drbd: Limit the time we are waiting for the first packet on an accepted socket

Before the patch
'drbd: Keep the listening socket open while trying to connect to the peer'

the newly created socket inherited the receive timeout from the listen
socket. The listen socket had a receive timeout of connect-intervall
+- 30% random jitter.

The real issue is that after the mentioned patch we had no timeout at all.
Now use 4 times the ping-timeout.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_receiver.c

@@ -791,8 +791,18 @@ static int receive_first_packet(struct drbd_connection *connection, struct socke
 {
 	unsigned int header_size = drbd_header_size(connection);
 	struct packet_info pi;
+	struct net_conf *nc;
 	int err;
 
+	rcu_read_lock();
+	nc = rcu_dereference(connection->net_conf);
+	if (!nc) {
+		rcu_read_unlock();
+		return -EIO;
+	}
+	sock->sk->sk_rcvtimeo = nc->ping_timeo * 4 * HZ / 10;
+	rcu_read_unlock();
+
 	err = drbd_recv_short(sock, connection->data.rbuf, header_size, 0);
 	if (err != header_size) {
 		if (err >= 0)