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 __read_mostly = 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 __read_mostly = 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 __read_mostly = 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 __read_mostly =      2 MINS;
  96 unsigned int nf_ct_tcp_timeout_syn_recv __read_mostly =     60 SECS;
  97 unsigned int nf_ct_tcp_timeout_established __read_mostly =   5 DAYS;
  98 unsigned int nf_ct_tcp_timeout_fin_wait __read_mostly =      2 MINS;
  99 unsigned int nf_ct_tcp_timeout_close_wait __read_mostly =   60 SECS;
 100 unsigned int nf_ct_tcp_timeout_last_ack __read_mostly =     30 SECS;
 101 unsigned int nf_ct_tcp_timeout_time_wait __read_mostly =     2 MINS;
 102 unsigned int nf_ct_tcp_timeout_close __read_mostly =        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 __read_mostly =   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->last_win == win)
 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->last_win = win;
 700                                 state->retrans = 0;
 701                         }
 702                 }
 703                 /*
 704                  * Close the window of disabled window tracking :-)
 705                  */
 706                 if (sender->loose)
 707                         sender->loose--;
 708
 709                 res = 1;
 710         } else {
 711                 if (LOG_INVALID(IPPROTO_TCP))
 712                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 713                         "nf_ct_tcp: %s ",
 714                         before(seq, sender->td_maxend + 1) ?
 715                         after(end, sender->td_end - receiver->td_maxwin - 1) ?
 716                         before(sack, receiver->td_end + 1) ?
 717                         after(ack, receiver->td_end - MAXACKWINDOW(sender)) ? "BUG"
 718                         : "ACK is under the lower bound (possible overly delayed ACK)"
 719                         : "ACK is over the upper bound (ACKed data not seen yet)"
 720                         : "SEQ is under the lower bound (already ACKed data retransmitted)"
 721                         : "SEQ is over the upper bound (over the window of the receiver)");
 722
 723                 res = nf_ct_tcp_be_liberal;
 724         }
 725
 726         DEBUGP("tcp_in_window: res=%i sender end=%u maxend=%u maxwin=%u "
 727                "receiver end=%u maxend=%u maxwin=%u\n",
 728                 res, sender->td_end, sender->td_maxend, sender->td_maxwin,
 729                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin);
 730
 731         return res;
 732 }
 733
 734 #ifdef CONFIG_IP_NF_NAT_NEEDED
 735 /* Update sender->td_end after NAT successfully mangled the packet */
 736 /* Caller must linearize skb at tcp header. */
 737 void nf_conntrack_tcp_update(struct sk_buff *skb,
 738                              unsigned int dataoff,
 739                              struct nf_conn *conntrack,
 740                              int dir)
 741 {
 742         struct tcphdr *tcph = (void *)skb->data + dataoff;
 743         __u32 end;
 744 #ifdef DEBUGP_VARS
 745         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[dir];
 746         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[!dir];
 747 #endif
 748
 749         end = segment_seq_plus_len(ntohl(tcph->seq), skb->len, dataoff, tcph);
 750
 751         write_lock_bh(&tcp_lock);
 752         /*
 753          * We have to worry for the ack in the reply packet only...
 754          */
 755         if (after(end, conntrack->proto.tcp.seen[dir].td_end))
 756                 conntrack->proto.tcp.seen[dir].td_end = end;
 757         conntrack->proto.tcp.last_end = end;
 758         write_unlock_bh(&tcp_lock);
 759         DEBUGP("tcp_update: sender end=%u maxend=%u maxwin=%u scale=%i "
 760                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 761                 sender->td_end, sender->td_maxend, sender->td_maxwin,
 762                 sender->td_scale,
 763                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 764                 receiver->td_scale);
 765 }
 766
 767 #endif
 768
 769 #define TH_FIN  0x01
 770 #define TH_SYN  0x02
 771 #define TH_RST  0x04
 772 #define TH_PUSH 0x08
 773 #define TH_ACK  0x10
 774 #define TH_URG  0x20
 775 #define TH_ECE  0x40
 776 #define TH_CWR  0x80
 777
 778 /* table of valid flag combinations - ECE and CWR are always valid */
 779 static u8 tcp_valid_flags[(TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG) + 1] =
 780 {
 781         [TH_SYN]                        = 1,
 782         [TH_SYN|TH_ACK]                 = 1,
 783         [TH_SYN|TH_PUSH]                = 1,
 784         [TH_SYN|TH_ACK|TH_PUSH]         = 1,
 785         [TH_RST]                        = 1,
 786         [TH_RST|TH_ACK]                 = 1,
 787         [TH_RST|TH_ACK|TH_PUSH]         = 1,
 788         [TH_FIN|TH_ACK]                 = 1,
 789         [TH_ACK]                        = 1,
 790         [TH_ACK|TH_PUSH]                = 1,
 791         [TH_ACK|TH_URG]                 = 1,
 792         [TH_ACK|TH_URG|TH_PUSH]         = 1,
 793         [TH_FIN|TH_ACK|TH_PUSH]         = 1,
 794         [TH_FIN|TH_ACK|TH_URG]          = 1,
 795         [TH_FIN|TH_ACK|TH_URG|TH_PUSH]  = 1,
 796 };
 797
 798 /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c.  */
 799 static int tcp_error(struct sk_buff *skb,
 800                      unsigned int dataoff,
 801                      enum ip_conntrack_info *ctinfo,
 802                      int pf,
 803                      unsigned int hooknum)
 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 checksum is assumed to be correct.
 829          */
 830         /* FIXME: Source route IP option packets --RR */
 831         if (nf_conntrack_checksum &&
 832             ((pf == PF_INET && hooknum == NF_IP_PRE_ROUTING) ||
 833              (pf == PF_INET6 && hooknum == NF_IP6_PRE_ROUTING)) &&
 834             nf_checksum(skb, hooknum, dataoff, IPPROTO_TCP, pf)) {
 835                 if (LOG_INVALID(IPPROTO_TCP))
 836                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 837                                   "nf_ct_tcp: bad TCP checksum ");
 838                 return -NF_ACCEPT;
 839         }
 840
 841         /* Check TCP flags. */
 842         tcpflags = (((u_int8_t *)th)[13] & ~(TH_ECE|TH_CWR));
 843         if (!tcp_valid_flags[tcpflags]) {
 844                 if (LOG_INVALID(IPPROTO_TCP))
 845                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 846                                   "nf_ct_tcp: invalid TCP flag combination ");
 847                 return -NF_ACCEPT;
 848         }
 849
 850         return NF_ACCEPT;
 851 }
 852
 853 /* Returns verdict for packet, or -1 for invalid. */
 854 static int tcp_packet(struct nf_conn *conntrack,
 855                       const struct sk_buff *skb,
 856                       unsigned int dataoff,
 857                       enum ip_conntrack_info ctinfo,
 858                       int pf,
 859                       unsigned int hooknum)
 860 {
 861         enum tcp_conntrack new_state, old_state;
 862         enum ip_conntrack_dir dir;
 863         struct tcphdr *th, _tcph;
 864         unsigned long timeout;
 865         unsigned int index;
 866
 867         th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
 868         BUG_ON(th == NULL);
 869
 870         write_lock_bh(&tcp_lock);
 871         old_state = conntrack->proto.tcp.state;
 872         dir = CTINFO2DIR(ctinfo);
 873         index = get_conntrack_index(th);
 874         new_state = tcp_conntracks[dir][index][old_state];
 875
 876         switch (new_state) {
 877         case TCP_CONNTRACK_IGNORE:
 878                 /* Ignored packets:
 879                  *
 880                  * a) SYN in ORIGINAL
 881                  * b) SYN/ACK in REPLY
 882                  * c) ACK in reply direction after initial SYN in original.
 883                  */
 884                 if (index == TCP_SYNACK_SET
 885                     && conntrack->proto.tcp.last_index == TCP_SYN_SET
 886                     && conntrack->proto.tcp.last_dir != dir
 887                     && ntohl(th->ack_seq) ==
 888                              conntrack->proto.tcp.last_end) {
 889                         /* This SYN/ACK acknowledges a SYN that we earlier
 890                          * ignored as invalid. This means that the client and
 891                          * the server are both in sync, while the firewall is
 892                          * not. We kill this session and block the SYN/ACK so
 893                          * that the client cannot but retransmit its SYN and
 894                          * thus initiate a clean new session.
 895                          */
 896                         write_unlock_bh(&tcp_lock);
 897                         if (LOG_INVALID(IPPROTO_TCP))
 898                                 nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 899                                           "nf_ct_tcp: killing out of sync session ");
 900                         if (del_timer(&conntrack->timeout))
 901                                 conntrack->timeout.function((unsigned long)
 902                                                             conntrack);
 903                         return -NF_DROP;
 904                 }
 905                 conntrack->proto.tcp.last_index = index;
 906                 conntrack->proto.tcp.last_dir = dir;
 907                 conntrack->proto.tcp.last_seq = ntohl(th->seq);
 908                 conntrack->proto.tcp.last_end =
 909                     segment_seq_plus_len(ntohl(th->seq), skb->len, dataoff, th);
 910
 911                 write_unlock_bh(&tcp_lock);
 912                 if (LOG_INVALID(IPPROTO_TCP))
 913                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 914                                   "nf_ct_tcp: invalid packed ignored ");
 915                 return NF_ACCEPT;
 916         case TCP_CONNTRACK_MAX:
 917                 /* Invalid packet */
 918                 DEBUGP("nf_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
 919                        dir, get_conntrack_index(th),
 920                        old_state);
 921                 write_unlock_bh(&tcp_lock);
 922                 if (LOG_INVALID(IPPROTO_TCP))
 923                         nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
 924                                   "nf_ct_tcp: invalid state ");
 925                 return -NF_ACCEPT;
 926         case TCP_CONNTRACK_SYN_SENT:
 927                 if (old_state < TCP_CONNTRACK_TIME_WAIT)
 928                         break;
 929                 if ((conntrack->proto.tcp.seen[dir].flags &
 930                         IP_CT_TCP_FLAG_CLOSE_INIT)
 931                     || after(ntohl(th->seq),
 932                              conntrack->proto.tcp.seen[dir].td_end)) {
 933                         /* Attempt to reopen a closed connection.
 934                         * Delete this connection and look up again. */
 935                         write_unlock_bh(&tcp_lock);
 936                         if (del_timer(&conntrack->timeout))
 937                                 conntrack->timeout.function((unsigned long)
 938                                                             conntrack);
 939                         return -NF_REPEAT;
 940                 } else {
 941                         write_unlock_bh(&tcp_lock);
 942                         if (LOG_INVALID(IPPROTO_TCP))
 943                                 nf_log_packet(pf, 0, skb, NULL, NULL,
 944                                               NULL, "nf_ct_tcp: invalid SYN");
 945                         return -NF_ACCEPT;
 946                 }
 947         case TCP_CONNTRACK_CLOSE:
 948                 if (index == TCP_RST_SET
 949                     && ((test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)
 950                          && conntrack->proto.tcp.last_index == TCP_SYN_SET)
 951                         || (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
 952                             && conntrack->proto.tcp.last_index == TCP_ACK_SET))
 953                     && ntohl(th->ack_seq) == conntrack->proto.tcp.last_end) {
 954                         /* RST sent to invalid SYN or ACK we had let through
 955                          * at a) and c) above:
 956                          *
 957                          * a) SYN was in window then
 958                          * c) we hold a half-open connection.
 959                          *
 960                          * Delete our connection entry.
 961                          * We skip window checking, because packet might ACK
 962                          * segments we ignored. */
 963                         goto in_window;
 964                 }
 965                 /* Just fall through */
 966         default:
 967                 /* Keep compilers happy. */
 968                 break;
 969         }
 970
 971         if (!tcp_in_window(&conntrack->proto.tcp, dir, index,
 972                            skb, dataoff, th, pf)) {
 973                 write_unlock_bh(&tcp_lock);
 974                 return -NF_ACCEPT;
 975         }
 976      in_window:
 977         /* From now on we have got in-window packets */
 978         conntrack->proto.tcp.last_index = index;
 979
 980         DEBUGP("tcp_conntracks: src=%u.%u.%u.%u:%hu dst=%u.%u.%u.%u:%hu "
 981                "syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
 982                 NIPQUAD(iph->saddr), ntohs(th->source),
 983                 NIPQUAD(iph->daddr), ntohs(th->dest),
 984                 (th->syn ? 1 : 0), (th->ack ? 1 : 0),
 985                 (th->fin ? 1 : 0), (th->rst ? 1 : 0),
 986                 old_state, new_state);
 987
 988         conntrack->proto.tcp.state = new_state;
 989         if (old_state != new_state
 990             && (new_state == TCP_CONNTRACK_FIN_WAIT
 991                 || new_state == TCP_CONNTRACK_CLOSE))
 992                 conntrack->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
 993         timeout = conntrack->proto.tcp.retrans >= nf_ct_tcp_max_retrans
 994                   && *tcp_timeouts[new_state] > nf_ct_tcp_timeout_max_retrans
 995                   ? nf_ct_tcp_timeout_max_retrans : *tcp_timeouts[new_state];
 996         write_unlock_bh(&tcp_lock);
 997
 998         nf_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
 999         if (new_state != old_state)
1000                 nf_conntrack_event_cache(IPCT_PROTOINFO, skb);
1001
1002         if (!test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
1003                 /* If only reply is a RST, we can consider ourselves not to
1004                    have an established connection: this is a fairly common
1005                    problem case, so we can delete the conntrack
1006                    immediately.  --RR */
1007                 if (th->rst) {
1008                         if (del_timer(&conntrack->timeout))
1009                                 conntrack->timeout.function((unsigned long)
1010                                                             conntrack);
1011                         return NF_ACCEPT;
1012                 }
1013         } else if (!test_bit(IPS_ASSURED_BIT, &conntrack->status)
1014                    && (old_state == TCP_CONNTRACK_SYN_RECV
1015                        || old_state == TCP_CONNTRACK_ESTABLISHED)
1016                    && new_state == TCP_CONNTRACK_ESTABLISHED) {
1017                 /* Set ASSURED if we see see valid ack in ESTABLISHED
1018                    after SYN_RECV or a valid answer for a picked up
1019                    connection. */
1020                 set_bit(IPS_ASSURED_BIT, &conntrack->status);
1021                 nf_conntrack_event_cache(IPCT_STATUS, skb);
1022         }
1023         nf_ct_refresh_acct(conntrack, ctinfo, skb, timeout);
1024
1025         return NF_ACCEPT;
1026 }
1027
1028 /* Called when a new connection for this protocol found. */
1029 static int tcp_new(struct nf_conn *conntrack,
1030                    const struct sk_buff *skb,
1031                    unsigned int dataoff)
1032 {
1033         enum tcp_conntrack new_state;
1034         struct tcphdr *th, _tcph;
1035 #ifdef DEBUGP_VARS
1036         struct ip_ct_tcp_state *sender = &conntrack->proto.tcp.seen[0];
1037         struct ip_ct_tcp_state *receiver = &conntrack->proto.tcp.seen[1];
1038 #endif
1039
1040         th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
1041         BUG_ON(th == NULL);
1042
1043         /* Don't need lock here: this conntrack not in circulation yet */
1044         new_state
1045                 = tcp_conntracks[0][get_conntrack_index(th)]
1046                 [TCP_CONNTRACK_NONE];
1047
1048         /* Invalid: delete conntrack */
1049         if (new_state >= TCP_CONNTRACK_MAX) {
1050                 DEBUGP("nf_ct_tcp: invalid new deleting.\n");
1051                 return 0;
1052         }
1053
1054         if (new_state == TCP_CONNTRACK_SYN_SENT) {
1055                 /* SYN packet */
1056                 conntrack->proto.tcp.seen[0].td_end =
1057                         segment_seq_plus_len(ntohl(th->seq), skb->len,
1058                                              dataoff, th);
1059                 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1060                 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1061                         conntrack->proto.tcp.seen[0].td_maxwin = 1;
1062                 conntrack->proto.tcp.seen[0].td_maxend =
1063                         conntrack->proto.tcp.seen[0].td_end;
1064
1065                 tcp_options(skb, dataoff, th, &conntrack->proto.tcp.seen[0]);
1066                 conntrack->proto.tcp.seen[1].flags = 0;
1067                 conntrack->proto.tcp.seen[0].loose =
1068                 conntrack->proto.tcp.seen[1].loose = 0;
1069         } else if (nf_ct_tcp_loose == 0) {
1070                 /* Don't try to pick up connections. */
1071                 return 0;
1072         } else {
1073                 /*
1074                  * We are in the middle of a connection,
1075                  * its history is lost for us.
1076                  * Let's try to use the data from the packet.
1077                  */
1078                 conntrack->proto.tcp.seen[0].td_end =
1079                         segment_seq_plus_len(ntohl(th->seq), skb->len,
1080                                              dataoff, th);
1081                 conntrack->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
1082                 if (conntrack->proto.tcp.seen[0].td_maxwin == 0)
1083                         conntrack->proto.tcp.seen[0].td_maxwin = 1;
1084                 conntrack->proto.tcp.seen[0].td_maxend =
1085                         conntrack->proto.tcp.seen[0].td_end +
1086                         conntrack->proto.tcp.seen[0].td_maxwin;
1087                 conntrack->proto.tcp.seen[0].td_scale = 0;
1088
1089                 /* We assume SACK. Should we assume window scaling too? */
1090                 conntrack->proto.tcp.seen[0].flags =
1091                 conntrack->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM;
1092                 conntrack->proto.tcp.seen[0].loose =
1093                 conntrack->proto.tcp.seen[1].loose = nf_ct_tcp_loose;
1094         }
1095
1096         conntrack->proto.tcp.seen[1].td_end = 0;
1097         conntrack->proto.tcp.seen[1].td_maxend = 0;
1098         conntrack->proto.tcp.seen[1].td_maxwin = 1;
1099         conntrack->proto.tcp.seen[1].td_scale = 0;
1100
1101         /* tcp_packet will set them */
1102         conntrack->proto.tcp.state = TCP_CONNTRACK_NONE;
1103         conntrack->proto.tcp.last_index = TCP_NONE_SET;
1104
1105         DEBUGP("tcp_new: sender end=%u maxend=%u maxwin=%u scale=%i "
1106                "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
1107                 sender->td_end, sender->td_maxend, sender->td_maxwin,
1108                 sender->td_scale,
1109                 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
1110                 receiver->td_scale);
1111         return 1;
1112 }
1113
1114 #if defined(CONFIG_NF_CT_NETLINK) || \
1115     defined(CONFIG_NF_CT_NETLINK_MODULE)
1116
1117 #include <linux/netfilter/nfnetlink.h>
1118 #include <linux/netfilter/nfnetlink_conntrack.h>
1119
1120 static int tcp_to_nfattr(struct sk_buff *skb, struct nfattr *nfa,
1121                          const struct nf_conn *ct)
1122 {
1123         struct nfattr *nest_parms;
1124
1125         read_lock_bh(&tcp_lock);
1126         nest_parms = NFA_NEST(skb, CTA_PROTOINFO_TCP);
1127         NFA_PUT(skb, CTA_PROTOINFO_TCP_STATE, sizeof(u_int8_t),
1128                 &ct->proto.tcp.state);
1129         read_unlock_bh(&tcp_lock);
1130
1131         NFA_NEST_END(skb, nest_parms);
1132
1133         return 0;
1134
1135 nfattr_failure:
1136         read_unlock_bh(&tcp_lock);
1137         return -1;
1138 }
1139
1140 static const size_t cta_min_tcp[CTA_PROTOINFO_TCP_MAX] = {
1141         [CTA_PROTOINFO_TCP_STATE-1]     = sizeof(u_int8_t),
1142 };
1143
1144 static int nfattr_to_tcp(struct nfattr *cda[], struct nf_conn *ct)
1145 {
1146         struct nfattr *attr = cda[CTA_PROTOINFO_TCP-1];
1147         struct nfattr *tb[CTA_PROTOINFO_TCP_MAX];
1148
1149         /* updates could not contain anything about the private
1150          * protocol info, in that case skip the parsing */
1151         if (!attr)
1152                 return 0;
1153
1154         nfattr_parse_nested(tb, CTA_PROTOINFO_TCP_MAX, attr);
1155
1156         if (nfattr_bad_size(tb, CTA_PROTOINFO_TCP_MAX, cta_min_tcp))
1157                 return -EINVAL;
1158
1159         if (!tb[CTA_PROTOINFO_TCP_STATE-1])
1160                 return -EINVAL;
1161
1162         write_lock_bh(&tcp_lock);
1163         ct->proto.tcp.state =
1164                 *(u_int8_t *)NFA_DATA(tb[CTA_PROTOINFO_TCP_STATE-1]);
1165         write_unlock_bh(&tcp_lock);
1166
1167         return 0;
1168 }
1169 #endif
1170
1171 struct nf_conntrack_protocol nf_conntrack_protocol_tcp4 =
1172 {
1173         .l3proto                = PF_INET,
1174         .proto                  = IPPROTO_TCP,
1175         .name                   = "tcp",
1176         .pkt_to_tuple           = tcp_pkt_to_tuple,
1177         .invert_tuple           = tcp_invert_tuple,
1178         .print_tuple            = tcp_print_tuple,
1179         .print_conntrack        = tcp_print_conntrack,
1180         .packet                 = tcp_packet,
1181         .new                    = tcp_new,
1182         .error                  = tcp_error,
1183 #if defined(CONFIG_NF_CT_NETLINK) || \
1184     defined(CONFIG_NF_CT_NETLINK_MODULE)
1185         .to_nfattr              = tcp_to_nfattr,
1186         .from_nfattr            = nfattr_to_tcp,
1187         .tuple_to_nfattr        = nf_ct_port_tuple_to_nfattr,
1188         .nfattr_to_tuple        = nf_ct_port_nfattr_to_tuple,
1189 #endif
1190 };
1191
1192 struct nf_conntrack_protocol nf_conntrack_protocol_tcp6 =
1193 {
1194         .l3proto                = PF_INET6,
1195         .proto                  = IPPROTO_TCP,
1196         .name                   = "tcp",
1197         .pkt_to_tuple           = tcp_pkt_to_tuple,
1198         .invert_tuple           = tcp_invert_tuple,
1199         .print_tuple            = tcp_print_tuple,
1200         .print_conntrack        = tcp_print_conntrack,
1201         .packet                 = tcp_packet,
1202         .new                    = tcp_new,
1203         .error                  = tcp_error,
1204 #if defined(CONFIG_NF_CT_NETLINK) || \
1205     defined(CONFIG_NF_CT_NETLINK_MODULE)
1206         .to_nfattr              = tcp_to_nfattr,
1207         .from_nfattr            = nfattr_to_tcp,
1208         .tuple_to_nfattr        = nf_ct_port_tuple_to_nfattr,
1209         .nfattr_to_tuple        = nf_ct_port_nfattr_to_tuple,
1210 #endif
1211 };
1212
1213 EXPORT_SYMBOL(nf_conntrack_protocol_tcp4);
1214 EXPORT_SYMBOL(nf_conntrack_protocol_tcp6);