fix(iosxr): configure L2 and L3 MTU for different interface types

internal/provider/cisco/iosxr/intf.go

@@ -12,6 +12,16 @@ import (
 	"github.com/ironcore-dev/network-operator/internal/transport/gnmiext"
 )
 
+// DefaultLinkMTU is calculated based on the default MTU of 1500 bytes for routed interfaces on IOS-XR and the addition of 14 bytes for the L2 header.
+// L2-payload + L2-header (1500 + 14)
+const DefaultLinkMTU int32 = 1514
+
+// DefaultL3MTU configures the maximum packet size of that protocol which includes the L3 header
+// For subinterfaces automatically
+// add 4 bytes for each VLAN tag configured on the sub-interface.
+// add 8 bytes for a IEEE 802.1Q tunneling (QinQ) sub-interface.
+const DefaultL3MTU int32 = 1500
+
 var (
 	bundleEtherRE       = regexp.MustCompile(`^(Bundle-Ether|bundle-ether)(\d+)(\.\d+)?$`)
 	physicalInterfaceRE = regexp.MustCompile(`^(TenGigE|TwentyFiveGigE|FortyGigE|HundredGigE|GigabitEthernet)(\d){1}(\/\d){2}(\/\d+){1}(.\d{1,5})?$`)
@@ -96,7 +106,7 @@ type Statistics struct {
 
 type IPv4Network struct {
 	Addresses AddressesIPv4 `json:"addresses"`
-	Mtu       uint16        `json:"mtu,omitzero"`
+	MTU       uint16        `json:"mtu,omitzero"`
 }
 
 type AddressesIPv4 struct {
@@ -109,7 +119,7 @@ type Primary struct {
 }
 
 type IPv6Network struct {
-	Mtu       uint16        `json:"mtu"`
+	MTU       uint16        `json:"mtu"`
 	Addresses AddressesIPv6 `json:"addresses"`
 }
 

internal/provider/cisco/iosxr/intf_test.go

@@ -32,10 +32,10 @@ func init() {
 					Netmask: "255.255.255.0",
 				},
 			},
-			Mtu: 1000,
+			MTU: 1000,
 		},
 		IPv6Network: IPv6Network{
-			Mtu: 2100,
+			MTU: 2100,
 			Addresses: AddressesIPv6{
 				RegularAddresses: RegularAddresses{
 					RegularAddress: []RegularAddress{

internal/provider/cisco/iosxr/provider.go

@@ -121,9 +121,20 @@ func (p *Provider) Reprovision(_ context.Context, conn *deviceutil.Connection) e
 	return errors.New("IOS XR Provider does not support reprovisioning")
 }
 
+// EnsureInterface configures the interface based on the provided request.
+// MTU configuration rules:
+//   - Physical interface:
+//     Configure L2 MTU and, if an IP address is present, configure L3 MTU.
+//   - Bundle interface:
+//     Configure only the L2 MTU.
+//   - Bundle member interface (Physical):
+//     Do not configure MTU settings directly.
+//     L2 MTU is inherited from the bundle interface, and L3 MTU is configured
+//     on the corresponding subinterface.
+//   - Subinterface (physical or bundle):
+//     Configure only the L3 MTU, using a default value of 1500 bytes.
 func (p *Provider) EnsureInterface(ctx context.Context, req *provider.EnsureInterfaceRequest) error {
 	// TODO(sven-rosenweig): Make use of the VRF information in the request to assign the interface to the correct VRF.
-	// FIXME(sven-rosenweig): Use the ExtractOwnerFromInterfaceName function in the ValidateInterfaceName function
 	name := req.Interface.Spec.Name
 
 	if err := ValidateInterfaceName(name); err != nil {
@@ -162,13 +173,11 @@ func (p *Provider) EnsureInterface(ctx context.Context, req *provider.EnsureInte
 			}
 			iface.IPv4Network = ipv4
 
-			if req.Interface.Spec.MTU != 0 {
-				mtu, err := NewMTU(name, req.Interface.Spec.MTU)
-				if err != nil {
-					return err
-				}
-				iface.MTUs = mtu
+			mtu, err := NewMTU(name, req.Interface.Spec.MTU)
+			if err != nil {
+				return err
 			}
+			iface.MTUs = mtu
 		}
 
 		// Make interface part of a bundle
@@ -274,14 +283,6 @@ func (p *Provider) EnsureInterface(ctx context.Context, req *provider.EnsureInte
 			iface.SubInterface.VlanIdentifier.VlanType = "vlan-type-dot1ad"
 		}
 
-		if req.Interface.Spec.MTU != 0 {
-			mtu, err := NewMTU(name, req.Interface.Spec.MTU)
-			if err != nil {
-				return err
-			}
-			iface.MTUs = mtu
-		}
-
 		ipv4, err := NewIPv4(req.Interface.Spec.IPv4)
 		if err != nil {
 			return err
@@ -303,8 +304,13 @@ func NewMTU(intName string, mtu int32) (MTUs, error) {
 		message := "failed to extract MTU owner from interface name" + intName
 		return MTUs{}, errors.New(message)
 	}
+
+	mtuValue := mtu
+	if mtu == 0 {
+		mtuValue = DefaultLinkMTU
+	}
 	return MTUs{MTU: []MTU{{
-		MTU:   mtu,
+		MTU:   mtuValue,
 		Owner: string(owner),
 	}}}, nil
 }
@@ -329,6 +335,7 @@ func NewIPv4(ips *v1alpha1.InterfaceIPv4) (IPv4Network, error) {
 				Netmask: netmask,
 			},
 		},
+		MTU: uint16(DefaultL3MTU),
 	}, nil
 }
 

internal/provider/cisco/iosxr/provider_test.go

@@ -218,3 +218,50 @@ func Test_GetState(t *testing.T) {
 		t.Fatalf("GetInterfaceStatus() expected OperStatus=true, got false")
 	}
 }
+
+func Test_NewMTU(t *testing.T) {
+	tests := []struct {
+		name          string
+		interfaceName string
+		mtu           int32
+		wantMTU       int32
+		wantErr       bool
+	}{
+		{
+			name:          "empty MTU should return default link MTU",
+			interfaceName: "TwentyFiveGigE0/0/0/14",
+			mtu:           0,
+			wantMTU:       DefaultLinkMTU,
+			wantErr:       false,
+		},
+		{
+			name:          "jumbo MTU value of 9000",
+			interfaceName: "TwentyFiveGigE0/0/0/14",
+			mtu:           9000,
+			wantMTU:       9000,
+			wantErr:       false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := NewMTU(tt.interfaceName, tt.mtu)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("NewMTU() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !tt.wantErr {
+				if len(got.MTU) == 0 {
+					t.Errorf("NewMTU() returned empty MTU slice")
+					return
+				}
+				if got.MTU[0].MTU != tt.wantMTU {
+					t.Errorf("NewMTU() MTU = %v, want %v", got.MTU[0].MTU, tt.wantMTU)
+				}
+				if got.MTU[0].Owner != "TwentyFiveGigE" {
+					t.Errorf("NewMTU() Owner = %v, want TwentyFiveGigE", got.MTU[0].Owner)
+				}
+			}
+		})
+	}
+}