crash under docker container

[birosndr]

Hi,

I have a crash problem under docker container. I first start the docker run -ti -v /sys:/sys --privileged bash container and under that run the uhubctl and I get the following error: "Current status for hub 1 [1d6b:0002 Linux 5.10.107-android13-4-gd0319d1066a9-dirty dummy_hcd Dummy host controller dummy_hcd.0, USB 2.00, 1 ports, ppps] Port 1: 0100 power Current status for hub 3 [1d6b:0003 Linux 5.10.107-android13-4-gd0319d1066a9-dirty xhci-hcd xHCI Host Controller xhci-hcd-exynos.4.auto, USB 3.10, 1 ports, ppps] Port 1: 02a0 power 5gbps Rx.Detect Current status for hub 2 [1d6b:0002 Linux 5.10.107-android13-4-gd0319d1066a9-dirty xhci-hcd xHCI Host Controller xhci-hcd-exynos.4.auto, USB 2.00, 1 ports, ppps] Port 1: 0503 power highspeed enable connect [0424:4216] Segmentation fault (core dumped)"

First I want to know where can I found this core dump? What other folder should I mount into the docker container?

Thank you, Best regards.

[birosndr]

I solved it! you have to the docker run command the -v /dev:/dev because the uhubctl want to open files from there.

[DeqingSun]

It seems mapping /dev:/dev will work when the system is normal.

However when hub is replugged, running uhubctl will not work with a seg fault. On host machine it was OK.

In docker I can type

uhubctl -l 1-3.1 -p 1 -a 2

And I get

No compatible devices detected at location 1-3.1!
Run with -h to get usage info. 
Segmentation fault ( core dumped)

And dmesg showed the seg fault happen in libusb-1.0.so.0.3.0

With some printf debugging. For the replugged hubs, in docker, this line

https://github.com/mvp/uhubctl/blob/f37dcb5cbfc7ded79f8a91335b0affd982213414/uhubctl.c#L410C10-L410C21

returns LIBUSB_ERROR_NO_DEVICE error. I believe it is a docker issue rather than uhubctl issue.

I tried to use the script from https://github.com/balena-io-library/base-images/blob/master/balena-base-images/amd64/ubuntu/lunar/run/entry.sh it worked with hotplug hub, but it will prevent you from opening another terminal in host due to permission problems.

[DeqingSun]

Here I'll summarize what I found and solved in the past 3 days. Hope this will help anyone in the future who want to use docker with uhubctl, or do hotplug/replug of USB devices in general in docker.

In general, docker will work well with any hardware already connected in host machine if the container in run in privileged mode and map /dev from host to container. However, once connected, the host and container will have /dev disconnected. And new devices in host will not be synced with container anymore so those devices will not be accessible to containers.

The host uses udev to deal with new devices, and the container can also use udevadm monitor to observe all events, but I did not successfully got udev working in container or know anyone did it. So there need some work to do the udev job by ourselves.

There is a balena project solve the problem with a script to link /dev/ptmx in container. But doing so will prevent the host machine from opening new terminals. Unless we run chmod 666 /dev/pts/ptmx in host after start up container. There is a github issue but no solution yet. I tested this approach and it worked. But I do not understand how it works so far, and I prefer not to do anything on the host that is easy to forget.

I also see another stack-overflow post suggesting doing mknod and rm for the /dev/ttyACM* devices in plug and unplug events. It worked well for my Arduinos but not for USB hubs. So if the hub got disconnected and reconnected for any reason. uhubctl will not work anymore. I found a presentation slide and on page 57, it mentioned a way to use docker to access hot-plugged smartphones for testing. It seems the method also work for USB hub.

So in my application, I have a python script constantly listening to output of udevadm monitor. If there is new add event of hub or serial device, it will run mknod to create the node. And those node got removed in remove event.

Here I attached a minimal docker environment that works with hot-plugging CH335F HUB and Arduino Zero. There is more detailed comment in it.

usbPlugTest.zip