利用c实现简易的ping

测延时也可以发送ICMP报文，通过SOCKET创建ICMP的socket。代码也一并贴出。

#include <stdio.h>#include <signal.h>#include <arpa/inet.h>#include <sys/types.h>#include <sys/socket.h>#include <unistd.h>#include <netinet/in.h>#include <netinet/ip.h>#include <netinet/ip_icmp.h>#include <netdb.h>#include <setjmp.h>#include <errno.h>#define PACKET_SIZE     4096#define MAX_WAIT_TIME   5#define MAX_ICMP_PACKETS  4 char sendpacket[PACKET_SIZE];char recvpacket[PACKET_SIZE];int sockfd,datalen = 56;int nsend = 0,nreceived = 0;struct sockaddr_in dest_addr;pid_t pid;struct sockaddr_in from;struct timeval tvrecv;void statistics(int signo);unsigned short cal_chksum(unsigned short *addr,int len);int pack(int pack_no);void send_packet(void);void recv_packet(void);int unpack(char *buf,int len);void tv_sub(struct timeval *out,struct timeval *in);void statistics(int signo){      printf("\n--------------------PING statistics-------------------\n");    printf("%d packets transmitted, %d received , %%%d lost\n",nsend,nreceived,                        (nsend-nreceived)/nsend*100);    close(sockfd);    exit(1);}/*校验和算法*/unsigned short cal_chksum(unsigned short *addr,int len){      int nleft=len;    int sum=0;    unsigned short *w=addr;    unsigned short answer=0;        /*把ICMP报头二进制数据以2字节为单位累加起来*/    while(nleft>1)    {       sum+=*w++;        nleft-=2;    }        /*若ICMP报头为奇数个字节，会剩下最后一字节。把最后一个字节视为一个2字节数据的高字节，这个2字节数据的低字节为0，继续累加*/    if( nleft==1)    {       *(unsigned char *)(&answer)=*(unsigned char *)w;        sum+=answer;    }    sum=(sum>>16)+(sum&0xffff);    sum+=(sum>>16);    answer=~sum;    return answer;}/*设置ICMP报头*/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 = pid;    packsize = 8 + datalen;    tval = (struct timeval *)icmp->icmp_data;    gettimeofday(tval,NULL);    /*记录发送时间*/    icmp->icmp_cksum = cal_chksum( (unsigned short *)icmp,packsize); /*校验算法*/    return packsize;}/*发送四个ICMP报文*/void send_packet(){       int packetsize;    while( nsend < MAX_ICMP_PACKETS)    {          nsend++;        packetsize = pack(nsend); /*设置ICMP报头*/        if( sendto(sockfd,sendpacket,packetsize,0,                          (struct sockaddr *)&dest_addr,sizeof(dest_addr) ) < 0  )        {                perror("sendto error");         continue;        }    }}/*接收所有ICMP报文*/void recv_packet(){       int n,fromlen;    extern int errno;    signal(SIGALRM,statistics);    fromlen = sizeof(from);    while( nreceived < nsend)    {alarm(MAX_WAIT_TIME);        if( (n = recvfrom(sockfd,recvpacket,sizeof(recvpacket),0,                                (struct sockaddr *)&from,&fromlen)) <0)        {       if(errno == EINTR)continue;            perror("recvfrom error");            continue;        }        gettimeofday(&tvrecv,NULL);  /*记录接收时间*/        if(unpack(recvpacket,n)==-1)continue;        nreceived++;    }}/*剥去ICMP报头*/int unpack(char *buf,int len){       int i,iphdrlen;    struct ip *ip;    struct icmp *icmp;    struct timeval *tvsend;    double rtt;    ip = (struct ip *)buf;    iphdrlen = ip->ip_hl<<2;    /*求ip报头长度,即ip报头的长度标志乘4*/    icmp = (struct icmp *)(buf+iphdrlen);  /*越过ip报头,指向ICMP报头*/    len -= iphdrlen;            /*ICMP报头及ICMP数据报的总长度*/    if( len < 8)                /*小于ICMP报头长度则不合理*/    {       printf("ICMP packets\'s length is less than 8\n");        return -1;    }        /*确保所接收的是我所发的的ICMP的回应*/    if( (icmp->icmp_type==ICMP_ECHOREPLY) && (icmp->icmp_id==pid) )    {       tvsend=(struct timeval *)icmp->icmp_data;                tv_sub(&tvrecv,tvsend);  /*接收和发送的时间差*/                rtt=tvrecv.tv_sec*1000+tvrecv.tv_usec/1000;  /*以毫秒为单位计算rtt*/                /*显示相关信息*/                printf("%d byte from %s: icmp_seq=%u ttl=%d rtt=%.3f ms\n",                        len,                        inet_ntoa(from.sin_addr),                        icmp->icmp_seq,                        ip->ip_ttl,                        rtt);        }        else    return -1;}int main(int argc,char *argv[]){       struct hostent *host;    struct protoent *protocol;    unsigned long inaddr = 0l;    int waittime = MAX_WAIT_TIME;    int size = 50*1024;        if(argc < 2)    {       printf("usage:%s hostname/IP address\n",argv[0]);        exit(1);    }    if( (protocol = getprotobyname("icmp") )== NULL)    {       perror("getprotobyname");        exit(1);    }    /*生成使用ICMP的原始套接字*/    if( (sockfd = socket(AF_INET,SOCK_RAW,protocol->p_proto) )<0)    {       perror("socket error");        exit(1);    }    /* 回收root权限,设置当前用户权限*/    setuid(getuid());        /*扩大套接字接收缓冲区到50K这样做主要为了减小接收缓冲区溢出的    的可能性,若无意中ping一个广播地址或多播地址,将会引来大量应答*/        setsockopt(sockfd,SOL_SOCKET,SO_RCVBUF,&size,sizeof(size) );    bzero(&dest_addr,sizeof(dest_addr));    dest_addr.sin_family = AF_INET;        /*判断是主机名还是ip地址*/    if( inaddr = inet_addr(argv[1]) == INADDR_NONE)    {       if((host = gethostbyname(argv[1]) )== NULL) /*是主机名*/        {       perror("gethostbyname error");            exit(1);        }        memcpy( (char *)&dest_addr.sin_addr,host->h_addr,host->h_length);    }    else    /*是ip地址*/        memcpy( (char *)&dest_addr,(char *)&inaddr,host->h_length);        /*获取进程id,用于设置ICMP的标志符*/    pid = getpid();    printf("PING %s(%s): %d bytes data in ICMP packets.\n",argv[1],                        inet_ntoa(dest_addr.sin_addr),datalen);        send_packet();  /*发送所有ICMP报文*/    recv_packet();  /*接收所有ICMP报文*/    statistics(SIGALRM); /*进行统计*/    return 0;}/*两个timeval结构相减*/void tv_sub(struct timeval *out,struct timeval *in){       if( (out->tv_usec-=in->tv_usec)<0)    {       --out->tv_sec;        out->tv_usec+=1000000;    }    out->tv_sec-=in->tv_sec;}/*------------- The End -----------*/