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// Copyright 2015-2017 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
//
// 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 ns
import (
"crypto/rand"
"fmt"
"os"
"path"
"runtime"
"sync"
"golang.org/x/sys/unix"
)
// Returns an object representing the current OS thread's network namespace
func GetCurrentNS() (NetNS, error) {
return GetNS(getCurrentThreadNetNSPath())
}
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())
}
// Creates a new persistent network namespace and returns an object
// representing that namespace, without switching to it
func NewNS() (NetNS, error) {
const nsRunDir = "/var/run/netns"
b := make([]byte, 16)
_, err := rand.Reader.Read(b)
if err != nil {
return nil, fmt.Errorf("failed to generate random netns name: %v", err)
}
err = os.MkdirAll(nsRunDir, 0755)
if err != nil {
return nil, err
}
// create an empty file at the mount point
nsName := fmt.Sprintf("cni-%x-%x-%x-%x-%x", b[0:4], b[4:6], b[6:8], b[8:10], b[10:])
nsPath := path.Join(nsRunDir, nsName)
mountPointFd, err := os.Create(nsPath)
if err != nil {
return nil, err
}
mountPointFd.Close()
// 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 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
var fd *os.File
go (func() {
defer wg.Done()
runtime.LockOSThread()
var origNS NetNS
origNS, err = GetNS(getCurrentThreadNetNSPath())
if err != nil {
return
}
defer origNS.Close()
// create a new netns on the current thread
err = unix.Unshare(unix.CLONE_NEWNET)
if err != nil {
return
}
defer origNS.Set()
// bind mount the new netns from the current thread onto the mount point
err = unix.Mount(getCurrentThreadNetNSPath(), nsPath, "none", unix.MS_BIND, "")
if err != nil {
return
}
fd, err = os.Open(nsPath)
if err != nil {
return
}
})()
wg.Wait()
if err != nil {
unix.Unmount(nsPath, unix.MNT_DETACH)
return nil, fmt.Errorf("failed to create namespace: %v", err)
}
return &netNS{file: fd, mounted: true}, nil
}
func (ns *netNS) Close() error {
if err := ns.errorIfClosed(); err != nil {
return err
}
if err := ns.file.Close(); err != nil {
return fmt.Errorf("Failed to close %q: %v", ns.file.Name(), err)
}
ns.closed = true
if ns.mounted {
if err := unix.Unmount(ns.file.Name(), unix.MNT_DETACH); err != nil {
return fmt.Errorf("Failed to unmount namespace %s: %v", ns.file.Name(), err)
}
if err := os.RemoveAll(ns.file.Name()); err != nil {
return fmt.Errorf("Failed to clean up namespace %s: %v", ns.file.Name(), err)
}
ns.mounted = false
}
return nil
}
func (ns *netNS) Set() error {
if err := ns.errorIfClosed(); err != nil {
return err
}
if err := unix.Setns(int(ns.Fd()), unix.CLONE_NEWNET); err != nil {
return fmt.Errorf("Error switching to ns %v: %v", ns.file.Name(), err)
}
return nil
}
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