tcp: add route_req method to tcp_request_sock_ops

Create wrappers with same signature for the IPv4/IPv6 request routing
calls and use these wrappers (via route_req method from
tcp_request_sock_ops) in tcp_v4_conn_request and tcp_v6_conn_request
with the purpose of unifying the two functions in a later patch.

We can later drop the wrapper functions and modify inet_csk_route_req
and inet6_cks_route_req to use the same signature.

Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 086d00e..59fcc59 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1605,6 +1605,9 @@
 	__u32 (*cookie_init_seq)(struct sock *sk, const struct sk_buff *skb,
 				 __u16 *mss);
 #endif
+	struct dst_entry *(*route_req)(struct sock *sk, struct flowi *fl,
+				       const struct request_sock *req,
+				       bool *strict);
 };
 
 #ifdef CONFIG_SYN_COOKIES