tcp: ipv6: bind() use stronger condition for bind_conflict

We must try harder to get unique (addr, port) pairs when
doing port autoselection for sockets with SO_REUSEADDR
option set.

This is a continuation of commit aacd9289
for IPv6.
Signed-off-by: NFlavio Leitner <fbl@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/inet6_connection_sock.c

@@ -54,6 +54,10 @@ int inet6_csk_bind_conflict(const struct sock *sk,
 				if (ipv6_rcv_saddr_equal(sk, sk2))
 					break;
 			}
+			if (!relax && reuse && sk2->sk_reuse &&
+			    sk2->sk_state != TCP_LISTEN &&
+			    ipv6_rcv_saddr_equal(sk, sk2))
+				break;
 		}
 	}