[Commotion-dev] OLSR sensitivity to node's local time, repeater nodes sporadically don't find default gateway

[Ben West]

I've filed this as an issue on the Commotion-OpenWRT queue, so that it can
be revisited later if needed:
https://code.commotionwireless.net/issues/331

On Thu, Jun 28, 2012 at 5:02 AM, Ben West <me at benwest.name> wrote:

> I'm starting this as a separate thread, in case the problem also arises
> for the folks testing on Android.
>
> I've found that if a repeater node boots up with its local time grossly
> out of sync (ath5k devices especially), and it is unable to sync its local
> time via ntpdate, then it may not find its gateway route and thus not pass
> any client traffic.  The node will still be accessible to SSH from other
> nodes on the mesh, so you can login manually to set a default route and
> update local time, but the OLSR assignment of default route appears to fail
> until local time is updated.
>
> A further complication is that a repeater node with badly out-of-sync
> local time seems to also cause neighboring repeater nodes to also not find
> their default route, i.e. spreading the problem to more than one node.
>  This problem, as I've observed it, is extremely sporadic.  E.g. rebooting
> all nodes in the mesh can fix it.
>
> The best measure I've found to avoid the problem is to use the OLSR
> SmartGateway feature (which Commotion OpenWRT does), along with a recurring
> ntpdate job that periodically sync the node's local time.  That is, if
> ntpdate doesn't succeed on boot-up due to no Internet access, it will run
> again (and again) after a few minutes, until the gateway node is available.
>  (The images I just published in the previous thread do this.)
>
> I had posed this question on the olsr-users listserv a while back,
> although no one was quite sure what caused the problem.  OLSRd itself
> shouldn't have a hard dependency on whether the node's local time is in
> sync.
>
> Finally, do please note this problem is not unique to Commotion.  I've
> experienced it on mesh nodes running ROBIN and plain vanilla OpenWRT
> Backfire.
>
> --
> Ben West
> me at benwest.name
>
>


-- 
Ben West
me at benwest.name
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