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

From: Jamal Hadi Salim <[email-masked]>
Date: Thu, 18 Sep 2014 07:38:13 -0400

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 <[email-masked]>
> CC: Jamal Hadi Salim <[email-masked]>
> Signed-off-by: John Fastabend <[email-masked]>

Looks good to me.
Acked-by: Jamal Hadi Salim <[email-masked]>

cheers,
jamal