net-tcp: Fast Open client - cookie cache

With help from Eric Dumazet, add Fast Open metrics in tcp metrics cache.
The basic ones are MSS and the cookies. Later patch will cache more to
handle unfriendly middleboxes.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 5aed371..e601da1 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -405,6 +405,10 @@
 extern bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst, bool paws_check);
 extern bool tcp_remember_stamp(struct sock *sk);
 extern bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
+extern void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
+				   struct tcp_fastopen_cookie *cookie);
+extern void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
+				   struct tcp_fastopen_cookie *cookie);
 extern void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
 extern void tcp_disable_fack(struct tcp_sock *tp);
 extern void tcp_close(struct sock *sk, long timeout);