1 .. SPDX-License-Identifier: BSD-3-Clause
2 Copyright(c) 2010-2014 Intel Corporation.
4 Link Status Interrupt Sample Application
5 ========================================
7 The Link Status Interrupt sample application is a simple example of packet processing using
8 the Data Plane Development Kit (DPDK) that
9 demonstrates how network link status changes for a network port can be captured and
10 used by a DPDK application.
15 The Link Status Interrupt sample application registers a user space callback for the link status interrupt of each port
16 and performs L2 forwarding for each packet that is received on an RX_PORT.
17 The following operations are performed:
19 * RX_PORT and TX_PORT are paired with available ports one-by-one according to the core mask
21 * The source MAC address is replaced by the TX_PORT MAC address
23 * The destination MAC address is replaced by 02:00:00:00:00:TX_PORT_ID
25 This application can be used to demonstrate the usage of link status interrupt and its user space callbacks
26 and the behavior of L2 forwarding each time the link status changes.
28 Compiling the Application
29 -------------------------
31 To compile the sample application see :doc:`compiling`.
33 The application is located in the ``link_status_interrupt`` sub-directory.
35 Running the Application
36 -----------------------
38 The application requires a number of command line options:
40 .. code-block:: console
42 ./build/link_status_interrupt [EAL options] -- -p PORTMASK [-q NQ][-T PERIOD]
46 * -p PORTMASK: A hexadecimal bitmask of the ports to configure
48 * -q NQ: A number of queues (=ports) per lcore (default is 1)
50 * -T PERIOD: statistics will be refreshed each PERIOD seconds (0 to disable, 10 default)
52 To run the application in a linuxapp environment with 4 lcores, 4 memory channels, 16 ports and 8 RX queues per lcore,
55 .. code-block:: console
57 $ ./build/link_status_interrupt -l 0-3 -n 4-- -q 8 -p ffff
59 Refer to the *DPDK Getting Started Guide* for general information on running applications
60 and the Environment Abstraction Layer (EAL) options.
65 The following sections provide some explanation of the code.
67 Command Line Arguments
68 ~~~~~~~~~~~~~~~~~~~~~~
70 The Link Status Interrupt sample application takes specific parameters,
71 in addition to Environment Abstraction Layer (EAL) arguments (see Section `Running the Application`_).
73 Command line parsing is done in the same way as it is done in the L2 Forwarding Sample Application.
74 See :ref:`l2_fwd_app_cmd_arguments` for more information.
76 Mbuf Pool Initialization
77 ~~~~~~~~~~~~~~~~~~~~~~~~
79 Mbuf pool initialization is done in the same way as it is done in the L2 Forwarding Sample Application.
80 See :ref:`l2_fwd_app_mbuf_init` for more information.
85 The main part of the code in the main() function relates to the initialization of the driver.
86 To fully understand this code, it is recommended to study the chapters that related to the Poll Mode Driver in the
87 *DPDK Programmer's Guide and the DPDK API Reference*.
91 if (rte_pci_probe() < 0)
92 rte_exit(EXIT_FAILURE, "Cannot probe PCI\n");
94 nb_ports = rte_eth_dev_count();
96 rte_exit(EXIT_FAILURE, "No Ethernet ports - bye\n");
99 * Each logical core is assigned a dedicated TX queue on each port.
102 for (portid = 0; portid < nb_ports; portid++) {
103 /* skip ports that are not enabled */
105 if ((lsi_enabled_port_mask & (1 << portid)) == 0)
108 /* save the destination port id */
110 if (nb_ports_in_mask % 2) {
111 lsi_dst_ports[portid] = portid_last;
112 lsi_dst_ports[portid_last] = portid;
115 portid_last = portid;
119 rte_eth_dev_info_get((uint8_t) portid, &dev_info);
124 * rte_pci_probe() parses the devices on the PCI bus and initializes recognized devices.
126 The next step is to configure the RX and TX queues.
127 For each port, there is only one RX queue (only one lcore is able to poll a given port).
128 The number of TX queues depends on the number of available lcores.
129 The rte_eth_dev_configure() function is used to configure the number of queues for a port:
133 ret = rte_eth_dev_configure((uint8_t) portid, 1, 1, &port_conf);
135 rte_exit(EXIT_FAILURE, "Cannot configure device: err=%d, port=%u\n", ret, portid);
137 The global configuration is stored in a static structure:
141 static const struct rte_eth_conf port_conf = {
144 .header_split = 0, /**< Header Split disabled */
145 .hw_ip_checksum = 0, /**< IP checksum offload disabled */
146 .hw_vlan_filter = 0, /**< VLAN filtering disabled */
147 .hw_strip_crc= 0, /**< CRC stripped by hardware */
151 .lsc = 1, /**< link status interrupt feature enabled */
155 Configuring lsc to 0 (the default) disables the generation of any link status change interrupts in kernel space
156 and no user space interrupt event is received.
157 The public interface rte_eth_link_get() accesses the NIC registers directly to update the link status.
158 Configuring lsc to non-zero enables the generation of link status change interrupts in kernel space
159 when a link status change is present and calls the user space callbacks registered by the application.
160 The public interface rte_eth_link_get() just reads the link status in a global structure
161 that would be updated in the interrupt host thread only.
163 Interrupt Callback Registration
164 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
166 The application can register one or more callbacks to a specific port and interrupt event.
167 An example callback function that has been written as indicated below.
172 lsi_event_callback(uint16_t port_id, enum rte_eth_event_type type, void *param)
174 struct rte_eth_link link;
178 printf("\n\nIn registered callback...\n");
180 printf("Event type: %s\n", type == RTE_ETH_EVENT_INTR_LSC ? "LSC interrupt" : "unknown event");
182 rte_eth_link_get_nowait(port_id, &link);
184 if (link.link_status) {
185 printf("Port %d Link Up - speed %u Mbps - %s\n\n", port_id, (unsigned)link.link_speed,
186 (link.link_duplex == ETH_LINK_FULL_DUPLEX) ? ("full-duplex") : ("half-duplex"));
188 printf("Port %d Link Down\n\n", port_id);
191 This function is called when a link status interrupt is present for the right port.
192 The port_id indicates which port the interrupt applies to.
193 The type parameter identifies the interrupt event type,
194 which currently can be RTE_ETH_EVENT_INTR_LSC only, but other types can be added in the future.
195 The param parameter is the address of the parameter for the callback.
196 This function should be implemented with care since it will be called in the interrupt host thread,
197 which is different from the main thread of its caller.
199 The application registers the lsi_event_callback and a NULL parameter to the link status interrupt event on each port:
203 rte_eth_dev_callback_register((uint8_t)portid, RTE_ETH_EVENT_INTR_LSC, lsi_event_callback, NULL);
205 This registration can be done only after calling the rte_eth_dev_configure() function and before calling any other function.
206 If lsc is initialized with 0, the callback is never called since no interrupt event would ever be present.
208 RX Queue Initialization
209 ~~~~~~~~~~~~~~~~~~~~~~~
211 The application uses one lcore to poll one or several ports, depending on the -q option,
212 which specifies the number of queues per lcore.
214 For example, if the user specifies -q 4, the application is able to poll four ports with one lcore.
215 If there are 16 ports on the target (and if the portmask argument is -p ffff),
216 the application will need four lcores to poll all the ports.
220 ret = rte_eth_rx_queue_setup((uint8_t) portid, 0, nb_rxd, SOCKET0, &rx_conf, lsi_pktmbuf_pool);
222 rte_exit(EXIT_FAILURE, "rte_eth_rx_queue_setup: err=%d, port=%u\n", ret, portid);
224 The list of queues that must be polled for a given lcore is stored in a private structure called struct lcore_queue_conf.
228 struct lcore_queue_conf {
230 unsigned rx_port_list[MAX_RX_QUEUE_PER_LCORE]; unsigned tx_queue_id;
231 struct mbuf_table tx_mbufs[LSI_MAX_PORTS];
234 struct lcore_queue_conf lcore_queue_conf[RTE_MAX_LCORE];
236 The n_rx_port and rx_port_list[] fields are used in the main packet processing loop
237 (see `Receive, Process and Transmit Packets`_).
239 The global configuration for the RX queues is stored in a static structure:
243 static const struct rte_eth_rxconf rx_conf = {
245 .pthresh = RX_PTHRESH,
246 .hthresh = RX_HTHRESH,
247 .wthresh = RX_WTHRESH,
251 TX Queue Initialization
252 ~~~~~~~~~~~~~~~~~~~~~~~
254 Each lcore should be able to transmit on any port.
255 For every port, a single TX queue is initialized.
259 /* init one TX queue logical core on each port */
263 ret = rte_eth_tx_queue_setup(portid, 0, nb_txd, rte_eth_dev_socket_id(portid), &tx_conf);
265 rte_exit(EXIT_FAILURE, "rte_eth_tx_queue_setup: err=%d,port=%u\n", ret, (unsigned) portid);
267 The global configuration for TX queues is stored in a static structure:
271 static const struct rte_eth_txconf tx_conf = {
273 .pthresh = TX_PTHRESH,
274 .hthresh = TX_HTHRESH,
275 .wthresh = TX_WTHRESH,
277 .tx_free_thresh = RTE_TEST_TX_DESC_DEFAULT + 1, /* disable feature */
280 Receive, Process and Transmit Packets
281 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
283 In the lsi_main_loop() function, the main task is to read ingress packets from the RX queues.
284 This is done using the following code:
289 * Read packet from RX queues
292 for (i = 0; i < qconf->n_rx_port; i++) {
293 portid = qconf->rx_port_list[i];
294 nb_rx = rte_eth_rx_burst((uint8_t) portid, 0, pkts_burst, MAX_PKT_BURST);
295 port_statistics[portid].rx += nb_rx;
297 for (j = 0; j < nb_rx; j++) {
299 rte_prefetch0(rte_pktmbuf_mtod(m, void *));
300 lsi_simple_forward(m, portid);
304 Packets are read in a burst of size MAX_PKT_BURST.
305 The rte_eth_rx_burst() function writes the mbuf pointers in a local table and returns the number of available mbufs in the table.
307 Then, each mbuf in the table is processed by the lsi_simple_forward() function.
308 The processing is very simple: processes the TX port from the RX port and then replaces the source and destination MAC addresses.
312 In the following code, the two lines for calculating the output port require some explanation.
313 If portId is even, the first line does nothing (as portid & 1 will be 0), and the second line adds 1.
314 If portId is odd, the first line subtracts one and the second line does nothing.
315 Therefore, 0 goes to 1, and 1 to 0, 2 goes to 3 and 3 to 2, and so on.
320 lsi_simple_forward(struct rte_mbuf *m, unsigned portid)
322 struct ether_hdr *eth;
324 unsigned dst_port = lsi_dst_ports[portid];
326 eth = rte_pktmbuf_mtod(m, struct ether_hdr *);
328 /* 02:00:00:00:00:xx */
330 tmp = ð->d_addr.addr_bytes[0];
332 *((uint64_t *)tmp) = 0x000000000002 + (dst_port << 40);
335 ether_addr_copy(&lsi_ports_eth_addr[dst_port], ð->s_addr);
337 lsi_send_packet(m, dst_port);
340 Then, the packet is sent using the lsi_send_packet(m, dst_port) function.
341 For this test application, the processing is exactly the same for all packets arriving on the same RX port.
342 Therefore, it would have been possible to call the lsi_send_burst() function directly from the main loop
343 to send all the received packets on the same TX port using
344 the burst-oriented send function, which is more efficient.
346 However, in real-life applications (such as, L3 routing),
347 packet N is not necessarily forwarded on the same port as packet N-1.
348 The application is implemented to illustrate that so the same approach can be reused in a more complex application.
350 The lsi_send_packet() function stores the packet in a per-lcore and per-txport table.
351 If the table is full, the whole packets table is transmitted using the lsi_send_burst() function:
355 /* Send the packet on an output interface */
358 lsi_send_packet(struct rte_mbuf *m, uint16_t port)
360 unsigned lcore_id, len;
361 struct lcore_queue_conf *qconf;
363 lcore_id = rte_lcore_id();
364 qconf = &lcore_queue_conf[lcore_id];
365 len = qconf->tx_mbufs[port].len;
366 qconf->tx_mbufs[port].m_table[len] = m;
369 /* enough pkts to be sent */
371 if (unlikely(len == MAX_PKT_BURST)) {
372 lsi_send_burst(qconf, MAX_PKT_BURST, port);
375 qconf->tx_mbufs[port].len = len;
380 To ensure that no packets remain in the tables, each lcore does a draining of the TX queue in its main loop.
381 This technique introduces some latency when there are not many packets to send.
382 However, it improves performance:
386 cur_tsc = rte_rdtsc();
389 * TX burst queue drain
392 diff_tsc = cur_tsc - prev_tsc;
394 if (unlikely(diff_tsc > drain_tsc)) {
395 /* this could be optimized (use queueid instead of * portid), but it is not called so often */
397 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++) {
398 if (qconf->tx_mbufs[portid].len == 0)
401 lsi_send_burst(&lcore_queue_conf[lcore_id],
402 qconf->tx_mbufs[portid].len, (uint8_t) portid);
403 qconf->tx_mbufs[portid].len = 0;
406 /* if timer is enabled */
408 if (timer_period > 0) {
409 /* advance the timer */
411 timer_tsc += diff_tsc;
413 /* if timer has reached its timeout */
415 if (unlikely(timer_tsc >= (uint64_t) timer_period)) {
416 /* do this only on master core */
418 if (lcore_id == rte_get_master_lcore()) {
421 /* reset the timer */