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/types.h>
  28 #include <linux/sched.h>
  29 #include <linux/timer.h>
  30 #include <linux/netfilter.h>
  31 #include <linux/module.h>
  32 #include <linux/in.h>
  33 #include <linux/tcp.h>
  34 #include <linux/spinlock.h>
  35 #include <linux/skbuff.h>
  36 #include <linux/ipv6.h>
  37 #include <net/ip6_checksum.h>
  38
  39 #include <net/tcp.h>
  40
  41 #include <linux/netfilter.h>
  42 #include <linux/netfilter_ipv4.h>
  43 #include <linux/netfilter_ipv6.h>
  44 #include <net/netfilter/nf_conntrack.h>
  45 #include <net/netfilter/nf_conntrack_protocol.h>
  46
  47 #if 0
  48 #define DEBUGP printk
  49 #define DEBUGP_VARS
  50 #else
  51 #define DEBUGP(format, args...)
  52 #endif
  53
  54 /* Protects conntrack->proto.tcp */
  55 static DEFINE_RWLOCK(tcp_lock);
  56
  57 /* "Be conservative in what you do,
  58     be liberal in what you accept from others."
  59     If it's non-zero, we mark only out of window RST segments as INVALID. */
  60 int nf_ct_tcp_be_liberal = 0;
  61
  62 /* When connection is picked up from the middle, how many packets are required
  63    to pass in each direction when we assume we are in sync - if any side uses
  64    window scaling, we lost the game.
  65    If it is set to zero, we disable picking up already established
  66    connections. */
  67 int nf_ct_tcp_loose = 3;
  68
  69 /* Max number of the retransmitted packets without receiving an (acceptable)
  70    ACK from the destination. If this number is reached, a shorter timer
  71    will be started. */
  72 int nf_ct_tcp_max_retrans = 3;
  73
  74   /* FIXME: Examine ipfilter's timeouts and conntrack transitions more
  75      closely.  They're more complex. --RR */
  76
  77 static const char *tcp_conntrack_names[] = {
  78         "NONE",
  79         "SYN_SENT",
  80         "SYN_RECV",
  81         "ESTABLISHED",
  82         "FIN_WAIT",
  83         "CLOSE_WAIT",
  84         "LAST_ACK",
  85         "TIME_WAIT",
  86         "CLOSE",
  87         "LISTEN"
  88 };
  89
  90 #define SECS * HZ
  91 #define MINS * 60 SECS
  92 #define HOURS * 60 MINS
  93 #define DAYS * 24 HOURS
  94
  95 unsigned int nf_ct_tcp_timeout_syn_sent =      2 MINS;
  96 unsigned int nf_ct_tcp_timeout_syn_recv =     60 SECS;
  97 unsigned int nf_ct_tcp_timeout_established =   5 DAYS;
  98 unsigned int nf_ct_tcp_timeout_fin_wait =      2 MINS;
  99 unsigned int nf_ct_tcp_timeout_close_wait =   60 SECS;
 100 unsigned int nf_ct_tcp_timeout_last_ack =     30 SECS;
 101 unsigned int nf_ct_tcp_timeout_time_wait =     2 MINS;
 102 unsigned int nf_ct_tcp_timeout_close =        10 SECS;
 103
 104 /* RFC1122 says the R2 limit should be at least 100 seconds.
 105    Linux uses 15 packets as limit, which corresponds
 106    to ~13-30min depending on RTO. */
 107 unsigned int nf_ct_tcp_timeout_max_retrans =     5 MINS;
 108
 109 static unsigned int * tcp_timeouts[]
 110 = { NULL,                              /* TCP_CONNTRACK_NONE */
 111     &nf_ct_tcp_timeout_syn_sent,       /* TCP_CONNTRACK_SYN_SENT, */
 112     &nf_ct_tcp_timeout_syn_recv,       /* TCP_CONNTRACK_SYN_RECV, */
 113     &nf_ct_tcp_timeout_established,    /* TCP_CONNTRACK_ESTABLISHED, */
 114     &nf_ct_tcp_timeout_fin_wait,       /* TCP_CONNTRACK_FIN_WAIT, */
 115     &nf_ct_tcp_timeout_close_wait,     /* TCP_CONNTRACK_CLOSE_WAIT, */
 116     &nf_ct_tcp_timeout_last_ack,       /* TCP_CONNTRACK_LAST_ACK, */
 117     &nf_ct_tcp_timeout_time_wait,      /* TCP_CONNTRACK_TIME_WAIT, */
 118     &nf_ct_tcp_timeout_close,          /* TCP_CONNTRACK_CLOSE, */
 119     NULL,                              /* TCP_CONNTRACK_LISTEN */
 120  };
 121
 122 #define sNO TCP_CONNTRACK_NONE
 123 #define sSS TCP_CONNTRACK_SYN_SENT
 124 #define sSR TCP_CONNTRACK_SYN_RECV
 125 #define sES TCP_CONNTRACK_ESTABLISHED
 126 #define sFW TCP_CONNTRACK_FIN_WAIT
 127 #define sCW TCP_CONNTRACK_CLOSE_WAIT
 128 #define sLA TCP_CONNTRACK_LAST_ACK
 129 #define sTW TCP_CONNTRACK_TIME_WAIT
 130 #define sCL TCP_CONNTRACK_CLOSE
 131 #define sLI TCP_CONNTRACK_LISTEN
 132 #define sIV TCP_CONNTRACK_MAX
 133 #define sIG TCP_CONNTRACK_IGNORE
 134
 135 /* What TCP flags are set from RST/SYN/FIN/ACK. */
 136 enum tcp_bit_set {
 137         TCP_SYN_SET,
 138         TCP_SYNACK_SET,
 139         TCP_FIN_SET,
 140         TCP_ACK_SET,
 141         TCP_RST_SET,
 142         TCP_NONE_SET,
 143 };
 144
 145 /*
 146  * The TCP state transition table needs a few words...
 147  *
 148  * We are the man in the middle. All the packets go through us
 149  * but might get lost in transit to the destination.
 150  * It is assumed that the destinations can't receive segments
 151  * we haven't seen.
 152  *
 153  * The checked segment is in window, but our windows are *not*
 154  * equivalent with the ones of the sender/receiver. We always
 155  * try to guess the state of the current sender.
 156  *
 157  * The meaning of the states are:
 158  *
 159  * NONE:        initial state
 160  * SYN_SENT:    SYN-only packet seen
 161  * SYN_RECV:    SYN-ACK packet seen
 162  * ESTABLISHED: ACK packet seen
 163  * FIN_WAIT:    FIN packet seen
 164  * CLOSE_WAIT:  ACK seen (after FIN)
 165  * LAST_ACK:    FIN seen (after FIN)
 166  * TIME_WAIT:   last ACK seen
 167  * CLOSE:       closed connection
 168  *
 169  * LISTEN state is not used.
 170  *
 171  * Packets marked as IGNORED (sIG):
 172  *      if they may be either invalid or valid
 173  *      and the receiver may send back a connection
 174  *      closing RST or a SYN/ACK.
 175  *
 176  * Packets marked as INVALID (sIV):
 177  *      if they are invalid
 178  *      or we do not support the request (simultaneous open)
 179  */
 180 static enum tcp_conntrack tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = {
 181         {
 182 /* ORIGINAL */
 183 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 184 /*syn*/    { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sIV },
 185 /*
 186  *      sNO -> sSS      Initialize a new connection
 187  *      sSS -> sSS      Retransmitted SYN
 188  *      sSR -> sIG      Late retransmitted SYN?
 189  *      sES -> sIG      Error: SYNs in window outside the SYN_SENT state
 190  *                      are errors. Receiver will reply with RST
 191  *                      and close the connection.
 192  *                      Or we are not in sync and hold a dead connection.
 193  *      sFW -> sIG
 194  *      sCW -> sIG
 195  *      sLA -> sIG
 196  *      sTW -> sSS      Reopened connection (RFC 1122).
 197  *      sCL -> sSS
 198  */
 199 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 200 /*synack*/ { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
 201 /*
 202  * A SYN/ACK from the client is always invalid:
 203  *      - either it tries to set up a simultaneous open, which is
 204  *        not supported;
 205  *      - or the firewall has just been inserted between the two hosts
 206  *        during the session set-up. The SYN will be retransmitted
 207  *        by the true client (or it'll time out).
 208  */
 209 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 210 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
 211 /*
 212  *      sNO -> sIV      Too late and no reason to do anything...
 213  *      sSS -> sIV      Client migth not send FIN in this state:
 214  *                      we enforce waiting for a SYN/ACK reply first.
 215  *      sSR -> sFW      Close started.
 216  *      sES -> sFW
 217  *      sFW -> sLA      FIN seen in both directions, waiting for
 218  *                      the last ACK.
 219  *                      Migth be a retransmitted FIN as well...
 220  *      sCW -> sLA
 221  *      sLA -> sLA      Retransmitted FIN. Remain in the same state.
 222  *      sTW -> sTW
 223  *      sCL -> sCL
 224  */
 225 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 226 /*ack*/    { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV },
 227 /*
 228  *      sNO -> sES      Assumed.
 229  *      sSS -> sIV      ACK is invalid: we haven't seen a SYN/ACK yet.
 230  *      sSR -> sES      Established state is reached.
 231  *      sES -> sES      :-)
 232  *      sFW -> sCW      Normal close request answered by ACK.
 233  *      sCW -> sCW
 234  *      sLA -> sTW      Last ACK detected.
 235  *      sTW -> sTW      Retransmitted last ACK. Remain in the same state.
 236  *      sCL -> sCL
 237  */
 238 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 239 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
 240 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
 241         },
 242         {
 243 /* REPLY */
 244 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 245 /*syn*/    { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV },
 246 /*
 247  *      sNO -> sIV      Never reached.
 248  *      sSS -> sIV      Simultaneous open, not supported
 249  *      sSR -> sIV      Simultaneous open, not supported.
 250  *      sES -> sIV      Server may not initiate a connection.
 251  *      sFW -> sIV
 252  *      sCW -> sIV
 253  *      sLA -> sIV
 254  *      sTW -> sIV      Reopened connection, but server may not do it.
 255  *      sCL -> sIV
 256  */
 257 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 258 /*synack*/ { sIV, sSR, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIV },
 259 /*
 260  *      sSS -> sSR      Standard open.
 261  *      sSR -> sSR      Retransmitted SYN/ACK.
 262  *      sES -> sIG      Late retransmitted SYN/ACK?
 263  *      sFW -> sIG      Might be SYN/ACK answering ignored SYN
 264  *      sCW -> sIG
 265  *      sLA -> sIG
 266  *      sTW -> sIG
 267  *      sCL -> sIG
 268  */
 269 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 270 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
 271 /*
 272  *      sSS -> sIV      Server might not send FIN in this state.
 273  *      sSR -> sFW      Close started.
 274  *      sES -> sFW
 275  *      sFW -> sLA      FIN seen in both directions.
 276  *      sCW -> sLA
 277  *      sLA -> sLA      Retransmitted FIN.
 278  *      sTW -> sTW
 279  *      sCL -> sCL
 280  */
 281 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 282 /*ack*/    { sIV, sIG, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIV },
 283 /*
 284  *      sSS -> sIG      Might be a half-open connection.
 285  *      sSR -> sSR      Might answer late resent SYN.
 286  *      sES -> sES      :-)
 287  *      sFW -> sCW      Normal close request answered by ACK.
 288  *      sCW -> sCW
 289  *      sLA -> sTW      Last ACK detected.
 290  *      sTW -> sTW      Retransmitted last ACK.
 291  *      sCL -> sCL
 292  */
 293 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sLI   */
 294 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sIV },
 295 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
 296         }
 297 };
 298
 299 static int tcp_pkt_to_tuple(const struct sk_buff *skb,
 300                             unsigned int dataoff,
 301                             struct nf_conntrack_tuple *tuple)
 302 {
 303         struct tcphdr _hdr, *hp;
 304
 305         /* Actually only need first 8 bytes. */
 306         hp = skb_header_pointer(skb, dataoff, 8, &_hdr);
 307         if (hp == NULL)
 308                 return 0;
 309
 310         tuple->src.u.tcp.port = hp->source;
 311         tuple->dst.u.tcp.port = hp->dest;
 312
 313         return 1;
 314 }
 315
 316 static int tcp_invert_tuple(struct nf_conntrack_tuple *tuple,
 317                             const struct nf_conntrack_tuple *orig)
 318 {
 319         tuple->src.u.tcp.port = orig->dst.u.tcp.port;
 320         tuple->dst.u.tcp.port = orig->src.u.tcp.port;
 321         return 1;
 322 }
 323
 324 /* Print out the per-protocol part of the tuple. */
 325 static int tcp_print_tuple(struct seq_file *s,
 326                            const struct nf_conntrack_tuple *tuple)
 327 {
 328         return seq_printf(s, "sport=%hu dport=%hu ",
 329                           ntohs(tuple->src.u.tcp.port),
 330                           ntohs(tuple->dst.u.tcp.port));
 331 }
 332
 333 /* Print out the private part of the conntrack. */
 334 static int tcp_print_conntrack(struct seq_file *s,
 335                                const struct nf_conn *conntrack)
 336 {
 337         enum tcp_conntrack state;
 338
 339         read_lock_bh(&tcp_lock);
 340         state = conntrack->proto.tcp.state;
 341         read_unlock_bh(&tcp_lock);
 342
 343         return seq_printf(s, "%s ", tcp_conntrack_names[state]);
 344 }
 345
 346 static unsigned int get_conntrack_index(const struct tcphdr *tcph)
 347 {
 348         if (tcph->rst) return TCP_RST_SET;
 349         else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET);
 350         else if (tcph->fin) return TCP_FIN_SET;
 351         else if (tcph->ack) return TCP_ACK_SET;
 352         else return TCP_NONE_SET;
 353 }
 354
 355 /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering
 356    in IP Filter' by Guido van Rooij.
 357
 358    http://www.nluug.nl/events/sane2000/papers.html
 359    http://www.iae.nl/users/guido/papers/tcp_filtering.ps.gz
 360
 361    The boundaries and the conditions are changed according to RFC793:
 362    the packet must intersect the window (i.e. segments may be
 363    after the right or before the left edge) and thus receivers may ACK
 364    segments after the right edge of the window.
 365
 366         td_maxend = max(sack + max(win,1)) seen in reply packets
 367         td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets
 368         td_maxwin += seq + len - sender.td_maxend
 369                         if seq + len > sender.td_maxend
 370         td_end    = max(seq + len) seen in sent packets
 371
 372    I.   Upper bound for valid data:     seq <= sender.td_maxend
 373    II.  Lower bound for valid data:     seq + len >= sender.td_end - receiver.td_maxwin
 374    III. Upper bound for valid ack:      sack <= receiver.td_end
 375    IV.  Lower bound for valid ack:      ack >= receiver.td_end - MAXACKWINDOW
 376
 377    where sack is the highest right edge of sack block found in the packet.
 378
 379    The upper bound limit for a valid ack is not ignored -
 380    we doesn't have to deal with fragments.
 381 */
 382
 383 static inline __u32 segment_seq_plus_len(__u32 seq,
 384                                          size_t len,
 385                                          unsigned int dataoff,
 386                                          struct tcphdr *tcph)
 387 {
 388         /* XXX Should I use payload length field in IP/IPv6 header ?
 389          * - YK */
 390         return (seq + len - dataoff - tcph->doff*4
 391                 + (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0));
 392 }
 393
 394 /* Fixme: what about big packets? */
 395 #define MAXACKWINCONST                  66000
 396 #define MAXACKWINDOW(sender)                                            \
 397         ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin     \
 398                                               : MAXACKWINCONST)
 399
 400 /*
 401  * Simplified tcp_parse_options routine from tcp_input.c
 402  */
 403 static void tcp_options(const struct sk_buff *skb,
 404                         unsigned int dataoff,
 405                         struct tcphdr *tcph,
 406                         struct ip_ct_tcp_state *state)
 407 {
 408         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
 409         unsigned char *ptr;
 410         int length = (tcph->doff*4) - sizeof(struct tcphdr);
 411
 412         if (!length)
 413                 return;
 414
 415         ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr),
 416                                  length, buff);
 417         BUG_ON(ptr == NULL);
 418
 419         state->td_scale =
 420         state->flags = 0;
 421
 422         while (length > 0) {
 423                 int opcode=*ptr++;
 424                 int opsize;
 425
 426                 switch (opcode) {
 427                 case TCPOPT_EOL:
 428                         return;
 429                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 430                         length--;
 431                         continue;
 432                 default:
 433                         opsize=*ptr++;
 434                         if (opsize < 2) /* "silly options" */
 435                                 return;
 436                         if (opsize > length)
 437                                 break;  /* don't parse partial options */
 438
 439                         if (opcode == TCPOPT_SACK_PERM
 440                             && opsize == TCPOLEN_SACK_PERM)
 441                                 state->flags |= IP_CT_TCP_FLAG_SACK_PERM;
 442                         else if (opcode == TCPOPT_WINDOW
 443                                  && opsize == TCPOLEN_WINDOW) {
 444                                 state->td_scale = *(u_int8_t *)ptr;
 445
 446                                 if (state->td_scale > 14) {
 447                                         /* See RFC1323 */
 448                                         state->td_scale = 14;
 449                                 }
 450                                 state->flags |=
 451                                         IP_CT_TCP_FLAG_WINDOW_SCALE;
 452                         }
 453                         ptr += opsize - 2;
 454                         length -= opsize;
 455                 }
 456         }
 457 }
 458
 459 static void tcp_sack(const struct sk_buff *skb, unsigned int dataoff,
 460                      struct tcphdr *tcph, __u32 *sack)
 461 {
 462         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
 463         unsigned char *ptr;
 464         int length = (tcph->doff*4) - sizeof(struct tcphdr);
 465         __u32 tmp;
 466
 467         if (!length)
 468                 return;
 469
 470         ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr),
 471                                  length, buff);
 472         BUG_ON(ptr == NULL);
 473
 474         /* Fast path for timestamp-only option */
 475         if (length == TCPOLEN_TSTAMP_ALIGNED*4
 476             && *(__u32 *)ptr ==
 477                 __constant_ntohl((TCPOPT_NOP << 24)
 478                                  | (TCPOPT_NOP << 16)
 479                                  | (TCPOPT_TIMESTAMP << 8)
 480                                  | TCPOLEN_TIMESTAMP))
 481                 return;
 482
 483         while (length > 0) {
 484                 int opcode = *ptr++;
 485                 int opsize, i;
 486
 487                 switch (opcode) {
 488                 case TCPOPT_EOL:
 489                         return;
 490                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 491                         length--;
 492                         continue;
 493                 default:
 494                         opsize = *ptr++;
 495                         if (opsize < 2) /* "silly options" */
 496                                 return;
 497                         if (opsize > length)
 498                                 break;  /* don't parse partial options */
 499
 500                         if (opcode == TCPOPT_SACK
 501                             && opsize >= (TCPOLEN_SACK_BASE
 502                                           + TCPOLEN_SACK_PERBLOCK)
 503                             && !((opsize - TCPOLEN_SACK_BASE)
 504                                  % TCPOLEN_SACK_PERBLOCK)) {
 505                                 for (i = 0;
 506                                      i < (opsize - TCPOLEN_SACK_BASE);
 507                                      i += TCPOLEN_SACK_PERBLOCK) {
 508                                         memcpy(&tmp, (__u32 *)(ptr + i) + 1,
 509                                                sizeof(__u32));
 510                                         tmp = ntohl(tmp);
 511
 512                                         if (after(tmp, *sack))
 513                                                 *sack = tmp;
 514                                 }
 515                                 return;
 516                         }
 517                         ptr += opsize - 2;
 518                         length -= opsize;
 519                 }
 520         }
 521 }
 522
 523 static int tcp_in_window(struct ip_ct_tcp *state,
 524                          enum ip_conntrack_dir dir,
 525                          unsigned int index,
 526                          const struct sk_buff *skb,
 527                          unsigned int dataoff,
 528                          struct tcphdr *tcph,
 529                          int pf)
 530 {
 531         struct ip_ct_tcp_state *sender = &state->seen[dir];
 532         struct ip_ct_tcp_state *receiver = &state->seen[!dir];
 533         __u32 seq, ack, sack, end, win, swin;
 534         int res;
 535
 536         /*
 537          * Get the required data from the packet.
 538          */
 539         seq = ntohl(tcph->seq);
 540         ack = sack = ntohl(tcph->ack_seq);
 541         win = ntohs(tcph->window);
 542         end = segment_seq_plus_len(seq, skb->len, dataoff, tcph);
 543
 544         if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
 545                 tcp_sack(skb, dataoff, tcph, &sack);
 546
 547         DEBUGP("tcp_in_window: START\n");
 548         DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 549                "seq=%u ack=%u sack=%u win=%u end=%u\n",
 550                 NIPQUAD(iph->saddr), ntohs(tcph->source),
 551                 NIPQUAD(iph->daddr), ntohs(tcph->dest),
 552                 seq, ack, sack, win, end);
 553         DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
 554                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 555                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 556                 sender->td_scale,
 557                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 558                 receiver->td_scale);
 559
 560         if (sender->td_end == 0) {
 561                 /*
 562                  * Initialize sender data.
 563                  */
 564                 if (tcph->syn && tcph->ack) {
 565                         /*
 566                          * Outgoing SYN-ACK in reply to a SYN.
 567                          */
 568                         sender->td_end =
 569                         sender->td_maxend = end;
 570                         sender->td_maxwin = (win == 0 ? 1 : win);
 571
 572                         tcp_options(skb, dataoff, tcph, sender);
 573                         /*
 574                          * RFC 1323:
 575                          * Both sides must send the Window Scale option
 576                          * to enable window scaling in either direction.
 577                          */
 578                         if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE
 579                               && receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE))
 580                                 sender->td_scale =
 581                                 receiver->td_scale = 0;
 582                 } else {
 583                         /*
 584                          * We are in the middle of a connection,
 585                          * its history is lost for us.
 586                          * Let's try to use the data from the packet.
 587                          */
 588                         sender->td_end = end;
 589                         sender->td_maxwin = (win == 0 ? 1 : win);
 590                         sender->td_maxend = end + sender->td_maxwin;
 591                 }
 592         } else if (((state->state == TCP_CONNTRACK_SYN_SENT
 593                      && dir == IP_CT_DIR_ORIGINAL)
 594                    || (state->state == TCP_CONNTRACK_SYN_RECV
 595                      && dir == IP_CT_DIR_REPLY))
 596                    && after(end, sender->td_end)) {
 597                 /*
 598                  * RFC 793: "if a TCP is reinitialized ... then it need
 599                  * not wait at all; it must only be sure to use sequence
 600                  * numbers larger than those recently used."
 601                  */
 602                 sender->td_end =
 603                 sender->td_maxend = end;
 604                 sender->td_maxwin = (win == 0 ? 1 : win);
 605
 606                 tcp_options(skb, dataoff, tcph, sender);
 607         }
 608
 609         if (!(tcph->ack)) {
 610                 /*
 611                  * If there is no ACK, just pretend it was set and OK.
 612                  */
 613                 ack = sack = receiver->td_end;
 614         } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
 615                     (TCP_FLAG_ACK|TCP_FLAG_RST))
 616                    && (ack == 0)) {
 617                 /*
 618                  * Broken TCP stacks, that set ACK in RST packets as well
 619                  * with zero ack value.
 620                  */
 621                 ack = sack = receiver->td_end;
 622         }
 623
 624         if (seq == end
 625             && (!tcph->rst
 626                 || (seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)))
 627                 /*
 628                  * Packets contains no data: we assume it is valid
 629                  * and check the ack value only.
 630                  * However RST segments are always validated by their
 631                  * SEQ number, except when seq == 0 (reset sent answering
 632                  * SYN.
 633                  */
 634                 seq = end = sender->td_end;
 635
 636         DEBUGP("tcp_in_window: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 637                "seq=%u ack=%u sack =%u win=%u end=%u\n",
 638                 NIPQUAD(iph->saddr), ntohs(tcph->source),
 639                 NIPQUAD(iph->daddr), ntohs(tcph->dest),
 640                 seq, ack, sack, win, end);
 641         DEBUGP("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
 642                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 643                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 644                 sender->td_scale,
 645                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 646                 receiver->td_scale);
 647
 648         DEBUGP("tcp_in_window: I=%i II=%i III=%i IV=%i\n",
 649                 before(seq, sender->td_maxend + 1),
 650                 after(end, sender->td_end - receiver->td_maxwin - 1),
 651                 before(sack, receiver->td_end + 1),
 652                 after(ack, receiver->td_end - MAXACKWINDOW(sender)));
 653
 654         if (sender->loose || receiver->loose ||
 655             (before(seq, sender->td_maxend + 1) &&
 656              after(end, sender->td_end - receiver->td_maxwin - 1) &&
 657              before(sack, receiver->td_end + 1) &&
 658              after(ack, receiver->td_end - MAXACKWINDOW(sender)))) {
 659                 /*
 660                  * Take into account window scaling (RFC 1323).
 661                  */
 662                 if (!tcph->syn)
 663                         win <<= sender->td_scale;
 664
 665                 /*
 666                  * Update sender data.
 667                  */
 668                 swin = win + (sack - ack);
 669                 if (sender->td_maxwin < swin)
 670                         sender->td_maxwin = swin;
 671                 if (after(end, sender->td_end))
 672                         sender->td_end = end;
 673                 /*
 674                  * Update receiver data.
 675                  */
 676                 if (after(end, sender->td_maxend))
 677                         receiver->td_maxwin += end - sender->td_maxend;
 678                 if (after(sack + win, receiver->td_maxend - 1)) {
 679                         receiver->td_maxend = sack + win;
 680                         if (win == 0)
 681                                 receiver->td_maxend++;
 682                 }
 683
 684                 /*
 685                  * Check retransmissions.
 686                  */
 687                 if (index == TCP_ACK_SET) {
 688                         if (state->last_dir == dir
 689                             && state->last_seq == seq
 690                             && state->last_ack == ack
 691                             && state->last_end == end)
 692                                 state->retrans++;
 693                         else {
 694                                 state->last_dir = dir;
 695                                 state->last_seq = seq;
 696                                 state->last_ack = ack;
 697                                 state->last_end = end;
 698                                 state->retrans = 0;
 699                         }
 700                 }
 701                 /*
 702                  * Close the window of disabled window tracking :-)
 703                  */
 704                 if (sender->loose)
 705                         sender->loose--;
 706
 707                 res = 1;
 708         } else {
 709                 if (LOG_INVALID(IPPROTO_TCP))
 710                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 711                         "nf_ct_tcp: %s ",
 712                         before(seq, sender->td_maxend + 1) ?
 713                         after(end, sender->td_end - receiver->td_maxwin - 1) ?
 714                         before(sack, receiver->td_end + 1) ?
 715                         after(ack, receiver->td_end - MAXACKWINDOW(sender)) ? "BUG"
 716                         : "ACK is under the lower bound (possible overly delayed ACK)"
 717                         : "ACK is over the upper bound (ACKed data not seen yet)"
 718                         : "SEQ is under the lower bound (already ACKed data retransmitted)"
 719                         : "SEQ is over the upper bound (over the window of the receiver)");
 720
 721                 res = nf_ct_tcp_be_liberal;
 722         }
 723
 724         DEBUGP("tcp_in_window: res=%i sender end=%u maxend=%u maxwin=%u "
 725                "receiver end=%u maxend=%u maxwin=%u\n",
 726                 res, sender->td_end, sender->td_maxend, sender->td_maxwin,
 727                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin);
 728
 729         return res;
 730 }
 731
 732 #ifdef CONFIG_IP_NF_NAT_NEEDED
 733 /* Update sender->td_end after NAT successfully mangled the packet */
 734 /* Caller must linearize skb at tcp header. */
 735 void nf_conntrack_tcp_update(struct sk_buff *skb,
 736                              unsigned int dataoff,
 737                              struct nf_conn *conntrack,
 738                              int dir)
 739 {
 740         struct tcphdr *tcph = (void *)skb->data + dataoff;
 741         __u32 end;
 742 #ifdef DEBUGP_VARS
 743         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[dir];
 744         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[!dir];
 745 #endif
 746
 747         end = segment_seq_plus_len(ntohl(tcph->seq), skb->len, dataoff, tcph);
 748
 749         write_lock_bh(&tcp_lock);
 750         /*
 751          * We have to worry for the ack in the reply packet only...
 752          */
 753         if (after(end, conntrack->proto.tcp.seen[dir].td_end))
 754                 conntrack->proto.tcp.seen[dir].td_end = end;
 755         conntrack->proto.tcp.last_end = end;
 756         write_unlock_bh(&tcp_lock);
 757         DEBUGP("tcp_update: sender end=%u maxend=%u maxwin=%u scale=%i "
 758                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 759                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 760                 sender->td_scale,
 761                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 762                 receiver->td_scale);
 763 }
 764
 765 #endif
 766
 767 #define TH_FIN  0x01
 768 #define TH_SYN  0x02
 769 #define TH_RST  0x04
 770 #define TH_PUSH 0x08
 771 #define TH_ACK  0x10
 772 #define TH_URG  0x20
 773 #define TH_ECE  0x40
 774 #define TH_CWR  0x80
 775
 776 /* table of valid flag combinations - ECE and CWR are always valid */
 777 static u8 tcp_valid_flags[(TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG) + 1] =
 778 {
 779         [TH_SYN]                        = 1,
 780         [TH_SYN|TH_ACK]                 = 1,
 781         [TH_SYN|TH_PUSH]                = 1,
 782         [TH_SYN|TH_ACK|TH_PUSH]         = 1,
 783         [TH_RST]                        = 1,
 784         [TH_RST|TH_ACK]                 = 1,
 785         [TH_RST|TH_ACK|TH_PUSH]         = 1,
 786         [TH_FIN|TH_ACK]                 = 1,
 787         [TH_ACK]                        = 1,
 788         [TH_ACK|TH_PUSH]                = 1,
 789         [TH_ACK|TH_URG]                 = 1,
 790         [TH_ACK|TH_URG|TH_PUSH]         = 1,
 791         [TH_FIN|TH_ACK|TH_PUSH]         = 1,
 792         [TH_FIN|TH_ACK|TH_URG]          = 1,
 793         [TH_FIN|TH_ACK|TH_URG|TH_PUSH]  = 1,
 794 };
 795
 796 /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c.  */
 797 static int tcp_error(struct sk_buff *skb,
 798                      unsigned int dataoff,
 799                      enum ip_conntrack_info *ctinfo,
 800                      int pf,
 801                      unsigned int hooknum)
 802 {
 803         struct tcphdr _tcph, *th;
 804         unsigned int tcplen = skb->len - dataoff;
 805         u_int8_t tcpflags;
 806
 807         /* Smaller that minimal TCP header? */
 808         th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
 809         if (th == NULL) {
 810                 if (LOG_INVALID(IPPROTO_TCP))
 811                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 812                                 "nf_ct_tcp: short packet ");
 813                 return -NF_ACCEPT;
 814         }
 815
 816         /* Not whole TCP header or malformed packet */
 817         if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {
 818                 if (LOG_INVALID(IPPROTO_TCP))
 819                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 820                                 "nf_ct_tcp: truncated/malformed packet ");
 821                 return -NF_ACCEPT;
 822         }
 823
 824         /* Checksum invalid? Ignore.
 825          * We skip checking packets on the outgoing path
 826          * because the semantic of CHECKSUM_HW is different there
 827          * and moreover root might send raw packets.
 828          */
 829         /* FIXME: Source route IP option packets --RR */
 830         if (nf_conntrack_checksum &&
 831             ((pf == PF_INET && hooknum == NF_IP_PRE_ROUTING) ||
 832              (pf == PF_INET6 && hooknum == NF_IP6_PRE_ROUTING)) &&
 833             nf_checksum(skb, hooknum, dataoff, IPPROTO_TCP, pf)) {
 834                 if (LOG_INVALID(IPPROTO_TCP))
 835                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 836                                   "nf_ct_tcp: bad TCP checksum ");
 837                 return -NF_ACCEPT;
 838         }
 839
 840         /* Check TCP flags. */
 841         tcpflags = (((u_int8_t *)th)[13] & ~(TH_ECE|TH_CWR));
 842         if (!tcp_valid_flags[tcpflags]) {
 843                 if (LOG_INVALID(IPPROTO_TCP))
 844                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 845                                   "nf_ct_tcp: invalid TCP flag combination ");
 846                 return -NF_ACCEPT;
 847         }
 848
 849         return NF_ACCEPT;
 850 }
 851
 852 /* Returns verdict for packet, or -1 for invalid. */
 853 static int tcp_packet(struct nf_conn *conntrack,
 854                       const struct sk_buff *skb,
 855                       unsigned int dataoff,
 856                       enum ip_conntrack_info ctinfo,
 857                       int pf,
 858                       unsigned int hooknum)
 859 {
 860         enum tcp_conntrack new_state, old_state;
 861         enum ip_conntrack_dir dir;
 862         struct tcphdr *th, _tcph;
 863         unsigned long timeout;
 864         unsigned int index;
 865
 866         th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
 867         BUG_ON(th == NULL);
 868
 869         write_lock_bh(&tcp_lock);
 870         old_state = conntrack->proto.tcp.state;
 871         dir = CTINFO2DIR(ctinfo);
 872         index = get_conntrack_index(th);
 873         new_state = tcp_conntracks[dir][index][old_state];
 874
 875         switch (new_state) {
 876         case TCP_CONNTRACK_IGNORE:
 877                 /* Ignored packets:
 878                  *
 879                  * a) SYN in ORIGINAL
 880                  * b) SYN/ACK in REPLY
 881                  * c) ACK in reply direction after initial SYN in original.
 882                  */
 883                 if (index == TCP_SYNACK_SET
 884                     && conntrack->proto.tcp.last_index == TCP_SYN_SET
 885                     && conntrack->proto.tcp.last_dir != dir
 886                     && ntohl(th->ack_seq) ==
 887                              conntrack->proto.tcp.last_end) {
 888                         /* This SYN/ACK acknowledges a SYN that we earlier
 889                          * ignored as invalid. This means that the client and
 890                          * the server are both in sync, while the firewall is
 891                          * not. We kill this session and block the SYN/ACK so
 892                          * that the client cannot but retransmit its SYN and
 893                          * thus initiate a clean new session.
 894                          */
 895                         write_unlock_bh(&tcp_lock);
 896                         if (LOG_INVALID(IPPROTO_TCP))
 897                                 nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 898                                           "nf_ct_tcp: killing out of sync session ");
 899                         if (del_timer(&conntrack->timeout))
 900                                 conntrack->timeout.function((unsigned long)
 901                                                             conntrack);
 902                         return -NF_DROP;
 903                 }
 904                 conntrack->proto.tcp.last_index = index;
 905                 conntrack->proto.tcp.last_dir = dir;
 906                 conntrack->proto.tcp.last_seq = ntohl(th->seq);
 907                 conntrack->proto.tcp.last_end =
 908                     segment_seq_plus_len(ntohl(th->seq), skb->len, dataoff, th);
 909
 910                 write_unlock_bh(&tcp_lock);
 911                 if (LOG_INVALID(IPPROTO_TCP))
 912                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 913                                   "nf_ct_tcp: invalid packed ignored ");
 914                 return NF_ACCEPT;
 915         case TCP_CONNTRACK_MAX:
 916                 /* Invalid packet */
 917                 DEBUGP("nf_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
 918                        dir, get_conntrack_index(th),
 919                        old_state);
 920                 write_unlock_bh(&tcp_lock);
 921                 if (LOG_INVALID(IPPROTO_TCP))
 922                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 923                                   "nf_ct_tcp: invalid state ");
 924                 return -NF_ACCEPT;
 925         case TCP_CONNTRACK_SYN_SENT:
 926                 if (old_state < TCP_CONNTRACK_TIME_WAIT)
 927                         break;
 928                 if ((conntrack->proto.tcp.seen[dir].flags &
 929                         IP_CT_TCP_FLAG_CLOSE_INIT)
 930                     || after(ntohl(th->seq),
 931                              conntrack->proto.tcp.seen[dir].td_end)) {
 932                         /* Attempt to reopen a closed connection.
 933                         * Delete this connection and look up again. */
 934                         write_unlock_bh(&tcp_lock);
 935                         if (del_timer(&conntrack->timeout))
 936                                 conntrack->timeout.function((unsigned long)
 937                                                             conntrack);
 938                         return -NF_REPEAT;
 939                 } else {
 940                         write_unlock_bh(&tcp_lock);
 941                         if (LOG_INVALID(IPPROTO_TCP))
 942                                 nf_log_packet(pf, 0, skb, NULL, NULL,
 943                                               NULL, "nf_ct_tcp: invalid SYN");
 944                         return -NF_ACCEPT;
 945                 }
 946         case TCP_CONNTRACK_CLOSE:
 947                 if (index == TCP_RST_SET
 948                     && ((test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)
 949                          && conntrack->proto.tcp.last_index == TCP_SYN_SET)
 950                         || (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
 951                             && conntrack->proto.tcp.last_index == TCP_ACK_SET))
 952                     && ntohl(th->ack_seq) == conntrack->proto.tcp.last_end) {
 953                         /* RST sent to invalid SYN or ACK we had let through
 954                          * at a) and c) above:
 955                          *
 956                          * a) SYN was in window then
 957                          * c) we hold a half-open connection.
 958                          *
 959                          * Delete our connection entry.
 960                          * We skip window checking, because packet might ACK
 961                          * segments we ignored. */
 962                         goto in_window;
 963                 }
 964                 /* Just fall through */
 965         default:
 966                 /* Keep compilers happy. */
 967                 break;
 968         }
 969
 970         if (!tcp_in_window(&conntrack->proto.tcp, dir, index,
 971                            skb, dataoff, th, pf)) {
 972                 write_unlock_bh(&tcp_lock);
 973                 return -NF_ACCEPT;
 974         }
 975      in_window:
 976         /* From now on we have got in-window packets */
 977         conntrack->proto.tcp.last_index = index;
 978
 979         DEBUGP("tcp_conntracks: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 980                "syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
 981                 NIPQUAD(iph->saddr), ntohs(th->source),
 982                 NIPQUAD(iph->daddr), ntohs(th->dest),
 983                 (th->syn ? 1 : 0), (th->ack ? 1 : 0),
 984                 (th->fin ? 1 : 0), (th->rst ? 1 : 0),
 985                 old_state, new_state);
 986
 987         conntrack->proto.tcp.state = new_state;
 988         if (old_state != new_state
 989             && (new_state == TCP_CONNTRACK_FIN_WAIT
 990                 || new_state == TCP_CONNTRACK_CLOSE))
 991                 conntrack->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
 992         timeout = conntrack->proto.tcp.retrans >= nf_ct_tcp_max_retrans
 993                   && *tcp_timeouts[new_state] > nf_ct_tcp_timeout_max_retrans
 994                   ? nf_ct_tcp_timeout_max_retrans : *tcp_timeouts[new_state];
 995         write_unlock_bh(&tcp_lock);
 996
 997         nf_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
 998         if (new_state != old_state)
 999                 nf_conntrack_event_cache(IPCT_PROTOINFO, skb);
1000
1001         if (!test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
1002                 /* If only reply is a RST, we can consider ourselves not to
1003                    have an established connection: this is a fairly common
1004                    problem case, so we can delete the conntrack
1005                    immediately.  --RR */
1006                 if (th->rst) {
1007                         if (del_timer(&conntrack->timeout))
1008                                 conntrack->timeout.function((unsigned long)
1009                                                             conntrack);
1010                         return NF_ACCEPT;
1011                 }
1012         } else if (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
1013                    && (old_state == TCP_CONNTRACK_SYN_RECV
1014                        || old_state == TCP_CONNTRACK_ESTABLISHED)
1015                    && new_state == TCP_CONNTRACK_ESTABLISHED) {
1016                 /* Set ASSURED if we see see valid ack in ESTABLISHED
1017                    after SYN_RECV or a valid answer for a picked up
1018                    connection. */
1019                 set_bit(IPS_ASSURED_BIT, &conntrack->status);
1020                 nf_conntrack_event_cache(IPCT_STATUS, skb);
1021         }
1022         nf_ct_refresh_acct(conntrack, ctinfo, skb, timeout);
1023
1024         return NF_ACCEPT;
1025 }
1026
1027 /* Called when a new connection for this protocol found. */
1028 static int tcp_new(struct nf_conn *conntrack,
1029                    const struct sk_buff *skb,
1030                    unsigned int dataoff)
1031 {
1032         enum tcp_conntrack new_state;
1033         struct tcphdr *th, _tcph;
1034 #ifdef DEBUGP_VARS
1035         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[0];
1036         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[1];
1037 #endif
1038
1039         th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
1040         BUG_ON(th == NULL);
1041
1042         /* Don't need lock here: this conntrack not in circulation yet */
1043         new_state
1044                 = tcp_conntracks[0][get_conntrack_index(th)]
1045                 [TCP_CONNTRACK_NONE];
1046
1047         /* Invalid: delete conntrack */
1048         if (new_state >= TCP_CONNTRACK_MAX) {
1049                 DEBUGP("nf_ct_tcp: invalid new deleting.\n");
1050                 return 0;
1051         }
1052
1053         if (new_state == TCP_CONNTRACK_SYN_SENT) {
1054                 /* SYN packet */
1055                 conntrack->proto.tcp.seen[0].td_end =
1056                         segment_seq_plus_len(ntohl(th->seq), skb->len,
1057                                              dataoff, th);
1058                 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1059                 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1060                         conntrack->proto.tcp.seen[0].td_maxwin = 1;
1061                 conntrack->proto.tcp.seen[0].td_maxend =
1062                         conntrack->proto.tcp.seen[0].td_end;
1063
1064                 tcp_options(skb, dataoff, th, &conntrack->proto.tcp.seen[0]);
1065                 conntrack->proto.tcp.seen[1].flags = 0;
1066                 conntrack->proto.tcp.seen[0].loose =
1067                 conntrack->proto.tcp.seen[1].loose = 0;
1068         } else if (nf_ct_tcp_loose == 0) {
1069                 /* Don't try to pick up connections. */
1070                 return 0;
1071         } else {
1072                 /*
1073                  * We are in the middle of a connection,
1074                  * its history is lost for us.
1075                  * Let's try to use the data from the packet.
1076                  */
1077                 conntrack->proto.tcp.seen[0].td_end =
1078                         segment_seq_plus_len(ntohl(th->seq), skb->len,
1079                                              dataoff, th);
1080                 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1081                 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1082                         conntrack->proto.tcp.seen[0].td_maxwin = 1;
1083                 conntrack->proto.tcp.seen[0].td_maxend =
1084                         conntrack->proto.tcp.seen[0].td_end +
1085                         conntrack->proto.tcp.seen[0].td_maxwin;
1086                 conntrack->proto.tcp.seen[0].td_scale = 0;
1087
1088                 /* We assume SACK. Should we assume window scaling too? */
1089                 conntrack->proto.tcp.seen[0].flags =
1090                 conntrack->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM;
1091                 conntrack->proto.tcp.seen[0].loose =
1092                 conntrack->proto.tcp.seen[1].loose = nf_ct_tcp_loose;
1093         }
1094
1095         conntrack->proto.tcp.seen[1].td_end = 0;
1096         conntrack->proto.tcp.seen[1].td_maxend = 0;
1097         conntrack->proto.tcp.seen[1].td_maxwin = 1;
1098         conntrack->proto.tcp.seen[1].td_scale = 0;
1099
1100         /* tcp_packet will set them */
1101         conntrack->proto.tcp.state = TCP_CONNTRACK_NONE;
1102         conntrack->proto.tcp.last_index = TCP_NONE_SET;
1103
1104         DEBUGP("tcp_new: sender end=%u maxend=%u maxwin=%u scale=%i "
1105                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
1106                 sender->td_end, sender->td_maxend, sender->td_maxwin,
1107                 sender->td_scale,
1108                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
1109                 receiver->td_scale);
1110         return 1;
1111 }
1112
1113 #if defined(CONFIG_NF_CT_NETLINK) || \
1114     defined(CONFIG_NF_CT_NETLINK_MODULE)
1115
1116 #include <linux/netfilter/nfnetlink.h>
1117 #include <linux/netfilter/nfnetlink_conntrack.h>
1118
1119 static int tcp_to_nfattr(struct sk_buff *skb, struct nfattr *nfa,
1120                          const struct nf_conn *ct)
1121 {
1122         struct nfattr *nest_parms;
1123
1124         read_lock_bh(&tcp_lock);
1125         nest_parms = NFA_NEST(skb, CTA_PROTOINFO_TCP);
1126         NFA_PUT(skb, CTA_PROTOINFO_TCP_STATE, sizeof(u_int8_t),
1127                 &ct->proto.tcp.state);
1128         read_unlock_bh(&tcp_lock);
1129
1130         NFA_NEST_END(skb, nest_parms);
1131
1132         return 0;
1133
1134 nfattr_failure:
1135         read_unlock_bh(&tcp_lock);
1136         return -1;
1137 }
1138
1139 static const size_t cta_min_tcp[CTA_PROTOINFO_TCP_MAX] = {
1140         [CTA_PROTOINFO_TCP_STATE-1]     = sizeof(u_int8_t),
1141 };
1142
1143 static int nfattr_to_tcp(struct nfattr *cda[], struct nf_conn *ct)
1144 {
1145         struct nfattr *attr = cda[CTA_PROTOINFO_TCP-1];
1146         struct nfattr *tb[CTA_PROTOINFO_TCP_MAX];
1147
1148         /* updates could not contain anything about the private
1149          * protocol info, in that case skip the parsing */
1150         if (!attr)
1151                 return 0;
1152
1153         nfattr_parse_nested(tb, CTA_PROTOINFO_TCP_MAX, attr);
1154
1155         if (nfattr_bad_size(tb, CTA_PROTOINFO_TCP_MAX, cta_min_tcp))
1156                 return -EINVAL;
1157
1158         if (!tb[CTA_PROTOINFO_TCP_STATE-1])
1159                 return -EINVAL;
1160
1161         write_lock_bh(&tcp_lock);
1162         ct->proto.tcp.state =
1163                 *(u_int8_t *)NFA_DATA(tb[CTA_PROTOINFO_TCP_STATE-1]);
1164         write_unlock_bh(&tcp_lock);
1165
1166         return 0;
1167 }
1168 #endif
1169
1170 struct nf_conntrack_protocol nf_conntrack_protocol_tcp4 =
1171 {
1172         .l3proto                = PF_INET,
1173         .proto                  = IPPROTO_TCP,
1174         .name                   = "tcp",
1175         .pkt_to_tuple           = tcp_pkt_to_tuple,
1176         .invert_tuple           = tcp_invert_tuple,
1177         .print_tuple            = tcp_print_tuple,
1178         .print_conntrack        = tcp_print_conntrack,
1179         .packet                 = tcp_packet,
1180         .new                    = tcp_new,
1181         .error                  = tcp_error,
1182 #if defined(CONFIG_NF_CT_NETLINK) || \
1183     defined(CONFIG_NF_CT_NETLINK_MODULE)
1184         .to_nfattr              = tcp_to_nfattr,
1185         .from_nfattr            = nfattr_to_tcp,
1186         .tuple_to_nfattr        = nf_ct_port_tuple_to_nfattr,
1187         .nfattr_to_tuple        = nf_ct_port_nfattr_to_tuple,
1188 #endif
1189 };
1190
1191 struct nf_conntrack_protocol nf_conntrack_protocol_tcp6 =
1192 {
1193         .l3proto                = PF_INET6,
1194         .proto                  = IPPROTO_TCP,
1195         .name                   = "tcp",
1196         .pkt_to_tuple           = tcp_pkt_to_tuple,
1197         .invert_tuple           = tcp_invert_tuple,
1198         .print_tuple            = tcp_print_tuple,
1199         .print_conntrack        = tcp_print_conntrack,
1200         .packet                 = tcp_packet,
1201         .new                    = tcp_new,
1202         .error                  = tcp_error,
1203 #if defined(CONFIG_NF_CT_NETLINK) || \
1204     defined(CONFIG_NF_CT_NETLINK_MODULE)
1205         .to_nfattr              = tcp_to_nfattr,
1206         .from_nfattr            = nfattr_to_tcp,
1207         .tuple_to_nfattr        = nf_ct_port_tuple_to_nfattr,
1208         .nfattr_to_tuple        = nf_ct_port_nfattr_to_tuple,
1209 #endif
1210 };
1211
1212 EXPORT_SYMBOL(nf_conntrack_protocol_tcp4);
1213 EXPORT_SYMBOL(nf_conntrack_protocol_tcp6);