21. KNI Poll Mode Driver
KNI PMD is wrapper to the librte_kni library.
This PMD enables using KNI without having a KNI specific application, any forwarding application can use PMD interface for KNI.
Sending packets to any DPDK controlled interface or sending to the Linux networking stack will be transparent to the DPDK application.
To create a KNI device net_kni#
device name should be used, and this
will create kni#
Linux virtual network interface.
There is no physical device backend for the virtual KNI device.
Packets sent to the KNI Linux interface will be received by the DPDK application, and DPDK application may forward packets to a physical NIC or to a virtual device (like another KNI interface or PCAP interface).
To forward any traffic from physical NIC to the Linux networking stack, an application should control a physical port and create one virtual KNI port, and forward between two.
Using this PMD requires KNI kernel module be inserted.
21.1. Usage
EAL --vdev
argument can be used to create KNI device instance, like:
testpmd --vdev=net_kni0 --vdev=net_kn1 -- -i
Above command will create kni0
and kni1
Linux network interfaces,
those interfaces can be controlled by standard Linux tools.
When testpmd forwarding starts, any packets sent to kni0
interface
forwarded to the kni1
interface and vice versa.
There is no hard limit on number of interfaces that can be created.
21.2. Default interface configuration
librte_kni
can create Linux network interfaces with different features,
feature set controlled by a configuration struct, and KNI PMD uses a fixed
configuration:
Interface name: kni# force bind kernel thread to a core : NO mbuf size: MAX_PACKET_SZ
KNI control path is not supported with the PMD, since there is no physical backend device by default.
21.3. PMD arguments
no_request_thread
, by default PMD creates a phtread for each KNI interface
to handle Linux network interface control commands, like ifconfig kni0 up
With no_request_thread
option, pthread is not created and control commands
not handled by PMD.
By default request thread is enabled. And this argument should not be used most of the time, unless this PMD used with customized DPDK application to handle requests itself.
Argument usage:
testpmd --vdev "net_kni0,no_request_thread=1" -- -i
21.4. PMD log messages
If KNI kernel module (rte_kni.ko) not inserted, following error log printed:
"KNI: KNI subsystem has not been initialized. Invoke rte_kni_init() first"
21.5. PMD testing
It is possible to test PMD quickly using KNI kernel module loopback feature:
Insert KNI kernel module with loopback support:
insmod build/kmod/rte_kni.ko lo_mode=lo_mode_fifo_skb
Start testpmd with no physical device but two KNI virtual devices:
./testpmd --vdev net_kni0 --vdev net_kni1 -- -i
... Configuring Port 0 (socket 0) KNI: pci: 00:00:00 c580:b8 Port 0: 1A:4A:5B:7C:A2:8C Configuring Port 1 (socket 0) KNI: pci: 00:00:00 600:b9 Port 1: AE:95:21:07:93:DD Checking link statuses... Port 0 Link Up - speed 10000 Mbps - full-duplex Port 1 Link Up - speed 10000 Mbps - full-duplex Done testpmd>
Observe Linux interfaces
$ ifconfig kni0 && ifconfig kni1 kni0: flags=4098<BROADCAST,MULTICAST> mtu 1500 ether ae:8e:79:8e:9b:c8 txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 kni1: flags=4098<BROADCAST,MULTICAST> mtu 1500 ether 9e:76:43:53:3e:9b txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
Start forwarding with tx_first:
testpmd> start tx_first
Quit and check forwarding stats:
testpmd> quit Telling cores to stop... Waiting for lcores to finish... ---------------------- Forward statistics for port 0 ---------------------- RX-packets: 35637905 RX-dropped: 0 RX-total: 35637905 TX-packets: 35637947 TX-dropped: 0 TX-total: 35637947 ---------------------------------------------------------------------------- ---------------------- Forward statistics for port 1 ---------------------- RX-packets: 35637915 RX-dropped: 0 RX-total: 35637915 TX-packets: 35637937 TX-dropped: 0 TX-total: 35637937 ---------------------------------------------------------------------------- +++++++++++++++ Accumulated forward statistics for all ports+++++++++++++++ RX-packets: 71275820 RX-dropped: 0 RX-total: 71275820 TX-packets: 71275884 TX-dropped: 0 TX-total: 71275884 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++