res_rtp_asterisk: Make P2P bridge Asymmetric codec aware

Introduce a new property to rtp-engine to make it aware of
the desire for assymetric codecs or not.  If asymmetric codecs
is not allowed, the bridge will compare read/write formats
and shut down the p2p bridge if needed

ASTERISK-26745 #close

Change-Id: I0d9c83e5356df81661e58d40a8db565833501a6f

channels/chan_pjsip.c

@@ -727,14 +727,11 @@ static struct ast_frame *chan_pjsip_read(struct ast_channel *ast)
 
 	session = channel->session;
 
-	if (ast_format_cap_iscompatible_format(ast_channel_nativeformats(ast), f->subclass.format) == AST_FORMAT_CMP_NOT_EQUAL) {
+	/*
-		ast_debug(1, "Oooh, got a frame with format of %s on channel '%s' when it has not been negotiated\n",
+	 * Asymmetric RTP only has one native format set at a time.
-			ast_format_get_name(f->subclass.format), ast_channel_name(ast));
+	 * Therefore we need to update the native format to the current
-
+	 * raw read format BEFORE the native format check
-		ast_frfree(f);
+	 */
-		return &ast_null_frame;
-	}
-
 	if (!session->endpoint->asymmetric_rtp_codec &&
 		ast_format_cmp(ast_channel_rawwriteformat(ast), f->subclass.format) == AST_FORMAT_CMP_NOT_EQUAL) {
 		struct ast_format_cap *caps;
@@ -761,6 +758,14 @@ static struct ast_frame *chan_pjsip_read(struct ast_channel *ast)
 		}
 	}
 
+	if (ast_format_cap_iscompatible_format(ast_channel_nativeformats(ast), f->subclass.format) == AST_FORMAT_CMP_NOT_EQUAL) {
+		ast_debug(1, "Oooh, got a frame with format of %s on channel '%s' when it has not been negotiated\n",
+			ast_format_get_name(f->subclass.format), ast_channel_name(ast));
+
+		ast_frfree(f);
+		return &ast_null_frame;
+	}
+
 	if (session->dsp) {
 		int dsp_features;
 

include/asterisk/rtp_engine.h

@@ -114,6 +114,8 @@ enum ast_rtp_property {
 	AST_RTP_PROPERTY_STUN,
 	/*! Enable RTCP support */
 	AST_RTP_PROPERTY_RTCP,
+	/*! Enable Asymmetric RTP Codecs */
+	AST_RTP_PROPERTY_ASYMMETRIC_CODEC,
 
 	/*!
 	 * \brief Maximum number of RTP properties supported

res/res_pjsip_sdp_rtp.c

@@ -241,6 +241,7 @@ static int create_rtp(struct ast_sip_session *session, struct ast_sip_session_me
 	}
 
 	ast_rtp_instance_set_prop(session_media->rtp, AST_RTP_PROPERTY_NAT, session->endpoint->media.rtp.symmetric);
+	ast_rtp_instance_set_prop(session_media->rtp, AST_RTP_PROPERTY_ASYMMETRIC_CODEC, session->endpoint->asymmetric_rtp_codec);
 
 	if (!session->endpoint->media.rtp.ice_support && (ice = ast_rtp_instance_get_ice(session_media->rtp))) {
 		ice->stop(session_media->rtp);

res/res_rtp_asterisk.c

@@ -302,6 +302,7 @@ struct ast_rtp {
 	void *data;
 	struct ast_rtcp *rtcp;
 	struct ast_rtp *bridged;        /*!< Who we are Packet bridged to */
+	unsigned int asymmetric_codec;  /*!< Indicate if asymmetric send/receive codecs are allowed */
 
 	enum strict_rtp_state strict_rtp_state; /*!< Current state that strict RTP protection is in */
 	struct ast_sockaddr strict_rtp_address;  /*!< Remote address information for strict RTP purposes */
@@ -4879,6 +4880,23 @@ static int bridge_p2p_rtp_write(struct ast_rtp_instance *instance,
 		return -1;
 	}
 
+
+	ao2_replace(rtp->lastrxformat, payload_type->format);
+	ao2_replace(bridged->lasttxformat, payload_type->format);
+
+	/*
+	 * If bridged peer has already received rtp, perform the asymmetric codec check
+	 * if that feature has been activated
+	 */
+	if (!bridged->asymmetric_codec && bridged->lastrxformat != ast_format_none) {
+		if (ast_format_cmp(bridged->lasttxformat, bridged->lastrxformat) == AST_FORMAT_CMP_NOT_EQUAL) {
+			ast_debug(1, "Asymmetric RTP codecs detected (TX: %s, RX: %s) sending frame to core\n",
+					ast_format_get_name(bridged->lasttxformat),
+					ast_format_get_name(bridged->lastrxformat));
+			return -1;
+		}
+	}
+
 	/* If the marker bit has been explicitly set turn it on */
 	if (ast_test_flag(rtp, FLAG_NEED_MARKER_BIT)) {
 		mark = 1;
@@ -5531,6 +5549,8 @@ static void ast_rtp_prop_set(struct ast_rtp_instance *instance, enum ast_rtp_pro
 				rtp->rtcp = NULL;
 			}
 		}
+	} else if (property == AST_RTP_PROPERTY_ASYMMETRIC_CODEC) {
+		rtp->asymmetric_codec = value;
 	}
 }