linux下ping的C语言实现

  1 #include <stdio.h>
  2 #include <signal.h>
  3 #include <arpa/inet.h>
  4 #include <sys/types.h>
  5 #include <sys/socket.h>
  6 #include <unistd.h>
  7 #include <netinet/in.h>
  8 #include <netinet/ip.h>
  9 #include <netinet/ip_icmp.h>
 10 #include <netdb.h>
 11 #include <setjmp.h>
 12 #include <errno.h>
 13 #define PACKET_SIZE     4096
 14 #define MAX_WAIT_TIME   5
 15 #define MAX_NO_PACKETS  3
 16 char sendpacket[PACKET_SIZE];
 17 char recvpacket[PACKET_SIZE];
 18 int sockfd,datalen=56;
 19 int nsend=0,nreceived=0;
 20 struct sockaddr_in dest_addr;
 21 pid_t pid;
 22 struct sockaddr_in from;
 23 struct timeval tvrecv;
 24 void statistics(int signo);
 25 unsigned short cal_chksum(unsigned short *addr,int len);
 26 int pack(int pack_no);
 27 void send_packet(void);
 28 void recv_packet(void);
 29 int unpack(char *buf,int len);
 30 void tv_sub(struct timeval *out,struct timeval *in);
 31 void statistics(int signo)
 32 {       printf("\n--------------------PING statistics-------------------\n");
 33         printf("%d packets transmitted, %d received , %%%d lost\n",nsend,nreceived,
 34                         (nsend-nreceived)/nsend*100);
 35         close(sockfd);
 36         exit(1);
 37 }
 38 /*校验和算法*/
 39 unsigned short cal_chksum(unsigned short *addr,int len)
 40 {       int nleft=len;
 41         int sum=0;
 42         unsigned short *w=addr;
 43         unsigned short answer=0;
 44         
 45 /*把ICMP报头二进制数据以2字节为单位累加起来*/
 46         while(nleft>1)
 47         {       sum+=*w++;
 48                 nleft-=2;
 49         }
 50         /*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*/
 51         if( nleft==1)
 52         {       *(unsigned char *)(&answer)=*(unsigned char *)w;
 53                 sum+=answer;
 54         }
 55         sum=(sum>>16)+(sum&0xffff);
 56         sum+=(sum>>16);
 57         answer=~sum;
 58         return answer;
 59 }
 60 /*设置ICMP报头*/
 61 int pack(int pack_no)
 62 {       int i,packsize;
 63         struct icmp *icmp;
 64         struct timeval *tval;
 65         icmp=(struct icmp*)sendpacket;
 66         icmp->icmp_type=ICMP_ECHO;
 67         icmp->icmp_code=0;
 68         icmp->icmp_cksum=0;
 69         icmp->icmp_seq=pack_no;
 70         icmp->icmp_id=pid;
 71         packsize=8+datalen;
 72         tval= (struct timeval *)icmp->icmp_data;
 73         gettimeofday(tval,NULL);    /*记录发送时间*/
 74         icmp->icmp_cksum=cal_chksum( (unsigned short *)icmp,packsize); /*校验算法*/
 75         return packsize;
 76 }
 77 /*发送三个ICMP报文*/
 78 void send_packet()
 79 {       int packetsize;
 80         while( nsend<MAX_NO_PACKETS)
 81         {       nsend++;
 82                 packetsize=pack(nsend); /*设置ICMP报头*/
 83                 if( sendto(sockfd,sendpacket,packetsize,0,
 84                           (struct sockaddr *)&dest_addr,sizeof(dest_addr) )<0  )
 85                 {       perror("sendto error");
 86                         continue;
 87                 }
 88                 sleep(1); /*每隔一秒发送一个ICMP报文*/
 89         }
 90 }
 91 /*接收所有ICMP报文*/
 92 void recv_packet()
 93 {       int n,fromlen;
 94         extern int errno;
 95         signal(SIGALRM,statistics);
 96         fromlen=sizeof(from);
 97         while( nreceived<nsend)
 98         {       alarm(MAX_WAIT_TIME);
 99                 if( (n=recvfrom(sockfd,recvpacket,sizeof(recvpacket),0,
100                                 (struct sockaddr *)&from,&fromlen)) <0)
101                 {       if(errno==EINTR)continue;
102                         perror("recvfrom error");
103                         continue;
104                 }
105                 gettimeofday(&tvrecv,NULL);  /*记录接收时间*/
106                 if(unpack(recvpacket,n)==-1)continue;
107                 nreceived++;
108         }
109 }
110 /*剥去ICMP报头*/
111 int unpack(char *buf,int len)
112 {       int i,iphdrlen;
113         struct ip *ip;
114         struct icmp *icmp;
115         struct timeval *tvsend;
116         double rtt;
117         ip=(struct ip *)buf;
118         iphdrlen=ip->ip_hl<<2;    /*求ip报头长度,即ip报头的长度标志乘4*/
119         icmp=(struct icmp *)(buf+iphdrlen);  /*越过ip报头,指向ICMP报头*/
120         len-=iphdrlen;            /*ICMP报头及ICMP数据报的总长度*/
121         if( len<8)                /*小于ICMP报头长度则不合理*/
122         {       printf("ICMP packets\‘s length is less than 8\n");
123                 return -1;
124         }
125         /*确保所接收的是我所发的的ICMP的回应*/
126         if( (icmp->icmp_type==ICMP_ECHOREPLY) && (icmp->icmp_id==pid) )
127         {       tvsend=(struct timeval *)icmp->icmp_data;
128                 tv_sub(&tvrecv,tvsend);  /*接收和发送的时间差*/
129                 rtt=tvrecv.tv_sec*1000+tvrecv.tv_usec/1000;  /*以毫秒为单位计算rtt*/
130                 /*显示相关信息*/
131                 printf("%d byte from %s: icmp_seq=%u ttl=%d rtt=%.3f ms\n",
132                         len,
133                         inet_ntoa(from.sin_addr),
134                         icmp->icmp_seq,
135                         ip->ip_ttl,
136                         rtt);
137         }
138         else    return -1;
139 }
140 main(int argc,char *argv[])
141 {       struct hostent *host;
142         struct protoent *protocol;
143         unsigned long inaddr=0l;
144         int waittime=MAX_WAIT_TIME;
145         int size=50*1024;
146         if(argc<2)
147         {       printf("usage:%s hostname/IP address\n",argv[0]);
148                 exit(1);
149         }
150         if( (protocol=getprotobyname("icmp") )==NULL)
151         {       perror("getprotobyname");
152                 exit(1);
153         }
154         /*生成使用ICMP的原始套接字,这种套接字只有root才能生成*/
155         if( (sockfd=socket(AF_INET,SOCK_RAW,protocol->p_proto) )<0)
156         {       perror("socket error");
157                 exit(1);
158         }
159         /* 回收root权限,设置当前用户权限*/
160         setuid(getuid());
161         /*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
162           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*/
163         setsockopt(sockfd,SOL_SOCKET,SO_RCVBUF,&size,sizeof(size) );
164         bzero(&dest_addr,sizeof(dest_addr));
165         dest_addr.sin_family=AF_INET;
166         /*判断是主机名还是ip地址*/
167         if( inaddr=inet_addr(argv[1])==INADDR_NONE)
168         {       if((host=gethostbyname(argv[1]) )==NULL) /*是主机名*/
169                 {       perror("gethostbyname error");
170                         exit(1);
171                 }
172                 memcpy( (char *)&dest_addr.sin_addr,host->h_addr,host->h_length);
173         }
174         else    /*是ip地址*/
175                 memcpy( (char *)&dest_addr,(char *)&inaddr,host->h_length);
176         /*获取main的进程id,用于设置ICMP的标志符*/
177         pid=getpid();
178         printf("PING %s(%s): %d bytes data in ICMP packets.\n",argv[1],
179                         inet_ntoa(dest_addr.sin_addr),datalen);
180         send_packet();  /*发送所有ICMP报文*/
181         recv_packet();  /*接收所有ICMP报文*/
182         statistics(SIGALRM); /*进行统计*/
183         return 0;
184 }
185 /*两个timeval结构相减*/
186 void tv_sub(struct timeval *out,struct timeval *in)
187 {       if( (out->tv_usec-=in->tv_usec)<0)
188         {       --out->tv_sec;
189                 out->tv_usec+=1000000;
190         }
191         out->tv_sec-=in->tv_sec;
192 }
193 /*------------- The End -----------*/

1 sudo gcc myping.c -o myping
2 sudo chmod u+s myping
3 ./myping www.baidu.com

1 PING www.baidu.com(180.97.33.107): 56 bytes data in ICMP packets.
2 64 byte from 180.97.33.107: icmp_seq=1 ttl=128 rtt=3003.000 ms
3 64 byte from 180.97.33.107: icmp_seq=2 ttl=128 rtt=2002.000 ms
4 64 byte from 180.97.33.107: icmp_seq=3 ttl=128 rtt=1001.000 ms
5 
6 --------------------PING statistics-------------------
7 3 packets transmitted, 3 received , %0 lost