Tun module in dockerized Microsoft Azure Functions to run openvpn

Question

I want to create a dockerized Azure function that routes all the http traffic through an openvpn tunnel and switches the vpn connection config every X minutes. However openvpn in the container cannot work dince openvpn cannot create the tun/tap interface, and if i try to load the tun module, it is not found.

My dockerfile looks like this:

FROM mcr.microsoft.com/azure-functions/dotnet-isolated:4-dotnet-isolated8.0-appservice

RUN apt-get update && \
    apt-get install -y openvpn iputils-ping psmisc kmod iproute2 wget unzip

COPY .pass /etc/openvpn/.pass
WORKDIR /etc/openvpn

# download list of ovpn configs and unzip them

ENV AzureWebJobsScriptRoot=/home/site/wwwroot \
    AzureFunctionsJobHost__Logging__Console__IsEnabled=true

COPY --from=installer-env /home/site/wwwroot /home/site/wwwroot
COPY startup.sh /home/site/wwwroot/startup.sh
RUN chmod +x /home/site/wwwroot/startup.sh

ENTRYPOINT ["/bin/bash", "/home/site/wwwroot/startup.sh"]

And my startup script does this to both run the function and switch the VPN connection:

while true; do
    CONFIG_FILE=$(find $CONFIG_DIR -type f -name "*.ovpn" | shuf -n 1)
    kill_vpn
    sleep 5
    start_vpn "$CONFIG_FILE"
    sleep 30
    if ping -c 1 -W 10 8.8.8.8 > /dev/null; then
        echo "$(date): VPN successfully connected." >> $LOGFILE
    else
        echo "$(date): VPN connection failed." >> $LOGFILE
    fi
    sleep 600
done &
# Start the Azure Function after the VPN is up and running
echo "Starting Azure Function"
cd /home/site/wwwroot || exit
dotnet exec /azure-functions-host/Microsoft.Azure.WebJobs.Script.WebHost.dll

I pushed the image on Container registry and deployed on a simple Container instance. However it seems that ovpn cannot work since there is no tun/tap device on the host.

ERROR: Cannot open TUN/TAP dev /dev/net/tun: No such file or directory (errno=2)

If I ssh and try to modprobe tun I get the following error:

modprobe: FATAL: Module tun not found in directory /lib/modules/5.10.102.2-microsoft-standard

Is it possible to get a tun device on microsoft azure ? or what do you suggest as an alternative to achieve a scalable soluton to many instances of functions each one connected to a switching vpn with openvpn ?

Tun module in dockerized Microsoft Azure Functions to run openvpn

Answers (1)

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