dns_system_resolver.c File Reference

The default DNS resolver for Asterisk. More...

#include "asterisk.h"
#include "asterisk/_private.h"
#include "asterisk/astobj2.h"
#include "asterisk/dns.h"
#include "asterisk/dns_core.h"
#include "asterisk/dns_resolver.h"
#include "asterisk/linkedlists.h"
#include "asterisk/taskprocessor.h"
#include "asterisk/utils.h"

Include dependency graph for dns_system_resolver.c:

Go to the source code of this file.

Macros
#define	DNS_SYSTEM_RESOLVER_FAILURE   -1
	Resolver return code upon failure.
#define	DNS_SYSTEM_RESOLVER_PRIORITY   INT_MAX
	The consideration priority for this resolver implementation.
#define	DNS_SYSTEM_RESOLVER_SUCCESS   0
	Resolver return code upon success.

Functions
int	ast_dns_system_resolver_init (void)
	Initializes the resolver.
static int	dns_system_resolver_add_record (void *context, unsigned char *record, int record_len, int ttl)
	Callback to handle processing resource records.
static int	dns_system_resolver_cancel (struct ast_dns_query *query)
	Cancels processing resolution for a given query.
static void	dns_system_resolver_destroy (void)
	Destructor.
static int	dns_system_resolver_process_query (void *data)
	Callback to handle processing the query from the ast_taskprocessor instance.
static int	dns_system_resolver_resolve (struct ast_dns_query *query)
	Resolves a DNS query.
static int	dns_system_resolver_set_response (void *context, unsigned char *dns_response, int dns_response_len, int rcode)
	Callback to handle initializing the results field.

Variables
struct ast_dns_resolver	dns_system_resolver_base
	The base definition for the dns_system_resolver.
static struct ast_taskprocessor *	dns_system_resolver_tp
	The task processor to use for making DNS searches asynchronous.

Detailed Description

The default DNS resolver for Asterisk.

• See also res_resolver_unbound.c

Author

Ashley Sanders asand.nosp@m.ers@.nosp@m.digiu.nosp@m.m.co.nosp@m.m

Definition in file dns_system_resolver.c.

Macro Definition Documentation

DNS_SYSTEM_RESOLVER_FAILURE

#define DNS_SYSTEM_RESOLVER_FAILURE   -1

Resolver return code upon failure.

Definition at line 46 of file dns_system_resolver.c.

DNS_SYSTEM_RESOLVER_PRIORITY

#define DNS_SYSTEM_RESOLVER_PRIORITY   INT_MAX

The consideration priority for this resolver implementation.

Definition at line 40 of file dns_system_resolver.c.

DNS_SYSTEM_RESOLVER_SUCCESS

#define DNS_SYSTEM_RESOLVER_SUCCESS   0

Resolver return code upon success.

Definition at line 43 of file dns_system_resolver.c.

Function Documentation

ast_dns_system_resolver_init()

int ast_dns_system_resolver_init

(

void

)

Initializes the resolver.

Return values

0	on success
-1	on failure

Definition at line 244 of file dns_system_resolver.c.

{
    /* Register the base resolver */
    int res = ast_dns_resolver_register(&dns_system_resolver_base);
 
    if (res) {
        return DNS_SYSTEM_RESOLVER_FAILURE;
    }
 
    /* Instantiate the task processor */
    dns_system_resolver_tp = ast_taskprocessor_get("dns_system_resolver_tp",
                                                    TPS_REF_DEFAULT);
 
    /* Return error if the task processor failed to instantiate */
    if (!dns_system_resolver_tp) {
        return DNS_SYSTEM_RESOLVER_FAILURE;
    }
 
    /* Register the cleanup function */
    ast_register_cleanup(dns_system_resolver_destroy);
 
    return DNS_SYSTEM_RESOLVER_SUCCESS;
}

References ast_dns_resolver_register(), ast_register_cleanup(), ast_taskprocessor_get(), dns_system_resolver_base, dns_system_resolver_destroy(), DNS_SYSTEM_RESOLVER_FAILURE, DNS_SYSTEM_RESOLVER_SUCCESS, dns_system_resolver_tp, and TPS_REF_DEFAULT.

Referenced by asterisk_daemon().

dns_system_resolver_add_record()

static int dns_system_resolver_add_record ( void *  context, unsigned char *  record, int  record_len, int  ttl  )

static

Callback to handle processing resource records.

Adds an individual resource record discovered with ast_search_dns_ex to the ast_dns_query currently being resolved.

Definition at line 84 of file dns_system_resolver.c.

{
    struct ast_dns_query *query = context;
 
    /* Add the record to the query.*/
    return ast_dns_resolver_add_record(query,
                                       ast_dns_query_get_rr_type(query),
                                       ast_dns_query_get_rr_class(query),
                                       ttl,
                                       (const char*) record,
                                       record_len);
}

References ast_dns_query_get_rr_class(), ast_dns_query_get_rr_type(), and ast_dns_resolver_add_record().

Referenced by dns_system_resolver_process_query().

dns_system_resolver_cancel()

static int dns_system_resolver_cancel ( struct ast_dns_query *  query )

static

Cancels processing resolution for a given query.

Note

The system API calls block so there is no way to cancel them. Therefore, this function always returns failure when invoked.

Definition at line 110 of file dns_system_resolver.c.

{
    return DNS_SYSTEM_RESOLVER_FAILURE;
}

References DNS_SYSTEM_RESOLVER_FAILURE.

dns_system_resolver_destroy()

static void dns_system_resolver_destroy ( void  )

static

Destructor.

Definition at line 120 of file dns_system_resolver.c.

{
    /* Unreference the task processor */
    dns_system_resolver_tp = ast_taskprocessor_unreference(dns_system_resolver_tp);
 
    /* Unregister the base resolver */
    ast_dns_resolver_unregister(&dns_system_resolver_base);
}

References ast_dns_resolver_unregister(), ast_taskprocessor_unreference(), dns_system_resolver_base, and dns_system_resolver_tp.

Referenced by ast_dns_system_resolver_init().

dns_system_resolver_process_query()

static int dns_system_resolver_process_query ( void *  data )

static

Callback to handle processing the query from the ast_taskprocessor instance.

Definition at line 140 of file dns_system_resolver.c.

{
    struct ast_dns_query *query = data;
 
    /* Perform the DNS search */
    enum ast_dns_search_result res = ast_search_dns_ex(query,
                                                       ast_dns_query_get_name(query),
                                                       ast_dns_query_get_rr_class(query),
                                                       ast_dns_query_get_rr_type(query),
                                                       dns_system_resolver_set_response,
                                                       dns_system_resolver_add_record);
 
    /* Handle the possible return values from the DNS search */
    if (res == AST_DNS_SEARCH_FAILURE) {
        ast_debug(1, "DNS search failed for query: '%s'\n",
                ast_dns_query_get_name(query));
    } else if (res == AST_DNS_SEARCH_NO_RECORDS) {
        ast_debug(1, "DNS search failed to yield any results for query: '%s'\n",
                ast_dns_query_get_name(query));
    }
 
    /* Mark the query as complete */
    ast_dns_resolver_completed(query);
 
    /* Reduce the reference count on the query object */
    ao2_ref(query, -1);
 
    return res;
}

References ao2_ref, ast_debug, ast_dns_query_get_name(), ast_dns_query_get_rr_class(), ast_dns_query_get_rr_type(), ast_dns_resolver_completed(), AST_DNS_SEARCH_FAILURE, AST_DNS_SEARCH_NO_RECORDS, ast_search_dns_ex(), dns_system_resolver_add_record(), and dns_system_resolver_set_response().

Referenced by dns_system_resolver_resolve().

dns_system_resolver_resolve()

static int dns_system_resolver_resolve ( struct ast_dns_query *  query )

static

Resolves a DNS query.

Definition at line 180 of file dns_system_resolver.c.

{
    /* Add query processing handler to the task processor */
    int res = ast_taskprocessor_push(dns_system_resolver_tp,
                                     dns_system_resolver_process_query,
                                     ao2_bump(query));
 
    /* The query processing handler was not added to the task processor */
    if (res < 0) {
        ast_log(LOG_ERROR, "Failed to perform async DNS resolution of '%s'\n",
                ast_dns_query_get_name(query));
        ao2_ref(query, -1);
    }
 
    /* Return the result of adding the query processing handler to the task processor */
    return res;
}

References ao2_bump, ao2_ref, ast_dns_query_get_name(), ast_log, ast_taskprocessor_push(), dns_system_resolver_process_query(), dns_system_resolver_tp, and LOG_ERROR.

dns_system_resolver_set_response()

static int dns_system_resolver_set_response ( void *  context, unsigned char *  dns_response, int  dns_response_len, int  rcode  )

static

Callback to handle initializing the results field.

Definition at line 211 of file dns_system_resolver.c.

{
    struct ast_dns_query *query = context;
    int res;
 
    /* Instantiate the query's result field (if necessary). */
    if (!ast_dns_query_get_result(query)) {
        res = ast_dns_resolver_set_result(query,
                                          0,
                                          0,
                                          rcode,
                                          ast_dns_query_get_name(query),
                                          (const char*) dns_response,
                                          dns_response_len);
 
        if (res) {
            /* There was a problem instantiating the results field. */
            ast_log(LOG_ERROR, "Could not instantiate the results field for query: '%s'\n",
                    ast_dns_query_get_name(query));
        }
    } else {
        res = DNS_SYSTEM_RESOLVER_SUCCESS;
    }
 
    return res;
}

References ast_dns_query_get_name(), ast_dns_query_get_result(), ast_dns_resolver_set_result(), ast_log, DNS_SYSTEM_RESOLVER_SUCCESS, and LOG_ERROR.

Referenced by dns_system_resolver_process_query().

Variable Documentation

dns_system_resolver_base

struct ast_dns_resolver dns_system_resolver_base

The base definition for the dns_system_resolver.

Definition at line 61 of file dns_system_resolver.c.

                                                   {
    .name = "system",
    .priority = DNS_SYSTEM_RESOLVER_PRIORITY,
    .resolve = dns_system_resolver_resolve,
    .cancel = dns_system_resolver_cancel,
};

Referenced by ast_dns_system_resolver_init(), and dns_system_resolver_destroy().

dns_system_resolver_tp

struct ast_taskprocessor* dns_system_resolver_tp

static

The task processor to use for making DNS searches asynchronous.

Definition at line 58 of file dns_system_resolver.c.

Referenced by ast_dns_system_resolver_init(), dns_system_resolver_destroy(), and dns_system_resolver_resolve().