fix(canopen): stop a block download's sub-block batch when the transfer ends

[dborgards]

What does this change?

Fixes finding C9 of the 2026-09-30 deep review: a block download sent its sub-block as one ordered batch that nothing could stop. After a server abort or a cancel the rest of the segments still went out, and a server without a session reads them as command specifiers, in the worst case as expedited writes into its dictionary. The batch now checks before each frame whether the transfer's task is complete.

Type of change

• feat — new behaviour (minor release)
• fix / perf — bug or performance fix (patch release)
• docs / test / refactor / chore / ci — no release
• Breaking change (! in the title, plus a BREAKING CHANGE: footer explaining the migration)

Checklist

• dotnet build CanKit.Pro.sln -c Release succeeds (with -p:CI=true)
• dotnet test CanKit.Pro.sln -c Release passes (net10.0, --no-build)
• Public API changes are documented with XML comments — none
• New behaviour is covered by a test — both endings (server abort, cancel); fails with the check disabled
• The requirement or ADR this relates to is referenced — FR-CO-004

Also run: dotnet format --verify-no-changes, dotnet pack + eng/verify-packages.py.

Notes

• The no-more-segments assertion has a 300 ms negative window (nothing signals "nothing more is coming"); it can only pass falsely on a slow host, never fail falsely.
• Not changed: the block-upload server's batch, whose peer is a client that ignores stray segments.

🤖 Generated with Claude Code

[cursor]

PR Summary

Medium Risk
Touches CANopen SDO block TX ordering on a background send path; behavior change is narrow (stop stray segments) but wire-protocol mistakes could affect remote object dictionaries.

Overview
Fixes a case where block download still transmitted the rest of a sub-block after the transfer had already finished (peer abort, caller cancel, timeout, or dispose). Those frames could hit a server with no session and be parsed as SDO command specifiers.

SendOrderedControlFrames now accepts an optional shouldStop predicate, evaluated on the send task before each frame. Block download passes session.Tcs.Task.IsCompleted so the ordered segment batch exits once the transfer task has completed.

A new test covers server abort and caller cancel mid sub-block (first segment held on deferred echo) and asserts no further segments are transmitted.

^{Reviewed by Cursor Bugbot for commit c0bdff5. Bugbot is set up for automated code reviews on this repo. Configure here.}

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-02T04:03:00.214231Z	c0bdff5	PR opened

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