rdata.h

非常好的dns解析软件

/*
 * Copyright (C) 2004, 2005  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 1998-2003  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: rdata.h,v 1.60.18.3 2005/05/19 04:59:56 marka Exp $ */

#ifndef DNS_RDATA_H
#define DNS_RDATA_H 1

/*****
 ***** Module Info
 *****/

/*! \file
 * \brief
 * Provides facilities for manipulating DNS rdata, including conversions to
 * and from wire format and text format.
 *
 * Given the large amount of rdata possible in a nameserver, it was important
 * to come up with a very efficient way of storing rdata, but at the same
 * time allow it to be manipulated.
 *
 * The decision was to store rdata in uncompressed wire format,
 * and not to make it a fully abstracted object; i.e. certain parts of the
 * server know rdata is stored that way.  This saves a lot of memory, and
 * makes adding rdata to messages easy.  Having much of the server know
 * the representation would be perilous, and we certainly don't want each
 * user of rdata to be manipulating such a low-level structure.  This is
 * where the rdata module comes in.  The module allows rdata handles to be
 * created and attached to uncompressed wire format regions.  All rdata
 * operations and conversions are done through these handles.
 *
 * Implementation Notes:
 *
 *\li	The routines in this module are expected to be synthesized by the
 *	build process from a set of source files, one per rdata type.  For
 *	portability, it's probably best that the building be done by a C
 *	program.  Adding a new rdata type will be a simple matter of adding
 *	a file to a directory and rebuilding the server.  *All* knowlege of
 *	the format of a particular rdata type is in this file.
 *
 * MP:
 *\li	Clients of this module must impose any required synchronization.
 *
 * Reliability:
 *\li	This module deals with low-level byte streams.  Errors in any of
 *	the functions are likely to crash the server or corrupt memory.
 *
 *\li	Rdata is typed, and the caller must know what type of rdata it has.
 *	A caller that gets this wrong could crash the server.
 *
 *\li	The fromstruct() and tostruct() routines use a void * pointer to
 *	represent the structure.  The caller must ensure that it passes a
 *	pointer to the appropriate type, or the server could crash or memory
 *	could be corrupted.
 *
 * Resources:
 *\li	None.
 *
 * Security:
 *
 *\li	*** WARNING ***
 *	dns_rdata_fromwire() deals with raw network data.  An error in
 *	this routine could result in the failure or hijacking of the server.
 *
 * Standards:
 *\li	RFC1035
 *\li	Draft EDNS0 (0)
 *\li	Draft EDNS1 (0)
 *\li	Draft Binary Labels (2)
 *\li	Draft Local Compression (1)
 *\li	Various RFCs for particular types; these will be documented in the
 *	 sources files of the types.
 *
 */

/***
 *** Imports
 ***/

#include <isc/lang.h>

#include <dns/types.h>
#include <dns/name.h>

ISC_LANG_BEGINDECLS


/***
 *** Types
 ***/

/*%
 ***** An 'rdata' is a handle to a binary region.  The handle has an RR
 ***** class and type, and the data in the binary region is in the format
 ***** of the given class and type.
 *****/
/*%
 * Clients are strongly discouraged from using this type directly, with
 * the exception of the 'link' field which may be used directly for whatever
 * purpose the client desires.
 */
struct dns_rdata {
	unsigned char *			data;
	unsigned int			length;
	dns_rdataclass_t		rdclass;
	dns_rdatatype_t			type;
	unsigned int			flags;
	ISC_LINK(dns_rdata_t)		link;
};

#define DNS_RDATA_INIT { NULL, 0, 0, 0, 0, {(void*)(-1), (void *)(-1)}}

#define DNS_RDATA_UPDATE	0x0001		/*%< update pseudo record */

/*
 * Flags affecting rdata formatting style.  Flags 0xFFFF0000
 * are used by masterfile-level formatting and defined elsewhere.
 * See additional comments at dns_rdata_tofmttext().
 */

/*% Split the rdata into multiple lines to try to keep it
 within the "width". */
#define DNS_STYLEFLAG_MULTILINE		0x00000001U

/*% Output explanatory comments. */
#define DNS_STYLEFLAG_COMMENT		0x00000002U

#define DNS_RDATA_DOWNCASE		DNS_NAME_DOWNCASE
#define DNS_RDATA_CHECKNAMES		DNS_NAME_CHECKNAMES
#define DNS_RDATA_CHECKNAMESFAIL	DNS_NAME_CHECKNAMESFAIL
#define DNS_RDATA_CHECKREVERSE		DNS_NAME_CHECKREVERSE
#define DNS_RDATA_CHECKMX		DNS_NAME_CHECKMX
#define DNS_RDATA_CHECKMXFAIL		DNS_NAME_CHECKMXFAIL

/***
 *** Initialization
 ***/

void
dns_rdata_init(dns_rdata_t *rdata);
/*%<
 * Make 'rdata' empty.
 *
 * Requires:
 *	'rdata' is a valid rdata (i.e. not NULL, points to a struct dns_rdata)
 */

void
dns_rdata_reset(dns_rdata_t *rdata);
/*%<
 * Make 'rdata' empty.
 *
 * Requires:
 *\li	'rdata' is a previously initialized rdata and is not linked.
 */

void
dns_rdata_clone(const dns_rdata_t *src, dns_rdata_t *target);
/*%<
 * Clone 'target' from 'src'.
 *
 * Requires:
 *\li	'src' to be initialized.
 *\li	'target' to be initialized.
 */

/***
 *** Comparisons
 ***/

int
dns_rdata_compare(const dns_rdata_t *rdata1, const dns_rdata_t *rdata2);
/*%<
 * Determine the relative ordering under the DNSSEC order relation of
 * 'rdata1' and 'rdata2'.
 *
 * Requires:
 *
 *\li	'rdata1' is a valid, non-empty rdata
 *
 *\li	'rdata2' is a valid, non-empty rdata
 *
 * Returns:
 *\li	< 0		'rdata1' is less than 'rdata2'
 *\li	0		'rdata1' is equal to 'rdata2'
 *\li	> 0		'rdata1' is greater than 'rdata2'
 */

/***
 *** Conversions
 ***/

void
dns_rdata_fromregion(dns_rdata_t *rdata, dns_rdataclass_t rdclass,
		     dns_rdatatype_t type, isc_region_t *r);
/*%<
 * Make 'rdata' refer to region 'r'.
 *
 * Requires:
 *
 *\li	The data in 'r' is properly formatted for whatever type it is.
 */

void
dns_rdata_toregion(const dns_rdata_t *rdata, isc_region_t *r);
/*%<
 * Make 'r' refer to 'rdata'.
 */

isc_result_t
dns_rdata_fromwire(dns_rdata_t *rdata, dns_rdataclass_t rdclass,
		   dns_rdatatype_t type, isc_buffer_t *source,
		   dns_decompress_t *dctx, unsigned int options,
		   isc_buffer_t *target);
/*%<
 * Copy the possibly-compressed rdata at source into the target region.
 *
 * Notes:
 *\li	Name decompression policy is controlled by 'dctx'.
 *
 *	'options'
 *\li	DNS_RDATA_DOWNCASE	downcase domain names when they are copied
 *				into target.
 *
 * Requires:
 *
 *\li	'rdclass' and 'type' are valid.
 *
 *\li	'source' is a valid buffer, and the active region of 'source'
 *	references the rdata to be processed.
 *
 *\li	'target' is a valid buffer.
 *
 *\li	'dctx' is a valid decompression context.
 *
 * Ensures,
 *	if result is success:
 *	\li 	If 'rdata' is not NULL, it is attached to the target.
 *	\li	The conditions dns_name_fromwire() ensures for names hold
 *		for all names in the rdata.
 *	\li	The current location in source is advanced, and the used space
 *		in target is updated.
 *
 * Result:
 *\li	Success
 *\li	Any non-success status from dns_name_fromwire()
 *\li	Various 'Bad Form' class failures depending on class and type
 *\li	Bad Form: Input too short
 *\li	Resource Limit: Not enough space
 */

isc_result_t
dns_rdata_towire(dns_rdata_t *rdata, dns_compress_t *cctx,
		 isc_buffer_t *target);
/*%<
 * Convert 'rdata' into wire format, compressing it as specified by the
 * compression context 'cctx', and storing the result in 'target'.
 *
 * Notes:
 *\li	If the compression context allows global compression, then the
 *	global compression table may be updated.
 *
 * Requires:
 *\li	'rdata' is a valid, non-empty rdata
 *
 *\li	target is a valid buffer
 *
 *\li	Any offsets specified in a global compression table are valid
 *	for target.
 *
 * Ensures,
 *	if the result is success:
 *	\li	The used space in target is updated.
 *
 * Returns:
 *\li	Success
 *\li	Any non-success status from dns_name_towire()
 *\li	Resource Limit: Not enough space
 */

isc_result_t
dns_rdata_fromtext(dns_rdata_t *rdata, dns_rdataclass_t rdclass,
		   dns_rdatatype_t type, isc_lex_t *lexer, dns_name_t *origin,
		   unsigned int options, isc_mem_t *mctx,
		   isc_buffer_t *target, dns_rdatacallbacks_t *callbacks);
/*%<
 * Convert the textual representation of a DNS rdata into uncompressed wire
 * form stored in the target region.  Tokens constituting the text of the rdata
 * are taken from 'lexer'.
 *
 * Notes:
 *\li	Relative domain names in the rdata will have 'origin' appended to them.
 *	A NULL origin implies "origin == dns_rootname".
 *
 *
 *	'options'
 *\li	DNS_RDATA_DOWNCASE	downcase domain names when they are copied
 *				into target.
 *\li	DNS_RDATA_CHECKNAMES 	perform checknames checks.
 *\li	DNS_RDATA_CHECKNAMESFAIL fail if the checknames check fail.  If
 *				not set a warning will be issued.
 *\li	DNS_RDATA_CHECKREVERSE  this should set if the owner name ends
 *				in IP6.ARPA, IP6.INT or IN-ADDR.ARPA.
 *
 * Requires:
 *
 *\li	'rdclass' and 'type' are valid.
 *
 *\li	'lexer' is a valid isc_lex_t.
 *
 *\li	'mctx' is a valid isc_mem_t.
 *
 *\li	'target' is a valid region.
 *
 *\li	'origin' if non NULL it must be absolute.
 *	
 *\li	'callbacks' to be NULL or callbacks->warn and callbacks->error be
 *	initialized.
 *
 * Ensures, 
 *	if result is success:
 *\li	 	If 'rdata' is not NULL, it is attached to the target.

 *\li		The conditions dns_name_fromtext() ensures for names hold
 *		for all names in the rdata.

 *\li		The used space in target is updated.
 *
 * Result:
 *\li	Success
 *\li	Translated result codes from isc_lex_gettoken
 *\li	Various 'Bad Form' class failures depending on class and type
 *\li	Bad Form: Input too short
 *\li	Resource Limit: Not enough space
 *\li	Resource Limit: Not enough memory
 */