Make network and netmask configurable via environment parameter

[tkaefer]

This will enable the setup to have different networks and netmasks being used.

[tkaefer]

One example for setting up a aka cluster with own IP network/netmask:

version: '2'
services:
  seed:
    image: mhamrah/clustering:0.3
    ports:
      - '1600:1600'
    environment:
      CLUSTER_PORT: 1600
#      CLUSTER_IP: seed
      SEED_PORT_1600_TCP_ADDR: 100.64.1.10
      HOST: seed
    networks:
      backend:
        ipv4_address: 100.64.1.10

  c1:
    image: mhamrah/clustering:0.3
    ports:
      - '1601:1601'
    environment:
      CLUSTER_PORT: 1601
#      CLUSTER_IP: 100.64.1.11
      SEED_PORT_1600_TCP_ADDR: 100.64.1.10
      HOST: c1
    networks:
      backend:
        ipv4_address: 100.64.1.11

  c2:
    image: mhamrah/clustering:0.3
    ports:
      - '1602:1602'
    environment:
      CLUSTER_PORT: 1602
#      CLUSTER_IP: 100.64.1.12
      SEED_PORT_1600_TCP_ADDR: 100.64.1.10
      HOST: c2
    networks:
      backend:
        ipv4_address: 100.64.1.12

  proxy:
    image: tkaefer/docker-mac-network
    ports:
      - "127.0.0.1:13194:13194"
    command: TCP-LISTEN:13194,fork TCP:100.64.1.20:1194
    networks:
      backend:

  openvpn:
    image: kylemanna/openvpn
    volumes:
      - ./config:/etc/openvpn
      - ./local:/local
    cap_add:
      - NET_ADMIN
    environment:
      dest: akka-mac-docker.ovpn
      DEBUG: '1'
      DOCKER_NETWORK: 100.64.1.0
      DOCKER_NETMASK: 255.255.255.192
    command: /local/helpers/run.sh
    networks:
      backend:
        ipv4_address: 100.64.1.20

networks:
  backend:
    driver: bridge
    ipam:
      driver: default
      config:
        - subnet: 100.64.1.0/26
          gateway: 100.64.1.1

The environment variables exposed as:

      DOCKER_NETWORK: 100.64.1.0
      DOCKER_NETMASK: 255.255.255.192

will ensure the right routing in the OpenVPN client config file.

[wojas]

@tkaefer Sorry for the late response. Merging, thanks!