/net/bridge/netfilter/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 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
 46static 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
 54static 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
 95static 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
102static 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
108static void __net_exit broute_net_exit(struct net *net)
109{
110	ebt_unregister_table(net, net->xt.broute_table, &ebt_ops_broute);
111}
112
113static struct pernet_operations broute_net_ops = {
114	.init = broute_net_init,
115	.exit = broute_net_exit,
116};
117
118static int __init ebtable_broute_init(void)
119{
120	return register_pernet_subsys(&broute_net_ops);
121}
122
123static void __exit ebtable_broute_fini(void)
124{
125	unregister_pernet_subsys(&broute_net_ops);
126}
127
128module_init(ebtable_broute_init);
129module_exit(ebtable_broute_fini);
130MODULE_LICENSE("GPL");