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Linux/net/bridge/br_input.c

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  1 /*
  2  *      Handle incoming frames
  3  *      Linux ethernet bridge
  4  *
  5  *      Authors:
  6  *      Lennert Buytenhek               <buytenh@gnu.org>
  7  *
  8  *      This program is free software; you can redistribute it and/or
  9  *      modify it under the terms of the GNU General Public License
 10  *      as published by the Free Software Foundation; either version
 11  *      2 of the License, or (at your option) any later version.
 12  */
 13 
 14 #include <linux/slab.h>
 15 #include <linux/kernel.h>
 16 #include <linux/netdevice.h>
 17 #include <linux/etherdevice.h>
 18 #include <linux/netfilter_bridge.h>
 19 #include <linux/neighbour.h>
 20 #include <net/arp.h>
 21 #include <linux/export.h>
 22 #include <linux/rculist.h>
 23 #include "br_private.h"
 24 
 25 /* Hook for brouter */
 26 br_should_route_hook_t __rcu *br_should_route_hook __read_mostly;
 27 EXPORT_SYMBOL(br_should_route_hook);
 28 
 29 static int
 30 br_netif_receive_skb(struct net *net, struct sock *sk, struct sk_buff *skb)
 31 {
 32         return netif_receive_skb(skb);
 33 }
 34 
 35 static int br_pass_frame_up(struct sk_buff *skb)
 36 {
 37         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
 38         struct net_bridge *br = netdev_priv(brdev);
 39         struct net_bridge_vlan_group *vg;
 40         struct pcpu_sw_netstats *brstats = this_cpu_ptr(br->stats);
 41 
 42         u64_stats_update_begin(&brstats->syncp);
 43         brstats->rx_packets++;
 44         brstats->rx_bytes += skb->len;
 45         u64_stats_update_end(&brstats->syncp);
 46 
 47         vg = br_vlan_group_rcu(br);
 48         /* Bridge is just like any other port.  Make sure the
 49          * packet is allowed except in promisc modue when someone
 50          * may be running packet capture.
 51          */
 52         if (!(brdev->flags & IFF_PROMISC) &&
 53             !br_allowed_egress(vg, skb)) {
 54                 kfree_skb(skb);
 55                 return NET_RX_DROP;
 56         }
 57 
 58         indev = skb->dev;
 59         skb->dev = brdev;
 60         skb = br_handle_vlan(br, vg, skb);
 61         if (!skb)
 62                 return NET_RX_DROP;
 63 
 64         return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN,
 65                        dev_net(indev), NULL, skb, indev, NULL,
 66                        br_netif_receive_skb);
 67 }
 68 
 69 static void br_do_proxy_arp(struct sk_buff *skb, struct net_bridge *br,
 70                             u16 vid, struct net_bridge_port *p)
 71 {
 72         struct net_device *dev = br->dev;
 73         struct neighbour *n;
 74         struct arphdr *parp;
 75         u8 *arpptr, *sha;
 76         __be32 sip, tip;
 77 
 78         BR_INPUT_SKB_CB(skb)->proxyarp_replied = false;
 79 
 80         if (dev->flags & IFF_NOARP)
 81                 return;
 82 
 83         if (!pskb_may_pull(skb, arp_hdr_len(dev))) {
 84                 dev->stats.tx_dropped++;
 85                 return;
 86         }
 87         parp = arp_hdr(skb);
 88 
 89         if (parp->ar_pro != htons(ETH_P_IP) ||
 90             parp->ar_op != htons(ARPOP_REQUEST) ||
 91             parp->ar_hln != dev->addr_len ||
 92             parp->ar_pln != 4)
 93                 return;
 94 
 95         arpptr = (u8 *)parp + sizeof(struct arphdr);
 96         sha = arpptr;
 97         arpptr += dev->addr_len;        /* sha */
 98         memcpy(&sip, arpptr, sizeof(sip));
 99         arpptr += sizeof(sip);
100         arpptr += dev->addr_len;        /* tha */
101         memcpy(&tip, arpptr, sizeof(tip));
102 
103         if (ipv4_is_loopback(tip) ||
104             ipv4_is_multicast(tip))
105                 return;
106 
107         n = neigh_lookup(&arp_tbl, &tip, dev);
108         if (n) {
109                 struct net_bridge_fdb_entry *f;
110 
111                 if (!(n->nud_state & NUD_VALID)) {
112                         neigh_release(n);
113                         return;
114                 }
115 
116                 f = __br_fdb_get(br, n->ha, vid);
117                 if (f && ((p->flags & BR_PROXYARP) ||
118                           (f->dst && (f->dst->flags & BR_PROXYARP_WIFI)))) {
119                         arp_send(ARPOP_REPLY, ETH_P_ARP, sip, skb->dev, tip,
120                                  sha, n->ha, sha);
121                         BR_INPUT_SKB_CB(skb)->proxyarp_replied = true;
122                 }
123 
124                 neigh_release(n);
125         }
126 }
127 
128 /* note: already called with rcu_read_lock */
129 int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
130 {
131         const unsigned char *dest = eth_hdr(skb)->h_dest;
132         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
133         struct net_bridge *br;
134         struct net_bridge_fdb_entry *dst;
135         struct net_bridge_mdb_entry *mdst;
136         struct sk_buff *skb2;
137         bool unicast = true;
138         u16 vid = 0;
139 
140         if (!p || p->state == BR_STATE_DISABLED)
141                 goto drop;
142 
143         if (!br_allowed_ingress(p->br, nbp_vlan_group_rcu(p), skb, &vid))
144                 goto out;
145 
146         /* insert into forwarding database after filtering to avoid spoofing */
147         br = p->br;
148         if (p->flags & BR_LEARNING)
149                 br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false);
150 
151         if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
152             br_multicast_rcv(br, p, skb, vid))
153                 goto drop;
154 
155         if (p->state == BR_STATE_LEARNING)
156                 goto drop;
157 
158         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
159 
160         /* The packet skb2 goes to the local host (NULL to skip). */
161         skb2 = NULL;
162 
163         if (br->dev->flags & IFF_PROMISC)
164                 skb2 = skb;
165 
166         dst = NULL;
167 
168         if (IS_ENABLED(CONFIG_INET) && skb->protocol == htons(ETH_P_ARP))
169                 br_do_proxy_arp(skb, br, vid, p);
170 
171         if (is_broadcast_ether_addr(dest)) {
172                 skb2 = skb;
173                 unicast = false;
174         } else if (is_multicast_ether_addr(dest)) {
175                 mdst = br_mdb_get(br, skb, vid);
176                 if ((mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) &&
177                     br_multicast_querier_exists(br, eth_hdr(skb))) {
178                         if ((mdst && mdst->mglist) ||
179                             br_multicast_is_router(br))
180                                 skb2 = skb;
181                         br_multicast_forward(mdst, skb, skb2);
182                         skb = NULL;
183                         if (!skb2)
184                                 goto out;
185                 } else
186                         skb2 = skb;
187 
188                 unicast = false;
189                 br->dev->stats.multicast++;
190         } else if ((dst = __br_fdb_get(br, dest, vid)) &&
191                         dst->is_local) {
192                 skb2 = skb;
193                 /* Do not forward the packet since it's local. */
194                 skb = NULL;
195         }
196 
197         if (skb) {
198                 if (dst) {
199                         dst->used = jiffies;
200                         br_forward(dst->dst, skb, skb2);
201                 } else
202                         br_flood_forward(br, skb, skb2, unicast);
203         }
204 
205         if (skb2)
206                 return br_pass_frame_up(skb2);
207 
208 out:
209         return 0;
210 drop:
211         kfree_skb(skb);
212         goto out;
213 }
214 EXPORT_SYMBOL_GPL(br_handle_frame_finish);
215 
216 /* note: already called with rcu_read_lock */
217 static int br_handle_local_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
218 {
219         struct net_bridge_port *p = br_port_get_rcu(skb->dev);
220         u16 vid = 0;
221 
222         /* check if vlan is allowed, to avoid spoofing */
223         if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid))
224                 br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
225         return 0;        /* process further */
226 }
227 
228 /*
229  * Return NULL if skb is handled
230  * note: already called with rcu_read_lock
231  */
232 rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
233 {
234         struct net_bridge_port *p;
235         struct sk_buff *skb = *pskb;
236         const unsigned char *dest = eth_hdr(skb)->h_dest;
237         br_should_route_hook_t *rhook;
238 
239         if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
240                 return RX_HANDLER_PASS;
241 
242         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
243                 goto drop;
244 
245         skb = skb_share_check(skb, GFP_ATOMIC);
246         if (!skb)
247                 return RX_HANDLER_CONSUMED;
248 
249         p = br_port_get_rcu(skb->dev);
250 
251         if (unlikely(is_link_local_ether_addr(dest))) {
252                 u16 fwd_mask = p->br->group_fwd_mask_required;
253 
254                 /*
255                  * See IEEE 802.1D Table 7-10 Reserved addresses
256                  *
257                  * Assignment                           Value
258                  * Bridge Group Address         01-80-C2-00-00-00
259                  * (MAC Control) 802.3          01-80-C2-00-00-01
260                  * (Link Aggregation) 802.3     01-80-C2-00-00-02
261                  * 802.1X PAE address           01-80-C2-00-00-03
262                  *
263                  * 802.1AB LLDP                 01-80-C2-00-00-0E
264                  *
265                  * Others reserved for future standardization
266                  */
267                 switch (dest[5]) {
268                 case 0x00:      /* Bridge Group Address */
269                         /* If STP is turned off,
270                            then must forward to keep loop detection */
271                         if (p->br->stp_enabled == BR_NO_STP ||
272                             fwd_mask & (1u << dest[5]))
273                                 goto forward;
274                         break;
275 
276                 case 0x01:      /* IEEE MAC (Pause) */
277                         goto drop;
278 
279                 default:
280                         /* Allow selective forwarding for most other protocols */
281                         fwd_mask |= p->br->group_fwd_mask;
282                         if (fwd_mask & (1u << dest[5]))
283                                 goto forward;
284                 }
285 
286                 /* Deliver packet to local host only */
287                 if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN,
288                             dev_net(skb->dev), NULL, skb, skb->dev, NULL,
289                             br_handle_local_finish)) {
290                         return RX_HANDLER_CONSUMED; /* consumed by filter */
291                 } else {
292                         *pskb = skb;
293                         return RX_HANDLER_PASS; /* continue processing */
294                 }
295         }
296 
297 forward:
298         switch (p->state) {
299         case BR_STATE_FORWARDING:
300                 rhook = rcu_dereference(br_should_route_hook);
301                 if (rhook) {
302                         if ((*rhook)(skb)) {
303                                 *pskb = skb;
304                                 return RX_HANDLER_PASS;
305                         }
306                         dest = eth_hdr(skb)->h_dest;
307                 }
308                 /* fall through */
309         case BR_STATE_LEARNING:
310                 if (ether_addr_equal(p->br->dev->dev_addr, dest))
311                         skb->pkt_type = PACKET_HOST;
312 
313                 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING,
314                         dev_net(skb->dev), NULL, skb, skb->dev, NULL,
315                         br_handle_frame_finish);
316                 break;
317         default:
318 drop:
319                 kfree_skb(skb);
320         }
321         return RX_HANDLER_CONSUMED;
322 }
323 

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