smoltcp is written to allow multiple adapters, so 0.0.0.0 as
the binding for UDP is illegal. However, in Rust, it seems that
0.0.0.0 is "totally fine" and most OSes will resolve this to
a "default" adapter.
this patch introduces the behavior of taking 0.0.0.0 and mapping
it to a default adapter. In fact, we only allow binding to the
default adapter. The reasoning behind this is that if our IP
address changes, we would expect that 0.0.0.0 resolves to that.
Where this scheme fails is if someone binds to 127.0.0.1 expecting
it to not respond to packets coming in from the outside, e.g.
they are using UDP as a loopback interface. I think this isn't
a common use case for Xous, but if it does become one I suppose
we could add a code path to also check for the 127.0.0.1 case
and try to handle it...
the refactor changes the way sockets are handled, so now, when
the interface is rebound we are certain to get panics.
working on resolving this detail now, but at least the interface
is working now and it seems more stable than before.
