skeleton

FWD

./build/basicfwd -l 0-3 -n 4 -d librte_pmd_e1000.so -d librte_mempool_ring.so  -- -q 8 -p 0x3

struct rte_mempool *mbuf_pool; //memory pool is introduced because of the ports
unsigned nb_ports; // number of ports
uint8_t portid; // port id


/* Initialize the Environment Abstraction Layer (EAL). */
int ret = rte_eal_init(argc, argv);


nb_ports = rte_eth_dev_count(); // counting the number of available ports



/* Creates a new mempool in memory to hold the mbufs. */
mbuf_pool = rte_pktmbuf_pool_create("MBUF_POOL", // name of the packet pool
                                     NUM_MBUFS * nb_ports, // number of elements in mbuf pool
                                     MBUF_CACHE_SIZE, // per core cache size
                                     0, // private data size
                                     RTE_MBUF_DEFAULT_BUF_SIZE, // size of the data buffer in each mbuf
                                     rte_socket_id()); // this is the master core

/* Initialize all ports. */
for (portid = 0; portid < nb_ports; portid++)
      port_init(portid, mbuf_pool);

first initialize all the pthreads for each logical cores
secondly count the number of available NICs thirdly, create a memory pool with the capacity of handling all the packets from the enabled ports

• step into port_init

  struct rte_eth_conf port_conf = port_conf_default;  //port configuration
	const uint16_t rx_rings = 1, tx_rings = 1;
	int retval;
	uint16_t q;


  /* Configure the Ethernet device. */
  retval = rte_eth_dev_configure(port, rx_rings, tx_rings, &port_conf);


  /* Allocate and set up 1 RX queue per Ethernet port. */
  for (q = 0; q < rx_rings; q++)
        rte_eth_rx_queue_setup(port, // The port identifier of the Ethernet device.
                               q, // The index of the receive queue to set up. The value must be in the range [0, nb_rx_queue - 1]
                               RX_RING_SIZE,
                               rte_eth_dev_socket_id(port), // used for NUMA
                               NULL, // rx configuration, in case of NULL - default
                               mbuf_pool); // pointer to memory poll to allocate rte_mbuf


  for (q = 0; q < tx_rings; q++) {
        rte_eth_tx_queue_setup(port, // The port identifier of the Ethernet device.
                               q, // The index of the transmit queue to set up. The value must be in the range [0, nb_tx_queue - 1
                               TX_RING_SIZE,
                               rte_eth_dev_socket_id(port),
                               NULL);

  /* Start the Ethernet port. */
 	rte_eth_dev_start(port);

  /* Enable RX in promiscuous mode for the Ethernet device. */
	rte_eth_promiscuous_enable(port);

each port will be set with the configuration
each port will be signed with rx and tx rings (queues)
the rx queue will have the pointer of the memory pool because it needs the space for saving the received RTE-BUFF
initiate the port
intiate the promiscuous mode

/* Call lcore_main on the master core only. */
lcore_main();

• step into lcore_main()

/* Run until the application is quit or killed. */
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, // port identifier
                                                0,    // queue id
                                                bufs, //rte_buff
                                                BURST_SIZE); // number of packets to retrieve

        /* 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]);
  			}
  }
}

set the number of packets that will be received from the rx-queue
set the number of packets that will be sent by the tx-queue
free the packets that was ignored by the above process