Unable to connect to other addons

[CooperRS]

Problem/Motivation

I have a HAOS installation on my Raspberry Pi. Besides some other addons, this HAOS installation runs the following two addons:

1. WireGuard Client (this repository)
2. TVHeadend (https://github.com/dfigus/addon-tvheadend)

The HAOS WireGuard client is connected to a WireGuard Server in the internet. In addition, there are other WireGuard clients connected to that server.

Now, all WireGuard clients can open the Home Assistant UI (<IP>:8123) just fine. However, no WireGuard client can open the TVHeadend page (<IP>:9981).

Expected behavior

Connecting to TVHeadend (<IP>:9981) opens the TVHeadend page.

Actual behavior

Connecting to TVHeadend (<IP>:9981) returns "Not Authorized".

Steps to reproduce

1. Setup a HAOS installation
2. Install the Wireguard Client Addon
3. Install the TVHeadend Addon
4. Connect to the WireGuard VPN
5. Try to access TVHeadend via VPN

Proposed changes

I suspect it has something to do with the Docker environment and it's network settings used by HAOS. But I'm unsure how to fix it 🤔