Fix bgp_attach_ip_to_interface not applied to Service VIPs (#1744)

shouldAddServiceIP() checks BGPAttachIPToInterface on a per-service
config struct. NewInstance() builds that struct fresh for each Service,
copying over most fields from the global config, missing this one. As
a result the flag has no effect regardless of its value, and BGP-mode
Service VIPs are never bound to the interface.

Copy the field at both construction sites where it's built, and add
a regression test covering the propagation.

Signed-off-by: Justin Cichra <jrcichra@yahoo.com>

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Fixed
+- Propagate `bgp_attach_ip_to_interface` into per-service config so it attaches BGP-mode Service VIPs to the interface as configured.
 - Add a configurable kube-vip instance name and use it to isolate internal nftables egress tables, persist table ownership on Services, and migrate per-Service chains without affecting other deployments. Fixes #1634.
 - Retry on 403 Forbidden and 401 Unauthorized in `ServicesWatcher` at startup with exponential backoff. Fixes #1464.
 - Reintroduce BGP config via node annotations. Fixes #1488.

pkg/instance/instance.go

@@ -203,6 +203,7 @@ func NewInstance(ctx context.Context, svc *v1.Service, config *kubevip.Config,
 			SingleNode:                  true,
 			EnableARP:                   config.EnableARP,
 			EnableBGP:                   config.EnableBGP,
+			BGPAttachIPToInterface:      config.BGPAttachIPToInterface,
 			VIPSubnet:                   subnet,
 			EnableRoutingTable:          config.EnableRoutingTable,
 			RoutingTableID:              config.RoutingTableID,
@@ -269,6 +270,7 @@ func NewInstance(ctx context.Context, svc *v1.Service, config *kubevip.Config,
 			SingleNode:             true,
 			EnableARP:              config.EnableARP,
 			EnableBGP:              config.EnableBGP,
+			BGPAttachIPToInterface: config.BGPAttachIPToInterface,
 			VIPSubnet:              config.VIPSubnet,
 			EnableRoutingTable:     config.EnableRoutingTable,
 			RoutingTableID:         config.RoutingTableID,

pkg/instance/instance_bgp_attach_test.go

@@ -0,0 +1,62 @@
+package instance_test
+
+import (
+	"context"
+	"sync"
+	"testing"
+
+	v1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+
+	"github.com/kube-vip/kube-vip/pkg/arp"
+	"github.com/kube-vip/kube-vip/pkg/instance"
+	"github.com/kube-vip/kube-vip/pkg/kubevip"
+	"github.com/kube-vip/kube-vip/pkg/networkinterface"
+	"github.com/kube-vip/kube-vip/pkg/route"
+)
+
+func TestNewInstance_PropagatesBGPAttachIPToInterface(t *testing.T) {
+	tests := []struct {
+		name   string
+		attach bool
+	}{
+		{name: "attach enabled is propagated", attach: true},
+		{name: "attach disabled is propagated", attach: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			globalConfig := &kubevip.Config{
+				Interface:              "lo",
+				VIPSubnet:              "32",
+				EnableBGP:              true,
+				BGPAttachIPToInterface: tt.attach,
+			}
+
+			svc := &v1.Service{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "test-svc",
+					Namespace: "default",
+					Annotations: map[string]string{
+						kubevip.LoadbalancerIPAnnotation: "10.0.1.2",
+					},
+				},
+			}
+
+			inst, err := instance.NewInstance(context.Background(), svc, globalConfig,
+				networkinterface.NewManager(), arp.NewManager(globalConfig), route.NewManager(),
+				nil, &sync.WaitGroup{})
+			if err != nil {
+				t.Fatalf("NewInstance() error = %v", err)
+			}
+
+			if len(inst.VIPConfigs) != 1 {
+				t.Fatalf("VIPConfigs len = %d, want 1", len(inst.VIPConfigs))
+			}
+
+			if got := inst.VIPConfigs[0].BGPAttachIPToInterface; got != tt.attach {
+				t.Fatalf("BGPAttachIPToInterface = %t, want %t", got, tt.attach)
+			}
+		})
+	}
+}