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module-rtp-sap: Add retry code for when start_sap() fails due to ENODEV

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This commit is contained in:
Carlos Rafael Giani 2025-10-23 16:39:51 +02:00
parent b57bd00be0
commit 80e7302a05
1 changed files with 64 additions and 5 deletions
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69
src/modules/module-rtp-sap.c
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@ -267,6 +267,10 @@ struct impl {
struct pw_timer sap_send_timer;
/* This timer is used when the first start_sap() call fails because
* of an ENODEV error (see the start_sap() code for details) */
struct pw_timer start_sap_retry_timer;
char *ifname;
uint32_t ttl;
bool mcast_loop;
@ -322,6 +326,7 @@ static const struct format_info *find_audio_format_info(const char *mime)
return NULL;
}
static int start_sap(struct impl *impl);
static int send_sap(struct impl *impl, struct session *sess, bool bye);
@ -978,6 +983,13 @@ static void on_sap_send_timer_event(void *data)
on_sap_send_timer_event, impl);
}
static void on_start_sap_retry_timer_event(void *data)
{
struct impl *impl = data;
pw_log_debug("trying again to start SAP send after previous attempt failed with ENODEV");
start_sap(impl);
}
static struct session *session_find(struct impl *impl, const struct sdp_info *info)
{
struct session *sess;
@ -1668,18 +1680,62 @@ on_sap_io(void *data, int fd, uint32_t mask)
static int start_sap(struct impl *impl)
{
int fd = -1, res;
int fd = -1, res = 0;
char addr[128] = "invalid";
pw_log_info("starting SAP send timer");
/* start_sap() might be called more than once. See the make_recv_socket()
* call below for why that can happen. In such a case, the timer was
* started already. The easiest way of handling it is to just cancel it.
* Such cases are not expected to occur often, so canceling and then
* adding the timer again is acceptable. */
pw_timer_queue_cancel(&impl->sap_send_timer);
if ((res = pw_timer_queue_add(impl->timer_queue, &impl->sap_send_timer,
NULL, SAP_INTERVAL_SEC * SPA_NSEC_PER_SEC,
on_sap_send_timer_event, impl)) < 0) {
pw_log_error("can't add SAP send timer: %s", spa_strerror(res));
goto error;
}
if ((fd = make_recv_socket(&impl->sap_addr, impl->sap_len, impl->ifname)) < 0)
return fd;
if ((fd = make_recv_socket(&impl->sap_addr, impl->sap_len, impl->ifname)) < 0) {
/* If make_recv_socket() tries to create a socket and join to a multicast
* group while the network interfaces are not ready yet to do so
* (usually because a network manager component is still setting up
* those network interfaces), ENODEV will be returned. This is essentially
* a race condition. There is no discernible way to be notified when the
* network interfaces are ready for that operation, so the next best
* approach is to essentially do a form of polling by retrying the
* start_sap() call after some time. The start_sap_retry_timer exists
* precisely for that purpose. This means that ENODEV is not treated as
* an error, but instead, it triggers the creation of that timer. */
if (fd == -ENODEV) {
pw_log_warn("failed to create receiver socket because network device "
"is not ready and present yet; will try again");
pw_timer_queue_cancel(&impl->start_sap_retry_timer);
/* Use a 1-second retry interval. The network interfaces
* are likely to be up and running then. */
pw_timer_queue_add(impl->timer_queue, &impl->start_sap_retry_timer,
NULL, 1 * SPA_NSEC_PER_SEC,
on_start_sap_retry_timer_event, impl);
/* It is important to return 0 in this case. Otherwise, the nonzero return
* value will later be propagated through the core as an error. */
res = 0;
goto finish;
} else {
pw_log_error("failed to create socket: %s", spa_strerror(-fd));
/* If ENODEV was returned earlier, and the start_sap_retry_timer
* was consequently created, but then a non-ENODEV error occurred,
* the timer must be stopped and removed. */
pw_timer_queue_cancel(&impl->start_sap_retry_timer);
res = fd;
goto error;
}
}
/* Cleanup the timer in case ENODEV occurred earlier, and this time,
* the socket creation succeeded. */
pw_timer_queue_cancel(&impl->start_sap_retry_timer);
pw_net_get_ip(&impl->sap_addr, addr, sizeof(addr), NULL, NULL);
pw_log_info("starting SAP listener on %s", addr);
@ -1690,11 +1746,13 @@ static int start_sap(struct impl *impl)
goto error;
}
return 0;
finish:
return res;
error:
if (fd > 0)
close(fd);
return res;
goto finish;
}
static void node_event_info(void *data, const struct pw_node_info *info)
@ -1825,6 +1883,7 @@ static void impl_destroy(struct impl *impl)
pw_core_disconnect(impl->core);
pw_timer_queue_cancel(&impl->sap_send_timer);
pw_timer_queue_cancel(&impl->start_sap_retry_timer);
if (impl->sap_source)
pw_loop_destroy_source(impl->loop, impl->sap_source);