P0: opt-in negotiated MMS NameList wire pipeline with exact response routing

[masarray]

P0 milestone: bounded, negotiated wire-level GetNameList pipelining (opt-in)

Baseline main bcbebc32ad19836cfd79ab05c1dec73e295b8721. Builds on merged #185 (measured wire budget) and #187 (orphan invoke-ID fail-closed). No existing concurrent dispatcher, no additional receive threads, no duplicate MMS client, no rewrite.

Root cause and implementation

Serial exchange_confirmed waits for every response before the next independent per-domain NameList request. Actual MMS Initiate-Response can strictly negotiate maxOutstandingCalling > 1; today this remains unused. Naively multithreading calls would race socket receive and COTP reassembly.

• New exchange_confirmed_batch is a single association-owned synchronous dispatcher: validate every confirmed P-DATA + unique invoke ID and verified negotiated calling window before sending, serialize complete MMS/COTP sends, receive from the one authoritative socket, route interleaved InformationReports, accept out-of-order confirmation by exact registered invoke-ID, reject unregistered/duplicate/stale responses, and return deterministic input-order results.
• Strictly decoded, positive peer window required. Tolerant ACSE decode cannot claim concurrency; effective cap min(peer maxOutstandingCalling, 8, operator request). No external std::async, concurrent sockets, arbitrary sleep or cyclic Read.
• MmsLiveDiscoveryClient introduces optional bounded domain/class GetNameList chains; each chain's continuation pages remain sequential and preserve exact case-sensitive identifiers, name order, bounds and failure evidence. Unattempted/unverified pages are never fabricated. Serial is unchanged by default; unknown peer capabilities safely fall back to serial.
• Field-lab CLI opt-in: ariec61850_live_discover <host> --name-list-window 4 (valid 1..8, default 1). Workbench and other existing consumers retain serial mode by default.
• Zero-traffic KPI: actual fully transmitted GetNameList request count plus highest issued-but-not-yet-read name-list window in discovery summary. Number of MMS service requests should remain equal for equivalent models; latency reduction is not claimed until same-IED repeat runs with packet evidence.

Negative and parity regression

• 2-LD fixture: serial vs four independent outstanding chains, responses delivered in inverse invoke order, with pagination. Exact full variable/DataSet inventories and wire-request count parity.
• Interleaved InformationReport, mismatched/duplicate invoke-ID and oversized batch must not map false results; no unsent request passes as successful.
• Caller send receipts persist after timeout/fault; batch aborts/connection closes and can reconnect. Truncated/no-forward-progress continuation fails closed without fabricating missing variables. Faulted association retains only VMD-proven domains.
• Existing MMS SCL, Reporting/RCB, Qt Workbench and Studio unchanged at their respective ownership boundaries.

Acceptance gates

Require exact-head completed C++ CI (GCC/Clang/MSVC), native Workbench, SCL-assisted, protocol/security and Product Naming Guard, plus review-thread clearance. Do not merge pending/skipped checks. Physical IED acceptance, Windows installed Workbench acceptance, and measurable speedup remain separate gates.

Known unrelated current main IED Simulator Release Hardening failure: Windows NSIS Chocolatey feed HTTP 503 on dependency retrieval, before build, not evidence of protocol regression; distinguish infra from actual build/test failures.

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-16T11:10:04.887781Z	b491387	PR opened

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