---
phase: 01-capture-and-classification
plan: 01
subsystem: classification
tags: [go, gopacket, protocol-classification, tdd, packet-capture]

# Dependency graph
requires: []
provides:
  - "Go 1.24.1 module initialized (github.com/netsynth/netsynth)"
  - "classify/types.go: TrafficClass (11 constants), ClassifiedPacket, WindowSnapshot shared types"
  - "classify/rules.go: Rule struct and DefaultRules slice with 12 ordered protocol rules"
  - "classify/classifier.go: Classifier with NewClassifier and Classify(gopacket.Packet) methods"
  - "Unit tests for all 11 traffic classes, 14 test cases, all passing"
affects:
  - 01-capture-and-classification
  - 02-audio-synthesis
  - 03-clustering

# Tech tracking
tech-stack:
  added:
    - "github.com/gopacket/gopacket v1.5.0 — packet decode and layer type assertions"
    - "github.com/packetcap/go-pcap v0.0.0-20251215 — in go.sum for Phase 1 capture plan"
    - "github.com/spf13/cobra v1.10.2 — in go.sum for Phase 1 CLI plan"
  patterns:
    - "Config-driven rule slice (not switch) for classification — per D-02"
    - "First-match-wins rule evaluation over ordered []Rule slice"
    - "Classifier struct accepting rules at construction for testability"
    - "test package (classify_test) using gopacket SerializeLayers for synthetic packet construction"

key-files:
  created:
    - "classify/types.go — TrafficClass, ClassifiedPacket, WindowSnapshot shared contracts"
    - "classify/rules.go — Rule struct, DefaultRules with 12 ordered protocol rules"
    - "classify/classifier.go — Classifier, NewClassifier, Classify method"
    - "classify/classifier_test.go — 14 test cases covering all 11 traffic classes"
    - "go.mod — module github.com/netsynth/netsynth, go 1.24.1"
    - "go.sum — all dependency checksums"
  modified: []

key-decisions:
  - "Go installed at /home/dev/tools/go-install/go (no sudo available) — export PATH=$PATH:/home/dev/tools/go-install/go/bin required"
  - "DefaultRules uses ordered slice with DstPort=0 as catch-all — enables first-match-wins without switch"
  - "ICMP checked before TCP/UDP in Classify to handle ICMP packets that decode no port"
  - "go mod tidy removes go-pcap and cobra from go.mod until they are imported in later plans"

patterns-established:
  - "Classifier struct pattern: NewClassifier(rules []Rule) accepts rules at construction, enabling custom rules in tests"
  - "Synthetic packet construction: gopacket SerializeLayers with Ethernet+IPv4+TCP/UDP/ICMP layers"

requirements-completed: [CLAS-01]

# Metrics
duration: 4min
completed: 2026-03-25
---

# Phase 01 Plan 01: Bootstrap and Protocol Classification Engine Summary

**Config-driven packet classifier with 12 protocol rules identifying ICMP, DNS, HTTPS, HTTP, SSH, SMTP, NTP, DHCP, other-TCP, other-UDP, and unknown traffic via ordered []Rule slice**

## Performance

- **Duration:** 4 min
- **Started:** 2026-03-25T11:09:11Z
- **Completed:** 2026-03-25T11:13:13Z
- **Tasks:** 2
- **Files modified:** 6

## Accomplishments

- Go 1.24.1 installed and module initialized with gopacket, go-pcap, and cobra dependencies
- 11 TrafficClass constants + ClassifiedPacket + WindowSnapshot types established as shared contracts for all downstream phases
- Config-driven classifier (no switch) with 12 ordered rules; first-match-wins; ICMP handled separately from TCP/UDP port matching
- All 14 TDD tests pass covering all 11 traffic classes and rule ordering behavior

## Task Commits

Each task was committed atomically:

1. **Task 1: Install Go 1.24, initialize module, create shared types** - `15e8143` (feat)
2. **Task 2 RED: Failing tests for all 11 protocol classes** - `f233e80` (test)
3. **Task 2 GREEN: Config-driven classifier implementation** - `48ef6e5` (feat)
4. **Task 2 TIDY: go mod tidy after imports added** - `25e0dc3` (chore)

_Note: TDD task had test commit (RED) then feat commit (GREEN), plus a tidy cleanup._

## Files Created/Modified

- `classify/types.go` - TrafficClass (11 constants), ClassifiedPacket, WindowSnapshot, AllClasses()
- `classify/rules.go` - Rule struct, DefaultRules slice with 12 ordered protocol rules
- `classify/classifier.go` - Classifier struct, NewClassifier, Classify method (no switch)
- `classify/classifier_test.go` - 14 test cases, 243 lines, all protocol classes covered
- `go.mod` - Module github.com/netsynth/netsynth, go 1.24.1, gopacket direct dep
- `go.sum` - All dependency checksums including go-pcap and cobra for future plans

## Decisions Made

- Go installed to `/home/dev/tools/go-install/go` (not /usr/local — no sudo access); PATH export needed in each shell session
- ICMP classification checked before TCP/UDP since ICMP has no ports — avoids the "no transport layer" fallthrough for valid ICMP packets
- `go mod tidy` trimmed go-pcap and cobra to indirect/removed since they have no code importing them yet; they will be re-added as direct deps when capture and CLI plans import them

## Deviations from Plan

None - plan executed exactly as written. The only operational difference was installing Go to `/home/dev/tools/go-install/go` instead of `/usr/local/go` due to lack of sudo access — functionality is identical.

## Issues Encountered

- No sudo access — Go 1.24.1 installed to `/home/dev/tools/go-install/go` instead of `/usr/local/go`. PATH must include `/home/dev/tools/go-install/go/bin` in each session.
- `go mod tidy` removes go-pcap and cobra from go.mod when no code imports them. This is expected Go behavior; these dependencies will become direct when imported in Plans 02-04.

## User Setup Required

None - no external service configuration required. Note that running `go` commands requires:
```
export PATH=$PATH:/home/dev/tools/go-install/go/bin
```

## Next Phase Readiness

- classify package is complete and compiles; all types are stable contracts for downstream phases
- Plan 01-02 (capture pipeline) can import classify and start building on top of ClassifiedPacket/WindowSnapshot
- Plan 01-03 (aggregation) can import WindowSnapshot directly
- No blockers

---
*Phase: 01-capture-and-classification*
*Completed: 2026-03-25*