rtspsrc: Fix usage of IPv6 connections in SETUP

If the SETUP request returns an IPv6 server address in the Transport
field, we would generate an incorrect URI, and multiudpsink would fail
to initialize:

```
     rtspsrc gstrtspsrc.c:9780:dump_key_value:<source>    key: 'Transport', value: 'RTP/AVP;unicast;source=fe80::dc27:25ff:fe5e:bd13:8080;client_port=62696-62697;server_port=4000-4001'
...
     rtspsrc gstrtspsrc.c:4595:gst_rtspsrc_stream_configure_udp_sinks:<source> configure RTP UDP sink for fe80::dc27:25ff:fe5e:bd13:8080:4000
...
multiudpsink gstmultiudpsink.c:1229:gst_multiudpsink_configure_client:<udpsink0> error: Invalid address family (got 23)
```

We can't look at stream->is_ipv6 because we can't rely on the server
returning the right value there. In the issue reported about this,
server reported itself as `KuP RTSP Server/0.1`, and the SDP was:

```
c=IN IP4
m=video 54608 RTP/AVP 96
a=rtpmap:96 H264/90000
```

So we need to parse the string value and figure out the family
ourselves.

Fixes https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/1058

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1819>

subprojects/gst-plugins-good/gst/rtsp/gstrtspsrc.c

@@ -4383,12 +4383,43 @@ gst_rtspsrc_get_transport_info (GstRTSPSrc * src, GstRTSPStream * stream,
   }
 }
 
+static GstElement *
+element_make_from_addr (const GstURIType type, const char *addr_s,
+    int port, const char *name, GError ** error)
+{
+  GInetAddress *addr;
+  GstElement *element = NULL;
+  char *uri = NULL;
+
+  addr = g_inet_address_new_from_string (addr_s);
+
+  switch (g_inet_address_get_family (addr)) {
+    case G_SOCKET_FAMILY_IPV6:
+      uri = g_strdup_printf ("udp://[%s]:%i", addr_s, port);
+      break;
+    case G_SOCKET_FAMILY_INVALID:
+      GST_ERROR ("Unknown family type for %s", addr_s);
+      goto out;
+    case G_SOCKET_FAMILY_UNIX:
+      GST_ERROR ("Unexpected family type UNIX for %s", addr_s);
+      goto out;
+    case G_SOCKET_FAMILY_IPV4:
+      uri = g_strdup_printf ("udp://%s:%i", addr_s, port);
+      break;
+  }
+
+  element = gst_element_make_from_uri (type, uri, name, error);
+out:
+  g_object_unref (addr);
+  g_free (uri);
+  return element;
+}
+
 /* For multicast create UDP sources and join the multicast group. */
 static gboolean
 gst_rtspsrc_stream_configure_mcast (GstRTSPSrc * src, GstRTSPStream * stream,
     GstRTSPTransport * transport, GstPad ** outpad)
 {
-  gchar *uri;
   const gchar *destination;
   gint min, max;
 
@@ -4413,10 +4444,8 @@ gst_rtspsrc_stream_configure_mcast (GstRTSPSrc * src, GstRTSPStream * stream,
 
   /* creating UDP source for RTP */
   if (min != -1) {
-    uri = g_strdup_printf ("udp://%s:%d", destination, min);
     stream->udpsrc[0] =
-        gst_element_make_from_uri (GST_URI_SRC, uri, NULL, NULL);
+        element_make_from_addr (GST_URI_SRC, destination, min, NULL, NULL);
-    g_free (uri);
     if (stream->udpsrc[0] == NULL)
       goto no_element;
 
@@ -4440,10 +4469,8 @@ gst_rtspsrc_stream_configure_mcast (GstRTSPSrc * src, GstRTSPStream * stream,
   if (max != -1) {
     GstCaps *caps;
 
-    uri = g_strdup_printf ("udp://%s:%d", destination, max);
     stream->udpsrc[1] =
-        gst_element_make_from_uri (GST_URI_SRC, uri, NULL, NULL);
+        element_make_from_addr (GST_URI_SRC, destination, max, NULL, NULL);
-    g_free (uri);
     if (stream->udpsrc[1] == NULL)
       goto no_element;
 
@@ -4583,7 +4610,7 @@ gst_rtspsrc_stream_configure_udp_sinks (GstRTSPSrc * src,
   gint rtp_port, rtcp_port;
   gboolean do_rtp, do_rtcp;
   const gchar *destination;
-  gchar *uri, *name;
+  gchar *name;
   guint ttl = 0;
   GSocket *socket;
 
@@ -4607,10 +4634,8 @@ gst_rtspsrc_stream_configure_udp_sinks (GstRTSPSrc * src,
     GST_DEBUG_OBJECT (src, "configure RTP UDP sink for %s:%d", destination,
         rtp_port);
 
-    uri = g_strdup_printf ("udp://%s:%d", destination, rtp_port);
+    stream->udpsink[0] = element_make_from_addr (GST_URI_SINK, destination,
-    stream->udpsink[0] =
+        rtp_port, NULL, NULL);
-        gst_element_make_from_uri (GST_URI_SINK, uri, NULL, NULL);
-    g_free (uri);
     if (stream->udpsink[0] == NULL)
       goto no_sink_element;
 
@@ -4672,10 +4697,8 @@ gst_rtspsrc_stream_configure_udp_sinks (GstRTSPSrc * src,
     GST_DEBUG_OBJECT (src, "configure RTCP UDP sink for %s:%d", destination,
         rtcp_port);
 
-    uri = g_strdup_printf ("udp://%s:%d", destination, rtcp_port);
+    stream->udpsink[1] = element_make_from_addr (GST_URI_SINK, destination,
-    stream->udpsink[1] =
+        rtcp_port, NULL, NULL);
-        gst_element_make_from_uri (GST_URI_SINK, uri, NULL, NULL);
-    g_free (uri);
     if (stream->udpsink[1] == NULL)
       goto no_sink_element;