netdev - Re: [PATCH net-next] ipv4: use next hop exceptions also for input routes

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Date:	Fri, 28 Jun 2013 21:28:37 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	ja@....bg
Cc:	timo.teras@....fi, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] ipv4: use next hop exceptions also for input
 routes

From: Julian Anastasov <ja@....bg>
Date: Thu, 27 Jun 2013 11:52:14 +0300 (EEST)

> 
> 	Hello,
> 
> On Thu, 27 Jun 2013, Timo Teräs wrote:
> 
>> Commit d2d68ba9 (ipv4: Cache input routes in fib_info nexthops)
>> assmued that "locally destined, and routed packets, never trigger
>> PMTU events or redirects that will be processed by us".
>> 
>> However, it seems that tunnel devices do trigger PMTU events in certain
>> cases. At least ip_gre, ip6_gre, sit, and ipip do use the inner flow's
>> skb_dst(skb)->ops->update_pmtu to propage mtu information from the
>> outer flows. These can cause the inner flow mtu to be decreased. If
>> next hop exceptions are not consulted for pmtu, IP fragmentation will
>> not be done properly for these routes.
>> 
>> It also seems that we really need to have the PMTU information always
>> for netfilter TCPMSS clamp-to-pmtu feature to work properly.
>> 
>> So for the time being, cache separate copies of input routes for
>> each next hop exception.
>> 
>> Signed-off-by: Timo Teräs <timo.teras@....fi>
> 
> 	Looks good to me
> 
> Reviewed-by: Julian Anastasov <ja@....bg>

Applied to net-next, thanks everyone.
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