Script to debug a vsock issue. This happen when a connecting socket is bound to a port in the guest, the guest close the socket while the host still have it opened.

vsock_connected_sock_issue.py

#!/usr/bin/python3

import argparse
import sys
import socket

def vsock_server(vsock, args):
    vsock.listen()

    while True:
        vsock_name = vsock.getsockname()
        print(f"Waiting on CID: {vsock_name[0]} port: {vsock_name[1]}")

        conn, _ = vsock.accept()
        print(conn.getpeername())

        data = []
        while (buf := conn.recv(4096)):
            data.append(buf)

        # Adding s.close() here fixes the issue
        if args.fix:
            print("socket closed")
            conn.close()

def vsock_client(vsock, args):
    vsock.connect((args.host, args.port))

    vsock.send(b'Hello, world!\n')

    vsock.close()

def parse_args():

    parser = argparse.ArgumentParser(
            description='VSOCK tests',
            epilog='Please report bugs to Stefano Garzarella <sgarzare@redhat.com>.')

    group = parser.add_mutually_exclusive_group()
    group.add_argument('-s', '--server', dest='server',
                      action='store_true', default=False,
                      help='run in server more, listening on port')
    group.add_argument('-c', '--client', dest='host', type=str,
                      help='run in client mode, connecting to HOST')

    parser.add_argument('-p', '--port', dest='port', type=int,
                      help='server port to connect to')

    parser.add_argument('--fix', dest='fix',
                      action='store_true', default=False,
                       help='enable fix: close socket on the server')
    parser.add_argument('--tcp', dest='tcp',
                      action='store_true', default=False,
                       help='use tcp instead of vsock')

    parser.add_argument('--bind-port', dest='bind_port', type=int, default=socket.VMADDR_PORT_ANY,
                      help='PORT to bind')

    return parser.parse_args()

def main():
    args = parse_args()
    print(args)

    if args.tcp:
        if args.bind_port == socket.VMADDR_PORT_ANY:
            args.bind_port = 0
        vsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        vsock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        vsock.bind(('localhost', args.bind_port))
    else:
        vsock = socket.socket(socket.AF_VSOCK, socket.SOCK_STREAM)
        vsock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        vsock.bind((socket.VMADDR_CID_ANY, args.bind_port))
        if args.host is not None:
            args.host=int(args.host)

    if args.server:
        vsock_server(vsock, args)
    elif args.host is not None:
        vsock_client(vsock, args)

    return 0

if __name__ == '__main__':
    sys.exit(main())