ping2.c

实现ping功能,返回ping的结果.可以直接调用此函数,通则返回true,不通则返回false.

/***********************************************************
* 作者:黄勇才                       *
* 时间:2007年8月                           *
* 名称：myping.c                             *
* 说明:本程序用于演示ping命令的实现原理             *
***********************************************************/
#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   32
#define MAX_WAIT_TIME   500//ms
#define MAX_SEND_PACKETS 1//发送包的个数

char sendpacket[PACKET_SIZE];
char recvpacket[PACKET_SIZE];
int sockfd,datalen=56;
int nsend=0,nreceived=0;
int result=0,timer_flag=0;
struct sockaddr_in dest_addr;
pid_t pid;
struct sockaddr_in from;
struct timeval tvrecv;
int 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);
//int ping(char *ip);
int statistics(int signo)
{
printf("nsend=%d\n",nsend);
printf("nreceived=%d\n",nreceived);
    printf("\n--------------------PING statistics-------------------\n");
    printf("%d packets transmitted, %d received , %d%% lost\n",nsend,nreceived,(int)((float)(nsend-nreceived)/(float)nsend*100));
    close(sockfd);
//	exit(0);
timer_flag=1;
	if(nsend==nreceived)
   result=1;
	else
result=0;
	  
}
/*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_SEND_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;
          }
          usleep(2000); /*每隔一秒发送一个ICMP报文*/
    }
  //printf("nsend=%d\n",nsend);
}

/*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)
    {     

//打开定时器
         ualarm(MAX_WAIT_TIME*1000,0);
          if( (n=recvfrom(sockfd,recvpacket,sizeof(recvpacket),0,(struct sockaddr *)&from,&fromlen)) <0)
          {    
            if(errno==EINTR)
		continue;
	//	break;	
       //         perror("recvfrom error");
       break;
          }
          gettimeofday(&tvrecv,NULL); /*记录接收时间*/
          if(unpack(recvpacket,n)==-1)
		  	continue;
       nreceived++;
	   
			   printf("nreceived=%d\n",nreceived);
    }
	 if(timer_flag==0)
statistics(SIGALRM);
}
/*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*/
	printf("len=%d\n",len);
    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;
    }
printf("icmp->icmp_type=%d\n",icmp->icmp_type);
printf("ICMP_ECHOREPLY=%d\n",ICMP_ECHOREPLY);
    /*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[])
{
char ip[20];
 if(argc<2)
    {    
           printf("usage:%s hostname/IP address\n",argv[0]);
           exit(1);
    }
strcpy(ip,argv[1]);
ping(ip);
if(result)
   printf("ping success!\n");
else
	printf("ping fail!\n");
}

void ping(char *ip)
{     
    struct hostent *host;
    struct protoent *protocol;
    unsigned long inaddr=0l;
    int waittime=MAX_WAIT_TIME;
    int size=50*1024;
    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;






if ((host=gethostbyname(ip)) == NULL)
{
/* get the host info */
herror("gethostbyname");
exit(1);
}
printf("Host name : %s\n", host->h_name);
// printf("IP Address : %s\n",inet_ntoa(*((struct in_addr *)Dest->h_addr)));

dest_addr.sin_addr = *((struct in_addr *)host->h_addr);
dest_addr.sin_family = AF_INET;
bzero(&(dest_addr.sin_zero), 8); 



/*	
   
    if( inaddr=inet_addr(ip)==INADDR_NONE)
    {     

	if((host=gethostbyname(ip) )==NULL) 
          {     
          perror("gethostbyname error");
                exit(1);
          }
          memcpy( (char *)&dest_addr.sin_addr,host->h_addr,host->h_length);
    }
    else  
      //    memcpy( (char *)&dest_addr,(char *)&inaddr,host->h_length);
    	{
         memcpy( (char *)&dest_addr.sin_addr,(char *)&inaddr, sizeof(dest_addr.sin_addr));
    	}*/
    /*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",ip,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*/
//  return  statistics(SIGALRM); /*进行统计*/
return 1;
}
/*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+=500000;
    }
    out->tv_sec-=in->tv_sec;
}
/*------------- The End -----------*/