1 files changed, 256 insertions, 0 deletions
diff --git a/src/common/notification.c b/src/common/notification.c
new file mode 100644
index 00000000..9351ec04
--- /dev/null
+++ b/src/common/notification.c
@@ -0,0 +1,256 @@
+/* Maintain and generate ASCI notifications */
+
+/*
+ * (C) 2023 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
+ * All Rights Reserved
+ *
+ * SPDX-License-Identifier: AGPL-3.0+
+ *
+ * Author: Harald Welte
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <errno.h>
+
+#include <osmocom/core/bitvec.h>
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/gsm/protocol/gsm_08_58.h>
+
+#include <osmo-bts/bts.h>
+#include <osmo-bts/logging.h>
+#include <osmo-bts/notification.h>
+
+static struct asci_notification *bts_asci_notification_find(struct gsm_bts *bts, const uint8_t *group_call_ref)
+{
+	struct asci_notification *n;
+	llist_for_each_entry(n, &bts->asci.notifications, list) {
+		if (!memcmp(n->group_call_ref, group_call_ref, sizeof(n->group_call_ref)))
+			return n;
+	}
+	return NULL;
+}
+
+int bts_asci_notification_add(struct gsm_bts *bts, const uint8_t *group_call_ref, const uint8_t *chan_desc,
+			      uint8_t chan_desc_len, const struct rsl_ie_nch_drx_info *nch_drx_info)
+{
+	struct asci_notification *n;
+
+	if (bts_asci_notification_find(bts, group_call_ref))
+		return -EEXIST;
+
+	n = talloc_zero(bts, struct asci_notification);
+	if (!n)
+		return -ENOMEM;
+
+	memcpy(n->group_call_ref, group_call_ref, sizeof(n->group_call_ref));
+	if (chan_desc && chan_desc_len) {
+		n->chan_desc.present = true;
+		n->chan_desc.len = chan_desc_len;
+		memcpy(&n->chan_desc.value, chan_desc, chan_desc_len);
+	}
+	if (nch_drx_info) {
+		n->nch_drx_info.present = true;
+		n->nch_drx_info.value = *nch_drx_info;
+	}
+
+	LOGP(DASCI, LOGL_INFO, "Added ASCI Notification for group call reference %s\n",
+	     osmo_hexdump_nospc(n->group_call_ref, ARRAY_SIZE(n->group_call_ref)));
+
+	/* add at beginning of "queue" to make sure a new call is notified first */
+	llist_add(&n->list, &bts->asci.notifications);
+
+	bts->asci.notification_entries++;
+	bts->asci.notification_count = 0;
+	bts->asci.nln = (bts->asci.nln + 1) % 4;
+
+	return 0;
+}
+
+int bts_asci_notification_del(struct gsm_bts *bts, const uint8_t *group_call_ref)
+{
+	struct asci_notification *n = bts_asci_notification_find(bts, group_call_ref);
+	if (!n)
+		return -ENODEV;
+
+	LOGP(DASCI, LOGL_INFO, "Deleting ASCI Notification for group call reference %s\n",
+	     osmo_hexdump_nospc(n->group_call_ref, ARRAY_SIZE(n->group_call_ref)));
+
+	llist_del(&n->list);
+	talloc_free(n);
+
+	bts->asci.notification_entries--;
+	bts->asci.notification_count = 0;
+	bts->asci.nln_status = (bts->asci.nln_status + 1) % 2;
+
+	return 0;
+}
+
+int bts_asci_notification_reset(struct gsm_bts *bts)
+{
+	struct asci_notification *n, *n2;
+
+	LOGP(DASCI, LOGL_INFO, "Deleting all %u ASCI Notifications of BTS\n",
+	     llist_count(&bts->asci.notifications));
+
+	llist_for_each_entry_safe(n, n2, &bts->asci.notifications, list) {
+		llist_del(&n->list);
+		talloc_free(n);
+	}
+
+	bts->asci.notification_entries = 0;
+	bts->asci.notification_count = 0;
+	bts->asci.nln_status = (bts->asci.nln_status + 1) % 2;
+
+	return 0;
+}
+
+const struct asci_notification *bts_asci_notification_get_next(struct gsm_bts *bts)
+{
+	struct asci_notification *n;
+
+	n = llist_first_entry_or_null(&bts->asci.notifications, struct asci_notification, list);
+	if (!n)
+		return NULL;
+
+	/* move to end of list to iterate over them */
+	llist_del(&n->list);
+	llist_add_tail(&n->list, &bts->asci.notifications);
+
+	return n;
+}
+
+
+/*! append a "Group Call Information" CSN.1 structure to the caller-provided bit-vector.
+ *  \param[out] bv caller-provided output bit-vector
+ *  \param[in] gcr 5-byte group call reference
+ *  \param[in] ch_desc optional group channel description (may be NULL)
+ *  \param[in] ch_desc_len length of group channel description (in bytes) */
+void append_group_call_information(struct bitvec *bv, const uint8_t *gcr, const uint8_t *ch_desc, uint8_t ch_desc_len)
+{
+	/* spec reference: TS 44.018 Section 9.1.21a */
+
+	/* <Group Call Reference : bit(36)> */
+	struct bitvec *gcr_bv = bitvec_alloc(5*8, NULL);
+	OSMO_ASSERT(gcr_bv);
+	bitvec_unpack(gcr_bv, gcr);
+	for (unsigned int i = 0; i < 36; i++)
+		bitvec_set_bit(bv, bitvec_get_bit_pos(gcr_bv, i));
+
+	/* Group Channel Description */
+	if (ch_desc && ch_desc_len) {
+		struct bitvec *chd_bv = bitvec_alloc(ch_desc_len*8, NULL);
+		OSMO_ASSERT(chd_bv);
+		bitvec_unpack(chd_bv, ch_desc);
+		bitvec_set_bit(bv, 1);
+		/* <Channel Description : bit(24)> */
+		for (unsigned int i = 0; i < ch_desc_len * 8; i++)
+			bitvec_set_bit(bv, bitvec_get_bit_pos(chd_bv, i));
+		bitvec_free(chd_bv);
+		/* FIXME: hopping */
+		bitvec_set_bit(bv, 0);
+	} else {
+		bitvec_set_bit(bv, 0);
+	}
+
+	bitvec_free(gcr_bv);
+}
+
+#define L2_PLEN(len)	(((len - 1) << 2) | 0x01)
+
+int bts_asci_notify_nch_gen_msg(struct gsm_bts *bts, uint8_t *out_buf)
+{
+	struct gsm48_notification_nch *nn = (struct gsm48_notification_nch *) out_buf;
+	const struct asci_notification *notif;
+	unsigned int ro_len;
+
+	notif = bts_asci_notification_get_next(bts);
+
+	*nn = (struct gsm48_notification_nch) {
+		.proto_discr = GSM48_PDISC_RR,
+		.msg_type = GSM48_MT_RR_NOTIF_NCH,
+	};
+
+	nn->l2_plen = L2_PLEN(nn->data - out_buf);
+
+	/* Pad remaining octets with constant '2B'O */
+	ro_len = GSM_MACBLOCK_LEN - (nn->data - out_buf);
+	memset(nn->data, GSM_MACBLOCK_PADDING, ro_len);
+
+	struct bitvec bv = {
+		.data_len = ro_len,
+		.data = nn->data,
+	};
+
+	/* {0 | 1 < NLN(NCH) : bit (2) >}
+	 * Only send NLN, at the last notifications.
+	 * When the phone receives two NLN with the same value, it knows that all notifications has been received.
+	 * Also send NLN if no notification is available. */
+	if (bts->asci.notification_count >= bts->asci.notification_entries - 1) {
+		bitvec_set_bit(&bv, 1);
+		bitvec_set_uint(&bv, bts->asci.nln, 2);
+	} else {
+		bitvec_set_bit(&bv, 0);
+	}
+
+	/* Count NLN. */
+	if (++bts->asci.notification_count >= bts->asci.notification_entries)
+		bts->asci.notification_count = 0;
+
+	/* < List of Group Call NCH information > ::=
+	 *   { 0 | 1 < Group Call information > < List of Group Call NCH information > } ; */
+	if (notif) {
+		bitvec_set_bit(&bv, 1);
+		append_group_call_information(&bv, notif->group_call_ref,
+						   notif->chan_desc.present ? notif->chan_desc.value : NULL,
+						   notif->chan_desc.len);
+	}
+	bitvec_set_bit(&bv, 0);	/* End of list */
+
+	/* TODO: Additions in Release 6 */
+	/* TODO: Additions in Release 7 */
+
+	return GSM_MACBLOCK_LEN;
+}
+
+int bts_asci_notify_facch_gen_msg(struct gsm_bts *bts, uint8_t *out_buf, const uint8_t *group_call_ref,
+				  const uint8_t *chan_desc, uint8_t chan_desc_len)
+{
+	struct gsm48_hdr_sh *sh = (struct gsm48_hdr_sh *) out_buf;
+	unsigned int ro_len;
+
+	*sh = (struct gsm48_hdr_sh) {
+		.rr_short_pd = GSM48_PDISC_SH_RR,
+		.msg_type = GSM48_MT_RR_SH_FACCH,
+		.l2_header = 0,
+	};
+
+	/* Pad remaining octets with constant '2B'O */
+	ro_len = GSM_MACBLOCK_LEN - (sh->data - out_buf);
+	memset(sh->data, GSM_MACBLOCK_PADDING, ro_len);
+
+	struct bitvec bv = {
+		.data_len = ro_len,
+		.data = sh->data,
+	};
+
+	/*  0 < Group Call information > */
+	bitvec_set_bit(&bv, 0);
+	append_group_call_information(&bv, group_call_ref, chan_desc, chan_desc_len);
+
+	/* TODO: Additions in Release 6 */
+	/* TODO: Additions in Release 7 */
+
+	return GSM_MACBLOCK_LEN;
+}