gstreamer/subprojects/gst-plugins-bad/ext/mdns/gstmicrodnsdevice.c
Jan Schmidt 1b0b1fc0fd mdns: Fix a crash on context error
Make sure not to free the microdns provider context until the
device provider asks it to stop. Fixes a crash if there is
an error (such as MDNS port being busy) that makes the
mdns listener exit early.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5198>
2023-08-18 10:40:50 +00:00

442 lines
12 KiB
C

/* GStreamer
* Copyright (C) 2019 Mathieu Duponchelle <mathieu@centricular.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#include <microdns/microdns.h>
#include "gstmicrodnsdevice.h"
typedef struct _ListenerContext ListenerContext;
struct _GstMDNSDeviceProvider
{
GstDeviceProvider parent;
ListenerContext *current_ctx;
};
#define LISTEN_INTERVAL_SECONDS 2
/* #GstDeviceProvider.stop() is synchronous, but libmicrodns' stop mechanism
* isn't, as it polls and queries the application's provided stop function
* before each new loop crank. This means there can potentially exist N
* contexts at any given time, if the provider is started and stopped in
* rapid succession. At most one of them can be active however (stop == false),
* with the other N - 1 in the process of stopping (stop == true).
*
* Additionally, mdns_listen() is a blocking call, thus the need to run it in
* its own thread.
*/
struct _ListenerContext
{
GMutex lock;
GCond stop_cond;
GstDeviceProvider *provider;
/* The following fields are protected by @lock */
bool stop;
GHashTable *devices;
GSequence *last_seen_devices;
};
G_DEFINE_TYPE (GstMDNSDeviceProvider, gst_mdns_device_provider,
GST_TYPE_DEVICE_PROVIDER);
struct _GstMDNSDevice
{
GstDevice parent;
GstURIType uri_type;
gchar *uri;
GSequenceIter *iter;
gint64 last_seen;
};
G_DEFINE_TYPE (GstMDNSDevice, gst_mdns_device, GST_TYPE_DEVICE);
static gint
cmp_last_seen (GstMDNSDevice * a, GstMDNSDevice * b,
gpointer G_GNUC_UNUSED user_data)
{
if (a->last_seen < b->last_seen)
return -1;
if (a->last_seen == b->last_seen)
return 0;
return 1;
}
static gint
cmp_last_seen_iter (GSequenceIter * ia, GSequenceIter * ib, gpointer user_data)
{
return cmp_last_seen (GST_MDNS_DEVICE (g_sequence_get (ia)),
GST_MDNS_DEVICE (g_sequence_get (ib)), user_data);
}
static void
gst_mdns_device_finalize (GObject * object)
{
GstMDNSDevice *self = GST_MDNS_DEVICE (object);
g_free (self->uri);
G_OBJECT_CLASS (gst_mdns_device_parent_class)->finalize (object);
}
static GstElement *
gst_mdns_device_create_element (GstDevice * device, const gchar * name)
{
GstMDNSDevice *self = GST_MDNS_DEVICE (device);
GstElement *ret;
GError *err = NULL;
ret = gst_element_make_from_uri (self->uri_type, self->uri, name, &err);
if (!ret) {
GST_ERROR_OBJECT (self, "Failed to create element for URI %s: %s",
self->uri, err->message);
g_clear_error (&err);
}
return ret;
}
static void
gst_mdns_device_init (GstMDNSDevice * self)
{
}
static void
gst_mdns_device_class_init (GstMDNSDeviceClass * klass)
{
GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
GstDeviceClass *gst_device_class = GST_DEVICE_CLASS (klass);
gobject_class->finalize = GST_DEBUG_FUNCPTR (gst_mdns_device_finalize);
gst_device_class->create_element =
GST_DEBUG_FUNCPTR (gst_mdns_device_create_element);
}
/* Slightly unoptimized, ideally add gst_element_factory_from_uri */
static GstElementFactory *
get_factory_for_uri (GstURIType type, const gchar * uri)
{
GError *err = NULL;
GstElementFactory *ret = NULL;
GstElement *elem = gst_element_make_from_uri (type, uri, NULL, &err);
if (!elem) {
GST_LOG ("Failed to make element from uri: %s", err->message);
g_clear_error (&err);
goto done;
}
ret = gst_element_get_factory (elem);
gst_object_unref (elem);
done:
return ret;
}
static GstDevice *
gst_mdns_device_new (GstElementFactory * factory, const gchar * name,
const gchar * uri)
{
GstDevice *ret = NULL;
const GList *templates;
GstCaps *caps;
templates = gst_element_factory_get_static_pad_templates (factory);
caps = gst_static_pad_template_get_caps ((GstStaticPadTemplate *)
templates->data);
ret = GST_DEVICE (g_object_new (GST_TYPE_MDNS_DEVICE,
"display-name", name,
"device-class", gst_element_factory_get_metadata (factory, "klass"),
"caps", caps, NULL));
GST_MDNS_DEVICE (ret)->uri = g_strdup (uri);
GST_MDNS_DEVICE (ret)->uri_type = gst_element_factory_get_uri_type (factory);
gst_caps_unref (caps);
return ret;
}
static void
remove_old_devices (ListenerContext * ctx)
{
GstMDNSDeviceProvider *self = GST_MDNS_DEVICE_PROVIDER (ctx->provider);
GstClockTime now = g_get_monotonic_time ();
GSequenceIter *iter = g_sequence_get_begin_iter (ctx->last_seen_devices);
while (!g_sequence_iter_is_end (iter)) {
GstMDNSDevice *dev = GST_MDNS_DEVICE (g_sequence_get (iter));
GstClockTime age = now - dev->last_seen;
GST_LOG_OBJECT (self,
"Device %" GST_PTR_FORMAT " last seen %" GST_TIME_FORMAT " ago", dev,
GST_TIME_ARGS (age));
if (age > 4 * LISTEN_INTERVAL_SECONDS * G_USEC_PER_SEC) {
GSequenceIter *next = g_sequence_iter_next (iter);
GST_INFO_OBJECT (self, "Removing device %" GST_PTR_FORMAT, dev);
gst_device_provider_device_remove (ctx->provider, GST_DEVICE (dev));
g_hash_table_remove (ctx->devices, dev->uri);
g_sequence_remove (iter);
iter = next;
} else {
GST_LOG_OBJECT (self, "Keeping device %" GST_PTR_FORMAT, dev);
iter = g_sequence_get_end_iter (ctx->last_seen_devices);
}
}
}
static bool
stop (void *p_cookie)
{
bool ret;
ListenerContext *ctx = (ListenerContext *) p_cookie;
g_mutex_lock (&ctx->lock);
ret = ctx->stop;
if (!ctx->stop) {
remove_old_devices (ctx);
}
g_mutex_unlock (&ctx->lock);
return ret;
}
static void
callback (void *p_cookie, gint status, const struct rr_entry *entry)
{
ListenerContext *ctx = (ListenerContext *) p_cookie;
gchar err[128];
const struct rr_entry *tmp;
GHashTable *srvs = g_hash_table_new (g_str_hash, g_str_equal);
GstMDNSDeviceProvider *self = GST_MDNS_DEVICE_PROVIDER (ctx->provider);
g_mutex_lock (&ctx->lock);
if (ctx->stop)
goto done;
GST_DEBUG_OBJECT (self, "received new entries");
if (status < 0) {
mdns_strerror (status, err, sizeof (err));
GST_ERROR ("MDNS error: %s", err);
goto done;
}
for (tmp = entry; tmp; tmp = tmp->next) {
if (tmp->type == RR_SRV) {
g_hash_table_insert (srvs, (gpointer) tmp->name, (gpointer) tmp);
}
}
for (tmp = entry; tmp; tmp = tmp->next) {
if (tmp->type == RR_TXT) {
const struct rr_entry *srv;
srv = (const struct rr_entry *) g_hash_table_lookup (srvs, tmp->name);
if (!srv) {
GST_LOG_OBJECT (self, "No SRV associated with TXT entry for %s",
tmp->name);
continue;
}
if (g_str_has_suffix (tmp->name, "._rtsp._tcp.local")) {
gchar *path = NULL;
gchar *uri;
struct rr_data_txt *tmp_txt;
GstMDNSDevice *dev;
for (tmp_txt = tmp->data.TXT; tmp_txt; tmp_txt = tmp_txt->next) {
if (g_str_has_prefix (tmp_txt->txt, "path=")) {
path = tmp_txt->txt + 5;
}
}
if (path) {
uri =
g_strdup_printf ("rtsp://%s:%d/%s", srv->data.SRV.target,
srv->data.SRV.port, path);
} else {
uri =
g_strdup_printf ("rtsp://%s:%d", srv->data.SRV.target,
srv->data.SRV.port);
}
dev = GST_MDNS_DEVICE (g_hash_table_lookup (ctx->devices, uri));
GST_LOG_OBJECT (self, "Saw device at uri %s", uri);
if (dev) {
dev->last_seen = g_get_monotonic_time ();
GST_LOG_OBJECT (self,
"updating last_seen for device %" GST_PTR_FORMAT ": %"
G_GINT64_FORMAT, dev, dev->last_seen);
g_sequence_sort_changed_iter (dev->iter, cmp_last_seen_iter, NULL);
} else {
GstElementFactory *factory;
gchar *display_name;
if (!(factory = get_factory_for_uri (GST_URI_SRC, uri))) {
GST_LOG_OBJECT (self,
"Not registering device %s as no compatible factory was found",
tmp->name);
goto done;
}
display_name = g_strndup (tmp->name, strlen (tmp->name) - 17);
dev =
GST_MDNS_DEVICE (gst_mdns_device_new (factory, display_name,
uri));
g_free (display_name);
dev->last_seen = g_get_monotonic_time ();
GST_INFO_OBJECT (self,
"Saw new device %" GST_PTR_FORMAT " at %" G_GINT64_FORMAT
" with factory %" GST_PTR_FORMAT, dev, dev->last_seen, factory);
dev->iter =
g_sequence_insert_sorted (ctx->last_seen_devices, (gpointer) dev,
(GCompareDataFunc) cmp_last_seen, NULL);
g_hash_table_insert (ctx->devices, g_strdup (uri),
gst_object_ref (dev));
gst_device_provider_device_add (ctx->provider, GST_DEVICE (dev));
}
g_free (uri);
} else {
GST_LOG_OBJECT (self, "unknown protocol for %s", tmp->name);
continue;
}
}
}
done:
g_hash_table_unref (srvs);
g_mutex_unlock (&ctx->lock);
}
static gpointer
_listen (ListenerContext * ctx)
{
gint r = 0;
gchar err[128];
struct mdns_ctx *mctx;
const gchar *ppsz_names[] = { "_rtsp._tcp.local" };
gint i_nb_names = 1;
if ((r = mdns_init (&mctx, MDNS_ADDR_IPV4, MDNS_PORT)) < 0)
goto err;
GST_INFO_OBJECT (ctx->provider, "Start listening");
if ((r = mdns_listen (mctx, ppsz_names, i_nb_names, RR_PTR,
LISTEN_INTERVAL_SECONDS, stop, callback, ctx)) < 0) {
mdns_destroy (mctx);
goto err;
}
done:
GST_INFO_OBJECT (ctx->provider, "Done listening");
/* Wait until we're told to stop, or gst_mdns_device_provider_stop()
can access a freed context */
g_mutex_lock (&ctx->lock);
while (!ctx->stop) {
g_cond_wait (&ctx->stop_cond, &ctx->lock);
}
g_mutex_unlock (&ctx->lock);
g_sequence_free (ctx->last_seen_devices);
g_hash_table_unref (ctx->devices);
g_mutex_clear (&ctx->lock);
g_cond_clear (&ctx->stop_cond);
g_free (ctx);
return NULL;
err:
if (r < 0) {
mdns_strerror (r, err, sizeof (err));
GST_ERROR ("MDNS error: %s", err);
}
goto done;
}
static gboolean
gst_mdns_device_provider_start (GstDeviceProvider * provider)
{
GstMDNSDeviceProvider *self = GST_MDNS_DEVICE_PROVIDER (provider);
ListenerContext *ctx = g_new0 (ListenerContext, 1);
g_mutex_init (&ctx->lock);
g_cond_init (&ctx->stop_cond);
ctx->provider = provider;
ctx->devices =
g_hash_table_new_full (g_str_hash, g_str_equal, g_free, g_object_unref);
ctx->last_seen_devices = g_sequence_new (NULL);
self->current_ctx = ctx;
g_thread_new (NULL, (GThreadFunc) _listen, ctx);
return TRUE;
}
static void
gst_mdns_device_provider_stop (GstDeviceProvider * provider)
{
GstMDNSDeviceProvider *self = GST_MDNS_DEVICE_PROVIDER (provider);
g_assert (self->current_ctx);
g_mutex_lock (&self->current_ctx->lock);
self->current_ctx->stop = true;
g_cond_broadcast (&self->current_ctx->stop_cond);
g_mutex_unlock (&self->current_ctx->lock);
self->current_ctx = NULL;
}
static void
gst_mdns_device_provider_init (GstMDNSDeviceProvider * self)
{
}
static void
gst_mdns_device_provider_class_init (GstMDNSDeviceProviderClass * klass)
{
GstDeviceProviderClass *dm_class = GST_DEVICE_PROVIDER_CLASS (klass);
dm_class->start = GST_DEBUG_FUNCPTR (gst_mdns_device_provider_start);
dm_class->stop = GST_DEBUG_FUNCPTR (gst_mdns_device_provider_stop);
gst_device_provider_class_set_static_metadata (dm_class,
"MDNS Device Provider", "Source/Network",
"List and provides MDNS-advertised source devices",
"Mathieu Duponchelle <mathieu@centricular.com>");
}