[笔记] libpcap编译及使用

tar -zxvf libpcap-1.10.4
cd libpcap-1.10.4 
./configure
make && make install

#include <iostream>
#include <pcap.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <netinet/ether.h>
void packetHandler(unsigned char* userData, const struct pcap_pkthdr* pkthdr, const unsigned char* packetData) {
    struct ethhdr* ethHeader = (struct ethhdr*)packetData;
    if (ntohs(ethHeader->h_proto) == ETH_P_IP) {
        struct iphdr* ipHeader = (struct iphdr*)(packetData + sizeof(struct ethhdr));
        if (ipHeader->protocol == IPPROTO_TCP) {
            struct tcphdr* tcpHeader = (struct tcphdr*)(packetData + sizeof(struct ethhdr) + ipHeader->ihl * 4);
            if (tcpHeader->syn) {
                char source_ip[INET_ADDRSTRLEN];
                char dest_ip[INET_ADDRSTRLEN];
                inet_ntop(AF_INET, &ipHeader->saddr, source_ip, INET_ADDRSTRLEN);
                inet_ntop(AF_INET, &ipHeader->daddr, dest_ip, INET_ADDRSTRLEN);
                printf("Received TCP SYN packet from %s:%u to %s:%u\n",
                        source_ip, ntohs(tcpHeader->source),
                        dest_ip, ntohs(tcpHeader->dest));
            }
        }
    }
}
int main2(int argc, char *argv[])
{
  char *dev, errbuf[PCAP_ERRBUF_SIZE];
  dev = pcap_lookupdev(errbuf);
  if (dev == NULL) {
    fprintf(stderr, "Couldn't find default device: %s\n", errbuf);
    return(2);
  }
  printf("Device: %s\n", dev);
  return(0);
}
int main3() {
    char errbuf[PCAP_ERRBUF_SIZE];
    pcap_if_t* alldevs;
    pcap_if_t* device;
    // 获取系统上的所有网络设备
    if (pcap_findalldevs(&alldevs, errbuf) == -1) {
        std::cerr << "Error finding devices: " << errbuf << std::endl;
        return 1;
    }
    // 遍历并打印设备列表
    int deviceCount = 0;
    for (device = alldevs; device != nullptr; device = device->next) {
        deviceCount++;
        std::cout << "Device " << deviceCount << ": " << device->name << std::endl;
        if (device->description)
            std::cout << "    Description: " << device->description << std::endl;
        else
            std::cout << "    Description: N/A" << std::endl;
    }
    // 释放设备列表
    pcap_freealldevs(alldevs);
    return 0;
}
int main() {
    char errbuf[PCAP_ERRBUF_SIZE];
    pcap_t* handle;
    // 打开网络设备或捕获文件，这里使用默认网络设备 "eth0"，你需要根据实际情况修改
    handle = pcap_open_live("ens33", BUFSIZ, 1, 1000, errbuf);
    if (handle == nullptr) {
        std::cerr << "Error opening device: " << errbuf << std::endl;
        return 1;
    }
    // 开始捕获数据包，packetHandler 是回调函数，每捕获一个数据包都会调用它
    if (pcap_loop(handle, 0, packetHandler, nullptr) < 0) {
        std::cerr << "Error in pcap_loop" << std::endl;
        return 1;
    }
    // 关闭捕获会话
    pcap_close(handle);
    return 0;
}