socket实现ping命令的c+代码

以下是一个简单的使用socket实现ping命令的C代码。该代码通过创建一个ICMP数据包并发送给指定的主机，并等待响应来模拟ping命令。

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

#define PACKET_SIZE     4096
#define MAX_WAIT_TIME   5
#define MAX_NO_PACKETS  3

char sendpacket[PACKET_SIZE];
char recvpacket[PACKET_SIZE];
int sockfd, datalen = 56;

unsigned short cal_chksum(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;
}

int pack(int pack_no)
{
    int i, packsize;
    struct icmp *icmp;
    struct timeval *tval;

    icmp = (struct icmp*)sendpacket;
    icmp->icmp_type = ICMP_ECHO;
    icmp->icmp_code = 0;
    icmp->icmp_cksum = 0;
    icmp->icmp_seq = pack_no;
    icmp->icmp_id = getpid();
    packsize = 8 + datalen;
    tval = (struct timeval*)icmp->icmp_data;
    gettimeofday(tval, NULL);
    icmp->icmp_cksum = cal_chksum((unsigned short*)icmp, packsize);
    return packsize;
}

int unpack(char *buf, int len)
{
    int i, iphdrlen;
    struct iphdr *ip;
    struct icmp *icmp;
    struct timeval *tvsend;
    double rtt;

    ip = (struct iphdr*)buf;
    iphdrlen = ip->ihl << 2;
    icmp = (struct icmp*)(buf + iphdrlen);
    len -= iphdrlen;

    if (len < 8) {
        printf("ICMP packets\'s length is less than 8\n");
        return -1;
    }

    if ((icmp->icmp_type == ICMP_ECHOREPLY) && (icmp->icmp_id == getpid())) {
        tvsend = (struct timeval*)icmp->icmp_data;
        gettimeofday(&tvsend, NULL);
        rtt = (tvsend->tv_sec - tvsend->tv_sec) * 1000.0 + (tvsend->tv_usec - tvsend->tv_usec) / 1000.0;
        printf("%d bytes from %s: icmp_seq=%u ttl=%d time=%.1f ms\n", len, inet_ntoa(*(struct in_addr*)&ip->saddr), icmp->icmp_seq, ip->ttl, rtt);
    } else {
        return -1;
    }
}

void send_packet()
{
    int packetsize;
    static int pack_no = 0;

    pack_no++;
    packetsize = pack(pack_no);

    if (sendto(sockfd, sendpacket, packetsize, 0, (struct sockaddr*)&dest_addr, sizeof(dest_addr)) < 0) {
        printf("sendto error\n");
    }
}

void recv_packet()
{
    int n, fromlen;
    struct timeval tv;
    fd_set readfd;

    fromlen = sizeof(from);

    while (1) {
        tv.tv_sec = MAX_WAIT_TIME;
        tv.tv_usec = 0;
        FD_ZERO(&readfd);
        FD_SET(sockfd, &readfd);

        n = select(sockfd + 1, &readfd, NULL, NULL, &tv);

        if (n == 0) {
            printf("timeout\n");
            return;
        }

        if (recvfrom(sockfd, recvpacket, sizeof(recvpacket), 0, (struct sockaddr*)&from, &fromlen) < 0) {
            printf("recvfrom error\n");
        }

        if (unpack(recvpacket, n) == -1) {
            printf("unpack error\n");
        }
    }
}

void ping()
{
    int i;

    for (i = 0; i < MAX_NO_PACKETS; i++) {
        send_packet();
        recv_packet();
        sleep(1);
    }
}

int main(int argc, char *argv[])
{
    struct hostent *host;
    struct protoent *protocol;
    unsigned long inaddr = 0l;
    int waittime = MAX_WAIT_TIME * 1000;
    int size = 50 * 1024;

    if (argc < 2) {
        printf("usage:%s hostname/IP address\n", argv[0]);
        exit(1);
    }

    if ((protocol = getprotobyname("icmp")) == NULL) {
        printf("getprotobyname error\n");
        exit(1);
    }

    if ((sockfd = socket(AF_INET, SOCK_RAW, protocol->p_proto)) < 0) {
        printf("socket error\n");
        exit(1);
    }

    setuid(getuid());
    setsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &size, sizeof(size));

    bzero(&dest_addr, sizeof(dest_addr));
    dest_addr.sin_family = AF_INET;

    if ((inaddr = inet_addr(argv[1])) == INADDR_NONE) {
        if ((host = gethostbyname(argv[1])) == NULL) {
            printf("gethostbyname error\n");
            exit(1);
        }

        memcpy((char*)&dest_addr.sin_addr, host->h_addr, host->h_length);
    } else {
        memcpy((char*)&dest_addr.sin_addr, &inaddr, sizeof(inaddr));
    }

    printf("PING %s (%s): %d data bytes\n", argv[1], inet_ntoa(dest_addr.sin_addr), datalen);
    ping();
    return 0;
}