ebtable_broute.c

  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 */
 24static struct ebt_entries initial_chain = {
 25	.name		= "BROUTING",
 26	.policy		= EBT_ACCEPT,
 27};
 28
 29static 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
 39static const struct ebt_table broute_table = {
 40	.name		= "broute",
 41	.table		= &initial_table,
 42	.valid_hooks	= 1 << NF_BR_BROUTING,
 43	.me		= THIS_MODULE,
 44};
 45
 46static unsigned int ebt_broute(void *priv, struct sk_buff *skb,
 47			       const struct nf_hook_state *s)
 48{
 49	struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 50	struct nf_hook_state state;
 51	unsigned char *dest;
 52	int ret;
 53
 54	if (!p || p->state != BR_STATE_FORWARDING)
 55		return NF_ACCEPT;
 56
 57	nf_hook_state_init(&state, NF_BR_BROUTING,
 58			   NFPROTO_BRIDGE, s->in, NULL, NULL,
 59			   s->net, NULL);
 60
 61	ret = ebt_do_table(priv, skb, &state);
 62	if (ret != NF_DROP)
 63		return ret;
 64
 65	/* DROP in ebtables -t broute means that the
 66	 * skb should be routed, not bridged.
 67	 * This is awkward, but can't be changed for compatibility
 68	 * reasons.
 69	 *
 70	 * We map DROP to ACCEPT and set the ->br_netfilter_broute flag.
 71	 */
 72	BR_INPUT_SKB_CB(skb)->br_netfilter_broute = 1;
 73
 74	/* undo PACKET_HOST mangling done in br_input in case the dst
 75	 * address matches the logical bridge but not the port.
 76	 */
 77	dest = eth_hdr(skb)->h_dest;
 78	if (skb->pkt_type == PACKET_HOST &&
 79	    !ether_addr_equal(skb->dev->dev_addr, dest) &&
 80	     ether_addr_equal(p->br->dev->dev_addr, dest))
 81		skb->pkt_type = PACKET_OTHERHOST;
 82
 83	return NF_ACCEPT;
 84}
 85
 86static const struct nf_hook_ops ebt_ops_broute = {
 87	.hook		= ebt_broute,
 88	.pf		= NFPROTO_BRIDGE,
 89	.hooknum	= NF_BR_PRE_ROUTING,
 90	.priority	= NF_BR_PRI_FIRST,
 91};
 92
 93static int broute_table_init(struct net *net)
 94{
 95	return ebt_register_table(net, &broute_table, &ebt_ops_broute);
 96}
 97
 98static void __net_exit broute_net_pre_exit(struct net *net)
 99{
100	ebt_unregister_table_pre_exit(net, "broute");
101}
102
103static void __net_exit broute_net_exit(struct net *net)
104{
105	ebt_unregister_table(net, "broute");
106}
107
108static struct pernet_operations broute_net_ops = {
109	.exit = broute_net_exit,
110	.pre_exit = broute_net_pre_exit,
111};
112
113static int __init ebtable_broute_init(void)
114{
115	int ret = ebt_register_template(&broute_table, broute_table_init);
116
117	if (ret)
118		return ret;
119
120	ret = register_pernet_subsys(&broute_net_ops);
121	if (ret) {
122		ebt_unregister_template(&broute_table);
123		return ret;
124	}
125
126	return 0;
127}
128
129static void __exit ebtable_broute_fini(void)
130{
131	unregister_pernet_subsys(&broute_net_ops);
132	ebt_unregister_template(&broute_table);
133}
134
135module_init(ebtable_broute_init);
136module_exit(ebtable_broute_fini);
137MODULE_LICENSE("GPL");
138MODULE_DESCRIPTION("Force packets to be routed instead of bridged");