gsm: Fix encoding of gsm0808_cell_id_list2 with CGI-PS types

CGI-PS type doesn't exist in GSM 08.08 Cell Id lists. That type of cell
id is osmocom-specific and used internally. In here CGI-PS is
automatically converted to CGI (since the later is an extension of this
one).

The encode/decode_cell_id_u are left intact (comment added) since those
can still be used (and are used by RIM code) to encode/decode TS 48.018
Cell Identifiers.

Related: SYS#4909
Change-Id: Id74f4577c397c1ba696f00395858311bd82cb2c8

2 files changed, 63 insertions, 3 deletions

diff --git a/src/gsm/gsm0808_utils.c b/src/gsm/gsm0808_utils.c
index e0f0c28b..dda73adb 100644
--- a/src/gsm/gsm0808_utils.c
+++ b/src/gsm/gsm0808_utils.c
@@ -877,6 +877,7 @@ int gsm0808_decode_cell_id_u(union gsm0808_cell_id_u *out, enum CELL_IDENT discr
 		/* Does not have any list items */
 		break;
 	case CELL_IDENT_WHOLE_GLOBAL_PS:
+		/* 3GPP TS 48.018 sec 11.3.9 "Cell Identifier" */
 		if (len < 8)
 			return -EINVAL;
 		decode_lai(buf, (struct osmo_location_area_id *)&out->global_ps.rai); /* rai contains lai + non-decoded rac */
@@ -925,6 +926,7 @@ void gsm0808_msgb_put_cell_id_u(struct msgb *msg, enum CELL_IDENT id_discr, cons
 		/* Does not have any list items */
 		break;
 	case CELL_IDENT_WHOLE_GLOBAL_PS: {
+		/* 3GPP TS 48.018 sec 11.3.9 "Cell Identifier" */
 		const struct osmo_cell_global_id_ps *id = &u->global_ps;
 		struct gsm48_loc_area_id lai;
 		gsm48_generate_lai2(&lai, &id->rai.lac);
@@ -949,6 +951,7 @@ uint8_t gsm0808_enc_cell_id_list2(struct msgb *msg,
 	uint8_t *old_tail;
 	uint8_t *tlv_len;
 	unsigned int i;
+	uint8_t id_discr;
 
 	OSMO_ASSERT(msg);
 	OSMO_ASSERT(cil);
@@ -957,11 +960,25 @@ uint8_t gsm0808_enc_cell_id_list2(struct msgb *msg,
 	tlv_len = msgb_put(msg, 1);
 	old_tail = msg->tail;
 
-	msgb_put_u8(msg, cil->id_discr & 0x0f);
+	/* CGI-PS is an osmocom-specific type. In here we don't care about the
+	 * PS part, only the CS one. */
+	if (cil->id_discr == CELL_IDENT_WHOLE_GLOBAL_PS)
+		id_discr = CELL_IDENT_WHOLE_GLOBAL;
+	else
+		id_discr = cil->id_discr & 0x0f;
+
+	msgb_put_u8(msg, id_discr);
 
 	OSMO_ASSERT(cil->id_list_len <= GSM0808_CELL_ID_LIST2_MAXLEN);
-	for (i = 0; i < cil->id_list_len; i++)
-		gsm0808_msgb_put_cell_id_u(msg, cil->id_discr, &cil->id_list[i]);
+	for (i = 0; i < cil->id_list_len; i++) {
+		if (cil->id_discr == CELL_IDENT_WHOLE_GLOBAL_PS) {
+			union gsm0808_cell_id_u u;
+			cell_id_to_cgi(&u.global, cil->id_discr, &cil->id_list[i]);
+			gsm0808_msgb_put_cell_id_u(msg, CELL_IDENT_WHOLE_GLOBAL, &u);
+		} else {
+			gsm0808_msgb_put_cell_id_u(msg, cil->id_discr, &cil->id_list[i]);
+		}
+	}
 
 	*tlv_len = (uint8_t) (msg->tail - old_tail);
 	return *tlv_len + 2;
diff --git a/tests/gsm0808/gsm0808_test.c b/tests/gsm0808/gsm0808_test.c
index 7eb53c2b..04b3b727 100644
--- a/tests/gsm0808/gsm0808_test.c
+++ b/tests/gsm0808/gsm0808_test.c
@@ -1760,6 +1760,48 @@ static void test_gsm0808_enc_dec_cell_id_global()
 	msgb_free(msg);
 }
 
+static void test_gsm0808_enc_dec_cell_id_global_ps()
+{
+	struct gsm0808_cell_id enc_cgi = {
+		.id_discr = CELL_IDENT_WHOLE_GLOBAL,
+		.id.global = {
+			.lai = {
+				.plmn = { .mcc = 123, .mnc = 456 },
+				.lac = 0x2342
+			},
+			.cell_identity = 0x423,
+		}
+	};
+	struct gsm0808_cell_id enc_cgi_ps = {
+		.id_discr = CELL_IDENT_WHOLE_GLOBAL_PS,
+		.id.global_ps = {
+			.rai = {
+				.lac = {
+					.plmn = { .mcc = 123, .mnc = 456 },
+					.lac = 0x2342
+				},
+				.rac = 0xcc,
+			},
+			.cell_identity = 0x423,
+		}
+	};
+	struct msgb *msg_cgi, *msg_cgi_ps;
+	uint8_t rc_enc;
+
+	msg_cgi = msgb_alloc(1024, "output buffer (CGI)");
+	rc_enc = gsm0808_enc_cell_id(msg_cgi, &enc_cgi);
+	OSMO_ASSERT(rc_enc > 0);
+
+	msg_cgi_ps = msgb_alloc(1024, "output buffer (CGI-PS)");
+	rc_enc = gsm0808_enc_cell_id(msg_cgi_ps, &enc_cgi_ps);
+	OSMO_ASSERT(rc_enc > 0);
+
+	OSMO_ASSERT(msgb_eq(msg_cgi, msg_cgi_ps));
+
+	msgb_free(msg_cgi);
+	msgb_free(msg_cgi_ps);
+}
+
 static void test_gsm0808_sc_cfg_from_gsm48_mr_cfg_single(struct gsm48_multi_rate_conf *cfg)
 {
 	uint16_t s15_s0;
@@ -2462,6 +2504,7 @@ int main(int argc, char **argv)
 	test_gsm0808_enc_dec_cell_id_ci();
 	test_gsm0808_enc_dec_cell_id_lac_and_ci();
 	test_gsm0808_enc_dec_cell_id_global();
+	test_gsm0808_enc_dec_cell_id_global_ps();
 	test_gsm0808_sc_cfg_from_gsm48_mr_cfg();
 	test_gsm48_mr_cfg_from_gsm0808_sc_cfg();