OpenVPN and Transmission in docker-compose

docker-compose.yaml

version: '3.8'
  services:
    openvpn:
      build:
        context: .
        dockerfile: Dockerfile.openvpn
      cap_add:
        - NET_ADMIN
      devices:
        - "/dev/net/tun"
      volumes:
        - ./vpn.ovpn:/etc/openvpn/vpn.ovpn
      restart: always
      network_mode: "host"
    transmission:
      build:
        context: .
        dockerfile: Dockerfile.transmission
      volumes:
        - /home/media/torrents:/torrents
        - /home/media/transmission:/etc/transmission
      network_mode: "service:openvpn"
      restart: always
      depends_on:
        - "openvpn"