【5G核心网】free5GC 注销请求流程源码分析

末蓝、 2022-12-21 13:55 276阅读 0赞

**    注销流程可以两种发起：**

>     -  UE 通知网络它不再访问 5GS
> 
>     -  网络通知 UE 它不再有权访问 5GS

# 1. UE 发起 NAS Deregistration Request (UE Originating) #

Gmm 消息类型设置为 ***MsgTypeDeregistrationRequestUEOriginatingDeregistration***，NGAP UplinkNasTransport 消息 Present 设置为 ***NGAPPDUPresentInitiatingMessage***，ProcedureCode 设置为 ***ProcedureCodeUplinkNASTransport***

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70][] UplinkNASTransport，Deregistration request（UE originating）

# 2. AMF 处理 uplinkNASTransport 消息 #

HandleUplinkNasTransport

-->  HandleNAS

-->  Dispatch

-->  SendEvent ***GmmMessageEvent***

-->  Registered

Registered 中函数根据 nas 的 gmm ***MsgTypeDeregistrationRequestUEOriginatingDeregistration ***类型 直接进行状态转移

<table> 
 <tbody> 
  <tr> 
   <td>State</td> 
   <td>Event</td> 
   <td>From</td> 
   <td>To</td> 
  </tr> 
  <tr> 
   <td>Registered</td> 
   <td>GmmMessageEvent</td> 
   <td>Registered</td> 
   <td>Registered</td> 
  </tr> 
  <tr> 
   <td>Registered -&gt;&nbsp;DeregistrationInitiated</td> 
   <td>InitDeregistrationEvent</td> 
   <td>Registered</td> 
   <td>Registered</td> 
  </tr> 
 </tbody> 
</table>

func Registered(state *fsm.State, event fsm.EventType, args fsm.ArgsType) {
    	logger.GmmLog.Debugln("UE in GMM State[Registered]")
    
    	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.MsgTypeDeregistrationRequestUEOriginatingDeregistration:
    			if err := GmmFSM.SendEvent(state, InitDeregistrationEvent, fsm.ArgsType{
    				ArgAmfUe:      amfUe,
    				ArgAccessType: accessType,
    				ArgNASMessage: gmmMessage,
    			}); err != nil {
    				logger.GmmLog.Errorln(err)
    			}

###    2.1 DeregisteredInitiated 函数 ###

处理函数为 HandleDeregistrationRequest

func DeregisteredInitiated(state *fsm.State, event fsm.EventType, args fsm.ArgsType) {
    	logger.GmmLog.Debugln("UE in GMM State[DeregisteredInitiated]")
    
    	switch event {
    	case fsm.EntryEvent:
    		amfUe := args[ArgAmfUe].(*context.AmfUe)
    		gmmMessage := args[ArgNASMessage].(*nas.GmmMessage)
    		accessType := args[ArgAccessType].(models.AccessType)
    		if err := HandleDeregistrationRequest(amfUe, accessType,
    			gmmMessage.DeregistrationRequestUEOriginatingDeregistration); err != nil {
    			logger.GmmLog.Errorln(err)
    		}

# 3. HandleDeregistrationRequest 函数 #

如果存在 UE 的 SM 上下文，则发起释放 SM 上下文的请求，

// TS 23.502 4.2.2.3
    func HandleDeregistrationRequest(ue *context.AmfUe, anType models.AccessType,
    	deregistrationRequest *nasMessage.DeregistrationRequestUEOriginatingDeregistration) error {
    
    	logger.GmmLog.Info("[AMF] Handle Deregistration Request(UE Originating)")
    
    	targetDeregistrationAccessType := deregistrationRequest.GetAccessType()
    	for pduSessionId, smContext := range ue.SmContextList {
    		if smContext.PduSessionContext.AccessType != anType &&
    			targetDeregistrationAccessType != nasMessage.AccessTypeBoth {
    			continue
    		}
    
    		releaseData := consumer.BuildReleaseSmContextRequest(ue, nil, "", nil)
    		problemDetail, err := consumer.SendReleaseSmContextRequest(ue, pduSessionId, releaseData)
    		if problemDetail != nil {
    			logger.GmmLog.Errorf("Release SmContext Failed Problem[%+v]", problemDetail)
    		} else if err != nil {
    			logger.GmmLog.Errorf("Release SmContext Error[%v]", err.Error())
    		}
    	}

###    3.1 SendDeregistrationAccept 函数 ###

发送 DownlinkNASTransport 请求，Deregistration accept 消息

func SendDeregistrationAccept(ue *context.RanUe) {
    
    	logger.GmmLog.Info("[NAS] Send Deregistration Accept")
    
    	nasMsg, err := BuildDeregistrationAccept()
    	if err != nil {
    		logger.GmmLog.Error(err.Error())
    		return
    	}
    	ngap_message.SendDownlinkNasTransport(ue, nasMsg, nil)
    }

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 1][] DownlinkNASTransport，Deregistration accept（UE originating）

###    3.2  SendUEContextReleaseCommand 函数 ###

状态转移

// TS 23.502 4.2.6, 4.12.3
    switch targetDeregistrationAccessType {
    case nasMessage.AccessType3GPP:
    	if ue.RanUe[models.AccessType__3_GPP_ACCESS] != nil {
    		ngap_message.SendUEContextReleaseCommand(ue.RanUe[models.AccessType__3_GPP_ACCESS],
    			context.UeContextReleaseUeContext, ngapType.CausePresentNas, ngapType.CauseNasPresentDeregister)
    	}
    	return GmmFSM.SendEvent(ue.State[models.AccessType__3_GPP_ACCESS], DeregistrationAcceptEvent, fsm.ArgsType{
    		ArgAmfUe:      ue,
    		ArgAccessType: anType,
    	})

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 2][] UEContextReleaseCommand

# 4. 发送 NGAP UE Context Release Complete #

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 3][] UEContextReleaseComplete

###    4.1 AMF 处理 NGAP UE Context Release Complete ###

func HandleUEContextReleaseComplete(ran *context.AmfRan, message *ngapType.NGAPPDU) {
    
    	var aMFUENGAPID *ngapType.AMFUENGAPID
    	var rANUENGAPID *ngapType.RANUENGAPID
    	var userLocationInformation *ngapType.UserLocationInformation
    	var infoOnRecommendedCellsAndRANNodesForPaging *ngapType.InfoOnRecommendedCellsAndRANNodesForPaging
    	var pDUSessionResourceList *ngapType.PDUSessionResourceListCxtRelCpl
    	var criticalityDiagnostics *ngapType.CriticalityDiagnostics

释放 RAN 等缓存信息

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