import socket
import os


def create_fds():
    (sk1, sk2) = socket.socketpair(socket.AF_UNIX, socket.SOCK_STREAM)
    (sk3, sk4) = socket.socketpair(socket.AF_UNIX, socket.SOCK_STREAM)
    return [(sk1.makefile("wb"), sk2.makefile("rb")),
            (sk3.makefile("wb"), sk4.makefile("rb"))]


def __sock_ino(sockf):
    return os.fstat(sockf.fileno()).st_ino


def filename(sockf):
    return 'socket:[%d]' % __sock_ino(sockf)


def dump_opts(sockf):
    return ['--external', 'unix[%d]' % __sock_ino(sockf)]