llc: Implement LLGM-TRIGGER.req

Change-Id: Id1af5912f407fe055a59a4bb217936307697975f
---
M include/osmocom/gprs/llc/llc_prim.h
M include/osmocom/gprs/llc/llc_private.h
M src/llc/llc.c
M src/llc/llc_llgmm.c
M tests/llc/llc_prim_test.c
M tests/llc/llc_prim_test.err
M tests/llc/llc_prim_test.ok
7 files changed, 130 insertions(+), 3 deletions(-)

diff --git a/include/osmocom/gprs/llc/llc_prim.h b/include/osmocom/gprs/llc/llc_prim.h
index d675954..c03f396 100644
--- a/include/osmocom/gprs/llc/llc_prim.h
+++ b/include/osmocom/gprs/llc/llc_prim.h
@@ -88,6 +88,16 @@
 	return get_value_string(osmo_gprs_llc_bssgp_prim_type_names, val);
 }
 
+/* TS 04.64 Section 7.2.1.3 LLGMM-TRIGGER */
+/* 3GPP TS 24.008 2.1.2 "Cell Notification" is considered a different trigger
+ * type than Cell Update since lower layers behave different (tx LLC NULL vs UI
+ * frame). Furthermore, the one knowing about requirement to use one or the other
+ * is the upper layer (GMM), as well as the one responsible of READY timer. */
+enum osmo_gprs_llc_llgmm_trigger_type {
+	OSMO_GPRS_LLC_LLGM_TRIGGER_CELL_UPDATE,
+	OSMO_GPRS_LLC_LLGM_TRIGGER_CELL_NOTIFICATION,
+	OSMO_GPRS_LLC_LLGM_TRIGGER_PAGE_RESP,
+};
 
 /* Parameters for OSMO_GPRS_LLC_LLGMM_* prims */
 struct osmo_gprs_llc_llgmm_prim {
@@ -104,7 +114,7 @@
 		} assign_req;
 		/* OSMO_GPRS_LLC_LLGMM_TRIGGER | Req */
 		struct {
-			uint8_t cause;
+			uint8_t cause; /* enum osmo_gprs_llc_llgmm_trigger_type */
 		} trigger_req;
 		/* OSMO_GPRS_LLC_LLGMM_SUSPEND | Req */
 		struct {
diff --git a/include/osmocom/gprs/llc/llc_private.h b/include/osmocom/gprs/llc/llc_private.h
index ed68c7b..78e6e9f 100644
--- a/include/osmocom/gprs/llc/llc_private.h
+++ b/include/osmocom/gprs/llc/llc_private.h
@@ -323,6 +323,7 @@
 int gprs_llc_lle_tx_xid_req(struct gprs_llc_lle *lle, uint8_t *l3par, unsigned int l3par_len);
 int gprs_llc_lle_tx_xid_resp(struct gprs_llc_lle *lle, uint8_t *l3par, unsigned int l3par_len);
 int gprs_llc_lle_tx_ui(struct gprs_llc_lle *lle, uint8_t *l3_pdu, size_t l3_pdu_len, bool encryptable);
+int gprs_llc_lle_tx_null(const struct gprs_llc_lle *lle);
 
 /* llc_prim.c: */
 struct osmo_gprs_llc_prim *gprs_llc_prim_alloc(enum osmo_gprs_llc_prim_sap sap, unsigned int type,
diff --git a/src/llc/llc.c b/src/llc/llc.c
index 4be7a9a..93a11ec 100644
--- a/src/llc/llc.c
+++ b/src/llc/llc.c
@@ -292,6 +292,46 @@
 	return 0;
 }
 
+/* 6.4.1.7 NULL command */
+int gprs_llc_lle_tx_null(const struct gprs_llc_lle *lle)
+{
+	int rc;
+	struct msgb *msg;
+	struct gprs_llc_pdu_decoded pdu_dec = {
+		.sapi = lle->sapi,
+		.fmt = OSMO_GPRS_LLC_FMT_U,
+		.func = OSMO_GPRS_LLC_FUNC_NULL,
+		.flags = 0 /* P=0 */,
+	};
+	struct osmo_gprs_llc_prim *llc_prim;
+
+	/* LLC payload is put directly below: */
+	if (g_llc_ctx->location == OSMO_GPRS_LLC_LOCATION_SGSN)
+		llc_prim = gprs_llc_prim_alloc_bssgp_dl_unitdata_req(lle->llme->tlli, NULL, 4096 - sizeof(llc_prim));
+	else
+		llc_prim = gprs_llc_prim_alloc_grr_unitdata_req(lle->llme->tlli, NULL, 4096 - sizeof(llc_prim));
+	msg = llc_prim->oph.msg;
+	msg->l3h = msg->tail;
+
+	rc = gprs_llc_pdu_encode(msg, &pdu_dec);
+	if (rc < 0) {
+		LOGLLC(LOGL_NOTICE, "Failed to encode U DM\n");
+		msgb_free(msg);
+		return rc;
+	}
+	if (g_llc_ctx->location == OSMO_GPRS_LLC_LOCATION_MS) {
+		llc_prim->bssgp.ll_pdu = msgb_l3(msg);
+		llc_prim->bssgp.ll_pdu_len = msgb_l3len(msg);
+	} else {
+		llc_prim->grr.ll_pdu = msgb_l3(msg);
+		llc_prim->grr.ll_pdu_len = msgb_l3len(msg);
+	}
+
+	/* Send BSSGP-DL-UNITDATA.req (SGSN) / GRR-UNITDATA.req (MS) */
+	gprs_llc_prim_call_down_cb(llc_prim);
+	return 0;
+}
+
 /* Transmit a UI frame over the given SAPI:
    'encryptable' indicates whether particular message can be encrypted according
    to 3GPP TS 24.008 § 4.7.1.2
diff --git a/src/llc/llc_llgmm.c b/src/llc/llc_llgmm.c
index bf161e3..d85a30e 100644
--- a/src/llc/llc_llgmm.c
+++ b/src/llc/llc_llgmm.c
@@ -274,6 +274,46 @@
 	return rc;
 }
 
+/* 7.2.1.3 LLGMM-TRIGGER.req (SGSN):*/
+static int llc_prim_handle_llgmm_trigger_req(struct osmo_gprs_llc_prim *llc_prim)
+{
+	struct gprs_llc_lle *lle;
+	int rc;
+	struct gprs_llc_llme *llme = gprs_llc_find_llme_by_tlli(llc_prim->llgmm.tlli);
+
+	if (!llme) {
+		LOGLLC(LOGL_NOTICE, "Rx %s: Unknown TLLI 0x%08x\n",
+			osmo_gprs_llc_prim_name(llc_prim), llc_prim->llgmm.tlli);
+		rc = -ENOKEY;
+		goto ret_free;
+	}
+	LOGLLME(llme, LOGL_INFO, "%s\n", osmo_gprs_llc_prim_name(llc_prim));
+
+	lle = gprs_llc_llme_get_lle(llme, OSMO_GPRS_LLC_SAPI_GMM);
+
+	/* "If there is a frame waiting to be transmitted in the MS, then this
+	 * frame shall be transmitted on the corresponding SAPI or optionally a
+	 * UI frame with no information field shall be transmitted on any SAPI.
+	 * Otherwise if Cause indicates Cell Update and if Cell Notification is
+	 * indicated by the SGSN (see 3GPP TS 24.008 [8a]), then a NULL frame
+	 * with P=0 shall be transmitted on any SAPI."
+	 */
+	switch (llc_prim->llgmm.trigger_req.cause) {
+	case OSMO_GPRS_LLC_LLGM_TRIGGER_CELL_NOTIFICATION:
+		rc = gprs_llc_lle_tx_null(lle);
+		break;
+	case OSMO_GPRS_LLC_LLGM_TRIGGER_CELL_UPDATE:
+	case OSMO_GPRS_LLC_LLGM_TRIGGER_PAGE_RESP:
+	default:
+		rc = gprs_llc_lle_tx_ui(lle, NULL, 0, false);
+		break;
+	}
+
+ret_free:
+	msgb_free(llc_prim->oph.msg);
+	return rc;
+}
+
 /* 7.2.1.4 LLGMM-SUSPEND.req (MS/SGSN):*/
 static int llc_prim_handle_llgmm_suspend_req(struct osmo_gprs_llc_prim *llc_prim)
 {
@@ -332,7 +372,7 @@
 		break;
 	case OSMO_PRIM(OSMO_GPRS_LLC_LLGMM_TRIGGER, PRIM_OP_REQUEST):
 		OSMO_ASSERT(g_llc_ctx->location == OSMO_GPRS_LLC_LOCATION_MS);
-		rc = gprs_llc_prim_handle_unsupported(llc_prim);
+		rc = llc_prim_handle_llgmm_trigger_req(llc_prim);
 		break;
 	case OSMO_PRIM(OSMO_GPRS_LLC_LLGMM_SUSPEND, PRIM_OP_REQUEST):
 		OSMO_ASSERT(g_llc_ctx->location == OSMO_GPRS_LLC_LOCATION_MS ||
diff --git a/tests/llc/llc_prim_test.c b/tests/llc/llc_prim_test.c
index b3ff512..bcba783 100644
--- a/tests/llc/llc_prim_test.c
+++ b/tests/llc/llc_prim_test.c
@@ -172,13 +172,31 @@
 	rc = osmo_gprs_llc_prim_upper_down(llc_prim);
 	OSMO_ASSERT(rc == 0);
 
-	/* Rx LLC-GMM-Attach-Req at MS from SGSN (should be a response message
+	/* Rx LLC-GMM-Attach-Accept at MS from SGSN (should be a response message
 	 * but we don't care about upper layers here): */
 	llc_prim = osmo_gprs_llc_prim_alloc_grr_unitdata_ind(tlli, pdu_llc_gmm_att_req, sizeof(pdu_llc_gmm_att_req));
 	OSMO_ASSERT(llc_prim);
 	rc = osmo_gprs_llc_prim_lower_up(llc_prim);
 	OSMO_ASSERT(rc == 0);
 
+	/* Test GMM asking LLC to transmit a response for a Paging Request: */
+	llc_prim = osmo_gprs_llc_prim_alloc_llgmm_trigger_req(tlli, OSMO_GPRS_LLC_LLGM_TRIGGER_PAGE_RESP);
+	OSMO_ASSERT(llc_prim);
+	rc = osmo_gprs_llc_prim_upper_down(llc_prim);
+	OSMO_ASSERT(rc == 0);
+
+	/* Test GMM asking LLC to transmit for Cell Update: */
+	llc_prim = osmo_gprs_llc_prim_alloc_llgmm_trigger_req(tlli, OSMO_GPRS_LLC_LLGM_TRIGGER_CELL_UPDATE);
+	OSMO_ASSERT(llc_prim);
+	rc = osmo_gprs_llc_prim_upper_down(llc_prim);
+	OSMO_ASSERT(rc == 0);
+
+	/* Test GMM asking LLC to transmit for Cell Notification: */
+	llc_prim = osmo_gprs_llc_prim_alloc_llgmm_trigger_req(tlli, OSMO_GPRS_LLC_LLGM_TRIGGER_CELL_NOTIFICATION);
+	OSMO_ASSERT(llc_prim);
+	rc = osmo_gprs_llc_prim_upper_down(llc_prim);
+	OSMO_ASSERT(rc == 0);
+
 	printf("==== %s() [end] ====\n", __func__);
 }
 
diff --git a/tests/llc/llc_prim_test.err b/tests/llc/llc_prim_test.err
index 444f3da..7cc72f5 100644
--- a/tests/llc/llc_prim_test.err
+++ b/tests/llc/llc_prim_test.err
@@ -3,6 +3,12 @@
 DLGLOBAL INFO Rx from lower layers: GRR-UNITDATA.indication
 DLGLOBAL DEBUG Rx GRR-UNITDATA.indication: SAPI=1 (GMM), UI func=UI C/R=0 PM=0 E=0 IP=0 N(U)=0 FCS=f218e2
 DLGLOBAL DEBUG LLE(ffffffff/f43cec71,GMM){UNASSIGNED} Rx SAPI=1 (GMM), UI func=UI C/R=0 PM=0 E=0 IP=0 N(U)=0 FCS=f218e2
+DLGLOBAL INFO Rx from upper layers: LLGMM-TRIGGER.request
+DLGLOBAL INFO LLME(ffffffff/f43cec71){UNASSIGNED} LLGMM-TRIGGER.request
+DLGLOBAL INFO Rx from upper layers: LLGMM-TRIGGER.request
+DLGLOBAL INFO LLME(ffffffff/f43cec71){UNASSIGNED} LLGMM-TRIGGER.request
+DLGLOBAL INFO Rx from upper layers: LLGMM-TRIGGER.request
+DLGLOBAL INFO LLME(ffffffff/f43cec71){UNASSIGNED} LLGMM-TRIGGER.request
 DLGLOBAL INFO Rx from lower layers: BSSGP-UL-UNITDATA.indication
 DLGLOBAL DEBUG Rx BSSGP-UL-UNITDATA.indication: SAPI=1 (GMM), UI func=UI C/R=0 PM=0 E=0 IP=0 N(U)=0 FCS=f218e2
 DLGLOBAL NOTICE LLME(ffffffff/e1c5d364){UNASSIGNED} LLC RX: unknown TLLI 0xe1c5d364, creating LLME on the fly
diff --git a/tests/llc/llc_prim_test.ok b/tests/llc/llc_prim_test.ok
index 4534568..ee381e6 100644
--- a/tests/llc/llc_prim_test.ok
+++ b/tests/llc/llc_prim_test.ok
@@ -1,6 +1,9 @@
 ==== test_llc_prim_ms() [start] ====
 test_llc_prim_down_cb(): Rx GRR-UNITDATA.request l3=[01 c0 01 08 01 02 e5 e0 01 0a 00 05 f4 f4 3c ec 71 32 f4 07 00 05 00 17 19 33 43 2b 37 15 9e f9 88 79 cb a2 8c 66 21 e7 26 88 b1 98 87 9c 00 17 05 22 96 cc ]
 test_llc_prim_up_cb(): Rx LL-UNITDATA.indication TLLI=0xf43cec71 SAPI=GMM l3=[08 01 01 d5 71 00 00 08 29 26 24 00 00 00 00 71 62 f2 24 6c 84 44 04 11 e5 10 00 ]
+test_llc_prim_down_cb(): Rx GRR-UNITDATA.request l3=[01 c0 05 4a 85 74 ]
+test_llc_prim_down_cb(): Rx GRR-UNITDATA.request l3=[01 c0 09 ce 0d f7 ]
+test_llc_prim_down_cb(): Rx GRR-UNITDATA.request l3=[01 e0 1c a2 b3 ]
 ==== test_llc_prim_ms() [end] ====
 ==== test_llc_prim_sgsn() [start] ====
 test_llc_prim_up_cb(): Rx LL-UNITDATA.indication TLLI=0xe1c5d364 SAPI=GMM l3=[08 01 01 d5 71 00 00 08 29 26 24 00 00 00 00 71 62 f2 24 6c 84 44 04 11 e5 10 00 ]

