【5G核心网】free5GC 注册请求流程源码分析

    本文分析 Free5GC Registration request procedure 注册请求流程

1. UE 发起注册请求

    NAS Message 结构体，包括安全头部，移动管理以及会话管理消息

// Message TODO：description
type Message struct {SecurityHeader*GmmMessage*GsmMessage
}

    根据 NAS N1 MM 消息定义

    注册请求设置移动管理类型为 MsgTypeRegistrationRequest，NAS 消息需包裹在 NGAP 消息中，包括的参数为： 

• ExtendedProtocolDiscriminator
• Security header type
• Spare half octet
• Message Type
• ngksi
• 5GS mobile identity 9.11.3.4
• 5GMM capability 9.11.3.1
• UE security capability 9.11.3.54
• NSSAI 9.11.3.37
• Uplink data status 9.11.3.57

registrationRequest.MobileIdentity5GS = mobileIdentity
registrationRequest.Capability5GMM = &nasType.Capability5GMM{Iei:   nasMessage.RegistrationRequestCapability5GMMType,Len:   1,Octet: [13]uint8{0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
}
registrationRequest.UESecurityCapability = ueSecurityCapability
registrationRequest.RequestedNSSAI = requestedNSSAI
registrationRequest.UplinkDataStatus = uplinkDataStatus

    设置的 NGAP 消息 Present 为 NGAPPDUPresentInitiatingMessage，初始消息 ProcedureCode 为 ProcedureCodeInitialUEMessage，包括一些 IE 信息：

    -  RAN UE NGAP ID，

    -  NAS-PDU，

    -  User Location Information，

    -  RRC Establishment Cause，

    -  5G-S-TSMI (optional)，

    -  AMF Set ID (optional)，

    -  UE Context Request (optional)，

    -  Allowed NSSAI (optional)

 2 AMF 处理注册请求

    根据 NGAPPDUPresentInitiatingMessage 和 ProcedureCodeInitialUEMessage 定位到 HandleInitialUEMessage 函数

    请求的 IE 包括：

• id-RAN- UE-NGAP-ID
• id-NAS-PDU
• id-UserLocationInformation
• id-RRCEStablishmentCause
• id-UEContextRequest

func HandleInitialUEMessage(ran *context.AmfRan, message *ngapType.NGAPPDU) {amfSelf := context.AMF_Self()var rANUENGAPID *ngapType.RANUENGAPIDvar nASPDU *ngapType.NASPDUvar userLocationInformation *ngapType.UserLocationInformationvar rRCEstablishmentCause *ngapType.RRCEstablishmentCausevar fiveGSTMSI *ngapType.FiveGSTMSI// var aMFSetID *ngapType.AMFSetIDvar uEContextRequest *ngapType.UEContextRequest// var allowedNSSAI *ngapType.AllowedNSSAI

     <5G-S-TMSI> := <AMF Set ID><AMF Pointer><5G-TMSI>

     GUAMI := <MCC><MNC><AMF Region ID><AMF Set ID><AMF Pointer>

     5G-GUTI := <GUAMI><5G-TMSI>

    2.1 场景对应无 UDSF 部署情况

     无 UDSF 部署情况： 如果 UE 的  5G-GUTI （全局唯一的临时 UE 标识）包含在注册请求，且从上次注册过程服务的 AMF 已更改，新的 AMF 向旧的 AMF 调用 Namf_Communication_UEContextTransfer 服务，包括完成注册服务 NAS 消息，可以是完整性保护，也可以是接入类型，来请求 UE 的 SUPI 和 UE 上下文。旧的 AMF 即使用 5G-GUTI 和完成性保护完成注册请求 NAS 消息，或者 SUPI，以及 UE 从新 AMF 验证的指示。旧 AMF 还将每个 NF消费者（UE）的事件订阅信息传给新 AMF。

if ranUe == nil {ranUe = ran.NewRanUe()ranUe.RanUeNgapId = rANUENGAPID.ValueNgaplog.Debugf("New RanUe [RanUeNgapID: %d]", ranUe.RanUeNgapId)if fiveGSTMSI != nil {Ngaplog.Debug("Receive 5G-S-TMSI")servedGuami := amfSelf.ServedGuamiList[0]// <5G-S-TMSI> := <AMF Set ID><AMF Pointer><5G-TMSI>// GUAMI := <MCC><MNC><AMF Region ID><AMF Set ID><AMF Pointer>// 5G-GUTI := <GUAMI><5G-TMSI>tmpReginID, _, _ := ngapConvert.AmfIdToNgap(servedGuami.AmfId)amfID := ngapConvert.AmfIdToModels(tmpReginID, fiveGSTMSI.AMFSetID.Value, fiveGSTMSI.AMFPointer.Value)tmsi := hex.EncodeToString(fiveGSTMSI.FiveGTMSI.Value)guti := servedGuami.PlmnId.Mcc + servedGuami.PlmnId.Mnc + amfID + tmsi// TODO: invoke Namf_Communication_UEContextTransfer if serving AMF has changed since last Registration Request procedure// Described in TS 23.502 4.2.2.2.2 step 4 (without UDSF deployment)

    进入核心函数 nas.HandleNAS  处理的类型为 ProcedureCodeInitialUEMessage

    HandleNAS

             -->  Dispatch  设置类型为 EVENT_GMM_MESSAGE，根据初始 ue 状态为 Deregistered

func Dispatch(ue *context.AmfUe, accessType models.AccessType, procedureCode int64, msg *nas.Message) error {return gmm.GmmFSM.SendEvent(ue.State[accessType], gmm.GmmMessageEvent, fsm.ArgsType{gmm.ArgAmfUe:         ue,gmm.ArgAccessType:    accessType,gmm.ArgNASMessage:    msg.GmmMessage,gmm.ArgProcedureCode: procedureCode,})
}

            根据 DeRegistered 函数中，事件类型为 EVENT_GMM_MESSAGE 和 gmm 类型为 MsgTypeRegistrationRequest 定位到函数HandleRegistrationRequest，如果成功状态由事务 AuthRestartEvent DeRegistered --> Authentication

    2.2 HandleRegistrationRequest 函数

    根据前提为 3GPP，根据 EVENT_GMM_MESSAGE 和 MsgTypeRegistrationRequest 定位到 HandleRegistrationRequest 函数

func HandleRegistrationRequest(ue *context.AmfUe, anType models.AccessType, procedureCode int64, registrationRequest *nasMessage.RegistrationRequest) error {logger.GmmLog.Info("[AMF] Handle Registration Request")util.ClearT3513(ue)util.ClearT3565(ue)var guamiFromUeGuti models.GuamiamfSelf := context.AMF_Self()

    根据 nasType.MobileIdentity5GS 中第一个字节类型为 0x01 类型为 suci

    根据  suci(imsi) = "suci-0-${mcc}-${mnc}-${routingIndentifier}-${protectionScheme}-${homeNetworkPublicKeyIdentifier}-${schemeOutput}"

          suci   -0   -460-03     -0   -0  -0    -0000007487 

    如果 NAS 消息为 RegistrationType5GSInitialRegistration 则传输设置为 “INIT_REG”

    根觉 NAS 消息类型为 MobileIdentity5GSTypeSuci

mobileIdentity5GSContents := registrationRequest.MobileIdentity5GS.GetMobileIdentity5GSContents()
ue.IdentityTypeUsedForRegistration = nasConvert.GetTypeOfIdentity(mobileIdentity5GSContents[0])
switch ue.IdentityTypeUsedForRegistration { // get type of identity
case nasMessage.MobileIdentity5GSTypeNoIdentity:logger.GmmLog.Debugf("No Identity")
case nasMessage.MobileIdentity5GSTypeSuci:var plmnId stringue.Suci, plmnId = nasConvert.SuciToString(mobileIdentity5GSContents)ue.PlmnId = util.PlmnIdStringToModels(plmnId)logger.GmmLog.Debugf("SUCI: %s", ue.Suci)ue.IsCleartext = true

   如果 ue 不再 amf 服务小区，则发送注册 reject  

// Check TAI
if !context.InTaiList(ue.Tai, amfSelf.SupportTaiLists) {gmm_message.SendRegistrationReject(ue.RanUe[anType], nasMessage.Cause5GMMTrackingAreaNotAllowed, "")return fmt.Errorf("Registration Reject[Tracking area not allowed]")
}

     2.2.1 如果更换 AMF的情况 

     新的 AMF 向旧的 AMF 调用 Namf_Communication_UEContextTransfer，包括完成的注册请求 NAS 消息，来请求 UE 的 SUPI 和 UE 上下文（对应步骤 4）

// TODO (TS 23.502 4.2.2.2 step 4): if UE's 5g-GUTI is included & serving AMF has changed since last registration procedure,
// new AMF may invoke Namf_Communication_UEContextTransfer to old AMF, including the complete registration request nas
// msg, to request UE's SUPI & UE Context
if ue.ServingAmfChanged {

    向旧的 AMF 发起请求 Namf_Communication_UEContextTransfer /ue-contexts/{ueContextId}/transfer，旧的 AMF 处理函数为 UEContextTransfer，将事件设置为 EventUEContextTransfer，发送到待处理的 channel 中，定位到函数 HTTPUEContextTransfer，流转到函数 HandleUEContextTransferRequest

     2.2.2 HandleUEContextTransferRequest 函数

     旧的 AMF 根据消息中的 imsi / imei / 5g-guti，查找是否存在该 UE，如果存在则根据传输原因 “INIT_REG” 或者 “MOBI_REG”，如果是 “INIT_REG” 则发送 UE 上下文，包括 SUPI；如果是 “MOBI_REG”，看代码也是一样的 UE 上下文

state	event	From	To
Deregistered	GmmMessageEvent	Deregistered	Deregistered
Deregistered -> Authentication	StartAuthEvent	Deregistered	Authentication

func (fsm *FSM) SendEvent(state *State, event EventType, args ArgsType) error {key := eventKey{From:  state.Current(),Event: event,}if trans, ok := fsm.transitions[key]; ok {// exit callbackif trans.From != trans.To {fsm.callbacks[trans.From](state, ExitEvent, args)}// event callbackfsm.callbacks[trans.From](state, event, args)// entry callbackif trans.From != trans.To {state.Set(trans.To)fsm.callbacks[trans.To](state, EntryEvent, args)}return nil} else {return fmt.Errorf("Unknown transition[From: %s, Event: %s]", state.Current(), event)}
}

    根据 SendEvent 函数中，状态转移，由  Deregistered -> Authentication，From -> To（Deregistered, Authenticaion），进入 Authentication 

 

3 Authentication 函数

func Authentication(state *fsm.State, event fsm.EventType, args fsm.ArgsType) {logger.GmmLog.Debugln("UE in GMM State [Authentication]")switch event {case fsm.EntryEvent:fallthroughcase AuthRestartEvent:amfUe := args[ArgAmfUe].(*context.AmfUe)accessType := args[ArgAccessType].(models.AccessType)pass, err := AuthenticationProcedure(amfUe, accessType)if err != nil {logger.GmmLog.Errorln(err)}if pass {if err := GmmFSM.SendEvent(state, AuthSuccessEvent, fsm.ArgsType{ArgAmfUe:      amfUe,ArgAccessType: accessType,}); err != nil {logger.GmmLog.Errorln(err)}}

 

   3.1 AuthenticationProcedure 函数

     如果发起的请求中未包含 SUCI/SUPI，则发起 TS 23.502 步骤6

func AuthenticationProcedure(ue *context.AmfUe, accessType models.AccessType) (bool, error) {logger.GmmLog.Info("Authentication procedure")// Check whether UE has SUCI and SUPIif IdentityVerification(ue) {logger.GmmLog.Debugln("UE has SUCI / SUPI")if ue.SecurityContextIsValid() {logger.GmmLog.Debugln("UE has a valid security context - skip the authentication procedure")return true, nil}} else {// Request UE's SUCI by sending identity requestgmm_message.SendIdentityRequest(ue.RanUe[accessType], nasMessage.MobileIdentity5GSTypeSuci)return false, nil}

    向 NRF 发送服务发现 AUSF 功能，向 AUSF 发送认证 Nausf_UEAuthentication，包括 servingNetworkName，UE 的 SUCI，向 AUSF 发送 POST 请求 /ue-authentications

    AMF 向 AUSF 发起认证请求

      AUSF 处理的请求：

Location:[https://ausf:29509/nausf-auth/v1/ue-authentications/suci-0-208-93-0-0-0-00007487]] 201 {5G_AKA {391894b3403ae1a7e712067772fdd9a0 eff8a686c72075259d2ab857e788cb11 cc62613e215e8000a8125d9fbd1b18c9} map[link:{https://ausf:29509/nausf-auth/v1/ue-authentications/suci-0-208-93-0-0-0-00007487/5g-aka-confirmation}] 5G:mnc093.mcc208.3gppnetwork.org}

   3.2 SendAuthenticationRequest 函数

     BuildAuthenticationRequest 函数创建到 UE 的 gmm 消息，BuildDownlinkNasTransport 函数构造 NGAP 消息

     STCP 协议连接发送到 RAN

     T3560 启动定时器，超过六妙将重发 SendDownlinkNasTransport，超过4次将关闭定时器

    3.3 UE 向 AMF 应答 Authentication 

     NAS 消息类型为 MsgTypeAuthenticationResponse，发送上行数据 NGAP 包裹 NSA 响应消息，类型为 NGAPPDUPresentInitiatingMessage，InitiatingMessage 类型为 ProcedureCodeUplinkNASTransport 和 InitiatingMessagePresentUplinkNASTransport，包括的 IE 有：

    -  AMF UE NGAP ID，

    -  RAN UE NGAP ID，

    -  NAS-PDU，

    -  User Location Information

 

    3.4 AMF 处理 Authentication Response 消息

     根据 NGAPPDUPresentInitiatingMessage 和 ProcedureCodeUplinkNASTransport 定位到 HandleUplinkNasTransport 函数

func HandleUplinkNasTransport(ran *context.AmfRan, message *ngapType.NGAPPDU) {var aMFUENGAPID *ngapType.AMFUENGAPIDvar rANUENGAPID *ngapType.RANUENGAPIDvar nASPDU *ngapType.NASPDUvar userLocationInformation *ngapType.UserLocationInformationif ran == nil {logger.NgapLog.Error("ran is nil")return}

     核心处理函数 HandleNAS，根据 3GPP 事件，消息设置为 EVENT_GMM_MESSAGE，AUTHENTICATION 函数中定位到 MsgTypeAuthenticationResponse 函数

func HandleAuthenticationResponse(ue *context.AmfUe, anType models.AccessType, authenticationResponse *nasMessage.AuthenticationResponse) error {logger.GmmLog.Info("[AMF] Handle Authentication Response")util.ClearT3560(ue)

    SendAuth5gAkaConfirmRequest 由 AMF 向 AUSF 调用 Nausf_UEAuthentication，/ue-authentications/{authCtxId}/5g-aka-confirmation，由 AUSF 返回 AMF 数据

200 {AUTHENTICATION_SUCCESS imsi-2089300007487 ad15bdad357c72e4d11d9dfb67d84a5a308e594740bef031e4fdf64cecdeeb01}}
[GIN] 2020/07/14 - 07:53:29 | 200 |   46.750921ms |    10.200.200.3 | PUT      /nausf-auth/v1/ue-authentications/suci-0-XX-XX-0-0-0-00007487/5g-aka-confirmation

     根据返回的数据结果为 AUTHENTICATION_SUCCESS，则状态转移

state	event	From	To
Deregistered -> Authentication	StartAuthEvent	Deregistered	Authentication
Authentication	AuthSuccessEvent	Authentication	SecurityMode

switch response.AuthResult {
case models.AuthResult_SUCCESS:ue.UnauthenticatedSupi = falseue.Kseaf = response.Kseafue.Supi = response.Supiue.DerivateKamf()logger.GmmLog.Debugln("ue.DerivateKamf()", ue.Kamf)return GmmFSM.SendEvent(ue.State[accessType], AuthSuccessEvent, fsm.ArgsType{ArgAmfUe:      ue,ArgAccessType: accessType,ArgEAPSuccess: false,ArgEAPMessage: "",})

   3.5 SecurityMode 函数

func SecurityMode(state *fsm.State, event fsm.EventType, args fsm.ArgsType) {logger.GmmLog.Debugln("UE in GMM State[SecurityMode]")switch event {case fsm.EntryEvent:amfUe := args[ArgAmfUe].(*context.AmfUe)accessType := args[ArgAccessType].(models.AccessType)if amfUe.SecurityContextIsValid() {} else {eapSuccess := args[ArgEAPSuccess].(bool)eapMessage := args[ArgEAPMessage].(string)// Select enc/int algorithm based on ue security capability & amf's policy,amfSelf := context.AMF_Self()amfUe.SelectSecurityAlg(amfSelf.SecurityAlgorithm.IntegrityOrder, amfSelf.SecurityAlgorithm.CipheringOrder)// Generate KnasEnc, KnasIntamfUe.DerivateAlgKey()gmm_message.SendSecurityModeCommand(amfUe.RanUe[accessType], eapSuccess, eapMessage)}

        SendSecurityModeCommand 函数发送安全模式命令，NAS 消息中 MM 类型为 MsgTypeSecurityModeCommand，SendDownlinkNasTransport 函数建立 NGAP 消息包裹 NAS 消息，类型为 NGAPPDUPresentInitiatingMessage，ProcedureCodeDownlinkNASTransport，InitiatingMessagePresentDownlinkNASTransport 发送到 (R)AN 

   3.6 (R)AN 发送安全模式完成消息

     NAS 消息类型为 MsgTypeSecurityModeComplete，NGAP 消息类型为 NGAPPDUPresentInitiatingMessage，ProcedureCodeUplinkNASTransport，InitiatingMessagePresentUplinkNASTransport

   3.7 AMF 处理收到的 Security mode complete

      HandleSecurityModeComplete，最后到 SendEvent 函数将状态转移，事件 SecurityModeSuccessEvent

state	event	From	To
Deregistered -> Authentication	StartAuthEvent	Deregistered	Authentication
Authentication	AuthSuccessEvent	Authentication	SecurityMode
SecurityMode	SecurityModeSuccessEvent	SecurityMode	ContextSetup

func SecurityMode(state *fsm.State, event fsm.EventType, args fsm.ArgsType) {logger.GmmLog.Debugln("UE in GMM State[SecurityMode]")switch event {case GmmMessageEvent:amfUe := args[ArgAmfUe].(*context.AmfUe)procedureCode := args[ArgProcedureCode].(int64)gmmMessage := args[ArgNASMessage].(*nas.GmmMessage)accessType := args[ArgAccessType].(models.AccessType)switch gmmMessage.GetMessageType() {case nas.MsgTypeSecurityModeComplete:if err := HandleSecurityModeComplete(amfUe, accessType, procedureCode, gmmMessage.SecurityModeComplete); err != nil {logger.GmmLog.Errorln(err)}

   3.8 HandleInitialRegistration 函数，继续以下的其他流程

func HandleInitialRegistration(ue *context.AmfUe, anType models.AccessType) error {logger.GmmLog.Infoln("[AMF] Handle InitialRegistration")amfSelf := context.AMF_Self()// update Kgnb/Kn3iwfue.UpdateSecurityContext(anType)

    3.8.1 getSubscribedNssai 函数

    SearchUdmSdmInstace 从 nrf 查找 UDM 实例，SDMGetSliceSelectionSubscriptionData 函数从 UDM 根据 plmnId查找 NSSAI 信息，包含 DefaultSingleNssais 和 SingleNssais 

func getSubscribedNssai(ue *context.AmfUe) {err := consumer.SearchUdmSdmInstance(ue, amfSelf.NrfUri, models.NfType_UDM, models.NfType_AMF, &param)problemDetails, err := consumer.SDMGetSliceSelectionSubscriptionData(ue)}

 

      3.8.2 Namf_Communication_RegistrationCompleteNotify 对应步骤 10

      如果 AMF 已经更改，新的 AMF 调用 Namf_Communication_RegistrationCompleteNotify 服务操作来通知旧的 AMF， UE 在新的 AMF 注册完成

      Namf_Communication_RegistrationCompleteNotify，/ue-contexts/{ueContextId}/transfer-update

// TODO (step 10 optional): send Namf_Communication_RegistrationCompleteNotify to old AMF if need
if ue.ServingAmfChanged {// If the AMF has changed the new AMF notifies the old AMF that the registration of the UE in the new AMF is completedreq := models.UeRegStatusUpdateReqData{TransferStatus: models.UeContextTransferStatus_TRANSFERRED,}// TODO: based on locol policy, decide if need to change serving PCF for UEregStatusTransferComplete, problemDetails, err := consumer.RegistrationStatusUpdate(ue, req)if problemDetails != nil {logger.GmmLog.Errorf("Registration Status Update Failed Problem[%+v]", problemDetails)} else if err != nil {logger.GmmLog.Errorf("Registration Status Update Error[%+v]", err)} else {if regStatusTransferComplete {logger.GmmLog.Infof("[AMF] Registration Status Transfer complete")}}
}

      3.8.3 SendIdentityRequest 对应步骤 11

     如果 UE 未提供 PEI 也未从旧 AMF 取到 PEI，则 AMF 向 UE 发送身份请求消息以获取 PEI。

     除非 UE 执行紧急注册且无法进行身份验证，否则 PEI 应加密传输

      NAS MM 消息类型为 MsgTypeIdentityRequest

if len(ue.Pei) == 0 {gmm_message.SendIdentityRequest(ue.RanUe[anType], nasMessage.MobileIdentity5GSTypeImei)return nil
}

    3.8.4 UDM Selection 对应步骤 13

if ue.ServingAmfChanged || ue.State[models.AccessType_NON_3_GPP_ACCESS].Is(context.Registered) ||!ue.ContextValid {if err := communicateWithUDM(ue, anType); err != nil {return err}
}

      如果要执行步骤 14，基于 SUPI 的新 AMF 选择 UDM，然后 UDM 可以选择 UDR 实例，TS 23.501 [2], clause 6.3.9

      AMF 选择 UDM TS 23.501 [2], clause 6.3.8

      NRF 向 AMF 回应 UDM 信息

    3.8.5 Nudm_UECM_Registration 对应步骤 14

    如果自从上次注册程序，AMF 已经更改。新 AMF 使用 Nudm_UECM_Registration 向 UDM 注册，如果 AMF 没有 UE 的订阅数据， AMF 使用 Nudm_SDM_Get 检索 AM 订阅数据，SMF 选择订阅数据，在 SMF 中的 UE 上下文。UDM 可以通过 Nudr_DM_Query 从 UDR 检索此信息。

problemDetails, err := consumer.UeCmRegistration(ue, anType, true)
if problemDetails != nil {logger.GmmLog.Errorf("UECM_Registration Failed Problem[%+v]", problemDetails)
} else if err != nil {logger.GmmLog.Errorf("UECM_Registration Error[%+v]", err)
}problemDetails, err = consumer.SDMGetAmData(ue)
if problemDetails != nil {logger.GmmLog.Errorf("SDM_Get AmData Failed Problem[%+v]", problemDetails)
} else if err != nil {logger.GmmLog.Errorf("SDM_Get AmData Error[%+v]", err)
}problemDetails, err = consumer.SDMGetSmfSelectData(ue)
if problemDetails != nil {logger.GmmLog.Errorf("SDM_Get SmfSelectData Failed Problem[%+v]", problemDetails)
} else if err != nil {logger.GmmLog.Errorf("SDM_Get SmfSelectData Error[%+v]", err)
}problemDetails, err = consumer.SDMGetUeContextInSmfData(ue)
if problemDetails != nil {logger.GmmLog.Errorf("SDM_Get UeContextInSmfData Failed Problem[%+v]", problemDetails)
} else if err != nil {logger.GmmLog.Errorf("SDM_Get UeContextInSmfData Error[%+v]", err)
}

 

    3.8.6 PCF selection

param := Nnrf_NFDiscovery.SearchNFInstancesParamOpts{Supi: optional.NewString(ue.Supi),
}
for {resp, err := consumer.SendSearchNFInstances(amfSelf.NrfUri, models.NfType_PCF, models.NfType_AMF, &param)if err != nil {logger.GmmLog.Error("AMF can not select an PCF by NRF")}

   3.9 AMPolicyControlCreate （对应步骤 16）

      新的 AMF 执行一个 AM Policy Association Establishment/Modification，对于紧急注册将忽略

policyAssociationRequest := models.PolicyAssociationRequest{NotificationUri: amfSelf.GetIPv4Uri() + "/namf-callback/v1/am-policy/",Supi:            ue.Supi,Pei:             ue.Pei,Gpsi:            ue.Gpsi,AccessType:      anType,ServingPlmn: &models.NetworkId{Mcc: ue.PlmnId.Mcc,Mnc: ue.PlmnId.Mnc,},Guami: &amfSelf.ServedGuamiList[0],
}

    步骤 17，未体现：

       对于紧急请求的 UE，当注册类型为移动性注册更新，该步骤才应用 。AMF 在以下场景调用 Nsmf_PDUSession_UpdateSMContext

    3.10 步骤 18，19 UE Context Modification Request N3IWF/TNGFW-AGF

      对于非 3GPP 未支持

// TODO (step 18 optional):
// If the AMF has changed and the old AMF has indicated an existing NGAP UE association towards a N3IWF, the new AMF
// creates an NGAP UE association towards the N3IWF to which the UE is connectedsend N2 AMF mobility request to N3IWF
// if anType == models.AccessType_NON_3_GPP_ACCESS && ue.ServingAmfChanged {
// 	TODO: send N2 AMF Mobility Request
// }

    3.11 AMF 向 UE 发送 “Registration Accept”（步骤 21）

      BuildRegistrationAccept 函数，NAS 消息类型为 MsgTypeRegistrationAccept

      BuildInitialContextSetupRequest，NGAP 类型为 NGAPPDUPresentInitiatingMessage，ProcedureCodeInitialContextSetup，包括 IE 有：

    -  AMF UE NGAP ID

    -  RAN UE NGAP ID

    -  Old AMF (optional)

    -  UE Aggregate Maximum Bit Rate (conditional: if pdu session resource setup)

    -  Core Network Assistance Information (optional)

    -  GUAMI

    -  PDU Session Resource Setup Request List

    -  Allowed NSSAI

    -  UE Security Capabilities

    -  Security Key

    -  Trace Activation (optional)

    -  Mobility Restriction List (optional)

    -  UE Radio Capability (optional)

    -  Index to RAT/Frequency Selection Priority (optional)

    -  Masked IMEISV (optional)

    -  NAS-PDU (optional)

    -  RRC Inactive Transition Report Request (optional)

    -  UE Radio Capability for Paging (optional)

 

 

4. send ngap Initial Context Setup Response Msg

    NGAP 消息类型为  NGAPPDUPresentSuccessfulOutcome，ProcedureCodeInitialContextSetup

   4.1 AMF 处理 Registration Response 消息

func HandleInitialContextSetupResponse(ran *context.AmfRan, message *ngapType.NGAPPDU) {var aMFUENGAPID *ngapType.AMFUENGAPIDvar rANUENGAPID *ngapType.RANUENGAPIDvar pDUSessionResourceSetupResponseList *ngapType.PDUSessionResourceSetupListCxtResvar pDUSessionResourceFailedToSetupList *ngapType.PDUSessionResourceFailedToSetupListCxtResvar criticalityDiagnostics *ngapType.CriticalityDiagnostics

    4.1.1 如果应答消息包含 PDU 会话资源

    向 SMF 更新 SM 上下文

if pDUSessionResourceSetupResponseList != nil {Ngaplog.Trace("[NGAP] Send PDUSessionResourceSetupResponseTransfer to SMF")for _, item := range pDUSessionResourceSetupResponseList.List {pduSessionID := int32(item.PDUSessionID.Value)transfer := item.PDUSessionResourceSetupResponseTransferresponse, _, _, err := consumer.SendUpdateSmContextN2Info(amfUe, pduSessionID, models.N2SmInfoType_PDU_RES_SETUP_RSP, transfer)if err != nil {Ngaplog.Errorf("SendUpdateSmContextN2Info[PDUSessionResourceSetupResponseTransfer] Error:\n%s", err.Error())}// RAN initiated QoS Flow Mobility in subclause 5.2.2.3.7if response != nil && response.BinaryDataN2SmInformation != nil {// TODO: n2SmInfo send to RAN} else if response == nil {// TODO: error handling}}
}

 

5. send NAS Registration Complete Msg（步骤22）

    NAS 消息类型为 MsgTypeRegistrationComplete

    BuildUplinkNasTransport 函数，NGAP 消息类型为 NGAPPDUPresentInitiatingMessage，ProcedureCodeUplinkNASTransport，包括 IE 有：

    -  AMF UE NGAP ID

    -  RAN UE NGAP ID

    -  NAS-PDU

    -  User Location Information

   5.1 AMF 处理 HandleUplinkNasTransport

    定位到函数  HandleUplinkNasTransport

func HandleUplinkNasTransport(ran *context.AmfRan, message *ngapType.NGAPPDU) {var aMFUENGAPID *ngapType.AMFUENGAPIDvar rANUENGAPID *ngapType.RANUENGAPIDvar nASPDU *ngapType.NASPDUvar userLocationInformation *ngapType.UserLocationInformation

   5.2 HandleRegistrationComplete 函数

    步骤 23 24 未实现，将状态移到 REGISTERED 状态

    状态转移

state	event	From	To
Deregistered -> Authentication	StartAuthEvent	Deregistered	Authentication
Authentication	AuthSuccessEvent	Authentication	SecurityMode
SecurityMode	SecurityModeSuccessEvent	SecurityMode	ContextSetup
ContextSetup	GmmMessageEvent	ContextSetup	Registered

func HandleRegistrationComplete(ue *context.AmfUe, accessType models.AccessType,registrationComplete *nasMessage.RegistrationComplete) error {logger.GmmLog.Info("[AMF] Handle Registration Complete")util.StopT3550(ue)// if registrationComplete.SORTransparentContainer != nil {// 	TODO: if at regsitration procedure 14b, udm provide amf Steering of Roaming info & request an ack,// 	AMF provides the UE's ack with Nudm_SDM_Info (SOR not supportted in this stage)// }// TODO: if//	1. AMF has evaluated the support of IMS Voice over PS Sessions (TS 23.501 5.16.3.2)//	2. AMF determines that it needs to update the Homogeneous Support of IMS Voice over PS Sessions (TS 23.501 5.16.3.3)// Then invoke Nudm_UECM_Update to send "Homogeneous Support of IMS Voice over PS Sessions" indication to udmif ue.RegistrationRequest.UplinkDataStatus == nil &&ue.RegistrationRequest.GetFOR() == nasMessage.FollowOnRequestNoPending {ngap_message.SendUEContextReleaseCommand(ue.RanUe[accessType], context.UeContextN2NormalRelease,ngapType.CausePresentNas, ngapType.CauseNasPresentNormalRelease)}return GmmFSM.SendEvent(ue.State[accessType], ContextSetupSuccessEvent, fsm.ArgsType{ArgAmfUe:      ue,ArgAccessType: accessType,})
}

 

6. Registered 函数

state	event	From	To
Deregistered -> Authentication	StartAuthEvent	Deregistered	Authentication
Authentication	AuthSuccessEvent	Authentication	SecurityMode
SecurityMode	SecurityModeSuccessEvent	SecurityMode	ContextSetup
ContextSetup	GmmMessageEvent	ContextSetup	Registered
Registered	GmmMessageEvent	Registered	Registered

 

参考：

   github， free5gc 3.0.4