[笔记] libpcap编译及使用

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前言

官网

libpcap库安装

环境：
centos 7.9

安装编译

libpcap 下载

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

./configure 时 报错：Neither flex nor lex was found

yum install flex lex

libpcap库使用

https://www.tcpdump.org/pcap.html

此处实现的是抓tcp syn包

#include 
#include 
#include 
#include 
#include 

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;
}

注意：
使用vscode，c++ debug时 链接pcap库 g++执行加“-lpcap“
并且 加 “-std=gnu++0x” 避免c++11特性不支持报错

总结

以上就是今天要讲的内容，本文仅仅简单介绍了libpcap安装和使用。

参考：
libpcap库使用
libpcap简单使用

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