实现ping命令的代码

实现ping命令的代码2015-05-03
#include<stdio.h>#include<sys/time.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<netdb.h>#include<setjmp.h>#include<errno.h>#include<netinet/ip_icmp.h>#include<string.h>#include<stdlib.h>#definePACKET_SIZE 4096/**/#define MAX_WAIT_TIME 5#define MAX_NO_PACKETS 3char 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（"
-----------------PING statistics----------------
"）; printf（"%d packet transmitted,%d received,%%%d lost 
",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，会剩下最后一个字节。把最后一个字节视为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 packsize; struct icmp *icmpp; struct timeval *tval; icmpp=（struct icmp *）sendpacket; icmpp->icmp_type=ICMP_ECHO; icmpp->icmp_code=0; icmpp->icmp_cksum=0; icmpp->icmp_seq=pack_no; icmpp->icmp_id=pid; packsize=8+datalen; tval=（struct timeval *）icmpp->icmp_data; gettimeofday（tval,NULL）;/*记录发送时间*/ icmpp->icmp_cksum=cal_chksum（（unsigned short*）icmpp,packsize）;/*校验算法*/ return packsize;}/*发送3个ICMP报文*/void send_packet（）{ int packetsize; while（nsend<MAX_NO_PACKETS） { nsend++; packetsize=pack（nsend）;/*设置ICMP报文*/ if（sendto（sockfd,sendpacket,packetsize,0,（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<10） { alarm（MAX_WAIT_TIME）; if（（n=recvfrom（sockfd,recvpacket,sizeof（recvpacket）,0,（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 iphdrlen; struct ip *ipp; struct icmp *icmpp; struct timeval *tvsend; int rtt; ipp=（struct ip *）buf; iphdrlen=（ipp->ip_hl）*4;/*求IP报头长度，即IP报头的长度标志乘4*/ icmpp=（struct icmp*）（buf+iphdrlen）;/*超过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
"）; return -1; } /*确保所接收的是用户所发的ICMP的回应*/ if（（icmpp->icmp_type==ICMP_ECHOREPLY）&&（icmpp->icmp_id==pid）） { tvsend=（struct timeval *）icmpp->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=%dms
", len,inet_ntoa（from.sin_addr）,icmpp->icmp_seq,ipp->ip_ttl,rtt）; } else return -1;}void tv_sub（struct timeval *out,struct timeval *in）{ if（（out->tv_usec-=in->tv_usec）<0） { out->tv_sec-=1; out->tv_usec+=1000000; } out->tv_sec-=in->tv_sec;}int main（int argc,char **argv）{ struct hostent *host; struct protoent *protocol; int size=50*1024; if（argc<2） { printf（"usage : %s hostname/IP address 
",argv[0]）; exit（1）; } if（（protocol=getprotobyname（"icmp"））==NULL） { perror（"getprotobyname
"）; exit（1）; } /*生成使用ICMP的原始套接字，这种套接字只是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，这样做主要为了减少接收缓冲区溢出的可能性，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（argv[1]））==NULL） { perror（"gethostbyname error
"）; exit（1）; } dest_addr.sin_addr=*（（struct in_addr *）host->h_addr）; pid=getpid（）; printf（"PING %s（%s）: %d bytes data in ICMP packets.
",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;}
本文出自 “好好活着” 博客，请务必保留此出处http://wolfword.blog.51cto.com/4892126/1225685