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A command-line tool for discovering IPv6 path MTU and detecting TCP MSS clamping.

• IPv6 Path MTU Discovery using ICMP6 probes
• TCP MSS clamping detection (client and server modes)
• MSS integrity verification and tampering detection
• Binary search algorithm for efficient MTU discovery
• Cross-platform support (Linux, macOS, Windows)
• Detailed progress reporting and statistics
• Network error scenario handling
• Concurrent operation support

• Go 1.19 or later
• Root/Administrator privileges (for raw socket operations)
• IPv6 network connectivity

git clone <repository-url>
cd ipv6-mtu-discovery
make deps
make build

make install

# Basic MTU discovery
sudo ./ipv6-mtu-discovery -t 2001:db8::1

# Verbose output
sudo ./ipv6-mtu-discovery -t 2001:db8::1 -v

# Custom timeout
sudo ./ipv6-mtu-discovery -t 2001:db8::1 -T 10

# Client mode MSS detection
sudo ./ipv6-mtu-discovery -t 2001:db8::1 -m tcp-client -p 80

# Server mode MSS detection
sudo ./ipv6-mtu-discovery -t :: -m tcp-server -p 8080

# MSS integrity verification
sudo ./ipv6-mtu-discovery -t 2001:db8::1 -m mss-integrity -p 80 --control-port 8080 --test-mss 1460

• -t, --target: Target IPv6 address (required)
• -m, --mode: Operation mode (mtu, tcp-client, tcp-server, mss-integrity) [default: mtu]
• -p, --port: TCP port for MSS detection [default: 80]
• -v, --verbose: Enable verbose output
• -T, --timeout: Timeout in seconds [default: 5]

• --min-mtu: Minimum MTU value [default: 68]
• --max-mtu: Maximum MTU value [default: 1500]

• --control-port: Control connection port
• --test-mss: Test MSS value

• --log-level: Log level (debug, info, warn, error)
• --log-file: Enable file logging
• --log-path: Log file path

make build      # Build the binary
make test       # Run tests
make clean      # Clean build artifacts
make deps       # Download dependencies
make lint       # Format and vet code
make install    # Install system-wide

make test

# Run all tests (including integration tests)
./test_integration.sh

# Run unit tests only
./test_integration.sh unit

# Run integration tests only
./test_integration.sh integration

The tool is organized into several packages:

• cmd/: Main application entry point
• internal/app/: Application logic and state management
• internal/cli/: Command line interface and argument parsing
• internal/probe/: ICMP6 probing and packet handling
• internal/network/: TCP connection and MSS detection
• internal/validator/: IPv6 address and permission validation
• internal/algorithm/: Binary search implementation
• internal/display/: Result formatting and display
• internal/config/: Configuration management
• internal/stats/: Statistics collection
• internal/logging/: Logging system
• internal/platform/: Platform-specific functionality

Performs IPv6 Path MTU Discovery using ICMP6 echo requests:

• Uses binary search algorithm for efficient MTU determination
• Handles ICMP6 "Packet Too Big" responses
• Provides detailed probe progress and statistics

Detects MSS clamping as a TCP client:

• Connects to specified server and port
• Detects negotiated MSS value
• Identifies MSS clamping scenarios

Detects MSS clamping as a TCP server:

• Listens on specified port for connections
• Captures client MSS values
• Analyzes MSS modifications

Verifies MSS value integrity:

• Establishes control connection for verification exchange
• Detects MSS tampering and modifications
• Provides detailed integrity analysis reports

# Discover path MTU to Google IPv6 DNS
sudo ./ipv6-mtu-discovery -t 2001:4860:4860::8888 -v

# Example output:
# Starting IPv6 Path MTU Discovery to 2001:4860:4860::8888
# Testing MTU 784... Success
# Testing MTU 1142... Success  
# Testing MTU 1321... Failed (Packet Too Big, reported MTU: 1280)
# Testing MTU 1280... Success
# 
# MTU Discovery Results:
# Final MTU: 1280 bytes
# Probe attempts: 4
# Success rate: 75%

# Verify if MSS is modified by intermediate devices
sudo ./ipv6-mtu-discovery -t 2001:db8::1 -m mss-integrity \
  -p 80 --control-port 8080 --test-mss 1460 -v

# Example output:
# Starting MSS Integrity Verification
# Test MSS: 1460, Control Port: 8080
# Establishing control connection...
# Performing MSS integrity verification...
# 
# MSS Integrity Results:
# Client sent MSS: 1460
# Server received MSS: 1440
# MSS Modified: Yes
# Modification Delta: -20
# Tampering Detected: Yes (Medium severity)

Supports YAML configuration file for advanced settings:

# config.yaml example
network:
  timeout_ms: 5000
  max_retries: 3
  
mtu_discovery:
  min_mtu: 68
  max_mtu: 1500
  probe_timeout_ms: 3000
  
mss_verification:
  session_timeout_ms: 10000
  handshake_timeout_ms: 5000
  
logging:
  level: "info"
  file_enabled: true
  file_path: "logs/ipv6-mtu-discovery.log"

1. Permission Denied

   # Error: socket: operation not permitted
   # Solution: Run with sudo
   sudo ./ipv6-mtu-discovery -t ::1

2. IPv6 Not Supported

   # Check IPv6 support
   ip -6 addr show
   # Enable IPv6 loopback
   sudo sysctl net.ipv6.conf.lo.disable_ipv6=0

3. Firewall Blocking

   # Temporarily allow ICMP6
   sudo ip6tables -I INPUT -p ipv6-icmp -j ACCEPT

• Integration Tests Documentation
• Architecture Design
• API Documentation

[License information to be added]

Contributions are welcome! Please see Contributing Guidelines.

1. Clone the repository
2. Install Go 1.19+
3. Run make deps to install dependencies
4. Run make test to ensure tests pass
5. Use make lint to check code quality

For questions or suggestions:

1. Check the FAQ
2. Search existing Issues
3. Create a new Issue describing the problem

Note: This tool requires raw socket privileges. Please ensure you use it in a trusted environment.