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31 .. _l2_fwd_app_real_and_virtual:
33 L2 Forwarding Sample Application (in Real and Virtualized Environments)
34 =======================================================================
36 The L2 Forwarding sample application is a simple example of packet processing using
37 the Data Plane Development Kit (DPDK) which
38 also takes advantage of Single Root I/O Virtualization (SR-IOV) features in a virtualized environment.
42 Please note that previously a separate L2 Forwarding in Virtualized Environments sample application was used,
43 however, in later DPDK versions these sample applications have been merged.
48 The L2 Forwarding sample application, which can operate in real and virtualized environments,
49 performs L2 forwarding for each packet that is received on an RX_PORT.
50 The destination port is the adjacent port from the enabled portmask, that is,
51 if the first four ports are enabled (portmask 0xf),
52 ports 1 and 2 forward into each other, and ports 3 and 4 forward into each other.
53 Also, the MAC addresses are affected as follows:
55 * The source MAC address is replaced by the TX_PORT MAC address
57 * The destination MAC address is replaced by 02:00:00:00:00:TX_PORT_ID
59 This application can be used to benchmark performance using a traffic-generator, as shown in the :numref:`figure_l2_fwd_benchmark_setup`.
61 The application can also be used in a virtualized environment as shown in :numref:`figure_l2_fwd_virtenv_benchmark_setup`.
63 The L2 Forwarding application can also be used as a starting point for developing a new application based on the DPDK.
65 .. _figure_l2_fwd_benchmark_setup:
67 .. figure:: img/l2_fwd_benchmark_setup.*
69 Performance Benchmark Setup (Basic Environment)
72 .. _figure_l2_fwd_virtenv_benchmark_setup:
74 .. figure:: img/l2_fwd_virtenv_benchmark_setup.*
76 Performance Benchmark Setup (Virtualized Environment)
80 Virtual Function Setup Instructions
81 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
83 This application can use the virtual function available in the system and
84 therefore can be used in a virtual machine without passing through
85 the whole Network Device into a guest machine in a virtualized scenario.
86 The virtual functions can be enabled in the host machine or the hypervisor with the respective physical function driver.
88 For example, in a Linux* host machine, it is possible to enable a virtual function using the following command:
90 .. code-block:: console
92 modprobe ixgbe max_vfs=2,2
94 This command enables two Virtual Functions on each of Physical Function of the NIC,
95 with two physical ports in the PCI configuration space.
96 It is important to note that enabled Virtual Function 0 and 2 would belong to Physical Function 0
97 and Virtual Function 1 and 3 would belong to Physical Function 1,
98 in this case enabling a total of four Virtual Functions.
100 Compiling the Application
101 -------------------------
103 #. Go to the example directory:
105 .. code-block:: console
107 export RTE_SDK=/path/to/rte_sdk
108 cd ${RTE_SDK}/examples/l2fwd
110 #. Set the target (a default target is used if not specified). For example:
112 .. code-block:: console
114 export RTE_TARGET=x86_64-native-linuxapp-gcc
116 *See the DPDK Getting Started Guide* for possible RTE_TARGET values.
118 #. Build the application:
120 .. code-block:: console
124 Running the Application
125 -----------------------
127 The application requires a number of command line options:
129 .. code-block:: console
131 ./build/l2fwd [EAL options] -- -p PORTMASK [-q NQ]
135 * p PORTMASK: A hexadecimal bitmask of the ports to configure
137 * q NQ: A number of queues (=ports) per lcore (default is 1)
139 To run the application in linuxapp environment with 4 lcores, 16 ports and 8 RX queues per lcore, issue the command:
141 .. code-block:: console
143 $ ./build/l2fwd -c f -n 4 -- -q 8 -p ffff
145 Refer to the *DPDK Getting Started Guide* for general information on running applications
146 and the Environment Abstraction Layer (EAL) options.
151 The following sections provide some explanation of the code.
153 .. _l2_fwd_app_cmd_arguments:
155 Command Line Arguments
156 ~~~~~~~~~~~~~~~~~~~~~~
158 The L2 Forwarding sample application takes specific parameters,
159 in addition to Environment Abstraction Layer (EAL) arguments.
160 The preferred way to parse parameters is to use the getopt() function,
161 since it is part of a well-defined and portable library.
163 The parsing of arguments is done in the l2fwd_parse_args() function.
164 The method of argument parsing is not described here.
165 Refer to the *glibc getopt(3)* man page for details.
167 EAL arguments are parsed first, then application-specific arguments.
168 This is done at the beginning of the main() function:
174 ret = rte_eal_init(argc, argv);
176 rte_exit(EXIT_FAILURE, "Invalid EAL arguments\n");
181 /* parse application arguments (after the EAL ones) */
183 ret = l2fwd_parse_args(argc, argv);
185 rte_exit(EXIT_FAILURE, "Invalid L2FWD arguments\n");
187 .. _l2_fwd_app_mbuf_init:
189 Mbuf Pool Initialization
190 ~~~~~~~~~~~~~~~~~~~~~~~~
192 Once the arguments are parsed, the mbuf pool is created.
193 The mbuf pool contains a set of mbuf objects that will be used by the driver
194 and the application to store network packet data:
198 /* create the mbuf pool */
200 l2fwd_pktmbuf_pool = rte_mempool_create("mbuf_pool", NB_MBUF, MBUF_SIZE, 32, sizeof(struct rte_pktmbuf_pool_private),
201 rte_pktmbuf_pool_init, NULL, rte_pktmbuf_init, NULL, SOCKET0, 0);
203 if (l2fwd_pktmbuf_pool == NULL)
204 rte_panic("Cannot init mbuf pool\n");
206 The rte_mempool is a generic structure used to handle pools of objects.
207 In this case, it is necessary to create a pool that will be used by the driver,
208 which expects to have some reserved space in the mempool structure,
209 sizeof(struct rte_pktmbuf_pool_private) bytes.
210 The number of allocated pkt mbufs is NB_MBUF, with a size of MBUF_SIZE each.
211 A per-lcore cache of 32 mbufs is kept.
212 The memory is allocated in NUMA socket 0,
213 but it is possible to extend this code to allocate one mbuf pool per socket.
215 Two callback pointers are also given to the rte_mempool_create() function:
217 * The first callback pointer is to rte_pktmbuf_pool_init() and is used
218 to initialize the private data of the mempool, which is needed by the driver.
219 This function is provided by the mbuf API, but can be copied and extended by the developer.
221 * The second callback pointer given to rte_mempool_create() is the mbuf initializer.
222 The default is used, that is, rte_pktmbuf_init(), which is provided in the rte_mbuf library.
223 If a more complex application wants to extend the rte_pktmbuf structure for its own needs,
224 a new function derived from rte_pktmbuf_init( ) can be created.
226 .. _l2_fwd_app_dvr_init:
228 Driver Initialization
229 ~~~~~~~~~~~~~~~~~~~~~
231 The main part of the code in the main() function relates to the initialization of the driver.
232 To fully understand this code, it is recommended to study the chapters that related to the Poll Mode Driver
233 in the *DPDK Programmer's Guide* - Rel 1.4 EAR and the *DPDK API Reference*.
237 if (rte_eal_pci_probe() < 0)
238 rte_exit(EXIT_FAILURE, "Cannot probe PCI\n");
240 nb_ports = rte_eth_dev_count();
243 rte_exit(EXIT_FAILURE, "No Ethernet ports - bye\n");
245 if (nb_ports > RTE_MAX_ETHPORTS)
246 nb_ports = RTE_MAX_ETHPORTS;
248 /* reset l2fwd_dst_ports */
250 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++)
251 l2fwd_dst_ports[portid] = 0;
256 * Each logical core is assigned a dedicated TX queue on each port.
259 for (portid = 0; portid < nb_ports; portid++) {
260 /* skip ports that are not enabled */
262 if ((l2fwd_enabled_port_mask & (1 << portid)) == 0)
265 if (nb_ports_in_mask % 2) {
266 l2fwd_dst_ports[portid] = last_port;
267 l2fwd_dst_ports[last_port] = portid;
274 rte_eth_dev_info_get((uint8_t) portid, &dev_info);
279 * rte_igb_pmd_init_all() simultaneously registers the driver as a PCI driver and as an Ethernet* Poll Mode Driver.
281 * rte_eal_pci_probe() parses the devices on the PCI bus and initializes recognized devices.
283 The next step is to configure the RX and TX queues.
284 For each port, there is only one RX queue (only one lcore is able to poll a given port).
285 The number of TX queues depends on the number of available lcores.
286 The rte_eth_dev_configure() function is used to configure the number of queues for a port:
290 ret = rte_eth_dev_configure((uint8_t)portid, 1, 1, &port_conf);
292 rte_exit(EXIT_FAILURE, "Cannot configure device: "
296 The global configuration is stored in a static structure:
300 static const struct rte_eth_conf port_conf = {
303 .header_split = 0, /**< Header Split disabled */
304 .hw_ip_checksum = 0, /**< IP checksum offload disabled */
305 .hw_vlan_filter = 0, /**< VLAN filtering disabled */
306 .jumbo_frame = 0, /**< Jumbo Frame Support disabled */
307 .hw_strip_crc= 0, /**< CRC stripped by hardware */
311 .mq_mode = ETH_DCB_NONE
315 .. _l2_fwd_app_rx_init:
317 RX Queue Initialization
318 ~~~~~~~~~~~~~~~~~~~~~~~
320 The application uses one lcore to poll one or several ports, depending on the -q option,
321 which specifies the number of queues per lcore.
323 For example, if the user specifies -q 4, the application is able to poll four ports with one lcore.
324 If there are 16 ports on the target (and if the portmask argument is -p ffff ),
325 the application will need four lcores to poll all the ports.
329 ret = rte_eth_rx_queue_setup((uint8_t) portid, 0, nb_rxd, SOCKET0, &rx_conf, l2fwd_pktmbuf_pool);
332 rte_exit(EXIT_FAILURE, "rte_eth_rx_queue_setup: "
336 The list of queues that must be polled for a given lcore is stored in a private structure called struct lcore_queue_conf.
340 struct lcore_queue_conf {
342 unsigned rx_port_list[MAX_RX_QUEUE_PER_LCORE];
343 struct mbuf_table tx_mbufs[L2FWD_MAX_PORTS];
346 struct lcore_queue_conf lcore_queue_conf[RTE_MAX_LCORE];
348 The values n_rx_port and rx_port_list[] are used in the main packet processing loop
349 (see :ref:`l2_fwd_app_rx_tx_packets`).
351 The global configuration for the RX queues is stored in a static structure:
355 static const struct rte_eth_rxconf rx_conf = {
357 .pthresh = RX_PTHRESH,
358 .hthresh = RX_HTHRESH,
359 .wthresh = RX_WTHRESH,
363 .. _l2_fwd_app_tx_init:
365 TX Queue Initialization
366 ~~~~~~~~~~~~~~~~~~~~~~~
368 Each lcore should be able to transmit on any port. For every port, a single TX queue is initialized.
372 /* init one TX queue on each port */
376 ret = rte_eth_tx_queue_setup((uint8_t) portid, 0, nb_txd, rte_eth_dev_socket_id(portid), &tx_conf);
378 rte_exit(EXIT_FAILURE, "rte_eth_tx_queue_setup:err=%d, port=%u\n", ret, (unsigned) portid);
380 The global configuration for TX queues is stored in a static structure:
384 static const struct rte_eth_txconf tx_conf = {
386 .pthresh = TX_PTHRESH,
387 .hthresh = TX_HTHRESH,
388 .wthresh = TX_WTHRESH,
390 .tx_free_thresh = RTE_TEST_TX_DESC_DEFAULT + 1, /* disable feature */
393 .. _l2_fwd_app_rx_tx_packets:
395 Receive, Process and Transmit Packets
396 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
398 In the l2fwd_main_loop() function, the main task is to read ingress packets from the RX queues.
399 This is done using the following code:
404 * Read packet from RX queues
407 for (i = 0; i < qconf->n_rx_port; i++) {
408 portid = qconf->rx_port_list[i];
409 nb_rx = rte_eth_rx_burst((uint8_t) portid, 0, pkts_burst, MAX_PKT_BURST);
411 for (j = 0; j < nb_rx; j++) {
413 rte_prefetch0[rte_pktmbuf_mtod(m, void *)); l2fwd_simple_forward(m, portid);
417 Packets are read in a burst of size MAX_PKT_BURST.
418 The rte_eth_rx_burst() function writes the mbuf pointers in a local table and returns the number of available mbufs in the table.
420 Then, each mbuf in the table is processed by the l2fwd_simple_forward() function.
421 The processing is very simple: process the TX port from the RX port, then replace the source and destination MAC addresses.
425 In the following code, one line for getting the output port requires some explanation.
427 During the initialization process, a static array of destination ports (l2fwd_dst_ports[]) is filled such that for each source port,
428 a destination port is assigned that is either the next or previous enabled port from the portmask.
429 Naturally, the number of ports in the portmask must be even, otherwise, the application exits.
434 l2fwd_simple_forward(struct rte_mbuf *m, unsigned portid)
436 struct ether_hdr *eth;
440 dst_port = l2fwd_dst_ports[portid];
442 eth = rte_pktmbuf_mtod(m, struct ether_hdr *);
444 /* 02:00:00:00:00:xx */
446 tmp = ð->d_addr.addr_bytes[0];
448 *((uint64_t *)tmp) = 0x000000000002 + ((uint64_t) dst_port << 40);
452 ether_addr_copy(&l2fwd_ports_eth_addr[dst_port], ð->s_addr);
454 l2fwd_send_packet(m, (uint8_t) dst_port);
457 Then, the packet is sent using the l2fwd_send_packet (m, dst_port) function.
458 For this test application, the processing is exactly the same for all packets arriving on the same RX port.
459 Therefore, it would have been possible to call the l2fwd_send_burst() function directly from the main loop
460 to send all the received packets on the same TX port,
461 using the burst-oriented send function, which is more efficient.
463 However, in real-life applications (such as, L3 routing),
464 packet N is not necessarily forwarded on the same port as packet N-1.
465 The application is implemented to illustrate that, so the same approach can be reused in a more complex application.
467 The l2fwd_send_packet() function stores the packet in a per-lcore and per-txport table.
468 If the table is full, the whole packets table is transmitted using the l2fwd_send_burst() function:
472 /* Send the packet on an output interface */
475 l2fwd_send_packet(struct rte_mbuf *m, uint8_t port)
477 unsigned lcore_id, len;
478 struct lcore_queue_conf \*qconf;
480 lcore_id = rte_lcore_id();
481 qconf = &lcore_queue_conf[lcore_id];
482 len = qconf->tx_mbufs[port].len;
483 qconf->tx_mbufs[port].m_table[len] = m;
486 /* enough pkts to be sent */
488 if (unlikely(len == MAX_PKT_BURST)) {
489 l2fwd_send_burst(qconf, MAX_PKT_BURST, port);
493 qconf->tx_mbufs[port].len = len; return 0;
496 To ensure that no packets remain in the tables, each lcore does a draining of TX queue in its main loop.
497 This technique introduces some latency when there are not many packets to send,
498 however it improves performance:
502 cur_tsc = rte_rdtsc();
505 * TX burst queue drain
508 diff_tsc = cur_tsc - prev_tsc;
510 if (unlikely(diff_tsc > drain_tsc)) {
511 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++) {
512 if (qconf->tx_mbufs[portid].len == 0)
515 l2fwd_send_burst(&lcore_queue_conf[lcore_id], qconf->tx_mbufs[portid].len, (uint8_t) portid);
517 qconf->tx_mbufs[portid].len = 0;
520 /* if timer is enabled */
522 if (timer_period > 0) {
523 /* advance the timer */
525 timer_tsc += diff_tsc;
527 /* if timer has reached its timeout */
529 if (unlikely(timer_tsc >= (uint64_t) timer_period)) {
530 /* do this only on master core */
532 if (lcore_id == rte_get_master_lcore()) {
535 /* reset the timer */