cisco-nxos-provider: configure ISIS

Configure ISIS on a NXOS device allowing the parametrization of: 1) the
instance name, 2) the Network Entitity Title, 3) the type ("Level1",
"Level2", and "Level12"), 4) the number of seconds of the on-startup
overload bit, and 5) two address families: IPv4 and IPv6 unicast. With
this package we support the minimum configuration required to build the
underlay as in this example:

```
router isis UNDERLAY
  net 49.0001.0001.0000.0001.00
  is-type level-1
  set-overload-bit on-startup 61
  address-family ipv4 unicast
  address-family ipv6 unicast
```

Author: nikatza

internal/provider/cisco/nxos/isis/isis.go

@@ -0,0 +1,106 @@
+// SPDX-FileCopyrightText: 2025 SAP SE or an SAP affiliate company
+// SPDX-License-Identifier: Apache-2.0
+
+package isis
+
+import (
+	"fmt"
+
+	"github.com/openconfig/ygot/ygot"
+
+	nxos "github.com/ironcore-dev/network-operator/internal/provider/cisco/nxos/genyang"
+	"github.com/ironcore-dev/network-operator/internal/provider/cisco/nxos/gnmiext"
+)
+
+var _ gnmiext.DeviceConf = (*ISIS)(nil)
+
+type ISIS struct {
+	// name of the ISIS process, e.g., `router isis UNDERLAY`
+	Name string
+	// Network Entity Title, e.g., `net 49.0001.0001.0000.0001.00`
+	NET string
+	// Level is type. e.g., `is-type level-1`
+	Level ISISType
+	// overloadbit options
+	OverloadBit *OverloadBit
+	// supported families
+	AddressFamilies []ISISAFType
+}
+
+type OverloadBit struct {
+	OnStartup uint32
+}
+
+//go:generate stringer -type=ISISType
+type ISISType int
+
+const (
+	Level1 ISISType = iota + 1
+	Level2
+	Level12
+)
+
+type ISISAFType int
+
+const (
+	IPv4Unicast = iota + 1
+	IPv6Unicast
+)
+
+func (i *ISIS) ToYGOT(_ gnmiext.Client) ([]gnmiext.Update, error) {
+	if i.Name == "" {
+		return nil, fmt.Errorf("isis: name must be set")
+	}
+	if i.NET == "" {
+		return nil, fmt.Errorf("isis: NET must be set")
+	}
+	instList := &nxos.Cisco_NX_OSDevice_System_IsisItems_InstItems_InstList{
+		Name: ygot.String(i.Name),
+	}
+
+	domList := instList.GetOrCreateDomItems().GetOrCreateDomList("default")
+	domList.Net = ygot.String(i.NET)
+	switch i.Level {
+	case Level1:
+		domList.IsType = nxos.Cisco_NX_OSDevice_Isis_IsT_l1
+	case Level2:
+		domList.IsType = nxos.Cisco_NX_OSDevice_Isis_IsT_l2
+	case Level12:
+		domList.IsType = nxos.Cisco_NX_OSDevice_Isis_IsT_l12
+	default:
+		return nil, fmt.Errorf("isis: invalid level type %d", i.Level)
+	}
+
+	if i.OverloadBit != nil {
+		olItems := domList.GetOrCreateOverloadItems()
+		olItems.AdminSt = nxos.Cisco_NX_OSDevice_Isis_OverloadAdminSt_bootup
+		olItems.StartupTime = ygot.Uint32(i.OverloadBit.OnStartup)
+	}
+
+	for af := range i.AddressFamilies {
+		switch i.AddressFamilies[af] {
+		case IPv4Unicast:
+			domList.GetOrCreateAfItems().GetOrCreateDomAfList(nxos.Cisco_NX_OSDevice_Isis_AfT_v4)
+		case IPv6Unicast:
+			domList.GetOrCreateAfItems().GetOrCreateDomAfList(nxos.Cisco_NX_OSDevice_Isis_AfT_v6)
+		default:
+			return nil, fmt.Errorf("isis: invalid address family type %d", i.AddressFamilies[af])
+		}
+	}
+
+	return []gnmiext.Update{
+		gnmiext.ReplacingUpdate{
+			XPath: "System/isis-items/inst-items/Inst-list[name=" + i.Name + "]",
+			Value: instList,
+		},
+	}, nil
+}
+
+// Reset removes the ISIS process with the given name from the device.
+func (i *ISIS) Reset(_ gnmiext.Client) ([]gnmiext.Update, error) {
+	return []gnmiext.Update{
+		gnmiext.DeletingUpdate{
+			XPath: "System/isis-items/inst-items/Inst-list[name=" + i.Name + "]",
+		},
+	}, nil
+}

internal/provider/cisco/nxos/isis/isis_test.go

@@ -0,0 +1,168 @@
+// SPDX-FileCopyrightText: 2025 SAP SE or an SAP affiliate company
+// SPDX-License-Identifier: Apache-2.0
+package isis
+
+import (
+	"testing"
+
+	nxos "github.com/ironcore-dev/network-operator/internal/provider/cisco/nxos/genyang"
+	"github.com/ironcore-dev/network-operator/internal/provider/cisco/nxos/gnmiext"
+)
+
+// TestToYGOT tests a configuration with only ISIS for IPv6
+func TestToYGOT(t *testing.T) {
+	isis := &ISIS{
+		Name:  "UNDERLAY",
+		NET:   "49.0001.0001.0000.0001.00",
+		Level: Level12,
+		OverloadBit: &OverloadBit{
+			OnStartup: 61, // seconds
+		},
+		AddressFamilies: []ISISAFType{
+			IPv6Unicast,
+		},
+	}
+	got, err := isis.ToYGOT(nil)
+	if err != nil {
+		t.Fatalf("ToYGOT() error = %v", err)
+	}
+	if len(got) != 1 {
+		t.Fatalf("ToYGOT() expected 1 update, got %d", len(got))
+	}
+	update, ok := got[0].(gnmiext.ReplacingUpdate)
+	if !ok {
+		t.Errorf("expected value to be of type ReplacingUpdate")
+	}
+	if update.XPath != "System/isis-items/inst-items/Inst-list[name=UNDERLAY]" {
+		t.Errorf("expected XPath 'System/isis-items/inst-items/Inst-list[name=UNDERLAY]', got %s", update.XPath)
+	}
+	instList, ok := update.Value.(*nxos.Cisco_NX_OSDevice_System_IsisItems_InstItems_InstList)
+	if !ok {
+		t.Errorf("expected value to be of type *nxos.Cisco_NX_OSDevice_System_IsisItems_InstItems_InstList")
+	}
+	if instList.Name == nil || *instList.Name != "UNDERLAY" {
+		t.Errorf("expected instList.Name to be 'UNDERLAY', got %v", instList.Name)
+	}
+	domList := instList.GetDomItems().GetDomList("default")
+	if domList == nil {
+		t.Fatalf("expected domList for default to be present")
+	}
+	if *domList.Net != isis.NET {
+		t.Errorf("Net not set correctly")
+	}
+	if domList.IsType != nxos.Cisco_NX_OSDevice_Isis_IsT_l12 {
+		t.Errorf("Level not set correctly")
+	}
+	if domList.GetOverloadItems().AdminSt != nxos.Cisco_NX_OSDevice_Isis_OverloadAdminSt_bootup {
+		t.Errorf("OverloadBit AdminSt not set correctly")
+	}
+	if *domList.GetOverloadItems().StartupTime != isis.OverloadBit.OnStartup {
+		t.Errorf("OverloadBit StartupTime not set correctly")
+	}
+	if len(domList.GetAfItems().DomAfList) != 1 {
+		t.Errorf("expected 1 address family")
+	}
+	if domList.GetAfItems().GetDomAfList(nxos.Cisco_NX_OSDevice_Isis_AfT_v6) == nil {
+		t.Errorf("expected IPv6 unicast to be enabled, but it is disabled")
+	}
+}
+
+func TestISIS_ToYGOT_InvalidLevel(t *testing.T) {
+	isis := &ISIS{
+		Name:            "UNDERLAY",
+		NET:             "49.0001.0001.0000.0001.00",
+		Level:           ISISType(99),
+		AddressFamilies: []ISISAFType{IPv4Unicast},
+	}
+	_, err := isis.ToYGOT(&gnmiext.ClientMock{})
+	if err == nil {
+		t.Error("expected error for invalid level, got nil")
+	}
+}
+
+func TestISIS_ToYGOT_InvalidAddressFamily(t *testing.T) {
+	isis := &ISIS{
+		Name:            "UNDERLAY",
+		NET:             "49.0001.0001.0000.0001.00",
+		Level:           Level1,
+		AddressFamilies: []ISISAFType{ISISAFType(99)},
+	}
+	_, err := isis.ToYGOT(&gnmiext.ClientMock{})
+	if err == nil {
+		t.Error("expected error for invalid address family, got nil")
+	}
+}
+
+func TestISIS_ToYGOT_NoOverloadBit(t *testing.T) {
+	isis := &ISIS{
+		Name:            "UNDERLAY",
+		NET:             "49.0001.0001.0000.0001.00",
+		Level:           Level1,
+		AddressFamilies: []ISISAFType{IPv4Unicast},
+		OverloadBit:     nil,
+	}
+	_, err := isis.ToYGOT(&gnmiext.ClientMock{})
+	if err != nil {
+		t.Errorf("unexpected error when OverloadBit is nil: %v", err)
+	}
+}
+
+func TestISIS_ToYGOT_EmptyAddressFamilies(t *testing.T) {
+	isis := &ISIS{
+		Name:            "UNDERLAY",
+		NET:             "49.0001.0001.0000.0001.00",
+		Level:           Level1,
+		AddressFamilies: []ISISAFType{},
+	}
+	updates, err := isis.ToYGOT(&gnmiext.ClientMock{})
+	if err != nil {
+		t.Errorf("unexpected error for empty address families: %v", err)
+	}
+	if len(updates) != 1 {
+		t.Errorf("expected 1 update, got %d", len(updates))
+	}
+}
+
+func TestISIS_Reset(t *testing.T) {
+	isis := &ISIS{Name: "UNDERLAY"}
+	updates, err := isis.Reset(&gnmiext.ClientMock{})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if len(updates) != 1 {
+		t.Fatalf("expected 1 update, got %d", len(updates))
+	}
+	du, ok := updates[0].(gnmiext.DeletingUpdate)
+	if !ok {
+		t.Fatalf("expected DeletingUpdate, got %T", updates[0])
+	}
+	expectedXPath := "System/isis-items/inst-items/Inst-list[name=UNDERLAY]"
+	if du.XPath != expectedXPath {
+		t.Errorf("expected XPath %q, got %q", expectedXPath, du.XPath)
+	}
+}
+
+func TestISIS_MissingMandatoryFields(t *testing.T) {
+	t.Run("missing name", func(t *testing.T) {
+		isis := &ISIS{
+			NET:             "49.0001.0001.0000.0001.00",
+			Level:           Level1,
+			AddressFamilies: []ISISAFType{IPv4Unicast},
+		}
+		_, err := isis.ToYGOT(&gnmiext.ClientMock{})
+		if err == nil {
+			t.Error("expected error for empty name, got nil")
+		}
+	})
+	t.Run("missing NET", func(t *testing.T) {
+		isis := &ISIS{
+			Name:            "UNDERLAY",
+			Level:           Level1,
+			AddressFamilies: []ISISAFType{IPv4Unicast},
+		}
+		_, err := isis.ToYGOT(&gnmiext.ClientMock{})
+		if err == nil {
+			t.Error("expected error for empty NET, got nil")
+		}
+	})
+}