如何在C++里使用ICMP进行网络诊断

在C++中，使用ICMP（Internet Control Message Protocol）进行网络诊断通常涉及到创建原始套接字并发送和接收ICMP数据包

#include<iostream>
#include <cstring>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/ip_icmp.h>
#include <sys/socket.h>
#include <netdb.h>

const int ICMP_DATA_LEN = 56;
const int TIMEOUT = 2; // 设置超时时间（单位：秒）

// ICMP数据包结构
struct ICMPPacket {
    struct icmphdr header;
    char data[ICMP_DATA_LEN];
};

int main(int argc, char *argv[]) {
    if (argc != 2) {
        std::cerr << "Usage: "<< argv[0] << " hostname"<< std::endl;
        return 1;
    }

    // 获取目标主机的IP地址
    struct hostent *host = gethostbyname(argv[1]);
    if (!host) {
        std::cerr << "Error: Cannot resolve hostname"<< std::endl;
        return 1;
    }

    // 创建原始套接字
    int sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
    if (sockfd == -1) {
        std::cerr << "Error: Cannot create raw socket"<< std::endl;
        return 1;
    }

    // 设置接收超时
    struct timeval timeout;
    timeout.tv_sec = TIMEOUT;
    timeout.tv_usec = 0;
    setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(timeout));

    // 构造ICMP请求数据包
    struct ICMPPacket packet;
    memset(&packet, 0, sizeof(packet));
    packet.header.type = ICMP_ECHO;
    packet.header.code = 0;
    packet.header.checksum = 0;
    packet.header.un.echo.id = htons(getpid());
    packet.header.un.echo.sequence = htons(1);

    // 计算校验和
    unsigned short checksum = 0;
    unsigned short *buf = reinterpret_cast<unsigned short *>(&packet);
    for (int i = 0; i< sizeof(packet) / 2; ++i) {
        checksum += buf[i];
    }
    while (checksum >> 16) {
        checksum = (checksum & 0xffff) + (checksum >> 16);
    }
    packet.header.checksum = ~checksum;

    // 发送ICMP请求数据包
    struct sockaddr_in target;
    memset(&target, 0, sizeof(target));
    target.sin_family = AF_INET;
    target.sin_addr = *reinterpret_cast<struct in_addr *>(host->h_addr_list[0]);
    sendto(sockfd, &packet, sizeof(packet), 0, reinterpret_cast<struct sockaddr *>(&target), sizeof(target));

    // 接收ICMP响应数据包
    struct sockaddr_in source;
    socklen_t source_len = sizeof(source);
    ssize_t recv_len = recvfrom(sockfd, &packet, sizeof(packet), 0, reinterpret_cast<struct sockaddr *>(&source), &source_len);
    if (recv_len == -1) {
        std::cerr << "Error: Request timed out"<< std::endl;
        close(sockfd);
        return 1;
    }

    // 检查ICMP响应数据包的类型和代码
    if (packet.header.type == ICMP_ECHOREPLY && packet.header.code == 0) {
        std::cout << "Ping successful"<< std::endl;
    } else {
        std::cerr << "Error: Invalid response"<< std::endl;
    }

    close(sockfd);
    return 0;
}

这个示例程序实现了一个简单的ping命令。它首先解析目标主机名，然后创建一个原始套接字，设置接收超时，构造ICMP请求数据包，计算校验和，发送数据包，接收ICMP响应数据包，并检查响应数据包的类型和代码。如果一切正常，程序将输出“Ping successful”。

请注意，运行此程序可能需要root权限，因为创建原始套接字通常需要特权。在Linux系统上，可以使用sudo命令运行程序。