Change in osmo-bsc[master]: fix CM Re-Establishment Request: allocate new A conn

neels gerrit-no-reply at lists.osmocom.org
Fri Jul 23 21:57:52 UTC 2021


neels has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bsc/+/25036 )


Change subject: fix CM Re-Establishment Request: allocate new A conn
......................................................................

fix CM Re-Establishment Request: allocate new A conn

For a call re-establishment, the MS shows up on a different cell and
requests CM Re-Establishment (3GPP TS 24.008 9.2.4). As soon as the
Layer 3 is established, the MSC will clear the first A-connection; the
re-establishment *has* to happen on a new separate A-connection. So for
a brief moment we must allow two distinct A-interface connections to be
used for the same subscriber.

Related: SYS#5130
Change-Id: I2da9a971dd36c4289a78040adfe85704c8282c59
---
M src/osmo-bsc/gsm_08_08.c
1 file changed, 7 insertions(+), 2 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-bsc refs/changes/36/25036/1

diff --git a/src/osmo-bsc/gsm_08_08.c b/src/osmo-bsc/gsm_08_08.c
index 80ed874..1f6b38e 100644
--- a/src/osmo-bsc/gsm_08_08.c
+++ b/src/osmo-bsc/gsm_08_08.c
@@ -415,8 +415,13 @@
 
 	/* If this Mobile Identity already has an active bsc_subscr, look whether there also is an active A-interface
 	 * conn for this subscriber. This may be the case during a Perform Location Request (LCS) from the MSC that
-	 * started on an IDLE MS, and now the MS is becoming active. Associate with the existing conn. */
-	if (bsub)
+	 * started on an IDLE MS, and now the MS is becoming active. Associate with the existing conn.
+	 *
+	 * However, for a CM Re-Establishment Request, we must *not* re-use the existing conn, but allocate a second
+	 * conn for the same bsub. The previous conn will be Clear'ed by the MSC as soon as it receives the L3 Complete
+	 * message == the CM Re-Establishment Request.
+	 */
+	if (bsub && !(pdisc == GSM48_PDISC_MM && mtype == GSM48_MT_MM_CM_REEST_REQ))
 		conn = bsc_conn_by_bsub(bsub);
 
 	if (!conn) {

-- 
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Gerrit-Project: osmo-bsc
Gerrit-Branch: master
Gerrit-Change-Id: I2da9a971dd36c4289a78040adfe85704c8282c59
Gerrit-Change-Number: 25036
Gerrit-PatchSet: 1
Gerrit-Owner: neels <nhofmeyr at sysmocom.de>
Gerrit-MessageType: newchange
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