Re: [ewg] DHCP over InfiniBand Update

sebastien dugue
2010-09-06T13:26:12Z

On Mon, 6 Sep 2010 09:15:50 -0400
Hal Rosenstock <hal.rosenstock-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> Hi Sébastien,
>
> On Mon, Sep 6, 2010 at 9:03 AM, sebastien dugue
> <sebastien.dugue-6ktuUTfB/bM@public.gmane.org> wrote:
> >  Hi Hal,
> >
> > On Tue, 31 Aug 2010 16:09:19 -0400
> > Hal Rosenstock <hal.rosenstock-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >
> >> Hi,
> >>
> >> There appear to be two basic approaches to supporting DHCP (over
> >> InfiniBand) in Linux. There's LPF support (4.1.1 based) and older
> >> (3.0.4 based) socket support.
> >>
> >> The 4.1.1 LPF patches are:
> >> http://lists.openfabrics.org/pipermail/ewg/2010-May/015265.html
> >> http://lists.openfabrics.org/pipermail/ewg/2010-May/015266.html
> >> http://lists.openfabrics.org/pipermail/ewg/2010-May/015264.html
> >> The last being Matthieu Hautreux's <matthieu.hautreux at cea.fr>
> >> improved XID generation (same as
> >> https://lists.isc.org/mailman/htdig/dhcp-hackers/2009-January/001773.html).
> >>
> >> AFAIT an LPF based approach will only work on older kernels (due to
> >> elimination of CONFIG_FILTER support). Is this accurate ?
> >
> >  Where have you seen that the LPF approach does not work on recent kernels?
> > AFAICR, the CONFIG_FILTER disappeared a long time ago. Unless I'm missing
> > something, you only need the CONFIG_PACKET option.
>
> The question was based on the README and some code in lpf.c but it
> sounds those comments relating to CONFIG_FILTER relate to 2.4 and not
> to 2.6 based kernels then. All that is needed with a 2.6 kernel is
> CONFIG_PACKET so the PF_PACKET socket can be created and used by lpf.
> Right ?

Absolutely right.

>
> Out of curiousity, why did you choose a PF_PACKET rather than a UDP
> socket based approach ? The UDP socket approach seems simpler but
> maybe has some other pitfalls.

For unknown reasons which I did not have time to investigate at the
time, I could not make it work using a plain UDP socket which I agree
should be straightforward. So I did it the LPF way.

Sébastien.

>
> Thanks again.
>
> -- Hal
>
> >  Sébastien.
> >
> >
> >>
> >> OFED has two patches for 3.0.4 for a socket approach in
> >> http://www.openfabrics.org/git/?p=~tziporet/docs.git;a=tree;f=dhcp;h=aec68a2905559c8ed91f1157fa11d78cccb266cd;hb=ofed_1_5
> >> dhcp-3.0.4.patch
> >> 0001-Make-DHCP-server-print-HW-info.patch
> >>
> >> I've been upporting those to a 4.x based DHCP and have a fundamental
> >> question which occurs even with the 3.0.4 socket based version. On the
> >> client machine, the DHCPOFFER in response to the DHCPDISCOVER is
> >> received (seen with tcpdump) but never seems to make it to the
> >> dhclient application. I can't see any kernel stack error counters
> >> incremented so I'm mystified as to what could be going wrong. I've
> >> also tried this on a number of different kernels. Any idea on why this
> >> might be or how to figure out where that packet is going ? I do see
> >> the dhcp client port with netstat -a --udp -n
> >> udp        0      0 0.0.0.0:68                  0.0.0.0:*
> >> udp        0      0 0.0.0.0:68                  0.0.0.0:*
> >> Any idea on what I'm missing ?
> >>
> >> Also, is any of this work making it's way into a released DHCP ?
> >> What's the process for this ? Is there some branch in a source
> >> repository where this work is available ?
> >>
> >> Thanks in advance for any pointers on all this.
> >>
> >> -- Hal
> >> _______________________________________________
> >> ewg mailing list
> >> ewg-ZwoEplunGu1OwGhvXhtEPSCwEArCW2h5@public.gmane.org
> >> http://lists.openfabrics.org/cgi-bin/mailman/listinfo/ewg
> >>
> >
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