104 lines
3.8 KiB
Python
104 lines
3.8 KiB
Python
#!/usr/bin/env python3
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"""
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UDP relay for Docker Desktop on Windows (issue #374, #386).
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Docker Desktop on Windows multiplexes inbound UDP from multiple source IPs to
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a single source IP inside the container, which causes packets from all but one
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ESP32 node to be silently dropped at the WSL/Hyper-V boundary.
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This relay listens on the host, then re-emits each datagram from its own
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single socket back to a localhost port that Docker forwards into the
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container. Because every forwarded datagram now has the same source IP/port
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(the relay's loopback socket), Docker passes them all through.
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Usage:
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# Default: listen on host:5005, forward to 127.0.0.1:5006
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# Container should be started with -p 5006:5005/udp.
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python scripts/udp-relay.py
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# Custom ports
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python scripts/udp-relay.py --listen-port 5005 --forward-port 5006
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# Verbose (one line per packet)
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python scripts/udp-relay.py --verbose
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"""
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import argparse
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import socket
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import sys
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import time
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def run_relay(listen_host: str, listen_port: int, forward_host: str,
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forward_port: int, stats_interval: float, verbose: bool) -> int:
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rx = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
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rx.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
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try:
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rx.bind((listen_host, listen_port))
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except OSError as e:
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print(f"udp-relay: failed to bind {listen_host}:{listen_port}: {e}",
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file=sys.stderr)
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return 1
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tx = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
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forward_addr = (forward_host, forward_port)
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print(f"udp-relay: listening on {listen_host}:{listen_port} "
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f"-> forwarding to {forward_host}:{forward_port}")
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print("udp-relay: collapses multi-source UDP to a single loopback source "
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"so Docker Desktop on Windows forwards every packet (issue #374).")
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sources: dict[tuple[str, int], int] = {}
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total = 0
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last_stats = time.monotonic()
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try:
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while True:
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data, src = rx.recvfrom(65535)
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tx.sendto(data, forward_addr)
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total += 1
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sources[src] = sources.get(src, 0) + 1
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if verbose:
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print(f"udp-relay: {src[0]}:{src[1]} -> "
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f"{forward_host}:{forward_port} ({len(data)}B)")
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now = time.monotonic()
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if now - last_stats >= stats_interval:
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print(f"udp-relay: forwarded {total} pkts from "
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f"{len(sources)} sources in last {stats_interval:.0f}s")
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sources.clear()
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total = 0
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last_stats = now
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except KeyboardInterrupt:
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print("udp-relay: stopping")
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return 0
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finally:
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rx.close()
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tx.close()
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def main() -> int:
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p = argparse.ArgumentParser(description=__doc__,
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formatter_class=argparse.RawDescriptionHelpFormatter)
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p.add_argument("--listen-host", default="0.0.0.0",
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help="Host interface to bind (default: 0.0.0.0)")
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p.add_argument("--listen-port", type=int, default=5005,
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help="Port the ESP32 nodes send to (default: 5005)")
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p.add_argument("--forward-host", default="127.0.0.1",
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help="Where to forward packets (default: 127.0.0.1)")
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p.add_argument("--forward-port", type=int, default=5006,
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help="Port Docker maps into the container (default: 5006)")
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p.add_argument("--stats-interval", type=float, default=10.0,
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help="Seconds between stats lines (default: 10)")
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p.add_argument("--verbose", action="store_true",
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help="Log every forwarded packet")
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args = p.parse_args()
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return run_relay(args.listen_host, args.listen_port, args.forward_host,
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args.forward_port, args.stats_interval, args.verbose)
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if __name__ == "__main__":
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sys.exit(main())
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