150 lines
3.8 KiB
Go
150 lines
3.8 KiB
Go
// Copyright 2015-2017 CNI authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package ns
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import (
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"crypto/rand"
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"fmt"
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"os"
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"path"
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"runtime"
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"sync"
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"golang.org/x/sys/unix"
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)
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// Returns an object representing the current OS thread's network namespace
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func GetCurrentNS() (NetNS, error) {
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return GetNS(getCurrentThreadNetNSPath())
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}
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func getCurrentThreadNetNSPath() string {
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// /proc/self/ns/net returns the namespace of the main thread, not
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// of whatever thread this goroutine is running on. Make sure we
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// use the thread's net namespace since the thread is switching around
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return fmt.Sprintf("/proc/%d/task/%d/ns/net", os.Getpid(), unix.Gettid())
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}
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// Creates a new persistent network namespace and returns an object
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// representing that namespace, without switching to it
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func NewNS() (NetNS, error) {
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const nsRunDir = "/var/run/netns"
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b := make([]byte, 16)
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_, err := rand.Reader.Read(b)
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if err != nil {
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return nil, fmt.Errorf("failed to generate random netns name: %v", err)
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}
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err = os.MkdirAll(nsRunDir, 0755)
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if err != nil {
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return nil, err
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}
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// create an empty file at the mount point
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nsName := fmt.Sprintf("cni-%x-%x-%x-%x-%x", b[0:4], b[4:6], b[6:8], b[8:10], b[10:])
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nsPath := path.Join(nsRunDir, nsName)
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mountPointFd, err := os.Create(nsPath)
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if err != nil {
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return nil, err
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}
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mountPointFd.Close()
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// Ensure the mount point is cleaned up on errors; if the namespace
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// was successfully mounted this will have no effect because the file
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// is in-use
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defer os.RemoveAll(nsPath)
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var wg sync.WaitGroup
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wg.Add(1)
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// do namespace work in a dedicated goroutine, so that we can safely
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// Lock/Unlock OSThread without upsetting the lock/unlock state of
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// the caller of this function
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var fd *os.File
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go (func() {
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defer wg.Done()
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runtime.LockOSThread()
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var origNS NetNS
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origNS, err = GetNS(getCurrentThreadNetNSPath())
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if err != nil {
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return
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}
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defer origNS.Close()
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// create a new netns on the current thread
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err = unix.Unshare(unix.CLONE_NEWNET)
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if err != nil {
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return
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}
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defer origNS.Set()
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// bind mount the new netns from the current thread onto the mount point
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err = unix.Mount(getCurrentThreadNetNSPath(), nsPath, "none", unix.MS_BIND, "")
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if err != nil {
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return
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}
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fd, err = os.Open(nsPath)
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if err != nil {
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return
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}
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})()
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wg.Wait()
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if err != nil {
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unix.Unmount(nsPath, unix.MNT_DETACH)
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return nil, fmt.Errorf("failed to create namespace: %v", err)
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}
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return &netNS{file: fd, mounted: true}, nil
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}
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func (ns *netNS) Close() error {
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if err := ns.errorIfClosed(); err != nil {
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return err
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}
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if err := ns.file.Close(); err != nil {
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return fmt.Errorf("Failed to close %q: %v", ns.file.Name(), err)
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}
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ns.closed = true
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if ns.mounted {
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if err := unix.Unmount(ns.file.Name(), unix.MNT_DETACH); err != nil {
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return fmt.Errorf("Failed to unmount namespace %s: %v", ns.file.Name(), err)
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}
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if err := os.RemoveAll(ns.file.Name()); err != nil {
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return fmt.Errorf("Failed to clean up namespace %s: %v", ns.file.Name(), err)
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}
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ns.mounted = false
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}
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return nil
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}
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func (ns *netNS) Set() error {
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if err := ns.errorIfClosed(); err != nil {
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return err
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}
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if err := unix.Setns(int(ns.Fd()), unix.CLONE_NEWNET); err != nil {
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return fmt.Errorf("Error switching to ns %v: %v", ns.file.Name(), err)
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}
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return nil
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}
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