[Asterisk-code-review] res_rtp_asterisk: Automatically refresh stunaddr from DNS (asterisk[18])
George Joseph
asteriskteam at digium.com
Wed Sep 1 10:29:22 CDT 2021
George Joseph has submitted this change. ( https://gerrit.asterisk.org/c/asterisk/+/16167 )
Change subject: res_rtp_asterisk: Automatically refresh stunaddr from DNS
......................................................................
res_rtp_asterisk: Automatically refresh stunaddr from DNS
This allows the STUN server to change its IP address without having to
reload the res_rtp_asterisk module.
The refresh of the name resolution occurs first when the module is
loaded, then recurringly, slightly after the previous DNS answer TTL
expires.
ASTERISK-29508 #close
Change-Id: I7955a046293f913ba121bbd82153b04439e3465f
---
M configs/samples/rtp.conf.sample
A doc/CHANGES-staging/res_rtp_asterisk_stunaddr_recurring_resolution.txt
M main/dns_recurring.c
M res/res_rtp_asterisk.c
4 files changed, 137 insertions(+), 9 deletions(-)
Approvals:
Kevin Harwell: Looks good to me, but someone else must approve
George Joseph: Looks good to me, approved
Friendly Automation: Approved for Submit
diff --git a/configs/samples/rtp.conf.sample b/configs/samples/rtp.conf.sample
index 1207c78..3027b95 100644
--- a/configs/samples/rtp.conf.sample
+++ b/configs/samples/rtp.conf.sample
@@ -63,7 +63,8 @@
; Hostname or address for the STUN server used when determining the external
; IP address and port an RTP session can be reached at. The port number is
; optional. If omitted the default value of 3478 will be used. This option is
-; disabled by default.
+; disabled by default. Name resolution will occur at load time, and if DNS is
+; used, name resolution will occur repeatedly after the TTL expires.
;
; e.g. stundaddr=mystun.server.com:3478
;
diff --git a/doc/CHANGES-staging/res_rtp_asterisk_stunaddr_recurring_resolution.txt b/doc/CHANGES-staging/res_rtp_asterisk_stunaddr_recurring_resolution.txt
new file mode 100644
index 0000000..c78f4f5
--- /dev/null
+++ b/doc/CHANGES-staging/res_rtp_asterisk_stunaddr_recurring_resolution.txt
@@ -0,0 +1,6 @@
+Subject: res_rtp_asterisk
+
+When the address of the STUN server (stunaddr) is a name resolved via DNS, the
+stunaddr will be recurringly resolved when the DNS answer Time-To-Live (TTL)
+expires. This allows the STUN server to change its IP address without having to
+reload the res_rtp_asterisk module.
diff --git a/main/dns_recurring.c b/main/dns_recurring.c
index 294438f..6a953fa 100644
--- a/main/dns_recurring.c
+++ b/main/dns_recurring.c
@@ -39,6 +39,11 @@
#include <arpa/nameser.h>
+/* \brief Delay between TTL expiration and the next DNS query, to make sure the
+resolver cache really expired. */
+#define EXTRA_TTL 2
+#define MAX_TTL ((INT_MAX - EXTRA_TTL) / 1000)
+
/*! \brief Destructor for a DNS query */
static void dns_query_recurring_destroy(void *data)
{
@@ -91,10 +96,10 @@
/* So.. if something has not externally cancelled this we can reschedule based on the TTL */
if (!recurring->cancelled) {
const struct ast_dns_result *result = ast_dns_query_get_result(query);
- int ttl = MIN(ast_dns_result_get_lowest_ttl(result), INT_MAX / 1000);
+ int ttl = MIN(ast_dns_result_get_lowest_ttl(result), MAX_TTL);
if (ttl) {
- recurring->timer = ast_sched_add(ast_dns_get_sched(), ttl * 1000, dns_query_recurring_scheduled_callback, ao2_bump(recurring));
+ recurring->timer = ast_sched_add(ast_dns_get_sched(), (ttl + EXTRA_TTL) * 1000, dns_query_recurring_scheduled_callback, ao2_bump(recurring));
if (recurring->timer < 0) {
/* It is impossible for this to be the last reference as the query has a reference to it */
ao2_ref(recurring, -1);
diff --git a/res/res_rtp_asterisk.c b/res/res_rtp_asterisk.c
index 5227e94..6da4824 100644
--- a/res/res_rtp_asterisk.c
+++ b/res/res_rtp_asterisk.c
@@ -36,6 +36,11 @@
#include "asterisk.h"
+#include <arpa/nameser.h>
+#include "asterisk/dns_core.h"
+#include "asterisk/dns_internal.h"
+#include "asterisk/dns_recurring.h"
+
#include <sys/time.h>
#include <signal.h>
#include <fcntl.h>
@@ -230,6 +235,10 @@
static struct ast_acl_list *stun_acl = NULL;
static ast_rwlock_t stun_acl_lock = AST_RWLOCK_INIT_VALUE;
+/*! stunaddr recurring resolution */
+static ast_rwlock_t stunaddr_lock = AST_RWLOCK_INIT_VALUE;
+static struct ast_dns_query_recurring *stunaddr_resolver = NULL;
+
/*! \brief Pool factory used by pjlib to allocate memory. */
static pj_caching_pool cachingpool;
@@ -646,6 +655,9 @@
static int __rtp_sendto(struct ast_rtp_instance *instance, void *buf, size_t size, int flags, struct ast_sockaddr *sa, int rtcp, int *via_ice, int use_srtp);
+static void stunaddr_resolve_callback(const struct ast_dns_query *query);
+static int store_stunaddr_resolved(const struct ast_dns_query *query);
+
#if defined(HAVE_OPENSSL) && (OPENSSL_VERSION_NUMBER >= 0x10001000L) && !defined(OPENSSL_NO_SRTP)
static int dtls_bio_new(BIO *bio)
{
@@ -3529,6 +3541,7 @@
pj_sockaddr pjtmp;
struct ast_ice_host_candidate *candidate;
int af_inet_ok = 0, af_inet6_ok = 0;
+ struct sockaddr_in stunaddr_copy;
if (ast_sockaddr_is_ipv4(addr)) {
af_inet_ok = 1;
@@ -3638,8 +3651,12 @@
freeifaddrs(ifa);
}
+ ast_rwlock_rdlock(&stunaddr_lock);
+ memcpy(&stunaddr_copy, &stunaddr, sizeof(stunaddr));
+ ast_rwlock_unlock(&stunaddr_lock);
+
/* If configured to use a STUN server to get our external mapped address do so */
- if (stunaddr.sin_addr.s_addr && !stun_address_is_blacklisted(addr) &&
+ if (stunaddr_copy.sin_addr.s_addr && !stun_address_is_blacklisted(addr) &&
(ast_sockaddr_is_ipv4(addr) || ast_sockaddr_is_any(addr)) &&
count < PJ_ICE_MAX_CAND) {
struct sockaddr_in answer;
@@ -3656,7 +3673,7 @@
*/
ao2_unlock(instance);
rsp = ast_stun_request(component == AST_RTP_ICE_COMPONENT_RTCP
- ? rtp->rtcp->s : rtp->s, &stunaddr, NULL, &answer);
+ ? rtp->rtcp->s : rtp->s, &stunaddr_copy, NULL, &answer);
ao2_lock(instance);
if (!rsp) {
struct ast_rtp_engine_ice_candidate *candidate;
@@ -9009,6 +9026,72 @@
return 0;
}
+static void stunaddr_resolve_callback(const struct ast_dns_query *query)
+{
+ const int lowest_ttl = ast_dns_result_get_lowest_ttl(ast_dns_query_get_result(query));
+ const char *stunaddr_name = ast_dns_query_get_name(query);
+ const char *stunaddr_resolved_str;
+
+ if (!store_stunaddr_resolved(query)) {
+ ast_log(LOG_WARNING, "Failed to resolve stunaddr '%s'. Cancelling recurring resolution.\n", stunaddr_name);
+ return;
+ }
+
+ if (DEBUG_ATLEAST(2)) {
+ ast_rwlock_rdlock(&stunaddr_lock);
+ stunaddr_resolved_str = ast_inet_ntoa(stunaddr.sin_addr);
+ ast_rwlock_unlock(&stunaddr_lock);
+
+ ast_debug_stun(2, "Resolved stunaddr '%s' to '%s'. Lowest TTL = %d.\n",
+ stunaddr_name,
+ stunaddr_resolved_str,
+ lowest_ttl);
+ }
+
+ if (!lowest_ttl) {
+ ast_log(LOG_WARNING, "Resolution for stunaddr '%s' returned TTL = 0. Recurring resolution was cancelled.\n", ast_dns_query_get_name(query));
+ }
+}
+
+static int store_stunaddr_resolved(const struct ast_dns_query *query)
+{
+ const struct ast_dns_result *result = ast_dns_query_get_result(query);
+ const struct ast_dns_record *record;
+
+ for (record = ast_dns_result_get_records(result); record; record = ast_dns_record_get_next(record)) {
+ const size_t data_size = ast_dns_record_get_data_size(record);
+ const unsigned char *data = (unsigned char *)ast_dns_record_get_data(record);
+ const int rr_type = ast_dns_record_get_rr_type(record);
+
+ if (rr_type == ns_t_a && data_size == 4) {
+ ast_rwlock_wrlock(&stunaddr_lock);
+ memcpy(&stunaddr.sin_addr, data, data_size);
+ stunaddr.sin_family = AF_INET;
+ ast_rwlock_unlock(&stunaddr_lock);
+
+ return 1;
+ } else {
+ ast_debug_stun(3, "Unrecognized rr_type '%u' or data_size '%zu' from DNS query for stunaddr '%s'\n",
+ rr_type, data_size, ast_dns_query_get_name(query));
+ continue;
+ }
+ }
+ return 0;
+}
+
+static void clean_stunaddr(void) {
+ if (stunaddr_resolver) {
+ if (ast_dns_resolve_recurring_cancel(stunaddr_resolver)) {
+ ast_log(LOG_ERROR, "Failed to cancel recurring DNS resolution of previous stunaddr.\n");
+ }
+ ao2_ref(stunaddr_resolver, -1);
+ stunaddr_resolver = NULL;
+ }
+ ast_rwlock_wrlock(&stunaddr_lock);
+ memset(&stunaddr, 0, sizeof(stunaddr));
+ ast_rwlock_unlock(&stunaddr_lock);
+}
+
#if defined(HAVE_OPENSSL) && (OPENSSL_VERSION_NUMBER >= 0x10001000L) && !defined(OPENSSL_NO_SRTP)
/*! \pre instance is locked */
static int ast_rtp_activate(struct ast_rtp_instance *instance)
@@ -9106,6 +9189,7 @@
static char *handle_cli_rtp_settings(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
+ struct sockaddr_in stunaddr_copy;
switch (cmd) {
case CLI_INIT:
e->command = "rtp show settings";
@@ -9138,6 +9222,11 @@
ast_cli(a->fd, " Replay Protect: %s\n", AST_CLI_YESNO(srtp_replay_protection));
#ifdef HAVE_PJPROJECT
ast_cli(a->fd, " ICE support: %s\n", AST_CLI_YESNO(icesupport));
+
+ ast_rwlock_rdlock(&stunaddr_lock);
+ memcpy(&stunaddr_copy, &stunaddr, sizeof(stunaddr));
+ ast_rwlock_unlock(&stunaddr_lock);
+ ast_cli(a->fd, " STUN address: %s:%d\n", ast_inet_ntoa(stunaddr_copy.sin_addr), htons(stunaddr_copy.sin_port));
#endif
return CLI_SUCCESS;
}
@@ -9386,7 +9475,7 @@
icesupport = DEFAULT_ICESUPPORT;
stun_software_attribute = DEFAULT_STUN_SOFTWARE_ATTRIBUTE;
turnport = DEFAULT_TURN_PORT;
- memset(&stunaddr, 0, sizeof(stunaddr));
+ clean_stunaddr();
turnaddr = pj_str(NULL);
turnusername = pj_str(NULL);
turnpassword = pj_str(NULL);
@@ -9464,9 +9553,35 @@
stun_software_attribute = ast_true(s);
}
if ((s = ast_variable_retrieve(cfg, "general", "stunaddr"))) {
- stunaddr.sin_port = htons(STANDARD_STUN_PORT);
- if (ast_parse_arg(s, PARSE_INADDR, &stunaddr)) {
- ast_log(LOG_WARNING, "Invalid STUN server address: %s\n", s);
+ char *hostport, *host, *port;
+ unsigned int port_parsed = STANDARD_STUN_PORT;
+ struct ast_sockaddr stunaddr_parsed;
+
+ hostport = ast_strdupa(s);
+
+ if (!ast_parse_arg(hostport, PARSE_ADDR, &stunaddr_parsed)) {
+ ast_debug_stun(3, "stunaddr = '%s' does not need name resolution\n",
+ ast_sockaddr_stringify_host(&stunaddr_parsed));
+ if (!ast_sockaddr_port(&stunaddr_parsed)) {
+ ast_sockaddr_set_port(&stunaddr_parsed, STANDARD_STUN_PORT);
+ }
+ ast_rwlock_wrlock(&stunaddr_lock);
+ ast_sockaddr_to_sin(&stunaddr_parsed, &stunaddr);
+ ast_rwlock_unlock(&stunaddr_lock);
+ } else if (ast_sockaddr_split_hostport(hostport, &host, &port, 0)) {
+ if (port) {
+ ast_parse_arg(port, PARSE_UINT32|PARSE_IN_RANGE, &port_parsed, 1, 65535);
+ }
+ stunaddr.sin_port = htons(port_parsed);
+
+ stunaddr_resolver = ast_dns_resolve_recurring(host, T_A, C_IN,
+ &stunaddr_resolve_callback, NULL);
+ if (!stunaddr_resolver) {
+ ast_log(LOG_ERROR, "Failed to setup recurring DNS resolution of stunaddr '%s'",
+ host);
+ }
+ } else {
+ ast_log(LOG_ERROR, "Failed to parse stunaddr '%s'", hostport);
}
}
if ((s = ast_variable_retrieve(cfg, "general", "turnaddr"))) {
@@ -9726,6 +9841,7 @@
acl_change_sub = stasis_unsubscribe_and_join(acl_change_sub);
rtp_unload_acl(&ice_acl_lock, &ice_acl);
rtp_unload_acl(&stun_acl_lock, &stun_acl);
+ clean_stunaddr();
#endif
return 0;
--
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Gerrit-Project: asterisk
Gerrit-Branch: 18
Gerrit-Change-Id: I7955a046293f913ba121bbd82153b04439e3465f
Gerrit-Change-Number: 16167
Gerrit-PatchSet: 5
Gerrit-Owner: Sébastien Duthil <sduthil at wazo.community>
Gerrit-Reviewer: Friendly Automation
Gerrit-Reviewer: George Joseph <gjoseph at digium.com>
Gerrit-Reviewer: Joshua Colp <jcolp at sangoma.com>
Gerrit-Reviewer: Kevin Harwell <kharwell at digium.com>
Gerrit-MessageType: merged
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