Linux Kernel  3.7.1
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br_input.c
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1 /*
2  * Handle incoming frames
3  * Linux ethernet bridge
4  *
5  * Authors:
6  * Lennert Buytenhek <[email protected]>
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/export.h>
20 #include "br_private.h"
21 
22 /* Bridge group multicast address 802.1d (pg 51). */
23 const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
24 
25 /* Hook for brouter */
27 EXPORT_SYMBOL(br_should_route_hook);
28 
29 static int br_pass_frame_up(struct sk_buff *skb)
30 {
31  struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
32  struct net_bridge *br = netdev_priv(brdev);
33  struct br_cpu_netstats *brstats = this_cpu_ptr(br->stats);
34 
35  u64_stats_update_begin(&brstats->syncp);
36  brstats->rx_packets++;
37  brstats->rx_bytes += skb->len;
38  u64_stats_update_end(&brstats->syncp);
39 
40  indev = skb->dev;
41  skb->dev = brdev;
42 
43  return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
45 }
46 
47 /* note: already called with rcu_read_lock */
49 {
50  const unsigned char *dest = eth_hdr(skb)->h_dest;
51  struct net_bridge_port *p = br_port_get_rcu(skb->dev);
52  struct net_bridge *br;
53  struct net_bridge_fdb_entry *dst;
54  struct net_bridge_mdb_entry *mdst;
55  struct sk_buff *skb2;
56 
57  if (!p || p->state == BR_STATE_DISABLED)
58  goto drop;
59 
60  /* insert into forwarding database after filtering to avoid spoofing */
61  br = p->br;
62  br_fdb_update(br, p, eth_hdr(skb)->h_source);
63 
64  if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
65  br_multicast_rcv(br, p, skb))
66  goto drop;
67 
68  if (p->state == BR_STATE_LEARNING)
69  goto drop;
70 
71  BR_INPUT_SKB_CB(skb)->brdev = br->dev;
72 
73  /* The packet skb2 goes to the local host (NULL to skip). */
74  skb2 = NULL;
75 
76  if (br->dev->flags & IFF_PROMISC)
77  skb2 = skb;
78 
79  dst = NULL;
80 
81  if (is_broadcast_ether_addr(dest))
82  skb2 = skb;
83  else if (is_multicast_ether_addr(dest)) {
84  mdst = br_mdb_get(br, skb);
85  if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) {
86  if ((mdst && mdst->mglist) ||
87  br_multicast_is_router(br))
88  skb2 = skb;
89  br_multicast_forward(mdst, skb, skb2);
90  skb = NULL;
91  if (!skb2)
92  goto out;
93  } else
94  skb2 = skb;
95 
96  br->dev->stats.multicast++;
97  } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
98  skb2 = skb;
99  /* Do not forward the packet since it's local. */
100  skb = NULL;
101  }
102 
103  if (skb) {
104  if (dst) {
105  dst->used = jiffies;
106  br_forward(dst->dst, skb, skb2);
107  } else
108  br_flood_forward(br, skb, skb2);
109  }
110 
111  if (skb2)
112  return br_pass_frame_up(skb2);
113 
114 out:
115  return 0;
116 drop:
117  kfree_skb(skb);
118  goto out;
119 }
120 
121 /* note: already called with rcu_read_lock */
122 static int br_handle_local_finish(struct sk_buff *skb)
123 {
124  struct net_bridge_port *p = br_port_get_rcu(skb->dev);
125 
126  br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
127  return 0; /* process further */
128 }
129 
130 /* Does address match the link local multicast address.
131  * 01:80:c2:00:00:0X
132  */
133 static inline int is_link_local(const unsigned char *dest)
134 {
135  __be16 *a = (__be16 *)dest;
136  static const __be16 *b = (const __be16 *)br_group_address;
137  static const __be16 m = cpu_to_be16(0xfff0);
138 
139  return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
140 }
141 
142 /*
143  * Return NULL if skb is handled
144  * note: already called with rcu_read_lock
145  */
147 {
148  struct net_bridge_port *p;
149  struct sk_buff *skb = *pskb;
150  const unsigned char *dest = eth_hdr(skb)->h_dest;
151  br_should_route_hook_t *rhook;
152 
153  if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
154  return RX_HANDLER_PASS;
155 
156  if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
157  goto drop;
158 
159  skb = skb_share_check(skb, GFP_ATOMIC);
160  if (!skb)
161  return RX_HANDLER_CONSUMED;
162 
163  p = br_port_get_rcu(skb->dev);
164 
165  if (unlikely(is_link_local(dest))) {
166  /*
167  * See IEEE 802.1D Table 7-10 Reserved addresses
168  *
169  * Assignment Value
170  * Bridge Group Address 01-80-C2-00-00-00
171  * (MAC Control) 802.3 01-80-C2-00-00-01
172  * (Link Aggregation) 802.3 01-80-C2-00-00-02
173  * 802.1X PAE address 01-80-C2-00-00-03
174  *
175  * 802.1AB LLDP 01-80-C2-00-00-0E
176  *
177  * Others reserved for future standardization
178  */
179  switch (dest[5]) {
180  case 0x00: /* Bridge Group Address */
181  /* If STP is turned off,
182  then must forward to keep loop detection */
183  if (p->br->stp_enabled == BR_NO_STP)
184  goto forward;
185  break;
186 
187  case 0x01: /* IEEE MAC (Pause) */
188  goto drop;
189 
190  default:
191  /* Allow selective forwarding for most other protocols */
192  if (p->br->group_fwd_mask & (1u << dest[5]))
193  goto forward;
194  }
195 
196  /* Deliver packet to local host only */
197  if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
198  NULL, br_handle_local_finish)) {
199  return RX_HANDLER_CONSUMED; /* consumed by filter */
200  } else {
201  *pskb = skb;
202  return RX_HANDLER_PASS; /* continue processing */
203  }
204  }
205 
206 forward:
207  switch (p->state) {
208  case BR_STATE_FORWARDING:
210  if (rhook) {
211  if ((*rhook)(skb)) {
212  *pskb = skb;
213  return RX_HANDLER_PASS;
214  }
215  dest = eth_hdr(skb)->h_dest;
216  }
217  /* fall through */
218  case BR_STATE_LEARNING:
219  if (ether_addr_equal(p->br->dev->dev_addr, dest))
220  skb->pkt_type = PACKET_HOST;
221 
224  break;
225  default:
226 drop:
227  kfree_skb(skb);
228  }
229  return RX_HANDLER_CONSUMED;
230 }