netfilter: Pass socket pointer down through okfn().

On the output paths in particular, we have to sometimes deal with two
socket contexts.  First, and usually skb->sk, is the local socket that
generated the frame.

And second, is potentially the socket used to control a tunneling
socket, such as one the encapsulates using UDP.

We do not want to disassociate skb->sk when encapsulating in order
to fix this, because that would break socket memory accounting.

The most extreme case where this can cause huge problems is an
AF_PACKET socket transmitting over a vxlan device.  We hit code
paths doing checks that assume they are dealing with an ipv4
socket, but are actually operating upon the AF_PACKET one.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/decnet/dn_nsp_in.c b/net/decnet/dn_nsp_in.c
index fe5f014..a321eac 100644
--- a/net/decnet/dn_nsp_in.c
+++ b/net/decnet/dn_nsp_in.c
@@ -714,7 +714,7 @@
 	return ret;
 }
 
-static int dn_nsp_rx_packet(struct sk_buff *skb)
+static int dn_nsp_rx_packet(struct sock *sk2, struct sk_buff *skb)
 {
 	struct dn_skb_cb *cb = DN_SKB_CB(skb);
 	struct sock *sk = NULL;
@@ -814,7 +814,8 @@
 
 int dn_nsp_rx(struct sk_buff *skb)
 {
-	return NF_HOOK(NFPROTO_DECNET, NF_DN_LOCAL_IN, skb, skb->dev, NULL,
+	return NF_HOOK(NFPROTO_DECNET, NF_DN_LOCAL_IN, NULL, skb,
+		       skb->dev, NULL,
 		       dn_nsp_rx_packet);
 }