netfilter: bridge: use rcu hook to resolve br_netfilter dependency

e5de75b ("netfilter: bridge: move DNAT helper to br_netfilter") results
in the following link problem:

net/bridge/br_device.c:29: undefined reference to `br_nf_prerouting_finish_bridge`

Moreover it creates a hard dependency between br_netfilter and the
bridge core, which is what we've been trying to avoid so far.

Resolve this problem by using a hook structure so we reduce #ifdef
pollution and keep bridge netfilter specific code under br_netfilter.c
which was the original intention.

Reported-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index f0a0438dbd6d..b46fa0c5b8ec 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -763,17 +763,17 @@ static inline int br_vlan_enabled(struct net_bridge *br)
 }
 #endif
 
+struct nf_br_ops {
+        int (*br_dev_xmit_hook)(struct sk_buff *skb);
+};
+extern const struct nf_br_ops __rcu *nf_br_ops;
+
 /* br_netfilter.c */
 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
-int br_nf_prerouting_finish_bridge(struct sk_buff *skb);
 int br_nf_core_init(void);
 void br_nf_core_fini(void);
 void br_netfilter_rtable_init(struct net_bridge *);
 #else
-static inline int br_nf_prerouting_finish_bridge(struct sk_buff *skb)
-{
-        return 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)