[Galene] Re: Logging

[Juliusz Chroboczek <jch@irif.fr>]

>> The direct connection was successful, so the TURN server was never
>> contacted.

> Right, I see. What are the conditions where a direct connection fails?
> Is it just when the client is behind a NAT?

If only one side is behind NAT, you should get a direct connection with no
outside help.

If both sides are behind NAT, they will attempt to establish a paired set
of NAT mappings by synchronising through a STUN server, and then establish
a direct connection (TURN is a superset of STUN, no need to set up
a dedicated STUN server if you've got TURN).  This is usually successful,
but might occasionally fail due to packet loss.

If there is a firewall in the way that drops UDP traffic, or traffic to
high-numbered ports, then the peers will fall back to TURN.  TURN supports
both UDP and TCP proxying, since some networks allow outgoing UDP only to
some ports (typically 1194 for OpenVPN and 10000 for the Cisco VPN client).

ICE-TCP adds an additional step by allowing direct connections over TCP.
It is not designed for peer-to-peer communication, only for client-server
communication, so it should be a perfect fit for Galène.

Once a functioning pair is found, ICE will stick to it.  In Galène, we
restart ICE whenever the connection fails, and also when the user types
"/renegotiate".  (I'd like to detect client-side network changes and restart
ICE automatically, but current browsers don't give me a suitable event
handler.)

All of this happens in parallel, with arbitrary timeouts, so the actual
behaviour tends to be non-deterministic and next to impossible to debug.
See for example

  https://github.com/pion/ice/issues/305

> As for just logging, Galene does propagate JSON parsing errors from the
> Go JSON parser, but because the files are not read on startup you can
> start up the daemon and everything looks fine until someone tries to
> connect...

Hmm... I'm actually using the current behaviour, by using undefined fields
in my JSON files ("contact" and "comment").

But I think you're right.  This will happen in background, so you'll only
get warnings in the log.  After 0.2 is out, though, since Galène is frozen
right now.

-- Juliusz