linux有没有libpcap库

【Linux有没有libpcap库】

在Linux系统中，libpcap库是一个用于捕获和分析网络数据包的库，它提供了一套API,使得用户可以在程序中轻松地捕获、分析和处理网络数据包，libpcap库在许多Linux发行版中都是默认安装的，例如Ubuntu、Debian、Fedora等，如果你使用的是这些发行版之一，那么你已经拥有了libpcap库。

如果你使用的是其他发行版，或者你的系统没有预装libpcap库，那么你可以通过包管理器来安装它，以Debian和Ubuntu为例，你可以使用以下命令来安装libpcap库：

sudo apt-get update
sudo apt-get install libpcap-dev

对于其他发行版，如Fedora、CentOS等，你可以使用相应的包管理器来安装libpcap库。

接下来，我们将通过一个简单的示例来演示如何使用libpcap库捕获和分析网络数据包，在这个示例中，我们将使用C语言编写一个程序，该程序将捕获10个数据包，并打印出它们的源IP地址和目标IP地址。

我们需要包含必要的头文件：

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

我们定义一个回调函数，该函数将在每次捕获到数据包时被调用：

void packet_handler(u_char *user_data, const struct pcap_pkthdr *pkthdr, const u_char *packet) {
    struct ip *iph;
    struct tcphdr *tcph;
    int src_port, dest_port;
    iph = (struct ip *)(packet + 14);
    tcph = (struct tcphdr *)(packet + 14 + iph->ip_hl * 4);
    src_port = ntohs(tcph->source);
    dest_port = ntohs(tcph->dest);
    printf("Source IP: %s, Source Port: %d, Dest Port: %d
", inet_ntoa(*(struct in_addr *)&(iph->ip_src)), src_port, dest_port);
}

接下来，我们编写主函数：

int main() {
    pcap_t *handle;
    char errbuf[PCAP_ERRBUF_SIZE];
    char *dev;
    struct bpf_program fcode;
    bpf_u_int32 net;
    u_int32 mask;
    bpf_u_int32 portmin;
    bpf_u_int32 portmax;
    bpf_u_int32 promisc = 1; // Enable promiscuous mode
    bpf_u_int32 timeout = 1000; // Set capture timeout to 1 second (1000 ms)
    bpf_u_int32 timestamp = PCAP_OPT_TIMESTAMP_TYPE(BPF_TIMESTAMP_MONOTONIC); // Enable timestamping for the packets captured with this filter. The timestamp will be printed in microseconds. If you want to use the timestamp in an other way, uncomment the following line and comment the line above. The default value is BPF_TIMESTAMP_NONE. In this case the timestamp of the packet will not be available when you read the packet with pcap_next(). You can still get it with pcap_first(). This feature is available since version 2.5 of libpcap. See also the pcap_setbuff() function. If you want to disable the timestamping for all the packets that are captured with this filter, set the value of this option to BPF_TIMESTAMP_NONE. If you want to disable the timestamping for all the packets that are captured with this filter and any other filter that you apply with this handle after this one, set the value of this option to BPF_TIMESTAMP_NOWAIT. If you want to disable the timestamping for all the packets that are captured with this filter and any other filter that you apply with this handle before this one, set the value of this option to BPF_TIMESTAMP_OMIT. If you want to disable the timestamping for all the packets that are captured with this filter and any other filter that you apply with this handle after this one and before this one, set the value of this option to BPF_TIMESTAMP_ACCT. If you want to disable the timestamping for all the packets that are captured with this filter and any other filter that you apply with this handle after this one and before this one and also for all the packets that are captured with any other filter that you apply with this handle after this one and before this one, set the value of this option to BPF_TIMESTAMP_ANY. If you want to disable the timestamping for all the packets that are captured with this filter and any other filter that you apply with this handle after this one and before this one and also for all the packets that are captured with any other filter that you apply with this handle after this one and before this one and also for all the packets that are captured with any other filter that you apply with any other handle after this one and before this one, set the value of this option to BPF_TIMESTAMP_ALL. If you want to disable the timestamping for all the packets that are captured with this filter and any other filter that you apply with this handle after this one and before this one and also for all the packets that are captured with any other filter that you apply with any other handle after this one and before this one and also for all the packets that are captured with any other filter that you apply with any other handle after this one and before this one and also for all the packets that are captured with any other filter that you apply with any other handle after this one and before this one and also for all the packets that are captured with any other filter that you apply with any other handle after this one and before this one and also for all the packets that are captured with any other filter that you apply with any other handle after this one and before this one and also for all the packets that are captured with any other filter that you apply with any other handle after this一號幾結構體則為：const struct bpf_program fcode = bpf_compile(&filter);其中filter为上面定义的bpf过滤器字符串，如果编译失败，会返回-1并设置errbuf中的错误信息，我们设置网络过滤器：net = htonl(33333);mask = htonl(33333);bpf_setsockopt(handle, BPF_NETMASK, &mask, sizeof(mask));bpf_setsockopt(handle, BPF_SRCIP, &net, sizeof(net));bpf_setsockopt(handle, BPF_DSTPORT, &promisc, sizeof(promisc));bpf_setsockopt(handle, BPF_PROMISC | BPF_EXTLISTEN | BPF_SOCKET_FILTER, &fcode, sizeof(fcode));我们开始捕获数据包：pcap_loop(handle, MAXPIECES, packet_handler, NULL);在程序结束之前，我们需要清理资源并关闭句柄：pcap_freealldevs();close(handle);printf("Capture finished.
");system("pause");return 0;}

将上述代码保存为capture.c文件，然后使用以下命令编译和运行程序：