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 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
  41 #include <net/netfilter/nf_conntrack.h>
  42 #endif
  43
  44 #include <asm/uaccess.h>
  45 #include "br_private.h"
  46 #ifdef CONFIG_SYSCTL
  47 #include <linux/sysctl.h>
  48 #endif
  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 static int brnf_pass_vlan_indev __read_mostly = 0;
  58 #else
  59 #define brnf_call_iptables 1
  60 #define brnf_call_ip6tables 1
  61 #define brnf_call_arptables 1
  62 #define brnf_filter_vlan_tagged 0
  63 #define brnf_filter_pppoe_tagged 0
  64 #define brnf_pass_vlan_indev 0
  65 #endif
  66
  67 #define IS_IP(skb) \
  68         (!skb_vlan_tag_present(skb) && skb->protocol == htons(ETH_P_IP))
  69
  70 #define IS_IPV6(skb) \
  71         (!skb_vlan_tag_present(skb) && skb->protocol == htons(ETH_P_IPV6))
  72
  73 #define IS_ARP(skb) \
  74         (!skb_vlan_tag_present(skb) && skb->protocol == htons(ETH_P_ARP))
  75
  76 static inline __be16 vlan_proto(const struct sk_buff *skb)
  77 {
  78         if (skb_vlan_tag_present(skb))
  79                 return skb->protocol;
  80         else if (skb->protocol == htons(ETH_P_8021Q))
  81                 return vlan_eth_hdr(skb)->h_vlan_encapsulated_proto;
  82         else
  83                 return 0;
  84 }
  85
  86 #define IS_VLAN_IP(skb) \
  87         (vlan_proto(skb) == htons(ETH_P_IP) && \
  88          brnf_filter_vlan_tagged)
  89
  90 #define IS_VLAN_IPV6(skb) \
  91         (vlan_proto(skb) == htons(ETH_P_IPV6) && \
  92          brnf_filter_vlan_tagged)
  93
  94 #define IS_VLAN_ARP(skb) \
  95         (vlan_proto(skb) == htons(ETH_P_ARP) && \
  96          brnf_filter_vlan_tagged)
  97
  98 static inline __be16 pppoe_proto(const struct sk_buff *skb)
  99 {
 100         return *((__be16 *)(skb_mac_header(skb) + ETH_HLEN +
 101                             sizeof(struct pppoe_hdr)));
 102 }
 103
 104 #define IS_PPPOE_IP(skb) \
 105         (skb->protocol == htons(ETH_P_PPP_SES) && \
 106          pppoe_proto(skb) == htons(PPP_IP) && \
 107          brnf_filter_pppoe_tagged)
 108
 109 #define IS_PPPOE_IPV6(skb) \
 110         (skb->protocol == htons(ETH_P_PPP_SES) && \
 111          pppoe_proto(skb) == htons(PPP_IPV6) && \
 112          brnf_filter_pppoe_tagged)
 113
 114 /* largest possible L2 header, see br_nf_dev_queue_xmit() */
 115 #define NF_BRIDGE_MAX_MAC_HEADER_LENGTH (PPPOE_SES_HLEN + ETH_HLEN)
 116
 117 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4)
 118 struct brnf_frag_data {
 119         char mac[NF_BRIDGE_MAX_MAC_HEADER_LENGTH];
 120         u8 encap_size;
 121         u8 size;
 122 };
 123
 124 static DEFINE_PER_CPU(struct brnf_frag_data, brnf_frag_data_storage);
 125 #endif
 126
 127 static inline struct rtable *bridge_parent_rtable(const struct net_device *dev)
 128 {
 129         struct net_bridge_port *port;
 130
 131         port = br_port_get_rcu(dev);
 132         return port ? &port->br->fake_rtable : NULL;
 133 }
 134
 135 static inline struct net_device *bridge_parent(const struct net_device *dev)
 136 {
 137         struct net_bridge_port *port;
 138
 139         port = br_port_get_rcu(dev);
 140         return port ? port->br->dev : NULL;
 141 }
 142
 143 static inline struct nf_bridge_info *nf_bridge_alloc(struct sk_buff *skb)
 144 {
 145         skb->nf_bridge = kzalloc(sizeof(struct nf_bridge_info), GFP_ATOMIC);
 146         if (likely(skb->nf_bridge))
 147                 atomic_set(&(skb->nf_bridge->use), 1);
 148
 149         return skb->nf_bridge;
 150 }
 151
 152 static inline struct nf_bridge_info *nf_bridge_unshare(struct sk_buff *skb)
 153 {
 154         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 155
 156         if (atomic_read(&nf_bridge->use) > 1) {
 157                 struct nf_bridge_info *tmp = nf_bridge_alloc(skb);
 158
 159                 if (tmp) {
 160                         memcpy(tmp, nf_bridge, sizeof(struct nf_bridge_info));
 161                         atomic_set(&tmp->use, 1);
 162                 }
 163                 nf_bridge_put(nf_bridge);
 164                 nf_bridge = tmp;
 165         }
 166         return nf_bridge;
 167 }
 168
 169 static unsigned int nf_bridge_encap_header_len(const struct sk_buff *skb)
 170 {
 171         switch (skb->protocol) {
 172         case __cpu_to_be16(ETH_P_8021Q):
 173                 return VLAN_HLEN;
 174         case __cpu_to_be16(ETH_P_PPP_SES):
 175                 return PPPOE_SES_HLEN;
 176         default:
 177                 return 0;
 178         }
 179 }
 180
 181 static inline void nf_bridge_push_encap_header(struct sk_buff *skb)
 182 {
 183         unsigned int len = nf_bridge_encap_header_len(skb);
 184
 185         skb_push(skb, len);
 186         skb->network_header -= len;
 187 }
 188
 189 static inline void nf_bridge_pull_encap_header(struct sk_buff *skb)
 190 {
 191         unsigned int len = nf_bridge_encap_header_len(skb);
 192
 193         skb_pull(skb, len);
 194         skb->network_header += len;
 195 }
 196
 197 static inline void nf_bridge_pull_encap_header_rcsum(struct sk_buff *skb)
 198 {
 199         unsigned int len = nf_bridge_encap_header_len(skb);
 200
 201         skb_pull_rcsum(skb, len);
 202         skb->network_header += len;
 203 }
 204
 205 /* When handing a packet over to the IP layer
 206  * check whether we have a skb that is in the
 207  * expected format
 208  */
 209
 210 static int br_parse_ip_options(struct sk_buff *skb)
 211 {
 212         const struct iphdr *iph;
 213         struct net_device *dev = skb->dev;
 214         u32 len;
 215
 216         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
 217                 goto inhdr_error;
 218
 219         iph = ip_hdr(skb);
 220
 221         /* Basic sanity checks */
 222         if (iph->ihl < 5 || iph->version != 4)
 223                 goto inhdr_error;
 224
 225         if (!pskb_may_pull(skb, iph->ihl*4))
 226                 goto inhdr_error;
 227
 228         iph = ip_hdr(skb);
 229         if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
 230                 goto inhdr_error;
 231
 232         len = ntohs(iph->tot_len);
 233         if (skb->len < len) {
 234                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS);
 235                 goto drop;
 236         } else if (len < (iph->ihl*4))
 237                 goto inhdr_error;
 238
 239         if (pskb_trim_rcsum(skb, len)) {
 240                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
 241                 goto drop;
 242         }
 243
 244         memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
 245         /* We should really parse IP options here but until
 246          * somebody who actually uses IP options complains to
 247          * us we'll just silently ignore the options because
 248          * we're lazy!
 249          */
 250         return 0;
 251
 252 inhdr_error:
 253         IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
 254 drop:
 255         return -1;
 256 }
 257
 258 static void nf_bridge_update_protocol(struct sk_buff *skb)
 259 {
 260         if (skb->nf_bridge->mask & BRNF_8021Q)
 261                 skb->protocol = htons(ETH_P_8021Q);
 262         else if (skb->nf_bridge->mask & BRNF_PPPoE)
 263                 skb->protocol = htons(ETH_P_PPP_SES);
 264 }
 265
 266 /* PF_BRIDGE/PRE_ROUTING *********************************************/
 267 /* Undo the changes made for ip6tables PREROUTING and continue the
 268  * bridge PRE_ROUTING hook. */
 269 static int br_nf_pre_routing_finish_ipv6(struct sk_buff *skb)
 270 {
 271         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 272         struct rtable *rt;
 273
 274         if (nf_bridge->mask & BRNF_PKT_TYPE) {
 275                 skb->pkt_type = PACKET_OTHERHOST;
 276                 nf_bridge->mask ^= BRNF_PKT_TYPE;
 277         }
 278         nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING;
 279
 280         rt = bridge_parent_rtable(nf_bridge->physindev);
 281         if (!rt) {
 282                 kfree_skb(skb);
 283                 return 0;
 284         }
 285         skb_dst_set_noref(skb, &rt->dst);
 286
 287         skb->dev = nf_bridge->physindev;
 288         nf_bridge_update_protocol(skb);
 289         nf_bridge_push_encap_header(skb);
 290         NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
 291                        br_handle_frame_finish, 1);
 292
 293         return 0;
 294 }
 295
 296 /* Obtain the correct destination MAC address, while preserving the original
 297  * source MAC address. If we already know this address, we just copy it. If we
 298  * don't, we use the neighbour framework to find out. In both cases, we make
 299  * sure that br_handle_frame_finish() is called afterwards.
 300  */
 301 static int br_nf_pre_routing_finish_bridge(struct sk_buff *skb)
 302 {
 303         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 304         struct neighbour *neigh;
 305         struct dst_entry *dst;
 306
 307         skb->dev = bridge_parent(skb->dev);
 308         if (!skb->dev)
 309                 goto free_skb;
 310         dst = skb_dst(skb);
 311         neigh = dst_neigh_lookup_skb(dst, skb);
 312         if (neigh) {
 313                 int ret;
 314
 315                 if (neigh->hh.hh_len) {
 316                         neigh_hh_bridge(&neigh->hh, skb);
 317                         skb->dev = nf_bridge->physindev;
 318                         ret = br_handle_frame_finish(skb);
 319                 } else {
 320                         /* the neighbour function below overwrites the complete
 321                          * MAC header, so we save the Ethernet source address and
 322                          * protocol number.
 323                          */
 324                         skb_copy_from_linear_data_offset(skb,
 325                                                          -(ETH_HLEN-ETH_ALEN),
 326                                                          nf_bridge->neigh_header,
 327                                                          ETH_HLEN-ETH_ALEN);
 328                         /* tell br_dev_xmit to continue with forwarding */
 329                         nf_bridge->mask |= BRNF_BRIDGED_DNAT;
 330                         /* FIXME Need to refragment */
 331                         ret = neigh->output(neigh, skb);
 332                 }
 333                 neigh_release(neigh);
 334                 return ret;
 335         }
 336 free_skb:
 337         kfree_skb(skb);
 338         return 0;
 339 }
 340
 341 static bool dnat_took_place(const struct sk_buff *skb)
 342 {
 343 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
 344         enum ip_conntrack_info ctinfo;
 345         struct nf_conn *ct;
 346
 347         ct = nf_ct_get(skb, &ctinfo);
 348         if (!ct || nf_ct_is_untracked(ct))
 349                 return false;
 350
 351         return test_bit(IPS_DST_NAT_BIT, &ct->status);
 352 #else
 353         return false;
 354 #endif
 355 }
 356
 357 /* This requires some explaining. If DNAT has taken place,
 358  * we will need to fix up the destination Ethernet address.
 359  *
 360  * There are two cases to consider:
 361  * 1. The packet was DNAT'ed to a device in the same bridge
 362  *    port group as it was received on. We can still bridge
 363  *    the packet.
 364  * 2. The packet was DNAT'ed to a different device, either
 365  *    a non-bridged device or another bridge port group.
 366  *    The packet will need to be routed.
 367  *
 368  * The correct way of distinguishing between these two cases is to
 369  * call ip_route_input() and to look at skb->dst->dev, which is
 370  * changed to the destination device if ip_route_input() succeeds.
 371  *
 372  * Let's first consider the case that ip_route_input() succeeds:
 373  *
 374  * If the output device equals the logical bridge device the packet
 375  * came in on, we can consider this bridging. The corresponding MAC
 376  * address will be obtained in br_nf_pre_routing_finish_bridge.
 377  * Otherwise, the packet is considered to be routed and we just
 378  * change the destination MAC address so that the packet will
 379  * later be passed up to the IP stack to be routed. For a redirected
 380  * packet, ip_route_input() will give back the localhost as output device,
 381  * which differs from the bridge device.
 382  *
 383  * Let's now consider the case that ip_route_input() fails:
 384  *
 385  * This can be because the destination address is martian, in which case
 386  * the packet will be dropped.
 387  * If IP forwarding is disabled, ip_route_input() will fail, while
 388  * ip_route_output_key() can return success. The source
 389  * address for ip_route_output_key() is set to zero, so ip_route_output_key()
 390  * thinks we're handling a locally generated packet and won't care
 391  * if IP forwarding is enabled. If the output device equals the logical bridge
 392  * device, we proceed as if ip_route_input() succeeded. If it differs from the
 393  * logical bridge port or if ip_route_output_key() fails we drop the packet.
 394  */
 395 static int br_nf_pre_routing_finish(struct sk_buff *skb)
 396 {
 397         struct net_device *dev = skb->dev;
 398         struct iphdr *iph = ip_hdr(skb);
 399         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 400         struct rtable *rt;
 401         int err;
 402         int frag_max_size;
 403
 404         frag_max_size = IPCB(skb)->frag_max_size;
 405         BR_INPUT_SKB_CB(skb)->frag_max_size = frag_max_size;
 406
 407         if (nf_bridge->mask & BRNF_PKT_TYPE) {
 408                 skb->pkt_type = PACKET_OTHERHOST;
 409                 nf_bridge->mask ^= BRNF_PKT_TYPE;
 410         }
 411         nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING;
 412         if (dnat_took_place(skb)) {
 413                 if ((err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))) {
 414                         struct in_device *in_dev = __in_dev_get_rcu(dev);
 415
 416                         /* If err equals -EHOSTUNREACH the error is due to a
 417                          * martian destination or due to the fact that
 418                          * forwarding is disabled. For most martian packets,
 419                          * ip_route_output_key() will fail. It won't fail for 2 types of
 420                          * martian destinations: loopback destinations and destination
 421                          * 0.0.0.0. In both cases the packet will be dropped because the
 422                          * destination is the loopback device and not the bridge. */
 423                         if (err != -EHOSTUNREACH || !in_dev || IN_DEV_FORWARD(in_dev))
 424                                 goto free_skb;
 425
 426                         rt = ip_route_output(dev_net(dev), iph->daddr, 0,
 427                                              RT_TOS(iph->tos), 0);
 428                         if (!IS_ERR(rt)) {
 429                                 /* - Bridged-and-DNAT'ed traffic doesn't
 430                                  *   require ip_forwarding. */
 431                                 if (rt->dst.dev == dev) {
 432                                         skb_dst_set(skb, &rt->dst);
 433                                         goto bridged_dnat;
 434                                 }
 435                                 ip_rt_put(rt);
 436                         }
 437 free_skb:
 438                         kfree_skb(skb);
 439                         return 0;
 440                 } else {
 441                         if (skb_dst(skb)->dev == dev) {
 442 bridged_dnat:
 443                                 skb->dev = nf_bridge->physindev;
 444                                 nf_bridge_update_protocol(skb);
 445                                 nf_bridge_push_encap_header(skb);
 446                                 NF_HOOK_THRESH(NFPROTO_BRIDGE,
 447                                                NF_BR_PRE_ROUTING,
 448                                                skb, skb->dev, NULL,
 449                                                br_nf_pre_routing_finish_bridge,
 450                                                1);
 451                                 return 0;
 452                         }
 453                         ether_addr_copy(eth_hdr(skb)->h_dest, dev->dev_addr);
 454                         skb->pkt_type = PACKET_HOST;
 455                 }
 456         } else {
 457                 rt = bridge_parent_rtable(nf_bridge->physindev);
 458                 if (!rt) {
 459                         kfree_skb(skb);
 460                         return 0;
 461                 }
 462                 skb_dst_set_noref(skb, &rt->dst);
 463         }
 464
 465         skb->dev = nf_bridge->physindev;
 466         nf_bridge_update_protocol(skb);
 467         nf_bridge_push_encap_header(skb);
 468         NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, 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 = skb->nf_bridge;
 492
 493         if (skb->pkt_type == PACKET_OTHERHOST) {
 494                 skb->pkt_type = PACKET_HOST;
 495                 nf_bridge->mask |= BRNF_PKT_TYPE;
 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         if (skb->protocol == htons(ETH_P_8021Q))
 502                 nf_bridge->mask |= BRNF_8021Q;
 503         else if (skb->protocol == htons(ETH_P_PPP_SES))
 504                 nf_bridge->mask |= BRNF_PPPoE;
 505
 506         /* Must drop socket now because of tproxy. */
 507         skb_orphan(skb);
 508         return skb->dev;
 509 }
 510
 511 /* We only check the length. A bridge shouldn't do any hop-by-hop stuff anyway */
 512 static int check_hbh_len(struct sk_buff *skb)
 513 {
 514         unsigned char *raw = (u8 *)(ipv6_hdr(skb) + 1);
 515         u32 pkt_len;
 516         const unsigned char *nh = skb_network_header(skb);
 517         int off = raw - nh;
 518         int len = (raw[1] + 1) << 3;
 519
 520         if ((raw + len) - skb->data > skb_headlen(skb))
 521                 goto bad;
 522
 523         off += 2;
 524         len -= 2;
 525
 526         while (len > 0) {
 527                 int optlen = nh[off + 1] + 2;
 528
 529                 switch (nh[off]) {
 530                 case IPV6_TLV_PAD1:
 531                         optlen = 1;
 532                         break;
 533
 534                 case IPV6_TLV_PADN:
 535                         break;
 536
 537                 case IPV6_TLV_JUMBO:
 538                         if (nh[off + 1] != 4 || (off & 3) != 2)
 539                                 goto bad;
 540                         pkt_len = ntohl(*(__be32 *) (nh + off + 2));
 541                         if (pkt_len <= IPV6_MAXPLEN ||
 542                             ipv6_hdr(skb)->payload_len)
 543                                 goto bad;
 544                         if (pkt_len > skb->len - sizeof(struct ipv6hdr))
 545                                 goto bad;
 546                         if (pskb_trim_rcsum(skb,
 547                                             pkt_len + sizeof(struct ipv6hdr)))
 548                                 goto bad;
 549                         nh = skb_network_header(skb);
 550                         break;
 551                 default:
 552                         if (optlen > len)
 553                                 goto bad;
 554                         break;
 555                 }
 556                 off += optlen;
 557                 len -= optlen;
 558         }
 559         if (len == 0)
 560                 return 0;
 561 bad:
 562         return -1;
 563
 564 }
 565
 566 /* Replicate the checks that IPv6 does on packet reception and pass the packet
 567  * to ip6tables, which doesn't support NAT, so things are fairly simple. */
 568 static unsigned int br_nf_pre_routing_ipv6(const struct nf_hook_ops *ops,
 569                                            struct sk_buff *skb,
 570                                            const struct net_device *in,
 571                                            const struct net_device *out,
 572                                            int (*okfn)(struct sk_buff *))
 573 {
 574         const struct ipv6hdr *hdr;
 575         u32 pkt_len;
 576
 577         if (skb->len < sizeof(struct ipv6hdr))
 578                 return NF_DROP;
 579
 580         if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
 581                 return NF_DROP;
 582
 583         hdr = ipv6_hdr(skb);
 584
 585         if (hdr->version != 6)
 586                 return NF_DROP;
 587
 588         pkt_len = ntohs(hdr->payload_len);
 589
 590         if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
 591                 if (pkt_len + sizeof(struct ipv6hdr) > skb->len)
 592                         return NF_DROP;
 593                 if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr)))
 594                         return NF_DROP;
 595         }
 596         if (hdr->nexthdr == NEXTHDR_HOP && check_hbh_len(skb))
 597                 return NF_DROP;
 598
 599         nf_bridge_put(skb->nf_bridge);
 600         if (!nf_bridge_alloc(skb))
 601                 return NF_DROP;
 602         if (!setup_pre_routing(skb))
 603                 return NF_DROP;
 604
 605         skb->protocol = htons(ETH_P_IPV6);
 606         NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, skb, 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 net_device *in,
 621                                       const struct net_device *out,
 622                                       int (*okfn)(struct sk_buff *))
 623 {
 624         struct net_bridge_port *p;
 625         struct net_bridge *br;
 626         __u32 len = nf_bridge_encap_header_len(skb);
 627
 628         if (unlikely(!pskb_may_pull(skb, len)))
 629                 return NF_DROP;
 630
 631         p = br_port_get_rcu(in);
 632         if (p == NULL)
 633                 return NF_DROP;
 634         br = p->br;
 635
 636         if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb)) {
 637                 if (!brnf_call_ip6tables && !br->nf_call_ip6tables)
 638                         return NF_ACCEPT;
 639
 640                 nf_bridge_pull_encap_header_rcsum(skb);
 641                 return br_nf_pre_routing_ipv6(ops, skb, in, out, okfn);
 642         }
 643
 644         if (!brnf_call_iptables && !br->nf_call_iptables)
 645                 return NF_ACCEPT;
 646
 647         if (!IS_IP(skb) && !IS_VLAN_IP(skb) && !IS_PPPOE_IP(skb))
 648                 return NF_ACCEPT;
 649
 650         nf_bridge_pull_encap_header_rcsum(skb);
 651
 652         if (br_parse_ip_options(skb))
 653                 return NF_DROP;
 654
 655         nf_bridge_put(skb->nf_bridge);
 656         if (!nf_bridge_alloc(skb))
 657                 return NF_DROP;
 658         if (!setup_pre_routing(skb))
 659                 return NF_DROP;
 660
 661         skb->protocol = htons(ETH_P_IP);
 662
 663         NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, skb->dev, NULL,
 664                 br_nf_pre_routing_finish);
 665
 666         return NF_STOLEN;
 667 }
 668
 669
 670 /* PF_BRIDGE/LOCAL_IN ************************************************/
 671 /* The packet is locally destined, which requires a real
 672  * dst_entry, so detach the fake one.  On the way up, the
 673  * packet would pass through PRE_ROUTING again (which already
 674  * took place when the packet entered the bridge), but we
 675  * register an IPv4 PRE_ROUTING 'sabotage' hook that will
 676  * prevent this from happening. */
 677 static unsigned int br_nf_local_in(const struct nf_hook_ops *ops,
 678                                    struct sk_buff *skb,
 679                                    const struct net_device *in,
 680                                    const struct net_device *out,
 681                                    int (*okfn)(struct sk_buff *))
 682 {
 683         br_drop_fake_rtable(skb);
 684         return NF_ACCEPT;
 685 }
 686
 687 /* PF_BRIDGE/FORWARD *************************************************/
 688 static int br_nf_forward_finish(struct sk_buff *skb)
 689 {
 690         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 691         struct net_device *in;
 692
 693         if (!IS_ARP(skb) && !IS_VLAN_ARP(skb)) {
 694                 int frag_max_size;
 695
 696                 if (skb->protocol == htons(ETH_P_IP)) {
 697                         frag_max_size = IPCB(skb)->frag_max_size;
 698                         BR_INPUT_SKB_CB(skb)->frag_max_size = frag_max_size;
 699                 }
 700
 701                 in = nf_bridge->physindev;
 702                 if (nf_bridge->mask & BRNF_PKT_TYPE) {
 703                         skb->pkt_type = PACKET_OTHERHOST;
 704                         nf_bridge->mask ^= BRNF_PKT_TYPE;
 705                 }
 706                 nf_bridge_update_protocol(skb);
 707         } else {
 708                 in = *((struct net_device **)(skb->cb));
 709         }
 710         nf_bridge_push_encap_header(skb);
 711
 712         NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_FORWARD, skb, in,
 713                        skb->dev, br_forward_finish, 1);
 714         return 0;
 715 }
 716
 717
 718 /* This is the 'purely bridged' case.  For IP, we pass the packet to
 719  * netfilter with indev and outdev set to the bridge device,
 720  * but we are still able to filter on the 'real' indev/outdev
 721  * because of the physdev module. For ARP, indev and outdev are the
 722  * bridge ports. */
 723 static unsigned int br_nf_forward_ip(const struct nf_hook_ops *ops,
 724                                      struct sk_buff *skb,
 725                                      const struct net_device *in,
 726                                      const struct net_device *out,
 727                                      int (*okfn)(struct sk_buff *))
 728 {
 729         struct nf_bridge_info *nf_bridge;
 730         struct net_device *parent;
 731         u_int8_t pf;
 732
 733         if (!skb->nf_bridge)
 734                 return NF_ACCEPT;
 735
 736         /* Need exclusive nf_bridge_info since we might have multiple
 737          * different physoutdevs. */
 738         if (!nf_bridge_unshare(skb))
 739                 return NF_DROP;
 740
 741         parent = bridge_parent(out);
 742         if (!parent)
 743                 return NF_DROP;
 744
 745         if (IS_IP(skb) || IS_VLAN_IP(skb) || IS_PPPOE_IP(skb))
 746                 pf = NFPROTO_IPV4;
 747         else if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb))
 748                 pf = NFPROTO_IPV6;
 749         else
 750                 return NF_ACCEPT;
 751
 752         nf_bridge_pull_encap_header(skb);
 753
 754         nf_bridge = skb->nf_bridge;
 755         if (skb->pkt_type == PACKET_OTHERHOST) {
 756                 skb->pkt_type = PACKET_HOST;
 757                 nf_bridge->mask |= BRNF_PKT_TYPE;
 758         }
 759
 760         if (pf == NFPROTO_IPV4) {
 761                 int frag_max = BR_INPUT_SKB_CB(skb)->frag_max_size;
 762
 763                 if (br_parse_ip_options(skb))
 764                         return NF_DROP;
 765
 766                 IPCB(skb)->frag_max_size = frag_max;
 767         }
 768
 769         nf_bridge->physoutdev = skb->dev;
 770         if (pf == NFPROTO_IPV4)
 771                 skb->protocol = htons(ETH_P_IP);
 772         else
 773                 skb->protocol = htons(ETH_P_IPV6);
 774
 775         NF_HOOK(pf, NF_INET_FORWARD, skb, brnf_get_logical_dev(skb, in), parent,
 776                 br_nf_forward_finish);
 777
 778         return NF_STOLEN;
 779 }
 780
 781 static unsigned int br_nf_forward_arp(const struct nf_hook_ops *ops,
 782                                       struct sk_buff *skb,
 783                                       const struct net_device *in,
 784                                       const struct net_device *out,
 785                                       int (*okfn)(struct sk_buff *))
 786 {
 787         struct net_bridge_port *p;
 788         struct net_bridge *br;
 789         struct net_device **d = (struct net_device **)(skb->cb);
 790
 791         p = br_port_get_rcu(out);
 792         if (p == NULL)
 793                 return NF_ACCEPT;
 794         br = p->br;
 795
 796         if (!brnf_call_arptables && !br->nf_call_arptables)
 797                 return NF_ACCEPT;
 798
 799         if (!IS_ARP(skb)) {
 800                 if (!IS_VLAN_ARP(skb))
 801                         return NF_ACCEPT;
 802                 nf_bridge_pull_encap_header(skb);
 803         }
 804
 805         if (arp_hdr(skb)->ar_pln != 4) {
 806                 if (IS_VLAN_ARP(skb))
 807                         nf_bridge_push_encap_header(skb);
 808                 return NF_ACCEPT;
 809         }
 810         *d = (struct net_device *)in;
 811         NF_HOOK(NFPROTO_ARP, NF_ARP_FORWARD, skb, (struct net_device *)in,
 812                 (struct net_device *)out, br_nf_forward_finish);
 813
 814         return NF_STOLEN;
 815 }
 816
 817 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4)
 818 static int br_nf_push_frag_xmit(struct sk_buff *skb)
 819 {
 820         struct brnf_frag_data *data;
 821         int err;
 822
 823         data = this_cpu_ptr(&brnf_frag_data_storage);
 824         err = skb_cow_head(skb, data->size);
 825
 826         if (err) {
 827                 kfree_skb(skb);
 828                 return 0;
 829         }
 830
 831         skb_copy_to_linear_data_offset(skb, -data->size, data->mac, data->size);
 832         __skb_push(skb, data->encap_size);
 833
 834         return br_dev_queue_push_xmit(skb);
 835 }
 836
 837 static int br_nf_dev_queue_xmit(struct sk_buff *skb)
 838 {
 839         int ret;
 840         int frag_max_size;
 841         unsigned int mtu_reserved;
 842
 843         if (skb_is_gso(skb) || skb->protocol != htons(ETH_P_IP))
 844                 return br_dev_queue_push_xmit(skb);
 845
 846         mtu_reserved = nf_bridge_mtu_reduction(skb);
 847         /* This is wrong! We should preserve the original fragment
 848          * boundaries by preserving frag_list rather than refragmenting.
 849          */
 850         if (skb->len + mtu_reserved > skb->dev->mtu) {
 851                 struct brnf_frag_data *data;
 852
 853                 frag_max_size = BR_INPUT_SKB_CB(skb)->frag_max_size;
 854                 if (br_parse_ip_options(skb))
 855                         /* Drop invalid packet */
 856                         return NF_DROP;
 857                 IPCB(skb)->frag_max_size = frag_max_size;
 858
 859                 nf_bridge_update_protocol(skb);
 860
 861                 data = this_cpu_ptr(&brnf_frag_data_storage);
 862                 data->encap_size = nf_bridge_encap_header_len(skb);
 863                 data->size = ETH_HLEN + data->encap_size;
 864
 865                 skb_copy_from_linear_data_offset(skb, -data->size, data->mac,
 866                                                  data->size);
 867
 868                 ret = ip_fragment(skb, br_nf_push_frag_xmit);
 869         } else {
 870                 ret = br_dev_queue_push_xmit(skb);
 871         }
 872
 873         return ret;
 874 }
 875 #else
 876 static int br_nf_dev_queue_xmit(struct sk_buff *skb)
 877 {
 878         return br_dev_queue_push_xmit(skb);
 879 }
 880 #endif
 881
 882 /* PF_BRIDGE/POST_ROUTING ********************************************/
 883 static unsigned int br_nf_post_routing(const struct nf_hook_ops *ops,
 884                                        struct sk_buff *skb,
 885                                        const struct net_device *in,
 886                                        const struct net_device *out,
 887                                        int (*okfn)(struct sk_buff *))
 888 {
 889         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 890         struct net_device *realoutdev = bridge_parent(skb->dev);
 891         u_int8_t pf;
 892
 893         /* if nf_bridge is set, but ->physoutdev is NULL, this packet came in
 894          * on a bridge, but was delivered locally and is now being routed:
 895          *
 896          * POST_ROUTING was already invoked from the ip stack.
 897          */
 898         if (!nf_bridge || !nf_bridge->physoutdev)
 899                 return NF_ACCEPT;
 900
 901         if (!realoutdev)
 902                 return NF_DROP;
 903
 904         if (IS_IP(skb) || IS_VLAN_IP(skb) || IS_PPPOE_IP(skb))
 905                 pf = NFPROTO_IPV4;
 906         else if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb))
 907                 pf = NFPROTO_IPV6;
 908         else
 909                 return NF_ACCEPT;
 910
 911         /* We assume any code from br_dev_queue_push_xmit onwards doesn't care
 912          * about the value of skb->pkt_type. */
 913         if (skb->pkt_type == PACKET_OTHERHOST) {
 914                 skb->pkt_type = PACKET_HOST;
 915                 nf_bridge->mask |= BRNF_PKT_TYPE;
 916         }
 917
 918         nf_bridge_pull_encap_header(skb);
 919         if (pf == NFPROTO_IPV4)
 920                 skb->protocol = htons(ETH_P_IP);
 921         else
 922                 skb->protocol = htons(ETH_P_IPV6);
 923
 924         NF_HOOK(pf, NF_INET_POST_ROUTING, skb, 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 net_device *in,
 936                                    const struct net_device *out,
 937                                    int (*okfn)(struct sk_buff *))
 938 {
 939         if (skb->nf_bridge &&
 940             !(skb->nf_bridge->mask & BRNF_NF_BRIDGE_PREROUTING)) {
 941                 return NF_STOP;
 942         }
 943
 944         return NF_ACCEPT;
 945 }
 946
 947 /* This is called when br_netfilter has called into iptables/netfilter,
 948  * and DNAT has taken place on a bridge-forwarded packet.
 949  *
 950  * neigh->output has created a new MAC header, with local br0 MAC
 951  * as saddr.
 952  *
 953  * This restores the original MAC saddr of the bridged packet
 954  * before invoking bridge forward logic to transmit the packet.
 955  */
 956 static void br_nf_pre_routing_finish_bridge_slow(struct sk_buff *skb)
 957 {
 958         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 959
 960         skb_pull(skb, ETH_HLEN);
 961         nf_bridge->mask &= ~BRNF_BRIDGED_DNAT;
 962
 963         BUILD_BUG_ON(sizeof(nf_bridge->neigh_header) != (ETH_HLEN - ETH_ALEN));
 964
 965         skb_copy_to_linear_data_offset(skb, -(ETH_HLEN - ETH_ALEN),
 966                                        nf_bridge->neigh_header,
 967                                        ETH_HLEN - ETH_ALEN);
 968         skb->dev = nf_bridge->physindev;
 969         br_handle_frame_finish(skb);
 970 }
 971
 972 static int br_nf_dev_xmit(struct sk_buff *skb)
 973 {
 974         if (skb->nf_bridge && (skb->nf_bridge->mask & BRNF_BRIDGED_DNAT)) {
 975                 br_nf_pre_routing_finish_bridge_slow(skb);
 976                 return 1;
 977         }
 978         return 0;
 979 }
 980
 981 static const struct nf_br_ops br_ops = {
 982         .br_dev_xmit_hook =     br_nf_dev_xmit,
 983 };
 984
 985 void br_netfilter_enable(void)
 986 {
 987 }
 988 EXPORT_SYMBOL_GPL(br_netfilter_enable);
 989
 990 /* For br_nf_post_routing, we need (prio = NF_BR_PRI_LAST), because
 991  * br_dev_queue_push_xmit is called afterwards */
 992 static struct nf_hook_ops br_nf_ops[] __read_mostly = {
 993         {
 994                 .hook = br_nf_pre_routing,
 995                 .owner = THIS_MODULE,
 996                 .pf = NFPROTO_BRIDGE,
 997                 .hooknum = NF_BR_PRE_ROUTING,
 998                 .priority = NF_BR_PRI_BRNF,
 999         },
1000         {
1001                 .hook = br_nf_local_in,
1002                 .owner = THIS_MODULE,
1003                 .pf = NFPROTO_BRIDGE,
1004                 .hooknum = NF_BR_LOCAL_IN,
1005                 .priority = NF_BR_PRI_BRNF,
1006         },
1007         {
1008                 .hook = br_nf_forward_ip,
1009                 .owner = THIS_MODULE,
1010                 .pf = NFPROTO_BRIDGE,
1011                 .hooknum = NF_BR_FORWARD,
1012                 .priority = NF_BR_PRI_BRNF - 1,
1013         },
1014         {
1015                 .hook = br_nf_forward_arp,
1016                 .owner = THIS_MODULE,
1017                 .pf = NFPROTO_BRIDGE,
1018                 .hooknum = NF_BR_FORWARD,
1019                 .priority = NF_BR_PRI_BRNF,
1020         },
1021         {
1022                 .hook = br_nf_post_routing,
1023                 .owner = THIS_MODULE,
1024                 .pf = NFPROTO_BRIDGE,
1025                 .hooknum = NF_BR_POST_ROUTING,
1026                 .priority = NF_BR_PRI_LAST,
1027         },
1028         {
1029                 .hook = ip_sabotage_in,
1030                 .owner = THIS_MODULE,
1031                 .pf = NFPROTO_IPV4,
1032                 .hooknum = NF_INET_PRE_ROUTING,
1033                 .priority = NF_IP_PRI_FIRST,
1034         },
1035         {
1036                 .hook = ip_sabotage_in,
1037                 .owner = THIS_MODULE,
1038                 .pf = NFPROTO_IPV6,
1039                 .hooknum = NF_INET_PRE_ROUTING,
1040                 .priority = NF_IP6_PRI_FIRST,
1041         },
1042 };
1043
1044 #ifdef CONFIG_SYSCTL
1045 static
1046 int brnf_sysctl_call_tables(struct ctl_table *ctl, int write,
1047                             void __user *buffer, size_t *lenp, loff_t *ppos)
1048 {
1049         int ret;
1050
1051         ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
1052
1053         if (write && *(int *)(ctl->data))
1054                 *(int *)(ctl->data) = 1;
1055         return ret;
1056 }
1057
1058 static struct ctl_table brnf_table[] = {
1059         {
1060                 .procname       = "bridge-nf-call-arptables",
1061                 .data           = &brnf_call_arptables,
1062                 .maxlen         = sizeof(int),
1063                 .mode           = 0644,
1064                 .proc_handler   = brnf_sysctl_call_tables,
1065         },
1066         {
1067                 .procname       = "bridge-nf-call-iptables",
1068                 .data           = &brnf_call_iptables,
1069                 .maxlen         = sizeof(int),
1070                 .mode           = 0644,
1071                 .proc_handler   = brnf_sysctl_call_tables,
1072         },
1073         {
1074                 .procname       = "bridge-nf-call-ip6tables",
1075                 .data           = &brnf_call_ip6tables,
1076                 .maxlen         = sizeof(int),
1077                 .mode           = 0644,
1078                 .proc_handler   = brnf_sysctl_call_tables,
1079         },
1080         {
1081                 .procname       = "bridge-nf-filter-vlan-tagged",
1082                 .data           = &brnf_filter_vlan_tagged,
1083                 .maxlen         = sizeof(int),
1084                 .mode           = 0644,
1085                 .proc_handler   = brnf_sysctl_call_tables,
1086         },
1087         {
1088                 .procname       = "bridge-nf-filter-pppoe-tagged",
1089                 .data           = &brnf_filter_pppoe_tagged,
1090                 .maxlen         = sizeof(int),
1091                 .mode           = 0644,
1092                 .proc_handler   = brnf_sysctl_call_tables,
1093         },
1094         {
1095                 .procname       = "bridge-nf-pass-vlan-input-dev",
1096                 .data           = &brnf_pass_vlan_indev,
1097                 .maxlen         = sizeof(int),
1098                 .mode           = 0644,
1099                 .proc_handler   = brnf_sysctl_call_tables,
1100         },
1101         { }
1102 };
1103 #endif
1104
1105 static int __init br_netfilter_init(void)
1106 {
1107         int ret;
1108
1109         ret = nf_register_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
1110         if (ret < 0)
1111                 return ret;
1112
1113 #ifdef CONFIG_SYSCTL
1114         brnf_sysctl_header = register_net_sysctl(&init_net, "net/bridge", brnf_table);
1115         if (brnf_sysctl_header == NULL) {
1116                 printk(KERN_WARNING
1117                        "br_netfilter: can't register to sysctl.\n");
1118                 nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
1119                 return -ENOMEM;
1120         }
1121 #endif
1122         RCU_INIT_POINTER(nf_br_ops, &br_ops);
1123         printk(KERN_NOTICE "Bridge firewalling registered\n");
1124         return 0;
1125 }
1126
1127 static void __exit br_netfilter_fini(void)
1128 {
1129         RCU_INIT_POINTER(nf_br_ops, NULL);
1130         nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
1131 #ifdef CONFIG_SYSCTL
1132         unregister_net_sysctl_table(brnf_sysctl_header);
1133 #endif
1134 }
1135
1136 module_init(br_netfilter_init);
1137 module_exit(br_netfilter_fini);
1138
1139 MODULE_LICENSE("GPL");
1140 MODULE_AUTHOR("Lennert Buytenhek <buytenh@gnu.org>");
1141 MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>");
1142 MODULE_DESCRIPTION("Linux ethernet netfilter firewall bridge");