# vim: set fileencoding=utf-8
# vim: ts=4:sw=4:et:ai:sts=4
# passfd.py: Python library to pass file descriptors across UNIX domain sockets.
'''This simple extension provides two functions to pass and receive file
descriptors across UNIX domain sockets, using the BSD-4.3+ sendmsg() and
Direct bindings to sendmsg and recvmsg are not provided, as the API does
not map nicely into Python.
Please note that this only supports BSD-4.3+ style file descriptor
passing, and was only tested on Linux. Patches are welcomed!
For more information, see one of the R. Stevens' books:
- Richard Stevens: Unix Network Programming, Prentice Hall, 1990;
- Richard Stevens: Advanced Programming in the UNIX Environment,
Addison-Wesley, 1993; chapter 15.3
# Please note that this only supports BSD-4.3+ style file descriptor passing,
# and was only tested on Linux. Patches are welcomed!
# Copyright © 2010 Martín Ferrari <email@example.com>
# Inspired by Socket::PassAccessRights, which is:
# Copyright (c) 2000 Sampo Kellomaki <firstname.lastname@example.org>
# For more information, see one of the R. Stevens' books:
# - Richard Stevens: Unix Network Programming, Prentice Hall, 1990;
# chapter 6.10
# - Richard Stevens: Advanced Programming in the UNIX Environment,
# Addison-Wesley, 1993; chapter 15.3
# This program is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by the Free
# Software Foundation; either version 2 of the License, or (at your option)
# any later version.
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
# more details.
# You should have received a copy of the GNU General Public License along with
# this program; if not, write to the Free Software Foundation, Inc., 51
# Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
import os, socket
if hasattr(sock, 'family') and sock.family != socket.AF_UNIX:
raise ValueError("Only AF_UNIX sockets are allowed")
if hasattr(sock, 'fileno'):
sock = sock.fileno()
if not isinstance(sock, int):
raise TypeError("An socket object or file descriptor was expected")
fd = fd.fileno()
if not isinstance(fd, int):
raise TypeError("An file object or file descriptor was expected")
def sendfd(sock, fd, message = "NONE"):
"""Sends a message and piggybacks a file descriptor through a Unix
Note that the file descriptor cannot be sent by itself, at least
one byte of payload needs to be sent also.
sock: socket object or file descriptor for an AF_UNIX socket
fd: file object or file descriptor to pass
message: message to send
On success, sendfd returns the number of bytes sent, not including
the file descriptor nor the control data. If there was no message
to send, 0 is returned."""
return _passfd.sendfd(__check_socket(sock), __check_fd(fd), message)
def recvfd(sock, msg_buf = 4096):
"""Receive a message and a file descriptor from a Unix domain socket.
sock: file descriptor or socket object for an AF_UNIX socket
buffersize: maximum message size to receive
On success, recvfd returns a tuple containing the received
file descriptor and message. If recvmsg fails, an OSError exception
is raised. If the received data does not carry exactly one file
descriptor, or if the received file descriptor is not valid,
RuntimeError is raised."""
(ret, msg) = _passfd.recvfd(__check_socket(sock), msg_buf)
# -1 should raise OSError
if ret == -2:
raise RuntimeError("The message received did not contain exactly one" +
" file descriptor")
if ret == -3:
raise RuntimeError("The received file descriptor is not valid")
assert ret >= 0
return (ret, msg)