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
  39 #include <asm/uaccess.h>
  40 #include "br_private.h"
  41 #ifdef CONFIG_SYSCTL
  42 #include <linux/sysctl.h>
  43 #endif
  44
  45 #define skb_origaddr(skb)        (((struct bridge_skb_cb *) \
  46                                  (skb->nf_bridge->data))->daddr.ipv4)
  47 #define store_orig_dstaddr(skb)  (skb_origaddr(skb) = ip_hdr(skb)->daddr)
  48 #define dnat_took_place(skb)     (skb_origaddr(skb) != ip_hdr(skb)->daddr)
  49
  50 #ifdef CONFIG_SYSCTL
  51 static struct ctl_table_header *brnf_sysctl_header;
  52 static int brnf_call_iptables __read_mostly = 1;
  53 static int brnf_call_ip6tables __read_mostly = 1;
  54 static int brnf_call_arptables __read_mostly = 1;
  55 static int brnf_filter_vlan_tagged __read_mostly = 0;
  56 static int brnf_filter_pppoe_tagged __read_mostly = 0;
  57 #else
  58 #define brnf_call_iptables 1
  59 #define brnf_call_ip6tables 1
  60 #define brnf_call_arptables 1
  61 #define brnf_filter_vlan_tagged 0
  62 #define brnf_filter_pppoe_tagged 0
  63 #endif
  64
  65 static inline __be16 vlan_proto(const struct sk_buff *skb)
  66 {
  67         if (vlan_tx_tag_present(skb))
  68                 return skb->protocol;
  69         else if (skb->protocol == htons(ETH_P_8021Q))
  70                 return vlan_eth_hdr(skb)->h_vlan_encapsulated_proto;
  71         else
  72                 return 0;
  73 }
  74
  75 #define IS_VLAN_IP(skb) \
  76         (vlan_proto(skb) == htons(ETH_P_IP) && \
  77          brnf_filter_vlan_tagged)
  78
  79 #define IS_VLAN_IPV6(skb) \
  80         (vlan_proto(skb) == htons(ETH_P_IPV6) && \
  81          brnf_filter_vlan_tagged)
  82
  83 #define IS_VLAN_ARP(skb) \
  84         (vlan_proto(skb) == htons(ETH_P_ARP) && \
  85          brnf_filter_vlan_tagged)
  86
  87 static inline __be16 pppoe_proto(const struct sk_buff *skb)
  88 {
  89         return *((__be16 *)(skb_mac_header(skb) + ETH_HLEN +
  90                             sizeof(struct pppoe_hdr)));
  91 }
  92
  93 #define IS_PPPOE_IP(skb) \
  94         (skb->protocol == htons(ETH_P_PPP_SES) && \
  95          pppoe_proto(skb) == htons(PPP_IP) && \
  96          brnf_filter_pppoe_tagged)
  97
  98 #define IS_PPPOE_IPV6(skb) \
  99         (skb->protocol == htons(ETH_P_PPP_SES) && \
 100          pppoe_proto(skb) == htons(PPP_IPV6) && \
 101          brnf_filter_pppoe_tagged)
 102
 103 static void fake_update_pmtu(struct dst_entry *dst, u32 mtu)
 104 {
 105 }
 106
 107 static struct dst_ops fake_dst_ops = {
 108         .family =               AF_INET,
 109         .protocol =             cpu_to_be16(ETH_P_IP),
 110         .update_pmtu =          fake_update_pmtu,
 111 };
 112
 113 /*
 114  * Initialize bogus route table used to keep netfilter happy.
 115  * Currently, we fill in the PMTU entry because netfilter
 116  * refragmentation needs it, and the rt_flags entry because
 117  * ipt_REJECT needs it.  Future netfilter modules might
 118  * require us to fill additional fields.
 119  */
 120 void br_netfilter_rtable_init(struct net_bridge *br)
 121 {
 122         struct rtable *rt = &br->fake_rtable;
 123
 124         atomic_set(&rt->dst.__refcnt, 1);
 125         rt->dst.dev = br->dev;
 126         rt->dst.path = &rt->dst;
 127         dst_metric_set(&rt->dst, RTAX_MTU, 1500);
 128         rt->dst.flags   = DST_NOXFRM;
 129         rt->dst.ops = &fake_dst_ops;
 130 }
 131
 132 static inline struct rtable *bridge_parent_rtable(const struct net_device *dev)
 133 {
 134         struct net_bridge_port *port;
 135
 136         port = br_port_get_rcu(dev);
 137         return port ? &port->br->fake_rtable : NULL;
 138 }
 139
 140 static inline struct net_device *bridge_parent(const struct net_device *dev)
 141 {
 142         struct net_bridge_port *port;
 143
 144         port = br_port_get_rcu(dev);
 145         return port ? port->br->dev : NULL;
 146 }
 147
 148 static inline struct nf_bridge_info *nf_bridge_alloc(struct sk_buff *skb)
 149 {
 150         skb->nf_bridge = kzalloc(sizeof(struct nf_bridge_info), GFP_ATOMIC);
 151         if (likely(skb->nf_bridge))
 152                 atomic_set(&(skb->nf_bridge->use), 1);
 153
 154         return skb->nf_bridge;
 155 }
 156
 157 static inline struct nf_bridge_info *nf_bridge_unshare(struct sk_buff *skb)
 158 {
 159         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 160
 161         if (atomic_read(&nf_bridge->use) > 1) {
 162                 struct nf_bridge_info *tmp = nf_bridge_alloc(skb);
 163
 164                 if (tmp) {
 165                         memcpy(tmp, nf_bridge, sizeof(struct nf_bridge_info));
 166                         atomic_set(&tmp->use, 1);
 167                 }
 168                 nf_bridge_put(nf_bridge);
 169                 nf_bridge = tmp;
 170         }
 171         return nf_bridge;
 172 }
 173
 174 static inline void nf_bridge_push_encap_header(struct sk_buff *skb)
 175 {
 176         unsigned int len = nf_bridge_encap_header_len(skb);
 177
 178         skb_push(skb, len);
 179         skb->network_header -= len;
 180 }
 181
 182 static inline void nf_bridge_pull_encap_header(struct sk_buff *skb)
 183 {
 184         unsigned int len = nf_bridge_encap_header_len(skb);
 185
 186         skb_pull(skb, len);
 187         skb->network_header += len;
 188 }
 189
 190 static inline void nf_bridge_pull_encap_header_rcsum(struct sk_buff *skb)
 191 {
 192         unsigned int len = nf_bridge_encap_header_len(skb);
 193
 194         skb_pull_rcsum(skb, len);
 195         skb->network_header += len;
 196 }
 197
 198 static inline void nf_bridge_save_header(struct sk_buff *skb)
 199 {
 200         int header_size = ETH_HLEN + nf_bridge_encap_header_len(skb);
 201
 202         skb_copy_from_linear_data_offset(skb, -header_size,
 203                                          skb->nf_bridge->data, header_size);
 204 }
 205
 206 static inline void nf_bridge_update_protocol(struct sk_buff *skb)
 207 {
 208         if (skb->nf_bridge->mask & BRNF_8021Q)
 209                 skb->protocol = htons(ETH_P_8021Q);
 210         else if (skb->nf_bridge->mask & BRNF_PPPoE)
 211                 skb->protocol = htons(ETH_P_PPP_SES);
 212 }
 213
 214 /* When handing a packet over to the IP layer
 215  * check whether we have a skb that is in the
 216  * expected format
 217  */
 218
 219 static int br_parse_ip_options(struct sk_buff *skb)
 220 {
 221         struct ip_options *opt;
 222         struct iphdr *iph;
 223         struct net_device *dev = skb->dev;
 224         u32 len;
 225
 226         iph = ip_hdr(skb);
 227         opt = &(IPCB(skb)->opt);
 228
 229         /* Basic sanity checks */
 230         if (iph->ihl < 5 || iph->version != 4)
 231                 goto inhdr_error;
 232
 233         if (!pskb_may_pull(skb, iph->ihl*4))
 234                 goto inhdr_error;
 235
 236         iph = ip_hdr(skb);
 237         if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
 238                 goto inhdr_error;
 239
 240         len = ntohs(iph->tot_len);
 241         if (skb->len < len) {
 242                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS);
 243                 goto drop;
 244         } else if (len < (iph->ihl*4))
 245                 goto inhdr_error;
 246
 247         if (pskb_trim_rcsum(skb, len)) {
 248                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
 249                 goto drop;
 250         }
 251
 252         memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
 253         if (iph->ihl == 5)
 254                 return 0;
 255
 256         opt->optlen = iph->ihl*4 - sizeof(struct iphdr);
 257         if (ip_options_compile(dev_net(dev), opt, skb))
 258                 goto inhdr_error;
 259
 260         /* Check correct handling of SRR option */
 261         if (unlikely(opt->srr)) {
 262                 struct in_device *in_dev = __in_dev_get_rcu(dev);
 263                 if (in_dev && !IN_DEV_SOURCE_ROUTE(in_dev))
 264                         goto drop;
 265
 266                 if (ip_options_rcv_srr(skb))
 267                         goto drop;
 268         }
 269
 270         return 0;
 271
 272 inhdr_error:
 273         IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
 274 drop:
 275         return -1;
 276 }
 277
 278 /* Fill in the header for fragmented IP packets handled by
 279  * the IPv4 connection tracking code.
 280  */
 281 int nf_bridge_copy_header(struct sk_buff *skb)
 282 {
 283         int err;
 284         unsigned int header_size;
 285
 286         nf_bridge_update_protocol(skb);
 287         header_size = ETH_HLEN + nf_bridge_encap_header_len(skb);
 288         err = skb_cow_head(skb, header_size);
 289         if (err)
 290                 return err;
 291
 292         skb_copy_to_linear_data_offset(skb, -header_size,
 293                                        skb->nf_bridge->data, header_size);
 294         __skb_push(skb, nf_bridge_encap_header_len(skb));
 295         return 0;
 296 }
 297
 298 /* PF_BRIDGE/PRE_ROUTING *********************************************/
 299 /* Undo the changes made for ip6tables PREROUTING and continue the
 300  * bridge PRE_ROUTING hook. */
 301 static int br_nf_pre_routing_finish_ipv6(struct sk_buff *skb)
 302 {
 303         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 304         struct rtable *rt;
 305
 306         if (nf_bridge->mask & BRNF_PKT_TYPE) {
 307                 skb->pkt_type = PACKET_OTHERHOST;
 308                 nf_bridge->mask ^= BRNF_PKT_TYPE;
 309         }
 310         nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING;
 311
 312         rt = bridge_parent_rtable(nf_bridge->physindev);
 313         if (!rt) {
 314                 kfree_skb(skb);
 315                 return 0;
 316         }
 317         skb_dst_set_noref(skb, &rt->dst);
 318
 319         skb->dev = nf_bridge->physindev;
 320         nf_bridge_update_protocol(skb);
 321         nf_bridge_push_encap_header(skb);
 322         NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
 323                        br_handle_frame_finish, 1);
 324
 325         return 0;
 326 }
 327
 328 /* Obtain the correct destination MAC address, while preserving the original
 329  * source MAC address. If we already know this address, we just copy it. If we
 330  * don't, we use the neighbour framework to find out. In both cases, we make
 331  * sure that br_handle_frame_finish() is called afterwards.
 332  */
 333 static int br_nf_pre_routing_finish_bridge(struct sk_buff *skb)
 334 {
 335         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 336         struct dst_entry *dst;
 337
 338         skb->dev = bridge_parent(skb->dev);
 339         if (!skb->dev)
 340                 goto free_skb;
 341         dst = skb_dst(skb);
 342         if (dst->hh) {
 343                 neigh_hh_bridge(dst->hh, skb);
 344                 skb->dev = nf_bridge->physindev;
 345                 return br_handle_frame_finish(skb);
 346         } else if (dst->neighbour) {
 347                 /* the neighbour function below overwrites the complete
 348                  * MAC header, so we save the Ethernet source address and
 349                  * protocol number. */
 350                 skb_copy_from_linear_data_offset(skb, -(ETH_HLEN-ETH_ALEN), skb->nf_bridge->data, ETH_HLEN-ETH_ALEN);
 351                 /* tell br_dev_xmit to continue with forwarding */
 352                 nf_bridge->mask |= BRNF_BRIDGED_DNAT;
 353                 return dst->neighbour->output(skb);
 354         }
 355 free_skb:
 356         kfree_skb(skb);
 357         return 0;
 358 }
 359
 360 /* This requires some explaining. If DNAT has taken place,
 361  * we will need to fix up the destination Ethernet address.
 362  *
 363  * There are two cases to consider:
 364  * 1. The packet was DNAT'ed to a device in the same bridge
 365  *    port group as it was received on. We can still bridge
 366  *    the packet.
 367  * 2. The packet was DNAT'ed to a different device, either
 368  *    a non-bridged device or another bridge port group.
 369  *    The packet will need to be routed.
 370  *
 371  * The correct way of distinguishing between these two cases is to
 372  * call ip_route_input() and to look at skb->dst->dev, which is
 373  * changed to the destination device if ip_route_input() succeeds.
 374  *
 375  * Let's first consider the case that ip_route_input() succeeds:
 376  *
 377  * If the output device equals the logical bridge device the packet
 378  * came in on, we can consider this bridging. The corresponding MAC
 379  * address will be obtained in br_nf_pre_routing_finish_bridge.
 380  * Otherwise, the packet is considered to be routed and we just
 381  * change the destination MAC address so that the packet will
 382  * later be passed up to the IP stack to be routed. For a redirected
 383  * packet, ip_route_input() will give back the localhost as output device,
 384  * which differs from the bridge device.
 385  *
 386  * Let's now consider the case that ip_route_input() fails:
 387  *
 388  * This can be because the destination address is martian, in which case
 389  * the packet will be dropped.
 390  * If IP forwarding is disabled, ip_route_input() will fail, while
 391  * ip_route_output_key() can return success. The source
 392  * address for ip_route_output_key() is set to zero, so ip_route_output_key()
 393  * thinks we're handling a locally generated packet and won't care
 394  * if IP forwarding is enabled. If the output device equals the logical bridge
 395  * device, we proceed as if ip_route_input() succeeded. If it differs from the
 396  * logical bridge port or if ip_route_output_key() fails we drop the packet.
 397  */
 398 static int br_nf_pre_routing_finish(struct sk_buff *skb)
 399 {
 400         struct net_device *dev = skb->dev;
 401         struct iphdr *iph = ip_hdr(skb);
 402         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 403         struct rtable *rt;
 404         int err;
 405
 406         if (nf_bridge->mask & BRNF_PKT_TYPE) {
 407                 skb->pkt_type = PACKET_OTHERHOST;
 408                 nf_bridge->mask ^= BRNF_PKT_TYPE;
 409         }
 410         nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING;
 411         if (dnat_took_place(skb)) {
 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                                                skb, skb->dev, NULL,
 448                                                br_nf_pre_routing_finish_bridge,
 449                                                1);
 450                                 return 0;
 451                         }
 452                         memcpy(eth_hdr(skb)->h_dest, dev->dev_addr, ETH_ALEN);
 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, skb, skb->dev, NULL,
 468                        br_handle_frame_finish, 1);
 469
 470         return 0;
 471 }
 472
 473 /* Some common code for IPv4/IPv6 */
 474 static struct net_device *setup_pre_routing(struct sk_buff *skb)
 475 {
 476         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 477
 478         if (skb->pkt_type == PACKET_OTHERHOST) {
 479                 skb->pkt_type = PACKET_HOST;
 480                 nf_bridge->mask |= BRNF_PKT_TYPE;
 481         }
 482
 483         nf_bridge->mask |= BRNF_NF_BRIDGE_PREROUTING;
 484         nf_bridge->physindev = skb->dev;
 485         skb->dev = bridge_parent(skb->dev);
 486         if (skb->protocol == htons(ETH_P_8021Q))
 487                 nf_bridge->mask |= BRNF_8021Q;
 488         else if (skb->protocol == htons(ETH_P_PPP_SES))
 489                 nf_bridge->mask |= BRNF_PPPoE;
 490
 491         return skb->dev;
 492 }
 493
 494 /* We only check the length. A bridge shouldn't do any hop-by-hop stuff anyway */
 495 static int check_hbh_len(struct sk_buff *skb)
 496 {
 497         unsigned char *raw = (u8 *)(ipv6_hdr(skb) + 1);
 498         u32 pkt_len;
 499         const unsigned char *nh = skb_network_header(skb);
 500         int off = raw - nh;
 501         int len = (raw[1] + 1) << 3;
 502
 503         if ((raw + len) - skb->data > skb_headlen(skb))
 504                 goto bad;
 505
 506         off += 2;
 507         len -= 2;
 508
 509         while (len > 0) {
 510                 int optlen = nh[off + 1] + 2;
 511
 512                 switch (nh[off]) {
 513                 case IPV6_TLV_PAD0:
 514                         optlen = 1;
 515                         break;
 516
 517                 case IPV6_TLV_PADN:
 518                         break;
 519
 520                 case IPV6_TLV_JUMBO:
 521                         if (nh[off + 1] != 4 || (off & 3) != 2)
 522                                 goto bad;
 523                         pkt_len = ntohl(*(__be32 *) (nh + off + 2));
 524                         if (pkt_len <= IPV6_MAXPLEN ||
 525                             ipv6_hdr(skb)->payload_len)
 526                                 goto bad;
 527                         if (pkt_len > skb->len - sizeof(struct ipv6hdr))
 528                                 goto bad;
 529                         if (pskb_trim_rcsum(skb,
 530                                             pkt_len + sizeof(struct ipv6hdr)))
 531                                 goto bad;
 532                         nh = skb_network_header(skb);
 533                         break;
 534                 default:
 535                         if (optlen > len)
 536                                 goto bad;
 537                         break;
 538                 }
 539                 off += optlen;
 540                 len -= optlen;
 541         }
 542         if (len == 0)
 543                 return 0;
 544 bad:
 545         return -1;
 546
 547 }
 548
 549 /* Replicate the checks that IPv6 does on packet reception and pass the packet
 550  * to ip6tables, which doesn't support NAT, so things are fairly simple. */
 551 static unsigned int br_nf_pre_routing_ipv6(unsigned int hook,
 552                                            struct sk_buff *skb,
 553                                            const struct net_device *in,
 554                                            const struct net_device *out,
 555                                            int (*okfn)(struct sk_buff *))
 556 {
 557         struct ipv6hdr *hdr;
 558         u32 pkt_len;
 559
 560         if (skb->len < sizeof(struct ipv6hdr))
 561                 return NF_DROP;
 562
 563         if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
 564                 return NF_DROP;
 565
 566         hdr = ipv6_hdr(skb);
 567
 568         if (hdr->version != 6)
 569                 return NF_DROP;
 570
 571         pkt_len = ntohs(hdr->payload_len);
 572
 573         if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
 574                 if (pkt_len + sizeof(struct ipv6hdr) > skb->len)
 575                         return NF_DROP;
 576                 if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr)))
 577                         return NF_DROP;
 578         }
 579         if (hdr->nexthdr == NEXTHDR_HOP && check_hbh_len(skb))
 580                 return NF_DROP;
 581
 582         nf_bridge_put(skb->nf_bridge);
 583         if (!nf_bridge_alloc(skb))
 584                 return NF_DROP;
 585         if (!setup_pre_routing(skb))
 586                 return NF_DROP;
 587
 588         skb->protocol = htons(ETH_P_IPV6);
 589         NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, skb, skb->dev, NULL,
 590                 br_nf_pre_routing_finish_ipv6);
 591
 592         return NF_STOLEN;
 593 }
 594
 595 /* Direct IPv6 traffic to br_nf_pre_routing_ipv6.
 596  * Replicate the checks that IPv4 does on packet reception.
 597  * Set skb->dev to the bridge device (i.e. parent of the
 598  * receiving device) to make netfilter happy, the REDIRECT
 599  * target in particular.  Save the original destination IP
 600  * address to be able to detect DNAT afterwards. */
 601 static unsigned int br_nf_pre_routing(unsigned int hook, struct sk_buff *skb,
 602                                       const struct net_device *in,
 603                                       const struct net_device *out,
 604                                       int (*okfn)(struct sk_buff *))
 605 {
 606         struct net_bridge_port *p;
 607         struct net_bridge *br;
 608         __u32 len = nf_bridge_encap_header_len(skb);
 609
 610         if (unlikely(!pskb_may_pull(skb, len)))
 611                 return NF_DROP;
 612
 613         p = br_port_get_rcu(in);
 614         if (p == NULL)
 615                 return NF_DROP;
 616         br = p->br;
 617
 618         if (skb->protocol == htons(ETH_P_IPV6) || IS_VLAN_IPV6(skb) ||
 619             IS_PPPOE_IPV6(skb)) {
 620                 if (!brnf_call_ip6tables && !br->nf_call_ip6tables)
 621                         return NF_ACCEPT;
 622
 623                 nf_bridge_pull_encap_header_rcsum(skb);
 624                 return br_nf_pre_routing_ipv6(hook, skb, in, out, okfn);
 625         }
 626
 627         if (!brnf_call_iptables && !br->nf_call_iptables)
 628                 return NF_ACCEPT;
 629
 630         if (skb->protocol != htons(ETH_P_IP) && !IS_VLAN_IP(skb) &&
 631             !IS_PPPOE_IP(skb))
 632                 return NF_ACCEPT;
 633
 634         nf_bridge_pull_encap_header_rcsum(skb);
 635
 636         if (br_parse_ip_options(skb))
 637                 return NF_DROP;
 638
 639         nf_bridge_put(skb->nf_bridge);
 640         if (!nf_bridge_alloc(skb))
 641                 return NF_DROP;
 642         if (!setup_pre_routing(skb))
 643                 return NF_DROP;
 644         store_orig_dstaddr(skb);
 645         skb->protocol = htons(ETH_P_IP);
 646
 647         NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, skb->dev, NULL,
 648                 br_nf_pre_routing_finish);
 649
 650         return NF_STOLEN;
 651 }
 652
 653
 654 /* PF_BRIDGE/LOCAL_IN ************************************************/
 655 /* The packet is locally destined, which requires a real
 656  * dst_entry, so detach the fake one.  On the way up, the
 657  * packet would pass through PRE_ROUTING again (which already
 658  * took place when the packet entered the bridge), but we
 659  * register an IPv4 PRE_ROUTING 'sabotage' hook that will
 660  * prevent this from happening. */
 661 static unsigned int br_nf_local_in(unsigned int hook, struct sk_buff *skb,
 662                                    const struct net_device *in,
 663                                    const struct net_device *out,
 664                                    int (*okfn)(struct sk_buff *))
 665 {
 666         struct rtable *rt = skb_rtable(skb);
 667
 668         if (rt && rt == bridge_parent_rtable(in))
 669                 skb_dst_drop(skb);
 670
 671         return NF_ACCEPT;
 672 }
 673
 674 /* PF_BRIDGE/FORWARD *************************************************/
 675 static int br_nf_forward_finish(struct sk_buff *skb)
 676 {
 677         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 678         struct net_device *in;
 679
 680         if (skb->protocol != htons(ETH_P_ARP) && !IS_VLAN_ARP(skb)) {
 681                 in = nf_bridge->physindev;
 682                 if (nf_bridge->mask & BRNF_PKT_TYPE) {
 683                         skb->pkt_type = PACKET_OTHERHOST;
 684                         nf_bridge->mask ^= BRNF_PKT_TYPE;
 685                 }
 686                 nf_bridge_update_protocol(skb);
 687         } else {
 688                 in = *((struct net_device **)(skb->cb));
 689         }
 690         nf_bridge_push_encap_header(skb);
 691
 692         NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_FORWARD, skb, in,
 693                        skb->dev, br_forward_finish, 1);
 694         return 0;
 695 }
 696
 697 /* This is the 'purely bridged' case.  For IP, we pass the packet to
 698  * netfilter with indev and outdev set to the bridge device,
 699  * but we are still able to filter on the 'real' indev/outdev
 700  * because of the physdev module. For ARP, indev and outdev are the
 701  * bridge ports. */
 702 static unsigned int br_nf_forward_ip(unsigned int hook, struct sk_buff *skb,
 703                                      const struct net_device *in,
 704                                      const struct net_device *out,
 705                                      int (*okfn)(struct sk_buff *))
 706 {
 707         struct nf_bridge_info *nf_bridge;
 708         struct net_device *parent;
 709         u_int8_t pf;
 710
 711         if (!skb->nf_bridge)
 712                 return NF_ACCEPT;
 713
 714         /* Need exclusive nf_bridge_info since we might have multiple
 715          * different physoutdevs. */
 716         if (!nf_bridge_unshare(skb))
 717                 return NF_DROP;
 718
 719         parent = bridge_parent(out);
 720         if (!parent)
 721                 return NF_DROP;
 722
 723         if (skb->protocol == htons(ETH_P_IP) || IS_VLAN_IP(skb) ||
 724             IS_PPPOE_IP(skb))
 725                 pf = PF_INET;
 726         else if (skb->protocol == htons(ETH_P_IPV6) || IS_VLAN_IPV6(skb) ||
 727                  IS_PPPOE_IPV6(skb))
 728                 pf = PF_INET6;
 729         else
 730                 return NF_ACCEPT;
 731
 732         nf_bridge_pull_encap_header(skb);
 733
 734         nf_bridge = skb->nf_bridge;
 735         if (skb->pkt_type == PACKET_OTHERHOST) {
 736                 skb->pkt_type = PACKET_HOST;
 737                 nf_bridge->mask |= BRNF_PKT_TYPE;
 738         }
 739
 740         if (br_parse_ip_options(skb))
 741                 return NF_DROP;
 742
 743         /* The physdev module checks on this */
 744         nf_bridge->mask |= BRNF_BRIDGED;
 745         nf_bridge->physoutdev = skb->dev;
 746         if (pf == PF_INET)
 747                 skb->protocol = htons(ETH_P_IP);
 748         else
 749                 skb->protocol = htons(ETH_P_IPV6);
 750
 751         NF_HOOK(pf, NF_INET_FORWARD, skb, bridge_parent(in), parent,
 752                 br_nf_forward_finish);
 753
 754         return NF_STOLEN;
 755 }
 756
 757 static unsigned int br_nf_forward_arp(unsigned int hook, struct sk_buff *skb,
 758                                       const struct net_device *in,
 759                                       const struct net_device *out,
 760                                       int (*okfn)(struct sk_buff *))
 761 {
 762         struct net_bridge_port *p;
 763         struct net_bridge *br;
 764         struct net_device **d = (struct net_device **)(skb->cb);
 765
 766         p = br_port_get_rcu(out);
 767         if (p == NULL)
 768                 return NF_ACCEPT;
 769         br = p->br;
 770
 771         if (!brnf_call_arptables && !br->nf_call_arptables)
 772                 return NF_ACCEPT;
 773
 774         if (skb->protocol != htons(ETH_P_ARP)) {
 775                 if (!IS_VLAN_ARP(skb))
 776                         return NF_ACCEPT;
 777                 nf_bridge_pull_encap_header(skb);
 778         }
 779
 780         if (arp_hdr(skb)->ar_pln != 4) {
 781                 if (IS_VLAN_ARP(skb))
 782                         nf_bridge_push_encap_header(skb);
 783                 return NF_ACCEPT;
 784         }
 785         *d = (struct net_device *)in;
 786         NF_HOOK(NFPROTO_ARP, NF_ARP_FORWARD, skb, (struct net_device *)in,
 787                 (struct net_device *)out, br_nf_forward_finish);
 788
 789         return NF_STOLEN;
 790 }
 791
 792 #if defined(CONFIG_NF_CONNTRACK_IPV4) || defined(CONFIG_NF_CONNTRACK_IPV4_MODULE)
 793 static int br_nf_dev_queue_xmit(struct sk_buff *skb)
 794 {
 795         int ret;
 796
 797         if (skb->nfct != NULL && skb->protocol == htons(ETH_P_IP) &&
 798             skb->len + nf_bridge_mtu_reduction(skb) > skb->dev->mtu &&
 799             !skb_is_gso(skb)) {
 800                 if (br_parse_ip_options(skb))
 801                         /* Drop invalid packet */
 802                         return NF_DROP;
 803                 ret = ip_fragment(skb, br_dev_queue_push_xmit);
 804         } else
 805                 ret = br_dev_queue_push_xmit(skb);
 806
 807         return ret;
 808 }
 809 #else
 810 static int br_nf_dev_queue_xmit(struct sk_buff *skb)
 811 {
 812         return br_dev_queue_push_xmit(skb);
 813 }
 814 #endif
 815
 816 /* PF_BRIDGE/POST_ROUTING ********************************************/
 817 static unsigned int br_nf_post_routing(unsigned int hook, struct sk_buff *skb,
 818                                        const struct net_device *in,
 819                                        const struct net_device *out,
 820                                        int (*okfn)(struct sk_buff *))
 821 {
 822         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 823         struct net_device *realoutdev = bridge_parent(skb->dev);
 824         u_int8_t pf;
 825
 826         if (!nf_bridge || !(nf_bridge->mask & BRNF_BRIDGED))
 827                 return NF_ACCEPT;
 828
 829         if (!realoutdev)
 830                 return NF_DROP;
 831
 832         if (skb->protocol == htons(ETH_P_IP) || IS_VLAN_IP(skb) ||
 833             IS_PPPOE_IP(skb))
 834                 pf = PF_INET;
 835         else if (skb->protocol == htons(ETH_P_IPV6) || IS_VLAN_IPV6(skb) ||
 836                  IS_PPPOE_IPV6(skb))
 837                 pf = PF_INET6;
 838         else
 839                 return NF_ACCEPT;
 840
 841         /* We assume any code from br_dev_queue_push_xmit onwards doesn't care
 842          * about the value of skb->pkt_type. */
 843         if (skb->pkt_type == PACKET_OTHERHOST) {
 844                 skb->pkt_type = PACKET_HOST;
 845                 nf_bridge->mask |= BRNF_PKT_TYPE;
 846         }
 847
 848         nf_bridge_pull_encap_header(skb);
 849         nf_bridge_save_header(skb);
 850         if (pf == PF_INET)
 851                 skb->protocol = htons(ETH_P_IP);
 852         else
 853                 skb->protocol = htons(ETH_P_IPV6);
 854
 855         NF_HOOK(pf, NF_INET_POST_ROUTING, skb, NULL, realoutdev,
 856                 br_nf_dev_queue_xmit);
 857
 858         return NF_STOLEN;
 859 }
 860
 861 /* IP/SABOTAGE *****************************************************/
 862 /* Don't hand locally destined packets to PF_INET(6)/PRE_ROUTING
 863  * for the second time. */
 864 static unsigned int ip_sabotage_in(unsigned int hook, struct sk_buff *skb,
 865                                    const struct net_device *in,
 866                                    const struct net_device *out,
 867                                    int (*okfn)(struct sk_buff *))
 868 {
 869         if (skb->nf_bridge &&
 870             !(skb->nf_bridge->mask & BRNF_NF_BRIDGE_PREROUTING)) {
 871                 return NF_STOP;
 872         }
 873
 874         return NF_ACCEPT;
 875 }
 876
 877 /* For br_nf_post_routing, we need (prio = NF_BR_PRI_LAST), because
 878  * br_dev_queue_push_xmit is called afterwards */
 879 static struct nf_hook_ops br_nf_ops[] __read_mostly = {
 880         {
 881                 .hook = br_nf_pre_routing,
 882                 .owner = THIS_MODULE,
 883                 .pf = PF_BRIDGE,
 884                 .hooknum = NF_BR_PRE_ROUTING,
 885                 .priority = NF_BR_PRI_BRNF,
 886         },
 887         {
 888                 .hook = br_nf_local_in,
 889                 .owner = THIS_MODULE,
 890                 .pf = PF_BRIDGE,
 891                 .hooknum = NF_BR_LOCAL_IN,
 892                 .priority = NF_BR_PRI_BRNF,
 893         },
 894         {
 895                 .hook = br_nf_forward_ip,
 896                 .owner = THIS_MODULE,
 897                 .pf = PF_BRIDGE,
 898                 .hooknum = NF_BR_FORWARD,
 899                 .priority = NF_BR_PRI_BRNF - 1,
 900         },
 901         {
 902                 .hook = br_nf_forward_arp,
 903                 .owner = THIS_MODULE,
 904                 .pf = PF_BRIDGE,
 905                 .hooknum = NF_BR_FORWARD,
 906                 .priority = NF_BR_PRI_BRNF,
 907         },
 908         {
 909                 .hook = br_nf_post_routing,
 910                 .owner = THIS_MODULE,
 911                 .pf = PF_BRIDGE,
 912                 .hooknum = NF_BR_POST_ROUTING,
 913                 .priority = NF_BR_PRI_LAST,
 914         },
 915         {
 916                 .hook = ip_sabotage_in,
 917                 .owner = THIS_MODULE,
 918                 .pf = PF_INET,
 919                 .hooknum = NF_INET_PRE_ROUTING,
 920                 .priority = NF_IP_PRI_FIRST,
 921         },
 922         {
 923                 .hook = ip_sabotage_in,
 924                 .owner = THIS_MODULE,
 925                 .pf = PF_INET6,
 926                 .hooknum = NF_INET_PRE_ROUTING,
 927                 .priority = NF_IP6_PRI_FIRST,
 928         },
 929 };
 930
 931 #ifdef CONFIG_SYSCTL
 932 static
 933 int brnf_sysctl_call_tables(ctl_table * ctl, int write,
 934                             void __user * buffer, size_t * lenp, loff_t * ppos)
 935 {
 936         int ret;
 937
 938         ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
 939
 940         if (write && *(int *)(ctl->data))
 941                 *(int *)(ctl->data) = 1;
 942         return ret;
 943 }
 944
 945 static ctl_table brnf_table[] = {
 946         {
 947                 .procname       = "bridge-nf-call-arptables",
 948                 .data           = &brnf_call_arptables,
 949                 .maxlen         = sizeof(int),
 950                 .mode           = 0644,
 951                 .proc_handler   = brnf_sysctl_call_tables,
 952         },
 953         {
 954                 .procname       = "bridge-nf-call-iptables",
 955                 .data           = &brnf_call_iptables,
 956                 .maxlen         = sizeof(int),
 957                 .mode           = 0644,
 958                 .proc_handler   = brnf_sysctl_call_tables,
 959         },
 960         {
 961                 .procname       = "bridge-nf-call-ip6tables",
 962                 .data           = &brnf_call_ip6tables,
 963                 .maxlen         = sizeof(int),
 964                 .mode           = 0644,
 965                 .proc_handler   = brnf_sysctl_call_tables,
 966         },
 967         {
 968                 .procname       = "bridge-nf-filter-vlan-tagged",
 969                 .data           = &brnf_filter_vlan_tagged,
 970                 .maxlen         = sizeof(int),
 971                 .mode           = 0644,
 972                 .proc_handler   = brnf_sysctl_call_tables,
 973         },
 974         {
 975                 .procname       = "bridge-nf-filter-pppoe-tagged",
 976                 .data           = &brnf_filter_pppoe_tagged,
 977                 .maxlen         = sizeof(int),
 978                 .mode           = 0644,
 979                 .proc_handler   = brnf_sysctl_call_tables,
 980         },
 981         { }
 982 };
 983
 984 static struct ctl_path brnf_path[] = {
 985         { .procname = "net", },
 986         { .procname = "bridge", },
 987         { }
 988 };
 989 #endif
 990
 991 int __init br_netfilter_init(void)
 992 {
 993         int ret;
 994
 995         ret = dst_entries_init(&fake_dst_ops);
 996         if (ret < 0)
 997                 return ret;
 998
 999         ret = nf_register_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
1000         if (ret < 0) {
1001                 dst_entries_destroy(&fake_dst_ops);
1002                 return ret;
1003         }
1004 #ifdef CONFIG_SYSCTL
1005         brnf_sysctl_header = register_sysctl_paths(brnf_path, brnf_table);
1006         if (brnf_sysctl_header == NULL) {
1007                 printk(KERN_WARNING
1008                        "br_netfilter: can't register to sysctl.\n");
1009                 nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
1010                 dst_entries_destroy(&fake_dst_ops);
1011                 return -ENOMEM;
1012         }
1013 #endif
1014         printk(KERN_NOTICE "Bridge firewalling registered\n");
1015         return 0;
1016 }
1017
1018 void br_netfilter_fini(void)
1019 {
1020         nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
1021 #ifdef CONFIG_SYSCTL
1022         unregister_sysctl_table(brnf_sysctl_header);
1023 #endif
1024         dst_entries_destroy(&fake_dst_ops);
1025 }