224 lines
6.1 KiB
Go
224 lines
6.1 KiB
Go
// +build linux
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package netns
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import (
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"fmt"
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"io/ioutil"
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"os"
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"path/filepath"
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"runtime"
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"strconv"
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"strings"
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"syscall"
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)
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// SYS_SETNS syscall allows changing the namespace of the current process.
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var SYS_SETNS = map[string]uintptr{
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"386": 346,
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"amd64": 308,
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"arm64": 268,
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"arm": 375,
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"mips": 4344,
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"mipsle": 4344,
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"ppc64": 350,
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"ppc64le": 350,
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"s390x": 339,
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}[runtime.GOARCH]
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// Deprecated: use syscall pkg instead (go >= 1.5 needed).
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const (
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CLONE_NEWUTS = 0x04000000 /* New utsname group? */
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CLONE_NEWIPC = 0x08000000 /* New ipcs */
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CLONE_NEWUSER = 0x10000000 /* New user namespace */
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CLONE_NEWPID = 0x20000000 /* New pid namespace */
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CLONE_NEWNET = 0x40000000 /* New network namespace */
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CLONE_IO = 0x80000000 /* Get io context */
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)
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// Setns sets namespace using syscall. Note that this should be a method
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// in syscall but it has not been added.
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func Setns(ns NsHandle, nstype int) (err error) {
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_, _, e1 := syscall.Syscall(SYS_SETNS, uintptr(ns), uintptr(nstype), 0)
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if e1 != 0 {
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err = e1
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}
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return
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}
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// Set sets the current network namespace to the namespace represented
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// by NsHandle.
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func Set(ns NsHandle) (err error) {
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return Setns(ns, CLONE_NEWNET)
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}
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// New creates a new network namespace and returns a handle to it.
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func New() (ns NsHandle, err error) {
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if err := syscall.Unshare(CLONE_NEWNET); err != nil {
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return -1, err
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}
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return Get()
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}
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// Get gets a handle to the current threads network namespace.
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func Get() (NsHandle, error) {
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return GetFromThread(os.Getpid(), syscall.Gettid())
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}
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// GetFromPath gets a handle to a network namespace
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// identified by the path
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func GetFromPath(path string) (NsHandle, error) {
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fd, err := syscall.Open(path, syscall.O_RDONLY, 0)
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if err != nil {
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return -1, err
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}
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return NsHandle(fd), nil
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}
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// GetFromName gets a handle to a named network namespace such as one
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// created by `ip netns add`.
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func GetFromName(name string) (NsHandle, error) {
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return GetFromPath(fmt.Sprintf("/var/run/netns/%s", name))
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}
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// GetFromPid gets a handle to the network namespace of a given pid.
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func GetFromPid(pid int) (NsHandle, error) {
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return GetFromPath(fmt.Sprintf("/proc/%d/ns/net", pid))
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}
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// GetFromThread gets a handle to the network namespace of a given pid and tid.
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func GetFromThread(pid, tid int) (NsHandle, error) {
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return GetFromPath(fmt.Sprintf("/proc/%d/task/%d/ns/net", pid, tid))
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}
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// GetFromDocker gets a handle to the network namespace of a docker container.
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// Id is prefixed matched against the running docker containers, so a short
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// identifier can be used as long as it isn't ambiguous.
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func GetFromDocker(id string) (NsHandle, error) {
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pid, err := getPidForContainer(id)
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if err != nil {
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return -1, err
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}
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return GetFromPid(pid)
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}
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// borrowed from docker/utils/utils.go
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func findCgroupMountpoint(cgroupType string) (string, error) {
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output, err := ioutil.ReadFile("/proc/mounts")
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if err != nil {
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return "", err
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}
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// /proc/mounts has 6 fields per line, one mount per line, e.g.
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// cgroup /sys/fs/cgroup/devices cgroup rw,relatime,devices 0 0
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for _, line := range strings.Split(string(output), "\n") {
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parts := strings.Split(line, " ")
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if len(parts) == 6 && parts[2] == "cgroup" {
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for _, opt := range strings.Split(parts[3], ",") {
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if opt == cgroupType {
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return parts[1], nil
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}
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}
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}
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}
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return "", fmt.Errorf("cgroup mountpoint not found for %s", cgroupType)
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}
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// Returns the relative path to the cgroup docker is running in.
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// borrowed from docker/utils/utils.go
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// modified to get the docker pid instead of using /proc/self
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func getThisCgroup(cgroupType string) (string, error) {
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dockerpid, err := ioutil.ReadFile("/var/run/docker.pid")
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if err != nil {
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return "", err
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}
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result := strings.Split(string(dockerpid), "\n")
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if len(result) == 0 || len(result[0]) == 0 {
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return "", fmt.Errorf("docker pid not found in /var/run/docker.pid")
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}
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pid, err := strconv.Atoi(result[0])
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if err != nil {
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return "", err
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}
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output, err := ioutil.ReadFile(fmt.Sprintf("/proc/%d/cgroup", pid))
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if err != nil {
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return "", err
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}
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for _, line := range strings.Split(string(output), "\n") {
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parts := strings.Split(line, ":")
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// any type used by docker should work
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if parts[1] == cgroupType {
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return parts[2], nil
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}
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}
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return "", fmt.Errorf("cgroup '%s' not found in /proc/%d/cgroup", cgroupType, pid)
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}
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// Returns the first pid in a container.
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// borrowed from docker/utils/utils.go
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// modified to only return the first pid
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// modified to glob with id
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// modified to search for newer docker containers
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func getPidForContainer(id string) (int, error) {
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pid := 0
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// memory is chosen randomly, any cgroup used by docker works
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cgroupType := "memory"
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cgroupRoot, err := findCgroupMountpoint(cgroupType)
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if err != nil {
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return pid, err
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}
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cgroupThis, err := getThisCgroup(cgroupType)
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if err != nil {
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return pid, err
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}
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id += "*"
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attempts := []string{
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filepath.Join(cgroupRoot, cgroupThis, id, "tasks"),
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// With more recent lxc versions use, cgroup will be in lxc/
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filepath.Join(cgroupRoot, cgroupThis, "lxc", id, "tasks"),
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// With more recent docker, cgroup will be in docker/
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filepath.Join(cgroupRoot, cgroupThis, "docker", id, "tasks"),
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// Even more recent docker versions under systemd use docker-<id>.scope/
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filepath.Join(cgroupRoot, "system.slice", "docker-"+id+".scope", "tasks"),
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// Even more recent docker versions under cgroup/systemd/docker/<id>/
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filepath.Join(cgroupRoot, "..", "systemd", "docker", id, "tasks"),
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}
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var filename string
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for _, attempt := range attempts {
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filenames, _ := filepath.Glob(attempt)
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if len(filenames) > 1 {
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return pid, fmt.Errorf("Ambiguous id supplied: %v", filenames)
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} else if len(filenames) == 1 {
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filename = filenames[0]
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break
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}
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}
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if filename == "" {
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return pid, fmt.Errorf("Unable to find container: %v", id[:len(id)-1])
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}
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output, err := ioutil.ReadFile(filename)
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if err != nil {
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return pid, err
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}
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result := strings.Split(string(output), "\n")
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if len(result) == 0 || len(result[0]) == 0 {
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return pid, fmt.Errorf("No pid found for container")
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}
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pid, err = strconv.Atoi(result[0])
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if err != nil {
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return pid, fmt.Errorf("Invalid pid '%s': %s", result[0], err)
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}
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return pid, nil
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}
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