Sorry for the slow response. The answer is to add more decoding at the collector. You could refer to the "sflowtool" source code for a simple example.
The "struct sampled_ipv4" record (flow sample type 0:3) is only there in case there is a device somewhere that has that decoded information, but somehow cannot access the original packet that was sampled (believe it or not, there was a router once that found itself in this unlikely predicament). Since OVS has the original packet it is required to export that instead. Much better. This is how the simplest layer-2 switch can provide visibility into higher-layers, tunnels, complex relationships etc. without having to do anything more than sample packets in a stateless way. In fact, when OVS sends samples up from the kernel to sFlow it does rather more packet-decoding work that it strictly needs to. We could trim a few cycles there, but it's hardly worth changing because it only happens for sampled packets and typical sampling rates are of the order of 1:1000. Regards, Neil ------ Neil McKee InMon Corp. http://www.inmon.com On Tue, Feb 17, 2015 at 11:34 AM, Ben Pfaff <[email protected]> wrote: > I'm adding Neil McKee, who knows much more about sflow than I do. > > On Tue, Feb 17, 2015 at 07:28:33PM +0200, George Shuklin wrote: > > We're playing with sFlow features of OVS. We want to collect sflow > > with em-sflow <https://github.com/normelton/em-sflow> library (ruby, > > ttps://github.com/normelton/em-sflow > > <https://github.com/normelton/em-sflow>). Unfortunately it can not > > process received sflow packets deep enough. > > > > After some research I found there are few types of sFlow packes, > > with different structure. As far as I understand it parse payload > > only for the sampleType_tag 0:3, but it leaves unprocessed header in > > sampleType_tag 0:1 (which is fine according to specs). > > > > Is any way to configure OVS to send sFlow samples of type 3? > > I don't think OVS has knobs like that. It's not obvious to me whether > the correct solution here is to improve the library you're using or to > change OVS to do something different. Neil? > > Thanks, > > Ben. >
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