Asterisk - The Open Source Telephony Project  GIT-master-a24979a
dns_recurring.c
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1 /*
2  * Asterisk -- An open source telephony toolkit.
3  *
4  * Copyright (C) 2015, Digium, Inc.
5  *
6  * Joshua Colp <jcolp@digium.com>
7  *
8  * See http://www.asterisk.org for more information about
9  * the Asterisk project. Please do not directly contact
10  * any of the maintainers of this project for assistance;
11  * the project provides a web site, mailing lists and IRC
12  * channels for your use.
13  *
14  * This program is free software, distributed under the terms of
15  * the GNU General Public License Version 2. See the LICENSE file
16  * at the top of the source tree.
17  */
18 
19 /*! \file
20  *
21  * \brief DNS Recurring Query Support
22  *
23  * \author Joshua Colp <jcolp@digium.com>
24  */
25 
26 /*** MODULEINFO
27  <support_level>core</support_level>
28  ***/
29 
30 #include "asterisk.h"
31 
32 #include "asterisk/astobj2.h"
33 #include "asterisk/linkedlists.h"
34 #include "asterisk/sched.h"
35 #include "asterisk/strings.h"
36 #include "asterisk/dns_core.h"
37 #include "asterisk/dns_recurring.h"
38 #include "asterisk/dns_internal.h"
39 
40 #include <arpa/nameser.h>
41 
42 /*! \brief Delay between TTL expiration and the next DNS query, to make sure the
43 resolver cache really expired. */
44 #define EXTRA_TTL 2
45 #define MAX_TTL ((INT_MAX - EXTRA_TTL) / 1000)
46 
47 /*! \brief Destructor for a DNS query */
48 static void dns_query_recurring_destroy(void *data)
49 {
50  struct ast_dns_query_recurring *recurring = data;
51 
52  ao2_cleanup(recurring->user_data);
53 }
54 
55 static void dns_query_recurring_resolution_callback(const struct ast_dns_query *query);
56 
57 /*! \brief Scheduled recurring query callback */
58 static int dns_query_recurring_scheduled_callback(const void *data)
59 {
60  struct ast_dns_query_recurring *recurring = (struct ast_dns_query_recurring *)data;
61 
62  ao2_lock(recurring);
63  recurring->timer = -1;
64  if (!recurring->cancelled) {
65  recurring->active = ast_dns_resolve_async(recurring->name, recurring->rr_type, recurring->rr_class, dns_query_recurring_resolution_callback,
66  recurring);
67  }
68  ao2_unlock(recurring);
69 
70  ao2_ref(recurring, -1);
71 
72  return 0;
73 }
74 
75 /*! \brief Query resolution callback */
77 {
78  struct ast_dns_query_recurring *recurring = ast_dns_query_get_data(query);
79  struct ast_dns_query *callback_query;
80 
81  /* Create a separate query to invoke the user specific callback on as the
82  * recurring query user data may get used externally (by the unit test)
83  * and thus changing it is problematic
84  */
85  callback_query = dns_query_alloc(query->name, query->rr_type, query->rr_class,
86  recurring->callback, recurring->user_data);
87  if (callback_query) {
88  /* The result is immutable at this point and can be safely provided */
89  callback_query->result = query->result;
90  callback_query->callback(callback_query);
91  callback_query->result = NULL;
92  ao2_ref(callback_query, -1);
93  }
94 
95  ao2_lock(recurring);
96  /* So.. if something has not externally cancelled this we can reschedule based on the TTL */
97  if (!recurring->cancelled) {
98  const struct ast_dns_result *result = ast_dns_query_get_result(query);
100 
101  if (ttl) {
103  if (recurring->timer < 0) {
104  /* It is impossible for this to be the last reference as the query has a reference to it */
105  ao2_ref(recurring, -1);
106  }
107  }
108  }
109 
110  ao2_replace(recurring->active, NULL);
111  ao2_unlock(recurring);
112 }
113 
115 {
116  struct ast_dns_query_recurring *recurring;
117 
119  return NULL;
120  }
121 
122  recurring = ao2_alloc(sizeof(*recurring) + strlen(name) + 1, dns_query_recurring_destroy);
123  if (!recurring) {
124  return NULL;
125  }
126 
127  recurring->callback = callback;
128  recurring->user_data = ao2_bump(data);
129  recurring->timer = -1;
130  recurring->rr_type = rr_type;
131  recurring->rr_class = rr_class;
132  strcpy(recurring->name, name); /* SAFE */
133 
135  if (!recurring->active) {
136  ao2_ref(recurring, -1);
137  return NULL;
138  }
139 
140  return recurring;
141 }
142 
144 {
145  int res = 0;
146 
147  ao2_lock(recurring);
148 
149  recurring->cancelled = 1;
150  AST_SCHED_DEL_UNREF(ast_dns_get_sched(), recurring->timer, ao2_ref(recurring, -1));
151 
152  if (recurring->active) {
153  res = ast_dns_resolve_cancel(recurring->active);
154  ao2_replace(recurring->active, NULL);
155  }
156 
157  ao2_unlock(recurring);
158 
159  return res;
160 }
Asterisk main include file. File version handling, generic pbx functions.
#define ao2_cleanup(obj)
Definition: astobj2.h:1934
#define ao2_unlock(a)
Definition: astobj2.h:729
#define ao2_replace(dst, src)
Replace one object reference with another cleaning up the original.
Definition: astobj2.h:501
#define ao2_lock(a)
Definition: astobj2.h:717
#define ao2_ref(o, delta)
Reference/unreference an object and return the old refcount.
Definition: astobj2.h:459
#define ao2_bump(obj)
Bump refcount on an AO2 object by one, returning the object.
Definition: astobj2.h:480
#define ao2_alloc(data_size, destructor_fn)
Definition: astobj2.h:409
static PGresult * result
Definition: cel_pgsql.c:84
Core DNS API.
struct ast_dns_result * ast_dns_query_get_result(const struct ast_dns_query *query)
Get the result information for a DNS query.
Definition: dns_core.c:77
int ast_dns_resolve_cancel(struct ast_dns_query_active *active)
Cancel an asynchronous DNS resolution.
Definition: dns_core.c:272
void * ast_dns_query_get_data(const struct ast_dns_query *query)
Get the user specific data of a DNS query.
Definition: dns_core.c:72
int ast_dns_result_get_lowest_ttl(const struct ast_dns_result *result)
Retrieve the lowest TTL from a result.
Definition: dns_core.c:112
void(* ast_dns_resolve_callback)(const struct ast_dns_query *query)
Callback invoked when a query completes.
Definition: dns_core.h:171
struct ast_dns_query_active * ast_dns_resolve_async(const char *name, int rr_type, int rr_class, ast_dns_resolve_callback callback, void *data)
Asynchronously resolve a DNS query.
Definition: dns_core.c:247
Internal DNS structure definitions.
struct ast_dns_query * dns_query_alloc(const char *name, int rr_type, int rr_class, ast_dns_resolve_callback callback, void *data)
Allocate a DNS query (but do not start resolution)
Definition: dns_core.c:193
struct ast_sched_context * ast_dns_get_sched(void)
Retrieve the DNS scheduler context.
Definition: dns_core.c:52
#define EXTRA_TTL
Delay between TTL expiration and the next DNS query, to make sure the resolver cache really expired.
Definition: dns_recurring.c:44
int ast_dns_resolve_recurring_cancel(struct ast_dns_query_recurring *recurring)
Cancel an asynchronous recurring DNS resolution.
#define MAX_TTL
Definition: dns_recurring.c:45
static void dns_query_recurring_destroy(void *data)
Destructor for a DNS query.
Definition: dns_recurring.c:48
static void dns_query_recurring_resolution_callback(const struct ast_dns_query *query)
Query resolution callback.
Definition: dns_recurring.c:76
struct ast_dns_query_recurring * ast_dns_resolve_recurring(const char *name, int rr_type, int rr_class, ast_dns_resolve_callback callback, void *data)
Asynchronously resolve a DNS query, and continue resolving it according to the lowest TTL available.
static int dns_query_recurring_scheduled_callback(const void *data)
Scheduled recurring query callback.
Definition: dns_recurring.c:58
DNS Recurring Resolution API.
static const char name[]
Definition: format_mp3.c:68
A set of macros to manage forward-linked lists.
#define NULL
Definition: resample.c:96
Scheduler Routines (derived from cheops)
#define AST_SCHED_DEL_UNREF(sched, id, refcall)
schedule task to get deleted and call unref function
Definition: sched.h:82
int ast_sched_add(struct ast_sched_context *con, int when, ast_sched_cb callback, const void *data) attribute_warn_unused_result
Adds a scheduled event.
Definition: sched.c:567
String manipulation functions.
static force_inline int attribute_pure ast_strlen_zero(const char *s)
Definition: strings.h:65
A recurring DNS query.
Definition: dns_internal.h:157
void * user_data
User-specific data.
Definition: dns_internal.h:161
ast_dns_resolve_callback callback
Callback to invoke upon completion.
Definition: dns_internal.h:159
unsigned int cancelled
The recurring query has been cancelled.
Definition: dns_internal.h:165
struct ast_dns_query_active * active
Current active query.
Definition: dns_internal.h:163
int rr_class
Resource record class.
Definition: dns_internal.h:171
int rr_type
Resource record type.
Definition: dns_internal.h:169
int timer
Scheduled timer for next resolution.
Definition: dns_internal.h:167
char name[0]
The name of what is being resolved.
Definition: dns_internal.h:173
A DNS query.
Definition: dns_internal.h:137
ast_dns_resolve_callback callback
Callback to invoke upon completion.
Definition: dns_internal.h:139
struct ast_dns_result * result
Result of the DNS query.
Definition: dns_internal.h:147
int rr_class
Resource record class.
Definition: dns_internal.h:151
int rr_type
Resource record type.
Definition: dns_internal.h:149
char name[0]
The name of what is being resolved.
Definition: dns_internal.h:153
The result of a DNS query.
Definition: dns_internal.h:117
#define MIN(a, b)
Definition: utils.h:226