Signal-ios: Does not support IPv6-only networks.

[echarlie]

• [X] I have searched open and closed issues for duplicates

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Bug description

Messages cannot be sent on IPv6-only network without transition mechanisms.

Steps to reproduce

• Connect to wireless IPv6-only network without transition mechanisms (NAT64, 4rd, DNS64, etc.).
• Try to send message, debug log.
• It _will_ fail.

Actual result: Message fails to send, Signal claims to be "offline"
Expected result: Message is sent, Signal functions normally.

Screenshots

This won't show anything of use.

Device info

Device: iPhone 5S
iOS version: 9.3.1
Signal version: 2.2

Link to debug log

Can't send debug log on IPv6-only either. Sorry.

[aaronraimist]

I don't have any way to test this but just a note for the developers: this needs to be fixed soon, all new updates to apps will need to support IPV6 networks by June 1, 2016.

@michaelkirk

[echarlie]

The only reason I was able to test is because my employers have a wireless IPv6-only network; they use it to annoy the vendors. I know that anything running on AWS _cannot_ support IPv6, github included, iirc. However, Apple's demand there is rather hypocritical: _most_ of their own apps break on an IPv6-only network; they assume the use of transition mechanisms as stated in their developer page, though.

[michaelkirk]

I don't have at hand an IPV6 network which _doesn't_ support NAT64.

But interestingly enough, one of the Apple recommended ways to verify that your app is ipv6 ready is to connect your iDevice to a local NAT64 network shared from your Mac.

After connecting to this network, I verified that no relevant ipv4 traffic was transmitted while Signal messages were exchanged.

The issue of ipv6 networks without transition mechanisms isn't settled, but WRT to meeting apples app store requirements, I haven't found any ipv4 offenders in the codebase and consider it a good sign that Apple's own recommended ipv6 test setup doesn't immediately flunk Signal from getting accepted into the app store.

[michaelkirk]

To update, we've had confirmation that Signal works with Apple's ipv6 testing setup.

@echarlie - is it still the case that Signal doesn't work on your employers network? Could it be related to port restriction vs ipv6?

Read more on port restriction here: http://support.whispersystems.org/hc/en-us/articles/213697218-Which-TCP-UDP-ports-need-to-be-available-

[echarlie]

I went through quite a few hoops on my home network to break IPv4. With an IPv6-only network without transition mechanisms, I can still confirm that Signal is broken. I'd assume this is because Signal's central Servers are IPv4-only, or at least don't have AAAA records in DNS. I have confirmed that it works on an IPv6-only NAT64/DNS64 network.

For reference, current iOS version is 10.3.3