_INET6 && hooknum  == NF_IP6_PRE_ROUTING))
 834             && skb->ip_summed != CHECKSUM_UNNECESSARY
 835             && csum(skb, dataoff)) {
 836                 if (LOG_INVALID(IPPROTO_TCP))
 837                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 838                                   "nf_ct_tcp: bad TCP checksum ");
 839                 return -NF_ACCEPT;
 840         }
 841
 842         /* Check TCP flags. */
 843         tcpflags = (((u_int8_t *)th)[13] & ~(TH_ECE|TH_CWR));
 844         if (!tcp_valid_flags[tcpflags]) {
 845                 if (LOG_INVALID(IPPROTO_TCP))
 846                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 847                                   "nf_ct_tcp: invalid TCP flag combination ");
 848                 return -NF_ACCEPT;
 849         }
 850
 851         return NF_ACCEPT;
 852 }
 853
 854 static int csum4(const struct sk_buff *skb, unsigned int dataoff)
 855 {
 856         return csum_tcpudp_magic(skb->nh.iph->saddr, skb->nh.iph->daddr,
 857                                  skb->len - dataoff, IPPROTO_TCP,
 858                                  skb->ip_summed == CHECKSUM_HW ? skb->csum
 859                                  : skb_checksum(skb, dataoff,
 860                                                 skb->len - dataoff, 0));
 861 }
 862
 863 static int csum6(const struct sk_buff *skb, unsigned int dataoff)
 864 {
 865         return csum_ipv6_magic(&skb->nh.ipv6h->saddr, &skb->nh.ipv6h->daddr,
 866                                skb->len - dataoff, IPPROTO_TCP,
 867                                skb->ip_summed == CHECKSUM_HW ? skb->csum
 868                                : skb_checksum(skb, dataoff, skb->len - dataoff,
 869                                               0));
 870 }
 871
 872 static int tcp_error4(struct sk_buff *skb,
 873                       unsigned int dataoff,
 874                       enum ip_conntrack_info *ctinfo,
 875                       int pf,
 876                       unsigned int hooknum)
 877 {
 878         return tcp_error(skb, dataoff, ctinfo, pf, hooknum, csum4);
 879 }
 880
 881 static int tcp_error6(struct sk_buff *skb,
 882                       unsigned int dataoff,
 883                       enum ip_conntrack_info *ctinfo,
 884                       int pf,
 885                       unsigned int hooknum)
 886 {
 887         return tcp_error(skb, dataoff, ctinfo, pf, hooknum, csum6);
 888 }
 889
 890 /* Returns verdict for packet, or -1 for invalid. */
 891 static int tcp_packet(struct nf_conn *conntrack,
 892                       const struct sk_buff *skb,
 893                       unsigned int dataoff,
 894                       enum ip_conntrack_info ctinfo,
 895                       int pf,
 896                       unsigned int hooknum)
 897 {
 898         enum tcp_conntrack new_state, old_state;
 899         enum ip_conntrack_dir dir;
 900         struct tcphdr *th, _tcph;
 901         unsigned long timeout;
 902         unsigned int index;
 903
 904         th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
 905         BUG_ON(th == NULL);
 906
 907         write_lock_bh(&tcp_lock);
 908         old_state = conntrack->proto.tcp.state;
 909         dir = CTINFO2DIR(ctinfo);
 910         index = get_conntrack_index(th);
 911         new_state = tcp_conntracks[dir][index][old_state];
 912
 913         switch (new_state) {
 914         case TCP_CONNTRACK_IGNORE:
 915                 /* Either SYN in ORIGINAL
 916                  * or SYN/ACK in REPLY. */
 917                 if (index == TCP_SYNACK_SET
 918                     && conntrack->proto.tcp.last_index == TCP_SYN_SET
 919                     && conntrack->proto.tcp.last_dir != dir
 920                     && ntohl(th->ack_seq) ==
 921                              conntrack->proto.tcp.last_end) {
 922                         /* This SYN/ACK acknowledges a SYN that we earlier
 923                          * ignored as invalid. This means that the client and
 924                          * the server are both in sync, while the firewall is
 925                          * not. We kill this session and block the SYN/ACK so
 926                          * that the client cannot but retransmit its SYN and
 927                          * thus initiate a clean new session.
 928                          */
 929                         write_unlock_bh(&tcp_lock);
 930                         if (LOG_INVALID(IPPROTO_TCP))
 931                                 nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 932                                           "nf_ct_tcp: killing out of sync session ");
 933                         if (del_timer(&conntrack->timeout))
 934                                 conntrack->timeout.function((unsigned long)
 935                                                             conntrack);
 936                         return -NF_DROP;
 937                 }
 938                 conntrack->proto.tcp.last_index = index;
 939                 conntrack->proto.tcp.last_dir = dir;
 940                 conntrack->proto.tcp.last_seq = ntohl(th->seq);
 941                 conntrack->proto.tcp.last_end =
 942                     segment_seq_plus_len(ntohl(th->seq), skb->len, dataoff, th);
 943
 944                 write_unlock_bh(&tcp_lock);
 945                 if (LOG_INVALID(IPPROTO_TCP))
 946                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 947                                   "nf_ct_tcp: invalid packed ignored ");
 948                 return NF_ACCEPT;
 949         case TCP_CONNTRACK_MAX:
 950                 /* Invalid packet */
 951                 DEBUGP("nf_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
 952                        dir, get_conntrack_index(th),
 953                        old_state);
 954                 write_unlock_bh(&tcp_lock);
 955                 if (LOG_INVALID(IPPROTO_TCP))
 956                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 957                                   "nf_ct_tcp: invalid state ");
 958                 return -NF_ACCEPT;
 959         case TCP_CONNTRACK_SYN_SENT:
 960                 if (old_state < TCP_CONNTRACK_TIME_WAIT)
 961                         break;
 962                 if ((conntrack->proto.tcp.seen[dir].flags &
 963                         IP_CT_TCP_FLAG_CLOSE_INIT)
 964                     || after(ntohl(th->seq),
 965                              conntrack->proto.tcp.seen[dir].td_end)) {
 966                         /* Attempt to reopen a closed connection.
 967                         * Delete this connection and look up again. */
 968                         write_unlock_bh(&tcp_lock);
 969                         if (del_timer(&conntrack->timeout))
 970                                 conntrack->timeout.function((unsigned long)
 971                                                             conntrack);
 972                         return -NF_REPEAT;
 973                 }
 974         case TCP_CONNTRACK_CLOSE:
 975                 if (index == TCP_RST_SET
 976                     && test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)
 977                     && conntrack->proto.tcp.last_index == TCP_SYN_SET
 978                     && ntohl(th->ack_seq) == conntrack->proto.tcp.last_end) {
 979                         /* RST sent to invalid SYN we had let trough
 980                          * SYN was in window then, tear down connection.
 981                          * We skip window checking, because packet might ACK
 982                          * segments we ignored in the SYN. */
 983                         goto in_window;
 984                 }
 985                 /* Just fall trough */
 986         default:
 987                 /* Keep compilers happy. */
 988                 break;
 989         }
 990
 991         if (!tcp_in_window(&conntrack->proto.tcp, dir, index,
 992                            skb, dataoff, th, pf)) {
 993                 write_unlock_bh(&tcp_lock);
 994                 return -NF_ACCEPT;
 995         }
 996      in_window:
 997         /* From now on we have got in-window packets */
 998         conntrack->proto.tcp.last_index = index;
 999
1000         DEBUGP("tcp_conntracks: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
1001                "syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
1002                 NIPQUAD(iph->saddr), ntohs(th->source),
1003                 NIPQUAD(iph->daddr), ntohs(th->dest),
1004                 (th->syn ? 1 : 0), (th->ack ? 1 : 0),
1005                 (th->fin ? 1 : 0), (th->rst ? 1 : 0),
1006                 old_state, new_state);
1007
1008         conntrack->proto.tcp.state = new_state;
1009         if (old_state != new_state
1010             && (new_state == TCP_CONNTRACK_FIN_WAIT
1011                 || new_state == TCP_CONNTRACK_CLOSE))
1012                 conntrack->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
1013         timeout = conntrack->proto.tcp.retrans >= nf_ct_tcp_max_retrans
1014                   && *tcp_timeouts[new_state] > nf_ct_tcp_timeout_max_retrans
1015                   ? nf_ct_tcp_timeout_max_retrans : *tcp_timeouts[new_state];
1016         write_unlock_bh(&tcp_lock);
1017
1018         nf_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
1019         if (new_state != old_state)
1020                 nf_conntrack_event_cache(IPCT_PROTOINFO, skb);
1021
1022         if (!test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
1023                 /* If only reply is a RST, we can consider ourselves not to
1024                    have an established connection: this is a fairly common
1025                    problem case, so we can delete the conntrack
1026                    immediately.  --RR */
1027                 if (th->rst) {
1028                         if (del_timer(&conntrack->timeout))
1029                                 conntrack->timeout.function((unsigned long)
1030                                                             conntrack);
1031                         return NF_ACCEPT;
1032                 }
1033         } else if (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
1034                    && (old_state == TCP_CONNTRACK_SYN_RECV
1035                        || old_state == TCP_CONNTRACK_ESTABLISHED)
1036                    && new_state == TCP_CONNTRACK_ESTABLISHED) {
1037                 /* Set ASSURED if we see see valid ack in ESTABLISHED
1038                    after SYN_RECV or a valid answer for a picked up
1039                    connection. */
1040                 set_bit(IPS_ASSURED_BIT, &conntrack->status);
1041                 nf_conntrack_event_cache(IPCT_STATUS, skb);
1042         }
1043         nf_ct_refresh_acct(conntrack, ctinfo, skb, timeout);
1044
1045         return NF_ACCEPT;
1046 }
1047
1048 /* Called when a new connection for this protocol found. */
1049 static int tcp_new(struct nf_conn *conntrack,
1050                    const struct sk_buff *skb,
1051                    unsigned int dataoff)
1052 {
1053         enum tcp_conntrack new_state;
1054         struct tcphdr *th, _tcph;
1055 #ifdef DEBUGP_VARS
1056         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[0];
1057         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[1];
1058 #endif
1059
1060         th = skb_header_pointer(skb, dataoff, 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("nf_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                                              dataoff, 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, dataoff, 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 (nf_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                                              dataoff, 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 = nf_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 nf_conntrack_protocol nf_conntrack_protocol_tcp4 =
1135 {
1136         .l3proto                = PF_INET,
1137         .proto                  = IPPROTO_TCP,
1138         .name                   = "tcp",
1139         .pkt_to_tuple           = tcp_pkt_to_tuple,
1140         .invert_tuple           = tcp_invert_tuple,
1141         .print_tuple            = tcp_print_tuple,
1142         .print_conntrack        = tcp_print_conntrack,
1143         .packet                 = tcp_packet,
1144         .new                    = tcp_new,
1145         .error                  = tcp_error4,
1146 };
1147
1148 struct nf_conntrack_protocol nf_conntrack_protocol_tcp6 =
1149 {
1150         .l3proto                = PF_INET6,
1151         .proto                  = IPPROTO_TCP,
1152         .name                   = "tcp",
1153         .pkt_to_tuple           = tcp_pkt_to_tuple,
1154         .invert_tuple           = tcp_invert_tuple,
1155         .print_tuple            = tcp_print_tuple,
1156         .print_conntrack        = tcp_print_conntrack,
1157         .packet                 = tcp_packet,
1158         .new                    = tcp_new,
1159         .error                  = tcp_error6,
1160 };
1161
1162 EXPORT_SYMBOL(nf_conntrack_protocol_tcp4);
1163 EXPORT_SYMBOL(nf_conntrack_protocol_tcp6);