/*
* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, you can obtain one at https://mozilla.org/MPL/2.0/.
*
* See the COPYRIGHT file distributed with this work for additional
* information regarding copyright ownership.
*/
#ifndef DNS_COMPRESS_H
#define DNS_COMPRESS_H 1
#include <inttypes.h>
#include <stdbool.h>
#include <isc/lang.h>
#include <isc/region.h>
#include <dns/name.h>
#include <dns/types.h>
ISC_LANG_BEGINDECLS
/*! \file dns/compress.h
* Direct manipulation of the structures is strongly discouraged.
*
* A name compression context handles compression of multiple DNS names
* in relation to a single DNS message. The context can be used to
* selectively turn on/off compression for specific names (depending on
* the RR type) by using \c dns_compress_setmethods(). Alternately,
* compression can be disabled completely using \c
* dns_compress_disable().
*
* \c dns_compress_setmethods() is intended for use by RDATA towire()
* implementations, whereas \c dns_compress_disable() is intended to be
* used by a nameserver's configuration manager.
*/
#define DNS_COMPRESS_NONE 0x00 /*%< no compression */
#define DNS_COMPRESS_GLOBAL14 0x01 /*%< "normal" compression. */
#define DNS_COMPRESS_ALL 0x01 /*%< all compression. */
#define DNS_COMPRESS_CASESENSITIVE 0x02 /*%< case sensitive compression. */
#define DNS_COMPRESS_ENABLED 0x04
/*
* DNS_COMPRESS_TABLESIZE must be a power of 2. The compress code
* utilizes this assumption.
*/
#define DNS_COMPRESS_TABLEBITS 6
#define DNS_COMPRESS_TABLESIZE (1U << DNS_COMPRESS_TABLEBITS)
#define DNS_COMPRESS_TABLEMASK (DNS_COMPRESS_TABLESIZE - 1)
#define DNS_COMPRESS_INITIALNODES 24
#define DNS_COMPRESS_ARENA_SIZE 640
typedef struct dns_compressnode dns_compressnode_t;
struct dns_compressnode {
dns_compressnode_t *next;
uint16_t offset;
uint16_t count;
isc_region_t r;
dns_name_t name;
};
struct dns_compress {
unsigned int magic; /*%< Magic number. */
unsigned int allowed; /*%< Allowed methods. */
int edns; /*%< Edns version or -1. */
/*% Global compression table. */
dns_compressnode_t *table[DNS_COMPRESS_TABLESIZE];
/*% Preallocated arena for names. */
unsigned char arena[DNS_COMPRESS_ARENA_SIZE];
off_t arena_off;
/*% Preallocated nodes for the table. */
dns_compressnode_t initialnodes[DNS_COMPRESS_INITIALNODES];
uint16_t count; /*%< Number of nodes. */
isc_mem_t *mctx; /*%< Memory context. */
};
typedef enum {
DNS_DECOMPRESS_ANY, /*%< Any compression */
DNS_DECOMPRESS_STRICT, /*%< Allowed compression */
DNS_DECOMPRESS_NONE /*%< No compression */
} dns_decompresstype_t;
struct dns_decompress {
unsigned int magic; /*%< Magic number. */
unsigned int allowed; /*%< Allowed methods. */
int edns; /*%< Edns version or -1. */
dns_decompresstype_t type; /*%< Strict checking */
};
isc_result_t
dns_compress_init(dns_compress_t *cctx, int edns, isc_mem_t *mctx);
/*%<
* Initialise the compression context structure pointed to by
* 'cctx'. A freshly initialized context has name compression
* enabled, but no methods are set. Please use \c
* dns_compress_setmethods() to set a compression method.
*
* Requires:
* \li 'cctx' is a valid dns_compress_t structure.
* \li 'mctx' is an initialized memory context.
* Ensures:
* \li cctx->global is initialized.
*
* Returns:
* \li #ISC_R_SUCCESS
*/
void
dns_compress_invalidate(dns_compress_t *cctx);
/*%<
* Invalidate the compression structure pointed to by cctx.
*
* Requires:
*\li 'cctx' to be initialized.
*/
void
dns_compress_setmethods(dns_compress_t *cctx, unsigned int allowed);
/*%<
* Sets allowed compression methods.
*
* Requires:
*\li 'cctx' to be initialized.
*/
unsigned int
dns_compress_getmethods(dns_compress_t *cctx);
/*%<
* Gets allowed compression methods.
*
* Requires:
*\li 'cctx' to be initialized.
*
* Returns:
*\li allowed compression bitmap.
*/
void
dns_compress_disable(dns_compress_t *cctx);
/*%<
* Disables all name compression in the context. Once disabled,
* name compression cannot currently be re-enabled.
*
* Requires:
*\li 'cctx' to be initialized.
*
*/
void
dns_compress_setsensitive(dns_compress_t *cctx, bool sensitive);
/*
* Preserve the case of compressed domain names.
*
* Requires:
* 'cctx' to be initialized.
*/
bool
dns_compress_getsensitive(dns_compress_t *cctx);
/*
* Return whether case is to be preserved when compressing
* domain names.
*
* Requires:
* 'cctx' to be initialized.
*/
int
dns_compress_getedns(dns_compress_t *cctx);
/*%<
* Gets edns value.
*
* Requires:
*\li 'cctx' to be initialized.
*
* Returns:
*\li -1 .. 255
*/
bool
dns_compress_findglobal(dns_compress_t *cctx, const dns_name_t *name,
dns_name_t *prefix, uint16_t *offset);
/*%<
* Finds longest possible match of 'name' in the global compression table.
*
* Requires:
*\li 'cctx' to be initialized.
*\li 'name' to be a absolute name.
*\li 'prefix' to be initialized.
*\li 'offset' to point to an uint16_t.
*
* Ensures:
*\li 'prefix' and 'offset' are valid if true is returned.
*
* Returns:
*\li #true / #false
*/
void
dns_compress_add(dns_compress_t *cctx, const dns_name_t *name,
const dns_name_t *prefix, uint16_t offset);
/*%<
* Add compression pointers for 'name' to the compression table,
* not replacing existing pointers.
*
* Requires:
*\li 'cctx' initialized
*
*\li 'name' must be initialized and absolute, and must remain
* valid until the message compression is complete.
*
*\li 'prefix' must be a prefix returned by
* dns_compress_findglobal(), or the same as 'name'.
*/
void
dns_compress_rollback(dns_compress_t *cctx, uint16_t offset);
/*%<
* Remove any compression pointers from global table >= offset.
*
* Requires:
*\li 'cctx' is initialized.
*/
void
dns_decompress_init(dns_decompress_t *dctx, int edns,
dns_decompresstype_t type);
/*%<
* Initializes 'dctx'.
* Records 'edns' and 'type' into the structure.
*
* Requires:
*\li 'dctx' to be a valid pointer.
*/
void
dns_decompress_invalidate(dns_decompress_t *dctx);
/*%<
* Invalidates 'dctx'.
*
* Requires:
*\li 'dctx' to be initialized
*/
void
dns_decompress_setmethods(dns_decompress_t *dctx, unsigned int allowed);
/*%<
* Sets 'dctx->allowed' to 'allowed'.
*
* Requires:
*\li 'dctx' to be initialized
*/
unsigned int
dns_decompress_getmethods(dns_decompress_t *dctx);
/*%<
* Returns 'dctx->allowed'
*
* Requires:
*\li 'dctx' to be initialized
*/
int
dns_decompress_edns(dns_decompress_t *dctx);
/*%<
* Returns 'dctx->edns'
*
* Requires:
*\li 'dctx' to be initialized
*/
dns_decompresstype_t
dns_decompress_type(dns_decompress_t *dctx);
/*%<
* Returns 'dctx->type'
*
* Requires:
*\li 'dctx' to be initialized
*/
ISC_LANG_ENDDECLS
#endif /* DNS_COMPRESS_H */
