[master] deb,rpm: add kmod as recommended dependency to provide modprobe

[thaJeztah]

• relates to Dockerfile: make sure modprobe is available in dev-container moby/moby#48992
• relates to Only enable bridge netfiltering when needed moby/moby#48492
• relates to Fix br_netfilter module loading logic moby/moby#48960

Depending on the host configuration, the br_netfilter module may not be loaded by default. In this situation, docker will try to load the module through modprobe.

Older versions of docker would silently ignore failing to do so, log a message, and continue;

time="2024-11-29T20:04:58.538404376Z" level=warning msg="Running modprobe bridge br_netfilter failed with message: , error: exec: \"modprobe\": executable file not found in $PATH"

However, starting with db25b0dcd0461802289e962aa0df3abd323d1994 and 264c15bfc427d1321c5b302e48e16d113b06ef92, we now produce an error:

=== FAIL: libnetwork/drivers/bridge TestCreateFullOptions (0.04s)
time="2024-11-29T19:03:44Z" level=error msg="Running modprobe br_netfilter failed with message: " error="exec: \"modprobe\": executable file not found in $PATH"
    bridge_linux_test.go:280: Failed to create bridge: loadBridgeNetFilterModule failed: cannot restrict inter-container communication: modprobe br_netfilter failed: exec: "modprobe": executable file not found in $PATH

This patch updates the packages to add kmod (which provides modprobe) as a recommended dependency. We should probably look for alternatives in our code to not require modprobe.

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[thaJeztah]

Thanks for reviewing! Since opening this PR, I also discussed a bit with @robmry @neersighted to look for possible alternatives that don't require modprobe (more so because running modprobe inside a container doesn't work for what we try to do.

I was a bit hesitant on adding a new dependency, but pending an alternative in the daemon itself, I think it's the most correct thing to do for the time being (i.e., we need modprobe in some cases, so we may as well reflect that in the package).

Once we have an alternative for calling modprobe, this is probably fine to bring in (just need a reminder to "self" to remove it again once we no longer need it.

Also opened a backport for 27.x;

• [27.x backport] deb,rpm: add kmod as recommended dependency to provide modprobe #1121

[robmry]

I just tried an equivalent to the ip link show trick, based on https://github.com/weaveworks/go-odp/blob/master/odp/dpif.go#L70-L90

It worked perfectly in a (privileged) docker-in-docker container on a Debian host that didn't have ip6_tables loaded. So I'll get a PR raised soon.

I'll make it try to fall-back to real modprobe ... so maybe it's still a good idea to add this dependency?

[laurazard]

LGTM

[thaJeztah]

Thanks @robmry ! Yeah, I think this patch is still OK to have.