Adding traffic forwarding via RTP to remote application

Instead of forwarding traffic through MNCC interface, traffic can
now be forwarded to a given RTP destination. A special MNCC message
is used for that. The traffic can still be forwarded through MNCC
interface when this special MNCC message is not used.

It also works with E1 based BTSs.

In conjunction with LCR's "rtp-bridge" feature, the RTP traffic
can be directly exchanged with a remote SIP endpoint, so that the
traffic is not forwarded by LCR itself. This way the performance
of handling traffic only depends on OpenBSC and the remote SIP
endpoint. Also the traffic is exchanged with the SIP endpoint
without transcoding, to have maximum performance.

4 files changed, 19 insertions, 2 deletions

diff --git a/include/osmocom/bsc/gsm_04_08.h b/include/osmocom/bsc/gsm_04_08.h
index 2f5aaa98c..068672059 100644
--- a/include/osmocom/bsc/gsm_04_08.h
+++ b/include/osmocom/bsc/gsm_04_08.h
@@ -6,6 +6,7 @@
 #include <osmocom/gsm/protocol/gsm_04_08.h>
 
 #include <openbsc/meas_rep.h>
+#include <openbsc/mncc.h>
 
 struct msgb;
 struct gsm_bts;
@@ -72,4 +73,6 @@ void gsm48_lchan2chan_desc(struct gsm48_chan_desc *cd,
 void release_security_operation(struct gsm_subscriber_connection *conn);
 void allocate_security_operation(struct gsm_subscriber_connection *conn);
 
+int tch_frame_down(struct gsm_network *net, uint32_t callref, struct gsm_data_frame *data);
+
 #endif
diff --git a/include/osmocom/bsc/mncc.h b/include/osmocom/bsc/mncc.h
index 4a99bb11b..12a6ec833 100644
--- a/include/osmocom/bsc/mncc.h
+++ b/include/osmocom/bsc/mncc.h
@@ -92,9 +92,13 @@ struct gsm_call {
 #define MNCC_FRAME_RECV		0x0201
 #define MNCC_FRAME_DROP		0x0202
 #define MNCC_LCHAN_MODIFY	0x0203
+#define MNCC_RTP_CREATE		0x0204
+#define MNCC_RTP_CONNECT	0x0205
+#define MNCC_RTP_FREE		0x0206
 
 #define GSM_TCHF_FRAME		0x0300
 #define GSM_TCHF_FRAME_EFR	0x0301
+#define GSM_TCHF_FRAME_HR	0x0302
 
 #define MNCC_SOCKET_HELLO	0x0400
 
@@ -176,6 +180,13 @@ struct gsm_mncc_hello {
 	uint32_t	lchan_type_offset;
 };
 
+struct gsm_mncc_rtp {
+	uint32_t	msg_type;
+	uint32_t	callref;
+	uint32_t	ip;
+	uint16_t	port;
+};
+
 char *get_mncc_name(int value);
 void mncc_set_cause(struct gsm_mncc *data, int loc, int val);
 void cc_tx_to_mncc(struct gsm_network *net, struct msgb *msg);
diff --git a/include/osmocom/bsc/rtp_proxy.h b/include/osmocom/bsc/rtp_proxy.h
index 26cac0df4..a7d692c56 100644
--- a/include/osmocom/bsc/rtp_proxy.h
+++ b/include/osmocom/bsc/rtp_proxy.h
@@ -36,8 +36,9 @@
 
 enum rtp_rx_action {
 	RTP_NONE,
-	RTP_PROXY,
-	RTP_RECV_UPSTREAM,
+	RTP_PROXY, /* forward from BTS to BTS */
+	RTP_RECV_UPSTREAM, /* forward to L4 application */
+	RTP_RECV_L4, /* receive RTP frames from L4 application */
 };
 
 enum rtp_tx_action {
diff --git a/include/osmocom/bsc/transaction.h b/include/osmocom/bsc/transaction.h
index b6c859c71..6f4258d10 100644
--- a/include/osmocom/bsc/transaction.h
+++ b/include/osmocom/bsc/transaction.h
@@ -28,6 +28,7 @@ struct gsm_trans {
 
 	/* reference from MNCC or other application */
 	uint32_t callref;
+	uint32_t callref_keep; /* to remember callref, even if it is removed */
 
 	/* if traffic channel receive was requested */
 	int tch_recv;
@@ -46,6 +47,7 @@ struct gsm_trans {
 			int T308_second;	/* used to send release again */
 			struct osmo_timer_list timer;
 			struct gsm_mncc msg;	/* stores setup/disconnect/release message */
+			struct rtp_socket *rs;	/* L4 traffic via RTP */
 		} cc;
 		struct {
 			struct gsm411_smc_inst smc_inst;