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_dir>/examples/dpdk-l2fwd [EAL options] -- -p PORTMASK
98 [--portmap="(port, port)[,(port, port)]"]
102 * p PORTMASK: A hexadecimal bitmask of the ports to configure
104 * P: Optional, set all ports to promiscuous mode
105 so that packets are accepted regardless of the MAC destination address.
106 Without this option, only packets with the MAC destination address
107 set to the Ethernet address of the port are accepted.
109 * q NQ: A number of queues (=ports) per lcore (default is 1)
111 * --[no-]mac-updating: Enable or disable MAC addresses updating (enabled by default)
113 * --portmap="(port,port)[,(port,port)]": Determines forwarding ports mapping.
115 To run the application in linux environment with 4 lcores, 16 ports and 8 RX queues per lcore and MAC address
116 updating enabled, issue the command:
118 .. code-block:: console
120 $ ./<build_dir>/examples/dpdk-l2fwd -l 0-3 -n 4 -- -q 8 -p ffff
122 To run the application in linux environment with 4 lcores, 4 ports, 8 RX queues
123 per lcore, to forward RX traffic of ports 0 & 1 on ports 2 & 3 respectively and
124 vice versa, issue the command:
126 .. code-block:: console
128 $ ./<build_dir>/examples/dpdk-l2fwd -l 0-3 -n 4 -- -q 8 -p f --portmap="(0,2)(1,3)"
130 Refer to the *DPDK Getting Started Guide* for general information on running applications
131 and the Environment Abstraction Layer (EAL) options.
136 The following sections provide some explanation of the code.
138 .. _l2_fwd_app_cmd_arguments:
140 Command Line Arguments
141 ~~~~~~~~~~~~~~~~~~~~~~
143 The L2 Forwarding sample application takes specific parameters,
144 in addition to Environment Abstraction Layer (EAL) arguments.
145 The preferred way to parse parameters is to use the getopt() function,
146 since it is part of a well-defined and portable library.
148 The parsing of arguments is done in the l2fwd_parse_args() function.
149 The method of argument parsing is not described here.
150 Refer to the *glibc getopt(3)* man page for details.
152 EAL arguments are parsed first, then application-specific arguments.
153 This is done at the beginning of the main() function:
155 .. literalinclude:: ../../../examples/l2fwd/main.c
157 :start-after: Init EAL. 8<
158 :end-before: >8 End of init EAL.
161 .. _l2_fwd_app_mbuf_init:
163 Mbuf Pool Initialization
164 ~~~~~~~~~~~~~~~~~~~~~~~~
166 Once the arguments are parsed, the mbuf pool is created.
167 The mbuf pool contains a set of mbuf objects that will be used by the driver
168 and the application to store network packet data:
170 .. literalinclude:: ../../../examples/l2fwd/main.c
172 :start-after: Create the mbuf pool. 8<
173 :end-before: >8 End of create the mbuf pool.
176 The rte_mempool is a generic structure used to handle pools of objects.
177 In this case, it is necessary to create a pool that will be used by the driver.
178 The number of allocated pkt mbufs is NB_MBUF, with a data room size of
179 RTE_MBUF_DEFAULT_BUF_SIZE each.
180 A per-lcore cache of 32 mbufs is kept.
181 The memory is allocated in NUMA socket 0,
182 but it is possible to extend this code to allocate one mbuf pool per socket.
184 The rte_pktmbuf_pool_create() function uses the default mbuf pool and mbuf
185 initializers, respectively rte_pktmbuf_pool_init() and rte_pktmbuf_init().
186 An advanced application may want to use the mempool API to create the
187 mbuf pool with more control.
189 .. _l2_fwd_app_dvr_init:
191 Driver Initialization
192 ~~~~~~~~~~~~~~~~~~~~~
194 The main part of the code in the main() function relates to the initialization of the driver.
195 To fully understand this code, it is recommended to study the chapters that related to the Poll Mode Driver
196 in the *DPDK Programmer's Guide* - Rel 1.4 EAR and the *DPDK API Reference*.
198 .. literalinclude:: ../../../examples/l2fwd/main.c
200 :start-after: Initialization of the driver. 8<
201 :end-before: >8 End of initialization of the driver.
204 The next step is to configure the RX and TX queues.
205 For each port, there is only one RX queue (only one lcore is able to poll a given port).
206 The number of TX queues depends on the number of available lcores.
207 The rte_eth_dev_configure() function is used to configure the number of queues for a port:
209 .. literalinclude:: ../../../examples/l2fwd/main.c
211 :start-after: Configure the number of queues for a port.
212 :end-before: >8 End of configuration of the number of queues for a port.
215 .. _l2_fwd_app_rx_init:
217 RX Queue Initialization
218 ~~~~~~~~~~~~~~~~~~~~~~~
220 The application uses one lcore to poll one or several ports, depending on the -q option,
221 which specifies the number of queues per lcore.
223 For example, if the user specifies -q 4, the application is able to poll four ports with one lcore.
224 If there are 16 ports on the target (and if the portmask argument is -p ffff ),
225 the application will need four lcores to poll all the ports.
227 .. literalinclude:: ../../../examples/l2fwd/main.c
229 :start-after: RX queue setup. 8<
230 :end-before: >8 End of RX queue setup.
233 The list of queues that must be polled for a given lcore is stored in a private structure called struct lcore_queue_conf.
235 .. literalinclude:: ../../../examples/l2fwd/main.c
237 :start-after: List of queues to be polled for a given lcore. 8<
238 :end-before: >8 End of list of queues to be polled for a given lcore.
240 The values n_rx_port and rx_port_list[] are used in the main packet processing loop
241 (see :ref:`l2_fwd_app_rx_tx_packets`).
243 .. _l2_fwd_app_tx_init:
245 TX Queue Initialization
246 ~~~~~~~~~~~~~~~~~~~~~~~
248 Each lcore should be able to transmit on any port. For every port, a single TX queue is initialized.
250 .. literalinclude:: ../../../examples/l2fwd/main.c
252 :start-after: Init one TX queue on each port. 8<
253 :end-before: >8 End of init one TX queue on each port.
256 .. _l2_fwd_app_rx_tx_packets:
258 Receive, Process and Transmit Packets
259 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
261 In the l2fwd_main_loop() function, the main task is to read ingress packets from the RX queues.
262 This is done using the following code:
264 .. literalinclude:: ../../../examples/l2fwd/main.c
266 :start-after: Read packet from RX queues. 8<
267 :end-before: >8 End of read packet from RX queues.
270 Packets are read in a burst of size MAX_PKT_BURST.
271 The rte_eth_rx_burst() function writes the mbuf pointers in a local table and returns the number of available mbufs in the table.
273 Then, each mbuf in the table is processed by the l2fwd_simple_forward() function.
274 The processing is very simple: process the TX port from the RX port, then replace the source and destination MAC addresses if MAC
275 addresses updating is enabled.
279 In the following code, one line for getting the output port requires some explanation.
281 During the initialization process, a static array of destination ports (l2fwd_dst_ports[]) is filled such that for each source port,
282 a destination port is assigned that is either the next or previous enabled port from the portmask.
283 Naturally, the number of ports in the portmask must be even, otherwise, the application exits.
285 .. literalinclude:: ../../../examples/l2fwd/main.c
287 :start-after: Simple forward. 8<
288 :end-before: >8 End of simple forward.
291 Then, the packet is sent using the l2fwd_send_packet (m, dst_port) function.
292 For this test application, the processing is exactly the same for all packets arriving on the same RX port.
293 Therefore, it would have been possible to call the l2fwd_send_burst() function directly from the main loop
294 to send all the received packets on the same TX port,
295 using the burst-oriented send function, which is more efficient.
297 However, in real-life applications (such as, L3 routing),
298 packet N is not necessarily forwarded on the same port as packet N-1.
299 The application is implemented to illustrate that, so the same approach can be reused in a more complex application.
301 The l2fwd_send_packet() function stores the packet in a per-lcore and per-txport table.
302 If the table is full, the whole packets table is transmitted using the l2fwd_send_burst() function:
304 .. literalinclude:: ../../../examples/l2fwd-crypto/main.c
306 :start-after: Enqueue packets for TX and prepare them to be sent. 8<
307 :end-before: >8 End of Enqueuing packets for TX.
309 To ensure that no packets remain in the tables, each lcore does a draining of TX queue in its main loop.
310 This technique introduces some latency when there are not many packets to send,
311 however it improves performance:
313 .. literalinclude:: ../../../examples/l2fwd/main.c
315 :start-after: Drains TX queue in its main loop. 8<
316 :end-before: >8 End of draining TX queue.