Docker container hangs internet connection

Bugs
1

Here is the interesting situation:

My host machine is Ubuntu. VirtualBox is installed.

In VirtualBox I have a Debian machine.

In the Debian machine I run the container:

docker run --name my-cge-container --volume="${HOME}":/home/sharedhome/ -it kambi/castle-engine-cloud-builds-tools:cge-unstable bash

Everything is OK. There is Internet connection in the container.

After container runs for about 1 minute:

There is no Internet connection inside the container,

and no Internet in Debian machine, while there is Internet in Ubuntu host machine.

I stop container. Immediately there is Internet in Debian machine.

Start the container again. The situation repeats - no internet after 1 minutes and Internet is available after stopping container.

I repeated it several times/restarted Debian machine etc.

I installed docker tools via snap on the Debian machine. Maybe this is the problem while I am not sure. Maybe it’s something with Castle’s Dockerfile.

2

Well, I think the problem is because I installed docker tools from snap on Debian machine. I tried other containers:

docker run --name my-debian -it debian:bookworm-slim bas
docker run --name my-ubuntu -it ubuntu bash

The result is exactly the same. So it’s not related to CGE docker file.
While I also tried on Ubuntu host machine with normally installed docker tools - CGE container works fine.

3

Hi,

My first guess would be to blame Virtual Box connection settings – maybe you have non-standard settings that somehow make the network drivers in the virtual machine “overloaded” after 1 minute? IOW, it would be independent from Docker at all. Searching the Internet I found a raport https://www.reddit.com/r/virtualbox/comments/sjzy14/vm_loses_network_connection_1_minute_after_startup/ ,

Those VMs network adapters are NAT. Not sure why that fixes it, but it does.

In my Virtual Box usage, I see my network cards are indeed NAT.

As for Docker from snap – personally I’m always installing it using DEB packages, following Install Docker Engine on Ubuntu | Docker Docs . This approach has worked for me. So, as you say, maybe the problem is because of snap? Switching your installation to use DEB packages and testing should answer this.

4

My network adapter is NAT. I uninstalled docker engine (installed by snap), removed traces. Then installed docker from DEB packages. The issues remains. Then I found the topics networking - Docker container loses Internet access after setting Docker to use manually created bridge - Server Fault and VBox & Docker NAT/Bridge issues · Issue #4329 · moby/moby · GitHub

So the solution is to use (I verified it works with CGE container):

docker run --net=host

By default in docker bridge is used and the problem is with the bridge.

  • bridge The default network driver.
  • host Remove network isolation between the container and the Docker host.

So the problem was in fact related to aspects of running docker in VirtualBox machine.

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