use netns package from c/common

The netns package was moved to c/common so we should use this and remove
the package from podman.

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

vendor/github.com/containers/common/pkg/netns/netns_linux.go

@@ -0,0 +1,210 @@
+// Copyright 2018 CNI 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
+//
+//     https://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.
+
+// This file was originally a part of the containernetworking/plugins
+// repository.
+// It was copied here and modified for local use by the libpod maintainers.
+
+package netns
+
+import (
+	"crypto/rand"
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+
+	"github.com/containernetworking/plugins/pkg/ns"
+	"github.com/containers/common/pkg/util"
+	"github.com/containers/storage/pkg/unshare"
+	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/unix"
+)
+
+// GetNSRunDir returns the dir of where to create the netNS. When running
+// rootless, it needs to be at a location writable by user.
+func GetNSRunDir() (string, error) {
+	if unshare.IsRootless() {
+		rootlessDir, err := util.GetRuntimeDir()
+		if err != nil {
+			return "", err
+		}
+		return filepath.Join(rootlessDir, "netns"), nil
+	}
+	return "/run/netns", nil
+}
+
+// NewNS creates a new persistent (bind-mounted) network namespace and returns
+// an object representing that namespace, without switching to it.
+func NewNS() (ns.NetNS, error) {
+	b := make([]byte, 16)
+	_, err := rand.Reader.Read(b)
+	if err != nil {
+		return nil, fmt.Errorf("failed to generate random netns name: %v", err)
+	}
+	nsName := fmt.Sprintf("netns-%x-%x-%x-%x-%x", b[0:4], b[4:6], b[6:8], b[8:10], b[10:])
+	return NewNSWithName(nsName)
+}
+
+// NewNSWithName creates a new persistent (bind-mounted) network namespace and returns
+// an object representing that namespace, without switching to it.
+func NewNSWithName(name string) (ns.NetNS, error) {
+	nsRunDir, err := GetNSRunDir()
+	if err != nil {
+		return nil, err
+	}
+
+	// Create the directory for mounting network namespaces
+	// This needs to be a shared mountpoint in case it is mounted in to
+	// other namespaces (containers)
+	err = os.MkdirAll(nsRunDir, 0755)
+	if err != nil {
+		return nil, err
+	}
+
+	// Remount the namespace directory shared. This will fail if it is not
+	// already a mountpoint, so bind-mount it on to itself to "upgrade" it
+	// to a mountpoint.
+	err = unix.Mount("", nsRunDir, "none", unix.MS_SHARED|unix.MS_REC, "")
+	if err != nil {
+		if err != unix.EINVAL {
+			return nil, fmt.Errorf("mount --make-rshared %s failed: %q", nsRunDir, err)
+		}
+
+		// Recursively remount /run/netns on itself. The recursive flag is
+		// so that any existing netns bindmounts are carried over.
+		err = unix.Mount(nsRunDir, nsRunDir, "none", unix.MS_BIND|unix.MS_REC, "")
+		if err != nil {
+			return nil, fmt.Errorf("mount --rbind %s %s failed: %q", nsRunDir, nsRunDir, err)
+		}
+
+		// Now we can make it shared
+		err = unix.Mount("", nsRunDir, "none", unix.MS_SHARED|unix.MS_REC, "")
+		if err != nil {
+			return nil, fmt.Errorf("mount --make-rshared %s failed: %q", nsRunDir, err)
+		}
+	}
+
+	// create an empty file at the mount point
+	nsPath := path.Join(nsRunDir, name)
+	mountPointFd, err := os.Create(nsPath)
+	if err != nil {
+		return nil, err
+	}
+	if err := mountPointFd.Close(); err != nil {
+		return nil, err
+	}
+
+	// Ensure the mount point is cleaned up on errors; if the namespace
+	// was successfully mounted this will have no effect because the file
+	// is in-use
+	defer func() {
+		_ = os.RemoveAll(nsPath)
+	}()
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+
+	// do namespace work in a dedicated goroutine, so that we can safely
+	// Lock/Unlock OSThread without upsetting the lock/unlock state of
+	// the caller of this function
+	go (func() {
+		defer wg.Done()
+		runtime.LockOSThread()
+		// Don't unlock. By not unlocking, golang will kill the OS thread when the
+		// goroutine is done (for go1.10+)
+
+		threadNsPath := getCurrentThreadNetNSPath()
+
+		var origNS ns.NetNS
+		origNS, err = ns.GetNS(threadNsPath)
+		if err != nil {
+			logrus.Warnf("Cannot open current network namespace %s: %q", threadNsPath, err)
+			return
+		}
+		defer func() {
+			if err := origNS.Close(); err != nil {
+				logrus.Errorf("Unable to close namespace: %q", err)
+			}
+		}()
+
+		// create a new netns on the current thread
+		err = unix.Unshare(unix.CLONE_NEWNET)
+		if err != nil {
+			logrus.Warnf("Cannot create a new network namespace: %q", err)
+			return
+		}
+
+		// Put this thread back to the orig ns, since it might get reused (pre go1.10)
+		defer func() {
+			if err := origNS.Set(); err != nil {
+				if unshare.IsRootless() && strings.Contains(err.Error(), "operation not permitted") {
+					// When running in rootless mode it will fail to re-join
+					// the network namespace owned by root on the host.
+					return
+				}
+				logrus.Warnf("Unable to reset namespace: %q", err)
+			}
+		}()
+
+		// bind mount the netns from the current thread (from /proc) onto the
+		// mount point. This causes the namespace to persist, even when there
+		// are no threads in the ns. Make this a shared mount; it needs to be
+		// back-propagated to the host
+		err = unix.Mount(threadNsPath, nsPath, "none", unix.MS_BIND|unix.MS_SHARED|unix.MS_REC, "")
+		if err != nil {
+			err = fmt.Errorf("failed to bind mount ns at %s: %v", nsPath, err)
+		}
+	})()
+	wg.Wait()
+
+	if err != nil {
+		return nil, fmt.Errorf("failed to create namespace: %v", err)
+	}
+
+	return ns.GetNS(nsPath)
+}
+
+// UnmountNS unmounts the NS held by the netns object
+func UnmountNS(netns ns.NetNS) error {
+	nsRunDir, err := GetNSRunDir()
+	if err != nil {
+		return err
+	}
+
+	nsPath := netns.Path()
+	// Only unmount if it's been bind-mounted (don't touch namespaces in /proc...)
+	if strings.HasPrefix(nsPath, nsRunDir) {
+		if err := unix.Unmount(nsPath, unix.MNT_DETACH); err != nil {
+			return fmt.Errorf("failed to unmount NS: at %s: %v", nsPath, err)
+		}
+
+		if err := os.Remove(nsPath); err != nil {
+			return fmt.Errorf("failed to remove ns path %s: %v", nsPath, err)
+		}
+	}
+
+	return nil
+}
+
+// getCurrentThreadNetNSPath copied from pkg/ns
+func getCurrentThreadNetNSPath() string {
+	// /proc/self/ns/net returns the namespace of the main thread, not
+	// of whatever thread this goroutine is running on.  Make sure we
+	// use the thread's net namespace since the thread is switching around
+	return fmt.Sprintf("/proc/%d/task/%d/ns/net", os.Getpid(), unix.Gettid())
+}