C语言实现ping的代码

以下是C语言实现ping的代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/select.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip_icmp.h>
#include <arpa/inet.h>
#include <netdb.h>

#define DATALEN 56
#define MAX_RECV 2048

unsigned short get_checksum(unsigned short *addr, int len)
{
    int nleft = len;
    int sum = 0;
    unsigned short *w = addr;
    unsigned short answer = 0;

    while (nleft > 1)
    {
        sum += *w++;
        nleft -= 2;
    }

    if (nleft == 1)
    {
        *(unsigned char *)(&answer) = *(unsigned char *)w;
        sum += answer;
    }

    sum = (sum >> 16) + (sum & 0xffff);
    sum += (sum >> 16);
    answer = ~sum;
    return answer;
}

void build_pkt(struct icmp *icmp_pkt, int seq)
{
    memset(icmp_pkt, 0, sizeof(struct icmp));
    icmp_pkt->icmp_type = ICMP_ECHO;
    icmp_pkt->icmp_code = 0;
    icmp_pkt->icmp_seq = seq;
    icmp_pkt->icmp_id = getpid();
    icmp_pkt->icmp_cksum = get_checksum((unsigned short *)icmp_pkt, DATALEN + 8);
}

float diff_time(struct timeval *begin, struct timeval *end)
{
    float diff = ((end->tv_sec - begin->tv_sec) * 1000.0f + (end->tv_usec -begin->tv_usec) / 1000.0f);
    return diff;
}

void ping(const char *ip)
{
    int sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
    if (sockfd < 0)
    {
        perror("socket");
        exit(-1);
    }

    struct sockaddr_in addr;
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(0);
    addr.sin_addr.s_addr = inet_addr(ip);

    char recvbuf[MAX_RECV];
    memset(recvbuf, 0, sizeof(recvbuf));

    int seq = 1;
    struct timeval begin, end;

    while (seq <= 4)
    {
        struct icmp icmp_pkt;
        build_pkt(&icmp_pkt, seq);

        if (sendto(sockfd, &icmp_pkt, sizeof(icmp_pkt), 0, (struct sockaddr *)&addr, sizeof(addr)) < 0)
        {
            perror("sendto");
            close(sockfd);
            exit(-1);
        }

        gettimeofday(&begin, NULL);

        fd_set read_set;
        FD_ZERO(&read_set);
        FD_SET(sockfd, &read_set);
        int ret = select(sockfd + 1, &read_set, NULL, NULL, NULL);
        if (ret < 0)
        {
            perror("select");
            close(sockfd);
            exit(-1);
        }
        else if (ret == 0)
        {
            printf("timeout\n");
        }
        else
        {
            struct sockaddr_in recv_addr;
            socklen_t recv_addr_len = sizeof(recv_addr);
            int nrecv = recvfrom(sockfd, recvbuf, MAX_RECV, 0, (struct sockaddr*)&recv_addr, &recv_addr_len);
            if (nrecv < 0)
            {
                perror("recvfrom");
                close(sockfd);
                exit(-1);
            }

            gettimeofday(&end, NULL);

            struct iphdr *ip_hdr = (struct iphdr *)recvbuf;
            int ip_len = ip_hdr->ihl * 4;
            struct icmp *icmp_pkt_reply = (struct icmp *)(recvbuf + ip_len);

            if (icmp_pkt_reply->icmp_type == ICMP_ECHOREPLY)
            {
                printf("from %s %d bytes icmp_seq=%d ttl=%d time=%.1f ms\n", inet_ntoa(recv_addr.sin_addr), nrecv, icmp_pkt_reply->icmp_seq, ip_hdr->ttl, diff_time(&begin, &end));
            }
            else
            {
                printf("error: packet type %d\n", icmp_pkt_reply->icmp_type);
            }
        }

        sleep(1); 

        seq++;
    }

    close(sockfd);
}

int main(int argc, char *argv[])
{
    if (argc < 2)
    {
        printf("Usage: %s ip\n", argv[0]);
        exit(0);
    }

    ping(argv[1]);

    return 0;
}