The WWDC "Your App and Next Generation Networks" presentation discusses how the NSURLSession and CFNetworkAPIs in iOS 9 can synthesize IPv6 addresses when presented with IPv4 literals on an IPv6-only network.
For those of us who still need to use sockets-level APIs due to existing code frameworks, is this procedure documented somewhere? Or is there any API available to just do the translation process?
I guess, you are right, it is RFC 7050.
During heavy googling I found this email post by David Schinazi, Apple CoreOS Networking Engineer:
https://www.ietf.org/mail-archive/web/v6ops/current/msg22324.html
Here is an excerpt:
...if you use NSURLSession to connect to an IPv4 literal on an IPv6-only NAT64-DNS64 network, the API will bump in a IPv6 literal synthesized using RFC 7050. Note that this will not happen when using sockets directly. We do not support under-the-sockets bump-in-API (RFC 3338) and we do not support 464XLAT...