[SOCK]: Introduce sk_clone

Out of tcp_create_openreq_child, will be used in
dccp_create_openreq_child, and is a nice sock function anyway.

Signed-off-by: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/sock.h b/include/net/sock.h
index bdae0a5..828dc08 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -737,6 +737,8 @@
 					  unsigned int __nocast priority,
 					  struct proto *prot, int zero_it);
 extern void			sk_free(struct sock *sk);
+extern struct sock		*sk_clone(const struct sock *sk,
+					  const unsigned int __nocast priority);
 
 extern struct sk_buff		*sock_wmalloc(struct sock *sk,
 					      unsigned long size, int force,