以下是一个简单的DPDK应用程序示例，演示如何使用nDPI库识别HTTP协议并对其进行处理。在本例中，我们假设已经配置了DPDK环境，并且已经安装了nDPI库和相关依赖项。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>

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

#include "ndpi_api.h"

#define RX_RING_SIZE 128
#define TX_RING_SIZE 512

#define NUM_MBUFS 8192
#define MBUF_CACHE_SIZE 256

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

static volatile bool quit_signal = false;

// nDPI context and detection module handle
static ndpi_detection_module_struct_t *ndpi_mod;
static ndpi_workflow_t *workflow;

// callback function for nDPI packet processing
void ndpi_packet_processing(struct rte_mbuf *pkt, ndpi_workflow_t *wf) {
    // create a flow from the packet and process it with nDPI
    ndpi_flow_info_t flow_info;
    memset(&flow_info, 0, sizeof(ndpi_flow_info_t));
    flow_info.ip_version = (pkt->packet_type & RTE_PTYPE_L3_MASK) == RTE_PTYPE_L3_IPV4 ? 4 : 6;
    if (flow_info.ip_version == 4) {
        rte_memcpy(flow_info.l3.tcp_ip_hdr.ipv4.saddr, &(pkt->ipv4_hdr.src_addr), sizeof(uint32_t));
        rte_memcpy(flow_info.l3.tcp_ip_hdr.ipv4.daddr, &(pkt->ipv4_hdr.dst_addr), sizeof(uint32_t));
    } else {
        rte_memcpy(flow_info.l3.tcp_ip_hdr.ipv6.src, &(pkt->ipv6_hdr.src_addr), sizeof(struct in6_addr));
        rte_memcpy(flow_info.l3.tcp_ip_hdr.ipv6.dst, &(pkt->ipv6_hdr.dst_addr), sizeof(struct in6_addr));
    }
    flow_info.protocol = (pkt->packet_type & RTE_PTYPE_L4_MASK) == RTE_PTYPE_L4_TCP ? IPPROTO_TCP : IPPROTO_UDP;
    flow_info.src_port = pkt->l4.tcp.hdr.src_port;
    flow_info.dst_port = pkt->l4.tcp.hdr.dst_port;
    ndpi_workflow_process_packet(wf, pkt->data_len, rte_pktmbuf_mtod(pkt, char *), &flow_info);
}

// signal handler for CTRL+C
void signal_handler(int signum) {
    if (signum == SIGINT || signum == SIGTERM) {
        printf("\nReceived signal %d. Exiting...\n", signum);
        quit_signal = true;
    }
}

int main(int argc, char **argv) {
    // initialize DPDK EAL
    int ret = rte_eal_init(argc, argv);
    if (ret < 0)
        rte_exit(EXIT_FAILURE, "Cannot initialize EAL\n");

    argc -= ret;
    argv += ret;

    // check number of available ports
    uint16_t nb_ports = rte_eth_dev_count_avail();
    if (nb_ports < 1)
        rte_exit(EXIT_FAILURE, "No Ethernet ports found!\n");

    // set signal handlers
     signal(SIGINT, signal_handler);
     signal(SIGTERM, signal_handler);

     // initialize nDPI context and detection module
     ndpi_mod = ndpi_init_detection_module();
     workflow = ndpi_workflow_init(ndpi_mod);

     // configure DPDK port(s)
     uint16_t portid;
     RTE_ETH_FOREACH_DEV(portid) {
         struct rte_eth_conf port_conf = port_conf_default;
         ret = rte_eth_dev_configure(portid, 1, 1, &port_conf);
         if (ret < 0)
             rte_exit(EXIT_FAILURE, "Cannot configure ethdev %u\n", portid);

         // set up RX and TX queues
         ret = rte_eth_rx_queue_setup(portid, 0, RX_RING_SIZE,
                                       rte_eth_dev_socket_id(portid), NULL,
                                       rte_pktmbuf_pool_create("RX_POOL", NUM_MBUFS * nb_ports,
                                                               MBUF_CACHE_SIZE, 0, RTE_MBUF_DEFAULT_BUF_SIZE,
                                                               rte_socket_id()));
         if (ret < 0)
             rte_exit(EXIT_FAILURE, "Cannot setup RX queue for ethdev %u\n", portid);
         
         ret = rte_eth_tx_queue_setup(portid, 0, TX_RING_SIZE,
                                       rte_eth_dev_socket_id(portid), NULL);
         if (ret < 0)
             rte_exit(EXIT_FAILURE, "Cannot setup TX queue for ethdev %u\n", portid);

         // start the Ethernet device
        ret = rte_eth_dev_start(portid);
        if (ret < 0)
            rte_exit(EXIT_FAILURE, "Cannot start ethdev %u\n", portid);

        // enable promiscuous mode on the Ethernet device
        rte_eth_promiscuous_enable(portid);
    }

    printf("DPDK and nDPI initialization completed.\n");

    while (!quit_signal) {
        RTE_ETH_FOREACH_DEV(portid) {
            struct rte_mbuf *pkt_burst[32];
            const uint16_t nb_rx = rte_eth_rx_burst(portid, 0, pkt_burst, 32);
            if (nb_rx == 0)
                continue;

            // process received packets with nDPI
            for (int i = 0; i < nb_rx; i++) {
                ndpi_packet_processing(pkt_burst[i], workflow);
            }

            // transmit the packets to their destination
            const uint16_t nb_tx = rte_eth_tx_burst(portid, 0, pkt_burst, nb_rx);
            for (int i = nb_tx; i < nb_rx; i++) {
                rte_pktmbuf_free(pkt_burst[i]);
            }
        }
    }

    printf("Exiting...\n");

    // cleanup nDPI resources
    ndpi_workflow_destroy(workflow);
    ndpi_exit_detection_module(ndpi_mod);

    return 0;
}

这个例子主要实现了DPDK应用程序的基本结构和流量处理逻辑。在每次接收到数据包时，使用ndpi_packet_processing方法将其交给nDPI库进行协议识别，并根据需要对HTTP流量进行进一步处理。可以根据具体需求修改代码来实现更复杂的功能。