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32 PTP Client Sample Application
33 =============================
35 The PTP (Precision Time Protocol) client sample application is a simple
36 example of using the DPDK IEEE1588 API to communicate with a PTP master clock
37 to synchronize the time on the NIC and, optionally, on the Linux system.
39 Note, PTP is a time syncing protocol and cannot be used within DPDK as a
40 time-stamping mechanism. See the following for an explanation of the protocol:
41 `Precision Time Protocol
42 <https://en.wikipedia.org/wiki/Precision_Time_Protocol>`_.
48 The PTP sample application is intended as a simple reference implementation of
49 a PTP client using the DPDK IEEE1588 API.
50 In order to keep the application simple the following assumptions are made:
52 * The first discovered master is the master for the session.
53 * Only L2 PTP packets are supported.
54 * Only the PTP v2 protocol is supported.
55 * Only the slave clock is implemented.
58 How the Application Works
59 -------------------------
61 .. _figure_ptpclient_highlevel:
63 .. figure:: img/ptpclient.*
65 PTP Synchronization Protocol
67 The PTP synchronization in the sample application works as follows:
69 * Master sends *Sync* message - the slave saves it as T2.
70 * Master sends *Follow Up* message and sends time of T1.
71 * Slave sends *Delay Request* frame to PTP Master and stores T3.
72 * Master sends *Delay Response* T4 time which is time of received T3.
74 The adjustment for slave can be represented as:
76 adj = -[(T2-T1)-(T4 - T3)]/2
78 If the command line parameter ``-T 1`` is used the application also
79 synchronizes the PTP PHC clock with the Linux kernel clock.
81 Compiling the Application
82 -------------------------
84 To compile the sample application see :doc:`compiling`.
86 The application is located in the ``ptpclient`` sub-directory.
89 To compile the application edit the ``config/common_linuxapp`` configuration file to enable IEEE1588
90 and then recompile DPDK:
92 .. code-block:: console
94 CONFIG_RTE_LIBRTE_IEEE1588=y
96 Running the Application
97 -----------------------
99 To run the example in a ``linuxapp`` environment:
101 .. code-block:: console
103 ./build/ptpclient -l 1 -n 4 -- -p 0x1 -T 0
105 Refer to *DPDK Getting Started Guide* for general information on running
106 applications and the Environment Abstraction Layer (EAL) options.
108 * ``-p portmask``: Hexadecimal portmask.
109 * ``-T 0``: Update only the PTP slave clock.
110 * ``-T 1``: Update the PTP slave clock and synchronize the Linux Kernel to the PTP clock.
116 The following sections provide an explanation of the main components of the
119 All DPDK library functions used in the sample code are prefixed with ``rte_``
120 and are explained in detail in the *DPDK API Documentation*.
126 The ``main()`` function performs the initialization and calls the execution
127 threads for each lcore.
129 The first task is to initialize the Environment Abstraction Layer (EAL). The
130 ``argc`` and ``argv`` arguments are provided to the ``rte_eal_init()``
131 function. The value returned is the number of parsed arguments:
135 int ret = rte_eal_init(argc, argv);
137 rte_exit(EXIT_FAILURE, "Error with EAL initialization\n");
139 And than we parse application specific arguments
146 ret = ptp_parse_args(argc, argv);
148 rte_exit(EXIT_FAILURE, "Error with PTP initialization\n");
150 The ``main()`` also allocates a mempool to hold the mbufs (Message Buffers)
151 used by the application:
155 mbuf_pool = rte_pktmbuf_pool_create("MBUF_POOL", NUM_MBUFS * nb_ports,
156 MBUF_CACHE_SIZE, 0, RTE_MBUF_DEFAULT_BUF_SIZE, rte_socket_id());
158 Mbufs are the packet buffer structure used by DPDK. They are explained in
159 detail in the "Mbuf Library" section of the *DPDK Programmer's Guide*.
161 The ``main()`` function also initializes all the ports using the user defined
162 ``port_init()`` function with portmask provided by user:
166 for (portid = 0; portid < nb_ports; portid++)
167 if ((ptp_enabled_port_mask & (1 << portid)) != 0) {
169 if (port_init(portid, mbuf_pool) == 0) {
170 ptp_enabled_ports[ptp_enabled_port_nb] = portid;
171 ptp_enabled_port_nb++;
173 rte_exit(EXIT_FAILURE, "Cannot init port %"PRIu8 "\n",
179 Once the initialization is complete, the application is ready to launch a
180 function on an lcore. In this example ``lcore_main()`` is called on a single
187 The ``lcore_main()`` function is explained below.
193 As we saw above the ``main()`` function calls an application function on the
196 The main work of the application is done within the loop:
200 for (portid = 0; portid < ptp_enabled_port_nb; portid++) {
202 portid = ptp_enabled_ports[portid];
203 nb_rx = rte_eth_rx_burst(portid, 0, &m, 1);
205 if (likely(nb_rx == 0))
208 if (m->ol_flags & PKT_RX_IEEE1588_PTP)
209 parse_ptp_frames(portid, m);
214 Packets are received one by one on the RX ports and, if required, PTP response
215 packets are transmitted on the TX ports.
217 If the offload flags in the mbuf indicate that the packet is a PTP packet then
218 the packet is parsed to determine which type:
222 if (m->ol_flags & PKT_RX_IEEE1588_PTP)
223 parse_ptp_frames(portid, m);
226 All packets are freed explicitly using ``rte_pktmbuf_free()``.
228 The forwarding loop can be interrupted and the application closed using
235 The ``parse_ptp_frames()`` function processes PTP packets, implementing slave
236 PTP IEEE1588 L2 functionality.
241 parse_ptp_frames(uint16_t portid, struct rte_mbuf *m) {
242 struct ptp_header *ptp_hdr;
243 struct ether_hdr *eth_hdr;
246 eth_hdr = rte_pktmbuf_mtod(m, struct ether_hdr *);
247 eth_type = rte_be_to_cpu_16(eth_hdr->ether_type);
249 if (eth_type == PTP_PROTOCOL) {
251 ptp_data.portid = portid;
252 ptp_hdr = (struct ptp_header *)(rte_pktmbuf_mtod(m, char *)
253 + sizeof(struct ether_hdr));
255 switch (ptp_hdr->msgtype) {
257 parse_sync(&ptp_data);
260 parse_fup(&ptp_data);
263 parse_drsp(&ptp_data);
264 print_clock_info(&ptp_data);
272 There are 3 types of packets on the RX path which we must parse to create a minimal
273 implementation of the PTP slave client:
277 * DELAY RESPONSE packet.
279 When we parse the *FOLLOW UP* packet we also create and send a *DELAY_REQUEST* packet.
280 Also when we parse the *DELAY RESPONSE* packet, and all conditions are met we adjust the PTP slave clock.