net/bridge/br_nf_core.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      Handle firewalling core
   4  *      Linux ethernet bridge
   5  *
   6  *      Authors:
   7  *      Lennert Buytenhek               <buytenh@gnu.org>
   8  *      Bart De Schuymer                <bdschuym@pandora.be>
   9  *
  10  *      Lennert dedicates this file to Kerstin Wurdinger.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/kernel.h>
  15 #include <linux/in_route.h>
  16 #include <linux/inetdevice.h>
  17 #include <net/route.h>
  18
  19 #include "br_private.h"
  20 #ifdef CONFIG_SYSCTL
  21 #include <linux/sysctl.h>
  22 #endif
  23
  24 static void fake_update_pmtu(struct dst_entry *dst, struct sock *sk,
  25                              struct sk_buff *skb, u32 mtu)
  26 {
  27 }
  28
  29 static void fake_redirect(struct dst_entry *dst, struct sock *sk,
  30                           struct sk_buff *skb)
  31 {
  32 }
  33
  34 static u32 *fake_cow_metrics(struct dst_entry *dst, unsigned long old)
  35 {
  36         return NULL;
  37 }
  38
  39 static struct neighbour *fake_neigh_lookup(const struct dst_entry *dst,
  40                                            struct sk_buff *skb,
  41                                            const void *daddr)
  42 {
  43         return NULL;
  44 }
  45
  46 static unsigned int fake_mtu(const struct dst_entry *dst)
  47 {
  48         return dst->dev->mtu;
  49 }
  50
  51 static struct dst_ops fake_dst_ops = {
  52         .family         = AF_INET,
  53         .update_pmtu    = fake_update_pmtu,
  54         .redirect       = fake_redirect,
  55         .cow_metrics    = fake_cow_metrics,
  56         .neigh_lookup   = fake_neigh_lookup,
  57         .mtu            = fake_mtu,
  58 };
  59
  60 /*
  61  * Initialize bogus route table used to keep netfilter happy.
  62  * Currently, we fill in the PMTU entry because netfilter
  63  * refragmentation needs it, and the rt_flags entry because
  64  * ipt_REJECT needs it.  Future netfilter modules might
  65  * require us to fill additional fields.
  66  */
  67 static const u32 br_dst_default_metrics[RTAX_MAX] = {
  68         [RTAX_MTU - 1] = 1500,
  69 };
  70
  71 void br_netfilter_rtable_init(struct net_bridge *br)
  72 {
  73         struct rtable *rt = &br->fake_rtable;
  74
  75         atomic_set(&rt->dst.__refcnt, 1);
  76         rt->dst.dev = br->dev;
  77         dst_init_metrics(&rt->dst, br_dst_default_metrics, true);
  78         rt->dst.flags   = DST_NOXFRM | DST_FAKE_RTABLE;
  79         rt->dst.ops = &fake_dst_ops;
  80 }
  81
  82 int __init br_nf_core_init(void)
  83 {
  84         return dst_entries_init(&fake_dst_ops);
  85 }
  86
  87 void br_nf_core_fini(void)
  88 {
  89         dst_entries_destroy(&fake_dst_ops);
  90 }