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, 12 insertions, 10 deletions

diff --git a/src/libmsc/osmo_msc.c b/src/libmsc/osmo_msc.c
index 95e58182c..c847b78f1 100644
--- a/src/libmsc/osmo_msc.c
+++ b/src/libmsc/osmo_msc.c
@@ -21,6 +21,7 @@
  *
  */
 
+#include <openbsc/osmo_msc.h>
 #include <openbsc/bsc_api.h>
 #include <openbsc/debug.h>
 #include <openbsc/transaction.h>
@@ -69,9 +70,10 @@ static void subscr_conn_bump(struct gsm_subscriber_connection *conn)
 	osmo_fsm_inst_dispatch(conn->conn_fsm, SUBSCR_CONN_E_BUMP, NULL);
 }
 
-/* Receive a COMPLETE LAYER3 INFO from BSC */
-static int msc_compl_l3(struct gsm_subscriber_connection *conn, struct msgb *msg,
-			uint16_t chosen_channel)
+/* receive a Level 3 Complete message and return MSC_CONN_ACCEPT or
+ * MSC_CONN_REJECT */
+static int msc_compl_l3(struct gsm_subscriber_connection *conn,
+			struct msgb *msg, uint16_t chosen_channel)
 {
 	/* Ownership of the gsm_subscriber_connection is still a bit mucky
 	 * between libbsc and libmsc. In libmsc, we use ref counting, but not
@@ -87,7 +89,7 @@ static int msc_compl_l3(struct gsm_subscriber_connection *conn, struct msgb *msg
 		/* keep the use_count reserved, libbsc will discard. If we
 		 * released the ref count and discarded here, libbsc would
 		 * double-free. And we will not change bsc_api semantics. */
-		return BSC_API_CONN_POL_REJECT;
+		return MSC_CONN_REJECT;
 	}
 	DEBUGP(DMM, "compl_l3: Keeping conn\n");
 
@@ -96,7 +98,7 @@ static int msc_compl_l3(struct gsm_subscriber_connection *conn, struct msgb *msg
 
 	/* If this should be kept, the conn->conn_fsm has placed a use_count */
 	msc_subscr_conn_put(conn);
-	return BSC_API_CONN_POL_ACCEPT;
+	return MSC_CONN_ACCEPT;
 
 #if 0
 	/*
@@ -105,14 +107,14 @@ static int msc_compl_l3(struct gsm_subscriber_connection *conn, struct msgb *msg
 	 * pending transaction or ongoing operation.
 	 */
 	if (conn->silent_call)
-		return BSC_API_CONN_POL_ACCEPT;
-	if (conn->sec_operation || conn->anch_operation)
-		return BSC_API_CONN_POL_ACCEPT;
+		return MSC_CONN_ACCEPT;
+	if (conn->loc_operation || conn->sec_operation || conn->anch_operation)
+		return MSC_CONN_ACCEPT;
 	if (trans_has_conn(conn))
-		return BSC_API_CONN_POL_ACCEPT;
+		return MSC_CONN_ACCEPT;
 
 	LOGP(DRR, LOGL_INFO, "MSC Complete L3: Rejecting connection.\n");
-	return BSC_API_CONN_POL_REJECT;
+	return MSC_CONN_REJECT;
 #endif
 }