src/network/dns_parse.c

   1 #include <string.h>
   2
   3 int __dns_parse(const unsigned char *r, int rlen, int (*callback)(void *, int, const void *, int, const void *), void *ctx)
   4 {
   5         int qdcount, ancount;
   6         const unsigned char *p;
   7         int len;
   8
   9         if (rlen<12) return -1;
  10         if ((r[3]&15)) return 0;
  11         p = r+12;
  12         qdcount = r[4]*256 + r[5];
  13         ancount = r[6]*256 + r[7];
  14         if (qdcount+ancount > 64) return -1;
  15         while (qdcount--) {
  16                 while (p-r < rlen && *p-1U < 127) p++;
  17                 if (*p>193 || (*p==193 && p[1]>254) || p>r+rlen-6)
  18                         return -1;
  19                 p += 5 + !!*p;
  20         }
  21         while (ancount--) {
  22                 while (p-r < rlen && *p-1U < 127) p++;
  23                 if (*p>193 || (*p==193 && p[1]>254) || p>r+rlen-6)
  24                         return -1;
  25                 p += 1 + !!*p;
  26                 len = p[8]*256 + p[9];
  27                 if (p+len > r+rlen) return -1;
  28                 if (callback(ctx, p[1], p+10, len, r) < 0) return -1;
  29                 p += 10 + len;
  30         }
  31         return 0;
  32 }