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// +build linux
package netns
import (
"fmt"
"io/ioutil"
"os"
"path/filepath"
"runtime"
"strconv"
"strings"
"syscall"
)
// SYS_SETNS syscall allows changing the namespace of the current process.
var SYS_SETNS = map[string]uintptr{
"386": 346,
"amd64": 308,
"arm64": 268,
"arm": 375,
"mips": 4344,
"mipsle": 4344,
"ppc64": 350,
"ppc64le": 350,
"s390x": 339,
}[runtime.GOARCH]
// Deprecated: use syscall pkg instead (go >= 1.5 needed).
const (
CLONE_NEWUTS = 0x04000000 /* New utsname group? */
CLONE_NEWIPC = 0x08000000 /* New ipcs */
CLONE_NEWUSER = 0x10000000 /* New user namespace */
CLONE_NEWPID = 0x20000000 /* New pid namespace */
CLONE_NEWNET = 0x40000000 /* New network namespace */
CLONE_IO = 0x80000000 /* Get io context */
)
// Setns sets namespace using syscall. Note that this should be a method
// in syscall but it has not been added.
func Setns(ns NsHandle, nstype int) (err error) {
_, _, e1 := syscall.Syscall(SYS_SETNS, uintptr(ns), uintptr(nstype), 0)
if e1 != 0 {
err = e1
}
return
}
// Set sets the current network namespace to the namespace represented
// by NsHandle.
func Set(ns NsHandle) (err error) {
return Setns(ns, CLONE_NEWNET)
}
// New creates a new network namespace and returns a handle to it.
func New() (ns NsHandle, err error) {
if err := syscall.Unshare(CLONE_NEWNET); err != nil {
return -1, err
}
return Get()
}
// Get gets a handle to the current threads network namespace.
func Get() (NsHandle, error) {
return GetFromThread(os.Getpid(), syscall.Gettid())
}
// GetFromPath gets a handle to a network namespace
// identified by the path
func GetFromPath(path string) (NsHandle, error) {
fd, err := syscall.Open(path, syscall.O_RDONLY, 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(fmt.Sprintf("/var/run/netns/%s", 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) (string, error) {
output, err := ioutil.ReadFile("/proc/mounts")
if err != nil {
return "", 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 && parts[2] == "cgroup" {
for _, opt := range strings.Split(parts[3], ",") {
if opt == cgroupType {
return parts[1], nil
}
}
}
}
return "", 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 getThisCgroup(cgroupType string) (string, error) {
dockerpid, err := ioutil.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 := ioutil.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 parts[1] == cgroupType {
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
func getPidForContainer(id string) (int, error) {
pid := 0
// memory is chosen randomly, any cgroup used by docker works
cgroupType := "memory"
cgroupRoot, err := findCgroupMountpoint(cgroupType)
if err != nil {
return pid, err
}
cgroupThis, err := getThisCgroup(cgroupType)
if err != nil {
return pid, err
}
id += "*"
attempts := []string{
filepath.Join(cgroupRoot, cgroupThis, id, "tasks"),
// With more recent lxc versions use, cgroup will be in lxc/
filepath.Join(cgroupRoot, cgroupThis, "lxc", id, "tasks"),
// With more recent docker, cgroup will be in docker/
filepath.Join(cgroupRoot, cgroupThis, "docker", id, "tasks"),
// Even more recent docker versions under systemd use docker-<id>.scope/
filepath.Join(cgroupRoot, "system.slice", "docker-"+id+".scope", "tasks"),
// Even more recent docker versions under cgroup/systemd/docker/<id>/
filepath.Join(cgroupRoot, "..", "systemd", "docker", id, "tasks"),
}
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 := ioutil.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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