【5G核心网】free5GC SMF启动流程源码分析

骑猪看日落 2023-03-01 10:25 91阅读 0赞

# PFCP 消息头 #

> 字节1 按位设置：  
>         - 位1： 代表 SEID 标记
> 
>         - 位2： 代表 MP 标记（message priority）
> 
>        - 位3-5： spare，发送者设置为0，接收将忽略
> 
>         - 位6-8： 版本
> 
>   字节 2 是消息类型  
>   字节3、4是两字节的消息长度  
>   可选项 SEID，占8字节  
>   最后3字节序列号.

![20200724095655511.png][]

Figure 7.2.2.1-1: General format of PFCP Header

>      - if S = 0, SEID field is not present, k = 0, m = 0 and n = 5;
> 
>      - if S = 1, SEID field is present, k = 1, m = 5 and n = 13.  
>

##     结构体 PFCP Header ##

>     type Header struct {
>     	Version         uint8
>     	MP              uint8
>     	S               uint8
>     	MessageType     MessageType
>     	MessageLength   uint16
>     	SEID            uint64
>     	SequenceNumber  uint32
>     	MessagePriority uint8
>     }

##    UserPlaneInformation 结构体 ##

>     userplane_information:
>       up_nodes:
>         gNB1:
>           type: AN
>           an_ip: 192.188.2.3
>         BranchingUPF:
>           type: UPF
>           node_id: 10.200.200.102
>           up_resource_ip: 192.188.2.2
>         AnchorUPF1:
>           type: UPF
>           node_id: 10.200.200.101
>           up_resource_ip: 192.188.2.23
>         AnchorUPF2:
>           type: UPF
>           node_id: 10.200.200.103
>           up_resource_ip: 192.188.2.24
>       links:
>         - A: gNB1
>           B: BranchingUPF
>         - A: BranchingUPF
>           B: AnchorUPF1
>         - A: BranchingUPF
>           B: AnchorUPF2

// UserPlaneInformation describe core network userplane information
    type UserPlaneInformation struct {
       UPNodes map[string]UPNode `yaml:"up_nodes"`
       Links   []UPLink          `yaml:"links"`
    }

##    UERoutingInfo 结构体 ##

>     ueRoutingInfo:
>       - SUPI: imsi-2089300007487
>         AN: 10.200.200.101
>         PathList:
>           - DestinationIP: 60.60.0.101
>             UPF: !!seq
>               - BranchingUPF
>               - AnchorUPF1
>     
>           - DestinationIP: 60.60.0.103
>             UPF: !!seq
>               - BranchingUPF
>               - AnchorUPF2

>     type Path struct {
>     	DestinationIP string `yaml:"DestinationIP,omitempty"`
>     
>     	DestinationPort string `yaml:"DestinationPort,omitempty"`
>     
>     	UPF []string `yaml:"UPF,omitempty"`
>     }
>     
>     type UERoutingInfo struct {
>     	SUPI string `yaml:"SUPI,omitempty"`
>     
>     	AN string `yaml:"AN,omitempty"`
>     
>     	PathList []Path `yaml:"PathList,omitempty"`
>     }

# 1. PFCP Association PFCP 关联请求 #

参看： [https://blog.csdn.net/zhonglinzhang/article/details/107542866][https_blog.csdn.net_zhonglinzhang_article_details_107542866] 第 2.1 章节

###     1.1 由 SMF 向 UPF 发起 PFCP 关联请求 ###

根据所有配置文件定义的 UPF 发起 PFCP 关联请求，SMF PFCP 服务端端口 8805

for _, upf := range context.SMF_Self().UserPlaneInformation.UPFs {
    	addr := new(net.UDPAddr)
    	addr.IP = net.IP(upf.NodeID.NodeIdValue)
    
    	addr.Port = pfcpUdp.PFCP_PORT
    
    	logger.AppLog.Infof("Send PFCP Association Request to UPF[%s]\n", addr.String())
    	message.SendPfcpAssociationSetupRequest(addr)
    }

**    1.1.1 SendPfcpAssociationSetupRequest 函数**

创建 body，这里发送方未 CP 功能

>     - Node ID，发送方以为的标识符
> 
>     - Recovery Time Stamp，当 CP 或 CP 已经启动的时间戳
> 
>     - UP Function Features，指示 UP 功能支持的特性（UP 发送）
> 
>     - CP Function Features，指示 CP 功能支持的特性（CP 发送）
> 
>     - User Plane IP Resource Information，包含 IPv4 / IPv6，还有 TEID，用来在 UP 分配 GTP-U F-TEID（UP 发送）

func BuildPfcpAssociationSetupRequest() (pfcp.PFCPAssociationSetupRequest, error) {
    	msg := pfcp.PFCPAssociationSetupRequest{}
    
    	msg.NodeID = &context.SMF_Self().CPNodeID
    
    	msg.RecoveryTimeStamp = &pfcpType.RecoveryTimeStamp{
    		RecoveryTimeStamp: udp.ServerStartTime,
    	}
    
    	msg.CPFunctionFeatures = &pfcpType.CPFunctionFeatures{
    		SupportedFeatures: 0,
    	}
    
    	return msg, nil
    }

**    1.1.1.1 PFCP 消息填充**

**   ** 消息类型为：PFCP\_ASSOCIATION\_SETUP\_REQUEST，S 设置为 0

message := pfcp.Message{
    	Header: pfcp.Header{
    		Version:        pfcp.PfcpVersion,
    		MP:             0,
    		S:              pfcp.SEID_NOT_PRESENT,
    		MessageType:    pfcp.PFCP_ASSOCIATION_SETUP_REQUEST,
    		SequenceNumber: getSeqNumber(),
    	},
    	Body: pfcpMsg,
    }

**    1.1.2 SMF 处理 PFCP Association Response**

**   ** 如果原因设置为** **CauseRequestAccepted 更新 UPF 信息状态为 AssociatedSetUpSuccess

func HandlePfcpAssociationSetupResponse(msg *pfcpUdp.Message) {
    	req := msg.PfcpMessage.Body.(pfcp.PFCPAssociationSetupResponse)
    
    	nodeID := req.NodeID
    	if req.Cause.CauseValue == pfcpType.CauseRequestAccepted {
    		if nodeID == nil {
    			logger.PfcpLog.Errorln("pfcp association needs NodeID")
    			return
    		}
    
    		upf := smf_context.RetrieveUPFNodeByNodeID(*req.NodeID)
    		upf.UPFStatus = smf_context.AssociatedSetUpSuccess
    
    		if req.UserPlaneIPResourceInformation != nil {
    			upf.UPIPInfo = *req.UserPlaneIPResourceInformation
    			logger.PfcpLog.Infof("UPF(%s)[%s] setup association", upf.NodeID.ResolveNodeIdToIp().String(), upf.UPIPInfo.NetworkInstance)
    		} else {
    			logger.PfcpLog.Errorln("pfcp association setup response has no UserPlane IP Resource Information")
    		}
    	}
    }

# 2. ApplySmPolicyFromDecision #

NRF 中注册的 SMF

> \{  
>     "\_id": ObjectId("5f1a9c2364d2e538cb1309d4"),  
>     "ipv4Addresses": \[  
>         "smf"  
>     \],  
>     "smfInfo": \{  
>         "sNssaiSmfInfoList": null  
>     \},  
>     "nfServices": \[  
>         \{  
>             "serviceInstanceId": "e1b3436a-f9b9-4820-b075-d16fb4814ddansmf-pdusession",  
>             *"serviceName": "nsmf-pdusession",*  
>             "versions": \[  
>                 \{  
>                     "expiry": "2020-07-24T08:30:27Z",  
>                     "apiVersionInUri": "v1",  
>                     "apiFullVersion": "https://smf:29502/nsmf-pdusession/v1"  
>                 \}  
>             \],  
>             "scheme": "https",  
>             "nfServiceStatus": "REGISTERED",  
>             "apiPrefix": "https://smf:29502"  
>         \},  
>         \{  
>             "serviceName": *"nsmf-event-exposure"*,  
>             "versions": \[  
>                 \{  
>                     "apiVersionInUri": "v1",  
>                     "apiFullVersion": "https://smf:29502/nsmf-pdusession/v1",  
>                     "expiry": "2020-07-24T08:30:27Z"  
>                 \}  
>             \],  
>             "scheme": "https",  
>             "nfServiceStatus": "REGISTERED",  
>             "apiPrefix": "https://smf:29502",  
>             "serviceInstanceId": "e1b3436a-f9b9-4820-b075-d16fb4814ddansmf-event-exposure"  
>         \}  
>     \],  
>     "nfInstanceId": "e1b3436a-f9b9-4820-b075-d16fb4814dda",  
>     "nfType": "SMF",  
>     "nfStatus": "REGISTERED",  
>     "plmnList": \[  
>         \{  
>             "mcc": "208",  
>             "mnc": "93"  
>         \}  
>     \]  
> \}

**总结：SMF 处理方法函数包括 **

>   -  PFCPMessage
> 
>   -  PDUSessionSMContextCreate
> 
>   -  PDUSessionSMContextUpdate
> 
>   -  PDUSessionSMContextRelease
> 
>   -  OAMGetUEPDUSessionInfo
> 
>   -  SMPolicyUpdateNotify

[20200724095655511.png]: /images/20230208/a3ef7a33b5ab400580519aff9bcb5c45.png
[https_blog.csdn.net_zhonglinzhang_article_details_107542866]: https://blog.csdn.net/zhonglinzhang/article/details/107542866