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  */
  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");