Signal-desktop: Add IPv6 connectivity to Signal server

[freswa]

As described in #2327 the servers reachable with the fqdn textsecure-service.whispersystems.org only have A records so they are not available from IPv6 only networks.
As #2327 got closed I'd like to fill this as a request for enhancement to make these server available via IPv6.
Thanks

[ogelpre]

It is even worse: Signal Desktop does not work in ipv6only environments with NAT64. This has to be fixed.

[motp]

I am just attending the RIPE78 meeting and could test in an IPv6-only environment with NAT64:
The bug is still present in the current Version v1.24.1of signal-desktop, if no local CLAT is running.
With CLAT, signal works like expected.

A tcpdump reveals connections to 34.196.194.172, which was the first match to textsecure-service.whispersystems.org at that time, on the clat interface.

This is what probably happens: Although the Sourcecode only mentions textsecure-service.whispersystems.org, the actual socket is opened to the first IPv4 Address of
this DNS RR.

This means:
a) You are only trying to open an IPv4-only Socket and the syntethic DNS64 answer is ignored (bad)
b) You are trying to connect to a literal IPv4 Address (very bad)

Please fix this. It breaks anything else than IPv4-only networking.

[ogelpre]

I am attending the RIPE78 meeting, too. Same issue here.

[mdavids]

https://github.com/signalapp/Signal-Desktop/issues/2327#issuecomment-565377322

[iLennart21]

Just to warm this Feature Request up: Here in Germany (and probably some other countries) some major ISPs only provide DS-Lite (Native v6, tunneled+nated v4) connectivity to their customers. This means all IPv4 traffic has to be relayed through a Gateway which adds some Latency. Usually the impact isn't too big but Google's statistics show that often v6 connections benefit from lower latency. Both Googles and Facebook's stats show worldwide v6 adoption is at roughly 30%. In some Countries it is as high as 60%.

It looks like the textsecure-service endpoint is hosted on AWS EC2. Even though v6 configuration requires some effort it should be possible by now to run a v6 capable service including load balancing.

[treysis]

Yes, please enable IPv6 on the textsecure endpoint and also add AAAA records to the DNS, please!