138 lines
3.3 KiB
Go
138 lines
3.3 KiB
Go
// +build linux
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package main
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import (
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"os"
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"os/signal"
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"syscall" // only for Signal
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"github.com/opencontainers/runc/libcontainer"
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"github.com/opencontainers/runc/libcontainer/system"
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"github.com/opencontainers/runc/libcontainer/utils"
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"github.com/sirupsen/logrus"
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"golang.org/x/sys/unix"
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)
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const signalBufferSize = 2048
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// newSignalHandler returns a signal handler for processing SIGCHLD and SIGWINCH signals
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// while still forwarding all other signals to the process.
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// If notifySocket is present, use it to read systemd notifications from the container and
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// forward them to notifySocketHost.
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func newSignalHandler(enableSubreaper bool, notifySocket *notifySocket) *signalHandler {
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if enableSubreaper {
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// set us as the subreaper before registering the signal handler for the container
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if err := system.SetSubreaper(1); err != nil {
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logrus.Warn(err)
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}
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}
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// ensure that we have a large buffer size so that we do not miss any signals
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// incase we are not processing them fast enough.
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s := make(chan os.Signal, signalBufferSize)
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// handle all signals for the process.
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signal.Notify(s)
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return &signalHandler{
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signals: s,
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notifySocket: notifySocket,
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}
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}
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// exit models a process exit status with the pid and
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// exit status.
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type exit struct {
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pid int
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status int
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}
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type signalHandler struct {
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signals chan os.Signal
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notifySocket *notifySocket
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}
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// forward handles the main signal event loop forwarding, resizing, or reaping depending
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// on the signal received.
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func (h *signalHandler) forward(process *libcontainer.Process, tty *tty, detach bool) (int, error) {
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// make sure we know the pid of our main process so that we can return
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// after it dies.
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if detach && h.notifySocket == nil {
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return 0, nil
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}
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pid1, err := process.Pid()
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if err != nil {
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return -1, err
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}
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if h.notifySocket != nil {
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if detach {
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h.notifySocket.run(pid1)
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return 0, nil
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} else {
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go h.notifySocket.run(0)
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}
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}
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// perform the initial tty resize.
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tty.resize()
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for s := range h.signals {
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switch s {
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case unix.SIGWINCH:
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tty.resize()
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case unix.SIGCHLD:
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exits, err := h.reap()
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if err != nil {
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logrus.Error(err)
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}
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for _, e := range exits {
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logrus.WithFields(logrus.Fields{
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"pid": e.pid,
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"status": e.status,
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}).Debug("process exited")
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if e.pid == pid1 {
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// call Wait() on the process even though we already have the exit
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// status because we must ensure that any of the go specific process
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// fun such as flushing pipes are complete before we return.
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process.Wait()
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if h.notifySocket != nil {
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h.notifySocket.Close()
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}
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return e.status, nil
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}
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}
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default:
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logrus.Debugf("sending signal to process %s", s)
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if err := unix.Kill(pid1, s.(syscall.Signal)); err != nil {
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logrus.Error(err)
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}
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}
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}
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return -1, nil
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}
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// reap runs wait4 in a loop until we have finished processing any existing exits
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// then returns all exits to the main event loop for further processing.
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func (h *signalHandler) reap() (exits []exit, err error) {
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var (
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ws unix.WaitStatus
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rus unix.Rusage
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)
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for {
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pid, err := unix.Wait4(-1, &ws, unix.WNOHANG, &rus)
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if err != nil {
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if err == unix.ECHILD {
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return exits, nil
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}
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return nil, err
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}
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if pid <= 0 {
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return exits, nil
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}
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exits = append(exits, exit{
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pid: pid,
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status: utils.ExitStatus(ws),
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})
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}
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}
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