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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, if MAC addresses updating is enabled, 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`,
60 or in a virtualized environment as shown in :numref:`figure_l2_fwd_virtenv_benchmark_setup`.
62 .. _figure_l2_fwd_benchmark_setup:
64 .. figure:: img/l2_fwd_benchmark_setup.*
66 Performance Benchmark Setup (Basic Environment)
68 .. _figure_l2_fwd_virtenv_benchmark_setup:
70 .. figure:: img/l2_fwd_virtenv_benchmark_setup.*
72 Performance Benchmark Setup (Virtualized Environment)
74 This application may be used for basic VM to VM communication as shown in :numref:`figure_l2_fwd_vm2vm`,
75 when MAC addresses updating is disabled.
77 .. _figure_l2_fwd_vm2vm:
79 .. figure:: img/l2_fwd_vm2vm.*
81 Virtual Machine to Virtual Machine communication.
83 The L2 Forwarding application can also be used as a starting point for developing a new application based on the DPDK.
87 Virtual Function Setup Instructions
88 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
90 This application can use the virtual function available in the system and
91 therefore can be used in a virtual machine without passing through
92 the whole Network Device into a guest machine in a virtualized scenario.
93 The virtual functions can be enabled in the host machine or the hypervisor with the respective physical function driver.
95 For example, in a Linux* host machine, it is possible to enable a virtual function using the following command:
97 .. code-block:: console
99 modprobe ixgbe max_vfs=2,2
101 This command enables two Virtual Functions on each of Physical Function of the NIC,
102 with two physical ports in the PCI configuration space.
103 It is important to note that enabled Virtual Function 0 and 2 would belong to Physical Function 0
104 and Virtual Function 1 and 3 would belong to Physical Function 1,
105 in this case enabling a total of four Virtual Functions.
107 Compiling the Application
108 -------------------------
110 To compile the sample application see :doc:`compiling`.
112 The application is located in the ``l2fwd`` sub-directory.
114 Running the Application
115 -----------------------
117 The application requires a number of command line options:
119 .. code-block:: console
121 ./build/l2fwd [EAL options] -- -p PORTMASK [-q NQ] --[no-]mac-updating
125 * p PORTMASK: A hexadecimal bitmask of the ports to configure
127 * q NQ: A number of queues (=ports) per lcore (default is 1)
129 * --[no-]mac-updating: Enable or disable MAC addresses updating (enabled by default).
131 To run the application in linuxapp environment with 4 lcores, 16 ports and 8 RX queues per lcore and MAC address
132 updating enabled, issue the command:
134 .. code-block:: console
136 $ ./build/l2fwd -l 0-3 -n 4 -- -q 8 -p ffff
138 Refer to the *DPDK Getting Started Guide* for general information on running applications
139 and the Environment Abstraction Layer (EAL) options.
144 The following sections provide some explanation of the code.
146 .. _l2_fwd_app_cmd_arguments:
148 Command Line Arguments
149 ~~~~~~~~~~~~~~~~~~~~~~
151 The L2 Forwarding sample application takes specific parameters,
152 in addition to Environment Abstraction Layer (EAL) arguments.
153 The preferred way to parse parameters is to use the getopt() function,
154 since it is part of a well-defined and portable library.
156 The parsing of arguments is done in the l2fwd_parse_args() function.
157 The method of argument parsing is not described here.
158 Refer to the *glibc getopt(3)* man page for details.
160 EAL arguments are parsed first, then application-specific arguments.
161 This is done at the beginning of the main() function:
167 ret = rte_eal_init(argc, argv);
169 rte_exit(EXIT_FAILURE, "Invalid EAL arguments\n");
174 /* parse application arguments (after the EAL ones) */
176 ret = l2fwd_parse_args(argc, argv);
178 rte_exit(EXIT_FAILURE, "Invalid L2FWD arguments\n");
180 .. _l2_fwd_app_mbuf_init:
182 Mbuf Pool Initialization
183 ~~~~~~~~~~~~~~~~~~~~~~~~
185 Once the arguments are parsed, the mbuf pool is created.
186 The mbuf pool contains a set of mbuf objects that will be used by the driver
187 and the application to store network packet data:
191 /* create the mbuf pool */
193 l2fwd_pktmbuf_pool = rte_pktmbuf_pool_create("mbuf_pool", NB_MBUF,
194 MEMPOOL_CACHE_SIZE, 0, RTE_MBUF_DEFAULT_BUF_SIZE,
197 if (l2fwd_pktmbuf_pool == NULL)
198 rte_panic("Cannot init mbuf pool\n");
200 The rte_mempool is a generic structure used to handle pools of objects.
201 In this case, it is necessary to create a pool that will be used by the driver.
202 The number of allocated pkt mbufs is NB_MBUF, with a data room size of
203 RTE_MBUF_DEFAULT_BUF_SIZE each.
204 A per-lcore cache of 32 mbufs is kept.
205 The memory is allocated in NUMA socket 0,
206 but it is possible to extend this code to allocate one mbuf pool per socket.
208 The rte_pktmbuf_pool_create() function uses the default mbuf pool and mbuf
209 initializers, respectively rte_pktmbuf_pool_init() and rte_pktmbuf_init().
210 An advanced application may want to use the mempool API to create the
211 mbuf pool with more control.
213 .. _l2_fwd_app_dvr_init:
215 Driver Initialization
216 ~~~~~~~~~~~~~~~~~~~~~
218 The main part of the code in the main() function relates to the initialization of the driver.
219 To fully understand this code, it is recommended to study the chapters that related to the Poll Mode Driver
220 in the *DPDK Programmer's Guide* - Rel 1.4 EAR and the *DPDK API Reference*.
224 if (rte_pci_probe() < 0)
225 rte_exit(EXIT_FAILURE, "Cannot probe PCI\n");
227 nb_ports = rte_eth_dev_count();
230 rte_exit(EXIT_FAILURE, "No Ethernet ports - bye\n");
232 /* reset l2fwd_dst_ports */
234 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++)
235 l2fwd_dst_ports[portid] = 0;
240 * Each logical core is assigned a dedicated TX queue on each port.
243 for (portid = 0; portid < nb_ports; portid++) {
244 /* skip ports that are not enabled */
246 if ((l2fwd_enabled_port_mask & (1 << portid)) == 0)
249 if (nb_ports_in_mask % 2) {
250 l2fwd_dst_ports[portid] = last_port;
251 l2fwd_dst_ports[last_port] = portid;
258 rte_eth_dev_info_get((uint8_t) portid, &dev_info);
263 * rte_igb_pmd_init_all() simultaneously registers the driver as a PCI driver and as an Ethernet* Poll Mode Driver.
265 * rte_pci_probe() parses the devices on the PCI bus and initializes recognized devices.
267 The next step is to configure the RX and TX queues.
268 For each port, there is only one RX queue (only one lcore is able to poll a given port).
269 The number of TX queues depends on the number of available lcores.
270 The rte_eth_dev_configure() function is used to configure the number of queues for a port:
274 ret = rte_eth_dev_configure((uint8_t)portid, 1, 1, &port_conf);
276 rte_exit(EXIT_FAILURE, "Cannot configure device: "
280 The global configuration is stored in a static structure:
284 static const struct rte_eth_conf port_conf = {
287 .header_split = 0, /**< Header Split disabled */
288 .hw_ip_checksum = 0, /**< IP checksum offload disabled */
289 .hw_vlan_filter = 0, /**< VLAN filtering disabled */
290 .jumbo_frame = 0, /**< Jumbo Frame Support disabled */
291 .hw_strip_crc= 0, /**< CRC stripped by hardware */
295 .mq_mode = ETH_DCB_NONE
299 .. _l2_fwd_app_rx_init:
301 RX Queue Initialization
302 ~~~~~~~~~~~~~~~~~~~~~~~
304 The application uses one lcore to poll one or several ports, depending on the -q option,
305 which specifies the number of queues per lcore.
307 For example, if the user specifies -q 4, the application is able to poll four ports with one lcore.
308 If there are 16 ports on the target (and if the portmask argument is -p ffff ),
309 the application will need four lcores to poll all the ports.
313 ret = rte_eth_rx_queue_setup((uint8_t) portid, 0, nb_rxd, SOCKET0, &rx_conf, l2fwd_pktmbuf_pool);
316 rte_exit(EXIT_FAILURE, "rte_eth_rx_queue_setup: "
320 The list of queues that must be polled for a given lcore is stored in a private structure called struct lcore_queue_conf.
324 struct lcore_queue_conf {
326 unsigned rx_port_list[MAX_RX_QUEUE_PER_LCORE];
327 struct mbuf_table tx_mbufs[L2FWD_MAX_PORTS];
330 struct lcore_queue_conf lcore_queue_conf[RTE_MAX_LCORE];
332 The values n_rx_port and rx_port_list[] are used in the main packet processing loop
333 (see :ref:`l2_fwd_app_rx_tx_packets`).
335 The global configuration for the RX queues is stored in a static structure:
339 static const struct rte_eth_rxconf rx_conf = {
341 .pthresh = RX_PTHRESH,
342 .hthresh = RX_HTHRESH,
343 .wthresh = RX_WTHRESH,
347 .. _l2_fwd_app_tx_init:
349 TX Queue Initialization
350 ~~~~~~~~~~~~~~~~~~~~~~~
352 Each lcore should be able to transmit on any port. For every port, a single TX queue is initialized.
356 /* init one TX queue on each port */
360 ret = rte_eth_tx_queue_setup((uint8_t) portid, 0, nb_txd, rte_eth_dev_socket_id(portid), &tx_conf);
362 rte_exit(EXIT_FAILURE, "rte_eth_tx_queue_setup:err=%d, port=%u\n", ret, (unsigned) portid);
364 The global configuration for TX queues is stored in a static structure:
368 static const struct rte_eth_txconf tx_conf = {
370 .pthresh = TX_PTHRESH,
371 .hthresh = TX_HTHRESH,
372 .wthresh = TX_WTHRESH,
374 .tx_free_thresh = RTE_TEST_TX_DESC_DEFAULT + 1, /* disable feature */
377 .. _l2_fwd_app_rx_tx_packets:
379 Receive, Process and Transmit Packets
380 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
382 In the l2fwd_main_loop() function, the main task is to read ingress packets from the RX queues.
383 This is done using the following code:
388 * Read packet from RX queues
391 for (i = 0; i < qconf->n_rx_port; i++) {
392 portid = qconf->rx_port_list[i];
393 nb_rx = rte_eth_rx_burst((uint8_t) portid, 0, pkts_burst, MAX_PKT_BURST);
395 for (j = 0; j < nb_rx; j++) {
397 rte_prefetch0[rte_pktmbuf_mtod(m, void *)); l2fwd_simple_forward(m, portid);
401 Packets are read in a burst of size MAX_PKT_BURST.
402 The rte_eth_rx_burst() function writes the mbuf pointers in a local table and returns the number of available mbufs in the table.
404 Then, each mbuf in the table is processed by the l2fwd_simple_forward() function.
405 The processing is very simple: process the TX port from the RX port, then replace the source and destination MAC addresses if MAC
406 addresses updating is enabled.
410 In the following code, one line for getting the output port requires some explanation.
412 During the initialization process, a static array of destination ports (l2fwd_dst_ports[]) is filled such that for each source port,
413 a destination port is assigned that is either the next or previous enabled port from the portmask.
414 Naturally, the number of ports in the portmask must be even, otherwise, the application exits.
419 l2fwd_simple_forward(struct rte_mbuf *m, unsigned portid)
421 struct ether_hdr *eth;
425 dst_port = l2fwd_dst_ports[portid];
427 eth = rte_pktmbuf_mtod(m, struct ether_hdr *);
429 /* 02:00:00:00:00:xx */
431 tmp = ð->d_addr.addr_bytes[0];
433 *((uint64_t *)tmp) = 0x000000000002 + ((uint64_t) dst_port << 40);
437 ether_addr_copy(&l2fwd_ports_eth_addr[dst_port], ð->s_addr);
439 l2fwd_send_packet(m, (uint8_t) dst_port);
442 Then, the packet is sent using the l2fwd_send_packet (m, dst_port) function.
443 For this test application, the processing is exactly the same for all packets arriving on the same RX port.
444 Therefore, it would have been possible to call the l2fwd_send_burst() function directly from the main loop
445 to send all the received packets on the same TX port,
446 using the burst-oriented send function, which is more efficient.
448 However, in real-life applications (such as, L3 routing),
449 packet N is not necessarily forwarded on the same port as packet N-1.
450 The application is implemented to illustrate that, so the same approach can be reused in a more complex application.
452 The l2fwd_send_packet() function stores the packet in a per-lcore and per-txport table.
453 If the table is full, the whole packets table is transmitted using the l2fwd_send_burst() function:
457 /* Send the packet on an output interface */
460 l2fwd_send_packet(struct rte_mbuf *m, uint16_t port)
462 unsigned lcore_id, len;
463 struct lcore_queue_conf *qconf;
465 lcore_id = rte_lcore_id();
466 qconf = &lcore_queue_conf[lcore_id];
467 len = qconf->tx_mbufs[port].len;
468 qconf->tx_mbufs[port].m_table[len] = m;
471 /* enough pkts to be sent */
473 if (unlikely(len == MAX_PKT_BURST)) {
474 l2fwd_send_burst(qconf, MAX_PKT_BURST, port);
478 qconf->tx_mbufs[port].len = len; return 0;
481 To ensure that no packets remain in the tables, each lcore does a draining of TX queue in its main loop.
482 This technique introduces some latency when there are not many packets to send,
483 however it improves performance:
487 cur_tsc = rte_rdtsc();
490 * TX burst queue drain
493 diff_tsc = cur_tsc - prev_tsc;
495 if (unlikely(diff_tsc > drain_tsc)) {
496 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++) {
497 if (qconf->tx_mbufs[portid].len == 0)
500 l2fwd_send_burst(&lcore_queue_conf[lcore_id], qconf->tx_mbufs[portid].len, (uint8_t) portid);
502 qconf->tx_mbufs[portid].len = 0;
505 /* if timer is enabled */
507 if (timer_period > 0) {
508 /* advance the timer */
510 timer_tsc += diff_tsc;
512 /* if timer has reached its timeout */
514 if (unlikely(timer_tsc >= (uint64_t) timer_period)) {
515 /* do this only on master core */
517 if (lcore_id == rte_get_master_lcore()) {
520 /* reset the timer */