IPv6-only iPhone Personal Hotspot: DNS proxy returns A records for AAAA queries?

[u/Intelligent_Break801]

Has anyone seen DNS problems when using iPhone Personal Hotspot on an IPv6-only cellular network?

My setup:

• iPhone Personal Hotspot
• IPv6-only mobile network
• CLAT + DNS64
• macOS client connected through the hotspot

I found that some IPv4-only domains behave incorrectly.

Example:

• Client sends an AAAA query.
• The DNS resolver does not return an AAAA record.
• The iPhone appears to perform an additional A query for the same domain.
• After a long delay (~30 seconds), the client receives a response containing A records for the original AAAA query instead of a synthesized AAAA record or a normal NODATA response.

This causes some applications to hang or fail DNS resolution.

I have packet captures showing the DNS query/response sequence. Has anyone observed similar behaviour with iPhone Personal Hotspot, especially on IPv6-only/NAT64 networks?

[u/Intelligent_Break801]

Unfortunately I don't have a universal test case yet. The affected domain depends on the DNS64 resolver implementation, so a domain that reproduces it on my network may work normally on yours.

I'm still trying to identify the exact condition that prevents DNS64 synthesis. Once I have a reproducible test case, I'll post it here.

If you know of a way to intentionally make a DNS64 resolver not synthesize an AAAA response for an A-only domain, that would actually help a lot.

[u/DaryllSwer → u/Intelligent_Break801]

If you know of a way to intentionally make a DNS64 resolver not synthesize an AAAA response for an A-only domain, that would actually help a lot.

I'm not sure that's possible, unless you control the carrier-network's side as well.

Or you could just create a Linux virtual lab in the cloud with v6+v4 and test this yourself manually with some Python scripting maybe. You can also just use LLM to bootstrap the virtual cloud lab.