[systemd-devel] Systemd-networkd, default route and multiple interfaces

[Tom Gundersen]

On Tue, Jun 3, 2014 at 8:58 PM, Lennart Poettering
<lennart at poettering.net> wrote:
> On Mon, 02.06.14 21:02, Tom Gundersen (teg at jklm.no) wrote:
>
>> On Mon, Jun 2, 2014 at 8:47 PM, Reventlov
>> <contact+systemd+ml at volcanis.me> wrote:
>> > Since network files are applied to links whenever the links
>> > appear, how do systemd manage the "disappearance" of a default route ?
>>
>> You can have several default routes, so we just configure them all and
>> let the kernel handle it for us. We probably should improve the config
>> options to make it possible to override the priority of the routes.
>
> Windows initializes the route metric value for each route from the
> "speed" of the interface. If there are multiple links and for one we
> know it's a gigabit ethernet link, and the other is a 54mbit wlan link,
> then the former would automatically get preference... it's a bit black
> magic, but kinda cool black magic i think...
>
> that said, i am not sure we even have a sane API to determine the speed
> of links... maybe ethtool reports it at least for wired ethernet? but
> for wlan?

I suppose we could figure out the link speed in various ways, but how
useful is that going to be? I mean the _actual_ speed may be entirely
unrelated? I guess it is an ok hack if we have no other info
(currently it is basically random), though I would be a lot more
excited about it if there was a unified (and preferably sane) API to
getting this info.

If anyone would hack up a patch, I'd not object :)

-t