ipn/store: add common package for instantiating ipn.StateStores

Also move KubeStore and MemStore into their own package.

RELNOTE: tsnet now supports providing a custom ipn.StateStore.

Signed-off-by: Maisem Ali <maisem@tailscale.com>

ipn/store/kubestore/store_kube.go

@@ -0,0 +1,85 @@
+// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package kubestore contains an ipn.StateStore implementation using Kubernetes Secrets.
+
+package kubestore
+
+import (
+	"context"
+	"time"
+
+	"tailscale.com/ipn"
+	"tailscale.com/kube"
+	"tailscale.com/types/logger"
+)
+
+// Store is an ipn.StateStore that uses a Kubernetes Secret for persistence.
+type Store struct {
+	client     *kube.Client
+	secretName string
+}
+
+// New returns a new Store that persists to the named secret.
+func New(_ logger.Logf, secretName string) (*Store, error) {
+	c, err := kube.New()
+	if err != nil {
+		return nil, err
+	}
+	return &Store{
+		client:     c,
+		secretName: secretName,
+	}, nil
+}
+
+func (s *Store) String() string { return "kube.Store" }
+
+// ReadState implements the StateStore interface.
+func (s *Store) ReadState(id ipn.StateKey) ([]byte, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	secret, err := s.client.GetSecret(ctx, s.secretName)
+	if err != nil {
+		if st, ok := err.(*kube.Status); ok && st.Code == 404 {
+			return nil, ipn.ErrStateNotExist
+		}
+		return nil, err
+	}
+	b, ok := secret.Data[string(id)]
+	if !ok {
+		return nil, ipn.ErrStateNotExist
+	}
+	return b, nil
+}
+
+// WriteState implements the StateStore interface.
+func (s *Store) WriteState(id ipn.StateKey, bs []byte) error {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	secret, err := s.client.GetSecret(ctx, s.secretName)
+	if err != nil {
+		if st, ok := err.(*kube.Status); ok && st.Code == 404 {
+			return s.client.CreateSecret(ctx, &kube.Secret{
+				TypeMeta: kube.TypeMeta{
+					APIVersion: "v1",
+					Kind:       "Secret",
+				},
+				ObjectMeta: kube.ObjectMeta{
+					Name: s.secretName,
+				},
+				Data: map[string][]byte{
+					string(id): bs,
+				},
+			})
+		}
+		return err
+	}
+	secret.Data[string(id)] = bs
+	if err := s.client.UpdateSecret(ctx, secret); err != nil {
+		return err
+	}
+	return err
+}