Initial commit: DHCP whitelist service for direct link connections

Features:
- Docker-based DHCP server with MAC address whitelisting
- Binds to specific ethernet interface only
- NO DNS/gateway advertised (direct link only, not a router)
- Configurable network parameters (subnet, DHCP range, lease times)
- Systemd service integration for Arch/Manjaro
- Test environment with isolated network (172.20.0.0/24)
- Auto-configuration script to detect network settings
- Complete Makefile with management targets

Security:
- Only responds to whitelisted MAC addresses
- deny unknown-clients configuration
- Runs in Docker container for isolation

Configuration:
- Copy .example files to create your config
- interface.conf: Network interface to bind to
- whitelist.conf: Allowed MAC addresses
- network.conf: Network parameters (optional)

Makefile

@@ -0,0 +1,78 @@
+.PHONY: up down install service_up service_down test autoconfig clean help
+
+# Default target
+help:
+	@echo "Available targets:"
+	@echo "  up           - Start DHCP server in userland mode"
+	@echo "  down         - Stop DHCP server"
+	@echo "  install      - Install as systemd service (requires sudo)"
+	@echo "  service_up   - Enable and start systemd service"
+	@echo "  service_down - Disable and stop systemd service"
+	@echo "  test         - Run test environment with virtual network (172.20.0.0/24)"
+	@echo "  test-clean   - Clean up test environment"
+	@echo "  autoconfig   - Auto-generate configuration from current network"
+	@echo "  clean        - Remove all containers and generated files"
+
+# Start DHCP server in userland mode
+up:
+	@echo "Building DHCP server image..."
+	@docker-compose build
+	@echo "Starting DHCP server..."
+	@docker-compose up -d
+	@echo "DHCP server started. Check logs with: docker-compose logs -f"
+
+# Stop DHCP server
+down:
+	@echo "Stopping DHCP server..."
+	@docker-compose down
+	@echo "DHCP server stopped."
+
+# Install as systemd service (requires sudo)
+install:
+	@echo "Installing systemd service..."
+	@bash scripts/install-service.sh
+	@echo "Service installed. Use 'make service_up' to start."
+
+# Enable and start systemd service
+service_up:
+	@echo "Enabling and starting systemd service..."
+	@systemctl --user enable dhcp-whitelist.service 2>/dev/null || sudo systemctl enable dhcp-whitelist.service
+	@systemctl --user start dhcp-whitelist.service 2>/dev/null || sudo systemctl start dhcp-whitelist.service
+	@echo "Service started. Check status with: systemctl status dhcp-whitelist"
+
+# Disable and stop systemd service
+service_down:
+	@echo "Stopping and disabling systemd service..."
+	@systemctl --user stop dhcp-whitelist.service 2>/dev/null || sudo systemctl stop dhcp-whitelist.service
+	@systemctl --user disable dhcp-whitelist.service 2>/dev/null || sudo systemctl disable dhcp-whitelist.service
+	@echo "Service stopped."
+
+# Run test environment
+test:
+	@echo "Building test environment..."
+	@docker-compose -f docker-compose.test.yml build
+	@echo "Running tests..."
+	@docker-compose -f docker-compose.test.yml up --abort-on-container-exit
+	@$(MAKE) test-clean
+	@echo "Tests completed."
+
+# Clean up test environment (always runs, even on test failure)
+test-clean:
+	@echo "Cleaning up test environment..."
+	@docker-compose -f docker-compose.test.yml down -v --remove-orphans 2>/dev/null || true
+	@docker network rm service-dhcp-direct-link-only_test-net 2>/dev/null || true
+	@echo "Test cleanup complete."
+
+# Auto-generate configuration
+autoconfig:
+	@echo "Auto-generating configuration..."
+	@bash scripts/autoconfig.sh
+	@echo "Configuration generated. Review config/ directory before starting."
+
+# Clean up
+clean:
+	@echo "Cleaning up..."
+	@docker-compose down 2>/dev/null || true
+	@$(MAKE) test-clean
+	@rm -f config/*.tmp
+	@echo "Cleanup complete."