Change in osmo-msc[master]: fix: incoming call during ongoing call

[Neels Hofmeyr]

Neels Hofmeyr has uploaded this change for review. ( https://gerrit.osmocom.org/12400


Change subject: fix: incoming call during ongoing call
......................................................................

fix: incoming call during ongoing call

If a call is already busy and another call is coming in, do not try to
immediately assign an lchan (before this patch, it fails because there already
is an mgcp_ctx for the conn). Leave the second CC transaction waiting.

When a call is hung up, as soon as the old mgcp_ctx is discarded, look for
other CC transactions that are waiting. If there is one, trigger assignment, so
a new mgcp_ctx is set up for the new call.

This fixes the following scenario:

- from A, call B.
- from C, call B; B rings during ongoing call.
- in B, pick up the call, choose to drop the old call.

After this patch, and with osmo-bsc patch with change-id
  I0c00ec2c120e5008281755adcd4944a3ce4d8355
we are now able to talk to the new caller.

Related: OS#3735
Change-Id: I0ba216b737909e92080a722db26e3577726c63cb
---
M src/libmsc/msc_mgcp.c
1 file changed, 31 insertions(+), 0 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-msc refs/changes/00/12400/1

diff --git a/src/libmsc/msc_mgcp.c b/src/libmsc/msc_mgcp.c
index 8e2e7a9..4c17768 100644
--- a/src/libmsc/msc_mgcp.c
+++ b/src/libmsc/msc_mgcp.c
@@ -962,6 +962,10 @@
 	struct ran_conn *conn = trans->conn;
 	if (trans->cc.assignment_started)
 		return 0;
+	if (conn->rtp.mgcp_ctx) {
+		LOGPFSMSL(conn->fi, DMGCP, LOGL_INFO, "Another call is already ongoing, not assigning yet\n");
+		return 0;
+	}
 	LOGPFSMSL(conn->fi, DMGCP, LOGL_INFO, "Starting call assignment\n");
 	trans->cc.assignment_started = true;
 	return msc_mgcp_call_assignment(trans);
@@ -1152,6 +1156,23 @@
 	return 0;
 }
 
+static struct gsm_trans *find_waiting_call(struct ran_conn *conn)
+{
+	struct gsm_trans *trans;
+	struct gsm_network *net = conn->network;
+
+	llist_for_each_entry(trans, &net->trans_list, entry) {
+		if (trans->conn != conn)
+			continue;
+		if (trans->protocol != GSM48_PDISC_CC)
+			continue;
+		if (trans->cc.assignment_started)
+			continue;
+		return trans;
+	}
+	return NULL;
+}
+
 /* Release ongoing call.
  * Parameter:
  * trans: connection context.
@@ -1160,6 +1181,7 @@
 {
 	struct mgcp_ctx *mgcp_ctx;
 	struct ran_conn *conn = trans->conn;
+	struct gsm_trans *waiting_trans;
 
 	OSMO_ASSERT(trans);
 
@@ -1203,5 +1225,14 @@
 	 * all related context information */
 	conn->rtp.mgcp_ctx = NULL;
 
+	/* If there is another call still waiting to be activated, this is the time when the mgcp_ctx is available again
+	 * and the other call can start assigning. */
+	waiting_trans = find_waiting_call(conn);
+	if (waiting_trans) {
+		LOGP(DMGCP, LOGL_DEBUG, "(ti %02x %s) Call waiting: starting Assignment\n",
+		     waiting_trans->transaction_id, vlr_subscr_name(trans->vsub));
+		msc_mgcp_try_call_assignment(waiting_trans);
+	}
+
 	return 0;
 }

-- 
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Gerrit-Project: osmo-msc
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: I0ba216b737909e92080a722db26e3577726c63cb
Gerrit-Change-Number: 12400
Gerrit-PatchSet: 1
Gerrit-Owner: Neels Hofmeyr <nhofmeyr at sysmocom.de>
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