diff options
Diffstat (limited to 'doc/guides/sample_app_ug/ptpclient.rst')
| -rw-r--r-- | doc/guides/sample_app_ug/ptpclient.rst | 306 |
1 files changed, 306 insertions, 0 deletions
diff --git a/doc/guides/sample_app_ug/ptpclient.rst b/doc/guides/sample_app_ug/ptpclient.rst new file mode 100644 index 00000000..6e425b79 --- /dev/null +++ b/doc/guides/sample_app_ug/ptpclient.rst @@ -0,0 +1,306 @@ +.. 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 +<https://en.wikipedia.org/wiki/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. |