9. DPDK packet capture libraries and tools
This document describes how the Data Plane Development Kit (DPDK) Packet Capture Framework is used for capturing packets on DPDK ports. It is intended for users of DPDK who want to know more about the Packet Capture feature and for those who want to monitor traffic on DPDK-controlled devices.
The DPDK packet capture framework was introduced in DPDK v16.07
and enhanced in 21.11.
The DPDK packet capture framework consists of the libraries
for collecting packets
and writing packets to a file
There are two sample applications:
dpdk-dumpcap and older
The librte_pdump library provides the API required to allow users to initialize the packet capture framework and to enable or disable packet capture. The library works on a multi-process communication model and its usage is recommended for debugging purposes.
The librte_pcapng library provides the API to format packets and write them to a file in Pcapng format.
The dpdk-dumpcap is a tool that captures packets in
like Wireshark dumpcap does for Linux.
It runs as a DPDK secondary process and captures packets
from one or more interfaces and writes them to a file in Pcapng format.
dpdk-dumpcap tool is designed to take
most of the same options as the Wireshark
Without any options it will use the packet capture framework to capture traffic from the first available DPDK port.
dpdk-testpmd application can be used to initialize
the packet capture framework and acts as a server,
dpdk-dumpcap tool acts as a client.
To view Rx or Tx packets of
the application should be launched first,
and then the
dpdk-testpmd will be sent to the tool,
and then to the Pcapng file.
Some things to note:
- All tools using
librte_pdumpcan only be used in conjunction with a primary application which has the packet capture framework initialized already. In dpdk, only
testpmdis modified to initialize packet capture framework, other applications remain untouched. So, if the
dpdk-dumpcaptool has to be used with any application other than the testpmd, the user needs to explicitly modify that application to call the packet capture framework initialization code. Refer to the
app/test-pmd/testpmd.ccode and look for
pdumpkeyword to see how this is done.
dpdk-pdumptool is an older tool created as demonstration of
dpdk-pdumptool provides more limited functionality and depends on the Pcap PMD. It is retained only for compatibility reasons; users should use
9.2. Test Environment
The overview of using the Packet Capture Framework and the
for packet capturing on the DPDK port in
9.3. Running the Application
The following steps demonstrate how to run the
dpdk-dumpcap tool to capture
Rx side packets on dpdk_port0 in Fig. 9.1 and
inspect them using
Launch testpmd as the primary application:
sudo <build_dir>/app/dpdk-testpmd -c 0xf0 -n 4 -- -i --port-topology=chained
Launch the dpdk-dumpcap as follows:
sudo <build_dir>/app/dpdk-dumpcap -w /tmp/capture.pcapng
Send traffic to dpdk_port0 from traffic generator. Inspect packets captured in the file capture.pcapng using a tool such as tcpdump or tshark that can interpret Pcapng files:
$ tcpdump -nr /tmp/capture.pcapng reading from file /tmp/capture.pcap, link-type EN10MB (Ethernet) 11:11:36.891404 IP 188.8.131.52.whois++ > 184.108.40.206.whois++: UDP, length 18 11:11:36.891442 IP 220.127.116.11.whois++ > 18.104.22.168.whois++: UDP, length 18 11:11:36.891445 IP 22.214.171.124.whois++ > 126.96.36.199.whois++: UDP, length 18