Fix lint in Unix environments

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

pkg/netns/netns_linux.go

@@ -1,5 +1,3 @@
-// +build !windows
-
 /*
    Copyright The containerd Authors.
 
@@ -25,6 +23,7 @@
 //     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
@@ -40,12 +39,11 @@ import (
 	"runtime"
 	"sync"
 
+	"github.com/containerd/containerd/mount"
 	cnins "github.com/containernetworking/plugins/pkg/ns"
 	"github.com/docker/docker/pkg/symlink"
 	"github.com/pkg/errors"
 	"golang.org/x/sys/unix"
-
-	osinterface "github.com/containerd/cri/pkg/os"
 )
 
 const nsRunDir = "/var/run/netns"
@@ -141,7 +139,7 @@ func unmountNS(path string) error {
 	if err != nil {
 		return errors.Wrap(err, "failed to follow symlink")
 	}
-	if err := osinterface.Unmount(path); err != nil && !os.IsNotExist(err) {
+	if err := mount.Unmount(path, unix.MNT_DETACH); err != nil && !os.IsNotExist(err) {
 		return errors.Wrap(err, "failed to umount netns")
 	}
 	if err := os.RemoveAll(path); err != nil {

pkg/netns/netns_other.go

@@ -0,0 +1,58 @@
+// +build !windows,!linux
+
+/*
+   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 netns
+
+import (
+	"github.com/pkg/errors"
+)
+
+var errNotImplementedOnUnix = errors.New("not implemented on unix")
+
+// NetNS holds network namespace.
+type NetNS struct {
+	path string
+}
+
+// NewNetNS creates a network namespace.
+func NewNetNS() (*NetNS, error) {
+	return nil, errNotImplementedOnUnix
+}
+
+// LoadNetNS loads existing network namespace.
+func LoadNetNS(path string) *NetNS {
+	return &NetNS{path: path}
+}
+
+// Remove removes network namepace. Remove is idempotent, meaning it might
+// be invoked multiple times and provides consistent result.
+func (n *NetNS) Remove() error {
+	return errNotImplementedOnUnix
+}
+
+// Closed checks whether the network namespace has been closed.
+func (n *NetNS) Closed() (bool, error) {
+	return false, errNotImplementedOnUnix
+}
+
+// GetPath returns network namespace path for sandbox container
+func (n *NetNS) GetPath() string {
+	return n.path
+}
+
+// NOTE: Do function is not supported.