go-i2p Implementation Roadmap - go-i2p/go-i2p

go-i2p Implementation Roadmap

Completed Components ✅

Transport Layer (NTCP2)

  • ✅ Core NTCP2 Implementation: Complete functional NTCP2 transport
    • ✅ Session handshake using noise protocol
    • ✅ Inbound and outbound connection management
    • ✅ I2NP message framing and unframing
    • ✅ Session lifecycle management with proper cleanup
    • ✅ Message queuing with background workers
    • ✅ RouterInfo compatibility checking
    • ✅ Error handling and session recovery

I2NP Message System

  • ✅ Core Message Infrastructure: Complete I2NP message framework
    • ✅ Message parsing and serialization (NTCP format)
    • ✅ Interface-based message system with factory patterns
    • ✅ Data, DeliveryStatus, TunnelData message implementations
    • ✅ Database Store/Lookup message structures
    • ✅ DatabaseStore LeaseSet type field parsing (bits 3-0) for LeaseSet2 support
    • ✅ Tunnel Build/Reply message structures
    • ✅ Build Request/Response Record parsing and interfaces

Tunnel Building System

  • ✅ Active Tunnel Management: Complete tunnel building coordination
    • ✅ Tunnel building coordination and state machine
    • ✅ Build request/response handling with retry logic
    • ✅ Short Tunnel Build Message (STBM) support (modern I2P standard)
    • ✅ Gateway and endpoint implementations
    • ✅ Message ID correlation for request/reply tracking
    • ✅ 90-second timeout enforcement with cleanup

Tunnel Participation System

  • ✅ Resource Exhaustion Protection: Complete protection against tunnel flooding
    • ✅ Global participating tunnel limits (configurable, default 15000)
    • ✅ Two-tier rejection: soft limit (50%) with probabilistic rejection, hard limit (100%)
    • ✅ Per-source rate limiting with token bucket algorithm
    • ✅ Automatic banning for excessive requesters (>10 rejections triggers 5min ban)
    • ✅ Incoming tunnel build request handler (ProcessBuildRequest wired into MessageProcessor)

Tunnel Pool Management

  • ✅ Automatic Pool Maintenance: Complete pool lifecycle management
    • ✅ Configurable min/max tunnel counts (default 4-6 per pool)
    • ✅ Automatic tunnel building when below threshold
    • ✅ Proactive replacement before expiration (2min before 10min lifetime)
    • ✅ Round-robin tunnel selection with load balancing
    • ✅ Exponential backoff on build failures
    • ✅ Background maintenance goroutine with graceful shutdown
    • ✅ Support for inbound and outbound pool types
    • ✅ Pool statistics and health monitoring

Tunnel Message Processing

  • ✅ Message Structure Handling: Tunnel message framework
    • ✅ Delivery Instructions parsing and validation
    • ✅ Fragment handling and reassembly logic
    • ✅ Tunnel message structure parsing
    • ✅ Build record interface implementations

Tunnel Cryptography

  • ✅ Security Layer Implementation: Complete tunnel encryption
    • ✅ ECIES-X25519-AEAD encryption (modern I2P standard)
    • ✅ AES-256-CBC legacy support for backward compatibility
    • ✅ Integration with github.com/go-i2p/crypto/tunnel
    • ✅ Participant tunnel processing (decrypt/re-encrypt)
    • ✅ Gateway and endpoint crypto operations
    • ✅ Comprehensive test coverage with real encryption

End-to-End Garlic Encryption

  • ✅ ECIES-X25519-AEAD-Ratchet Implementation: Modern garlic encryption
    • ✅ Garlic message construction with delivery instructions
    • ✅ ECIES-X25519 key agreement integration
    • ✅ ChaCha20/Poly1305 AEAD encryption (native implementation)
    • ✅ Ratchet protocol for forward secrecy (DH, Symmetric, Tag ratchets)
    • ✅ Session management with automatic cleanup
    • ✅ New Session and Existing Session message handling
    • ✅ Proper HKDF key derivation from ECIES shared secrets
    • ✅ O(1) hash-based session tag lookup with tag window management
    • ✅ Comprehensive test coverage (>85% for session logic)
    • ✅ Message format compliance with I2P specification

I2CP Implementation

  • ✅ I2CP Protocol Server: Complete I2CP v2.10.0 server
    • ✅ TCP server socket on localhost:7654
    • ✅ Protocol message handling (CreateSession, DestroySession, ReconfigureSession)
    • ✅ Session management and multi-client support
    • ✅ Message framing and serialization
    • ✅ Integration framework for LeaseSet and message delivery
    • ✅ SendMessage and MessagePayload handlers

NetDb Implementation

  • ✅ Database Store Integration:
    • ✅ Database Store message handling implementation
    • ✅ RouterInfo storage and retrieval
    • ✅ LeaseSet management and storage
    • ✅ LeaseSet2 support with type discrimination
    • ✅ Database lookup system
    • ✅ Peer selection logic (basic implementation)
    • ✅ Floodfill router selection using Kademlia XOR distance metric
    • ✅ LeaseSet distribution to closest floodfill routers

Common Data Structures

  • ✅ Complete Data Structure Support: All I2P data types implemented
    • ✅ Keys and Certificates, Router Info/Address
    • ✅ Session Keys, Hashes, Signatures
    • Lease and LeaseSet structures

I2CP Client Tunnel Lifecycle

  • ✅ Application Layer Integration: Complete I2CP session lifecycle
    • ✅ CreateLeaseSet implementation
    • ✅ SendMessage and ReceiveMessage handlers
    • ✅ LeaseSet maintenance and rotation
    • ✅ End-to-end integration testing
    • ✅ Message queue management
    • ✅ Test coverage >85%

Message Routing System

  • ✅ End-to-End Message Delivery: Connect I2CP, tunnels, and garlic encryption
    • ✅ Route outbound I2CP messages through tunnel system
    • ✅ Decrypt and deliver inbound tunnel messages to I2CP sessions
    • ✅ LeaseSet publishing to NetDB
    • ✅ Destination lookup and resolution
    • ✅ Message fragment handling across tunnel boundaries
    • ✅ Integration testing for outbound message flow
    • ✅ Integration testing for full end-to-end message delivery

Advanced NetDb Features

  • Enhanced Database Operations:
    • ✅ Floodfill router functionality
    • ✅ Client/Router NetDb isolation
    • ✅ LeaseSet2 (LS2) support (storage, retrieval, type discrimination)
    • ✅ Pluggable peer selection algorithm interface
    • ✅ Database exploration and publishings (random selection, XOR distance, floodfill routing)
    • ✅ EncryptedLeaseSet and MetaLeaseSet support (storage, retrieval, expiration tracking, client-side decryption, pointer resolution)

Application Layer

  • ✅ Client Applications:
    • ✅ I2CP implementation (goes in github.com/go-i2p/go-i2cp)
    • ✅ Streaming library (goes in github.com/go-i2p/go-streaming)
    • ✅ Datagram support (goes in github.com/go-i2p/go-datagrams)

In Progress Components 🚧

SSU2 Transport

  • Core Transport:
    • ✅ SSU2 handshake implementation (XK pattern via go-noise)
    • ✅ UDP-based session management
    • ✅ I2NP message send/receive over SSU2 sessions
    • ✅ Congestion control and RTT estimation
    • ✅ Relay tag allocation and introducer registry
    • 🚧 NAT traversal: PeerTest initiation wired (peer test protocol completion in progress)
    • 🚧 Introducer publishing: registration wired, RouterInfo advertisement pending

NetDB Explorer

  • ✅ Explorer instantiated and started at router startup
  • ✅ Random-key XOR lookup for peer discovery
  • 🚧 Scheduling tuning (exploration interval based on netdb size)

FloodfillServer

  • ✅ FloodfillServer instantiated and wired to DatabaseLookup dispatch
  • ✅ DatabaseStore/DatabaseSearchReply responses implemented
  • ✅ Per-peer rate limiting
  • 🚧 Enabled only when netdb.floodfill_enabled = true in config (disabled by default)

Next Priority Components 🎯

Next Focus: Application Layer (I2CP client library, streaming)

Test Coverage: Core components have strong test coverage:

  • Garlic session management: >80% coverage
  • Garlic message construction: >95% coverage
  • Tunnel pool management: >80% coverage
  • Tunnel building: Comprehensive integration tests
  • NTCP2 sessions: Unit and integration tests
  • I2NP message processing: Protocol compliance tests
  • NetDB LeaseSet operations: Comprehensive validation and thread-safety tests for all types (LeaseSet, LeaseSet2, EncryptedLeaseSet, MetaLeaseSet)