net/netfilter/nf_flow_table_ip.c

   1 #include <linux/kernel.h>
   2 #include <linux/init.h>
   3 #include <linux/module.h>
   4 #include <linux/netfilter.h>
   5 #include <linux/rhashtable.h>
   6 #include <linux/ip.h>
   7 #include <linux/ipv6.h>
   8 #include <linux/netdevice.h>
   9 #include <net/ip.h>
  10 #include <net/ipv6.h>
  11 #include <net/ip6_route.h>
  12 #include <net/neighbour.h>
  13 #include <net/netfilter/nf_flow_table.h>
  14 /* For layer 4 checksum field offset. */
  15 #include <linux/tcp.h>
  16 #include <linux/udp.h>
  17
  18 static int nf_flow_state_check(struct flow_offload *flow, int proto,
  19                                struct sk_buff *skb, unsigned int thoff)
  20 {
  21         struct tcphdr *tcph;
  22
  23         if (proto != IPPROTO_TCP)
  24                 return 0;
  25
  26         if (!pskb_may_pull(skb, thoff + sizeof(*tcph)))
  27                 return -1;
  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 int 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         if (!pskb_may_pull(skb, thoff + sizeof(*tcph)) ||
  44             skb_try_make_writable(skb, thoff + sizeof(*tcph)))
  45                 return -1;
  46
  47         tcph = (void *)(skb_network_header(skb) + thoff);
  48         inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, true);
  49
  50         return 0;
  51 }
  52
  53 static int nf_flow_nat_ip_udp(struct sk_buff *skb, unsigned int thoff,
  54                               __be32 addr, __be32 new_addr)
  55 {
  56         struct udphdr *udph;
  57
  58         if (!pskb_may_pull(skb, thoff + sizeof(*udph)) ||
  59             skb_try_make_writable(skb, thoff + sizeof(*udph)))
  60                 return -1;
  61
  62         udph = (void *)(skb_network_header(skb) + thoff);
  63         if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
  64                 inet_proto_csum_replace4(&udph->check, skb, addr,
  65                                          new_addr, true);
  66                 if (!udph->check)
  67                         udph->check = CSUM_MANGLED_0;
  68         }
  69
  70         return 0;
  71 }
  72
  73 static int nf_flow_nat_ip_l4proto(struct sk_buff *skb, struct iphdr *iph,
  74                                   unsigned int thoff, __be32 addr,
  75                                   __be32 new_addr)
  76 {
  77         switch (iph->protocol) {
  78         case IPPROTO_TCP:
  79                 if (nf_flow_nat_ip_tcp(skb, thoff, addr, new_addr) < 0)
  80                         return NF_DROP;
  81                 break;
  82         case IPPROTO_UDP:
  83                 if (nf_flow_nat_ip_udp(skb, thoff, addr, new_addr) < 0)
  84                         return NF_DROP;
  85                 break;
  86         }
  87
  88         return 0;
  89 }
  90
  91 static int nf_flow_snat_ip(const struct flow_offload *flow, struct sk_buff *skb,
  92                            struct iphdr *iph, unsigned int thoff,
  93                            enum flow_offload_tuple_dir dir)
  94 {
  95         __be32 addr, new_addr;
  96
  97         switch (dir) {
  98         case FLOW_OFFLOAD_DIR_ORIGINAL:
  99                 addr = iph->saddr;
 100                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_v4.s_addr;
 101                 iph->saddr = new_addr;
 102                 break;
 103         case FLOW_OFFLOAD_DIR_REPLY:
 104                 addr = iph->daddr;
 105                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_v4.s_addr;
 106                 iph->daddr = new_addr;
 107                 break;
 108         default:
 109                 return -1;
 110         }
 111         csum_replace4(&iph->check, addr, new_addr);
 112
 113         return nf_flow_nat_ip_l4proto(skb, iph, thoff, addr, new_addr);
 114 }
 115
 116 static int nf_flow_dnat_ip(const struct flow_offload *flow, struct sk_buff *skb,
 117                            struct iphdr *iph, unsigned int thoff,
 118                            enum flow_offload_tuple_dir dir)
 119 {
 120         __be32 addr, new_addr;
 121
 122         switch (dir) {
 123         case FLOW_OFFLOAD_DIR_ORIGINAL:
 124                 addr = iph->daddr;
 125                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.src_v4.s_addr;
 126                 iph->daddr = new_addr;
 127                 break;
 128         case FLOW_OFFLOAD_DIR_REPLY:
 129                 addr = iph->saddr;
 130                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.dst_v4.s_addr;
 131                 iph->saddr = new_addr;
 132                 break;
 133         default:
 134                 return -1;
 135         }
 136         csum_replace4(&iph->check, addr, new_addr);
 137
 138         return nf_flow_nat_ip_l4proto(skb, iph, thoff, addr, new_addr);
 139 }
 140
 141 static int nf_flow_nat_ip(const struct flow_offload *flow, struct sk_buff *skb,
 142                           unsigned int thoff, enum flow_offload_tuple_dir dir)
 143 {
 144         struct iphdr *iph = ip_hdr(skb);
 145
 146         if (flow->flags & FLOW_OFFLOAD_SNAT &&
 147             (nf_flow_snat_port(flow, skb, thoff, iph->protocol, dir) < 0 ||
 148              nf_flow_snat_ip(flow, skb, iph, thoff, dir) < 0))
 149                 return -1;
 150         if (flow->flags & FLOW_OFFLOAD_DNAT &&
 151             (nf_flow_dnat_port(flow, skb, thoff, iph->protocol, dir) < 0 ||
 152              nf_flow_dnat_ip(flow, skb, iph, thoff, dir) < 0))
 153                 return -1;
 154
 155         return 0;
 156 }
 157
 158 static bool ip_has_options(unsigned int thoff)
 159 {
 160         return thoff != sizeof(struct iphdr);
 161 }
 162
 163 static int nf_flow_tuple_ip(struct sk_buff *skb, const struct net_device *dev,
 164                             struct flow_offload_tuple *tuple)
 165 {
 166         struct flow_ports *ports;
 167         unsigned int thoff;
 168         struct iphdr *iph;
 169
 170         if (!pskb_may_pull(skb, sizeof(*iph)))
 171                 return -1;
 172
 173         iph = ip_hdr(skb);
 174         thoff = iph->ihl * 4;
 175
 176         if (ip_is_fragment(iph) ||
 177             unlikely(ip_has_options(thoff)))
 178                 return -1;
 179
 180         if (iph->protocol != IPPROTO_TCP &&
 181             iph->protocol != IPPROTO_UDP)
 182                 return -1;
 183
 184         thoff = iph->ihl * 4;
 185         if (!pskb_may_pull(skb, thoff + sizeof(*ports)))
 186                 return -1;
 187
 188         ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
 189
 190         tuple->src_v4.s_addr    = iph->saddr;
 191         tuple->dst_v4.s_addr    = iph->daddr;
 192         tuple->src_port         = ports->source;
 193         tuple->dst_port         = ports->dest;
 194         tuple->l3proto          = AF_INET;
 195         tuple->l4proto          = iph->protocol;
 196         tuple->iifidx           = dev->ifindex;
 197
 198         return 0;
 199 }
 200
 201 /* Based on ip_exceeds_mtu(). */
 202 static bool nf_flow_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
 203 {
 204         if (skb->len <= mtu)
 205                 return false;
 206
 207         if (skb_is_gso(skb) && skb_gso_validate_network_len(skb, mtu))
 208                 return false;
 209
 210         return true;
 211 }
 212
 213 unsigned int
 214 nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
 215                         const struct nf_hook_state *state)
 216 {
 217         struct flow_offload_tuple_rhash *tuplehash;
 218         struct nf_flowtable *flow_table = priv;
 219         struct flow_offload_tuple tuple = {};
 220         enum flow_offload_tuple_dir dir;
 221         struct flow_offload *flow;
 222         struct net_device *outdev;
 223         struct rtable *rt;
 224         unsigned int thoff;
 225         struct iphdr *iph;
 226         __be32 nexthop;
 227
 228         if (skb->protocol != htons(ETH_P_IP))
 229                 return NF_ACCEPT;
 230
 231         if (nf_flow_tuple_ip(skb, state->in, &tuple) < 0)
 232                 return NF_ACCEPT;
 233
 234         tuplehash = flow_offload_lookup(flow_table, &tuple);
 235         if (tuplehash == NULL)
 236                 return NF_ACCEPT;
 237
 238         outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.oifidx);
 239         if (!outdev)
 240                 return NF_ACCEPT;
 241
 242         dir = tuplehash->tuple.dir;
 243         flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
 244         rt = (struct rtable *)flow->tuplehash[dir].tuple.dst_cache;
 245
 246         if (unlikely(nf_flow_exceeds_mtu(skb, flow->tuplehash[dir].tuple.mtu)) &&
 247             (ip_hdr(skb)->frag_off & htons(IP_DF)) != 0)
 248                 return NF_ACCEPT;
 249
 250         if (skb_try_make_writable(skb, sizeof(*iph)))
 251                 return NF_DROP;
 252
 253         thoff = ip_hdr(skb)->ihl * 4;
 254         if (nf_flow_state_check(flow, ip_hdr(skb)->protocol, skb, thoff))
 255                 return NF_ACCEPT;
 256
 257         if (flow->flags & (FLOW_OFFLOAD_SNAT | FLOW_OFFLOAD_DNAT) &&
 258             nf_flow_nat_ip(flow, skb, thoff, dir) < 0)
 259                 return NF_DROP;
 260
 261         flow->timeout = (u32)jiffies + NF_FLOW_TIMEOUT;
 262         iph = ip_hdr(skb);
 263         ip_decrease_ttl(iph);
 264
 265         skb->dev = outdev;
 266         nexthop = rt_nexthop(rt, flow->tuplehash[!dir].tuple.src_v4.s_addr);
 267         skb_dst_set_noref(skb, &rt->dst);
 268         neigh_xmit(NEIGH_ARP_TABLE, outdev, &nexthop, skb);
 269
 270         return NF_STOLEN;
 271 }
 272 EXPORT_SYMBOL_GPL(nf_flow_offload_ip_hook);
 273
 274 static int nf_flow_nat_ipv6_tcp(struct sk_buff *skb, unsigned int thoff,
 275                                 struct in6_addr *addr,
 276                                 struct in6_addr *new_addr)
 277 {
 278         struct tcphdr *tcph;
 279
 280         if (!pskb_may_pull(skb, thoff + sizeof(*tcph)) ||
 281             skb_try_make_writable(skb, thoff + sizeof(*tcph)))
 282                 return -1;
 283
 284         tcph = (void *)(skb_network_header(skb) + thoff);
 285         inet_proto_csum_replace16(&tcph->check, skb, addr->s6_addr32,
 286                                   new_addr->s6_addr32, true);
 287
 288         return 0;
 289 }
 290
 291 static int nf_flow_nat_ipv6_udp(struct sk_buff *skb, unsigned int thoff,
 292                                 struct in6_addr *addr,
 293                                 struct in6_addr *new_addr)
 294 {
 295         struct udphdr *udph;
 296
 297         if (!pskb_may_pull(skb, thoff + sizeof(*udph)) ||
 298             skb_try_make_writable(skb, thoff + sizeof(*udph)))
 299                 return -1;
 300
 301         udph = (void *)(skb_network_header(skb) + thoff);
 302         if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
 303                 inet_proto_csum_replace16(&udph->check, skb, addr->s6_addr32,
 304                                           new_addr->s6_addr32, true);
 305                 if (!udph->check)
 306                         udph->check = CSUM_MANGLED_0;
 307         }
 308
 309         return 0;
 310 }
 311
 312 static int nf_flow_nat_ipv6_l4proto(struct sk_buff *skb, struct ipv6hdr *ip6h,
 313                                     unsigned int thoff, struct in6_addr *addr,
 314                                     struct in6_addr *new_addr)
 315 {
 316         switch (ip6h->nexthdr) {
 317         case IPPROTO_TCP:
 318                 if (nf_flow_nat_ipv6_tcp(skb, thoff, addr, new_addr) < 0)
 319                         return NF_DROP;
 320                 break;
 321         case IPPROTO_UDP:
 322                 if (nf_flow_nat_ipv6_udp(skb, thoff, addr, new_addr) < 0)
 323                         return NF_DROP;
 324                 break;
 325         }
 326
 327         return 0;
 328 }
 329
 330 static int nf_flow_snat_ipv6(const struct flow_offload *flow,
 331                              struct sk_buff *skb, struct ipv6hdr *ip6h,
 332                              unsigned int thoff,
 333                              enum flow_offload_tuple_dir dir)
 334 {
 335         struct in6_addr addr, new_addr;
 336
 337         switch (dir) {
 338         case FLOW_OFFLOAD_DIR_ORIGINAL:
 339                 addr = ip6h->saddr;
 340                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_v6;
 341                 ip6h->saddr = new_addr;
 342                 break;
 343         case FLOW_OFFLOAD_DIR_REPLY:
 344                 addr = ip6h->daddr;
 345                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_v6;
 346                 ip6h->daddr = new_addr;
 347                 break;
 348         default:
 349                 return -1;
 350         }
 351
 352         return nf_flow_nat_ipv6_l4proto(skb, ip6h, thoff, &addr, &new_addr);
 353 }
 354
 355 static int nf_flow_dnat_ipv6(const struct flow_offload *flow,
 356                              struct sk_buff *skb, struct ipv6hdr *ip6h,
 357                              unsigned int thoff,
 358                              enum flow_offload_tuple_dir dir)
 359 {
 360         struct in6_addr addr, new_addr;
 361
 362         switch (dir) {
 363         case FLOW_OFFLOAD_DIR_ORIGINAL:
 364                 addr = ip6h->daddr;
 365                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.src_v6;
 366                 ip6h->daddr = new_addr;
 367                 break;
 368         case FLOW_OFFLOAD_DIR_REPLY:
 369                 addr = ip6h->saddr;
 370                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.dst_v6;
 371                 ip6h->saddr = new_addr;
 372                 break;
 373         default:
 374                 return -1;
 375         }
 376
 377         return nf_flow_nat_ipv6_l4proto(skb, ip6h, thoff, &addr, &new_addr);
 378 }
 379
 380 static int nf_flow_nat_ipv6(const struct flow_offload *flow,
 381                             struct sk_buff *skb,
 382                             enum flow_offload_tuple_dir dir)
 383 {
 384         struct ipv6hdr *ip6h = ipv6_hdr(skb);
 385         unsigned int thoff = sizeof(*ip6h);
 386
 387         if (flow->flags & FLOW_OFFLOAD_SNAT &&
 388             (nf_flow_snat_port(flow, skb, thoff, ip6h->nexthdr, dir) < 0 ||
 389              nf_flow_snat_ipv6(flow, skb, ip6h, thoff, dir) < 0))
 390                 return -1;
 391         if (flow->flags & FLOW_OFFLOAD_DNAT &&
 392             (nf_flow_dnat_port(flow, skb, thoff, ip6h->nexthdr, dir) < 0 ||
 393              nf_flow_dnat_ipv6(flow, skb, ip6h, thoff, dir) < 0))
 394                 return -1;
 395
 396         return 0;
 397 }
 398
 399 static int nf_flow_tuple_ipv6(struct sk_buff *skb, const struct net_device *dev,
 400                               struct flow_offload_tuple *tuple)
 401 {
 402         struct flow_ports *ports;
 403         struct ipv6hdr *ip6h;
 404         unsigned int thoff;
 405
 406         if (!pskb_may_pull(skb, sizeof(*ip6h)))
 407                 return -1;
 408
 409         ip6h = ipv6_hdr(skb);
 410
 411         if (ip6h->nexthdr != IPPROTO_TCP &&
 412             ip6h->nexthdr != IPPROTO_UDP)
 413                 return -1;
 414
 415         thoff = sizeof(*ip6h);
 416         if (!pskb_may_pull(skb, thoff + sizeof(*ports)))
 417                 return -1;
 418
 419         ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
 420
 421         tuple->src_v6           = ip6h->saddr;
 422         tuple->dst_v6           = ip6h->daddr;
 423         tuple->src_port         = ports->source;
 424         tuple->dst_port         = ports->dest;
 425         tuple->l3proto          = AF_INET6;
 426         tuple->l4proto          = ip6h->nexthdr;
 427         tuple->iifidx           = dev->ifindex;
 428
 429         return 0;
 430 }
 431
 432 unsigned int
 433 nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 434                           const struct nf_hook_state *state)
 435 {
 436         struct flow_offload_tuple_rhash *tuplehash;
 437         struct nf_flowtable *flow_table = priv;
 438         struct flow_offload_tuple tuple = {};
 439         enum flow_offload_tuple_dir dir;
 440         struct flow_offload *flow;
 441         struct net_device *outdev;
 442         struct in6_addr *nexthop;
 443         struct ipv6hdr *ip6h;
 444         struct rt6_info *rt;
 445
 446         if (skb->protocol != htons(ETH_P_IPV6))
 447                 return NF_ACCEPT;
 448
 449         if (nf_flow_tuple_ipv6(skb, state->in, &tuple) < 0)
 450                 return NF_ACCEPT;
 451
 452         tuplehash = flow_offload_lookup(flow_table, &tuple);
 453         if (tuplehash == NULL)
 454                 return NF_ACCEPT;
 455
 456         outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.oifidx);
 457         if (!outdev)
 458                 return NF_ACCEPT;
 459
 460         dir = tuplehash->tuple.dir;
 461         flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
 462         rt = (struct rt6_info *)flow->tuplehash[dir].tuple.dst_cache;
 463
 464         if (unlikely(nf_flow_exceeds_mtu(skb, flow->tuplehash[dir].tuple.mtu)))
 465                 return NF_ACCEPT;
 466
 467         if (nf_flow_state_check(flow, ipv6_hdr(skb)->nexthdr, skb,
 468                                 sizeof(*ip6h)))
 469                 return NF_ACCEPT;
 470
 471         if (skb_try_make_writable(skb, sizeof(*ip6h)))
 472                 return NF_DROP;
 473
 474         if (flow->flags & (FLOW_OFFLOAD_SNAT | FLOW_OFFLOAD_DNAT) &&
 475             nf_flow_nat_ipv6(flow, skb, dir) < 0)
 476                 return NF_DROP;
 477
 478         flow->timeout = (u32)jiffies + NF_FLOW_TIMEOUT;
 479         ip6h = ipv6_hdr(skb);
 480         ip6h->hop_limit--;
 481
 482         skb->dev = outdev;
 483         nexthop = rt6_nexthop(rt, &flow->tuplehash[!dir].tuple.src_v6);
 484         skb_dst_set_noref(skb, &rt->dst);
 485         neigh_xmit(NEIGH_ND_TABLE, outdev, nexthop, skb);
 486
 487         return NF_STOLEN;
 488 }
 489 EXPORT_SYMBOL_GPL(nf_flow_offload_ipv6_hook);