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                              bool confirm_neigh)
  27 {
  28 }
  29
  30 static void fake_redirect(struct dst_entry *dst, struct sock *sk,
  31                           struct sk_buff *skb)
  32 {
  33 }
  34
  35 static u32 *fake_cow_metrics(struct dst_entry *dst, unsigned long old)
  36 {
  37         return NULL;
  38 }
  39
  40 static struct neighbour *fake_neigh_lookup(const struct dst_entry *dst,
  41                                            struct sk_buff *skb,
  42                                            const void *daddr)
  43 {
  44         return NULL;
  45 }
  46
  47 static unsigned int fake_mtu(const struct dst_entry *dst)
  48 {
  49         return dst->dev->mtu;
  50 }
  51
  52 static struct dst_ops fake_dst_ops = {
  53         .family         = AF_INET,
  54         .update_pmtu    = fake_update_pmtu,
  55         .redirect       = fake_redirect,
  56         .cow_metrics    = fake_cow_metrics,
  57         .neigh_lookup   = fake_neigh_lookup,
  58         .mtu            = fake_mtu,
  59 };
  60
  61 /*
  62  * Initialize bogus route table used to keep netfilter happy.
  63  * Currently, we fill in the PMTU entry because netfilter
  64  * refragmentation needs it, and the rt_flags entry because
  65  * ipt_REJECT needs it.  Future netfilter modules might
  66  * require us to fill additional fields.
  67  */
  68 static const u32 br_dst_default_metrics[RTAX_MAX] = {
  69         [RTAX_MTU - 1] = 1500,
  70 };
  71
  72 void br_netfilter_rtable_init(struct net_bridge *br)
  73 {
  74         struct rtable *rt = &br->fake_rtable;
  75
  76         atomic_set(&rt->dst.__refcnt, 1);
  77         rt->dst.dev = br->dev;
  78         dst_init_metrics(&rt->dst, br_dst_default_metrics, true);
  79         rt->dst.flags   = DST_NOXFRM | DST_FAKE_RTABLE;
  80         rt->dst.ops = &fake_dst_ops;
  81 }
  82
  83 int __init br_nf_core_init(void)
  84 {
  85         return dst_entries_init(&fake_dst_ops);
  86 }
  87
  88 void br_nf_core_fini(void)
  89 {
  90         dst_entries_destroy(&fake_dst_ops);
  91 }