On Do, 2015-04-02 at 21:08 +0300, Roman Gushchin wrote: > >> The next question I have is about the behavior of the new setting > >> in the presence of an RA MTU option. It seems like the sysctl > >> doesn't override that RA MTU option, but rather just clamps it. > >> > >> And then if it's in range, this controls only whether the default > >> route has it's MTU adjusted. > >> > >> That doesn't make any sense to me if we then go and do the > >> rt6_mtu_change() call unconditionally. The route metric update > >> and the rt6_mtu_change() go hand in hand. > > > > Agreed but that gets interesting: > > > > I guess during testing the cnf.mtu6 value was equal to the newly > > announced mtu value, so the rt6_mtu_change call does not happen. We > > update cnf.mtu6 so a second RA packet would actually bring the system > > into the desired state but we have a moment where the default route > > carries a too big MTU. That's not good. > > Agreed. > > > Easiest solution is to reorder those calls but that also leaves us with > > a time frame where we carry the incorrect MTU on the default route. > > Otherwise we must conditionally filter out the default routes. > > Roman, any ideas? > > I think, such approach will work on practise, but looks not very beatiful. > > May be, a better idea is to serarate per-route and per-device MTU, > so an updating of per-device MTU will not affect per-route MTU. > Actual MTU can always been calculated as min(route_mtu, device_mtu), > but we wouldn't need to update mtu on each route on receiving RA MTU option, > for instance. > > Do you see any problems with such approach?
If I understood you correct this actually seems to be quite an intrusive change? :/ Can you show me some code how to do this? I would also dislike adding a filtering capability to the route mtu updates. Currently I don't have a god idea, sorry. Bye, Hannes -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
