netdev - Re: [PATCH net-next] sched: act_csum: don't mangle TCP and UDP GSO packets

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Date:   Thu, 23 Mar 2017 17:40:57 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dcaratti@...hat.com
Cc:     jhs@...atatu.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] sched: act_csum: don't mangle TCP and UDP GSO
 packets

From: Davide Caratti <dcaratti@...hat.com>
Date: Thu, 23 Mar 2017 10:39:40 +0100

> after act_csum computes the checksum on skbs carrying GSO TCP/UDP packets,
> subsequent segmentation fails because skb_needs_check(skb, true) returns
> true. Because of that, skb_warn_bad_offload() is invoked and the following
> message is displayed:
> 
> WARNING: CPU: 3 PID: 28 at net/core/dev.c:2553 skb_warn_bad_offload+0xf0/0xfd
> <...>
> 
>   [<ffffffff8171f486>] skb_warn_bad_offload+0xf0/0xfd
>   [<ffffffff8161304c>] __skb_gso_segment+0xec/0x110
>   [<ffffffff8161340d>] validate_xmit_skb+0x12d/0x2b0
>   [<ffffffff816135d2>] validate_xmit_skb_list+0x42/0x70
>   [<ffffffff8163c560>] sch_direct_xmit+0xd0/0x1b0
>   [<ffffffff8163c760>] __qdisc_run+0x120/0x270
>   [<ffffffff81613b3d>] __dev_queue_xmit+0x23d/0x690
>   [<ffffffff81613fa0>] dev_queue_xmit+0x10/0x20
> 
> Since GSO is able to compute checksum on individual segments of such skbs,
> we can simply skip mangling the packet.
> 
> Signed-off-by: Davide Caratti <dcaratti@...hat.com>

Seems reasonable, applied, thanks.