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         snet->tmpl = ct;
 353
 354         snet->stats = alloc_percpu(struct synproxy_stats);
 355         if (snet->stats == NULL)
 356                 goto err2;
 357
 358         err = synproxy_proc_init(net);
 359         if (err < 0)
 360                 goto err3;
 361
 362         return 0;
 363
 364 err3:
 365         free_percpu(snet->stats);
 366 err2:
 367         nf_ct_tmpl_free(ct);
 368 err1:
 369         return err;
 370 }
 371
 372 static void __net_exit synproxy_net_exit(struct net *net)
 373 {
 374         struct synproxy_net *snet = synproxy_pernet(net);
 375
 376         nf_ct_put(snet->tmpl);
 377         synproxy_proc_exit(net);
 378         free_percpu(snet->stats);
 379 }
 380
 381 static struct pernet_operations synproxy_net_ops = {
 382         .init           = synproxy_net_init,
 383         .exit           = synproxy_net_exit,
 384         .id             = &synproxy_net_id,
 385         .size           = sizeof(struct synproxy_net),
 386 };
 387
 388 static int __init synproxy_core_init(void)
 389 {
 390         int err;
 391
 392         err = nf_ct_extend_register(&nf_ct_synproxy_extend);
 393         if (err < 0)
 394                 goto err1;
 395
 396         err = register_pernet_subsys(&synproxy_net_ops);
 397         if (err < 0)
 398                 goto err2;
 399
 400         return 0;
 401
 402 err2:
 403         nf_ct_extend_unregister(&nf_ct_synproxy_extend);
 404 err1:
 405         return err;
 406 }
 407
 408 static void __exit synproxy_core_exit(void)
 409 {
 410         unregister_pernet_subsys(&synproxy_net_ops);
 411         nf_ct_extend_unregister(&nf_ct_synproxy_extend);
 412 }
 413
 414 module_init(synproxy_core_init);
 415 module_exit(synproxy_core_exit);
 416
 417 static struct iphdr *
 418 synproxy_build_ip(struct net *net, struct sk_buff *skb, __be32 saddr,
 419                   __be32 daddr)
 420 {
 421         struct iphdr *iph;
 422
 423         skb_reset_network_header(skb);
 424         iph = skb_put(skb, sizeof(*iph));
 425         iph->version    = 4;
 426         iph->ihl        = sizeof(*iph) / 4;
 427         iph->tos        = 0;
 428         iph->id         = 0;
 429         iph->frag_off   = htons(IP_DF);
 430         iph->ttl        = READ_ONCE(net->ipv4.sysctl_ip_default_ttl);
 431         iph->protocol   = IPPROTO_TCP;
 432         iph->check      = 0;
 433         iph->saddr      = saddr;
 434         iph->daddr      = daddr;
 435
 436         return iph;
 437 }
 438
 439 static void
 440 synproxy_send_tcp(struct net *net,
 441                   const struct sk_buff *skb, struct sk_buff *nskb,
 442                   struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
 443                   struct iphdr *niph, struct tcphdr *nth,
 444                   unsigned int tcp_hdr_size)
 445 {
 446         nth->check = ~tcp_v4_check(tcp_hdr_size, niph->saddr, niph->daddr, 0);
 447         nskb->ip_summed   = CHECKSUM_PARTIAL;
 448         nskb->csum_start  = (unsigned char *)nth - nskb->head;
 449         nskb->csum_offset = offsetof(struct tcphdr, check);
 450
 451         skb_dst_set_noref(nskb, skb_dst(skb));
 452         nskb->protocol = htons(ETH_P_IP);
 453         if (ip_route_me_harder(net, nskb->sk, nskb, RTN_UNSPEC))
 454                 goto free_nskb;
 455
 456         if (nfct) {
 457                 nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo);
 458                 nf_conntrack_get(nfct);
 459         }
 460
 461         ip_local_out(net, nskb->sk, nskb);
 462         return;
 463
 464 free_nskb:
 465         kfree_skb(nskb);
 466 }
 467
 468 void
 469 synproxy_send_client_synack(struct net *net,
 470                             const struct sk_buff *skb, const struct tcphdr *th,
 471                             const struct synproxy_options *opts)
 472 {
 473         struct sk_buff *nskb;
 474         struct iphdr *iph, *niph;
 475         struct tcphdr *nth;
 476         unsigned int tcp_hdr_size;
 477         u16 mss = opts->mss_encode;
 478
 479         iph = ip_hdr(skb);
 480
 481         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
 482         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
 483                          GFP_ATOMIC);
 484         if (!nskb)
 485                 return;
 486         skb_reserve(nskb, MAX_TCP_HEADER);
 487
 488         niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
 489
 490         skb_reset_transport_header(nskb);
 491         nth = skb_put(nskb, tcp_hdr_size);
 492         nth->source     = th->dest;
 493         nth->dest       = th->source;
 494         nth->seq        = htonl(__cookie_v4_init_sequence(iph, th, &mss));
 495         nth->ack_seq    = htonl(ntohl(th->seq) + 1);
 496         tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK;
 497         if (opts->options & NF_SYNPROXY_OPT_ECN)
 498                 tcp_flag_word(nth) |= TCP_FLAG_ECE;
 499         nth->doff       = tcp_hdr_size / 4;
 500         nth->window     = 0;
 501         nth->check      = 0;
 502         nth->urg_ptr    = 0;
 503
 504         synproxy_build_options(nth, opts);
 505
 506         synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
 507                           IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
 508 }
 509 EXPORT_SYMBOL_GPL(synproxy_send_client_synack);
 510
 511 static void
 512 synproxy_send_server_syn(struct net *net,
 513                          const struct sk_buff *skb, const struct tcphdr *th,
 514                          const struct synproxy_options *opts, u32 recv_seq)
 515 {
 516         struct synproxy_net *snet = synproxy_pernet(net);
 517         struct sk_buff *nskb;
 518         struct iphdr *iph, *niph;
 519         struct tcphdr *nth;
 520         unsigned int tcp_hdr_size;
 521
 522         iph = ip_hdr(skb);
 523
 524         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
 525         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
 526                          GFP_ATOMIC);
 527         if (!nskb)
 528                 return;
 529         skb_reserve(nskb, MAX_TCP_HEADER);
 530
 531         niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
 532
 533         skb_reset_transport_header(nskb);
 534         nth = skb_put(nskb, tcp_hdr_size);
 535         nth->source     = th->source;
 536         nth->dest       = th->dest;
 537         nth->seq        = htonl(recv_seq - 1);
 538         /* ack_seq is used to relay our ISN to the synproxy hook to initialize
 539          * sequence number translation once a connection tracking entry exists.
 540          */
 541         nth->ack_seq    = htonl(ntohl(th->ack_seq) - 1);
 542         tcp_flag_word(nth) = TCP_FLAG_SYN;
 543         if (opts->options & NF_SYNPROXY_OPT_ECN)
 544                 tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR;
 545         nth->doff       = tcp_hdr_size / 4;
 546         nth->window     = th->window;
 547         nth->check      = 0;
 548         nth->urg_ptr    = 0;
 549
 550         synproxy_build_options(nth, opts);
 551
 552         synproxy_send_tcp(net, skb, nskb, &snet->tmpl->ct_general, IP_CT_NEW,
 553                           niph, nth, tcp_hdr_size);
 554 }
 555
 556 static void
 557 synproxy_send_server_ack(struct net *net,
 558                          const struct ip_ct_tcp *state,
 559                          const struct sk_buff *skb, const struct tcphdr *th,
 560                          const struct synproxy_options *opts)
 561 {
 562         struct sk_buff *nskb;
 563         struct iphdr *iph, *niph;
 564         struct tcphdr *nth;
 565         unsigned int tcp_hdr_size;
 566
 567         iph = ip_hdr(skb);
 568
 569         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
 570         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
 571                          GFP_ATOMIC);
 572         if (!nskb)
 573                 return;
 574         skb_reserve(nskb, MAX_TCP_HEADER);
 575
 576         niph = synproxy_build_ip(net, nskb, iph->daddr, iph->saddr);
 577
 578         skb_reset_transport_header(nskb);
 579         nth = skb_put(nskb, tcp_hdr_size);
 580         nth->source     = th->dest;
 581         nth->dest       = th->source;
 582         nth->seq        = htonl(ntohl(th->ack_seq));
 583         nth->ack_seq    = htonl(ntohl(th->seq) + 1);
 584         tcp_flag_word(nth) = TCP_FLAG_ACK;
 585         nth->doff       = tcp_hdr_size / 4;
 586         nth->window     = htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin);
 587         nth->check      = 0;
 588         nth->urg_ptr    = 0;
 589
 590         synproxy_build_options(nth, opts);
 591
 592         synproxy_send_tcp(net, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);
 593 }
 594
 595 static void
 596 synproxy_send_client_ack(struct net *net,
 597                          const struct sk_buff *skb, const struct tcphdr *th,
 598                          const struct synproxy_options *opts)
 599 {
 600         struct sk_buff *nskb;
 601         struct iphdr *iph, *niph;
 602         struct tcphdr *nth;
 603         unsigned int tcp_hdr_size;
 604
 605         iph = ip_hdr(skb);
 606
 607         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
 608         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
 609                          GFP_ATOMIC);
 610         if (!nskb)
 611                 return;
 612         skb_reserve(nskb, MAX_TCP_HEADER);
 613
 614         niph = synproxy_build_ip(net, nskb, iph->saddr, iph->daddr);
 615
 616         skb_reset_transport_header(nskb);
 617         nth = skb_put(nskb, tcp_hdr_size);
 618         nth->source     = th->source;
 619         nth->dest       = th->dest;
 620         nth->seq        = htonl(ntohl(th->seq) + 1);
 621         nth->ack_seq    = th->ack_seq;
 622         tcp_flag_word(nth) = TCP_FLAG_ACK;
 623         nth->doff       = tcp_hdr_size / 4;
 624         nth->window     = htons(ntohs(th->window) >> opts->wscale);
 625         nth->check      = 0;
 626         nth->urg_ptr    = 0;
 627
 628         synproxy_build_options(nth, opts);
 629
 630         synproxy_send_tcp(net, skb, nskb, skb_nfct(skb),
 631                           IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);
 632 }
 633
 634 bool
 635 synproxy_recv_client_ack(struct net *net,
 636                          const struct sk_buff *skb, const struct tcphdr *th,
 637                          struct synproxy_options *opts, u32 recv_seq)
 638 {
 639         struct synproxy_net *snet = synproxy_pernet(net);
 640         int mss;
 641
 642         mss = __cookie_v4_check(ip_hdr(skb), th, ntohl(th->ack_seq) - 1);
 643         if (mss == 0) {
 644                 this_cpu_inc(snet->stats->cookie_invalid);
 645                 return false;
 646         }
 647
 648         this_cpu_inc(snet->stats->cookie_valid);
 649         opts->mss_option = mss;
 650         opts->options |= NF_SYNPROXY_OPT_MSS;
 651
 652         if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
 653                 synproxy_check_timestamp_cookie(opts);
 654
 655         synproxy_send_server_syn(net, skb, th, opts, recv_seq);
 656         return true;
 657 }
 658 EXPORT_SYMBOL_GPL(synproxy_recv_client_ack);
 659
 660 unsigned int
 661 ipv4_synproxy_hook(void *priv, struct sk_buff *skb,
 662                    const struct nf_hook_state *nhs)
 663 {
 664         struct net *net = nhs->net;
 665         struct synproxy_net *snet = synproxy_pernet(net);
 666         enum ip_conntrack_info ctinfo;
 667         struct nf_conn *ct;
 668         struct nf_conn_synproxy *synproxy;
 669         struct synproxy_options opts = {};
 670         const struct ip_ct_tcp *state;
 671         struct tcphdr *th, _th;
 672         unsigned int thoff;
 673
 674         ct = nf_ct_get(skb, &ctinfo);
 675         if (!ct)
 676                 return NF_ACCEPT;
 677
 678         synproxy = nfct_synproxy(ct);
 679         if (!synproxy)
 680                 return NF_ACCEPT;
 681
 682         if (nf_is_loopback_packet(skb) ||
 683             ip_hdr(skb)->protocol != IPPROTO_TCP)
 684                 return NF_ACCEPT;
 685
 686         thoff = ip_hdrlen(skb);
 687         th = skb_header_pointer(skb, thoff, sizeof(_th), &_th);
 688         if (!th)
 689                 return NF_DROP;
 690
 691         state = &ct->proto.tcp;
 692         switch (state->state) {
 693         case TCP_CONNTRACK_CLOSE:
 694                 if (th->rst && CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
 695                         nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
 696                                                       ntohl(th->seq) + 1);
 697                         break;
 698                 }
 699
 700                 if (!th->syn || th->ack ||
 701                     CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
 702                         break;
 703
 704                 /* Reopened connection - reset the sequence number and timestamp
 705                  * adjustments, they will get initialized once the connection is
 706                  * reestablished.
 707                  */
 708                 nf_ct_seqadj_init(ct, ctinfo, 0);
 709                 synproxy->tsoff = 0;
 710                 this_cpu_inc(snet->stats->conn_reopened);
 711                 fallthrough;
 712         case TCP_CONNTRACK_SYN_SENT:
 713                 if (!synproxy_parse_options(skb, thoff, th, &opts))
 714                         return NF_DROP;
 715
 716                 if (!th->syn && th->ack &&
 717                     CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
 718                         /* Keep-Alives are sent with SEG.SEQ = SND.NXT-1,
 719                          * therefore we need to add 1 to make the SYN sequence
 720                          * number match the one of first SYN.
 721                          */
 722                         if (synproxy_recv_client_ack(net, skb, th, &opts,
 723                                                      ntohl(th->seq) + 1)) {
 724                                 this_cpu_inc(snet->stats->cookie_retrans);
 725                                 consume_skb(skb);
 726                                 return NF_STOLEN;
 727                         } else {
 728                                 return NF_DROP;
 729                         }
 730                 }
 731
 732                 synproxy->isn = ntohl(th->ack_seq);
 733                 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP)
 734                         synproxy->its = opts.tsecr;
 735
 736                 nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
 737                 break;
 738         case TCP_CONNTRACK_SYN_RECV:
 739                 if (!th->syn || !th->ack)
 740                         break;
 741
 742                 if (!synproxy_parse_options(skb, thoff, th, &opts))
 743                         return NF_DROP;
 744
 745                 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP) {
 746                         synproxy->tsoff = opts.tsval - synproxy->its;
 747                         nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
 748                 }
 749
 750                 opts.options &= ~(NF_SYNPROXY_OPT_MSS |
 751                                   NF_SYNPROXY_OPT_WSCALE |
 752                                   NF_SYNPROXY_OPT_SACK_PERM);
 753
 754                 swap(opts.tsval, opts.tsecr);
 755                 synproxy_send_server_ack(net, state, skb, th, &opts);
 756
 757                 nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq));
 758                 nf_conntrack_event_cache(IPCT_SEQADJ, ct);
 759
 760                 swap(opts.tsval, opts.tsecr);
 761                 synproxy_send_client_ack(net, skb, th, &opts);
 762
 763                 consume_skb(skb);
 764                 return NF_STOLEN;
 765         default:
 766                 break;
 767         }
 768
 769         synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
 770         return NF_ACCEPT;
 771 }
 772 EXPORT_SYMBOL_GPL(ipv4_synproxy_hook);
 773
 774 static const struct nf_hook_ops ipv4_synproxy_ops[] = {
 775         {
 776                 .hook           = ipv4_synproxy_hook,
 777                 .pf             = NFPROTO_IPV4,
 778                 .hooknum        = NF_INET_LOCAL_IN,
 779                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
 780         },
 781         {
 782                 .hook           = ipv4_synproxy_hook,
 783                 .pf             = NFPROTO_IPV4,
 784                 .hooknum        = NF_INET_POST_ROUTING,
 785                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
 786         },
 787 };
 788
 789 int nf_synproxy_ipv4_init(struct synproxy_net *snet, struct net *net)
 790 {
 791         int err;
 792
 793         if (snet->hook_ref4 == 0) {
 794                 err = nf_register_net_hooks(net, ipv4_synproxy_ops,
 795                                             ARRAY_SIZE(ipv4_synproxy_ops));
 796                 if (err)
 797                         return err;
 798         }
 799
 800         snet->hook_ref4++;
 801         return 0;
 802 }
 803 EXPORT_SYMBOL_GPL(nf_synproxy_ipv4_init);
 804
 805 void nf_synproxy_ipv4_fini(struct synproxy_net *snet, struct net *net)
 806 {
 807         snet->hook_ref4--;
 808         if (snet->hook_ref4 == 0)
 809                 nf_unregister_net_hooks(net, ipv4_synproxy_ops,
 810                                         ARRAY_SIZE(ipv4_synproxy_ops));
 811 }
 812 EXPORT_SYMBOL_GPL(nf_synproxy_ipv4_fini);
 813
 814 #if IS_ENABLED(CONFIG_IPV6)
 815 static struct ipv6hdr *
 816 synproxy_build_ip_ipv6(struct net *net, struct sk_buff *skb,
 817                        const struct in6_addr *saddr,
 818                        const struct in6_addr *daddr)
 819 {
 820         struct ipv6hdr *iph;
 821
 822         skb_reset_network_header(skb);
 823         iph = skb_put(skb, sizeof(*iph));
 824         ip6_flow_hdr(iph, 0, 0);
 825         iph->hop_limit  = net->ipv6.devconf_all->hop_limit;
 826         iph->nexthdr    = IPPROTO_TCP;
 827         iph->saddr      = *saddr;
 828         iph->daddr      = *daddr;
 829
 830         return iph;
 831 }
 832
 833 static void
 834 synproxy_send_tcp_ipv6(struct net *net,
 835                        const struct sk_buff *skb, struct sk_buff *nskb,
 836                        struct nf_conntrack *nfct, enum ip_conntrack_info ctinfo,
 837                        struct ipv6hdr *niph, struct tcphdr *nth,
 838                        unsigned int tcp_hdr_size)
 839 {
 840         struct dst_entry *dst;
 841         struct flowi6 fl6;
 842         int err;
 843
 844         nth->check = ~tcp_v6_check(tcp_hdr_size, &niph->saddr, &niph->daddr, 0);
 845         nskb->ip_summed   = CHECKSUM_PARTIAL;
 846         nskb->csum_start  = (unsigned char *)nth - nskb->head;
 847         nskb->csum_offset = offsetof(struct tcphdr, check);
 848
 849         memset(&fl6, 0, sizeof(fl6));
 850         fl6.flowi6_proto = IPPROTO_TCP;
 851         fl6.saddr = niph->saddr;
 852         fl6.daddr = niph->daddr;
 853         fl6.fl6_sport = nth->source;
 854         fl6.fl6_dport = nth->dest;
 855         security_skb_classify_flow((struct sk_buff *)skb,
 856                                    flowi6_to_flowi_common(&fl6));
 857         err = nf_ip6_route(net, &dst, flowi6_to_flowi(&fl6), false);
 858         if (err) {
 859                 goto free_nskb;
 860         }
 861
 862         dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
 863         if (IS_ERR(dst))
 864                 goto free_nskb;
 865
 866         skb_dst_set(nskb, dst);
 867
 868         if (nfct) {
 869                 nf_ct_set(nskb, (struct nf_conn *)nfct, ctinfo);
 870                 nf_conntrack_get(nfct);
 871         }
 872
 873         ip6_local_out(net, nskb->sk, nskb);
 874         return;
 875
 876 free_nskb:
 877         kfree_skb(nskb);
 878 }
 879
 880 void
 881 synproxy_send_client_synack_ipv6(struct net *net,
 882                                  const struct sk_buff *skb,
 883                                  const struct tcphdr *th,
 884                                  const struct synproxy_options *opts)
 885 {
 886         struct sk_buff *nskb;
 887         struct ipv6hdr *iph, *niph;
 888         struct tcphdr *nth;
 889         unsigned int tcp_hdr_size;
 890         u16 mss = opts->mss_encode;
 891
 892         iph = ipv6_hdr(skb);
 893
 894         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
 895         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
 896                          GFP_ATOMIC);
 897         if (!nskb)
 898                 return;
 899         skb_reserve(nskb, MAX_TCP_HEADER);
 900
 901         niph = synproxy_build_ip_ipv6(net, nskb, &iph->daddr, &iph->saddr);
 902
 903         skb_reset_transport_header(nskb);
 904         nth = skb_put(nskb, tcp_hdr_size);
 905         nth->source     = th->dest;
 906         nth->dest       = th->source;
 907         nth->seq        = htonl(nf_ipv6_cookie_init_sequence(iph, th, &mss));
 908         nth->ack_seq    = htonl(ntohl(th->seq) + 1);
 909         tcp_flag_word(nth) = TCP_FLAG_SYN | TCP_FLAG_ACK;
 910         if (opts->options & NF_SYNPROXY_OPT_ECN)
 911                 tcp_flag_word(nth) |= TCP_FLAG_ECE;
 912         nth->doff       = tcp_hdr_size / 4;
 913         nth->window     = 0;
 914         nth->check      = 0;
 915         nth->urg_ptr    = 0;
 916
 917         synproxy_build_options(nth, opts);
 918
 919         synproxy_send_tcp_ipv6(net, skb, nskb, skb_nfct(skb),
 920                                IP_CT_ESTABLISHED_REPLY, niph, nth,
 921                                tcp_hdr_size);
 922 }
 923 EXPORT_SYMBOL_GPL(synproxy_send_client_synack_ipv6);
 924
 925 static void
 926 synproxy_send_server_syn_ipv6(struct net *net, const struct sk_buff *skb,
 927                               const struct tcphdr *th,
 928                               const struct synproxy_options *opts, u32 recv_seq)
 929 {
 930         struct synproxy_net *snet = synproxy_pernet(net);
 931         struct sk_buff *nskb;
 932         struct ipv6hdr *iph, *niph;
 933         struct tcphdr *nth;
 934         unsigned int tcp_hdr_size;
 935
 936         iph = ipv6_hdr(skb);
 937
 938         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
 939         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
 940                          GFP_ATOMIC);
 941         if (!nskb)
 942                 return;
 943         skb_reserve(nskb, MAX_TCP_HEADER);
 944
 945         niph = synproxy_build_ip_ipv6(net, nskb, &iph->saddr, &iph->daddr);
 946
 947         skb_reset_transport_header(nskb);
 948         nth = skb_put(nskb, tcp_hdr_size);
 949         nth->source     = th->source;
 950         nth->dest       = th->dest;
 951         nth->seq        = htonl(recv_seq - 1);
 952         /* ack_seq is used to relay our ISN to the synproxy hook to initialize
 953          * sequence number translation once a connection tracking entry exists.
 954          */
 955         nth->ack_seq    = htonl(ntohl(th->ack_seq) - 1);
 956         tcp_flag_word(nth) = TCP_FLAG_SYN;
 957         if (opts->options & NF_SYNPROXY_OPT_ECN)
 958                 tcp_flag_word(nth) |= TCP_FLAG_ECE | TCP_FLAG_CWR;
 959         nth->doff       = tcp_hdr_size / 4;
 960         nth->window     = th->window;
 961         nth->check      = 0;
 962         nth->urg_ptr    = 0;
 963
 964         synproxy_build_options(nth, opts);
 965
 966         synproxy_send_tcp_ipv6(net, skb, nskb, &snet->tmpl->ct_general,
 967                                IP_CT_NEW, niph, nth, tcp_hdr_size);
 968 }
 969
 970 static void
 971 synproxy_send_server_ack_ipv6(struct net *net, const struct ip_ct_tcp *state,
 972                               const struct sk_buff *skb,
 973                               const struct tcphdr *th,
 974                               const struct synproxy_options *opts)
 975 {
 976         struct sk_buff *nskb;
 977         struct ipv6hdr *iph, *niph;
 978         struct tcphdr *nth;
 979         unsigned int tcp_hdr_size;
 980
 981         iph = ipv6_hdr(skb);
 982
 983         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
 984         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
 985                          GFP_ATOMIC);
 986         if (!nskb)
 987                 return;
 988         skb_reserve(nskb, MAX_TCP_HEADER);
 989
 990         niph = synproxy_build_ip_ipv6(net, nskb, &iph->daddr, &iph->saddr);
 991
 992         skb_reset_transport_header(nskb);
 993         nth = skb_put(nskb, tcp_hdr_size);
 994         nth->source     = th->dest;
 995         nth->dest       = th->source;
 996         nth->seq        = htonl(ntohl(th->ack_seq));
 997         nth->ack_seq    = htonl(ntohl(th->seq) + 1);
 998         tcp_flag_word(nth) = TCP_FLAG_ACK;
 999         nth->doff       = tcp_hdr_size / 4;
1000         nth->window     = htons(state->seen[IP_CT_DIR_ORIGINAL].td_maxwin);
1001         nth->check      = 0;
1002         nth->urg_ptr    = 0;
1003
1004         synproxy_build_options(nth, opts);
1005
1006         synproxy_send_tcp_ipv6(net, skb, nskb, NULL, 0, niph, nth,
1007                                tcp_hdr_size);
1008 }
1009
1010 static void
1011 synproxy_send_client_ack_ipv6(struct net *net, const struct sk_buff *skb,
1012                               const struct tcphdr *th,
1013                               const struct synproxy_options *opts)
1014 {
1015         struct sk_buff *nskb;
1016         struct ipv6hdr *iph, *niph;
1017         struct tcphdr *nth;
1018         unsigned int tcp_hdr_size;
1019
1020         iph = ipv6_hdr(skb);
1021
1022         tcp_hdr_size = sizeof(*nth) + synproxy_options_size(opts);
1023         nskb = alloc_skb(sizeof(*niph) + tcp_hdr_size + MAX_TCP_HEADER,
1024                          GFP_ATOMIC);
1025         if (!nskb)
1026                 return;
1027         skb_reserve(nskb, MAX_TCP_HEADER);
1028
1029         niph = synproxy_build_ip_ipv6(net, nskb, &iph->saddr, &iph->daddr);
1030
1031         skb_reset_transport_header(nskb);
1032         nth = skb_put(nskb, tcp_hdr_size);
1033         nth->source     = th->source;
1034         nth->dest       = th->dest;
1035         nth->seq        = htonl(ntohl(th->seq) + 1);
1036         nth->ack_seq    = th->ack_seq;
1037         tcp_flag_word(nth) = TCP_FLAG_ACK;
1038         nth->doff       = tcp_hdr_size / 4;
1039         nth->window     = htons(ntohs(th->window) >> opts->wscale);
1040         nth->check      = 0;
1041         nth->urg_ptr    = 0;
1042
1043         synproxy_build_options(nth, opts);
1044
1045         synproxy_send_tcp_ipv6(net, skb, nskb, skb_nfct(skb),
1046                                IP_CT_ESTABLISHED_REPLY, niph, nth,
1047                                tcp_hdr_size);
1048 }
1049
1050 bool
1051 synproxy_recv_client_ack_ipv6(struct net *net,
1052                               const struct sk_buff *skb,
1053                               const struct tcphdr *th,
1054                               struct synproxy_options *opts, u32 recv_seq)
1055 {
1056         struct synproxy_net *snet = synproxy_pernet(net);
1057         int mss;
1058
1059         mss = nf_cookie_v6_check(ipv6_hdr(skb), th, ntohl(th->ack_seq) - 1);
1060         if (mss == 0) {
1061                 this_cpu_inc(snet->stats->cookie_invalid);
1062                 return false;
1063         }
1064
1065         this_cpu_inc(snet->stats->cookie_valid);
1066         opts->mss_option = mss;
1067         opts->options |= NF_SYNPROXY_OPT_MSS;
1068
1069         if (opts->options & NF_SYNPROXY_OPT_TIMESTAMP)
1070                 synproxy_check_timestamp_cookie(opts);
1071
1072         synproxy_send_server_syn_ipv6(net, skb, th, opts, recv_seq);
1073         return true;
1074 }
1075 EXPORT_SYMBOL_GPL(synproxy_recv_client_ack_ipv6);
1076
1077 unsigned int
1078 ipv6_synproxy_hook(void *priv, struct sk_buff *skb,
1079                    const struct nf_hook_state *nhs)
1080 {
1081         struct net *net = nhs->net;
1082         struct synproxy_net *snet = synproxy_pernet(net);
1083         enum ip_conntrack_info ctinfo;
1084         struct nf_conn *ct;
1085         struct nf_conn_synproxy *synproxy;
1086         struct synproxy_options opts = {};
1087         const struct ip_ct_tcp *state;
1088         struct tcphdr *th, _th;
1089         __be16 frag_off;
1090         u8 nexthdr;
1091         int thoff;
1092
1093         ct = nf_ct_get(skb, &ctinfo);
1094         if (!ct)
1095                 return NF_ACCEPT;
1096
1097         synproxy = nfct_synproxy(ct);
1098         if (!synproxy)
1099                 return NF_ACCEPT;
1100
1101         if (nf_is_loopback_packet(skb))
1102                 return NF_ACCEPT;
1103
1104         nexthdr = ipv6_hdr(skb)->nexthdr;
1105         thoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr,
1106                                  &frag_off);
1107         if (thoff < 0 || nexthdr != IPPROTO_TCP)
1108                 return NF_ACCEPT;
1109
1110         th = skb_header_pointer(skb, thoff, sizeof(_th), &_th);
1111         if (!th)
1112                 return NF_DROP;
1113
1114         state = &ct->proto.tcp;
1115         switch (state->state) {
1116         case TCP_CONNTRACK_CLOSE:
1117                 if (th->rst && CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL) {
1118                         nf_ct_seqadj_init(ct, ctinfo, synproxy->isn -
1119                                                       ntohl(th->seq) + 1);
1120                         break;
1121                 }
1122
1123                 if (!th->syn || th->ack ||
1124                     CTINFO2DIR(ctinfo) != IP_CT_DIR_ORIGINAL)
1125                         break;
1126
1127                 /* Reopened connection - reset the sequence number and timestamp
1128                  * adjustments, they will get initialized once the connection is
1129                  * reestablished.
1130                  */
1131                 nf_ct_seqadj_init(ct, ctinfo, 0);
1132                 synproxy->tsoff = 0;
1133                 this_cpu_inc(snet->stats->conn_reopened);
1134                 fallthrough;
1135         case TCP_CONNTRACK_SYN_SENT:
1136                 if (!synproxy_parse_options(skb, thoff, th, &opts))
1137                         return NF_DROP;
1138
1139                 if (!th->syn && th->ack &&
1140                     CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
1141                         /* Keep-Alives are sent with SEG.SEQ = SND.NXT-1,
1142                          * therefore we need to add 1 to make the SYN sequence
1143                          * number match the one of first SYN.
1144                          */
1145                         if (synproxy_recv_client_ack_ipv6(net, skb, th, &opts,
1146                                                           ntohl(th->seq) + 1)) {
1147                                 this_cpu_inc(snet->stats->cookie_retrans);
1148                                 consume_skb(skb);
1149                                 return NF_STOLEN;
1150                         } else {
1151                                 return NF_DROP;
1152                         }
1153                 }
1154
1155                 synproxy->isn = ntohl(th->ack_seq);
1156                 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP)
1157                         synproxy->its = opts.tsecr;
1158
1159                 nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
1160                 break;
1161         case TCP_CONNTRACK_SYN_RECV:
1162                 if (!th->syn || !th->ack)
1163                         break;
1164
1165                 if (!synproxy_parse_options(skb, thoff, th, &opts))
1166                         return NF_DROP;
1167
1168                 if (opts.options & NF_SYNPROXY_OPT_TIMESTAMP) {
1169                         synproxy->tsoff = opts.tsval - synproxy->its;
1170                         nf_conntrack_event_cache(IPCT_SYNPROXY, ct);
1171                 }
1172
1173                 opts.options &= ~(NF_SYNPROXY_OPT_MSS |
1174                                   NF_SYNPROXY_OPT_WSCALE |
1175                                   NF_SYNPROXY_OPT_SACK_PERM);
1176
1177                 swap(opts.tsval, opts.tsecr);
1178                 synproxy_send_server_ack_ipv6(net, state, skb, th, &opts);
1179
1180                 nf_ct_seqadj_init(ct, ctinfo, synproxy->isn - ntohl(th->seq));
1181                 nf_conntrack_event_cache(IPCT_SEQADJ, ct);
1182
1183                 swap(opts.tsval, opts.tsecr);
1184                 synproxy_send_client_ack_ipv6(net, skb, th, &opts);
1185
1186                 consume_skb(skb);
1187                 return NF_STOLEN;
1188         default:
1189                 break;
1190         }
1191
1192         synproxy_tstamp_adjust(skb, thoff, th, ct, ctinfo, synproxy);
1193         return NF_ACCEPT;
1194 }
1195 EXPORT_SYMBOL_GPL(ipv6_synproxy_hook);
1196
1197 static const struct nf_hook_ops ipv6_synproxy_ops[] = {
1198         {
1199                 .hook           = ipv6_synproxy_hook,
1200                 .pf             = NFPROTO_IPV6,
1201                 .hooknum        = NF_INET_LOCAL_IN,
1202                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
1203         },
1204         {
1205                 .hook           = ipv6_synproxy_hook,
1206                 .pf             = NFPROTO_IPV6,
1207                 .hooknum        = NF_INET_POST_ROUTING,
1208                 .priority       = NF_IP_PRI_CONNTRACK_CONFIRM - 1,
1209         },
1210 };
1211
1212 int
1213 nf_synproxy_ipv6_init(struct synproxy_net *snet, struct net *net)
1214 {
1215         int err;
1216
1217         if (snet->hook_ref6 == 0) {
1218                 err = nf_register_net_hooks(net, ipv6_synproxy_ops,
1219                                             ARRAY_SIZE(ipv6_synproxy_ops));
1220                 if (err)
1221                         return err;
1222         }
1223
1224         snet->hook_ref6++;
1225         return 0;
1226 }
1227 EXPORT_SYMBOL_GPL(nf_synproxy_ipv6_init);
1228
1229 void
1230 nf_synproxy_ipv6_fini(struct synproxy_net *snet, struct net *net)
1231 {
1232         snet->hook_ref6--;
1233         if (snet->hook_ref6 == 0)
1234                 nf_unregister_net_hooks(net, ipv6_synproxy_ops,
1235                                         ARRAY_SIZE(ipv6_synproxy_ops));
1236 }
1237 EXPORT_SYMBOL_GPL(nf_synproxy_ipv6_fini);
1238 #endif /* CONFIG_IPV6 */
1239
1240 MODULE_LICENSE("GPL");
1241 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
1242 MODULE_DESCRIPTION("nftables SYNPROXY expression support");