DPDK的examples：l2fwd源码阅读、注释

直接贴源码与注释，后续再详细展开

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/*-
 *   BSD LICENSE
 *
 *   Copyright(c) 2010-2016 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.
 */

#include 
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static volatile bool force_quit;

/* MAC updating enabled by default */
static int mac_updating = 1;

#define RTE_LOGTYPE_L2FWD RTE_LOGTYPE_USER1

#define NB_MBUF   8192

#define MAX_PKT_BURST 32
#define BURST_TX_DRAIN_US 100 /* TX drain every ~100us */
#define MEMPOOL_CACHE_SIZE 256

/*
 * Configurable number of RX/TX ring descriptors
 */
#define RTE_TEST_RX_DESC_DEFAULT 128
#define RTE_TEST_TX_DESC_DEFAULT 512
static uint16_t nb_rxd = RTE_TEST_RX_DESC_DEFAULT;
static uint16_t nb_txd = RTE_TEST_TX_DESC_DEFAULT;

/* ethernet addresses of ports */
static struct ether_addr l2fwd_ports_eth_addr[RTE_MAX_ETHPORTS];

/* mask of enabled ports */
static uint32_t l2fwd_enabled_port_mask = 0;

/* list of enabled ports */
static uint32_t l2fwd_dst_ports[RTE_MAX_ETHPORTS];

static unsigned int l2fwd_rx_queue_per_lcore = 1;

#define MAX_RX_QUEUE_PER_LCORE 16
#define MAX_TX_QUEUE_PER_PORT 16
struct lcore_queue_conf {
	unsigned n_rx_port;
	unsigned rx_port_list[MAX_RX_QUEUE_PER_LCORE];
} __rte_cache_aligned;
struct lcore_queue_conf lcore_queue_conf[RTE_MAX_LCORE];

static struct rte_eth_dev_tx_buffer *tx_buffer[RTE_MAX_ETHPORTS];

static const struct rte_eth_conf port_conf = {
	.rxmode = {
		.split_hdr_size = 0,
		.header_split   = 0, /**< Header Split disabled */
		.hw_ip_checksum = 0, /**< IP checksum offload disabled */
		.hw_vlan_filter = 0, /**< VLAN filtering disabled */
		.jumbo_frame    = 0, /**< Jumbo Frame Support disabled */
		.hw_strip_crc   = 1, /**< CRC stripped by hardware */
	},
	.txmode = {
		.mq_mode = ETH_MQ_TX_NONE,
	},
};

struct rte_mempool * l2fwd_pktmbuf_pool = NULL;

/* Per-port statistics struct */
struct l2fwd_port_statistics {
	uint64_t tx;
	uint64_t rx;
	uint64_t dropped;
} __rte_cache_aligned;
struct l2fwd_port_statistics port_statistics[RTE_MAX_ETHPORTS];

#define MAX_TIMER_PERIOD 86400 /* 1 day max */
/* A tsc-based timer responsible for triggering statistics printout */
static uint64_t timer_period = 10; /* default period is 10 seconds */

/* Print out statistics on packets dropped */
static void
print_stats(void)
{
	uint64_t total_packets_dropped, total_packets_tx, total_packets_rx;
	unsigned portid;

	total_packets_dropped = 0;
	total_packets_tx = 0;
	total_packets_rx = 0;

	const char clr[] = { 27, '[', '2', 'J', '\0' };
	const char topLeft[] = { 27, '[', '1', ';', '1', 'H','\0' };

		/* Clear screen and move to top left */
	printf("%s%s", clr, topLeft);

	printf("\nPort statistics ====================================");

	for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++) {
		/* skip disabled ports */
		if ((l2fwd_enabled_port_mask & (1 << portid)) == 0)
			continue;
		printf("\nStatistics for port %u ------------------------------"
			   "\nPackets sent: %24"PRIu64
			   "\nPackets received: %20"PRIu64
			   "\nPackets dropped: %21"PRIu64,
			   portid,
			   port_statistics[portid].tx,
			   port_statistics[portid].rx,
			   port_statistics[portid].dropped);

		total_packets_dropped += port_statistics[portid].dropped;
		total_packets_tx += port_statistics[portid].tx;
		total_packets_rx += port_statistics[portid].rx;
	}
	printf("\nAggregate statistics ==============================="
		   "\nTotal packets sent: %18"PRIu64
		   "\nTotal packets received: %14"PRIu64
		   "\nTotal packets dropped: %15"PRIu64,
		   total_packets_tx,
		   total_packets_rx,
		   total_packets_dropped);
	printf("\n====================================================\n");
}

//替换源MAC地址和目的MAC地址
static void
l2fwd_mac_updating(struct rte_mbuf *m, unsigned dest_portid)
{
	struct ether_hdr *eth;
	void *tmp;

	eth = rte_pktmbuf_mtod(m, struct ether_hdr *);

	/* 02:00:00:00:00:xx */
	tmp = &eth->d_addr.addr_bytes[0];
	*((uint64_t *)tmp) = 0x000000000002 + ((uint64_t)dest_portid << 40);

	/* src addr */
	ether_addr_copy(&l2fwd_ports_eth_addr[dest_portid], &eth->s_addr);
}
//转发
static void
l2fwd_simple_forward(struct rte_mbuf *m, unsigned portid)
{
	unsigned dst_port;
	int sent;
	struct rte_eth_dev_tx_buffer *buffer;

	dst_port = l2fwd_dst_ports[portid];

	if (mac_updating)
		l2fwd_mac_updating(m, dst_port);

	buffer = tx_buffer[dst_port];
	sent = rte_eth_tx_buffer(dst_port, 0, buffer, m);
	if (sent)
		port_statistics[dst_port].tx += sent;
}

/* main processing loop */
static void
l2fwd_main_loop(void)
{
	struct rte_mbuf *pkts_burst[MAX_PKT_BURST];
	struct rte_mbuf *m;
	int sent;
	unsigned lcore_id;
	uint64_t prev_tsc, diff_tsc, cur_tsc, timer_tsc;
	unsigned i, j, portid, nb_rx;
	struct lcore_queue_conf *qconf;
	const uint64_t drain_tsc = (rte_get_tsc_hz() + US_PER_S - 1) / US_PER_S *
			BURST_TX_DRAIN_US;
	struct rte_eth_dev_tx_buffer *buffer;

	prev_tsc = 0;
	timer_tsc = 0;
//获取coreid
	lcore_id = rte_lcore_id();
	qconf = &lcore_queue_conf[lcore_id];

	if (qconf->n_rx_port == 0) {
		RTE_LOG(INFO, L2FWD, "lcore %u has nothing to do\n", lcore_id);
		return;
	}
//进入主循环
	RTE_LOG(INFO, L2FWD, "entering main loop on lcore %u\n", lcore_id);

	for (i = 0; i < qconf->n_rx_port; i++) {

		portid = qconf->rx_port_list[i];
		RTE_LOG(INFO, L2FWD, " -- lcoreid=%u portid=%u\n", lcore_id,
			portid);

	}
//强制退出，ctrl+c

	while (!force_quit) {

		cur_tsc = rte_rdtsc();

		/*
		 * TX burst queue drain
		 */
//计算时间
		diff_tsc = cur_tsc - prev_tsc;
		if (unlikely(diff_tsc > drain_tsc)) {

			for (i = 0; i < qconf->n_rx_port; i++) {

				portid = l2fwd_dst_ports[qconf->rx_port_list[i]];
				buffer = tx_buffer[portid];

				sent = rte_eth_tx_buffer_flush(portid, 0, buffer);
				if (sent)
					port_statistics[portid].tx += sent;

			}
//到里时间间隔，打印端口数据
			/* if timer is enabled */
			if (timer_period > 0) {

				/* advance the timer */
				timer_tsc += diff_tsc;

				/* if timer has reached its timeout */
				if (unlikely(timer_tsc >= timer_period)) {

					/* do this only on master core */
					if (lcore_id == rte_get_master_lcore()) {
						print_stats();
						/* reset the timer */
						timer_tsc = 0;
					}
				}
			}

			prev_tsc = cur_tsc;
		}

		/*
		 * Read packet from RX queues
		 */
//读接收队列的报文
		for (i = 0; i < qconf->n_rx_port; i++) {

			portid = qconf->rx_port_list[i];
//收包，一次最多收取MAX_PKT_BURST个数据包
			nb_rx = rte_eth_rx_burst((uint8_t) portid, 0,
						 pkts_burst, MAX_PKT_BURST);
//更新统计数据
			port_statistics[portid].rx += nb_rx;

			for (j = 0; j < nb_rx; j++) {
				m = pkts_burst[j];
				rte_prefetch0(rte_pktmbuf_mtod(m, void *));
转发，替换源MAC地址和目的MAC地址
				l2fwd_simple_forward(m, portid);
			}
		}
	}
}

static int
l2fwd_launch_one_lcore(__attribute__((unused)) void *dummy)
{
	l2fwd_main_loop();
	return 0;
}

/* display usage */
static void
l2fwd_usage(const char *prgname)
{
	printf("%s [EAL options] -- -p PORTMASK [-q NQ]\n"
	       "  -p PORTMASK: hexadecimal bitmask of ports to configure\n"
	       "  -q NQ: number of queue (=ports) per lcore (default is 1)\n"
		   "  -T PERIOD: statistics will be refreshed each PERIOD seconds (0 to disable, 10 default, 86400 maximum)\n"
		   "  --[no-]mac-updating: Enable or disable MAC addresses updating (enabled by default)\n"
		   "      When enabled:\n"
		   "       - The source MAC address is replaced by the TX port MAC address\n"
		   "       - The destination MAC address is replaced by 02:00:00:00:00:TX_PORT_ID\n",
	       prgname);
}

static int
l2fwd_parse_portmask(const char *portmask)
{
	char *end = NULL;
	unsigned long pm;

	/* parse hexadecimal string */
	pm = strtoul(portmask, &end, 16);
	if ((portmask[0] == '\0') || (end == NULL) || (*end != '\0'))
		return -1;

	if (pm == 0)
		return -1;

	return pm;
}

static unsigned int
l2fwd_parse_nqueue(const char *q_arg)
{
	char *end = NULL;
	unsigned long n;

	/* parse hexadecimal string */
	n = strtoul(q_arg, &end, 10);
	if ((q_arg[0] == '\0') || (end == NULL) || (*end != '\0'))
		return 0;
	if (n == 0)
		return 0;
	if (n >= MAX_RX_QUEUE_PER_LCORE)
		return 0;

	return n;
}

static int
l2fwd_parse_timer_period(const char *q_arg)
{
	char *end = NULL;
	int n;

	/* parse number string */
	n = strtol(q_arg, &end, 10);
	if ((q_arg[0] == '\0') || (end == NULL) || (*end != '\0'))
		return -1;
	if (n >= MAX_TIMER_PERIOD)
		return -1;

	return n;
}

static const char short_options[] =
	"p:"  /* portmask */
	"q:"  /* number of queues */
	"T:"  /* timer period */
	;

#define CMD_LINE_OPT_MAC_UPDATING "mac-updating"
#define CMD_LINE_OPT_NO_MAC_UPDATING "no-mac-updating"

enum {
	/* long options mapped to a short option */

	/* first long only option value must be >= 256, so that we won't
	 * conflict with short options */
	CMD_LINE_OPT_MIN_NUM = 256,
};

static const struct option lgopts[] = {
	{ CMD_LINE_OPT_MAC_UPDATING, no_argument, &mac_updating, 1},
	{ CMD_LINE_OPT_NO_MAC_UPDATING, no_argument, &mac_updating, 0},
	{NULL, 0, 0, 0}
};

/* Parse the argument given in the command line of the application */
static int
l2fwd_parse_args(int argc, char **argv)
{
	int opt, ret, timer_secs;
	char **argvopt;
	int option_index;
	char *prgname = argv[0];

	argvopt = argv;

	while ((opt = getopt_long(argc, argvopt, short_options,
				  lgopts, &option_index)) != EOF) {

		switch (opt) {
		/* portmask */
		case 'p':
			l2fwd_enabled_port_mask = l2fwd_parse_portmask(optarg);
			if (l2fwd_enabled_port_mask == 0) {
				printf("invalid portmask\n");
				l2fwd_usage(prgname);
				return -1;
			}
			break;

		/* nqueue */
		case 'q':
			l2fwd_rx_queue_per_lcore = l2fwd_parse_nqueue(optarg);
			if (l2fwd_rx_queue_per_lcore == 0) {
				printf("invalid queue number\n");
				l2fwd_usage(prgname);
				return -1;
			}
			break;

		/* timer period */
		case 'T':
			timer_secs = l2fwd_parse_timer_period(optarg);
			if (timer_secs < 0) {
				printf("invalid timer period\n");
				l2fwd_usage(prgname);
				return -1;
			}
			timer_period = timer_secs;
			break;

		/* long options */
		case 0:
			break;

		default:
			l2fwd_usage(prgname);
			return -1;
		}
	}

	if (optind >= 0)
		argv[optind-1] = prgname;

	ret = optind-1;
	optind = 1; /* reset getopt lib */
	return ret;
}

/* Check the link status of all ports in up to 9s, and print them finally */
static void
check_all_ports_link_status(uint8_t port_num, uint32_t port_mask)
{
#define CHECK_INTERVAL 100 /* 100ms */
#define MAX_CHECK_TIME 90 /* 9s (90 * 100ms) in total */
	uint8_t portid, count, all_ports_up, print_flag = 0;
	struct rte_eth_link link;

	printf("\nChecking link status");
	fflush(stdout);
	for (count = 0; count <= MAX_CHECK_TIME; count++) {
		if (force_quit)
			return;
		all_ports_up = 1;
		for (portid = 0; portid < port_num; portid++) {
			if (force_quit)
				return;
			if ((port_mask & (1 << portid)) == 0)
				continue;
			memset(&link, 0, sizeof(link));
			rte_eth_link_get_nowait(portid, &link);
			/* print link status if flag set */
			if (print_flag == 1) {
				if (link.link_status)
					printf("Port %d Link Up - speed %u "
						"Mbps - %s\n", (uint8_t)portid,
						(unsigned)link.link_speed,
				(link.link_duplex == ETH_LINK_FULL_DUPLEX) ?
					("full-duplex") : ("half-duplex\n"));
				else
					printf("Port %d Link Down\n",
						(uint8_t)portid);
				continue;
			}
			/* clear all_ports_up flag if any link down */
			if (link.link_status == ETH_LINK_DOWN) {
				all_ports_up = 0;
				break;
			}
		}
		/* after finally printing all link status, get out */
		if (print_flag == 1)
			break;

		if (all_ports_up == 0) {
			printf(".");
			fflush(stdout);
			rte_delay_ms(CHECK_INTERVAL);
		}

		/* set the print_flag if all ports up or timeout */
		if (all_ports_up == 1 || count == (MAX_CHECK_TIME - 1)) {
			print_flag = 1;
			printf("done\n");
		}
	}
}

static void
signal_handler(int signum)
{
	if (signum == SIGINT || signum == SIGTERM) {
		printf("\n\nSignal %d received, preparing to exit...\n",
				signum);
		force_quit = true;
	}
}


// 命令行解析
//参数输入 ./l2fwd -c 0x3 -n 4 -- -p 3 -q 1
//其中-c 为十六进制的分配的逻辑内核数量，-n 为十进制的内存通道数量，EAL参数和程序参数用--分开
// -q 为分配给每个核心的收发队列数量（端口数量），-p为十六进制的分配的端口数，-t 为可选默认10s打印时间间隔参数
int
main(int argc, char **argv)
{
	struct lcore_queue_conf *qconf;
	struct rte_eth_dev_info dev_info;
	int ret;
	uint8_t nb_ports;
	uint8_t nb_ports_available;
	uint8_t portid, last_port;
	unsigned lcore_id, rx_lcore_id;
	unsigned nb_ports_in_mask = 0;

	/* init EAL */
//初始化EAL参数，并解析参数，系统函数getopt以及getopt_long，这些处理命令行参数的函数，处理到“--”时就会停止，分割参数
	ret = rte_eal_init(argc, argv);
	if (ret < 0)
		rte_exit(EXIT_FAILURE, "Invalid EAL arguments\n");
//argc减去EAL参数的同时，argv加上EAL的参数，保证解析程序参数的时候已经跳过了EAL参数
	argc -= ret;
	argv += ret;

	force_quit = false;
	signal(SIGINT, signal_handler);
	signal(SIGTERM, signal_handler);

	/* parse application arguments (after the EAL ones) */
//解析l2fwd程序参数
	ret = l2fwd_parse_args(argc, argv);
	if (ret < 0)
		rte_exit(EXIT_FAILURE, "Invalid L2FWD arguments\n");

	printf("MAC updating %s\n", mac_updating ? "enabled" : "disabled");

	/* convert to number of cycles */
//-t参数，打印时间间隔
	timer_period *= rte_get_timer_hz();

	/* create the mbuf pool */
//DPDK运行时创建的大页内存中，创建报文内存池，其中socket不是套接字，是numa框架中的socket，每个socket都有数个node，每个node右包括数个core。每个socket都有自己的内存，每个socket里的处理器访问自己内存的速度最快，访问其他socket的内存则较慢。

	l2fwd_pktmbuf_pool = rte_pktmbuf_pool_create("mbuf_pool", NB_MBUF,
		MEMPOOL_CACHE_SIZE, 0, RTE_MBUF_DEFAULT_BUF_SIZE,
		rte_socket_id());
	if (l2fwd_pktmbuf_pool == NULL)
		rte_exit(EXIT_FAILURE, "Cannot init mbuf pool\n");

	nb_ports = rte_eth_dev_count();
	if (nb_ports == 0)
		rte_exit(EXIT_FAILURE, "No Ethernet ports - bye\n");

	/* reset l2fwd_dst_ports */
//设置二层转发目的端口
	for (portid = 0; portid < RTE_MAX_ETHPORTS; portid++)
//初始化所有的目的端口为0
		l2fwd_dst_ports[portid] = 0;
	last_port = 0;

	/*
	 * Each logical core is assigned a dedicated TX queue on each port.
	 */
	for (portid = 0; portid < nb_ports; portid++) {
		/* skip ports that are not enabled */
//l2fwd_enabled_port_mask 可用端口位掩码 
//跳过未分配或是不可用端口。可用端口位掩码表示，左数第n位如果为1，表示端口n可用，如果左数第n位如果为0，表示端口n不可用。要得到第x位为1还是0，我们的方法是将1左移x位，得到一个只在x位为1，其他位都为0的数，再与位掩码相与。结果为1，那么第x位为1，结果位0，那么第x位为0.
		if ((l2fwd_enabled_port_mask & (1 << portid)) == 0)
			continue;
//此处，当输入端口数,即nb_ports为1时，dst_port[0] = 0;
//此处，当输入端口数,即nb_ports为2时,dst_port[0] = 0,dst_port[2] = 1,dst_port[1] = 2;
//此处，当输入端口数,即nb_ports为3时,dst_port[0] = 0,dst_port[2] = 1,dst_port[1] = 2;
//此处，当输入端口数,即nb_ports为4时,....dst_port[4] = 3,dst_port[3] = 4;

		if (nb_ports_in_mask % 2) {
			l2fwd_dst_ports[portid] = last_port;
			l2fwd_dst_ports[last_port] = portid;
		}
		else
			last_port = portid;

		nb_ports_in_mask++;

		rte_eth_dev_info_get(portid, &dev_info);
	}
	if (nb_ports_in_mask % 2) {
		printf("Notice: odd number of ports in portmask.\n");
		l2fwd_dst_ports[last_port] = last_port;
	}

	rx_lcore_id = 0;
	qconf = NULL;

	/* Initialize the port/queue configuration of each logical core */
//参数q，判断每个逻辑核绑定的端口有没有超出限制（输入的参数q），没超过就继续绑定
	for (portid = 0; portid < nb_ports; portid++) {
		/* skip ports that are not enabled */
		if ((l2fwd_enabled_port_mask & (1 << portid)) == 0)
			continue;

		/* get the lcore_id for this port */
//l2fwd_rx_queue_per_lcore即参数-q
		while (rte_lcore_is_enabled(rx_lcore_id) == 0 ||
		       lcore_queue_conf[rx_lcore_id].n_rx_port ==
		       l2fwd_rx_queue_per_lcore) {
			rx_lcore_id++;
			if (rx_lcore_id >= RTE_MAX_LCORE)
				rte_exit(EXIT_FAILURE, "Not enough cores\n");
		}

		if (qconf != &lcore_queue_conf[rx_lcore_id])
			/* Assigned a new logical core in the loop above. */
			qconf = &lcore_queue_conf[rx_lcore_id];

		qconf->rx_port_list[qconf->n_rx_port] = portid;
		qconf->n_rx_port++;
		printf("Lcore %u: RX port %u\n", rx_lcore_id, (unsigned) portid);
	}

	nb_ports_available = nb_ports;

	/* Initialise each port */
//初始化每个端口
	for (portid = 0; portid < nb_ports; portid++) {
		/* skip ports that are not enabled */
		if ((l2fwd_enabled_port_mask & (1 << portid)) == 0) {
			printf("Skipping disabled port %u\n", (unsigned) portid);
			nb_ports_available--;
			continue;
		}
		/* init port */
		printf("Initializing port %u... ", (unsigned) portid);
//清除读写缓冲区
		fflush(stdout);
///配置端口，将一些配置写进设备dev的一些字段，以及检查设备支持什么类型的中断、支持的包大小
		ret = rte_eth_dev_configure(portid, 1, 1, &port_conf);
		if (ret < 0)
			rte_exit(EXIT_FAILURE, "Cannot configure device: err=%d, port=%u\n",
				  ret, (unsigned) portid);

		ret = rte_eth_dev_adjust_nb_rx_tx_desc(portid, &nb_rxd,
						       &nb_txd);
		if (ret < 0)
			rte_exit(EXIT_FAILURE,
				 "Cannot adjust number of descriptors: err=%d, port=%u\n",
				 ret, (unsigned) portid);

//获取设备的MAC地址，存入l2fwd_ports_eth_addr[]数组，后续打印MAC地址
		rte_eth_macaddr_get(portid,&l2fwd_ports_eth_addr[portid]);

		/* init one RX queue */
//清除读写缓冲区
		fflush(stdout);
//设置接收队列，nb_rxd指收取队列的大小，最大能够存储mbuf的数量
		ret = rte_eth_rx_queue_setup(portid, 0, nb_rxd,
					     rte_eth_dev_socket_id(portid),
					     NULL,
					     l2fwd_pktmbuf_pool);
		if (ret < 0)
			rte_exit(EXIT_FAILURE, "rte_eth_rx_queue_setup:err=%d, port=%u\n",
				  ret, (unsigned) portid);

		/* init one TX queue on each port */
		fflush(stdout);
//初始化一个发送队列，nb_txd指发送队列的大小，最大能够存储mbuf的数量
		ret = rte_eth_tx_queue_setup(portid, 0, nb_txd,
				rte_eth_dev_socket_id(portid),
				NULL);
		if (ret < 0)
			rte_exit(EXIT_FAILURE, "rte_eth_tx_queue_setup:err=%d, port=%u\n",
				ret, (unsigned) portid);

		/* Initialize TX buffers */
//为每个端口分配接收缓冲区，根据numa架构的socket就近分配
		tx_buffer[portid] = rte_zmalloc_socket("tx_buffer",
				RTE_ETH_TX_BUFFER_SIZE(MAX_PKT_BURST), 0,
				rte_eth_dev_socket_id(portid));
		if (tx_buffer[portid] == NULL)
			rte_exit(EXIT_FAILURE, "Cannot allocate buffer for tx on port %u\n",
					(unsigned) portid);

//初始化发送缓冲区
		rte_eth_tx_buffer_init(tx_buffer[portid], MAX_PKT_BURST);

		ret = rte_eth_tx_buffer_set_err_callback(tx_buffer[portid],
				rte_eth_tx_buffer_count_callback,
				&port_statistics[portid].dropped);
		if (ret < 0)
				rte_exit(EXIT_FAILURE, "Cannot set error callback for "
						"tx buffer on port %u\n", (unsigned) portid);

		/* Start device */
//启动端口
		ret = rte_eth_dev_start(portid);
		if (ret < 0)
			rte_exit(EXIT_FAILURE, "rte_eth_dev_start:err=%d, port=%u\n",
				  ret, (unsigned) portid);

		printf("done: \n");

		rte_eth_promiscuous_enable(portid);

		printf("Port %u, MAC address: %02X:%02X:%02X:%02X:%02X:%02X\n\n",
				(unsigned) portid,
				l2fwd_ports_eth_addr[portid].addr_bytes[0],
				l2fwd_ports_eth_addr[portid].addr_bytes[1],
				l2fwd_ports_eth_addr[portid].addr_bytes[2],
				l2fwd_ports_eth_addr[portid].addr_bytes[3],
				l2fwd_ports_eth_addr[portid].addr_bytes[4],
				l2fwd_ports_eth_addr[portid].addr_bytes[5]);

		/* initialize port stats */
//初始化端口数据，就是后面要打印的，接收、发送、drop的包数
		memset(&port_statistics, 0, sizeof(port_statistics));
	}

	if (!nb_ports_available) {
		rte_exit(EXIT_FAILURE,
			"All available ports are disabled. Please set portmask.\n");
	}
//检查每个端口的连接状态
	check_all_ports_link_status(nb_ports, l2fwd_enabled_port_mask);

	ret = 0;
	/* launch per-lcore init on every lcore */
//在每个逻辑内核上启动线程，开始转发，l2fwd_launch_one_lcore实际上运行的是l2fwd_main_loop
	rte_eal_mp_remote_launch(l2fwd_launch_one_lcore, NULL, CALL_MASTER);
	RTE_LCORE_FOREACH_SLAVE(lcore_id) {
		if (rte_eal_wait_lcore(lcore_id) < 0) {
			ret = -1;
			break;
		}
	}

	for (portid = 0; portid < nb_ports; portid++) {
		if ((l2fwd_enabled_port_mask & (1 << portid)) == 0)
			continue;
		printf("Closing port %d...", portid);
		rte_eth_dev_stop(portid);
		rte_eth_dev_close(portid);
		printf(" Done\n");
	}
	printf("Bye...\n");

	return ret;
}