dns_query_set.c

Go to the documentation of this file.

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2015, Digium, Inc.
 *
 * Joshua Colp <jcolp@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 DNS Query Set API
 *
 * \author Joshua Colp <jcolp@digium.com>
 */
 
/*** MODULEINFO
    <support_level>core</support_level>
 ***/
 
#include "asterisk.h"
 
#include "asterisk/vector.h"
#include "asterisk/astobj2.h"
#include "asterisk/utils.h"
#include "asterisk/linkedlists.h"
#include "asterisk/dns_core.h"
#include "asterisk/dns_query_set.h"
#include "asterisk/dns_internal.h"
#include "asterisk/dns_resolver.h"
 
/*! \brief The default number of expected queries to be added to the query set */
#define DNS_QUERY_SET_EXPECTED_QUERY_COUNT 5
 
/*! \brief Destructor for DNS query set */
static void dns_query_set_destroy(void *data)
{
    struct ast_dns_query_set *query_set = data;
    int idx;
 
    for (idx = 0; idx < AST_VECTOR_SIZE(&query_set->queries); ++idx) {
        struct dns_query_set_query *query = AST_VECTOR_GET_ADDR(&query_set->queries, idx);
 
        ao2_ref(query->query, -1);
    }
    AST_VECTOR_FREE(&query_set->queries);
 
    ao2_cleanup(query_set->user_data);
}
 
struct ast_dns_query_set *ast_dns_query_set_create(void)
{
    struct ast_dns_query_set *query_set;
 
    query_set = ao2_alloc_options(sizeof(*query_set), dns_query_set_destroy, AO2_ALLOC_OPT_LOCK_NOLOCK);
    if (!query_set) {
        return NULL;
    }
 
    if (AST_VECTOR_INIT(&query_set->queries, DNS_QUERY_SET_EXPECTED_QUERY_COUNT)) {
        ao2_ref(query_set, -1);
        return NULL;
    }
 
    return query_set;
}
 
/*! \brief Callback invoked upon completion of a DNS query */
static void dns_query_set_callback(const struct ast_dns_query *query)
{
    struct ast_dns_query_set *query_set = ast_dns_query_get_data(query);
 
    /* The reference count of the query set is bumped here in case this query holds the last reference */
    ao2_ref(query_set, +1);
 
    /* Drop the query set from the query so the query set can be destroyed if this is the last one */
    ao2_cleanup(((struct ast_dns_query *)query)->user_data);
    ((struct ast_dns_query *)query)->user_data = NULL;
 
    if (ast_atomic_fetchadd_int(&query_set->queries_completed, +1) != (AST_VECTOR_SIZE(&query_set->queries) - 1)) {
        ao2_ref(query_set, -1);
        return;
    }
 
    /* All queries have been completed, invoke final callback */
    if (query_set->queries_cancelled != AST_VECTOR_SIZE(&query_set->queries)) {
        query_set->callback(query_set);
    }
 
    ao2_cleanup(query_set->user_data);
    query_set->user_data = NULL;
 
    ao2_ref(query_set, -1);
}
 
int ast_dns_query_set_add(struct ast_dns_query_set *query_set, const char *name, int rr_type, int rr_class)
{
    struct dns_query_set_query query = {
        .started = 0,
    };
 
    ast_assert(!query_set->in_progress);
    if (query_set->in_progress) {
        ast_log(LOG_ERROR, "Attempted to add additional query to query set '%p' after resolution has started\n",
            query_set);
        return -1;
    }
 
    /*
     * We are intentionally passing NULL for the user data even
     * though dns_query_set_callback() is not NULL tolerant.  Doing
     * this avoids a circular reference chain until the queries are
     * started.  ast_dns_query_set_resolve_async() will set the
     * query user_data for us later when we actually kick off the
     * queries.
     */
    query.query = dns_query_alloc(name, rr_type, rr_class, dns_query_set_callback, NULL);
    if (!query.query) {
        return -1;
    }
 
    if (AST_VECTOR_APPEND(&query_set->queries, query)) {
        ao2_ref(query.query, -1);
        return -1;
    }
 
    return 0;
}
 
size_t ast_dns_query_set_num_queries(const struct ast_dns_query_set *query_set)
{
    return AST_VECTOR_SIZE(&query_set->queries);
}
 
struct ast_dns_query *ast_dns_query_set_get(const struct ast_dns_query_set *query_set, unsigned int index)
{
    /* Only once all queries have been completed can results be retrieved */
    if (query_set->queries_completed != AST_VECTOR_SIZE(&query_set->queries)) {
        return NULL;
    }
 
    /* If the index exceeds the number of queries... no query for you */
    if (index >= AST_VECTOR_SIZE(&query_set->queries)) {
        return NULL;
    }
 
    return AST_VECTOR_GET_ADDR(&query_set->queries, index)->query;
}
 
void *ast_dns_query_set_get_data(const struct ast_dns_query_set *query_set)
{
    return query_set->user_data;
}
 
void ast_dns_query_set_resolve_async(struct ast_dns_query_set *query_set, ast_dns_query_set_callback callback, void *data)
{
    int idx;
 
    ast_assert(!query_set->in_progress);
    if (query_set->in_progress) {
        ast_log(LOG_ERROR, "Attempted to start asynchronous resolution of query set '%p' when it has already started\n",
            query_set);
        return;
    }
 
    query_set->in_progress = 1;
    query_set->callback = callback;
    query_set->user_data = ao2_bump(data);
 
    /*
     * Bump the query_set ref in case all queries complete
     * before we are done kicking them off.
     */
    ao2_ref(query_set, +1);
    for (idx = 0; idx < AST_VECTOR_SIZE(&query_set->queries); ++idx) {
        struct dns_query_set_query *query = AST_VECTOR_GET_ADDR(&query_set->queries, idx);
 
        query->query->user_data = ao2_bump(query_set);
 
        if (!query->query->resolver->resolve(query->query)) {
            query->started = 1;
            continue;
        }
 
        dns_query_set_callback(query->query);
    }
    if (!idx) {
        /*
         * There were no queries in the set;
         * therefore all queries are "completed".
         * Invoke the final callback.
         */
        query_set->callback(query_set);
        ao2_cleanup(query_set->user_data);
        query_set->user_data = NULL;
    }
    ao2_ref(query_set, -1);
}
 
/*! \brief Structure used for signaling back for synchronous resolution completion */
struct dns_synchronous_resolve {
    /*! \brief Lock used for signaling */
    ast_mutex_t lock;
    /*! \brief Condition used for signaling */
    ast_cond_t cond;
    /*! \brief Whether the query has completed */
    unsigned int completed;
};
 
/*! \brief Destructor for synchronous resolution structure */
static void dns_synchronous_resolve_destroy(void *data)
{
    struct dns_synchronous_resolve *synchronous = data;
 
    ast_mutex_destroy(&synchronous->lock);
    ast_cond_destroy(&synchronous->cond);
}
 
/*! \brief Callback used to implement synchronous resolution */
static void dns_synchronous_resolve_callback(const struct ast_dns_query_set *query_set)
{
    struct dns_synchronous_resolve *synchronous = ast_dns_query_set_get_data(query_set);
 
    ast_mutex_lock(&synchronous->lock);
    synchronous->completed = 1;
    ast_cond_signal(&synchronous->cond);
    ast_mutex_unlock(&synchronous->lock);
}
 
int ast_query_set_resolve(struct ast_dns_query_set *query_set)
{
    struct dns_synchronous_resolve *synchronous;
 
    synchronous = ao2_alloc_options(sizeof(*synchronous), dns_synchronous_resolve_destroy, AO2_ALLOC_OPT_LOCK_NOLOCK);
    if (!synchronous) {
        return -1;
    }
 
    ast_mutex_init(&synchronous->lock);
    ast_cond_init(&synchronous->cond, NULL);
 
    ast_dns_query_set_resolve_async(query_set, dns_synchronous_resolve_callback, synchronous);
 
    /* Wait for resolution to complete */
    ast_mutex_lock(&synchronous->lock);
    while (!synchronous->completed) {
        ast_cond_wait(&synchronous->cond, &synchronous->lock);
    }
    ast_mutex_unlock(&synchronous->lock);
 
    ao2_ref(synchronous, -1);
 
    return 0;
}
 
int ast_dns_query_set_resolve_cancel(struct ast_dns_query_set *query_set)
{
    int idx;
    size_t query_count = AST_VECTOR_SIZE(&query_set->queries);
 
    for (idx = 0; idx < AST_VECTOR_SIZE(&query_set->queries); ++idx) {
        struct dns_query_set_query *query = AST_VECTOR_GET_ADDR(&query_set->queries, idx);
 
        if (query->started) {
            if (!query->query->resolver->cancel(query->query)) {
                query_set->queries_cancelled++;
                dns_query_set_callback(query->query);
            }
        } else {
            query_set->queries_cancelled++;
        }
    }
 
    return (query_set->queries_cancelled == query_count) ? 0 : -1;
}