netdev - Re: [net-next PATCH 2/2] net: sched: cls_u32 changes to knode must appear atomic to readers

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Message-ID: <541AC425.2090300@mojatatu.com>
Date:	Thu, 18 Sep 2014 07:38:13 -0400
From:	Jamal Hadi Salim <jhs@...atatu.com>
To:	John Fastabend <john.fastabend@...il.com>,
	xiyou.wangcong@...il.com, davem@...emloft.net,
	eric.dumazet@...il.com
CC:	netdev@...r.kernel.org
Subject: Re: [net-next PATCH 2/2] net: sched: cls_u32 changes to knode must
 appear atomic to readers

On 09/17/14 15:12, John Fastabend wrote:
> Changes to the cls_u32 classifier must appear atomic to the
> readers. Before this patch if a change is requested for both
> the exts and ifindex, first the ifindex is updated then the
> exts with tcf_exts_change(). This opens a small window where
> a reader can have a exts chain with an incorrect ifindex. This
> violates the the RCU semantics.
>
> Here we resolve this by always passing u32_set_parms() a copy
> of the tc_u_knode to work on and then inserting it into the hash
> table after the updates have been successfully applied.
>
> Tested with the following short script:
>

>
> #tc filter add dev p3p2 parent 8001:0 protocol ip prio 99 handle 1: \
> 	       u32 divisor 256
>
> #tc filter add dev p3p2 parent 8001:0 protocol ip prio 99 \
> 	       u32 link 1: hashkey mask ffffff00 at 12    \
> 	       match ip src 192.168.8.0/2
>
> #tc filter add dev p3p2 parent 8001:0 protocol ip prio 102    \
> 	       handle 1::10 u32 classid 1:2 ht 1: 	      \
> 	       match ip src 192.168.8.0/8 match ip tos 0x0a 1e
>
> #tc filter change dev p3p2 parent 8001:0 protocol ip prio 102 \
> 		 handle 1::10 u32 classid 1:2 ht 1:        \
> 		 match ip src 1.1.0.0/8 match ip tos 0x0b 1e
>
> CC: Eric Dumazet <edumazet@...gle.com>
> CC: Jamal Hadi Salim <jhs@...atatu.com>
> Signed-off-by: John Fastabend <john.r.fastabend@...el.com>


Looks good to me.
Acked-by: Jamal Hadi Salim <jhs@...atatu.com>

cheers,
jamal
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