Re: parsing sflow question (sflowtool.c vs spec)

thanks a ton for pointing this out and helping me !

mike

On Mon, Sep 11, 2006 at 09:45:03AM -0700, Peter Phaal wrote:
> The SFLOW-DATAGRAM5.txt file contains the structure definitions for the
> sFlow datagram, but it doesn't describe the transfer encoding. If you look
> at the full sFlow specification (http://www.sflow.org/sflow_version_5.txt)
> you will see that sFlow uses XDR to encode these structures (see
> http://www.ietf.org/rfc/rfc1832.txt).
>
> The when using XDR to encode a variable length array:
> sample_record samples<>;
> you need to insert the length of the array as an unsigned 32 bit integer
> before transmitting the array contents.
>
> When sending a variable length opaque you also need to insert the length
> before sending the content:
> opaque sample_data<>;
>
> Peter
>
>
> -----Original Message-----
> From: owner-sflow@sflow.org [mailto:owner-sflow@sflow.org] On Behalf Of Mike
> Haberman
> Sent: Sunday, September 10, 2006 9:56 PM
> To: sflow@sflow.org
> Cc: mikeh@ncsa.edu
> Subject: [sFlow] parsing sflow question (sflowtool.c vs spec)
>
> Hi,
>
> I am writing a Java based parser for sFlows. I am having a problem
> resolving what sflowtool.c does and what the SFLOW-DATAGRAM5.txt
> shows.
>
> 1. When sflowtool.c reads in a sample datagram, it does
>
> ...
> sample->sequenceNo = getData32(sample);
> sample->sysUpTime = getData32(sample);
> samplesInPacket = getData32(sample);
>
>
> Where samplesInPacket is even described in SFLOW-DATAGRAM5.txt. ?
>
>
> 2. When sflowtool.c dispatchs on the sample type ...
>
> switch(sample->sampleType) {
> case SFLFLOW_SAMPLE: readFlowSample(sample, NO); break;
> case SFLCOUNTERS_SAMPLE: readCountersSample(sample, NO); break;
> case SFLFLOW_SAMPLE_EXPANDED: readFlowSample(sample, YES); break;
> case SFLCOUNTERS_SAMPLE_EXPANDED: readCountersSample(sample, YES);
> break;
>
> Each of those functions first does a read to get the sample length:
>
> sampleLength = getData32(sample);
> sample->samplesGenerated = getData32(sample);
>
>
> Where is sampleLength described in SFLOW-DATAGRAM5.txt ?
>
>
> I must not be reading something properly.. Thanks to anyone
> who can set me straight.
>
>
> thanks
>
> mike
>
>
>
> --
> ----------------------------------
> Mike Haberman
> Senior Network Research Engineer
> NCSA
> ----------------------------------

-- 
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Mike Haberman
Senior Network Research Engineer
NCSA
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