281 lines
13 KiB
C
281 lines
13 KiB
C
/* The RAN (Radio Access Network) side of an A- or Iu-connection, which is closely tied to an SCCP connection.
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* (as opposed to the NAS side.)
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*
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* The SCCP connection is located with the MSC-I role, while the MSC-A responsible for subscriber management may be at a
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* remote MSC behind an E-interface connection. In that case we need to forward the L2 messages over the E-interface and
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* the BSSAP or RANAP messages get decoded and interpreted at MSC-A.
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*
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* The life cycle of a DTAP message from RAN to MSC-A -- starting from the bottom left:
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*
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* ------------------>[ 3GPP TS 24.008 ]------------------->|
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* ^ (Request) (Response) |
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* | v
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* msc_a_up_l3() msc_a_tx_dtap_to_i(dtap_msgb)
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* ^ |
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* | v
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* msc_a_nas_decode_cb(struct nas_dec_msg) msc_a_nas_enc(struct nas_enc_msg)
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* ^ ^ . |
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* | -Decode NAS- | . NAS v
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* | | . ran_infra[type]->nas_encode(struct nas_enc_msg)
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* nas_a_decode_l2() nas_iu_decode_l2() . | |
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* ^ ^ . v v
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* | | . nas_a_encode() nas_iu_encode()
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* ran_infra[type]->nas_dec_l2() | |
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* ^ | -Encode BSSAP/RANAP- |
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* | v v
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* msc_a_nas_dec() msub_tx_an_apdu(from MSC_ROLE_A to MSC_ROLE_I)
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* ^ |
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* | MSC-A v
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* . msc_a FSM . . . . . . . . . . . . . . . . msc_a FSM . . . . . . . . . .
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* ^ |
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* | MSC_A_EV_FROM_I_PROCESS_ACCESS_SIGNALLING_REQUEST v
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* | data = an_apdu [possibly
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* | via GSUP
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* [possibly from remote MSC-A]
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* via GSUP |
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* to remote MSC-A] | MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST
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* ^ | data = an_apdu
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* | v
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* . msc_i FSM . . . . . . . . . . . . . . . . msc_i FSM . . . . . . . . . .
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* ^ MSC-I |
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* | MSC_EV_FROM_RAN_UP_L2 V
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* | data = an_apdu msc_i_down_l2(an_apdu->msg)
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* | |
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* ran_peer FSM V
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* ^ ran_conn_down_l2_co();
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* | RAN_PEER_EV_MSG_UP_CO |
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* | data = struct ran_peer_ev_ctx | RAN_PEER_EV_MSG_DOWN_CO
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* | | data = struct ran_peer_ev_ctx
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* ran_peer_up_l2() V
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* (ran_infa->sccp_ran_ops.up_l2) ran_peer FSM
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* ^ ^ |
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* | | v
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* sccp_ran_sap_up() sccp_ran_down_l2_co(conn_id, msg)
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* ^ ^ | |
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* | | |SCCP|
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* |SCCP| v v
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* | | <------------------------------------------------------
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* BSC RNC
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* | |
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* BTS NodeB
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* | |
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* MS UE
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*
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* sccp_ran:
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* - handles receiving of SCCP primitives from the SCCP layer.
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* - extracts L2 msg
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* - passes on L2 msg and conn_id by calling sccp_ran_ops.up_l2 == ran_peer_up_l2().
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*
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* On Connection-Oriented *Initial* message
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* ========================================
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*
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* ran_peer_up_l2()
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* - notices an unknown, new osmo_rat_type:conn_id and
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* - first creates an "empty" msub with new local MSC-I and MSC-A roles;
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* in this case always a *local* MSC-A (never remote on Initial messages).
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* - Passes the L2 msgb containing the BSSAP or RANAP as AN-APDU
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* in MSC_A_EV_FROM_I_COMPLETE_LAYER_3 to the MSC-A role FSM instance.
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*
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* MSC-A:
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* - Receives MSC_A_EV_FROM_I_COMPLETE_LAYER_3 AN-APDU, notices an_proto indicating BSSAP or RANAP.
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* - Passes L2 message to ran_infra[]->nas_dec_l2(), which decodes the BSSAP or RANAP.
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* - contained information is passed to msc_a_nas_decode_cb().
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* - which msc_a starts Complete-L3 and VLR procedures,
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* - associates msub with a vlr_subscr,
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* - sends DTAP requests back down by calling msc_a_tx_dtap_to_i() (possibly other more specialized tx functions)
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* - according to ran_infra[]->nas_encode(), the nas_enc_msg gets encoded as BSSAP or RANAP.
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* - passes as AN-APDU to MSC-I in MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST signal.
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*
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* MSC-I, receiving AN-APDU from local MSC-A:
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* - feeds L2 msgb to the ran_peer FSM as RAN_PEER_EV_MSG_DOWN_CO, passing the SCCP conn_id.
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*
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* sccp_ran_down_l2_co()
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* - wraps in SCCP prim,
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* - sends down.
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*
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*
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* On (non-Initial) Connection-Oriented DTAP
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* =========================================
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*
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* ran_peer_up_l2()
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* - notices an already known conn_id by looking up a matching osmo_rat_type:ran_conn.
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* - ran_conn already associated with an MSC-I role.
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* - Now forwards AN-APDU like above, only using MSC_A_EV_FROM_I_PROCESS_ACCESS_SIGNALLING_REQUEST.
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*
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*
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* MSC-A and MSC-I roles on separate MSC instances
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* ===============================================
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*
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* After inter-MSC handover, the MSC-I and MSC-A roles can be on separate MSC instances, typically physically distant /
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* possibly belonging to a different operator. This will never see Complete-L3.
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* Assuming that both instances are osmo-msc, then:
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*
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* At MSC-B:
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* initially, via GSUP:
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* - receives Handover Request from remote MSC-A,
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* - creates msub with local MSC-T role,
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* - sets up the ran_conn with a new SCCP conn_id, and waits for the MS/UE to show up.
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* - (fast-forward to successful Handover)
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* - MSC-T role becomes MSC-I for the remote MSC-A.
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*
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* Then for DTAP from the MS:
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*
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* sccp_ran:
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* - receives SCCP,
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* - extracts L2 and passes on to ran_peer_up_l2().
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*
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* ran_peer_up_l2()
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* - notices an already known conn_id by looking up a matching ran_conn.
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* - ran_conn already associated with an MSC-I role and an msub.
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* - forwards AN-APDU in MSC_A_EV_FROM_I_PROCESS_ACCESS_SIGNALLING_REQUEST to the MSC-A role.
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*
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* At MSC-B, the "MSC-A role" is a *remote* implementation,
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* meaning there is an msc_a_remote FSM instance in MSC-B's msub:
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*
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* MSC-A-Remote:
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* - msc_a_remote receives MSC_A_EV_FROM_I_PROCESS_ACCESS_SIGNALLING_REQUEST,
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* - wraps AN-APDU in GSUP message,
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* - sends to remote MSC-A.
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*
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* At MSC-A:
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* Here, msub has a *remote* MSC-I role,
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* meaning it is an msc_i_remote FSM instance:
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*
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* MSC-I-Remote:
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* - msc_i_remote receives and decodes GSUP message,
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* - passes AN-APDU to MSC-A FSM instance via MSC_A_EV_FROM_I_PROCESS_ACCESS_SIGNALLING_REQUEST.
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*
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* MSC-A role:
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* - Receives MSC_A_EV_FROM_I_PROCESS_ACCESS_SIGNALLING_REQUEST, notices an_proto indicating BSSAP or RANAP.
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* - Passes L2 message to ran_infra[]->nas_dec_l2(), which decodes the BSSAP or RANAP.
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* - contained information is passed to msc_a_nas_decode_cb().
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* - sends DTAP requests back down by calling msc_a_tx_dtap_to_i() (possibly other more specialized tx functions)
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* - according to ran_infra[]->nas_encode(), the nas_enc_msg gets encoded as BSSAP or RANAP.
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* - passes as AN-APDU to MSC-I in MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST signal.
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*
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* MSC-I-Remote:
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* - msc_i_remote wraps AN-APDU in GSUP message,
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* - sends to MSC-B
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*
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* At MSC-B:
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* MSC-A-Remote:
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* - msc_a_remote receives GSUP message,
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* - passes AN-APDU to msc_i in MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST.
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*
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* MSC-I:
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* - BSSAP or RANAP is indicated both by the AN-APDU an_proto, as well as the ran_conn state for that subscriber.
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* - feeds L2 msgb to the ran_peer FSM as RAN_PEER_EV_MSG_DOWN_CO, passing the SCCP conn_id.
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*
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* sccp_ran_down_l2_co()
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* - wraps in SCCP prim,
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* - sends down.
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*
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*/
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#pragma once
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#include <stdint.h>
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#include <osmocom/core/tdef.h>
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#include <osmocom/gsm/gsm_utils.h>
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#include <osmocom/gsm/gsm0808_utils.h>
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#include <osmocom/sigtran/sccp_sap.h>
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#include <osmocom/msc/paging.h>
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struct msgb;
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struct ran_infra;
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struct sccp_ran_inst;
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#define LOG_SCCP_RAN_CO(sri, peer_addr, conn_id, level, fmt, args...) \
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LOGP((sri) && (sri)->ran? (sri)->ran->log_subsys : DMSC, level, "(%s-%u%s%s) " fmt, \
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osmo_rat_type_name((sri) && (sri)->ran? (sri)->ran->type : -1), conn_id, \
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peer_addr ? " from " : "", \
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peer_addr ? osmo_sccp_inst_addr_name((sri)->sccp, peer_addr) : "", \
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## args)
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#define LOG_SCCP_RAN_CL_CAT(sri, peer_addr, subsys, level, fmt, args...) \
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LOGP(subsys, level, "(%s%s%s) " fmt, \
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osmo_rat_type_name((sri) && (sri)->ran? (sri)->ran->type : -1), \
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peer_addr ? " from " : "", \
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peer_addr ? osmo_sccp_inst_addr_name((sri)->sccp, peer_addr) : "", \
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## args)
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#define LOG_SCCP_RAN_CL(sri, peer_addr, level, fmt, args...) \
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LOG_SCCP_RAN_CL_CAT(sri, peer_addr, (sri) && (sri)->ran? (sri)->ran->log_subsys : DMSC, level, fmt, ##args)
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#define LOG_SCCP_RAN_CAT(sri, subsys, level, fmt, args...) \
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LOG_SCCP_RAN_CL_CAT(sri, NULL, subsys, level, fmt, ##args)
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#define LOG_SCCP_RAN(sri, level, fmt, args...) \
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LOG_SCCP_RAN_CL(sri, NULL, level, fmt, ##args)
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extern struct osmo_tdef g_sccp_tdefs[];
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enum reset_msg_type {
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SCCP_RAN_MSG_NON_RESET = 0,
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SCCP_RAN_MSG_RESET,
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SCCP_RAN_MSG_RESET_ACK,
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};
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struct sccp_ran_ops {
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/* Implemented to receive L2 messages (e.g. BSSAP or RANAP passed to ran_peer).
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* - ConnectionLess messages: co = false, calling_addr != NULL, conn_id == 0;
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* - ConnectionOriented Initial messages: co = true, calling_addr != NULL;
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* - ConnectionOriented non-Initial messages: co = true, calling_addr == NULL;
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*/
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int (* up_l2 )(struct sccp_ran_inst *sri, const struct osmo_sccp_addr *calling_addr, bool co, uint32_t conn_id,
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struct msgb *l2);
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/* Implemented to finally remove a connection state. Last event in a connection-oriented exchange. If the
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* N-DISCONNECT contained l2 data, it was dispatched via up_l2() before this is called. */
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void (* disconnect )(struct sccp_ran_inst *sri, uint32_t conn_id);
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/* Return whether the given l2_cl message is a RESET, RESET ACKNOWLEDGE, or RESET-unrelated message.
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* This callback is stored in struct sccp_ran_inst to provide RESET handling to the caller (ran_peer),
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* it is not used in sccp_ran.c. */
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enum reset_msg_type (* is_reset_msg )(const struct sccp_ran_inst *sri, const struct msgb *l2_cl);
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/* Return a RESET or RESET ACK message for this RAN type.
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* This callback is stored in struct sccp_ran_inst to provide RESET handling to the caller (ran_peer),
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* it is not used in sccp_ran.c. */
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struct msgb* (* make_reset_msg )(const struct sccp_ran_inst *sri, enum reset_msg_type);
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/* Return a PAGING message towards the given Cell Identifier, to page for the given TMSI or IMSI.
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* Page for TMSI if TMSI != GSM_RESERVED_TMSI, otherwise page for IMSI. */
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struct msgb* (* make_paging_msg )(const struct sccp_ran_inst *sri, const struct gsm0808_cell_id *page_cell_id,
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const char *imsi, uint32_t tmsi, enum paging_cause cause);
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/* Return a human printable name for the msgb */
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const char* (* msg_name )(const struct sccp_ran_inst *sri, const struct msgb *l2);
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};
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struct sccp_ran_inst {
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struct ran_infra *ran;
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struct osmo_sccp_instance *sccp;
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struct osmo_sccp_user *scu;
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struct osmo_sccp_addr local_sccp_addr;
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struct llist_head ran_peers;
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struct llist_head ran_conns;
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void *user_data;
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/* Compatibility with legacy osmo-hnbgw that was unable to properly handle RESET messages. Set to 'false' to
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* require proper RESET procedures, set to 'true' to implicitly put a ran_peer in RAN_PEER_ST_READY upon the
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* first CO message. Default is false = be strict. */
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bool ignore_missing_reset;
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};
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struct sccp_ran_inst *sccp_ran_init(void *talloc_ctx, struct osmo_sccp_instance *sccp, enum osmo_sccp_ssn ssn,
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const char *sccp_user_name, struct ran_infra *ran, void *user_data);
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int sccp_ran_down_l2_co_initial(struct sccp_ran_inst *sri,
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const struct osmo_sccp_addr *called_addr,
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uint32_t conn_id, struct msgb *l2);
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int sccp_ran_down_l2_co(struct sccp_ran_inst *sri, uint32_t conn_id, struct msgb *l2);
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int sccp_ran_down_l2_cl(struct sccp_ran_inst *sri, const struct osmo_sccp_addr *called_addr, struct msgb *l2);
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int sccp_ran_disconnect(struct sccp_ran_inst *ran, uint32_t conn_id, uint32_t cause);
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