udp: fix l4 hash after reconnect

After the blamed commit below, udp_rehash() is supposed to be called
with both local and remote addresses set.

Currently that is already the case for IPv6 sockets, but for IPv4 the
destination address is updated after rehashing.

Address the issue moving the destination address and port initialization
before rehashing.

Fixes: 1b29a73 ("ipv6/udp: Add 4-tuple hash for connected socket")
Reviewed-by: Eric Dumazet <[email protected]>
Link: https://patch.msgid.link/4761e466ab9f7542c68cdc95f248987d127044d2.1733499715.git.pabeni@redhat.com
Signed-off-by: Paolo Abeni <[email protected]>

net/ipv4/datagram.c

@@ -61,15 +61,17 @@ int __ip4_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len
 		err = -EACCES;
 		goto out;
 	}
+
+	/* Update addresses before rehashing */
+	inet->inet_daddr = fl4->daddr;
+	inet->inet_dport = usin->sin_port;
 	if (!inet->inet_saddr)
-		inet->inet_saddr = fl4->saddr;	/* Update source address */
+		inet->inet_saddr = fl4->saddr;
 	if (!inet->inet_rcv_saddr) {
 		inet->inet_rcv_saddr = fl4->saddr;
 		if (sk->sk_prot->rehash)
 			sk->sk_prot->rehash(sk);
 	}
-	inet->inet_daddr = fl4->daddr;
-	inet->inet_dport = usin->sin_port;
 	reuseport_has_conns_set(sk);
 	sk->sk_state = TCP_ESTABLISHED;
 	sk_set_txhash(sk);