add osmo_tdef API, originally adopted from osmo-bsc T_def

Move T_def from osmo-bsc to libosmocore as osmo_tdef. Adjust naming to be more
consistent. Upgrade to first class API:
- add timer grouping
- add generic vty support
- add mising API doc
- add C test
- add VTY transcript tests, also as examples for using the API

From osmo_fsm_inst_state_chg() API doc, cross reference to osmo_tdef API.

The root reason for moving to libosmocore is that I want to use the
mgw_endpoint_fsm in osmo-msc for inter-MSC handover, and hence want to move the
FSM to libosmo-mgcp-client. This FSM uses the T_def from osmo-bsc. Though the
mgw_endpoint_fsm's use of T_def is minimal, I intend to use the osmo_tdef API
in osmo-msc (and probably elsewhere) as well. libosmocore is the most sensible
place for this.

osmo_tdef provides:

- a list of Tnnnn (GSM) timers with description, unit and default value.
- vty UI to allow users to configure non-default timeouts.
- API to tie T timers to osmo_fsm states and set them on state transitions.

- a few standard units (minute, second, millisecond) as well as a custom unit
  (which relies on the timer's human readable description to indicate the
  meaning of the value).
- conversion for standard units: for example, some GSM timers are defined in
  minutes, while our FSM definitions need timeouts in seconds. Conversion is
  for convenience only and can be easily avoided via the custom unit.

By keeping separate osmo_tdef arrays, several groups of timers can be kept
separately. The VTY tests in tests/tdef/ showcase different schemes:

- tests/vty/tdef_vty_test_config_root.c:
  Keep several timer definitions in separately named groups: showcase the
  osmo_tdef_vty_groups*() API. Each timer group exists exactly once.

- tests/vty/tdef_vty_test_config_subnode.c:
  Keep a single list of timers without separate grouping.
  Put this list on a specific subnode below the CONFIG_NODE.
  There could be several separate subnodes with timers like this, i.e.
  continuing from this example, sets timers could be separated by placing
  timers in specific config subnodes instead of using the global group name.

- tests/vty/tdef_vty_test_dynamic.c:
  Dynamically allocate timer definitions per each new created object.
  Thus there can be an arbitrary number of independent timer definitions, one
  per allocated object.

T_def was introduced during the recent osmo-bsc refactoring for inter-BSC
handover, and has proven useful:

- without osmo_tdef, each invocation of osmo_fsm_inst_state_chg() needs to be
  programmed with the right timeout value, for all code paths that invoke this
  state change. It is a likely source of errors to get one of them wrong.  By
  defining a T timer exactly for an FSM state, the caller can merely invoke the
  state change and trust on the original state definition to apply the correct
  timeout.

- it is helpful to have a standardized config file UI to provide user
  configurable timeouts, instead of inventing new VTY commands for each
  separate application of T timer numbers.

Change-Id: Ibd6b1ed7f1bd6e1f2e0fde53352055a4468f23e5

1 files changed, 67 insertions, 0 deletions

diff --git a/include/osmocom/vty/tdef_vty.h b/include/osmocom/vty/tdef_vty.h
new file mode 100644
index 00000000..f55239ad
--- /dev/null
+++ b/include/osmocom/vty/tdef_vty.h
@@ -0,0 +1,67 @@
+/*! \file tdef_vty.h
+ * API to configure osmo_tdef Tnnn timers from VTY configuration.
+ */
+/* (C) 2018-2019 by sysmocom - s.f.m.c. GmbH <info@sysmocom.de>
+ *
+ * Author: Neels Hofmeyr <neels@hofmeyr.de>
+ *
+ * All Rights Reserved
+ *
+ * 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/>.
+ */
+#pragma once
+
+#include <stdint.h>
+
+struct vty;
+
+/*! \defgroup Tdef_VTY  Tnnn timer VTY configuration
+ * @{
+ * \file tdef_vty.h
+ */
+
+struct osmo_tdef;
+struct osmo_tdef_group;
+
+#define OSMO_TDEF_VTY_ARG_T "TNNNN"
+#define OSMO_TDEF_VTY_DOC_T "T-number, optionally preceded by 't' or 'T'.\n"
+#define OSMO_TDEF_VTY_ARG_T_OPTIONAL "[" OSMO_TDEF_VTY_ARG_T "]"
+
+#define OSMO_TDEF_VTY_ARG_VAL "(<0-2147483647>|default)"
+#define OSMO_TDEF_VTY_DOC_VAL "New timer value\n" "Set to default timer value\n"
+#define OSMO_TDEF_VTY_ARG_VAL_OPTIONAL "[" OSMO_TDEF_VTY_ARG_VAL "]"
+
+#define OSMO_TDEF_VTY_ARG_SET	OSMO_TDEF_VTY_ARG_T " " OSMO_TDEF_VTY_ARG_VAL
+#define OSMO_TDEF_VTY_DOC_SET	OSMO_TDEF_VTY_DOC_T OSMO_TDEF_VTY_DOC_VAL
+#define OSMO_TDEF_VTY_ARG_SET_OPTIONAL	OSMO_TDEF_VTY_ARG_T_OPTIONAL " " OSMO_TDEF_VTY_ARG_VAL_OPTIONAL
+
+int osmo_tdef_vty_set_cmd(struct vty *vty, struct osmo_tdef *tdefs, const char **args);
+int osmo_tdef_vty_show_cmd(struct vty *vty, struct osmo_tdef *tdefs, const char *T_arg,
+			   const char *prefix_fmt, ...);
+void osmo_tdef_vty_write(struct vty *vty, struct osmo_tdef *tdefs,
+			 const char *prefix_fmt, ...);
+
+void osmo_tdef_vty_out_one(struct vty *vty, struct osmo_tdef *t, const char *prefix_fmt, ...);
+void osmo_tdef_vty_out_all(struct vty *vty, struct osmo_tdef *tdefs, const char *prefix_fmt, ...);
+
+void osmo_tdef_vty_out_one_va(struct vty *vty, struct osmo_tdef *t, const char *prefix_fmt, va_list va);
+void osmo_tdef_vty_out_all_va(struct vty *vty, struct osmo_tdef *tdefs, const char *prefix_fmt, va_list va);
+
+struct osmo_tdef *osmo_tdef_vty_parse_T_arg(struct vty *vty, struct osmo_tdef *tdefs, const char *osmo_tdef_str);
+unsigned long osmo_tdef_vty_parse_val_arg(const char *val_arg, unsigned long default_val);
+
+void osmo_tdef_vty_groups_init(enum node_type parent_node, struct osmo_tdef_group *groups);
+void osmo_tdef_vty_groups_write(struct vty *vty, const char *indent);
+
+/*! @} */