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: efb6de9 ("netfilter: bridge: forward IPv6 fragmented packets")
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

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_ */

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