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