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/*
* 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 SRV Record Support
*
* \author Joshua Colp <jcolp@digium.com>
*/
/*** MODULEINFO
<support_level>core</support_level>
***/
#include "asterisk.h"
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>
#include "asterisk/dns_core.h"
#include "asterisk/dns_srv.h"
#include "asterisk/linkedlists.h"
#include "asterisk/dns_internal.h"
#include "asterisk/utils.h"
struct ast_dns_record *dns_srv_alloc(struct ast_dns_query *query, const char *data, const size_t size)
{
uint16_t priority;
uint16_t weight;
uint16_t port;
const char *ptr;
const char *end_of_record;
struct ast_dns_srv_record *srv;
int host_size;
char host[NI_MAXHOST] = "";
ptr = dns_find_record(data, size, query->result->answer, query->result->answer_size);
ast_assert(ptr != NULL);
end_of_record = ptr + size;
/* PRIORITY */
ptr += dns_parse_short((unsigned char *) ptr, &priority);
if (ptr >= end_of_record) {
return NULL;
}
/* WEIGHT */
ptr += dns_parse_short((unsigned char *) ptr, &weight);
if (ptr >= end_of_record) {
return NULL;
}
/* PORT */
ptr += dns_parse_short((unsigned char *) ptr, &port);
if (ptr >= end_of_record) {
return NULL;
}
host_size = dn_expand((unsigned char *)query->result->answer, (unsigned char *) end_of_record, (unsigned char *) ptr, host, sizeof(host) - 1);
if (host_size < 0) {
ast_log(LOG_ERROR, "Failed to expand domain name: %s\n", strerror(errno));
return NULL;
}
if (!strcmp(host, ".")) {
return NULL;
}
srv = ast_calloc(1, sizeof(*srv) + size + host_size + 1);
if (!srv) {
return NULL;
}
srv->priority = priority;
srv->weight = weight;
srv->port = port;
srv->host = srv->data + size;
strcpy((char *)srv->host, host); /* SAFE */
((char *)srv->host)[host_size] = '\0';
srv->generic.data_ptr = srv->data;
return (struct ast_dns_record *)srv;
}
/* This implementation was taken from the existing srv.c which, after reading the RFC, implements it
* as it should.
*/
void dns_srv_sort(struct ast_dns_result *result)
{
struct ast_dns_record *current;
struct dns_records newlist = AST_LIST_HEAD_NOLOCK_INIT_VALUE;
while (AST_LIST_FIRST(&result->records)) {
unsigned short cur_priority = ((struct ast_dns_srv_record *)(AST_LIST_FIRST(&result->records)))->priority;
struct dns_records temp_list = AST_LIST_HEAD_NOLOCK_INIT_VALUE;
/* Find the lowest current priority to work on, but if the priority is already zero there is no lower priority */
if (cur_priority) {
AST_LIST_TRAVERSE(&result->records, current, list) {
if (((struct ast_dns_srv_record *)current)->priority < cur_priority) {
cur_priority = ((struct ast_dns_srv_record *)current)->priority;
}
}
}
/* Find all records which match this priority */
AST_LIST_TRAVERSE_SAFE_BEGIN(&result->records, current, list) {
if (((struct ast_dns_srv_record *)current)->priority != cur_priority) {
continue;
}
AST_LIST_REMOVE_CURRENT(list);
/* Records with a weight of zero must always be at the head */
if (((struct ast_dns_srv_record *)current)->weight == 0) {
AST_LIST_INSERT_HEAD(&temp_list, current, list);
} else {
AST_LIST_INSERT_TAIL(&temp_list, current, list);
}
}
AST_LIST_TRAVERSE_SAFE_END;
/* Apply weighting - as each record is passed the sum of all previous weights (plus its own) is stored away, and then a random weight
* is calculated. The first record with a weight sum greater than the random weight is put in the new list and the whole thing starts
* once again.
*/
while (AST_LIST_FIRST(&temp_list)) {
unsigned int weight_sum = 0;
unsigned int random_weight;
AST_LIST_TRAVERSE(&temp_list, current, list) {
((struct ast_dns_srv_record *)current)->weight_sum = weight_sum += ((struct ast_dns_srv_record *)current)->weight;
}
/* if all the remaining entries have weight == 0,
then just append them to the result list and quit */
if (weight_sum == 0) {
AST_LIST_APPEND_LIST(&newlist, &temp_list, list);
break;
}
random_weight = 1 + (unsigned int) ((float) weight_sum * (ast_random() / ((float) RAND_MAX + 1.0)));
AST_LIST_TRAVERSE_SAFE_BEGIN(&temp_list, current, list) {
if (((struct ast_dns_srv_record *)current)->weight_sum < random_weight) {
continue;
}
AST_LIST_MOVE_CURRENT(&newlist, list);
break;
}
AST_LIST_TRAVERSE_SAFE_END;
}
}
/* now that the new list has been ordered,
put it in place */
AST_LIST_APPEND_LIST(&result->records, &newlist, list);
}
const char *ast_dns_srv_get_host(const struct ast_dns_record *record)
{
struct ast_dns_srv_record *srv = (struct ast_dns_srv_record *) record;
ast_assert(ast_dns_record_get_rr_type(record) == T_SRV);
return srv->host;
}
unsigned short ast_dns_srv_get_priority(const struct ast_dns_record *record)
{
struct ast_dns_srv_record *srv = (struct ast_dns_srv_record *) record;
ast_assert(ast_dns_record_get_rr_type(record) == T_SRV);
return srv->priority;
}
unsigned short ast_dns_srv_get_weight(const struct ast_dns_record *record)
{
struct ast_dns_srv_record *srv = (struct ast_dns_srv_record *) record;
ast_assert(ast_dns_record_get_rr_type(record) == T_SRV);
return srv->weight;
}
unsigned short ast_dns_srv_get_port(const struct ast_dns_record *record)
{
struct ast_dns_srv_record *srv = (struct ast_dns_srv_record *) record;
ast_assert(ast_dns_record_get_rr_type(record) == T_SRV);
return srv->port;
}
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