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Linux/net/bridge/br_netfilter_hooks.c

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  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/addrconf.h>
 38 #include <net/route.h>
 39 #include <net/netfilter/br_netfilter.h>
 40 
 41 #include <asm/uaccess.h>
 42 #include "br_private.h"
 43 #ifdef CONFIG_SYSCTL
 44 #include <linux/sysctl.h>
 45 #endif
 46 
 47 #ifdef CONFIG_SYSCTL
 48 static struct ctl_table_header *brnf_sysctl_header;
 49 static int brnf_call_iptables __read_mostly = 1;
 50 static int brnf_call_ip6tables __read_mostly = 1;
 51 static int brnf_call_arptables __read_mostly = 1;
 52 static int brnf_filter_vlan_tagged __read_mostly;
 53 static int brnf_filter_pppoe_tagged __read_mostly;
 54 static int brnf_pass_vlan_indev __read_mostly;
 55 #else
 56 #define brnf_call_iptables 1
 57 #define brnf_call_ip6tables 1
 58 #define brnf_call_arptables 1
 59 #define brnf_filter_vlan_tagged 0
 60 #define brnf_filter_pppoe_tagged 0
 61 #define brnf_pass_vlan_indev 0
 62 #endif
 63 
 64 #define IS_IP(skb) \
 65         (!skb_vlan_tag_present(skb) && skb->protocol == htons(ETH_P_IP))
 66 
 67 #define IS_IPV6(skb) \
 68         (!skb_vlan_tag_present(skb) && skb->protocol == htons(ETH_P_IPV6))
 69 
 70 #define IS_ARP(skb) \
 71         (!skb_vlan_tag_present(skb) && skb->protocol == htons(ETH_P_ARP))
 72 
 73 static inline __be16 vlan_proto(const struct sk_buff *skb)
 74 {
 75         if (skb_vlan_tag_present(skb))
 76                 return skb->protocol;
 77         else if (skb->protocol == htons(ETH_P_8021Q))
 78                 return vlan_eth_hdr(skb)->h_vlan_encapsulated_proto;
 79         else
 80                 return 0;
 81 }
 82 
 83 #define IS_VLAN_IP(skb) \
 84         (vlan_proto(skb) == htons(ETH_P_IP) && \
 85          brnf_filter_vlan_tagged)
 86 
 87 #define IS_VLAN_IPV6(skb) \
 88         (vlan_proto(skb) == htons(ETH_P_IPV6) && \
 89          brnf_filter_vlan_tagged)
 90 
 91 #define IS_VLAN_ARP(skb) \
 92         (vlan_proto(skb) == htons(ETH_P_ARP) && \
 93          brnf_filter_vlan_tagged)
 94 
 95 static inline __be16 pppoe_proto(const struct sk_buff *skb)
 96 {
 97         return *((__be16 *)(skb_mac_header(skb) + ETH_HLEN +
 98                             sizeof(struct pppoe_hdr)));
 99 }
100 
101 #define IS_PPPOE_IP(skb) \
102         (skb->protocol == htons(ETH_P_PPP_SES) && \
103          pppoe_proto(skb) == htons(PPP_IP) && \
104          brnf_filter_pppoe_tagged)
105 
106 #define IS_PPPOE_IPV6(skb) \
107         (skb->protocol == htons(ETH_P_PPP_SES) && \
108          pppoe_proto(skb) == htons(PPP_IPV6) && \
109          brnf_filter_pppoe_tagged)
110 
111 /* largest possible L2 header, see br_nf_dev_queue_xmit() */
112 #define NF_BRIDGE_MAX_MAC_HEADER_LENGTH (PPPOE_SES_HLEN + ETH_HLEN)
113 
114 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4) || IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
115 struct brnf_frag_data {
116         char mac[NF_BRIDGE_MAX_MAC_HEADER_LENGTH];
117         u8 encap_size;
118         u8 size;
119         u16 vlan_tci;
120         __be16 vlan_proto;
121 };
122 
123 static DEFINE_PER_CPU(struct brnf_frag_data, brnf_frag_data_storage);
124 #endif
125 
126 static void nf_bridge_info_free(struct sk_buff *skb)
127 {
128         if (skb->nf_bridge) {
129                 nf_bridge_put(skb->nf_bridge);
130                 skb->nf_bridge = NULL;
131         }
132 }
133 
134 static inline struct net_device *bridge_parent(const struct net_device *dev)
135 {
136         struct net_bridge_port *port;
137 
138         port = br_port_get_rcu(dev);
139         return port ? port->br->dev : NULL;
140 }
141 
142 static inline struct nf_bridge_info *nf_bridge_unshare(struct sk_buff *skb)
143 {
144         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
145 
146         if (atomic_read(&nf_bridge->use) > 1) {
147                 struct nf_bridge_info *tmp = nf_bridge_alloc(skb);
148 
149                 if (tmp) {
150                         memcpy(tmp, nf_bridge, sizeof(struct nf_bridge_info));
151                         atomic_set(&tmp->use, 1);
152                 }
153                 nf_bridge_put(nf_bridge);
154                 nf_bridge = tmp;
155         }
156         return nf_bridge;
157 }
158 
159 unsigned int nf_bridge_encap_header_len(const struct sk_buff *skb)
160 {
161         switch (skb->protocol) {
162         case __cpu_to_be16(ETH_P_8021Q):
163                 return VLAN_HLEN;
164         case __cpu_to_be16(ETH_P_PPP_SES):
165                 return PPPOE_SES_HLEN;
166         default:
167                 return 0;
168         }
169 }
170 
171 static inline void nf_bridge_pull_encap_header(struct sk_buff *skb)
172 {
173         unsigned int len = nf_bridge_encap_header_len(skb);
174 
175         skb_pull(skb, len);
176         skb->network_header += len;
177 }
178 
179 static inline void nf_bridge_pull_encap_header_rcsum(struct sk_buff *skb)
180 {
181         unsigned int len = nf_bridge_encap_header_len(skb);
182 
183         skb_pull_rcsum(skb, len);
184         skb->network_header += len;
185 }
186 
187 /* When handing a packet over to the IP layer
188  * check whether we have a skb that is in the
189  * expected format
190  */
191 
192 static int br_validate_ipv4(struct sk_buff *skb)
193 {
194         const struct iphdr *iph;
195         struct net_device *dev = skb->dev;
196         u32 len;
197 
198         if (!pskb_may_pull(skb, sizeof(struct iphdr)))
199                 goto inhdr_error;
200 
201         iph = ip_hdr(skb);
202 
203         /* Basic sanity checks */
204         if (iph->ihl < 5 || iph->version != 4)
205                 goto inhdr_error;
206 
207         if (!pskb_may_pull(skb, iph->ihl*4))
208                 goto inhdr_error;
209 
210         iph = ip_hdr(skb);
211         if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
212                 goto inhdr_error;
213 
214         len = ntohs(iph->tot_len);
215         if (skb->len < len) {
216                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS);
217                 goto drop;
218         } else if (len < (iph->ihl*4))
219                 goto inhdr_error;
220 
221         if (pskb_trim_rcsum(skb, len)) {
222                 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS);
223                 goto drop;
224         }
225 
226         memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
227         /* We should really parse IP options here but until
228          * somebody who actually uses IP options complains to
229          * us we'll just silently ignore the options because
230          * we're lazy!
231          */
232         return 0;
233 
234 inhdr_error:
235         IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
236 drop:
237         return -1;
238 }
239 
240 void nf_bridge_update_protocol(struct sk_buff *skb)
241 {
242         switch (skb->nf_bridge->orig_proto) {
243         case BRNF_PROTO_8021Q:
244                 skb->protocol = htons(ETH_P_8021Q);
245                 break;
246         case BRNF_PROTO_PPPOE:
247                 skb->protocol = htons(ETH_P_PPP_SES);
248                 break;
249         case BRNF_PROTO_UNCHANGED:
250                 break;
251         }
252 }
253 
254 /* Obtain the correct destination MAC address, while preserving the original
255  * source MAC address. If we already know this address, we just copy it. If we
256  * don't, we use the neighbour framework to find out. In both cases, we make
257  * sure that br_handle_frame_finish() is called afterwards.
258  */
259 int br_nf_pre_routing_finish_bridge(struct sock *sk, struct sk_buff *skb)
260 {
261         struct neighbour *neigh;
262         struct dst_entry *dst;
263 
264         skb->dev = bridge_parent(skb->dev);
265         if (!skb->dev)
266                 goto free_skb;
267         dst = skb_dst(skb);
268         neigh = dst_neigh_lookup_skb(dst, skb);
269         if (neigh) {
270                 struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
271                 int ret;
272 
273                 if (neigh->hh.hh_len) {
274                         neigh_hh_bridge(&neigh->hh, skb);
275                         skb->dev = nf_bridge->physindev;
276                         ret = br_handle_frame_finish(sk, skb);
277                 } else {
278                         /* the neighbour function below overwrites the complete
279                          * MAC header, so we save the Ethernet source address and
280                          * protocol number.
281                          */
282                         skb_copy_from_linear_data_offset(skb,
283                                                          -(ETH_HLEN-ETH_ALEN),
284                                                          nf_bridge->neigh_header,
285                                                          ETH_HLEN-ETH_ALEN);
286                         /* tell br_dev_xmit to continue with forwarding */
287                         nf_bridge->bridged_dnat = 1;
288                         /* FIXME Need to refragment */
289                         ret = neigh->output(neigh, skb);
290                 }
291                 neigh_release(neigh);
292                 return ret;
293         }
294 free_skb:
295         kfree_skb(skb);
296         return 0;
297 }
298 
299 static inline bool
300 br_nf_ipv4_daddr_was_changed(const struct sk_buff *skb,
301                              const struct nf_bridge_info *nf_bridge)
302 {
303         return ip_hdr(skb)->daddr != nf_bridge->ipv4_daddr;
304 }
305 
306 /* This requires some explaining. If DNAT has taken place,
307  * we will need to fix up the destination Ethernet address.
308  * This is also true when SNAT takes place (for the reply direction).
309  *
310  * There are two cases to consider:
311  * 1. The packet was DNAT'ed to a device in the same bridge
312  *    port group as it was received on. We can still bridge
313  *    the packet.
314  * 2. The packet was DNAT'ed to a different device, either
315  *    a non-bridged device or another bridge port group.
316  *    The packet will need to be routed.
317  *
318  * The correct way of distinguishing between these two cases is to
319  * call ip_route_input() and to look at skb->dst->dev, which is
320  * changed to the destination device if ip_route_input() succeeds.
321  *
322  * Let's first consider the case that ip_route_input() succeeds:
323  *
324  * If the output device equals the logical bridge device the packet
325  * came in on, we can consider this bridging. The corresponding MAC
326  * address will be obtained in br_nf_pre_routing_finish_bridge.
327  * Otherwise, the packet is considered to be routed and we just
328  * change the destination MAC address so that the packet will
329  * later be passed up to the IP stack to be routed. For a redirected
330  * packet, ip_route_input() will give back the localhost as output device,
331  * which differs from the bridge device.
332  *
333  * Let's now consider the case that ip_route_input() fails:
334  *
335  * This can be because the destination address is martian, in which case
336  * the packet will be dropped.
337  * If IP forwarding is disabled, ip_route_input() will fail, while
338  * ip_route_output_key() can return success. The source
339  * address for ip_route_output_key() is set to zero, so ip_route_output_key()
340  * thinks we're handling a locally generated packet and won't care
341  * if IP forwarding is enabled. If the output device equals the logical bridge
342  * device, we proceed as if ip_route_input() succeeded. If it differs from the
343  * logical bridge port or if ip_route_output_key() fails we drop the packet.
344  */
345 static int br_nf_pre_routing_finish(struct sock *sk, struct sk_buff *skb)
346 {
347         struct net_device *dev = skb->dev;
348         struct iphdr *iph = ip_hdr(skb);
349         struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
350         struct rtable *rt;
351         int err;
352 
353         nf_bridge->frag_max_size = IPCB(skb)->frag_max_size;
354 
355         if (nf_bridge->pkt_otherhost) {
356                 skb->pkt_type = PACKET_OTHERHOST;
357                 nf_bridge->pkt_otherhost = false;
358         }
359         nf_bridge->in_prerouting = 0;
360         if (br_nf_ipv4_daddr_was_changed(skb, nf_bridge)) {
361                 if ((err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))) {
362                         struct in_device *in_dev = __in_dev_get_rcu(dev);
363 
364                         /* If err equals -EHOSTUNREACH the error is due to a
365                          * martian destination or due to the fact that
366                          * forwarding is disabled. For most martian packets,
367                          * ip_route_output_key() will fail. It won't fail for 2 types of
368                          * martian destinations: loopback destinations and destination
369                          * 0.0.0.0. In both cases the packet will be dropped because the
370                          * destination is the loopback device and not the bridge. */
371                         if (err != -EHOSTUNREACH || !in_dev || IN_DEV_FORWARD(in_dev))
372                                 goto free_skb;
373 
374                         rt = ip_route_output(dev_net(dev), iph->daddr, 0,
375                                              RT_TOS(iph->tos), 0);
376                         if (!IS_ERR(rt)) {
377                                 /* - Bridged-and-DNAT'ed traffic doesn't
378                                  *   require ip_forwarding. */
379                                 if (rt->dst.dev == dev) {
380                                         skb_dst_set(skb, &rt->dst);
381                                         goto bridged_dnat;
382                                 }
383                                 ip_rt_put(rt);
384                         }
385 free_skb:
386                         kfree_skb(skb);
387                         return 0;
388                 } else {
389                         if (skb_dst(skb)->dev == dev) {
390 bridged_dnat:
391                                 skb->dev = nf_bridge->physindev;
392                                 nf_bridge_update_protocol(skb);
393                                 nf_bridge_push_encap_header(skb);
394                                 NF_HOOK_THRESH(NFPROTO_BRIDGE,
395                                                NF_BR_PRE_ROUTING,
396                                                sk, skb, skb->dev, NULL,
397                                                br_nf_pre_routing_finish_bridge,
398                                                1);
399                                 return 0;
400                         }
401                         ether_addr_copy(eth_hdr(skb)->h_dest, dev->dev_addr);
402                         skb->pkt_type = PACKET_HOST;
403                 }
404         } else {
405                 rt = bridge_parent_rtable(nf_bridge->physindev);
406                 if (!rt) {
407                         kfree_skb(skb);
408                         return 0;
409                 }
410                 skb_dst_set_noref(skb, &rt->dst);
411         }
412 
413         skb->dev = nf_bridge->physindev;
414         nf_bridge_update_protocol(skb);
415         nf_bridge_push_encap_header(skb);
416         NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, sk, skb,
417                        skb->dev, NULL,
418                        br_handle_frame_finish, 1);
419 
420         return 0;
421 }
422 
423 static struct net_device *brnf_get_logical_dev(struct sk_buff *skb, const struct net_device *dev)
424 {
425         struct net_device *vlan, *br;
426 
427         br = bridge_parent(dev);
428         if (brnf_pass_vlan_indev == 0 || !skb_vlan_tag_present(skb))
429                 return br;
430 
431         vlan = __vlan_find_dev_deep_rcu(br, skb->vlan_proto,
432                                     skb_vlan_tag_get(skb) & VLAN_VID_MASK);
433 
434         return vlan ? vlan : br;
435 }
436 
437 /* Some common code for IPv4/IPv6 */
438 struct net_device *setup_pre_routing(struct sk_buff *skb)
439 {
440         struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
441 
442         if (skb->pkt_type == PACKET_OTHERHOST) {
443                 skb->pkt_type = PACKET_HOST;
444                 nf_bridge->pkt_otherhost = true;
445         }
446 
447         nf_bridge->in_prerouting = 1;
448         nf_bridge->physindev = skb->dev;
449         skb->dev = brnf_get_logical_dev(skb, skb->dev);
450 
451         if (skb->protocol == htons(ETH_P_8021Q))
452                 nf_bridge->orig_proto = BRNF_PROTO_8021Q;
453         else if (skb->protocol == htons(ETH_P_PPP_SES))
454                 nf_bridge->orig_proto = BRNF_PROTO_PPPOE;
455 
456         /* Must drop socket now because of tproxy. */
457         skb_orphan(skb);
458         return skb->dev;
459 }
460 
461 /* Direct IPv6 traffic to br_nf_pre_routing_ipv6.
462  * Replicate the checks that IPv4 does on packet reception.
463  * Set skb->dev to the bridge device (i.e. parent of the
464  * receiving device) to make netfilter happy, the REDIRECT
465  * target in particular.  Save the original destination IP
466  * address to be able to detect DNAT afterwards. */
467 static unsigned int br_nf_pre_routing(const struct nf_hook_ops *ops,
468                                       struct sk_buff *skb,
469                                       const struct nf_hook_state *state)
470 {
471         struct nf_bridge_info *nf_bridge;
472         struct net_bridge_port *p;
473         struct net_bridge *br;
474         __u32 len = nf_bridge_encap_header_len(skb);
475 
476         if (unlikely(!pskb_may_pull(skb, len)))
477                 return NF_DROP;
478 
479         p = br_port_get_rcu(state->in);
480         if (p == NULL)
481                 return NF_DROP;
482         br = p->br;
483 
484         if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb)) {
485                 if (!brnf_call_ip6tables && !br->nf_call_ip6tables)
486                         return NF_ACCEPT;
487 
488                 nf_bridge_pull_encap_header_rcsum(skb);
489                 return br_nf_pre_routing_ipv6(ops, skb, state);
490         }
491 
492         if (!brnf_call_iptables && !br->nf_call_iptables)
493                 return NF_ACCEPT;
494 
495         if (!IS_IP(skb) && !IS_VLAN_IP(skb) && !IS_PPPOE_IP(skb))
496                 return NF_ACCEPT;
497 
498         nf_bridge_pull_encap_header_rcsum(skb);
499 
500         if (br_validate_ipv4(skb))
501                 return NF_DROP;
502 
503         nf_bridge_put(skb->nf_bridge);
504         if (!nf_bridge_alloc(skb))
505                 return NF_DROP;
506         if (!setup_pre_routing(skb))
507                 return NF_DROP;
508 
509         nf_bridge = nf_bridge_info_get(skb);
510         nf_bridge->ipv4_daddr = ip_hdr(skb)->daddr;
511 
512         skb->protocol = htons(ETH_P_IP);
513 
514         NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, state->sk, skb,
515                 skb->dev, NULL,
516                 br_nf_pre_routing_finish);
517 
518         return NF_STOLEN;
519 }
520 
521 
522 /* PF_BRIDGE/LOCAL_IN ************************************************/
523 /* The packet is locally destined, which requires a real
524  * dst_entry, so detach the fake one.  On the way up, the
525  * packet would pass through PRE_ROUTING again (which already
526  * took place when the packet entered the bridge), but we
527  * register an IPv4 PRE_ROUTING 'sabotage' hook that will
528  * prevent this from happening. */
529 static unsigned int br_nf_local_in(const struct nf_hook_ops *ops,
530                                    struct sk_buff *skb,
531                                    const struct nf_hook_state *state)
532 {
533         br_drop_fake_rtable(skb);
534         return NF_ACCEPT;
535 }
536 
537 /* PF_BRIDGE/FORWARD *************************************************/
538 static int br_nf_forward_finish(struct sock *sk, struct sk_buff *skb)
539 {
540         struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
541         struct net_device *in;
542 
543         if (!IS_ARP(skb) && !IS_VLAN_ARP(skb)) {
544 
545                 if (skb->protocol == htons(ETH_P_IP))
546                         nf_bridge->frag_max_size = IPCB(skb)->frag_max_size;
547 
548                 if (skb->protocol == htons(ETH_P_IPV6))
549                         nf_bridge->frag_max_size = IP6CB(skb)->frag_max_size;
550 
551                 in = nf_bridge->physindev;
552                 if (nf_bridge->pkt_otherhost) {
553                         skb->pkt_type = PACKET_OTHERHOST;
554                         nf_bridge->pkt_otherhost = false;
555                 }
556                 nf_bridge_update_protocol(skb);
557         } else {
558                 in = *((struct net_device **)(skb->cb));
559         }
560         nf_bridge_push_encap_header(skb);
561 
562         NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_FORWARD, sk, skb,
563                        in, skb->dev, br_forward_finish, 1);
564         return 0;
565 }
566 
567 
568 /* This is the 'purely bridged' case.  For IP, we pass the packet to
569  * netfilter with indev and outdev set to the bridge device,
570  * but we are still able to filter on the 'real' indev/outdev
571  * because of the physdev module. For ARP, indev and outdev are the
572  * bridge ports. */
573 static unsigned int br_nf_forward_ip(const struct nf_hook_ops *ops,
574                                      struct sk_buff *skb,
575                                      const struct nf_hook_state *state)
576 {
577         struct nf_bridge_info *nf_bridge;
578         struct net_device *parent;
579         u_int8_t pf;
580 
581         if (!skb->nf_bridge)
582                 return NF_ACCEPT;
583 
584         /* Need exclusive nf_bridge_info since we might have multiple
585          * different physoutdevs. */
586         if (!nf_bridge_unshare(skb))
587                 return NF_DROP;
588 
589         nf_bridge = nf_bridge_info_get(skb);
590         if (!nf_bridge)
591                 return NF_DROP;
592 
593         parent = bridge_parent(state->out);
594         if (!parent)
595                 return NF_DROP;
596 
597         if (IS_IP(skb) || IS_VLAN_IP(skb) || IS_PPPOE_IP(skb))
598                 pf = NFPROTO_IPV4;
599         else if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb))
600                 pf = NFPROTO_IPV6;
601         else
602                 return NF_ACCEPT;
603 
604         nf_bridge_pull_encap_header(skb);
605 
606         if (skb->pkt_type == PACKET_OTHERHOST) {
607                 skb->pkt_type = PACKET_HOST;
608                 nf_bridge->pkt_otherhost = true;
609         }
610 
611         if (pf == NFPROTO_IPV4) {
612                 if (br_validate_ipv4(skb))
613                         return NF_DROP;
614                 IPCB(skb)->frag_max_size = nf_bridge->frag_max_size;
615         }
616 
617         if (pf == NFPROTO_IPV6) {
618                 if (br_validate_ipv6(skb))
619                         return NF_DROP;
620                 IP6CB(skb)->frag_max_size = nf_bridge->frag_max_size;
621         }
622 
623         nf_bridge->physoutdev = skb->dev;
624         if (pf == NFPROTO_IPV4)
625                 skb->protocol = htons(ETH_P_IP);
626         else
627                 skb->protocol = htons(ETH_P_IPV6);
628 
629         NF_HOOK(pf, NF_INET_FORWARD, NULL, skb,
630                 brnf_get_logical_dev(skb, state->in),
631                 parent, br_nf_forward_finish);
632 
633         return NF_STOLEN;
634 }
635 
636 static unsigned int br_nf_forward_arp(const struct nf_hook_ops *ops,
637                                       struct sk_buff *skb,
638                                       const struct nf_hook_state *state)
639 {
640         struct net_bridge_port *p;
641         struct net_bridge *br;
642         struct net_device **d = (struct net_device **)(skb->cb);
643 
644         p = br_port_get_rcu(state->out);
645         if (p == NULL)
646                 return NF_ACCEPT;
647         br = p->br;
648 
649         if (!brnf_call_arptables && !br->nf_call_arptables)
650                 return NF_ACCEPT;
651 
652         if (!IS_ARP(skb)) {
653                 if (!IS_VLAN_ARP(skb))
654                         return NF_ACCEPT;
655                 nf_bridge_pull_encap_header(skb);
656         }
657 
658         if (arp_hdr(skb)->ar_pln != 4) {
659                 if (IS_VLAN_ARP(skb))
660                         nf_bridge_push_encap_header(skb);
661                 return NF_ACCEPT;
662         }
663         *d = state->in;
664         NF_HOOK(NFPROTO_ARP, NF_ARP_FORWARD, state->sk, skb,
665                 state->in, state->out, br_nf_forward_finish);
666 
667         return NF_STOLEN;
668 }
669 
670 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4) || IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
671 static int br_nf_push_frag_xmit(struct sock *sk, struct sk_buff *skb)
672 {
673         struct brnf_frag_data *data;
674         int err;
675 
676         data = this_cpu_ptr(&brnf_frag_data_storage);
677         err = skb_cow_head(skb, data->size);
678 
679         if (err) {
680                 kfree_skb(skb);
681                 return 0;
682         }
683 
684         if (data->vlan_tci) {
685                 skb->vlan_tci = data->vlan_tci;
686                 skb->vlan_proto = data->vlan_proto;
687         }
688 
689         skb_copy_to_linear_data_offset(skb, -data->size, data->mac, data->size);
690         __skb_push(skb, data->encap_size);
691 
692         nf_bridge_info_free(skb);
693         return br_dev_queue_push_xmit(sk, skb);
694 }
695 #endif
696 
697 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4)
698 static int br_nf_ip_fragment(struct sock *sk, struct sk_buff *skb,
699                              int (*output)(struct sock *, struct sk_buff *))
700 {
701         unsigned int mtu = ip_skb_dst_mtu(skb);
702         struct iphdr *iph = ip_hdr(skb);
703         struct rtable *rt = skb_rtable(skb);
704         struct net_device *dev = rt->dst.dev;
705 
706         if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->ignore_df) ||
707                      (IPCB(skb)->frag_max_size &&
708                       IPCB(skb)->frag_max_size > mtu))) {
709                 IP_INC_STATS(dev_net(dev), IPSTATS_MIB_FRAGFAILS);
710                 kfree_skb(skb);
711                 return -EMSGSIZE;
712         }
713 
714         return ip_do_fragment(sk, skb, output);
715 }
716 #endif
717 
718 static unsigned int nf_bridge_mtu_reduction(const struct sk_buff *skb)
719 {
720         if (skb->nf_bridge->orig_proto == BRNF_PROTO_PPPOE)
721                 return PPPOE_SES_HLEN;
722         return 0;
723 }
724 
725 static int br_nf_dev_queue_xmit(struct sock *sk, struct sk_buff *skb)
726 {
727         struct nf_bridge_info *nf_bridge;
728         unsigned int mtu_reserved;
729 
730         mtu_reserved = nf_bridge_mtu_reduction(skb);
731 
732         if (skb_is_gso(skb) || skb->len + mtu_reserved <= skb->dev->mtu) {
733                 nf_bridge_info_free(skb);
734                 return br_dev_queue_push_xmit(sk, skb);
735         }
736 
737         nf_bridge = nf_bridge_info_get(skb);
738 
739 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4)
740         /* This is wrong! We should preserve the original fragment
741          * boundaries by preserving frag_list rather than refragmenting.
742          */
743         if (skb->protocol == htons(ETH_P_IP)) {
744                 struct brnf_frag_data *data;
745 
746                 if (br_validate_ipv4(skb))
747                         goto drop;
748 
749                 IPCB(skb)->frag_max_size = nf_bridge->frag_max_size;
750 
751                 nf_bridge_update_protocol(skb);
752 
753                 data = this_cpu_ptr(&brnf_frag_data_storage);
754 
755                 data->vlan_tci = skb->vlan_tci;
756                 data->vlan_proto = skb->vlan_proto;
757                 data->encap_size = nf_bridge_encap_header_len(skb);
758                 data->size = ETH_HLEN + data->encap_size;
759 
760                 skb_copy_from_linear_data_offset(skb, -data->size, data->mac,
761                                                  data->size);
762 
763                 return br_nf_ip_fragment(sk, skb, br_nf_push_frag_xmit);
764         }
765 #endif
766 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
767         if (skb->protocol == htons(ETH_P_IPV6)) {
768                 const struct nf_ipv6_ops *v6ops = nf_get_ipv6_ops();
769                 struct brnf_frag_data *data;
770 
771                 if (br_validate_ipv6(skb))
772                         goto drop;
773 
774                 IP6CB(skb)->frag_max_size = nf_bridge->frag_max_size;
775 
776                 nf_bridge_update_protocol(skb);
777 
778                 data = this_cpu_ptr(&brnf_frag_data_storage);
779                 data->encap_size = nf_bridge_encap_header_len(skb);
780                 data->size = ETH_HLEN + data->encap_size;
781 
782                 skb_copy_from_linear_data_offset(skb, -data->size, data->mac,
783                                                  data->size);
784 
785                 if (v6ops)
786                         return v6ops->fragment(sk, skb, br_nf_push_frag_xmit);
787 
788                 kfree_skb(skb);
789                 return -EMSGSIZE;
790         }
791 #endif
792         nf_bridge_info_free(skb);
793         return br_dev_queue_push_xmit(sk, skb);
794  drop:
795         kfree_skb(skb);
796         return 0;
797 }
798 
799 /* PF_BRIDGE/POST_ROUTING ********************************************/
800 static unsigned int br_nf_post_routing(const struct nf_hook_ops *ops,
801                                        struct sk_buff *skb,
802                                        const struct nf_hook_state *state)
803 {
804         struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
805         struct net_device *realoutdev = bridge_parent(skb->dev);
806         u_int8_t pf;
807 
808         /* if nf_bridge is set, but ->physoutdev is NULL, this packet came in
809          * on a bridge, but was delivered locally and is now being routed:
810          *
811          * POST_ROUTING was already invoked from the ip stack.
812          */
813         if (!nf_bridge || !nf_bridge->physoutdev)
814                 return NF_ACCEPT;
815 
816         if (!realoutdev)
817                 return NF_DROP;
818 
819         if (IS_IP(skb) || IS_VLAN_IP(skb) || IS_PPPOE_IP(skb))
820                 pf = NFPROTO_IPV4;
821         else if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb))
822                 pf = NFPROTO_IPV6;
823         else
824                 return NF_ACCEPT;
825 
826         /* We assume any code from br_dev_queue_push_xmit onwards doesn't care
827          * about the value of skb->pkt_type. */
828         if (skb->pkt_type == PACKET_OTHERHOST) {
829                 skb->pkt_type = PACKET_HOST;
830                 nf_bridge->pkt_otherhost = true;
831         }
832 
833         nf_bridge_pull_encap_header(skb);
834         if (pf == NFPROTO_IPV4)
835                 skb->protocol = htons(ETH_P_IP);
836         else
837                 skb->protocol = htons(ETH_P_IPV6);
838 
839         NF_HOOK(pf, NF_INET_POST_ROUTING, state->sk, skb,
840                 NULL, realoutdev,
841                 br_nf_dev_queue_xmit);
842 
843         return NF_STOLEN;
844 }
845 
846 /* IP/SABOTAGE *****************************************************/
847 /* Don't hand locally destined packets to PF_INET(6)/PRE_ROUTING
848  * for the second time. */
849 static unsigned int ip_sabotage_in(const struct nf_hook_ops *ops,
850                                    struct sk_buff *skb,
851                                    const struct nf_hook_state *state)
852 {
853         if (skb->nf_bridge && !skb->nf_bridge->in_prerouting)
854                 return NF_STOP;
855 
856         return NF_ACCEPT;
857 }
858 
859 /* This is called when br_netfilter has called into iptables/netfilter,
860  * and DNAT has taken place on a bridge-forwarded packet.
861  *
862  * neigh->output has created a new MAC header, with local br0 MAC
863  * as saddr.
864  *
865  * This restores the original MAC saddr of the bridged packet
866  * before invoking bridge forward logic to transmit the packet.
867  */
868 static void br_nf_pre_routing_finish_bridge_slow(struct sk_buff *skb)
869 {
870         struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
871 
872         skb_pull(skb, ETH_HLEN);
873         nf_bridge->bridged_dnat = 0;
874 
875         BUILD_BUG_ON(sizeof(nf_bridge->neigh_header) != (ETH_HLEN - ETH_ALEN));
876 
877         skb_copy_to_linear_data_offset(skb, -(ETH_HLEN - ETH_ALEN),
878                                        nf_bridge->neigh_header,
879                                        ETH_HLEN - ETH_ALEN);
880         skb->dev = nf_bridge->physindev;
881 
882         nf_bridge->physoutdev = NULL;
883         br_handle_frame_finish(NULL, skb);
884 }
885 
886 static int br_nf_dev_xmit(struct sk_buff *skb)
887 {
888         if (skb->nf_bridge && skb->nf_bridge->bridged_dnat) {
889                 br_nf_pre_routing_finish_bridge_slow(skb);
890                 return 1;
891         }
892         return 0;
893 }
894 
895 static const struct nf_br_ops br_ops = {
896         .br_dev_xmit_hook =     br_nf_dev_xmit,
897 };
898 
899 void br_netfilter_enable(void)
900 {
901 }
902 EXPORT_SYMBOL_GPL(br_netfilter_enable);
903 
904 /* For br_nf_post_routing, we need (prio = NF_BR_PRI_LAST), because
905  * br_dev_queue_push_xmit is called afterwards */
906 static struct nf_hook_ops br_nf_ops[] __read_mostly = {
907         {
908                 .hook = br_nf_pre_routing,
909                 .owner = THIS_MODULE,
910                 .pf = NFPROTO_BRIDGE,
911                 .hooknum = NF_BR_PRE_ROUTING,
912                 .priority = NF_BR_PRI_BRNF,
913         },
914         {
915                 .hook = br_nf_local_in,
916                 .owner = THIS_MODULE,
917                 .pf = NFPROTO_BRIDGE,
918                 .hooknum = NF_BR_LOCAL_IN,
919                 .priority = NF_BR_PRI_BRNF,
920         },
921         {
922                 .hook = br_nf_forward_ip,
923                 .owner = THIS_MODULE,
924                 .pf = NFPROTO_BRIDGE,
925                 .hooknum = NF_BR_FORWARD,
926                 .priority = NF_BR_PRI_BRNF - 1,
927         },
928         {
929                 .hook = br_nf_forward_arp,
930                 .owner = THIS_MODULE,
931                 .pf = NFPROTO_BRIDGE,
932                 .hooknum = NF_BR_FORWARD,
933                 .priority = NF_BR_PRI_BRNF,
934         },
935         {
936                 .hook = br_nf_post_routing,
937                 .owner = THIS_MODULE,
938                 .pf = NFPROTO_BRIDGE,
939                 .hooknum = NF_BR_POST_ROUTING,
940                 .priority = NF_BR_PRI_LAST,
941         },
942         {
943                 .hook = ip_sabotage_in,
944                 .owner = THIS_MODULE,
945                 .pf = NFPROTO_IPV4,
946                 .hooknum = NF_INET_PRE_ROUTING,
947                 .priority = NF_IP_PRI_FIRST,
948         },
949         {
950                 .hook = ip_sabotage_in,
951                 .owner = THIS_MODULE,
952                 .pf = NFPROTO_IPV6,
953                 .hooknum = NF_INET_PRE_ROUTING,
954                 .priority = NF_IP6_PRI_FIRST,
955         },
956 };
957 
958 #ifdef CONFIG_SYSCTL
959 static
960 int brnf_sysctl_call_tables(struct ctl_table *ctl, int write,
961                             void __user *buffer, size_t *lenp, loff_t *ppos)
962 {
963         int ret;
964 
965         ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
966 
967         if (write && *(int *)(ctl->data))
968                 *(int *)(ctl->data) = 1;
969         return ret;
970 }
971 
972 static struct ctl_table brnf_table[] = {
973         {
974                 .procname       = "bridge-nf-call-arptables",
975                 .data           = &brnf_call_arptables,
976                 .maxlen         = sizeof(int),
977                 .mode           = 0644,
978                 .proc_handler   = brnf_sysctl_call_tables,
979         },
980         {
981                 .procname       = "bridge-nf-call-iptables",
982                 .data           = &brnf_call_iptables,
983                 .maxlen         = sizeof(int),
984                 .mode           = 0644,
985                 .proc_handler   = brnf_sysctl_call_tables,
986         },
987         {
988                 .procname       = "bridge-nf-call-ip6tables",
989                 .data           = &brnf_call_ip6tables,
990                 .maxlen         = sizeof(int),
991                 .mode           = 0644,
992                 .proc_handler   = brnf_sysctl_call_tables,
993         },
994         {
995                 .procname       = "bridge-nf-filter-vlan-tagged",
996                 .data           = &brnf_filter_vlan_tagged,
997                 .maxlen         = sizeof(int),
998                 .mode           = 0644,
999                 .proc_handler   = brnf_sysctl_call_tables,
1000         },
1001         {
1002                 .procname       = "bridge-nf-filter-pppoe-tagged",
1003                 .data           = &brnf_filter_pppoe_tagged,
1004                 .maxlen         = sizeof(int),
1005                 .mode           = 0644,
1006                 .proc_handler   = brnf_sysctl_call_tables,
1007         },
1008         {
1009                 .procname       = "bridge-nf-pass-vlan-input-dev",
1010                 .data           = &brnf_pass_vlan_indev,
1011                 .maxlen         = sizeof(int),
1012                 .mode           = 0644,
1013                 .proc_handler   = brnf_sysctl_call_tables,
1014         },
1015         { }
1016 };
1017 #endif
1018 
1019 static int __init br_netfilter_init(void)
1020 {
1021         int ret;
1022 
1023         ret = nf_register_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
1024         if (ret < 0)
1025                 return ret;
1026 
1027 #ifdef CONFIG_SYSCTL
1028         brnf_sysctl_header = register_net_sysctl(&init_net, "net/bridge", brnf_table);
1029         if (brnf_sysctl_header == NULL) {
1030                 printk(KERN_WARNING
1031                        "br_netfilter: can't register to sysctl.\n");
1032                 nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
1033                 return -ENOMEM;
1034         }
1035 #endif
1036         RCU_INIT_POINTER(nf_br_ops, &br_ops);
1037         printk(KERN_NOTICE "Bridge firewalling registered\n");
1038         return 0;
1039 }
1040 
1041 static void __exit br_netfilter_fini(void)
1042 {
1043         RCU_INIT_POINTER(nf_br_ops, NULL);
1044         nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
1045 #ifdef CONFIG_SYSCTL
1046         unregister_net_sysctl_table(brnf_sysctl_header);
1047 #endif
1048 }
1049 
1050 module_init(br_netfilter_init);
1051 module_exit(br_netfilter_fini);
1052 
1053 MODULE_LICENSE("GPL");
1054 MODULE_AUTHOR("Lennert Buytenhek <buytenh@gnu.org>");
1055 MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>");
1056 MODULE_DESCRIPTION("Linux ethernet netfilter firewall bridge");
1057 

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