Move namespaces to pkg/namespaces

Signed-off-by: Derek McGowan <derek@mcg.dev>

pkg/namespaces/context.go

@@ -0,0 +1,78 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package namespaces
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/containerd/containerd/v2/pkg/errdefs"
+	"github.com/containerd/containerd/v2/pkg/identifiers"
+)
+
+const (
+	// NamespaceEnvVar is the environment variable key name
+	NamespaceEnvVar = "CONTAINERD_NAMESPACE"
+	// Default is the name of the default namespace
+	Default = "default"
+)
+
+type namespaceKey struct{}
+
+// WithNamespace sets a given namespace on the context
+func WithNamespace(ctx context.Context, namespace string) context.Context {
+	ctx = context.WithValue(ctx, namespaceKey{}, namespace) // set our key for namespace
+	// also store on the grpc and ttrpc headers so it gets picked up by any clients that
+	// are using this.
+	return withTTRPCNamespaceHeader(withGRPCNamespaceHeader(ctx, namespace), namespace)
+}
+
+// NamespaceFromEnv uses the namespace defined in CONTAINERD_NAMESPACE or
+// default
+func NamespaceFromEnv(ctx context.Context) context.Context {
+	namespace := os.Getenv(NamespaceEnvVar)
+	if namespace == "" {
+		namespace = Default
+	}
+	return WithNamespace(ctx, namespace)
+}
+
+// Namespace returns the namespace from the context.
+//
+// The namespace is not guaranteed to be valid.
+func Namespace(ctx context.Context) (string, bool) {
+	namespace, ok := ctx.Value(namespaceKey{}).(string)
+	if !ok {
+		if namespace, ok = fromGRPCHeader(ctx); !ok {
+			return fromTTRPCHeader(ctx)
+		}
+	}
+	return namespace, ok
+}
+
+// NamespaceRequired returns the valid namespace from the context or an error.
+func NamespaceRequired(ctx context.Context) (string, error) {
+	namespace, ok := Namespace(ctx)
+	if !ok || namespace == "" {
+		return "", fmt.Errorf("namespace is required: %w", errdefs.ErrFailedPrecondition)
+	}
+	if err := identifiers.Validate(namespace); err != nil {
+		return "", fmt.Errorf("namespace validation: %w", err)
+	}
+	return namespace, nil
+}