OpenGrok

/*
 * util/data/dname.h - domain name handling
 *
 * Copyright (c) 2007, NLnet Labs. All rights reserved.
 *
 * This software is open source.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the NLNET LABS nor the names of its contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * \file
 *
 * This file contains domain name handling functions.
 */

#include "config.h"
#include <ctype.h>
#include "util/data/dname.h"
#include "util/data/msgparse.h"
#include "util/log.h"
#include "util/storage/lookup3.h"
#include "sldns/sbuffer.h"

/* determine length of a dname in buffer, no compression pointers allowed */
size_t
query_dname_len(sldns_buffer* query)
{
	size_t len = 0;
	size_t labellen;
	while(1) {
		if(sldns_buffer_remaining(query) < 1)
			return 0; /* parse error, need label len */
		labellen = sldns_buffer_read_u8(query);
		if((labellen&0xc0))
			return 0; /* no compression allowed in queries */
		len += labellen + 1;
		if(len > LDNS_MAX_DOMAINLEN)
			return 0; /* too long */
		if(labellen == 0)
			return len;
		if(sldns_buffer_remaining(query) < labellen)
			return 0; /* parse error, need content */
		sldns_buffer_skip(query, (ssize_t)labellen);
	}
}

size_t
dname_valid(uint8_t* dname, size_t maxlen)
{
	size_t len = 0;
	size_t labellen;
	if(maxlen == 0)
		return 0; /* too short, shortest is '0' root label */
	labellen = *dname++;
	while(labellen) {
		if((labellen&0xc0))
			return 0; /* no compression ptrs allowed */
		len += labellen + 1;
		if(len >= LDNS_MAX_DOMAINLEN)
			return 0; /* too long */
		if(len > maxlen)
			return 0; /* does not fit in memory allocation */
		dname += labellen;
		labellen = *dname++;
	}
	len += 1;
	if(len > maxlen)
		return 0; /* does not fit in memory allocation */
	return len;
}

/** compare uncompressed, noncanonical, registers are hints for speed */
int
query_dname_compare(register uint8_t* d1, register uint8_t* d2)
{
	register uint8_t lab1, lab2;
	log_assert(d1 && d2);
	lab1 = *d1++;
	lab2 = *d2++;
	while( lab1 != 0 || lab2 != 0 ) {
		/* compare label length */
		/* if one dname ends, it has labellength 0 */
		if(lab1 != lab2) {
			if(lab1 < lab2)
				return -1;
			return 1;
		}
		log_assert(lab1 == lab2 && lab1 != 0);
		/* compare lowercased labels. */
		while(lab1--) {
			/* compare bytes first for speed */
			if(*d1 != *d2 &&
				tolower((unsigned char)*d1) != tolower((unsigned char)*d2)) {
				if(tolower((unsigned char)*d1) < tolower((unsigned char)*d2))
					return -1;
				return 1;
			}
			d1++;
			d2++;
		}
		/* next pair of labels. */
		lab1 = *d1++;
		lab2 = *d2++;
	}
	return 0;
}

void
query_dname_tolower(uint8_t* dname)
{
	/* the dname is stored uncompressed */
	uint8_t labellen;
	labellen = *dname;
	while(labellen) {
		dname++;
		while(labellen--) {
			*dname = (uint8_t)tolower((unsigned char)*dname);
			dname++;
		}
		labellen = *dname;
	}
}

void
pkt_dname_tolower(sldns_buffer* pkt, uint8_t* dname)
{
	uint8_t lablen;
	int count = 0;
	if(dname >= sldns_buffer_end(pkt))
		return;
	lablen = *dname++;
	while(lablen) {
		if(LABEL_IS_PTR(lablen)) {
			if((size_t)PTR_OFFSET(lablen, *dname)
				>= sldns_buffer_limit(pkt))
				return;
			dname = sldns_buffer_at(pkt, PTR_OFFSET(lablen, *dname));
			lablen = *dname++;
			if(count++ > MAX_COMPRESS_PTRS)
				return;
			continue;
		}
		if(dname+lablen >= sldns_buffer_end(pkt))
			return;
		while(lablen--) {
			*dname = (uint8_t)tolower((unsigned char)*dname);
			dname++;
		}
		if(dname >= sldns_buffer_end(pkt))
			return;
		lablen = *dname++;
	}
}


size_t
pkt_dname_len(sldns_buffer* pkt)
{
	size_t len = 0;
	int ptrcount = 0;
	uint8_t labellen;
	size_t endpos = 0;

	/* read dname and determine length */
	/* check compression pointers, loops, out of bounds */
	while(1) {
		/* read next label */
		if(sldns_buffer_remaining(pkt) < 1)
			goto fail;
		labellen = sldns_buffer_read_u8(pkt);
		if(LABEL_IS_PTR(labellen)) {
			/* compression ptr */
			uint16_t ptr;
			if(sldns_buffer_remaining(pkt) < 1)
				goto fail;
			ptr = PTR_OFFSET(labellen, sldns_buffer_read_u8(pkt));
			if(ptrcount++ > MAX_COMPRESS_PTRS)
				goto fail; /* loop! */
			if(sldns_buffer_limit(pkt) <= ptr)
				goto fail; /* out of bounds! */
			if(!endpos)
				endpos = sldns_buffer_position(pkt);
			sldns_buffer_set_position(pkt, ptr);
		} else {
			/* label contents */
			if(labellen > 0x3f)
				goto fail; /* label too long */
			len += 1 + labellen;
			if(len > LDNS_MAX_DOMAINLEN)
				goto fail;
			if(labellen == 0) {
				/* end of dname */
				break;
			}
			if(sldns_buffer_remaining(pkt) < labellen)
				goto fail;
			sldns_buffer_skip(pkt, (ssize_t)labellen);
		}
	}
	if(endpos)
		sldns_buffer_set_position(pkt, endpos);

	return len;
fail:
	/* Restore the position on failure too: callers (rdata_copy) compute
	 * the consumed field length from the buffer position and must not
	 * see a partial walk of a name that failed to parse. */
	if(endpos)
		sldns_buffer_set_position(pkt, endpos);
	return 0;
}

int
dname_pkt_compare(sldns_buffer* pkt, uint8_t* d1, uint8_t* d2)
{
	uint8_t len1, len2;
	int count1 = 0, count2 = 0;
	log_assert(pkt && d1 && d2);
	len1 = *d1++;
	len2 = *d2++;
	while( len1 != 0 || len2 != 0 ) {
		/* resolve ptrs */
		if(LABEL_IS_PTR(len1)) {
			if((size_t)PTR_OFFSET(len1, *d1)
				>= sldns_buffer_limit(pkt))
				return -1;
			if(count1++ > MAX_COMPRESS_PTRS)
				return -1;
			d1 = sldns_buffer_at(pkt, PTR_OFFSET(len1, *d1));
			len1 = *d1++;
			continue;
		}
		if(LABEL_IS_PTR(len2)) {
			if((size_t)PTR_OFFSET(len2, *d2)
				>= sldns_buffer_limit(pkt))
				return 1;
			if(count2++ > MAX_COMPRESS_PTRS)
				return 1;
			d2 = sldns_buffer_at(pkt, PTR_OFFSET(len2, *d2));
			len2 = *d2++;
			continue;
		}
		/* check label length */
		log_assert(len1 <= LDNS_MAX_LABELLEN);
		log_assert(len2 <= LDNS_MAX_LABELLEN);
		if(len1 != len2) {
			if(len1 < len2) return -1;
			return 1;
		}
		log_assert(len1 == len2 && len1 != 0);
		/* compare labels */
		while(len1--) {
			if(tolower((unsigned char)*d1) != tolower((unsigned char)*d2)) {
				if(tolower((unsigned char)*d1) < tolower((unsigned char)*d2))
					return -1;
				return 1;
			}
			d1++;
			d2++;
		}
		len1 = *d1++;
		len2 = *d2++;
	}
	return 0;
}

hashvalue_type
dname_query_hash(uint8_t* dname, hashvalue_type h)
{
	uint8_t labuf[LDNS_MAX_LABELLEN+1];
	uint8_t lablen;
	int i;

	/* preserve case of query, make hash label by label */
	lablen = *dname++;
	while(lablen) {
		log_assert(lablen <= LDNS_MAX_LABELLEN);
		labuf[0] = lablen;
		i=0;
		while(lablen--) {
			labuf[++i] = (uint8_t)tolower((unsigned char)*dname);
			dname++;
		}
		h = hashlittle(labuf, labuf[0] + 1, h);
		lablen = *dname++;
	}

	return h;
}

hashvalue_type
dname_pkt_hash(sldns_buffer* pkt, uint8_t* dname, hashvalue_type h)
{
	uint8_t labuf[LDNS_MAX_LABELLEN+1];
	uint8_t lablen;
	int i;
	int count = 0;

	/* preserve case of query, make hash label by label */
	lablen = *dname++;
	while(lablen) {
		if(LABEL_IS_PTR(lablen)) {
			/* follow pointer */
			if((size_t)PTR_OFFSET(lablen, *dname)
				>= sldns_buffer_limit(pkt))
				return h;
			if(count++ > MAX_COMPRESS_PTRS)
				return h;
			dname = sldns_buffer_at(pkt, PTR_OFFSET(lablen, *dname));
			lablen = *dname++;
			continue;
		}
		log_assert(lablen <= LDNS_MAX_LABELLEN);
		labuf[0] = lablen;
		i=0;
		while(lablen--) {
			labuf[++i] = (uint8_t)tolower((unsigned char)*dname);
			dname++;
		}
		h = hashlittle(labuf, labuf[0] + 1, h);
		lablen = *dname++;
	}

	return h;
}

void dname_pkt_copy(sldns_buffer* pkt, uint8_t* to, uint8_t* dname)
{
	/* copy over the dname and decompress it at the same time */
	size_t comprcount = 0;
	size_t len = 0;
	uint8_t lablen;
	lablen = *dname++;
	while(lablen) {
		if(LABEL_IS_PTR(lablen)) {
			if(comprcount++ > MAX_COMPRESS_PTRS) {
				/* too many compression pointers */
				*to = 0; /* end the result prematurely */
				return;
			}
			/* follow pointer */
			if((size_t)PTR_OFFSET(lablen, *dname)
				>= sldns_buffer_limit(pkt))
				return;
			dname = sldns_buffer_at(pkt, PTR_OFFSET(lablen, *dname));
			lablen = *dname++;
			continue;
		}
		if(lablen > LDNS_MAX_LABELLEN) {
			*to = 0; /* end the result prematurely */
			return;
		}
		log_assert(lablen <= LDNS_MAX_LABELLEN);
		len += (size_t)lablen+1;
		if(len >= LDNS_MAX_DOMAINLEN) {
			*to = 0; /* end the result prematurely */
			log_err("bad dname in dname_pkt_copy");
			return;
		}
		*to++ = lablen;
		memmove(to, dname, lablen);
		dname += lablen;
		to += lablen;
		lablen = *dname++;
	}
	/* copy last \0 */
	*to = 0;
}

void dname_print(FILE* out, struct sldns_buffer* pkt, uint8_t* dname)
{
	uint8_t lablen;
	int count = 0;
	if(!out) out = stdout;
	if(!dname) return;

	lablen = *dname++;
	if(!lablen)
		fputc('.', out);
	while(lablen) {
		if(LABEL_IS_PTR(lablen)) {
			/* follow pointer */
			if(!pkt) {
				fputs("??compressionptr??", out);
				return;
			}
			if((size_t)PTR_OFFSET(lablen, *dname)
				>= sldns_buffer_limit(pkt)) {
				fputs("??compressionptr??", out);
				return;
			}
			if(count++ > MAX_COMPRESS_PTRS) {
				fputs("??compressionptr??", out);
				return;
			}
			dname = sldns_buffer_at(pkt, PTR_OFFSET(lablen, *dname));
			lablen = *dname++;
			continue;
		}
		if(lablen > LDNS_MAX_LABELLEN) {
			fputs("??extendedlabel??", out);
			return;
		}
		while(lablen--)
			fputc((int)*dname++, out);
		fputc('.', out);
		lablen = *dname++;
	}
}

int
dname_count_labels(uint8_t* dname)
{
	uint8_t lablen;
	int labs = 1;

	lablen = *dname++;
	while(lablen) {
		labs++;
		dname += lablen;
		lablen = *dname++;
	}
	return labs;
}

int
dname_count_size_labels(uint8_t* dname, size_t* size)
{
	uint8_t lablen;
	int labs = 1;
	size_t sz = 1;

	lablen = *dname++;
	while(lablen) {
		labs++;
		sz += lablen+1;
		dname += lablen;
		lablen = *dname++;
	}
	*size = sz;
	return labs;
}

/**
 * Compare labels in memory, lowercase while comparing.
 * @param p1: label 1
 * @param p2: label 2
 * @param len: number of bytes to compare.
 * @return: 0, -1, +1 comparison result.
 */
static int
memlowercmp(uint8_t* p1, uint8_t* p2, uint8_t len)
{
	while(len--) {
		if(*p1 != *p2 && tolower((unsigned char)*p1) != tolower((unsigned char)*p2)) {
			if(tolower((unsigned char)*p1) < tolower((unsigned char)*p2))
				return -1;
			return 1;
		}
		p1++;
		p2++;
	}
	return 0;
}

int
dname_lab_cmp(uint8_t* d1, int labs1, uint8_t* d2, int labs2, int* mlabs)
{
	uint8_t len1, len2;
	int atlabel = labs1;
	int lastmlabs;
	int lastdiff = 0;
	/* first skip so that we compare same label. */
	if(labs1 > labs2) {
		while(atlabel > labs2) {
			len1 = *d1++;
			d1 += len1;
			atlabel--;
		}
		log_assert(atlabel == labs2);
	} else if(labs1 < labs2) {
		atlabel = labs2;
		while(atlabel > labs1) {
			len2 = *d2++;
			d2 += len2;
			atlabel--;
		}
		log_assert(atlabel == labs1);
	}
	lastmlabs = atlabel+1;
	/* now at same label in d1 and d2, atlabel */
	/* www.example.com.                  */
	/* 4   3       2  1   atlabel number */
	/* repeat until at root label (which is always the same) */
	while(atlabel > 1) {
		len1 = *d1++;
		len2 = *d2++;
		if(len1 != len2) {
			log_assert(len1 != 0 && len2 != 0);
			if(len1<len2)
				lastdiff = -1;
			else	lastdiff = 1;
			lastmlabs = atlabel;
			d1 += len1;
			d2 += len2;
		} else {
			/* memlowercmp is inlined here; or just like
			 * if((c=memlowercmp(d1, d2, len1)) != 0) {
			 *	lastdiff = c;
			 *	lastmlabs = atlabel; } apart from d1++,d2++ */
			while(len1) {
				if(*d1 != *d2 && tolower((unsigned char)*d1)
					!= tolower((unsigned char)*d2)) {
					if(tolower((unsigned char)*d1) <
						tolower((unsigned char)*d2)) {
						lastdiff = -1;
						lastmlabs = atlabel;
						d1 += len1;
						d2 += len1;
						break;
					}
					lastdiff = 1;
					lastmlabs = atlabel;
					d1 += len1;
					d2 += len1;
					break; /* out of memlowercmp */
				}
				d1++;
				d2++;
				len1--;
			}
		}
		atlabel--;
	}
	/* last difference atlabel number, so number of labels matching,
	 * at the right side, is one less. */
	*mlabs = lastmlabs-1;
	if(lastdiff == 0) {
		/* all labels compared were equal, check if one has more
		 * labels, so that example.com. > com. */
		if(labs1 > labs2)
			return 1;
		else if(labs1 < labs2)
			return -1;
	}
	return lastdiff;
}

int
dname_lab_startswith(uint8_t* label, char* prefix, char** endptr)
{
	size_t plen = strlen(prefix);
	size_t orig_plen = plen;
	size_t lablen = (size_t)*label;
	if(plen > lablen)
		return 0;
	label++;
	while(plen--) {
		if(*prefix != tolower((unsigned char)*label)) {
			return 0;
		}
		prefix++; label++;
	}
	if(orig_plen < lablen)
		*endptr = (char *)label;
	else
		/* prefix length == label length */
		*endptr = NULL;
	return 1;
}

int
dname_has_label(uint8_t* dname, size_t dnamelen, uint8_t* label)
{
	size_t len;

	/* 1 byte needed for the label length */
	if(dnamelen < 1)
		return 0;

	len = *dname;
	while(len <= dnamelen) {
		if(!(*dname)) {
			if(*dname == *label)
				return 1; /* empty label match */
			/* termination label found, stop iterating */
			return 0;
		}
		if(*dname == *label && *label &&
			memlowercmp(dname+1, label+1, *dname) == 0)
			return 1;
		len += *dname;
		dname += *dname;
		dname++;
		len++;
	}
	return 0;
}

int
dname_buffer_write(sldns_buffer* pkt, uint8_t* dname)
{
	uint8_t lablen;

	if(sldns_buffer_remaining(pkt) < 1)
		return 0;
	lablen = *dname++;
	sldns_buffer_write_u8(pkt, lablen);
	while(lablen) {
		if(sldns_buffer_remaining(pkt) < (size_t)lablen+1)
			return 0;
		sldns_buffer_write(pkt, dname, lablen);
		dname += lablen;
		lablen = *dname++;
		sldns_buffer_write_u8(pkt, lablen);
	}
	return 1;
}

void dname_str(uint8_t* dname, char* str)
{
	size_t len = 0;
	uint8_t lablen = 0;
	char* s = str;
	if(!dname || !*dname) {
		*s++ = '.';
		*s = 0;
		return;
	}
	lablen = *dname++;
	while(lablen) {
		len += lablen+1;
		if(len >= LDNS_MAX_DOMAINLEN) {
			if ((s-str) >= (LDNS_MAX_DOMAINLEN-1))
				s = str + LDNS_MAX_DOMAINLEN - 2;
			*s++ = '&';
			*s = 0;
			return;
		}
		if(lablen > LDNS_MAX_LABELLEN) {
			*s++ = '#';
			*s = 0;
			return;
		}
		while(lablen--) {
			if(isalnum((unsigned char)*dname)
				|| *dname == '-' || *dname == '_'
				|| *dname == '*')
				*s++ = *(char*)dname++;
			else	{
				*s++ = '?';
				dname++;
			}
		}
		*s++ = '.';
		lablen = *dname++;
	}
	*s = 0;
}

int
dname_strict_subdomain(uint8_t* d1, int labs1, uint8_t* d2, int labs2)
{
	int m;
	/* check subdomain: d1: www.example.com. and d2: example.com. */
	if(labs2 >= labs1)
		return 0;
	if(dname_lab_cmp(d1, labs1, d2, labs2, &m) > 0) {
		/* subdomain if all labels match */
		return (m == labs2);
	}
	return 0;
}

int
dname_strict_subdomain_c(uint8_t* d1, uint8_t* d2)
{
	return dname_strict_subdomain(d1, dname_count_labels(d1), d2,
		dname_count_labels(d2));
}

int
dname_subdomain_c(uint8_t* d1, uint8_t* d2)
{
	int m;
	/* check subdomain: d1: www.example.com. and d2: example.com. */
	/*  	or 	    d1: example.com. and d2: example.com. */
	int labs1 = dname_count_labels(d1);
	int labs2 = dname_count_labels(d2);
	if(labs2 > labs1)
		return 0;
	if(dname_lab_cmp(d1, labs1, d2, labs2, &m) < 0) {
		/* must have been example.com , www.example.com - wrong */
		/* or otherwise different dnames */
		return 0;
	}
	return (m == labs2);
}

int
dname_is_root(uint8_t* dname)
{
	uint8_t len;
	log_assert(dname);
	len = dname[0];
	log_assert(!LABEL_IS_PTR(len));
	return (len == 0);
}

void
dname_remove_label(uint8_t** dname, size_t* len)
{
	size_t lablen;
	log_assert(dname && *dname && len);
	lablen = (*dname)[0];
	log_assert(!LABEL_IS_PTR(lablen));
	log_assert(*len > lablen);
	if(lablen == 0)
		return; /* do not modify root label */
	*len -= lablen+1;
	*dname += lablen+1;
}

int
dname_remove_label_limit_len(uint8_t** dname, size_t* len, size_t lenlimit)
{
	size_t lablen;
	log_assert(dname && *dname && len);
	lablen = (*dname)[0];
	log_assert(!LABEL_IS_PTR(lablen));
	log_assert(*len > lablen);
	if(lablen == 0)
		return 0; /* do not modify root label */
	if(*len - (lablen + 1) < lenlimit) return 0;
	*len -= lablen+1;
	*dname += lablen+1;
	return 1;
}

void
dname_remove_labels(uint8_t** dname, size_t* len, int n)
{
	int i;
	for(i=0; i<n; i++)
		dname_remove_label(dname, len);
}

int
dname_signame_label_count(uint8_t* dname)
{
	uint8_t lablen;
	int count = 0;
	if(!*dname)
		return 0;
	if(dname[0] == 1 && dname[1] == '*')
		dname += 2;
	lablen = dname[0];
	while(lablen) {
		count++;
		dname += lablen;
		dname += 1;
		lablen = dname[0];
	}
	return count;
}

int
dname_is_wild(uint8_t* dname)
{
	return (dname[0] == 1 && dname[1] == '*');
}

/**
 * Compare labels in memory, lowercase while comparing.
 * Returns canonical order for labels. If all is equal, the
 * shortest is first.
 *
 * @param p1: label 1
 * @param len1: length of label 1.
 * @param p2: label 2
 * @param len2: length of label 2.
 * @return: 0, -1, +1 comparison result.
 */
static int
memcanoncmp(uint8_t* p1, uint8_t len1, uint8_t* p2, uint8_t len2)
{
	uint8_t min = (len1<len2)?len1:len2;
	int c = memlowercmp(p1, p2, min);
	if(c != 0)
		return c;
	/* equal, see who is shortest */
	if(len1 < len2)
		return -1;
	if(len1 > len2)
		return 1;
	return 0;
}


int
dname_canon_lab_cmp(uint8_t* d1, int labs1, uint8_t* d2, int labs2, int* mlabs)
{
	/* like dname_lab_cmp, but with different label comparison,
	 * empty character sorts before \000.
	 * So   ylyly is before z. */
	uint8_t len1, len2;
	int atlabel = labs1;
	int lastmlabs;
	int lastdiff = 0;
	int c;
	/* first skip so that we compare same label. */
	if(labs1 > labs2) {
		while(atlabel > labs2) {
			len1 = *d1++;
			d1 += len1;
			atlabel--;
		}
		log_assert(atlabel == labs2);
	} else if(labs1 < labs2) {
		atlabel = labs2;
		while(atlabel > labs1) {
			len2 = *d2++;
			d2 += len2;
			atlabel--;
		}
		log_assert(atlabel == labs1);
	}
	lastmlabs = atlabel+1;
	/* now at same label in d1 and d2, atlabel */
	/* www.example.com.                  */
	/* 4   3       2  1   atlabel number */
	/* repeat until at root label (which is always the same) */
	while(atlabel > 1) {
		len1 = *d1++;
		len2 = *d2++;

		if((c=memcanoncmp(d1, len1, d2, len2)) != 0) {
			if(c<0)
				lastdiff = -1;
			else	lastdiff = 1;
			lastmlabs = atlabel;
		}

		d1 += len1;
		d2 += len2;
		atlabel--;
	}
	/* last difference atlabel number, so number of labels matching,
	 * at the right side, is one less. */
	*mlabs = lastmlabs-1;
	if(lastdiff == 0) {
		/* all labels compared were equal, check if one has more
		 * labels, so that example.com. > com. */
		if(labs1 > labs2)
			return 1;
		else if(labs1 < labs2)
			return -1;
	}
	return lastdiff;
}

int
dname_canonical_compare(uint8_t* d1, uint8_t* d2)
{
	int labs1, labs2, m;
	labs1 = dname_count_labels(d1);
	labs2 = dname_count_labels(d2);
	return dname_canon_lab_cmp(d1, labs1, d2, labs2, &m);
}

uint8_t* dname_get_shared_topdomain(uint8_t* d1, uint8_t* d2)
{
	int labs1, labs2, m;
	size_t len = LDNS_MAX_DOMAINLEN;
	labs1 = dname_count_labels(d1);
	labs2 = dname_count_labels(d2);
	(void)dname_lab_cmp(d1, labs1, d2, labs2, &m);
	dname_remove_labels(&d1, &len, labs1-m);
	return d1;
}