net/netfilter/nf_synproxy_core.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (c) 2013 Patrick McHardy <kaber@trash.net>
   4  */
   5
   6 #include <linux/module.h>
   7 #include <linux/skbuff.h>
   8 #include <asm/unaligned.h>
   9 #include <net/tcp.h>
  10 #include <net/netns/generic.h>
  11 #include <linux/proc_fs.h>
  12
  13 #include <linux/netfilter_ipv6.h>
  14 #include <linux/netfilter/nf_synproxy.h>
  15
  16 #include <net/netfilter/nf_conntrack.h>
  17 #include <net/netfilter/nf_conntrack_ecache.h>
  18 #include <net/netfilter/nf_conntrack_extend.h>
  19 #include <net/netfilter/nf_conntrack_seqadj.h>
  20 #include <net/netfilter/nf_conntrack_synproxy.h>
  21 #include <net/netfilter/nf_conntrack_zones.h>
  22 #include <net/netfilter/nf_synproxy.h>
  23
  24 unsigned int synproxy_net_id;
  25 EXPORT_SYMBOL_GPL(synproxy_net_id);
  26
  27 bool
  28 synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
  29                        const struct tcphdr *th, struct synproxy_options *opts)
  30 {
  31         int length = (th->doff * 4) - sizeof(*th);
  32         u8 buf[40], *ptr;
  33
  34         if (unlikely(length < 0))
  35                 return false;
  36
  37         ptr = skb_header_pointer(skb, doff + sizeof(*th), length, buf);
  38         if (ptr == NULL)
  39                 return false;
  40
  41         opts->options = 0;
  42         while (length > 0) {
  43                 int opcode = *ptr++;
  44                 int opsize;
  45
  46                 switch (opcode) {
  47                 case TCPOPT_EOL:
  48                         return true;
  49                 case TCPOPT_NOP:
  50                         length--;
  51                         continue;
  52                 default:
  53                         if (length < 2)
  54                                 return true;
  55                         opsize = *ptr++;
  56                         if (opsize < 2)
  57                                 return true;
  58                         if (opsize > length)
  59                                 return true;
  60
  61                         switch (opcode) {
  62                         case TCPOPT_MSS:
  63                                 if (opsize == TCPOLEN_MSS) {
  64                                         opts->mss_option = get_unaligned_be16(ptr);
  65                                         opts->options |= NF_SYNPROXY_OPT_MSS;
  66                                 }
  67                                 break;
  68                         case TCPOPT_WINDOW:
  69                                 if (opsize == TCPOLEN_WINDOW) {
  70                                         opts->wscale = *ptr;
  71                                         if (opts->wscale > TCP_MAX_WSCALE)
  72                                                 opts->wscale = TCP_MAX_WSCALE;
  73                                         opts->options |= NF_SYNPROXY_OPT_WSCALE;
  74                                 }
  75                                 break;
  76                         case TCPOPT_TIMESTAMP:
  77                                 if (opsize == TCPOLEN_TIMESTAMP) {
  78                                         opts->tsval = get_unaligned_be32(ptr);
  79                                         opts->tsecr = get_unaligned_be32(ptr + 4);
  80                                         opts->options |= NF_SYNPROXY_OPT_TIMESTAMP;
  81                                 }
  82                                 break;
  83                         case TCPOPT_SACK_PERM:
  84                                 if (opsize == TCPOLEN_SACK_PERM)
  85                                         opts->options |= NF_SYNPROXY_OPT_SACK_PERM;
  86                                 break;
  87                         }
  88
  89                         ptr += opsize - 2;
  90                         length -= opsize;
  91                 }
  92         }
  93         return true;
  94 }
  95 EXPORT_SYMBOL_GPL(synproxy_parse_options);
  96
  97 static unsigned int
  98 synproxy_options_size(const struct synproxy_options *opts)
  99 {
 100         unsigned int size = 0;
 101
 102         if (opts->options & NF_SYNPROXY_OPT_MSS)
 103                 size += TCPOLEN_MSS_ALIGNED;
 104         if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
 105                 size += TCPOLEN_TSTAMP_ALIGNED;
 106         else if (opts->options & NF_SYNPROXY_OPT_SACK_PERM)
 107                 size += TCPOLEN_SACKPERM_ALIGNED;
 108         if (opts->options & NF_SYNPROXY_OPT_WSCALE)
 109                 size += TCPOLEN_WSCALE_ALIGNED;
 110
 111         return size;
 112 }
 113
 114 static void
 115 synproxy_build_options(struct tcphdr *th, const struct synproxy_options *opts)
 116 {
 117         __be32 *ptr = (__be32 *)(th + 1);
 118         u8 options = opts->options;
 119
 120         if (options & NF_SYNPROXY_OPT_MSS)
 121                 *ptr++ = htonl((TCPOPT_MSS << 24) |
 122                                (TCPOLEN_MSS << 16) |
 123                                opts->mss_option);
 124
 125         if (options & NF_SYNPROXY_OPT_TIMESTAMP) {
 126                 if (options & NF_SYNPROXY_OPT_SACK_PERM)
 127                         *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
 128                                        (TCPOLEN_SACK_PERM << 16) |
 129                                        (TCPOPT_TIMESTAMP << 8) |
 130                                        TCPOLEN_TIMESTAMP);
 131                 else
 132                         *ptr++ = htonl((TCPOPT_NOP << 24) |
 133                                        (TCPOPT_NOP << 16) |
 134                                        (TCPOPT_TIMESTAMP << 8) |
 135                                        TCPOLEN_TIMESTAMP);
 136
 137                 *ptr++ = htonl(opts->tsval);
 138                 *ptr++ = htonl(opts->tsecr);
 139         } else if (options & NF_SYNPROXY_OPT_SACK_PERM)
 140                 *ptr++ = htonl((TCPOPT_NOP << 24) |
 141                                (TCPOPT_NOP << 16) |
 142                                (TCPOPT_SACK_PERM << 8) |
 143                                TCPOLEN_SACK_PERM);
 144
 145         if (options & NF_SYNPROXY_OPT_WSCALE)
 146                 *ptr++ = htonl((TCPOPT_NOP << 24) |
 147                                (TCPOPT_WINDOW << 16) |
 148                                (TCPOLEN_WINDOW << 8) |
 149                                opts->wscale);
 150 }
 151
 152 void synproxy_init_timestamp_cookie(const struct nf_synproxy_info *info,
 153                                     struct synproxy_options *opts)
 154 {
 155         opts->tsecr = opts->tsval;
 156         opts->tsval = tcp_time_stamp_raw() & ~0x3f;
 157
 158         if (opts->options & NF_SYNPROXY_OPT_WSCALE) {
 159                 opts->tsval |= opts->wscale;
 160                 opts->wscale = info->wscale;
 161         } else
 162                 opts->tsval |= 0xf;
 163
 164         if (opts->options & NF_SYNPROXY_OPT_SACK_PERM)
 165                 opts->tsval |= 1 << 4;
 166
 167         if (opts->options & NF_SYNPROXY_OPT_ECN)
 168                 opts->tsval |= 1 << 5;
 169 }
 170 EXPORT_SYMBOL_GPL(synproxy_init_timestamp_cookie);
 171
 172 static void
 173 synproxy_check_timestamp_cookie(struct synproxy_options *opts)
 174 {
 175         opts->wscale = opts->tsecr & 0xf;
 176         if (opts->wscale != 0xf)
 177                 opts->options |= NF_SYNPROXY_OPT_WSCALE;
 178
 179         opts->options |= opts->tsecr & (1 << 4) ? NF_SYNPROXY_OPT_SACK_PERM : 0;
 180
 181         opts->options |= opts->tsecr & (1 << 5) ? NF_SYNPROXY_OPT_ECN : 0;
 182 }
 183
 184 static unsigned int
 185 synproxy_tstamp_adjust(struct sk_buff *skb, unsigned int protoff,
 186                        struct tcphdr *th, struct nf_conn *ct,
 187                        enum ip_conntrack_info ctinfo,
 188                        const struct nf_conn_synproxy *synproxy)
 189 {
 190         unsigned int optoff, optend;
 191         __be32 *ptr, old;
 192
 193         if (synproxy->tsoff == 0)
 194                 return 1;
 195
 196         optoff = protoff + sizeof(struct tcphdr);
 197         optend = protoff + th->doff * 4;
 198
 199         if (skb_ensure_writable(skb, optend))
 200                 return 0;
 201
 202         while (optoff < optend) {
 203                 unsigned char *op = skb->data + optoff;
 204
 205                 switch (op[0]) {
 206                 case TCPOPT_EOL:
 207                         return 1;
 208                 case TCPOPT_NOP:
 209                         optoff++;
 210                         continue;
 211                 default:
 212                         if (optoff + 1 == optend ||
 213                             optoff + op[1] > optend ||
 214                             op[1] < 2)
 215                                 return 0;
 216                         if (op[0] == TCPOPT_TIMESTAMP &&
 217                             op[1] == TCPOLEN_TIMESTAMP) {
 218                                 if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
 219                                         ptr = (__be32 *)&op[2];
 220                                         old = *ptr;
 221                                         *ptr = htonl(ntohl(*ptr) -
 222                                                      synproxy->tsoff);
 223                                 } else {
 224                                         ptr = (__be32 *)&op[6];
 225                                         old = *ptr;
 226                                         *ptr = htonl(ntohl(*ptr) +
 227                                                      synproxy->tsoff);
 228                                 }
 229                                 inet_proto_csum_replace4(&th->check, skb,
 230                                                          old, *ptr, false);
 231                                 return 1;
 232                         }
 233                         optoff += op[1];
 234                 }
 235         }
 236         return 1;
 237 }
 238
 239 static struct nf_ct_ext_type nf_ct_synproxy_extend __read_mostly = {
 240         .len            = sizeof(struct nf_conn_synproxy),
 241         .align          = __alignof__(struct nf_conn_synproxy),
 242         .id             = NF_CT_EXT_SYNPROXY,
 243 };
 244
 245 #ifdef CONFIG_PROC_FS
 246 static void *synproxy_cpu_seq_start(struct seq_file *seq, loff_t *pos)
 247 {
 248         struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq));
 249         int cpu;
 250
 251         if (*pos == 0)
 252                 return SEQ_START_TOKEN;
 253
 254         for (cpu = *pos - 1; cpu < nr_cpu_ids; cpu++) {
 255                 if (!cpu_possible(cpu))
 256                         continue;
 257                 *pos = cpu + 1;
 258                 return per_cpu_ptr(snet->stats, cpu);
 259         }
 260
 261         return NULL;
 262 }
 263
 264 static void *synproxy_cpu_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 265 {
 266         struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq));
 267         int cpu;
 268
 269         for (cpu = *pos; cpu < nr_cpu_ids; cpu++) {
 270                 if (!cpu_possible(cpu))
 271                         continue;
 272                 *pos = cpu + 1;
 273                 return per_cpu_ptr(snet->stats, cpu);
 274         }
 275         (*pos)++;
 276         return NULL;
 277 }
 278
 279 static void synproxy_cpu_seq_stop(struct seq_file *seq, void *v)
 280 {
 281         return;
 282 }
 283
 284 static int synproxy_cpu_seq_show(struct seq_file *seq, void *v)
 285 {
 286         struct synproxy_stats *stats = v;
 287
 288         if (v == SEQ_START_TOKEN) {
 289                 seq_puts(seq, "entries\t\tsyn_received\t"
 290                               "cookie_invalid\tcookie_valid\t"
 291                               "cookie_retrans\tconn_reopened\n");
 292                 return 0;
 293         }
 294
 295         seq_printf(seq, "%08x\t%08x\t%08x\t%08x\t%08x\t%08x\n", 0,
 296                    stats->syn_received,
 297                    stats->cookie_invalid,
 298                    stats->cookie_valid,
 299                    stats->cookie_retrans,
 300                    stats->conn_reopened);
 301
 302         return 0;
 303 }
 304
 305 static const struct seq_operations synproxy_cpu_seq_ops = {
 306         .start          = synproxy_cpu_seq_start,
 307         .next           = synproxy_cpu_seq_next,
 308         .stop           = synproxy_cpu_seq_stop,
 309         .show           = synproxy_cpu_seq_show,
 310 };
 311
 312 static int __net_init synproxy_proc_init(struct net *net)
 313 {
 314         if (!proc_create_net("synproxy", 0444, net->proc_net_stat,
 315                         &synproxy_cpu_seq_ops, sizeof(struct seq_net_private)))
 316                 return -ENOMEM;
 317         return 0;
 318 }
 319
 320 static void __net_exit synproxy_proc_exit(struct net *net)
 321 {
 322         remove_proc_entry("synproxy", net->proc_net_stat);
 323 }
 324 #else
 325 static int __net_init synproxy_proc_init(struct net *net)
 326 {
 327         return 0;
 328 }
 329
 330 static void __net_exit synproxy_proc_exit(struct net *net)
 331 {
 332         return;
 333 }
 334 #endif /* CONFIG_PROC_FS */
 335
 336 static int __net_init synproxy_net_init(struct net *net)
 337 {
 338         struct synproxy_net *snet = synproxy_pernet(net);
 339         struct nf_conn *ct;
 340         int err = -ENOMEM;
 341
 342         ct = nf_ct_tmpl_alloc(net, &nf_ct_zone_dflt, GFP_KERNEL);
 343         if (!ct)
 344                 goto err1;
 345
 346         if (!nfct_seqadj_ext_add(ct))
 347                 goto err2;
 348         if (!nfct_synproxy_ext_add(ct))
 349                 goto err2;
 350
 351         __set_bit(IPS_CONFIRMED_BIT, &ct->status);
 352         nf_conntrack_get(&ct->ct_general);
 353         snet->tmpl = ct;
 354
 355         snet->stats = alloc_percpu(struct synproxy_stats);
 356         if (snet->stats == NULL)
 357                 goto err2;
 358
 359         err = synproxy_proc_init(net);
 360         if (err < 0)
 361                 goto err3;
 362
 363         return 0;
 364
 365 err3:
 366         free_percpu(snet->stats);
 367 err2:
 368         nf_ct_tmpl_free(ct);
 369 err1:
 370         return err;
 371 }
 372
 373 static void __net_exit synproxy_net_exit(struct net *net)
 374 {
 375         struct synproxy_net *snet = synproxy_pernet(net);
 376
 377         nf_ct_put(snet->tmpl);
 378         synproxy_proc_exit(net);
 379         free_percpu(snet->stats);
 380 }
 381
 382 static struct pernet_operations synproxy_net_ops = {
 383         .init           = synproxy_net_init,
 384         .exit           = synproxy_net_exit,
 385         .id             = &synproxy_net_id,
 386         .size           = sizeof(struct synproxy_net),
 387 };
 388
 389 static int __init synproxy_core_init(void)
 390 {
 391         int err;
 392
 393         err = nf_ct_extend_register(&nf_ct_synproxy_extend);
 394         if (err < 0)
 395                 goto err1;
 396
 397         err = register_pernet_subsys(&synproxy_net_ops);
 398         if (err < 0)
 399                 goto err2;
 400
 401         return 0;
 402
 403 err2:
 404         nf_ct_extend_unregister(&nf_ct_synproxy_extend);
 405 err1:
 406         return err;
 407 }
 408
 409 static void __exit synproxy_core_exit(void)
 410 {
 411         unregister_pernet_subsys(&synproxy_net_ops);
 412         nf_ct_extend_unregister(&nf_ct_synproxy_extend);
 413 }
 414
 415 module_init(synproxy_core_init);
 416 module_exit(synproxy_core_exit);
 417
 418 static struct iphdr *
 419 synproxy_build_ip(struct net *net, struct sk_buff *skb, __be32 saddr,
 420                   __be32 daddr)
 421 {
 422         struct iphdr *iph;
 423
 424         skb_reset_network_header(skb);
 425         iph = skb_put(skb, sizeof(*iph));
 426         iph->version    = 4;
 427         iph->ihl        = sizeof(*iph) / 4;
 428         iph->tos        = 0;
 429         iph->id         = 0;
 430         iph->frag_off   = htons(IP_DF);
 431         iph->ttl        = net->ipv4.sysctl_ip_default_ttl;
 432         iph->protocol   = IPPROTO_TCP;
 433         iph->check      = 0;
 434         iph->saddr      = saddr;
 435         iph->daddr      = daddr;
 436
 437         return iph;
 438 }
 439
 440 static void
 441 synproxy_send_tcp(struct net *net,
 442                   const struct sk_buff *skb, struct sk_buff *nskb,
 443                   struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
 444                   struct iphdr *niph, struct tcphdr *nth,
 445                   unsigned int tcp_hdr_size)
 446 {
 447         nth->check = ~tcp_v4_check(tcp_hdr_size, niph->saddr, niph->daddr, 0);
 448         nskb->ip_summed   = CHECKSUM_PARTIAL;
 449         nskb->csum_start  = (unsigned char *)nth - nskb->head;
 450         nskb->csum_offset = offsetof(struct tcphdr, check);
 451
 452         skb_dst_set_noref(nskb, skb_dst(skb));
 453         nskb->protocol = htons(ETH_P_IP);
 454         if (ip_route_me_harder(net, nskb->sk, nskb, RTN_UNSPEC))
 455                 goto free_nskb;
 456
 457         if (nfct) {
 458                 nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo);
 459                 nf_conntrack_get(nfct);
 460         }
 461
 462         ip_local_out(net, nskb->sk, nskb);
 463         return;
 464
 465 free_nskb:
 466         kfree_skb(nskb);
 467 }
 468
 469 void
 470 synproxy_send_client_synack(struct net *net,
 471                             const struct sk_buff *skb, const struct tcphdr *th,
 472                             const struct synproxy_options *opts)
 473 {
 474         struct sk_buff *nskb;
 475         struct iphdr *iph, *niph;
 476         struct tcphdr *nth;
 477         unsigned int tcp_hdr_size;
 478         u16 mss = opts->mss_encode;
 479
 480         iph = ip_hdr(skb);
 481
 482         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
 483         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
 484                          GFP_ATOMIC);
 485         if (!nskb)
 486                 return;
 487         skb_reserve(nskb, MAX_TCP_HEADER);
 488
 489         niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
 490
 491         skb_reset_transport_header(nskb);
 492         nth = skb_put(nskb, tcp_hdr_size);
 493         nth->source     = th->dest;
 494         nth->dest       = th->source;
 495         nth->seq        = htonl(__cookie_v4_init_sequence(iph, th, &mss));
 496         nth->ack_seq    = htonl(ntohl(th->seq) + 1);
 497         tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK;
 498         if (opts->options & NF_SYNPROXY_OPT_ECN)
 499                 tcp_flag_word(nth) |= TCP_FLAG_ECE;
 500         nth->doff       = tcp_hdr_size / 4;
 501         nth->window     = 0;
 502         nth->check      = 0;
 503         nth->urg_ptr    = 0;
 504
 505         synproxy_build_options(nth, opts);
 506
 507         synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
 508                           IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
 509 }
 510 EXPORT_SYMBOL_GPL(synproxy_send_client_synack);
 511
 512 static void
 513 synproxy_send_server_syn(struct net *net,
 514                          const struct sk_buff *skb, const struct tcphdr *th,
 515                          const struct synproxy_options *opts, u32 recv_seq)
 516 {
 517         struct synproxy_net *snet = synproxy_pernet(net);
 518         struct sk_buff *nskb;
 519         struct iphdr *iph, *niph;
 520         struct tcphdr *nth;
 521         unsigned int tcp_hdr_size;
 522
 523         iph = ip_hdr(skb);
 524
 525         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
 526         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
 527                          GFP_ATOMIC);
 528         if (!nskb)
 529                 return;
 530         skb_reserve(nskb, MAX_TCP_HEADER);
 531
 532         niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
 533
 534         skb_reset_transport_header(nskb);
 535         nth = skb_put(nskb, tcp_hdr_size);
 536         nth->source     = th->source;
 537         nth->dest       = th->dest;
 538         nth->seq        = htonl(recv_seq - 1);
 539         /* ack_seq is used to relay our ISN to the synproxy hook to initialize
 540          * sequence number translation once a connection tracking entry exists.
 541          */
 542         nth->ack_seq    = htonl(ntohl(th->ack_seq) - 1);
 543         tcp_flag_word(nth) = TCP_FLAG_SYN;
 544         if (opts->options & NF_SYNPROXY_OPT_ECN)
 545                 tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR;
 546         nth->doff       = tcp_hdr_size / 4;
 547         nth->window     = th->window;
 548         nth->check      = 0;
 549         nth->urg_ptr    = 0;
 550
 551         synproxy_build_options(nth, opts);
 552
 553         synproxy_send_tcp(net, skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW,
 554                           niph, nth, tcp_hdr_size);
 555 }
 556
 557 static void
 558 synproxy_send_server_ack(struct net *net,
 559                          const struct ip_ct_tcp *state,
 560                          const struct sk_buff *skb, const struct tcphdr *th,
 561                          const struct synproxy_options *opts)
 562 {
 563         struct sk_buff *nskb;
 564         struct iphdr *iph, *niph;
 565         struct tcphdr *nth;
 566         unsigned int tcp_hdr_size;
 567
 568         iph = ip_hdr(skb);
 569
 570         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
 571         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
 572                          GFP_ATOMIC);
 573         if (!nskb)
 574                 return;
 575         skb_reserve(nskb, MAX_TCP_HEADER);
 576
 577         niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
 578
 579         skb_reset_transport_header(nskb);
 580         nth = skb_put(nskb, tcp_hdr_size);
 581         nth->source     = th->dest;
 582         nth->dest       = th->source;
 583         nth->seq        = htonl(ntohl(th->ack_seq));
 584         nth->ack_seq    = htonl(ntohl(th->seq) + 1);
 585         tcp_flag_word(nth) = TCP_FLAG_ACK;
 586         nth->doff       = tcp_hdr_size / 4;
 587         nth->window     = htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin);
 588         nth->check      = 0;
 589         nth->urg_ptr    = 0;
 590
 591         synproxy_build_options(nth, opts);
 592
 593         synproxy_send_tcp(net, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
 594 }
 595
 596 static void
 597 synproxy_send_client_ack(struct net *net,
 598                          const struct sk_buff *skb, const struct tcphdr *th,
 599                          const struct synproxy_options *opts)
 600 {
 601         struct sk_buff *nskb;
 602         struct iphdr *iph, *niph;
 603         struct tcphdr *nth;
 604         unsigned int tcp_hdr_size;
 605
 606         iph = ip_hdr(skb);
 607
 608         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
 609         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
 610                          GFP_ATOMIC);
 611         if (!nskb)
 612                 return;
 613         skb_reserve(nskb, MAX_TCP_HEADER);
 614
 615         niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
 616
 617         skb_reset_transport_header(nskb);
 618         nth = skb_put(nskb, tcp_hdr_size);
 619         nth->source     = th->source;
 620         nth->dest       = th->dest;
 621         nth->seq        = htonl(ntohl(th->seq) + 1);
 622         nth->ack_seq    = th->ack_seq;
 623         tcp_flag_word(nth) = TCP_FLAG_ACK;
 624         nth->doff       = tcp_hdr_size / 4;
 625         nth->window     = htons(ntohs(th->window) >> opts->wscale);
 626         nth->check      = 0;
 627         nth->urg_ptr    = 0;
 628
 629         synproxy_build_options(nth, opts);
 630
 631         synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
 632                           IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
 633 }
 634
 635 bool
 636 synproxy_recv_client_ack(struct net *net,
 637                          const struct sk_buff *skb, const struct tcphdr *th,
 638                          struct synproxy_options *opts, u32 recv_seq)
 639 {
 640         struct synproxy_net *snet = synproxy_pernet(net);
 641         int mss;
 642
 643         mss = __cookie_v4_check(ip_hdr(skb), th, ntohl(th->ack_seq) - 1);
 644         if (mss == 0) {
 645                 this_cpu_inc(snet->stats->cookie_invalid);
 646                 return false;
 647         }
 648
 649         this_cpu_inc(snet->stats->cookie_valid);
 650         opts->mss_option = mss;
 651         opts->options |= NF_SYNPROXY_OPT_MSS;
 652
 653         if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
 654                 synproxy_check_timestamp_cookie(opts);
 655
 656         synproxy_send_server_syn(net, skb, th, opts, recv_seq);
 657         return true;
 658 }
 659 EXPORT_SYMBOL_GPL(synproxy_recv_client_ack);
 660
 661 unsigned int
 662 ipv4_synproxy_hook(void *priv, struct sk_buff *skb,
 663                    const struct nf_hook_state *nhs)
 664 {
 665         struct net *net = nhs->net;
 666         struct synproxy_net *snet = synproxy_pernet(net);
 667         enum ip_conntrack_info ctinfo;
 668         struct nf_conn *ct;
 669         struct nf_conn_synproxy *synproxy;
 670         struct synproxy_options opts = {};
 671         const struct ip_ct_tcp *state;
 672         struct tcphdr *th, _th;
 673         unsigned int thoff;
 674
 675         ct = nf_ct_get(skb, &ctinfo);
 676         if (!ct)
 677                 return NF_ACCEPT;
 678
 679         synproxy = nfct_synproxy(ct);
 680         if (!synproxy)
 681                 return NF_ACCEPT;
 682
 683         if (nf_is_loopback_packet(skb) ||
 684             ip_hdr(skb)->protocol != IPPROTO_TCP)
 685                 return NF_ACCEPT;
 686
 687         thoff = ip_hdrlen(skb);
 688         th = skb_header_pointer(skb, thoff, sizeof(_th), &_th);
 689         if (!th)
 690                 return NF_DROP;
 691
 692         state = &ct->proto.tcp;
 693         switch (state->state) {
 694         case TCP_CONNTRACK_CLOSE:
 695                 if (th->rst && CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
 696                         nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
 697                                                       ntohl(th->seq) + 1);
 698                         break;
 699                 }
 700
 701                 if (!th->syn || th->ack ||
 702                     CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
 703                         break;
 704
 705                 /* Reopened connection - reset the sequence number and timestamp
 706                  * adjustments, they will get initialized once the connection is
 707                  * reestablished.
 708                  */
 709                 nf_ct_seqadj_init(ct, ctinfo, 0);
 710                 synproxy->tsoff = 0;
 711                 this_cpu_inc(snet->stats->conn_reopened);
 712                 fallthrough;
 713         case TCP_CONNTRACK_SYN_SENT:
 714                 if (!synproxy_parse_options(skb, thoff, th, &opts))
 715                         return NF_DROP;
 716
 717                 if (!th->syn && th->ack &&
 718                     CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
 719                         /* Keep-Alives are sent with SEG.SEQ = SND.NXT-1,
 720                          * therefore we need to add 1 to make the SYN sequence
 721                          * number match the one of first SYN.
 722                          */
 723                         if (synproxy_recv_client_ack(net, skb, th, &opts,
 724                                                      ntohl(th->seq) + 1)) {
 725                                 this_cpu_inc(snet->stats->cookie_retrans);
 726                                 consume_skb(skb);
 727                                 return NF_STOLEN;
 728                         } else {
 729                                 return NF_DROP;
 730                         }
 731                 }
 732
 733                 synproxy->isn = ntohl(th->ack_seq);
 734                 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP)
 735                         synproxy->its = opts.tsecr;
 736
 737                 nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
 738                 break;
 739         case TCP_CONNTRACK_SYN_RECV:
 740                 if (!th->syn || !th->ack)
 741                         break;
 742
 743                 if (!synproxy_parse_options(skb, thoff, th, &opts))
 744                         return NF_DROP;
 745
 746                 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP) {
 747                         synproxy->tsoff = opts.tsval - synproxy->its;
 748                         nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
 749                 }
 750
 751                 opts.options &= ~(NF_SYNPROXY_OPT_MSS |
 752                                   NF_SYNPROXY_OPT_WSCALE |
 753                                   NF_SYNPROXY_OPT_SACK_PERM);
 754
 755                 swap(opts.tsval, opts.tsecr);
 756                 synproxy_send_server_ack(net, state, skb, th, &opts);
 757
 758                 nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq));
 759                 nf_conntrack_event_cache(IPCT_SEQADJ, ct);
 760
 761                 swap(opts.tsval, opts.tsecr);
 762                 synproxy_send_client_ack(net, skb, th, &opts);
 763
 764                 consume_skb(skb);
 765                 return NF_STOLEN;
 766         default:
 767                 break;
 768         }
 769
 770         synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
 771         return NF_ACCEPT;
 772 }
 773 EXPORT_SYMBOL_GPL(ipv4_synproxy_hook);
 774
 775 static const struct nf_hook_ops ipv4_synproxy_ops[] = {
 776         {
 777                 .hook           = ipv4_synproxy_hook,
 778                 .pf             = NFPROTO_IPV4,
 779                 .hooknum        = NF_INET_LOCAL_IN,
 780                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
 781         },
 782         {
 783                 .hook           = ipv4_synproxy_hook,
 784                 .pf             = NFPROTO_IPV4,
 785                 .hooknum        = NF_INET_POST_ROUTING,
 786                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
 787         },
 788 };
 789
 790 int nf_synproxy_ipv4_init(struct synproxy_net *snet, struct net *net)
 791 {
 792         int err;
 793
 794         if (snet->hook_ref4 == 0) {
 795                 err = nf_register_net_hooks(net, ipv4_synproxy_ops,
 796                                             ARRAY_SIZE(ipv4_synproxy_ops));
 797                 if (err)
 798                         return err;
 799         }
 800
 801         snet->hook_ref4++;
 802         return 0;
 803 }
 804 EXPORT_SYMBOL_GPL(nf_synproxy_ipv4_init);
 805
 806 void nf_synproxy_ipv4_fini(struct synproxy_net *snet, struct net *net)
 807 {
 808         snet->hook_ref4--;
 809         if (snet->hook_ref4 == 0)
 810                 nf_unregister_net_hooks(net, ipv4_synproxy_ops,
 811                                         ARRAY_SIZE(ipv4_synproxy_ops));
 812 }
 813 EXPORT_SYMBOL_GPL(nf_synproxy_ipv4_fini);
 814
 815 #if IS_ENABLED(CONFIG_IPV6)
 816 static struct ipv6hdr *
 817 synproxy_build_ip_ipv6(struct net *net, struct sk_buff *skb,
 818                        const struct in6_addr *saddr,
 819                        const struct in6_addr *daddr)
 820 {
 821         struct ipv6hdr *iph;
 822
 823         skb_reset_network_header(skb);
 824         iph = skb_put(skb, sizeof(*iph));
 825         ip6_flow_hdr(iph, 0, 0);
 826         iph->hop_limit  = net->ipv6.devconf_all->hop_limit;
 827         iph->nexthdr    = IPPROTO_TCP;
 828         iph->saddr      = *saddr;
 829         iph->daddr      = *daddr;
 830
 831         return iph;
 832 }
 833
 834 static void
 835 synproxy_send_tcp_ipv6(struct net *net,
 836                        const struct sk_buff *skb, struct sk_buff *nskb,
 837                        struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
 838                        struct ipv6hdr *niph, struct tcphdr *nth,
 839                        unsigned int tcp_hdr_size)
 840 {
 841         struct dst_entry *dst;
 842         struct flowi6 fl6;
 843         int err;
 844
 845         nth->check = ~tcp_v6_check(tcp_hdr_size, &niph->saddr, &niph->daddr, 0);
 846         nskb->ip_summed   = CHECKSUM_PARTIAL;
 847         nskb->csum_start  = (unsigned char *)nth - nskb->head;
 848         nskb->csum_offset = offsetof(struct tcphdr, check);
 849
 850         memset(&fl6, 0, sizeof(fl6));
 851         fl6.flowi6_proto = IPPROTO_TCP;
 852         fl6.saddr = niph->saddr;
 853         fl6.daddr = niph->daddr;
 854         fl6.fl6_sport = nth->source;
 855         fl6.fl6_dport = nth->dest;
 856         security_skb_classify_flow((struct sk_buff *)skb,
 857                                    flowi6_to_flowi_common(&fl6));
 858         err = nf_ip6_route(net, &dst, flowi6_to_flowi(&fl6), false);
 859         if (err) {
 860                 goto free_nskb;
 861         }
 862
 863         dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
 864         if (IS_ERR(dst))
 865                 goto free_nskb;
 866
 867         skb_dst_set(nskb, dst);
 868
 869         if (nfct) {
 870                 nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo);
 871                 nf_conntrack_get(nfct);
 872         }
 873
 874         ip6_local_out(net, nskb->sk, nskb);
 875         return;
 876
 877 free_nskb:
 878         kfree_skb(nskb);
 879 }
 880
 881 void
 882 synproxy_send_client_synack_ipv6(struct net *net,
 883                                  const struct sk_buff *skb,
 884                                  const struct tcphdr *th,
 885                                  const struct synproxy_options *opts)
 886 {
 887         struct sk_buff *nskb;
 888         struct ipv6hdr *iph, *niph;
 889         struct tcphdr *nth;
 890         unsigned int tcp_hdr_size;
 891         u16 mss = opts->mss_encode;
 892
 893         iph = ipv6_hdr(skb);
 894
 895         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
 896         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
 897                          GFP_ATOMIC);
 898         if (!nskb)
 899                 return;
 900         skb_reserve(nskb, MAX_TCP_HEADER);
 901
 902         niph = synproxy_build_ip_ipv6(net, nskb, &iph->daddr, &iph->saddr);
 903
 904         skb_reset_transport_header(nskb);
 905         nth = skb_put(nskb, tcp_hdr_size);
 906         nth->source     = th->dest;
 907         nth->dest       = th->source;
 908         nth->seq        = htonl(nf_ipv6_cookie_init_sequence(iph, th, &mss));
 909         nth->ack_seq    = htonl(ntohl(th->seq) + 1);
 910         tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK;
 911         if (opts->options & NF_SYNPROXY_OPT_ECN)
 912                 tcp_flag_word(nth) |= TCP_FLAG_ECE;
 913         nth->doff       = tcp_hdr_size / 4;
 914         nth->window     = 0;
 915         nth->check      = 0;
 916         nth->urg_ptr    = 0;
 917
 918         synproxy_build_options(nth, opts);
 919
 920         synproxy_send_tcp_ipv6(net, skb, nskb, skb_nfct(skb),
 921                                IP_CT_ESTABLISHED_REPLY, niph, nth,
 922                                tcp_hdr_size);
 923 }
 924 EXPORT_SYMBOL_GPL(synproxy_send_client_synack_ipv6);
 925
 926 static void
 927 synproxy_send_server_syn_ipv6(struct net *net, const struct sk_buff *skb,
 928                               const struct tcphdr *th,
 929                               const struct synproxy_options *opts, u32 recv_seq)
 930 {
 931         struct synproxy_net *snet = synproxy_pernet(net);
 932         struct sk_buff *nskb;
 933         struct ipv6hdr *iph, *niph;
 934         struct tcphdr *nth;
 935         unsigned int tcp_hdr_size;
 936
 937         iph = ipv6_hdr(skb);
 938
 939         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
 940         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
 941                          GFP_ATOMIC);
 942         if (!nskb)
 943                 return;
 944         skb_reserve(nskb, MAX_TCP_HEADER);
 945
 946         niph = synproxy_build_ip_ipv6(net, nskb, &iph->saddr, &iph->daddr);
 947
 948         skb_reset_transport_header(nskb);
 949         nth = skb_put(nskb, tcp_hdr_size);
 950         nth->source     = th->source;
 951         nth->dest       = th->dest;
 952         nth->seq        = htonl(recv_seq - 1);
 953         /* ack_seq is used to relay our ISN to the synproxy hook to initialize
 954          * sequence number translation once a connection tracking entry exists.
 955          */
 956         nth->ack_seq    = htonl(ntohl(th->ack_seq) - 1);
 957         tcp_flag_word(nth) = TCP_FLAG_SYN;
 958         if (opts->options & NF_SYNPROXY_OPT_ECN)
 959                 tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR;
 960         nth->doff       = tcp_hdr_size / 4;
 961         nth->window     = th->window;
 962         nth->check      = 0;
 963         nth->urg_ptr    = 0;
 964
 965         synproxy_build_options(nth, opts);
 966
 967         synproxy_send_tcp_ipv6(net, skb, nskb, &snet->tmpl->ct_general,
 968                                IP_CT_NEW, niph, nth, tcp_hdr_size);
 969 }
 970
 971 static void
 972 synproxy_send_server_ack_ipv6(struct net *net, const struct ip_ct_tcp *state,
 973                               const struct sk_buff *skb,
 974                               const struct tcphdr *th,
 975                               const struct synproxy_options *opts)
 976 {
 977         struct sk_buff *nskb;
 978         struct ipv6hdr *iph, *niph;
 979         struct tcphdr *nth;
 980         unsigned int tcp_hdr_size;
 981
 982         iph = ipv6_hdr(skb);
 983
 984         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
 985         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
 986                          GFP_ATOMIC);
 987         if (!nskb)
 988                 return;
 989         skb_reserve(nskb, MAX_TCP_HEADER);
 990
 991         niph = synproxy_build_ip_ipv6(net, nskb, &iph->daddr, &iph->saddr);
 992
 993         skb_reset_transport_header(nskb);
 994         nth = skb_put(nskb, tcp_hdr_size);
 995         nth->source     = th->dest;
 996         nth->dest       = th->source;
 997         nth->seq        = htonl(ntohl(th->ack_seq));
 998         nth->ack_seq    = htonl(ntohl(th->seq) + 1);
 999         tcp_flag_word(nth) = TCP_FLAG_ACK;
1000         nth->doff       = tcp_hdr_size / 4;
1001         nth->window     = htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin);
1002         nth->check      = 0;
1003         nth->urg_ptr    = 0;
1004
1005         synproxy_build_options(nth, opts);
1006
1007         synproxy_send_tcp_ipv6(net, skb, nskb, NULL, 0, niph, nth,
1008                                tcp_hdr_size);
1009 }
1010
1011 static void
1012 synproxy_send_client_ack_ipv6(struct net *net, const struct sk_buff *skb,
1013                               const struct tcphdr *th,
1014                               const struct synproxy_options *opts)
1015 {
1016         struct sk_buff *nskb;
1017         struct ipv6hdr *iph, *niph;
1018         struct tcphdr *nth;
1019         unsigned int tcp_hdr_size;
1020
1021         iph = ipv6_hdr(skb);
1022
1023         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
1024         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
1025                          GFP_ATOMIC);
1026         if (!nskb)
1027                 return;
1028         skb_reserve(nskb, MAX_TCP_HEADER);
1029
1030         niph = synproxy_build_ip_ipv6(net, nskb, &iph->saddr, &iph->daddr);
1031
1032         skb_reset_transport_header(nskb);
1033         nth = skb_put(nskb, tcp_hdr_size);
1034         nth->source     = th->source;
1035         nth->dest       = th->dest;
1036         nth->seq        = htonl(ntohl(th->seq) + 1);
1037         nth->ack_seq    = th->ack_seq;
1038         tcp_flag_word(nth) = TCP_FLAG_ACK;
1039         nth->doff       = tcp_hdr_size / 4;
1040         nth->window     = htons(ntohs(th->window) >> opts->wscale);
1041         nth->check      = 0;
1042         nth->urg_ptr    = 0;
1043
1044         synproxy_build_options(nth, opts);
1045
1046         synproxy_send_tcp_ipv6(net, skb, nskb, skb_nfct(skb),
1047                                IP_CT_ESTABLISHED_REPLY, niph, nth,
1048                                tcp_hdr_size);
1049 }
1050
1051 bool
1052 synproxy_recv_client_ack_ipv6(struct net *net,
1053                               const struct sk_buff *skb,
1054                               const struct tcphdr *th,
1055                               struct synproxy_options *opts, u32 recv_seq)
1056 {
1057         struct synproxy_net *snet = synproxy_pernet(net);
1058         int mss;
1059
1060         mss = nf_cookie_v6_check(ipv6_hdr(skb), th, ntohl(th->ack_seq) - 1);
1061         if (mss == 0) {
1062                 this_cpu_inc(snet->stats->cookie_invalid);
1063                 return false;
1064         }
1065
1066         this_cpu_inc(snet->stats->cookie_valid);
1067         opts->mss_option = mss;
1068         opts->options |= NF_SYNPROXY_OPT_MSS;
1069
1070         if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
1071                 synproxy_check_timestamp_cookie(opts);
1072
1073         synproxy_send_server_syn_ipv6(net, skb, th, opts, recv_seq);
1074         return true;
1075 }
1076 EXPORT_SYMBOL_GPL(synproxy_recv_client_ack_ipv6);
1077
1078 unsigned int
1079 ipv6_synproxy_hook(void *priv, struct sk_buff *skb,
1080                    const struct nf_hook_state *nhs)
1081 {
1082         struct net *net = nhs->net;
1083         struct synproxy_net *snet = synproxy_pernet(net);
1084         enum ip_conntrack_info ctinfo;
1085         struct nf_conn *ct;
1086         struct nf_conn_synproxy *synproxy;
1087         struct synproxy_options opts = {};
1088         const struct ip_ct_tcp *state;
1089         struct tcphdr *th, _th;
1090         __be16 frag_off;
1091         u8 nexthdr;
1092         int thoff;
1093
1094         ct = nf_ct_get(skb, &ctinfo);
1095         if (!ct)
1096                 return NF_ACCEPT;
1097
1098         synproxy = nfct_synproxy(ct);
1099         if (!synproxy)
1100                 return NF_ACCEPT;
1101
1102         if (nf_is_loopback_packet(skb))
1103                 return NF_ACCEPT;
1104
1105         nexthdr = ipv6_hdr(skb)->nexthdr;
1106         thoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr,
1107                                  &frag_off);
1108         if (thoff < 0 || nexthdr != IPPROTO_TCP)
1109                 return NF_ACCEPT;
1110
1111         th = skb_header_pointer(skb, thoff, sizeof(_th), &_th);
1112         if (!th)
1113                 return NF_DROP;
1114
1115         state = &ct->proto.tcp;
1116         switch (state->state) {
1117         case TCP_CONNTRACK_CLOSE:
1118                 if (th->rst && CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
1119                         nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
1120                                                       ntohl(th->seq) + 1);
1121                         break;
1122                 }
1123
1124                 if (!th->syn || th->ack ||
1125                     CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
1126                         break;
1127
1128                 /* Reopened connection - reset the sequence number and timestamp
1129                  * adjustments, they will get initialized once the connection is
1130                  * reestablished.
1131                  */
1132                 nf_ct_seqadj_init(ct, ctinfo, 0);
1133                 synproxy->tsoff = 0;
1134                 this_cpu_inc(snet->stats->conn_reopened);
1135                 fallthrough;
1136         case TCP_CONNTRACK_SYN_SENT:
1137                 if (!synproxy_parse_options(skb, thoff, th, &opts))
1138                         return NF_DROP;
1139
1140                 if (!th->syn && th->ack &&
1141                     CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
1142                         /* Keep-Alives are sent with SEG.SEQ = SND.NXT-1,
1143                          * therefore we need to add 1 to make the SYN sequence
1144                          * number match the one of first SYN.
1145                          */
1146                         if (synproxy_recv_client_ack_ipv6(net, skb, th, &opts,
1147                                                           ntohl(th->seq) + 1)) {
1148                                 this_cpu_inc(snet->stats->cookie_retrans);
1149                                 consume_skb(skb);
1150                                 return NF_STOLEN;
1151                         } else {
1152                                 return NF_DROP;
1153                         }
1154                 }
1155
1156                 synproxy->isn = ntohl(th->ack_seq);
1157                 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP)
1158                         synproxy->its = opts.tsecr;
1159
1160                 nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
1161                 break;
1162         case TCP_CONNTRACK_SYN_RECV:
1163                 if (!th->syn || !th->ack)
1164                         break;
1165
1166                 if (!synproxy_parse_options(skb, thoff, th, &opts))
1167                         return NF_DROP;
1168
1169                 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP) {
1170                         synproxy->tsoff = opts.tsval - synproxy->its;
1171                         nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
1172                 }
1173
1174                 opts.options &= ~(NF_SYNPROXY_OPT_MSS |
1175                                   NF_SYNPROXY_OPT_WSCALE |
1176                                   NF_SYNPROXY_OPT_SACK_PERM);
1177
1178                 swap(opts.tsval, opts.tsecr);
1179                 synproxy_send_server_ack_ipv6(net, state, skb, th, &opts);
1180
1181                 nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq));
1182                 nf_conntrack_event_cache(IPCT_SEQADJ, ct);
1183
1184                 swap(opts.tsval, opts.tsecr);
1185                 synproxy_send_client_ack_ipv6(net, skb, th, &opts);
1186
1187                 consume_skb(skb);
1188                 return NF_STOLEN;
1189         default:
1190                 break;
1191         }
1192
1193         synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
1194         return NF_ACCEPT;
1195 }
1196 EXPORT_SYMBOL_GPL(ipv6_synproxy_hook);
1197
1198 static const struct nf_hook_ops ipv6_synproxy_ops[] = {
1199         {
1200                 .hook           = ipv6_synproxy_hook,
1201                 .pf             = NFPROTO_IPV6,
1202                 .hooknum        = NF_INET_LOCAL_IN,
1203                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
1204         },
1205         {
1206                 .hook           = ipv6_synproxy_hook,
1207                 .pf             = NFPROTO_IPV6,
1208                 .hooknum        = NF_INET_POST_ROUTING,
1209                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
1210         },
1211 };
1212
1213 int
1214 nf_synproxy_ipv6_init(struct synproxy_net *snet, struct net *net)
1215 {
1216         int err;
1217
1218         if (snet->hook_ref6 == 0) {
1219                 err = nf_register_net_hooks(net, ipv6_synproxy_ops,
1220                                             ARRAY_SIZE(ipv6_synproxy_ops));
1221                 if (err)
1222                         return err;
1223         }
1224
1225         snet->hook_ref6++;
1226         return 0;
1227 }
1228 EXPORT_SYMBOL_GPL(nf_synproxy_ipv6_init);
1229
1230 void
1231 nf_synproxy_ipv6_fini(struct synproxy_net *snet, struct net *net)
1232 {
1233         snet->hook_ref6--;
1234         if (snet->hook_ref6 == 0)
1235                 nf_unregister_net_hooks(net, ipv6_synproxy_ops,
1236                                         ARRAY_SIZE(ipv6_synproxy_ops));
1237 }
1238 EXPORT_SYMBOL_GPL(nf_synproxy_ipv6_fini);
1239 #endif /* CONFIG_IPV6 */
1240
1241 MODULE_LICENSE("GPL");
1242 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
1243 MODULE_DESCRIPTION("nftables SYNPROXY expression support");