osbase/net/dns/kubernetes: add Kubernetes DNS handler
This adds a DNS server handler for Kubernetes DNS service discovery. It
is partially based on the CoreDNS Kubernetes plugin. The query handler
however is written completely from scratch. The handler in the CoreDNS
plugin is very weird; it first handles each query type separately, and
generates msg.Service objects which then need to be converted to dns
records. The new implementation is much simpler, and also more correct:
It handles ANY queries, and follows the rules for NXDOMAIN (If a name is
NXDOMAIN for one qtype, it is NXDOMAIN for all qtypes, and subdomains of
the name are also NXDOMAIN.)
Change-Id: Id1d498ca5384a3b047587ed73e95e4871d82d499
Reviewed-on: https://review.monogon.dev/c/monogon/+/3259
Reviewed-by: Lorenz Brun <lorenz@monogon.tech>
Tested-by: Jenkins CI
diff --git a/osbase/net/dns/kubernetes/object/object.go b/osbase/net/dns/kubernetes/object/object.go
new file mode 100644
index 0000000..05724fc
--- /dev/null
+++ b/osbase/net/dns/kubernetes/object/object.go
@@ -0,0 +1,106 @@
+// Package object holds functions that convert the objects from the k8s API in
+// to a more memory efficient structures.
+//
+// Adding new fields to any of the structures defined in pod.go, endpoint.go
+// and service.go should not be done lightly as this increases the memory use
+// and will leads to OOMs in the k8s scale test.
+package object
+
+// Taken and modified from the Kubernetes plugin of CoreDNS, under Apache 2.0.
+
+import (
+ v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+ "k8s.io/apimachinery/pkg/runtime/schema"
+ "k8s.io/apimachinery/pkg/types"
+ "k8s.io/client-go/tools/cache"
+)
+
+// ToFunc converts one v1.Object to another v1.Object.
+type ToFunc func(v1.Object) (v1.Object, error)
+
+// ProcessorBuilder returns function to process cache events.
+type ProcessorBuilder func(cache.Indexer, cache.ResourceEventHandler) cache.ProcessFunc
+
+// Empty is an empty struct.
+type Empty struct{}
+
+// GetObjectKind implements the ObjectKind interface as a noop.
+func (e *Empty) GetObjectKind() schema.ObjectKind { return schema.EmptyObjectKind }
+
+// GetGenerateName implements the metav1.Object interface.
+func (e *Empty) GetGenerateName() string { return "" }
+
+// SetGenerateName implements the metav1.Object interface.
+func (e *Empty) SetGenerateName(name string) {}
+
+// GetUID implements the metav1.Object interface.
+func (e *Empty) GetUID() types.UID { return "" }
+
+// SetUID implements the metav1.Object interface.
+func (e *Empty) SetUID(uid types.UID) {}
+
+// GetGeneration implements the metav1.Object interface.
+func (e *Empty) GetGeneration() int64 { return 0 }
+
+// SetGeneration implements the metav1.Object interface.
+func (e *Empty) SetGeneration(generation int64) {}
+
+// GetSelfLink implements the metav1.Object interface.
+func (e *Empty) GetSelfLink() string { return "" }
+
+// SetSelfLink implements the metav1.Object interface.
+func (e *Empty) SetSelfLink(selfLink string) {}
+
+// GetCreationTimestamp implements the metav1.Object interface.
+func (e *Empty) GetCreationTimestamp() v1.Time { return v1.Time{} }
+
+// SetCreationTimestamp implements the metav1.Object interface.
+func (e *Empty) SetCreationTimestamp(timestamp v1.Time) {}
+
+// GetDeletionTimestamp implements the metav1.Object interface.
+func (e *Empty) GetDeletionTimestamp() *v1.Time { return &v1.Time{} }
+
+// SetDeletionTimestamp implements the metav1.Object interface.
+func (e *Empty) SetDeletionTimestamp(timestamp *v1.Time) {}
+
+// GetDeletionGracePeriodSeconds implements the metav1.Object interface.
+func (e *Empty) GetDeletionGracePeriodSeconds() *int64 { return nil }
+
+// SetDeletionGracePeriodSeconds implements the metav1.Object interface.
+func (e *Empty) SetDeletionGracePeriodSeconds(*int64) {}
+
+// GetLabels implements the metav1.Object interface.
+func (e *Empty) GetLabels() map[string]string { return nil }
+
+// SetLabels implements the metav1.Object interface.
+func (e *Empty) SetLabels(labels map[string]string) {}
+
+// GetAnnotations implements the metav1.Object interface.
+func (e *Empty) GetAnnotations() map[string]string { return nil }
+
+// SetAnnotations implements the metav1.Object interface.
+func (e *Empty) SetAnnotations(annotations map[string]string) {}
+
+// GetFinalizers implements the metav1.Object interface.
+func (e *Empty) GetFinalizers() []string { return nil }
+
+// SetFinalizers implements the metav1.Object interface.
+func (e *Empty) SetFinalizers(finalizers []string) {}
+
+// GetOwnerReferences implements the metav1.Object interface.
+func (e *Empty) GetOwnerReferences() []v1.OwnerReference { return nil }
+
+// SetOwnerReferences implements the metav1.Object interface.
+func (e *Empty) SetOwnerReferences([]v1.OwnerReference) {}
+
+// GetZZZ_DeprecatedClusterName implements the metav1.Object interface.
+func (e *Empty) GetZZZ_DeprecatedClusterName() string { return "" }
+
+// SetZZZ_DeprecatedClusterName implements the metav1.Object interface.
+func (e *Empty) SetZZZ_DeprecatedClusterName(clusterName string) {}
+
+// GetManagedFields implements the metav1.Object interface.
+func (e *Empty) GetManagedFields() []v1.ManagedFieldsEntry { return nil }
+
+// SetManagedFields implements the metav1.Object interface.
+func (e *Empty) SetManagedFields(managedFields []v1.ManagedFieldsEntry) {}