How to deal with ip4 and ip6?

[jbenet]

Having /ip4 and /ip6 explicit is very useful and nice. Though there are use cases where people want to be able to represent either, such as being able to have a /dns multiaddr like:

/dns/example.com/tcp/80

Resolve to either ip4 or ip6 addresses, depending on the application's capabilities

/ip4/1.2.3.4/tcp/80
/ip6/aaaa::1/tcp/80

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• I'm not convinced this is necessary, we can likely do without.
• But opening issue to gather thoughts
• This is also related to combinations of multiaddrs

We could have /ip which decides on /ip4 vs. /ip6 the same way as /dns will decide. RFC 6555 describes the Happy Eyeballs algorithm for this decision. Browser vendors all do this a little differently, even differing between platforms.