[akira2501]

It seems like the explanation might be right there in that issue. The server is occasionally not successfully sending the A record and you're getting bad fallback behavior due to the way the dial call is imprecisely constructed and this is masking the underlying problem. The code, as written, is doing exactly what you would expect in this scenario.

Should it be your DNS resolver library that takes stock of your OS environment and only make calls for A records and not AAAA records when it "detects" some configuration?

Shouldn't your application itself have an environment variable or command line option that allows you to specify that your dials should only be done using tcp4? Wouldn't this be immensely useful to have outside of "auto detection" in some library somewhere?

[tsimionescu]

Why should every application be aware of whether it is running on a v4 or v6 network? If the application merely wants to connect to an external service, that is firmly in the OS's job to decide.

As a user, if ipv6 is flaky today, I want one central place to configure for ipv4 only, I don't want to go and change every application'settings only to revert that tomorrow.

[j16sdiz]

Oh.. right. So we need another configuration for each and every application for something almost always system wide and can change dynamically (like wifi reconnecting) ?