From 7f14b479d3c47dba39530e193941d8b871a2fe4f Mon Sep 17 00:00:00 2001
From: Sree Iyer <sbiyer@google.com>
Date: Wed, 23 Sep 2026 10:37:52 +0000
Subject: [PATCH] Prevent unconnected ports from reporting oper status up

Signed-off-by: Sree Iyer <sbiyer@google.com>
---
 dataplane/saiserver/ports.go      | 33 ++++++++++++++++++++++++++---
 dataplane/saiserver/ports_test.go | 35 +++++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+), 3 deletions(-)

diff --git a/dataplane/saiserver/ports.go b/dataplane/saiserver/ports.go
index 9ab6f834e..ceccb29be 100644
--- a/dataplane/saiserver/ports.go
+++ b/dataplane/saiserver/ports.go
@@ -244,7 +244,7 @@ func (port *port) CreatePort(ctx context.Context, req *saipb.CreatePortRequest)
 			attrs.OperStatus = saipb.PortOperStatus_PORT_OPER_STATUS_NOT_PRESENT.Enum()
 			port.mgr.StoreAttributes(id, attrs)
 			// TODO: This should be a real error, improve once we a correct config solution.
-			// For now, create dummy port with no actions so we don't get a bunch error for a nonexistant port.
+			// For now, create dummy port with no actions so we don't get a bunch error for a nonexistent port.
 			fwdPort := &fwdpb.PortCreateRequest{
 				ContextId: &fwdpb.ContextId{Id: port.dataplane.ID()},
 				Port: &fwdpb.PortDesc{
@@ -527,7 +527,7 @@ func (port *port) createCPUPort(ctx context.Context) (uint64, error) {
 // SetPortAttributes sets the attributes in the request.
 func (port *port) SetPortAttribute(ctx context.Context, req *saipb.SetPortAttributeRequest) (*saipb.SetPortAttributeResponse, error) {
 	if req.AdminState != nil {
-		// Skip ports that don't exsit.
+		// Skip ports that don't exist.
 		attrReq := &saipb.GetPortAttributeRequest{Oid: req.GetOid(), AttrType: []saipb.PortAttr{saipb.PortAttr_PORT_ATTR_OPER_STATUS}}
 		p := &saipb.GetPortAttributeResponse{}
 		if err := port.mgr.PopulateAttributes(attrReq, p); err != nil {
@@ -537,6 +537,33 @@ func (port *port) SetPortAttribute(ctx context.Context, req *saipb.SetPortAttrib
 			return nil, nil
 		}
 
+		// Do not apply admin-state changes to the fallback TAP created for a
+		// kernel-backed port whose real lane interface is absent.
+		if port.opts.PortType == fwdpb.PortType_PORT_TYPE_KERNEL && req.GetAdminState() {
+			attrReq := &saipb.GetPortAttributeRequest{
+				Oid:      req.GetOid(),
+				AttrType: []saipb.PortAttr{saipb.PortAttr_PORT_ATTR_HW_LANE_LIST},
+			}
+			p := &saipb.GetPortAttributeResponse{}
+			if err := port.mgr.PopulateAttributes(attrReq, p); err != nil {
+				return nil, err
+			}
+			attr := p.GetAttr()
+			if attr == nil {
+				return nil, fmt.Errorf("failed to get attributes for port %d", req.GetOid())
+			}
+			lanes := attr.GetHwLaneList()
+			if len(lanes) == 0 {
+				return nil, fmt.Errorf("port %d has no hardware lanes", req.GetOid())
+			}
+			dev := fmt.Sprintf("eth%d", lanes[0])
+			if _, err := getInterface(dev); err != nil {
+				slog.InfoContext(ctx, "ignoring admin-state update for port without backing interface",
+					"oid", req.GetOid(), "device", dev, "admin_state", req.GetAdminState())
+				return &saipb.SetPortAttributeResponse{}, nil
+			}
+		}
+
 		stateReq := &fwdpb.PortStateRequest{
 			ContextId: &fwdpb.ContextId{Id: port.dataplane.ID()},
 			PortId:    &fwdpb.PortId{ObjectId: &fwdpb.ObjectId{Id: fmt.Sprint(req.GetOid())}},
@@ -709,7 +736,7 @@ func (port *port) RemovePort(ctx context.Context, req *saipb.RemovePortRequest)
 }
 
 func (port *port) Reset() {
-	slog.Info("reseting port")
+	slog.Info("resetting port")
 }
 
 type lagMember struct {
diff --git a/dataplane/saiserver/ports_test.go b/dataplane/saiserver/ports_test.go
index 6b853a41b..0458c523c 100644
--- a/dataplane/saiserver/ports_test.go
+++ b/dataplane/saiserver/ports_test.go
@@ -362,6 +362,41 @@ func TestSetPortAttribute(t *testing.T) {
 			}
 		})
 	}
+
+	t.Run("admin status ignored without backing interface", func(t *testing.T) {
+		oldGetInterface := getInterface
+		defer func() { getInterface = oldGetInterface }()
+
+		getInterface = func(name string) (*net.Interface, error) {
+			if name != "eth125" {
+				t.Errorf("getInterface() got %q, want eth125", name)
+			}
+			return nil, fmt.Errorf("link not found")
+		}
+
+		dplane := &fakeSwitchDataplane{}
+		c, mgr, stopFn := newTestPort(t, dplane, &dplaneopts.Options{
+			PortType: fwdpb.PortType_PORT_TYPE_KERNEL,
+		})
+		defer stopFn()
+
+		mgr.StoreAttributes(3, &saipb.PortAttribute{
+			OperStatus: saipb.PortOperStatus_PORT_OPER_STATUS_DOWN.Enum(),
+			HwLaneList: []uint32{125, 126, 127, 128},
+		})
+
+		_, err := c.SetPortAttribute(context.Background(), &saipb.SetPortAttributeRequest{
+			Oid:        3,
+			AdminState: proto.Bool(true),
+		})
+		if err != nil {
+			t.Fatalf("SetPortAttribute() unexpected error: %v", err)
+		}
+		if got := len(dplane.gotPortStateReq); got != 0 {
+			t.Fatalf("SetPortAttribute() sent %d PortState requests, want 0", got)
+		}
+	})
+
 	fecTests := []struct {
 		desc    string
 		req     *saipb.SetPortAttributeRequest