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, 25 insertions, 5 deletions

diff --git a/include/openbsc/gsm_data.h b/include/openbsc/gsm_data.h
index fa2fed778..17b3d7172 100644
--- a/include/openbsc/gsm_data.h
+++ b/include/openbsc/gsm_data.h
@@ -26,6 +26,7 @@ struct gsm_subscriber_group;
 struct bsc_subscr;
 struct vlr_instance;
 struct vlr_subscr;
+struct ue_conn_ctx;
 
 #define OBSC_LINKID_CB(__msgb)	(__msgb)->cb[3]
 
@@ -117,6 +118,12 @@ struct gsm_classmark {
 	uint8_t classmark3[14]; /* if cm3 gets extended by spec, it will be truncated */
 };
 
+enum integrity_protection_state {
+	INTEGRITY_PROTECTION_NONE	= 0,
+	INTEGRITY_PROTECTION_IK		= 1,
+	INTEGRITY_PROTECTION_IK_CK	= 2,
+};
+
 /* active radio connection of a mobile subscriber */
 struct gsm_subscriber_connection {
 	/* global linked list of subscriber_connections */
@@ -176,6 +183,15 @@ struct gsm_subscriber_connection {
 	enum ran_type via_ran;
 
 	struct gsm_classmark classmark;
+
+	uint16_t lac;
+	struct gsm_encr encr;
+
+	/* which Iu-CS connection, if any. */
+	struct {
+		struct ue_conn_ctx *ue_ctx;
+		int integrity_protection;
+	} iu;
 };
 
 
@@ -311,6 +327,12 @@ struct gsm_tz {
 };
 
 struct gsm_network {
+	/* TODO MSCSPLIT the gsm_network struct is basically a kitchen sink for
+	 * global settings and variables, "madly" mixing BSC and MSC stuff. Split
+	 * this in e.g. struct osmo_bsc and struct osmo_msc, with the things
+	 * these have in common, like country and network code, put in yet
+	 * separate structs and placed as members in osmo_bsc and osmo_msc. */
+
 	/* global parameters */
 	uint16_t country_code;
 	uint16_t network_code;
@@ -416,6 +438,9 @@ struct gsm_network {
 	uint16_t gsup_server_port;
 
 	struct vlr_instance *vlr;
+
+	/* Periodic location update default value */
+	uint8_t t3212;
 };
 
 struct osmo_esme;
@@ -471,10 +496,6 @@ extern void talloc_ctx_init(void *ctx_root);
 
 int gsm_set_bts_type(struct gsm_bts *bts, enum gsm_bts_type type);
 
-/* Get reference to a neighbor cell on a given BCCH ARFCN */
-struct gsm_bts *gsm_bts_neighbor(const struct gsm_bts *bts,
-				 uint16_t arfcn, uint8_t bsic);
-
 enum gsm_bts_type parse_btstype(const char *arg);
 const char *btstype2str(enum gsm_bts_type type);
 struct gsm_bts *gsm_bts_by_lac(struct gsm_network *net, unsigned int lac,
@@ -557,7 +578,6 @@ int bts_gprs_mode_is_compat(struct gsm_bts *bts, enum bts_gprs_mode mode);
 
 int gsm48_ra_id_by_bts(uint8_t *buf, struct gsm_bts *bts);
 void gprs_ra_id_by_bts(struct gprs_ra_id *raid, struct gsm_bts *bts);
-struct gsm_meas_rep *lchan_next_meas_rep(struct gsm_lchan *lchan);
 
 int gsm_btsmodel_set_feature(struct gsm_bts_model *model, enum gsm_bts_features feat);
 int gsm_bts_model_register(struct gsm_bts_model *model);