large refactoring: use FSMs for lchans; add inter-BSC HO

Add FSMs:

- timeslot_fsm: handle dynamic timeslots and OML+RSL availability.
- lchan_fsm: handle an individual lchan activation, RTP stream and release,
  signal the appropriate calling FSMs on success, failure, release.
- mgw_endpoint_fsm: handle one entire endpoint with several CI.
- assignment_fsm: BSSMAP Assignment Request.
- handover_fsm: all of intra, inter-MO and inter-MT handover.

Above FSMs absorb large parts of the gscon FSM. The gscon FSM was surpassing
the maximum amount events (32), and it is more logical to treat assignment,
handover and MGW procedures in separate FSMs.

- Add logging macros for each FSM type:
  - LOG_TS()
  - LOG_LCHAN()
  - LOG_MGWEP(), LOG_CI()
  - LOG_ASSIGNMENT()
  - LOG_HO()
  These log with the osmo_fsm_inst where present.
  New style decision: logging without a final newline char is awkward,
  especially for gsmtap logging and when other logs interleave LOGPC() calls;
  we have various cases where the final \n goes missing, and also this invokes
  the log category checking N times instead of once.
  So I decided to make these macros *always* append a newline, but only if
  there is no final newline yet. I hope that the compiler optimizes the
  strlen() of the constant format strings away. Thus I can log with or without
  typing "\n" and always get an \n termination anyway.

General:

- replace osmo_timers, state enums and program-wide osmo_signal_dispatch()
  with dedicated FSM timeouts, states and events.

- introduce a common way to handle Tnnn timers: gsm_timers.h/.c: struct T_def.
  These can be used (with some macro magic) to define a state's timeout once,
  and not make mistakes for each osmo_fsm_inst_state_chg().

Details:

bsc_subscr_conn_fsm.c:

- move most states of this FSM to lchan_fsm, assignment_fsm, handover_fsm and
  mgw_endpoint_fsm.

- There is exactly one state for an ongoing Assignment, with all details
  handled in conn->assignment.fi. The state relies on the assignment_fsm's
  timeout.

- There is one state for an ongoing Handover; except for an incoming Handover
  from a remote BSS, the gscon remains in ST_INIT until the new lchan and conn
  are both established.

- move bssmap_add_lcls_status() to osmo_bsc_lcls.c

abis_rsl.c:

- move all dynamic timeslot logic away into timeslot_fsm. Only keep plain send/receive functions in
  abis_rsl.c

- reduce some rsl functions to merely send a message, rename to "_tx_".
  - rsl_ipacc_mdcx(): add '_tx_' in the name; move parts that change the lchan state out into the
    lchan_fsm, the lchan->abis_ip.* are now set there prior to invoking this function.

- move all timers and error/release handling away into various FSMs.

- tweak ipa_smod_s_for_lchan() and ipa_rtp_pt_for_lchan() to not require an
  lchan passed, but just mode,type that they require. Rename to
  ipacc_speech_mode*() and ipacc_payload_type().

- add rsl_forward_layer3_info, used for inter-BSC HO MO, to just send the RR
  message received during BSSMAP Handover Command.

- move various logging to LOG_LCHAN() in order to log with the lchan FSM instance.
  One drawback is that the lchan FSM is limited to one logging category, i.e. this moves some logging
  from DRR to DRSL. It might actually make sense to combine those categories.

- lose LOGP...LOGPC logging cascades: they are bad for gsmtap logging and for performance.

- handle_classmark_chg(): change logging, move cm2 len check out of the cm3 condition (I hope that's
  correct).

- gsm48_send_ho_cmd(): split off gsm48_make_ho_cmd() which doesn't send right away, so that during
  inter-bsc HO we can make an RR Handover Command to send via the MSC to the remote BSS.

assignment_fsm.c:

- the Chan Mode Modify in case of re-using the same lchan is not implemented
  yet, because this was also missing in the previous implementation (OS#3357).

osmo_bsc_api.c:

- simplify bsc_mr_config() and move to lchan_fsm.c, the only caller; rename to
  lchan_mr_config(). (bsc_mr_config() used to copy the values to mr_bts_lv
  twice, once by member assignment and then again with a memcpy.)

- During handover, we used to copy the MR config from the old lchan. Since we
  may handover between FR and HR, rather set the MR Config anew every time, so
  that FR rates are always available on FR lchans, and never on HR lchans.

Depends: I03ee7ce840ecfa0b6a33358e7385528aabd4873f (libosmocore),
         I1f2918418c38918c5ac70acaa51a47adfca12b5e (libosmocore)
Change-Id: I82e3f918295daa83274a4cf803f046979f284366

4 files changed, 6 insertions, 38 deletions

diff --git a/src/utils/Makefile.am b/src/utils/Makefile.am
index 42118a05c..914a6042d 100644
--- a/src/utils/Makefile.am
+++ b/src/utils/Makefile.am
@@ -46,7 +46,6 @@ endif
 
 bs11_config_SOURCES = \
 	bs11_config.c \
-	stubs.c \
 	$(NULL)
 
 bs11_config_LDADD = \
@@ -118,7 +117,6 @@ osmo_meas_udp2db_CFLAGS = \
 
 meas_json_SOURCES = \
 	meas_json.c \
-	stubs.c \
 	$(NULL)
 
 meas_json_LDADD = \
diff --git a/src/utils/bs11_config.c b/src/utils/bs11_config.c
index ae307c796..7fac3e39a 100644
--- a/src/utils/bs11_config.c
+++ b/src/utils/bs11_config.c
@@ -980,3 +980,6 @@ int osmo_bsc_sigtran_open_conn(struct gsm_subscriber_connection *conn, struct ms
 {
 	return 0;
 }
+
+void ts_fsm_alloc(struct gsm_bts_trx_ts *ts) {}
+int abis_rsl_rcvmsg(struct msgb *msg) { return 0; }
diff --git a/src/utils/meas_json.c b/src/utils/meas_json.c
index b91e78b88..365b450f4 100644
--- a/src/utils/meas_json.c
+++ b/src/utils/meas_json.c
@@ -187,3 +187,6 @@ int main(int argc, char **argv)
 
 	exit(0);
 }
+
+void ts_fsm_alloc(struct gsm_bts_trx_ts *ts) {}
+int abis_rsl_rcvmsg(struct msgb *msg) { return 0; }
diff --git a/src/utils/stubs.c b/src/utils/stubs.c
deleted file mode 100644
index 624797fde..000000000
--- a/src/utils/stubs.c
+++ /dev/null
@@ -1,36 +0,0 @@
-/* Stubs required for linking */
-
-/* (C) 2018 by sysmocom s.f.m.c. GmbH <info@sysmocom.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/>.
- *
- */
-
-#include <stdbool.h>
-struct gsm_bts_trx_ts;
-struct msgb;
-
-bool on_gsm_ts_init(struct gsm_bts_trx_ts *ts)
-{
-	/* No TS init required here. */
-	return true;
-}
-
-int abis_rsl_rcvmsg(struct msgb *msg)
-{
-	/* No RSL handling here */
-	return 0;
-}