docs(ab): native transport, Transport switch, known gaps and the type-check change

2026-10-07 19:12:32 -04:00
parent 9a576599e1
commit c7f7c940a8
5 changed files with 141 additions and 1 deletions
@@ -76,12 +76,78 @@ the driver's `DriverConfig` JSON. Key fields:
 - **`Devices`** — one `AbCipDeviceOptions` per PLC (`HostAddress`, `PlcFamily`, optional `DeviceName`, per-device `AllowPacking` / `ConnectionSize` overrides).
 - **`Tags`** — pre-declared `AbCipTagDefinition` list; `Members` for UDT fan-out, `SafetyTag` for GuardLogix safety-partition tags.
 - **`Probe`** — connectivity-probe `Enabled` / `Interval` / `Timeout` / `ProbeTagPath`.
+- **`Transport`** — `Libplctag` (default) or `Native`; see [Transport](#transport-transport-option).
 - **Discovery** — `EnableControllerBrowse` (`@tags` walk) and `EnableDeclarationOnlyUdtGrouping` (whole-UDT read fast path).
 - **Alarms** — `EnableAlarmProjection` + `AlarmPollInterval` for the ALMD projection.

 Full per-field descriptions live in `AbCipDriverOptions.cs`. The JSON skeleton is
 reproduced in [docs/v2/driver-specs.md §3](../v2/driver-specs.md).

+## Transport (`transport` option)
+
+The driver has two interchangeable wire transports, selected by one `DriverConfig` key:
+
+| Key | Values | Default | Serialization |
+|---|---|---|---|
+| `transport` | `Libplctag` \| `Native` | `Libplctag` | string, case-insensitive on read, written as `"Libplctag"` / `"Native"` |
+
+- **`Libplctag`** (default) drives the libplctag native library, as before.
+- **`Native`** is a managed in-process EtherNet/IP + CIP client (`Driver.Ab.Transport`). It is **opt-in**:
+  the default stays `Libplctag` until the real-press read-only gate has run and the default is flipped.
+- A bad value fails like a bad `PlcFamily`; the Test Connect probe reports "Config JSON is invalid".
+- A change takes effect when the driver instance is **recreated**. A deploy that changes `DriverConfig`
+  does this (`DriverHostActor` respawns the child, #516). `ReinitializeAsync` alone keeps the transport
+  it was constructed with.
+- AdminUI: the **Transport** dropdown in the advanced section of the AbCip driver form ("libplctag
+  (default)" / "Native (managed)"). Saving another field preserves it.
+- The driver logs `transport=<X>` at Information on every init, including reconnect re-inits. AbCip
+  drivers now receive the host logger (they previously ran on a null logger, so none of their warnings
+  reached the node log); expect previously invisible warnings, e.g. a probe enabled with no probe tag path.
+- CLI: `--transport native|libplctag` (default `libplctag`).
+- libplctag is confined to `Libplctag*.cs` adapters, enforced by a source-scan guard
+  (`LibplctagConfinementGuardTests`), so removing it later is mechanical.
+
+## Native transport behaviour
+
+- **One CIP connection and one request scheduler per device** (`DeviceSessionPool`), shared by reads,
+  writes, browse and template reads. The Multiple Service Packet scheduler coalesces requests with one
+  request in flight; large reads (listing pages, Read Template) are sent unpacked and exclusive.
+- **Forward Open throttle:** at most one attempt in flight, at least 1 s between starts, bounded by the
+  open budget.
+- `ConnectionSize` / `Timeout` are honoured per pooled connection, and the **first** driver/device to open
+  a given device key wins.
+- **Routing:** Micro800 is connected with an empty route regardless of `UseConnectedMessaging`.
+  SLC500/MicroLogix/PLC-5 over this driver are direct. `logixpccc` uses UnconnectedSend; its SLC framing is
+  **unverified**.
+- ⚠️ **Type check (client-visible change).** The native path compares the type code the controller returns
+  with the authored `DataType` and reports **`BadTypeMismatch`** on disagreement. libplctag never checks it,
+  so a same-width mis-authored tag read as **Good garbage**: authoring a tag as `DINT` while the controller
+  holds a `REAL` returns the REAL's bits as an integer with a Good status under libplctag, and
+  `BadTypeMismatch` natively. That is the fix working, but a consumer will see Bad quality on tags that
+  previously looked healthy: correct the authored type. Same-width signed/unsigned pairs are exempt, and
+  writes are gated on a mismatch too.
+- Malformed tag names put the device into backoff, as under libplctag (#570). STRING capacity includes the
+  alignment pad (84, not 82) (#570).
+- Status-bit sub-element writes (e.g. `T4:0/DN`) are Unsupported natively (they would clobber the control
+  word); nothing goes on the wire. Sub-element arrays are Unsupported natively.
+
+## Known gaps
+
+- ⚠️ **Native writes are verified against `ab_server` only (simulator-only), never a real controller.** The
+  real-press gate (Task 21) is **read-only** and **has not run yet**; this page makes no real-controller
+  claim for the native transport. Results land in
+  [native-ab-transport-gate-results](../plans/2026-10-07-native-ab-transport-gate-results.md).
+- **libplctag cannot be deleted** until a bench controller allows write verification.
+- Wide-struct fragmented writes (8-byte alignment) are unit-tested only, never proven on a controller (#567).
+- Native browse: listing pages are unpaced, and template reads outside an enumeration open a connection per
+  call (#572).
+- Micro800, routed and `logixpccc` paths are covered by `ab_server` only. The Micro800 profile passes
+  natively; the planned default flip excludes `logixpccc`.
+- Follow-up issues for this workstream: #564 to #577.
+- Fixed along the way (pre-existing on master): `ab://host:44818/` with an empty CIP path (Micro800,
+  unrouted MicroLogix) failed on libplctag with `ErrorBadData` because the adapter sent `Path=""`; it now
+  sends no path.
+
 ## Alarm Projection

 `IAlarmSource` is served by `AbCipAlarmProjection`, which polls each subscribed
@@ -190,7 +256,7 @@ UDT-typed tags found in the walk.
 - **Native heap is invisible to the GC.** libplctag's native `Tag` heap does not show up in CLR allocation figures. Watch whole-process RSS, and use `ReinitializeAsync` (tears down + re-creates every device's libplctag handles) as the remediation for native-heap growth. (There is no per-driver footprint number to consult: `IDriver.GetMemoryFootprint()` was deleted as unconsumed in Gitea #525.)
 - **Handle eviction on failure** — a non-zero libplctag status or a transport exception evicts the cached tag runtime so the next read/write re-creates a fresh handle, mirroring the probe loop's recreate-on-failure behaviour.
 - **Read statuses carry the libplctag cause** — a tag the controller does not have reads `BadNodeIdUnknown` (not `BadCommunicationError`), and it does **not** open the device's connect-backoff window (the controller answered; before this, one typo throttled every sibling tag on the device). A genuine connection failure still opens it.
- **Width check on scalar reads** — libplctag never checks the CIP type the controller returns. A scalar atomic read whose buffer is not the authored type's width (e.g. a REAL authored as INT — the legacy Kepware export does exactly this for some press tags) reads `BadTypeMismatch` instead of Good garbage. Same-width mistakes (DINT vs REAL) are still undetectable.
+- **Width check on scalar reads** — libplctag never checks the CIP type the controller returns. A scalar atomic read whose buffer is not the authored type's width (e.g. a REAL authored as INT — the legacy Kepware export does exactly this for some press tags) reads `BadTypeMismatch` instead of Good garbage. Same-width mistakes (DINT vs REAL) are undetectable under libplctag; the `Native` transport reports them as `BadTypeMismatch` (see [Native transport behaviour](#native-transport-behaviour)).
 - **Module-defined I/O tags** — `Local:1:I.Data`, `ABB_OmniCore:I.ConnectionFaulted` and similar colon-bearing base names are valid tag paths (controller scope only).
 - **User string arrays** — `STR0016[N]` and similar arrays stride by the actual element size (read buffer ÷ count); libplctag.NET 1.5.2 leaves `ElementSize` unset after a read.
 - **Declaration-only UDT grouping is a footgun unless verified** — only enable `EnableDeclarationOnlyUdtGrouping` when every UDT's member declaration order has been hand-verified against the controller's compiled layout.
@@ -32,6 +32,17 @@ still the primary coverage. All tests tagged `[Trait("Category", "Unit")]`.
 The driver accepts `IAbLegacyTagFactory` via ctor DI; every test
 supplies a `FakeAbLegacyTag`.

+## Per-transport suites and capture recipe
+
+The `AbLegacy.IntegrationTests` suites now run **once per transport** (`TransportMatrix`: `Libplctag` and
+`Native`). Set `AB_LEGACY_COMPOSE_PROFILE` to the running profile. On the 2026-10-07 run native passed
+everything libplctag passed on `slc500`, `micrologix` and `plc5` (the PLC-5 test reads N7 only, so the PLC-5
+refusal paths and status-bit writes are not exercised by it). Native PCCC is **simulator-only**. Write-capable
+tests (the SLC500 N7:5 round trip) require `AB_SERVER_ALLOW_WRITES=1`. Golden frames:
+`scripts/ab-capture/capture.sh`, fixtures under
+`tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Ab.Transport.Tests/Captures/`. Evidence:
+[native-ab-transport-gate-results](../plans/2026-10-07-native-ab-transport-gate-results.md).
+
 ## What it actually covers (unit only)

 - `AbLegacyAddressTests` — PCCC address parsing for SLC / MicroLogix / PLC-5
@@ -93,10 +93,39 @@ binds from the driver's `DriverConfig` JSON:
 - **`Devices`** — one `AbLegacyDeviceOptions` per PLC (`HostAddress`, `PlcFamily`, optional `DeviceName`).
 - **`Tags`** — pre-declared `AbLegacyTagDefinition` list (`Name`, `DeviceHostAddress`, `Address`, `DataType`, `Writable`, `WriteIdempotent`).
 - **`Probe`** — connectivity-probe `Enabled` / `Interval` / `Timeout` / `ProbeAddress`.
+- **`Transport`** — `Libplctag` (default) or `Native`; see [Transport](#transport-transport-option).

 Full per-field descriptions live in the contracts assembly. The JSON skeleton is
 reproduced in [docs/v2/driver-specs.md §4](../v2/driver-specs.md).

+## Transport (`transport` option)
+
+Same switch as AB CIP: `transport` = `Libplctag` (default) \| `Native`, a string (case-insensitive on read,
+written as `"Libplctag"` / `"Native"`). `Native` is a managed PCCC-over-EtherNet/IP client
+(`Driver.Ab.Transport`) and is **opt-in**; the default stays `Libplctag` pending the real-press gate and the
+default flip. A change takes effect when the driver instance is recreated (a deploy that changes
+`DriverConfig`); the AdminUI form has a **Transport** dropdown in the advanced section, and the driver logs
+`transport=<X>` on every init. CLI: `--transport native|libplctag`. See
+[AbCip.md §Transport](AbCip.md#transport-transport-option) for the shared behaviour (one pooled connection
+per device, Forward Open throttle, routing).
+
+Native routing: SLC500/MicroLogix/PLC-5 are direct; `logixpccc` uses UnconnectedSend and its SLC framing is
+**unverified**.
+
+### Native known gaps
+
+- ⚠️ **Simulator-only.** PCCC reads and writes are verified against `ab_server` only. No real SLC/MicroLogix/
+  PLC-5 has been exercised, and the real-press gate (Task 21) is read-only and has not run yet.
+- **PLC-5 native is N-file reads only.** Every other file type and all PLC-5 writes are refused, currently
+  surfacing as `BadCommunicationError` rather than `BadNotSupported` (#571). The planned default flip excludes
+  PLC-5 and `logixpccc`.
+- Status-bit sub-element writes (e.g. `T4:0/DN`, `C5:0/DN`) are Unsupported natively (they would clobber the
+  control word); nothing goes on the wire. Sub-element arrays are Unsupported natively. L-file bit indexes
+  above 15 are allowed.
+- **ST (string) file layout is uncaptured**, so the string byte order is unverified natively.
+- Capture recipe for golden frames: `scripts/ab-capture/capture.sh` (see
+  [AbLegacy-Test-Fixture.md](AbLegacy-Test-Fixture.md)). Follow-up issues: #564 to #577.
+
 ## Testing

 - **Unit tests** — `tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.Tests/` cover the driver, the PCCC address parser, and the host-address parser via fake tag runtimes.
@@ -33,6 +33,28 @@ quirk. UDT / alarm / quirk behavior is verified only by unit tests with
 - **Endpoint override**: `AB_SERVER_ENDPOINT=host:port` points the
  fixture at a real PLC instead of the local container.

+## Per-transport suites and capture recipe
+
+Every integration test in `AbCip.IntegrationTests` now runs **once per transport** (`TransportMatrix`:
+`Libplctag` and `Native`). Run one compose profile at a time and name it with `AB_SERVER_COMPOSE_PROFILE`
+(all profiles bind `:44818`, so set it to the running profile). On the 2026-10-07 run native passed everything
+libplctag passed on all seven profiles; on `micro800` libplctag failed on the empty-path defect described in
+[AbCip.md](AbCip.md#known-gaps) and native passed. Evidence:
+[native-ab-transport-gate-results](../plans/2026-10-07-native-ab-transport-gate-results.md).
+
+- Write-capable tests (the Logix Emulate ALMD test) require `AB_SERVER_ALLOW_WRITES=1` and refuse while
+  `AB_DIFF_ENDPOINT` is set.
+- **Differential harness** (`AbCip.IntegrationTests/Differential`, `LiveIntegration`) compares libplctag and
+  native on browse, template and read parity against one endpoint. It is read-only by construction, aborts on
+  the first connection failure, never retries, and caps the native phase at one Forward Open. Env:
+  `AB_DIFF_ENDPOINT`, `AB_DIFF_PATH`, `AB_DIFF_FAMILY`, `AB_DIFF_TAGS`, `AB_DIFF_MAX_TAGS` (at most 500),
+  `AB_DIFF_MAX_TEMPLATES`, `AB_DIFF_PACE_MS` (default 20), `AB_DIFF_COUNT_OPENS`. Always run with
+  `--filter "FullyQualifiedName~Differential"` and `AB_SERVER_ENDPOINT=127.0.0.1:1`.
+- ab_server serves no UDTs and refuses 1-byte writes, so template parity is vacuous there and BOOL/SINT
+  parity is weak evidence. Native writes remain simulator-only.
+- **Golden-frame capture:** `scripts/ab-capture/capture.sh` (capture client in `scripts/ab-capture/client`);
+  fixtures live in `tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Ab.Transport.Tests/Captures/` with a README.
+
 ## What it actually covers

 - Read path: driver → libplctag → CIP-over-EtherNet/IP → simulator → back.