dpdk接收到udp报文后，自己构造一个udp报文，将收到的报文中的源mac，目的mac，源ip，目的ip，源端口和目的端口交换下顺序填充到新的udp报文中，报文中的负载数据和收到的udp保持一致。

注：需要在udp发送端设置静态arp信息（dpdk绑定网卡的ip和mac地址映射），目前该程序还未对arp报文做处理

udp报文格式：

#include <rte_eal.h>
#include <rte_ethdev.h>
#include <rte_mbuf.h>
#include <stdio.h>
#include <arpa/inet.h>#define NUM_MBUFS (4096-1) // 内存池中 mbuf 的数量
#define BURST_SIZE 32static uint32_t gSrcIp, gDstIp;
static uint8_t gSrcMac[RTE_ETHER_ADDR_LEN], gDstMac[RTE_ETHER_ADDR_LEN];
static uint16_t gSrcPort, gDstPort;int gDpdkPortId = 0;static const struct rte_eth_conf port_conf_default = {.rxmode = {.max_rx_pkt_len = RTE_ETHER_MAX_LEN}
};static void ng_init_port(struct rte_mempool *mbuf_pool) {//dpdk绑定的网卡数量uint16_t nb_sys_ports = rte_eth_dev_count_avail();if (nb_sys_ports == 0) {rte_exit(EXIT_FAILURE, "not support eth\n");}struct rte_eth_dev_info dev_info;/*获取以太网设备的配置和状态信息。它通常用于初始化网络设备、*配置网络设备或者获取网络设备的状态信息。*这里的端口号和网卡是一一对应的*/rte_eth_dev_info_get(gDpdkPortId, &dev_info);const int num_rx_queues = 1;	//接收队列个数const int num_tx_queues = 1;	//发送队列个数struct rte_eth_conf port_conf = port_conf_default;rte_eth_dev_configure(gDpdkPortId, num_rx_queues, num_tx_queues, &port_conf);// 0是0号接收队列// 128是队列长度if (rte_eth_rx_queue_setup(gDpdkPortId, 0, 128, rte_eth_dev_socket_id(gDpdkPortId), NULL, mbuf_pool) < 0) {rte_exit(EXIT_FAILURE, "Could not setup RX queue\n");}struct rte_eth_txconf txq_conf = dev_info.default_txconf;//offloads 成员是一个 64 位无符号整数，每个比特位表示不同的接收功能选项txq_conf.offloads = port_conf.rxmode.offloads;/* 0是0号发送队列 * 1024是队列长度* 发送队列长度设置太小运行时会报错:Invalid value for nb_tx_desc(=128), should be: <= 4096, >= 512, and a product of 1*/if (rte_eth_tx_queue_setup(gDpdkPortId, 0, 1024, rte_eth_dev_socket_id(gDpdkPortId), &txq_conf) < 0) {rte_exit(EXIT_FAILURE, "Could not setup TX queue\n");}if (rte_eth_dev_start(gDpdkPortId) < 0) {rte_exit(EXIT_FAILURE, "Could not start\n");}}static void ng_encode_udp_pkt(uint8_t *msg, unsigned char *data, uint16_t total_len) {//设置以太网头struct rte_ether_hdr *eth = (struct rte_ether_hdr *)msg;rte_memcpy(eth->s_addr.addr_bytes, gSrcMac, RTE_ETHER_ADDR_LEN);rte_memcpy(eth->d_addr.addr_bytes, gDstMac, RTE_ETHER_ADDR_LEN);eth->ether_type = htons(RTE_ETHER_TYPE_IPV4);//设置ipv4头struct rte_ipv4_hdr *ip = (struct rte_ipv4_hdr *)(eth + 1);ip->version_ihl = 0x45;ip->type_of_service = 0;ip->total_length = htons(total_len - sizeof(struct rte_ether_hdr));ip->packet_id = 0;ip->fragment_offset = 0;ip->time_to_live = 64;//dpdk中没有UDP类型的定义，使用内核的协议类型ip->next_proto_id = IPPROTO_UDP;ip->src_addr = gSrcIp;ip->dst_addr = gDstIp;//计算ip头部校验和时，先把该字段置为0(ip校验和只包括头部)ip->hdr_checksum = 0;ip->hdr_checksum = rte_ipv4_cksum(ip);//设置udp头struct rte_udp_hdr *udp = (struct rte_udp_hdr *)(ip + 1);udp->src_port = gSrcPort;udp->dst_port = gDstPort;uint16_t udp_len = total_len - sizeof(struct rte_ether_hdr) - sizeof(struct rte_ipv4_hdr);udp->dgram_len = htons(udp_len);memcpy((uint8_t *)(udp + 1), data, udp_len - sizeof(struct rte_udp_hdr));//计算udp校验和，udp校验位包括负载数据udp->dgram_cksum = 0;udp->dgram_cksum = rte_ipv4_udptcp_cksum(ip, udp);
}static struct rte_mbuf *ng_send(struct rte_mempool *mbuf_pool, unsigned char *data, uint16_t length) {const unsigned total_len = sizeof(struct rte_ether_hdr) + sizeof(struct rte_ipv4_hdr) + length;//从内存中申请一个mbufstruct rte_mbuf *mbuf = rte_pktmbuf_alloc(mbuf_pool);if (mbuf == NULL) {rte_exit(EXIT_FAILURE, "rte_pktmbuf_alloc\n");}mbuf->pkt_len = total_len;mbuf->data_len = total_len;//用于将数据包缓冲区（packet buffer）转换为指定类型的数据指针，也就是mbuf存储数据包的首地址uint8_t *pktdata = rte_pktmbuf_mtod(mbuf, uint8_t*);ng_encode_udp_pkt(pktdata, data, total_len);return mbuf;
}int main(int argc, char *argv[]) {/*dpdk初始化资源*用于初始化 Environment Abstraction Layer (EAL)。EAL 是 DPDK 的一个核心组件，*负责抽象和管理硬件和操作系统依赖性，使得上层应用可以在不同的硬件和操作系统上*以统一的方式运行。*/if (rte_eal_init(argc, argv) < 0) {rte_exit(EXIT_FAILURE, "Error with EAL initialization\n");}//内存池，接收的数据存在该内存池中struct rte_mempool *mbuf_pool = rte_pktmbuf_pool_create("mbuf_pool", NUM_MBUFS,0, 0, RTE_MBUF_DEFAULT_BUF_SIZE, rte_socket_id());if (mbuf_pool == NULL) {rte_exit(EXIT_FAILURE, "Could not create mbuf pool\n");}ng_init_port(mbuf_pool);//获取dpdk绑定的网卡源macrte_eth_macaddr_get(gDpdkPortId, (struct rte_ether_addr *)gSrcMac);while(1) {struct rte_mbuf *mbufs[BURST_SIZE] = {0};unsigned num_recvd = rte_eth_rx_burst(gDpdkPortId, 0, mbufs, BURST_SIZE);if (num_recvd > BURST_SIZE) {rte_exit(EXIT_FAILURE, "Error receive from eth\n");}unsigned int i = 0;for (i = 0; i < num_recvd; i++) {struct rte_ether_hdr *ehdr = rte_pktmbuf_mtod(mbufs[i], struct rte_ether_hdr*);if (ehdr->ether_type != rte_cpu_to_be_16(RTE_ETHER_TYPE_IPV4)) {rte_pktmbuf_free(mbufs[i]);continue;}struct rte_ipv4_hdr *iphdr = rte_pktmbuf_mtod_offset(mbufs[i], struct rte_ipv4_hdr*, sizeof(struct rte_ether_hdr));if (iphdr->next_proto_id == IPPROTO_UDP) {struct rte_udp_hdr *udphdr = (struct rte_udp_hdr *)(iphdr + 1);//两个字节以上的变量是需要大小端转换uint16_t length = ntohs(udphdr->dgram_len);*((char*)udphdr + length) = '\0';struct in_addr addr;addr.s_addr = iphdr->src_addr;printf("src: %s:%d, ", inet_ntoa(addr), ntohs(udphdr->src_port));addr.s_addr = iphdr->dst_addr;printf("dst: %s:%d, %s\n", inet_ntoa(addr), ntohs(udphdr->dst_port), (char *)(udphdr+1));//构造发送数据包rte_memcpy(gDstMac, ehdr->s_addr.addr_bytes, RTE_ETHER_ADDR_LEN);gSrcIp = iphdr->dst_addr;gDstIp = iphdr->src_addr;gSrcPort = udphdr->dst_port;gDstPort = udphdr->src_port;struct rte_mbuf *txbuf = ng_send(mbuf_pool, (unsigned char *)(udphdr+1), length);//发送报文rte_eth_tx_burst(gDpdkPortId, 0, &txbuf, 1);rte_pktmbuf_free(txbuf);}rte_pktmbuf_free(mbufs[i]);}}return 0;
}