net/netfilter/nf_conntrack_proto_tcp.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* (C) 1999-2001 Paul `Rusty' Russell
   3  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   4  * (C) 2002-2013 Jozsef Kadlecsik <kadlec@netfilter.org>
   5  * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
   6  */
   7
   8 #include <linux/types.h>
   9 #include <linux/timer.h>
  10 #include <linux/module.h>
  11 #include <linux/in.h>
  12 #include <linux/tcp.h>
  13 #include <linux/spinlock.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/ipv6.h>
  16 #include <net/ip6_checksum.h>
  17 #include <asm/unaligned.h>
  18
  19 #include <net/tcp.h>
  20
  21 #include <linux/netfilter.h>
  22 #include <linux/netfilter_ipv4.h>
  23 #include <linux/netfilter_ipv6.h>
  24 #include <net/netfilter/nf_conntrack.h>
  25 #include <net/netfilter/nf_conntrack_l4proto.h>
  26 #include <net/netfilter/nf_conntrack_ecache.h>
  27 #include <net/netfilter/nf_conntrack_seqadj.h>
  28 #include <net/netfilter/nf_conntrack_synproxy.h>
  29 #include <net/netfilter/nf_conntrack_timeout.h>
  30 #include <net/netfilter/nf_log.h>
  31 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
  32 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
  33
  34   /* FIXME: Examine ipfilter's timeouts and conntrack transitions more
  35      closely.  They're more complex. --RR */
  36
  37 static const char *const tcp_conntrack_names[] = {
  38         "NONE",
  39         "SYN_SENT",
  40         "SYN_RECV",
  41         "ESTABLISHED",
  42         "FIN_WAIT",
  43         "CLOSE_WAIT",
  44         "LAST_ACK",
  45         "TIME_WAIT",
  46         "CLOSE",
  47         "SYN_SENT2",
  48 };
  49
  50 #define SECS * HZ
  51 #define MINS * 60 SECS
  52 #define HOURS * 60 MINS
  53 #define DAYS * 24 HOURS
  54
  55 static const unsigned int tcp_timeouts[TCP_CONNTRACK_TIMEOUT_MAX] = {
  56         [TCP_CONNTRACK_SYN_SENT]        = 2 MINS,
  57         [TCP_CONNTRACK_SYN_RECV]        = 60 SECS,
  58         [TCP_CONNTRACK_ESTABLISHED]     = 5 DAYS,
  59         [TCP_CONNTRACK_FIN_WAIT]        = 2 MINS,
  60         [TCP_CONNTRACK_CLOSE_WAIT]      = 60 SECS,
  61         [TCP_CONNTRACK_LAST_ACK]        = 30 SECS,
  62         [TCP_CONNTRACK_TIME_WAIT]       = 2 MINS,
  63         [TCP_CONNTRACK_CLOSE]           = 10 SECS,
  64         [TCP_CONNTRACK_SYN_SENT2]       = 2 MINS,
  65 /* RFC1122 says the R2 limit should be at least 100 seconds.
  66    Linux uses 15 packets as limit, which corresponds
  67    to ~13-30min depending on RTO. */
  68         [TCP_CONNTRACK_RETRANS]         = 5 MINS,
  69         [TCP_CONNTRACK_UNACK]           = 5 MINS,
  70 };
  71
  72 #define sNO TCP_CONNTRACK_NONE
  73 #define sSS TCP_CONNTRACK_SYN_SENT
  74 #define sSR TCP_CONNTRACK_SYN_RECV
  75 #define sES TCP_CONNTRACK_ESTABLISHED
  76 #define sFW TCP_CONNTRACK_FIN_WAIT
  77 #define sCW TCP_CONNTRACK_CLOSE_WAIT
  78 #define sLA TCP_CONNTRACK_LAST_ACK
  79 #define sTW TCP_CONNTRACK_TIME_WAIT
  80 #define sCL TCP_CONNTRACK_CLOSE
  81 #define sS2 TCP_CONNTRACK_SYN_SENT2
  82 #define sIV TCP_CONNTRACK_MAX
  83 #define sIG TCP_CONNTRACK_IGNORE
  84
  85 /* What TCP flags are set from RST/SYN/FIN/ACK. */
  86 enum tcp_bit_set {
  87         TCP_SYN_SET,
  88         TCP_SYNACK_SET,
  89         TCP_FIN_SET,
  90         TCP_ACK_SET,
  91         TCP_RST_SET,
  92         TCP_NONE_SET,
  93 };
  94
  95 /*
  96  * The TCP state transition table needs a few words...
  97  *
  98  * We are the man in the middle. All the packets go through us
  99  * but might get lost in transit to the destination.
 100  * It is assumed that the destinations can't receive segments
 101  * we haven't seen.
 102  *
 103  * The checked segment is in window, but our windows are *not*
 104  * equivalent with the ones of the sender/receiver. We always
 105  * try to guess the state of the current sender.
 106  *
 107  * The meaning of the states are:
 108  *
 109  * NONE:        initial state
 110  * SYN_SENT:    SYN-only packet seen
 111  * SYN_SENT2:   SYN-only packet seen from reply dir, simultaneous open
 112  * SYN_RECV:    SYN-ACK packet seen
 113  * ESTABLISHED: ACK packet seen
 114  * FIN_WAIT:    FIN packet seen
 115  * CLOSE_WAIT:  ACK seen (after FIN)
 116  * LAST_ACK:    FIN seen (after FIN)
 117  * TIME_WAIT:   last ACK seen
 118  * CLOSE:       closed connection (RST)
 119  *
 120  * Packets marked as IGNORED (sIG):
 121  *      if they may be either invalid or valid
 122  *      and the receiver may send back a connection
 123  *      closing RST or a SYN/ACK.
 124  *
 125  * Packets marked as INVALID (sIV):
 126  *      if we regard them as truly invalid packets
 127  */
 128 static const u8 tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = {
 129         {
 130 /* ORIGINAL */
 131 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2   */
 132 /*syn*/    { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sS2 },
 133 /*
 134  *      sNO -> sSS      Initialize a new connection
 135  *      sSS -> sSS      Retransmitted SYN
 136  *      sS2 -> sS2      Late retransmitted SYN
 137  *      sSR -> sIG
 138  *      sES -> sIG      Error: SYNs in window outside the SYN_SENT state
 139  *                      are errors. Receiver will reply with RST
 140  *                      and close the connection.
 141  *                      Or we are not in sync and hold a dead connection.
 142  *      sFW -> sIG
 143  *      sCW -> sIG
 144  *      sLA -> sIG
 145  *      sTW -> sSS      Reopened connection (RFC 1122).
 146  *      sCL -> sSS
 147  */
 148 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2   */
 149 /*synack*/ { sIV, sIV, sSR, sIV, sIV, sIV, sIV, sIV, sIV, sSR },
 150 /*
 151  *      sNO -> sIV      Too late and no reason to do anything
 152  *      sSS -> sIV      Client can't send SYN and then SYN/ACK
 153  *      sS2 -> sSR      SYN/ACK sent to SYN2 in simultaneous open
 154  *      sSR -> sSR      Late retransmitted SYN/ACK in simultaneous open
 155  *      sES -> sIV      Invalid SYN/ACK packets sent by the client
 156  *      sFW -> sIV
 157  *      sCW -> sIV
 158  *      sLA -> sIV
 159  *      sTW -> sIV
 160  *      sCL -> sIV
 161  */
 162 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2   */
 163 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
 164 /*
 165  *      sNO -> sIV      Too late and no reason to do anything...
 166  *      sSS -> sIV      Client migth not send FIN in this state:
 167  *                      we enforce waiting for a SYN/ACK reply first.
 168  *      sS2 -> sIV
 169  *      sSR -> sFW      Close started.
 170  *      sES -> sFW
 171  *      sFW -> sLA      FIN seen in both directions, waiting for
 172  *                      the last ACK.
 173  *                      Migth be a retransmitted FIN as well...
 174  *      sCW -> sLA
 175  *      sLA -> sLA      Retransmitted FIN. Remain in the same state.
 176  *      sTW -> sTW
 177  *      sCL -> sCL
 178  */
 179 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2   */
 180 /*ack*/    { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV },
 181 /*
 182  *      sNO -> sES      Assumed.
 183  *      sSS -> sIV      ACK is invalid: we haven't seen a SYN/ACK yet.
 184  *      sS2 -> sIV
 185  *      sSR -> sES      Established state is reached.
 186  *      sES -> sES      :-)
 187  *      sFW -> sCW      Normal close request answered by ACK.
 188  *      sCW -> sCW
 189  *      sLA -> sTW      Last ACK detected (RFC5961 challenged)
 190  *      sTW -> sTW      Retransmitted last ACK. Remain in the same state.
 191  *      sCL -> sCL
 192  */
 193 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2   */
 194 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL },
 195 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
 196         },
 197         {
 198 /* REPLY */
 199 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2   */
 200 /*syn*/    { sIV, sS2, sIV, sIV, sIV, sIV, sIV, sSS, sIV, sS2 },
 201 /*
 202  *      sNO -> sIV      Never reached.
 203  *      sSS -> sS2      Simultaneous open
 204  *      sS2 -> sS2      Retransmitted simultaneous SYN
 205  *      sSR -> sIV      Invalid SYN packets sent by the server
 206  *      sES -> sIV
 207  *      sFW -> sIV
 208  *      sCW -> sIV
 209  *      sLA -> sIV
 210  *      sTW -> sSS      Reopened connection, but server may have switched role
 211  *      sCL -> sIV
 212  */
 213 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2   */
 214 /*synack*/ { sIV, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIG, sSR },
 215 /*
 216  *      sSS -> sSR      Standard open.
 217  *      sS2 -> sSR      Simultaneous open
 218  *      sSR -> sIG      Retransmitted SYN/ACK, ignore it.
 219  *      sES -> sIG      Late retransmitted SYN/ACK?
 220  *      sFW -> sIG      Might be SYN/ACK answering ignored SYN
 221  *      sCW -> sIG
 222  *      sLA -> sIG
 223  *      sTW -> sIG
 224  *      sCL -> sIG
 225  */
 226 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2   */
 227 /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
 228 /*
 229  *      sSS -> sIV      Server might not send FIN in this state.
 230  *      sS2 -> sIV
 231  *      sSR -> sFW      Close started.
 232  *      sES -> sFW
 233  *      sFW -> sLA      FIN seen in both directions.
 234  *      sCW -> sLA
 235  *      sLA -> sLA      Retransmitted FIN.
 236  *      sTW -> sTW
 237  *      sCL -> sCL
 238  */
 239 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2   */
 240 /*ack*/    { sIV, sIG, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIG },
 241 /*
 242  *      sSS -> sIG      Might be a half-open connection.
 243  *      sS2 -> sIG
 244  *      sSR -> sSR      Might answer late resent SYN.
 245  *      sES -> sES      :-)
 246  *      sFW -> sCW      Normal close request answered by ACK.
 247  *      sCW -> sCW
 248  *      sLA -> sTW      Last ACK detected (RFC5961 challenged)
 249  *      sTW -> sTW      Retransmitted last ACK.
 250  *      sCL -> sCL
 251  */
 252 /*           sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2   */
 253 /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL },
 254 /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
 255         }
 256 };
 257
 258 #ifdef CONFIG_NF_CONNTRACK_PROCFS
 259 /* Print out the private part of the conntrack. */
 260 static void tcp_print_conntrack(struct seq_file *s, struct nf_conn *ct)
 261 {
 262         if (test_bit(IPS_OFFLOAD_BIT, &ct->status))
 263                 return;
 264
 265         seq_printf(s, "%s ", tcp_conntrack_names[ct->proto.tcp.state]);
 266 }
 267 #endif
 268
 269 static unsigned int get_conntrack_index(const struct tcphdr *tcph)
 270 {
 271         if (tcph->rst) return TCP_RST_SET;
 272         else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET);
 273         else if (tcph->fin) return TCP_FIN_SET;
 274         else if (tcph->ack) return TCP_ACK_SET;
 275         else return TCP_NONE_SET;
 276 }
 277
 278 /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering
 279    in IP Filter' by Guido van Rooij.
 280
 281    http://www.sane.nl/events/sane2000/papers.html
 282    http://www.darkart.com/mirrors/www.obfuscation.org/ipf/
 283
 284    The boundaries and the conditions are changed according to RFC793:
 285    the packet must intersect the window (i.e. segments may be
 286    after the right or before the left edge) and thus receivers may ACK
 287    segments after the right edge of the window.
 288
 289         td_maxend = max(sack + max(win,1)) seen in reply packets
 290         td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets
 291         td_maxwin += seq + len - sender.td_maxend
 292                         if seq + len > sender.td_maxend
 293         td_end    = max(seq + len) seen in sent packets
 294
 295    I.   Upper bound for valid data:     seq <= sender.td_maxend
 296    II.  Lower bound for valid data:     seq + len >= sender.td_end - receiver.td_maxwin
 297    III. Upper bound for valid (s)ack:   sack <= receiver.td_end
 298    IV.  Lower bound for valid (s)ack:   sack >= receiver.td_end - MAXACKWINDOW
 299
 300    where sack is the highest right edge of sack block found in the packet
 301    or ack in the case of packet without SACK option.
 302
 303    The upper bound limit for a valid (s)ack is not ignored -
 304    we doesn't have to deal with fragments.
 305 */
 306
 307 static inline __u32 segment_seq_plus_len(__u32 seq,
 308                                          size_t len,
 309                                          unsigned int dataoff,
 310                                          const struct tcphdr *tcph)
 311 {
 312         /* XXX Should I use payload length field in IP/IPv6 header ?
 313          * - YK */
 314         return (seq + len - dataoff - tcph->doff*4
 315                 + (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0));
 316 }
 317
 318 /* Fixme: what about big packets? */
 319 #define MAXACKWINCONST                  66000
 320 #define MAXACKWINDOW(sender)                                            \
 321         ((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin     \
 322                                               : MAXACKWINCONST)
 323
 324 /*
 325  * Simplified tcp_parse_options routine from tcp_input.c
 326  */
 327 static void tcp_options(const struct sk_buff *skb,
 328                         unsigned int dataoff,
 329                         const struct tcphdr *tcph,
 330                         struct ip_ct_tcp_state *state)
 331 {
 332         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
 333         const unsigned char *ptr;
 334         int length = (tcph->doff*4) - sizeof(struct tcphdr);
 335
 336         if (!length)
 337                 return;
 338
 339         ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr),
 340                                  length, buff);
 341         if (!ptr)
 342                 return;
 343
 344         state->td_scale = 0;
 345         state->flags &= IP_CT_TCP_FLAG_BE_LIBERAL;
 346
 347         while (length > 0) {
 348                 int opcode=*ptr++;
 349                 int opsize;
 350
 351                 switch (opcode) {
 352                 case TCPOPT_EOL:
 353                         return;
 354                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 355                         length--;
 356                         continue;
 357                 default:
 358                         if (length < 2)
 359                                 return;
 360                         opsize=*ptr++;
 361                         if (opsize < 2) /* "silly options" */
 362                                 return;
 363                         if (opsize > length)
 364                                 return; /* don't parse partial options */
 365
 366                         if (opcode == TCPOPT_SACK_PERM
 367                             && opsize == TCPOLEN_SACK_PERM)
 368                                 state->flags |= IP_CT_TCP_FLAG_SACK_PERM;
 369                         else if (opcode == TCPOPT_WINDOW
 370                                  && opsize == TCPOLEN_WINDOW) {
 371                                 state->td_scale = *(u_int8_t *)ptr;
 372
 373                                 if (state->td_scale > TCP_MAX_WSCALE)
 374                                         state->td_scale = TCP_MAX_WSCALE;
 375
 376                                 state->flags |=
 377                                         IP_CT_TCP_FLAG_WINDOW_SCALE;
 378                         }
 379                         ptr += opsize - 2;
 380                         length -= opsize;
 381                 }
 382         }
 383 }
 384
 385 static void tcp_sack(const struct sk_buff *skb, unsigned int dataoff,
 386                      const struct tcphdr *tcph, __u32 *sack)
 387 {
 388         unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];
 389         const unsigned char *ptr;
 390         int length = (tcph->doff*4) - sizeof(struct tcphdr);
 391         __u32 tmp;
 392
 393         if (!length)
 394                 return;
 395
 396         ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr),
 397                                  length, buff);
 398         if (!ptr)
 399                 return;
 400
 401         /* Fast path for timestamp-only option */
 402         if (length == TCPOLEN_TSTAMP_ALIGNED
 403             && *(__be32 *)ptr == htonl((TCPOPT_NOP << 24)
 404                                        | (TCPOPT_NOP << 16)
 405                                        | (TCPOPT_TIMESTAMP << 8)
 406                                        | TCPOLEN_TIMESTAMP))
 407                 return;
 408
 409         while (length > 0) {
 410                 int opcode = *ptr++;
 411                 int opsize, i;
 412
 413                 switch (opcode) {
 414                 case TCPOPT_EOL:
 415                         return;
 416                 case TCPOPT_NOP:        /* Ref: RFC 793 section 3.1 */
 417                         length--;
 418                         continue;
 419                 default:
 420                         if (length < 2)
 421                                 return;
 422                         opsize = *ptr++;
 423                         if (opsize < 2) /* "silly options" */
 424                                 return;
 425                         if (opsize > length)
 426                                 return; /* don't parse partial options */
 427
 428                         if (opcode == TCPOPT_SACK
 429                             && opsize >= (TCPOLEN_SACK_BASE
 430                                           + TCPOLEN_SACK_PERBLOCK)
 431                             && !((opsize - TCPOLEN_SACK_BASE)
 432                                  % TCPOLEN_SACK_PERBLOCK)) {
 433                                 for (i = 0;
 434                                      i < (opsize - TCPOLEN_SACK_BASE);
 435                                      i += TCPOLEN_SACK_PERBLOCK) {
 436                                         tmp = get_unaligned_be32((__be32 *)(ptr+i)+1);
 437
 438                                         if (after(tmp, *sack))
 439                                                 *sack = tmp;
 440                                 }
 441                                 return;
 442                         }
 443                         ptr += opsize - 2;
 444                         length -= opsize;
 445                 }
 446         }
 447 }
 448
 449 static bool tcp_in_window(struct nf_conn *ct,
 450                           enum ip_conntrack_dir dir,
 451                           unsigned int index,
 452                           const struct sk_buff *skb,
 453                           unsigned int dataoff,
 454                           const struct tcphdr *tcph,
 455                           const struct nf_hook_state *hook_state)
 456 {
 457         struct ip_ct_tcp *state = &ct->proto.tcp;
 458         struct net *net = nf_ct_net(ct);
 459         struct nf_tcp_net *tn = nf_tcp_pernet(net);
 460         struct ip_ct_tcp_state *sender = &state->seen[dir];
 461         struct ip_ct_tcp_state *receiver = &state->seen[!dir];
 462         const struct nf_conntrack_tuple *tuple = &ct->tuplehash[dir].tuple;
 463         __u32 seq, ack, sack, end, win, swin;
 464         u16 win_raw;
 465         s32 receiver_offset;
 466         bool res, in_recv_win;
 467
 468         /*
 469          * Get the required data from the packet.
 470          */
 471         seq = ntohl(tcph->seq);
 472         ack = sack = ntohl(tcph->ack_seq);
 473         win_raw = ntohs(tcph->window);
 474         win = win_raw;
 475         end = segment_seq_plus_len(seq, skb->len, dataoff, tcph);
 476
 477         if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
 478                 tcp_sack(skb, dataoff, tcph, &sack);
 479
 480         /* Take into account NAT sequence number mangling */
 481         receiver_offset = nf_ct_seq_offset(ct, !dir, ack - 1);
 482         ack -= receiver_offset;
 483         sack -= receiver_offset;
 484
 485         pr_debug("tcp_in_window: START\n");
 486         pr_debug("tcp_in_window: ");
 487         nf_ct_dump_tuple(tuple);
 488         pr_debug("seq=%u ack=%u+(%d) sack=%u+(%d) win=%u end=%u\n",
 489                  seq, ack, receiver_offset, sack, receiver_offset, win, end);
 490         pr_debug("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
 491                  "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 492                  sender->td_end, sender->td_maxend, sender->td_maxwin,
 493                  sender->td_scale,
 494                  receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 495                  receiver->td_scale);
 496
 497         if (sender->td_maxwin == 0) {
 498                 /*
 499                  * Initialize sender data.
 500                  */
 501                 if (tcph->syn) {
 502                         /*
 503                          * SYN-ACK in reply to a SYN
 504                          * or SYN from reply direction in simultaneous open.
 505                          */
 506                         sender->td_end =
 507                         sender->td_maxend = end;
 508                         sender->td_maxwin = (win == 0 ? 1 : win);
 509
 510                         tcp_options(skb, dataoff, tcph, sender);
 511                         /*
 512                          * RFC 1323:
 513                          * Both sides must send the Window Scale option
 514                          * to enable window scaling in either direction.
 515                          */
 516                         if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE
 517                               && receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE))
 518                                 sender->td_scale =
 519                                 receiver->td_scale = 0;
 520                         if (!tcph->ack)
 521                                 /* Simultaneous open */
 522                                 return true;
 523                 } else {
 524                         /*
 525                          * We are in the middle of a connection,
 526                          * its history is lost for us.
 527                          * Let's try to use the data from the packet.
 528                          */
 529                         sender->td_end = end;
 530                         swin = win << sender->td_scale;
 531                         sender->td_maxwin = (swin == 0 ? 1 : swin);
 532                         sender->td_maxend = end + sender->td_maxwin;
 533                         if (receiver->td_maxwin == 0) {
 534                                 /* We haven't seen traffic in the other
 535                                  * direction yet but we have to tweak window
 536                                  * tracking to pass III and IV until that
 537                                  * happens.
 538                                  */
 539                                 receiver->td_end = receiver->td_maxend = sack;
 540                         } else if (sack == receiver->td_end + 1) {
 541                                 /* Likely a reply to a keepalive.
 542                                  * Needed for III.
 543                                  */
 544                                 receiver->td_end++;
 545                         }
 546
 547                 }
 548         } else if (((state->state == TCP_CONNTRACK_SYN_SENT
 549                      && dir == IP_CT_DIR_ORIGINAL)
 550                    || (state->state == TCP_CONNTRACK_SYN_RECV
 551                      && dir == IP_CT_DIR_REPLY))
 552                    && after(end, sender->td_end)) {
 553                 /*
 554                  * RFC 793: "if a TCP is reinitialized ... then it need
 555                  * not wait at all; it must only be sure to use sequence
 556                  * numbers larger than those recently used."
 557                  */
 558                 sender->td_end =
 559                 sender->td_maxend = end;
 560                 sender->td_maxwin = (win == 0 ? 1 : win);
 561
 562                 tcp_options(skb, dataoff, tcph, sender);
 563         }
 564
 565         if (!(tcph->ack)) {
 566                 /*
 567                  * If there is no ACK, just pretend it was set and OK.
 568                  */
 569                 ack = sack = receiver->td_end;
 570         } else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
 571                     (TCP_FLAG_ACK|TCP_FLAG_RST))
 572                    && (ack == 0)) {
 573                 /*
 574                  * Broken TCP stacks, that set ACK in RST packets as well
 575                  * with zero ack value.
 576                  */
 577                 ack = sack = receiver->td_end;
 578         }
 579
 580         if (tcph->rst && seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)
 581                 /*
 582                  * RST sent answering SYN.
 583                  */
 584                 seq = end = sender->td_end;
 585
 586         pr_debug("tcp_in_window: ");
 587         nf_ct_dump_tuple(tuple);
 588         pr_debug("seq=%u ack=%u+(%d) sack=%u+(%d) win=%u end=%u\n",
 589                  seq, ack, receiver_offset, sack, receiver_offset, win, end);
 590         pr_debug("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
 591                  "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 592                  sender->td_end, sender->td_maxend, sender->td_maxwin,
 593                  sender->td_scale,
 594                  receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 595                  receiver->td_scale);
 596
 597         /* Is the ending sequence in the receive window (if available)? */
 598         in_recv_win = !receiver->td_maxwin ||
 599                       after(end, sender->td_end - receiver->td_maxwin - 1);
 600
 601         pr_debug("tcp_in_window: I=%i II=%i III=%i IV=%i\n",
 602                  before(seq, sender->td_maxend + 1),
 603                  (in_recv_win ? 1 : 0),
 604                  before(sack, receiver->td_end + 1),
 605                  after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1));
 606
 607         if (before(seq, sender->td_maxend + 1) &&
 608             in_recv_win &&
 609             before(sack, receiver->td_end + 1) &&
 610             after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1)) {
 611                 /*
 612                  * Take into account window scaling (RFC 1323).
 613                  */
 614                 if (!tcph->syn)
 615                         win <<= sender->td_scale;
 616
 617                 /*
 618                  * Update sender data.
 619                  */
 620                 swin = win + (sack - ack);
 621                 if (sender->td_maxwin < swin)
 622                         sender->td_maxwin = swin;
 623                 if (after(end, sender->td_end)) {
 624                         sender->td_end = end;
 625                         sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
 626                 }
 627                 if (tcph->ack) {
 628                         if (!(sender->flags & IP_CT_TCP_FLAG_MAXACK_SET)) {
 629                                 sender->td_maxack = ack;
 630                                 sender->flags |= IP_CT_TCP_FLAG_MAXACK_SET;
 631                         } else if (after(ack, sender->td_maxack))
 632                                 sender->td_maxack = ack;
 633                 }
 634
 635                 /*
 636                  * Update receiver data.
 637                  */
 638                 if (receiver->td_maxwin != 0 && after(end, sender->td_maxend))
 639                         receiver->td_maxwin += end - sender->td_maxend;
 640                 if (after(sack + win, receiver->td_maxend - 1)) {
 641                         receiver->td_maxend = sack + win;
 642                         if (win == 0)
 643                                 receiver->td_maxend++;
 644                 }
 645                 if (ack == receiver->td_end)
 646                         receiver->flags &= ~IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
 647
 648                 /*
 649                  * Check retransmissions.
 650                  */
 651                 if (index == TCP_ACK_SET) {
 652                         if (state->last_dir == dir
 653                             && state->last_seq == seq
 654                             && state->last_ack == ack
 655                             && state->last_end == end
 656                             && state->last_win == win_raw)
 657                                 state->retrans++;
 658                         else {
 659                                 state->last_dir = dir;
 660                                 state->last_seq = seq;
 661                                 state->last_ack = ack;
 662                                 state->last_end = end;
 663                                 state->last_win = win_raw;
 664                                 state->retrans = 0;
 665                         }
 666                 }
 667                 res = true;
 668         } else {
 669                 res = false;
 670                 if (sender->flags & IP_CT_TCP_FLAG_BE_LIBERAL ||
 671                     tn->tcp_be_liberal)
 672                         res = true;
 673                 if (!res) {
 674                         bool seq_ok = before(seq, sender->td_maxend + 1);
 675
 676                         if (!seq_ok) {
 677                                 u32 overshot = end - sender->td_maxend + 1;
 678                                 bool ack_ok;
 679
 680                                 ack_ok = after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1);
 681
 682                                 if (in_recv_win &&
 683                                     ack_ok &&
 684                                     overshot <= receiver->td_maxwin &&
 685                                     before(sack, receiver->td_end + 1)) {
 686                                         /* Work around TCPs that send more bytes than allowed by
 687                                          * the receive window.
 688                                          *
 689                                          * If the (marked as invalid) packet is allowed to pass by
 690                                          * the ruleset and the peer acks this data, then its possible
 691                                          * all future packets will trigger 'ACK is over upper bound' check.
 692                                          *
 693                                          * Thus if only the sequence check fails then do update td_end so
 694                                          * possible ACK for this data can update internal state.
 695                                          */
 696                                         sender->td_end = end;
 697                                         sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
 698
 699                                         nf_ct_l4proto_log_invalid(skb, ct, hook_state,
 700                                                                   "%u bytes more than expected", overshot);
 701                                         return res;
 702                                 }
 703                         }
 704
 705                         nf_ct_l4proto_log_invalid(skb, ct, hook_state,
 706                         "%s",
 707                         before(seq, sender->td_maxend + 1) ?
 708                         in_recv_win ?
 709                         before(sack, receiver->td_end + 1) ?
 710                         after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1) ? "BUG"
 711                         : "ACK is under the lower bound (possible overly delayed ACK)"
 712                         : "ACK is over the upper bound (ACKed data not seen yet)"
 713                         : "SEQ is under the lower bound (already ACKed data retransmitted)"
 714                         : "SEQ is over the upper bound (over the window of the receiver)");
 715                 }
 716         }
 717
 718         pr_debug("tcp_in_window: res=%u sender end=%u maxend=%u maxwin=%u "
 719                  "receiver end=%u maxend=%u maxwin=%u\n",
 720                  res, sender->td_end, sender->td_maxend, sender->td_maxwin,
 721                  receiver->td_end, receiver->td_maxend, receiver->td_maxwin);
 722
 723         return res;
 724 }
 725
 726 /* table of valid flag combinations - PUSH, ECE and CWR are always valid */
 727 static const u8 tcp_valid_flags[(TCPHDR_FIN|TCPHDR_SYN|TCPHDR_RST|TCPHDR_ACK|
 728                                  TCPHDR_URG) + 1] =
 729 {
 730         [TCPHDR_SYN]                            = 1,
 731         [TCPHDR_SYN|TCPHDR_URG]                 = 1,
 732         [TCPHDR_SYN|TCPHDR_ACK]                 = 1,
 733         [TCPHDR_RST]                            = 1,
 734         [TCPHDR_RST|TCPHDR_ACK]                 = 1,
 735         [TCPHDR_FIN|TCPHDR_ACK]                 = 1,
 736         [TCPHDR_FIN|TCPHDR_ACK|TCPHDR_URG]      = 1,
 737         [TCPHDR_ACK]                            = 1,
 738         [TCPHDR_ACK|TCPHDR_URG]                 = 1,
 739 };
 740
 741 static void tcp_error_log(const struct sk_buff *skb,
 742                           const struct nf_hook_state *state,
 743                           const char *msg)
 744 {
 745         nf_l4proto_log_invalid(skb, state, IPPROTO_TCP, "%s", msg);
 746 }
 747
 748 /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c.  */
 749 static bool tcp_error(const struct tcphdr *th,
 750                       struct sk_buff *skb,
 751                       unsigned int dataoff,
 752                       const struct nf_hook_state *state)
 753 {
 754         unsigned int tcplen = skb->len - dataoff;
 755         u8 tcpflags;
 756
 757         /* Not whole TCP header or malformed packet */
 758         if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {
 759                 tcp_error_log(skb, state, "truncated packet");
 760                 return true;
 761         }
 762
 763         /* Checksum invalid? Ignore.
 764          * We skip checking packets on the outgoing path
 765          * because the checksum is assumed to be correct.
 766          */
 767         /* FIXME: Source route IP option packets --RR */
 768         if (state->net->ct.sysctl_checksum &&
 769             state->hook == NF_INET_PRE_ROUTING &&
 770             nf_checksum(skb, state->hook, dataoff, IPPROTO_TCP, state->pf)) {
 771                 tcp_error_log(skb, state, "bad checksum");
 772                 return true;
 773         }
 774
 775         /* Check TCP flags. */
 776         tcpflags = (tcp_flag_byte(th) & ~(TCPHDR_ECE|TCPHDR_CWR|TCPHDR_PSH));
 777         if (!tcp_valid_flags[tcpflags]) {
 778                 tcp_error_log(skb, state, "invalid tcp flag combination");
 779                 return true;
 780         }
 781
 782         return false;
 783 }
 784
 785 static noinline bool tcp_new(struct nf_conn *ct, const struct sk_buff *skb,
 786                              unsigned int dataoff,
 787                              const struct tcphdr *th)
 788 {
 789         enum tcp_conntrack new_state;
 790         struct net *net = nf_ct_net(ct);
 791         const struct nf_tcp_net *tn = nf_tcp_pernet(net);
 792         const struct ip_ct_tcp_state *sender = &ct->proto.tcp.seen[0];
 793         const struct ip_ct_tcp_state *receiver = &ct->proto.tcp.seen[1];
 794
 795         /* Don't need lock here: this conntrack not in circulation yet */
 796         new_state = tcp_conntracks[0][get_conntrack_index(th)][TCP_CONNTRACK_NONE];
 797
 798         /* Invalid: delete conntrack */
 799         if (new_state >= TCP_CONNTRACK_MAX) {
 800                 pr_debug("nf_ct_tcp: invalid new deleting.\n");
 801                 return false;
 802         }
 803
 804         if (new_state == TCP_CONNTRACK_SYN_SENT) {
 805                 memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp));
 806                 /* SYN packet */
 807                 ct->proto.tcp.seen[0].td_end =
 808                         segment_seq_plus_len(ntohl(th->seq), skb->len,
 809                                              dataoff, th);
 810                 ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
 811                 if (ct->proto.tcp.seen[0].td_maxwin == 0)
 812                         ct->proto.tcp.seen[0].td_maxwin = 1;
 813                 ct->proto.tcp.seen[0].td_maxend =
 814                         ct->proto.tcp.seen[0].td_end;
 815
 816                 tcp_options(skb, dataoff, th, &ct->proto.tcp.seen[0]);
 817         } else if (tn->tcp_loose == 0) {
 818                 /* Don't try to pick up connections. */
 819                 return false;
 820         } else {
 821                 memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp));
 822                 /*
 823                  * We are in the middle of a connection,
 824                  * its history is lost for us.
 825                  * Let's try to use the data from the packet.
 826                  */
 827                 ct->proto.tcp.seen[0].td_end =
 828                         segment_seq_plus_len(ntohl(th->seq), skb->len,
 829                                              dataoff, th);
 830                 ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
 831                 if (ct->proto.tcp.seen[0].td_maxwin == 0)
 832                         ct->proto.tcp.seen[0].td_maxwin = 1;
 833                 ct->proto.tcp.seen[0].td_maxend =
 834                         ct->proto.tcp.seen[0].td_end +
 835                         ct->proto.tcp.seen[0].td_maxwin;
 836
 837                 /* We assume SACK and liberal window checking to handle
 838                  * window scaling */
 839                 ct->proto.tcp.seen[0].flags =
 840                 ct->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM |
 841                                               IP_CT_TCP_FLAG_BE_LIBERAL;
 842         }
 843
 844         /* tcp_packet will set them */
 845         ct->proto.tcp.last_index = TCP_NONE_SET;
 846
 847         pr_debug("%s: sender end=%u maxend=%u maxwin=%u scale=%i "
 848                  "receiver end=%u maxend=%u maxwin=%u scale=%i\n",
 849                  __func__,
 850                  sender->td_end, sender->td_maxend, sender->td_maxwin,
 851                  sender->td_scale,
 852                  receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
 853                  receiver->td_scale);
 854         return true;
 855 }
 856
 857 static bool tcp_can_early_drop(const struct nf_conn *ct)
 858 {
 859         switch (ct->proto.tcp.state) {
 860         case TCP_CONNTRACK_FIN_WAIT:
 861         case TCP_CONNTRACK_LAST_ACK:
 862         case TCP_CONNTRACK_TIME_WAIT:
 863         case TCP_CONNTRACK_CLOSE:
 864         case TCP_CONNTRACK_CLOSE_WAIT:
 865                 return true;
 866         default:
 867                 break;
 868         }
 869
 870         return false;
 871 }
 872
 873 static void nf_ct_tcp_state_reset(struct ip_ct_tcp_state *state)
 874 {
 875         state->td_end           = 0;
 876         state->td_maxend        = 0;
 877         state->td_maxwin        = 0;
 878         state->td_maxack        = 0;
 879         state->td_scale         = 0;
 880         state->flags            &= IP_CT_TCP_FLAG_BE_LIBERAL;
 881 }
 882
 883 /* Returns verdict for packet, or -1 for invalid. */
 884 int nf_conntrack_tcp_packet(struct nf_conn *ct,
 885                             struct sk_buff *skb,
 886                             unsigned int dataoff,
 887                             enum ip_conntrack_info ctinfo,
 888                             const struct nf_hook_state *state)
 889 {
 890         struct net *net = nf_ct_net(ct);
 891         struct nf_tcp_net *tn = nf_tcp_pernet(net);
 892         struct nf_conntrack_tuple *tuple;
 893         enum tcp_conntrack new_state, old_state;
 894         unsigned int index, *timeouts;
 895         enum ip_conntrack_dir dir;
 896         const struct tcphdr *th;
 897         struct tcphdr _tcph;
 898         unsigned long timeout;
 899
 900         th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
 901         if (th == NULL)
 902                 return -NF_ACCEPT;
 903
 904         if (tcp_error(th, skb, dataoff, state))
 905                 return -NF_ACCEPT;
 906
 907         if (!nf_ct_is_confirmed(ct) && !tcp_new(ct, skb, dataoff, th))
 908                 return -NF_ACCEPT;
 909
 910         spin_lock_bh(&ct->lock);
 911         old_state = ct->proto.tcp.state;
 912         dir = CTINFO2DIR(ctinfo);
 913         index = get_conntrack_index(th);
 914         new_state = tcp_conntracks[dir][index][old_state];
 915         tuple = &ct->tuplehash[dir].tuple;
 916
 917         switch (new_state) {
 918         case TCP_CONNTRACK_SYN_SENT:
 919                 if (old_state < TCP_CONNTRACK_TIME_WAIT)
 920                         break;
 921                 /* RFC 1122: "When a connection is closed actively,
 922                  * it MUST linger in TIME-WAIT state for a time 2xMSL
 923                  * (Maximum Segment Lifetime). However, it MAY accept
 924                  * a new SYN from the remote TCP to reopen the connection
 925                  * directly from TIME-WAIT state, if..."
 926                  * We ignore the conditions because we are in the
 927                  * TIME-WAIT state anyway.
 928                  *
 929                  * Handle aborted connections: we and the server
 930                  * think there is an existing connection but the client
 931                  * aborts it and starts a new one.
 932                  */
 933                 if (((ct->proto.tcp.seen[dir].flags
 934                       | ct->proto.tcp.seen[!dir].flags)
 935                      & IP_CT_TCP_FLAG_CLOSE_INIT)
 936                     || (ct->proto.tcp.last_dir == dir
 937                         && ct->proto.tcp.last_index == TCP_RST_SET)) {
 938                         /* Attempt to reopen a closed/aborted connection.
 939                          * Delete this connection and look up again. */
 940                         spin_unlock_bh(&ct->lock);
 941
 942                         /* Only repeat if we can actually remove the timer.
 943                          * Destruction may already be in progress in process
 944                          * context and we must give it a chance to terminate.
 945                          */
 946                         if (nf_ct_kill(ct))
 947                                 return -NF_REPEAT;
 948                         return NF_DROP;
 949                 }
 950                 fallthrough;
 951         case TCP_CONNTRACK_IGNORE:
 952                 /* Ignored packets:
 953                  *
 954                  * Our connection entry may be out of sync, so ignore
 955                  * packets which may signal the real connection between
 956                  * the client and the server.
 957                  *
 958                  * a) SYN in ORIGINAL
 959                  * b) SYN/ACK in REPLY
 960                  * c) ACK in reply direction after initial SYN in original.
 961                  *
 962                  * If the ignored packet is invalid, the receiver will send
 963                  * a RST we'll catch below.
 964                  */
 965                 if (index == TCP_SYNACK_SET
 966                     && ct->proto.tcp.last_index == TCP_SYN_SET
 967                     && ct->proto.tcp.last_dir != dir
 968                     && ntohl(th->ack_seq) == ct->proto.tcp.last_end) {
 969                         /* b) This SYN/ACK acknowledges a SYN that we earlier
 970                          * ignored as invalid. This means that the client and
 971                          * the server are both in sync, while the firewall is
 972                          * not. We get in sync from the previously annotated
 973                          * values.
 974                          */
 975                         old_state = TCP_CONNTRACK_SYN_SENT;
 976                         new_state = TCP_CONNTRACK_SYN_RECV;
 977                         ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_end =
 978                                 ct->proto.tcp.last_end;
 979                         ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxend =
 980                                 ct->proto.tcp.last_end;
 981                         ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxwin =
 982                                 ct->proto.tcp.last_win == 0 ?
 983                                         1 : ct->proto.tcp.last_win;
 984                         ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_scale =
 985                                 ct->proto.tcp.last_wscale;
 986                         ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK;
 987                         ct->proto.tcp.seen[ct->proto.tcp.last_dir].flags =
 988                                 ct->proto.tcp.last_flags;
 989                         nf_ct_tcp_state_reset(&ct->proto.tcp.seen[dir]);
 990                         break;
 991                 }
 992                 ct->proto.tcp.last_index = index;
 993                 ct->proto.tcp.last_dir = dir;
 994                 ct->proto.tcp.last_seq = ntohl(th->seq);
 995                 ct->proto.tcp.last_end =
 996                     segment_seq_plus_len(ntohl(th->seq), skb->len, dataoff, th);
 997                 ct->proto.tcp.last_win = ntohs(th->window);
 998
 999                 /* a) This is a SYN in ORIGINAL. The client and the server
1000                  * may be in sync but we are not. In that case, we annotate
1001                  * the TCP options and let the packet go through. If it is a
1002                  * valid SYN packet, the server will reply with a SYN/ACK, and
1003                  * then we'll get in sync. Otherwise, the server potentially
1004                  * responds with a challenge ACK if implementing RFC5961.
1005                  */
1006                 if (index == TCP_SYN_SET && dir == IP_CT_DIR_ORIGINAL) {
1007                         struct ip_ct_tcp_state seen = {};
1008
1009                         ct->proto.tcp.last_flags =
1010                         ct->proto.tcp.last_wscale = 0;
1011                         tcp_options(skb, dataoff, th, &seen);
1012                         if (seen.flags & IP_CT_TCP_FLAG_WINDOW_SCALE) {
1013                                 ct->proto.tcp.last_flags |=
1014                                         IP_CT_TCP_FLAG_WINDOW_SCALE;
1015                                 ct->proto.tcp.last_wscale = seen.td_scale;
1016                         }
1017                         if (seen.flags & IP_CT_TCP_FLAG_SACK_PERM) {
1018                                 ct->proto.tcp.last_flags |=
1019                                         IP_CT_TCP_FLAG_SACK_PERM;
1020                         }
1021                         /* Mark the potential for RFC5961 challenge ACK,
1022                          * this pose a special problem for LAST_ACK state
1023                          * as ACK is intrepretated as ACKing last FIN.
1024                          */
1025                         if (old_state == TCP_CONNTRACK_LAST_ACK)
1026                                 ct->proto.tcp.last_flags |=
1027                                         IP_CT_EXP_CHALLENGE_ACK;
1028                 }
1029                 spin_unlock_bh(&ct->lock);
1030                 nf_ct_l4proto_log_invalid(skb, ct, state,
1031                                           "packet (index %d) in dir %d ignored, state %s",
1032                                           index, dir,
1033                                           tcp_conntrack_names[old_state]);
1034                 return NF_ACCEPT;
1035         case TCP_CONNTRACK_MAX:
1036                 /* Special case for SYN proxy: when the SYN to the server or
1037                  * the SYN/ACK from the server is lost, the client may transmit
1038                  * a keep-alive packet while in SYN_SENT state. This needs to
1039                  * be associated with the original conntrack entry in order to
1040                  * generate a new SYN with the correct sequence number.
1041                  */
1042                 if (nfct_synproxy(ct) && old_state == TCP_CONNTRACK_SYN_SENT &&
1043                     index == TCP_ACK_SET && dir == IP_CT_DIR_ORIGINAL &&
1044                     ct->proto.tcp.last_dir == IP_CT_DIR_ORIGINAL &&
1045                     ct->proto.tcp.seen[dir].td_end - 1 == ntohl(th->seq)) {
1046                         pr_debug("nf_ct_tcp: SYN proxy client keep alive\n");
1047                         spin_unlock_bh(&ct->lock);
1048                         return NF_ACCEPT;
1049                 }
1050
1051                 /* Invalid packet */
1052                 pr_debug("nf_ct_tcp: Invalid dir=%i index=%u ostate=%u\n",
1053                          dir, get_conntrack_index(th), old_state);
1054                 spin_unlock_bh(&ct->lock);
1055                 nf_ct_l4proto_log_invalid(skb, ct, state, "invalid state");
1056                 return -NF_ACCEPT;
1057         case TCP_CONNTRACK_TIME_WAIT:
1058                 /* RFC5961 compliance cause stack to send "challenge-ACK"
1059                  * e.g. in response to spurious SYNs.  Conntrack MUST
1060                  * not believe this ACK is acking last FIN.
1061                  */
1062                 if (old_state == TCP_CONNTRACK_LAST_ACK &&
1063                     index == TCP_ACK_SET &&
1064                     ct->proto.tcp.last_dir != dir &&
1065                     ct->proto.tcp.last_index == TCP_SYN_SET &&
1066                     (ct->proto.tcp.last_flags & IP_CT_EXP_CHALLENGE_ACK)) {
1067                         /* Detected RFC5961 challenge ACK */
1068                         ct->proto.tcp.last_flags &= ~IP_CT_EXP_CHALLENGE_ACK;
1069                         spin_unlock_bh(&ct->lock);
1070                         nf_ct_l4proto_log_invalid(skb, ct, state, "challenge-ack ignored");
1071                         return NF_ACCEPT; /* Don't change state */
1072                 }
1073                 break;
1074         case TCP_CONNTRACK_SYN_SENT2:
1075                 /* tcp_conntracks table is not smart enough to handle
1076                  * simultaneous open.
1077                  */
1078                 ct->proto.tcp.last_flags |= IP_CT_TCP_SIMULTANEOUS_OPEN;
1079                 break;
1080         case TCP_CONNTRACK_SYN_RECV:
1081                 if (dir == IP_CT_DIR_REPLY && index == TCP_ACK_SET &&
1082                     ct->proto.tcp.last_flags & IP_CT_TCP_SIMULTANEOUS_OPEN)
1083                         new_state = TCP_CONNTRACK_ESTABLISHED;
1084                 break;
1085         case TCP_CONNTRACK_CLOSE:
1086                 if (index != TCP_RST_SET)
1087                         break;
1088
1089                 /* If we are closing, tuple might have been re-used already.
1090                  * last_index, last_ack, and all other ct fields used for
1091                  * sequence/window validation are outdated in that case.
1092                  *
1093                  * As the conntrack can already be expired by GC under pressure,
1094                  * just skip validation checks.
1095                  */
1096                 if (tcp_can_early_drop(ct))
1097                         goto in_window;
1098
1099                 /* td_maxack might be outdated if we let a SYN through earlier */
1100                 if ((ct->proto.tcp.seen[!dir].flags & IP_CT_TCP_FLAG_MAXACK_SET) &&
1101                     ct->proto.tcp.last_index != TCP_SYN_SET) {
1102                         u32 seq = ntohl(th->seq);
1103
1104                         /* If we are not in established state and SEQ=0 this is most
1105                          * likely an answer to a SYN we let go through above (last_index
1106                          * can be updated due to out-of-order ACKs).
1107                          */
1108                         if (seq == 0 && !nf_conntrack_tcp_established(ct))
1109                                 break;
1110
1111                         if (before(seq, ct->proto.tcp.seen[!dir].td_maxack) &&
1112                             !tn->tcp_ignore_invalid_rst) {
1113                                 /* Invalid RST  */
1114                                 spin_unlock_bh(&ct->lock);
1115                                 nf_ct_l4proto_log_invalid(skb, ct, state, "invalid rst");
1116                                 return -NF_ACCEPT;
1117                         }
1118
1119                         if (!nf_conntrack_tcp_established(ct) ||
1120                             seq == ct->proto.tcp.seen[!dir].td_maxack)
1121                                 break;
1122
1123                         /* Check if rst is part of train, such as
1124                          *   foo:80 > bar:4379: P, 235946583:235946602(19) ack 42
1125                          *   foo:80 > bar:4379: R, 235946602:235946602(0)  ack 42
1126                          */
1127                         if (ct->proto.tcp.last_index == TCP_ACK_SET &&
1128                             ct->proto.tcp.last_dir == dir &&
1129                             seq == ct->proto.tcp.last_end)
1130                                 break;
1131
1132                         /* ... RST sequence number doesn't match exactly, keep
1133                          * established state to allow a possible challenge ACK.
1134                          */
1135                         new_state = old_state;
1136                 }
1137                 if (((test_bit(IPS_SEEN_REPLY_BIT, &ct->status)
1138                          && ct->proto.tcp.last_index == TCP_SYN_SET)
1139                         || (!test_bit(IPS_ASSURED_BIT, &ct->status)
1140                             && ct->proto.tcp.last_index == TCP_ACK_SET))
1141                     && ntohl(th->ack_seq) == ct->proto.tcp.last_end) {
1142                         /* RST sent to invalid SYN or ACK we had let through
1143                          * at a) and c) above:
1144                          *
1145                          * a) SYN was in window then
1146                          * c) we hold a half-open connection.
1147                          *
1148                          * Delete our connection entry.
1149                          * We skip window checking, because packet might ACK
1150                          * segments we ignored. */
1151                         goto in_window;
1152                 }
1153                 break;
1154         default:
1155                 /* Keep compilers happy. */
1156                 break;
1157         }
1158
1159         if (!tcp_in_window(ct, dir, index,
1160                            skb, dataoff, th, state)) {
1161                 spin_unlock_bh(&ct->lock);
1162                 return -NF_ACCEPT;
1163         }
1164      in_window:
1165         /* From now on we have got in-window packets */
1166         ct->proto.tcp.last_index = index;
1167         ct->proto.tcp.last_dir = dir;
1168
1169         pr_debug("tcp_conntracks: ");
1170         nf_ct_dump_tuple(tuple);
1171         pr_debug("syn=%i ack=%i fin=%i rst=%i old=%i new=%i\n",
1172                  (th->syn ? 1 : 0), (th->ack ? 1 : 0),
1173                  (th->fin ? 1 : 0), (th->rst ? 1 : 0),
1174                  old_state, new_state);
1175
1176         ct->proto.tcp.state = new_state;
1177         if (old_state != new_state
1178             && new_state == TCP_CONNTRACK_FIN_WAIT)
1179                 ct->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;
1180
1181         timeouts = nf_ct_timeout_lookup(ct);
1182         if (!timeouts)
1183                 timeouts = tn->timeouts;
1184
1185         if (ct->proto.tcp.retrans >= tn->tcp_max_retrans &&
1186             timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS])
1187                 timeout = timeouts[TCP_CONNTRACK_RETRANS];
1188         else if (unlikely(index == TCP_RST_SET))
1189                 timeout = timeouts[TCP_CONNTRACK_CLOSE];
1190         else if ((ct->proto.tcp.seen[0].flags | ct->proto.tcp.seen[1].flags) &
1191                  IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED &&
1192                  timeouts[new_state] > timeouts[TCP_CONNTRACK_UNACK])
1193                 timeout = timeouts[TCP_CONNTRACK_UNACK];
1194         else if (ct->proto.tcp.last_win == 0 &&
1195                  timeouts[new_state] > timeouts[TCP_CONNTRACK_RETRANS])
1196                 timeout = timeouts[TCP_CONNTRACK_RETRANS];
1197         else
1198                 timeout = timeouts[new_state];
1199         spin_unlock_bh(&ct->lock);
1200
1201         if (new_state != old_state)
1202                 nf_conntrack_event_cache(IPCT_PROTOINFO, ct);
1203
1204         if (!test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
1205                 /* If only reply is a RST, we can consider ourselves not to
1206                    have an established connection: this is a fairly common
1207                    problem case, so we can delete the conntrack
1208                    immediately.  --RR */
1209                 if (th->rst) {
1210                         nf_ct_kill_acct(ct, ctinfo, skb);
1211                         return NF_ACCEPT;
1212                 }
1213
1214                 if (index == TCP_SYN_SET && old_state == TCP_CONNTRACK_SYN_SENT) {
1215                         /* do not renew timeout on SYN retransmit.
1216                          *
1217                          * Else port reuse by client or NAT middlebox can keep
1218                          * entry alive indefinitely (including nat info).
1219                          */
1220                         return NF_ACCEPT;
1221                 }
1222
1223                 /* ESTABLISHED without SEEN_REPLY, i.e. mid-connection
1224                  * pickup with loose=1. Avoid large ESTABLISHED timeout.
1225                  */
1226                 if (new_state == TCP_CONNTRACK_ESTABLISHED &&
1227                     timeout > timeouts[TCP_CONNTRACK_UNACK])
1228                         timeout = timeouts[TCP_CONNTRACK_UNACK];
1229         } else if (!test_bit(IPS_ASSURED_BIT, &ct->status)
1230                    && (old_state == TCP_CONNTRACK_SYN_RECV
1231                        || old_state == TCP_CONNTRACK_ESTABLISHED)
1232                    && new_state == TCP_CONNTRACK_ESTABLISHED) {
1233                 /* Set ASSURED if we see valid ack in ESTABLISHED
1234                    after SYN_RECV or a valid answer for a picked up
1235                    connection. */
1236                 set_bit(IPS_ASSURED_BIT, &ct->status);
1237                 nf_conntrack_event_cache(IPCT_ASSURED, ct);
1238         }
1239         nf_ct_refresh_acct(ct, ctinfo, skb, timeout);
1240
1241         return NF_ACCEPT;
1242 }
1243
1244 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
1245
1246 #include <linux/netfilter/nfnetlink.h>
1247 #include <linux/netfilter/nfnetlink_conntrack.h>
1248
1249 static int tcp_to_nlattr(struct sk_buff *skb, struct nlattr *nla,
1250                          struct nf_conn *ct, bool destroy)
1251 {
1252         struct nlattr *nest_parms;
1253         struct nf_ct_tcp_flags tmp = {};
1254
1255         spin_lock_bh(&ct->lock);
1256         nest_parms = nla_nest_start(skb, CTA_PROTOINFO_TCP);
1257         if (!nest_parms)
1258                 goto nla_put_failure;
1259
1260         if (nla_put_u8(skb, CTA_PROTOINFO_TCP_STATE, ct->proto.tcp.state))
1261                 goto nla_put_failure;
1262
1263         if (destroy)
1264                 goto skip_state;
1265
1266         if (nla_put_u8(skb, CTA_PROTOINFO_TCP_WSCALE_ORIGINAL,
1267                        ct->proto.tcp.seen[0].td_scale) ||
1268             nla_put_u8(skb, CTA_PROTOINFO_TCP_WSCALE_REPLY,
1269                        ct->proto.tcp.seen[1].td_scale))
1270                 goto nla_put_failure;
1271
1272         tmp.flags = ct->proto.tcp.seen[0].flags;
1273         if (nla_put(skb, CTA_PROTOINFO_TCP_FLAGS_ORIGINAL,
1274                     sizeof(struct nf_ct_tcp_flags), &tmp))
1275                 goto nla_put_failure;
1276
1277         tmp.flags = ct->proto.tcp.seen[1].flags;
1278         if (nla_put(skb, CTA_PROTOINFO_TCP_FLAGS_REPLY,
1279                     sizeof(struct nf_ct_tcp_flags), &tmp))
1280                 goto nla_put_failure;
1281 skip_state:
1282         spin_unlock_bh(&ct->lock);
1283         nla_nest_end(skb, nest_parms);
1284
1285         return 0;
1286
1287 nla_put_failure:
1288         spin_unlock_bh(&ct->lock);
1289         return -1;
1290 }
1291
1292 static const struct nla_policy tcp_nla_policy[CTA_PROTOINFO_TCP_MAX+1] = {
1293         [CTA_PROTOINFO_TCP_STATE]           = { .type = NLA_U8 },
1294         [CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] = { .type = NLA_U8 },
1295         [CTA_PROTOINFO_TCP_WSCALE_REPLY]    = { .type = NLA_U8 },
1296         [CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]  = { .len = sizeof(struct nf_ct_tcp_flags) },
1297         [CTA_PROTOINFO_TCP_FLAGS_REPLY]     = { .len = sizeof(struct nf_ct_tcp_flags) },
1298 };
1299
1300 #define TCP_NLATTR_SIZE ( \
1301         NLA_ALIGN(NLA_HDRLEN + 1) + \
1302         NLA_ALIGN(NLA_HDRLEN + 1) + \
1303         NLA_ALIGN(NLA_HDRLEN + sizeof(struct nf_ct_tcp_flags)) + \
1304         NLA_ALIGN(NLA_HDRLEN + sizeof(struct nf_ct_tcp_flags)))
1305
1306 static int nlattr_to_tcp(struct nlattr *cda[], struct nf_conn *ct)
1307 {
1308         struct nlattr *pattr = cda[CTA_PROTOINFO_TCP];
1309         struct nlattr *tb[CTA_PROTOINFO_TCP_MAX+1];
1310         int err;
1311
1312         /* updates could not contain anything about the private
1313          * protocol info, in that case skip the parsing */
1314         if (!pattr)
1315                 return 0;
1316
1317         err = nla_parse_nested_deprecated(tb, CTA_PROTOINFO_TCP_MAX, pattr,
1318                                           tcp_nla_policy, NULL);
1319         if (err < 0)
1320                 return err;
1321
1322         if (tb[CTA_PROTOINFO_TCP_STATE] &&
1323             nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]) >= TCP_CONNTRACK_MAX)
1324                 return -EINVAL;
1325
1326         spin_lock_bh(&ct->lock);
1327         if (tb[CTA_PROTOINFO_TCP_STATE])
1328                 ct->proto.tcp.state = nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]);
1329
1330         if (tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]) {
1331                 struct nf_ct_tcp_flags *attr =
1332                         nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]);
1333                 ct->proto.tcp.seen[0].flags &= ~attr->mask;
1334                 ct->proto.tcp.seen[0].flags |= attr->flags & attr->mask;
1335         }
1336
1337         if (tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]) {
1338                 struct nf_ct_tcp_flags *attr =
1339                         nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]);
1340                 ct->proto.tcp.seen[1].flags &= ~attr->mask;
1341                 ct->proto.tcp.seen[1].flags |= attr->flags & attr->mask;
1342         }
1343
1344         if (tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] &&
1345             tb[CTA_PROTOINFO_TCP_WSCALE_REPLY] &&
1346             ct->proto.tcp.seen[0].flags & IP_CT_TCP_FLAG_WINDOW_SCALE &&
1347             ct->proto.tcp.seen[1].flags & IP_CT_TCP_FLAG_WINDOW_SCALE) {
1348                 ct->proto.tcp.seen[0].td_scale =
1349                         nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL]);
1350                 ct->proto.tcp.seen[1].td_scale =
1351                         nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_REPLY]);
1352         }
1353         spin_unlock_bh(&ct->lock);
1354
1355         return 0;
1356 }
1357
1358 static unsigned int tcp_nlattr_tuple_size(void)
1359 {
1360         static unsigned int size __read_mostly;
1361
1362         if (!size)
1363                 size = nla_policy_len(nf_ct_port_nla_policy, CTA_PROTO_MAX + 1);
1364
1365         return size;
1366 }
1367 #endif
1368
1369 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
1370
1371 #include <linux/netfilter/nfnetlink.h>
1372 #include <linux/netfilter/nfnetlink_cttimeout.h>
1373
1374 static int tcp_timeout_nlattr_to_obj(struct nlattr *tb[],
1375                                      struct net *net, void *data)
1376 {
1377         struct nf_tcp_net *tn = nf_tcp_pernet(net);
1378         unsigned int *timeouts = data;
1379         int i;
1380
1381         if (!timeouts)
1382                 timeouts = tn->timeouts;
1383         /* set default TCP timeouts. */
1384         for (i=0; i<TCP_CONNTRACK_TIMEOUT_MAX; i++)
1385                 timeouts[i] = tn->timeouts[i];
1386
1387         if (tb[CTA_TIMEOUT_TCP_SYN_SENT]) {
1388                 timeouts[TCP_CONNTRACK_SYN_SENT] =
1389                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_SENT]))*HZ;
1390         }
1391
1392         if (tb[CTA_TIMEOUT_TCP_SYN_RECV]) {
1393                 timeouts[TCP_CONNTRACK_SYN_RECV] =
1394                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_RECV]))*HZ;
1395         }
1396         if (tb[CTA_TIMEOUT_TCP_ESTABLISHED]) {
1397                 timeouts[TCP_CONNTRACK_ESTABLISHED] =
1398                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_ESTABLISHED]))*HZ;
1399         }
1400         if (tb[CTA_TIMEOUT_TCP_FIN_WAIT]) {
1401                 timeouts[TCP_CONNTRACK_FIN_WAIT] =
1402                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_FIN_WAIT]))*HZ;
1403         }
1404         if (tb[CTA_TIMEOUT_TCP_CLOSE_WAIT]) {
1405                 timeouts[TCP_CONNTRACK_CLOSE_WAIT] =
1406                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_CLOSE_WAIT]))*HZ;
1407         }
1408         if (tb[CTA_TIMEOUT_TCP_LAST_ACK]) {
1409                 timeouts[TCP_CONNTRACK_LAST_ACK] =
1410                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_LAST_ACK]))*HZ;
1411         }
1412         if (tb[CTA_TIMEOUT_TCP_TIME_WAIT]) {
1413                 timeouts[TCP_CONNTRACK_TIME_WAIT] =
1414                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_TIME_WAIT]))*HZ;
1415         }
1416         if (tb[CTA_TIMEOUT_TCP_CLOSE]) {
1417                 timeouts[TCP_CONNTRACK_CLOSE] =
1418                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_CLOSE]))*HZ;
1419         }
1420         if (tb[CTA_TIMEOUT_TCP_SYN_SENT2]) {
1421                 timeouts[TCP_CONNTRACK_SYN_SENT2] =
1422                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_SYN_SENT2]))*HZ;
1423         }
1424         if (tb[CTA_TIMEOUT_TCP_RETRANS]) {
1425                 timeouts[TCP_CONNTRACK_RETRANS] =
1426                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_RETRANS]))*HZ;
1427         }
1428         if (tb[CTA_TIMEOUT_TCP_UNACK]) {
1429                 timeouts[TCP_CONNTRACK_UNACK] =
1430                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_TCP_UNACK]))*HZ;
1431         }
1432
1433         timeouts[CTA_TIMEOUT_TCP_UNSPEC] = timeouts[CTA_TIMEOUT_TCP_SYN_SENT];
1434         return 0;
1435 }
1436
1437 static int
1438 tcp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
1439 {
1440         const unsigned int *timeouts = data;
1441
1442         if (nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_SENT,
1443                         htonl(timeouts[TCP_CONNTRACK_SYN_SENT] / HZ)) ||
1444             nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_RECV,
1445                          htonl(timeouts[TCP_CONNTRACK_SYN_RECV] / HZ)) ||
1446             nla_put_be32(skb, CTA_TIMEOUT_TCP_ESTABLISHED,
1447                          htonl(timeouts[TCP_CONNTRACK_ESTABLISHED] / HZ)) ||
1448             nla_put_be32(skb, CTA_TIMEOUT_TCP_FIN_WAIT,
1449                          htonl(timeouts[TCP_CONNTRACK_FIN_WAIT] / HZ)) ||
1450             nla_put_be32(skb, CTA_TIMEOUT_TCP_CLOSE_WAIT,
1451                          htonl(timeouts[TCP_CONNTRACK_CLOSE_WAIT] / HZ)) ||
1452             nla_put_be32(skb, CTA_TIMEOUT_TCP_LAST_ACK,
1453                          htonl(timeouts[TCP_CONNTRACK_LAST_ACK] / HZ)) ||
1454             nla_put_be32(skb, CTA_TIMEOUT_TCP_TIME_WAIT,
1455                          htonl(timeouts[TCP_CONNTRACK_TIME_WAIT] / HZ)) ||
1456             nla_put_be32(skb, CTA_TIMEOUT_TCP_CLOSE,
1457                          htonl(timeouts[TCP_CONNTRACK_CLOSE] / HZ)) ||
1458             nla_put_be32(skb, CTA_TIMEOUT_TCP_SYN_SENT2,
1459                          htonl(timeouts[TCP_CONNTRACK_SYN_SENT2] / HZ)) ||
1460             nla_put_be32(skb, CTA_TIMEOUT_TCP_RETRANS,
1461                          htonl(timeouts[TCP_CONNTRACK_RETRANS] / HZ)) ||
1462             nla_put_be32(skb, CTA_TIMEOUT_TCP_UNACK,
1463                          htonl(timeouts[TCP_CONNTRACK_UNACK] / HZ)))
1464                 goto nla_put_failure;
1465         return 0;
1466
1467 nla_put_failure:
1468         return -ENOSPC;
1469 }
1470
1471 static const struct nla_policy tcp_timeout_nla_policy[CTA_TIMEOUT_TCP_MAX+1] = {
1472         [CTA_TIMEOUT_TCP_SYN_SENT]      = { .type = NLA_U32 },
1473         [CTA_TIMEOUT_TCP_SYN_RECV]      = { .type = NLA_U32 },
1474         [CTA_TIMEOUT_TCP_ESTABLISHED]   = { .type = NLA_U32 },
1475         [CTA_TIMEOUT_TCP_FIN_WAIT]      = { .type = NLA_U32 },
1476         [CTA_TIMEOUT_TCP_CLOSE_WAIT]    = { .type = NLA_U32 },
1477         [CTA_TIMEOUT_TCP_LAST_ACK]      = { .type = NLA_U32 },
1478         [CTA_TIMEOUT_TCP_TIME_WAIT]     = { .type = NLA_U32 },
1479         [CTA_TIMEOUT_TCP_CLOSE]         = { .type = NLA_U32 },
1480         [CTA_TIMEOUT_TCP_SYN_SENT2]     = { .type = NLA_U32 },
1481         [CTA_TIMEOUT_TCP_RETRANS]       = { .type = NLA_U32 },
1482         [CTA_TIMEOUT_TCP_UNACK]         = { .type = NLA_U32 },
1483 };
1484 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
1485
1486 void nf_conntrack_tcp_init_net(struct net *net)
1487 {
1488         struct nf_tcp_net *tn = nf_tcp_pernet(net);
1489         int i;
1490
1491         for (i = 0; i < TCP_CONNTRACK_TIMEOUT_MAX; i++)
1492                 tn->timeouts[i] = tcp_timeouts[i];
1493
1494         /* timeouts[0] is unused, make it same as SYN_SENT so
1495          * ->timeouts[0] contains 'new' timeout, like udp or icmp.
1496          */
1497         tn->timeouts[0] = tcp_timeouts[TCP_CONNTRACK_SYN_SENT];
1498
1499         /* If it is set to zero, we disable picking up already established
1500          * connections.
1501          */
1502         tn->tcp_loose = 1;
1503
1504         /* "Be conservative in what you do,
1505          *  be liberal in what you accept from others."
1506          * If it's non-zero, we mark only out of window RST segments as INVALID.
1507          */
1508         tn->tcp_be_liberal = 0;
1509
1510         /* If it's non-zero, we turn off RST sequence number check */
1511         tn->tcp_ignore_invalid_rst = 0;
1512
1513         /* Max number of the retransmitted packets without receiving an (acceptable)
1514          * ACK from the destination. If this number is reached, a shorter timer
1515          * will be started.
1516          */
1517         tn->tcp_max_retrans = 3;
1518
1519 #if IS_ENABLED(CONFIG_NF_FLOW_TABLE)
1520         tn->offload_timeout = 30 * HZ;
1521 #endif
1522 }
1523
1524 const struct nf_conntrack_l4proto nf_conntrack_l4proto_tcp =
1525 {
1526         .l4proto                = IPPROTO_TCP,
1527 #ifdef CONFIG_NF_CONNTRACK_PROCFS
1528         .print_conntrack        = tcp_print_conntrack,
1529 #endif
1530         .can_early_drop         = tcp_can_early_drop,
1531 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
1532         .to_nlattr              = tcp_to_nlattr,
1533         .from_nlattr            = nlattr_to_tcp,
1534         .tuple_to_nlattr        = nf_ct_port_tuple_to_nlattr,
1535         .nlattr_to_tuple        = nf_ct_port_nlattr_to_tuple,
1536         .nlattr_tuple_size      = tcp_nlattr_tuple_size,
1537         .nlattr_size            = TCP_NLATTR_SIZE,
1538         .nla_policy             = nf_ct_port_nla_policy,
1539 #endif
1540 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
1541         .ctnl_timeout           = {
1542                 .nlattr_to_obj  = tcp_timeout_nlattr_to_obj,
1543                 .obj_to_nlattr  = tcp_timeout_obj_to_nlattr,
1544                 .nlattr_max     = CTA_TIMEOUT_TCP_MAX,
1545                 .obj_size       = sizeof(unsigned int) *
1546                                         TCP_CONNTRACK_TIMEOUT_MAX,
1547                 .nla_policy     = tcp_timeout_nla_policy,
1548         },
1549 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
1550 };