netdev - Re: [net-next PATCH v3 4/6] udp: Partially unroll handling of first segment and last segment

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAF=yD-Kn0qEJ_mshkEvQZkvKYVhNG0VEjcUHdH4bfXd==iS-bw@mail.gmail.com>
Date:   Mon, 7 May 2018 16:10:12 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        David Miller <davem@...emloft.net>
Subject: Re: [net-next PATCH v3 4/6] udp: Partially unroll handling of first
 segment and last segment

On Mon, May 7, 2018 at 3:59 PM, Alexander Duyck
<alexander.duyck@...il.com> wrote:
> On Mon, May 7, 2018 at 12:54 PM, Willem de Bruijn
> <willemdebruijn.kernel@...il.com> wrote:
>> On Mon, May 7, 2018 at 2:57 PM, Willem de Bruijn
>> <willemdebruijn.kernel@...il.com> wrote:
>>> On Mon, May 7, 2018 at 2:08 PM, Alexander Duyck
>>> <alexander.duyck@...il.com> wrote:
>>>> From: Alexander Duyck <alexander.h.duyck@...el.com>
>>>>
>>>> This patch allows us to take care of unrolling the first segment and the
>>>> last segment of the loop for processing the segmented skb. Part of the
>>>> motivation for this is that it makes it easier to process the fact that the
>>>> first fame and all of the frames in between should be mostly identical
>>>> in terms of header data, and the last frame has differences in the length
>>>> and partial checksum.
>>>>
>>>> In addition I am dropping the header length calculation since we don't
>>>> really need it for anything but the last frame and it can be easily
>>>> obtained by just pulling the data_len and offset of tail from the transport
>>>> header.
>>>>
>>>> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>

Acked-by: Willem de Bruijn <willemb@...gle.com>

>>> I'm not a fan of the more complicated control flow, as I pointed out
>>> before. It only seems to save one assignment to uh from segs.
>>>
>>> Both follow-up patches are now more complex, because they need
>>> to add the same code in two locations.
>>
>> With that said, if you feel strongly, I don't object.
>>
>> The removal of hdrlen and simplification of arguments is definitely
>> an improvement.
>
> Thanks for being understanding about this.
>
> My preference is to keep the loop unrolled as it is since that way it
> is not too different from the way we handle this for TCP so it will
> maintenance of the two easier. Otherwise I have to add a bunch of
> conditional checks inside the loop.
>
> The other advantage to unrolling it as I did is that I don't have to
> deal with a ton of extra indentation for an if statement inside of a
> while loop.

Both good reasons. Thanks a lot for the overall cleanup.