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

Michael Marineau michael.marineau at coreos.com
Fri May 15 12:55:49 PDT 2015

On Fri, May 15, 2015 at 12:52 PM, Lennart Poettering
<lennart at poettering.net> wrote:
> On Fri, 15.05.15 12:42, Michael Marineau (michael.marineau at coreos.com) wrote:
>> On Fri, May 15, 2015 at 12:18 PM, Lennart Poettering
>> <lennart at poettering.net> wrote:
>> > On Fri, 15.05.15 12:08, Nick Owens (nick.owens at coreos.com) wrote:
>> >
>> >> In 5a8bcb674f71a20e95df55319b34c556638378ce, IPForwarding was introduced
>> >> to set forwarding flags on interfaces in .network files. networkd sets
>> >> forwarding options regardless of the previous setting, even if it was
>> >> set by e.g. sysctl. This commit makes IPForwarding not change forwarding
>> >> settings, so that systems using sysctl continue to work even if
>> >> IPForwarding is unset in their .network files.
>> >>
>> >> See https://bugs.freedesktop.org/show_bug.cgi?id=89509 for the initial
>> >> bug report.
>> >
>> > I think there should be an explicit way to enable the "kernel default
>> > mode", i.e. the parser for this one option should consider a special
>> > value "kernel" or so to explicitly ask for the kernel default.
>> >
>> > I'd still prefer if we'd default to ip forwarding off, rather than ip
>> > forwarding as kernel default, for security reasons.
>> Well, in CoreOS we *have* to use the kernel default if the value is
>> unset, there simply is no way to safely upgrade existing systems to
>> the new configuration scheme from the old sysctl one. The semantics of
>> the two are too different. Even if there was a reasonable translation
>> we are not in the business of modifying user configs.
> Well, but I think I would prefer if upstream would default to "off",
> even if coreos then deviates from that and defaults to "kernel"...

Fair enough, should it be a option to configure then?

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