proxy-nginx: invalid proxy_pass address resolved when connected to a VPN

[mfranciszkiewicz]

While building the proxy-nginx Docker image and being connected to a VPN, the host address can be resolved to an invalid, VPN-specific address:

# proxy-nginx.Dockerfile
getent hosts host.docker.internal | awk '{ print $1 }'

the output, if present, is assigned to the HOST_ADDR variable:

# proxy-nginx.Dockerfile
sed -i "s/{HOST_ADDR}/$HOST_ADDR/" /etc/nginx/nginx.conf

and used as a proxy_pass destination:

# nginx.conf
proxy_pass http://{HOST_ADDR}:{MITM_PROXY_PORT};

the end result is that any yagna API call will be redirected to an invalid network address