Socket Connect hangs until timeout runs out in mirrored mode.

Windows Version

Microsoft Windows [Version 10.0.22631.2715]

WSL Version

2.0.9.0 and 2.0.14 tested

Are you using WSL 1 or WSL 2?

• WSL 2
• WSL 1

Kernel Version

5.15.133.1-1

Distro Version

Ubuntu 22.04

Other Software

No response

Repro Steps

Call this script in mirrored mode as normal user or sudo (try both):

import socket
import time
import os

def is_port_in_use(port):
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
        # s.settimeout(2)  # set timeout directly

        print(f"Socket type: {s.type}")
        print(f"Socket family: {s.family}")
        print(f"Socket timeout: {s.gettimeout()} seconds")
        # Get and print socket options
        print(f"SO_REUSEADDR option: {s.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR)}")
        print(f"SO_KEEPALIVE option: {s.getsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE)}")
        print(f"TCP_NODELAY option: {s.getsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY)}")
        print("checking: ", port)
        print("Timeout: ",s.gettimeout())
        return s.connect_ex(("localhost", port)) == 0
    
    
print("Uid: ", os.getuid())
start_time = time.time()
print("Is Port in use:", is_port_in_use(6006))
print("--- Runtime: %s seconds ---" % (time.time() - start_time))

Expected Behavior

It directly checks if the socket is in use or not.

Actual Behavior

Sometimes it takes over 132 seconds to return True or False. In not mirrored mode it always directly returns. I came across this issue using ros, where the roscore takes about 2 minutes to start, or starting tensorboard takes around 2 minutes aswell, so i build this script to reproduce the error.

If it directly returns true or false in mirrored mode, i start the script as sudo and then the problem occurs again.
What is interesting, is that if i set the socket timeout to a specific second, then it will return after that. Its like its blocked for the default timeout.

Diagnostic Logs

Without networking mode mirrored:

❯ python3 test_connect.py
Uid: 1000
Socket type: 1
Socket family: 2
Socket timeout: None seconds
SO_REUSEADDR option: 0
SO_KEEPALIVE option: 0
TCP_NODELAY option: 0
checking: 6006
Timeout: None
Is Port in use: False
--- Runtime: 0.0001404285430908203 seconds ---

With networking mode mirrored:

❯ python3 test_connect.py
Uid: 1000
Socket type: 1
Socket family: 2
Socket timeout: None seconds
SO_REUSEADDR option: 0
SO_KEEPALIVE option: 0
TCP_NODELAY option: 0
checking: 6006
Timeout: None
Is Port in use: False
--- Runtime: 132.54164338111877 seconds ---

Sometimes it works as fast as without mirrored. But sometimes not, even tho it results in the port is not in use.
If it works directly, starting the script with sudo will result again in this timeout.

With networking mode mirrored and setting timeout to a second with:
s.settimeout(1) before the connect_ex call

❯ python3 test_connect.py
Uid: 1000
Socket type: 1
Socket family: 2
Socket timeout: 1.0 seconds
SO_REUSEADDR option: 0
SO_KEEPALIVE option: 0
TCP_NODELAY option: 0
checking: 6006
Timeout: None
Is Port in use: False
--- Runtime: 1.001239538192749 seconds ---

Or with settimeout to 2 seconds:

❯ python3 test_connect.py
Uid: 1000
Socket type: 1
Socket family: 2
Socket timeout: 2.0 seconds
SO_REUSEADDR option: 0
SO_KEEPALIVE option: 0
TCP_NODELAY option: 0
checking: 6006
Timeout: 2.0
Is Port in use: False
--- Runtime: 2.0022153854370117 seconds ---