tcp: Use bhash2 for v4-mapped-v6 non-wildcard address.

While checking port availability in bind() or listen(), we used only
bhash for all v4-mapped-v6 addresses.  But there is no good reason not
to use bhash2 for v4-mapped-v6 non-wildcard addresses.

Let's do it by returning true in inet_use_bhash2_on_bind().  Then, we
also need to add a test in inet_bind2_bucket_match_addr_any() so that
::ffff:X.X.X.X will match with 0.0.0.0.

Note that sk->sk_rcv_saddr is initialised for v4-mapped-v6 sk in
__inet6_bind().
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/inet_connection_sock.c

@@ -159,8 +159,11 @@ static bool inet_use_bhash2_on_bind(const struct sock *sk)
 	if (sk->sk_family == AF_INET6) {
 		int addr_type = ipv6_addr_type(&sk->sk_v6_rcv_saddr);
 
-		return addr_type != IPV6_ADDR_ANY &&
-			addr_type != IPV6_ADDR_MAPPED;
+		if (addr_type == IPV6_ADDR_ANY)
+			return false;
+
+		if (addr_type != IPV6_ADDR_MAPPED)
+			return true;
 	}
 #endif
 	return sk->sk_rcv_saddr != htonl(INADDR_ANY);

net/ipv4/inet_hashtables.c

@@ -841,7 +841,8 @@ bool inet_bind2_bucket_match_addr_any(const struct inet_bind2_bucket *tb, const
 			return ipv6_addr_any(&tb->v6_rcv_saddr) ||
 				ipv6_addr_v4mapped_any(&tb->v6_rcv_saddr);
 
-		return false;
+		return ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr) &&
+			tb->rcv_saddr == 0;
 	}
 
 	if (sk->sk_family == AF_INET6)