[bug-n1wxwkrtcnds] add pod link-local NUD source

Co-Authored-By: Codex (GPT-5) <noreply@openai.com>

pkg/agent/netns_linux_test.go

@@ -0,0 +1,25 @@
+//go:build linux
+
+package agent
+
+import (
+	"testing"
+
+	"golang.org/x/sys/unix"
+)
+
+func TestPodLinkLocalAddr(t *testing.T) {
+	addr := podLinkLocalAddr()
+	if got, want := addr.IP.String(), "fe80::2"; got != want {
+		t.Fatalf("pod link-local IP = %s, want %s", got, want)
+	}
+	if ones, bits := addr.Mask.Size(); ones != 64 || bits != 128 {
+		t.Fatalf("pod link-local mask = %d/%d, want 64/128", ones, bits)
+	}
+	if addr.Flags&unix.IFA_F_NODAD == 0 {
+		t.Fatal("pod link-local address must disable DAD")
+	}
+	if addr.IP.Equal(linkLocalGW) {
+		t.Fatal("pod and gateway link-local addresses must differ")
+	}
+}