Re: [dpdk-users] KNI drive without supported NICs?

[Take Ceara <dumitru.ceara@gmail.com>]

Hi Vlad,

On Sun, Feb 5, 2017 at 6:34 PM, Lazarenko, Vlad (WorldQuant)
<Vlad.Lazarenko@worldquant.com> wrote:
> Gentlemen and gentleladies,
>
> I am trying to get the KNI working on my dev box. So I've loaded the rte_kni.ko module and made sure /dev/kni has correct permissions. But when I am trying to run the KNI example, it fails with "No supported Ethernet device found" error:
>
> $ build/kni -n 4 -c 0xf0 -- -P -p 0x3 --config="(0,4,6),(1,5,7)"
> EAL: Detected 24 lcore(s)
> EAL: PCI device 0000:01:00.0 on NUMA socket -1
> EAL:   probe driver: 8086:10d3 net_e1000_em
> EAL: Error - exiting with code: 1
>   Cause: No supported Ethernet device found
>
> My dev box does not in fact have supported NICs. But my understanding about KNI was that it allows to access Linux network stack trough the KNI kernel module, where applications create a virtual Ethernet devices (i.e. /sys/class/net/vEth*), thus there is no need for a real supported NIC or taking over the entire NIC.
>
> On the other hand, the example application calls rte_eth_dev_count() first, which in my case returns 0, and exits.
>
> Is my understanding about what KNI actually is wrong? Or am I missing something else?
>

As far as I know the KNI sample app actually forwards traffic to/from
the kernel and a physical port therefore the check for physical
interfaces. If you want to use KNI for something else there's nothing
stopping you from starting a DPDK app and adding a KNI interface
without having a real NIC bound to DPDK.

I don't have a better example right now but, if you want, you can take
a look at how we do it in warp17 (using DPDK) when you start it
without any physical interfaces:

https://github.com/Juniper/warp17#using-kernel-network-interface-kni-interfaces

If you look at the HTTP example there we actually start the
application without any physical interfaces (only one KNI):

./build/warp17 -c FC3 -n 4  -m 32768 -- --kni-ifs 1


> Thanks,
> Vlad

Hope this helps..

Regards,
Dumitru

>
>
>
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-- 
Dumitru Ceara