Add 'pre-defined/reserved' internal hostnames

[benoitf]

Feature request description

Some containers are using some predefined docker hosts like host.docker.internal or gateway.docker.internal

Then, these containers are failing during their execution as these hosts don't exists

It seems that there is host.containers.internal and gateway.containers.internal https://github.com/containers/gvisor-tap-vsock/blob/049be485f9a50ecbc8fb1aed9a040ceeead4e864/cmd/gvproxy/main.go#L187-L194

but for compatibility with Docker I think it would be nice if host.docker.internal and gateway.docker.internal were aliased to host.containers.internal. and gateway.containers.internal

Suggest potential solution

Add alias from host.docker.internal to host.containers.internal. and gateway.docker.internal to gateway.containers.internal

Have you considered any alternatives?

N/A

Additional context

I found that while testing digma-ai app with Podman

https://github.com/search?q=org%3Adigma-ai+host.docker.internal&type=code

related docker documentation: https://docs.docker.com/desktop/networking/#i-want-to-connect-from-a-container-to-a-service-on-the-host

[rhatdan]

@Luap99 PTAL

[Luap99]

I don't know the history of why we choose this name over the docker one but I will try to dig it up.
In general I have no issues in adding the docker entry as well, however that would need to happen both in gvproxy for podman machines and the normal /etc/hosts handling in c/common for the local podman.

[rhatdan]

We wanted to have a name without the letters "docker" but it turns out some customers built this functionality into the container images.

[Luap99]

I mean adding the entry is simple and because it helps converting existing workloads depending on it I think we should just add them.

[Luap99]

will be added with containers/gvisor-tap-vsock#251 and containers/common#1592