src/network/dns_parse.c

   1 #include <string.h>
   2 #include "lookup.h"
   3
   4 int __dns_parse(const unsigned char *r, int rlen, int (*callback)(void *, int, const void *, int, const void *, int), void *ctx)
   5 {
   6         int qdcount, ancount;
   7         const unsigned char *p;
   8         int len;
   9
  10         if (rlen<12) return -1;
  11         if ((r[3]&15)) return 0;
  12         p = r+12;
  13         qdcount = r[4]*256 + r[5];
  14         ancount = r[6]*256 + r[7];
  15         if (qdcount+ancount > 64) return -1;
  16         while (qdcount--) {
  17                 while (p-r < rlen && *p-1U < 127) p++;
  18                 if (p>r+rlen-6)
  19                         return -1;
  20                 p += 5 + !!*p;
  21         }
  22         while (ancount--) {
  23                 while (p-r < rlen && *p-1U < 127) p++;
  24                 if (p>r+rlen-12)
  25                         return -1;
  26                 p += 1 + !!*p;
  27                 len = p[8]*256 + p[9];
  28                 if (len+10 > r+rlen-p) return -1;
  29                 if (callback(ctx, p[1], p+10, len, r, rlen) < 0) return -1;
  30                 p += 10 + len;
  31         }
  32         return 0;
  33 }