Bind logic fails when net.ipv6.bindv6only is 0

[andrew-aladjev]

Hello, I am referring to this gist. I've also seen here issues about address is already in use. I want to talk about it.

First of all, I want to mention that net.ipv6.bindv6only = 0 is fairly legal for every Linux system because many developers may forget about ipv6, and this option should be enabled globally by default. This option enables binding to both 0.0.0.0 and :: when bind has been called with just 0.0.0.0. It allows programs to bind to IPv6 automatically.

So I am going to provide a pull request that will add the IPV6_V6ONLY option for socket when we are working with ipv6 protocol, because the current bind logic actually implies it.