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
97 [--portmap="(port, port)[,(port, port)]"]
101 * p PORTMASK: A hexadecimal bitmask of the ports to configure
103 * q NQ: A number of queues (=ports) per lcore (default is 1)
105 * --[no-]mac-updating: Enable or disable MAC addresses updating (enabled by default)
107 * --portmap="(port,port)[,(port,port)]": Determines forwarding ports mapping.
109 To run the application in linux environment with 4 lcores, 16 ports and 8 RX queues per lcore and MAC address
110 updating enabled, issue the command:
112 .. code-block:: console
114 $ ./build/l2fwd -l 0-3 -n 4 -- -q 8 -p ffff
116 To run the application in linux environment with 4 lcores, 4 ports, 8 RX queues
117 per lcore, to forward RX traffic of ports 0 & 1 on ports 2 & 3 respectively and
118 vice versa, issue the command:
120 .. code-block:: console
122 $ ./build/l2fwd -l 0-3 -n 4 -- -q 8 -p f --portmap="(0,2)(1,3)"
124 Refer to the *DPDK Getting Started Guide* for general information on running applications
125 and the Environment Abstraction Layer (EAL) options.
130 The following sections provide some explanation of the code.
132 .. _l2_fwd_app_cmd_arguments:
134 Command Line Arguments
135 ~~~~~~~~~~~~~~~~~~~~~~
137 The L2 Forwarding sample application takes specific parameters,
138 in addition to Environment Abstraction Layer (EAL) arguments.
139 The preferred way to parse parameters is to use the getopt() function,
140 since it is part of a well-defined and portable library.
142 The parsing of arguments is done in the l2fwd_parse_args() function.
143 The method of argument parsing is not described here.
144 Refer to the *glibc getopt(3)* man page for details.
146 EAL arguments are parsed first, then application-specific arguments.
147 This is done at the beginning of the main() function:
153 ret = rte_eal_init(argc, argv);
155 rte_exit(EXIT_FAILURE, "Invalid EAL arguments\n");
160 /* parse application arguments (after the EAL ones) */
162 ret = l2fwd_parse_args(argc, argv);
164 rte_exit(EXIT_FAILURE, "Invalid L2FWD arguments\n");
166 .. _l2_fwd_app_mbuf_init:
168 Mbuf Pool Initialization
169 ~~~~~~~~~~~~~~~~~~~~~~~~
171 Once the arguments are parsed, the mbuf pool is created.
172 The mbuf pool contains a set of mbuf objects that will be used by the driver
173 and the application to store network packet data:
177 /* create the mbuf pool */
179 l2fwd_pktmbuf_pool = rte_pktmbuf_pool_create("mbuf_pool", NB_MBUF,
180 MEMPOOL_CACHE_SIZE, 0, RTE_MBUF_DEFAULT_BUF_SIZE,
183 if (l2fwd_pktmbuf_pool == NULL)
184 rte_panic("Cannot init mbuf pool\n");
186 The rte_mempool is a generic structure used to handle pools of objects.
187 In this case, it is necessary to create a pool that will be used by the driver.
188 The number of allocated pkt mbufs is NB_MBUF, with a data room size of
189 RTE_MBUF_DEFAULT_BUF_SIZE each.
190 A per-lcore cache of 32 mbufs is kept.
191 The memory is allocated in NUMA socket 0,
192 but it is possible to extend this code to allocate one mbuf pool per socket.
194 The rte_pktmbuf_pool_create() function uses the default mbuf pool and mbuf
195 initializers, respectively rte_pktmbuf_pool_init() and rte_pktmbuf_init().
196 An advanced application may want to use the mempool API to create the
197 mbuf pool with more control.
199 .. _l2_fwd_app_dvr_init:
201 Driver Initialization
202 ~~~~~~~~~~~~~~~~~~~~~
204 The main part of the code in the main() function relates to the initialization of the driver.
205 To fully understand this code, it is recommended to study the chapters that related to the Poll Mode Driver
206 in the *DPDK Programmer's Guide* - Rel 1.4 EAR and the *DPDK API Reference*.
210 /* reset l2fwd_dst_ports */
212 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++)
213 l2fwd_dst_ports[portid] = 0;
218 * Each logical core is assigned a dedicated TX queue on each port.
221 RTE_ETH_FOREACH_DEV(portid) {
222 /* skip ports that are not enabled */
224 if ((l2fwd_enabled_port_mask & (1 << portid)) == 0)
227 if (nb_ports_in_mask % 2) {
228 l2fwd_dst_ports[portid] = last_port;
229 l2fwd_dst_ports[last_port] = portid;
236 rte_eth_dev_info_get((uint8_t) portid, &dev_info);
239 The next step is to configure the RX and TX queues.
240 For each port, there is only one RX queue (only one lcore is able to poll a given port).
241 The number of TX queues depends on the number of available lcores.
242 The rte_eth_dev_configure() function is used to configure the number of queues for a port:
246 ret = rte_eth_dev_configure((uint8_t)portid, 1, 1, &port_conf);
248 rte_exit(EXIT_FAILURE, "Cannot configure device: "
252 .. _l2_fwd_app_rx_init:
254 RX Queue Initialization
255 ~~~~~~~~~~~~~~~~~~~~~~~
257 The application uses one lcore to poll one or several ports, depending on the -q option,
258 which specifies the number of queues per lcore.
260 For example, if the user specifies -q 4, the application is able to poll four ports with one lcore.
261 If there are 16 ports on the target (and if the portmask argument is -p ffff ),
262 the application will need four lcores to poll all the ports.
266 ret = rte_eth_rx_queue_setup((uint8_t) portid, 0, nb_rxd, SOCKET0, &rx_conf, l2fwd_pktmbuf_pool);
269 rte_exit(EXIT_FAILURE, "rte_eth_rx_queue_setup: "
273 The list of queues that must be polled for a given lcore is stored in a private structure called struct lcore_queue_conf.
277 struct lcore_queue_conf {
279 unsigned rx_port_list[MAX_RX_QUEUE_PER_LCORE];
280 struct mbuf_table tx_mbufs[L2FWD_MAX_PORTS];
283 struct lcore_queue_conf lcore_queue_conf[RTE_MAX_LCORE];
285 The values n_rx_port and rx_port_list[] are used in the main packet processing loop
286 (see :ref:`l2_fwd_app_rx_tx_packets`).
288 .. _l2_fwd_app_tx_init:
290 TX Queue Initialization
291 ~~~~~~~~~~~~~~~~~~~~~~~
293 Each lcore should be able to transmit on any port. For every port, a single TX queue is initialized.
297 /* init one TX queue on each port */
301 ret = rte_eth_tx_queue_setup((uint8_t) portid, 0, nb_txd, rte_eth_dev_socket_id(portid), &tx_conf);
303 rte_exit(EXIT_FAILURE, "rte_eth_tx_queue_setup:err=%d, port=%u\n", ret, (unsigned) portid);
305 The global configuration for TX queues is stored in a static structure:
309 static const struct rte_eth_txconf tx_conf = {
311 .pthresh = TX_PTHRESH,
312 .hthresh = TX_HTHRESH,
313 .wthresh = TX_WTHRESH,
315 .tx_free_thresh = RTE_TEST_TX_DESC_DEFAULT + 1, /* disable feature */
318 .. _l2_fwd_app_rx_tx_packets:
320 Receive, Process and Transmit Packets
321 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
323 In the l2fwd_main_loop() function, the main task is to read ingress packets from the RX queues.
324 This is done using the following code:
329 * Read packet from RX queues
332 for (i = 0; i < qconf->n_rx_port; i++) {
333 portid = qconf->rx_port_list[i];
334 nb_rx = rte_eth_rx_burst((uint8_t) portid, 0, pkts_burst, MAX_PKT_BURST);
336 for (j = 0; j < nb_rx; j++) {
338 rte_prefetch0[rte_pktmbuf_mtod(m, void *)); l2fwd_simple_forward(m, portid);
342 Packets are read in a burst of size MAX_PKT_BURST.
343 The rte_eth_rx_burst() function writes the mbuf pointers in a local table and returns the number of available mbufs in the table.
345 Then, each mbuf in the table is processed by the l2fwd_simple_forward() function.
346 The processing is very simple: process the TX port from the RX port, then replace the source and destination MAC addresses if MAC
347 addresses updating is enabled.
351 In the following code, one line for getting the output port requires some explanation.
353 During the initialization process, a static array of destination ports (l2fwd_dst_ports[]) is filled such that for each source port,
354 a destination port is assigned that is either the next or previous enabled port from the portmask.
355 Naturally, the number of ports in the portmask must be even, otherwise, the application exits.
360 l2fwd_simple_forward(struct rte_mbuf *m, unsigned portid)
362 struct rte_ether_hdr *eth;
366 dst_port = l2fwd_dst_ports[portid];
368 eth = rte_pktmbuf_mtod(m, struct rte_ether_hdr *);
370 /* 02:00:00:00:00:xx */
372 tmp = ð->d_addr.addr_bytes[0];
374 *((uint64_t *)tmp) = 0x000000000002 + ((uint64_t) dst_port << 40);
378 rte_ether_addr_copy(&l2fwd_ports_eth_addr[dst_port], ð->s_addr);
380 l2fwd_send_packet(m, (uint8_t) dst_port);
383 Then, the packet is sent using the l2fwd_send_packet (m, dst_port) function.
384 For this test application, the processing is exactly the same for all packets arriving on the same RX port.
385 Therefore, it would have been possible to call the l2fwd_send_burst() function directly from the main loop
386 to send all the received packets on the same TX port,
387 using the burst-oriented send function, which is more efficient.
389 However, in real-life applications (such as, L3 routing),
390 packet N is not necessarily forwarded on the same port as packet N-1.
391 The application is implemented to illustrate that, so the same approach can be reused in a more complex application.
393 The l2fwd_send_packet() function stores the packet in a per-lcore and per-txport table.
394 If the table is full, the whole packets table is transmitted using the l2fwd_send_burst() function:
398 /* Send the packet on an output interface */
401 l2fwd_send_packet(struct rte_mbuf *m, uint16_t port)
403 unsigned lcore_id, len;
404 struct lcore_queue_conf *qconf;
406 lcore_id = rte_lcore_id();
407 qconf = &lcore_queue_conf[lcore_id];
408 len = qconf->tx_mbufs[port].len;
409 qconf->tx_mbufs[port].m_table[len] = m;
412 /* enough pkts to be sent */
414 if (unlikely(len == MAX_PKT_BURST)) {
415 l2fwd_send_burst(qconf, MAX_PKT_BURST, port);
419 qconf->tx_mbufs[port].len = len; return 0;
422 To ensure that no packets remain in the tables, each lcore does a draining of TX queue in its main loop.
423 This technique introduces some latency when there are not many packets to send,
424 however it improves performance:
428 cur_tsc = rte_rdtsc();
431 * TX burst queue drain
434 diff_tsc = cur_tsc - prev_tsc;
436 if (unlikely(diff_tsc > drain_tsc)) {
437 for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++) {
438 if (qconf->tx_mbufs[portid].len == 0)
441 l2fwd_send_burst(&lcore_queue_conf[lcore_id], qconf->tx_mbufs[portid].len, (uint8_t) portid);
443 qconf->tx_mbufs[portid].len = 0;
446 /* if timer is enabled */
448 if (timer_period > 0) {
449 /* advance the timer */
451 timer_tsc += diff_tsc;
453 /* if timer has reached its timeout */
455 if (unlikely(timer_tsc >= (uint64_t) timer_period)) {
456 /* do this only on master core */
458 if (lcore_id == rte_get_master_lcore()) {
461 /* reset the timer */