linux下ping的C语言实现（转）
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 { 33 printf("\n--------------------PING statistics-------------------\n"); 34 printf("%d packets transmitted, %d received , %%%d lost\n",nsend,nreceived,(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 { 41 int nleft=len; 42 int sum=0; 43 unsigned short *w=addr; 44 unsigned short answer=0; 45 46 /*把ICMP报头二进制数据以2字节为单位累加起来*/ 47 while(nleft>1) 48 { 49 sum+=*w++; 50 nleft-=2; 51 } 52 /*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*/ 53 if( nleft==1) 54 { 55 *(unsigned char *)(&answer)=*(unsigned char *)w; 56 sum+=answer; 57 } 58 sum=(sum>>16)+(sum&0xffff); 59 sum+=(sum>>16); 60 answer=~sum; 61 return answer; 62 } 63 /*设置ICMP报头*/ 64 int pack(int pack_no) 65 { 66 int i,packsize; 67 struct icmp *icmp; 68 struct timeval *tval; 69 icmp=(struct icmp*)sendpacket; 70 icmp->icmp_type=ICMP_ECHO; 71 icmp->icmp_code=0; 72 icmp->icmp_cksum=0; 73 icmp->icmp_seq=pack_no; 74 icmp->icmp_id=pid; 75 packsize=8+datalen; 76 tval= (struct timeval *)icmp->icmp_data; 77 gettimeofday(tval,NULL); /*记录发送时间*/ 78 icmp->icmp_cksum=cal_chksum( (unsigned short*)icmp,packsize); /*校验算法*/ 79 return packsize; 80 } 81 /*发送三个ICMP报文*/ 82 void send_packet() 83 { 84 int packetsize; 85 while( nsend<MAX_NO_PACKETS) 86 { 87 nsend++; 88 packetsize=pack(nsend); /*设置ICMP报头*/ 89 if( sendto(sockfd,sendpacket,packetsize,0,(struct sockaddr *)&dest_addr,sizeof(dest_addr) )<0 ) 90 { 91 perror("sendto error"); 92 continue; 93 } 94 sleep(1); /*每隔一秒发送一个ICMP报文*/ 95 } 96 } 97 /*接收所有ICMP报文*/ 98 void recv_packet() 99 { 100 int n,fromlen; 101 extern int errno; 102 signal(SIGALRM,statistics); 103 fromlen=sizeof(from); 104 while( nreceived<nsend) 105 { 106 alarm(MAX_WAIT_TIME); 107 if( (n=recvfrom(sockfd,recvpacket,sizeof(recvpacket),0, (struct sockaddr *)&from,&fromlen)) <0) 108 { 109 if(errno==EINTR) 110 continue; 111 perror("recvfrom error"); 112 continue; 113 } 114 gettimeofday(&tvrecv,NULL); /*记录接收时间*/ 115 if(unpack(recvpacket,n)==-1) 116 continue; 117 nreceived++; 118 } 119 } 120 /*剥去ICMP报头*/ 121 int unpack(char *buf,int len) 122 { 123 int i,iphdrlen; 124 struct ip *ip; 125 struct icmp *icmp; 126 struct timeval *tvsend; 127 double rtt; 128 ip=(struct ip *)buf; 129 iphdrlen=ip->ip_hl<<2; /*求ip报头长度,即ip报头的长度标志乘4*/ 130 icmp=(struct icmp *)(buf+iphdrlen); /*越过ip报头,指向ICMP报头*/ 131 len-=iphdrlen; /*ICMP报头及ICMP数据报的总长度*/ 132 if( len<8) /*小于ICMP报头长度则不合理*/ 133 { 134 printf("ICMP packets\'s length is less than 8\n"); 135 return -1; 136 } 137 /*确保所接收的是我所发的的ICMP的回应*/ 138 if( (icmp->icmp_type==ICMP_ECHOREPLY) && (icmp->icmp_id==pid) ) 139 { 140 tvsend=(struct timeval *)icmp->icmp_data; 141 tv_sub(&tvrecv,tvsend); /*接收和发送的时间差*/ 142 rtt=tvrecv.tv_sec*1000+tvrecv.tv_usec/1000; /*以毫秒为单位计算rtt*/ 143 /*显示相关信息*/ 144 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);} 145 else 146 return -1; 147 } 148 main(int argc,char *argv[]) 149 { 150 struct hostent *host; 151 struct protoent *protocol; 152 unsigned long inaddr=0l; 153 int waittime=MAX_WAIT_TIME; 154 int size=50*1024; 155 if(argc<2) 156 { 157 printf("usage:%s hostname/IP address\n",argv[0]); 158 exit(1); 159 } 160 if( (protocol=getprotobyname("icmp") )==NULL) 161 { 162 perror("getprotobyname"); 163 exit(1); 164 } 165 /*生成使用ICMP的原始套接字,这种套接字只有root才能生成*/ 166 if( (sockfd=socket(AF_INET,SOCK_RAW,protocol->p_proto) )<0) 167 { 168 perror("socket error"); 169 exit(1); 170 } 171 /* 回收root权限,设置当前用户权限*/ 172 setuid(getuid()); 173 /*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*/ 174 setsockopt(sockfd,SOL_SOCKET,SO_RCVBUF,&size,sizeof(size) ); 175 bzero(&dest_addr,sizeof(dest_addr)); 176 dest_addr.sin_family=AF_INET; 177 /*判断是主机名还是ip地址*/ 178 if( inaddr=inet_addr(argv[1])==INADDR_NONE) 179 { 180 if((host=gethostbyname(argv[1]) )==NULL) /*是主机名*/ 181 { 182 perror("gethostbyname error"); 183 exit(1); 184 } 185 memcpy( (char *)&dest_addr.sin_addr,host->h_addr,host->h_length); 186 } 187 else /*是ip地址*/ 188 memcpy( (char *)&dest_addr,(char *)&inaddr,host->h_length); 189 /*获取main的进程id,用于设置ICMP的标志符*/ 190 pid=getpid(); 191 printf("PING %s(%s): %d bytes data in ICMP packets.\n",argv[1],inet_ntoa(dest_addr.sin_addr),datalen); 192 send_packet(); /*发送所有ICMP报文*/ 193 recv_packet(); /*接收所有ICMP报文*/ 194 statistics(SIGALRM); /*进行统计*/ 195 return 0; 196 } 197 /*两个timeval结构相减*/ 198 void tv_sub(struct timeval *out,struct timeval *in) 199 { 200 if( (out->tv_usec-=in->tv_usec)<0) 201 { 202 --out->tv_sec; 203 out->tv_usec+=1000000; 204 } 205 out->tv_sec-=in->tv_sec; 206 } 207 /*------------- The End -----------*/
仍然需要注意权限的问题，按照如下方式编译：
sudo gcc myping.c -o myping
sudo chmod u+s myping
./myping www.163.com
运行显示结果：
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
