Vagrant should only consider the host-only interfaces used by the
virtual machine in the IPv6 fixup code. There may be other interfaces
present on the system with IPv6 addresses that for various reasons
would fail the routing check (for example, an interface with no
machines attached).
The patch changes the behavior to not scan all of the host-only
interfaces and adds a unit test for the behavior (that the correct IP
is validated).
Lastly, there is a small fix here that may not be an issue for most
people where the IPv6 prefix was asummed to be a multiple of 16 for
the purposes of constructing the UDP probe datagram. This assumption
has been removed.
Fixes#6586
VirtualBox has a bug where the IPv6 route is lost on every other
configuration of a host-only network. This is also triggered when a VM
is booted.
To fix this, we test the route-ability of all IPv6 networks, and
reconfigure if necessary. This is very fast but we still only do this if
we have any IPv6 networks.
Seth Vargo
Timur Alperovich
Mitchell Hashimoto