Re: [ewg] DHCP over InfiniBand Update

Hal Rosenstock
2010-09-06T13:15:50Z

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 ?

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.

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
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