netfilter: bridge: move br_netfilter out of the core

Jesper reported that br_netfilter always registers the hooks since
this is part of the bridge core. This harms performance for people that
don't need this.

This patch modularizes br_netfilter so it can be rmmod'ed, thus,
the hooks can be unregistered. I think the bridge netfilter should have
been a separated module since the beginning, Patrick agreed on that.

Note that this is breaking compatibility for users that expect that
bridge netfilter is going to be available after explicitly 'modprobe
bridge' or via automatic load through brctl.

However, the damage can be easily undone by modprobing br_netfilter.
The bridge core also spots a message to provide a clue to people that
didn't notice that this has been deprecated.

On top of that, the plan is that nftables will not rely on this software
layer, but integrate the connection tracking into the bridge layer to
enable stateful filtering and NAT, which is was bridge netfilter users
seem to require.

This patch still keeps the fake_dst_ops in the bridge core, since this
is required by when the bridge port is initialized. So we can safely
modprobe/rmmod br_netfilter anytime.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Florian Westphal <fw@strlen.de>

1 files changed, 16 insertions, 72 deletions

diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
index 61929a7cd815..97e43937aaca 100644
--- a/net/bridge/br_netfilter.c
+++ b/net/bridge/br_netfilter.c
@@ -111,66 +111,6 @@ static inline __be16 pppoe_proto(const struct sk_buff *skb)
 	 pppoe_proto(skb) == htons(PPP_IPV6) && \
 	 brnf_filter_pppoe_tagged)
 
-static void fake_update_pmtu(struct dst_entry *dst, struct sock *sk,
-			     struct sk_buff *skb, u32 mtu)
-{
-}
-
-static void fake_redirect(struct dst_entry *dst, struct sock *sk,
-			  struct sk_buff *skb)
-{
-}
-
-static u32 *fake_cow_metrics(struct dst_entry *dst, unsigned long old)
-{
-	return NULL;
-}
-
-static struct neighbour *fake_neigh_lookup(const struct dst_entry *dst,
-					   struct sk_buff *skb,
-					   const void *daddr)
-{
-	return NULL;
-}
-
-static unsigned int fake_mtu(const struct dst_entry *dst)
-{
-	return dst->dev->mtu;
-}
-
-static struct dst_ops fake_dst_ops = {
-	.family =		AF_INET,
-	.protocol =		cpu_to_be16(ETH_P_IP),
-	.update_pmtu =		fake_update_pmtu,
-	.redirect =		fake_redirect,
-	.cow_metrics =		fake_cow_metrics,
-	.neigh_lookup =		fake_neigh_lookup,
-	.mtu =			fake_mtu,
-};
-
-/*
- * Initialize bogus route table used to keep netfilter happy.
- * Currently, we fill in the PMTU entry because netfilter
- * refragmentation needs it, and the rt_flags entry because
- * ipt_REJECT needs it.  Future netfilter modules might
- * require us to fill additional fields.
- */
-static const u32 br_dst_default_metrics[RTAX_MAX] = {
-	[RTAX_MTU - 1] = 1500,
-};
-
-void br_netfilter_rtable_init(struct net_bridge *br)
-{
-	struct rtable *rt = &br->fake_rtable;
-
-	atomic_set(&rt->dst.__refcnt, 1);
-	rt->dst.dev = br->dev;
-	rt->dst.path = &rt->dst;
-	dst_init_metrics(&rt->dst, br_dst_default_metrics, true);
-	rt->dst.flags	= DST_NOXFRM | DST_FAKE_RTABLE;
-	rt->dst.ops = &fake_dst_ops;
-}
-
 static inline struct rtable *bridge_parent_rtable(const struct net_device *dev)
 {
 	struct net_bridge_port *port;
@@ -1031,38 +971,42 @@ static struct ctl_table brnf_table[] = {
 };
 #endif
 
-int __init br_netfilter_init(void)
+static int __init br_netfilter_init(void)
 {
 	int ret;
 
-	ret = dst_entries_init(&fake_dst_ops);
+	ret = nf_register_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
 	if (ret < 0)
 		return ret;
 
-	ret = nf_register_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
-	if (ret < 0) {
-		dst_entries_destroy(&fake_dst_ops);
-		return ret;
-	}
 #ifdef CONFIG_SYSCTL
 	brnf_sysctl_header = register_net_sysctl(&init_net, "net/bridge", brnf_table);
 	if (brnf_sysctl_header == NULL) {
 		printk(KERN_WARNING
 		       "br_netfilter: can't register to sysctl.\n");
-		nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
-		dst_entries_destroy(&fake_dst_ops);
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto err1;
 	}
 #endif
 	printk(KERN_NOTICE "Bridge firewalling registered\n");
 	return 0;
+err1:
+	nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
+	return ret;
 }
 
-void br_netfilter_fini(void)
+static void __exit br_netfilter_fini(void)
 {
 	nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
 #ifdef CONFIG_SYSCTL
 	unregister_net_sysctl_table(brnf_sysctl_header);
 #endif
-	dst_entries_destroy(&fake_dst_ops);
 }
+
+module_init(br_netfilter_init);
+module_exit(br_netfilter_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Lennert Buytenhek <buytenh@gnu.org>");
+MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>");
+MODULE_DESCRIPTION("Linux ethernet netfilter firewall bridge");