linux下ping的C语言实现（转）

 #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_NO_PACKETS  3
 char sendpacket[PACKET_SIZE];
 char recvpacket[PACKET_SIZE];
 int sockfd,datalen=;
 int nsend=,nreceived=;
 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*);
     close(sockfd);
     exit();
 }
 /*校验和算法*/
 unsigned short cal_chksum(unsigned short *addr,int len)
 {
     int nleft=len;
     int sum=;
     unsigned short *w=addr;
     unsigned short answer=;

 /*把ICMP报头二进制数据以2字节为单位累加起来*/
     while(nleft>)
     {
         sum+=*w++;
         nleft-=;
     }
 /*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==)
     {
         *(unsigned char *)(&answer)=*(unsigned char *)w;
         sum+=answer;
     }
     sum=(sum>>)+(sum&0xffff);
     sum+=(sum>>);
     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=;
     icmp->icmp_cksum=;
     icmp->icmp_seq=pack_no;
     icmp->icmp_id=pid;
     packsize=+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;
 }
 /*发送三个ICMP报文*/
 void send_packet()
 {
     int packetsize;
     while( nsend<MAX_NO_PACKETS)
     {
         nsend++;
         packetsize=pack(nsend); /*设置ICMP报头*/
         if( sendto(sockfd,sendpacket,packetsize,,(struct sockaddr *)&dest_addr,sizeof(dest_addr) )<  )
         {
             perror("sendto error");
             continue;
         }
         sleep(); /*每隔一秒发送一个ICMP报文*/
     }
 }
 /*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),, (struct sockaddr *)&from,&fromlen)) <)
        {
             if(errno==EINTR)
                 continue;
             perror("recvfrom error");
             continue;
        }
        gettimeofday(&tvrecv,NULL);  /*记录接收时间*/
        if(unpack(recvpacket,n)==-)
             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<<;    /*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<)                /*小于ICMP报头长度则不合理*/
     {
         printf("ICMP packets\'s length is less than 8\n");
         return -;
     }
     /*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*+tvrecv.tv_usec/;  /*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 -;
 }
 main(int argc,char *argv[])
 {
     struct hostent *host;
     struct protoent *protocol;
     unsigned long inaddr=0l;
     int waittime=MAX_WAIT_TIME;
     int size=*;
     if(argc<)
     {
         printf("usage:%s hostname/IP address\n",argv[]);
         exit();
     }
     if( (protocol=getprotobyname("icmp") )==NULL)
     {
         perror("getprotobyname");
         exit();
     }
     /*生成使用ICMP的原始套接字,这种套接字只有root才能生成*/
     if( (sockfd=socket(AF_INET,SOCK_RAW,protocol->p_proto) )<)
     {
         perror("socket error");
         exit();
     }
     /* 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[])==INADDR_NONE)
      {
         if((host=gethostbyname(argv[]) )==NULL) /*是主机名*/
         {
             perror("gethostbyname error");
             exit();
         }
         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main的进程id,用于设置ICMP的标志符*/
     pid=getpid();
     printf("PING %s(%s): %d bytes data in ICMP packets.\n",argv[],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 ;
 }
 /*两个timeval结构相减*/
 void tv_sub(struct timeval *out,struct timeval *in)
 {
     if( (out->tv_usec-=in->tv_usec)<)
     {
         --out->tv_sec;
         out->tv_usec+=;
     }
     out->tv_sec-=in->tv_sec;
 }
 /*------------- The End -----------*/                    

仍然需要注意权限的问题，按照如下方式编译：

sudo gcc myping.c -o myping

sudo chmod u+s myping

./myping www.163.com

运行显示结果：

PING www.cn.ibm.com(121.195.178.238): 56 bytes data in ICMP packets.

64 byte from 121.195.178.238: icmp_seq=1 ttl=242 rtt=3029.000 ms

64 byte from 121.195.178.238: icmp_seq=2 ttl=242 rtt=2020.000 ms

64 byte from 121.195.178.238: icmp_seq=3 ttl=242 rtt=1010.000 ms

--------------------PING statistics-------------------

3 packets transmitted, 3 received , %0 lost