rdataslab.c

非常好的dns解析软件

/*
 * Copyright (C) 2004-2006  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 1999-2003  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/* $Id: rdataslab.c,v 1.35.18.5 2006/03/05 23:58:51 marka Exp $ */

/*! \file */

#include <config.h>

#include <stdlib.h>

#include <isc/mem.h>
#include <isc/region.h>
#include <isc/string.h>		/* Required for HP/UX (and others?) */
#include <isc/util.h>

#include <dns/result.h>
#include <dns/rdata.h>
#include <dns/rdataset.h>
#include <dns/rdataslab.h>

/*
 * The rdataslab structure allows iteration to occur in both load order
 * and DNSSEC order.  The structure is as follows:
 *
 *	header		(reservelen bytes)
 *	record count	(2 bytes)
 *	offset table	(4 x record count bytes in load order)
 *	data records
 *		data length	(2 bytes)
 *		order		(2 bytes)
 *		data		(data length bytes)
 *
 * Offsets are from the end of the header.
 *
 * Load order traversal is performed by walking the offset table to find
 * the start of the record.
 *
 * DNSSEC order traversal is performed by walking the data records.
 *
 * The order is stored with record to allow for efficient reconstuction of
 * of the offset table following a merge or subtraction.
 *
 * The iterator methods here currently only support DNSSEC order iteration.
 *
 * The iterator methods in rbtdb support both load order and DNSSEC order
 * iteration.
 *
 * WARNING:
 *	rbtdb.c directly interacts with the slab's raw structures.  If the
 *	structure changes then rbtdb.c also needs to be updated to reflect
 *	the changes.  See the areas tagged with "RDATASLAB".
 */

struct xrdata {
	dns_rdata_t	rdata;
	unsigned int	order;
};

/*% Note: the "const void *" are just to make qsort happy.  */
static int
compare_rdata(const void *p1, const void *p2) {
	const struct xrdata *x1 = p1;
	const struct xrdata *x2 = p2;
	return (dns_rdata_compare(&x1->rdata, &x2->rdata));
}

static void
fillin_offsets(unsigned char *offsetbase, unsigned int *offsettable,
	       unsigned length)
{
	unsigned int i, j;
	unsigned char *raw;

	for (i = 0, j = 0; i < length; i++) {

		if (offsettable[i] == 0)
			continue;

		/*
		 * Fill in offset table.
		 */
		raw = &offsetbase[j*4 + 2];
		*raw++ = (offsettable[i] & 0xff000000) >> 24;
		*raw++ = (offsettable[i] & 0xff0000) >> 16;
		*raw++ = (offsettable[i] & 0xff00) >> 8;
		*raw = offsettable[i] & 0xff;

		/*
		 * Fill in table index.
		 */
		raw = offsetbase + offsettable[i] + 2;
		*raw++ = (j & 0xff00) >> 8;
		*raw = j++ & 0xff;
	}
}

isc_result_t
dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
			   isc_region_t *region, unsigned int reservelen)
{
	struct xrdata  *x;
	unsigned char  *rawbuf;
	unsigned char  *offsetbase;
	unsigned int	buflen;
	isc_result_t	result;
	unsigned int	nitems;
	unsigned int	nalloc;
	unsigned int	i;
	unsigned int   *offsettable;

	buflen = reservelen + 2;

	nalloc = dns_rdataset_count(rdataset);
	nitems = nalloc;
	if (nitems == 0)
		return (ISC_R_FAILURE);

	if (nalloc > 0xffff)
		return (ISC_R_NOSPACE);

	x = isc_mem_get(mctx, nalloc * sizeof(struct xrdata));
	if (x == NULL)
		return (ISC_R_NOMEMORY);

	/*
	 * Save all of the rdata members into an array.
	 */
	result = dns_rdataset_first(rdataset);
	if (result != ISC_R_SUCCESS)
		goto free_rdatas;
	for (i = 0; i < nalloc && result == ISC_R_SUCCESS; i++) {
		INSIST(result == ISC_R_SUCCESS);
		dns_rdata_init(&x[i].rdata);
		dns_rdataset_current(rdataset, &x[i].rdata);
		x[i].order = i;
		result = dns_rdataset_next(rdataset);
	}
	if (result != ISC_R_NOMORE)
		goto free_rdatas;
	if (i != nalloc) {
		/*
		 * Somehow we iterated over fewer rdatas than
		 * dns_rdataset_count() said there were!
		 */
		result = ISC_R_FAILURE;
		goto free_rdatas;
	}

	/*
	 * Put into DNSSEC order.
	 */
	qsort(x, nalloc, sizeof(struct xrdata), compare_rdata);

	/*
	 * Remove duplicates and compute the total storage required.
	 *
	 * If an rdata is not a duplicate, accumulate the storage size
	 * required for the rdata.  We do not store the class, type, etc,
	 * just the rdata, so our overhead is 2 bytes for the number of
	 * records, and 8 for each rdata, (length(2), offset(4) and order(2))
	 * and then the rdata itself.
	 */
	for (i = 1; i < nalloc; i++) {
		if (compare_rdata(&x[i-1].rdata, &x[i].rdata) == 0) {
			x[i-1].rdata.data = NULL;
			x[i-1].rdata.length = 0;
			/*
			 * Preserve the least order so A, B, A -> A, B
			 * after duplicate removal.
			 */
			if (x[i-1].order < x[i].order)
				x[i].order = x[i-1].order;
			nitems--;
		} else
			buflen += (8 + x[i-1].rdata.length);
	}
	/*
	 * Don't forget the last item!
	 */
	buflen += (8 + x[i-1].rdata.length);

	/*
	 * Ensure that singleton types are actually singletons.
	 */
	if (nitems > 1 && dns_rdatatype_issingleton(rdataset->type)) {
		/*
		 * We have a singleton type, but there's more than one
		 * RR in the rdataset.
		 */
		result = DNS_R_SINGLETON;
		goto free_rdatas;
	}

	/*
	 * Allocate the memory, set up a buffer, start copying in
	 * data.
	 */
	rawbuf = isc_mem_get(mctx, buflen);
	if (rawbuf == NULL) {
		result = ISC_R_NOMEMORY;
		goto free_rdatas;
	}
	
	/* Allocate temporary offset table. */
	offsettable = isc_mem_get(mctx, nalloc * sizeof(unsigned int));
	if (offsettable == NULL) {
		isc_mem_put(mctx, rawbuf, buflen);
		result = ISC_R_NOMEMORY;
		goto free_rdatas;
	}
	memset(offsettable, 0, nalloc * sizeof(unsigned int));

	region->base = rawbuf;
	region->length = buflen;

	rawbuf += reservelen;
	offsetbase = rawbuf;

	*rawbuf++ = (nitems & 0xff00) >> 8;
	*rawbuf++ = (nitems & 0x00ff);

	/* Skip load order table.  Filled in later. */
	rawbuf += nitems * 4;

	for (i = 0; i < nalloc; i++) {
		if (x[i].rdata.data == NULL)
			continue;
		offsettable[x[i].order] = rawbuf - offsetbase;
		*rawbuf++ = (x[i].rdata.length & 0xff00) >> 8;
		*rawbuf++ = (x[i].rdata.length & 0x00ff);
		rawbuf += 2;	/* filled in later */
		memcpy(rawbuf, x[i].rdata.data, x[i].rdata.length);
		rawbuf += x[i].rdata.length;
	}
	
	fillin_offsets(offsetbase, offsettable, nalloc);

	isc_mem_put(mctx, offsettable, nalloc * sizeof(unsigned int));

	result = ISC_R_SUCCESS;

 free_rdatas:
	isc_mem_put(mctx, x, nalloc * sizeof(struct xrdata));
	return (result);
}

static void
rdataset_disassociate(dns_rdataset_t *rdataset) {
	UNUSED(rdataset);
}

static isc_result_t
rdataset_first(dns_rdataset_t *rdataset) {
	unsigned char *raw = rdataset->private3;
	unsigned int count;

	count = raw[0] * 256 + raw[1];
	if (count == 0) {
		rdataset->private5 = NULL;
		return (ISC_R_NOMORE);
	}
	raw += 2 + (4 * count);
	/*
	 * The privateuint4 field is the number of rdata beyond the cursor
	 * position, so we decrement the total count by one before storing
	 * it.
	 */
	count--;
	rdataset->privateuint4 = count;
	rdataset->private5 = raw;

	return (ISC_R_SUCCESS);
}

static isc_result_t
rdataset_next(dns_rdataset_t *rdataset) {
	unsigned int count;
	unsigned int length;
	unsigned char *raw;

	count = rdataset->privateuint4;
	if (count == 0)
		return (ISC_R_NOMORE);
	count--;
	rdataset->privateuint4 = count;
	raw = rdataset->private5;
	length = raw[0] * 256 + raw[1];
	raw += length + 4;
	rdataset->private5 = raw;

	return (ISC_R_SUCCESS);
}

static void
rdataset_current(dns_rdataset_t *rdataset, dns_rdata_t *rdata) {
	unsigned char *raw = rdataset->private5;
	isc_region_t r;

	REQUIRE(raw != NULL);

	r.length = raw[0] * 256 + raw[1];
	raw += 4;
	r.base = raw;
	dns_rdata_fromregion(rdata, rdataset->rdclass, rdataset->type, &r);
}

static void
rdataset_clone(dns_rdataset_t *source, dns_rdataset_t *target) {
	*target = *source;

	/*
	 * Reset iterator state.
	 */
	target->privateuint4 = 0;
	target->private5 = NULL;
}

static unsigned int
rdataset_count(dns_rdataset_t *rdataset) {
	unsigned char *raw = rdataset->private3;
	unsigned int count;

	count = raw[0] * 256 + raw[1];

	return (count);
}

static dns_rdatasetmethods_t rdataset_methods = {
	rdataset_disassociate,
	rdataset_first,
	rdataset_next,
	rdataset_current,
	rdataset_clone,
	rdataset_count,
	NULL,
	NULL,
	NULL,
	NULL,
	NULL
};

void
dns_rdataslab_tordataset(unsigned char *slab, unsigned int reservelen,
			 dns_rdataclass_t rdclass, dns_rdatatype_t rdtype,
			 dns_rdatatype_t covers, dns_ttl_t ttl,
			 dns_rdataset_t *rdataset)
{
	REQUIRE(slab != NULL);
	REQUIRE(!dns_rdataset_isassociated(rdataset));

	rdataset->methods = &rdataset_methods;
	rdataset->rdclass = rdclass;
	rdataset->type = rdtype;
	rdataset->covers = covers;
	rdataset->ttl = ttl;
	rdataset->trust = 0;
	rdataset->private1 = NULL;
	rdataset->private2 = NULL;
	rdataset->private3 = slab + reservelen;

	/*
	 * Reset iterator state.
	 */
	rdataset->privateuint4 = 0;
	rdataset->private5 = NULL;
}

unsigned int
dns_rdataslab_size(unsigned char *slab, unsigned int reservelen) {
	unsigned int count, length;
	unsigned char *current;

	REQUIRE(slab != NULL);

	current = slab + reservelen;
	count = *current++ * 256;
	count += *current++;
	current += (4 * count);
	while (count > 0) {
		count--;
		length = *current++ * 256;
		length += *current++;
		current += length + 2;
	}

	return ((unsigned int)(current - slab));
}

/*
 * Make the dns_rdata_t 'rdata' refer to the slab item
 * beginning at '*current', which is part of a slab of type
 * 'type' and class 'rdclass', and advance '*current' to
 * point to the next item in the slab.
 */
static inline void
rdata_from_slab(unsigned char **current,
	      dns_rdataclass_t rdclass, dns_rdatatype_t type,
	      dns_rdata_t *rdata)
{
	unsigned char *tcurrent = *current;
	isc_region_t region;

	region.length = *tcurrent++ * 256;
	region.length += *tcurrent++;
	tcurrent += 2;
	region.base = tcurrent;
	tcurrent += region.length;
	dns_rdata_fromregion(rdata, rdclass, type, &region);
	*current = tcurrent;
}

/*
 * Return true iff 'slab' (slab data of type 'type' and class 'rdclass')
 * contains an rdata identical to 'rdata'.  This does case insensitive
 * comparisons per DNSSEC.
 */
static inline isc_boolean_t
rdata_in_slab(unsigned char *slab, unsigned int reservelen,
	      dns_rdataclass_t rdclass, dns_rdatatype_t type,
	      dns_rdata_t *rdata)
{
	unsigned int count, i;
	unsigned char *current;
	dns_rdata_t trdata = DNS_RDATA_INIT;
	int n;

	current = slab + reservelen;
	count = *current++ * 256;
	count += *current++;

	current += (4 * count);

	for (i = 0; i < count; i++) {
		rdata_from_slab(&current, rdclass, type, &trdata);
		
		n = dns_rdata_compare(&trdata, rdata);
		if (n == 0)
			return (ISC_TRUE);
		if (n > 0)	/* In DNSSEC order. */
			break;
		dns_rdata_reset(&trdata);
	}