netfilter: bridge: split ipv6 code into separated file

Resolve compilation breakage when CONFIG_IPV6 is not set by moving the IPv6
code into a separated br_netfilter_ipv6.c file.

Fixes: efb6de9b4ba0 ("netfilter: bridge: forward IPv6 fragmented packets")
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

4 files changed, 315 insertions, 239 deletions

diff --git a/include/net/netfilter/br_netfilter.h b/include/net/netfilter/br_netfilter.h
index 2aa6048a55c1..bab824bde92c 100644
--- a/include/net/netfilter/br_netfilter.h
+++ b/include/net/netfilter/br_netfilter.h
@@ -1,6 +1,66 @@
 #ifndef _BR_NETFILTER_H_
 #define _BR_NETFILTER_H_
 
+#include "../../../net/bridge/br_private.h"
+
+static inline struct nf_bridge_info *nf_bridge_alloc(struct sk_buff *skb)
+{
+	skb->nf_bridge = kzalloc(sizeof(struct nf_bridge_info), GFP_ATOMIC);
+
+	if (likely(skb->nf_bridge))
+		atomic_set(&(skb->nf_bridge->use), 1);
+
+	return skb->nf_bridge;
+}
+
+void nf_bridge_update_protocol(struct sk_buff *skb);
+
+static inline struct nf_bridge_info *
+nf_bridge_info_get(const struct sk_buff *skb)
+{
+	return skb->nf_bridge;
+}
+
+unsigned int nf_bridge_encap_header_len(const struct sk_buff *skb);
+
+static inline void nf_bridge_push_encap_header(struct sk_buff *skb)
+{
+	unsigned int len = nf_bridge_encap_header_len(skb);
+
+	skb_push(skb, len);
+	skb->network_header -= len;
+}
+
+int br_nf_pre_routing_finish_bridge(struct sock *sk, struct sk_buff *skb);
+
+static inline struct rtable *bridge_parent_rtable(const struct net_device *dev)
+{
+	struct net_bridge_port *port;
+
+	port = br_port_get_rcu(dev);
+	return port ? &port->br->fake_rtable : NULL;
+}
+
+struct net_device *setup_pre_routing(struct sk_buff *skb);
 void br_netfilter_enable(void);
 
+#if IS_ENABLED(CONFIG_IPV6)
+int br_validate_ipv6(struct sk_buff *skb);
+unsigned int br_nf_pre_routing_ipv6(const struct nf_hook_ops *ops,
+				    struct sk_buff *skb,
+				    const struct nf_hook_state *state);
+#else
+static inline int br_validate_ipv6(struct sk_buff *skb)
+{
+	return -1;
+}
+
+static inline unsigned int
+br_nf_pre_routing_ipv6(const struct nf_hook_ops *ops, struct sk_buff *skb,
+		       const struct nf_hook_state *state)
+{
+	return NF_DROP;
+}
+#endif
+
 #endif /* _BR_NETFILTER_H_ */
diff --git a/net/bridge/Makefile b/net/bridge/Makefile
index c52577ac718e..a1cda5d4718d 100644
--- a/net/bridge/Makefile
+++ b/net/bridge/Makefile
@@ -13,6 +13,7 @@ bridge-$(CONFIG_SYSFS) += br_sysfs_if.o br_sysfs_br.o
 bridge-$(subst m,y,$(CONFIG_BRIDGE_NETFILTER)) += br_nf_core.o
 
 br_netfilter-y := br_netfilter_hooks.o
+br_netfilter-$(subst m,y,$(CONFIG_IPV6)) += br_netfilter_ipv6.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_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c
index e4e5f2f29173..d89f4fac0bc5 100644
--- a/net/bridge/br_netfilter_hooks.c
+++ b/net/bridge/br_netfilter_hooks.c
@@ -123,11 +123,6 @@ struct brnf_frag_data {
 static DEFINE_PER_CPU(struct brnf_frag_data, brnf_frag_data_storage);
 #endif
 
-static struct nf_bridge_info *nf_bridge_info_get(const struct sk_buff *skb)
-{
-	return skb->nf_bridge;
-}
-
 static void nf_bridge_info_free(struct sk_buff *skb)
 {
 	if (skb->nf_bridge) {
@@ -136,14 +131,6 @@ static void nf_bridge_info_free(struct sk_buff *skb)
 	}
 }
 
-static inline struct rtable *bridge_parent_rtable(const struct net_device *dev)
-{
-	struct net_bridge_port *port;
-
-	port = br_port_get_rcu(dev);
-	return port ? &port->br->fake_rtable : NULL;
-}
-
 static inline struct net_device *bridge_parent(const struct net_device *dev)
 {
 	struct net_bridge_port *port;
@@ -152,15 +139,6 @@ static inline struct net_device *bridge_parent(const struct net_device *dev)
 	return port ? port->br->dev : NULL;
 }
 
-static inline struct nf_bridge_info *nf_bridge_alloc(struct sk_buff *skb)
-{
-	skb->nf_bridge = kzalloc(sizeof(struct nf_bridge_info), GFP_ATOMIC);
-	if (likely(skb->nf_bridge))
-		atomic_set(&(skb->nf_bridge->use), 1);
-
-	return skb->nf_bridge;
-}
-
 static inline struct nf_bridge_info *nf_bridge_unshare(struct sk_buff *skb)
 {
 	struct nf_bridge_info *nf_bridge = skb->nf_bridge;
@@ -178,7 +156,7 @@ static inline struct nf_bridge_info *nf_bridge_unshare(struct sk_buff *skb)
 	return nf_bridge;
 }
 
-static unsigned int nf_bridge_encap_header_len(const struct sk_buff *skb)
+unsigned int nf_bridge_encap_header_len(const struct sk_buff *skb)
 {
 	switch (skb->protocol) {
 	case __cpu_to_be16(ETH_P_8021Q):
@@ -190,14 +168,6 @@ static unsigned int nf_bridge_encap_header_len(const struct sk_buff *skb)
 	}
 }
 
-static inline void nf_bridge_push_encap_header(struct sk_buff *skb)
-{
-	unsigned int len = nf_bridge_encap_header_len(skb);
-
-	skb_push(skb, len);
-	skb->network_header -= len;
-}
-
 static inline void nf_bridge_pull_encap_header(struct sk_buff *skb)
 {
 	unsigned int len = nf_bridge_encap_header_len(skb);
@@ -267,112 +237,7 @@ drop:
 	return -1;
 }
 
-/* We only check the length. A bridge shouldn't do any hop-by-hop stuff
- * anyway
- */
-static int check_hbh_len(struct sk_buff *skb)
-{
-	unsigned char *raw = (u8 *)(ipv6_hdr(skb) + 1);
-	u32 pkt_len;
-	const unsigned char *nh = skb_network_header(skb);
-	int off = raw - nh;
-	int len = (raw[1] + 1) << 3;
-
-	if ((raw + len) - skb->data > skb_headlen(skb))
-		goto bad;
-
-	off += 2;
-	len -= 2;
-
-	while (len > 0) {
-		int optlen = nh[off + 1] + 2;
-
-		switch (nh[off]) {
-		case IPV6_TLV_PAD1:
-			optlen = 1;
-			break;
-
-		case IPV6_TLV_PADN:
-			break;
-
-		case IPV6_TLV_JUMBO:
-			if (nh[off + 1] != 4 || (off & 3) != 2)
-				goto bad;
-			pkt_len = ntohl(*(__be32 *)(nh + off + 2));
-			if (pkt_len <= IPV6_MAXPLEN ||
-			    ipv6_hdr(skb)->payload_len)
-				goto bad;
-			if (pkt_len > skb->len - sizeof(struct ipv6hdr))
-				goto bad;
-			if (pskb_trim_rcsum(skb,
-					    pkt_len + sizeof(struct ipv6hdr)))
-				goto bad;
-			nh = skb_network_header(skb);
-			break;
-		default:
-			if (optlen > len)
-				goto bad;
-			break;
-		}
-		off += optlen;
-		len -= optlen;
-	}
-	if (len == 0)
-		return 0;
-bad:
-	return -1;
-}
-
-/* Equivalent to br_validate_ipv4 for IPv6 */
-static int br_validate_ipv6(struct sk_buff *skb)
-{
-	const struct ipv6hdr *hdr;
-	struct net_device *dev = skb->dev;
-	struct inet6_dev *idev = in6_dev_get(skb->dev);
-	u32 pkt_len;
-	u8 ip6h_len = sizeof(struct ipv6hdr);
-
-	if (!pskb_may_pull(skb, ip6h_len))
-		goto inhdr_error;
-
-	if (skb->len < ip6h_len)
-		goto drop;
-
-	hdr = ipv6_hdr(skb);
-
-	if (hdr->version != 6)
-		goto inhdr_error;
-
-	pkt_len = ntohs(hdr->payload_len);
-
-	if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
-		if (pkt_len + ip6h_len > skb->len) {
-			IP6_INC_STATS_BH(dev_net(dev), idev,
-					 IPSTATS_MIB_INTRUNCATEDPKTS);
-			goto drop;
-		}
-		if (pskb_trim_rcsum(skb, pkt_len + ip6h_len)) {
-			IP6_INC_STATS_BH(dev_net(dev), idev,
-					 IPSTATS_MIB_INDISCARDS);
-			goto drop;
-		}
-	}
-	if (hdr->nexthdr == NEXTHDR_HOP && check_hbh_len(skb))
-		goto drop;
-
-	memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
-	/* No IP options in IPv6 header; however it should be
-	 * checked if some next headers need special treatment
-	 */
-	return 0;
-
-inhdr_error:
-	IP6_INC_STATS_BH(dev_net(dev), idev, IPSTATS_MIB_INHDRERRORS);
-drop:
-	return -1;
-}
-
-static void nf_bridge_update_protocol(struct sk_buff *skb)
+void nf_bridge_update_protocol(struct sk_buff *skb)
 {
 	switch (skb->nf_bridge->orig_proto) {
 	case BRNF_PROTO_8021Q:
@@ -391,7 +256,7 @@ static void nf_bridge_update_protocol(struct sk_buff *skb)
  * don't, we use the neighbour framework to find out. In both cases, we make
  * sure that br_handle_frame_finish() is called afterwards.
  */
-static int br_nf_pre_routing_finish_bridge(struct sock *sk, struct sk_buff *skb)
+int br_nf_pre_routing_finish_bridge(struct sock *sk, struct sk_buff *skb)
 {
 	struct neighbour *neigh;
 	struct dst_entry *dst;
@@ -431,77 +296,11 @@ free_skb:
 	return 0;
 }
 
-static bool daddr_was_changed(const struct sk_buff *skb,
-			      const struct nf_bridge_info *nf_bridge)
+static inline bool
+br_nf_ipv4_daddr_was_changed(const struct sk_buff *skb,
+			     const struct nf_bridge_info *nf_bridge)
 {
-	switch (skb->protocol) {
-	case htons(ETH_P_IP):
-		return ip_hdr(skb)->daddr != nf_bridge->ipv4_daddr;
-	case htons(ETH_P_IPV6):
-		return memcmp(&nf_bridge->ipv6_daddr, &ipv6_hdr(skb)->daddr,
-			      sizeof(ipv6_hdr(skb)->daddr)) != 0;
-	default:
-		return false;
-	}
-}
-
-/* PF_BRIDGE/PRE_ROUTING: Undo the changes made for ip6tables
- * PREROUTING and continue the bridge PRE_ROUTING hook. See comment
- * for br_nf_pre_routing_finish(), same logic is used here but
- * equivalent IPv6 function ip6_route_input() called indirectly.
- */
-static int br_nf_pre_routing_finish_ipv6(struct sock *sk, struct sk_buff *skb)
-{
-	struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
-	struct rtable *rt;
-	struct net_device *dev = skb->dev;
-	const struct nf_ipv6_ops *v6ops = nf_get_ipv6_ops();
-
-	nf_bridge->frag_max_size = IP6CB(skb)->frag_max_size;
-
-	if (nf_bridge->pkt_otherhost) {
-		skb->pkt_type = PACKET_OTHERHOST;
-		nf_bridge->pkt_otherhost = false;
-	}
-	nf_bridge->mask &= ~BRNF_NF_BRIDGE_PREROUTING;
-	if (daddr_was_changed(skb, nf_bridge)) {
-		skb_dst_drop(skb);
-		v6ops->route_input(skb);
-
-		if (skb_dst(skb)->error) {
-			kfree_skb(skb);
-			return 0;
-		}
-
-		if (skb_dst(skb)->dev == dev) {
-			skb->dev = nf_bridge->physindev;
-			nf_bridge_update_protocol(skb);
-			nf_bridge_push_encap_header(skb);
-			NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING,
-				       sk, skb, skb->dev, NULL,
-				       br_nf_pre_routing_finish_bridge,
-				       1);
-			return 0;
-		}
-		ether_addr_copy(eth_hdr(skb)->h_dest, dev->dev_addr);
-		skb->pkt_type = PACKET_HOST;
-	} else {
-		rt = bridge_parent_rtable(nf_bridge->physindev);
-		if (!rt) {
-			kfree_skb(skb);
-			return 0;
-		}
-		skb_dst_set_noref(skb, &rt->dst);
-	}
-
-	skb->dev = nf_bridge->physindev;
-	nf_bridge_update_protocol(skb);
-	nf_bridge_push_encap_header(skb);
-	NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, sk, skb,
-		       skb->dev, NULL,
-		       br_handle_frame_finish, 1);
-
-	return 0;
+	return ip_hdr(skb)->daddr != nf_bridge->ipv4_daddr;
 }
 
 /* This requires some explaining. If DNAT has taken place,
@@ -558,7 +357,7 @@ static int br_nf_pre_routing_finish(struct sock *sk, struct sk_buff *skb)
 		nf_bridge->pkt_otherhost = false;
 	}
 	nf_bridge->mask &= ~BRNF_NF_BRIDGE_PREROUTING;
-	if (daddr_was_changed(skb, nf_bridge)) {
+	if (br_nf_ipv4_daddr_was_changed(skb, nf_bridge)) {
 		if ((err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))) {
 			struct in_device *in_dev = __in_dev_get_rcu(dev);
 
@@ -636,7 +435,7 @@ static struct net_device *brnf_get_logical_dev(struct sk_buff *skb, const struct
 }
 
 /* Some common code for IPv4/IPv6 */
-static struct net_device *setup_pre_routing(struct sk_buff *skb)
+struct net_device *setup_pre_routing(struct sk_buff *skb)
 {
 	struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
 
@@ -659,35 +458,6 @@ static struct net_device *setup_pre_routing(struct sk_buff *skb)
 	return skb->dev;
 }
 
-/* Replicate the checks that IPv6 does on packet reception and pass the packet
- * to ip6tables.
- */
-static unsigned int br_nf_pre_routing_ipv6(const struct nf_hook_ops *ops,
-					   struct sk_buff *skb,
-					   const struct nf_hook_state *state)
-{
-	struct nf_bridge_info *nf_bridge;
-
-	if (br_validate_ipv6(skb))
-		return NF_DROP;
-
-	nf_bridge_put(skb->nf_bridge);
-	if (!nf_bridge_alloc(skb))
-		return NF_DROP;
-	if (!setup_pre_routing(skb))
-		return NF_DROP;
-
-	nf_bridge = nf_bridge_info_get(skb);
-	nf_bridge->ipv6_daddr = ipv6_hdr(skb)->daddr;
-
-	skb->protocol = htons(ETH_P_IPV6);
-	NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, state->sk, skb,
-		skb->dev, NULL,
-		br_nf_pre_routing_finish_ipv6);
-
-	return NF_STOLEN;
-}
-
 /* Direct IPv6 traffic to br_nf_pre_routing_ipv6.
  * Replicate the checks that IPv4 does on packet reception.
  * Set skb->dev to the bridge device (i.e. parent of the
diff --git a/net/bridge/br_netfilter_ipv6.c b/net/bridge/br_netfilter_ipv6.c
new file mode 100644
index 000000000000..6d12d2675c80
--- /dev/null
+++ b/net/bridge/br_netfilter_ipv6.c
@@ -0,0 +1,245 @@
+/*
+ *	Handle firewalling
+ *	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/slab.h>
+#include <linux/ip.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/if_arp.h>
+#include <linux/if_ether.h>
+#include <linux/if_vlan.h>
+#include <linux/if_pppox.h>
+#include <linux/ppp_defs.h>
+#include <linux/netfilter_bridge.h>
+#include <linux/netfilter_ipv4.h>
+#include <linux/netfilter_ipv6.h>
+#include <linux/netfilter_arp.h>
+#include <linux/in_route.h>
+#include <linux/inetdevice.h>
+
+#include <net/ip.h>
+#include <net/ipv6.h>
+#include <net/addrconf.h>
+#include <net/route.h>
+#include <net/netfilter/br_netfilter.h>
+
+#include <asm/uaccess.h>
+#include "br_private.h"
+#ifdef CONFIG_SYSCTL
+#include <linux/sysctl.h>
+#endif
+
+/* We only check the length. A bridge shouldn't do any hop-by-hop stuff
+ * anyway
+ */
+static int br_nf_check_hbh_len(struct sk_buff *skb)
+{
+	unsigned char *raw = (u8 *)(ipv6_hdr(skb) + 1);
+	u32 pkt_len;
+	const unsigned char *nh = skb_network_header(skb);
+	int off = raw - nh;
+	int len = (raw[1] + 1) << 3;
+
+	if ((raw + len) - skb->data > skb_headlen(skb))
+		goto bad;
+
+	off += 2;
+	len -= 2;
+
+	while (len > 0) {
+		int optlen = nh[off + 1] + 2;
+
+		switch (nh[off]) {
+		case IPV6_TLV_PAD1:
+			optlen = 1;
+			break;
+
+		case IPV6_TLV_PADN:
+			break;
+
+		case IPV6_TLV_JUMBO:
+			if (nh[off + 1] != 4 || (off & 3) != 2)
+				goto bad;
+			pkt_len = ntohl(*(__be32 *)(nh + off + 2));
+			if (pkt_len <= IPV6_MAXPLEN ||
+			    ipv6_hdr(skb)->payload_len)
+				goto bad;
+			if (pkt_len > skb->len - sizeof(struct ipv6hdr))
+				goto bad;
+			if (pskb_trim_rcsum(skb,
+					    pkt_len + sizeof(struct ipv6hdr)))
+				goto bad;
+			nh = skb_network_header(skb);
+			break;
+		default:
+			if (optlen > len)
+				goto bad;
+			break;
+		}
+		off += optlen;
+		len -= optlen;
+	}
+	if (len == 0)
+		return 0;
+bad:
+	return -1;
+}
+
+int br_validate_ipv6(struct sk_buff *skb)
+{
+	const struct ipv6hdr *hdr;
+	struct net_device *dev = skb->dev;
+	struct inet6_dev *idev = in6_dev_get(skb->dev);
+	u32 pkt_len;
+	u8 ip6h_len = sizeof(struct ipv6hdr);
+
+	if (!pskb_may_pull(skb, ip6h_len))
+		goto inhdr_error;
+
+	if (skb->len < ip6h_len)
+		goto drop;
+
+	hdr = ipv6_hdr(skb);
+
+	if (hdr->version != 6)
+		goto inhdr_error;
+
+	pkt_len = ntohs(hdr->payload_len);
+
+	if (pkt_len || hdr->nexthdr != NEXTHDR_HOP) {
+		if (pkt_len + ip6h_len > skb->len) {
+			IP6_INC_STATS_BH(dev_net(dev), idev,
+					 IPSTATS_MIB_INTRUNCATEDPKTS);
+			goto drop;
+		}
+		if (pskb_trim_rcsum(skb, pkt_len + ip6h_len)) {
+			IP6_INC_STATS_BH(dev_net(dev), idev,
+					 IPSTATS_MIB_INDISCARDS);
+			goto drop;
+		}
+	}
+	if (hdr->nexthdr == NEXTHDR_HOP && br_nf_check_hbh_len(skb))
+		goto drop;
+
+	memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
+	/* No IP options in IPv6 header; however it should be
+	 * checked if some next headers need special treatment
+	 */
+	return 0;
+
+inhdr_error:
+	IP6_INC_STATS_BH(dev_net(dev), idev, IPSTATS_MIB_INHDRERRORS);
+drop:
+	return -1;
+}
+
+static inline bool
+br_nf_ipv6_daddr_was_changed(const struct sk_buff *skb,
+			     const struct nf_bridge_info *nf_bridge)
+{
+	return memcmp(&nf_bridge->ipv6_daddr, &ipv6_hdr(skb)->daddr,
+		      sizeof(ipv6_hdr(skb)->daddr)) != 0;
+}
+
+/* PF_BRIDGE/PRE_ROUTING: Undo the changes made for ip6tables
+ * PREROUTING and continue the bridge PRE_ROUTING hook. See comment
+ * for br_nf_pre_routing_finish(), same logic is used here but
+ * equivalent IPv6 function ip6_route_input() called indirectly.
+ */
+static int br_nf_pre_routing_finish_ipv6(struct sock *sk, struct sk_buff *skb)
+{
+	struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
+	struct rtable *rt;
+	struct net_device *dev = skb->dev;
+	const struct nf_ipv6_ops *v6ops = nf_get_ipv6_ops();
+
+	nf_bridge->frag_max_size = IP6CB(skb)->frag_max_size;
+
+	if (nf_bridge->pkt_otherhost) {
+		skb->pkt_type = PACKET_OTHERHOST;
+		nf_bridge->pkt_otherhost = false;
+	}
+	nf_bridge->mask &= ~BRNF_NF_BRIDGE_PREROUTING;
+	if (br_nf_ipv6_daddr_was_changed(skb, nf_bridge)) {
+		skb_dst_drop(skb);
+		v6ops->route_input(skb);
+
+		if (skb_dst(skb)->error) {
+			kfree_skb(skb);
+			return 0;
+		}
+
+		if (skb_dst(skb)->dev == dev) {
+			skb->dev = nf_bridge->physindev;
+			nf_bridge_update_protocol(skb);
+			nf_bridge_push_encap_header(skb);
+			NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING,
+				       sk, skb, skb->dev, NULL,
+				       br_nf_pre_routing_finish_bridge,
+				       1);
+			return 0;
+		}
+		ether_addr_copy(eth_hdr(skb)->h_dest, dev->dev_addr);
+		skb->pkt_type = PACKET_HOST;
+	} else {
+		rt = bridge_parent_rtable(nf_bridge->physindev);
+		if (!rt) {
+			kfree_skb(skb);
+			return 0;
+		}
+		skb_dst_set_noref(skb, &rt->dst);
+	}
+
+	skb->dev = nf_bridge->physindev;
+	nf_bridge_update_protocol(skb);
+	nf_bridge_push_encap_header(skb);
+	NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, sk, skb,
+		       skb->dev, NULL,
+		       br_handle_frame_finish, 1);
+
+	return 0;
+}
+
+/* Replicate the checks that IPv6 does on packet reception and pass the packet
+ * to ip6tables.
+ */
+unsigned int br_nf_pre_routing_ipv6(const struct nf_hook_ops *ops,
+				    struct sk_buff *skb,
+				    const struct nf_hook_state *state)
+{
+	struct nf_bridge_info *nf_bridge;
+
+	if (br_validate_ipv6(skb))
+		return NF_DROP;
+
+	nf_bridge_put(skb->nf_bridge);
+	if (!nf_bridge_alloc(skb))
+		return NF_DROP;
+	if (!setup_pre_routing(skb))
+		return NF_DROP;
+
+	nf_bridge = nf_bridge_info_get(skb);
+	nf_bridge->ipv6_daddr = ipv6_hdr(skb)->daddr;
+
+	skb->protocol = htons(ETH_P_IPV6);
+	NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, state->sk, skb,
+		skb->dev, NULL,
+		br_nf_pre_routing_finish_ipv6);
+
+	return NF_STOLEN;
+}