[Nottingham] How to remote diagnose network issues?

[Jason Irwin]

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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