As of Docker version 18.03, you can use the host.docker.internal hostname to connect to your Docker host from inside a Docker container.
This works fine on Docker for Mac and Docker for Windows, but unfortunately, this is not was not supported on Linux until Docker 20.10.0was released in December 2020.
Starting from version 20.10 , the Docker Engine now also supports communicating with the Docker host via host.docker.internal on Linux. Unfortunately, this won't work out of the box on Linux because you need to add the extra — add-hostrun flag:
--add-host=host.docker.internal:host-gateway
This blog post demonstrates the issue on Linux using a simple example and also explains the configuration to make sure you have an identical behavior across Linux, Mac, and Windows.