Audio/Video calls fail on IPv6 Cellular Network

[RobusK]

• [X] I have searched open and closed issues for duplicates
• [X] I am submitting a bug report for existing functionality that does not work as intended
• [X] This isn't a feature request or a discussion topic

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Bug description

While using Cellular Data provider with a IPv6 APN (concrete technology unknown, connecting with IPv4 websites works fine), audio/video calls fail. Messaging works fine. I suspect the issue lies with IPv6 because the same provider uses a IPv4 APN for the iPhone hotspot. When using said hotspot, calls work fine. Censorship Circumvention does not fix the issue.

Steps to reproduce

• Call someone or be called

Actual result: When initiating a call, the status stays on "Connecting". Eventually, it switches to Call Failed. The recipient receives a Missed Call notification, but their phone never rings. Conversely, when being called, we only get a Missed Call notification.

Expected result: The call switches to "Ringing" / Is established successfully

Screenshots

Excerpt from the app System Status: hw monitor

Device info

Device: iPhone XS 64GB

iOS version: 14.2, but been observing this issue since at least iOS 13

Signal version: 3.22.0.8

Link to debug log

https://debuglogs.org/a4c9b4158f09f5c76ff9ea695dd4de64c88f4eb394642aed66406ff2d47a75cf.zip

[211217613]

Is my issue related? #4994

How would I check to see if my provider is using IPv6

[RobusK]

@211217613 sounds similar, you could download the app I mentioned ("System Status: hw monitor") and post it/compare to mine.

Note: as of 2021-05-16, I am still experiencing this issue.

[211217613]

I did some debugging and seems to be an issue with dual sim config on my iPhone.

[stale[bot]]

Is this still relevant? If so, what is blocking it? Is there anything you can do to help move it forward?

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.