Synapse: Synapse fails to talk to appservices that listen on an IPv6 address.

[jcgruenhage]

Description

Synapse fails to talk to appservices that listen on an IPv6 address.

Steps to reproduce

• Set up some appservice
• Use the IPv4 address to verify it's working
• Now change the registration file pointing to the appservice's IPv6
• The logs will now contain errors like this:

2018-10-24 16:44:23,723 - synapse.appservice.scheduler - 240 - INFO - - Retrying transaction 338847 for AS ID telegram                                                              
2018-10-24 16:44:23,725 - synapse.http.client - 96 - INFO - - Sending request PUT http://[::1]:8187/transactions/338847?access_token=<redacted>
2018-10-24 16:44:23,726 - synapse.http.client - 118 - INFO - - Error sending request to  PUT http://[::1]:8187/transactions/338847?access_token=<redacted>: IDNAError The label b'::1' is not a valid A-label
2018-10-24 16:44:23,727 - synapse.appservice.api - 249 - WARNING - - push_bulk to http://[::1]:8187/transactions/338847 threw exception The label b'::1' is not a valid A-label

Maybe there is more info on this here, but I tried to get all the relevant things into this issue.

Version information

• Homeserver: jcg.re
• Version: v0.33.7
• Install method: docker
• Platform: Fedora Host, official docker image, running with network_mode=host in docker-compose

[hawkowl]

Related issue: https://github.com/python-hyper/hyperlink/issues/68

[silkeh]

Workaround: use ip6-localhost instead of [::1] (assuming it is defined in /etc/hosts)