Using Windows Proxy Settings in WSL2

Setting up a Proxy for WSL2

WSL2 (Windows Subsystem for Linux 2) utilizes a virtual machine approach, separating its network from Windows. This means that network traffic no longer shares the same subnet as the Windows host, making it more challenging to use the host's proxy settings.

Obtaining the Host IP in WSL

In WSL, the IP address changes with each reboot, so you cannot set a static proxy. WSL2 writes the IP address to /etc/resolv.conf, allowing you to retrieve the host's IP using the following command:

cat /etc/resolv.conf | grep nameserver | awk '{ print $2 }'

To obtain WSL2's IP address, you can use:

hostname -I | awk '{print $1}'

Setting up the Proxy

With the host's IP address, you can set up the proxy by exporting environment variables. Replace <Port> with your proxy's port number, and don't forget to allow connections from the local network in your proxy software.

export http_proxy='http://<Windows IP>:<Port>'
export https_proxy='http://<Windows IP>:<Port>'

However, this method requires you to reset the proxy every time you restart the terminal, and you'll need to manually enter the IP address, which can be cumbersome. This is where a script comes in handy!

#!/bin/sh
hostip=$(cat /etc/resolv.conf | grep nameserver | awk '{ print $2 }')
wslip=$(hostname -I | awk '{print $1}')
port=<PORT>

PROXY_HTTP="http://${hostip}:${port}"

set_proxy(){
    export http_proxy="${PROXY_HTTP}"
    export HTTP_PROXY="${PROXY_HTTP}"

    export https_proxy="${PROXY_HTTP}"
    export HTTPS_proxy="${PROXY_HTTP}"
}

unset_proxy(){
    unset http_proxy
    unset HTTP_PROXY
    unset https_proxy
    unset HTTPS_PROXY
}

test_setting(){
    echo "Host ip:" ${hostip}
    echo "WSL ip:" ${wslip}
    echo "Current proxy:" $https_proxy
}

if [ "$1" = "set" ]
then
    set_proxy

elif [ "$1" = "unset" ]
then
    unset_proxy

elif [ "$1" = "test" ]
then
    test_setting
else
    echo "Unsupported arguments."
fi

Remember to replace <PORT> on line 4 with your proxy's port number!

If you want Git to use the proxy as well, add the following commands to the set_proxy and unset_proxy functions:

// Add proxy
git config --global http.proxy "${PROXY_HTTP}"
git config --global https.proxy "${PROXY_HTTP}"

// Remove proxy
git config --global --unset http.proxy
git config --global --unset https.proxy

After that, run . ./proxy.sh set to automatically set the proxy. Use unset to cancel the proxy and test to check the proxy status and verify if the environment variables are correctly modified.

Remember to include the . before running the script (e.g., . ./proxy.sh set or source ./proxy.sh set). Running the script directly (e.g., ./proxy.sh set or sh proxy.sh set) will execute it in a child shell, which won't affect the current shell's environment variables.

Additionally, you can add the following lines to your ~/.bashrc file, replacing the paths with the location of your script:

alias proxy="source /path/to/proxy.sh"
. /path/to/proxy.sh set

The first line sets an alias for the script, allowing you to use the proxy command from any directory to access the script's functionality. The second line runs the script during shell startup, automatically setting the proxy without additional steps.

Firewall Settings

If you've completed the previous steps and can already use the proxy successfully, you can skip this section. However, if the proxy is correctly set up, especially if you've allowed connections from the local network, but you still can't access the internet, and the proxy software isn't receiving requests, it's possible that the Windows Firewall is blocking the connection.

Try pinging the host IP and using telnet to connect to the proxy port to check if the connection is successful. If the connection fails, it's likely a firewall issue.

You can try allowing the proxy software through the firewall in the "Allow an app or feature through Windows Defender Firewall" section of the Control Panel's firewall settings.

Alternatively, you can create an inbound rule in the Advanced Settings. If you're unsure, you can allow any program using any protocol and permit inbound requests from the 172.16.0.0/12 and 192.168.0.0/16 remote IP ranges.