message.h 32.4 KB
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/*
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 * Copyright (C) 1999-2001  Internet Software Consortium.
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 *
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 * 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.
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 *
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 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM
 * DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
 * INTERNET SOFTWARE CONSORTIUM 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.
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 */

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/* $Id: message.h,v 1.102 2001/10/24 21:47:12 marka Exp $ */
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#ifndef DNS_MESSAGE_H
#define DNS_MESSAGE_H 1
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/***
 ***	Imports
 ***/

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#include <isc/lang.h>
#include <isc/magic.h>
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#include <dns/compress.h>
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#include <dns/masterdump.h>
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#include <dns/types.h>
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#include <dst/dst.h>

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/*
 * How this beast works:
 *
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 * When a dns message is received in a buffer, dns_message_fromwire() is called
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 * on the memory region.  Various items are checked including the format
 * of the message (if counts are right, if counts consume the entire sections,
 * and if sections consume the entire message) and known pseudo-RRs in the
 * additional data section are analyzed and removed.
 *
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 * TSIG checking is also done at this layer, and any DNSSEC transaction
 * signatures should also be checked here.
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 *
 * Notes on using the gettemp*() and puttemp*() functions:
 *
 * These functions return items (names, rdatasets, etc) allocated from some
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 * internal state of the dns_message_t.
 *
 * Names and rdatasets must be put back into the dns_message_t in
 * one of two ways.  Assume a name was allocated via
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 * dns_message_gettempname():
 *
 *	(1) insert it into a section, using dns_message_addname().
 *
 *	(2) return it to the message using dns_message_puttempname().
 *
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 * The same applies to rdatasets.
 *
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 * On the other hand, offsets, rdatalists and rdatas allocated using
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 * dns_message_gettemp*() will always be freed automatically
 * when the message is reset or destroyed; calling dns_message_puttemp*()
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 * on rdatalists and rdatas is optional and serves only to enable the item
 * to be reused multiple times during the lifetime of the message; offsets
 * cannot be reused.
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 *
 * Buffers allocated using isc_buffer_allocate() can be automatically freed
 * as well by giving the buffer to the message using dns_message_takebuffer().
 * Doing this will cause the buffer to be freed using isc_buffer_free()
 * when the section lists are cleared, such as in a reset or in a destroy.
 * Since the buffer itself exists until the message is destroyed, this sort
 * of code can be written:
 *
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 *	buffer = isc_buffer_allocate(mctx, 512);
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 *	name = NULL;
 *	name = dns_message_gettempname(message, &name);
 *	dns_name_init(name, NULL);
 *	result = dns_name_fromtext(name, &source, dns_rootname, ISC_FALSE,
 *				   buffer);
 *	dns_message_takebuffer(message, &buffer);
 *
 *
 * TODO:
 *
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 * XXX Needed:  ways to set and retrieve EDNS information, add rdata to a
 * section, move rdata from one section to another, remove rdata, etc.
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 */

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#define DNS_MESSAGEFLAG_QR		0x8000U
#define DNS_MESSAGEFLAG_AA		0x0400U
#define DNS_MESSAGEFLAG_TC		0x0200U
#define DNS_MESSAGEFLAG_RD		0x0100U
#define DNS_MESSAGEFLAG_RA		0x0080U
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#define DNS_MESSAGEFLAG_AD		0x0020U
#define DNS_MESSAGEFLAG_CD		0x0010U
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#define DNS_MESSAGEEXTFLAG_DO		0x8000U

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#define DNS_MESSAGE_REPLYPRESERVE	(DNS_MESSAGEFLAG_RD)
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#define DNS_MESSAGEEXTFLAG_REPLYPRESERVE (DNS_MESSAGEEXTFLAG_DO)
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#define DNS_MESSAGE_HEADERLEN		12 /* 6 isc_uint16_t's */

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#define DNS_MESSAGE_MAGIC		ISC_MAGIC('M','S','G','@')
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#define DNS_MESSAGE_VALID(msg)		ISC_MAGIC_VALID(msg, DNS_MESSAGE_MAGIC)
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/*
 * Ordering here matters.  DNS_SECTION_ANY must be the lowest and negative,
 * and DNS_SECTION_MAX must be one greater than the last used section.
 */
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typedef int dns_section_t;
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#define DNS_SECTION_ANY			(-1)
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#define DNS_SECTION_QUESTION		0
#define DNS_SECTION_ANSWER		1
#define DNS_SECTION_AUTHORITY		2
#define DNS_SECTION_ADDITIONAL		3
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#define DNS_SECTION_MAX			4
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typedef int dns_pseudosection_t;
#define DNS_PSEUDOSECTION_ANY		(-1)
#define DNS_PSEUDOSECTION_OPT           0
#define DNS_PSEUDOSECTION_TSIG          1
#define DNS_PSEUDOSECTION_SIG0          2
#define DNS_PSEUDOSECTION_MAX           3

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typedef int dns_messagetextflag_t;
#define DNS_MESSAGETEXTFLAG_NOCOMMENTS	0x0001
#define DNS_MESSAGETEXTFLAG_NOHEADERS	0x0002
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/*
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 * Dynamic update names for these sections.
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 */
#define DNS_SECTION_ZONE		DNS_SECTION_QUESTION
#define DNS_SECTION_PREREQUISITE	DNS_SECTION_ANSWER
#define DNS_SECTION_UPDATE		DNS_SECTION_AUTHORITY
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/*
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 * These tell the message library how the created dns_message_t will be used.
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 */
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#define DNS_MESSAGE_INTENTUNKNOWN	0 /* internal use only */
#define DNS_MESSAGE_INTENTPARSE		1 /* parsing messages */
#define DNS_MESSAGE_INTENTRENDER	2 /* rendering */
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/*
 * Control behavior of parsing
 */
#define DNS_MESSAGEPARSE_PRESERVEORDER	0x0001	/* preserve rdata order */
#define DNS_MESSAGEPARSE_BESTEFFORT	0x0002	/* return a message if a
						   recoverable parse error
						   occurs */
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#define DNS_MESSAGEPARSE_CLONEBUFFER	0x0004	/* save a copy of the
						   source buffer */
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/*
 * Control behavior of rendering
 */
#define DNS_MESSAGERENDER_ORDERED	0x0001	/* don't change order */
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#define DNS_MESSAGERENDER_PARTIAL	0x0002	/* allow a partial rdataset */
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typedef struct dns_msgblock dns_msgblock_t;

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struct dns_message {
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	/* public from here down */
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	unsigned int			magic;
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	dns_messageid_t			id;
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	unsigned int			flags;
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	dns_rcode_t			rcode;
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	unsigned int			opcode;
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	dns_rdataclass_t		rdclass;
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	/* 4 real, 1 pseudo */
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	unsigned int			counts[DNS_SECTION_MAX];
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	/* private from here down */
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	dns_namelist_t			sections[DNS_SECTION_MAX];
	dns_name_t		       *cursors[DNS_SECTION_MAX];
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	dns_rdataset_t		       *opt;
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	dns_rdataset_t		       *sig0;
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	dns_rdataset_t		       *tsig;
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	int				state;
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	unsigned int			from_to_wire : 2;
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	unsigned int			header_ok : 1;
	unsigned int			question_ok : 1;
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	unsigned int			tcp_continuation : 1;
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	unsigned int			verified_sig : 1;
	unsigned int			verify_attempted : 1;
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	unsigned int			free_query : 1;
	unsigned int			free_saved : 1;
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	unsigned int			opt_reserved;
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	unsigned int			sig_reserved;
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	unsigned int			reserved; /* reserved space (render) */
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	isc_buffer_t		       *buffer;
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	dns_compress_t		       *cctx;
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	isc_mem_t		       *mctx;
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	isc_mempool_t		       *namepool;
	isc_mempool_t		       *rdspool;

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	isc_bufferlist_t		scratchpad;
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	isc_bufferlist_t		cleanup;

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	ISC_LIST(dns_msgblock_t)	rdatas;
	ISC_LIST(dns_msgblock_t)	rdatalists;
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	ISC_LIST(dns_msgblock_t)	offsets;
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	ISC_LIST(dns_rdata_t)		freerdata;
	ISC_LIST(dns_rdatalist_t)	freerdatalist;
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	dns_rcode_t			tsigstatus;
	dns_rcode_t			querytsigstatus;
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	dns_name_t		       *tsigname;
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	dns_rdataset_t		       *querytsig;
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	dns_tsigkey_t		       *tsigkey;
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	dst_context_t		       *tsigctx;
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	int				sigstart;
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	int				timeadjust;
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	dns_name_t		       *sig0name;
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	dst_key_t		       *sig0key;
	dns_rcode_t			sig0status;
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	isc_region_t			query;
	isc_region_t			saved;
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	dns_rdatasetorderfunc_t		order;
	void *				order_arg;
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};
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/***
 *** Functions
 ***/

ISC_LANG_BEGINDECLS

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isc_result_t
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dns_message_create(isc_mem_t *mctx, unsigned int intent, dns_message_t **msgp);
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/*
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 * Create msg structure.
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 *
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 * This function will allocate some internal blocks of memory that are
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 * expected to be needed for parsing or rendering nearly any type of message.
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 *
 * Requires:
 *	'mctx' be a valid memory context.
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 *
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 *	'msgp' be non-null and '*msg' be NULL.
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 *
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 *	'intent' must be one of DNS_MESSAGE_INTENTPARSE or
 *	DNS_MESSAGE_INTENTRENDER.
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 *
 * Ensures:
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 *	The data in "*msg" is set to indicate an unused and empty msg
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 *	structure.
 *
 * Returns:
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 *	ISC_R_NOMEMORY		-- out of memory
 *	ISC_R_SUCCESS		-- success
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 */

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void
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dns_message_reset(dns_message_t *msg, unsigned int intent);
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/*
 * Reset a message structure to default state.  All internal lists are freed
 * or reset to a default state as well.  This is simply a more efficient
 * way to call dns_message_destroy() followed by dns_message_allocate(),
 * since it avoid many memory allocations.
 *
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 * If any data loanouts (buffers, names, rdatas, etc) were requested,
 * the caller must no longer use them after this call.
 *
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 * The intended next use of the message will be 'intent'.
 *
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 * Requires:
 *
 *	'msg' be valid.
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 *
 *	'intent' is DNS_MESSAGE_INTENTPARSE or DNS_MESSAGE_INTENTRENDER
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 */
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void
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dns_message_destroy(dns_message_t **msgp);
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/*
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 * Destroy all state in the message.
 *
 * Requires:
 *
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 *	'msgp' be valid.
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 *
 * Ensures:
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 *	'*msgp' == NULL
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 */

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isc_result_t
dns_message_sectiontotext(dns_message_t *msg, dns_section_t section,
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			  const dns_master_style_t *style,
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			  dns_messagetextflag_t flags,
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			  isc_buffer_t *target);
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isc_result_t
dns_message_pseudosectiontotext(dns_message_t *msg,
				dns_pseudosection_t section,
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				const dns_master_style_t *style,
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				dns_messagetextflag_t flags,
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				isc_buffer_t *target);
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/*
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 * Convert section 'section' or 'pseudosection' of message 'msg' to
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 * a cleartext representation
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 *
 * Notes:
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 *      See dns_message_totext for meanings of flags.
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 *
 * Requires:
 *
 *	'msg' is a valid message.
 *
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 *	'style' is a valid master dump style.
 *
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 *	'target' is a valid buffer.
 *
 *	'section' is a valid section label.
 *
 * Ensures:
 *
 *	If the result is success:
 *
 *		The used space in 'target' is updated.
 *
 * Returns:
 *
 *	ISC_R_SUCCESS
 *	ISC_R_NOSPACE
 *	ISC_R_NOMORE
 *
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 *	Note: On error return, *target may be partially filled with data.
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*/

isc_result_t
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dns_message_totext(dns_message_t *msg, const dns_master_style_t *style,
		   dns_messagetextflag_t flags, isc_buffer_t *target);
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/*
 * Convert all sections of message 'msg' to a cleartext representation
 *
 * Notes:
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 *      In flags, If DNS_MESSAGETEXTFLAG_OMITDOT is set, then the
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 *      final '.' in absolute names will not be emitted.  If
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 *      DNS_MESSAGETEXTFLAG_NOCOMMENTS is cleared, lines beginning
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 *      with ";;" will be emitted indicating section name.  If
 *      DNS_MESSAGETEXTFLAG_NOHEADERS is cleared, header lines will
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 *      be emitted.
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 *
 * Requires:
 *
 *	'msg' is a valid message.
 *
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 *	'style' is a valid master dump style.
 *
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 *	'target' is a valid buffer.
 *
 * Ensures:
 *
 *	If the result is success:
 *
 *		The used space in 'target' is updated.
 *
 * Returns:
 *
 *	ISC_R_SUCCESS
 *	ISC_R_NOSPACE
 *	ISC_R_NOMORE
 *
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 *	Note: On error return, *target may be partially filled with data.
 */
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isc_result_t
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dns_message_parse(dns_message_t *msg, isc_buffer_t *source,
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		  unsigned int options);
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/*
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 * Parse raw wire data in 'source' as a DNS message.
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 *
 * OPT records are detected and stored in the pseudo-section "opt".
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 * TSIGs are detected and stored in the pseudo-section "tsig".
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 *
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 * If DNS_MESSAGEPARSE_PRESERVEORDER is set, or if the opcode of the message
 * is UPDATE, a separate dns_name_t object will be created for each RR in the
 * message.  Each such dns_name_t will have a single rdataset containing the
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 * single RR, and the order of the RRs in the message is preserved.
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 * Otherwise, only one dns_name_t object will be created for each unique
 * owner name in the section, and each such dns_name_t will have a list
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 * of rdatasets.  To access the names and their data, use
 * dns_message_firstname() and dns_message_nextname().
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 *
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 * If DNS_MESSAGEPARSE_BESTEFFORT is set, errors in message content will
 * not be considered FORMERRs.  If the entire message can be parsed, it
 * will be returned and DNS_R_RECOVERABLE will be returned.
 *
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 * OPT and TSIG records are always handled specially, regardless of the
 * 'preserve_order' setting.
 *
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 * Requires:
 *	"msg" be valid.
 *
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 *	"buffer" be a wire format buffer.
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 *
 * Ensures:
 *	The buffer's data format is correct.
 *
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 *	The buffer's contents verify as correct regarding header bits, buffer
 * 	and rdata sizes, etc.
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 *
 * Returns:
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 *	ISC_R_SUCCESS		-- all is well
 *	ISC_R_NOMEMORY		-- no memory
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 *	DNS_R_RECOVERABLE	-- the message parsed properly, but contained
 *				   errors.
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 *	Many other errors possible XXXMLG
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 */

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isc_result_t
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dns_message_renderbegin(dns_message_t *msg, dns_compress_t *cctx,
			isc_buffer_t *buffer);
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/*
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 * Begin rendering on a message.  Only one call can be made to this function
 * per message.
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 *
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 * The compression context is "owned" by the message library until
 * dns_message_renderend() is called.  It must be invalidated by the caller.
 *
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 * The buffer is "owned" by the message library until dns_message_renderend()
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 * is called.
 *
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 * Requires:
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 *
 *	'msg' be valid.
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 *
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 *	'cctx' be valid.
 *
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 *	'buffer' is a valid buffer.
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 *
 * Side Effects:
 *
 *	The buffer is cleared before it is used.
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 *
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 * Returns:
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 *	ISC_R_SUCCESS		-- all is well
 *	ISC_R_NOSPACE		-- output buffer is too small
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 */

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isc_result_t
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dns_message_renderchangebuffer(dns_message_t *msg, isc_buffer_t *buffer);
/*
 * Reset the buffer.  This can be used after growing the old buffer
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 * on a ISC_R_NOSPACE return from most of the render functions.
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 *
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 * On successful completion, the old buffer is no longer used by the
 * library.  The new buffer is owned by the library until
 * dns_message_renderend() is called.
 *
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 * Requires:
 *
 *	'msg' be valid.
 *
 *	dns_message_renderbegin() was called.
 *
 *	buffer != NULL.
 *
 * Returns:
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 *	ISC_R_NOSPACE		-- new buffer is too small
 *	ISC_R_SUCCESS		-- all is well.
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 */

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isc_result_t
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dns_message_renderreserve(dns_message_t *msg, unsigned int space);
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/*
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 * XXXMLG should use size_t rather than unsigned int once the buffer
 * API is cleaned up
 *
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 * Reserve "space" bytes in the given buffer.
 *
 * Requires:
 *
 *	'msg' be valid.
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 *
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 *	dns_message_renderbegin() was called.
 *
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 * Returns:
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 *	ISC_R_SUCCESS		-- all is well.
 *	ISC_R_NOSPACE		-- not enough free space in the buffer.
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 */

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void
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dns_message_renderrelease(dns_message_t *msg, unsigned int space);
/*
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 * XXXMLG should use size_t rather than unsigned int once the buffer
 * API is cleaned up
 *
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 * Release "space" bytes in the given buffer that was previously reserved.
 *
 * Requires:
 *
 *	'msg' be valid.
 *
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 *	'space' is less than or equal to the total amount of space reserved
 *	via prior calls to dns_message_renderreserve().
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 *
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 *	dns_message_renderbegin() was called.
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 */

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isc_result_t
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dns_message_rendersection(dns_message_t *msg, dns_section_t section,
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			  unsigned int options);
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/*
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 * Render all names, rdatalists, etc from the given section at the
 * specified priority or higher.
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 *
 * Requires:
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 *	'msg' be valid.
 *
 *	'section' be a valid section.
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 *
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 *	dns_message_renderbegin() was called.
 *
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 * Returns:
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 *	ISC_R_SUCCESS		-- all records were written, and there are
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 *				   no more records for this section.
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 *	ISC_R_NOSPACE		-- Not enough room in the buffer to write
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 *				   all records requested.
 *	DNS_R_MOREDATA		-- All requested records written, and there
 *				   are records remaining for this section.
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 */

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void
dns_message_renderheader(dns_message_t *msg, isc_buffer_t *target);
/*
 * Render the message header.  This is implicitly called by
 * dns_message_renderend().
 *
 * Requires:
 *
 *	'msg' be a valid message.
 *
 *	dns_message_renderbegin() was called.
 *
 *	'target' is a valid buffer with enough space to hold a message header
 */

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isc_result_t
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dns_message_renderend(dns_message_t *msg);
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/*
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 * Finish rendering to the buffer.  Note that more data can be in the
 * 'msg' structure.  Destroying the structure will free this, or in a multi-
 * part EDNS1 message this data can be rendered to another buffer later.
 *
 * Requires:
 *
 *	'msg' be a valid message.
 *
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 *	dns_message_renderbegin() was called.
 *
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 * Returns:
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 *	ISC_R_SUCCESS		-- all is well.
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 */
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void
dns_message_renderreset(dns_message_t *msg);
/*
 * Reset the message so that it may be rendered again.
 *
 * Notes:
 *
 *	If dns_message_renderbegin() has been called, dns_message_renderend()
 *	must be called before calling this function.
 *
 * Requires:
 *
 *	'msg' be a valid message with rendering intent.
 */
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isc_result_t
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dns_message_firstname(dns_message_t *msg, dns_section_t section);
/*
 * Set internal per-section name pointer to the beginning of the section.
 *
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 * The functions dns_message_firstname() and dns_message_nextname() may
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 * be used for iterating over the owner names in a section.
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 *
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 * Requires:
 *
 *   	'msg' be valid.
 *
 *	'section' be a valid section.
 *
 * Returns:
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 *	ISC_R_SUCCESS		-- All is well.
 *	ISC_R_NOMORE		-- No names on given section.
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 */

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isc_result_t
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dns_message_nextname(dns_message_t *msg, dns_section_t section);
/*
 * Sets the internal per-section name pointer to point to the next name
 * in that section.
 *
 * Requires:
 *
 *   	'msg' be valid.
 *
 *	'section' be a valid section.
 *
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 *	dns_message_firstname() must have been called on this section,
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 *	and the result was ISC_R_SUCCESS.
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 *
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 * Returns:
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 *	ISC_R_SUCCESS		-- All is well.
 *	ISC_R_NOMORE		-- No names in given section.
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 */

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void
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dns_message_currentname(dns_message_t *msg, dns_section_t section,
			dns_name_t **name);
/*
 * Sets 'name' to point to the name where the per-section internal name
 * pointer is currently set.
 *
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 * This function returns the name in the database, so any data associated
 * with it (via the name's "list" member) contains the actual rdatasets.
 *
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 * Requires:
 *
 *	'msg' be valid.
 *
 *	'name' be non-NULL, and *name be NULL.
 *
 *	'section' be a valid section.
 *
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 *	dns_message_firstname() must have been called on this section,
 *	and the result of it and any dns_message_nextname() calls was
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 *	ISC_R_SUCCESS.
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 */

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isc_result_t
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dns_message_findname(dns_message_t *msg, dns_section_t section,
		     dns_name_t *target, dns_rdatatype_t type,
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		     dns_rdatatype_t covers, dns_name_t **foundname,
		     dns_rdataset_t **rdataset);
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/*
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 * Search for a name in the specified section.  If it is found, *name is
 * set to point to the name, and *rdataset is set to point to the found
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 * rdataset (if type is specified as other than dns_rdatatype_any).
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 *
 * Requires:
 *	'msg' be valid.
 *
 *	'section' be a valid section.
 *
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 *	If a pointer to the name is desired, 'foundname' should be non-NULL.
 *	If it is non-NULL, '*foundname' MUST be NULL.
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 *
 *	If a type other than dns_datatype_any is searched for, 'rdataset'
 *	may be non-NULL, '*rdataset' be NULL, and will point at the found
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 *	rdataset.  If the type is dns_datatype_any, 'rdataset' must be NULL.
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 *
 *	'target' be a valid name.
 *
 *	'type' be a valid type.
 *
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 *	If 'type' is dns_rdatatype_sig, 'covers' must be a valid type.
 *	Otherwise it should be 0.
 *
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 * Returns:
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 *	ISC_R_SUCCESS		-- all is well.
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 *	DNS_R_NXDOMAIN		-- name does not exist in that section.
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 *	DNS_R_NXRRSET		-- The name does exist, but the desired
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 *				   type does not.
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 */

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isc_result_t
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dns_message_findtype(dns_name_t *name, dns_rdatatype_t type,
		     dns_rdatatype_t covers, dns_rdataset_t **rdataset);
/*
 * Search the name for the specified type.  If it is found, *rdataset is
 * filled in with a pointer to that rdataset.
 *
 * Requires:
 *	if '**rdataset' is non-NULL, *rdataset needs to be NULL.
 *
 *	'type' be a valid type, and NOT dns_rdatatype_any.
 *
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 *	If 'type' is dns_rdatatype_sig, 'covers' must be a valid type.
 *	Otherwise it should be 0.
 *
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 * Returns:
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 *	ISC_R_SUCCESS		-- all is well.
 *	ISC_R_NOTFOUND		-- the desired type does not exist.
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 */

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void
dns_message_movename(dns_message_t *msg, dns_name_t *name,
		     dns_section_t fromsection,
		     dns_section_t tosection);
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/*
 * Move a name from one section to another.
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 *
 * Requires:
 *
 *	'msg' be valid.
 *
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 *	'name' must be a name already in 'fromsection'.
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 *
 *	'fromsection' must be a valid section.
 *
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 *	'tosection' must be a valid section.
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 */

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void
dns_message_addname(dns_message_t *msg, dns_name_t *name,
		    dns_section_t section);
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/*
 * Adds the name to the given section.
 *
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 * It is the caller's responsibility to enforce any unique name requirements
 * in a section.
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 *
 * Requires:
 *
 *	'msg' be valid, and be a renderable message.
 *
 *	'name' be a valid name.
 *
 *	'section' be a named section.
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 */
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/*
 * LOANOUT FUNCTIONS
 *
 * Each of these functions loan a particular type of data to the caller.
 * The storage for these will vanish when the message is destroyed or
 * reset, and must NOT be used after these operations.
 */

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dns_message_gettempname(dns_message_t *msg, dns_name_t **item);
/*
 * Return a name that can be used for any temporary purpose, including
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 * inserting into the message's linked lists.  The name must be returned
 * to the message code using dns_message_puttempname() or inserted into
 * one of the message's sections before the message is destroyed.
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 *
 * It is the caller's responsibility to initialize this name.
 *
 * Requires:
 *	msg be a valid message
 *
 *	item != NULL && *item == NULL
 *
 * Returns:
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 *	ISC_R_SUCCESS		-- All is well.
 *	ISC_R_NOMEMORY		-- No item can be allocated.
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 */

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isc_result_t
dns_message_gettempoffsets(dns_message_t *msg, dns_offsets_t **item);
/*
 * Return an offsets array that can be used for any temporary purpose,
 * such as attaching to a temporary name.  The offsets will be freed
 * when the message is destroyed or reset.
 *
 * Requires:
 *	msg be a valid message
 *
 *	item != NULL && *item == NULL
 *
 * Returns:
 *	ISC_R_SUCCESS		-- All is well.
 *	ISC_R_NOMEMORY		-- No item can be allocated.
 */

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dns_message_gettemprdata(dns_message_t *msg, dns_rdata_t **item);
/*
 * Return a rdata that can be used for any temporary purpose, including
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 * inserting into the message's linked lists.  The rdata will be freed
 * when the message is destroyed or reset.
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 *
 * Requires:
 *	msg be a valid message
 *
 *	item != NULL && *item == NULL
 *
 * Returns:
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 *	ISC_R_SUCCESS		-- All is well.
 *	ISC_R_NOMEMORY		-- No item can be allocated.
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 */

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dns_message_gettemprdataset(dns_message_t *msg, dns_rdataset_t **item);
/*
 * Return a rdataset that can be used for any temporary purpose, including
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 * inserting into the message's linked lists. The name must be returned
 * to the message code using dns_message_puttempname() or inserted into
 * one of the message's sections before the message is destroyed.
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 *
 * Requires:
 *	msg be a valid message
 *
 *	item != NULL && *item == NULL
 *
 * Returns:
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 *	ISC_R_SUCCESS		-- All is well.
 *	ISC_R_NOMEMORY		-- No item can be allocated.
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 */

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dns_message_gettemprdatalist(dns_message_t *msg, dns_rdatalist_t **item);
/*
 * Return a rdatalist that can be used for any temporary purpose, including
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 * inserting into the message's linked lists.  The rdatalist will be
 * destroyed when the message is destroyed or reset.
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 *
 * Requires:
 *	msg be a valid message
 *
 *	item != NULL && *item == NULL
 *
 * Returns:
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 *	ISC_R_SUCCESS		-- All is well.
 *	ISC_R_NOMEMORY		-- No item can be allocated.
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 */

void
dns_message_puttempname(dns_message_t *msg, dns_name_t **item);
/*
 * Return a borrowed name to the message's name free list.
 *
 * Requires:
 *	msg be a valid message
 *
 *	item != NULL && *item point to a name returned by
 *	dns_message_gettempname()
 *
 * Ensures:
 *	*item == NULL
 */

void
dns_message_puttemprdata(dns_message_t *msg, dns_rdata_t **item);
/*
 * Return a borrowed rdata to the message's rdata free list.
 *
 * Requires:
 *	msg be a valid message
 *
 *	item != NULL && *item point to a rdata returned by
 *	dns_message_gettemprdata()
 *
 * Ensures:
 *	*item == NULL
 */

void
dns_message_puttemprdataset(dns_message_t *msg, dns_rdataset_t **item);
/*
 * Return a borrowed rdataset to the message's rdataset free list.
 *
 * Requires:
 *	msg be a valid message
 *
 *	item != NULL && *item point to a rdataset returned by
 *	dns_message_gettemprdataset()
 *
 * Ensures:
 *	*item == NULL
 */

void
dns_message_puttemprdatalist(dns_message_t *msg, dns_rdatalist_t **item);
/*
 * Return a borrowed rdatalist to the message's rdatalist free list.
 *
 * Requires:
 *	msg be a valid message
 *
 *	item != NULL && *item point to a rdatalist returned by
 *	dns_message_gettemprdatalist()
 *
 * Ensures:
 *	*item == NULL
 */

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isc_result_t
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dns_message_peekheader(isc_buffer_t *source, dns_messageid_t *idp,
		       unsigned int *flagsp);
/*
 * Assume the remaining region of "source" is a DNS message.  Peek into
 * it and fill in "*idp" with the message id, and "*flagsp" with the flags.
 *
 * Requires:
 *
 *	source != NULL
 *
 * Ensures:
 *
 *	if (idp != NULL) *idp == message id.
 *
 *	if (flagsp != NULL) *flagsp == message flags.
 *
 * Returns:
 *
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 *	ISC_R_SUCCESS		-- all is well.
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 *
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 *	ISC_R_UNEXPECTEDEND	-- buffer doesn't contain enough for a header.
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 */

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isc_result_t
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dns_message_reply(dns_message_t *msg, isc_boolean_t want_question_section);
/*
 * Start formatting a reply to the query in 'msg'.
 *
 * Requires:
 *
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 *	'msg' is a valid message with parsing intent, and contains a query.
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 *
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 * Ensures:
 *
 *	The message will have a rendering intent.  If 'want_question_section'
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 *	is true, the message opcode is query or notify, and the question
 *	section is present and properly formatted, then the question section
 *	will be included in the reply.  All other sections will be cleared.
 *	The QR flag will be set, the RD flag will be preserved, and all other
 *	flags will be cleared.
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 *
 * Returns:
 *
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 *	ISC_R_SUCCESS		-- all is well.
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 *
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 *	DNS_R_FORMERR		-- the header or question section of the
 *				   message is invalid, replying is impossible.
 *				   If DNS_R_FORMERR is returned when
 *				   want_question_section is ISC_FALSE, then
 *				   it's the header section that's bad;
 *				   otherwise either of the header or question
 *				   sections may be bad.
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 */

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dns_rdataset_t *
dns_message_getopt(dns_message_t *msg);
/*
 * Get the OPT record for 'msg'.
 *
 * Requires:
 *
 *	'msg' is a valid message.
 *
 * Returns:
 *
 *	The OPT rdataset of 'msg', or NULL if there isn't one.
 */

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isc_result_t
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dns_message_setopt(dns_message_t *msg, dns_rdataset_t *opt);
/*
 * Set the OPT record for 'msg'.
 *
 * Requires:
 *
 *	'msg' is a valid message with rendering intent,
 *	dns_message_renderbegin() has been called, and no sections have been
 *	rendered.
 *
 *	'opt' is a valid OPT record.
 *
 * Ensures:
 *
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 *	The OPT record has either been freed or ownership of it has
 *	been transferred to the message.
 *
 *	If ISC_R_SUCCESS was returned, the OPT record will be rendered 
 *	when dns_message_renderend() is called.
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 *
 * Returns:
 *
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 *	ISC_R_SUCCESS		-- all is well.
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 *
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 *	ISC_R_NOSPACE		-- there is no space for the OPT record.
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 */

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dns_rdataset_t *
dns_message_gettsig(dns_message_t *msg, dns_name_t **owner);
/*
 * Get the TSIG record and owner for 'msg'.
 *
 * Requires:
 *
 *	'msg' is a valid message.
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 *	'owner' is NULL or *owner is NULL.
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 *
 * Returns:
 *
 *	The TSIG rdataset of 'msg', or NULL if there isn't one.
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 *
 * Ensures:
 *
 * 	If 'owner' is not NULL, it will point to the owner name.
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 */

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dns_message_settsigkey(dns_message_t *msg, dns_tsigkey_t *key);
/*
 * Set the tsig key for 'msg'.  This is only necessary for when rendering a
 * query or parsing a response.  The key (if non-NULL) is attached to, and
 * will be detached when the message is destroyed.
 *
 * Requires:
 *
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 *	'msg' is a valid message with rendering intent,
 *	dns_message_renderbegin() has been called, and no sections have been
 *	rendered.
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 *	'key' is a valid tsig key or NULL.
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 *
 * Returns:
 *
 *	ISC_R_SUCCESS		-- all is well.
 *
 *	ISC_R_NOSPACE		-- there is no space for the TSIG record.
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 */

dns_tsigkey_t *
dns_message_gettsigkey(dns_message_t *msg);
/*
 * Gets the tsig key for 'msg'.
 *
 * Requires:
 *
 *	'msg' is a valid message
 */

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isc_result_t
dns_message_setquerytsig(dns_message_t *msg, isc_buffer_t *querytsig);
/*
 * Indicates that 'querytsig' is the TSIG from the signed query for which
 * 'msg' is the response.  This is also used for chained TSIGs in TCP
 * responses.
 *
 * Requires:
 *
 *	'querytsig' is a valid buffer as returned by dns_message_getquerytsig()
 *	or NULL
 *
 *	'msg' is a valid message
 *
 * Returns:
 *
 *	ISC_R_SUCCESS
 *	ISC_R_NOMEMORY
 */

isc_result_t
dns_message_getquerytsig(dns_message_t *msg, isc_mem_t *mctx,
			 isc_buffer_t **querytsig);
/*
 * Gets the tsig from the TSIG from the signed query 'msg'.  This is also used
 * for chained TSIGs in TCP responses.  Unlike dns_message_gettsig, this makes
 * a copy of the data, so can be used if the message is destroyed.
 *
 * Requires:
 *
 *	'msg' is a valid signed message
 *	'mctx' is a valid memory context
 *	querytsig != NULL && *querytsig == NULL
 *
 * Returns:
 *
 *	ISC_R_SUCCESS
 *	ISC_R_NOMEMORY
 *
 * Ensures:
 * 	'tsig' points to NULL or an allocated buffer which must be freed
 * 	by the caller.
 */

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dns_message_getsig0(dns_message_t *msg, dns_name_t **owner);
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/*
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 * Get the SIG(0) record and owner for 'msg'.
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 *
 * Requires:
 *
 *	'msg' is a valid message.
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 *	'owner' is NULL or *owner is NULL.
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 *
 * Returns:
 *
 *	The SIG(0) rdataset of 'msg', or NULL if there isn't one.
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 *
 * Ensures:
 *
 * 	If 'owner' is not NULL, it will point to the owner name.
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 */