The router used to call NmxSubscriptionMessage::parse_inner directly
on the COM-stub-delivered body, but the wire bytes arrive wrapped in
a ProcessDataReceived envelope (46-byte header + optional 4-byte
length prefix); parse_inner expects post-envelope bytes. Result:
every 0x33 DataUpdate that ever arrived was silently dropped.
Mirrors the .NET reference's MxNativeSession.OnCallbackReceived flow
at cs:582-606 — three sequential parse attempts:
1. NmxOperationStatusMessage::try_parse_process_data_received_body (already wired)
2. NmxReferenceRegistrationResultMessage::try_parse_... (NEW — was missing)
3. NmxSubscriptionMessage::try_parse_process_data_received_body (NEW — was wrong)
Adds:
- NmxSubscriptionMessage::try_parse_process_data_received_body — peels
envelope via NmxObservedEnvelope::parse_process_data_received_body_flexible,
then dispatches to existing parse_inner.
- NmxReferenceRegistrationResultMessage::try_parse_process_data_received_body —
same shape, for the 0x11 registration-result frame.
- Router branch for 0x11 — currently traces the assigned item_handle and
drops the frame (matches the .NET reference, which fires a
ReferenceRegistrationReceived event with no consumer in the codebase).
- Router fall-through trace! when neither path matches, so future
unparseable bodies surface in RUST_LOG=trace instead of vanishing.
- DcomCallbackSink::forward — trace! per inbound callback so
RUST_LOG=mxaccess_callback=trace surfaces opnum + size.
- crates/mxaccess-compat/tests/buffered_subscribe_live.rs — F49 step 1
live test that drives subscribe_buffered + a 500ms-cadence writer.
Also pulls tracing-subscriber as a dev-dep so the test can dump
router activity.
Existing router_task_decodes_callback_invoked_into_broadcast unit test
updated to wrap its synthetic 0x32 body in an envelope so the new
parse path actually accepts it.
Live result: F56 — the buffered round-trip *registers* successfully
(RegisterReference returns HRESULT 0; engine sends one 0x11
RegistrationResult + one 51-byte op-status per write, perfectly
clocked) but the engine never sends a 0x33 DataUpdate. Rust-port-
specific gap vs the .NET reference's working buffered path; root
cause is likely a field-level difference in the RegisterReference
body or a missing post-RegisterReference step. Captured as F56 in
design/followups.md, blocking F49 step 1; F56's DoD is the same
live test reporting >=3 DataChange arrivals.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Replace the hand-rolled CallbackExporter (TCP listener + custom
OBJREF) with a real `windows-rs` `#[implement]` COM class for
INmxSvcCallback, marshalled via CoMarshalInterface. NmxSvc validates
the callback OBJREF by calling IObjectExporter::ResolveOxid against
the local RPCSS at 127.0.0.1:135; hand-rolled OXIDs aren't registered
there, which is why RegisterEngine2 returned RPC_S_SERVER_UNAVAILABLE
(1722) on every live attempt. CoMarshalInterface registers the OXID
with RPCSS automatically, so the SCM-side resolution succeeds.
Mirrors MxNativeSession.CreateRegisteredService (cs:624), which is
the .NET reference's working path:
ComObjRefProvider.MarshalInterfaceObjRef(callback,
INmxSvcCallback, DifferentMachine)
Layout:
- mxaccess-callback::dcom_sink — INmxSvcCallback + DcomCallbackSink
+ create_dcom_callback_sink_objref. Forwards inbound calls into
the same CallbackEvent::CallbackInvoked { opnum, body } shape the
legacy exporter produces, so callback_router stays path-agnostic.
- Session::from_nmx_client — branched on `windows-com`. Real DCOM
sink when on; legacy CallbackExporter when off (kept for unit
tests that run against an in-process fake NMX peer).
- SessionInner.dcom_sink_holder: Option<IUnknownHolder> — keeps the
COM ref alive for the session's lifetime; shutdown_nmx drops it.
- mxaccess-rpc + mxaccess-callback: windows-rs 0.59 → 0.62. The 0.59
#[implement] macro generates code that doesn't compile under
edition 2024; 0.62 is fixed.
Live result: cargo test -p mxaccess-compat --features
live-windows-com --test lmx_write_complete_live -- --ignored
--nocapture passes end-to-end. RegisterEngine2 OK, write
round-trips, OnWriteComplete fires with the captured MxStatus shape.
Unblocks F49 step 5; F55 marked Resolved in design/followups.md.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Joseph Doherty