netdev - Re: [PATCH] net: Reduce skb_warn_bad

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Message-ID: <CAMDZJNVRqbByUfa5Oc_=xs+O_BJ4ehUJUSz9Y+wCPwj6kQGtLA@mail.gmail.com>
Date:   Tue, 8 Aug 2017 07:44:15 +0800
From:   Tonghao Zhang <xiangxia.m.yue@...il.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Pravin B Shelar <pshelar@....org>
Subject: Re: [PATCH] net: Reduce skb_warn_bad_offload() noise.

That is fine to me. I have tested it. Thanks.

On Mon, Aug 7, 2017 at 12:42 PM, Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
>> The openvswitch kernel module calls the __skb_gso_segment()(and sets
>> tx_path = false) when passing packets to userspace. The UFO will set
>> the ip_summed to CHECKSUM_NONE. There are a lot of warn logs. The warn
>> log is shown as below. I guess we should revert the patch.
>
> Indeed, the software UFO code computes the checksum and
> sets ip_summed to CHECKSUM_NONE, as is correct on the
> egress path.
>
> Commit 6e7bc478c9a0 ("net: skb_needs_check() accepts
> CHECKSUM_NONE for tx") revised the tx_path case in
> skb_needs_check to avoid the warning exactly for the UFO case.
>
> We cannot just make an exception for CHECKSUM_NONE in the
> !tx_path case, as the entire statement then becomes false:
>
>        return skb->ip_summed == CHECKSUM_NONE;
>
> Since on egress CHECKSUM_UNNECESSARY is equivalent to
> CHECKSUM_NONE, it should be fine to update the UFO code
> to set that, instead:
>
> @@ -235,7 +235,7 @@ static struct sk_buff *udp4_ufo_fragment(struct
> sk_buff *skb,
>         if (uh->check == 0)
>                 uh->check = CSUM_MANGLED_0;
>
> -       skb->ip_summed = CHECKSUM_NONE;
> +       skb->ip_summed = CHECKSUM_UNNECESSARY;