Date: Tue, 13 May 2014 14:21:34 +0900 From: Yonghyeon PYUN <pyunyh@gmail.com> To: Michael Tuexen <Michael.Tuexen@lurchi.franken.de> Cc: FreeBSD Net <freebsd-net@freebsd.org>, "Bjoern A. Zeeb" <bz@FreeBSD.org> Subject: Re: RX checksum offloading problem Message-ID: <20140513052134.GA1419@michelle.cdnetworks.com> In-Reply-To: <72BEDE7B-C1F1-4EE2-BA68-49AED7209E8A@lurchi.franken.de> References: <A345E6A0-D6FF-4E69-AFBD-9BB67B82F02E@FreeBSD.org> <B149FC4B-4F15-4619-A04F-F1A08DDC1741@lurchi.franken.de> <20140507075612.GA1376@michelle.cdnetworks.com> <36469814-FAC8-4172-A792-487E2AB8ECB9@lurchi.franken.de> <20140507083751.GB1376@michelle.cdnetworks.com> <415C1CB5-3AF9-44E4-943A-74116037980E@lurchi.franken.de> <20140509013556.GA3014@michelle.cdnetworks.com> <B4F16B70-825A-441A-82AA-F7ED28C9D254@lurchi.franken.de> <20140512013612.GA4085@michelle.cdnetworks.com> <72BEDE7B-C1F1-4EE2-BA68-49AED7209E8A@lurchi.franken.de>
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On Mon, May 12, 2014 at 01:22:03PM +0200, Michael Tuexen wrote:
> On 12 May 2014, at 03:36, Yonghyeon PYUN <pyunyh@gmail.com> wrote:
>
> > On Fri, May 09, 2014 at 12:46:48PM +0200, Michael Tuexen wrote:
> >> On 09 May 2014, at 03:35, Yonghyeon PYUN <pyunyh@gmail.com> wrote:
> >>
[...]
> > Oops, sorry. You're right. Probably I was confused with old memory
> > when I worked on that area. I've quickly read IP reassembly code
> > again and as you said, it should work. However it seems there is a
> > checksumming bug here.
> >
> > /*
> > * In order to do checksumming faster we do 'end-around carry' here
> > * (and not in for{} loop), though it implies we are not going to
> > * reassemble more than 64k fragments.
> > */
> > m->m_pkthdr.csum_data =
> > (m->m_pkthdr.csum_data & 0xffff) + (m->m_pkthdr.csum_data >> 16);
> >
> > I guess the line above didn't account possible carry happened after
> > the computation. Probably it could be rewritten as the following.
> >
> > while (m->m_pkthdr.csum_data & 0xffff0000)
> > m->m_pkthdr.csum_data = (m->m_pkthdr.csum_data & 0xffff) +
> > (m->m_pkthdr.csum_data >> 16);
> I think you are right here. Good catch. Will you fix it?
>
Done in r265942.
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