Skip to content

qoomon/docker-host

master
Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?
Code

Latest commit

I don't know why but i have multiple default routes in my container.
04ef11f

Git stats

Files

Permalink
Failed to load latest commit information.
Type
Name
Latest commit message
Commit time
March 17, 2023 11:13
October 5, 2018 07:37
February 7, 2023 10:28

docker-host Sparkline

GitHub release Docker Stars Build Workflow

Docker Image Tags:

  • latest
  • 3
  • 3.x.x

Docker image to forward TCP and UDP traffic to the docker host. This also works for (rootless) podman. This README.md uses the term docker, but you can read that as both docker and podman (it works for both), unless otherwise specified.

This container will determine docker host address in the following order

  • Use ip from environment variable DOCKER_HOST if set

    • This allows you to use this image to forward traffic to arbitrary destinations, not only the docker host.
  • Try to resolve host using DNS names e.g. getent ahostsv4 host.docker.internal

    • docker hostname host.docker.internal
    • podman hostname host.containers.internal
  • Defaults to default gateway (ip -4 route show default)

Ports

By default all ports (1-65535) are forwarded to docker host.

  • You may restrict ports by setting environment variable PORTS to a space and/or comma separated list of ports and/or port ranges e.g
    • docker run -e PORTS='443, 8000-9000' ....
  • You may also configure port mapping e.g. 443:8443, 8000-9000:5000-6000 (CONTAINER_PORT:HOST_PORT).

⚠️ On Linux systems

  • You have to bind your host applications to 0.0.0.0 or bridge network gateway in addition to 127.0.0.1.

    Use following docker command to get the bridge network gateway IP address

    docker network inspect bridge --format='{{( index .IPAM.Config 0).Gateway}}'

    NOTE: For (rootless) podman, it's sufficient to bind to localhost, assuming default podman installation.

  • You might need to configure your firewall of the host system to allow the docker-host container to communicate with the host on your relevant port, see #21.

⚠️ On MacOS systems

Podman Only
  • You probably need to add nf_nat kernal module to podman machine by running following commands

    podman machine ssh
    
    sudo modprobe nf_nat

Examples

These examples will send messages from docker container to docker host with netcat

Preparation

Start netcat server TCP on port 2323 to receive and display messages

nc -p 2323 -lk

Start netcat server UDP on port 5353 to receive and display messages

nc -p 5353 -lk -u

Docker Link

Run the dockerhost container.

docker run --rm \
  --name 'docker-host' \
  --cap-add=NET_ADMIN --cap-add=NET_RAW \
  --restart on-failure \
  -d qoomon/docker-host

Run your application container and link the dockerhost container. The dockerhost will be reachable through the domain/link dockerhost of the dockerhost container

This example will let you send messages to TCP netcat server on docker host.

docker run --rm \
  --link 'docker-host' \
  -it alpine nc 'docker-host' 2323 -v

This example will let you send messages to UDP netcat server on docker host.

docker run --rm \
  --link 'docker-host' \
  -it alpine nc 'docker-host' 5353 -u -v

Docker Network

Create the dockerhost network.

network_name="Network-$RANDOM"
docker network create "$network_name"

Run the dockerhost container within the dockerhost network.

docker run --name "${network_name}-docker-host" \
  --cap-add=NET_ADMIN --cap-add=NET_RAW \
  --restart on-failure \
  --net=${network_name} --network-alias 'docker-host' \
  qoomon/docker-host

Run your application container within the dockerhost network. The dockerhost will be reachable through the domain/link docker-host of the dockerhost container

This example will let you send messages to TCP netcat server on docker host.

docker run --rm \
  --link 'docker-host' \
  -it alpine nc 'docker-host' 2323 -v

This example will let you send messages to UDP netcat server on docker host.

docker run --rm \
  --link 'docker-host' \
  -it alpine nc 'docker-host' 5353 -u -v

Docker Compose

version: '2'

services:
    docker-host:
        image: qoomon/docker-host
        cap_add: [ 'NET_ADMIN', 'NET_RAW' ]
        mem_limit: 8M
        restart: on-failure
    tcp_message_emitter:
        depends_on: [ docker-host ]
        image: alpine
        command: [ "sh", "-c", "while :; do date; sleep 1; done | nc 'docker-host' 2323 -v"]
    udp_message_emitter:
        depends_on: [ docker-host ]
        image: alpine
        command: [ "sh", "-c", "while :; do date; sleep 1; done | nc 'docker-host' 5353 -u -v"]

External References