From 8771dabfdc2a25d16c4f214befb39696ab05923a Mon Sep 17 00:00:00 2001
From: Russell Joyce <russell.joyce@york.ac.uk>
Date: Fri, 24 Apr 2020 13:27:35 +0100
Subject: [PATCH] Force SSH command in client script to fail if requested port
 is in use

This stops a user from accidentally opening a connection without
actually creating a tunnel, but no error handling is done at the moment.

First step towards fixing #29.
---
 vlab.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/vlab.py b/vlab.py
index f099491..c9c19b4 100755
--- a/vlab.py
+++ b/vlab.py
@@ -173,7 +173,8 @@ def err(s):
 else:
 	relay_command = "{}:{}".format(parsed.board[0], ephemeral_port)
 
-ssh_cmd = "ssh -L {}:localhost:9001 -L {}:localhost:{} -o PasswordAuthentication=no -e none -i {} {} -p {} -tt {} {}"\
+ssh_cmd = "ssh -L {}:localhost:9001 -L {}:localhost:{} -o PasswordAuthentication=no -o ExitOnForwardFailure=yes " \
+          "-e none -i {} {} -p {} -tt {} {}"\
 	.format(
 	        parsed.webport[0],
 	        parsed.localport[0],