/
ns.go
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/
ns.go
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// Copyright 2015 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 (
"fmt"
"os"
"runtime"
"syscall"
)
var setNsMap = map[string]uintptr{
"386": 346,
"amd64": 308,
"arm": 374,
}
// SetNS sets the network namespace on a target file.
func SetNS(f *os.File, flags uintptr) error {
if runtime.GOOS != "linux" {
return fmt.Errorf("unsupported OS: %s", runtime.GOOS)
}
trap, ok := setNsMap[runtime.GOARCH]
if !ok {
return fmt.Errorf("unsupported arch: %s", runtime.GOARCH)
}
_, _, err := syscall.RawSyscall(trap, f.Fd(), flags, 0)
if err != 0 {
return err
}
return nil
}
// WithNetNSPath executes the passed closure under the given network
// namespace, restoring the original namespace afterwards.
// Changing namespaces must be done on a goroutine that has been
// locked to an OS thread. If lockThread arg is true, this function
// locks the goroutine prior to change namespace and unlocks before
// returning
func WithNetNSPath(nspath string, lockThread bool, f func(*os.File) error) error {
ns, err := os.Open(nspath)
if err != nil {
return fmt.Errorf("Failed to open %v: %v", nspath, err)
}
defer ns.Close()
return WithNetNS(ns, lockThread, f)
}
// WithNetNS executes the passed closure under the given network
// namespace, restoring the original namespace afterwards.
// Changing namespaces must be done on a goroutine that has been
// locked to an OS thread. If lockThread arg is true, this function
// locks the goroutine prior to change namespace and unlocks before
// returning. If the closure returns an error, WithNetNS attempts to
// restore the original namespace before returning.
func WithNetNS(ns *os.File, lockThread bool, f func(*os.File) error) error {
if lockThread {
runtime.LockOSThread()
defer runtime.UnlockOSThread()
}
// save a handle to current (host) network namespace
thisNS, err := os.Open("/proc/self/ns/net")
if err != nil {
return fmt.Errorf("Failed to open /proc/self/ns/net: %v", err)
}
defer thisNS.Close()
if err = SetNS(ns, syscall.CLONE_NEWNET); err != nil {
return fmt.Errorf("Error switching to ns %v: %v", ns.Name(), err)
}
defer SetNS(thisNS, syscall.CLONE_NEWNET) // switch back
if err = f(thisNS); err != nil {
return err
}
return nil
}