Introduce NACC support

A new nacc_fsm is introduced per MS object, with its partner priv
structure struct nacc_fsm_ctx, which exists and is available in the MS
object only during the duration of the NACC procedure.

The NACC context is created on an MS whenever a Pkt Cell Change
Notification is received on Uplink RLCMAC, which asks for neighbor
information of a given ARFCN+BSIC.

First, the target ARFCN+BSIC needs to be translated into a CGI-PS
(RAC+CI) address. That's done by asking the BSC through the Neighbour
Resolution Service available in osmo-bsc using the CTRL interface.

Once the CGI-PS of the target cell is known, PCU starts a RIM RAN-INFO
request against the SGSN (which will route the request as needed), and
wait for a response containing the SI bits from the target cell.

After the SI are received, the scheduler is instructed to eventually
poll a TBF for the MS originating the CCN, so that we can send the SI
encapsulated into multiple Packet Neighbor Cell Data messages on the
downlink.

One all the SI bits are sent, the scheduler is instructed to send a
Packet Cell Change Continue message.

Once the message above has been sent, the FSM autodestroys itself.

Caches are also introduced in this patch which allows for re-using
recently known translations ARFCN+BSIC -> CGI-PS and CGI-PS -> SI_INFO
respectively.

Change-Id: Id35f40d05f3e081f32fddbf1fa34cb338db452ca

1 files changed, 64 insertions, 0 deletions

diff --git a/src/nacc_fsm.h b/src/nacc_fsm.h
new file mode 100644
index 00000000..9107dafd
--- /dev/null
+++ b/src/nacc_fsm.h
@@ -0,0 +1,64 @@
+/* nacc_fsm.h
+ *
+ * Copyright (C) 2021 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
+ * Author: Pau Espin Pedrol <pespin@sysmocom.de>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ */
+#pragma once
+
+#include <osmocom/core/fsm.h>
+#include <osmocom/gsm/gsm23003.h>
+
+#include <neigh_cache.h>
+
+struct GprsMs;
+struct gprs_rlcmac_tbf;
+
+enum nacc_fsm_event {
+	NACC_EV_RX_CELL_CHG_NOTIFICATION, /* data: Packet_Cell_Change_Notification_t* */
+	NACC_EV_RX_RAC_CI, /* no data passed, RAC_CI became available in neigh_cache */
+	NACC_EV_RX_SI, /* data: struct si_cache_entry* */
+	NACC_EV_CREATE_RLCMAC_MSG, /* data: struct nacc_ev_create_rlcmac_msg_ctx* */
+};
+
+enum nacc_fsm_states {
+	NACC_ST_INITIAL,
+	NACC_ST_WAIT_RESOLVE_RAC_CI,
+	NACC_ST_WAIT_REQUEST_SI,
+	NACC_ST_TX_NEIGHBOUR_DATA,
+	NACC_ST_TX_CELL_CHG_CONTINUE,
+	NACC_ST_DONE,
+};
+
+struct nacc_fsm_ctx {
+	struct osmo_fsm_inst *fi;
+	struct GprsMs* ms; /* back pointer */
+	struct ctrl_handle *neigh_ctrl;
+	struct ctrl_connection *neigh_ctrl_conn;
+	struct neigh_cache_entry_key neigh_key; /* target cell info from MS */
+	struct osmo_cell_global_id_ps cgi_ps; /* target cell info resolved from req_{arfcn+bsic} */
+	struct si_cache_value si_info; /* SI info resolved from SGSN, to be sent to MS */
+	size_t si_info_bytes_sent; /* How many bytes out of si_info->si_len were already sent to MS */
+	size_t container_idx; /* Next container_idx to assign when sending Packet Neighbor Data message */
+};
+
+/* passed as data in NACC_EV_CREATE_RLCMAC_MSG */
+struct nacc_ev_create_rlcmac_msg_ctx {
+	struct gprs_rlcmac_tbf *tbf; /* target tbf to create messages for */
+	struct msgb *msg; /* to be filled by FSM during event processing */
+};
+
+struct nacc_fsm_ctx *nacc_fsm_alloc(struct GprsMs* ms);