net/netfilter/nf_flow_table_ip.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 #include <linux/kernel.h>
   3 #include <linux/init.h>
   4 #include <linux/module.h>
   5 #include <linux/netfilter.h>
   6 #include <linux/rhashtable.h>
   7 #include <linux/ip.h>
   8 #include <linux/ipv6.h>
   9 #include <linux/netdevice.h>
  10 #include <linux/if_ether.h>
  11 #include <net/ip.h>
  12 #include <net/ipv6.h>
  13 #include <net/ip6_route.h>
  14 #include <net/neighbour.h>
  15 #include <net/netfilter/nf_flow_table.h>
  16 #include <net/netfilter/nf_conntrack_acct.h>
  17 /* For layer 4 checksum field offset. */
  18 #include <linux/tcp.h>
  19 #include <linux/udp.h>
  20
  21 static int nf_flow_state_check(struct flow_offload *flow, int proto,
  22                                struct sk_buff *skb, unsigned int thoff)
  23 {
  24         struct tcphdr *tcph;
  25
  26         if (proto != IPPROTO_TCP)
  27                 return 0;
  28
  29         tcph = (void *)(skb_network_header(skb) + thoff);
  30         if (unlikely(tcph->fin || tcph->rst)) {
  31                 flow_offload_teardown(flow);
  32                 return -1;
  33         }
  34
  35         return 0;
  36 }
  37
  38 static void nf_flow_nat_ip_tcp(struct sk_buff *skb, unsigned int thoff,
  39                                __be32 addr, __be32 new_addr)
  40 {
  41         struct tcphdr *tcph;
  42
  43         tcph = (void *)(skb_network_header(skb) + thoff);
  44         inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, true);
  45 }
  46
  47 static void nf_flow_nat_ip_udp(struct sk_buff *skb, unsigned int thoff,
  48                                __be32 addr, __be32 new_addr)
  49 {
  50         struct udphdr *udph;
  51
  52         udph = (void *)(skb_network_header(skb) + thoff);
  53         if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
  54                 inet_proto_csum_replace4(&udph->check, skb, addr,
  55                                          new_addr, true);
  56                 if (!udph->check)
  57                         udph->check = CSUM_MANGLED_0;
  58         }
  59 }
  60
  61 static void nf_flow_nat_ip_l4proto(struct sk_buff *skb, struct iphdr *iph,
  62                                    unsigned int thoff, __be32 addr,
  63                                    __be32 new_addr)
  64 {
  65         switch (iph->protocol) {
  66         case IPPROTO_TCP:
  67                 nf_flow_nat_ip_tcp(skb, thoff, addr, new_addr);
  68                 break;
  69         case IPPROTO_UDP:
  70                 nf_flow_nat_ip_udp(skb, thoff, addr, new_addr);
  71                 break;
  72         }
  73 }
  74
  75 static void nf_flow_snat_ip(const struct flow_offload *flow,
  76                             struct sk_buff *skb, struct iphdr *iph,
  77                             unsigned int thoff, enum flow_offload_tuple_dir dir)
  78 {
  79         __be32 addr, new_addr;
  80
  81         switch (dir) {
  82         case FLOW_OFFLOAD_DIR_ORIGINAL:
  83                 addr = iph->saddr;
  84                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_v4.s_addr;
  85                 iph->saddr = new_addr;
  86                 break;
  87         case FLOW_OFFLOAD_DIR_REPLY:
  88                 addr = iph->daddr;
  89                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_v4.s_addr;
  90                 iph->daddr = new_addr;
  91                 break;
  92         }
  93         csum_replace4(&iph->check, addr, new_addr);
  94
  95         nf_flow_nat_ip_l4proto(skb, iph, thoff, addr, new_addr);
  96 }
  97
  98 static void nf_flow_dnat_ip(const struct flow_offload *flow,
  99                             struct sk_buff *skb, struct iphdr *iph,
 100                             unsigned int thoff, enum flow_offload_tuple_dir dir)
 101 {
 102         __be32 addr, new_addr;
 103
 104         switch (dir) {
 105         case FLOW_OFFLOAD_DIR_ORIGINAL:
 106                 addr = iph->daddr;
 107                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.src_v4.s_addr;
 108                 iph->daddr = new_addr;
 109                 break;
 110         case FLOW_OFFLOAD_DIR_REPLY:
 111                 addr = iph->saddr;
 112                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.dst_v4.s_addr;
 113                 iph->saddr = new_addr;
 114                 break;
 115         }
 116         csum_replace4(&iph->check, addr, new_addr);
 117
 118         nf_flow_nat_ip_l4proto(skb, iph, thoff, addr, new_addr);
 119 }
 120
 121 static void nf_flow_nat_ip(const struct flow_offload *flow, struct sk_buff *skb,
 122                           unsigned int thoff, enum flow_offload_tuple_dir dir,
 123                           struct iphdr *iph)
 124 {
 125         if (test_bit(NF_FLOW_SNAT, &flow->flags)) {
 126                 nf_flow_snat_port(flow, skb, thoff, iph->protocol, dir);
 127                 nf_flow_snat_ip(flow, skb, iph, thoff, dir);
 128         }
 129         if (test_bit(NF_FLOW_DNAT, &flow->flags)) {
 130                 nf_flow_dnat_port(flow, skb, thoff, iph->protocol, dir);
 131                 nf_flow_dnat_ip(flow, skb, iph, thoff, dir);
 132         }
 133 }
 134
 135 static bool ip_has_options(unsigned int thoff)
 136 {
 137         return thoff != sizeof(struct iphdr);
 138 }
 139
 140 static void nf_flow_tuple_encap(struct sk_buff *skb,
 141                                 struct flow_offload_tuple *tuple)
 142 {
 143         struct vlan_ethhdr *veth;
 144         struct pppoe_hdr *phdr;
 145         int i = 0;
 146
 147         if (skb_vlan_tag_present(skb)) {
 148                 tuple->encap[i].id = skb_vlan_tag_get(skb);
 149                 tuple->encap[i].proto = skb->vlan_proto;
 150                 i++;
 151         }
 152         switch (skb->protocol) {
 153         case htons(ETH_P_8021Q):
 154                 veth = (struct vlan_ethhdr *)skb_mac_header(skb);
 155                 tuple->encap[i].id = ntohs(veth->h_vlan_TCI);
 156                 tuple->encap[i].proto = skb->protocol;
 157                 break;
 158         case htons(ETH_P_PPP_SES):
 159                 phdr = (struct pppoe_hdr *)skb_mac_header(skb);
 160                 tuple->encap[i].id = ntohs(phdr->sid);
 161                 tuple->encap[i].proto = skb->protocol;
 162                 break;
 163         }
 164 }
 165
 166 static int nf_flow_tuple_ip(struct sk_buff *skb, const struct net_device *dev,
 167                             struct flow_offload_tuple *tuple, u32 *hdrsize,
 168                             u32 offset)
 169 {
 170         struct flow_ports *ports;
 171         unsigned int thoff;
 172         struct iphdr *iph;
 173
 174         if (!pskb_may_pull(skb, sizeof(*iph) + offset))
 175                 return -1;
 176
 177         iph = (struct iphdr *)(skb_network_header(skb) + offset);
 178         thoff = (iph->ihl * 4);
 179
 180         if (ip_is_fragment(iph) ||
 181             unlikely(ip_has_options(thoff)))
 182                 return -1;
 183
 184         thoff += offset;
 185
 186         switch (iph->protocol) {
 187         case IPPROTO_TCP:
 188                 *hdrsize = sizeof(struct tcphdr);
 189                 break;
 190         case IPPROTO_UDP:
 191                 *hdrsize = sizeof(struct udphdr);
 192                 break;
 193         default:
 194                 return -1;
 195         }
 196
 197         if (iph->ttl <= 1)
 198                 return -1;
 199
 200         if (!pskb_may_pull(skb, thoff + *hdrsize))
 201                 return -1;
 202
 203         iph = (struct iphdr *)(skb_network_header(skb) + offset);
 204         ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
 205
 206         tuple->src_v4.s_addr    = iph->saddr;
 207         tuple->dst_v4.s_addr    = iph->daddr;
 208         tuple->src_port         = ports->source;
 209         tuple->dst_port         = ports->dest;
 210         tuple->l3proto          = AF_INET;
 211         tuple->l4proto          = iph->protocol;
 212         tuple->iifidx           = dev->ifindex;
 213         nf_flow_tuple_encap(skb, tuple);
 214
 215         return 0;
 216 }
 217
 218 /* Based on ip_exceeds_mtu(). */
 219 static bool nf_flow_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
 220 {
 221         if (skb->len <= mtu)
 222                 return false;
 223
 224         if (skb_is_gso(skb) && skb_gso_validate_network_len(skb, mtu))
 225                 return false;
 226
 227         return true;
 228 }
 229
 230 static inline bool nf_flow_dst_check(struct flow_offload_tuple *tuple)
 231 {
 232         if (tuple->xmit_type != FLOW_OFFLOAD_XMIT_NEIGH &&
 233             tuple->xmit_type != FLOW_OFFLOAD_XMIT_XFRM)
 234                 return true;
 235
 236         return dst_check(tuple->dst_cache, tuple->dst_cookie);
 237 }
 238
 239 static unsigned int nf_flow_xmit_xfrm(struct sk_buff *skb,
 240                                       const struct nf_hook_state *state,
 241                                       struct dst_entry *dst)
 242 {
 243         skb_orphan(skb);
 244         skb_dst_set_noref(skb, dst);
 245         dst_output(state->net, state->sk, skb);
 246         return NF_STOLEN;
 247 }
 248
 249 static bool nf_flow_skb_encap_protocol(const struct sk_buff *skb, __be16 proto,
 250                                        u32 *offset)
 251 {
 252         struct vlan_ethhdr *veth;
 253
 254         switch (skb->protocol) {
 255         case htons(ETH_P_8021Q):
 256                 veth = (struct vlan_ethhdr *)skb_mac_header(skb);
 257                 if (veth->h_vlan_encapsulated_proto == proto) {
 258                         *offset += VLAN_HLEN;
 259                         return true;
 260                 }
 261                 break;
 262         case htons(ETH_P_PPP_SES):
 263                 if (nf_flow_pppoe_proto(skb) == proto) {
 264                         *offset += PPPOE_SES_HLEN;
 265                         return true;
 266                 }
 267                 break;
 268         }
 269
 270         return false;
 271 }
 272
 273 static void nf_flow_encap_pop(struct sk_buff *skb,
 274                               struct flow_offload_tuple_rhash *tuplehash)
 275 {
 276         struct vlan_hdr *vlan_hdr;
 277         int i;
 278
 279         for (i = 0; i < tuplehash->tuple.encap_num; i++) {
 280                 if (skb_vlan_tag_present(skb)) {
 281                         __vlan_hwaccel_clear_tag(skb);
 282                         continue;
 283                 }
 284                 switch (skb->protocol) {
 285                 case htons(ETH_P_8021Q):
 286                         vlan_hdr = (struct vlan_hdr *)skb->data;
 287                         __skb_pull(skb, VLAN_HLEN);
 288                         vlan_set_encap_proto(skb, vlan_hdr);
 289                         skb_reset_network_header(skb);
 290                         break;
 291                 case htons(ETH_P_PPP_SES):
 292                         skb->protocol = nf_flow_pppoe_proto(skb);
 293                         skb_pull(skb, PPPOE_SES_HLEN);
 294                         skb_reset_network_header(skb);
 295                         break;
 296                 }
 297         }
 298 }
 299
 300 static unsigned int nf_flow_queue_xmit(struct net *net, struct sk_buff *skb,
 301                                        const struct flow_offload_tuple_rhash *tuplehash,
 302                                        unsigned short type)
 303 {
 304         struct net_device *outdev;
 305
 306         outdev = dev_get_by_index_rcu(net, tuplehash->tuple.out.ifidx);
 307         if (!outdev)
 308                 return NF_DROP;
 309
 310         skb->dev = outdev;
 311         dev_hard_header(skb, skb->dev, type, tuplehash->tuple.out.h_dest,
 312                         tuplehash->tuple.out.h_source, skb->len);
 313         dev_queue_xmit(skb);
 314
 315         return NF_STOLEN;
 316 }
 317
 318 unsigned int
 319 nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
 320                         const struct nf_hook_state *state)
 321 {
 322         struct flow_offload_tuple_rhash *tuplehash;
 323         struct nf_flowtable *flow_table = priv;
 324         struct flow_offload_tuple tuple = {};
 325         enum flow_offload_tuple_dir dir;
 326         struct flow_offload *flow;
 327         struct net_device *outdev;
 328         u32 hdrsize, offset = 0;
 329         unsigned int thoff, mtu;
 330         struct rtable *rt;
 331         struct iphdr *iph;
 332         __be32 nexthop;
 333         int ret;
 334
 335         if (skb->protocol != htons(ETH_P_IP) &&
 336             !nf_flow_skb_encap_protocol(skb, htons(ETH_P_IP), &offset))
 337                 return NF_ACCEPT;
 338
 339         if (nf_flow_tuple_ip(skb, state->in, &tuple, &hdrsize, offset) < 0)
 340                 return NF_ACCEPT;
 341
 342         tuplehash = flow_offload_lookup(flow_table, &tuple);
 343         if (tuplehash == NULL)
 344                 return NF_ACCEPT;
 345
 346         dir = tuplehash->tuple.dir;
 347         flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
 348
 349         mtu = flow->tuplehash[dir].tuple.mtu + offset;
 350         if (unlikely(nf_flow_exceeds_mtu(skb, mtu)))
 351                 return NF_ACCEPT;
 352
 353         iph = (struct iphdr *)(skb_network_header(skb) + offset);
 354         thoff = (iph->ihl * 4) + offset;
 355         if (nf_flow_state_check(flow, iph->protocol, skb, thoff))
 356                 return NF_ACCEPT;
 357
 358         if (!nf_flow_dst_check(&tuplehash->tuple)) {
 359                 flow_offload_teardown(flow);
 360                 return NF_ACCEPT;
 361         }
 362
 363         if (skb_try_make_writable(skb, thoff + hdrsize))
 364                 return NF_DROP;
 365
 366         flow_offload_refresh(flow_table, flow);
 367
 368         nf_flow_encap_pop(skb, tuplehash);
 369         thoff -= offset;
 370
 371         iph = ip_hdr(skb);
 372         nf_flow_nat_ip(flow, skb, thoff, dir, iph);
 373
 374         ip_decrease_ttl(iph);
 375         skb->tstamp = 0;
 376
 377         if (flow_table->flags & NF_FLOWTABLE_COUNTER)
 378                 nf_ct_acct_update(flow->ct, tuplehash->tuple.dir, skb->len);
 379
 380         if (unlikely(tuplehash->tuple.xmit_type == FLOW_OFFLOAD_XMIT_XFRM)) {
 381                 rt = (struct rtable *)tuplehash->tuple.dst_cache;
 382                 memset(skb->cb, 0, sizeof(struct inet_skb_parm));
 383                 IPCB(skb)->iif = skb->dev->ifindex;
 384                 IPCB(skb)->flags = IPSKB_FORWARDED;
 385                 return nf_flow_xmit_xfrm(skb, state, &rt->dst);
 386         }
 387
 388         switch (tuplehash->tuple.xmit_type) {
 389         case FLOW_OFFLOAD_XMIT_NEIGH:
 390                 rt = (struct rtable *)tuplehash->tuple.dst_cache;
 391                 outdev = rt->dst.dev;
 392                 skb->dev = outdev;
 393                 nexthop = rt_nexthop(rt, flow->tuplehash[!dir].tuple.src_v4.s_addr);
 394                 skb_dst_set_noref(skb, &rt->dst);
 395                 neigh_xmit(NEIGH_ARP_TABLE, outdev, &nexthop, skb);
 396                 ret = NF_STOLEN;
 397                 break;
 398         case FLOW_OFFLOAD_XMIT_DIRECT:
 399                 ret = nf_flow_queue_xmit(state->net, skb, tuplehash, ETH_P_IP);
 400                 if (ret == NF_DROP)
 401                         flow_offload_teardown(flow);
 402                 break;
 403         }
 404
 405         return ret;
 406 }
 407 EXPORT_SYMBOL_GPL(nf_flow_offload_ip_hook);
 408
 409 static void nf_flow_nat_ipv6_tcp(struct sk_buff *skb, unsigned int thoff,
 410                                  struct in6_addr *addr,
 411                                  struct in6_addr *new_addr,
 412                                  struct ipv6hdr *ip6h)
 413 {
 414         struct tcphdr *tcph;
 415
 416         tcph = (void *)(skb_network_header(skb) + thoff);
 417         inet_proto_csum_replace16(&tcph->check, skb, addr->s6_addr32,
 418                                   new_addr->s6_addr32, true);
 419 }
 420
 421 static void nf_flow_nat_ipv6_udp(struct sk_buff *skb, unsigned int thoff,
 422                                  struct in6_addr *addr,
 423                                  struct in6_addr *new_addr)
 424 {
 425         struct udphdr *udph;
 426
 427         udph = (void *)(skb_network_header(skb) + thoff);
 428         if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
 429                 inet_proto_csum_replace16(&udph->check, skb, addr->s6_addr32,
 430                                           new_addr->s6_addr32, true);
 431                 if (!udph->check)
 432                         udph->check = CSUM_MANGLED_0;
 433         }
 434 }
 435
 436 static void nf_flow_nat_ipv6_l4proto(struct sk_buff *skb, struct ipv6hdr *ip6h,
 437                                      unsigned int thoff, struct in6_addr *addr,
 438                                      struct in6_addr *new_addr)
 439 {
 440         switch (ip6h->nexthdr) {
 441         case IPPROTO_TCP:
 442                 nf_flow_nat_ipv6_tcp(skb, thoff, addr, new_addr, ip6h);
 443                 break;
 444         case IPPROTO_UDP:
 445                 nf_flow_nat_ipv6_udp(skb, thoff, addr, new_addr);
 446                 break;
 447         }
 448 }
 449
 450 static void nf_flow_snat_ipv6(const struct flow_offload *flow,
 451                               struct sk_buff *skb, struct ipv6hdr *ip6h,
 452                               unsigned int thoff,
 453                               enum flow_offload_tuple_dir dir)
 454 {
 455         struct in6_addr addr, new_addr;
 456
 457         switch (dir) {
 458         case FLOW_OFFLOAD_DIR_ORIGINAL:
 459                 addr = ip6h->saddr;
 460                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_v6;
 461                 ip6h->saddr = new_addr;
 462                 break;
 463         case FLOW_OFFLOAD_DIR_REPLY:
 464                 addr = ip6h->daddr;
 465                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_v6;
 466                 ip6h->daddr = new_addr;
 467                 break;
 468         }
 469
 470         nf_flow_nat_ipv6_l4proto(skb, ip6h, thoff, &addr, &new_addr);
 471 }
 472
 473 static void nf_flow_dnat_ipv6(const struct flow_offload *flow,
 474                               struct sk_buff *skb, struct ipv6hdr *ip6h,
 475                               unsigned int thoff,
 476                               enum flow_offload_tuple_dir dir)
 477 {
 478         struct in6_addr addr, new_addr;
 479
 480         switch (dir) {
 481         case FLOW_OFFLOAD_DIR_ORIGINAL:
 482                 addr = ip6h->daddr;
 483                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.src_v6;
 484                 ip6h->daddr = new_addr;
 485                 break;
 486         case FLOW_OFFLOAD_DIR_REPLY:
 487                 addr = ip6h->saddr;
 488                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.dst_v6;
 489                 ip6h->saddr = new_addr;
 490                 break;
 491         }
 492
 493         nf_flow_nat_ipv6_l4proto(skb, ip6h, thoff, &addr, &new_addr);
 494 }
 495
 496 static void nf_flow_nat_ipv6(const struct flow_offload *flow,
 497                              struct sk_buff *skb,
 498                              enum flow_offload_tuple_dir dir,
 499                              struct ipv6hdr *ip6h)
 500 {
 501         unsigned int thoff = sizeof(*ip6h);
 502
 503         if (test_bit(NF_FLOW_SNAT, &flow->flags)) {
 504                 nf_flow_snat_port(flow, skb, thoff, ip6h->nexthdr, dir);
 505                 nf_flow_snat_ipv6(flow, skb, ip6h, thoff, dir);
 506         }
 507         if (test_bit(NF_FLOW_DNAT, &flow->flags)) {
 508                 nf_flow_dnat_port(flow, skb, thoff, ip6h->nexthdr, dir);
 509                 nf_flow_dnat_ipv6(flow, skb, ip6h, thoff, dir);
 510         }
 511 }
 512
 513 static int nf_flow_tuple_ipv6(struct sk_buff *skb, const struct net_device *dev,
 514                               struct flow_offload_tuple *tuple, u32 *hdrsize,
 515                               u32 offset)
 516 {
 517         struct flow_ports *ports;
 518         struct ipv6hdr *ip6h;
 519         unsigned int thoff;
 520
 521         thoff = sizeof(*ip6h) + offset;
 522         if (!pskb_may_pull(skb, thoff))
 523                 return -1;
 524
 525         ip6h = (struct ipv6hdr *)(skb_network_header(skb) + offset);
 526
 527         switch (ip6h->nexthdr) {
 528         case IPPROTO_TCP:
 529                 *hdrsize = sizeof(struct tcphdr);
 530                 break;
 531         case IPPROTO_UDP:
 532                 *hdrsize = sizeof(struct udphdr);
 533                 break;
 534         default:
 535                 return -1;
 536         }
 537
 538         if (ip6h->hop_limit <= 1)
 539                 return -1;
 540
 541         if (!pskb_may_pull(skb, thoff + *hdrsize))
 542                 return -1;
 543
 544         ip6h = (struct ipv6hdr *)(skb_network_header(skb) + offset);
 545         ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
 546
 547         tuple->src_v6           = ip6h->saddr;
 548         tuple->dst_v6           = ip6h->daddr;
 549         tuple->src_port         = ports->source;
 550         tuple->dst_port         = ports->dest;
 551         tuple->l3proto          = AF_INET6;
 552         tuple->l4proto          = ip6h->nexthdr;
 553         tuple->iifidx           = dev->ifindex;
 554         nf_flow_tuple_encap(skb, tuple);
 555
 556         return 0;
 557 }
 558
 559 unsigned int
 560 nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 561                           const struct nf_hook_state *state)
 562 {
 563         struct flow_offload_tuple_rhash *tuplehash;
 564         struct nf_flowtable *flow_table = priv;
 565         struct flow_offload_tuple tuple = {};
 566         enum flow_offload_tuple_dir dir;
 567         const struct in6_addr *nexthop;
 568         struct flow_offload *flow;
 569         struct net_device *outdev;
 570         unsigned int thoff, mtu;
 571         u32 hdrsize, offset = 0;
 572         struct ipv6hdr *ip6h;
 573         struct rt6_info *rt;
 574         int ret;
 575
 576         if (skb->protocol != htons(ETH_P_IPV6) &&
 577             !nf_flow_skb_encap_protocol(skb, htons(ETH_P_IPV6), &offset))
 578                 return NF_ACCEPT;
 579
 580         if (nf_flow_tuple_ipv6(skb, state->in, &tuple, &hdrsize, offset) < 0)
 581                 return NF_ACCEPT;
 582
 583         tuplehash = flow_offload_lookup(flow_table, &tuple);
 584         if (tuplehash == NULL)
 585                 return NF_ACCEPT;
 586
 587         dir = tuplehash->tuple.dir;
 588         flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
 589
 590         mtu = flow->tuplehash[dir].tuple.mtu + offset;
 591         if (unlikely(nf_flow_exceeds_mtu(skb, mtu)))
 592                 return NF_ACCEPT;
 593
 594         ip6h = (struct ipv6hdr *)(skb_network_header(skb) + offset);
 595         thoff = sizeof(*ip6h) + offset;
 596         if (nf_flow_state_check(flow, ip6h->nexthdr, skb, thoff))
 597                 return NF_ACCEPT;
 598
 599         if (!nf_flow_dst_check(&tuplehash->tuple)) {
 600                 flow_offload_teardown(flow);
 601                 return NF_ACCEPT;
 602         }
 603
 604         if (skb_try_make_writable(skb, thoff + hdrsize))
 605                 return NF_DROP;
 606
 607         flow_offload_refresh(flow_table, flow);
 608
 609         nf_flow_encap_pop(skb, tuplehash);
 610
 611         ip6h = ipv6_hdr(skb);
 612         nf_flow_nat_ipv6(flow, skb, dir, ip6h);
 613
 614         ip6h->hop_limit--;
 615         skb->tstamp = 0;
 616
 617         if (flow_table->flags & NF_FLOWTABLE_COUNTER)
 618                 nf_ct_acct_update(flow->ct, tuplehash->tuple.dir, skb->len);
 619
 620         if (unlikely(tuplehash->tuple.xmit_type == FLOW_OFFLOAD_XMIT_XFRM)) {
 621                 rt = (struct rt6_info *)tuplehash->tuple.dst_cache;
 622                 memset(skb->cb, 0, sizeof(struct inet6_skb_parm));
 623                 IP6CB(skb)->iif = skb->dev->ifindex;
 624                 IP6CB(skb)->flags = IP6SKB_FORWARDED;
 625                 return nf_flow_xmit_xfrm(skb, state, &rt->dst);
 626         }
 627
 628         switch (tuplehash->tuple.xmit_type) {
 629         case FLOW_OFFLOAD_XMIT_NEIGH:
 630                 rt = (struct rt6_info *)tuplehash->tuple.dst_cache;
 631                 outdev = rt->dst.dev;
 632                 skb->dev = outdev;
 633                 nexthop = rt6_nexthop(rt, &flow->tuplehash[!dir].tuple.src_v6);
 634                 skb_dst_set_noref(skb, &rt->dst);
 635                 neigh_xmit(NEIGH_ND_TABLE, outdev, nexthop, skb);
 636                 ret = NF_STOLEN;
 637                 break;
 638         case FLOW_OFFLOAD_XMIT_DIRECT:
 639                 ret = nf_flow_queue_xmit(state->net, skb, tuplehash, ETH_P_IPV6);
 640                 if (ret == NF_DROP)
 641                         flow_offload_teardown(flow);
 642                 break;
 643         }
 644
 645         return ret;
 646 }
 647 EXPORT_SYMBOL_GPL(nf_flow_offload_ipv6_hook);