gprs_gmm: send Service Reject when no PDP ctxs are available.

Look at PDP Context Status IE: if there are any PDP contexts which are
ACTIVE on MS side and there are no PDP contexts which are ACTIVE on the
network side, then send Service Reject with the cause "NO PDP
ACTIVATED". This forces MS to reactivate the PDP contexts.

3GPP TS 24.008 Section 4.7.13.4 Service request procedure not accepted
by the network. Cause # 40.

Fixes: OS#3937
Change-Id: If610cbef17c25ec44e65d4f1b2340d102c560437

3 files changed, 43 insertions, 1 deletions

diff --git a/src/gprs/gprs_gmm.c b/src/gprs/gprs_gmm.c
index 358bff909..a18a54e1b 100644
--- a/src/gprs/gprs_gmm.c
+++ b/src/gprs/gprs_gmm.c
@@ -1616,6 +1616,19 @@ static void process_ms_ctx_status(struct sgsn_mm_ctx *mmctx,
 	}
 }
 
+/* 3GPP TS 24.008 Section 4.7.13.4 Service request procedure not accepted by the
+ * network. Returns true if MS has active PDP contexts in pdp_status */
+bool pdp_status_has_active_nsapis(const uint8_t *pdp_status, const size_t pdp_status_len)
+{
+	size_t i;
+
+	for (i = 0; i < pdp_status_len; i++)
+		if (pdp_status[i] != 0)
+			return true;
+
+	return false;
+}
+
 /* Chapter 9.4.14: Routing area update request */
 static int gsm48_rx_gmm_ra_upd_req(struct sgsn_mm_ctx *mmctx, struct msgb *msg,
 				   struct gprs_llc_llme *llme)
@@ -1896,12 +1909,23 @@ static int gsm48_rx_gmm_service_req(struct sgsn_mm_ctx *ctx, struct msgb *msg)
 
 	ctx->iu.service.type = service_type;
 
-	/* TODO: Handle those only in case of accept? */
 	/* Look at PDP Context Status IE and see if MS's view of
 	 * activated/deactivated NSAPIs agrees with our view */
 	if (TLVP_PRESENT(&tp, GSM48_IE_GMM_PDP_CTX_STATUS)) {
 		const uint8_t *pdp_status = TLVP_VAL(&tp, GSM48_IE_GMM_PDP_CTX_STATUS);
+		const size_t pdp_status_len = TLVP_LEN(&tp, GSM48_IE_GMM_PDP_CTX_STATUS);
+
 		process_ms_ctx_status(ctx, pdp_status);
+
+		/* 3GPP TS 24.008 Section 4.7.13.4 Service request procedure not
+		 * accepted by the network. Cause #40. If MS has PDP Contexts in
+		 * Active state in pdp_status but there is no PDP contexts on
+		 * SGSN side then Reject with the cause will force the mobile to
+		 * reset PDP contexts */
+		if (llist_empty(&ctx->pdp_list) && pdp_status_has_active_nsapis(pdp_status, pdp_status_len)) {
+			reject_cause = GMM_CAUSE_NO_PDP_ACTIVATED;
+			goto rejected;
+		}
 	}
 
 
diff --git a/tests/sgsn/sgsn_test.c b/tests/sgsn/sgsn_test.c
index 614520600..23cb4fbc4 100644
--- a/tests/sgsn/sgsn_test.c
+++ b/tests/sgsn/sgsn_test.c
@@ -1575,6 +1575,22 @@ static void test_ggsn_selection(void)
 	cleanup_test();
 }
 
+bool pdp_status_has_active_nsapis(const uint8_t *pdp_status, const size_t pdp_status_len);
+
+static void test_pdp_status_has_active_nsapis(void)
+{
+	const size_t pdp_status_len = 2;
+	const uint8_t pdp_status1[] = { 0b00100000, 0b00000000 }; /* PDP NSAPI 5 active */
+	const uint8_t pdp_status2[] = { 0b00000000, 0b00000000 }; /* no active PDP NSAPI */
+	const uint8_t pdp_status3[] = { 0b00000000, 0b00000001 }; /* PDP NSAPI 8 active */
+
+	printf("Testing pdp_status_has_active_nsapis\n");
+
+	OSMO_ASSERT(pdp_status_has_active_nsapis(pdp_status1, pdp_status_len));
+	OSMO_ASSERT(!pdp_status_has_active_nsapis(pdp_status2, pdp_status_len));
+	OSMO_ASSERT(pdp_status_has_active_nsapis(pdp_status3, pdp_status_len));
+}
+
 static struct log_info_cat gprs_categories[] = {
 	[DMM] = {
 		.name = "DMM",
@@ -1657,6 +1673,7 @@ int main(int argc, char **argv)
 	test_gmm_cancel();
 	test_apn_matching();
 	test_ggsn_selection();
+	test_pdp_status_has_active_nsapis();
 	printf("Done\n");
 
 	talloc_report_full(osmo_sgsn_ctx, stderr);
diff --git a/tests/sgsn/sgsn_test.ok b/tests/sgsn/sgsn_test.ok
index e7e7cf6e4..35b1d7bb7 100644
--- a/tests/sgsn/sgsn_test.ok
+++ b/tests/sgsn/sgsn_test.ok
@@ -24,4 +24,5 @@ Testing GMM reject
 Testing cancellation
 Testing APN matching
 Testing GGSN selection
+Testing pdp_status_has_active_nsapis
 Done