Simpler and more reliable implementation for Windows 10+?

[dlenski]

There are some cases where it's apparently possible to delete the loopback route (127.0.0.0/8) on Windows. This prevents the IPv4-based dumb_socketpair from working, and it appears to be very difficult to recreate the required loopback route. Yay, Windows 🤷‍♂️.

This breaks OpenConnect for users who run route /f to nuke their routing table (presumably out of sheer desperation… yay, Windows again) and then reconnect to a network.

It seems that there is a way to make dumb_socketpair sidestep IPv4 brokenness altogether, since AF_UNIX+SOCK_STREAM are available on Windows 10+.

Implementing dumb_socketpair with AF_UNIX sockets would be simpler and more reliable. The function could try using AF_UNIX sockets first, and only fallback to the IPv4-based approach if that fails.

[DimitriPapadopoulos]

@dlenski I suggest you push a merge request into selectable-socketpair/selectable-socketpair in the short term.