tcp: md5: fix a typo in tcp_v4_md5_lookup()

Lookup key for tcp_md5_do_lookup() has to be taken
from addr_sk, not sk (which can be the listener)

Fixes: fd3a154 ("tcp: md5: get rid of tcp_v[46]_reqsk_md5_lookup()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_ipv4.c

@@ -897,9 +897,9 @@ EXPORT_SYMBOL(tcp_md5_do_lookup);
 struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
 					 const struct sock *addr_sk)
 {
-	union tcp_md5_addr *addr;
+	const union tcp_md5_addr *addr;
 
-	addr = (union tcp_md5_addr *)&sk->sk_daddr;
+	addr = (const union tcp_md5_addr *)&addr_sk->sk_daddr;
 	return tcp_md5_do_lookup(sk, addr, AF_INET);
 }
 EXPORT_SYMBOL(tcp_v4_md5_lookup);