Linux下DNS反向解析程序C原代码

#include <netdb.h> #include <stdio.h> #include <stdlib.h> #include <sys/socket.h> #include <netinet/in.h> #define MAX_MASK 0xffffffff void init_mask(unsigned long int *, unsigned short int); unsigned long int _stoi(char *); int main(int argc, char **argv) { struct hostent *host; unsigned long int Mask[33], addrn=0,addrnl,addrnh=0,addr; unsigned long int addri[4], addril[4], addrih[4], maskl=32; unsigned short int i=0, j=0, k=0,l=0; char addrs[4][4], addrsh[4][4],maskls[3], *c; for(i=0;i<4;i++) addrs[i][0]=addrsh[i][0]='\0'; maskls[0]='\0'; addril[0] = 1; addrih[0] = 223; addril[1] = 0; addrih[1] = 255; addril[2] = 0; addrih[2] = 255; addril[3] = 0; addrih[3] = 255; init_mask(Mask,32); /* Test of init_mask for(i=0; i< 33; i++) printf("Mask[%d]= %x\n",i, Mask[i]); exit(0); */ c = argv[0]; if(argc < 2) goto EXIT; i = 0; for(argv++; *argv!=NULL; argv++) { while(**argv!='\0') { if(k==0) { if(**argv >= '0' && **argv <= '9') { if(j>2) goto EXIT; addrs[i][j++]=*((*argv)++); addrs[i][j]='\0'; } else if(**argv == '.') { if(i>3) goto EXIT; i++; j=0; (*argv)++; } else if(**argv == '/') { (*argv)++; i=j=0; k=1; } else if(**argv == '-') { (*argv)++; i=j=0; k=2; } else goto EXIT; } else if (k==1) { if(**argv >= '0' && **argv <='9') { if(i>1) goto EXIT; maskls[i++]=*((*argv)++); maskls[i]='\0'; } else goto EXIT; } else { if(**argv >= '0' && **argv <= '9') { if(j>2) goto EXIT; addrsh[i][j++]=*((*argv)++); addrsh[i][j]='\0'; } else if(**argv == '.') { if(i>3) goto EXIT; i++, j=0; (*argv)++; } else goto EXIT; } } } /* Test IP address and mask read in for(i=0;i<4;i++) printf("Address string [i] is: %s\n",addrs[i]); printf("Mask length is: %s\n",maskls); exit(0); */ for(i=0;i<4;i++) { addri[i] = _stoi(addrs[i]); if((addri[i]<addril[i])||(addri[i]>addrih[i])) goto EXIT; } if(maskls[0]!='\0') maskl = _stoi(maskls); if(maskl>32) goto EXIT; /* Test Address and mask transform for(i=0;i<4;i++) printf("Address part [i] is: %d\n",addri[i]); printf("Mask length is: %d\n",maskl); exit(0); */ for(i=0;i<4;i++) addrn = (addrn << 8) | addri[i]; /* Test IP address printf("IP address in Hex mode is : %x\n",addrn); */ if(k==2) { addrnl = addrn; for(i=0; i<4 && addrsh[i][0]!='\0';i++); for(j=0,l=4-i; j<i; j++,l++) { addri[l] = _stoi(addrsh[j]); if((addri[l]<addril[l])||(addri[l]>addrih[l])) goto EXIT; } for(i=0;i<4;i++) addrnh = (addrnh << 8) | addri[i]; } else { addrnl = addrn & Mask[maskl]; addrnh = addrnl | (Mask[maskl]^MAX_MASK); } /* Test addrnl and addrnh printf("addrnl is %x\naddrnh is: %x\n", addrnl, addrnh); */ for(addrn = addrnl; addrn <= addrnh; addrn++) { addr = htonl(addrn); host=gethostbyaddr((void *)&addr,4,AF_INET); fprintf(stdout,"IP address: %s", inet_ntoa(addr)); if(host!=NULL) fprintf(stdout,"\tHostname: %s\n", host->h_name); else fprintf(stdout,"\n"); } exit(0); EXIT: fprintf(stdout,"Usage:\t%s X.Y.Y.Y/Z\n\ OR:\t%s X.Y.Y.Y - [[[X].Y].Y].Y]\n\ \tYou can add space or tab around the '/' or '-' at will \n\ \tX should be between 1 and 233\n\ \tY should be between 0 and 255\n\ \tZ should be between 0 and 32\n", c, c); exit(1); } void init_mask(unsigned long int * Mask, unsigned short int Maskl) { int i; Mask[Maskl] = MAX_MASK; for(i = Maskl; i>0; i--) Mask[i-1] = Mask[i] << 1; } unsigned long int _stoi(char *string) { unsigned long int num = 0; for(; *string != '\0'; string++) num = *string-'0'+num*10; return num; }