netdev - Re: [PATCHv2 net 2/2] ipv4: update RTNH_F

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Date:	Thu, 29 Oct 2015 22:15:51 +0200 (EET)
From:	Julian Anastasov <ja@....bg>
To:	Andy Gospodarek <gospo@...ulusnetworks.com>
cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCHv2 net 2/2] ipv4: update RTNH_F_LINKDOWN flag on UP
 event


	Hello,

On Tue, 27 Oct 2015, Andy Gospodarek wrote:

> > 	Of course, we have a semantic problem when setting
> > RTNH_F_LINKDOWN on last address removal, i.e. this event
> > has nothing to do with the link state. But it works because
> > RTNH_F_LINKDOWN is valid for lookups only when DEAD flag
> > is not set, so that is why my patch looks this way.
> The problem you describe here was a concern of mine as well.  I would
> really like the output of 'ip route show' to properly reflect the link
> state and fix the problem you describe, but it seems like it will not in
> this case with your current patch.  I'll do a bit more testing and let
> you know.

	Another option is to remove the RTNH_F_LINKDOWN
usage from any event, from FIB structs. In case only
netif_carrier_ok check is needed, it looks cheap to just
call it after the IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN check.
When showing it to user space we can again use netif_carrier_ok.

	The new fib_rebalance() is special, it still
needs to be called, just like now on NETDEV_CHANGE
event but only when ignore_routes_with_linkdown=1, i.e.
we can avoid calling fib_sync_up/fib_sync_down_dev in
fib_netdev_event if the flag is not set, guarded by 
CONFIG_IP_ROUTE_MULTIPATH check.

	To make this work we can also call somehow
fib_rebalance() from devinet_conf_proc() context when
the flag is changed, all this is for the
CONFIG_IP_ROUTE_MULTIPATH case.

Regards

--
Julian Anastasov <ja@....bg>
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