netdev - Re: [PATCH net v2 1/2] net: netem: fix backlog accounting for corrupted GSO frames

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Date:   Mon, 17 Jun 2019 15:32:57 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     David Miller <davem@...emloft.net>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>,
        netem@...ts.linux-foundation.org,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        oss-drivers@...ronome.com, Eric Dumazet <edumazet@...gle.com>,
        posk@...gle.com, Neil Horman <nhorman@...driver.com>
Subject: Re: [PATCH net v2 1/2] net: netem: fix backlog accounting for
 corrupted GSO frames

On Mon, Jun 17, 2019 at 11:11 AM Jakub Kicinski
<jakub.kicinski@...ronome.com> wrote:
>
> When GSO frame has to be corrupted netem uses skb_gso_segment()
> to produce the list of frames, and re-enqueues the segments one
> by one.  The backlog length has to be adjusted to account for
> new frames.
>
> The current calculation is incorrect, leading to wrong backlog
> lengths in the parent qdisc (both bytes and packets), and
> incorrect packet backlog count in netem itself.
>
> Parent backlog goes negative, netem's packet backlog counts
> all non-first segments twice (thus remaining non-zero even
> after qdisc is emptied).
>
> Move the variables used to count the adjustment into local
> scope to make 100% sure they aren't used at any stage in
> backports.
>
> Fixes: 6071bd1aa13e ("netem: Segment GSO packets on enqueue")
> Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
> Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@...ronome.com>

Looks good!

Acked-by: Cong Wang <xiyou.wangcong@...il.com>