Load kernel module from mac os sierra host to a docker container

Question

I've juste installed a custom kernel module to enable SCTP support on my Macbook

And I would like to load this kernel module inside my docker container.

I tried to start a container using the --cap-add SYS_MODULE flag and install the libsctp-dev lksctp-tools kmod packages in the container to enable sctp using "modprobe sctp"... but unsuccessfully:

modprobe: ERROR: ../libkmod/libkmod.c:586 kmod_search_moddep() could not open moddep file '/lib/modules/4.9.13-moby/modules.dep.bin' modprobe:
  FATAL: Module SCTP not found in directory /lib/modules/4.9.13-moby

On a linux host, some people advise do to do like that : Docker loading kernel modules but it's both uncompatible with macOS and "dirty"...

So my question is : Does anyone know how to use kernel module in a docker container using a macOs host ? Is that even possible ?

Answer 1

I found out that docker for mac runs over an hyperkit VM with alpine to get the linux kernel.

As mentionned by @DanLowe in the comments, we can access this VM using the following command : docker run --rm -it --privileged --pid=host debian nsenter -t 1 -m -u -n -i sh

The kernel sources used by this VM are available here : https://github.com/linuxkit/linuxkit

I edited the kernel/kernel_config file and set CONFIG_IP_SCTP=y to enable SCTP support in the kernel.

Then I recompiled the kernel and copied my newly compiled kernel file (bzImage) to the docker for mac /Applications/Docker.app/Contents/Resources/moby/vmlinuz64 kernel file.

Restarted docker for mac and...

host>docker run -it debian container>cat /proc/net/protocols protocol size sockets memory press maxhdr slab module cl co di ac io in de sh ss gs se re sp bi br ha uh gp em SCTPv6 1416 1 0 no 0 yes kernel y y y y y y y y y y y y n y y y y y y SCTP 1256 0 0 no 0 yes kernel y y y y y y y y y y y y n y y y y y y

Pull Request here.