#include <stdio.h>

 #include <signal.h>

 #include <arpa/inet.h>

 #include <pthread.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;

 pthread_t tid;

 void statistics();

 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()

 {       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;

         nsend++;

         packetsize=pack(nsend); /*设置ICMP报头*/

         if( sendto(sockfd,sendpacket,packetsize,,(struct sockaddr *)&dest_addr,sizeof(dest_addr) )<  )

         {

         perror("sendto error");

                 return;

         }

     alarm();

 }

 /*接收所有ICMP报文*/

 void recv_packet(void )

 {

     //int send = *(int *) arg;

     int n,fromlen;

         extern int errno;

         fromlen=sizeof(from);

     while()

         {    if( (n=recvfrom(sockfd,recvpacket,sizeof(recvpacket),, (struct sockaddr *)&from,&fromlen)) <)

             {

             if(errno==EINTR)

                     {

                 perror("recvfrom error");

             }

             continue;

             }

             gettimeofday(&tvrecv,NULL);  /*记录接收时间*/

         unpack(recvpacket,n);

             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);

         signal(SIGALRM,send_packet);

     signal(SIGINT,statistics);

         send_packet();  /*发送所有ICMP报文*/

         //recv_packet();  /*接收所有ICMP报文*/

     int ret = pthread_create(&tid, NULL, (void*)recv_packet, NULL);

     if(ret != )

     {

         printf("Thread Create Error\n");

         exit();

     }

         //statistics(SIGALRM); /*进行统计*/

     pthread_join(tid, NULL);

         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;

 }