dissolve libbsc: move all to src/osmo-bsc, link .o files

Move all of libbsc/ into osmo-bsc/, and separate/move some implementations to
allow linking from utils/* and ipaccess/* without pulling in unccessary
dependencies.

Some utilities use gsm_network and gsm_bts structs, which already include data
structures for fairly advanced uses. Move initialization that only osmo-bsc
needs into new bsc_network_init() and bsc_bts_alloc_register() functions, so
that the leaner tools can use the old gsm_* versions without the need to link
everything (e.g. handover and lchan alloc code).

In some instances, there need to be stubs if to cut off linking "just before
the RSL level" and prevent dependencies from creeping in.
- abis_rsl_rcvmsg(): the only program currently interpreting RSL messages is
  osmo-bsc, the utils are merely concerned with OML, if at all.
- paging_flush_bts(): ip.access nanobts models call this when the RSL link is
  dropped. Only osmo-bsc actually needs to do anything there.
- on_gsm_ts_init(): the mechanism to trigger timeslot initialization is related
  to OML, while this action to take on init would pull in RSL dependencies.
utils/ and ipaccess/ each have a stubs.c file to implement these stubs. Tests
implement stubs inline where required.

From src/utils/, src/ipaccess/ and tests/*/, link in .o files from osmo-bsc/.
In order for this to work, the osmo-bsc subdir must be built before the other
source trees. (An alternative would be to include the .c files as sources, but
that would re-compile them in every source tree. Not a large burden really, but
unless linking .o files gives problems, let's have the quicker build.)

Minor obvious cleanups creep in with this patch, I will not bother to name them
individually now unless code review asks me to.

Rationale:

1) libbsc has been separate to use it for osmo-nitb and osmo-bsc in the old
openbsc.git. This is no longer required, and spreading over libbsc and osmo-bsc
is distracting.

2) Recently, ridiculous linking requirements have made adding new functions
cumbersome, because libbsc has started depending on osmo-bsc/*.c
implementations: on gscon FSM and bssap functions. For example, neither
bs11_config nor ipaccess-config nor bts_test need handover_cfg or BSSMAP
message composition. It makes no sense to link the entire osmo-bsc to it, nor
do we want to keep adding stubs to each linking realm.

Change-Id: I36a586726f5818121abe54d25654819fc451d3bf

1 files changed, 205 insertions, 0 deletions

diff --git a/src/osmo-bsc/a_reset.c b/src/osmo-bsc/a_reset.c
new file mode 100644
index 000000000..b8f8c8cbd
--- /dev/null
+++ b/src/osmo-bsc/a_reset.c
@@ -0,0 +1,205 @@
+/* (C) 2017 by sysmocom s.f.m.c. GmbH
+ * All Rights Reserved
+ *
+ * Author: Philipp Maier
+ *
+ * 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 <osmocom/core/logging.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/core/timer.h>
+#include <osmocom/core/fsm.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <osmocom/bsc/debug.h>
+#include <osmocom/bsc/bsc_msc_data.h>
+#include <osmocom/bsc/osmo_bsc_sigtran.h>
+
+#define RESET_RESEND_INTERVAL 2		/* sec */
+#define RESET_RESEND_TIMER_NO 4		/* See also 3GPP TS 48.008 Chapter 3.1.4.1.3.1 */
+#define BAD_CONNECTION_THRESOLD 3	/* connection failures */
+
+/* Reset context data (callbacks, state machine etc...) */
+struct reset_ctx {
+	/* Connection failure counter. When this counter
+	 * reaches a certain threshold, the reset procedure
+	 * will be triggered */
+	int conn_loss_counter;
+
+	/* Callback function to be called when a connection
+	 * failure is detected and a rest must occur */
+	void (*cb)(void *priv);
+
+	/* Privated data for the callback function */
+	void *priv;
+};
+
+enum reset_fsm_states {
+	ST_DISC,		/* Disconnected from remote end */
+	ST_CONN,		/* We have a confirmed connection */
+};
+
+enum reset_fsm_evt {
+	EV_RESET_ACK,		/* got reset acknowlegement from remote end */
+	EV_N_DISCONNECT,	/* lost a connection */
+	EV_N_CONNECT,		/* made a successful connection */
+};
+
+static const struct value_string fsm_event_names[] = {
+	OSMO_VALUE_STRING(EV_RESET_ACK),
+	OSMO_VALUE_STRING(EV_N_DISCONNECT),
+	OSMO_VALUE_STRING(EV_N_CONNECT),
+	{0, NULL}
+};
+
+/* Disconnected state */
+static void fsm_disc_cb(struct osmo_fsm_inst *fi, uint32_t event, void *data)
+{
+	struct reset_ctx *reset_ctx = (struct reset_ctx *)fi->priv;
+	OSMO_ASSERT(reset_ctx);
+	LOGPFSML(fi, LOGL_NOTICE, "SIGTRAN connection succeded.\n");
+
+	reset_ctx->conn_loss_counter = 0;
+	osmo_fsm_inst_state_chg(fi, ST_CONN, 0, 0);
+}
+
+/* Connected state */
+static void fsm_conn_cb(struct osmo_fsm_inst *fi, uint32_t event, void *data)
+{
+	struct reset_ctx *reset_ctx = (struct reset_ctx *)fi->priv;
+	OSMO_ASSERT(reset_ctx);
+
+	switch (event) {
+	case EV_N_DISCONNECT:
+		if (reset_ctx->conn_loss_counter >= BAD_CONNECTION_THRESOLD) {
+			LOGPFSML(fi, LOGL_NOTICE, "SIGTRAN connection down, reconnecting...\n");
+			osmo_fsm_inst_state_chg(fi, ST_DISC, RESET_RESEND_INTERVAL, RESET_RESEND_TIMER_NO);
+		} else
+			reset_ctx->conn_loss_counter++;
+		break;
+	case EV_N_CONNECT:
+		reset_ctx->conn_loss_counter = 0;
+		break;
+	}
+}
+
+/* Timer callback to retransmit the reset signal */
+static int fsm_reset_ack_timeout_cb(struct osmo_fsm_inst *fi)
+{
+	struct reset_ctx *reset_ctx = (struct reset_ctx *)fi->priv;
+	OSMO_ASSERT(reset_ctx);
+
+	LOGPFSML(fi, LOGL_NOTICE, "(re)sending BSSMAP RESET message...\n");
+
+	reset_ctx->cb(reset_ctx->priv);
+
+	osmo_fsm_inst_state_chg(fi, ST_DISC, RESET_RESEND_INTERVAL, RESET_RESEND_TIMER_NO);
+	return 0;
+}
+
+static struct osmo_fsm_state reset_fsm_states[] = {
+	[ST_DISC] = {
+		     .in_event_mask = (1 << EV_RESET_ACK),
+		     .out_state_mask = (1 << ST_DISC) | (1 << ST_CONN),
+		     .name = "DISC",
+		     .action = fsm_disc_cb,
+		     },
+	[ST_CONN] = {
+		     .in_event_mask = (1 << EV_N_DISCONNECT) | (1 << EV_N_CONNECT),
+		     .out_state_mask = (1 << ST_DISC) | (1 << ST_CONN),
+		     .name = "CONN",
+		     .action = fsm_conn_cb,
+		     },
+};
+
+/* State machine definition */
+static struct osmo_fsm fsm = {
+	.name = "A-RESET",
+	.states = reset_fsm_states,
+	.num_states = ARRAY_SIZE(reset_fsm_states),
+	.log_subsys = DMSC,
+	.timer_cb = fsm_reset_ack_timeout_cb,
+	.event_names = fsm_event_names,
+};
+
+/* Create and start state machine which handles the reset/reset-ack procedure */
+struct osmo_fsm_inst *a_reset_alloc(void *ctx, const char *name, void *cb, void *priv)
+{
+	OSMO_ASSERT(name);
+
+	struct reset_ctx *reset_ctx;
+	struct osmo_fsm_inst *reset_fsm;
+
+	/* Register the fsm description (if not already done) */
+	if (osmo_fsm_find_by_name(fsm.name) != &fsm)
+		osmo_fsm_register(&fsm);
+
+	/* Allocate and configure a new fsm instance */
+	reset_ctx = talloc_zero(ctx, struct reset_ctx);
+	OSMO_ASSERT(reset_ctx);
+	reset_ctx->priv = priv;
+	reset_ctx->cb = cb;
+	reset_ctx->conn_loss_counter = 0;
+	reset_fsm = osmo_fsm_inst_alloc(&fsm, ctx, reset_ctx, LOGL_DEBUG, name);
+	OSMO_ASSERT(reset_fsm);
+
+	/* kick off reset-ack sending mechanism */
+	osmo_fsm_inst_state_chg(reset_fsm, ST_DISC, RESET_RESEND_INTERVAL, RESET_RESEND_TIMER_NO);
+
+	return reset_fsm;
+}
+
+/* Confirm that we sucessfully received a reset acknowlege message */
+void a_reset_ack_confirm(struct osmo_fsm_inst *reset_fsm)
+{
+	OSMO_ASSERT(reset_fsm);
+	osmo_fsm_inst_dispatch(reset_fsm, EV_RESET_ACK, NULL);
+}
+
+/* Report a failed connection */
+void a_reset_conn_fail(struct osmo_fsm_inst *reset_fsm)
+{
+	/* If no reset context is supplied, just drop the info */
+	if (!reset_fsm)
+		return;
+
+	osmo_fsm_inst_dispatch(reset_fsm, EV_N_DISCONNECT, NULL);
+}
+
+/* Report a successful connection */
+void a_reset_conn_success(struct osmo_fsm_inst *reset_fsm)
+{
+	/* If no reset context is supplied, just drop the info */
+	if (!reset_fsm)
+		return;
+
+	osmo_fsm_inst_dispatch(reset_fsm, EV_N_CONNECT, NULL);
+}
+
+/* Check if we have a connection to a specified msc */
+bool a_reset_conn_ready(struct osmo_fsm_inst *reset_fsm)
+{
+	/* If no reset context is supplied, we assume that
+	 * the connection can't be ready! */
+	if (!reset_fsm)
+		return false;
+
+	if (reset_fsm->state == ST_CONN)
+		return true;
+
+	return false;
+}