From f0a32ec58b12fe3fd4236f6eed682908002e2a60 Mon Sep 17 00:00:00 2001
From: donald1218 <donald.shih2000@gmail.com>
Date: Thu, 19 Sep 2024 12:53:33 +0000
Subject: [PATCH] fix: amf determine ue.rattype in registration

---
 internal/context/amf_ran.go | 26 ++++++++++++++++++++++++++
 internal/gmm/handler.go     |  6 ++++++
 2 files changed, 32 insertions(+)

diff --git a/internal/context/amf_ran.go b/internal/context/amf_ran.go
index a94c9c6..b4cda0e 100644
--- a/internal/context/amf_ran.go
+++ b/internal/context/amf_ran.go
@@ -17,6 +17,9 @@ const (
 	RanPresentGNbId   = 1
 	RanPresentNgeNbId = 2
 	RanPresentN3IwfId = 3
+	RanPresentTngfId  = 4
+	RanPresentTwifId  = 5
+	RanPresentWagfId  = 6
 )
 
 type AmfRan struct {
@@ -131,3 +134,26 @@ func (ran *AmfRan) RanID() string {
 		return ""
 	}
 }
+
+func (ran *AmfRan) UeRatType() models.RatType {
+	// In TS 23.501 5.3.2.3
+	// For 3GPP access the AMF determines the RAT type the UE is camping on based
+	// on the Global RAN Node IDs associated with the N2 interface and
+	// additionally the Tracking Area indicated by NG-RAN
+	switch ran.RanPresent {
+	case RanPresentGNbId:
+		return models.RatType_NR
+	case RanPresentNgeNbId:
+		return models.RatType_NR
+	case RanPresentN3IwfId:
+		return models.RatType_VIRTUAL
+	case RanPresentTngfId:
+		return models.RatType_TRUSTED_N3_GA
+	case RanPresentTwifId:
+		return models.RatType_TRUSTED_N3_GA
+	case RanPresentWagfId:
+		return models.RatType_WIRELINE
+	default:
+		return models.RatType_NR
+	}
+}
diff --git a/internal/gmm/handler.go b/internal/gmm/handler.go
index ed93dff..082765f 100644
--- a/internal/gmm/handler.go
+++ b/internal/gmm/handler.go
@@ -537,6 +537,11 @@ func HandleRegistrationRequest(ue *context.AmfUe, anType models.AccessType, proc
 	if ue.RanUe[anType] != nil {
 		ue.Location = ue.RanUe[anType].Location
 		ue.Tai = ue.RanUe[anType].Tai
+		if ue.RanUe[anType].Ran != nil {
+			// ue.Ratype TS 23.502 4.2.2.1
+			// The AMF determines Access Type and RAT Type as defined in clause 5.3.2.3 of TS 23.501 .
+			ue.RatType = ue.RanUe[anType].Ran.UeRatType()
+		}
 	}
 
 	// Check TAI
@@ -565,6 +570,7 @@ func HandleRegistrationRequest(ue *context.AmfUe, anType models.AccessType, proc
 			context.GetSelf().AllocateGutiToUe(ue) // refresh 5G-GUTI
 		}
 	}
+
 	return nil
 }