2. dpdk-pdump Application

The dpdk-pdump tool is a Data Plane Development Kit (DPDK) tool that runs as a DPDK secondary process and is capable of enabling packet capture on dpdk ports.

Note

  • The dpdk-pdump tool can only be used in conjunction with a primary application which has the packet capture framework initialized already. In dpdk, only the testpmd is modified to initialize packet capture framework, other applications remain untouched. So, if the dpdk-pdump tool has to be used with any application other than the testpmd, user needs to explicitly modify that application to call packet capture framework initialization code. Refer app/test-pmd/testpmd.c code to see how this is done.
  • The dpdk-pdump tool depends on libpcap based PMD which is disabled by default in the build configuration files, owing to an external dependency on the libpcap development files which must be installed on the board. Once the libpcap development files are installed, the libpcap based PMD can be enabled by setting CONFIG_RTE_LIBRTE_PMD_PCAP=y and recompiling the DPDK.

2.1. Running the Application

The tool has a number of command line options:

./build/app/dpdk-pdump --
                       --pdump '(port=<port id> | device_id=<pci id or vdev name>),
                                (queue=<queue_id>),
                                (rx-dev=<iface or pcap file> |
                                 tx-dev=<iface or pcap file>),
                                [ring-size=<ring size>],
                                [mbuf-size=<mbuf data size>],
                                [total-num-mbufs=<number of mbufs>]'
                       [--server-socket-path=<server socket dir>]
                       [--client-socket-path=<client socket dir>]

The --pdump command line option is mandatory and it takes various sub arguments which are described in below section.

Note

  • Parameters inside the parentheses represents mandatory parameters.
  • Parameters inside the square brackets represents optional parameters.
  • Multiple instances of --pdump can be passed to capture packets on different port and queue combinations.

The --server-socket-path command line option is optional. This represents the server socket directory. If no value is passed default values are used i.e. /var/run/.dpdk/ for root users and ~/.dpdk/ for non root users.

The --client-socket-path command line option is optional. This represents the client socket directory. If no value is passed default values are used i.e. /var/run/.dpdk/ for root users and ~/.dpdk/ for non root users.

2.1.1. The --pdump parameters

port: Port id of the eth device on which packets should be captured.

device_id: PCI address (or) name of the eth device on which packets should be captured.

Note

  • As of now the dpdk-pdump tool cannot capture the packets of virtual devices in the primary process due to a bug in the ethdev library. Due to this bug, in a multi process context, when the primary and secondary have different ports set, then the secondary process (here the dpdk-pdump tool) overwrites the rte_eth_devices[] entries of the primary process.

queue: Queue id of the eth device on which packets should be captured. The user can pass a queue value of * to enable packet capture on all queues of the eth device.

rx-dev: Can be either a pcap file name or any Linux iface.

tx-dev: Can be either a pcap file name or any Linux iface.

Note

  • To receive ingress packets only, rx-dev should be passed.
  • To receive egress packets only, tx-dev should be passed.
  • To receive ingress and egress packets separately rx-dev and tx-dev should both be passed with the different file names or the Linux iface names.
  • To receive ingress and egress packets together, rx-dev and tx-dev should both be passed with the same file name or the same Linux iface name.

ring-size: Size of the ring. This value is used internally for ring creation. The ring will be used to enqueue the packets from the primary application to the secondary. This is an optional parameter with default size 16384.

mbuf-size: Size of the mbuf data. This is used internally for mempool creation. Ideally this value must be same as the primary application’s mempool’s mbuf data size which is used for packet RX. This is an optional parameter with default size 2176.

total-num-mbufs: Total number mbufs in mempool. This is used internally for mempool creation. This is an optional parameter with default value 65535.

2.2. Example

$ sudo ./build/app/dpdk-pdump -- --pdump 'port=0,queue=*,rx-dev=/tmp/rx.pcap'