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| """ | |
| NAT Engine Module for VPN | |
| Implements Network Address Translation | |
| """ | |
| import asyncio | |
| import time | |
| from typing import Dict, Optional, Tuple | |
| from dataclasses import dataclass | |
| import logging | |
| import subprocess | |
| logger = logging.getLogger(__name__) | |
| class NATSession: | |
| virtual_ip: str | |
| virtual_port: int | |
| real_ip: str | |
| real_port: int | |
| host_port: int | |
| created_time: float | |
| last_activity: float | |
| bytes_in: int = 0 | |
| bytes_out: int = 0 | |
| class NATEngine: | |
| def __init__(self, logger_instance=None): | |
| self.sessions: Dict[str, NATSession] = {} | |
| self.port_mappings: Dict[int, Tuple[str, int]] = {} | |
| self.next_port = 10000 | |
| self.cleanup_interval = 300 # 5 minutes | |
| self._cleanup_task = None | |
| self.logger = logger_instance if logger_instance else logging.getLogger(__name__) | |
| async def start(self): | |
| """Start the NAT engine""" | |
| self._cleanup_task = asyncio.create_task(self._cleanup_loop()) | |
| self.logger.info("NAT engine started") | |
| async def stop(self): | |
| """Stop the NAT engine""" | |
| if self._cleanup_task: | |
| self._cleanup_task.cancel() | |
| try: | |
| await self._cleanup_task | |
| except asyncio.CancelledError: | |
| pass | |
| self.sessions.clear() | |
| self.port_mappings.clear() | |
| self.logger.info("NAT engine stopped") | |
| def create_session(self, virtual_ip: str, virtual_port: int, | |
| real_ip: str, real_port: int) -> NATSession: | |
| """Create a new NAT session""" | |
| host_port = self._allocate_port() | |
| session = NATSession( | |
| virtual_ip=virtual_ip, | |
| virtual_port=virtual_port, | |
| real_ip=real_ip, | |
| real_port=real_port, | |
| host_port=host_port, | |
| created_time=time.time(), | |
| last_activity=time.time() | |
| ) | |
| session_key = f"{virtual_ip}:{virtual_port}" | |
| self.sessions[session_key] = session | |
| self.port_mappings[host_port] = (virtual_ip, virtual_port) | |
| self.logger.debug(f"Created NAT session: {session_key} -> {real_ip}:{real_port}") | |
| return session | |
| def lookup_session(self, ip: str, port: int) -> Optional[NATSession]: | |
| """Look up a NAT session by real IP and port""" | |
| for session in self.sessions.values(): | |
| if session.real_ip == ip and session.real_port == port: | |
| return session | |
| return None | |
| def get_session_by_virtual(self, ip: str, port: int) -> Optional[NATSession]: | |
| """Get session by virtual IP and port""" | |
| return self.sessions.get(f"{ip}:{port}") | |
| def remove_session(self, session: NATSession): | |
| """Remove a NAT session""" | |
| session_key = f"{session.virtual_ip}:{session.virtual_port}" | |
| if session_key in self.sessions: | |
| del self.sessions[session_key] | |
| if session.host_port in self.port_mappings: | |
| del self.port_mappings[session.host_port] | |
| def _allocate_port(self) -> int: | |
| """Allocate a new port for NAT""" | |
| while self.next_port in self.port_mappings: | |
| self.next_port += 1 | |
| if self.next_port > 65535: | |
| self.next_port = 10000 | |
| return self.next_port | |
| async def _cleanup_loop(self): | |
| """Periodically clean up expired sessions""" | |
| while True: | |
| try: | |
| await asyncio.sleep(self.cleanup_interval) | |
| current_time = time.time() | |
| for session_key, session in list(self.sessions.items()): | |
| if current_time - session.last_activity > self.cleanup_interval: | |
| self.remove_session(session) | |
| self.logger.debug(f"Removed expired session: {session_key}") | |
| except asyncio.CancelledError: | |
| break | |
| except Exception as e: | |
| self.logger.error(f"Error in cleanup loop: {e}") | |
| def get_stats(self) -> Dict: | |
| """Get NAT engine statistics""" | |
| return { | |
| "active_sessions": len(self.sessions), | |
| "allocated_ports": len(self.port_mappings), | |
| "total_bytes_in": sum(s.bytes_in for s in self.sessions.values()), | |
| "total_bytes_out": sum(s.bytes_out for s in self.sessions.values()) | |
| } | |
| async def setup_nat(self, interface: str): | |
| """Setup NAT configuration""" | |
| # In this Windows implementation, NAT is handled at the application level | |
| # through the traffic forwarding engine and doesn't require system-level configuration | |
| logger.info(f"NAT configuration ready for interface {interface}") | |
| pass | |