dpdk20.11.1学习-2.skeleton

Posted 2021-06-12 龚喜发财+1

一.skeleton功能

基础的二层转发工具。将偶数个网口进行配对，从0接收到的包转发到1口中，从1接收到的包转发到0口中，以此类推。所以端口数需要是偶数个！，仅仅从一个网口抓取数据包转发到另外一个网口，这样做双向转发，相当于桥的功能。其他基础业务都不做。
该例程用到了内存缓冲池mbuf_pool以及mbuf进行接包转包。

二.编译及运行结果

cd examples/skeleton
make
cd build
sudo ./basicfwd

结果

EAL: Detected 1 lcore(s)
EAL: Detected 1 NUMA nodes
EAL: Detected shared linkage of DPDK
EAL: Multi-process socket /var/run/dpdk/rte/mp_socket
EAL: Selected IOVA mode 'PA'
EAL: No available hugepages reported in hugepages-1048576kB
EAL: Probing VFIO support...
EAL:   Invalid NUMA socket, default to 0
EAL:   Invalid NUMA socket, default to 0
EAL: Probe PCI driver: net_e1000_em (8086:100f) device: 0000:02:06.0 (socket 0)
EAL: Error reading from file descriptor 10: Input/output error
EAL:   Invalid NUMA socket, default to 0
EAL: Probe PCI driver: net_e1000_em (8086:100f) device: 0000:02:07.0 (socket 0)
EAL: Error reading from file descriptor 18: Input/output error
EAL: No legacy callbacks, legacy socket not created
EAL: Error enabling interrupts for fd 10 (Input/output error)
Port 0 MAC: 00 0c 29 9b cf 5b
EAL: Error enabling interrupts for fd 18 (Input/output error)
Port 1 MAC: 00 0c 29 9b cf 65

Core 0 forwarding packets. [Ctrl+C to quit]

三.源码分析

#include <stdint.h>
#include <inttypes.h>
#include <rte_eal.h>
#include <rte_ethdev.h>
#include <rte_cycles.h>
#include <rte_lcore.h>
#include <rte_mbuf.h>

#define RX_RING_SIZE 1024   //接收环的大小
#define TX_RING_SIZE 1024   //发送环的大小

#define NUM_MBUFS 8191
#define MBUF_CACHE_SIZE 250
#define BURST_SIZE 32

//以太网端口使用rte_eth_dev_configure()函数和port_conf_default结构以默认设置进行配置 ：
static const struct rte_eth_conf port_conf_default = {
	.rxmode = {
		.max_rx_pkt_len = RTE_ETHER_MAX_LEN,
	},
};

/* basicfwd.c: Basic DPDK skeleton forwarding example. */

/*
 * Initializes a given port using global settings and with the RX buffers
 * coming from the mbuf_pool passed as a parameter.
 */
 //基本转发应用程序中使用的端口初始化的主要功能部分
static inline int
port_init(uint16_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;
	uint16_t nb_rxd = RX_RING_SIZE;
	uint16_t nb_txd = TX_RING_SIZE;
	int retval;
	uint16_t q;
	struct rte_eth_dev_info dev_info;
	struct rte_eth_txconf txconf;

	if (!rte_eth_dev_is_valid_port(port))
		return -1;
	
	retval = rte_eth_dev_info_get(port, &dev_info);
	if (retval != 0) {
		printf("Error during getting device (port %u) info: %s\\n",
				port, strerror(-retval));
		return retval;
	}

	if (dev_info.tx_offload_capa & DEV_TX_OFFLOAD_MBUF_FAST_FREE)
		port_conf.txmode.offloads |=
			DEV_TX_OFFLOAD_MBUF_FAST_FREE;

    //配置以太网设备
	/* Configure the Ethernet device. */
	retval = rte_eth_dev_configure(port, rx_rings, tx_rings, &port_conf);
	if (retval != 0)
		return retval;

	retval = rte_eth_dev_adjust_nb_rx_tx_desc(port, &nb_rxd, &nb_txd);
	if (retval != 0)
		return retval;

    //每个以太网端口分配并设置1个RX队列
    //使用rte_eth_rx_queue_setup()和rte_eth_tx_queue_setup()功能将端口设置为1个RX和1个TX队列 
	/* 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, nb_rxd,
				rte_eth_dev_socket_id(port), NULL, mbuf_pool);
		if (retval < 0)
			return retval;
	}

	txconf = dev_info.default_txconf;
	txconf.offloads = port_conf.txmode.offloads;

    //每个以太网端口分配并设置1个TX队列
	/* 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, nb_txd,
				rte_eth_dev_socket_id(port), &txconf);
		if (retval < 0)
			return retval;
	}

//开始以太网端口
	/* Start the Ethernet port. */
	retval = rte_eth_dev_start(port);
	if (retval < 0)
		return retval;

//展示MAC地址
	/* Display the port MAC address. */
	struct rte_ether_addr addr;
	retval = rte_eth_macaddr_get(port, &addr);
	if (retval != 0)
		return retval;

	printf("Port %u MAC: %02" PRIx8 " %02" PRIx8 " %02" PRIx8
			   " %02" PRIx8 " %02" PRIx8 " %02" PRIx8 "\\n",
			port,
			addr.addr_bytes[0], addr.addr_bytes[1],
			addr.addr_bytes[2], addr.addr_bytes[3],
			addr.addr_bytes[4], addr.addr_bytes[5]);

//在混杂模式下为以太网设备启用RX
	/* Enable RX in promiscuous mode for the Ethernet device. */
	retval = rte_eth_promiscuous_enable(port);
	if (retval != 0)
		return retval;

	return 0;
}

//这是完成工作的主线程，它从输入端口读取并写入输出端口。
/*
 * The lcore main. This is the main thread that does the work, reading from
 * an input port and writing to an output port.
 */
 //正如我们在上面看到的，该main()函数在可用的lcore上调用应用程序函数
static __rte_noreturn void
lcore_main(void)
{
	uint16_t port;

	/*
	 * Check that the port is on the same NUMA node as the polling thread
	 * for best performance.
	 */
	 //检查端口是否与轮询线程在同一NUMA节点上，以获得最佳性能。
	RTE_ETH_FOREACH_DEV(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());

//该应用程序的主要工作是在循环内完成的
	/* 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.
		 */
		RTE_ETH_FOREACH_DEV(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]);
			}
		}
	}
}
//数据包在RX端口上以突发方式接收，并在TX端口上以突发方式发送。使用端口号上的XOR，使用简单的映射方案将端口成对分组：
/*
 * The main function, which does initialization and calls the per-lcore
 * functions.
 */
 
int
main(int argc, char *argv[])
{
	struct rte_mempool *mbuf_pool;
	unsigned nb_ports;
	uint16_t portid;
//第一项任务是初始化环境抽象层（EAL）。在 argc和argv参数提供给rte_eal_init() 函数。返回的值是已解析参数的数量：
	/* Initialize the Environment Abstraction Layer (EAL). */
	int ret = rte_eal_init(argc, argv);
	if (ret < 0)
		rte_exit(EXIT_FAILURE, "Error with EAL initialization\\n");

	argc -= ret;
	argv += ret;

    //端口数必须是偶数个 &是按位与运算，如果为奇数，则nb_ports最后一位是1,和1进行按位与运算结果为1，若为偶数，则最后一位为0，与1进行按位与则结果为0
	/* Check that there is an even number of ports to send/receive on. */
	nb_ports = rte_eth_dev_count_avail();
	if (nb_ports < 2 || (nb_ports & 1))
		rte_exit(EXIT_FAILURE, "Error: number of ports must be even\\n");
		
    //在main中分配一个内存池保持由应用程序使用的的mbuf（消息缓冲器），Mbuf是DPDK使用的数据包缓冲区结构  
	/* Creates a new mempool in memory to hold the mbufs. */
	mbuf_pool = rte_pktmbuf_pool_create("MBUF_POOL", NUM_MBUFS * nb_ports,
		MBUF_CACHE_SIZE, 0, RTE_MBUF_DEFAULT_BUF_SIZE, rte_socket_id());
    if (mbuf_pool == NULL)
		rte_exit(EXIT_FAILURE, "Cannot create mbuf pool\\n");
		
    //还使用用户定义的port_init()函数来初始化所有端口
	/* Initialize all ports. */
	RTE_ETH_FOREACH_DEV(portid)
		if (port_init(portid, mbuf_pool) != 0)
			rte_exit(EXIT_FAILURE, "Cannot init port %"PRIu16 "\\n",
					portid);

   //只需要一个内核
	if (rte_lcore_count() > 1)
		printf("\\nWARNING: Too many lcores enabled. Only 1 used.\\n");

//初始化完成后，应用程序即可在lcore上启动功能。在此示例lcore_main()中，在单个lcore上调用。
	/* Call lcore_main on the main core only. */
	lcore_main();

	return 0;
}

五.参考：https://blog.csdn.net/qq_39992615/article/details/103803632

https://blog.csdn.net/qq_34863439/article/details/102465309