DERP works for everything but adds relay latency. Add a parallel UDP
transport so peers with reachable endpoints can talk directly:
- wg/tunnel: track each peer's local boringtun index in PeerTunnel and
expose find_peer_by_local_index / find_peer_by_endpoint lookups
- daemon/lifecycle: bind a UdpSocket on 0.0.0.0:0 alongside DERP, run
the recv loop on a clone of an Arc<UdpSocket> so send and recv can
proceed concurrently
- run_wg_loop: new udp_in_rx select arm. For inbound UDP we identify
the source peer by parsing the WireGuard receiver_index out of the
packet header (msg types 2/3/4) and falling back to source-address
matching for type-1 handshake initiations
- dispatch_encap: SendUdp now actually forwards via the UDP channel
UDP failure is non-fatal — DERP can carry traffic alone if the bind
fails or packets are dropped.
Sienna Meridian Satterwhite
85d34bb035
