bridge: Fix br_forward crash in promiscuous mode
[linux-2.6.git] / net / bridge / br_input.c
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/kernel.h>
15 #include <linux/netdevice.h>
16 #include <linux/etherdevice.h>
17 #include <linux/netfilter_bridge.h>
18 #include "br_private.h"
19
20 /* Bridge group multicast address 802.1d (pg 51). */
21 const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
22
23 static int br_pass_frame_up(struct sk_buff *skb)
24 {
25         struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
26
27         brdev->stats.rx_packets++;
28         brdev->stats.rx_bytes += skb->len;
29
30         indev = skb->dev;
31         skb->dev = brdev;
32
33         return NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
34                        netif_receive_skb);
35 }
36
37 /* note: already called with rcu_read_lock (preempt_disabled) */
38 int br_handle_frame_finish(struct sk_buff *skb)
39 {
40         const unsigned char *dest = eth_hdr(skb)->h_dest;
41         struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
42         struct net_bridge *br;
43         struct net_bridge_fdb_entry *dst;
44         struct net_bridge_mdb_entry *mdst;
45         struct sk_buff *skb2;
46
47         if (!p || p->state == BR_STATE_DISABLED)
48                 goto drop;
49
50         /* insert into forwarding database after filtering to avoid spoofing */
51         br = p->br;
52         br_fdb_update(br, p, eth_hdr(skb)->h_source);
53
54         if (is_multicast_ether_addr(dest) &&
55             br_multicast_rcv(br, p, skb))
56                 goto drop;
57
58         if (p->state == BR_STATE_LEARNING)
59                 goto drop;
60
61         BR_INPUT_SKB_CB(skb)->brdev = br->dev;
62
63         /* The packet skb2 goes to the local host (NULL to skip). */
64         skb2 = NULL;
65
66         if (br->dev->flags & IFF_PROMISC)
67                 skb2 = skb;
68
69         dst = NULL;
70
71         if (is_multicast_ether_addr(dest)) {
72                 mdst = br_mdb_get(br, skb);
73                 if (mdst || BR_INPUT_SKB_CB(skb)->mrouters_only) {
74                         if ((mdst && !hlist_unhashed(&mdst->mglist)) ||
75                             br_multicast_is_router(br))
76                                 skb2 = skb;
77                         br_multicast_forward(mdst, skb, skb2);
78                         skb = NULL;
79                         if (!skb2)
80                                 goto out;
81                 } else
82                         skb2 = skb;
83
84                 br->dev->stats.multicast++;
85         } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
86                 skb2 = skb;
87                 /* Do not forward the packet since it's local. */
88                 skb = NULL;
89         }
90
91         if (skb) {
92                 if (dst)
93                         br_forward(dst->dst, skb, skb2);
94                 else
95                         br_flood_forward(br, skb, skb2);
96         }
97
98         if (skb2)
99                 return br_pass_frame_up(skb2);
100
101 out:
102         return 0;
103 drop:
104         kfree_skb(skb);
105         goto out;
106 }
107
108 /* note: already called with rcu_read_lock (preempt_disabled) */
109 static int br_handle_local_finish(struct sk_buff *skb)
110 {
111         struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
112
113         if (p)
114                 br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
115         return 0;        /* process further */
116 }
117
118 /* Does address match the link local multicast address.
119  * 01:80:c2:00:00:0X
120  */
121 static inline int is_link_local(const unsigned char *dest)
122 {
123         __be16 *a = (__be16 *)dest;
124         static const __be16 *b = (const __be16 *)br_group_address;
125         static const __be16 m = cpu_to_be16(0xfff0);
126
127         return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
128 }
129
130 /*
131  * Called via br_handle_frame_hook.
132  * Return NULL if skb is handled
133  * note: already called with rcu_read_lock (preempt_disabled)
134  */
135 struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
136 {
137         const unsigned char *dest = eth_hdr(skb)->h_dest;
138         int (*rhook)(struct sk_buff *skb);
139
140         if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
141                 goto drop;
142
143         skb = skb_share_check(skb, GFP_ATOMIC);
144         if (!skb)
145                 return NULL;
146
147         if (unlikely(is_link_local(dest))) {
148                 /* Pause frames shouldn't be passed up by driver anyway */
149                 if (skb->protocol == htons(ETH_P_PAUSE))
150                         goto drop;
151
152                 /* If STP is turned off, then forward */
153                 if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
154                         goto forward;
155
156                 if (NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
157                             NULL, br_handle_local_finish))
158                         return NULL;    /* frame consumed by filter */
159                 else
160                         return skb;     /* continue processing */
161         }
162
163 forward:
164         switch (p->state) {
165         case BR_STATE_FORWARDING:
166                 rhook = rcu_dereference(br_should_route_hook);
167                 if (rhook != NULL) {
168                         if (rhook(skb))
169                                 return skb;
170                         dest = eth_hdr(skb)->h_dest;
171                 }
172                 /* fall through */
173         case BR_STATE_LEARNING:
174                 if (!compare_ether_addr(p->br->dev->dev_addr, dest))
175                         skb->pkt_type = PACKET_HOST;
176
177                 NF_HOOK(PF_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
178                         br_handle_frame_finish);
179                 break;
180         default:
181 drop:
182                 kfree_skb(skb);
183         }
184         return NULL;
185 }