nxt_py_asgi_create_address with unix:

[echolimazulu]

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Who is affected?

- All users of the ASGI specification using a unix socket as a listener.

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Hello Nginx Team and Contributors,

Today I found a problem when using unix socket with ASGI spec.

I’ll note right away that at the time of testing, the WSGI specification using a tcp socket and a unix socket works correctly.
ASGI with tcp sockets also works fine.

When you use ASGI with a unix listener, you get an error (#635):

[alert] 32427#513572 [unit] #8: Python failed to create 'client' pair
[alert] 32427#513572 [unit] Python failed to call 'loop.call_soon'
Traceback (most recent call last):
  File "/home/shared/Builds/Python-3.10.2/lib/python3.10/asyncio/base_events.py", line 745, in call_soon
    self._check_closed()
ValueError: invalid literal for int() with base 10: ''

As I think, the problem is hidden initially in the function:
nxt_py_asgi_create_address which parses the address incorrectly and uses a "unix:" client address that cannot be replaced with "X-Forwarded-For" due to configuration validators that only allow replacement for source CIDR addresses that cannot be source when using unix-socket.

@VBart's suggestion of using the "X-Forwarded-For" header for unix sockets could be a solution if the config validator accepts options that match not only CIDR, but also specify a mask like: "*" or "unix" or "0.0.0.0/0" (applicable to unix sockets) that trusts any source address to replace and specify the client address when using a unix socket.

As far as I remember, something similar is used, for example, in the implementation of uWSGI and ALLOWED_HOSTS.

It is currently not possible to get a listener to work using a unix socket and ASGI at the same time. For me personally, this is a serious problem, given the specifics of tcp and unix sockets.

UPDATE:
After additional research of the problem, I came to the conclusion that this problem consists of two, in connection with this, I decided to separate the two different problems:

1. Another Issue: X-Forwarded-For (client_ip->source) with unix: #642
2. This issue: nxt_py_asgi_create_address with unix: #641

This issue is only partly related to issue #642, since the header: "X-Forwarded-For" may or may not be set, but ASGI spec should work with the unix: socket properly.

[mar0x]

Looks like a #635 duplicate.

[echolimazulu]

Looks like a #635 duplicate.

Good afternoon mar0x. Yes, this is a duplicate of the essence of the problem, but it gives detailed definitions without reference to the framework used, as was the case in #635. I hope that the information I have provided will help the community to quickly understand this problem and propose a solution. Since the problem was identified as a bug in #635, no working solution other than temporarily bypassing the problem by switching to a tcp socket has been proposed (thanks for that nonetheless).

[echolimazulu]

I am closing this PR as it duplicates the issue: #635.