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osmo-msc/include/osmocom/msc/msc_roles.h

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#pragma once
#include <osmocom/core/fsm.h>
#include <osmocom/core/utils.h>
#include <osmocom/gsm/gsm_utils.h>
#include <osmocom/gsm/gsup.h>
#include <osmocom/msc/msc_common.h>
#include <osmocom/msc/ran_infra.h>
/* Each subscriber connection is managed by different roles, as described in 3GPP TS 49.008 '4.3 Roles of MSC-A, MSC-I
* and MSC-T':
*
* MSC-A: subscriber management and control of all transactions (CC, SMS, USSD,...)
* MSC-I: "internal": the actual BSSMAP link to the BSS, or RANAP link to the RNC.
* MSC-T: "transitory": a new pending RAN link to a BSS or RNC, while handover is in progress.
* MSC-T becomes the new MSC-I once handover ends successfully.
*
* Without inter-MSC handover involved, all of the roles are managed by a single MSC instance. During inter-MSC
* handover negotiation, an MSC-T is set up at a remote MSC while MSC-A remains in the original MSC, and when handover
* concludes successfully, the remote MSC-T becomes the new remote MSC-I, replacing the local MSC-I role.
*
* Furthermore, the 3GPP specs use the following terms for naming MSC locations: MSC-A, MSC-B and MSC-B', as well as BSS
* or BSS-A, BSS-B and BSS-B':
*
* MSC-A: the first MSC the subscriber connected to.
* MSC-B: a remote MSC (if any).
* MSC-B': another remote MSC (if any, during Subsequent Handover).
*
* The full role assignments are spelled out in 3GPP TS 29.002.
*
* In Osmocom, the MAP protocol spoken between the MSCs is modeled using GSUP instead.
*
* Here are some diagrams of the lifecycle of a single subscriber's MSC-A,-I,-T roles at the locations MSC-A, MSC-B and
* MSC-B'.
*
* Initially:
*
* [MSC-A]
* BSS <-> MSC-I
*
* Then during inter-MSC handover negotiation:
*
* [MSC-A] <-MAP-> MSC-B
* BSS <-> MSC-I MSC-T <-> new BSS
*
* and when successful:
*
* [MSC-A] <-MAP-> MSC-B
* MSC-I <-> BSS
*
* Additional subsequent handover:
*
* [MSC-A] <-MAP-> MSC-B
* ^ MSC-I <-> BSS
* |
* +-------MAP-> MSC-B'
* MSC-T <-> new BSS
*
* (Here, quote, MSC-A "shall act as the target BSS towards the MSC-I and as the MSC towards the MSC-T.")
* and when successful:
*
* [MSC-A]
* ^
* |
* +-------MAP-> MSC-B
* MSC-I <-> BSS
*
* Subsequent handover back to the original MSC:
*
* [MSC-A] <-MAP-> MSC-B
* new BSS <-> MSC-T MSC-I <-> BSS
*
* and then
* [MSC-A]
* BSS <-> MSC-I
*
*
* Inter-BSC Handover is just a special case of inter-MSC Handover, where the same MSC-A takes on both MSC-I and MSC-T
* roles:
*
* [MSC-A]
* BSS <-> MSC-I
* new BSS <-> MSC-T
*
* The mechanism to take on different roles is implemented by different FSM instances. Each FSM kind has one
* implementation that acts locally, and another implementation to forward to a remote MSC. For example, in this
* scenario:
*
* [MSC-A] <-MAP-> MSC-B
* MSC-I <-> BSS
*
* the implementation is
*
* [MSC-A-----------------] [MSC-B-----------------]
* msc_a <-> msc_i_REMOTE <---GSUP---> msc_a_REMOTE <-> msc_i <--BSSMAP--> [BSS]
*
* MSC-A has a locally acting msc_a FSM implementation. The msc_i FSM implementation at MSC-A receives signals from the
* msc_a FSM and "merely" sends the MAP instructions to MSC-B.
*
* At MSC-B, in turn, the msc_a FSM's "remote" implementation receives the MAP messages and dispatches according events
* to the MSC-B's local msc_i FSM instance, which is implemented to directly act towards the BSS.
*
* To implement single-MSC operation, we have the separate MSC roles' local implementations on the same MSC instance
* instead of forwarding.
*
*
* Use of MAP procedures on GSUP towards HLR:
*
* The MSC <-> VLR communication does still happen locally in the MSC-A only. In other words, there may be MAP message
* handling between the MSCs (in the form of GSUP), but no MAP to talk to our internal VLR.
*
* From the VLR to the HLR, though, we again use GSUP for subscriber related HLR operations such as LU requesting and
* retrieving auth tokens.
*
* To complete the picture, the MSC-A <--GSUP--> MSC-B forwarding happens over the same GSUP connection
* as the VLR <--GSUP--> HLR link:
*
* OsmoMSC
* MSC-A <----------E-interface--->+--GSUP--> [IPA routing] ----E--> MSC-B
* ^ ^ (in osmo-hlr) \
* | (internal API) / \--D--> HLR
* v /
* VLR <------------D-interface-/
*/
struct inter_msc_link;
struct ran_conn;
enum msc_role {
MSC_ROLE_A,
MSC_ROLE_I,
MSC_ROLE_T,
MSC_ROLES_COUNT
};
extern const struct value_string msc_role_names[];
static inline const char *msc_role_name(enum msc_role role)
{ return get_value_string(msc_role_names, role); }
enum msc_common_events {
/* Explicitly start with 0 (first real event will be -1 + 1 = 0). */
OFFSET_MSC_COMMON_EV = -1,
MSC_REMOTE_EV_RX_GSUP,
MSC_EV_CALL_LEG_RTP_LOCAL_ADDR_AVAILABLE,
MSC_EV_CALL_LEG_RTP_COMPLETE,
MSC_EV_CALL_LEG_TERM,
/* MNCC has told us to RTP_CREATE, but local RTP port has not yet been set up.
* The MSC role should respond by calling mncc_set_rtp_stream() */
MSC_MNCC_EV_NEED_LOCAL_RTP,
MSC_MNCC_EV_CALL_PROCEEDING,
MSC_MNCC_EV_CALL_COMPLETE,
MSC_MNCC_EV_CALL_ENDED,
LAST_MSC_COMMON_EV,
};
/* The events that the msc_a_local and msc_a_remote FSM implementations can receive,
* according to specifications. Not all of these are necessarily implemented. */
enum msc_a_events {
OFFSET_MSC_A_EV = LAST_MSC_COMMON_EV - 1,
/* Establishing Layer 3 happens only at MSC-A (all-local MSC). To distinguish from the inter-MSC DTAP
* forwarding, keep this as a separate event. */
MSC_A_EV_FROM_I_COMPLETE_LAYER_3,
/* In inter-MSC situations, DTAP is forwarded transparently in AN-APDU IEs (formerly named
* BSS-APDU); see
* - 3GPP TS 49.008 4.2 'Transfer of DTAP and BSSMAP layer 3 messages on the * E-interface',
* - 3GPP TS 29.010 4.5.4 'BSSAP Messages transfer on E-Interface',
* - 3GPP TS 29.002 8.4.3 MAP_PROCESS_ACCESS_SIGNALLING service, 8.4.4 MAP_FORWARD_ACCESS_SIGNALLING service.
*
* MSC-B ---DTAP--> MSC-A MAP PROCESS ACCESS SIGNALLING request
* MSC-B <--DTAP--- MSC-A MAP FORWARD ACCESS SIGNALLING request
* (where neither will receive a "response")
*
* See 3GPP TS 49.008 6. 'BSSMAP messages transferred on the E-interface'.
* Depending on the RAN, the AN-APDU contains a BSSMAP or a RANAP encoded message.
* MSC-I to MSC-A:
* - Managing attach to one BSC+MSC:
* - CLASSMARK_UPDATE,
* - CIPHER_MODE_COMPLETE,
* - CIPHER_MODE_REJECT,
* - ASSIGNMENT_COMPLETE,
* - ASSIGNMENT_FAILURE,
* - CLEAR_REQUEST,
* - Handover related messages:
* - HANDOVER_REQUEST,
* - HANDOVER_PERFORMED,
* - HANDOVER_FAILURE,
* - Messages we don't need/support yet:
* - CHANNEL_MODIFY_REQUEST (MSC assisted codec changing handover),
* - SAPI_N_REJECT,
* - CONFUSION,
* - BSS_INVOKE_TRACE,
* - QUEUING_INDICATION,
* - PERFORM_LOCATION_REQUEST (*not* related to a Location Updating, but about passing the MS's geological
* position)
* - PERFORM_LOCATION_ABORT,
* - PERFORM_LOCATION_RESPONSE,
* - CONNECTION_ORIENTED_INFORMATION is listed in 48.008 3.2.1.70 as "(void)",
*/
MSC_A_EV_FROM_I_PROCESS_ACCESS_SIGNALLING_REQUEST,
MSC_A_EV_FROM_I_PREPARE_SUBSEQUENT_HANDOVER_REQUEST,
/* See 3GPP TS 29.002 8.4.2 MAP_SEND_END_SIGNAL service. */
MSC_A_EV_FROM_I_SEND_END_SIGNAL_REQUEST,
/* These BSSMAP messages are relevant for MSC-T -> MSC-A, i.e. from the transitory during inter-MSC handover:
*
* - Handover related messages:
* - HANDOVER_REQUEST_ACKNOWLEDGE,
* - HANDOVER_COMPLETE,
* - HANDOVER_FAILURE,
* - HANDOVER_DETECT,
* - CLEAR_REQUEST,
* - Messages we don't need/support yet:
* - CONFUSION,
* - QUEUING_INDICATION,
*/
MSC_A_EV_FROM_T_PROCESS_ACCESS_SIGNALLING_REQUEST,
/* Essentially the HO Request Ack. 3GPP TS 29.002 8.4.1 MAP_PREPARE_HANDOVER service. */
MSC_A_EV_FROM_T_PREPARE_HANDOVER_RESPONSE,
MSC_A_EV_FROM_T_PREPARE_HANDOVER_FAILURE,
/* Done establishing the radio link to the MS, for Handover.
* See 3GPP TS 29.002 8.4.2 MAP_SEND_END_SIGNAL service.
* Not to be confused with the MSC_I_EV_FROM_A_SEND_END_SIGNAL_RESPONSE that tells MSC-B to release. */
MSC_A_EV_FROM_T_SEND_END_SIGNAL_REQUEST,
/* gsm_04_08.c has successfully received a valid Complete Layer 3 message, i.e. Location Updating, CM Service
* Request, Paging Response or IMSI Detach. */
MSC_A_EV_COMPLETE_LAYER_3_OK,
/* Received a Classmark Update -- during GERAN ciphering, msc_a may have to wait for Classmark information to
* determine supported ciphers. */
MSC_A_EV_CLASSMARK_UPDATE,
/* LU or Process Access FSM have determined that the peer has verified its authenticity. */
MSC_A_EV_AUTHENTICATED,
/* A valid request is starting to be processed on the connection. Upon this event, msc_a moves from
* MSC_A_ST_AUTHENTICATED to MSC_A_ST_COMMUNICATING, and enters the only state without an expiry timeout. */
MSC_A_EV_TRANSACTION_ACCEPTED,
/* MSC originated close request, e.g. all done, failed authentication, ... */
MSC_A_EV_CN_CLOSE,
/* Subscriber originated close request */
MSC_A_EV_MO_CLOSE,
/* msc_a->use_count has reached a total of zero. */
MSC_A_EV_UNUSED,
MSC_A_EV_HANDOVER_REQUIRED,
MSC_A_EV_HANDOVER_END,
/* indicates nr of MSC_A events, keep this as last enum value */
LAST_MSC_A_EV
};
osmo_static_assert(LAST_MSC_A_EV <= 32, not_too_many_msc_a_events);
extern const struct value_string msc_a_fsm_event_names[];
enum msc_from_ran_events {
OFFSET_MSC_EV_FROM_RAN = LAST_MSC_COMMON_EV - 1,
MSC_EV_FROM_RAN_COMPLETE_LAYER_3,
/* A BSSMAP/RANAP message came in on the RAN conn. */
MSC_EV_FROM_RAN_UP_L2,
/* The RAN connection is gone, or busy going. */
MSC_EV_FROM_RAN_CONN_RELEASED,
LAST_MSC_EV_FROM_RAN
};
/* The events that the msc_i_local and msc_i_remote FSM implementations can receive.
* The MSC-I can also receive all msc_common_events and msc_from_ran_events. */
enum msc_i_events {
OFFSET_E_MSC_I = LAST_MSC_EV_FROM_RAN - 1,
/* BSSMAP/RANAP comes in from MSC-A to be sent out on the RAN conn.
* Depending on the RAN, the AN-APDU contains a BSSMAP or a RANAP encoded message.
* Relevant BSSMAP procedures, see 3GPP TS 49.008 6. 'BSSMAP messages transferred on the E-interface':
* - Managing attach to one BSC+MSC:
* - CLASSMARK_REQUEST,
* - CIPHER_MODE_COMMAND,
* - COMMON_ID,
* - ASSIGNMENT_REQUEST,
* - Handover related messages:
* - HANDOVER_REQUEST_ACKNOWLEDGE,
* - HANDOVER_FAILURE,
* - Messages we don't need/support yet:
* - CONFUSION,
* - MSC_INVOKE_TRACE,
* - QUEUING_INDICATION,
* - LSA_INFORMATION,
* - PERFORM_LOCATION_REQUEST, (*not* related to a Location Updating, but about passing the MS's geological position)
* - PERFORM_LOCATION_ABORT,
* - PERFORM_LOCATION_RESPONSE,
* - CONNECTION_ORIENTED_INFORMATION is listed in 48.008 3.2.1.70 as "(void)"
*/
MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST,
/* MSC-A tells us to release the RAN connection. */
MSC_I_EV_FROM_A_SEND_END_SIGNAL_RESPONSE,
MSC_I_EV_FROM_A_PREPARE_SUBSEQUENT_HANDOVER_RESULT,
MSC_I_EV_FROM_A_PREPARE_SUBSEQUENT_HANDOVER_ERROR,
LAST_MSC_I_EV
};
osmo_static_assert(LAST_MSC_I_EV <= 32, not_too_many_msc_i_events);
extern const struct value_string msc_i_fsm_event_names[];
/* The events that the msc_t_local and msc_t_remote FSM implementations can receive.
* The MSC-T can also receive all msc_common_events and msc_from_ran_events. */
enum msc_t_events {
/* sufficient would be to use LAST_MSC_EV_FROM_RAN as offset. But while we have enough numbers
* available, it is a good idea to keep MSC-I and MSC-T events separate, to catch errors of
* sending wrong event kinds. */
OFFSET_MSC_T_EV = LAST_MSC_I_EV - 1,
/* BSSMAP/RANAP comes in from MSC-A to be sent out on the RAN conn.
* Relevant BSSMAP procedures, see 3GPP TS 49.008 6. 'BSSMAP messages transferred on the E-interface':
* - Handover related messages:
* - HANDOVER_REQUEST,
* - CLASSMARK_UPDATE, (?)
* - Messages we don't need/support yet:
* - CONFUSION,
* - MSC_INVOKE_TRACE,
* - BSS_INVOKE_TRACE,
*/
MSC_T_EV_FROM_A_PREPARE_HANDOVER_REQUEST,
MSC_T_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST,
/* MSC originated close request, e.g. all done, failed handover, ... */
MSC_T_EV_CN_CLOSE,
/* Subscriber originated close request */
MSC_T_EV_MO_CLOSE,
MSC_T_EV_CLEAR_COMPLETE,
LAST_MSC_T_EV
};
osmo_static_assert(LAST_MSC_T_EV <= 32, not_too_many_msc_t_events);
extern const struct value_string msc_t_fsm_event_names[];
/* All MSC role FSM implementations share this at the start of their fi->priv struct.
* See struct msc_a, struct msc_i, struct msc_t in their individual headers. */
struct msc_role_common {
enum msc_role role;
struct osmo_fsm_inst *fi;
/* For a local implementation, this is NULL. Otherwise, this identifies how to reach the remote
* MSC that this "remote" implementation forwards messages to. */
struct e_link *remote_to;
struct msub *msub;
struct gsm_network *net;
struct ran_infra *ran;
};
/* AccessNetworkSignalInfo as in 3GPP TS 29.002. */
struct an_apdu {
/* accessNetworkProtocolId */
enum osmo_gsup_access_network_protocol an_proto;
/* signalInfo */
struct msgb *msg;
/* If this AN-APDU is sent between MSCs, additional information from the E-interface messaging, like the
* Handover Number, will placed/available here. Otherwise may be left NULL. */
const struct osmo_gsup_message *e_info;
};
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