docs: study NIC offload and low-latency networking

[div0rce]

Summary

• Add docs/nic_offload_study.md to document NIC offload, RSS, hardware timestamping, and vendor stack research boundaries.
• Add non-mutating make nic-offload-check / scripts/nic_offload_check.sh to classify host/NIC capability context without changing NIC, RSS, timestamping, driver, IRQ, CPU-affinity, or packet-generator state.
• Record results/nic_offload_environment.txt from the current macOS host as unsupported-host with Dirty inputs: no.
• Sync README, Linux performance notes, results policy, command lists, milestones, and progress state.

Definition of Done

• Docs distinguish research notes from measured artifacts.
• Hardware-specific measurements are only recorded when real hardware exists.
• No offload/latency claim without evidence.
• make check passes; PROGRESS.md updated.

Tests and Review

• git diff --check
• bash -n scripts/nic_offload_check.sh
• shellcheck scripts/nic_offload_check.sh scripts/qsl_common.sh
• shellcheck -S warning scripts/*.sh
• make nic-offload-check
• make check (232/232)
• CodeScene pre-commit quality gate: passed
• CodeScene change-set analysis against main: passed

Results

• results/nic_offload_environment.txt
  • Evidence class: unsupported-host
  • Dirty inputs: no
  • Offload settings changed: no
  • RSS settings changed: no
  • Timestamping configured: no
  • Driver binding changed: no
  • Packet generator ran: no
  • Latency benchmark ran: no

Limitations

• This PR records research context and environment classification only.
• The current host is macOS, so no Linux NIC capability observation or hardware-specific measurement exists in this artifact.
• No NIC offload, RSS, timestamping, kernel-bypass, throughput, or latency improvement is claimed.
• Hardware-specific evidence still requires a real Linux host/NIC setup with recorded device, driver, firmware, queue/RSS, timestamp, CPU/IRQ placement, workload, drops/backpressure, and provenance.

Do not merge by automation; human review and squash-merge only.

[codescene-delta-analysis]

No application code in the PR — skipped Code Health checks.

See analysis details in CodeScene

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[coderabbitai]

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: fd62297c-b9f4-4cdc-a1c8-35ba40aa1d5f

📥 Commits

Reviewing files that changed from the base of the PR and between c643b62 and 8280cfd.

📒 Files selected for processing (11)

• AGENTS.md
• CLAUDE.md
• MILESTONES.md
• Makefile
• PROGRESS.md
• README.md
• docs/linux_performance.md
• docs/nic_offload_study.md
• results/README.md
• results/nic_offload_environment.txt
• scripts/nic_offload_check.sh

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/m49-nic-offload-study

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