Same-LAN P2P was failing because MikroTik masquerade (like most
consumer NATs) doesn't support NAT hairpinning — the advertised
WAN reflex addr is unreachable from a peer on the same LAN as
the advertiser. Phase 5 got us Cone NAT classification and fixed
the measurement artifact, but same-LAN direct dials still had
nowhere to land.
Phase 5.5 adds ICE-style host candidates: each client enumerates
its LAN-local network interface addresses, includes them in the
DirectCallOffer/Answer alongside the reflex addr, and the
dual-path race fans out to ALL peer candidates in parallel.
Same-LAN peers find each other via their RFC1918 IPv4 + ULA /
global-unicast IPv6 addresses without touching the NAT at all.
Dual-stack IPv6 is in scope from the start — on modern ISPs
(including Starlink) the v6 path often works even when v4
hairpinning doesn't, because there's no NAT on the v6 side.
## Changes
### `wzp_client::reflect::local_host_candidates(port)` (new)
Enumerates network interfaces via `if-addrs` and returns
SocketAddrs paired with the caller's port. Filters:
- IPv4: RFC1918 (10/8, 172.16/12, 192.168/16) + CGNAT (100.64/10)
- IPv6: global unicast (2000::/3) + ULA (fc00::/7)
- Skipped: loopback, link-local (169.254, fe80::), public v4
(already covered by reflex-addr), unspecified
Safe from any thread, one `getifaddrs(3)` syscall.
### Wire protocol (wzp-proto/packet.rs)
Three new `#[serde(default, skip_serializing_if = "Vec::is_empty")]`
fields, backward-compat with pre-5.5 clients/relays by
construction:
- `DirectCallOffer.caller_local_addrs: Vec<String>`
- `DirectCallAnswer.callee_local_addrs: Vec<String>`
- `CallSetup.peer_local_addrs: Vec<String>`
### Call registry (wzp-relay/call_registry.rs)
`DirectCall` gains `caller_local_addrs` + `callee_local_addrs`
Vec<String> fields. New `set_caller_local_addrs` /
`set_callee_local_addrs` setters. Follow the same pattern as
the reflex addr fields.
### Relay cross-wiring (wzp-relay/main.rs)
Both the local-call and cross-relay-federation paths now track
the local_addrs through the registry and inject them into the
CallSetup's peer_local_addrs. Cross-wiring is identical to the
existing peer_direct_addr logic — each party's CallSetup
carries the OTHER party's LAN candidates.
### Client side (desktop/src-tauri/lib.rs)
- `place_call`: gathers local host candidates via
`local_host_candidates(signal_endpoint.local_addr().port())`
and includes them in `DirectCallOffer.caller_local_addrs`.
The port match is critical — it's the Phase 5 shared signal
socket, so incoming dials to these addrs land on the same
endpoint that's already listening.
- `answer_call`: same, AcceptTrusted only (privacy mode keeps
LAN addrs hidden too, for consistency with the reflex addr).
- `connect` Tauri command: new `peer_local_addrs: Vec<String>`
arg. Builds a `PeerCandidates` bundle and passes it to the
dual-path race.
- Recv loop's CallSetup handler: destructures + forwards the
new field to JS via the signal-event payload.
### `dual_path::race` (wzp-client/dual_path.rs)
Signature change: takes `PeerCandidates` (reflex + local Vec)
instead of a single SocketAddr. The D-role branch now fans out
N parallel dials via `tokio::task::JoinSet` — one per candidate
— and the first successful dial wins (losers are aborted
immediately via `set.abort_all()`). Only when ALL candidates
have failed do we return Err; individual candidate failures are
just traced at debug level and the race waits for the others.
LAN host candidates are tried BEFORE the reflex addr in
`PeerCandidates::dial_order()` — they're faster when they work,
and the reflex addr is the fallback for the not-on-same-LAN
case.
### JS side (desktop/main.ts)
`connect` invoke now passes `peerLocalAddrs: data.peer_local_addrs ?? []`
alongside the existing `peerDirectAddr`.
### Tests
All existing test callsites updated for the new Vec<String>
fields (defaults to Vec::new() in tests — they don't exercise
the multi-candidate path). `dual_path.rs` integration tests
wrap the single `dead_peer` / `acceptor_listen_addr` in a
`PeerCandidates { reflexive: Some(_), local: Vec::new() }`.
Full workspace test: 423 passing (same as before 5.5).
## Expected behavior on the reporter's setup
Two phones behind MikroTik, both on the same LAN:
place_call:host_candidates {"local_addrs": ["192.168.88.21:XXX", "2001:...:YY:XXX"]}
recv:DirectCallAnswer {"callee_local_addrs": ["192.168.88.22:ZZZ", "2001:...:WW:ZZZ"]}
recv:CallSetup {"peer_direct_addr":"150.228.49.65:NN",
"peer_local_addrs":["192.168.88.22:ZZZ","2001:...:WW:ZZZ"]}
connect:dual_path_race_start {"peer_reflex":"...","peer_local":[...]}
dual_path: direct dial succeeded on candidate 0 ← LAN v4 wins
connect:dual_path_race_won {"path":"Direct"}
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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