When remote peers communicate across networks with mixed connectivity (e.g.
a remote Linux node, a local Linux host, and a Windows VM guest under KVM):
- Previously, `WireguardTransport` immediately created and installed
unverified direct links into `RelayHub` in `notify_peer_capability` and
`open()`. When a remote peer had only unroutable private addresses
(e.g. 192.168.122.151 on a KVM NAT bridge), this dead direct link
preempted the working 2-hop relay, causing packet drops, failed handshakes,
and REKEY_TIMEOUT errors.
- Host-guest VM bridges (`virbr*`) were previously filtered out, preventing
the VM guest from discovering the host's bridge IP (192.168.122.1) and
forcing it to attempt cross-interface connections to host Wi-Fi/LAN.
- Concurrent activation of multiple networks sharing one `tsun0` interface
raced in `sync_addresses`, resulting in netlink `File exists (os error 17)`
and `The object already exists` on Windows.
Key fixes:
- In `crates/tsunagi-wireguard/src/transport.rs`:
- Implement bidirectional UDP probing with `TSUNAGI_WG_PROBE_V1` PING/PONG.
- In `open()`, probe candidate endpoints with retransmission up to 1200ms.
If unreachable, return `TransportError::Unreachable`, preventing dead
links from preempting valid relay routes in `RelayHub`.
- In `notify_peer_capability`, send hole-punching probes without prematurely
installing unverified links.
- In `accept_loop`, reply to PING probes with PONG and install confirmed
inbound links targeting the verified source address.
- In `WireguardLink::send`, inspect byte 74 of enveloped packets to detect
handshake initiations, ensuring confirmed links route data packets only
to the active target.
- In `crates/tsunagi-wireguard/src/plugin.rs`:
- Permit VM bridges (`virbr*`) as candidate interfaces (priority 10).
- Add `prioritize_local_subnet` to prioritize candidates sharing a local
IPv4 subnet with the receiver (e.g. 192.168.122.0/24).
- In `crates/tsunagi/src/overlay/interface.rs` & provisioners:
- Add async mutex `sync_lock` to serialize concurrent address syncs across networks.
- Handle netlink EEXIST (os error 17) and Windows already-exists errors
idempotently as success.
- In `crates/tsunagi-cli/src/main.rs`:
- Split `local addresses` in `tsunagi status` into `announced` (candidate
addresses in priority order with interface and rank), `not announced`
(container bridges/internal addresses with interface name), and `loopback`.
- Tests:
- Add `test_wireguard_transport_unreachable_probe_times_out` and
`test_matches_subnet` unit tests.
Validation on Linux:
- cargo fmt --all -- --check passed.
- cargo clippy --locked --workspace --all-targets -- -D warnings passed.
- cargo test --locked --workspace --all-targets passed (350+ tests passed).
Aleksandr Bogomiakov
35acc4d231