[systemd-devel] [PATCH v2] networkd: do not change kernel forwarding parameters when IPForwarding is unset

[Michael Marineau]

On Fri, May 15, 2015 at 1:49 PM, Tom Gundersen <teg at jklm.no> wrote:
> On Fri, May 15, 2015 at 10:02 PM, Lennart Poettering
> <lennart at poettering.net> wrote:
>> On Fri, 15.05.15 12:56, Michael Marineau (michael.marineau at coreos.com) wrote:
>>
>>> (build time option to ./configure that is)
>>
>> I guess I'd be OK with that...
>
> It would be a shame if we started diverging on the defaults I think.
> Would be nice if we could come up with some scheme that would work for
> everyone. Would an option be to use a script to append
> IPForward='kernel' to your network files on upgrades? Pretty dirty,
> but I don't know how you usually deal with config changes...

So far we don't do anything to modify user configs and try to ensure
we maintain compatibility. Since there are a limited number of things
in the CoreOS base image this usually isn't a problem. In the past we
have made incompatible changes, the biggest in order to follow
upstream docker[1] but it was well advertised in the docker community
and impacted users would have a pretty easily googlable situation. In
this case if we fail to migrate a user properly networking in a
container is going to silently stop and it won't be immediately
obvious why.

[1]: https://coreos.com/blog/docker-1-3-2-stable-channel/