Secure: send over TCP instead of UDP

[DavidCozens]

What this tag adds

A plain TCP transport, replacing UDP: SolidSyslogStreamSender over
SolidSyslogLwipRawTcpStream, with the collector on 5601 and records framed by
octet count (RFC 6587). Moves toward secure.

TCP lands before TLS deliberately — it is the smaller step (a stream, a connect and
a framing rule, no certificates), and it gives store-and-forward somewhere to spool
before crypto arrives. It also complements the sequenceId added earlier: the
transport detects loss where it happens, the sequence only reveals it afterwards.

  Flash         7,664 B     (+548)
  Static RAM    2,784 B     (+180)
  Heap            -32 B       (-8)
  Log stack       448 B         (0)
  Service stack   784 B       (+8)

The log stack does not move — a task that calls Log is unaffected by the transport
underneath it, and the cost lands on the service task, which does the connecting.

Checklist

• The diff is application-only — app/syslog/Syslog.c only. No build-system
  change was needed: SolidSyslogLwipRawTcpStream ships in the LwipRaw pack
  that is already named and linked.
• measurements/<State>.csv committed, and a row added to measurements/tags.tsv.
  Secure's row is already present; its CSV is frozen at the end of Secure's work,
  not here — see conventions.md.
• README cost table regenerated — nothing to regenerate until a state's CSV is
  frozen.
• ./run.sh green (build + QEMU + baseline self-check), record delivered over
  TCP and confirmed in the collector output.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Syslog collection now uses a TCP connection for improved stream-based delivery.
  • The collector port has been updated to 5601.

• Bug Fixes

  • Improved connection handling to prevent excessive retry spinning.
  • Updated verification results confirm successful delivery of boot messages with refreshed timestamps.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: d2d0d2bc-06b4-4b94-bf11-824ec44a9c49

📥 Commits

Reviewing files that changed from the base of the PR and between 9480f3a and 385737b.

📒 Files selected for processing (2)

• app/syslog/Syslog.c
• run-report.txt

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📝 Walkthrough

Walkthrough

Syslog transmission changes from UDP datagrams to an LWIP raw TCP stream on port 5601. A delay helper bounds connection retries, sender setup uses TCP stream configuration, and the run report records updated measurements and collector timestamps.

Changes

Syslog TCP migration

Layer / File(s)	Summary
Configure TCP stream transport app/syslog/Syslog.c	Replaces UDP sender setup with LWIP raw TCP stream configuration, changes the collector port to 5601, and adds FreeRTOS-based retry delay handling.
Update runtime validation run-report.txt	Updates simulated memory and stack measurements, size cross-check totals, and the timestamp of the collector-received BOOT event.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant SyslogLogger
  participant SolidSyslogStreamSender
  participant LwipRawTcpStream
  participant SyslogCollector
  SyslogLogger->>SolidSyslogStreamSender: enqueue and drain log messages
  SolidSyslogStreamSender->>LwipRawTcpStream: open TCP stream on port 5601
  LwipRawTcpStream->>SyslogCollector: deliver syslog stream

Loading

Possibly related PRs

• cososo-ltd/solid-syslog-example#10: Directly overlaps with the UDP-to-TCP sender wiring and collector port change.
• cososo-ltd/solid-syslog-example#12: Coordinates the TCP listener on port 5601 with this sender change.
• cososo-ltd/solid-syslog-example#14: Also changes Syslog.c from UDP toward TCP-based transport configuration.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: switching syslog delivery from UDP to TCP for a more secure transport.
Description check	✅ Passed	The description matches the required template and covers the added capability, rationale, target component, and checklist items.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch secure-tcp

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