bssgp: Handle BSSGP STATUS messages

Currently incoming BSSGP STATUS messages are just logged and apart
from that ignored. Since it is possible that the gbproxy can
eventually send both valid replies (from the primary SGSN) and
STATUS(unknown BVCI) messages (from the secondary SGSN). Since the
PCU assumes in this case that the BVC has been successfully reset and
unblocked, it will not send a BVC RESET message after receiving an
NS_UNBLOCK.

This commit changes gprs_bssgp_pcu_rcvmsg to pass BSSGP STATUS
messages to bssgp_rcvmsg() which will in turn call bssgp_prim_cb()
with primitive NM_STATUS. Then the BVC RESET or UNBLOCK procedure
will be started if the IE in the message matches and the PCU assumes
that the BVC should have been successfully reset and unblocked
respectively while the STATUS message tells otherwise.

Note that bssgp_rcvmsg() from libosmocore is otherwise used for the
SGSN side only, albeit it generally just decodes messages, does basic
protocol handling and eventually invokes PRIM indications. The only
exception here is the handling of BVC RESET, which is implemented
specifically for the SGSN.

Ticket: OW#1414
Sponsored-by: On-Waves ehf

1 files changed, 62 insertions, 5 deletions

diff --git a/src/gprs_bssgp_pcu.cpp b/src/gprs_bssgp_pcu.cpp
index daadc635..09047203 100644
--- a/src/gprs_bssgp_pcu.cpp
+++ b/src/gprs_bssgp_pcu.cpp
@@ -303,11 +303,10 @@ static int gprs_bssgp_pcu_rcvmsg(struct msgb *msg)
 	int rc = 0;
 	struct bssgp_bvc_ctx *bctx;
 
-	if (pdu_type == BSSGP_PDUT_STATUS) {
-		LOGP(DBSSGP, LOGL_NOTICE, "NSEI=%u/BVCI=%u received STATUS\n",
-			msgb_nsei(msg), ns_bvci);
-		return 0;
-	}
+	if (pdu_type == BSSGP_PDUT_STATUS)
+		/* Pass the message to the generic BSSGP parser, which handles
+		 * STATUS message in either direction. */
+		return bssgp_rcvmsg(msg);
 
 	/* Identifiers from DOWN: NSEI, BVCI (both in msg->cb) */
 
@@ -362,8 +361,66 @@ static int gprs_bssgp_pcu_rcvmsg(struct msgb *msg)
 	return rc;
 }
 
+static void handle_nm_status(struct osmo_bssgp_prim *bp)
+{
+	enum gprs_bssgp_cause cause;
+
+	LOGP(DPCU, LOGL_DEBUG,
+		"Got NM-STATUS.ind, BVCI=%d, NSEI=%d\n",
+		bp->bvci, bp->nsei);
+
+	if (!TLVP_PRESENT(bp->tp, BSSGP_IE_CAUSE))
+		return;
+
+	cause = (enum gprs_bssgp_cause)*TLVP_VAL(bp->tp, BSSGP_IE_CAUSE);
+
+	if (cause != BSSGP_CAUSE_BVCI_BLOCKED &&
+		cause != BSSGP_CAUSE_UNKNOWN_BVCI)
+		return;
+
+	if (!TLVP_PRESENT(bp->tp, BSSGP_IE_BVCI))
+		return;
+
+	if (gprs_bssgp_pcu_current_bctx()->bvci != bp->bvci) {
+		LOGP(DPCU, LOGL_NOTICE,
+			"Received BSSGP STATUS message for an unknown BVCI (%d), "
+			"ignored\n",
+			bp->bvci);
+		return;
+	}
+
+	switch (cause) {
+	case BSSGP_CAUSE_BVCI_BLOCKED:
+		if (the_pcu.bvc_unblocked) {
+			the_pcu.bvc_unblocked = 0;
+			bvc_timeout(NULL);
+		}
+		break;
+
+	case BSSGP_CAUSE_UNKNOWN_BVCI:
+		if (the_pcu.bvc_reset) {
+			the_pcu.bvc_reset = 0;
+			bvc_timeout(NULL);
+		}
+		break;
+	default:
+		break;
+	}
+}
+
 int bssgp_prim_cb(struct osmo_prim_hdr *oph, void *ctx)
 {
+	struct osmo_bssgp_prim *bp;
+	bp = container_of(oph, struct osmo_bssgp_prim, oph);
+
+	switch (oph->sap) {
+	case SAP_BSSGP_NM:
+		if (oph->primitive == PRIM_NM_STATUS)
+			handle_nm_status(bp);
+		break;
+	default:
+		break;
+	}
 	return 0;
 }