Federation doesn't play nice with IPv6 (SYN-254)

[matrixbot]

Servers with v6 resolvers seem to have problems federating - see synacktik from #matrix:matrix.org:

Feb 1 12:31
http://pastebin.com/giEhadsG

i have ipv6 running on this server, yeah
Feb 1 12:55
dual stack
Feb 1 12:59
well thats interesting
Feb 1 13:00
removed my v6 resolvers

(Imported from https://matrix.org/jira/browse/SYN-254)

(Reported by @ara4n)

[matrixbot]

Jira watchers: @ara4n

[matrixbot]

The problem seems to be that twisted's http agent is hardcoded to ipv4:
http://twistedmatrix.com/pipermail/twisted-python/2012-August/026012.html

-- @ara4n

[matrixbot]

...and our federation endpoint is hardcoded to ipv4 too:

    if ssl_context_factory is None:
        transport_endpoint = TCP4ClientEndpoint
        default_port = 8008
    else:
        transport_endpoint = SSL4ClientEndpoint
        endpoint_kw_args.update(sslContextFactory=ssl_context_factory)
        default_port = 8448

-- @ara4n

[matrixbot]

Twisted uses its own resolver lib, which plays nice with IPv4 addresses, but not with IPv6. Related to twisted ticket #4362.

python -m twisted.conch.stdio

>>> from twisted.names import client
>>> resolver = client.createResolver(servers=[('2001:4860:4860::8888', 53)])
>>> resolver.getHostByName('google.com')
<Deferred at 0x7f9fa9e14908 current result: <twisted.python.failure.Failure <class 'twisted.internet.error.InvalidAddressError'>>>
>>> resolver = client.createResolver(servers=[('8.8.8.8', 53)])
>>> resolver.getHostByName('google.com')
<Deferred at 0x7f9fa9e279e0 waiting on Deferred at 0x7f9fa9e27c68>
>>>

-- Sander Ruitenbeek

[PMaynard]

Is there any work around, I can't federate my homeserver until this is resolved?
I tried to bind the 8448 listener to my IPv4 address but it did not help.

[edit]
Not using IPv6 resolver is a temporary fix #1002
Though now it does appear to crash randomly.

[ara4n]

I think @kyrias is looking at this currently. If not, we'll get to it at some point soon although most of our synapse effort is currently going into next-generation homeserver work.

[kyrias]

I am working on it, though I can't make any promises on how much freetime I'll have to work on it. And next-gen HS work ey? ;D

[glyph]

See #1689 and #1690

[ara4n]

@glyph - many thanks for the PRs here. we'll have a play with them in the morning!

[ara4n]

fixed by the above and #1696