#!/usr/bin/env python3
"""TCP relay: listen on the netns veth IP:CDP_PORT, forward to 127.0.0.1:CDP_PORT.
Chromium binds DevTools to loopback only; this exposes it on the veth IP for
the host (and SSH-forwarded operators). Runs inside the netns. No dependencies.
Usage: netvm-cdp-relay.py <listen_ip> <listen_port> <target_ip> <target_port>
"""
import socket, threading, sys

def pipe(src, dst):
    try:
        while True:
            data = src.recv(65536)
            if not data:
                break
            dst.sendall(data)
    except OSError:
        pass
    finally:
        for s in (src, dst):
            try: s.shutdown(socket.SHUT_RDWR)
            except OSError: pass
            s.close()

def handle(client, target):
    try:
        upstream = socket.create_connection(target, timeout=10)
    except OSError:
        client.close()
        return
    threading.Thread(target=pipe, args=(client, upstream), daemon=True).start()
    pipe(upstream, client)

def main():
    listen_ip, listen_port, target_ip, target_port = sys.argv[1], int(sys.argv[2]), sys.argv[3], int(sys.argv[4])
    srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    srv.bind((listen_ip, listen_port))
    srv.listen(16)
    while True:
        client, _ = srv.accept()
        threading.Thread(target=handle, args=(client, (target_ip, target_port)), daemon=True).start()

if __name__ == "__main__":
    main()