The DNS SRV sorting code currently has an issue when records with a priority of zero exist with records of a non-zero priority. This occurs because the sorting code considers zero to mean unset when in reality is a valid value. If the current priority is zero it will get replaced with any remaining record that has a priority of non-zero, until no records of those exist after which the records of priority zero are handled. This change makes it so that the priority of the first remaining record is the current starting priority. There is also a small optimization to prevent iterating records when the starting priority is already zero. Change-Id: I103511f35b50428f770bd4db3ffef70fb6f82d35
215 lines
5.9 KiB
C
215 lines
5.9 KiB
C
/*
|
|
* 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"
|
|
|
|
ASTERISK_REGISTER_FILE()
|
|
|
|
#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) == ns_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) == ns_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) == ns_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) == ns_t_srv);
|
|
return srv->port;
|
|
}
|