udp: preserve the connected status if only UDP cmsg

If "udp_cmsg_send()" returned 0 (i.e. only UDP cmsg),
"connected" should not be set to 0. Otherwise it stops
the connected socket from using the cached route.

Fixes: 2e8de857 ("udp: add gso segment cmsg")
Signed-off-by: Yick Xie <yick.xie@gmail.com>
Cc: stable@vger.kernel.org
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20240418170610.867084-1-yick.xie@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/udp.c

@@ -1123,16 +1123,17 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 
 	if (msg->msg_controllen) {
 		err = udp_cmsg_send(sk, msg, &ipc.gso_size);
-		if (err > 0)
+		if (err > 0) {
 			err = ip_cmsg_send(sk, msg, &ipc,
 					   sk->sk_family == AF_INET6);
+			connected = 0;
+		}
 		if (unlikely(err < 0)) {
 			kfree(ipc.opt);
 			return err;
 		}
 		if (ipc.opt)
 			free = 1;
-		connected = 0;
 	}
 	if (!ipc.opt) {
 		struct ip_options_rcu *inet_opt;

net/ipv6/udp.c

@@ -1474,9 +1474,11 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		ipc6.opt = opt;
 
 		err = udp_cmsg_send(sk, msg, &ipc6.gso_size);
-		if (err > 0)
+		if (err > 0) {
 			err = ip6_datagram_send_ctl(sock_net(sk), sk, msg, fl6,
 						    &ipc6);
+			connected = false;
+		}
 		if (err < 0) {
 			fl6_sock_release(flowlabel);
 			return err;
@@ -1488,7 +1490,6 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		}
 		if (!(opt->opt_nflen|opt->opt_flen))
 			opt = NULL;
-		connected = false;
 	}
 	if (!opt) {
 		opt = txopt_get(np);