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