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 (nf_flow_nat_ip(flow, skb, thoff, dir) < 0)
 258                 return NF_DROP;
 259
 260         flow->timeout = (u32)jiffies + NF_FLOW_TIMEOUT;
 261         iph = ip_hdr(skb);
 262         ip_decrease_ttl(iph);
 263
 264         skb->dev = outdev;
 265         nexthop = rt_nexthop(rt, flow->tuplehash[!dir].tuple.src_v4.s_addr);
 266         skb_dst_set_noref(skb, &rt->dst);
 267         neigh_xmit(NEIGH_ARP_TABLE, outdev, &nexthop, skb);
 268
 269         return NF_STOLEN;
 270 }
 271 EXPORT_SYMBOL_GPL(nf_flow_offload_ip_hook);
 272
 273 static int nf_flow_nat_ipv6_tcp(struct sk_buff *skb, unsigned int thoff,
 274                                 struct in6_addr *addr,
 275                                 struct in6_addr *new_addr)
 276 {
 277         struct tcphdr *tcph;
 278
 279         if (!pskb_may_pull(skb, thoff + sizeof(*tcph)) ||
 280             skb_try_make_writable(skb, thoff + sizeof(*tcph)))
 281                 return -1;
 282
 283         tcph = (void *)(skb_network_header(skb) + thoff);
 284         inet_proto_csum_replace16(&tcph->check, skb, addr->s6_addr32,
 285                                   new_addr->s6_addr32, true);
 286
 287         return 0;
 288 }
 289
 290 static int nf_flow_nat_ipv6_udp(struct sk_buff *skb, unsigned int thoff,
 291                                 struct in6_addr *addr,
 292                                 struct in6_addr *new_addr)
 293 {
 294         struct udphdr *udph;
 295
 296         if (!pskb_may_pull(skb, thoff + sizeof(*udph)) ||
 297             skb_try_make_writable(skb, thoff + sizeof(*udph)))
 298                 return -1;
 299
 300         udph = (void *)(skb_network_header(skb) + thoff);
 301         if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
 302                 inet_proto_csum_replace16(&udph->check, skb, addr->s6_addr32,
 303                                           new_addr->s6_addr32, true);
 304                 if (!udph->check)
 305                         udph->check = CSUM_MANGLED_0;
 306         }
 307
 308         return 0;
 309 }
 310
 311 static int nf_flow_nat_ipv6_l4proto(struct sk_buff *skb, struct ipv6hdr *ip6h,
 312                                     unsigned int thoff, struct in6_addr *addr,
 313                                     struct in6_addr *new_addr)
 314 {
 315         switch (ip6h->nexthdr) {
 316         case IPPROTO_TCP:
 317                 if (nf_flow_nat_ipv6_tcp(skb, thoff, addr, new_addr) < 0)
 318                         return NF_DROP;
 319                 break;
 320         case IPPROTO_UDP:
 321                 if (nf_flow_nat_ipv6_udp(skb, thoff, addr, new_addr) < 0)
 322                         return NF_DROP;
 323                 break;
 324         }
 325
 326         return 0;
 327 }
 328
 329 static int nf_flow_snat_ipv6(const struct flow_offload *flow,
 330                              struct sk_buff *skb, struct ipv6hdr *ip6h,
 331                              unsigned int thoff,
 332                              enum flow_offload_tuple_dir dir)
 333 {
 334         struct in6_addr addr, new_addr;
 335
 336         switch (dir) {
 337         case FLOW_OFFLOAD_DIR_ORIGINAL:
 338                 addr = ip6h->saddr;
 339                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_v6;
 340                 ip6h->saddr = new_addr;
 341                 break;
 342         case FLOW_OFFLOAD_DIR_REPLY:
 343                 addr = ip6h->daddr;
 344                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_v6;
 345                 ip6h->daddr = new_addr;
 346                 break;
 347         default:
 348                 return -1;
 349         }
 350
 351         return nf_flow_nat_ipv6_l4proto(skb, ip6h, thoff, &addr, &new_addr);
 352 }
 353
 354 static int nf_flow_dnat_ipv6(const struct flow_offload *flow,
 355                              struct sk_buff *skb, struct ipv6hdr *ip6h,
 356                              unsigned int thoff,
 357                              enum flow_offload_tuple_dir dir)
 358 {
 359         struct in6_addr addr, new_addr;
 360
 361         switch (dir) {
 362         case FLOW_OFFLOAD_DIR_ORIGINAL:
 363                 addr = ip6h->daddr;
 364                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.src_v6;
 365                 ip6h->daddr = new_addr;
 366                 break;
 367         case FLOW_OFFLOAD_DIR_REPLY:
 368                 addr = ip6h->saddr;
 369                 new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.dst_v6;
 370                 ip6h->saddr = new_addr;
 371                 break;
 372         default:
 373                 return -1;
 374         }
 375
 376         return nf_flow_nat_ipv6_l4proto(skb, ip6h, thoff, &addr, &new_addr);
 377 }
 378
 379 static int nf_flow_nat_ipv6(const struct flow_offload *flow,
 380                             struct sk_buff *skb,
 381                             enum flow_offload_tuple_dir dir)
 382 {
 383         struct ipv6hdr *ip6h = ipv6_hdr(skb);
 384         unsigned int thoff = sizeof(*ip6h);
 385
 386         if (flow->flags & FLOW_OFFLOAD_SNAT &&
 387             (nf_flow_snat_port(flow, skb, thoff, ip6h->nexthdr, dir) < 0 ||
 388              nf_flow_snat_ipv6(flow, skb, ip6h, thoff, dir) < 0))
 389                 return -1;
 390         if (flow->flags & FLOW_OFFLOAD_DNAT &&
 391             (nf_flow_dnat_port(flow, skb, thoff, ip6h->nexthdr, dir) < 0 ||
 392              nf_flow_dnat_ipv6(flow, skb, ip6h, thoff, dir) < 0))
 393                 return -1;
 394
 395         return 0;
 396 }
 397
 398 static int nf_flow_tuple_ipv6(struct sk_buff *skb, const struct net_device *dev,
 399                               struct flow_offload_tuple *tuple)
 400 {
 401         struct flow_ports *ports;
 402         struct ipv6hdr *ip6h;
 403         unsigned int thoff;
 404
 405         if (!pskb_may_pull(skb, sizeof(*ip6h)))
 406                 return -1;
 407
 408         ip6h = ipv6_hdr(skb);
 409
 410         if (ip6h->nexthdr != IPPROTO_TCP &&
 411             ip6h->nexthdr != IPPROTO_UDP)
 412                 return -1;
 413
 414         thoff = sizeof(*ip6h);
 415         if (!pskb_may_pull(skb, thoff + sizeof(*ports)))
 416                 return -1;
 417
 418         ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
 419
 420         tuple->src_v6           = ip6h->saddr;
 421         tuple->dst_v6           = ip6h->daddr;
 422         tuple->src_port         = ports->source;
 423         tuple->dst_port         = ports->dest;
 424         tuple->l3proto          = AF_INET6;
 425         tuple->l4proto          = ip6h->nexthdr;
 426         tuple->iifidx           = dev->ifindex;
 427
 428         return 0;
 429 }
 430
 431 unsigned int
 432 nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 433                           const struct nf_hook_state *state)
 434 {
 435         struct flow_offload_tuple_rhash *tuplehash;
 436         struct nf_flowtable *flow_table = priv;
 437         struct flow_offload_tuple tuple = {};
 438         enum flow_offload_tuple_dir dir;
 439         struct flow_offload *flow;
 440         struct net_device *outdev;
 441         struct in6_addr *nexthop;
 442         struct ipv6hdr *ip6h;
 443         struct rt6_info *rt;
 444
 445         if (skb->protocol != htons(ETH_P_IPV6))
 446                 return NF_ACCEPT;
 447
 448         if (nf_flow_tuple_ipv6(skb, state->in, &tuple) < 0)
 449                 return NF_ACCEPT;
 450
 451         tuplehash = flow_offload_lookup(flow_table, &tuple);
 452         if (tuplehash == NULL)
 453                 return NF_ACCEPT;
 454
 455         outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.oifidx);
 456         if (!outdev)
 457                 return NF_ACCEPT;
 458
 459         dir = tuplehash->tuple.dir;
 460         flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
 461         rt = (struct rt6_info *)flow->tuplehash[dir].tuple.dst_cache;
 462
 463         if (unlikely(nf_flow_exceeds_mtu(skb, flow->tuplehash[dir].tuple.mtu)))
 464                 return NF_ACCEPT;
 465
 466         if (nf_flow_state_check(flow, ipv6_hdr(skb)->nexthdr, skb,
 467                                 sizeof(*ip6h)))
 468                 return NF_ACCEPT;
 469
 470         if (skb_try_make_writable(skb, sizeof(*ip6h)))
 471                 return NF_DROP;
 472
 473         if (nf_flow_nat_ipv6(flow, skb, dir) < 0)
 474                 return NF_DROP;
 475
 476         flow->timeout = (u32)jiffies + NF_FLOW_TIMEOUT;
 477         ip6h = ipv6_hdr(skb);
 478         ip6h->hop_limit--;
 479
 480         skb->dev = outdev;
 481         nexthop = rt6_nexthop(rt, &flow->tuplehash[!dir].tuple.src_v6);
 482         skb_dst_set_noref(skb, &rt->dst);
 483         neigh_xmit(NEIGH_ND_TABLE, outdev, nexthop, skb);
 484
 485         return NF_STOLEN;
 486 }
 487 EXPORT_SYMBOL_GPL(nf_flow_offload_ipv6_hook);