18. Tun/Tap Poll Mode Driver

The rte_eth_tap.c PMD creates a device using TUN/TAP interfaces on the local host. The PMD allows for DPDK and the host to communicate using a raw device interface on the host and in the DPDK application.

The device created is a TAP device, which sends/receives packet in a raw format with a L2 header. The usage for a TAP PMD is for connectivity to the local host using a TAP interface. When the TAP PMD is initialized it will create a number of tap devices in the host accessed via ifconfig -a or ip command. The commands can be used to assign and query the virtual like device.

These TAP interfaces can be used with Wireshark or tcpdump or Pktgen-DPDK along with being able to be used as a network connection to the DPDK application. The method enable one or more interfaces is to use the --vdev=net_tap0 option on the DPDK application command line. Each --vdev=net_tap1 option give will create an interface named dtap0, dtap1, and so on.

The interface name can be changed by adding the iface=foo0, for example:

--vdev=net_tap0,iface=foo0 --vdev=net_tap1,iface=foo1, ...

Also the speed of the interface can be changed from 10G to whatever number needed, but the interface does not enforce that speed, for example:


After the DPDK application is started you can send and receive packets on the interface using the standard rx_burst/tx_burst APIs in DPDK. From the host point of view you can use any host tool like tcpdump, Wireshark, ping, Pktgen and others to communicate with the DPDK application. The DPDK application may not understand network protocols like IPv4/6, UDP or TCP unless the application has been written to understand these protocols.

If you need the interface as a real network interface meaning running and has a valid IP address then you can do this with the following commands:

sudo ip link set dtap0 up; sudo ip addr add dev dtap0
sudo ip link set dtap1 up; sudo ip addr add dev dtap1

Please change the IP addresses as you see fit.

If routing is enabled on the host you can also communicate with the DPDK App over the internet via a standard socket layer application as long as you account for the protocol handing in the application.

If you have a Network Stack in your DPDK application or something like it you can utilize that stack to handle the network protocols. Plus you would be able to address the interface using an IP address assigned to the internal interface.

18.1. Example

The following is a simple example of using the TUN/TAP PMD with the Pktgen packet generator. It requires that the socat utility is installed on the test system.

Build DPDK, then pull down Pktgen and build pktgen using the DPDK SDK/Target used to build the dpdk you pulled down.

Run pktgen from the pktgen directory in a terminal with a commandline like the following:

sudo ./app/app/x86_64-native-linuxapp-gcc/app/pktgen -l 1-5 -n 4        \
 --proc-type auto --log-level 8 --socket-mem 512,512 --file-prefix pg   \
 --vdev=net_tap0 --vdev=net_tap1 -b 05:00.0 -b 05:00.1                  \
 -b 04:00.0 -b 04:00.1 -b 04:00.2 -b 04:00.3                            \
 -b 81:00.0 -b 81:00.1 -b 81:00.2 -b 81:00.3                            \
 -b 82:00.0 -b 83:00.0 -- -T -P -m [2:3].0 -m [4:5].1                   \
 -f themes/black-yellow.theme

Verify with ifconfig -a command in a different xterm window, should have a dtap0 and dtap1 interfaces created.

Next set the links for the two interfaces to up via the commands below:

sudo ip link set dtap0 up; sudo ip addr add dev dtap0
sudo ip link set dtap1 up; sudo ip addr add dev dtap1

Then use socat to create a loopback for the two interfaces:

sudo socat interface:dtap0 interface:dtap1

Then on the Pktgen command line interface you can start sending packets using the commands start 0 and start 1 or you can start both at the same time with start all. The command str is an alias for start all and stp is an alias for stop all.

While running you should see the 64 byte counters increasing to verify the traffic is being looped back. You can use set all size XXX to change the size of the packets after you stop the traffic. Use pktgen help command to see a list of all commands. You can also use the -f option to load commands at startup in command line or Lua script in pktgen.