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, 10 insertions, 58 deletions

diff --git a/src/libmsc/gsm_subscriber.c b/src/libmsc/gsm_subscriber.c
index e9b2e0e5d..69d79b0c7 100644
--- a/src/libmsc/gsm_subscriber.c
+++ b/src/libmsc/gsm_subscriber.c
@@ -41,43 +41,6 @@
 #include <openbsc/chan_alloc.h>
 #include <openbsc/vlr.h>
 
-void *tall_sub_req_ctx;
-
-int gsm48_secure_channel(struct gsm_subscriber_connection *conn, int key_seq,
-                         gsm_cbfn *cb, void *cb_data);
-
-
-/*
- * 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;
-};
-
-static struct bsc_subscr *vlr_subscr_to_bsc_sub(struct llist_head *bsc_subscribers,
-						struct vlr_subscr *vsub)
-{
-	struct bsc_subscr *sub;
-	/* TODO MSC split -- creating a BSC subscriber directly from MSC data
-	 * structures in RAM. At some point the MSC will send a message to the
-	 * BSC instead. */
-	sub = bsc_subscr_find_or_create_by_imsi(bsc_subscribers, vsub->imsi);
-	sub->tmsi = vsub->tmsi;
-	sub->lac = vsub->lac;
-	return sub;
-}
-
-/*
- * We got the channel assigned and can now hand this channel
- * over to one of our callbacks.
- */
 int subscr_paging_dispatch(unsigned int hooknum, unsigned int event,
 			   struct msgb *msg, void *data, void *param)
 {
@@ -85,22 +48,12 @@ int subscr_paging_dispatch(unsigned int hooknum, unsigned int event,
 	struct gsm_subscriber_connection *conn = data;
 	struct vlr_subscr *vsub = param;
 	struct paging_signal_data sig_data;
-	struct bsc_subscr *bsub;
-	struct gsm_network *net;
 
 	OSMO_ASSERT(vsub && vsub->cs.is_paging);
-	net = vsub->vlr->user_ctx;
-
-	/*
-	 * Stop paging on all other BTS. E.g. if this is
-	 * the first timeout on a BTS then the others will
-	 * timeout soon as well. Let's just stop everything
-	 * and forget we wanted to page.
-	 */
 
-	bsub = vlr_subscr_to_bsc_sub(conn->network->bsc_subscribers, vsub);
-	paging_request_stop(&net->bts_list, NULL, bsub, NULL, NULL);
-	bsc_subscr_put(bsub);
+	/* FIXME: implement stop paging in libmsc;
+	 * faking it for the unit tests to still work */
+	msc_fake_paging_request_stop(vsub);
 
 	/* Inform parts of the system we don't know */
 	sig_data.vsub	= vsub;
@@ -126,22 +79,21 @@ int subscr_paging_dispatch(unsigned int hooknum, unsigned int event,
 	return 0;
 }
 
-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)
 {
 	int rc;
 	struct subscr_request *request;
-	struct bsc_subscr *bsub;
-	struct gsm_network *net = vsub->vlr->user_ctx;
 
 	/* Start paging.. we know it is async so we can do it before */
 	if (!vsub->cs.is_paging) {
 		LOGP(DMM, LOGL_DEBUG, "Subscriber %s not paged yet.\n",
 		     vlr_subscr_name(vsub));
-		bsub = vlr_subscr_to_bsc_sub(net->bsc_subscribers, vsub);
-		rc = paging_request(net, bsub, channel_type, NULL, NULL);
-		bsc_subscr_put(bsub);
+
+		/* FIXME: implement paging in libmsc;
+		 * faking it for the unit tests to still work */
+		rc = msc_fake_paging_request(vsub);
+
 		if (rc <= 0) {
 			LOGP(DMM, LOGL_ERROR, "Subscriber %s paging failed: %d\n",
 			     vlr_subscr_name(vsub), rc);