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 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
  46 static 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
  86 static 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
  93 static int broute_table_init(struct net *net)
  94 {
  95         return ebt_register_table(net, &broute_table, &ebt_ops_broute);
  96 }
  97
  98 static void __net_exit broute_net_pre_exit(struct net *net)
  99 {
 100         ebt_unregister_table_pre_exit(net, "broute");
 101 }
 102
 103 static void __net_exit broute_net_exit(struct net *net)
 104 {
 105         ebt_unregister_table(net, "broute");
 106 }
 107
 108 static struct pernet_operations broute_net_ops = {
 109         .exit = broute_net_exit,
 110         .pre_exit = broute_net_pre_exit,
 111 };
 112
 113 static 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
 129 static void __exit ebtable_broute_fini(void)
 130 {
 131         unregister_pernet_subsys(&broute_net_ops);
 132         ebt_unregister_template(&broute_table);
 133 }
 134
 135 module_init(ebtable_broute_init);
 136 module_exit(ebtable_broute_fini);
 137 MODULE_LICENSE("GPL");
 138 MODULE_DESCRIPTION("Force packets to be routed instead of bridged");