Linux下Ping的实现代码

#include <stdio.h>#include <sys/socket.h>#include <netinet/in.h>#include <netinet/ip.h>#include <netinet/ip_icmp.h>#include <netdb.h>

#define PACKET_SIZE     4096#define ERROR           0#define SUCCESS         1

// 效验算法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;}

// Ping函数int ping( char *ips, int timeout){    struct timeval timeo;    int sockfd;    struct sockaddr_in addr;    struct sockaddr_in from;        struct timeval *tval;    struct ip *iph;    struct icmp *icmp;

    char sendpacket[PACKET_SIZE];    char recvpacket[PACKET_SIZE];        int n;    pid_t pid;    int maxfds = 0;    fd_set readfds;        // 设定Ip信息    bzero(&addr,sizeof(addr));    addr.sin_family = AF_INET;    addr.sin_addr.s_addr = inet_addr(ips);  

    // 取得socket    sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);    if (sockfd < 0)     {        syslog(LOG_INFO,"ip:%s,socket error",ips);        return ERROR;    }        // 设定TimeOut时间    timeo.tv_sec = timeout / 1000;    timeo.tv_usec = timeout % 1000;        if (setsockopt(sockfd, SOL_SOCKET, SO_SNDTIMEO, &timeo, sizeof(timeo)) == -1)    {        syslog(LOG_INFO,"ip:%s,setsockopt error",ips);        return ERROR;    }        // 设定Ping包    memset(sendpacket, 0, sizeof(sendpacket));        // 取得PID，作为Ping的Sequence ID    pid=getpid();    int i,packsize;    icmp=(struct icmp*)sendpacket;    icmp->icmp_type=ICMP_ECHO;    icmp->icmp_code=0;    icmp->icmp_cksum=0;    icmp->icmp_seq=0;    icmp->icmp_id=pid;    packsize=8+56;    tval= (struct timeval *)icmp->icmp_data;    gettimeofday(tval,NULL);    icmp->icmp_cksum=cal_chksum((unsigned short *)icmp,packsize);

    // 发包    n = sendto(sockfd, (char *)&sendpacket, packsize, 0, (struct sockaddr *)&addr, sizeof(addr));    if (n < 1)    {        syslog(LOG_INFO,"ip:%s,sendto error",ips);        return ERROR;    }

    // 接受    // 由于可能接受到其他Ping的应答消息，所以这里要用循环    while(1)    {        // 设定TimeOut时间，这次才是真正起作用的        FD_ZERO(&readfds);        FD_SET(sockfd, &readfds);        maxfds = sockfd + 1;        n = select(maxfds, &readfds, NULL, NULL, &timeo);        if (n <= 0)        {            syslog(LOG_INFO,"ip:%s,Time out error",ips);            close(sockfd);            return ERROR;        }

        // 接受        memset(recvpacket, 0, sizeof(recvpacket));        int fromlen = sizeof(from);        n = recvfrom(sockfd, recvpacket, sizeof(recvpacket), 0, (struct sockaddr *)&from, &fromlen);        if (n < 1) {            break;        }                // 判断是否是自己Ping的回复        char *from_ip = (char *)inet_ntoa(from.sin_addr);        syslog(LOG_INFO,"fomr ip:%s",from_ip);         if (strcmp(from_ip,ips) != 0)         {            syslog(LOG_INFO,"ip:%s,Ip wang",ips);            break;         }                iph = (struct ip *)recvpacket;            icmp=(struct icmp *)(recvpacket + (iph->ip_hl<<2));

        syslog(LOG_INFO,"ip:%s,icmp->icmp_type:%d,icmp->icmp_id:%d",ips,icmp->icmp_type,icmp->icmp_id);       // 判断Ping回复包的状态        if (icmp->icmp_type == ICMP_ECHOREPLY && icmp->icmp_id == pid)        {            // 正常就退出循环            break;        }         else        {            // 否则继续等            continue;        }    }        // 关闭socket    close(sockfd);

    syslog(LOG_INFO,"ip:%s,Success",ips);    return SUCCESS;}