QNX系统上如何实现网络数据包抓取和分析

本文介绍了在QNX操作系统上如何使用libpcap库实现对网络数据包的抓取和分析。首先通过socket获取网络数据包，然后使用libpcap库对数据包进行解析和过滤，最后统计和输出相关信息。实现方式简单易懂，适合初学者学习。

#include <pcap.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <netinet/tcp.h>
#include <netinet/ip.h>
#include <arpa/inet.h>

#define MAXBYTES2CAPTURE 2048 

void process_packet(u_char *arg, const struct pcap_pkthdr* pkthdr, const u_char * packet);

int main()
{
    char errbuf[PCAP_ERRBUF_SIZE];
    pcap_t* descr;
    struct bpf_program fp;      
    bpf_u_int32 maskp;
    bpf_u_int32 netp;
    // 获取网络接口名
    char* device = pcap_lookupdev(errbuf);         
    if(device == NULL)
    {
        printf("%s\n",errbuf);
        exit(1);
    }

    printf("网络接口名：%s\n", device);
    // 获取网络掩码和IP地址
     if(pcap_lookupnet(device, &netp, &maskp, errbuf) == -1)
    {
        printf("%s\n",errbuf);
        exit(1);
    }
    char str[INET_ADDRSTRLEN];
    printf("掩码：%s\n", inet_ntop(AF_INET, &maskp, str, INET_ADDRSTRLEN));
    printf("本机IP地址：%s\n", inet_ntop(AF_INET, &netp, str, INET_ADDRSTRLEN));
    // 打开网络接口
    descr = pcap_open_live(device, MAXBYTES2CAPTURE, 1, 0, errbuf);
    if(descr == NULL)
    {
        printf("pcap_open_live() failed：%s\n", errbuf);
        exit(1);
    }
    // 编译过滤器
    if(pcap_compile(descr, &fp, "tcp", 0, netp) == -1)
    {
        printf("Error calling pcap_compile\n");
        exit(1);
    }
    // 设置过滤器
    if(pcap_setfilter(descr, &fp) == -1)
    {
        printf("Error setting the filter\n");
        exit(1);
    }

    printf("正在抓包...\n");
    pcap_loop(descr, -1, process_packet, NULL);
    pcap_close(descr);
    return 0;
}

void process_packet(u_char *arg, const struct pcap_pkthdr* pkthdr, const u_char * packet)
{
    struct ip *ip_header;
    struct tcphdr *tcp_header;
    const char *payload;

    printf("--------------------\n");
    printf("抓到一个数据包，长度为：%d\n", pkthdr->len);
    ip_header = (struct ip*)(packet + sizeof(struct ether_header));
    printf("源IP地址：%s\n", inet_ntoa(ip_header->ip_src));
    printf("目标IP地址：%s\n", inet_ntoa(ip_header->ip_dst));
    tcp_header = (struct tcphdr*)(packet + sizeof(struct ether_header) + sizeof(struct ip));
    printf("源端口号：%d\n", ntohs(tcp_header->th_sport));
    printf("目标端口号：%d\n", ntohs(tcp_header->th_dport));
    payload = (u_char *)(packet + sizeof(struct ether_header) + sizeof(struct ip) + sizeof(struct tcphdr));
    printf("Payload：%.*s\n", PKTHDR->len, payload);

}

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