netdev - Re: [PATCH/RFC net-next 0/4] net/sched: cls_flower: avoid false matching of truncated packets

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Message-ID: <422d55da-f861-1bc6-983d-199fc383c113@mojatatu.com>
Date:   Fri, 28 Apr 2017 08:52:56 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Simon Horman <simon.horman@...ronome.com>,
        Jiri Pirko <jiri@...lanox.com>,
        Cong Wang <xiyou.wangcong@...il.com>
Cc:     Dinan Gunawardena <dinan.gunawardena@...ronome.com>,
        netdev@...r.kernel.org, oss-drivers@...ronome.com
Subject: Re: [PATCH/RFC net-next 0/4] net/sched: cls_flower: avoid false
 matching of truncated packets

On 17-04-28 08:00 AM, Simon Horman wrote:
> Hi,
>
> this series is intended to avoid false-positives which match
> truncated packets against flower classifiers which match on:
> * zero L4 ports or;
> * zero ICMP code or type
>
> This requires updating the flow dissector to return an error in such cases
> and updating flower to not match on the result of a failed dissection.
>
> In the case of UDP this results in a behavioural change to users of
> flow_keys_dissector_keys[] and flow_keys_dissector_symmetric_keys[] -
> dissection will fail on truncated packets where the IP protocol of the
> packets indicates ports should be present (according to skb_flow_get_ports()).

I think i understand the use case/need.
But would it be fair to say that the truncated vs non-truncated are two
different filter rules? Example what would offloading of 
header_parse_err_action mean?

cheers,
jamal