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Safety Plan — cpp-LIN

Document ID: SP-cpp-LIN-001
Revision: 0.1
Date: 2026-06-19
Author: Matt Jones
ASIL Target: ASIL-B (ISO 26262:2018 Part 6 — Software)
SIL Target: SIL-2 (IEC 61508:2010)

1. Scope

This Safety Plan governs the development of cpp-LIN, a C++ software component implementing the LIN (Local Interconnect Network) bus protocol, conformant to the RELAY specification v1.11.

cpp-LIN is classified as a Safety Element out of Context (SEooC) per ISO 26262-10 §9. It is intended for integration into automotive ECUs and other safety-related embedded systems at ASIL-B.

2. Safety Goals

ID Safety Goal ASIL
SG-01 cpp-LIN shall not corrupt LIN frame data during transmission or reception ASIL-B
SG-02 cpp-LIN shall detect and reject frames with invalid IDs (> 0x3F) ASIL-B
SG-03 cpp-LIN shall detect and reject frames with incorrect checksums ASIL-B
SG-04 cpp-LIN shall not cause unbounded memory growth under sustained load ASIL-B
SG-05 cpp-LIN shall detect E2E protection errors (CRC mismatch, sequence gaps) ASIL-B
SG-06 cpp-LIN shall enforce that diagnostic frames use Classic checksum only ASIL-B

3. Functional Safety Requirements

All functional safety requirements are tracked in .fusa-reqs.json and requirements/requirements.json. Requirements use the identifiers:

  • REQ-LIN-NNN — Core LIN protocol requirements
  • REQ-VIRT-NNN — Virtual bus requirements
  • REQ-E2E-NNN — End-to-End safety requirements
  • REQ-LDF-NNN — LDF parser requirements
  • REQ-MASTER-NNN — Master node requirements
  • REQ-SLAVE-NNN — Slave node requirements
  • REQ-RELAY-NNN — RELAY adapter requirements
  • REQ-CLI-NNN — CLI requirements
  • REQ-SEOOC-NNN — SEooC-level requirements

Each source file contains // fusa:req REQ-XXX-NNN annotations to trace implementation to requirements. Each test file contains // fusa:test REQ-XXX-NNN annotations to trace tests to requirements.

4. Development Process

4.1 Version Control

  • Git with DCO sign-off on all commits.
  • SLSA L3: two-party review required (CODEOWNERS enforces this).
  • All safety-critical files (.fusa-reqs.json, requirements/, HARA.md, SEOOC.md) require explicit owner approval.

4.2 Static Analysis

  • clang-tidy with bugprone-* and clang-analyzer-* checks.
  • Enabled in CI as a blocking gate.

4.3 Dynamic Analysis

  • AddressSanitizer (ASan) + UndefinedBehaviorSanitizer (UBSan) enabled in CI.
  • All tests pass under sanitizers with halt_on_error=1.

4.4 Coverage

  • Line coverage enforced at ≥ 70% (LCOV in CI).
  • MC/DC coverage analysis is a v1.0.0 goal.

4.5 Testing

  • Unit tests with Catch2.
  • RELAY conformance gate: relay conform --strict.
  • RELAY interop gate: relay interop --protocol LIN.
  • All tests must pass on Linux (GCC 12, Clang 14), macOS (Clang), and Windows (MSVC 2022).

4.6 FuSa Toolchain

  • cpfusa check — annotation completeness.
  • cpfusa trace — requirements traceability.
  • cpfusa qualify --asil ASIL-B — ASIL-B qualification gate.
  • cpfusa tara — TARA generation.
  • cpfusa fmea — FMEA generation.
  • cpfusa safety-case — GSN safety case.

5. Known Limitations (SEooC Assumptions)

See SEOOC.md for the full list of assumptions about the operational context that must be validated by the integrating system.

6. Hazard Analysis and Risk Assessment

See HARA.md.

7. Confirmation Measures

Measure Responsible Frequency
Code review (CODEOWNERS) @SoundMatt Every PR
CI pipeline (all gates) CI/CD Every commit
cpfusa qualify CI/CD Every commit
RELAY conform --strict CI/CD Every commit
ASan + UBSan test run CI/CD Every commit
Coverage gate (≥70%) CI/CD Every commit
Manual safety review @SoundMatt Every release

8. References

  • ISO 26262:2018 — Road vehicles — Functional safety
  • IEC 61508:2010 — Functional safety of E/E/PE safety-related systems
  • ISO/SAE 21434:2021 — Road vehicles — Cybersecurity engineering
  • LIN Specification Package, Revision 2.2A (LIN Consortium)
  • RELAY Specification v1.11 (SoundMatt)
  • .fusa-reqs.json — Machine-readable requirements
  • HARA.md — Hazard Analysis and Risk Assessment
  • SEOOC.md — Safety Element out of Context document