netdev - Re: [PATCH v2 net] ixgbe: fix parsing of TC actions for HW offload

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Message-Id: <20180531.230129.1440898141134890172.davem@davemloft.net>
Date:   Thu, 31 May 2018 23:01:29 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     jeffrey.t.kirsher@...el.com
Cc:     ohlavaty@...hat.com, netdev@...r.kernel.org,
        andrewx.bowers@...el.com
Subject: Re: [PATCH v2 net] ixgbe: fix parsing of TC actions for HW offload

From: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Date: Thu, 31 May 2018 14:46:08 -0700

> On Thu, 2018-05-31 at 23:21 +0200, Ondřej Hlavatý wrote:
>> The previous code was optimistic, accepting the offload of whole
>> action
>> chain when there was a single known action (drop/redirect). This
>> results
>> in offloading a rule which should not be offloaded, because its
>> behavior
>> cannot be reproduced in the hardware.
>> 
>> For example:
>> 
>> $ tc filter add dev eno1 parent ffff: protocol ip \
>>     u32 ht 800: order 1 match tcp src 42 FFFF \
>>     action mirred egress mirror dev enp1s16 pipe \
>>     drop
>> 
>> The controller is unable to mirror the packet to a VF, but still
>> offloads the rule by dropping the packet.
>> 
>> Change the approach of the function to a pessimistic one, rejecting
>> the
>> chain when an unknown action is found. This is better suited for
>> future
>> extensions.
>> 
>> Note that both recognized actions always return TC_ACT_SHOT,
>> therefore
>> it is safe to ignore actions behind them.
>> 
>> Signed-off-by: Ondřej Hlavatý <ohlavaty@...hat.com>
> 
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> 
> Note- I am having our validation move to testing with GCC 8.1.1 or
> later so that we can catch warnings like Dave found in the future.
> 
> Dave- Please go ahead and pick this up.

Ok, applied, thanks.