package netns
import (
"fmt"
"os"
"path"
"path/filepath"
"strconv"
"strings"
"golang.org/x/sys/unix"
)
// Deprecated: use golang.org/x/sys/unix pkg instead.
const (
CLONE_NEWUTS = unix.CLONE_NEWUTS /* New utsname group? */
CLONE_NEWIPC = unix.CLONE_NEWIPC /* New ipcs */
CLONE_NEWUSER = unix.CLONE_NEWUSER /* New user namespace */
CLONE_NEWPID = unix.CLONE_NEWPID /* New pid namespace */
CLONE_NEWNET = unix.CLONE_NEWNET /* New network namespace */
CLONE_IO = unix.CLONE_IO /* Get io context */
)
const bindMountPath = "/run/netns" /* Bind mount path for named netns */
// Setns sets namespace using golang.org/x/sys/unix.Setns.
//
// Deprecated: Use golang.org/x/sys/unix.Setns instead.
func Setns(ns NsHandle, nstype int) (err error) {
return unix.Setns(int(ns), nstype)
}
// Set sets the current network namespace to the namespace represented
// by NsHandle.
func Set(ns NsHandle) (err error) {
return unix.Setns(int(ns), unix.CLONE_NEWNET)
}
// New creates a new network namespace, sets it as current and returns
// a handle to it.
func New() (ns NsHandle, err error) {
if err := unix.Unshare(unix.CLONE_NEWNET); err != nil {
return -1, err
}
return Get()
}
// NewNamed creates a new named network namespace, sets it as current,
// and returns a handle to it
func NewNamed(name string) (NsHandle, error) {
if _, err := os.Stat(bindMountPath); os.IsNotExist(err) {
err = os.MkdirAll(bindMountPath, 0755)
if err != nil {
return None(), err
}
}
newNs, err := New()
if err != nil {
return None(), err
}
namedPath := path.Join(bindMountPath, name)
f, err := os.OpenFile(namedPath, os.O_CREATE|os.O_EXCL, 0444)
if err != nil {
newNs.Close()
return None(), err
}
f.Close()
nsPath := fmt.Sprintf("/proc/%d/task/%d/ns/net", os.Getpid(), unix.Gettid())
err = unix.Mount(nsPath, namedPath, "bind", unix.MS_BIND, "")
if err != nil {
newNs.Close()
return None(), err
}
return newNs, nil
}
// DeleteNamed deletes a named network namespace
func DeleteNamed(name string) error {
namedPath := path.Join(bindMountPath, name)
err := unix.Unmount(namedPath, unix.MNT_DETACH)
if err != nil {
return err
}
return os.Remove(namedPath)
}
// Get gets a handle to the current threads network namespace.
func Get() (NsHandle, error) {
return GetFromThread(os.Getpid(), unix.Gettid())
}
// GetFromPath gets a handle to a network namespace
// identified by the path
func GetFromPath(path string) (NsHandle, error) {
fd, err := unix.Open(path, unix.O_RDONLY|unix.O_CLOEXEC, 0)
if err != nil {
return -1, err
}
return NsHandle(fd), nil
}
// GetFromName gets a handle to a named network namespace such as one
// created by `ip netns add`.
func GetFromName(name string) (NsHandle, error) {
return GetFromPath(filepath.Join(bindMountPath, name))
}
// GetFromPid gets a handle to the network namespace of a given pid.
func GetFromPid(pid int) (NsHandle, error) {
return GetFromPath(fmt.Sprintf("/proc/%d/ns/net", pid))
}
// GetFromThread gets a handle to the network namespace of a given pid and tid.
func GetFromThread(pid, tid int) (NsHandle, error) {
return GetFromPath(fmt.Sprintf("/proc/%d/task/%d/ns/net", pid, tid))
}
// GetFromDocker gets a handle to the network namespace of a docker container.
// Id is prefixed matched against the running docker containers, so a short
// identifier can be used as long as it isn't ambiguous.
func GetFromDocker(id string) (NsHandle, error) {
pid, err := getPidForContainer(id)
if err != nil {
return -1, err
}
return GetFromPid(pid)
}
// borrowed from docker/utils/utils.go
func findCgroupMountpoint(cgroupType string) (int, string, error) {
output, err := os.ReadFile("/proc/mounts")
if err != nil {
return -1, "", err
}
// /proc/mounts has 6 fields per line, one mount per line, e.g.
// cgroup /sys/fs/cgroup/devices cgroup rw,relatime,devices 0 0
for _, line := range strings.Split(string(output), "\n") {
parts := strings.Split(line, " ")
if len(parts) == 6 {
switch parts[2] {
case "cgroup2":
return 2, parts[1], nil
case "cgroup":
for _, opt := range strings.Split(parts[3], ",") {
if opt == cgroupType {
return 1, parts[1], nil
}
}
}
}
}
return -1, "", fmt.Errorf("cgroup mountpoint not found for %s", cgroupType)
}
// Returns the relative path to the cgroup docker is running in.
// borrowed from docker/utils/utils.go
// modified to get the docker pid instead of using /proc/self
func getDockerCgroup(cgroupVer int, cgroupType string) (string, error) {
dockerpid, err := os.ReadFile("/var/run/docker.pid")
if err != nil {
return "", err
}
result := strings.Split(string(dockerpid), "\n")
if len(result) == 0 || len(result[0]) == 0 {
return "", fmt.Errorf("docker pid not found in /var/run/docker.pid")
}
pid, err := strconv.Atoi(result[0])
if err != nil {
return "", err
}
output, err := os.ReadFile(fmt.Sprintf("/proc/%d/cgroup", pid))
if err != nil {
return "", err
}
for _, line := range strings.Split(string(output), "\n") {
parts := strings.Split(line, ":")
// any type used by docker should work
if (cgroupVer == 1 && parts[1] == cgroupType) ||
(cgroupVer == 2 && parts[1] == "") {
return parts[2], nil
}
}
return "", fmt.Errorf("cgroup '%s' not found in /proc/%d/cgroup", cgroupType, pid)
}
// Returns the first pid in a container.
// borrowed from docker/utils/utils.go
// modified to only return the first pid
// modified to glob with id
// modified to search for newer docker containers
// modified to look for cgroups v2
func getPidForContainer(id string) (int, error) {
pid := 0
// memory is chosen randomly, any cgroup used by docker works
cgroupType := "memory"
cgroupVer, cgroupRoot, err := findCgroupMountpoint(cgroupType)
if err != nil {
return pid, err
}
cgroupDocker, err := getDockerCgroup(cgroupVer, cgroupType)
if err != nil {
return pid, err
}
id += "*"
var pidFile string
if cgroupVer == 1 {
pidFile = "tasks"
} else if cgroupVer == 2 {
pidFile = "cgroup.procs"
} else {
return -1, fmt.Errorf("Invalid cgroup version '%d'", cgroupVer)
}
attempts := []string{
filepath.Join(cgroupRoot, cgroupDocker, id, pidFile),
// With more recent lxc versions use, cgroup will be in lxc/
filepath.Join(cgroupRoot, cgroupDocker, "lxc", id, pidFile),
// With more recent docker, cgroup will be in docker/
filepath.Join(cgroupRoot, cgroupDocker, "docker", id, pidFile),
// Even more recent docker versions under systemd use docker-<id>.scope/
filepath.Join(cgroupRoot, "system.slice", "docker-"+id+".scope", pidFile),
// Even more recent docker versions under cgroup/systemd/docker/<id>/
filepath.Join(cgroupRoot, "..", "systemd", "docker", id, pidFile),
// Kubernetes with docker and CNI is even more different. Works for BestEffort and Burstable QoS
filepath.Join(cgroupRoot, "..", "systemd", "kubepods", "*", "pod*", id, pidFile),
// Same as above but for Guaranteed QoS
filepath.Join(cgroupRoot, "..", "systemd", "kubepods", "pod*", id, pidFile),
// Another flavor of containers location in recent kubernetes 1.11+. Works for BestEffort and Burstable QoS
filepath.Join(cgroupRoot, cgroupDocker, "kubepods.slice", "*.slice", "*", "docker-"+id+".scope", pidFile),
// Same as above but for Guaranteed QoS
filepath.Join(cgroupRoot, cgroupDocker, "kubepods.slice", "*", "docker-"+id+".scope", pidFile),
// When runs inside of a container with recent kubernetes 1.11+. Works for BestEffort and Burstable QoS
filepath.Join(cgroupRoot, "kubepods.slice", "*.slice", "*", "docker-"+id+".scope", pidFile),
// Same as above but for Guaranteed QoS
filepath.Join(cgroupRoot, "kubepods.slice", "*", "docker-"+id+".scope", pidFile),
}
var filename string
for _, attempt := range attempts {
filenames, _ := filepath.Glob(attempt)
if len(filenames) > 1 {
return pid, fmt.Errorf("Ambiguous id supplied: %v", filenames)
} else if len(filenames) == 1 {
filename = filenames[0]
break
}
}
if filename == "" {
return pid, fmt.Errorf("Unable to find container: %v", id[:len(id)-1])
}
output, err := os.ReadFile(filename)
if err != nil {
return pid, err
}
result := strings.Split(string(output), "\n")
if len(result) == 0 || len(result[0]) == 0 {
return pid, fmt.Errorf("No pid found for container")
}
pid, err = strconv.Atoi(result[0])
if err != nil {
return pid, fmt.Errorf("Invalid pid '%s': %s", result[0], err)
}
return pid, nil
}
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