netdev - Re: [Patch net] net: make pskb_trim_rcsum

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Message-ID: <5466e637-37d2-a11e-c30c-fc17a4dbeaf1@gmail.com>
Date:   Mon, 29 Oct 2018 19:25:05 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [Patch net] net: make pskb_trim_rcsum_slow() robust



On 10/29/2018 07:21 PM, Cong Wang wrote:
> On Mon, Oct 29, 2018 at 7:14 PM Eric Dumazet <eric.dumazet@...il.com> wrote:
>>
>> Would not it be simpler to set ip_summed to CHECKSUM_NONE (no need to save old_csum) ?
> 
> For !CHECKSUM_COMPLETE, ip_summed should be untouched, right?
> 
> If you mean only setting to CHECKSUM_NONE for CHECKSUM_COMPLETE case,
> the end result may not be simpler.

I meant to reinstate what was there before my patch in this error case

       if (skb->ip_summed == CHECKSUM_COMPLETE)
               skb->ip_summed = CHECKSUM_NONE;

That would only be run in error (quite unlikely) path, instead of saving old_csum in all cases.