Sofia DNS Resolver. More...

#include <stdarg.h>
#include "sofia-resolv/sres_config.h"

Include dependency graph for sres.h:

Defines
#define	SOFIA_RESOLV_SRES_H
	Defined when <sofia-resolv/sres.h> has been included.
Typedefs
typedef union sres_record	sres_record_t
	Type representing any DNS record.
typedef struct sres_cache	sres_cache_t
	Opaque type of DNS cache object.
typedef struct sres_resolver_s	sres_resolver_t
	Opaque type of DNS resolver object.
typedef struct sres_context_s	sres_context_t
	Application-defined type for sres_query_t context.
typedef struct sres_query_s	sres_query_t
	Opaque type of DNS query object.
typedef void	sres_answer_f (sres_context_t context, sres_query_t query, sres_record_t **answers)
	Prototype for callback function.
Enumerations
enum	{ SRES_RETRANSMIT_INTERVAL, SRES_RETRANSMIT_INTERVAL }
Functions
SRESPUBFUN sres_resolver_t *	sres_resolver_new (char const *resolv_conf_path)
	New resolver object.
SRESPUBFUN sres_resolver_t *	sres_resolver_copy (sres_resolver_t *)
	Copy a resolver.
SRESPUBFUN sres_resolver_t *	sres_resolver_new_with_cache (char const conf_file_path, sres_cache_t cache, char const *options,...)
	New resolver object.
SRESPUBFUN sres_resolver_t *	sres_resolver_new_with_cache_va (char const conf_file_path, sres_cache_t cache, char const *options, va_list va)
	New resolver object.
SRESPUBFUN sres_resolver_t *	sres_resolver_ref (sres_resolver_t *res)
	Increase reference count on a resolver object.
SRESPUBFUN void	sres_resolver_unref (sres_resolver_t *res)
	Decrease the reference count on a resolver object.
SRESPUBFUN int	sres_resolver_update (sres_resolver_t *res, int always)
	Re-read resolv.conf if needed.
SRESPUBFUN void *	sres_resolver_set_userdata (sres_resolver_t res, void userdata)
	Set userdata pointer.
SRESPUBFUN void *	sres_resolver_get_userdata (sres_resolver_t const *res)
	Get userdata pointer.
SRESPUBFUN sres_query_t *	sres_query (sres_resolver_t res, sres_answer_f callback, sres_context_t context, uint16_t type, char const domain)
	Make a DNS query.
SRESPUBFUN sres_query_t *	sres_search (sres_resolver_t res, sres_answer_f callback, sres_context_t context, uint16_t type, char const name)
	Search DNS.
SRESPUBFUN sres_query_t *	sres_query_sockaddr (sres_resolver_t res, sres_answer_f callback, sres_context_t context, uint16_t type, struct sockaddr const addr)
	Make a reverse DNS query.
SRESPUBFUN sres_query_t *	sres_query_make (sres_resolver_t res, sres_answer_f callback, sres_context_t context, int dummy, uint16_t type, char const domain)
	Make a DNS query with socket.
SRESPUBFUN sres_query_t *	sres_query_make_sockaddr (sres_resolver_t res, sres_answer_f callback, sres_context_t context, int dummy, uint16_t type, struct sockaddr const addr)
	Make a reverse DNS query with socket.
SRESPUBFUN void	sres_query_bind (sres_query_t q, sres_answer_f callback, sres_context_t *context)
	Rebind a DNS query.
SRESPUBFUN sres_record_t **	sres_cached_answers (sres_resolver_t res, uint16_t type, char const domain)
	Get a list of matching (type/domain) records from cache.
SRESPUBFUN sres_record_t **	sres_search_cached_answers (sres_resolver_t res, uint16_t type, char const name)
	Search for a list of matching (type/name) records from cache.
SRESPUBFUN sres_record_t **	sres_cached_answers_sockaddr (sres_resolver_t res, uint16_t type, struct sockaddr const addr)
	Get a list of matching (type/domain) records from cache.
SRESPUBFUN int	sres_set_cached_srv_priority (sres_resolver_t res, char const domain, char const *target, uint16_t port, uint32_t newttl, uint16_t newprio)
	Modify the priority of the specified SRV records.
SRESPUBFUN int	sres_blocking_query (sres_resolver_t res, uint16_t type, char const domain, int ignore_cache, sres_record_t ***return_records)
	Send a query, wait for answer, return results.
SRESPUBFUN int	sres_blocking_search (sres_resolver_t res, uint16_t type, char const name, int ignore_cache, sres_record_t ***return_records)
	Search DNS, return results.
SRESPUBFUN int	sres_blocking_query_sockaddr (sres_resolver_t res, uint16_t type, struct sockaddr const addr, int ignore_cache, sres_record_t ***return_records)
	Send a a reverse DNS query, wait for answer, return results.
SRESPUBFUN int	sres_is_blocking (sres_resolver_t *res)
	Return true (and set resolver in blocking mode) if resolver can block.
SRESPUBFUN int	sres_sort_answers (sres_resolver_t , sres_record_t *answers)
	Sort the list of records.
SRESPUBFUN int	sres_filter_answers (sres_resolver_t res, sres_record_t *answers, uint16_t type)
	Filter and sort the list of records.
SRESPUBFUN void	sres_free_answers (sres_resolver_t , sres_record_t *answers)
	Free the list records.
SRESPUBFUN void	sres_free_answer (sres_resolver_t res, sres_record_t answer)
	Free and zero one record.

Detailed Description

Sofia DNS Resolver.

Author:: Pekka Pessi <Pekka.Pessi@nokia-email.address.hidden>,; Teemu Jalava <Teemu.Jalava@nokia-email.address.hidden>,; Mikko Haataja <ext-Mikko.A.Haataja@nokia-email.address.hidden>.

Include Context

 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <sofia-resolv/sres.h>

Define Documentation

#define SOFIA_RESOLV_SRES_H

Defined when <sofia-resolv/sres.h> has been included.

Typedef Documentation

typedef void sres_answer_f(sres_context_t *context, sres_query_t *query, sres_record_t **answers)

Prototype for callback function.

This kind of function is called when a query is completed. The called function is responsible for freeing the list of answers and it must (eventually) call sres_free_answers().

typedef struct sres_cache sres_cache_t

Opaque type of DNS cache object.

typedef struct sres_context_s sres_context_t

Application-defined type for sres_query_t context.

typedef struct sres_query_s sres_query_t

Opaque type of DNS query object.

typedef union sres_record sres_record_t

Type representing any DNS record.

typedef struct sres_resolver_s sres_resolver_t

Opaque type of DNS resolver object.

Enumeration Type Documentation

anonymous enum

Enumerator:

SRES_RETRANSMIT_INTERVAL	Resolver timer interval in milliseconds.
SRES_RETRANSMIT_INTERVAL	Resolver timer interval in milliseconds.

Function Documentation

SRESPUBFUN int sres_blocking_query	(	sres_resolver_t *	res,
		uint16_t	type,
		char const *	domain,
		int	ignore_cache,
		sres_record_t ***	return_records
	)

Send a query, wait for answer, return results.

Sends a DNS query with specified type and domain to the DNS server, if ignore_cache is not given or no records are found from cache. Function returns an error record with nonzero status if no response is received from DNS server.

Parameters:

	res	pointer to resolver object
	type	record type to search (or sres_qtype_any for any record)
	domain	domain name to query
	ignore_cache	ignore cached answers if nonzero
	return_records	return-value parameter for dns records

Return values:

	>0	if query was responded
	0	if result was found from cache
	-1	upon error

Errors:

: EFAULT res or domain point outside the address space

: ENAMETOOLONG domain is longer than SRES_MAXDNAME

: ENETDOWN no DNS servers configured

: ENOMEM memory exhausted

: EOPNOTSUPP resolver res is in asynchronous mode

See also:: sres_query(), sres_blocking_search()

Note:: A blocking query converts a resolver object permanently into blocking mode. If you need to make blocking and non-blocking queries, use sres_resolver_copy() to make a separate resolver object for blocking queries.

SRESPUBFUN int sres_blocking_query_sockaddr	(	sres_resolver_t *	res,
		uint16_t	type,
		struct sockaddr const *	addr,
		int	ignore_cache,
		sres_record_t ***	return_records
	)

Send a a reverse DNS query, wait for answer, return results.

Sends a reverse DNS query with specified type and domain to the DNS server if ignore_cache is not given or no cached records are found from the cache. Function returns an error record with nonzero status if no response is received from DNS server.

Return values:

	>0	if query was responded
	0	if result was found from cache
	-1	upon error

Errors:

: EFAULT res or addr point outside the address space

: ENOMEM memory exhausted

: ENETDOWN no DNS servers configured

: EOPNOTSUPP resolver res is in asynchronous mode

See also:: sres_blocking_query(), sres_query_sockaddr(), sres_cached_answers_sockaddr()

Note:: A blocking query converts a resolver object permanently into blocking mode. If you need to make blocking and non-blocking queries, use sres_resolver_copy() to make a separate resolver object for blocking queries.

SRESPUBFUN int sres_blocking_search	(	sres_resolver_t *	res,
		uint16_t	type,
		char const *	name,
		int	ignore_cache,
		sres_record_t ***	return_records
	)

Search DNS, return results.

Search for name with specified type and name from the DNS server. If the name does not contain enought dots, the search domains are appended to the name and resulting domain name are also queried.

Parameters:

	res	pointer to resolver object
	type	record type to search (or sres_qtype_any for any record)
	name	host or domain name to search from DNS
	ignore_cache	ignore cached answers if nonzero
	return_records	return-value parameter for dns records

Return values:

	>0	if query was responded
	0	if result was found from cache
	-1	upon error

Errors:

: EFAULT res or domain point outside the address space

: ENAMETOOLONG domain is longer than SRES_MAXDNAME

: ENETDOWN no DNS servers configured

: ENOMEM memory exhausted

: EOPNOTSUPP resolver res is in asynchronous mode

See also:: sres_blocking_query(), sres_search()

Note:: A blocking query converts a resolver object permanently into blocking mode. If you need to make blocking and non-blocking queries, use sres_resolver_copy() to make a separate resolver object for blocking queries.

SRESPUBFUN sres_record_t** sres_cached_answers	(	sres_resolver_t *	res,
		uint16_t	type,
		char const *	domain
	)

Get a list of matching (type/domain) records from cache.

Returns:: pointer to an array of pointers to cached records, or NULL if no entry was found.

Errors:

: ENAMETOOLONG domain is longer than SRES_MAXDNAME

: ENOENT no cached records were found

: EFAULT res or domain point outside the address space

: ENOMEM memory exhausted

SRESPUBFUN sres_record_t** sres_cached_answers_sockaddr	(	sres_resolver_t *	res,
		uint16_t	type,
		struct sockaddr const *	addr
	)

Get a list of matching (type/domain) records from cache.

Parameters:

	res	pointer to resolver
	type	record type to query (or sres_qtype_any for any record)
	addr	socket address structure

The type should be sres_type_ptr. The addr should contain either IPv4 (AF_INET) or IPv6 (AF_INET6) address.

If the SRES_OPTIONS environment variable, RES_OPTIONS environment variable or an "options" entry in resolv.conf file contains an option "ip6-dotint", the IPv6 addresses are resolved using suffix ".ip6.int" instead of default ".ip6.arpa".

Return values:

pointer

to an array of pointers to cached records, or NULL if no entry was found.

Errors:

: EAFNOSUPPORT address family specified in addr is not supported

: ENOENT no cached records were found

: EFAULT res or addr point outside the address space

: ENOMEM memory exhausted

SRESPUBFUN void sres_free_answer	(	sres_resolver_t *	res,
		sres_record_t *	answer
	)

Free and zero one record.

SRESPUBFUN void sres_free_answers	(	sres_resolver_t *	res,
		sres_record_t **	answers
	)

Free the list records.

The array of records can be returned by sres_cached_answers() or given by callback function.

SRESPUBFUN int sres_is_blocking ( sres_resolver_t * res )

Return true (and set resolver in blocking mode) if resolver can block.

SRESPUBFUN sres_query_t* sres_query	(	sres_resolver_t *	res,
		sres_answer_f *	callback,
		sres_context_t *	context,
		uint16_t	type,
		char const *	domain
	)

Make a DNS query.

Sends a DNS query with specified type and domain to the DNS server. When an answer is received, the callback function is called with context and returned records as arguments.

The sres resolver takes care of retransmitting the query if a root object is associate with the resolver or if sres_resolver_timer() is called in regular intervals. It generates an error record with nonzero status if no response is received.

Parameters:

	res	pointer to resolver
	callback	function called when query is answered or times out
	context	pointer given as an extra argument to callback function
	type	record type to query (see sres_qtypes)
	domain	name to query

Query types also indicate the record type of the result. Any record can be queried with sres_qtype_any. Well-known query types understood and decoded by sres include sres_type_a, sres_type_aaaa, sres_type_cname, sres_type_ptr sres_type_soa, sres_type_aaaa, sres_type_srv, and sres_type_naptr.

Deprecated query type sres_type_a6 is also decoded.

Note:: The domain name is not concatenated with the domains from seach path or with the local domain. Use sres_search() in order to try domains in search path.

See also:: sres_search(), sres_blocking_query(), sres_cached_answers(), sres_query_sockaddr()

Errors:

: EFAULT res or domain point outside the address space

: ENAMETOOLONG domain is longer than SRES_MAXDNAME

: ENETDOWN no DNS servers configured

: ENOMEM memory exhausted

SRESPUBFUN void sres_query_bind	(	sres_query_t *	query,
		sres_answer_f *	callback,
		sres_context_t *	context
	)

Rebind a DNS query.

Parameters:

	query	pointer to a query object to bind
	callback	pointer to new callback function (may be NULL)
	context	pointer to callback context (may be NULL)

SRESPUBFUN sres_query_t* sres_query_make	(	sres_resolver_t *	res,
		sres_answer_f *	callback,
		sres_context_t *	context,
		int	dummy,
		uint16_t	type,
		char const *	domain
	)

Make a DNS query with socket.

Deprecated:

Make a DNS query with socket.

Deprecated:: Use sres_query() instead.

SRESPUBFUN sres_query_t* sres_query_make_sockaddr	(	sres_resolver_t *	res,
		sres_answer_f *	callback,
		sres_context_t *	context,
		int	dummy,
		uint16_t	type,
		struct sockaddr const *	addr
	)

Make a reverse DNS query with socket.

Deprecated:

Make a reverse DNS query with socket.

Deprecated:: Use sres_query_sockaddr() instead.

SRESPUBFUN sres_query_t* sres_query_sockaddr	(	sres_resolver_t *	res,
		sres_answer_f *	callback,
		sres_context_t *	context,
		uint16_t	type,
		struct sockaddr const *	addr
	)

Make a reverse DNS query.

Send a query to DNS server with specified type and domain name formed from the socket address addr. The sres resolver takes care of retransmitting the query if a root object is associate with the resolver or if sres_resolver_timer() is called in regular intervals. It generates an error record with nonzero status if no response is received.

Parameters:

	res	pointer to resolver
	callback	function called when query is answered or times out
	context	pointer given as an extra argument to callback function
	type	record type to query (or sres_qtype_any for any record)
	addr	socket address structure

The type should be sres_type_ptr. The addr should contain either IPv4 (AF_INET) or IPv6 (AF_INET6) address.

If the SRES_OPTIONS environment variable, RES_OPTIONS environment variable, or an "options" entry in resolv.conf file contains an option "ip6-dotint", the IPv6 addresses are resolved using suffix ".ip6.int" instead of the standard ".ip6.arpa" suffix.

Errors:

: EAFNOSUPPORT address family specified in addr is not supported

: ENETDOWN no DNS servers configured

: EFAULT res or addr point outside the address space

: ENOMEM memory exhausted

See also:: sres_query(), sres_blocking_query_sockaddr(), sres_cached_answers_sockaddr()

SRESPUBFUN sres_resolver_t* sres_resolver_copy ( sres_resolver_t * res )

Copy a resolver.

Make a copy of resolver sharing the configuration and cache with old resolver.

SRESPUBFUN void* sres_resolver_get_userdata ( sres_resolver_t const * res )

Get userdata pointer.

Returns:: Userdata pointer.

Errors:

: EFAULT res points outside the address space

SRESPUBFUN sres_resolver_t* sres_resolver_new ( char const * conf_file_path )

New resolver object.

Allocate and initialize a new sres resolver object. The resolver object contains the parsed resolv.conf file, a cache object containing past answers from DNS, and a list of active queries. The default resolv.conf file can be overriden by giving the name of the configuration file as conf_file_path.

Parameters:

conf_file_path

name of the resolv.conf configuration file

Returns:: A pointer to a newly created sres resolver object, or NULL upon an error.

SRESPUBFUN sres_resolver_t* sres_resolver_new_with_cache	(	char const *	conf_file_path,
		sres_cache_t *	cache,
		char const *	option,
			...
	)

New resolver object.

Allocate and initialize a new sres resolver object. The resolver object contains the parsed resolv.conf file, a cache object containing past answers from DNS, and a list of active queries. The default resolv.conf file can be overriden by giving the name of the configuration file as conf_file_path.

It is also possible to override the values in the resolv.conf and RES_OPTIONS by giving the directives in the NULL-terminated list.

Parameters:

	conf_file_path	name of the resolv.conf configuration file
	cache	optional pointer to a resolver cache (may be NULL)
	option,...	list of resolv.conf options directives (overriding options in conf_file)

Environment Variables

LOCALDOMAIN overrides domain or search directives
RES_OPTIONS overrides values of options in resolv.conf
SRES_OPTIONS overrides values of options in resolv.conf, RES_OPTIONS, and options, ... list given as argument for this function

Returns:: A pointer to a newly created sres resolver object, or NULL upon an error.

sres_resolver_t * sres_resolver_new_with_cache_va	(	char const *	conf_file_path,
		sres_cache_t *	cache,
		char const *	option,
		va_list	va
	)

New resolver object.

Create a resolver.

Allocate and initialize a new sres resolver object.

This is a stdarg version of sres_resolver_new_with_cache().

New resolver object.

Allocate and initialize a new sres resolver object.

This is a stdarg version of sres_resolver_new_with_cache().

SRESPUBFUN sres_resolver_t* sres_resolver_ref ( sres_resolver_t * res )

Increase reference count on a resolver object.

SRESPUBFUN void* sres_resolver_set_userdata	(	sres_resolver_t *	res,
		void *	userdata
	)

Set userdata pointer.

Returns:: New userdata pointer.

Errors:

: EFAULT res points outside the address space

SRESPUBFUN void sres_resolver_unref ( sres_resolver_t * res )

Decrease the reference count on a resolver object.

SRESPUBFUN int sres_resolver_update	(	sres_resolver_t *	res,
		int	always
	)

Re-read resolv.conf if needed.

Return values:

	0	when successful
	-1	upon an error

SRESPUBFUN sres_query_t* sres_search	(	sres_resolver_t *	res,
		sres_answer_f *	callback,
		sres_context_t *	context,
		uint16_t	type,
		char const *	name
	)

Search DNS.

Sends DNS queries with specified type and name to the DNS server. If the name does not contain enought dots, the search domains are appended to the name and resulting domain name are also queried. When answer to all the search domains is received, the callback function is called with context and combined records from answers as arguments.

The sres resolver takes care of retransmitting the queries if a root object is associate with the resolver or if sres_resolver_timer() is called in regular intervals. It generates an error record with nonzero status if no response is received.

Parameters:

	res	pointer to resolver object
	callback	pointer to completion function
	context	argument given to the completion function
	type	record type to search (or sres_qtype_any for any record)
	name	host or domain name to search from DNS

Errors:

: EFAULT res or domain point outside the address space

: ENAMETOOLONG domain is longer than SRES_MAXDNAME

: ENETDOWN no DNS servers configured

: ENOMEM memory exhausted

See also:: sres_query(), sres_blocking_search(), sres_search_cached_answers().

SRESPUBFUN sres_record_t** sres_search_cached_answers	(	sres_resolver_t *	res,
		uint16_t	type,
		char const *	name
	)

Search for a list of matching (type/name) records from cache.

Returns:: pointer to an array of pointers to cached records, or NULL if no entry was found.

Errors:

: ENAMETOOLONG name or resulting domain is longer than SRES_MAXDNAME

: ENOENT no cached records were found

: EFAULT res or domain point outside the address space

: ENOMEM memory exhausted

See also:: sres_search(), sres_cached_answers()

SRESPUBFUN int sres_set_cached_srv_priority	(	sres_resolver_t *	res,
		char const *	domain,
		char const *	target,
		uint16_t	port,
		uint32_t	ttl,
		uint16_t	priority
	)

Modify the priority of the specified SRV records.

The SRV records with the domain name, target and port are matched and their priority value is adjusted. This function is used to implement greylisting of SIP servers.

Parameters:

	res	pointer to resolver
	domain	domain name of the SRV record(s) to modify
	target	SRV target of the SRV record(s) to modify
	port	port number of SRV record(s) to modify (in host byte order)
	ttl	new ttl for SRV records of the domain
	priority	new priority value (0=highest, 65535=lowest)

See also:: sres_cache_set_srv_priority()

Since:: New in 1.12.8

sofia-resolv/sres.h File Reference

Defines

Typedefs

Enumerations

Functions

Detailed Description

Define Documentation

Typedef Documentation

Enumeration Type Documentation

Function Documentation