dns_parse.c raw

   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 *), 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>193 || (*p==193 && p[1]>254) || 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>193 || (*p==193 && p[1]>254) || p>r+rlen-6)
  25  			return -1;
  26  		p += 1 + !!*p;
  27  		len = p[8]*256 + p[9];
  28  		if (p+len > r+rlen) return -1;
  29  		if (callback(ctx, p[1], p+10, len, r) < 0) return -1;
  30  		p += 10 + len;
  31  	}
  32  	return 0;
  33  }
  34