linux下ping的C語言實現

#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 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); } /*校驗和算法*/ 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報頭二進制數據以2字節爲單位累加起來*/ while(nleft>1) { sum+=*w++; nleft-=2; } /*若ICMP報頭爲奇數個字節，會剩下最後一字節。把最後一個字節視爲一個2字節數據的高字節，這個2字節數據的低字節爲0，繼續累加*/ if( nleft==1) { *(unsigned char *)(&answer)=*(unsigned char *)w; sum+=answer; } sum=(sum>>16)+(sum&0xffff); sum+=(sum>>16); answer=~sum; return answer; } /*設置ICMP報頭*/ 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); /*記錄發送時間*/ icmp->icmp_cksum=cal_chksum( (unsigned short *)icmp,packsize); /*校驗算法*/ return packsize; } /*發送三個ICMP報文*/ void send_packet() { int packetsize; while( nsend<MAX_NO_PACKETS) { nsend++; packetsize=pack(nsend); /*設置ICMP報頭*/ if( sendto(sockfd,sendpacket,packetsize,0, (struct sockaddr *)&dest_addr,sizeof(dest_addr) )<0 ) { perror("sendto error"); continue; } sleep(1); /*每隔一秒發送一個ICMP報文*/ } } /*接收所有ICMP報文*/ 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),0, (struct sockaddr *)&from,&fromlen)) <0) { if(errno==EINTR)continue; perror("recvfrom error"); continue; } gettimeofday(&tvrecv,NULL); /*記錄接收時間*/ if(unpack(recvpacket,n)==-1)continue; nreceived++; } } /*剝去ICMP報頭*/ 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報頭長度,即ip報頭的長度標誌乘4*/ icmp=(struct icmp *)(buf+iphdrlen); /*越過ip報頭,指向ICMP報頭*/ len-=iphdrlen; /*ICMP報頭及ICMP數據報的總長度*/ if( len<8) /*小於ICMP報頭長度則不合理*/ { printf("ICMP packets/'s length is less than 8/n"); return -1; } /*確保所接收的是我所發的的ICMP的迴應*/ if( (icmp->icmp_type==ICMP_ECHOREPLY) && (icmp->icmp_id==pid) ) { tvsend=(struct timeval *)icmp->icmp_data; tv_sub(&tvrecv,tvsend); /*接收和發送的時間差*/ rtt=tvrecv.tv_sec*1000+tvrecv.tv_usec/1000; /*以毫秒爲單位計算rtt*/ /*顯示相關信息*/ 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=50*1024; 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,這種套接字只有root才能生成*/ if( (sockfd=socket(AF_INET,SOCK_RAW,protocol->p_proto) )<0) { perror("socket error"); exit(1); } /* 回收root權限,設置當前用戶權限*/ setuid(getuid()); /*擴大套接字接收緩衝區到50K這樣做主要爲了減小接收緩衝區溢出的 的可能性,若無意中ping一個廣播地址或多播地址,將會引來大量應答*/ setsockopt(sockfd,SOL_SOCKET,SO_RCVBUF,&size,sizeof(size) ); bzero(&dest_addr,sizeof(dest_addr)); dest_addr.sin_family=AF_INET; /*判斷是主機名還是ip地址*/ if( inaddr=inet_addr(argv[1])==INADDR_NONE) { if((host=gethostbyname(argv[1]) )==NULL) /*是主機名*/ { 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); /*獲取main的進程id,用於設置ICMP的標誌符*/ pid=getpid(); printf("PING %s(%s): %d bytes data in ICMP packets./n",argv[1], inet_ntoa(dest_addr.sin_addr),datalen); send_packet(); /*發送所有ICMP報文*/ recv_packet(); /*接收所有ICMP報文*/ statistics(SIGALRM); /*進行統計*/ return 0; } /*兩個timeval結構相減*/ 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 -----------*/ 

 

 

 

仍然需要注意權限的問題，按照如下方式編譯：

 

sudo gcc myping.c -o myping

 

sudo chmod u+s myping

 

./myping www.163.com

 

運行顯示結果：

 

 

PING www.cn.ibm.com(121.195.178.238): 56 bytes data in ICMP packets.

64 byte from 121.195.178.238: icmp_seq=1 ttl=242 rtt=3029.000 ms

64 byte from 121.195.178.238: icmp_seq=2 ttl=242 rtt=2020.000 ms

64 byte from 121.195.178.238: icmp_seq=3 ttl=242 rtt=1010.000 ms

--------------------PING statistics-------------------

3 packets transmitted, 3 received , %0 lost