socket.send_fds and socket.recv_fds ignore optional arguments ('flags' and 'address').

[miccoli]

Bug report

The implementation of socket.send_fds does not pass flags and address down to sock.sendmsg:

cpython/Lib/socket.py

Lines 553 to 559 in bf70774

	def send_fds(sock, buffers, fds, flags=0, address=None):
	""" send_fds(sock, buffers, fds[, flags[, address]]) -> integer
	Send the list of file descriptors fds over an AF_UNIX socket.
	"""
	return sock.sendmsg(buffers, [(_socket.SOL_SOCKET,
	_socket.SCM_RIGHTS, array.array("i", fds))])

The fix seems trivial, I can submit a PR.

Checklist

• I am confident this is a bug in CPython, not a bug in a third-party project
• I have searched the CPython issue tracker, and am confident this bug has not been reported before

A clear and concise description of the bug

import os
import socket

sock = socket.socket(family=socket.AF_UNIX, type=socket.SOCK_DGRAM)
fd = os.memfd_create("journal_entry")

socket.send_fds(sock=sock, buffers=[], fds=[fd], address="/run/systemd/journal/socket")

fails with

    return sock.sendmsg(buffers, [(_socket.SOL_SOCKET,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
OSError: [Errno 107] Transport endpoint is not connected

Your environment

• CPython versions tested on: 3.11.3
• Operating system and architecture: Linux-6.1.43-1-rpi-ARCH-armv7l-with-glibc2.35

Linked PRs

• gh-107898 socket.send_fds and socket.recv_fds honour optional arguments. #108243
• gh-107898: Do not ignore address and flags parameters in socket.{send,recv}_fds #128882

[corona10]

Please submit the PR :)

[miccoli]

Also on the receiving side, socket.recv_fds, the optional input flags are ignored and overwritten by the output flags.

cpython/Lib/socket.py

Lines 565 to 575 in ee40b3e

	def recv_fds(sock, bufsize, maxfds, flags=0):
	""" recv_fds(sock, bufsize, maxfds[, flags]) -> (data, list of file
	descriptors, msg_flags, address)
	Receive up to maxfds file descriptors returning the message
	data and a list containing the descriptors.
	"""
	# Array of ints
	fds = array.array("i")
	msg, ancdata, flags, addr = sock.recvmsg(bufsize,
	_socket.CMSG_LEN(maxfds * fds.itemsize))

I think that both should be considered the same issue and fixed by a single PR.

[miccoli]

I'm working on this issue on this branch. Although the fix is trivial, I'm trying to do also some sensible testing.

[miccoli]

Please submit the PR :)

Just a friendly ping: PR gh-108243 is awaiting a review.

[miccoli]

Another friendly ping: PR #108243 is awaiting a review.