Hello, On Sat, 28 Jun 2014 19:11:46 +0200 Michael Biebl <bi...@debian.org> wrote:
> >> This seems to create a race with the networking SysV init script > >> which runs also runs ifup for hotplugged interfaces in > >> ifup_hotplug(). > > Yes, I've noticed that quite a while ago, but haven't found a good > > way to resolve the issue. > Can't you just drop if_hotplug() from the networking SysV init script? > Is there any downside if you do so? I think a better thing would be to block ifup requests from udev script until networking initscript has finished, but what you say can be done as a temporary fix, yes. > >> Is there a need to ifup allow=hotplug interfaces from within the > >> networking init script, seeing that net.aget / 80-networking.rules > >> already cover hotplugged interfaces? > > Even if I remove that, there's still probability of races, as > > net.agent blocks on the state of the real interface, while it > > should wait for ifupdown to do its job first. > Not quite sure I see the race here, can you elaborate? When net.agent is called, it checks if lo is up by looking into /sys directory, and if it's not, it waits. The problem is that the first thing ifupdown does on boot is configuring lo, so udev script proceeds immediately causing the race. > Also given that systemd will be our default init for jessie, we need > to improve the current systemd integration. E.g. we should ship a > native .service file for the networking init script handling the > non-hotplug interfaces. For hotplug interfaces we already have a > native ifup@.service. I currently have no idea how those service files are written, but if you write one, I will add it. Speaking of the integration itself, I think it'd be good to have a possibility to depend on a specific interface being up. > We also need think about how to properly daemons which require > $network (or network.target in systemd). > I have a PoC at [1] which provides a ifupdown-wait-online service. > The implementation is pretty basic, e.g. the criteria for network-up > is simply that one interface is up (no matter if hotplugged or auto). > Tollef mentioned, that we should probably refine that, e.g. add > additional checks for a default gateway or wait for both IPv6 and IPv4 > configuration (given the interface is configured that way). > As said, it's a prove of concept and would be interested in your > feedback. Ideally this would go into ifupdown itself. Sure, that's the proper place for such code. The thing which bothers me is that ‘being online’ is not a well-defined concept, so we need to think about it more, I guess. > I hope you are open to work with us on improving the systemd/ifupdown > integration. Well, I don't use systemd myself, but I'm definitely open to work on this. If I only had more time... I've had many ideas on what could I change in ifupdown and how, but it's very difficult to allocate resources for that. -- Cheers, Andrew
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