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 void br_pass_frame_up(struct net_bridge *br, struct sk_buff *skb)
24 {
25 struct net_device *indev, *brdev = br->dev;
26
27 brdev->stats.rx_packets++;
28 brdev->stats.rx_bytes += skb->len;
29
30 indev = skb->dev;
31 skb->dev = brdev;
32
33 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 sk_buff *skb2;
45
46 if (!p || p->state == BR_STATE_DISABLED)
47 goto drop;
48
49 /* insert into forwarding database after filtering to avoid spoofing */
50 br = p->br;
51 br_fdb_update(br, p, eth_hdr(skb)->h_source);
52
53 if (p->state == BR_STATE_LEARNING)
54 goto drop;
55
56 /* The packet skb2 goes to the local host (NULL to skip). */
57 skb2 = NULL;
58
59 if (br->dev->flags & IFF_PROMISC)
60 skb2 = skb;
61
62 dst = NULL;
63
64 if (is_multicast_ether_addr(dest)) {
65 br->dev->stats.multicast++;
66 skb2 = skb;
67 } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
68 skb2 = skb;
69 /* Do not forward the packet since it's local. */
70 skb = NULL;
71 }
72
73 if (skb2 == skb)
74 skb2 = skb_clone(skb, GFP_ATOMIC);
75
76 if (skb2)
77 br_pass_frame_up(br, skb2);
78
79 if (skb) {
80 if (dst)
81 br_forward(dst->dst, skb);
82 else
83 br_flood_forward(br, skb);
84 }
85
86 out:
87 return 0;
88 drop:
89 kfree_skb(skb);
90 goto out;
91 }
92
93 /* note: already called with rcu_read_lock (preempt_disabled) */
94 static int br_handle_local_finish(struct sk_buff *skb)
95 {
96 struct net_bridge_port *p = rcu_dereference(skb->dev->br_port);
97
98 if (p)
99 br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
100 return 0; /* process further */
101 }
102
103 /* Does address match the link local multicast address.
104 * 01:80:c2:00:00:0X
105 */
106 static inline int is_link_local(const unsigned char *dest)
107 {
108 __be16 *a = (__be16 *)dest;
109 static const __be16 *b = (const __be16 *)br_group_address;
110 static const __be16 m = cpu_to_be16(0xfff0);
111
112 return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
113 }
114
115 /*
116 * Called via br_handle_frame_hook.
117 * Return NULL if skb is handled
118 * note: already called with rcu_read_lock (preempt_disabled)
119 */
120 struct sk_buff *br_handle_frame(struct net_bridge_port *p, struct sk_buff *skb)
121 {
122 const unsigned char *dest = eth_hdr(skb)->h_dest;
123 int (*rhook)(struct sk_buff *skb);
124
125 if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
126 goto drop;
127
128 skb = skb_share_check(skb, GFP_ATOMIC);
129 if (!skb)
130 return NULL;
131
132 if (unlikely(is_link_local(dest))) {
133 /* Pause frames shouldn't be passed up by driver anyway */
134 if (skb->protocol == htons(ETH_P_PAUSE))
135 goto drop;
136
137 /* If STP is turned off, then forward */
138 if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
139 goto forward;
140
141 if (NF_HOOK(PF_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
142 NULL, br_handle_local_finish))
143 return NULL; /* frame consumed by filter */
144 else
145 return skb; /* continue processing */
146 }
147
148 forward:
149 switch (p->state) {
150 case BR_STATE_FORWARDING:
151 rhook = rcu_dereference(br_should_route_hook);
152 if (rhook != NULL) {
153 if (rhook(skb))
154 return skb;
155 dest = eth_hdr(skb)->h_dest;
156 }
157 /* fall through */
158 case BR_STATE_LEARNING:
159 if (!compare_ether_addr(p->br->dev->dev_addr, dest))
160 skb->pkt_type = PACKET_HOST;
161
162 NF_HOOK(PF_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
163 br_handle_frame_finish);
164 break;
165 default:
166 drop:
167 kfree_skb(skb);
168 }
169 return NULL;
170 }
171
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