--- /dev/null
+.. BSD LICENSE
+ Copyright(c) 2015 Intel Corporation. All rights reserved.
+ All rights reserved.
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions
+ are met:
+
+ * Redistributions of source code must retain the above copyright
+ notice, this list of conditions and the following disclaimer.
+ * Redistributions in binary form must reproduce the above copyright
+ notice, this list of conditions and the following disclaimer in
+ the documentation and/or other materials provided with the
+ distribution.
+ * Neither the name of Intel Corporation nor the names of its
+ contributors may be used to endorse or promote products derived
+ from this software without specific prior written permission.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+Basic Forwarding Sample Application
+===================================
+
+The Basic Forwarding sample application is a simple *skeleton* example of a
+forwarding application.
+
+It is intended as a demonstration of the basic components of a DPDK forwarding
+application. For more detailed implementations see the L2 and L3 forwarding
+sample applications.
+
+
+Compiling the Application
+-------------------------
+
+To compile the application export the path to the DPDK source tree and go to
+the example directory:
+
+.. code-block:: console
+
+ export RTE_SDK=/path/to/rte_sdk
+
+ cd ${RTE_SDK}/examples/skeleton
+
+Set the target, for example:
+
+.. code-block:: console
+
+ export RTE_TARGET=x86_64-native-linuxapp-gcc
+
+See the *DPDK Getting Started* Guide for possible ``RTE_TARGET`` values.
+
+Build the application as follows:
+
+.. code-block:: console
+
+ make
+
+
+Running the Application
+-----------------------
+
+To run the example in a ``linuxapp`` environment:
+
+.. code-block:: console
+
+ ./build/basicfwd -c 2 -n 4
+
+Refer to *DPDK Getting Started Guide* for general information on running
+applications and the Environment Abstraction Layer (EAL) options.
+
+
+Explanation
+-----------
+
+The following sections provide an explanation of the main components of the
+code.
+
+All DPDK library functions used in the sample code are prefixed with ``rte_``
+and are explained in detail in the *DPDK API Documentation*.
+
+
+The Main Function
+~~~~~~~~~~~~~~~~~
+
+The ``main()`` function performs the initialization and calls the execution
+threads for each lcore.
+
+The first task is to initialize the Environment Abstraction Layer (EAL). The
+``argc`` and ``argv`` arguments are provided to the ``rte_eal_init()``
+function. The value returned is the number of parsed arguments:
+
+.. code-block:: c
+
+ int ret = rte_eal_init(argc, argv);
+ if (ret < 0)
+ rte_exit(EXIT_FAILURE, "Error with EAL initialization\n");
+
+
+The ``main()`` also allocates a mempool to hold the mbufs (Message Buffers)
+used by the application:
+
+.. code-block:: c
+
+ mbuf_pool = rte_mempool_create("MBUF_POOL",
+ NUM_MBUFS * nb_ports,
+ MBUF_SIZE,
+ MBUF_CACHE_SIZE,
+ sizeof(struct rte_pktmbuf_pool_private),
+ rte_pktmbuf_pool_init, NULL,
+ rte_pktmbuf_init, NULL,
+ rte_socket_id(),
+ 0);
+
+Mbufs are the packet buffer structure used by DPDK. They are explained in
+detail in the "Mbuf Library" section of the *DPDK Programmer's Guide*.
+
+The ``main()`` function also initializes all the ports using the user defined
+``port_init()`` function which is explained in the next section:
+
+.. code-block:: c
+
+ for (portid = 0; portid < nb_ports; portid++) {
+ if (port_init(portid, mbuf_pool) != 0) {
+ rte_exit(EXIT_FAILURE,
+ "Cannot init port %" PRIu8 "\n", portid);
+ }
+ }
+
+
+Once the initialization is complete, the application is ready to launch a
+function on an lcore. In this example ``lcore_main()`` is called on a single
+lcore.
+
+
+.. code-block:: c
+
+ lcore_main();
+
+The ``lcore_main()`` function is explained below.
+
+
+
+The Port Initialization Function
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The main functional part of the port initialization used in the Basic
+Forwarding application is shown below:
+
+.. code-block:: c
+
+ static inline int
+ port_init(uint8_t port, struct rte_mempool *mbuf_pool)
+ {
+ struct rte_eth_conf port_conf = port_conf_default;
+ const uint16_t rx_rings = 1, tx_rings = 1;
+ struct ether_addr addr;
+ int retval;
+ uint16_t q;
+
+ if (port >= rte_eth_dev_count())
+ return -1;
+
+ /* Configure the Ethernet device. */
+ retval = rte_eth_dev_configure(port, rx_rings, tx_rings, &port_conf);
+ if (retval != 0)
+ return retval;
+
+ /* Allocate and set up 1 RX queue per Ethernet port. */
+ for (q = 0; q < rx_rings; q++) {
+ retval = rte_eth_rx_queue_setup(port, q, RX_RING_SIZE,
+ rte_eth_dev_socket_id(port), NULL, mbuf_pool);
+ if (retval < 0)
+ return retval;
+ }
+
+ /* Allocate and set up 1 TX queue per Ethernet port. */
+ for (q = 0; q < tx_rings; q++) {
+ retval = rte_eth_tx_queue_setup(port, q, TX_RING_SIZE,
+ rte_eth_dev_socket_id(port), NULL);
+ if (retval < 0)
+ return retval;
+ }
+
+ /* Start the Ethernet port. */
+ retval = rte_eth_dev_start(port);
+ if (retval < 0)
+ return retval;
+
+ /* Enable RX in promiscuous mode for the Ethernet device. */
+ rte_eth_promiscuous_enable(port);
+
+ return 0;
+ }
+
+The Ethernet ports are configured with default settings using the
+``rte_eth_dev_configure()`` function and the ``port_conf_default`` struct:
+
+.. code-block:: c
+
+ static const struct rte_eth_conf port_conf_default = {
+ .rxmode = { .max_rx_pkt_len = ETHER_MAX_LEN }
+ };
+
+For this example the ports are set up with 1 RX and 1 TX queue using the
+``rte_eth_rx_queue_setup()`` and ``rte_eth_tx_queue_setup()`` functions.
+
+The Ethernet port is then started:
+
+.. code-block:: c
+
+ retval = rte_eth_dev_start(port);
+
+
+Finally the RX port is set in promiscuous mode:
+
+.. code-block:: c
+
+ rte_eth_promiscuous_enable(port);
+
+
+The Lcores Main
+~~~~~~~~~~~~~~~
+
+As we saw above the ``main()`` function calls an application function on the
+available lcores. For the Basic Forwarding application the lcore function
+looks like the following:
+
+.. code-block:: c
+
+ static __attribute__((noreturn)) void
+ lcore_main(void)
+ {
+ const uint8_t nb_ports = rte_eth_dev_count();
+ uint8_t port;
+
+ /*
+ * Check that the port is on the same NUMA node as the polling thread
+ * for best performance.
+ */
+ for (port = 0; port < nb_ports; port++)
+ if (rte_eth_dev_socket_id(port) > 0 &&
+ rte_eth_dev_socket_id(port) !=
+ (int)rte_socket_id())
+ printf("WARNING, port %u is on remote NUMA node to "
+ "polling thread.\n\tPerformance will "
+ "not be optimal.\n", port);
+
+ printf("\nCore %u forwarding packets. [Ctrl+C to quit]\n",
+ rte_lcore_id());
+
+ /* Run until the application is quit or killed. */
+ for (;;) {
+ /*
+ * Receive packets on a port and forward them on the paired
+ * port. The mapping is 0 -> 1, 1 -> 0, 2 -> 3, 3 -> 2, etc.
+ */
+ for (port = 0; port < nb_ports; port++) {
+
+ /* Get burst of RX packets, from first port of pair. */
+ struct rte_mbuf *bufs[BURST_SIZE];
+ const uint16_t nb_rx = rte_eth_rx_burst(port, 0,
+ bufs, BURST_SIZE);
+
+ if (unlikely(nb_rx == 0))
+ continue;
+
+ /* Send burst of TX packets, to second port of pair. */
+ const uint16_t nb_tx = rte_eth_tx_burst(port ^ 1, 0,
+ bufs, nb_rx);
+
+ /* Free any unsent packets. */
+ if (unlikely(nb_tx < nb_rx)) {
+ uint16_t buf;
+ for (buf = nb_tx; buf < nb_rx; buf++)
+ rte_pktmbuf_free(bufs[buf]);
+ }
+ }
+ }
+ }
+
+
+The main work of the application is done within the loop:
+
+.. code-block:: c
+
+ for (;;) {
+ for (port = 0; port < nb_ports; port++) {
+
+ /* Get burst of RX packets, from first port of pair. */
+ struct rte_mbuf *bufs[BURST_SIZE];
+ const uint16_t nb_rx = rte_eth_rx_burst(port, 0,
+ bufs, BURST_SIZE);
+
+ if (unlikely(nb_rx == 0))
+ continue;
+
+ /* Send burst of TX packets, to second port of pair. */
+ const uint16_t nb_tx = rte_eth_tx_burst(port ^ 1, 0,
+ bufs, nb_rx);
+
+ /* Free any unsent packets. */
+ if (unlikely(nb_tx < nb_rx)) {
+ uint16_t buf;
+ for (buf = nb_tx; buf < nb_rx; buf++)
+ rte_pktmbuf_free(bufs[buf]);
+ }
+ }
+ }
+
+Packets are received in bursts on the RX ports and transmitted in bursts on
+the TX ports. The ports are grouped in pairs with a simple mapping scheme
+using the an XOR on the port number::
+
+ 0 -> 1
+ 1 -> 0
+
+ 2 -> 3
+ 3 -> 2
+
+ etc.
+
+The ``rte_eth_tx_burst()`` function frees the memory buffers of packets that
+are transmitted. If packets fail to transmit, ``(nb_tx < nb_rx)``, then they
+must be freed explicitly using ``rte_pktmbuf_free()``.
+
+The forwarding loop can be interrupted and the application closed using
+``Ctrl-C``.
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