.. BSD LICENSE Copyright(c) 2015 Intel Corporation. All rights reserved. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. * Neither the name of Intel Corporation nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. PTP Client Sample Application ============================= The PTP (Precision Time Protocol) client sample application is a simple example of using the DPDK IEEE1588 API to communicate with a PTP master clock to synchronize the time on the NIC and, optionally, on the Linux system. Note, PTP is a time syncing protocol and cannot be used within DPDK as a time-stamping mechanism. See the following for an explanation of the protocol: `Precision Time Protocol `_. Limitations ----------- The PTP sample application is intended as a simple reference implementation of a PTP client using the DPDK IEEE1588 API. In order to keep the application simple the following assumptions are made: * The first discovered master is the master for the session. * Only L2 PTP packets are supported. * Only the PTP v2 protocol is supported. * Only the slave clock is implemented. How the Application Works ------------------------- .. _figure_ptpclient_highlevel: .. figure:: img/ptpclient.* PTP Synchronization Protocol The PTP synchronization in the sample application works as follows: * Master sends *Sync* message - the slave saves it as T2. * Master sends *Follow Up* message and sends time of T1. * Slave sends *Delay Request* frame to PTP Master and stores T3. * Master sends *Delay Response* T4 time which is time of received T3. The adjustment for slave can be represented as: adj = -[(T2-T1)-(T4 - T3)]/2 If the command line parameter ``-T 1`` is used the application also synchronizes the PTP PHC clock with the Linux kernel clock. Compiling the Application ------------------------- To compile the application, export the path to the DPDK source tree and edit the ``config/common_linuxapp`` configuration file to enable IEEE1588: .. code-block:: console export RTE_SDK=/path/to/rte_sdk # Edit common_linuxapp and set the following options: CONFIG_RTE_LIBRTE_IEEE1588=y Set the target, for example: .. code-block:: console export RTE_TARGET=x86_64-native-linuxapp-gcc See the *DPDK Getting Started* Guide for possible ``RTE_TARGET`` values. Build the application as follows: .. code-block:: console # Recompile DPDK. make install T=$RTE_TARGET # Compile the application. cd ${RTE_SDK}/examples/ptpclient make Running the Application ----------------------- To run the example in a ``linuxapp`` environment: .. code-block:: console ./build/ptpclient -c 2 -n 4 -- -p 0x1 -T 0 Refer to *DPDK Getting Started Guide* for general information on running applications and the Environment Abstraction Layer (EAL) options. * ``-p portmask``: Hexadecimal portmask. * ``-T 0``: Update only the PTP slave clock. * ``-T 1``: Update the PTP slave clock and synchronize the Linux Kernel to the PTP clock. Code Explanation ---------------- The following sections provide an explanation of the main components of the code. All DPDK library functions used in the sample code are prefixed with ``rte_`` and are explained in detail in the *DPDK API Documentation*. The Main Function ~~~~~~~~~~~~~~~~~ The ``main()`` function performs the initialization and calls the execution threads for each lcore. The first task is to initialize the Environment Abstraction Layer (EAL). The ``argc`` and ``argv`` arguments are provided to the ``rte_eal_init()`` function. The value returned is the number of parsed arguments: .. code-block:: c int ret = rte_eal_init(argc, argv); if (ret < 0) rte_exit(EXIT_FAILURE, "Error with EAL initialization\n"); And than we parse application specific arguments .. code-block:: c argc -= ret; argv += ret; ret = ptp_parse_args(argc, argv); if (ret < 0) rte_exit(EXIT_FAILURE, "Error with PTP initialization\n"); The ``main()`` also allocates a mempool to hold the mbufs (Message Buffers) used by the application: .. code-block:: c mbuf_pool = rte_mempool_create("MBUF_POOL", NUM_MBUFS * nb_ports, MBUF_SIZE, MBUF_CACHE_SIZE, sizeof(struct rte_pktmbuf_pool_private), rte_pktmbuf_pool_init, NULL, rte_pktmbuf_init, NULL, rte_socket_id(), 0); Mbufs are the packet buffer structure used by DPDK. They are explained in detail in the "Mbuf Library" section of the *DPDK Programmer's Guide*. The ``main()`` function also initializes all the ports using the user defined ``port_init()`` function with portmask provided by user: .. code-block:: c for (portid = 0; portid < nb_ports; portid++) if ((ptp_enabled_port_mask & (1 << portid)) != 0) { if (port_init(portid, mbuf_pool) == 0) { ptp_enabled_ports[ptp_enabled_port_nb] = portid; ptp_enabled_port_nb++; } else { rte_exit(EXIT_FAILURE, "Cannot init port %"PRIu8 "\n", portid); } } Once the initialization is complete, the application is ready to launch a function on an lcore. In this example ``lcore_main()`` is called on a single lcore. .. code-block:: c lcore_main(); The ``lcore_main()`` function is explained below. The Lcores Main ~~~~~~~~~~~~~~~ As we saw above the ``main()`` function calls an application function on the available lcores. The main work of the application is done within the loop: .. code-block:: c for (portid = 0; portid < ptp_enabled_port_nb; portid++) { portid = ptp_enabled_ports[portid]; nb_rx = rte_eth_rx_burst(portid, 0, &m, 1); if (likely(nb_rx == 0)) continue; if (m->ol_flags & PKT_RX_IEEE1588_PTP) parse_ptp_frames(portid, m); rte_pktmbuf_free(m); } Packets are received one by one on the RX ports and, if required, PTP response packets are transmitted on the TX ports. If the offload flags in the mbuf indicate that the packet is a PTP packet then the packet is parsed to determine which type: .. code-block:: c if (m->ol_flags & PKT_RX_IEEE1588_PTP) parse_ptp_frames(portid, m); All packets are freed explicitly using ``rte_pktmbuf_free()``. The forwarding loop can be interrupted and the application closed using ``Ctrl-C``. PTP parsing ~~~~~~~~~~~ The ``parse_ptp_frames()`` function processes PTP packets, implementing slave PTP IEEE1588 L2 functionality. .. code-block:: c void parse_ptp_frames(uint8_t portid, struct rte_mbuf *m) { struct ptp_header *ptp_hdr; struct ether_hdr *eth_hdr; uint16_t eth_type; eth_hdr = rte_pktmbuf_mtod(m, struct ether_hdr *); eth_type = rte_be_to_cpu_16(eth_hdr->ether_type); if (eth_type == PTP_PROTOCOL) { ptp_data.m = m; ptp_data.portid = portid; ptp_hdr = (struct ptp_header *)(rte_pktmbuf_mtod(m, char *) + sizeof(struct ether_hdr)); switch (ptp_hdr->msgtype) { case SYNC: parse_sync(&ptp_data); break; case FOLLOW_UP: parse_fup(&ptp_data); break; case DELAY_RESP: parse_drsp(&ptp_data); print_clock_info(&ptp_data); break; default: break; } } } There are 3 types of packets on the RX path which we must parse to create a minimal implementation of the PTP slave client: * SYNC packet. * FOLLOW UP packet * DELAY RESPONSE packet. When we parse the *FOLLOW UP* packet we also create and send a *DELAY_REQUEST* packet. Also when we parse the *DELAY RESPONSE* packet, and all conditions are met we adjust the PTP slave clock.