RDS: don't commit to queue till transport connection is up

A rouge application can flood the send queue by targeting a dead
or non-existing node. Don't commit any messages to the queue
till the legitimate connection to the peer is established.
Let application retry so that only legit connections can
get on to the send queue.

Orabug: 25393611
Reviewed-by: Sowmini Varadhan <[email protected]>
Signed-off-by: Santosh Shilimkar <[email protected]>

Author: SantoshShilimkar

net/rds/send.c

@@ -1388,6 +1388,11 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
 		goto out;
 	}
 
+	if (!rds_conn_up(conn)) {
+		ret = -EAGAIN;
+		goto out;
+	}
+
 	while (!rds_send_queue_rm(rs, conn, rm, rs->rs_bound_port,
 				  dport, &queued)) {
 		rds_stats_inc(s_send_queue_full);