Remove AmfRan from pool on SCTP connection close

VERSION

@@ -1 +1 @@
-3.1.2-dev
+3.1.2

ngap/dispatcher.go

@@ -144,7 +144,15 @@ func Dispatch(conn net.Conn, msg []byte) {
 
 	ran, ok := amfSelf.AmfRanFindByConn(conn)
 	if !ok {
-		logger.NgapLog.Infof("Create a new NG connection for: %s", conn.RemoteAddr().String())
+		if len(msg) == 0 {
+			// No existing RAN context for this connection: either the connection
+			// closed before any NGAP message arrived, or an SCTP notification
+			// already triggered ran.Remove(). Skip creating a transient context.
+			logger.NgapLog.Debugf("RAN context not found for closing connection[addr: %+v], nothing to remove",
+				conn.RemoteAddr())
+			return
+		}
+		logger.NgapLog.Infof("Create a new NG connection for: %+v", conn.RemoteAddr())
 		ran = amfSelf.NewAmfRan(conn)
 	}
 

ngap/dispatcher_test.go

@@ -7,12 +7,31 @@ package ngap
 
 import (
 	ctxt "context"
+	"net"
 	"testing"
+	"time"
 
 	"github.com/omec-project/amf/context"
 	"github.com/omec-project/amf/protos/sdcoreAmfServer"
 )
 
+// mockConn is a minimal net.Conn used to exercise Dispatch without a real SCTP socket.
+type mockConn struct{}
+
+type mockAddr struct{}
+
+func (a mockAddr) Network() string { return "sctp" }
+func (a mockAddr) String() string  { return "192.0.2.1:38412" }
+
+func (c *mockConn) RemoteAddr() net.Addr               { return mockAddr{} }
+func (c *mockConn) LocalAddr() net.Addr                { return mockAddr{} }
+func (c *mockConn) Read(_ []byte) (int, error)         { return 0, net.ErrClosed }
+func (c *mockConn) Write(_ []byte) (int, error)        { return 0, net.ErrClosed }
+func (c *mockConn) Close() error                       { return nil }
+func (c *mockConn) SetDeadline(_ time.Time) error      { return nil }
+func (c *mockConn) SetReadDeadline(_ time.Time) error  { return nil }
+func (c *mockConn) SetWriteDeadline(_ time.Time) error { return nil }
+
 func TestDispatchLbIgnoresMissingRanContext(t *testing.T) {
 	msg := &sdcoreAmfServer.SctplbMessage{
 		Msg: []byte{0x00},
@@ -38,3 +57,23 @@ func TestDispatchNgapMsgIgnoresNilPdu(t *testing.T) {
 
 	DispatchNgapMsg(ctxt.Background(), ran, nil, nil)
 }
+
+// TestDispatchEmptyMsgUnknownConnDoesNotPanic verifies that Dispatch does not panic
+// and does not create an AmfRan entry when it receives an empty (connection-close)
+// message for a connection that has no existing RAN context.
+func TestDispatchEmptyMsgUnknownConnDoesNotPanic(t *testing.T) {
+	conn := &mockConn{}
+
+	defer func() {
+		if r := recover(); r != nil {
+			t.Fatalf("Dispatch panicked with empty message and unknown conn: %v", r)
+		}
+	}()
+
+	Dispatch(conn, nil)
+
+	// Confirm that no AmfRan was created in the pool for this unknown connection.
+	if _, ok := context.AMF_Self().AmfRanFindByConn(conn); ok {
+		t.Error("Dispatch must not create an AmfRan for an unknown connection with an empty message")
+	}
+}

ngap/service/service.go

@@ -165,7 +165,7 @@ func listenAndServe(addr *sctp.SCTPAddr, handler NGAPHandler) {
 			logger.NgapLog.Debugf("set read timeout: %+v", readTimeout)
 		}
 
-		logger.NgapLog.Infof("[AMF] SCTP Accept from: %s", newConn.RemoteAddr().String())
+		logger.NgapLog.Infof("[AMF] SCTP Accept from: %+v", newConn.RemoteAddr())
 		connections.Store(newConn, true)
 
 		go handleConnection(newConn, readBufSize, handler)
@@ -196,6 +196,12 @@ func handleConnection(conn *sctp.SCTPConn, bufsize uint32, handler NGAPHandler)
 	defer func() {
 		connections.Delete(conn)
 
+		// Notify the NGAP dispatcher that this RAN connection has closed so that
+		// its AmfRan entry is removed from AmfRanPool
+		if handler.HandleMessage != nil {
+			handler.HandleMessage(conn, nil)
+		}
+
 		// if AMF call Stop(), then conn.Close() will return EBADF because conn has been closed inside Stop()
 		if err := conn.Close(); err != nil && err != syscall.EBADF {
 			logger.NgapLog.Errorf("close connection error: %+v", err)