Description

illia-v

opened on May 27, 2022

Issue body actions

Bug report

socket.socket.sendfile and asyncio.base_events.BaseEventLoop.sock_sendfile rely on st_size to determine an amount of bytes to be sent if count is not provided.

But st_size is equal to zero for pseudo files like /proc/cpuinfo on Linux. Therefore, the methods send no data for such files.

Related code

cpython/Lib/socket.py

Lines 355 to 360 in a637c09

	try:
	fsize = os.fstat(fileno).st_size
	except OSError as err:
	raise _GiveupOnSendfile(err) # not a regular file
	if not fsize:
	return 0 # empty file

cpython/Lib/asyncio/unix_events.py

Lines 361 to 367 in 13c10bf

	try:
	fsize = os.fstat(fileno).st_size
	except OSError:
	raise exceptions.SendfileNotAvailableError("not a regular file")
	blocksize = count if count else fsize
	if not blocksize:
	return 0 # empty file

Example

Assuming nc -lkU some.sock and ./python -m asyncio run in the same directory:

>>> import asyncio
>>> import socket
>>> sock = socket.socket(socket.AF_UNIX)
>>> loop = asyncio.get_running_loop()
>>> await loop.sock_connect(sock, "./some.sock")
>>> with open("/proc/cpuinfo", "rb") as cpuinfo_file:
...     os.fstat(cpuinfo_file.fileno()).st_size
...     await loop.sock_sendfile(sock, cpuinfo_file)
...     sock.sendfile(cpuinfo_file)
...     len(cpuinfo_file.read())
... 
0
0
0
18294

Activity

1. illia-v

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on May 27, 2022
2. kumaraditya303 commented on Jun 14, 2022

   

   kumaraditya303

   on Jun 14, 2022

   Contributor

   More actions

   Do you have any fix for this or idea of how this could be fixed? Also are there any use-case of sending pseudo files through sendfile ?
3. illia-v commented on Jun 17, 2022

   

   illia-v

   on Jun 17, 2022

   ContributorAuthor

   More actions

   @kumaraditya303 I do not have any use case, and I have not looked for fixing options.

   I was exploring peculiarities of using the copy_file_range syscall for a pseudo file, and checked if a similar issue related to pseudo files exists in Python. That is how I found this issue.
4. kumaraditya303 commented on Jun 19, 2022

   

   kumaraditya303

   on Jun 19, 2022

   Contributor

   More actions

   I don't think this is a bug and there is nothing actionable here so closing. However, this can be reopened if required.
5. kumaraditya303

   closed this as not plannedon Jun 19, 2022

Issue actions