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// Package netns allows ultra-simple network namespace handling. NsHandles
// can be retrieved and set. Note that the current namespace is thread
// local so actions that set and reset namespaces should use LockOSThread
// to make sure the namespace doesn't change due to a goroutine switch.
// It is best to close NsHandles when you are done with them. This can be
// accomplished via a `defer ns.Close()` on the handle. Changing namespaces
// requires elevated privileges, so in most cases this code needs to be run
// as root.
package netns
import (
"fmt"
"syscall"
)
// NsHandle is a handle to a network namespace. It can be cast directly
// to an int and used as a file descriptor.
type NsHandle int
// Equal determines if two network handles refer to the same network
// namespace. This is done by comparing the device and inode that the
// file descriptors point to.
func (ns NsHandle) Equal(other NsHandle) bool {
if ns == other {
return true
}
var s1, s2 syscall.Stat_t
if err := syscall.Fstat(int(ns), &s1); err != nil {
return false
}
if err := syscall.Fstat(int(other), &s2); err != nil {
return false
}
return (s1.Dev == s2.Dev) && (s1.Ino == s2.Ino)
}
// String shows the file descriptor number and its dev and inode.
func (ns NsHandle) String() string {
var s syscall.Stat_t
if ns == -1 {
return "NS(None)"
}
if err := syscall.Fstat(int(ns), &s); err != nil {
return fmt.Sprintf("NS(%d: unknown)", ns)
}
return fmt.Sprintf("NS(%d: %d, %d)", ns, s.Dev, s.Ino)
}
// UniqueId returns a string which uniquely identifies the namespace
// associated with the network handle.
func (ns NsHandle) UniqueId() string {
var s syscall.Stat_t
if ns == -1 {
return "NS(none)"
}
if err := syscall.Fstat(int(ns), &s); err != nil {
return "NS(unknown)"
}
return fmt.Sprintf("NS(%d:%d)", s.Dev, s.Ino)
}
// IsOpen returns true if Close() has not been called.
func (ns NsHandle) IsOpen() bool {
return ns != -1
}
// Close closes the NsHandle and resets its file descriptor to -1.
// It is not safe to use an NsHandle after Close() is called.
func (ns *NsHandle) Close() error {
if err := syscall.Close(int(*ns)); err != nil {
return err
}
(*ns) = -1
return nil
}
// None gets an empty (closed) NsHandle.
func None() NsHandle {
return NsHandle(-1)
}
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