libpcap读取本地pcap文件

假如本地已经通过抓包工具保存了pcap格式的数据包文件,通过libpcap的库也能简单地进行离线分析

pcap_t *
pcap_open_offline(const char *fname, char *errbuf)

函数打开保存的数据包文件,用于读取,返回文件描述符

fname参数指定了pcap文件名

errbuf依旧是函数出错的时候返回错误信息

这样直接分析离线数据包文件,然后通过pcap_next读取一个又一个包,最后close掉释放,可以简单如下来写

[lihui@master work]$ cat offline.c
#include <stdio.h>
#include <stdlib.h>
#include <pcap.h>

int main(){
    char ebuf[PCAP_ERRBUF_SIZE];
    char *pcap_file = “one.pcap”;
    pcap_t *p = pcap_open_offline(pcap_file, ebuf);
    struct pcap_pkthdr pkthdr;
    while (1){
        const u_char *pktStr = pcap_next(p, &pkthdr);
        if (!pktStr){
            printf(“Pcap file parse over !\n”);
            exit(1);
        }
        printf(“Length: %d\n”, pkthdr.len);
    }
    pcap_close(p);
    return 0;
}

[lihui@master work]$ gcc offline.c -lpcap
[lihui@master work]$ ./a.out
Length: 74
Length: 74
Length: 66
Length: 474
Length: 66
Length: 1480
Length: 66
Length: 1359
Length: 66
Length: 487
Length: 773
Length: 432
Length: 1480
Length: 859
Length: 66
Length: 66
Length: 66
Length: 66
Length: 66
Pcap file parse over !

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