1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  ebtable_broute
4  *
5  *	Authors:
6  *	Bart De Schuymer <bdschuym@pandora.be>
7  *
8  *  April, 2002
9  *
10  *  This table lets you choose between routing and bridging for frames
11  *  entering on a bridge enslaved nic. This table is traversed before any
12  *  other ebtables table. See net/bridge/br_input.c.
13  */
14 
15 #include <linux/netfilter_bridge/ebtables.h>
16 #include <linux/module.h>
17 #include <linux/if_bridge.h>
18 
19 #include "../br_private.h"
20 
21 /* EBT_ACCEPT means the frame will be bridged
22  * EBT_DROP means the frame will be routed
23  */
24 static struct ebt_entries initial_chain = {
25 	.name		= "BROUTING",
26 	.policy		= EBT_ACCEPT,
27 };
28 
29 static struct ebt_replace_kernel initial_table = {
30 	.name		= "broute",
31 	.valid_hooks	= 1 << NF_BR_BROUTING,
32 	.entries_size	= sizeof(struct ebt_entries),
33 	.hook_entry	= {
34 		[NF_BR_BROUTING]	= &initial_chain,
35 	},
36 	.entries	= (char *)&initial_chain,
37 };
38 
39 static int check(const struct ebt_table_info *info, unsigned int valid_hooks)
40 {
41 	if (valid_hooks & ~(1 << NF_BR_BROUTING))
42 		return -EINVAL;
43 	return 0;
44 }
45 
46 static const struct ebt_table broute_table = {
47 	.name		= "broute",
48 	.table		= &initial_table,
49 	.valid_hooks	= 1 << NF_BR_BROUTING,
50 	.check		= check,
51 	.me		= THIS_MODULE,
52 };
53 
54 static unsigned int ebt_broute(void *priv, struct sk_buff *skb,
55 			       const struct nf_hook_state *s)
56 {
57 	struct net_bridge_port *p = br_port_get_rcu(skb->dev);
58 	struct nf_hook_state state;
59 	unsigned char *dest;
60 	int ret;
61 
62 	if (!p || p->state != BR_STATE_FORWARDING)
63 		return NF_ACCEPT;
64 
65 	nf_hook_state_init(&state, NF_BR_BROUTING,
66 			   NFPROTO_BRIDGE, s->in, NULL, NULL,
67 			   s->net, NULL);
68 
69 	ret = ebt_do_table(skb, &state, state.net->xt.broute_table);
70 
71 	if (ret != NF_DROP)
72 		return ret;
73 
74 	/* DROP in ebtables -t broute means that the
75 	 * skb should be routed, not bridged.
76 	 * This is awkward, but can't be changed for compatibility
77 	 * reasons.
78 	 *
79 	 * We map DROP to ACCEPT and set the ->br_netfilter_broute flag.
80 	 */
81 	BR_INPUT_SKB_CB(skb)->br_netfilter_broute = 1;
82 
83 	/* undo PACKET_HOST mangling done in br_input in case the dst
84 	 * address matches the logical bridge but not the port.
85 	 */
86 	dest = eth_hdr(skb)->h_dest;
87 	if (skb->pkt_type == PACKET_HOST &&
88 	    !ether_addr_equal(skb->dev->dev_addr, dest) &&
89 	     ether_addr_equal(p->br->dev->dev_addr, dest))
90 		skb->pkt_type = PACKET_OTHERHOST;
91 
92 	return NF_ACCEPT;
93 }
94 
95 static const struct nf_hook_ops ebt_ops_broute = {
96 	.hook		= ebt_broute,
97 	.pf		= NFPROTO_BRIDGE,
98 	.hooknum	= NF_BR_PRE_ROUTING,
99 	.priority	= NF_BR_PRI_FIRST,
100 };
101 
102 static int __net_init broute_net_init(struct net *net)
103 {
104 	return ebt_register_table(net, &broute_table, &ebt_ops_broute,
105 				  &net->xt.broute_table);
106 }
107 
108 static void __net_exit broute_net_exit(struct net *net)
109 {
110 	ebt_unregister_table(net, net->xt.broute_table, &ebt_ops_broute);
111 }
112 
113 static struct pernet_operations broute_net_ops = {
114 	.init = broute_net_init,
115 	.exit = broute_net_exit,
116 };
117 
118 static int __init ebtable_broute_init(void)
119 {
120 	return register_pernet_subsys(&broute_net_ops);
121 }
122 
123 static void __exit ebtable_broute_fini(void)
124 {
125 	unregister_pernet_subsys(&broute_net_ops);
126 }
127 
128 module_init(ebtable_broute_init);
129 module_exit(ebtable_broute_fini);
130 MODULE_LICENSE("GPL");
131