Don't use os.NewFile or (*os.File).Close on the AF_ROUTE socket. It
apparently does weird things to the fd and at least doesn't seem to
close it. Just use the unix package.
The test doesn't actually fail reliably before the fix, though. It
was an attempt. But this fixes the integration tests.
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Previously tailscaled on macOS was running "/sbin/route monitor" as a
child process, but child processes aren't allowed in the Network
Extension / App Store sandbox. Instead, just do what "/sbin/route monitor"
itself does: unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, 0) and read that.
We also parse it now, but don't do anything with the parsed results yet.
We will over time, as we have with Linux netlink messages over time.
Currently any message is considered a signal to poll and see what changed.
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
