myping.c

来自「用C语言写的linux下的ping程序」· C语言 代码 · 共 264 行

/*
	this ping program will not be affected by any signals.
*/
#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>
#include <time.h>
#include <string.h>
#include <fcntl.h>

#define PACKET_SIZE     4096
#define MAX_WAIT_TIME   5
#define MAX_NO_PACKETS  2

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);
int recv_packet(void);
int unpack(char *buf,int len);
void tv_sub(struct timeval *out,struct timeval *in);
int nsleep(double sleep_time);
/*
void statistics(int signo)
{       printf("\n-------------PING statistics-------------------\n");
        printf("%d packets transmitted, %d received , %%%d lost\n",
               nsend,nreceived,(nsend-nreceived)/nsend*100);
        if (nreceived>0){
		printf("alive\n");
	}else{
		printf("not alive\n");
	}
        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()
{    
	//printf("begin send packet\n");
	int packetsize;
	//printf("send times:");
        while( nsend<MAX_NO_PACKETS)
        {    
        	//printf("%d...",nsend);
        	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");
                		;
                }
                nsleep(0.05); /*每隔一段时间发送一个ICMP报文*/
        }
	//printf("\n");
	//printf("send ok\n");
}

/*接收所有ICMP报文*/
int recv_packet()
{
	//printf("begin recv packet\n");	
	int num=0,times=0,fromlen=sizeof(struct sockaddr_in);
	//printf("recv times:");
	while( (nreceived<nsend) && (times<MAX_WAIT_TIME)){
		times++;		
		//printf("%d...",times);
		nsleep(0.2);
		if( (num=recvfrom(sockfd,recvpacket,sizeof(recvpacket),0,(struct sockaddr *)&from,&fromlen)) <0){
			//nsleep(0.2);
			continue;
		}
		gettimeofday(&tvrecv,NULL);  /*记录接收时间*/
		//printf("recvpacket=%s,n=%d\n",recvpacket,n);
		if(unpack(recvpacket,num)==-1){
			//nsleep(0.2);
			continue;
		}
		nreceived++;
		//printf("\n");
		//printf("recv ok\n");
		return 1;/*收到返回的icmp包则退出，判断设备在线*/
	}
	//printf("\n");
	return 0;
}
/*剥去ICMP报头*/
int unpack(char *buf,int len)
{       
	//printf("begin uppacket\n");
	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;
	}
	//printf("icmp->icmp_type=%d,icmp->icmp_id=%d\n",icmp->icmp_type,icmp->icmp_id);
        /*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*/
           /*以毫秒为单位计算rtt*/
		rtt=tvrecv.tv_sec*1000+tvrecv.tv_usec/1000;  
           /*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);
		return 0;
	}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=50*1024;
	int result;
        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;
	 fcntl(sockfd,F_SETFL,O_NONBLOCK);
        /*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*/
		//dest_addr.sin_addr.s_addr=inaddr;	     
            //memcpy( (char *)&dest_addr,(char *)&inaddr,host->h_length);
            inet_aton(argv[1],&dest_addr.sin_addr);
        /*获取main的进程id,用于设置ICMP的标志符*/
        pid=getpid();
        //printf("%d:PING %s(%s): %d bytes data in ICMP packets.\n",pid,argv[1],inet_ntoa(dest_addr.sin_addr),datalen);
        send_packet();  /*发送所有ICMP报文*/
        if((result=recv_packet())==1){  /*接收所有ICMP报文*/
		printf("alive\n");
	}else{
		printf("not alive\n");
	}
        close(sockfd);
        //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 -----------*/
int nsleep(double sleep_time)
{
	//printf("nsleep begin\n");
	struct timespec tv;
	/* Construct the timespec from the number of whole seconds... */
	tv.tv_sec = (time_t) sleep_time;
	/* ... and the remainder in nanoseconds. */
	tv.tv_nsec = (long) ((sleep_time - tv.tv_sec) * 1e+9);
		int rval = nanosleep (&tv, &tv);
		if (rval == 0){
	/* Completed the entire sleep time; all done. */
			//printf("nsleep end ok\n");
   			return 0;
		}else{
   /* Some other error; bail out. */
   			//printf("nsleep end fail\n");
			return rval;
   		}
	//printf("nsleep end ok\n");
	return 0;
}