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 "br_private.h"
20
21 /* Bridge group multicast address 802.1d (pg 51). */
22 const u8 br_group_address[ETH_ALEN] = { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 };
23
24 /* Hook for brouter */
25 br_should_route_hook_t __rcu *br_should_route_hook __read_mostly;
26 EXPORT_SYMBOL(br_should_route_hook);
27
br_pass_frame_up(struct sk_buff * skb)28 static int br_pass_frame_up(struct sk_buff *skb)
29 {
30 struct net_device *indev, *brdev = BR_INPUT_SKB_CB(skb)->brdev;
31 struct net_bridge *br = netdev_priv(brdev);
32 struct br_cpu_netstats *brstats = this_cpu_ptr(br->stats);
33
34 u64_stats_update_begin(&brstats->syncp);
35 brstats->rx_packets++;
36 brstats->rx_bytes += skb->len;
37 u64_stats_update_end(&brstats->syncp);
38
39 indev = skb->dev;
40 skb->dev = brdev;
41
42 return NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, indev, NULL,
43 netif_receive_skb);
44 }
45
46 /* note: already called with rcu_read_lock */
br_handle_frame_finish(struct sk_buff * skb)47 int br_handle_frame_finish(struct sk_buff *skb)
48 {
49 const unsigned char *dest = eth_hdr(skb)->h_dest;
50 struct net_bridge_port *p = br_port_get_rcu(skb->dev);
51 struct net_bridge *br;
52 struct net_bridge_fdb_entry *dst;
53 struct net_bridge_mdb_entry *mdst;
54 struct sk_buff *skb2;
55
56 if (!p || p->state == BR_STATE_DISABLED)
57 goto drop;
58
59 /* insert into forwarding database after filtering to avoid spoofing */
60 br = p->br;
61 br_fdb_update(br, p, eth_hdr(skb)->h_source);
62
63 if (is_multicast_ether_addr(dest) &&
64 br_multicast_rcv(br, p, skb))
65 goto drop;
66
67 if (p->state == BR_STATE_LEARNING)
68 goto drop;
69
70 BR_INPUT_SKB_CB(skb)->brdev = br->dev;
71
72 /* The packet skb2 goes to the local host (NULL to skip). */
73 skb2 = NULL;
74
75 if (br->dev->flags & IFF_PROMISC)
76 skb2 = skb;
77
78 dst = NULL;
79
80 if (is_multicast_ether_addr(dest)) {
81 mdst = br_mdb_get(br, skb);
82 if (mdst || BR_INPUT_SKB_CB_MROUTERS_ONLY(skb)) {
83 if ((mdst && mdst->mglist) ||
84 br_multicast_is_router(br))
85 skb2 = skb;
86 br_multicast_forward(mdst, skb, skb2);
87 skb = NULL;
88 if (!skb2)
89 goto out;
90 } else
91 skb2 = skb;
92
93 br->dev->stats.multicast++;
94 } else if ((dst = __br_fdb_get(br, dest)) && dst->is_local) {
95 skb2 = skb;
96 /* Do not forward the packet since it's local. */
97 skb = NULL;
98 }
99
100 if (skb) {
101 if (dst)
102 br_forward(dst->dst, skb, skb2);
103 else
104 br_flood_forward(br, skb, skb2);
105 }
106
107 if (skb2)
108 return br_pass_frame_up(skb2);
109
110 out:
111 return 0;
112 drop:
113 kfree_skb(skb);
114 goto out;
115 }
116
117 /* note: already called with rcu_read_lock */
br_handle_local_finish(struct sk_buff * skb)118 static int br_handle_local_finish(struct sk_buff *skb)
119 {
120 struct net_bridge_port *p = br_port_get_rcu(skb->dev);
121
122 br_fdb_update(p->br, p, eth_hdr(skb)->h_source);
123 return 0; /* process further */
124 }
125
126 /* Does address match the link local multicast address.
127 * 01:80:c2:00:00:0X
128 */
is_link_local(const unsigned char * dest)129 static inline int is_link_local(const unsigned char *dest)
130 {
131 __be16 *a = (__be16 *)dest;
132 static const __be16 *b = (const __be16 *)br_group_address;
133 static const __be16 m = cpu_to_be16(0xfff0);
134
135 return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | ((a[2] ^ b[2]) & m)) == 0;
136 }
137
138 /*
139 * Return NULL if skb is handled
140 * note: already called with rcu_read_lock
141 */
br_handle_frame(struct sk_buff ** pskb)142 rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
143 {
144 struct net_bridge_port *p;
145 struct sk_buff *skb = *pskb;
146 const unsigned char *dest = eth_hdr(skb)->h_dest;
147 br_should_route_hook_t *rhook;
148
149 if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
150 return RX_HANDLER_PASS;
151
152 if (!is_valid_ether_addr(eth_hdr(skb)->h_source))
153 goto drop;
154
155 skb = skb_share_check(skb, GFP_ATOMIC);
156 if (!skb)
157 return RX_HANDLER_CONSUMED;
158
159 p = br_port_get_rcu(skb->dev);
160
161 if (unlikely(is_link_local(dest))) {
162 /* Pause frames shouldn't be passed up by driver anyway */
163 if (skb->protocol == htons(ETH_P_PAUSE))
164 goto drop;
165
166 /* If STP is turned off, then forward */
167 if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
168 goto forward;
169
170 if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
171 NULL, br_handle_local_finish)) {
172 return RX_HANDLER_CONSUMED; /* consumed by filter */
173 } else {
174 *pskb = skb;
175 return RX_HANDLER_PASS; /* continue processing */
176 }
177 }
178
179 forward:
180 switch (p->state) {
181 case BR_STATE_FORWARDING:
182 rhook = rcu_dereference(br_should_route_hook);
183 if (rhook) {
184 if ((*rhook)(skb)) {
185 *pskb = skb;
186 return RX_HANDLER_PASS;
187 }
188 dest = eth_hdr(skb)->h_dest;
189 }
190 /* fall through */
191 case BR_STATE_LEARNING:
192 if (!compare_ether_addr(p->br->dev->dev_addr, dest))
193 skb->pkt_type = PACKET_HOST;
194
195 NF_HOOK(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
196 br_handle_frame_finish);
197 break;
198 default:
199 drop:
200 kfree_skb(skb);
201 }
202 return RX_HANDLER_CONSUMED;
203 }
204