[Asterisk-code-review] ASTERISK-25146: Created a system-level DNS resolver for the ... (asterisk[master])
Ashley Sanders
asteriskteam at digium.com
Tue Jun 30 13:32:58 CDT 2015
Ashley Sanders has uploaded a new change for review.
https://gerrit.asterisk.org/749
Change subject: ASTERISK-25146: Created a system-level DNS resolver for the DNS core.
......................................................................
ASTERISK-25146: Created a system-level DNS resolver for the DNS core.
Prior to this patch, the DNS core present in master had no default system-level
resolver implementation. Therefore, it was not possible for the DNS core to
perform resolutions unless the libunbound library was installed and the
res_resolver_unbound module was loaded.
This patch introduces a system-level DNS resolver implementation that will
register itself with the lowest consideration priority available (to ensure
that it is to be used only as a last resort). The resolver relies on low-level
DNS search functions to perform a rudimentary DNS search based on a provided
query and then supplies the search results to the DNS core.
Change-Id: I3b36ea17b889a98df4f8d80d50bb7ee175afa077
---
M include/asterisk/_private.h
M include/asterisk/dns.h
A include/asterisk/dns_system_resolver.h
M main/asterisk.c
M main/dns.c
A main/dns_system_resolver.c
6 files changed, 642 insertions(+), 19 deletions(-)
git pull ssh://gerrit.asterisk.org:29418/asterisk refs/changes/49/749/1
diff --git a/include/asterisk/_private.h b/include/asterisk/_private.h
index d49de17..3f9f094 100644
--- a/include/asterisk/_private.h
+++ b/include/asterisk/_private.h
@@ -29,6 +29,7 @@
int dnsmgr_init(void); /*!< Provided by dnsmgr.c */
void dnsmgr_start_refresh(void); /*!< Provided by dnsmgr.c */
int dnsmgr_reload(void); /*!< Provided by dnsmgr.c */
+int ast_dns_system_resolver_init(void); /*!< Provided by dns_system_resolver.c */
void threadstorage_init(void); /*!< Provided by threadstorage.c */
int ast_device_state_engine_init(void); /*!< Provided by devicestate.c */
int astobj2_init(void); /*!< Provided by astobj2.c */
diff --git a/include/asterisk/dns.h b/include/asterisk/dns.h
index 4899fa8..6f66ecc 100644
--- a/include/asterisk/dns.h
+++ b/include/asterisk/dns.h
@@ -24,17 +24,48 @@
#ifndef _ASTERISK_DNS_H
#define _ASTERISK_DNS_H
-/*! \brief Perform DNS lookup (used by DNS, enum and SRV lookups)
- \param context
- \param dname Domain name to lookup (host, SRV domain, TXT record name)
- \param class Record Class (see "man res_search")
- \param type Record type (see "man res_search")
- \param callback Callback function for handling DNS result
- \note Asterisk DNS is synchronus at this time. This means that if your DNS
- services does not work, Asterisk may lock while waiting for response.
-*/
+/*!
+ * \brief Perform DNS lookup (used by DNS, enum and SRV lookups)
+ *
+ * \param context Void pointer containing data to use in the callback function.
+ * \param dname Domain name to lookup (host, SRV domain, TXT record name).
+ * \param class Record Class (see "man res_search").
+ * \param type Record type (see "man res_search").
+ * \param answer The full DNS response.
+ * \param len The length of the full DNS response.
+ * \param callback Callback function for handling the discovered resource records from the DNS search.
+ *
+ * \retval -1 on search failure
+ * \retval 0 on no records found
+ * \retval 1 on success
+ *
+ * \note Asterisk DNS is synchronus at this time. This means that if your DNS
+ * services does not work, Asterisk may lock while waiting for response.
+ */
int ast_search_dns(void *context, const char *dname, int class, int type,
- int (*callback)(void *context, unsigned char *answer, int len, unsigned char *fullanswer));
+ int (*callback)(void *context, unsigned char *answer, int len, unsigned char *fullanswer));
+
+/*! \brief Extended version of the DNS search function. Performs a DNS lookup, (used by
+ * DNS, enum and SRV lookups), parses the results and notifies observers of any
+ * discovered resource records (used by ast_dns_system_resolver).
+ *
+ * \param context Void pointer containing data to use in the handler functions.
+ * \param dname Domain name to lookup (host, SRV domain, TXT record name).
+ * \param rr_class Record Class (see "man res_search").
+ * \param rr_type Record type (see "man res_search").
+ * \param response_handler Callback function for handling the DNS response.
+ * \param record_handler Callback function for handling the discovered resource records from the DNS search.
+ *
+ * \retval -1 on search failure
+ * \retval 0 on no records found
+ * \retval 1 on success
+ *
+ * \note Asterisk DNS is synchronus at this time. This means that if your DNS
+ * services does not work, Asterisk may lock while waiting for response.
+ */
+int ast_search_dns_ex(void *context, const char *dname, int rr_class, int rr_type,
+ int (*response_handler)(void *context, unsigned char *dns_response, int dns_response_len, int rcode),
+ int (*record_handler)(void *context, unsigned char *record, int record_len, int ttl));
/*! \brief Retrieve the configured nameservers of the system */
struct ao2_container *ast_dns_get_nameservers(void);
diff --git a/include/asterisk/dns_system_resolver.h b/include/asterisk/dns_system_resolver.h
new file mode 100755
index 0000000..f879777
--- /dev/null
+++ b/include/asterisk/dns_system_resolver.h
@@ -0,0 +1,32 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2015, Digium, Inc.
+ *
+ * Ashley Sanders <asanders at digium.com>
+ *
+ * See http://www.asterisk.org for more information about
+ * the Asterisk project. Please do not directly contact
+ * any of the maintainers of this project for assistance;
+ * the project provides a web site, mailing lists and IRC
+ * channels for your use.
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License Version 2. See the LICENSE file
+ * at the top of the source tree.
+ */
+
+/*! \file
+ *
+ * \brief Definitions for the default DNS resolver for Asterisk.
+ *
+ * \author Ashley Sanders <asanders at digium.com>
+ */
+
+/*!
+ * \brief Initializes the resolver.
+ *
+ * \retval 0 on success.
+ * \retval -1 on failure.
+ */
+int ast_dns_system_resolver_init(void);
diff --git a/main/asterisk.c b/main/asterisk.c
index 53bcead..0478f6c 100644
--- a/main/asterisk.c
+++ b/main/asterisk.c
@@ -4511,6 +4511,11 @@
exit(1);
}
+ if (ast_dns_system_resolver_init()) { /* Initialize the default DNS resolver */
+ printf("Failed: ast_dns_system_resolver_init\n%s", term_quit());
+ exit(1);
+ }
+
if ((moduleresult = load_modules(1))) { /* Load modules, pre-load only */
printf("Failed: load_modules\n%s", term_quit());
exit(moduleresult == -2 ? 2 : 1);
diff --git a/main/dns.c b/main/dns.c
index fd87420..a14eac7 100644
--- a/main/dns.c
+++ b/main/dns.c
@@ -45,7 +45,17 @@
#include "asterisk/dns.h"
#include "asterisk/endian.h"
+/*! \brief Size used for creating the DNS response container. */
#define MAX_SIZE 4096
+
+/*! \brief Return code upon failure. */
+#define DNS_SEARCH_FAILURE -1
+
+/*! \brief Return code upon no records found. */
+#define DNS_SEARCH_NO_RECORDS 0
+
+/*! \brief Return code upon success. */
+#define DNS_SEARCH_SUCCESS 1
#ifdef __PDP_ENDIAN
#if __BYTE_ORDER == __PDP_ENDIAN
@@ -57,6 +67,10 @@
#endif
#if __BYTE_ORDER == __LITTLE_ENDIAN
#define DETERMINED_BYTE_ORDER __LITTLE_ENDIAN
+#endif
+
+#ifndef HAVE_RES_NINIT
+AST_MUTEX_DEFINE_STATIC(res_lock);
#endif
/* The dns_HEADER structure definition below originated
@@ -156,12 +170,23 @@
} dns_HEADER;
struct dn_answer {
- unsigned short rtype;
- unsigned short class;
- unsigned int ttl;
- unsigned short size;
+ unsigned short rtype; /*!< The resource record type. */
+ unsigned short class; /*!< The resource record class. */
+ unsigned int ttl; /*!< The resource record time to live. */
+ unsigned short size; /*!< The resource record size. */
} __attribute__((__packed__));
+/*!
+ * \brief Tries to find the position of the next field in the DNS response.
+ *
+ * \internal
+ *
+ * \param s A char pointer to the current frame in the DNS response.
+ * \param len The remaining available length of the DNS response.
+ *
+ * \retval The position of the next field
+ * \retval -1 if there are no remaining fields
+ */
static int skip_name(unsigned char *s, int len)
{
int x = 0;
@@ -172,20 +197,151 @@
x++;
break;
}
+
if ((*s & 0xc0) == 0xc0) {
s += 2;
x += 2;
break;
}
+
x += *s + 1;
s += *s + 1;
}
+
+ /* If we are out of room to search, return failure. */
if (x >= len)
- return -1;
+ return DNS_SEARCH_FAILURE;
+
+ /* Return the value for the current position in the DNS response. This is the start
+ position of the next field. */
return x;
}
-/*! \brief Parse DNS lookup result, call callback */
+/*!
+ * \brief Updates the current frame in the DNS response by the requested `length
+ *
+ * \internal
+ *
+ * \param dns_response A char pointer to the current frame in the DNS response.
+ * \param remaining_len The remaining available length in the DNS response to search.
+ *
+ * \retval The remaining length in the DNS response
+ * \retval -1 there are no frames remaining in the DNS response
+ */
+static int dns_update_frame(unsigned char *dns_response, int remaining_len, int frame_size)
+{
+ dns_response += frame_size;
+ remaining_len -= frame_size;
+
+ if (remaining_len < 0) {
+ ast_log(LOG_WARNING, "Length of DNS answer exceeds frame\n");
+ return DNS_SEARCH_FAILURE;
+ }
+
+ return remaining_len;
+}
+
+/*!
+ * \brief Handles the DNS search if the system has RES_INIT.
+ *
+ * \internal
+ *
+ * \param dname Domain name to lookup (host, SRV domain, TXT record name).
+ * \param rr_class Record Class (see "man res_search").
+ * \param rr_type Record type (see "man res_search").
+ * \param dns_response The full DNS response.
+ * \param dns_response_len The length of the full DNS response.
+ *
+ * \retval The length of the DNS response
+ * \retval -1 on search failure
+ */
+static int dns_search_res_n(const char *dname, int rr_class, int rr_type,
+ unsigned char *dns_response, int dns_response_len)
+{
+
+#ifndef HAVE_RES_NINIT
+
+ struct __res_state dns_state;
+
+ ast_mutex_lock(&res_lock);
+ res_init();
+ dns_response_len = res_nsearch(&dns_state,
+ dname,
+ rr_class,
+ rr_type,
+ dns_response,
+ dns_response_len);
+
+#ifdef HAVE_RES_CLOSE
+ res_close();
+#endif
+
+ ast_mutex_unlock(&res_lock);
+ return dns_response_len; /* Search is complete */
+#endif
+
+ return DNS_SEARCH_FAILURE; /* No search performed */
+}
+
+/*!
+ * \brief Handles the DNS search if the system has RES_NINIT.
+ *
+ * \internal
+ *
+ * \param dname Domain name to lookup (host, SRV domain, TXT record name).
+ * \param rr_class Record Class (see "man res_search").
+ * \param rr_type Record type (see "man res_search").
+ * \param dns_response The full DNS response.
+ * \param dns_response_len The length of the full DNS response.
+ *
+ * \retval The length of the DNS response
+ * \retval -1 on search failure
+ */
+static int dns_search_res_ninit(const char *dname, int rr_class, int rr_type,
+ unsigned char *dns_response, int dns_response_len)
+{
+
+#ifdef HAVE_RES_NINIT
+ struct __res_state dns_state;
+
+ memset(&dns_state, 0, sizeof(dns_state));
+ res_ninit(&dns_state);
+ dns_response_len = res_nsearch(&dns_state,
+ dname,
+ rr_class,
+ rr_type,
+ dns_response,
+ dns_response_len);
+
+#ifdef HAVE_RES_NDESTROY
+ res_ndestroy(&dns_state);
+#else
+ res_nclose(&dns_state);
+#endif
+
+ return dns_response_len; /* Search is complete */
+#endif
+
+ return DNS_SEARCH_FAILURE; /* No search performed */
+}
+
+/*!
+ * \brief Parse DNS lookup result, call callback
+ *
+ * \internal
+ *
+ * \param context Void pointer containing data to use in the callback functions.
+ * \param dname Domain name to lookup (host, SRV domain, TXT record name).
+ * \param class Record Class (see "man res_search").
+ * \param type Record type (see "man res_search").
+ * \param answer The full DNS response.
+ * \param len The length of the full DNS response.
+ * \param callback Callback function for handling the discovered resource records from the DNS search.
+ *
+ * \retval -1 on search failure
+ * \retval 0 on no records found
+ * \retval 1 on success
+ */
static int dns_parse_answer(void *context,
int class, int type, unsigned char *answer, int len,
int (*callback)(void *context, unsigned char *answer, int len, unsigned char *fullanswer))
@@ -244,9 +400,97 @@
return ret;
}
-#ifndef HAVE_RES_NINIT
-AST_MUTEX_DEFINE_STATIC(res_lock);
-#endif
+/*!
+ * \brief Extended version of the DNS Parsing function. Parses the DNS lookup result and notifies
+ * the observer of each discovered resource record with the provided callback.
+ *
+ * \internal
+ *
+ * \param context Void pointer containing data to use in the callback functions.
+ * \param dname Domain name to lookup (host, SRV domain, TXT record name).
+ * \param rr_class Record Class (see "man res_search").
+ * \param rr_type Record type (see "man res_search").
+ * \param answer The full DNS response.
+ * \param answer_len The length of the full DNS response.
+ * \param response_handler Callback function for handling the DNS response.
+ * \param record_handler Callback function for handling the discovered resource records from the DNS search.
+ *
+ * \retval -1 on search failure
+ * \retval 0 on no records found
+ * \retval 1 on success
+ */
+static int dns_parse_answer_ex(void *context, int rr_class, int rr_type, unsigned char *answer, int answer_len,
+ int (*response_handler)(void *context, unsigned char *dns_response, int dns_response_len, int rcode),
+ int (*record_handler)(void *context, unsigned char *record, int record_len, int ttl))
+{
+ unsigned char *dns_response = answer;
+ dns_HEADER *dns_header = (dns_HEADER *)answer;
+
+ struct dn_answer *ans;
+ int res, x, pos, dns_response_len, ret;
+
+ dns_response_len = answer_len;
+ ret = DNS_SEARCH_NO_RECORDS;
+
+ /* Invoke the response_handler callback, if provided, to notify the observer of the raw DNS response */
+ if (response_handler) {
+ response_handler(context, dns_response, dns_response_len, ntohs(dns_header->rcode));
+ }
+
+ /* Verify there is something to parse */
+ if (answer_len == 0) {
+ return DNS_SEARCH_NO_RECORDS;
+ }
+
+ /* Try updating the cursors for the dns header */
+ if ((pos = dns_update_frame(answer, answer_len, sizeof(dns_HEADER))) < 0) {
+ return DNS_SEARCH_FAILURE;
+ }
+
+ /* Skip domain name and QCODE / QCLASS */
+ for (x = 0; x < ntohs(dns_header->qdcount); x++) {
+ if ((res = skip_name(answer, pos)) < 0) {
+ ast_log(LOG_WARNING, "Failed skipping name\n");
+ return DNS_SEARCH_FAILURE;
+ }
+
+ /* Try updating the cursors for the name and QCODE / QCLASS fields */
+ if ((pos = dns_update_frame(answer, pos, res + 4)) < 0) {
+ return DNS_SEARCH_FAILURE;
+ }
+ }
+
+ /* Extract the individual records */
+ for (x = 0; x < ntohs(dns_header->ancount); x++) {
+ if ((res = skip_name(answer, pos)) < 0) {
+ ast_log(LOG_WARNING, "Failed skipping name\n");
+ return DNS_SEARCH_FAILURE;
+ }
+
+ /* Try updating the cursors for the current record */
+ if ((pos = dns_update_frame(answer, pos, res + sizeof(struct dn_answer))) < 0) {
+ return DNS_SEARCH_FAILURE;
+ }
+
+ /* Cast the current value for the answer pointer as a dn_answer struct */
+ ans = (struct dn_answer *)answer;
+
+ /* Skip over the records that do not have the same resource record class and type we care about */
+ if (ntohs(ans->class) == rr_class && ntohs(ans->rtype) == rr_type) {
+ /* Invoke the callback, if provided, to deliver the discovered record */
+ if (record_handler) {
+ record_handler(context, answer, ntohs(ans->size), ans->ttl);
+ ret = DNS_SEARCH_SUCCESS;
+ }
+ }
+
+ /* Try and update the frame to the next record, but ignore any errors that come
+ * back because this may be the end of the line. */
+ pos = dns_update_frame(answer, pos, res + ntohs(ans->size));
+ }
+
+ return ret;
+}
/*! \brief Lookup record in DNS
\note Asterisk DNS is synchronus at this time. This means that if your DNS does
@@ -297,6 +541,48 @@
return ret;
}
+int ast_search_dns_ex(void *context, const char *dname, int rr_class, int rr_type,
+ int (*response_handler)(void *context, unsigned char *dns_response, int dns_response_len, int rcode),
+ int (*record_handler)(void *context, unsigned char *record, int record_len, int ttl))
+{
+ int ret, dns_response_len;
+ unsigned char dns_response[MAX_SIZE];
+
+ /* Try the DNS search. */
+ if ((dns_response_len = dns_search_res_ninit(dname,
+ rr_class,
+ rr_type,
+ dns_response,
+ sizeof(dns_response))) < 0) {
+ if ((dns_response_len = dns_search_res_n(dname,
+ rr_class,
+ rr_type,
+ dns_response,
+ sizeof(dns_response))) < 0) {
+ ast_log(LOG_WARNING, "DNS Search was not performed; System does not have either RES_INIT or RES_NINIT .");
+ return DNS_SEARCH_FAILURE;
+ }
+ }
+
+ /* Parse records from DNS response */
+ ret = dns_parse_answer_ex(context,
+ rr_class,
+ rr_type,
+ dns_response,
+ dns_response_len,
+ response_handler,
+ record_handler);
+
+ /* Handle parse result */
+ if (ret == DNS_SEARCH_FAILURE) {
+ ast_log(LOG_WARNING, "DNS Parse error for %s\n", dname); /* Parsing Error */
+ } else if (ret == DNS_SEARCH_NO_RECORDS) {
+ ast_log(LOG_WARNING, "DNS search yielded no results for %s\n", dname); /* No results found */
+ }
+
+ return ret;
+}
+
struct ao2_container *ast_dns_get_nameservers(void)
{
#ifdef HAVE_RES_NINIT
diff --git a/main/dns_system_resolver.c b/main/dns_system_resolver.c
new file mode 100755
index 0000000..3bb367b
--- /dev/null
+++ b/main/dns_system_resolver.c
@@ -0,0 +1,268 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2015, Digium, Inc.
+ *
+ * Ashley Sanders <asanders at digium.com>
+ *
+ * See http://www.asterisk.org for more information about
+ * the Asterisk project. Please do not directly contact
+ * any of the maintainers of this project for assistance;
+ * the project provides a web site, mailing lists and IRC
+ * channels for your use.
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License Version 2. See the LICENSE file
+ * at the top of the source tree.
+ */
+
+/*! \file
+ *
+ * \brief The default DNS resolver for Asterisk.
+ *
+ * \arg See also \ref res_resolver_unbound
+ *
+ * \author Ashley Sanders <asanders at digium.com>
+ */
+
+#include "asterisk.h"
+
+ASTERISK_REGISTER_FILE()
+
+#include "asterisk/astobj2.h"
+#include "asterisk/dns.h"
+#include "asterisk/dns_core.h"
+#include "asterisk/dns_system_resolver.h"
+#include "asterisk/dns_resolver.h"
+#include "asterisk/linkedlists.h"
+#include "asterisk/taskprocessor.h"
+
+/*! \brief The consideration priority for this resolver implementation. */
+#define DNS_SYSTEM_RESOLVER_PRIORITY INT_MAX
+
+/*! \brief Resolver return code upon success. */
+#define DNS_SYSTEM_RESOLVER_SUCCESS 0
+
+/*! \brief Resolver return code upon failure. */
+#define DNS_SYSTEM_RESOLVER_FAILURE -1
+
+
+static int dns_system_resolver_add_record(void *context, unsigned char *record, int record_len, int ttl);
+static int dns_system_resolver_cancel(struct ast_dns_query *query);
+static void dns_system_resolver_destroy(void);
+static int dns_system_resolver_process_query(void *data);
+static int dns_system_resolver_resolve(struct ast_dns_query *query);
+static int dns_system_resolver_set_response(void *context, unsigned char *dns_response, int dns_response_len, int rcode);
+
+
+/*! \brief The task processor to use for making DNS searches asynchronous. */
+static struct ast_taskprocessor *dns_system_resolver_tp;
+
+/*! \brief The base definition for the dns_system_resolver */
+struct ast_dns_resolver dns_system_resolver_base = {
+ .name = "system",
+ .priority = DNS_SYSTEM_RESOLVER_PRIORITY,
+ .resolve = dns_system_resolver_resolve,
+ .cancel = dns_system_resolver_cancel,
+};
+
+/*!
+ * \brief Callback to handle processing an individual resource record discovered from ast_search_dns_ex.
+ *
+ * \internal
+ *
+ * \param context A void pointer to the ast_dns_query being processed.
+ * \param record An individual resource record discovered during the DNS search.
+ * \param record_len The length of the resource record.
+ * \param ttl The resource record's expiration time limit (time to live).
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ */
+static int dns_system_resolver_add_record(void *context, unsigned char *record, int record_len, int ttl)
+{
+ struct ast_dns_query *query = context;
+
+ /* Add the record to the query.*/
+ return ast_dns_resolver_add_record(query, /* The DNS query */
+ ast_dns_query_get_rr_type(query), /* Resource record type */
+ ast_dns_query_get_rr_class(query), /* Resource record class */
+ ttl, /* TTL of the record */
+ (const char*)record, /* The raw DNS record */
+ record_len); /* The size of the raw DNS record */
+}
+
+/*!
+ * \brief 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.
+ *
+ * \internal
+ *
+ * \param query The ast_dns_query to cancel.
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ */
+static int dns_system_resolver_cancel(struct ast_dns_query *query)
+{
+ return DNS_SYSTEM_RESOLVER_FAILURE;
+}
+
+/*!
+ * \brief Destructor.
+ *
+ * \internal
+ */
+static void dns_system_resolver_destroy(void)
+{
+ /* 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);
+
+ return;
+}
+
+/*!
+ * \brief Callback to handle processing the query from the ast_taskprocessor instance.
+ *
+ * \internal
+ *
+ * \param data A void pointer to the ast_dns_query being processed.
+ *
+ * \retval -1 on search failure
+ * \retval 0 on no records found
+ * \retval 1 on success
+ */
+static int dns_system_resolver_process_query(void *data)
+{
+ struct ast_dns_query *query = data;
+
+ /* Perform the DNS search */
+ int 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 < 0) {
+ /* DNS parse error */
+ ast_log(LOG_ERROR, "DNS search failed for query: '%s'\n",
+ ast_dns_query_get_name(query));
+ } else if (res == 0) {
+ /* No results */
+ ast_log(LOG_ERROR, "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;
+}
+
+/*!
+ * \brief Resolves a DNS query.
+ *
+ * \internal
+ *
+ * \param query The ast_dns_query to resolve.
+ *
+ * \retval 0 on successful load of query handler to the ast_taskprocessor instance
+ * \retval -1 on failure to load the query handler to the ast_taskprocessor instance
+ */
+static int dns_system_resolver_resolve(struct ast_dns_query *query)
+{
+ /* 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 == DNS_SYSTEM_RESOLVER_FAILURE) {
+ 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;
+}
+
+/*!
+ * \brief Callback to handle initializing the results field.
+ *
+ * \internal
+ *
+ * \param dns_response The full DNS response.
+ * \param dns_response The length of the full DNS response.
+ * \param rcode The DNS response code.
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ */
+static int dns_system_resolver_set_response(void *context, unsigned char *dns_response, int dns_response_len, int rcode)
+{
+ 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, /* The DNS query */
+ 0, /* Is the result secure? */
+ 0, /* Is the result bogus? */
+ rcode, /* Optional response code */
+ ast_dns_query_get_name(query), /* Canonical name */
+ (const char*)dns_response, /* The raw DNS answer */
+ dns_response_len); /* The size of the raw DNS answer */
+
+ 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;
+}
+
+/*!
+ * \brief Initializes the resolver.
+ *
+ * \retval 0 on success
+ * \retval -1 on failure
+ */
+int ast_dns_system_resolver_init(void)
+{
+ /* 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) {
+ dns_system_resolver_destroy();
+ return DNS_SYSTEM_RESOLVER_FAILURE;
+ }
+
+ /* Register the cleanup function */
+ ast_register_cleanup(dns_system_resolver_destroy);
+
+ return DNS_SYSTEM_RESOLVER_SUCCESS;
+}
--
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Gerrit-MessageType: newchange
Gerrit-Change-Id: I3b36ea17b889a98df4f8d80d50bb7ee175afa077
Gerrit-PatchSet: 1
Gerrit-Project: asterisk
Gerrit-Branch: master
Gerrit-Owner: Ashley Sanders <asanders at digium.com>
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