avtp: Introduce AVTP sink element

This patch introduces the avtpsink elements which implements a typical
network sink. Implementation is pretty straightforward since the burden
is implemented by GstBaseSink class.

The avtpsink element defines three new properties: 1) network interface
from where AVTPDU should be transmitted, 2) destination MAC address
(usually a multicast address), and 3) socket priority (SO_PRIORITY).

Socket setup and teardown are done in start/stop virtual methods while
AVTPDU transmission is carried out by render(). AVTPDUs are encapsulated
into Ethernet frames and transmitted to the network via AF_PACKET socket
domain.  Linux requires CAP_NET_RAW capability in order to open an
AF_PACKET socket so the application that utilize this element must have
it. For further info about AF_PACKET socket domain see packet(7).

Finally, AVTPDUs are expected to be transmitted at specific times -
according to the GstBuffer presentation timestamp - so the 'sync'
property from GstBaseSink is set to TRUE by default.

ext/avtp/Makefile.am

@@ -5,7 +5,8 @@ libgstavtp_la_SOURCES = \
 	gstavtpaafdepay.c \
 	gstavtpaafpay.c \
 	gstavtpbasedepayload.c \
-	gstavtpbasepayload.c
+	gstavtpbasepayload.c \
+	gstavtpsink.c
 
 libgstavtp_la_CFLAGS = \
 	$(GST_PLUGINS_BASE_CFLAGS) \
@@ -25,4 +26,5 @@ noinst_HEADERS = \
 	gstavtpaafdepay.h \
 	gstavtpaafpay.h \
 	gstavtpbasedepayload.h \
-	gstavtpbasepayload.h
+	gstavtpbasepayload.h \
+	gstavtpsink.h

ext/avtp/gstavtp.c

@@ -52,6 +52,7 @@
 
 #include "gstavtpaafdepay.h"
 #include "gstavtpaafpay.h"
+#include "gstavtpsink.h"
 
 static gboolean
 plugin_init (GstPlugin * plugin)
@@ -60,6 +61,8 @@ plugin_init (GstPlugin * plugin)
     return FALSE;
   if (!gst_avtp_aaf_depay_plugin_init (plugin))
     return FALSE;
+  if (!gst_avtp_sink_plugin_init (plugin))
+    return FALSE;
 
   return TRUE;
 }

ext/avtp/gstavtpsink.c

@@ -0,0 +1,307 @@
+/*
+ * GStreamer AVTP Plugin
+ * Copyright (C) 2019 Intel Corporation
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301 USA
+ */
+
+/**
+ * SECTION:element-avtpsink
+ * @see_also: avtpsrc
+ *
+ * avtpsink is a network sink that sends AVTPDUs to the network. It should be
+ * combined with AVTP payloaders to implement an AVTP talker. For more
+ * information see https://standards.ieee.org/standard/1722-2016.html.
+ *
+ * <note>
+ * This element opens an AF_PACKET socket which requires CAP_NET_RAW
+ * capability. Therefore, applications must have that capability in order to
+ * successfully use this element. The capability can be dropped by the
+ * application after the element transitions to PAUSED state if wanted.
+ * </note>
+ *
+ * <refsect2>
+ * <title>Example pipeline</title>
+ * |[
+ * gst-launch-1.0 audiotestsrc ! audioconvert ! avtpaafpay ! avtpsink
+ * ]| This example pipeline implements an AVTP talker that transmit an AAF
+ * stream.
+ * </refsect2>
+ */
+
+#include <arpa/inet.h>
+#include <linux/if_packet.h>
+#include <net/ethernet.h>
+#include <net/if.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include "gstavtpsink.h"
+
+GST_DEBUG_CATEGORY_STATIC (avtpsink_debug);
+#define GST_CAT_DEFAULT (avtpsink_debug)
+
+#define DEFAULT_IFNAME "eth0"
+#define DEFAULT_ADDRESS "01:AA:AA:AA:AA:AA"
+#define DEFAULT_PRIORITY 0
+
+enum
+{
+  PROP_0,
+  PROP_IFNAME,
+  PROP_ADDRESS,
+  PROP_PRIORITY,
+};
+
+static GstStaticPadTemplate sink_template = GST_STATIC_PAD_TEMPLATE ("sink",
+    GST_PAD_SINK,
+    GST_PAD_ALWAYS,
+    GST_STATIC_CAPS ("application/x-avtp")
+    );
+
+#define gst_avtp_sink_parent_class parent_class
+G_DEFINE_TYPE (GstAvtpSink, gst_avtp_sink, GST_TYPE_BASE_SINK);
+
+static void gst_avtp_sink_finalize (GObject * gobject);
+static void gst_avtp_sink_set_property (GObject * object, guint prop_id,
+    const GValue * value, GParamSpec * pspec);
+static void gst_avtp_sink_get_property (GObject * object, guint prop_id,
+    GValue * value, GParamSpec * pspec);
+
+static gboolean gst_avtp_sink_start (GstBaseSink * basesink);
+static gboolean gst_avtp_sink_stop (GstBaseSink * basesink);
+static GstFlowReturn gst_avtp_sink_render (GstBaseSink * basesink, GstBuffer *
+    buffer);
+
+static void
+gst_avtp_sink_class_init (GstAvtpSinkClass * klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+  GstElementClass *element_class = GST_ELEMENT_CLASS (klass);
+  GstBaseSinkClass *basesink_class = GST_BASE_SINK_CLASS (klass);
+
+  object_class->finalize = gst_avtp_sink_finalize;
+  object_class->get_property = gst_avtp_sink_get_property;
+  object_class->set_property = gst_avtp_sink_set_property;
+
+  g_object_class_install_property (object_class, PROP_IFNAME,
+      g_param_spec_string ("ifname", "Interface Name",
+          "Network interface utilized to transmit AVTPDUs",
+          DEFAULT_IFNAME, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS |
+          GST_PARAM_MUTABLE_READY));
+  g_object_class_install_property (object_class, PROP_ADDRESS,
+      g_param_spec_string ("address", "Destination MAC address",
+          "Destination MAC address from Ethernet frames",
+          DEFAULT_ADDRESS, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS |
+          GST_PARAM_MUTABLE_READY));
+  g_object_class_install_property (object_class, PROP_PRIORITY,
+      g_param_spec_int ("priority", "Socket priority",
+          "Priority configured into socket (SO_PRIORITY)", 0, G_MAXINT,
+          DEFAULT_PRIORITY, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS |
+          GST_PARAM_MUTABLE_READY));
+
+  gst_element_class_add_static_pad_template (element_class, &sink_template);
+
+  gst_element_class_set_static_metadata (element_class,
+      "Audio/Video Transport Protocol (AVTP) Sink",
+      "Sink/Network", "Send AVTPDUs over the network",
+      "Andre Guedes <andre.guedes@intel.com>");
+
+  basesink_class->start = GST_DEBUG_FUNCPTR (gst_avtp_sink_start);
+  basesink_class->stop = GST_DEBUG_FUNCPTR (gst_avtp_sink_stop);
+  basesink_class->render = GST_DEBUG_FUNCPTR (gst_avtp_sink_render);
+
+  GST_DEBUG_CATEGORY_INIT (avtpsink_debug, "avtpsink", 0, "AVTP Sink");
+}
+
+static void
+gst_avtp_sink_init (GstAvtpSink * avtpsink)
+{
+  gst_base_sink_set_sync (GST_BASE_SINK (avtpsink), TRUE);
+
+  avtpsink->ifname = g_strdup (DEFAULT_IFNAME);
+  avtpsink->address = g_strdup (DEFAULT_ADDRESS);
+  avtpsink->priority = DEFAULT_PRIORITY;
+  avtpsink->sk_fd = -1;
+  memset (&avtpsink->sk_addr, 0, sizeof (avtpsink->sk_addr));
+}
+
+static void
+gst_avtp_sink_finalize (GObject * object)
+{
+  GstAvtpSink *avtpsink = GST_AVTP_SINK (object);
+
+  g_free (avtpsink->ifname);
+  g_free (avtpsink->address);
+
+  G_OBJECT_CLASS (parent_class)->finalize (object);
+}
+
+static void
+gst_avtp_sink_set_property (GObject * object, guint prop_id,
+    const GValue * value, GParamSpec * pspec)
+{
+  GstAvtpSink *avtpsink = GST_AVTP_SINK (object);
+
+  GST_DEBUG_OBJECT (avtpsink, "prop_id %u", prop_id);
+
+  switch (prop_id) {
+    case PROP_IFNAME:
+      g_free (avtpsink->ifname);
+      avtpsink->ifname = g_value_dup_string (value);
+      break;
+    case PROP_ADDRESS:
+      g_free (avtpsink->address);
+      avtpsink->address = g_value_dup_string (value);
+      break;
+    case PROP_PRIORITY:
+      avtpsink->priority = g_value_get_int (value);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}
+
+static void
+gst_avtp_sink_get_property (GObject * object, guint prop_id,
+    GValue * value, GParamSpec * pspec)
+{
+  GstAvtpSink *avtpsink = GST_AVTP_SINK (object);
+
+  GST_DEBUG_OBJECT (avtpsink, "prop_id %u", prop_id);
+
+  switch (prop_id) {
+    case PROP_IFNAME:
+      g_value_set_string (value, avtpsink->ifname);
+      break;
+    case PROP_ADDRESS:
+      g_value_set_string (value, avtpsink->address);
+      break;
+    case PROP_PRIORITY:
+      g_value_set_int (value, avtpsink->priority);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}
+
+static gboolean
+gst_avtp_sink_start (GstBaseSink * basesink)
+{
+  int fd, res;
+  struct ifreq req;
+  guint8 addr[ETH_ALEN];
+  struct sockaddr_ll sk_addr;
+  GstAvtpSink *avtpsink = GST_AVTP_SINK (basesink);
+
+  fd = socket (AF_PACKET, SOCK_DGRAM | SOCK_NONBLOCK, htons (ETH_P_TSN));
+  if (fd < 0) {
+    GST_ERROR_OBJECT (avtpsink, "Failed to open socket: %s", strerror (errno));
+    return FALSE;
+  }
+
+  res = setsockopt (fd, SOL_SOCKET, SO_PRIORITY, &avtpsink->priority,
+      sizeof (avtpsink->priority));
+  if (res < 0) {
+    GST_ERROR_OBJECT (avtpsink, "Failed to socket priority: %s", strerror
+        (errno));
+    goto err;
+  }
+
+  res = sscanf (avtpsink->address, "%hhx:%hhx:%hhx:%hhx:%hhx:%hhx",
+      &addr[0], &addr[1], &addr[2], &addr[3], &addr[4], &addr[5]);
+  if (res != 6) {
+    GST_ERROR_OBJECT (avtpsink, "Destination MAC address format not valid");
+    goto err;
+  }
+
+  snprintf (req.ifr_name, sizeof (req.ifr_name), "%s", avtpsink->ifname);
+  res = ioctl (fd, SIOCGIFINDEX, &req);
+  if (res < 0) {
+    GST_ERROR_OBJECT (avtpsink, "Failed to ioctl(): %s", strerror (errno));
+    goto err;
+  }
+
+  sk_addr.sll_family = AF_PACKET;
+  sk_addr.sll_protocol = htons (ETH_P_TSN);
+  sk_addr.sll_halen = ETH_ALEN;
+  sk_addr.sll_ifindex = req.ifr_ifindex;
+  sk_addr.sll_hatype = 0;
+  sk_addr.sll_pkttype = 0;
+  memcpy (sk_addr.sll_addr, addr, ETH_ALEN);
+
+  avtpsink->sk_fd = fd;
+  avtpsink->sk_addr = sk_addr;
+
+  GST_DEBUG_OBJECT (avtpsink, "AVTP sink started");
+  return TRUE;
+
+err:
+  close (fd);
+  return FALSE;
+}
+
+static gboolean
+gst_avtp_sink_stop (GstBaseSink * basesink)
+{
+  GstAvtpSink *avtpsink = GST_AVTP_SINK (basesink);
+
+  close (avtpsink->sk_fd);
+
+  GST_DEBUG_OBJECT (avtpsink, "AVTP sink stopped");
+  return TRUE;
+}
+
+static GstFlowReturn
+gst_avtp_sink_render (GstBaseSink * basesink, GstBuffer * buffer)
+{
+  ssize_t n;
+  GstMapInfo info;
+  GstAvtpSink *avtpsink = GST_AVTP_SINK (basesink);
+
+  if (!gst_buffer_map (buffer, &info, GST_MAP_READ)) {
+    GST_ERROR_OBJECT (avtpsink, "Failed to map buffer");
+    return GST_FLOW_ERROR;
+  }
+
+  n = sendto (avtpsink->sk_fd, info.data, info.size, 0,
+      (struct sockaddr *) &avtpsink->sk_addr, sizeof (avtpsink->sk_addr));
+  if (n < 0) {
+    GST_INFO_OBJECT (avtpsink, "Failed to send AVTPDU: %s", strerror (errno));
+    goto out;
+  }
+  if (n != info.size) {
+    GST_INFO_OBJECT (avtpsink, "Incomplete AVTPDU transmission");
+    goto out;
+  }
+
+out:
+  gst_buffer_unmap (buffer, &info);
+  return GST_FLOW_OK;
+}
+
+gboolean
+gst_avtp_sink_plugin_init (GstPlugin * plugin)
+{
+  return gst_element_register (plugin, "avtpsink", GST_RANK_NONE,
+      GST_TYPE_AVTP_SINK);
+}

ext/avtp/gstavtpsink.h

@@ -0,0 +1,67 @@
+/*
+ * GStreamer AVTP Plugin
+ * Copyright (C) 2019 Intel Corporation
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301 USA
+ */
+
+#ifndef __GST_AVTP_SINK_H__
+#define __GST_AVTP_SINK_H__
+
+#include <gst/base/gstbasesink.h>
+#include <gst/gst.h>
+#include <linux/if_packet.h>
+
+G_BEGIN_DECLS
+
+#define GST_TYPE_AVTP_SINK (gst_avtp_sink_get_type())
+#define GST_AVTP_SINK(obj) \
+  (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_AVTP_SINK,GstAvtpSink))
+#define GST_AVTP_SINK_CLASS(klass) \
+  (G_TYPE_CHECK_CLASS_CAST((klass),GST_TYPE_AVTP_SINK,GstAvtpSinkClass))
+#define GST_IS_AVTP_SINK(obj) \
+  (G_TYPE_CHECK_INSTANCE_TYPE((obj),GST_TYPE_AVTP_SINK))
+#define GST_IS_AVTP_SINK_CLASS(klass) \
+  (G_TYPE_CHECK_CLASS_TYPE((klass),GST_TYPE_AVTP_SINK))
+
+typedef struct _GstAvtpSink GstAvtpSink;
+typedef struct _GstAvtpSinkClass GstAvtpSinkClass;
+
+struct _GstAvtpSink
+{
+  GstBaseSink parent;
+
+  gchar * ifname;
+  gchar * address;
+  gint priority;
+
+  int sk_fd;
+  struct sockaddr_ll sk_addr;
+};
+
+struct _GstAvtpSinkClass
+{
+  GstBaseSinkClass parent_class;
+};
+
+GType gst_avtp_sink_get_type (void);
+
+gboolean gst_avtp_sink_plugin_init (GstPlugin * plugin);
+
+G_END_DECLS
+
+#endif /* __GST_AVTP_SINK_H__ */

ext/avtp/meson.build

@@ -4,6 +4,7 @@ avtp_sources = [
   'gstavtpaafpay.c',
   'gstavtpbasedepayload.c',
   'gstavtpbasepayload.c',
+  'gstavtpsink.c',
 ]
 
 avtp_dep = dependency('avtp', required: get_option('avtp'))