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, 22 insertions, 6 deletions

diff --git a/include/openbsc/gsm_subscriber.h b/include/openbsc/gsm_subscriber.h
index c65b8a315..60eb0cd65 100644
--- a/include/openbsc/gsm_subscriber.h
+++ b/include/openbsc/gsm_subscriber.h
@@ -19,8 +19,6 @@
 
 #define GSM_SUBSCRIBER_NO_EXPIRATION	0x0
 
-struct subscr_request;
-
 enum gsm_subscriber_field {
 	GSM_SUBSCRIBER_IMSI,
 	GSM_SUBSCRIBER_TMSI,
@@ -34,17 +32,35 @@ enum gsm_subscriber_update_reason {
 	GSM_SUBSCRIBER_UPDATE_EQUIPMENT,
 };
 
-int subscr_update(struct vlr_subscr *vsub, struct gsm_bts *bts, int reason);
+/*
+ * Struct for pending channel requests. This is managed in the
+ * llist_head requests of each subscriber. The reference counting
+ * should work in such a way that a subscriber with a pending request
+ * remains in memory.
+ */
+struct subscr_request {
+       struct llist_head entry;
+
+       /* the callback data */
+       gsm_cbfn *cbfn;
+       void *param;
+};
+
+int subscr_update(struct vlr_subscr *vsub, int reason);
 
 /*
  * Paging handling with authentication
  */
-struct subscr_request *subscr_request_channel(struct vlr_subscr *vsub,
-					      int channel_type,
-					      gsm_cbfn *cbfn, void *param);
+struct subscr_request *subscr_request_conn(struct vlr_subscr *vsub,
+					   int channel_type,
+					   gsm_cbfn *cbfn, void *param);
+
 void subscr_remove_request(struct subscr_request *req);
 
 int subscr_paging_dispatch(unsigned int hooknum, unsigned int event,
 			   struct msgb *msg, void *data, void *param);
 
+int msc_fake_paging_request(struct vlr_subscr *vsub);
+void msc_fake_paging_request_stop(struct vlr_subscr *vsub);
+
 #endif /* _GSM_SUBSCR_H */