[Nottingham] How to remote diagnose network issues?

[Chris Booth]

Does this page help?
http://0pointer.de/blog/projects/socket-activation.html


From: Nottingham [mailto:nottingham-bounces at mailman.lug.org.uk] On Behalf Of Jason Irwin
Sent: 06 September 2015 23:07
To: Notts GNU/Linux Users Group
Subject: [Nottingham] How to remote diagnose network issues?

I am trying to have a RasPi create a a reverse tunnel to a server so I can manage it. This should be simple enough. For some reason I have not yet been able to determine, the connection keeps dropping out. Even with autossh.

My first problem is, what has replaced /etc/network/if-up.d/ in systemd?
I know systemd defines things differently, but no amount of searching has given the the answer to "How to get systemd to run a script when the network is up".
Next is, how do I figure out *why* the connection drops? I've got autossh dumping its error messages to a log file that remains annoyingly empty, I just don't get it. I've run this same thing (autossh -f /path/cert -R 1234:here:22 foo at bar) numerous times and it just, well, works! Only thing different in this case is that the RasPi is on a VPN that can hiccup (which the Pi detects and restarts). Thing is, with autossh, I would expect it to re-connect back to me one the Pi has finished slapping ithe VPN around (regardless of any systemd muck).

Internet connection to the location is also woeful, so any video chat/desktop share is fraught; or I'd use TeamViewer or something access Cygwin on a local lappy. Luckily there is an IT adept out at the location for the next few days.
Any help gratefully received!
J.




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