#pragma once #include #include #include #include #include #include /* 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; };