Introduce new MNCC based proxy mode
Since the MNCC API can now send and receive frames to/from the MNCC
application, we can also implement a proxy this way. Not at the RTP/UDP packet
level, but at the 'TCH speech frame' level.
Especially for handover, we need this mode as the receiver in the BTS needs a
persistent SSRC and monotonic frame numbers / timestamps.
diff --git a/openbsc/src/mncc.c b/openbsc/src/mncc.c
index f53b15d..15e2978 100644
--- a/openbsc/src/mncc.c
+++ b/openbsc/src/mncc.c
@@ -30,6 +30,8 @@
#include <openbsc/mncc.h>
#include <openbsc/talloc.h>
#include <openbsc/gsm_data.h>
+#include <openbsc/transaction.h>
+#include <openbsc/rtp_proxy.h>
void *tall_call_ctx;
@@ -232,7 +234,8 @@
static int mncc_setup_cnf(struct gsm_call *call, int msg_type,
struct gsm_mncc *connect)
{
- struct gsm_mncc connect_ack;
+ struct gsm_mncc connect_ack, frame_recv;
+ struct gsm_network *net = call->net;
struct gsm_call *remote;
u_int32_t refs[2];
@@ -253,7 +256,26 @@
refs[0] = call->callref;
refs[1] = call->remote_ref;
DEBUGP(DMNCC, "(call %x) Bridging with remote.\n", call->callref);
- return mncc_send(call->net, MNCC_BRIDGE, refs);
+
+ /* in direct mode, we always have to bridge the channels */
+ if (ipacc_rtp_direct)
+ return mncc_send(call->net, MNCC_BRIDGE, refs);
+
+ /* proxy mode */
+ if (!net->handover.active) {
+ /* in the no-handover case, we can bridge, i.e. use
+ * the old RTP proxy code */
+ return mncc_send(call->net, MNCC_BRIDGE, refs);
+ } else {
+ /* in case of handover, we need to re-write the RTP
+ * SSRC, sequence and timestamp values and thus
+ * need to enable RTP receive for both directions */
+ memset(&frame_recv, 0, sizeof(struct gsm_mncc));
+ frame_recv.callref = call->callref;
+ mncc_send(call->net, MNCC_FRAME_RECV, &frame_recv);
+ frame_recv.callref = call->remote_ref;
+ return mncc_send(call->net, MNCC_FRAME_RECV, &frame_recv);
+ }
}
static int mncc_disc_ind(struct gsm_call *call, int msg_type,
@@ -301,6 +323,28 @@
return 0;
}
+/* receiving a TCH/F frame from the BSC code */
+static int mncc_rcv_tchf(struct gsm_call *call, int msg_type,
+ struct gsm_data_frame *dfr)
+{
+ struct gsm_trans *remote_trans;
+
+ remote_trans = trans_find_by_callref(call->net, call->remote_ref);
+
+ /* this shouldn't really happen */
+ if (!remote_trans || !remote_trans->lchan) {
+ LOGP(DMNCC, LOGL_ERROR, "No transaction or transaction without lchan?!?\n");
+ return -EIO;
+ }
+
+ /* RTP socket of remote end has meanwhile died */
+ if (!remote_trans->lchan->abis_ip.rtp_socket)
+ return -EIO;
+
+ return rtp_send_frame(remote_trans->lchan->abis_ip.rtp_socket, dfr);
+}
+
+
int mncc_recv(struct gsm_network *net, int msg_type, void *arg)
{
struct gsm_mncc *data = arg;
@@ -342,8 +386,15 @@
DEBUGP(DMNCC, "(call %x) Call created.\n", call->callref);
}
- DEBUGP(DMNCC, "(call %x) Received message %s\n", call->callref,
- get_mncc_name(msg_type));
+ switch (msg_type) {
+ case GSM_TCHF_FRAME:
+ case GSM_TCHF_FRAME_EFR:
+ break;
+ default:
+ DEBUGP(DMNCC, "(call %x) Received message %s\n", call->callref,
+ get_mncc_name(msg_type));
+ break;
+ }
switch(msg_type) {
case MNCC_SETUP_IND:
@@ -404,6 +455,10 @@
call->callref, data->cause.value);
rc = mncc_send(net, MNCC_RETRIEVE_REJ, data);
break;
+ case GSM_TCHF_FRAME:
+ case GSM_TCHF_FRAME_EFR:
+ rc = mncc_rcv_tchf(call, msg_type, arg);
+ break;
default:
LOGP(DMNCC, LOGL_NOTICE, "(call %x) Message unhandled\n", callref);
break;