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[M5] mxaccess: F26 step 2 — AsbTransport::connect TCP+preamble+handshake

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Adds the `tokio::net::TcpStream`-specialised async constructor that
owns the full transport-bring-up sequence:

  TCP connect → NMF preamble → DH Connect → AuthenticateMe (one-way)

Signature:
```
async fn connect(
    endpoint: SocketAddr,
    passphrase: &str,
    crypto_parameters: &CryptoParameters,
    via_uri: impl Into<String>,
    connection_id: [u8; 16],
) -> Result<(AsbTransport<TcpStream>, ConnectResponse), Error>
```

Returns the `ConnectResponse` alongside the transport so callers can
inspect the negotiated `connection_lifetime` (the `:V2` suffix
toggles Apollo vs Baktun encryption — see F23).

New error variant: `ConnectionError::TransportFailure { detail }`
covers all transport-bring-up failure modes (NMF / NBFX / auth /
peer Fault). The underlying error type is intentionally erased to
keep the public taxonomy small; `detail` carries the Display
representation.

Errors are mapped at the AsbClient / AuthError boundary via private
`map_client_error` / `map_auth_error` helpers.

1 new test:
* `connect_to_unreachable_endpoint_surfaces_connection_error` — TCP
  connect to 127.0.0.1:1 (TCPMUX-reserved) cleanly errors without
  panicking. Smoke test for the constructor signature + error path.

Stubbed for F26 step 3:
* `Session::connect_asb` constructor — the SessionInner refactor to
  host both NMX + ASB transports under one struct is heavier than
  this iteration's scope.
* Operation-routing layer that maps ASB result types (ItemStatus,
  RuntimeValue) back to mxaccess types (MxStatus, DataChange,
  MxValue).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Joseph Doherty
2026-05-05 12:14:16 -04:00
parent 8a0f92b6bc
commit 14bb5297a8
3 changed files with 103 additions and 4 deletions
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design/followups.md
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@@ -46,7 +46,11 @@ move to `## Resolved` with a date + commit hash.
**Resolves when:** F19-F26 are all closed and the four DoD bullets above pass.
**Cumulative execution log.** F19 + F23 (`ed17c07`); F24 (`7611d9e`); F20 (`9dfd193`); F22 (`43c10a1`); F21 (`5f98558`); F25 step 1 (`25dbd8d`); F25 step 2 (`a2b8989`); F25 step 3 (`c4bf0a0`); F25 step 4 (`1e59249`); F25 step 5 (`9b8133f`); F25 step 6 (`321b796`); F25 step 7 (`1b1ee1e`); F26 step 1 landed in this commit:
**Cumulative execution log.** F19 + F23 (`ed17c07`); F24 (`7611d9e`); F20 (`9dfd193`); F22 (`43c10a1`); F21 (`5f98558`); F25 step 1 (`25dbd8d`); F25 step 2 (`a2b8989`); F25 step 3 (`c4bf0a0`); F25 step 4 (`1e59249`); F25 step 5 (`9b8133f`); F25 step 6 (`321b796`); F25 step 7 (`1b1ee1e`); F26 step 1 (`8a0f92b`); F26 step 2 landed in this commit:
- F26 step 2: `AsbTransport::connect(endpoint, passphrase, crypto_parameters, via_uri, connection_id)` — `tokio::net::TcpStream`-specialised async constructor that owns the full transport-bring-up sequence: TCP connect → NMF preamble exchange → DH Connect handshake → AuthenticateMe one-way (signed). Returns `(AsbTransport<TcpStream>, ConnectResponse)` so callers can inspect the negotiated lifetime / Apollo-vs-Baktun flag from the response. New `ConnectionError::TransportFailure { detail }` variant carries the underlying error message (NMF / NBFX / auth / I/O) without exploding the public taxonomy. Errors are mapped at the AsbClient/Auth boundary via `map_client_error` / `map_auth_error` helpers. 1 new test confirms a connect to an unreachable endpoint (127.0.0.1:1, TCPMUX-reserved) surfaces an `Err` cleanly without panicking. **Stubbed for F26 step 3:** `Session::connect_asb` constructor (the SessionInner refactor needed to host both NMX + ASB transports under one struct is heavier than this iteration's scope), plus the operation-routing layer that maps ASB result types (`ItemStatus`, `RuntimeValue`) back to `mxaccess` types (`MxStatus`, `DataChange`, `MxValue`).
**Earlier slices:**
- F26 step 1 (commit `8a0f92b`):
- F26 step 1: `mxaccess::AsbTransport` — bridges F25's `AsbClient` into the M0 `Transport` trait. Generic over `T: AsyncRead + AsyncWrite + Unpin + Send + Sync + 'static` (the same bounds AsbClient takes). `Transport::capabilities()` returns the ASB-specific flags per `design/60-roadmap.md` M5: `buffered_subscribe = false`, `activate_suspend = false`, `operation_complete_frame = false`. `Transport::kind()` returns `TransportKind::Asb`. `AsbTransport::new(client)` / `into_client()` / `client_mut()` for transport↔client conversion. New deps: `mxaccess` now path-deps `mxaccess-asb` + `mxaccess-asb-nettcp`. Compile-time `Send + Sync + 'static` assertion guards the trait-bound contract. 2 new tests: kind == Asb; capabilities all false. **Stubbed for F26 step 2:** `Session::connect_asb` constructor that owns the full TCP-open + preamble + DH handshake orchestration, plus operation routing that maps ASB types (`ItemStatus`, `RuntimeValue`) back to `mxaccess` types (`MxStatus`, `DataChange`, `MxValue`). Stubbed for F26 step 3: subscription routing — `Session::subscribe` on ASB maps to a `CreateSubscription` + `AddMonitoredItems` + `Publish`-callback pipeline; F25 subscription operations themselves are not yet implemented.
**Earlier slices:**