Connect to host socket from within docker container

Question

I want to connect to a unix domain socket on the host from within a docker container. Specifically, I run this on the host:

socat - ABSTRACT-LISTEN:/tmp/.X11-unix/X1

And run this in the container:

socat ABSTRACT-CONNECT:/tmp/.X11-unix/X1 -

The expected result is bidirectional communication. But this is met only when the container is run with --net=host:

docker run -it --net=host ubuntu bash

Omitting --net=host gives me ECONNREFUSED (Connection refused):

docker run -it ubuntu bash

Question: Why does --net matter for a unix domain socket connection?

Question: Is it best practice to use --net=host only for allowing unix domain socket connection?

DannyB · Accepted Answer · 2021-07-09 04:59:24Z

1

One of the key selling points of docker is isolation. Using --net=host loosens the network isolation, and while you can definitely use for some cases, I would usually consider it a "code smell", and try other ways first.

In your case, I believe you need to mount any socket you want available in the containers (untested).

$ docker run -it -e DISPLAY -v /tmp/.X11-unix/X1:/tmp/.X11-unix/X1 ...

answered Jul 9, 2021 at 4:59

DannyB

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