Bug report

socket.setsockopt() and socket.getsockopt() apply the VSOCK-specific integer handling to every option on an AF_VSOCK socket, including SOL_SOCKET options. This rejects valid buffered options such as SO_LINGER before calling the operating system.

The following reproducer uses an owned, unconnected Unix socket FD to exercise the Python family dispatch. It does not require a VSOCK device, a VM, or a connection:

import socket
import struct

with socket.socket(socket.AF_UNIX, socket.SOCK_STREAM) as raw:
    linger = struct.pack('ii', 1, 0)
    raw.setsockopt(socket.SOL_SOCKET, socket.SO_LINGER, linger)
    with socket.socket(socket.AF_VSOCK, socket.SOCK_STREAM, 0,
                       fileno=raw.detach()) as sock:
        for operation in ('get', 'set'):
            try:
                if operation == 'get':
                    result = sock.getsockopt(socket.SOL_SOCKET,
                                             socket.SO_LINGER, len(linger))
                else:
                    result = sock.setsockopt(socket.SOL_SOCKET,
                                             socket.SO_LINGER, linger)
                print(operation, repr(result))
            except (OSError, TypeError) as error:
                print(operation, f'{type(error).__name__}: {error}')

On Python 3.15.0:

get OSError: getsockopt string buffer not allowed
set TypeError: setsockopt() argument 3 for AF_VSOCK must be an int (got bytes)

On a debug build of main at 3dee86d70560329437c2e774a1a89a3c57b14119, the get error is the same and the set error is TypeError: argument must be int, not bytes.

The expected result is the packed linger value for get and None for set, as with the original Unix socket. The VSOCK branches in socketmodule.c check the socket family but not the option level. Restricting these branches to level == AF_VSOCK restores the ordinary SOL_SOCKET paths while keeping the existing 64-bit VSOCK buffer-option handling.

This is separate from #159561 and its merged PR #159610, which removed a redundant type check without changing the option-level dispatch. I have a focused fix and regression test ready.

CPython versions tested on:

3.15, 3.16, CPython main branch

Operating systems tested on:

Linux

This report and the proposed fix were prepared with AI assistance.

Linked PRs

• gh-161657: Fix SOL_SOCKET options on AF_VSOCK sockets #161658