stdnet.NewNet and NewNetWithDiscover ended with
return n, n.UpdateInterfaces()
handing back a non-nil *Net together with the discovery error. Three of the
five call sites (Engine.newWgIface, ice.NewAgent, SingleSocketUDPMux) logged
the error and kept using the instance, which is only safe as long as the
instance still works after a failed discovery.
That stopped being true when Interfaces() gained a lazily refreshed cache:
updateInterfaces sets lastUpdate only on success, so after a failed
construction the 30s cache guard never holds and Interfaces() returns an
error rather than the empty list it used to return. Feeding such an instance
to pion is worse than passing nothing at all - ice.NewAgent falls back to its
own stdnet when Net is nil, and the interface blacklist is applied separately
through AgentConfig.InterfaceFilter, so the fallback loses nothing. Instead,
a transient discovery failure (the Android bridge at boot, or an interface
disappearing between net.Interfaces() and Interface.Addrs()) turned into a
hard "error getting local interfaces" from ice.NewAgent, and aborted the STUN
and TURN probes, which never even need the interface list.
Since the accessors already refresh a stale cache on demand, the eager
discovery in the constructors is redundant: drop it, make both constructors
infallible, and let the discovery error surface at the call that actually
needs the interfaces. UpdateInterfaces had no callers left and is not part of
transport.Net, so it is removed along with it.
InterfaceByIndex and InterfaceByName read the cached slice directly and never
refreshed it, so they would have kept reporting ErrInterfaceNotFound forever
on an instance whose first discovery failed. They now go through the same
refresh path as Interfaces().
This PR adds supports for the WireGuard userspace implementation
using Bind interface from wireguard-go.
The newly introduced ICEBind struct implements Bind with UDPMux-based
structs from pion/ice to handle hole punching using ICE.
The core implementation was taken from StdBind of wireguard-go.
The result is a single WireGuard port that is used for host and server reflexive candidates.
Relay candidates are still handled separately and will be integrated in the following PRs.
ICEBind checks the incoming packets for being STUN or WireGuard ones
and routes them to UDPMux (to handle hole punching) or to WireGuard respectively.
On Android, because of the hard SELinux policies can not list the
interfaces of the ICE package. Without it can not generate a host type
candidate. In this pull request, the list of interfaces comes via the Java
interface.
riccardom