netdev - Re: tc H/W offload issue with vxlan tunnels [was: nfp: flower vxlan tunnel offload]

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Date:   Wed, 27 Sep 2017 13:11:50 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     Or Gerlitz <gerlitz.or@...il.com>, Jiri Benc <jbenc@...hat.com>,
        Simon Horman <simon.horman@...ronome.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Linux Netdev List <netdev@...r.kernel.org>,
        oss-drivers@...ronome.com, John Hurley <john.hurley@...ronome.com>,
        Paul Blakey <paulb@...lanox.com>,
        Jiri Pirko <jiri@...lanox.com>, Roi Dayan <roid@...lanox.com>
Subject: Re: tc H/W offload issue with vxlan tunnels [was: nfp: flower vxlan
 tunnel offload]

Wed, Sep 27, 2017 at 11:46:58AM CEST, pabeni@...hat.com wrote:
>On Wed, 2017-09-27 at 11:17 +0200, Jiri Pirko wrote:
>> Wed, Sep 27, 2017 at 10:29:35AM CEST, pabeni@...hat.com wrote:
>> > So it looks like the H/W offload hook will still be called with the
>> > same arguments in both case, and 'bad' rule will still be pushed to the
>> > H/W as the driver itself has no way to distinct between the two
>> > scenarios.
>> 
>> Why "bad"?
>
>Such rule is coped differently by the SW and the HW data path.
>
>a rule like:
>
>tc filter add dev eth0 protocol ip parent ffff: flower \
>   enc_key_id 102 enc_dst_port 4789 src_ip 3.4.5.6 skip_hw \
>   action action mirred redirect eth0_vf_1
>
>will match 0 packets, while:
>
>tc filter add dev eth0 protocol ip parent ffff: flower \
>   enc_key_id 102 enc_dst_port 4789 src_ip 3.4.5.6 skip_sw \
>   action action mirred redirect eth0_vf_1
>
>[just flipped 'skip_sw' and 'skip_hw' ]
>will match the vxlan-tunneled packets. I understand that one of the
>design goal for the h/w offload path is being consistent with the sw
>one, but that does not hold in the above scenario.

Sure, the consistency is important. Howcome "skip_hw" won't match and
"skip_sw" will match? What's different?


>
>> Regarding the distinction, driver knows if user add a rule directly to
>> the eth0, or if the eth0 is egress device in the action. Those are 2
>> separete driver entrypoints - of course, talking about code with my
>> changes.
>
>ok, but than each driver should catch the scenario "rule with tunnel
>match over non tunnel device" and cope with them properly - never match
>it - why don't simply avoiding pushing such rules to the H/W ? 
>
>Cheers,
>
>Paolo