#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;
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) )<0 )
{ perror("sendto error");
continue;
}
sleep(1); /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)) <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_sec1000+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;
}
main(int argc,char argv[])
{ struct hostent host;
struct protoent protocol;
unsigned long inaddr=0l;
int waittime=MAX_WAIT_TIME;
int size=501024;
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,这种套接字只有root才能生成/
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[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 -----------*/
