netfilter: Pass net into okfn

This is immediately motivated by the bridge code that chains functions that
call into netfilter.  Without passing net into the okfns the bridge code would
need to guess about the best expression for the network namespace to process
packets in.

As net is frequently one of the first things computed in continuation functions
after netfilter has done it's job passing in the desired network namespace is in
many cases a code simplification.

To support this change the function dst_output_okfn is introduced to
simplify passing dst_output as an okfn.  For the moment dst_output_okfn
just silently drops the struct net.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
index fefcd2e..e930321 100644
--- a/net/decnet/dn_route.c
+++ b/net/decnet/dn_route.c
@@ -512,7 +512,7 @@
  *
  * Returns: result of input function if route is found, error code otherwise
  */
-static int dn_route_rx_packet(struct sock *sk, struct sk_buff *skb)
+static int dn_route_rx_packet(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 	struct dn_skb_cb *cb;
 	int err;
@@ -610,7 +610,7 @@
 	return NET_RX_DROP;
 }
 
-static int dn_route_discard(struct sock *sk, struct sk_buff *skb)
+static int dn_route_discard(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 	/*
 	 * I know we drop the packet here, but thats considered success in
@@ -620,7 +620,7 @@
 	return NET_RX_SUCCESS;
 }
 
-static int dn_route_ptp_hello(struct sock *sk, struct sk_buff *skb)
+static int dn_route_ptp_hello(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 	dn_dev_hello(skb);
 	dn_neigh_pointopoint_hello(skb);