github.com/afumu/libc@v0.0.6/musl/src/network/dns_parse.c (about)

     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  }