Re: ipv4 udplite broken in >=linux-3.0 ?

[Jinxin Zheng]

On Sat, Nov 19, 2011 at 7:27 AM, Gerrit Renker <gerrit@xxxxxxxxxxxxxx> wrote:
> Jinxin, -
> | On Fri, Nov 18, 2011 at 8:04 PM, Hagen Paul Pfeifer <hagen@xxxxxxxx> wrote:
> | > * Jinxin Zheng | 2011-11-18 12:09:25 [+0800]:
> | >
> | >>I don't know how to debug udplite. Can any one of you give me a tip on
> | >>how to get more debug info, then I can do further test and provide
> | >>with it?
> | >
> | > net-next works for me:
> That is very likely the point. Between 2.6.39 and 3.0 UDP-Lite checksum coverage was
> broken and got only recently fixed. The correct kernel version should have the
> commit shown below. Alternatively, you can check include/net/udplite.h, which
> should mention "Slow-path" and "Fast-Path" computation. UDP-Litev6 still uses the
> slow path, that is why it is not affected.
>
>
> commit f36c23bb9f822904dacf83a329518d0a5fde7968
> Author: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
> Date:   Mon Oct 17 19:07:30 2011 -0400
>
>    udplite: fast-path computation of checksum coverage
>
>    Commit 903ab86d195cca295379699299c5fc10beba31c7 of 1 March this year ("udp: Add
>    lockless transmit path") introduced a new fast TX path that broke the checksum
>    coverage computation of UDP-lite, which so far depended on up->len (only set
>    if the socket is locked and 0 in the fast path).
>
>    Fixed by providing both fast- and slow-path computation of checksum coverage.
>    The latter can be removed when UDP(-lite)v6 also uses a lockless transmit path.
>
>

Thanks, Gerrit. Upgrading to the upstream linux-3.2-rc2 fixed the problem :)

-- 
Zheng Jinxin
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