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socket.connect - support custom family value #92658
Description
Feature or enhancement
Currently socket.connect() accepts a wide range of values when connecting to a socket with the code in socketmodule.c transforming it based on the family the socket was created with. Unfortunately there is a check that fails the connection if the family is unrecognized
cpython/Modules/socketmodule.c
Lines 2530 to 2534 in 9d85aba
My proposal is to allow a caller to bypass this check if passing in a raw byte value to be used as the addr info on the native call.
Pitch
The reason why I am hoping for this feature is to support clients connecting to a Hyper-V socket. This uses the AF_HYPERV family which isn't known to Python so any attempts to connect to it won't work.
Currently I am using the following to work around this restriction by using ctypes to call the C API directly and using the fileno:
import ctypes
import socket
import uuid
HV_GUID_VM_SESSION_SERVICE_ID = uuid.UUID("999e53d4-3d5c-4c3e-8779-bed06ec056e1")
HV_GUID_VM_SESSION_SERVICE_ID_2 = uuid.UUID("a5201c21-2770-4c11-a68e-f182edb29220")
AF_HYPERV = 34
HV_PROTOCOL_RAW = 1
# This is the GUID of the Win VM to connect to
vm_id = uuid.UUID("...")
win32sock = ctypes.WinDLL("Ws2_32.dll")
raw_sock = win32sock.socket(AF_HYPERV, socket.SOCK_STREAM, HV_PROTOCOL_RAW)
if raw_sock == -1:
err = win32sock.WSAGetLastError()
raise ctypes.WinError(code=err)
try:
sock_addr = b"\x22\x00\x00\x00" + vm_id.bytes_le + HV_GUID_VM_SESSION_SERVICE_ID.bytes_le
res = win32sock.connect(raw_sock, sock_addr, len(sock_addr))
if res:
err = win32sock.WSAGetLastError()
raise ctypes.WinError(code=err)
sock = socket.socket(fileno=raw_sock)
except:
win32sock.closesocket(raw_sock)
raise
...
sock.close()It would be good to be able to do this instead
import socket
sock = socket.socket(AF_HYPERV, socket.SOCK_STREAM, HV_PROTOCOL_RAW)
sock_addr = b"\x22\x00\x00\x00" + vm_id.bytes_le + HV_GUID_VM_SESSION_SERVICE_ID.bytes_le
sock.connect(sock_addr)
...
sock.close()Currently that fails due to the hardcoded check against unknown families
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
OSError: connect(): bad familyAnother option is to add support for AF_HYPERV on Windows and support a tuple of (vm_id, service_id) and have Python create the struct. This could be done as a separate feature request potentially.
Activity
ronaldoussoren commentedon May 11, 2022
It would IMHO be better to add explicit support for this new address family.
jborean93 commentedon May 11, 2022
I agree, especially from a UX perspective but would it also be nice if it supported arbitrary bytes in the cases when Python does not support the family for other protocols, now and in the future?
jborean93 commentedon May 13, 2022
I've added a PR that adds explicit support for the new address family. I'm not too experienced on the C side so any pointers or comments would be greatly appreciated #92755.
gh-92658: Add Hyper-V socket support (GH-92755)
vstinner commentedon May 24, 2022
I don't think that it's a good idea. Each protocol is different and requires special code.
jborean93 commentedon May 25, 2022
Fair enough, I mostly only desired it for the Hyper V stuff and was mindful if I came across another family I would have the same problem but that makes sense.
gh-92658: AF_HYPERV is only supported on Windows (#93192)
pythongh-92658: Fix typo in docs and tests for `HV_GUID_PARENT`
gh-92658: Fix typo in docs and tests for `HV_GUID_PARENT` (GH-105267)
pythongh-92658: Fix typo in docs and tests for `HV_GUID_PARENT` (pyth…
gh-92658: Fix typo in docs and tests for `HV_GUID_PARENT` (GH-105267)