Accessing host from container

[g0loob]

Is there a recommended (cross-platform) way how to access host from a container? On Windows OS it works with host.docker.internal, but I don't know how to access on Linux (e.g. GitLab CI/CD pipeline).

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My use case is that I have Pact's mock server running on host machine. It can either listen on 127.0.0.1 or 0.0.0.0. In the test I need to start a Docker container and pass to it mock server's address as a command argument, e.g.

docker container run --rm my_image:tag -u mock-server.url # other arguments

I'm aware that I might need to replace the mock server with a Docker container, but I'm interested if there's a way with the current setup.

[HofmeisterAn]

I think for Linux, there is no default DNS name. I don't know much about the GitLab environment, but if you have a running container, you should get the host address from the Hostname property:

https://github.com/HofmeisterAn/dotnet-testcontainers/blob/de4c4a251152ee2cfdcd4061c8b1bcc0621e692f/src/DotNet.Testcontainers/Containers/TestcontainersContainer.cs#L85

If your service listens on 0.0.0.0, you should be able to access it. The Kafka configuration, for instance, uses the property during the container start to configure it own services:

https://github.com/HofmeisterAn/dotnet-testcontainers/blob/de4c4a251152ee2cfdcd4061c8b1bcc0621e692f/src/DotNet.Testcontainers/Configurations/Modules/MessageBrokers/KafkaTestcontainerConfiguration.cs#L78

[g0loob]

Thanks for the response. I'll mark it as answer, it will probably work in a "normal" scenario. I forgot that my tests in GitLab are executed in a container. I used container's ID to inspect it and get its IP address. Using the IP address of a container in which the tests are executed, and which hosts the mock server, I was able to access the mock server from the other container.