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31 Link Status Interrupt Sample Application
32 ========================================
34 The Link Status Interrupt sample application is a simple example of packet processing using
35 the Data Plane Development Kit (DPDK) that
36 demonstrates how network link status changes for a network port can be captured and
37 used by a DPDK application.
42 The Link Status Interrupt sample application registers a user space callback for the link status interrupt of each port
43 and performs L2 forwarding for each packet that is received on an RX_PORT.
44 The following operations are performed:
46 * RX_PORT and TX_PORT are paired with available ports one-by-one according to the core mask
48 * The source MAC address is replaced by the TX_PORT MAC address
50 * The destination MAC address is replaced by 02:00:00:00:00:TX_PORT_ID
52 This application can be used to demonstrate the usage of link status interrupt and its user space callbacks
53 and the behavior of L2 forwarding each time the link status changes.
55 Compiling the Application
56 -------------------------
58 To compile the sample application see :doc:`compiling`.
60 The application is located in the ``link_status_interrupt`` sub-directory.
62 Running the Application
63 -----------------------
65 The application requires a number of command line options:
67 .. code-block:: console
69 ./build/link_status_interrupt [EAL options] -- -p PORTMASK [-q NQ][-T PERIOD]
73 * -p PORTMASK: A hexadecimal bitmask of the ports to configure
75 * -q NQ: A number of queues (=ports) per lcore (default is 1)
77 * -T PERIOD: statistics will be refreshed each PERIOD seconds (0 to disable, 10 default)
79 To run the application in a linuxapp environment with 4 lcores, 4 memory channels, 16 ports and 8 RX queues per lcore,
82 .. code-block:: console
84 $ ./build/link_status_interrupt -l 0-3 -n 4-- -q 8 -p ffff
86 Refer to the *DPDK Getting Started Guide* for general information on running applications
87 and the Environment Abstraction Layer (EAL) options.
92 The following sections provide some explanation of the code.
94 Command Line Arguments
95 ~~~~~~~~~~~~~~~~~~~~~~
97 The Link Status Interrupt sample application takes specific parameters,
98 in addition to Environment Abstraction Layer (EAL) arguments (see Section `Running the Application`_).
100 Command line parsing is done in the same way as it is done in the L2 Forwarding Sample Application.
101 See :ref:`l2_fwd_app_cmd_arguments` for more information.
103 Mbuf Pool Initialization
104 ~~~~~~~~~~~~~~~~~~~~~~~~
106 Mbuf pool initialization is done in the same way as it is done in the L2 Forwarding Sample Application.
107 See :ref:`l2_fwd_app_mbuf_init` for more information.
109 Driver Initialization
110 ~~~~~~~~~~~~~~~~~~~~~
112 The main part of the code in the main() function relates to the initialization of the driver.
113 To fully understand this code, it is recommended to study the chapters that related to the Poll Mode Driver in the
114 *DPDK Programmer's Guide and the DPDK API Reference*.
118 if (rte_pci_probe() < 0)
119 rte_exit(EXIT_FAILURE, "Cannot probe PCI\n");
121 nb_ports = rte_eth_dev_count();
123 rte_exit(EXIT_FAILURE, "No Ethernet ports - bye\n");
126 * Each logical core is assigned a dedicated TX queue on each port.
129 for (portid = 0; portid < nb_ports; portid++) {
130 /* skip ports that are not enabled */
132 if ((lsi_enabled_port_mask & (1 << portid)) == 0)
135 /* save the destination port id */
137 if (nb_ports_in_mask % 2) {
138 lsi_dst_ports[portid] = portid_last;
139 lsi_dst_ports[portid_last] = portid;
142 portid_last = portid;
146 rte_eth_dev_info_get((uint8_t) portid, &dev_info);
151 * rte_pci_probe() parses the devices on the PCI bus and initializes recognized devices.
153 The next step is to configure the RX and TX queues.
154 For each port, there is only one RX queue (only one lcore is able to poll a given port).
155 The number of TX queues depends on the number of available lcores.
156 The rte_eth_dev_configure() function is used to configure the number of queues for a port:
160 ret = rte_eth_dev_configure((uint8_t) portid, 1, 1, &port_conf);
162 rte_exit(EXIT_FAILURE, "Cannot configure device: err=%d, port=%u\n", ret, portid);
164 The global configuration is stored in a static structure:
168 static const struct rte_eth_conf port_conf = {
171 .header_split = 0, /**< Header Split disabled */
172 .hw_ip_checksum = 0, /**< IP checksum offload disabled */
173 .hw_vlan_filter = 0, /**< VLAN filtering disabled */
174 .hw_strip_crc= 0, /**< CRC stripped by hardware */
178 .lsc = 1, /**< link status interrupt feature enabled */
182 Configuring lsc to 0 (the default) disables the generation of any link status change interrupts in kernel space
183 and no user space interrupt event is received.
184 The public interface rte_eth_link_get() accesses the NIC registers directly to update the link status.
185 Configuring lsc to non-zero enables the generation of link status change interrupts in kernel space
186 when a link status change is present and calls the user space callbacks registered by the application.
187 The public interface rte_eth_link_get() just reads the link status in a global structure
188 that would be updated in the interrupt host thread only.
190 Interrupt Callback Registration
191 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
193 The application can register one or more callbacks to a specific port and interrupt event.
194 An example callback function that has been written as indicated below.
199 lsi_event_callback(uint16_t port_id, enum rte_eth_event_type type, void *param)
201 struct rte_eth_link link;
205 printf("\n\nIn registered callback...\n");
207 printf("Event type: %s\n", type == RTE_ETH_EVENT_INTR_LSC ? "LSC interrupt" : "unknown event");
209 rte_eth_link_get_nowait(port_id, &link);
211 if (link.link_status) {
212 printf("Port %d Link Up - speed %u Mbps - %s\n\n", port_id, (unsigned)link.link_speed,
213 (link.link_duplex == ETH_LINK_FULL_DUPLEX) ? ("full-duplex") : ("half-duplex"));
215 printf("Port %d Link Down\n\n", port_id);
218 This function is called when a link status interrupt is present for the right port.
219 The port_id indicates which port the interrupt applies to.
220 The type parameter identifies the interrupt event type,
221 which currently can be RTE_ETH_EVENT_INTR_LSC only, but other types can be added in the future.
222 The param parameter is the address of the parameter for the callback.
223 This function should be implemented with care since it will be called in the interrupt host thread,
224 which is different from the main thread of its caller.
226 The application registers the lsi_event_callback and a NULL parameter to the link status interrupt event on each port:
230 rte_eth_dev_callback_register((uint8_t)portid, RTE_ETH_EVENT_INTR_LSC, lsi_event_callback, NULL);
232 This registration can be done only after calling the rte_eth_dev_configure() function and before calling any other function.
233 If lsc is initialized with 0, the callback is never called since no interrupt event would ever be present.
235 RX Queue Initialization
236 ~~~~~~~~~~~~~~~~~~~~~~~
238 The application uses one lcore to poll one or several ports, depending on the -q option,
239 which specifies the number of queues per lcore.
241 For example, if the user specifies -q 4, the application is able to poll four ports with one lcore.
242 If there are 16 ports on the target (and if the portmask argument is -p ffff),
243 the application will need four lcores to poll all the ports.
247 ret = rte_eth_rx_queue_setup((uint8_t) portid, 0, nb_rxd, SOCKET0, &rx_conf, lsi_pktmbuf_pool);
249 rte_exit(EXIT_FAILURE, "rte_eth_rx_queue_setup: err=%d, port=%u\n", ret, portid);
251 The list of queues that must be polled for a given lcore is stored in a private structure called struct lcore_queue_conf.
255 struct lcore_queue_conf {
257 unsigned rx_port_list[MAX_RX_QUEUE_PER_LCORE]; unsigned tx_queue_id;
258 struct mbuf_table tx_mbufs[LSI_MAX_PORTS];
261 struct lcore_queue_conf lcore_queue_conf[RTE_MAX_LCORE];
263 The n_rx_port and rx_port_list[] fields are used in the main packet processing loop
264 (see `Receive, Process and Transmit Packets`_).
266 The global configuration for the RX queues is stored in a static structure:
270 static const struct rte_eth_rxconf rx_conf = {
272 .pthresh = RX_PTHRESH,
273 .hthresh = RX_HTHRESH,
274 .wthresh = RX_WTHRESH,
278 TX Queue Initialization
279 ~~~~~~~~~~~~~~~~~~~~~~~
281 Each lcore should be able to transmit on any port.
282 For every port, a single TX queue is initialized.
286 /* init one TX queue logical core on each port */
290 ret = rte_eth_tx_queue_setup(portid, 0, nb_txd, rte_eth_dev_socket_id(portid), &tx_conf);
292 rte_exit(EXIT_FAILURE, "rte_eth_tx_queue_setup: err=%d,port=%u\n", ret, (unsigned) portid);
294 The global configuration for TX queues is stored in a static structure:
298 static const struct rte_eth_txconf tx_conf = {
300 .pthresh = TX_PTHRESH,
301 .hthresh = TX_HTHRESH,
302 .wthresh = TX_WTHRESH,
304 .tx_free_thresh = RTE_TEST_TX_DESC_DEFAULT + 1, /* disable feature */
307 Receive, Process and Transmit Packets
308 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
310 In the lsi_main_loop() function, the main task is to read ingress packets from the RX queues.
311 This is done using the following code:
316 * Read packet from RX queues
319 for (i = 0; i < qconf->n_rx_port; i++) {
320 portid = qconf->rx_port_list[i];
321 nb_rx = rte_eth_rx_burst((uint8_t) portid, 0, pkts_burst, MAX_PKT_BURST);
322 port_statistics[portid].rx += nb_rx;
324 for (j = 0; j < nb_rx; j++) {
326 rte_prefetch0(rte_pktmbuf_mtod(m, void *));
327 lsi_simple_forward(m, portid);
331 Packets are read in a burst of size MAX_PKT_BURST.
332 The rte_eth_rx_burst() function writes the mbuf pointers in a local table and returns the number of available mbufs in the table.
334 Then, each mbuf in the table is processed by the lsi_simple_forward() function.
335 The processing is very simple: processes the TX port from the RX port and then replaces the source and destination MAC addresses.
339 In the following code, the two lines for calculating the output port require some explanation.
340 If portId is even, the first line does nothing (as portid & 1 will be 0), and the second line adds 1.
341 If portId is odd, the first line subtracts one and the second line does nothing.
342 Therefore, 0 goes to 1, and 1 to 0, 2 goes to 3 and 3 to 2, and so on.
347 lsi_simple_forward(struct rte_mbuf *m, unsigned portid)
349 struct ether_hdr *eth;
351 unsigned dst_port = lsi_dst_ports[portid];
353 eth = rte_pktmbuf_mtod(m, struct ether_hdr *);
355 /* 02:00:00:00:00:xx */
357 tmp = ð->d_addr.addr_bytes[0];
359 *((uint64_t *)tmp) = 0x000000000002 + (dst_port << 40);
362 ether_addr_copy(&lsi_ports_eth_addr[dst_port], ð->s_addr);
364 lsi_send_packet(m, dst_port);
367 Then, the packet is sent using the lsi_send_packet(m, dst_port) function.
368 For this test application, the processing is exactly the same for all packets arriving on the same RX port.
369 Therefore, it would have been possible to call the lsi_send_burst() function directly from the main loop
370 to send all the received packets on the same TX port using
371 the burst-oriented send function, which is more efficient.
373 However, in real-life applications (such as, L3 routing),
374 packet N is not necessarily forwarded on the same port as packet N-1.
375 The application is implemented to illustrate that so the same approach can be reused in a more complex application.
377 The lsi_send_packet() function stores the packet in a per-lcore and per-txport table.
378 If the table is full, the whole packets table is transmitted using the lsi_send_burst() function:
382 /* Send the packet on an output interface */
385 lsi_send_packet(struct rte_mbuf *m, uint16_t port)
387 unsigned lcore_id, len;
388 struct lcore_queue_conf *qconf;
390 lcore_id = rte_lcore_id();
391 qconf = &lcore_queue_conf[lcore_id];
392 len = qconf->tx_mbufs[port].len;
393 qconf->tx_mbufs[port].m_table[len] = m;
396 /* enough pkts to be sent */
398 if (unlikely(len == MAX_PKT_BURST)) {
399 lsi_send_burst(qconf, MAX_PKT_BURST, port);
402 qconf->tx_mbufs[port].len = len;
407 To ensure that no packets remain in the tables, each lcore does a draining of the TX queue in its main loop.
408 This technique introduces some latency when there are not many packets to send.
409 However, it improves performance:
413 cur_tsc = rte_rdtsc();
416 * TX burst queue drain
419 diff_tsc = cur_tsc - prev_tsc;
421 if (unlikely(diff_tsc > drain_tsc)) {
422 /* this could be optimized (use queueid instead of * portid), but it is not called so often */
424 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++) {
425 if (qconf->tx_mbufs[portid].len == 0)
428 lsi_send_burst(&lcore_queue_conf[lcore_id],
429 qconf->tx_mbufs[portid].len, (uint8_t) portid);
430 qconf->tx_mbufs[portid].len = 0;
433 /* if timer is enabled */
435 if (timer_period > 0) {
436 /* advance the timer */
438 timer_tsc += diff_tsc;
440 /* if timer has reached its timeout */
442 if (unlikely(timer_tsc >= (uint64_t) timer_period)) {
443 /* do this only on master core */
445 if (lcore_id == rte_get_master_lcore()) {
448 /* reset the timer */