[MERGED] osmo-bsc[master]: abis_rsl: do not allow SACCH in MF mode on SAPI=0

[Harald Welte]

Harald Welte has submitted this change and it was merged.

Change subject: abis_rsl: do not allow SACCH in MF mode on SAPI=0
......................................................................


abis_rsl: do not allow SACCH in MF mode on SAPI=0

osmo-msc does currently not check if an MS attemts to establish an
SACCH link on SAPI=0. This combination is not permitted and should
be dropped.

- Make sure that establish indication for SAPI=0 and channel-type=SACCH
  is not permitted

See also TTCN3 Testcase:
BSC_Tests.TC_rll_est_ind_inval_sacch

Change-Id: I12962072c0ea689d2b9b5c2899ffb59be9310dcb
Closes: OS#2750
---
M src/libbsc/abis_rsl.c
1 file changed, 15 insertions(+), 0 deletions(-)

Approvals:
  Harald Welte: Looks good to me, approved
  Jenkins Builder: Verified



diff --git a/src/libbsc/abis_rsl.c b/src/libbsc/abis_rsl.c
index 1893166..261e6fe 100644
--- a/src/libbsc/abis_rsl.c
+++ b/src/libbsc/abis_rsl.c
@@ -2194,6 +2194,21 @@
 			break;
 		}
 
+		/* Note: Check for MF SACCH on SAPI=0 (not permitted). By
+		 * definition we establish a link in multiframe (MF) mode.
+		 * (see also 3GPP TS 48.058, chapter 3.1. However, on SAPI=0
+		 * SACCH is only allowed in UL mode, not in MF mode.
+		 * (see also 3GPP TS 44.005, figure 5) So we have to drop such
+		 * Establish Indications */
+		if (sapi == 0 && (rllh->link_id >> 6 & 0x03) == 1) {
+			LOGP(DRLL, LOGL_NOTICE, "MS attempted to establish an SACCH in MF mode on SAPI=0 (not permitted)\n");
+
+			/* Note: We do not need to close the channel,
+			 * since we might still get a proper Establish Ind.
+			 * If not, T3101 will close the channel on timeout. */
+			break;
+		}
+
 		msg->lchan->sapis[rllh->link_id & 0x7] = LCHAN_SAPI_MS;
 		osmo_timer_del(&msg->lchan->T3101);
 		if (msgb_l2len(msg) >

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Gerrit-MessageType: merged
Gerrit-Change-Id: I12962072c0ea689d2b9b5c2899ffb59be9310dcb
Gerrit-PatchSet: 2
Gerrit-Project: osmo-bsc
Gerrit-Branch: master
Gerrit-Owner: dexter <pmaier at sysmocom.de>
Gerrit-Reviewer: Harald Welte <laforge at gnumonks.org>
Gerrit-Reviewer: Jenkins Builder