kernel/net/bridge/br_netfilter.c

   1 /*
   2  *      Handle firewalling
   3  *      Linux ethernet bridge
   4  *
   5  *      Authors:
   6  *      Lennert Buytenhek               <buytenh@gnu.org>
   7  *      Bart De Schuymer                <bdschuym@pandora.be>
   8  *
   9  *      This program is free software; you can redistribute it and/or
  10  *      modify it under the terms of the GNU General Public License
  11  *      as published by the Free Software Foundation; either version
  12  *      2 of the License, or (at your option) any later version.
  13  *
  14  *      Lennert dedicates this file to Kerstin Wurdinger.
  15  */
  16
  17 #include <linux/module.h>
  18 #include <linux/kernel.h>
  19 #include <linux/slab.h>
  20 #include <linux/ip.h>
  21 #include <linux/netdevice.h>
  22 #include <linux/skbuff.h>
  23 #include <linux/if_arp.h>
  24 #include <linux/if_ether.h>
  25 #include <linux/if_vlan.h>
  26 #include <linux/if_pppox.h>
  27 #include <linux/ppp_defs.h>
  28 #include <linux/netfilter_bridge.h>
  29 #include <linux/netfilter_ipv4.h>
  30 #include <linux/netfilter_ipv6.h>
  31 #include <linux/netfilter_arp.h>
  32 #include <linux/in_route.h>
  33 #include <linux/inetdevice.h>
  34
  35 #include <net/ip.h>
  36 #include <net/ipv6.h>
  37 #include <net/route.h>
  38 #include <net/netfilter/br_netfilter.h>
  39
  40 #include <asm/uaccess.h>
  41 #include "br_private.h"
  42 #ifdef CONFIG_SYSCTL
  43 #include <linux/sysctl.h>
  44 #endif
  45
  46 #ifdef CONFIG_SYSCTL
  47 static struct ctl_table_header *brnf_sysctl_header;
  48 static int brnf_call_iptables __read_mostly = 1;
  49 static int brnf_call_ip6tables __read_mostly = 1;
  50 static int brnf_call_arptables __read_mostly = 1;
  51 static int brnf_filter_vlan_tagged __read_mostly = 0;
  52 static int brnf_filter_pppoe_tagged __read_mostly = 0;
  53 static int brnf_pass_vlan_indev __read_mostly = 0;
  54 #else
  55 #define brnf_call_iptables 1
  56 #define brnf_call_ip6tables 1
  57 #define brnf_call_arptables 1
  58 #define brnf_filter_vlan_tagged 0
  59 #define brnf_filter_pppoe_tagged 0
  60 #define brnf_pass_vlan_indev 0
  61 #endif
  62
  63 #define IS_IP(skb) \
  64         (!skb_vlan_tag_present(skb) && skb->protocol == htons(ETH_P_IP))
  65
  66 #define IS_IPV6(skb) \
  67         (!skb_vlan_tag_present(skb) && skb->protocol == htons(ETH_P_IPV6))
  68
  69 #define IS_ARP(skb) \
  70         (!skb_vlan_tag_present(skb) && skb->protocol == htons(ETH_P_ARP))
  71
  72 static inline __be16 vlan_proto(const struct sk_buff *skb)
  73 {
  74         if (skb_vlan_tag_present(skb))
  75                 return skb->protocol;
  76         else if (skb->protocol == htons(ETH_P_8021Q))
  77                 return vlan_eth_hdr(skb)->h_vlan_encapsulated_proto;
  78         else
  79                 return 0;
  80 }
  81
  82 #define IS_VLAN_IP(skb) \
  83         (vlan_proto(skb) == htons(ETH_P_IP) && \
  84          brnf_filter_vlan_tagged)
  85
  86 #define IS_VLAN_IPV6(skb) \
  87         (vlan_proto(skb) == htons(ETH_P_IPV6) && \
  88          brnf_filter_vlan_tagged)
  89
  90 #define IS_VLAN_ARP(skb) \
  91         (vlan_proto(skb) == htons(ETH_P_ARP) && \
  92          brnf_filter_vlan_tagged)
  93
  94 static inline __be16 pppoe_proto(const struct sk_buff *skb)
  95 {
  96         return *((__be16 *)(skb_mac_header(skb) + ETH_HLEN +
  97                             sizeof(struct pppoe_hdr)));
  98 }
  99
 100 #define IS_PPPOE_IP(skb) \
 101         (skb->protocol == htons(ETH_P_PPP_SES) && \
 102          pppoe_proto(skb) == htons(PPP_IP) && \
 103          brnf_filter_pppoe_tagged)
 104
 105 #define IS_PPPOE_IPV6(skb) \
 106         (skb->protocol == htons(ETH_P_PPP_SES) && \
 107          pppoe_proto(skb) == htons(PPP_IPV6) && \
 108          brnf_filter_pppoe_tagged)
 109
 110 /* largest possible L2 header, see br_nf_dev_queue_xmit() */
 111 #define NF_BRIDGE_MAX_MAC_HEADER_LENGTH (PPPOE_SES_HLEN + ETH_HLEN)
 112
 113 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4)
 114 struct brnf_frag_data {
 115         char mac[NF_BRIDGE_MAX_MAC_HEADER_LENGTH];
 116         u8 encap_size;
 117         u8 size;
 118 };
 119
 120 static DEFINE_PER_CPU(struct brnf_frag_data, brnf_frag_data_storage);
 121 #endif
 122
 123 static struct nf_bridge_info *nf_bridge_info_get(const struct sk_buff *skb)
 124 {
 125         return skb->nf_bridge;
 126 }
 127
 128 static inline struct rtable *bridge_parent_rtable(const struct net_device *dev)
 129 {
 130         struct net_bridge_port *port;
 131
 132         port = br_port_get_rcu(dev);
 133         return port ? &port->br->fake_rtable : NULL;
 134 }
 135
 136 static inline struct net_device *bridge_parent(const struct net_device *dev)
 137 {
 138         struct net_bridge_port *port;
 139
 140         port = br_port_get_rcu(dev);
 141         return port ? port->br->dev : NULL;
 142 }
 143
 144 static inline struct nf_bridge_info *nf_bridge_alloc(struct sk_buff *skb)
 145 {
 146         skb->nf_bridge = kzalloc(sizeof(struct nf_bridge_info), GFP_ATOMIC);
 147         if (likely(skb->nf_bridge))
 148                 atomic_set(&(skb->nf_bridge->use), 1);
 149
 150         return skb->nf_bridge;
 151 }
 152
 153 static inline struct nf_bridge_info *nf_bridge_unshare(struct sk_buff *skb)
 154 {
 155         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 156
 157         if (atomic_read(&nf_bridge->use) > 1) {
 158                 struct nf_bridge_info *tmp = nf_bridge_alloc(skb);
 159
 160                 if (tmp) {
 161                         memcpy(tmp, nf_bridge, sizeof(struct nf_bridge_info));
 162                         atomic_set(&tmp->use, 1);
 163                 }
 164                 nf_bridge_put(nf_bridge);
 165                 nf_bridge = tmp;
 166         }
 167         return nf_bridge;
 168 }
 169
 170 static unsigned int nf_bridge_encap_header_len(const struct sk_buff *skb)
 171 {
 172         switch (skb->protocol) {
 173         case __cpu_to_be16(ETH_P_8021Q):
 174                 return VLAN_HLEN;
 175         case __cpu_to_be16(ETH_P_PPP_SES):
 176                 return PPPOE_SES_HLEN;
 177         default:
 178                 return 0;
 179         }
 180 }
 181
 182 static inline void nf_bridge_push_encap_header(struct sk_buff *skb)
 183 {
 184         unsigned int len = nf_bridge_encap_header_len(skb);
 185
 186         skb_push(skb, len);
 187         skb->network_header -= len;
 188 }
 189
 190 static inline void nf_bridge_pull_encap_header(struct sk_buff *skb)
 191 {
 192         unsigned int len = nf_bridge_encap_header_len(skb);
 193
 194         skb_pull(skb, len);
 195         skb->network_header += len;
 196 }
 197
 198 static inline void nf_bridge_pull_encap_header_rcsum(struct sk_buff *skb)
 199 {
 200         unsigned int len = nf_bridge_encap_header_len(skb);
 201
 202         skb_pull_rcsum(skb, len);
 203         skb->network_header += len;
 204 }
 205
 206 /* When handing a packet over to the IP layer
 207  * check whether we have a skb that is in the
 208  * expected format
 209  */
 210
 211 static int br_parse_ip_options(struct sk_buff *skb)
 212 {
 213         const struct iphdr *iph;
 214         struct net_device *dev = skb->dev;
 215         u32 len;
 216
 217         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 218                 goto inhdr_error;
 219
 220         iph = ip_hdr(skb);
 221
 222         /* Basic sanity checks */
 223         if (iph->ihl < 5 || iph->version != 4)
 224                 goto inhdr_error;
 225
 226         if (!pskb_may_pull(skb, iph->ihl*4))
 227                 goto inhdr_error;
 228
 229         iph = ip_hdr(skb);
 230         if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
 231                 goto inhdr_error;
 232
 233         len = ntohs(iph->tot_len);
 234         if (skb->len < len) {
 235                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS);
 236                 goto drop;
 237         } else if (len < (iph->ihl*4))
 238                 goto inhdr_error;
 239
 240         if (pskb_trim_rcsum(skb, len)) {
 241                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
 242                 goto drop;
 243         }
 244
 245         memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
 246         /* We should really parse IP options here but until
 247          * somebody who actually uses IP options complains to
 248          * us we'll just silently ignore the options because
 249          * we're lazy!
 250          */
 251         return 0;
 252
 253 inhdr_error:
 254         IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
 255 drop:
 256         return -1;
 257 }
 258
 259 static void nf_bridge_update_protocol(struct sk_buff *skb)
 260 {
 261         switch (skb->nf_bridge->orig_proto) {
 262         case BRNF_PROTO_8021Q:
 263                 skb->protocol = htons(ETH_P_8021Q);
 264                 break;
 265         case BRNF_PROTO_PPPOE:
 266                 skb->protocol = htons(ETH_P_PPP_SES);
 267                 break;
 268         case BRNF_PROTO_UNCHANGED:
 269                 break;
 270         }
 271 }
 272
 273 /* PF_BRIDGE/PRE_ROUTING *********************************************/
 274 /* Undo the changes made for ip6tables PREROUTING and continue the
 275  * bridge PRE_ROUTING hook. */
 276 static int br_nf_pre_routing_finish_ipv6(struct sock *sk, struct sk_buff *skb)
 277 {
 278         struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
 279         struct rtable *rt;
 280
 281         if (nf_bridge->pkt_otherhost) {
 282                 skb->pkt_type = PACKET_OTHERHOST;
 283                 nf_bridge->pkt_otherhost = false;
 284         }
 285         nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING;
 286
 287         rt = bridge_parent_rtable(nf_bridge->physindev);
 288         if (!rt) {
 289                 kfree_skb(skb);
 290                 return 0;
 291         }
 292         skb_dst_set_noref(skb, &rt->dst);
 293
 294         skb->dev = nf_bridge->physindev;
 295         nf_bridge_update_protocol(skb);
 296         nf_bridge_push_encap_header(skb);
 297         NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, sk, skb,
 298                        skb->dev, NULL,
 299                        br_handle_frame_finish, 1);
 300
 301         return 0;
 302 }
 303
 304 /* Obtain the correct destination MAC address, while preserving the original
 305  * source MAC address. If we already know this address, we just copy it. If we
 306  * don't, we use the neighbour framework to find out. In both cases, we make
 307  * sure that br_handle_frame_finish() is called afterwards.
 308  */
 309 static int br_nf_pre_routing_finish_bridge(struct sock *sk, struct sk_buff *skb)
 310 {
 311         struct neighbour *neigh;
 312         struct dst_entry *dst;
 313
 314         skb->dev = bridge_parent(skb->dev);
 315         if (!skb->dev)
 316                 goto free_skb;
 317         dst = skb_dst(skb);
 318         neigh = dst_neigh_lookup_skb(dst, skb);
 319         if (neigh) {
 320                 struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
 321                 int ret;
 322
 323                 if (neigh->hh.hh_len) {
 324                         neigh_hh_bridge(&neigh->hh, skb);
 325                         skb->dev = nf_bridge->physindev;
 326                         ret = br_handle_frame_finish(sk, skb);
 327                 } else {
 328                         /* the neighbour function below overwrites the complete
 329                          * MAC header, so we save the Ethernet source address and
 330                          * protocol number.
 331                          */
 332                         skb_copy_from_linear_data_offset(skb,
 333                                                          -(ETH_HLEN-ETH_ALEN),
 334                                                          nf_bridge->neigh_header,
 335                                                          ETH_HLEN-ETH_ALEN);
 336                         /* tell br_dev_xmit to continue with forwarding */
 337                         nf_bridge->mask |= BRNF_BRIDGED_DNAT;
 338                         /* FIXME Need to refragment */
 339                         ret = neigh->output(neigh, skb);
 340                 }
 341                 neigh_release(neigh);
 342                 return ret;
 343         }
 344 free_skb:
 345         kfree_skb(skb);
 346         return 0;
 347 }
 348
 349 static bool daddr_was_changed(const struct sk_buff *skb,
 350                               const struct nf_bridge_info *nf_bridge)
 351 {
 352         return ip_hdr(skb)->daddr != nf_bridge->ipv4_daddr;
 353 }
 354
 355 /* This requires some explaining. If DNAT has taken place,
 356  * we will need to fix up the destination Ethernet address.
 357  * This is also true when SNAT takes place (for the reply direction).
 358  *
 359  * There are two cases to consider:
 360  * 1. The packet was DNAT'ed to a device in the same bridge
 361  *    port group as it was received on. We can still bridge
 362  *    the packet.
 363  * 2. The packet was DNAT'ed to a different device, either
 364  *    a non-bridged device or another bridge port group.
 365  *    The packet will need to be routed.
 366  *
 367  * The correct way of distinguishing between these two cases is to
 368  * call ip_route_input() and to look at skb->dst->dev, which is
 369  * changed to the destination device if ip_route_input() succeeds.
 370  *
 371  * Let's first consider the case that ip_route_input() succeeds:
 372  *
 373  * If the output device equals the logical bridge device the packet
 374  * came in on, we can consider this bridging. The corresponding MAC
 375  * address will be obtained in br_nf_pre_routing_finish_bridge.
 376  * Otherwise, the packet is considered to be routed and we just
 377  * change the destination MAC address so that the packet will
 378  * later be passed up to the IP stack to be routed. For a redirected
 379  * packet, ip_route_input() will give back the localhost as output device,
 380  * which differs from the bridge device.
 381  *
 382  * Let's now consider the case that ip_route_input() fails:
 383  *
 384  * This can be because the destination address is martian, in which case
 385  * the packet will be dropped.
 386  * If IP forwarding is disabled, ip_route_input() will fail, while
 387  * ip_route_output_key() can return success. The source
 388  * address for ip_route_output_key() is set to zero, so ip_route_output_key()
 389  * thinks we're handling a locally generated packet and won't care
 390  * if IP forwarding is enabled. If the output device equals the logical bridge
 391  * device, we proceed as if ip_route_input() succeeded. If it differs from the
 392  * logical bridge port or if ip_route_output_key() fails we drop the packet.
 393  */
 394 static int br_nf_pre_routing_finish(struct sock *sk, struct sk_buff *skb)
 395 {
 396         struct net_device *dev = skb->dev;
 397         struct iphdr *iph = ip_hdr(skb);
 398         struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
 399         struct rtable *rt;
 400         int err;
 401         int frag_max_size;
 402
 403         frag_max_size = IPCB(skb)->frag_max_size;
 404         BR_INPUT_SKB_CB(skb)->frag_max_size = frag_max_size;
 405
 406         if (nf_bridge->pkt_otherhost) {
 407                 skb->pkt_type = PACKET_OTHERHOST;
 408                 nf_bridge->pkt_otherhost = false;
 409         }
 410         nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING;
 411         if (daddr_was_changed(skb, nf_bridge)) {
 412                 if ((err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))) {
 413                         struct in_device *in_dev = __in_dev_get_rcu(dev);
 414
 415                         /* If err equals -EHOSTUNREACH the error is due to a
 416                          * martian destination or due to the fact that
 417                          * forwarding is disabled. For most martian packets,
 418                          * ip_route_output_key() will fail. It won't fail for 2 types of
 419                          * martian destinations: loopback destinations and destination
 420                          * 0.0.0.0. In both cases the packet will be dropped because the
 421                          * destination is the loopback device and not the bridge. */
 422                         if (err != -EHOSTUNREACH || !in_dev || IN_DEV_FORWARD(in_dev))
 423                                 goto free_skb;
 424
 425                         rt = ip_route_output(dev_net(dev), iph->daddr, 0,
 426                                              RT_TOS(iph->tos), 0);
 427                         if (!IS_ERR(rt)) {
 428                                 /* - Bridged-and-DNAT'ed traffic doesn't
 429                                  *   require ip_forwarding. */
 430                                 if (rt->dst.dev == dev) {
 431                                         skb_dst_set(skb, &rt->dst);
 432                                         goto bridged_dnat;
 433                                 }
 434                                 ip_rt_put(rt);
 435                         }
 436 free_skb:
 437                         kfree_skb(skb);
 438                         return 0;
 439                 } else {
 440                         if (skb_dst(skb)->dev == dev) {
 441 bridged_dnat:
 442                                 skb->dev = nf_bridge->physindev;
 443                                 nf_bridge_update_protocol(skb);
 444                                 nf_bridge_push_encap_header(skb);
 445                                 NF_HOOK_THRESH(NFPROTO_BRIDGE,
 446                                                NF_BR_PRE_ROUTING,
 447                                                sk, skb, skb->dev, NULL,
 448                                                br_nf_pre_routing_finish_bridge,
 449                                                1);
 450                                 return 0;
 451                         }
 452                         ether_addr_copy(eth_hdr(skb)->h_dest, dev->dev_addr);
 453                         skb->pkt_type = PACKET_HOST;
 454                 }
 455         } else {
 456                 rt = bridge_parent_rtable(nf_bridge->physindev);
 457                 if (!rt) {
 458                         kfree_skb(skb);
 459                         return 0;
 460                 }
 461                 skb_dst_set_noref(skb, &rt->dst);
 462         }
 463
 464         skb->dev = nf_bridge->physindev;
 465         nf_bridge_update_protocol(skb);
 466         nf_bridge_push_encap_header(skb);
 467         NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, sk, skb,
 468                        skb->dev, NULL,
 469                        br_handle_frame_finish, 1);
 470
 471         return 0;
 472 }
 473
 474 static struct net_device *brnf_get_logical_dev(struct sk_buff *skb, const struct net_device *dev)
 475 {
 476         struct net_device *vlan, *br;
 477
 478         br = bridge_parent(dev);
 479         if (brnf_pass_vlan_indev == 0 || !skb_vlan_tag_present(skb))
 480                 return br;
 481
 482         vlan = __vlan_find_dev_deep_rcu(br, skb->vlan_proto,
 483                                     skb_vlan_tag_get(skb) & VLAN_VID_MASK);
 484
 485         return vlan ? vlan : br;
 486 }
 487
 488 /* Some common code for IPv4/IPv6 */
 489 static struct net_device *setup_pre_routing(struct sk_buff *skb)
 490 {
 491         struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
 492
 493         if (skb->pkt_type == PACKET_OTHERHOST) {
 494                 skb->pkt_type = PACKET_HOST;
 495                 nf_bridge->pkt_otherhost = true;
 496         }
 497
 498         nf_bridge->mask |= BRNF_NF_BRIDGE_PREROUTING;
 499         nf_bridge->physindev = skb->dev;
 500         skb->dev = brnf_get_logical_dev(skb, skb->dev);
 501
 502         if (skb->protocol == htons(ETH_P_8021Q))
 503                 nf_bridge->orig_proto = BRNF_PROTO_8021Q;
 504         else if (skb->protocol == htons(ETH_P_PPP_SES))
 505                 nf_bridge->orig_proto = BRNF_PROTO_PPPOE;
 506
 507         /* Must drop socket now because of tproxy. */
 508         skb_orphan(skb);
 509         return skb->dev;
 510 }
 511
 512 /* We only check the length. A bridge shouldn't do any hop-by-hop stuff anyway */
 513 static int check_hbh_len(struct sk_buff *skb)
 514 {
 515         unsigned char *raw = (u8 *)(ipv6_hdr(skb) + 1);
 516         u32 pkt_len;
 517         const unsigned char *nh = skb_network_header(skb);
 518         int off = raw - nh;
 519         int len = (raw[1] + 1) << 3;
 520
 521         if ((raw + len) - skb->data > skb_headlen(skb))
 522                 goto bad;
 523
 524         off += 2;
 525         len -= 2;
 526
 527         while (len > 0) {
 528                 int optlen = nh[off + 1] + 2;
 529
 530                 switch (nh[off]) {
 531                 case IPV6_TLV_PAD1:
 532                         optlen = 1;
 533                         break;
 534
 535                 case IPV6_TLV_PADN:
 536                         break;
 537
 538                 case IPV6_TLV_JUMBO:
 539                         if (nh[off + 1] != 4 || (off & 3) != 2)
 540                                 goto bad;
 541                         pkt_len = ntohl(*(__be32 *) (nh + off + 2));
 542                         if (pkt_len <= IPV6_MAXPLEN ||
 543                             ipv6_hdr(skb)->payload_len)
 544                                 goto bad;
 545                         if (pkt_len > skb->len - sizeof(struct ipv6hdr))
 546                                 goto bad;
 547                         if (pskb_trim_rcsum(skb,
 548                                             pkt_len + sizeof(struct ipv6hdr)))
 549                                 goto bad;
 550                         nh = skb_network_header(skb);
 551                         break;
 552                 default:
 553                         if (optlen > len)
 554                                 goto bad;
 555                         break;
 556                 }
 557                 off += optlen;
 558                 len -= optlen;
 559         }
 560         if (len == 0)
 561                 return 0;
 562 bad:
 563         return -1;
 564
 565 }
 566
 567 /* Replicate the checks that IPv6 does on packet reception and pass the packet
 568  * to ip6tables, which doesn't support NAT, so things are fairly simple. */
 569 static unsigned int br_nf_pre_routing_ipv6(const struct nf_hook_ops *ops,
 570                                            struct sk_buff *skb,
 571                                            const struct nf_hook_state *state)
 572 {
 573         const struct ipv6hdr *hdr;
 574         u32 pkt_len;
 575
 576         if (skb->len < sizeof(struct ipv6hdr))
 577                 return NF_DROP;
 578
 579         if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
 580                 return NF_DROP;
 581
 582         hdr = ipv6_hdr(skb);
 583
 584         if (hdr->version != 6)
 585                 return NF_DROP;
 586
 587         pkt_len = ntohs(hdr->payload_len);
 588
 589         if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
 590                 if (pkt_len + sizeof(struct ipv6hdr) > skb->len)
 591                         return NF_DROP;
 592                 if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr)))
 593                         return NF_DROP;
 594         }
 595         if (hdr->nexthdr == NEXTHDR_HOP && check_hbh_len(skb))
 596                 return NF_DROP;
 597
 598         nf_bridge_put(skb->nf_bridge);
 599         if (!nf_bridge_alloc(skb))
 600                 return NF_DROP;
 601         if (!setup_pre_routing(skb))
 602                 return NF_DROP;
 603
 604         skb->protocol = htons(ETH_P_IPV6);
 605         NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, state->sk, skb,
 606                 skb->dev, NULL,
 607                 br_nf_pre_routing_finish_ipv6);
 608
 609         return NF_STOLEN;
 610 }
 611
 612 /* Direct IPv6 traffic to br_nf_pre_routing_ipv6.
 613  * Replicate the checks that IPv4 does on packet reception.
 614  * Set skb->dev to the bridge device (i.e. parent of the
 615  * receiving device) to make netfilter happy, the REDIRECT
 616  * target in particular.  Save the original destination IP
 617  * address to be able to detect DNAT afterwards. */
 618 static unsigned int br_nf_pre_routing(const struct nf_hook_ops *ops,
 619                                       struct sk_buff *skb,
 620                                       const struct nf_hook_state *state)
 621 {
 622         struct nf_bridge_info *nf_bridge;
 623         struct net_bridge_port *p;
 624         struct net_bridge *br;
 625         __u32 len = nf_bridge_encap_header_len(skb);
 626
 627         if (unlikely(!pskb_may_pull(skb, len)))
 628                 return NF_DROP;
 629
 630         p = br_port_get_rcu(state->in);
 631         if (p == NULL)
 632                 return NF_DROP;
 633         br = p->br;
 634
 635         if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb)) {
 636                 if (!brnf_call_ip6tables && !br->nf_call_ip6tables)
 637                         return NF_ACCEPT;
 638
 639                 nf_bridge_pull_encap_header_rcsum(skb);
 640                 return br_nf_pre_routing_ipv6(ops, skb, state);
 641         }
 642
 643         if (!brnf_call_iptables && !br->nf_call_iptables)
 644                 return NF_ACCEPT;
 645
 646         if (!IS_IP(skb) && !IS_VLAN_IP(skb) && !IS_PPPOE_IP(skb))
 647                 return NF_ACCEPT;
 648
 649         nf_bridge_pull_encap_header_rcsum(skb);
 650
 651         if (br_parse_ip_options(skb))
 652                 return NF_DROP;
 653
 654         nf_bridge_put(skb->nf_bridge);
 655         if (!nf_bridge_alloc(skb))
 656                 return NF_DROP;
 657         if (!setup_pre_routing(skb))
 658                 return NF_DROP;
 659
 660         nf_bridge = nf_bridge_info_get(skb);
 661         nf_bridge->ipv4_daddr = ip_hdr(skb)->daddr;
 662
 663         skb->protocol = htons(ETH_P_IP);
 664
 665         NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, state->sk, skb,
 666                 skb->dev, NULL,
 667                 br_nf_pre_routing_finish);
 668
 669         return NF_STOLEN;
 670 }
 671
 672
 673 /* PF_BRIDGE/LOCAL_IN ************************************************/
 674 /* The packet is locally destined, which requires a real
 675  * dst_entry, so detach the fake one.  On the way up, the
 676  * packet would pass through PRE_ROUTING again (which already
 677  * took place when the packet entered the bridge), but we
 678  * register an IPv4 PRE_ROUTING 'sabotage' hook that will
 679  * prevent this from happening. */
 680 static unsigned int br_nf_local_in(const struct nf_hook_ops *ops,
 681                                    struct sk_buff *skb,
 682                                    const struct nf_hook_state *state)
 683 {
 684         br_drop_fake_rtable(skb);
 685         return NF_ACCEPT;
 686 }
 687
 688 /* PF_BRIDGE/FORWARD *************************************************/
 689 static int br_nf_forward_finish(struct sock *sk, struct sk_buff *skb)
 690 {
 691         struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
 692         struct net_device *in;
 693
 694         if (!IS_ARP(skb) && !IS_VLAN_ARP(skb)) {
 695                 int frag_max_size;
 696
 697                 if (skb->protocol == htons(ETH_P_IP)) {
 698                         frag_max_size = IPCB(skb)->frag_max_size;
 699                         BR_INPUT_SKB_CB(skb)->frag_max_size = frag_max_size;
 700                 }
 701
 702                 in = nf_bridge->physindev;
 703                 if (nf_bridge->pkt_otherhost) {
 704                         skb->pkt_type = PACKET_OTHERHOST;
 705                         nf_bridge->pkt_otherhost = false;
 706                 }
 707                 nf_bridge_update_protocol(skb);
 708         } else {
 709                 in = *((struct net_device **)(skb->cb));
 710         }
 711         nf_bridge_push_encap_header(skb);
 712
 713         NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_FORWARD, sk, skb,
 714                        in, skb->dev, br_forward_finish, 1);
 715         return 0;
 716 }
 717
 718
 719 /* This is the 'purely bridged' case.  For IP, we pass the packet to
 720  * netfilter with indev and outdev set to the bridge device,
 721  * but we are still able to filter on the 'real' indev/outdev
 722  * because of the physdev module. For ARP, indev and outdev are the
 723  * bridge ports. */
 724 static unsigned int br_nf_forward_ip(const struct nf_hook_ops *ops,
 725                                      struct sk_buff *skb,
 726                                      const struct nf_hook_state *state)
 727 {
 728         struct nf_bridge_info *nf_bridge;
 729         struct net_device *parent;
 730         u_int8_t pf;
 731
 732         if (!skb->nf_bridge)
 733                 return NF_ACCEPT;
 734
 735         /* Need exclusive nf_bridge_info since we might have multiple
 736          * different physoutdevs. */
 737         if (!nf_bridge_unshare(skb))
 738                 return NF_DROP;
 739
 740         nf_bridge = nf_bridge_info_get(skb);
 741         if (!nf_bridge)
 742                 return NF_DROP;
 743
 744         parent = bridge_parent(state->out);
 745         if (!parent)
 746                 return NF_DROP;
 747
 748         if (IS_IP(skb) || IS_VLAN_IP(skb) || IS_PPPOE_IP(skb))
 749                 pf = NFPROTO_IPV4;
 750         else if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb))
 751                 pf = NFPROTO_IPV6;
 752         else
 753                 return NF_ACCEPT;
 754
 755         nf_bridge_pull_encap_header(skb);
 756
 757         if (skb->pkt_type == PACKET_OTHERHOST) {
 758                 skb->pkt_type = PACKET_HOST;
 759                 nf_bridge->pkt_otherhost = true;
 760         }
 761
 762         if (pf == NFPROTO_IPV4) {
 763                 int frag_max = BR_INPUT_SKB_CB(skb)->frag_max_size;
 764
 765                 if (br_parse_ip_options(skb))
 766                         return NF_DROP;
 767
 768                 IPCB(skb)->frag_max_size = frag_max;
 769         }
 770
 771         nf_bridge->physoutdev = skb->dev;
 772         if (pf == NFPROTO_IPV4)
 773                 skb->protocol = htons(ETH_P_IP);
 774         else
 775                 skb->protocol = htons(ETH_P_IPV6);
 776
 777         NF_HOOK(pf, NF_INET_FORWARD, NULL, skb,
 778                 brnf_get_logical_dev(skb, state->in),
 779                 parent, br_nf_forward_finish);
 780
 781         return NF_STOLEN;
 782 }
 783
 784 static unsigned int br_nf_forward_arp(const struct nf_hook_ops *ops,
 785                                       struct sk_buff *skb,
 786                                       const struct nf_hook_state *state)
 787 {
 788         struct net_bridge_port *p;
 789         struct net_bridge *br;
 790         struct net_device **d = (struct net_device **)(skb->cb);
 791
 792         p = br_port_get_rcu(state->out);
 793         if (p == NULL)
 794                 return NF_ACCEPT;
 795         br = p->br;
 796
 797         if (!brnf_call_arptables && !br->nf_call_arptables)
 798                 return NF_ACCEPT;
 799
 800         if (!IS_ARP(skb)) {
 801                 if (!IS_VLAN_ARP(skb))
 802                         return NF_ACCEPT;
 803                 nf_bridge_pull_encap_header(skb);
 804         }
 805
 806         if (arp_hdr(skb)->ar_pln != 4) {
 807                 if (IS_VLAN_ARP(skb))
 808                         nf_bridge_push_encap_header(skb);
 809                 return NF_ACCEPT;
 810         }
 811         *d = state->in;
 812         NF_HOOK(NFPROTO_ARP, NF_ARP_FORWARD, state->sk, skb,
 813                 state->in, state->out, br_nf_forward_finish);
 814
 815         return NF_STOLEN;
 816 }
 817
 818 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4)
 819 static int br_nf_push_frag_xmit(struct sock *sk, struct sk_buff *skb)
 820 {
 821         struct brnf_frag_data *data;
 822         int err;
 823
 824         data = this_cpu_ptr(&brnf_frag_data_storage);
 825         err = skb_cow_head(skb, data->size);
 826
 827         if (err) {
 828                 kfree_skb(skb);
 829                 return 0;
 830         }
 831
 832         skb_copy_to_linear_data_offset(skb, -data->size, data->mac, data->size);
 833         __skb_push(skb, data->encap_size);
 834
 835         return br_dev_queue_push_xmit(sk, skb);
 836 }
 837
 838 static int br_nf_dev_queue_xmit(struct sock *sk, struct sk_buff *skb)
 839 {
 840         int ret;
 841         int frag_max_size;
 842         unsigned int mtu_reserved;
 843
 844         if (skb_is_gso(skb) || skb->protocol != htons(ETH_P_IP))
 845                 return br_dev_queue_push_xmit(sk, skb);
 846
 847         mtu_reserved = nf_bridge_mtu_reduction(skb);
 848         /* This is wrong! We should preserve the original fragment
 849          * boundaries by preserving frag_list rather than refragmenting.
 850          */
 851         if (skb->len + mtu_reserved > skb->dev->mtu) {
 852                 struct brnf_frag_data *data;
 853
 854                 frag_max_size = BR_INPUT_SKB_CB(skb)->frag_max_size;
 855                 if (br_parse_ip_options(skb))
 856                         /* Drop invalid packet */
 857                         return NF_DROP;
 858                 IPCB(skb)->frag_max_size = frag_max_size;
 859
 860                 nf_bridge_update_protocol(skb);
 861
 862                 data = this_cpu_ptr(&brnf_frag_data_storage);
 863                 data->encap_size = nf_bridge_encap_header_len(skb);
 864                 data->size = ETH_HLEN + data->encap_size;
 865
 866                 skb_copy_from_linear_data_offset(skb, -data->size, data->mac,
 867                                                  data->size);
 868
 869                 ret = ip_fragment(sk, skb, br_nf_push_frag_xmit);
 870         } else {
 871                 ret = br_dev_queue_push_xmit(sk, skb);
 872         }
 873
 874         return ret;
 875 }
 876 #else
 877 static int br_nf_dev_queue_xmit(struct sock *sk, struct sk_buff *skb)
 878 {
 879         return br_dev_queue_push_xmit(sk, skb);
 880 }
 881 #endif
 882
 883 /* PF_BRIDGE/POST_ROUTING ********************************************/
 884 static unsigned int br_nf_post_routing(const struct nf_hook_ops *ops,
 885                                        struct sk_buff *skb,
 886                                        const struct nf_hook_state *state)
 887 {
 888         struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
 889         struct net_device *realoutdev = bridge_parent(skb->dev);
 890         u_int8_t pf;
 891
 892         /* if nf_bridge is set, but ->physoutdev is NULL, this packet came in
 893          * on a bridge, but was delivered locally and is now being routed:
 894          *
 895          * POST_ROUTING was already invoked from the ip stack.
 896          */
 897         if (!nf_bridge || !nf_bridge->physoutdev)
 898                 return NF_ACCEPT;
 899
 900         if (!realoutdev)
 901                 return NF_DROP;
 902
 903         if (IS_IP(skb) || IS_VLAN_IP(skb) || IS_PPPOE_IP(skb))
 904                 pf = NFPROTO_IPV4;
 905         else if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb))
 906                 pf = NFPROTO_IPV6;
 907         else
 908                 return NF_ACCEPT;
 909
 910         /* We assume any code from br_dev_queue_push_xmit onwards doesn't care
 911          * about the value of skb->pkt_type. */
 912         if (skb->pkt_type == PACKET_OTHERHOST) {
 913                 skb->pkt_type = PACKET_HOST;
 914                 nf_bridge->pkt_otherhost = true;
 915         }
 916
 917         nf_bridge_pull_encap_header(skb);
 918         if (pf == NFPROTO_IPV4)
 919                 skb->protocol = htons(ETH_P_IP);
 920         else
 921                 skb->protocol = htons(ETH_P_IPV6);
 922
 923         NF_HOOK(pf, NF_INET_POST_ROUTING, state->sk, skb,
 924                 NULL, realoutdev,
 925                 br_nf_dev_queue_xmit);
 926
 927         return NF_STOLEN;
 928 }
 929
 930 /* IP/SABOTAGE *****************************************************/
 931 /* Don't hand locally destined packets to PF_INET(6)/PRE_ROUTING
 932  * for the second time. */
 933 static unsigned int ip_sabotage_in(const struct nf_hook_ops *ops,
 934                                    struct sk_buff *skb,
 935                                    const struct nf_hook_state *state)
 936 {
 937         if (skb->nf_bridge &&
 938             !(skb->nf_bridge->mask & BRNF_NF_BRIDGE_PREROUTING)) {
 939                 return NF_STOP;
 940         }
 941
 942         return NF_ACCEPT;
 943 }
 944
 945 /* This is called when br_netfilter has called into iptables/netfilter,
 946  * and DNAT has taken place on a bridge-forwarded packet.
 947  *
 948  * neigh->output has created a new MAC header, with local br0 MAC
 949  * as saddr.
 950  *
 951  * This restores the original MAC saddr of the bridged packet
 952  * before invoking bridge forward logic to transmit the packet.
 953  */
 954 static void br_nf_pre_routing_finish_bridge_slow(struct sk_buff *skb)
 955 {
 956         struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
 957
 958         skb_pull(skb, ETH_HLEN);
 959         nf_bridge->mask &= ~BRNF_BRIDGED_DNAT;
 960
 961         BUILD_BUG_ON(sizeof(nf_bridge->neigh_header) != (ETH_HLEN - ETH_ALEN));
 962
 963         skb_copy_to_linear_data_offset(skb, -(ETH_HLEN - ETH_ALEN),
 964                                        nf_bridge->neigh_header,
 965                                        ETH_HLEN - ETH_ALEN);
 966         skb->dev = nf_bridge->physindev;
 967         br_handle_frame_finish(NULL, skb);
 968 }
 969
 970 static int br_nf_dev_xmit(struct sk_buff *skb)
 971 {
 972         if (skb->nf_bridge && (skb->nf_bridge->mask & BRNF_BRIDGED_DNAT)) {
 973                 br_nf_pre_routing_finish_bridge_slow(skb);
 974                 return 1;
 975         }
 976         return 0;
 977 }
 978
 979 static const struct nf_br_ops br_ops = {
 980         .br_dev_xmit_hook =     br_nf_dev_xmit,
 981 };
 982
 983 void br_netfilter_enable(void)
 984 {
 985 }
 986 EXPORT_SYMBOL_GPL(br_netfilter_enable);
 987
 988 /* For br_nf_post_routing, we need (prio = NF_BR_PRI_LAST), because
 989  * br_dev_queue_push_xmit is called afterwards */
 990 static struct nf_hook_ops br_nf_ops[] __read_mostly = {
 991         {
 992                 .hook = br_nf_pre_routing,
 993                 .owner = THIS_MODULE,
 994                 .pf = NFPROTO_BRIDGE,
 995                 .hooknum = NF_BR_PRE_ROUTING,
 996                 .priority = NF_BR_PRI_BRNF,
 997         },
 998         {
 999                 .hook = br_nf_local_in,
1000                 .owner = THIS_MODULE,
1001                 .pf = NFPROTO_BRIDGE,
1002                 .hooknum = NF_BR_LOCAL_IN,
1003                 .priority = NF_BR_PRI_BRNF,
1004         },
1005         {
1006                 .hook = br_nf_forward_ip,
1007                 .owner = THIS_MODULE,
1008                 .pf = NFPROTO_BRIDGE,
1009                 .hooknum = NF_BR_FORWARD,
1010                 .priority = NF_BR_PRI_BRNF - 1,
1011         },
1012         {
1013                 .hook = br_nf_forward_arp,
1014                 .owner = THIS_MODULE,
1015                 .pf = NFPROTO_BRIDGE,
1016                 .hooknum = NF_BR_FORWARD,
1017                 .priority = NF_BR_PRI_BRNF,
1018         },
1019         {
1020                 .hook = br_nf_post_routing,
1021                 .owner = THIS_MODULE,
1022                 .pf = NFPROTO_BRIDGE,
1023                 .hooknum = NF_BR_POST_ROUTING,
1024                 .priority = NF_BR_PRI_LAST,
1025         },
1026         {
1027                 .hook = ip_sabotage_in,
1028                 .owner = THIS_MODULE,
1029                 .pf = NFPROTO_IPV4,
1030                 .hooknum = NF_INET_PRE_ROUTING,
1031                 .priority = NF_IP_PRI_FIRST,
1032         },
1033         {
1034                 .hook = ip_sabotage_in,
1035                 .owner = THIS_MODULE,
1036                 .pf = NFPROTO_IPV6,
1037                 .hooknum = NF_INET_PRE_ROUTING,
1038                 .priority = NF_IP6_PRI_FIRST,
1039         },
1040 };
1041
1042 #ifdef CONFIG_SYSCTL
1043 static
1044 int brnf_sysctl_call_tables(struct ctl_table *ctl, int write,
1045                             void __user *buffer, size_t *lenp, loff_t *ppos)
1046 {
1047         int ret;
1048
1049         ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
1050
1051         if (write && *(int *)(ctl->data))
1052                 *(int *)(ctl->data) = 1;
1053         return ret;
1054 }
1055
1056 static struct ctl_table brnf_table[] = {
1057         {
1058                 .procname       = "bridge-nf-call-arptables",
1059                 .data           = &brnf_call_arptables,
1060                 .maxlen         = sizeof(int),
1061                 .mode           = 0644,
1062                 .proc_handler   = brnf_sysctl_call_tables,
1063         },
1064         {
1065                 .procname       = "bridge-nf-call-iptables",
1066                 .data           = &brnf_call_iptables,
1067                 .maxlen         = sizeof(int),
1068                 .mode           = 0644,
1069                 .proc_handler   = brnf_sysctl_call_tables,
1070         },
1071         {
1072                 .procname       = "bridge-nf-call-ip6tables",
1073                 .data           = &brnf_call_ip6tables,
1074                 .maxlen         = sizeof(int),
1075                 .mode           = 0644,
1076                 .proc_handler   = brnf_sysctl_call_tables,
1077         },
1078         {
1079                 .procname       = "bridge-nf-filter-vlan-tagged",
1080                 .data           = &brnf_filter_vlan_tagged,
1081                 .maxlen         = sizeof(int),
1082                 .mode           = 0644,
1083                 .proc_handler   = brnf_sysctl_call_tables,
1084         },
1085         {
1086                 .procname       = "bridge-nf-filter-pppoe-tagged",
1087                 .data           = &brnf_filter_pppoe_tagged,
1088                 .maxlen         = sizeof(int),
1089                 .mode           = 0644,
1090                 .proc_handler   = brnf_sysctl_call_tables,
1091         },
1092         {
1093                 .procname       = "bridge-nf-pass-vlan-input-dev",
1094                 .data           = &brnf_pass_vlan_indev,
1095                 .maxlen         = sizeof(int),
1096                 .mode           = 0644,
1097                 .proc_handler   = brnf_sysctl_call_tables,
1098         },
1099         { }
1100 };
1101 #endif
1102
1103 static int __init br_netfilter_init(void)
1104 {
1105         int ret;
1106
1107         ret = nf_register_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
1108         if (ret < 0)
1109                 return ret;
1110
1111 #ifdef CONFIG_SYSCTL
1112         brnf_sysctl_header = register_net_sysctl(&init_net, "net/bridge", brnf_table);
1113         if (brnf_sysctl_header == NULL) {
1114                 printk(KERN_WARNING
1115                        "br_netfilter: can't register to sysctl.\n");
1116                 nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
1117                 return -ENOMEM;
1118         }
1119 #endif
1120         RCU_INIT_POINTER(nf_br_ops, &br_ops);
1121         printk(KERN_NOTICE "Bridge firewalling registered\n");
1122         return 0;
1123 }
1124
1125 static void __exit br_netfilter_fini(void)
1126 {
1127         RCU_INIT_POINTER(nf_br_ops, NULL);
1128         nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
1129 #ifdef CONFIG_SYSCTL
1130         unregister_net_sysctl_table(brnf_sysctl_header);
1131 #endif
1132 }
1133
1134 module_init(br_netfilter_init);
1135 module_exit(br_netfilter_fini);
1136
1137 MODULE_LICENSE("GPL");
1138 MODULE_AUTHOR("Lennert Buytenhek <buytenh@gnu.org>");
1139 MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>");
1140 MODULE_DESCRIPTION("Linux ethernet netfilter firewall bridge");