Add configurable DSCP ToS for PeerConnections (meetecho#2055)

conf/janus.jcfg.sample.in

@@ -205,6 +205,16 @@ media: {
 	#slowlink_threshold = 4
 	#twcc_period = 100
 	#dtls_timeout = 500
+
+	# If you need DSCP packet marking and prioritization, you can configure
+	# the 'dscp_tos' property to a specific values, and Janus will try to
+	# set it on all outgoing packets using libnice. Normally, the specs
+	# suggest to use different values depending on whether audio, video
+	# or data are used, but since all PeerConnections in Janus are bundled,
+	# we can only use one. You can refer to this document for more info:
+	# https://tools.ietf.org/html/draft-ietf-tsvwg-rtcweb-qos-18#page-6
+	# That said, DON'T TOUCH THIS IF YOU DON'T KNOW WHAT IT MEANS!
+	#dscp_tos = 46
 }
 
 # NAT-related stuff: specifically, you can configure the STUN/TURN
@@ -311,7 +321,7 @@ nat: {
 	# your machine is ready. Note that Linux distributions offer such directives.
 	# You could use the following directive in systemd: 'After=network-online.target'
 	# https://www.freedesktop.org/software/systemd/man/systemd.unit.html#Before=
-	# ignore_unreachable_ice_server = true
+	#ignore_unreachable_ice_server = true
 }
 
 # You can choose which of the available plugins should be

ice.c

@@ -451,6 +451,18 @@ uint janus_get_twcc_period(void) {
 	return twcc_period;
 }
 
+/* DSCP Type of Service, which we can set via libnice: it's disabled by default */
+static int dscp_tos = 0;
+void janus_set_dscp_tos(int tos) {
+	dscp_tos = tos;
+	if(dscp_tos > 0) {
+		JANUS_LOG(LOG_VERB, "Setting DSCP Type of Service to %ds\n", dscp_tos);
+	}
+}
+int janus_get_dscp_tos(void) {
+	return dscp_tos;
+}
+
 
 static inline void janus_ice_free_rtp_packet(janus_rtp_packet *pkt) {
 	if(pkt == NULL) {
@@ -3443,6 +3455,10 @@ int janus_ice_setup_local(janus_ice_handle *handle, int offer, int audio, int vi
 	}
 	/* Now create an ICE stream for all the media we'll handle */
 	handle->stream_id = nice_agent_add_stream(handle->agent, 1);
+	if(dscp_tos > 0) {
+		/* A DSCP Type of Service was configured, pass it to libnice */
+		nice_agent_set_stream_tos(handle->agent, handle->stream_id, dscp_tos);
+	}
 	janus_ice_stream *stream = g_malloc0(sizeof(janus_ice_stream));
 	janus_refcount_init(&stream->ref, janus_ice_stream_free);
 	janus_refcount_increase(&handle->ref);

ice.h

@@ -151,6 +151,12 @@ void janus_set_twcc_period(uint period);
 /*! \brief Method to get the current TWCC period (see above)
  * @returns The current TWCC period */
 uint janus_get_twcc_period(void);
+/*! \brief Method to modify the DSCP Type of Service (TOS), which is disabled by default
+ * @param[in] tos The new TOS value (0 to disable) */
+void janus_set_dscp_tos(int period);
+/*! \brief Method to get the current DSCP Type of Service (see above)
+ * @returns The current TOS value (0 if disabled) */
+int janus_get_dscp_tos(void);
 /*! \brief Method to modify the event handler statistics period (i.e., the number of seconds that should pass before Janus notifies event handlers about media statistics for a PeerConnection)
  * @param[in] period The new period value, in seconds */
 void janus_ice_set_event_stats_period(int period);

janus.c

@@ -300,6 +300,8 @@ static json_t *janus_info(const char *transaction) {
 	json_object_set_new(info, "mdns-enabled", janus_ice_is_mdns_enabled() ? json_true() : json_false());
 	json_object_set_new(info, "min-nack-queue", json_integer(janus_get_min_nack_queue()));
 	json_object_set_new(info, "twcc-period", json_integer(janus_get_twcc_period()));
+	if(janus_get_dscp_tos() > 0)
+		json_object_set_new(info, "dscp-tos", json_integer(janus_get_dscp_tos()));
 	if(janus_ice_get_stun_server() != NULL) {
 		char server[255];
 		g_snprintf(server, 255, "%s:%"SCNu16, janus_ice_get_stun_server(), janus_ice_get_stun_port());
@@ -4636,6 +4638,18 @@ gint main(int argc, char *argv[])
 			                    " Expect trouble if this is supposed to work over the internet and not just in a LAN...\n", test_ip);
 		}
 	}
+
+	/* Is there any DSCP TOS to apply? */
+	item = janus_config_get(config, config_media, janus_config_type_item, "dscp_tos");
+	if(item && item->value) {
+		int tos = atoi(item->value);
+		if(tos < 0) {
+			JANUS_LOG(LOG_WARN, "Ignoring dscp_tos value as it's not a positive integer\n");
+		} else {
+			janus_set_dscp_tos(tos);
+		}
+	}
+
 	/* NACK related stuff */
 	item = janus_config_get(config, config_media, janus_config_type_item, "min_nack_queue");
 	if(item && item->value) {