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The rclone and sftp backends require starting a child process. The are first moved into the foreground and back into the background after the initial startup is done. However, this behavior is also active if restic itself is started in the background. In this case, restic changing the foreground process may confuse the shell and in case of bash causes it to exit. Thus, disable modification of the controlling process group of the tty if restic is run in the background.
97 lines
2.0 KiB
Go
97 lines
2.0 KiB
Go
//go:build !aix && !solaris && !windows
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// +build !aix,!solaris,!windows
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package util
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import (
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"os"
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"os/exec"
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"os/signal"
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"github.com/restic/restic/internal/debug"
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"github.com/restic/restic/internal/errors"
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"golang.org/x/sys/unix"
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)
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func tcgetpgrp(fd int) (int, error) {
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return unix.IoctlGetInt(fd, unix.TIOCGPGRP)
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}
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func tcsetpgrp(fd int, pid int) error {
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// IoctlSetPointerInt silently casts to int32 internally,
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// so this assumes pid fits in 31 bits.
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return unix.IoctlSetPointerInt(fd, unix.TIOCSPGRP, pid)
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}
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func startForeground(cmd *exec.Cmd) (bg func() error, err error) {
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// open the TTY, we need the file descriptor
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tty, err := os.OpenFile("/dev/tty", os.O_RDWR, 0)
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if err != nil {
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debug.Log("unable to open tty: %v", err)
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return startFallback(cmd)
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}
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// only move child process to foreground if restic is in the foreground
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prev, err := tcgetpgrp(int(tty.Fd()))
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if err != nil {
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_ = tty.Close()
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return nil, err
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}
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self := unix.Getpgrp()
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if prev != self {
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debug.Log("restic is not controlling the tty")
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if err := tty.Close(); err != nil {
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return nil, err
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}
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return startFallback(cmd)
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}
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// Prevent getting suspended when interacting with the tty
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signal.Ignore(unix.SIGTTIN)
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signal.Ignore(unix.SIGTTOU)
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// run the command in its own process group
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cmd.SysProcAttr = &unix.SysProcAttr{
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Setpgid: true,
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}
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// start the process
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err = cmd.Start()
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if err != nil {
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_ = tty.Close()
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return nil, errors.Wrap(err, "cmd.Start")
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}
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// move the command's process group into the foreground
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err = tcsetpgrp(int(tty.Fd()), cmd.Process.Pid)
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if err != nil {
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_ = tty.Close()
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return nil, err
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}
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bg = func() error {
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signal.Reset(unix.SIGTTIN)
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signal.Reset(unix.SIGTTOU)
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// reset the foreground process group
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err = tcsetpgrp(int(tty.Fd()), prev)
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if err != nil {
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_ = tty.Close()
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return err
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}
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return tty.Close()
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}
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return bg, nil
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}
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func startFallback(cmd *exec.Cmd) (bg func() error, err error) {
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bg = func() error {
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return nil
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}
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return bg, cmd.Start()
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}
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