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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 #. Go to the example directory:
112 .. code-block:: console
114 export RTE_SDK=/path/to/rte_sdk
115 cd ${RTE_SDK}/examples/l2fwd
117 #. Set the target (a default target is used if not specified). For example:
119 .. code-block:: console
121 export RTE_TARGET=x86_64-native-linuxapp-gcc
123 *See the DPDK Getting Started Guide* for possible RTE_TARGET values.
125 #. Build the application:
127 .. code-block:: console
131 Running the Application
132 -----------------------
134 The application requires a number of command line options:
136 .. code-block:: console
138 ./build/l2fwd [EAL options] -- -p PORTMASK [-q NQ] --[no-]mac-updating
142 * p PORTMASK: A hexadecimal bitmask of the ports to configure
144 * q NQ: A number of queues (=ports) per lcore (default is 1)
146 * --[no-]mac-updating: Enable or disable MAC addresses updating (enabled by default).
148 To run the application in linuxapp environment with 4 lcores, 16 ports and 8 RX queues per lcore and MAC address
149 updating enabled, issue the command:
151 .. code-block:: console
153 $ ./build/l2fwd -l 0-3 -n 4 -- -q 8 -p ffff
155 Refer to the *DPDK Getting Started Guide* for general information on running applications
156 and the Environment Abstraction Layer (EAL) options.
161 The following sections provide some explanation of the code.
163 .. _l2_fwd_app_cmd_arguments:
165 Command Line Arguments
166 ~~~~~~~~~~~~~~~~~~~~~~
168 The L2 Forwarding sample application takes specific parameters,
169 in addition to Environment Abstraction Layer (EAL) arguments.
170 The preferred way to parse parameters is to use the getopt() function,
171 since it is part of a well-defined and portable library.
173 The parsing of arguments is done in the l2fwd_parse_args() function.
174 The method of argument parsing is not described here.
175 Refer to the *glibc getopt(3)* man page for details.
177 EAL arguments are parsed first, then application-specific arguments.
178 This is done at the beginning of the main() function:
184 ret = rte_eal_init(argc, argv);
186 rte_exit(EXIT_FAILURE, "Invalid EAL arguments\n");
191 /* parse application arguments (after the EAL ones) */
193 ret = l2fwd_parse_args(argc, argv);
195 rte_exit(EXIT_FAILURE, "Invalid L2FWD arguments\n");
197 .. _l2_fwd_app_mbuf_init:
199 Mbuf Pool Initialization
200 ~~~~~~~~~~~~~~~~~~~~~~~~
202 Once the arguments are parsed, the mbuf pool is created.
203 The mbuf pool contains a set of mbuf objects that will be used by the driver
204 and the application to store network packet data:
208 /* create the mbuf pool */
210 l2fwd_pktmbuf_pool = rte_pktmbuf_pool_create("mbuf_pool", NB_MBUF,
211 MEMPOOL_CACHE_SIZE, 0, RTE_MBUF_DEFAULT_BUF_SIZE,
214 if (l2fwd_pktmbuf_pool == NULL)
215 rte_panic("Cannot init mbuf pool\n");
217 The rte_mempool is a generic structure used to handle pools of objects.
218 In this case, it is necessary to create a pool that will be used by the driver.
219 The number of allocated pkt mbufs is NB_MBUF, with a data room size of
220 RTE_MBUF_DEFAULT_BUF_SIZE each.
221 A per-lcore cache of 32 mbufs is kept.
222 The memory is allocated in NUMA socket 0,
223 but it is possible to extend this code to allocate one mbuf pool per socket.
225 The rte_pktmbuf_pool_create() function uses the default mbuf pool and mbuf
226 initializers, respectively rte_pktmbuf_pool_init() and rte_pktmbuf_init().
227 An advanced application may want to use the mempool API to create the
228 mbuf pool with more control.
230 .. _l2_fwd_app_dvr_init:
232 Driver Initialization
233 ~~~~~~~~~~~~~~~~~~~~~
235 The main part of the code in the main() function relates to the initialization of the driver.
236 To fully understand this code, it is recommended to study the chapters that related to the Poll Mode Driver
237 in the *DPDK Programmer's Guide* - Rel 1.4 EAR and the *DPDK API Reference*.
241 if (rte_pci_probe() < 0)
242 rte_exit(EXIT_FAILURE, "Cannot probe PCI\n");
244 nb_ports = rte_eth_dev_count();
247 rte_exit(EXIT_FAILURE, "No Ethernet ports - bye\n");
249 /* reset l2fwd_dst_ports */
251 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++)
252 l2fwd_dst_ports[portid] = 0;
257 * Each logical core is assigned a dedicated TX queue on each port.
260 for (portid = 0; portid < nb_ports; portid++) {
261 /* skip ports that are not enabled */
263 if ((l2fwd_enabled_port_mask & (1 << portid)) == 0)
266 if (nb_ports_in_mask % 2) {
267 l2fwd_dst_ports[portid] = last_port;
268 l2fwd_dst_ports[last_port] = portid;
275 rte_eth_dev_info_get((uint8_t) portid, &dev_info);
280 * rte_igb_pmd_init_all() simultaneously registers the driver as a PCI driver and as an Ethernet* Poll Mode Driver.
282 * rte_pci_probe() parses the devices on the PCI bus and initializes recognized devices.
284 The next step is to configure the RX and TX queues.
285 For each port, there is only one RX queue (only one lcore is able to poll a given port).
286 The number of TX queues depends on the number of available lcores.
287 The rte_eth_dev_configure() function is used to configure the number of queues for a port:
291 ret = rte_eth_dev_configure((uint8_t)portid, 1, 1, &port_conf);
293 rte_exit(EXIT_FAILURE, "Cannot configure device: "
297 The global configuration is stored in a static structure:
301 static const struct rte_eth_conf port_conf = {
304 .header_split = 0, /**< Header Split disabled */
305 .hw_ip_checksum = 0, /**< IP checksum offload disabled */
306 .hw_vlan_filter = 0, /**< VLAN filtering disabled */
307 .jumbo_frame = 0, /**< Jumbo Frame Support disabled */
308 .hw_strip_crc= 0, /**< CRC stripped by hardware */
312 .mq_mode = ETH_DCB_NONE
316 .. _l2_fwd_app_rx_init:
318 RX Queue Initialization
319 ~~~~~~~~~~~~~~~~~~~~~~~
321 The application uses one lcore to poll one or several ports, depending on the -q option,
322 which specifies the number of queues per lcore.
324 For example, if the user specifies -q 4, the application is able to poll four ports with one lcore.
325 If there are 16 ports on the target (and if the portmask argument is -p ffff ),
326 the application will need four lcores to poll all the ports.
330 ret = rte_eth_rx_queue_setup((uint8_t) portid, 0, nb_rxd, SOCKET0, &rx_conf, l2fwd_pktmbuf_pool);
333 rte_exit(EXIT_FAILURE, "rte_eth_rx_queue_setup: "
337 The list of queues that must be polled for a given lcore is stored in a private structure called struct lcore_queue_conf.
341 struct lcore_queue_conf {
343 unsigned rx_port_list[MAX_RX_QUEUE_PER_LCORE];
344 struct mbuf_table tx_mbufs[L2FWD_MAX_PORTS];
347 struct lcore_queue_conf lcore_queue_conf[RTE_MAX_LCORE];
349 The values n_rx_port and rx_port_list[] are used in the main packet processing loop
350 (see :ref:`l2_fwd_app_rx_tx_packets`).
352 The global configuration for the RX queues is stored in a static structure:
356 static const struct rte_eth_rxconf rx_conf = {
358 .pthresh = RX_PTHRESH,
359 .hthresh = RX_HTHRESH,
360 .wthresh = RX_WTHRESH,
364 .. _l2_fwd_app_tx_init:
366 TX Queue Initialization
367 ~~~~~~~~~~~~~~~~~~~~~~~
369 Each lcore should be able to transmit on any port. For every port, a single TX queue is initialized.
373 /* init one TX queue on each port */
377 ret = rte_eth_tx_queue_setup((uint8_t) portid, 0, nb_txd, rte_eth_dev_socket_id(portid), &tx_conf);
379 rte_exit(EXIT_FAILURE, "rte_eth_tx_queue_setup:err=%d, port=%u\n", ret, (unsigned) portid);
381 The global configuration for TX queues is stored in a static structure:
385 static const struct rte_eth_txconf tx_conf = {
387 .pthresh = TX_PTHRESH,
388 .hthresh = TX_HTHRESH,
389 .wthresh = TX_WTHRESH,
391 .tx_free_thresh = RTE_TEST_TX_DESC_DEFAULT + 1, /* disable feature */
394 .. _l2_fwd_app_rx_tx_packets:
396 Receive, Process and Transmit Packets
397 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
399 In the l2fwd_main_loop() function, the main task is to read ingress packets from the RX queues.
400 This is done using the following code:
405 * Read packet from RX queues
408 for (i = 0; i < qconf->n_rx_port; i++) {
409 portid = qconf->rx_port_list[i];
410 nb_rx = rte_eth_rx_burst((uint8_t) portid, 0, pkts_burst, MAX_PKT_BURST);
412 for (j = 0; j < nb_rx; j++) {
414 rte_prefetch0[rte_pktmbuf_mtod(m, void *)); l2fwd_simple_forward(m, portid);
418 Packets are read in a burst of size MAX_PKT_BURST.
419 The rte_eth_rx_burst() function writes the mbuf pointers in a local table and returns the number of available mbufs in the table.
421 Then, each mbuf in the table is processed by the l2fwd_simple_forward() function.
422 The processing is very simple: process the TX port from the RX port, then replace the source and destination MAC addresses if MAC
423 addresses updating is enabled.
427 In the following code, one line for getting the output port requires some explanation.
429 During the initialization process, a static array of destination ports (l2fwd_dst_ports[]) is filled such that for each source port,
430 a destination port is assigned that is either the next or previous enabled port from the portmask.
431 Naturally, the number of ports in the portmask must be even, otherwise, the application exits.
436 l2fwd_simple_forward(struct rte_mbuf *m, unsigned portid)
438 struct ether_hdr *eth;
442 dst_port = l2fwd_dst_ports[portid];
444 eth = rte_pktmbuf_mtod(m, struct ether_hdr *);
446 /* 02:00:00:00:00:xx */
448 tmp = ð->d_addr.addr_bytes[0];
450 *((uint64_t *)tmp) = 0x000000000002 + ((uint64_t) dst_port << 40);
454 ether_addr_copy(&l2fwd_ports_eth_addr[dst_port], ð->s_addr);
456 l2fwd_send_packet(m, (uint8_t) dst_port);
459 Then, the packet is sent using the l2fwd_send_packet (m, dst_port) function.
460 For this test application, the processing is exactly the same for all packets arriving on the same RX port.
461 Therefore, it would have been possible to call the l2fwd_send_burst() function directly from the main loop
462 to send all the received packets on the same TX port,
463 using the burst-oriented send function, which is more efficient.
465 However, in real-life applications (such as, L3 routing),
466 packet N is not necessarily forwarded on the same port as packet N-1.
467 The application is implemented to illustrate that, so the same approach can be reused in a more complex application.
469 The l2fwd_send_packet() function stores the packet in a per-lcore and per-txport table.
470 If the table is full, the whole packets table is transmitted using the l2fwd_send_burst() function:
474 /* Send the packet on an output interface */
477 l2fwd_send_packet(struct rte_mbuf *m, uint8_t port)
479 unsigned lcore_id, len;
480 struct lcore_queue_conf *qconf;
482 lcore_id = rte_lcore_id();
483 qconf = &lcore_queue_conf[lcore_id];
484 len = qconf->tx_mbufs[port].len;
485 qconf->tx_mbufs[port].m_table[len] = m;
488 /* enough pkts to be sent */
490 if (unlikely(len == MAX_PKT_BURST)) {
491 l2fwd_send_burst(qconf, MAX_PKT_BURST, port);
495 qconf->tx_mbufs[port].len = len; return 0;
498 To ensure that no packets remain in the tables, each lcore does a draining of TX queue in its main loop.
499 This technique introduces some latency when there are not many packets to send,
500 however it improves performance:
504 cur_tsc = rte_rdtsc();
507 * TX burst queue drain
510 diff_tsc = cur_tsc - prev_tsc;
512 if (unlikely(diff_tsc > drain_tsc)) {
513 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++) {
514 if (qconf->tx_mbufs[portid].len == 0)
517 l2fwd_send_burst(&lcore_queue_conf[lcore_id], qconf->tx_mbufs[portid].len, (uint8_t) portid);
519 qconf->tx_mbufs[portid].len = 0;
522 /* if timer is enabled */
524 if (timer_period > 0) {
525 /* advance the timer */
527 timer_tsc += diff_tsc;
529 /* if timer has reached its timeout */
531 if (unlikely(timer_tsc >= (uint64_t) timer_period)) {
532 /* do this only on master core */
534 if (lcore_id == rte_get_master_lcore()) {
537 /* reset the timer */