Sydent does not log IP addresses when X-Forwarded-For header exists and obey_x_forwarded_for = True

[michaelkaye]

Config file contains:

[http]
obey_x_forwarded_for = True

A sample request like so:

GET /_matrix/identity/api/v1 HTTP/1.1
Host: vector.im
Accept-Encoding: gzip
user-agent: Mozilla/5.0 (X11; Linux x86_64; rv:76.0) Gecko/20100101 Firefox/76.0
accept: */*
accept-language: en-US,en;q=0.5
origin: https://origin-server.com
dnt: 1
X-Forwarded-For: 1.2.3.4
X-Forwarded-Proto: https
X-Forwarded-For: 1.2.3.4

Logs only the raw load balancer IP in the sydent log files. It might be that there's two headers, but given they're identical, we should at least get one of them in the logs - neither is the one that is logged.

It looks like the logic is wrapped up in ip_from_request, but nothing actually seems to call this and/or twisted's http logging doesn't do the right thing with this.

https://github.com/matrix-org/sydent/blob/master/sydent/sydent.py#L274

[erikjohnston]

There seems to be three sets of HTTP servers, do we expect this option to apply to all of them or just the client API one?

[richvdh]

As per #300: it certainly doesn't want to be applied blindly to all three servers.