下面是一个简单的DPDK程序示例，用于填充UDP包头：

#include <stdio.h>
#include <string.h>
#include <stdint.h>

#include <rte_eal.h>
#include <rte_ethdev.h>
#include <rte_mbuf.h>

#define RX_RING_SIZE 1024
#define TX_RING_SIZE 1024

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

static const struct rte_eth_conf port_conf_default = {
    .rxmode = { .max_rx_pkt_len = ETHER_MAX_LEN }
};

int main(int argc, char **argv) {
    int ret;
    uint16_t nb_ports;
    uint16_t portid;
    
    // 初始化 DPDK 环境
    ret = rte_eal_init(argc, argv);
    if (ret < 0)
        rte_exit(EXIT_FAILURE, "Error with EAL initialization\n");
    
    nb_ports = rte_eth_dev_count_avail();
    
    // 配置每个网卡端口
    for (portid = 0; portid < nb_ports; portid++) {
        struct rte_eth_dev_info dev_info;
        struct rte_eth_txconf txconf;
        uint16_t q;
        
        memset(&dev_info, 0, sizeof(dev_info));
        rte_eth_dev_info_get(portid, &dev_info);
        
        if (dev_info.tx_offload_capa & DEV_TX_OFFLOAD_UDP_CKSUM) {
            printf("Port %u supports UDP checksum offload\n", portid);
        } else {
            printf("Port %u does not support UDP checksum offload\n", portid);
        }
        
        txconf = dev_info.default_txconf;
        txconf.offloads |= DEV_TX_OFFLOAD_UDP_CKSUM;
        
        // 配置网卡队列
        for (q = 0; q < dev_info.nb_tx_queues; q++) {
            ret = rte_eth_tx_queue_setup(portid, q, TX_RING_SIZE,
                                          rte_eth_dev_socket_id(portid),
                                          &txconf);
            if (ret < 0)
                rte_exit(EXIT_FAILURE, "Error configuring TX queue %u "
                         "for port %u\n", q, portid);
        }
        
        // 启动网卡端口
        ret = rte_eth_dev_start(portid);
        if (ret < 0)
            rte_exit(EXIT_FAILURE, "Error starting port %u\n", portid);

        // 开启混杂模式
        rte_eth_promiscuous_enable(portid);
    }

    struct rte_mempool *mbuf_pool;
    
    mbuf_pool = rte_pktmbuf_pool_create("MBUF_POOL", NUM_MBUFS,
                                        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");
    
    struct rte_mbuf *packet[BURST_SIZE];
    uint16_t nb_rx;
    
    while(1) {
        // 接收数据包
        for (portid = 0; portid < nb_ports; portid++) {
            nb_rx = rte_eth_rx_burst(portid, 0, packet, BURST_SIZE);
            for (int i = 0; i < nb_rx; i++) {
                struct ether_hdr *eth_hdr;
                struct ipv4_hdr *ip_hdr;
                struct udp_hdr *udp_hdr;
                
                eth_hdr = rte_pktmbuf_mtod(packet[i], struct ether_hdr *);
                ip_hdr = (struct ipv4_hdr *)((char *)eth_hdr + sizeof(struct ether_hdr));
                udp_hdr = (struct udp_hdr *)((char *)ip_hdr + sizeof(struct ipv4_hdr));
                
                // 填充UDP头
                udp_hdr->dgram_cksum = 0;
                udp_hdr->dgram_cksum = rte_ipv4_udptcp_cksum(ip_hdr, udp_hdr);
                
                // 发送数据包
                uint16_t nb_tx = rte_eth_tx_burst(portid, 0, packet, nb_rx);
            }
        }
    }
    
    return 0;
}

上述示例程序中，我们首先初始化DPDK环境，然后配置每个网卡端口的发送队列以支持UDP校验和计算。接着，我们创建一个rte_mempool对象用于存储数据包缓冲区，并通过调用rte_pktmbuf_pool_create函数来实现该对象。在主循环中，我们使用rte_eth_rx_burst函数接收网络数据包，并提取出其中的UDP头部信息。然后，我们使用rte_ipv4_udptcp_cksum函数填充UDP头部，并调用rte_eth_tx_burst函数将数据包发送到相应的网卡端口。