mscsplit: various preparations to separate MSC from BSC

Disable large parts of the code that depend on BSC presence. The code sections
disabled by #if BEFORE_MSCSPLIT shall be modified or dropped in the course of
adding the A-interface.

Don't set msg->lchan nor msg->dst.
Don't use lchan in libmsc.
Decouple lac from bts.

Prepare entry/exit point for MSC -> BSC and MSC -> RNC communication:
Add msc_ifaces.[hc], a_iface.c, with a general msc_tx_dtap() to redirect to
different interfaces depending on the actual subscriber connection.
While iu_tx() is going to be functional fairly soon, the a_tx() is going to be
just a dummy for some time (see comment).
Add Iu specific fields in gsm_subscriber_connection: the UE connection pointer
and an indicator for the Integrity Protection status on Iu (to be fully
implemented in later commits).
Add lac member to gsm_subscriber_connection, to allow decoupling from
bts->location_area_code. The conn->lac will actually be set in iu.c in an
upcoming commit ("add iucs.[hc]").

move to libcommon-cs: gsm48_extract_mi(), gsm48_paging_extract_mi().

libmsc: duplicate gsm0808 / gsm48 functions (towards BSC).
In osmo-nitb, libmsc would directly call the functions on the BSC level, not
always via the bsc_api. When separating libmsc from libbsc, some functions are
missing from the linkage.
Hence duplicate these functions to libmsc, add an msc_ prefix for clarity, also
add a _tx to gsm0808_cipher_mode():
* add msc_gsm0808_tx_cipher_mode() (dummy/stub)
* add msc_gsm48_tx_mm_serv_ack()
* add msc_gsm48_tx_mm_serv_rej()
Call these from libmsc instead of
* gsm0808_cipher_mode()
* gsm48_tx_mm_serv_ack()
* gsm48_tx_mm_serv_rej()
Also add a comment related to msc_gsm0808_tx_cipher_mode() in two places.

Remove internal RTP streaming code; OsmoNITB supported that, but for OsmoMSC,
this will be done with an external MGCP gateway.

Remove LCHAN_MODIFY from internal MNCC state machine.

Temporarily disable all paging to be able to link libmsc without libbsc.
Skip the paging part of channel_test because the paging is now disabled.
Employ fake paging shims in order for msc_vlr_tests to still work.

msc_compl_l3(): publish in .h, tweak return value.  Use new libmsc enum values
for return val, to avoid dependency on libbsc headers.  Make callable from
other scopes: publish in osmo_msc.h and remove 'static' in osmo_msc.c

add gsm_encr to subscr_conn
move subscr_request to gsm_subscriber.h
subscr_request_channel() -> subscr_request_conn()
move to libmsc: osmo_stats_vty_add_cmds()
gsm_04_08: remove apply_codec_restrictions()
gsm0408_test: use NULL for root ctx
move to libbsc: gsm_bts_neighbor()
move to libbsc: lchan_next_meas_rep()
move vty config for t3212 to network level (periodic lu)
remove unneccessary linking from some tests
remove handle_abisip_signal()
abis_rsl.c: don't use libvlr from libbsc

gsm_subscriber_connection: put the LAC here, so that it is available without
accessing conn->bts. In bsc_api.c, place this lac in conn for the sake of
transition: Iu and A will use this new field to pass the LAC around, but in a
completely separate OsmoBSC this is not actually needed. It can be removed
again from osmo-bsc.git when the time has come.

Siemens MRPCI: completely drop sending the MRPCI messages for now, they shall
be added in osmo-bsc once the A-Interface code has settled. See OS#2389.

Related: OS#1845 OS#2257 OS#2389
Change-Id: Id3705236350d5f69e447046b0a764bbabc3d493c

1 files changed, 45 insertions, 0 deletions

diff --git a/src/libmsc/a_iface.c b/src/libmsc/a_iface.c
new file mode 100644
index 000000000..1f471f97b
--- /dev/null
+++ b/src/libmsc/a_iface.c
@@ -0,0 +1,45 @@
+/* A-interface implementation, from MSC to BSC */
+
+/* (C) 2016 by sysmocom s.m.f.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 <osmocom/core/msgb.h>
+#include <osmocom/core/logging.h>
+
+#include <openbsc/debug.h>
+
+#include <openbsc/gsm_data.h>
+#include <openbsc/msc_ifaces.h>
+#include <openbsc/debug.h>
+
+int a_tx(struct msgb *msg)
+{
+	LOGP(DMSC, LOGL_ERROR, "message to be sent to BSC, but A-interface"
+	     " not implemented.\n%s\n", osmo_hexdump(msg->data, msg->len));
+	return -1;
+}
+
+int msc_gsm0808_tx_cipher_mode(struct gsm_subscriber_connection *conn, int cipher,
+			       const uint8_t *key, int len, int include_imeisv)
+{
+	/* TODO generalize for A- and Iu interfaces, don't name after 08.08 */
+	LOGP(DMSC, LOGL_ERROR, "gsm0808_cipher_mode(): message to be sent to"
+	     " BSC, but A interface not yet implemented.\n");
+	return -1;
+}