Before Phase 5 WarzonePhone used THREE separate UDP sockets per
client:
1. Signal endpoint (register_signal, client-only)
2. Reflect probe endpoints (one fresh socket per relay probe)
3. Dual-path race endpoint (fresh per call setup)
This broke two things in production on port-preserving NATs
(MikroTik masquerade, most consumer routers):
a. Phase 2 NAT detection was WRONG. Each probe used a fresh
internal port, so MikroTik mapped each one to a different
external port, and the classifier saw "different port per
relay" and labeled it SymmetricPort. The real NAT was
cone-like but measurement via fresh sockets hid that.
b. Phase 3.5 dual-path P2P race was BROKEN. The reflex addr
we advertised in DirectCallOffer was observed by the signal
endpoint's socket. The actual dual-path race listened on a
DIFFERENT fresh socket, on a different internal (and
therefore external) port. Peers dialed the advertised addr
and hit MikroTik's mapping for the signal socket, which
forwarded to the signal endpoint — a client-only endpoint
that doesn't accept incoming connections. Direct path
silently failed, relay always won the race.
Nebula-style fix: one socket for everything. The signal endpoint
is now dual-purpose (client + server_config), and both the
reflect probes and the dual-path race reuse it instead of
creating fresh ones. MikroTik's port-preservation then gives us
a stable external port across all flows → classifier correctly
sees Cone NAT → advertised reflex addr is the actual listening
port → direct dials from peers land on the right socket →
`endpoint.accept()` in the A-role branch of the dual-path race
picks up the incoming connection.
## Changes
### `register_signal` (desktop/src-tauri/src/lib.rs)
- Endpoint now created with `Some(server_config())` instead of
`None`. The socket can now accept incoming QUIC connections as
well as dial outbound.
- Every code path that previously read `sig.endpoint` for the
relay-dial reuse benefits automatically — same socket is now
ALSO listening for peer dials.
### `probe_reflect_addr` (wzp-client/src/reflect.rs)
- New `existing_endpoint: Option<Endpoint>` arg. `Some` reuses
the caller's socket (production: pass the signal endpoint).
`None` creates a fresh one (tests + pre-registration).
- Removed the `drop(endpoint)` at the end — was correct for
fresh endpoints (explicit early socket close) but incorrect
for shared ones. End-of-scope drop does the right thing in
both cases via Arc semantics.
### `detect_nat_type` (wzp-client/src/reflect.rs)
- New `shared_endpoint: Option<Endpoint>` arg, forwarded to
every probe in the JoinSet fan-out. One shared socket means
the classifier sees the true NAT type.
### `detect_nat_type` Tauri command (desktop/src-tauri/src/lib.rs)
- Reads `state.signal.endpoint` and passes it as the shared
endpoint. Falls back to None when not registered. NAT detection
now produces accurate classifications against MikroTik / most
consumer NATs.
### `dual_path::race` (wzp-client/src/dual_path.rs)
- New `shared_endpoint: Option<Endpoint>` arg.
- A-role: when `Some`, reuses it for `accept()`. This is the
critical change — the reflex addr advertised to peers is now
the address listening for incoming direct dials.
- D-role: when `Some`, reuses it for the outbound direct dial.
MikroTik keeps the same external port for the dial as for
the signal flow → direct dial through a cone-mapped NAT.
- Relay path: also reuses the shared endpoint so MikroTik has
a single consistent mapping across the whole call (saves one
extra external port and makes firewall traces cleaner).
- When `None`, falls back to fresh per-role endpoints as before.
### `connect` Tauri command (desktop/src-tauri/src/lib.rs)
- Reads `state.signal.endpoint` once when acquiring own reflex
addr and passes it through to `dual_path::race`.
### Tests
- `wzp-client/tests/dual_path.rs` and
`wzp-relay/tests/multi_reflect.rs` updated to pass `None` for
the new endpoint arg — tests use fresh sockets and that's
fine because the loopback harness doesn't care about
port-preserving NAT behavior.
Full workspace test: 423 passing (no regressions).
## Expected behavior after this commit on real hardware
Behind MikroTik + Starlink-bypass (the reporter's setup):
- Phase 2 NAT detect → **Cone NAT** (was SymmetricPort — false
positive from the measurement artifact)
- Phase 3.5 direct-P2P dial → succeeds for both cone-cone and
cone-CGNAT cases where the remote side was previously blocked
by our own socket mismatch
- LTE ↔ LTE cross-carrier → still likely relay fallback; that's
genuinely strict symmetric and needs Phase 5.5 port prediction.
## Phase 5.5 (next, separate PRD)
Multi-candidate port prediction + ICE-style candidate aggregation
for truly strict symmetric NATs. Not needed for the 95% case —
Phase 5 alone fixes most consumer-router setups.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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