Icpm ping包实现设置数据包大小的C++代码

下面是一个简单的使用 ICMP 协议发送 ping 包并设置数据包大小的 C++ 代码示例：

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <ctime>
#include <cerrno>
#include <chrono>
#include <thread>

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/select.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
#include <fcntl.h>

using namespace std;

const int PACKET_SIZE = 4096;
const int MAX_WAIT_TIME = 5;
const int MAX_NO_PACKETS = 4;

unsigned short checksum(unsigned short *buf, int len)
{
    unsigned long sum = 0;
    while (len > 1) {
        sum += *buf++;
        len -= 2;
    }
    if (len == 1) {
        sum += *(unsigned char*)buf;
    }
    sum = (sum >> 16) + (sum & 0xffff);
    sum += (sum >> 16);
    return (unsigned short)(~sum);
}

int ping(const char *ip, int packet_size)
{
    int sockfd;
    struct sockaddr_in addr;
    struct timeval tv_begin, tv_end, tv;
    struct icmphdr *icmp;
    char sendpacket[PACKET_SIZE];
    char recvpacket[PACKET_SIZE];
    int packetsize = packet_size;
    int nsend = 0, nreceived = 0, nerrors = 0;
    int i, j, len;
    double rtt;
    struct addrinfo hints, *res;
    struct timeval timeout = {0, 1000}; // 1ms

    memset(&hints, 0, sizeof(hints));
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_RAW;
    hints.ai_protocol = IPPROTO_ICMP;

    if (getaddrinfo(ip, NULL, &hints, &res) != 0) {
        return -1;
    }

    if ((sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP)) == -1) {
        return -1;
    }

    if (fcntl(sockfd, F_SETFL, O_NONBLOCK) < 0) {
        return -1;
    }

    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_addr = ((struct sockaddr_in*)res->ai_addr)->sin_addr;

    cout << "PING " << ip << " (" << inet_ntoa(addr.sin_addr) << ")" << endl;

    len = packetsize + sizeof(struct icmphdr);
    memset(sendpacket, 0, len);

    icmp = (struct icmphdr*)sendpacket;
    icmp->type = ICMP_ECHO;
    icmp->code = 0;
    icmp->checksum = 0;
    icmp->un.echo.id = getpid();
    for (i = 0; i < packetsize; ++i) {
        sendpacket[sizeof(struct icmphdr) + i] = 'A';
    }
    icmp->checksum = checksum((unsigned short*)sendpacket, len);

    gettimeofday(&tv_begin, NULL);

    for (i = 0; i < MAX_NO_PACKETS; ++i) {
        if (sendto(sockfd, sendpacket, len, 0, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
            ++nerrors;
            continue;
        }
        ++nsend;
        std::this_thread::sleep_for(std::chrono::milliseconds(10));
        fd_set fd_sets;
        FD_ZERO(&fd_sets);
        FD_SET(sockfd, &fd_sets);
        int ret = select(sockfd + 1, &fd_sets, NULL, NULL, &timeout);
        if (ret <= 0) {
            continue;
        }
        if (recvfrom(sockfd, recvpacket, sizeof(recvpacket), 0, NULL, NULL) < 0) {
            ++nerrors;
            continue;
        }
        ++nreceived;
        gettimeofday(&tv_end, NULL);
        tv = tv_end;
        timersub(&tv_end, &tv_begin, &tv);
        rtt = tv.tv_sec * 1000.0 + tv.tv_usec / 1000.0;
        struct iphdr *iph = (struct iphdr*)recvpacket;
        icmp = (struct icmphdr*)(recvpacket + iph->ihl * 4);
        if (icmp->type == ICMP_ECHOREPLY && icmp->un.echo.id == getpid()) {
            printf("%d bytes from %s: icmp_seq=%u ttl=%d time=%.2f ms\n",
                   packetsize, inet_ntoa(addr.sin_addr), icmp->un.echo.sequence, iph->ttl, rtt);
        } else {
            ++nerrors;
        }
    }

    printf("%d packets transmitted, %d received, %d%% packet loss, time %.2fms\n",
           nsend, nreceived, (nerrors + nsend - nreceived) * 100 / nsend, rtt);

    close(sockfd);

    return nreceived;
}

int main(int argc, char *argv[])
{
    if (argc < 2) {
        cout << "Usage: " << argv[0] << " <ip> [packet size]" << endl;
        return 1;
    }

    int packet_size = PACKET_SIZE;
    if (argc >= 3) {
        packet_size = atoi(argv[2]);
    }

    return ping(argv[1], packet_size);
}

你可以通过在命令行中运行命令 `g++ -o ping ping.cpp` 来编译这个程序，并使用 `./ping <ip> [packet size]` 来运行它。其中，`<ip>` 是你要 ping 的 IP 地址或主机名，`[packet size]` 是可选参数，表示 ping 包的数据包大小，如果不指定，默认为 4096 字节。