netdev - Re: [PATCH net-next 1/3] ipv4: properly refresh rtable entries on pmtu/redirect events

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Date:	Tue, 28 May 2013 22:44:30 +0300 (EEST)
From:	Julian Anastasov <ja@....bg>
To:	Timo Teras <timo.teras@....fi>
cc:	netdev@...r.kernel.org,
	Steffen Klassert <steffen.klassert@...unet.com>
Subject: Re: [PATCH net-next 1/3] ipv4: properly refresh rtable entries on
 pmtu/redirect events


	Hello,

On Tue, 28 May 2013, Timo Teras wrote:

> > > +static void fill_route_from_fnhe(struct rtable *rt, struct
> > > fib_nh_exception *fnhe) +{
> > > +	rt->rt_pmtu = fnhe->fnhe_pmtu;
> > > +	rt->dst.expires = fnhe->fnhe_expires;
> > 
> > 	The 'if (time_before' ... dst_set_expires() logic from
> > rt_bind_exception() is removed, may be it should be moved here,
> > i.e. fnhe_pmtu should be ignored if expired.
> 
> That code would not help much. The route's rt_pmtu is never reset to
> zero after the fnhe expires, so this would not make much difference.
> The old rt_pmtu and dst.expires would be left there anyway. All rt
> accesses check for expires too.

	I see, ipv4_mtu validates rt_pmtu expiration, so
such checks are not needed in rt_bind_exception and
fill_route_from_fnhe.

> This was actually intentional on the old code, as non-zero rt_pmtu
> implied that we had "next hop exception route" instead of "next hop
> route" and affected how the rt was invalidated in pmtu update.
> 
> If we want to clear out these fields, then it would make sense to have
> rt_bind_exception() to reset these on expiry to the struct
> fib_nh_exception directly and keep the direct assignments in
> fill_route_from_fnhe().
> 
> - Timo

Regards

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