1 .. SPDX-License-Identifier: BSD-3-Clause
2 Copyright(c) 2010-2014 Intel Corporation.
4 .. _l2_fwd_app_real_and_virtual:
6 L2 Forwarding Sample Application (in Real and Virtualized Environments)
7 =======================================================================
9 The L2 Forwarding sample application is a simple example of packet processing using
10 the Data Plane Development Kit (DPDK) which
11 also takes advantage of Single Root I/O Virtualization (SR-IOV) features in a virtualized environment.
15 Please note that previously a separate L2 Forwarding in Virtualized Environments sample application was used,
16 however, in later DPDK versions these sample applications have been merged.
21 The L2 Forwarding sample application, which can operate in real and virtualized environments,
22 performs L2 forwarding for each packet that is received on an RX_PORT.
23 The destination port is the adjacent port from the enabled portmask, that is,
24 if the first four ports are enabled (portmask 0xf),
25 ports 1 and 2 forward into each other, and ports 3 and 4 forward into each other.
26 Also, if MAC addresses updating is enabled, the MAC addresses are affected as follows:
28 * The source MAC address is replaced by the TX_PORT MAC address
30 * The destination MAC address is replaced by 02:00:00:00:00:TX_PORT_ID
32 This application can be used to benchmark performance using a traffic-generator, as shown in the :numref:`figure_l2_fwd_benchmark_setup`,
33 or in a virtualized environment as shown in :numref:`figure_l2_fwd_virtenv_benchmark_setup`.
35 .. _figure_l2_fwd_benchmark_setup:
37 .. figure:: img/l2_fwd_benchmark_setup.*
39 Performance Benchmark Setup (Basic Environment)
41 .. _figure_l2_fwd_virtenv_benchmark_setup:
43 .. figure:: img/l2_fwd_virtenv_benchmark_setup.*
45 Performance Benchmark Setup (Virtualized Environment)
47 This application may be used for basic VM to VM communication as shown in :numref:`figure_l2_fwd_vm2vm`,
48 when MAC addresses updating is disabled.
50 .. _figure_l2_fwd_vm2vm:
52 .. figure:: img/l2_fwd_vm2vm.*
54 Virtual Machine to Virtual Machine communication.
56 The L2 Forwarding application can also be used as a starting point for developing a new application based on the DPDK.
60 Virtual Function Setup Instructions
61 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
63 This application can use the virtual function available in the system and
64 therefore can be used in a virtual machine without passing through
65 the whole Network Device into a guest machine in a virtualized scenario.
66 The virtual functions can be enabled in the host machine or the hypervisor with the respective physical function driver.
68 For example, in a Linux* host machine, it is possible to enable a virtual function using the following command:
70 .. code-block:: console
72 modprobe ixgbe max_vfs=2,2
74 This command enables two Virtual Functions on each of Physical Function of the NIC,
75 with two physical ports in the PCI configuration space.
76 It is important to note that enabled Virtual Function 0 and 2 would belong to Physical Function 0
77 and Virtual Function 1 and 3 would belong to Physical Function 1,
78 in this case enabling a total of four Virtual Functions.
80 Compiling the Application
81 -------------------------
83 To compile the sample application see :doc:`compiling`.
85 The application is located in the ``l2fwd`` sub-directory.
87 Running the Application
88 -----------------------
90 The application requires a number of command line options:
92 .. code-block:: console
94 ./build/l2fwd [EAL options] -- -p PORTMASK [-q NQ] --[no-]mac-updating
98 * p PORTMASK: A hexadecimal bitmask of the ports to configure
100 * q NQ: A number of queues (=ports) per lcore (default is 1)
102 * --[no-]mac-updating: Enable or disable MAC addresses updating (enabled by default).
104 To run the application in linux environment with 4 lcores, 16 ports and 8 RX queues per lcore and MAC address
105 updating enabled, issue the command:
107 .. code-block:: console
109 $ ./build/l2fwd -l 0-3 -n 4 -- -q 8 -p ffff
111 Refer to the *DPDK Getting Started Guide* for general information on running applications
112 and the Environment Abstraction Layer (EAL) options.
117 The following sections provide some explanation of the code.
119 .. _l2_fwd_app_cmd_arguments:
121 Command Line Arguments
122 ~~~~~~~~~~~~~~~~~~~~~~
124 The L2 Forwarding sample application takes specific parameters,
125 in addition to Environment Abstraction Layer (EAL) arguments.
126 The preferred way to parse parameters is to use the getopt() function,
127 since it is part of a well-defined and portable library.
129 The parsing of arguments is done in the l2fwd_parse_args() function.
130 The method of argument parsing is not described here.
131 Refer to the *glibc getopt(3)* man page for details.
133 EAL arguments are parsed first, then application-specific arguments.
134 This is done at the beginning of the main() function:
140 ret = rte_eal_init(argc, argv);
142 rte_exit(EXIT_FAILURE, "Invalid EAL arguments\n");
147 /* parse application arguments (after the EAL ones) */
149 ret = l2fwd_parse_args(argc, argv);
151 rte_exit(EXIT_FAILURE, "Invalid L2FWD arguments\n");
153 .. _l2_fwd_app_mbuf_init:
155 Mbuf Pool Initialization
156 ~~~~~~~~~~~~~~~~~~~~~~~~
158 Once the arguments are parsed, the mbuf pool is created.
159 The mbuf pool contains a set of mbuf objects that will be used by the driver
160 and the application to store network packet data:
164 /* create the mbuf pool */
166 l2fwd_pktmbuf_pool = rte_pktmbuf_pool_create("mbuf_pool", NB_MBUF,
167 MEMPOOL_CACHE_SIZE, 0, RTE_MBUF_DEFAULT_BUF_SIZE,
170 if (l2fwd_pktmbuf_pool == NULL)
171 rte_panic("Cannot init mbuf pool\n");
173 The rte_mempool is a generic structure used to handle pools of objects.
174 In this case, it is necessary to create a pool that will be used by the driver.
175 The number of allocated pkt mbufs is NB_MBUF, with a data room size of
176 RTE_MBUF_DEFAULT_BUF_SIZE each.
177 A per-lcore cache of 32 mbufs is kept.
178 The memory is allocated in NUMA socket 0,
179 but it is possible to extend this code to allocate one mbuf pool per socket.
181 The rte_pktmbuf_pool_create() function uses the default mbuf pool and mbuf
182 initializers, respectively rte_pktmbuf_pool_init() and rte_pktmbuf_init().
183 An advanced application may want to use the mempool API to create the
184 mbuf pool with more control.
186 .. _l2_fwd_app_dvr_init:
188 Driver Initialization
189 ~~~~~~~~~~~~~~~~~~~~~
191 The main part of the code in the main() function relates to the initialization of the driver.
192 To fully understand this code, it is recommended to study the chapters that related to the Poll Mode Driver
193 in the *DPDK Programmer's Guide* - Rel 1.4 EAR and the *DPDK API Reference*.
197 /* reset l2fwd_dst_ports */
199 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++)
200 l2fwd_dst_ports[portid] = 0;
205 * Each logical core is assigned a dedicated TX queue on each port.
208 RTE_ETH_FOREACH_DEV(portid) {
209 /* skip ports that are not enabled */
211 if ((l2fwd_enabled_port_mask & (1 << portid)) == 0)
214 if (nb_ports_in_mask % 2) {
215 l2fwd_dst_ports[portid] = last_port;
216 l2fwd_dst_ports[last_port] = portid;
223 rte_eth_dev_info_get((uint8_t) portid, &dev_info);
226 The next step is to configure the RX and TX queues.
227 For each port, there is only one RX queue (only one lcore is able to poll a given port).
228 The number of TX queues depends on the number of available lcores.
229 The rte_eth_dev_configure() function is used to configure the number of queues for a port:
233 ret = rte_eth_dev_configure((uint8_t)portid, 1, 1, &port_conf);
235 rte_exit(EXIT_FAILURE, "Cannot configure device: "
239 .. _l2_fwd_app_rx_init:
241 RX Queue Initialization
242 ~~~~~~~~~~~~~~~~~~~~~~~
244 The application uses one lcore to poll one or several ports, depending on the -q option,
245 which specifies the number of queues per lcore.
247 For example, if the user specifies -q 4, the application is able to poll four ports with one lcore.
248 If there are 16 ports on the target (and if the portmask argument is -p ffff ),
249 the application will need four lcores to poll all the ports.
253 ret = rte_eth_rx_queue_setup((uint8_t) portid, 0, nb_rxd, SOCKET0, &rx_conf, l2fwd_pktmbuf_pool);
256 rte_exit(EXIT_FAILURE, "rte_eth_rx_queue_setup: "
260 The list of queues that must be polled for a given lcore is stored in a private structure called struct lcore_queue_conf.
264 struct lcore_queue_conf {
266 unsigned rx_port_list[MAX_RX_QUEUE_PER_LCORE];
267 struct mbuf_table tx_mbufs[L2FWD_MAX_PORTS];
270 struct lcore_queue_conf lcore_queue_conf[RTE_MAX_LCORE];
272 The values n_rx_port and rx_port_list[] are used in the main packet processing loop
273 (see :ref:`l2_fwd_app_rx_tx_packets`).
275 .. _l2_fwd_app_tx_init:
277 TX Queue Initialization
278 ~~~~~~~~~~~~~~~~~~~~~~~
280 Each lcore should be able to transmit on any port. For every port, a single TX queue is initialized.
284 /* init one TX queue on each port */
288 ret = rte_eth_tx_queue_setup((uint8_t) portid, 0, nb_txd, rte_eth_dev_socket_id(portid), &tx_conf);
290 rte_exit(EXIT_FAILURE, "rte_eth_tx_queue_setup:err=%d, port=%u\n", ret, (unsigned) portid);
292 The global configuration for TX queues is stored in a static structure:
296 static const struct rte_eth_txconf tx_conf = {
298 .pthresh = TX_PTHRESH,
299 .hthresh = TX_HTHRESH,
300 .wthresh = TX_WTHRESH,
302 .tx_free_thresh = RTE_TEST_TX_DESC_DEFAULT + 1, /* disable feature */
305 .. _l2_fwd_app_rx_tx_packets:
307 Receive, Process and Transmit Packets
308 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
310 In the l2fwd_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);
323 for (j = 0; j < nb_rx; j++) {
325 rte_prefetch0[rte_pktmbuf_mtod(m, void *)); l2fwd_simple_forward(m, portid);
329 Packets are read in a burst of size MAX_PKT_BURST.
330 The rte_eth_rx_burst() function writes the mbuf pointers in a local table and returns the number of available mbufs in the table.
332 Then, each mbuf in the table is processed by the l2fwd_simple_forward() function.
333 The processing is very simple: process the TX port from the RX port, then replace the source and destination MAC addresses if MAC
334 addresses updating is enabled.
338 In the following code, one line for getting the output port requires some explanation.
340 During the initialization process, a static array of destination ports (l2fwd_dst_ports[]) is filled such that for each source port,
341 a destination port is assigned that is either the next or previous enabled port from the portmask.
342 Naturally, the number of ports in the portmask must be even, otherwise, the application exits.
347 l2fwd_simple_forward(struct rte_mbuf *m, unsigned portid)
349 struct rte_ether_hdr *eth;
353 dst_port = l2fwd_dst_ports[portid];
355 eth = rte_pktmbuf_mtod(m, struct rte_ether_hdr *);
357 /* 02:00:00:00:00:xx */
359 tmp = ð->d_addr.addr_bytes[0];
361 *((uint64_t *)tmp) = 0x000000000002 + ((uint64_t) dst_port << 40);
365 rte_ether_addr_copy(&l2fwd_ports_eth_addr[dst_port], ð->s_addr);
367 l2fwd_send_packet(m, (uint8_t) dst_port);
370 Then, the packet is sent using the l2fwd_send_packet (m, dst_port) function.
371 For this test application, the processing is exactly the same for all packets arriving on the same RX port.
372 Therefore, it would have been possible to call the l2fwd_send_burst() function directly from the main loop
373 to send all the received packets on the same TX port,
374 using the burst-oriented send function, which is more efficient.
376 However, in real-life applications (such as, L3 routing),
377 packet N is not necessarily forwarded on the same port as packet N-1.
378 The application is implemented to illustrate that, so the same approach can be reused in a more complex application.
380 The l2fwd_send_packet() function stores the packet in a per-lcore and per-txport table.
381 If the table is full, the whole packets table is transmitted using the l2fwd_send_burst() function:
385 /* Send the packet on an output interface */
388 l2fwd_send_packet(struct rte_mbuf *m, uint16_t port)
390 unsigned lcore_id, len;
391 struct lcore_queue_conf *qconf;
393 lcore_id = rte_lcore_id();
394 qconf = &lcore_queue_conf[lcore_id];
395 len = qconf->tx_mbufs[port].len;
396 qconf->tx_mbufs[port].m_table[len] = m;
399 /* enough pkts to be sent */
401 if (unlikely(len == MAX_PKT_BURST)) {
402 l2fwd_send_burst(qconf, MAX_PKT_BURST, port);
406 qconf->tx_mbufs[port].len = len; return 0;
409 To ensure that no packets remain in the tables, each lcore does a draining of TX queue in its main loop.
410 This technique introduces some latency when there are not many packets to send,
411 however it improves performance:
415 cur_tsc = rte_rdtsc();
418 * TX burst queue drain
421 diff_tsc = cur_tsc - prev_tsc;
423 if (unlikely(diff_tsc > drain_tsc)) {
424 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++) {
425 if (qconf->tx_mbufs[portid].len == 0)
428 l2fwd_send_burst(&lcore_queue_conf[lcore_id], 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 */