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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__)
@dataclass
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
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