https://gitlab.com/tozd/docker/external-ip

Available as:

• tozd/external-ip
• registry.gitlab.com/tozd/docker/external-ip

tozd/base ← tozd/dinit ← tozd/external-ip

• ubuntu-bionic
• ubuntu-focal
• ubuntu-jammy
• alpine-38
• alpine-310
• alpine-312
• alpine-314
• alpine-316

• /var/log/dockergen: Log files when LOG_TO_STDOUT is not set to 1.

• DOCKER_HOST: Where to connect to access Docker daemon to monitor for new containers. Default is /var/run/docker.sock inside the container.
• LOG_TO_STDOUT: If set to 1 output logs to stdout (retrievable using docker logs) instead of log volumes.

Run:

$ docker run --detach \
 --net=host --cap-add=NET_ADMIN --cap-add=NET_RAW \
 --volume /var/run/docker.sock:/var/run/docker.sock \
 --volume /run/xtables.lock:/run/xtables.lock \
 tozd/external-ip:ubuntu-bionic

After that, if any other Docker container has an environment variable EXTERNAL_IP set, with an IP address to use for containers external IP, iptables will be configured to route container's traffic from that external IP. The external IP must be assigned on the host.

A chain named EXTERNAL_IP is created in the nat table into which all the rules are added. And one more empty chain is created after this one for any additional custom rules you might want to add, named AFTER_EXTERNAL_IP.

Please make sure /run/xtables.lock exists on the host before starting the container. This file ensures iptables locking is consistent between the host and the container, preventing race conditions that can cause containers to fail to start. If this file does not exist, Docker will incorrectly create it as a directory, which may cause issues both on the host and with the container.

When LOG_TO_STDOUT is set to 1, Docker image logs output to stdout and stderr. All stdout output is JSON.

version: '3'

services:
  nat_manager:
    image: tozd/external-ip:ubuntu-bionic
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - /run/xtables.lock:/run/xtables.lock
    network_mode: host
    cap_add:
      - NET_ADMIN
      - NET_RAW

  a:
    image: byrnedo/alpine-curl
    command: "-s http://ifconfig.me"
    environment:
      EXTERNAL_IP: XX.XX.XX.XX

  b:
    image: byrnedo/alpine-curl
    command: "-s http://ifconfig.me"
    environment:
      EXTERNAL_IP: YY.YY.YY.YY

Set XX.XX.XX.XX and YY.YY.YY.YY to your external IP address.

There is also a read-only GitHub mirror available, if you need to fork the project there.