Re: [PATCH 1/2 v2 nf-next] net: bridge: don't register netfilter call_iptables hooks by default

[Pablo Neira Ayuso <pablo@netfilter.org>]

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Hi Florian,

On Wed, Sep 17, 2014 at 05:52:16PM +0200, Florian Westphal wrote:
> Jesper reports that kernels with CONFIG_BRIDGE_NETFILTER=n show significantly
> better performance vs. CONFIG_BRIDGE_NETFILTER=y, even with
> bridge-nf-call-iptables=0.
>
> This is because bridge registers some bridge netfilter hooks at
> module load time, so the static key to bypass nf rule evaluation
> via NF_HOOK() is false.

I'm attaching a patch to decouple bridge netfilter from the bridge
core.  The idea is to encapsulate the hook registration and most of
its code in a separated module: br_netfilter. The bridge core will
still request this module to be loaded from the initialization path,
I think this will retain backward compatibility for users.

I also guess most distributors will use CONFIG_BRIDGE_NETFILTER=m.
Then, users will get a warning message to let them know that they will
have to modprobe br_netfilter in the future if they need it, so we can
remove the deferred request_module from the br init path.

The patch is slightly larger than yours, and I can probably split it
in two patches (one to move several skb-nf-bridge related functions as
static inline to prepare the one that decouples br_netfilter from
bridge).

Unless I'm missing anything, I think br_netfilter should have been a
separated module since the beginning. The hook registration in other
netfilter modules is also ruled by rmmod/modprobe, so better if we
recover that path in this code.

I still have to check later again for typical kbuild robot reports on
Kconfig (bridge=y, br_netfilter=m) and so on, btw. I also may include
part of your original patch description if you're OK with it.

Please, let me know if I overlook anything. Thanks.

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>From b4b2d36f8b4b1ab1737efc534c910f6211b4571a Mon Sep 17 00:00:00 2001
From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: Thu, 18 Sep 2014 11:29:03 +0200
Subject: [PATCH] netfilter: move br_netfilter out of the bridge core

Jesper reported that br_netfilter always registers the hooks
since it 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.

To retain backward compatibility, the bridge core will request
br_netfilter from the initialization path. I guess most
distributors will compile br_netfilter as a module. We also warn
that this automatic br_netfilter module load will be disabled
soon, so users have to update their scripts to modprobe it.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 include/linux/netfilter_bridge.h       |   50 +++++++++++---
 include/linux/skbuff.h                 |   12 ++--
 include/net/neighbour.h                |    2 +-
 include/net/netfilter/ipv4/nf_reject.h |    2 +-
 include/net/netfilter/ipv6/nf_reject.h |    2 +-
 net/Kconfig                            |    2 +-
 net/bridge/Makefile                    |    5 +-
 net/bridge/br.c                        |   44 ++++++++++--
 net/bridge/br_device.c                 |    4 +-
 net/bridge/br_forward.c                |    2 +
 net/bridge/br_input.c                  |    1 +
 net/bridge/br_netfilter.c              |  116 +++++---------------------------
 net/bridge/br_netlink.c                |    2 +-
 net/bridge/br_nf_core.c                |   96 ++++++++++++++++++++++++++
 net/bridge/br_private.h                |   12 ++--
 net/bridge/br_sysfs_br.c               |    4 +-
 16 files changed, 216 insertions(+), 140 deletions(-)
 create mode 100644 net/bridge/br_nf_core.c

diff --git a/include/linux/netfilter_bridge.h b/include/linux/netfilter_bridge.h
index 8ab1c27..c755e49 100644
--- a/include/linux/netfilter_bridge.h
+++ b/include/linux/netfilter_bridge.h
@@ -15,7 +15,7 @@ enum nf_br_hook_priorities {
 	NF_BR_PRI_LAST = INT_MAX,
 };
 
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 
 #define BRNF_PKT_TYPE			0x01
 #define BRNF_BRIDGED_DNAT		0x02
@@ -24,16 +24,6 @@ enum nf_br_hook_priorities {
 #define BRNF_8021Q			0x10
 #define BRNF_PPPoE			0x20
 
-/* Only used in br_forward.c */
-int nf_bridge_copy_header(struct sk_buff *skb);
-static inline int nf_bridge_maybe_copy_header(struct sk_buff *skb)
-{
-	if (skb->nf_bridge &&
-	    skb->nf_bridge->mask & (BRNF_BRIDGED | BRNF_BRIDGED_DNAT))
-		return nf_bridge_copy_header(skb);
-  	return 0;
-}
-
 static inline unsigned int nf_bridge_encap_header_len(const struct sk_buff *skb)
 {
 	switch (skb->protocol) {
@@ -46,6 +36,44 @@ static inline unsigned int nf_bridge_encap_header_len(const struct sk_buff *skb)
 	}
 }
 
+static inline void nf_bridge_update_protocol(struct sk_buff *skb)
+{
+	if (skb->nf_bridge->mask & BRNF_8021Q)
+		skb->protocol = htons(ETH_P_8021Q);
+	else if (skb->nf_bridge->mask & BRNF_PPPoE)
+		skb->protocol = htons(ETH_P_PPP_SES);
+}
+
+/* Fill in the header for fragmented IP packets handled by
+ * the IPv4 connection tracking code.
+ *
+ * Only used in br_forward.c
+ */
+static inline int nf_bridge_copy_header(struct sk_buff *skb)
+{
+	int err;
+	unsigned int header_size;
+
+	nf_bridge_update_protocol(skb);
+	header_size = ETH_HLEN + nf_bridge_encap_header_len(skb);
+	err = skb_cow_head(skb, header_size);
+	if (err)
+		return err;
+
+	skb_copy_to_linear_data_offset(skb, -header_size,
+				       skb->nf_bridge->data, header_size);
+	__skb_push(skb, nf_bridge_encap_header_len(skb));
+	return 0;
+}
+
+static inline int nf_bridge_maybe_copy_header(struct sk_buff *skb)
+{
+	if (skb->nf_bridge &&
+	    skb->nf_bridge->mask & (BRNF_BRIDGED | BRNF_BRIDGED_DNAT))
+		return nf_bridge_copy_header(skb);
+  	return 0;
+}
+
 static inline unsigned int nf_bridge_mtu_reduction(const struct sk_buff *skb)
 {
 	if (unlikely(skb->nf_bridge->mask & BRNF_PPPoE))
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 07c9fdd..c4ff43f 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -156,7 +156,7 @@ struct nf_conntrack {
 };
 #endif
 
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 struct nf_bridge_info {
 	atomic_t		use;
 	unsigned int		mask;
@@ -560,7 +560,7 @@ struct sk_buff {
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 	struct nf_conntrack	*nfct;
 #endif
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 	struct nf_bridge_info	*nf_bridge;
 #endif
 
@@ -2977,7 +2977,7 @@ static inline void nf_conntrack_get(struct nf_conntrack *nfct)
 		atomic_inc(&nfct->use);
 }
 #endif
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 static inline void nf_bridge_put(struct nf_bridge_info *nf_bridge)
 {
 	if (nf_bridge && atomic_dec_and_test(&nf_bridge->use))
@@ -2995,7 +2995,7 @@ static inline void nf_reset(struct sk_buff *skb)
 	nf_conntrack_put(skb->nfct);
 	skb->nfct = NULL;
 #endif
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 	nf_bridge_put(skb->nf_bridge);
 	skb->nf_bridge = NULL;
 #endif
@@ -3016,7 +3016,7 @@ static inline void __nf_copy(struct sk_buff *dst, const struct sk_buff *src)
 	nf_conntrack_get(src->nfct);
 	dst->nfctinfo = src->nfctinfo;
 #endif
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 	dst->nf_bridge  = src->nf_bridge;
 	nf_bridge_get(src->nf_bridge);
 #endif
@@ -3030,7 +3030,7 @@ static inline void nf_copy(struct sk_buff *dst, const struct sk_buff *src)
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 	nf_conntrack_put(dst->nfct);
 #endif
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 	nf_bridge_put(dst->nf_bridge);
 #endif
 	__nf_copy(dst, src);
diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index 47f4254..f60558d 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -373,7 +373,7 @@ static inline int neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
 	return 0;
 }
 
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 static inline int neigh_hh_bridge(struct hh_cache *hh, struct sk_buff *skb)
 {
 	unsigned int seq, hh_alen;
diff --git a/include/net/netfilter/ipv4/nf_reject.h b/include/net/netfilter/ipv4/nf_reject.h
index 931fbf8..f713b5a 100644
--- a/include/net/netfilter/ipv4/nf_reject.h
+++ b/include/net/netfilter/ipv4/nf_reject.h
@@ -98,7 +98,7 @@ static void nf_send_reset(struct sk_buff *oldskb, int hook)
 
 	nf_ct_attach(nskb, oldskb);
 
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 	/* If we use ip_local_out for bridged traffic, the MAC source on
 	 * the RST will be ours, instead of the destination's.  This confuses
 	 * some routers/firewalls, and they drop the packet.  So we need to
diff --git a/include/net/netfilter/ipv6/nf_reject.h b/include/net/netfilter/ipv6/nf_reject.h
index 710d17e..7a10cfc 100644
--- a/include/net/netfilter/ipv6/nf_reject.h
+++ b/include/net/netfilter/ipv6/nf_reject.h
@@ -147,7 +147,7 @@ static void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook)
 
 	nf_ct_attach(nskb, oldskb);
 
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 	/* If we use ip6_local_out for bridged traffic, the MAC source on
 	 * the RST will be ours, instead of the destination's.  This confuses
 	 * some routers/firewalls, and they drop the packet.  So we need to
diff --git a/net/Kconfig b/net/Kconfig
index 4051fdf..f545b34 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -176,7 +176,7 @@ config NETFILTER_ADVANCED
 	  If unsure, say Y.
 
 config BRIDGE_NETFILTER
-	bool "Bridged IP/ARP packets filtering"
+	tristate "Bridged IP/ARP packets filtering"
 	depends on BRIDGE && NETFILTER && INET
 	depends on NETFILTER_ADVANCED
 	default y
diff --git a/net/bridge/Makefile b/net/bridge/Makefile
index 8590b94..5e3eac5 100644
--- a/net/bridge/Makefile
+++ b/net/bridge/Makefile
@@ -6,11 +6,12 @@ obj-$(CONFIG_BRIDGE) += bridge.o
 
 bridge-y	:= br.o br_device.o br_fdb.o br_forward.o br_if.o br_input.o \
 			br_ioctl.o br_stp.o br_stp_bpdu.o \
-			br_stp_if.o br_stp_timer.o br_netlink.o
+			br_stp_if.o br_stp_timer.o br_netlink.o \
+			br_nf_core.o
 
 bridge-$(CONFIG_SYSFS) += br_sysfs_if.o br_sysfs_br.o
 
-bridge-$(CONFIG_BRIDGE_NETFILTER) += br_netfilter.o
+obj-$(CONFIG_BRIDGE_NETFILTER) += br_netfilter.o
 
 bridge-$(CONFIG_BRIDGE_IGMP_SNOOPING) += br_multicast.o br_mdb.o
 
diff --git a/net/bridge/br.c b/net/bridge/br.c
index 1a755a1..fa05345 100644
--- a/net/bridge/br.c
+++ b/net/bridge/br.c
@@ -143,6 +143,26 @@ static const struct stp_proto br_stp_proto = {
 	.rcv	= br_stp_rcv,
 };
 
+static void __br_nf_request_module(struct work_struct *w)
+{
+	kfree(w);
+	request_module("br_netfilter");
+}
+
+static int br_netfilter_request_module(void)
+{
+	struct work_struct *w;
+
+	w = kzalloc(sizeof(*w), GFP_KERNEL);
+	if (!w)
+		return -ENOMEM;
+
+	INIT_WORK(w, __br_nf_request_module);
+	schedule_work(w);
+
+	return 0;
+}
+
 static int __init br_init(void)
 {
 	int err;
@@ -161,7 +181,7 @@ static int __init br_init(void)
 	if (err)
 		goto err_out1;
 
-	err = br_netfilter_init();
+	err = br_nf_core_init();
 	if (err)
 		goto err_out2;
 
@@ -178,12 +198,27 @@ static int __init br_init(void)
 #if IS_ENABLED(CONFIG_ATM_LANE)
 	br_fdb_test_addr_hook = br_fdb_test_addr;
 #endif
+	err = br_netfilter_request_module();
+	if (err < 0)
+		goto err_out5;
+
+	pr_info("bridge: automatic filtering via arp/ip/ip6tables is "
+		"deprecated and it will not be enabled by the bridge "
+		"core anymore soon. Update your scripts to load "
+		"br_netfilter if you need this. ");
 
 	return 0;
+
+err_out5:
+#if IS_ENABLED(CONFIG_ATM_LANE)
+	br_fdb_test_addr_hook = NULL;
+#endif
+	brioctl_set(NULL);
+	br_netlink_fini();
 err_out4:
 	unregister_netdevice_notifier(&br_device_notifier);
 err_out3:
-	br_netfilter_fini();
+	br_nf_core_fini();
 err_out2:
 	unregister_pernet_subsys(&br_net_ops);
 err_out1:
@@ -196,20 +231,17 @@ err_out:
 static void __exit br_deinit(void)
 {
 	stp_proto_unregister(&br_stp_proto);
-
 	br_netlink_fini();
 	unregister_netdevice_notifier(&br_device_notifier);
 	brioctl_set(NULL);
-
 	unregister_pernet_subsys(&br_net_ops);
 
 	rcu_barrier(); /* Wait for completion of call_rcu()'s */
 
-	br_netfilter_fini();
+	br_nf_core_fini();
 #if IS_ENABLED(CONFIG_ATM_LANE)
 	br_fdb_test_addr_hook = NULL;
 #endif
-
 	br_fdb_fini();
 }
 
diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
index 568cccd..659cac1 100644
--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -36,7 +36,7 @@ netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 	u16 vid = 0;
 
 	rcu_read_lock();
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 	if (skb->nf_bridge && (skb->nf_bridge->mask & BRNF_BRIDGED_DNAT)) {
 		br_nf_pre_routing_finish_bridge_slow(skb);
 		rcu_read_unlock();
@@ -167,7 +167,7 @@ static int br_change_mtu(struct net_device *dev, int new_mtu)
 
 	dev->mtu = new_mtu;
 
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 	/* remember the MTU in the rtable for PMTU */
 	dst_metric_set(&br->fake_rtable.dst, RTAX_MTU, new_mtu);
 #endif
diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
index 056b67b..992ec49 100644
--- a/net/bridge/br_forward.c
+++ b/net/bridge/br_forward.c
@@ -49,6 +49,7 @@ int br_dev_queue_push_xmit(struct sk_buff *skb)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(br_dev_queue_push_xmit);
 
 int br_forward_finish(struct sk_buff *skb)
 {
@@ -56,6 +57,7 @@ int br_forward_finish(struct sk_buff *skb)
 		       br_dev_queue_push_xmit);
 
 }
+EXPORT_SYMBOL_GPL(br_forward_finish);
 
 static void __br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
 {
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index 366c436..6fd5522 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -140,6 +140,7 @@ drop:
 	kfree_skb(skb);
 	goto out;
 }
+EXPORT_SYMBOL_GPL(br_handle_frame_finish);
 
 /* note: already called with rcu_read_lock */
 static int br_handle_local_finish(struct sk_buff *skb)
diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
index a615264..97e4393 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;
@@ -245,14 +185,6 @@ static inline void nf_bridge_save_header(struct sk_buff *skb)
 					 skb->nf_bridge->data, header_size);
 }
 
-static inline void nf_bridge_update_protocol(struct sk_buff *skb)
-{
-	if (skb->nf_bridge->mask & BRNF_8021Q)
-		skb->protocol = htons(ETH_P_8021Q);
-	else if (skb->nf_bridge->mask & BRNF_PPPoE)
-		skb->protocol = htons(ETH_P_PPP_SES);
-}
-
 /* When handing a packet over to the IP layer
  * check whether we have a skb that is in the
  * expected format
@@ -320,26 +252,6 @@ drop:
 	return -1;
 }
 
-/* Fill in the header for fragmented IP packets handled by
- * the IPv4 connection tracking code.
- */
-int nf_bridge_copy_header(struct sk_buff *skb)
-{
-	int err;
-	unsigned int header_size;
-
-	nf_bridge_update_protocol(skb);
-	header_size = ETH_HLEN + nf_bridge_encap_header_len(skb);
-	err = skb_cow_head(skb, header_size);
-	if (err)
-		return err;
-
-	skb_copy_to_linear_data_offset(skb, -header_size,
-				       skb->nf_bridge->data, header_size);
-	__skb_push(skb, nf_bridge_encap_header_len(skb));
-	return 0;
-}
-
 /* PF_BRIDGE/PRE_ROUTING *********************************************/
 /* Undo the changes made for ip6tables PREROUTING and continue the
  * bridge PRE_ROUTING hook. */
@@ -1059,38 +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");
diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
index 90a91e1..0fa66b8 100644
--- a/net/bridge/br_netlink.c
+++ b/net/bridge/br_netlink.c
@@ -602,7 +602,7 @@ out_af:
 	return err;
 }
 
-void __exit br_netlink_fini(void)
+void br_netlink_fini(void)
 {
 	br_mdb_uninit();
 	rtnl_af_unregister(&br_af_ops);
diff --git a/net/bridge/br_nf_core.c b/net/bridge/br_nf_core.c
new file mode 100644
index 0000000..387cb3b
--- /dev/null
+++ b/net/bridge/br_nf_core.c
@@ -0,0 +1,96 @@
+/*
+ *	Handle firewalling core
+ *	Linux ethernet bridge
+ *
+ *	Authors:
+ *	Lennert Buytenhek		<buytenh@gnu.org>
+ *	Bart De Schuymer		<bdschuym@pandora.be>
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ *
+ *	Lennert dedicates this file to Kerstin Wurdinger.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/in_route.h>
+#include <linux/inetdevice.h>
+#include <net/route.h>
+
+#include "br_private.h"
+#ifdef CONFIG_SYSCTL
+#include <linux/sysctl.h>
+#endif
+
+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;
+}
+
+int __init br_nf_core_init(void)
+{
+	return dst_entries_init(&fake_dst_ops);
+}
+
+void br_nf_core_fini(void)
+{
+	dst_entries_destroy(&fake_dst_ops);
+}
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 62a7fa2..d304d75 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -221,7 +221,7 @@ struct net_bridge
 	struct pcpu_sw_netstats		__percpu *stats;
 	spinlock_t			hash_lock;
 	struct hlist_head		hash[BR_HASH_SIZE];
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 	struct rtable 			fake_rtable;
 	bool				nf_call_iptables;
 	bool				nf_call_ip6tables;
@@ -751,13 +751,13 @@ static inline int br_vlan_enabled(struct net_bridge *br)
 #endif
 
 /* br_netfilter.c */
-#ifdef CONFIG_BRIDGE_NETFILTER
-int br_netfilter_init(void);
-void br_netfilter_fini(void);
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
+int br_nf_core_init(void);
+void br_nf_core_fini(void);
 void br_netfilter_rtable_init(struct net_bridge *);
 #else
-#define br_netfilter_init()	(0)
-#define br_netfilter_fini()	do { } while (0)
+static inline int br_nf_core_init(void) { return 0; }
+static inline void br_nf_core_fini(void) {}
 #define br_netfilter_rtable_init(x)
 #endif
 
diff --git a/net/bridge/br_sysfs_br.c b/net/bridge/br_sysfs_br.c
index c9e2572..cb431c6 100644
--- a/net/bridge/br_sysfs_br.c
+++ b/net/bridge/br_sysfs_br.c
@@ -629,7 +629,7 @@ static ssize_t multicast_startup_query_interval_store(
 }
 static DEVICE_ATTR_RW(multicast_startup_query_interval);
 #endif
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 static ssize_t nf_call_iptables_show(
 	struct device *d, struct device_attribute *attr, char *buf)
 {
@@ -763,7 +763,7 @@ static struct attribute *bridge_attrs[] = {
 	&dev_attr_multicast_query_response_interval.attr,
 	&dev_attr_multicast_startup_query_interval.attr,
 #endif
-#ifdef CONFIG_BRIDGE_NETFILTER
+#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 	&dev_attr_nf_call_iptables.attr,
 	&dev_attr_nf_call_ip6tables.attr,
 	&dev_attr_nf_call_arptables.attr,
-- 
1.7.10.4