112 lines
2.6 KiB
Go
112 lines
2.6 KiB
Go
// Daemonization interface for Unix platforms (implementation)
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//go:build !windows && !plan9 && !js
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// +build !windows,!plan9,!js
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package daemonize
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import (
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"os"
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"strings"
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"syscall"
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"github.com/rclone/rclone/fs"
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)
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// StartDaemon runs background twin of current process.
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// It executes separate parts of code in child and parent processes.
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// Returns child process pid in the parent or nil in the child.
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// The method looks like a fork but safe for goroutines.
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func StartDaemon(args []string) (*os.Process, error) {
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if fs.IsDaemon() {
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// This process is already daemonized
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return nil, nil
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}
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env := append(os.Environ(), fs.DaemonMarkVar+"="+fs.DaemonMarkChild)
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me, err := os.Executable()
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if err != nil {
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me = os.Args[0]
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}
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// os.Executable might have resolved symbolic link to the executable
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// so we run the background process with pre-converted CLI arguments.
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// Double conversion is still probable but isn't a problem as it should
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// preserve the converted command line.
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if len(args) != 0 {
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args[0] = me
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}
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if fs.PassDaemonArgsAsEnviron {
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args, env = argsToEnv(args, env)
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}
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null, err := os.Open(os.DevNull)
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if err != nil {
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return nil, err
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}
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files := []*os.File{
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null, // (0) stdin
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null, // (1) stdout
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null, // (2) stderr
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}
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sysAttr := &syscall.SysProcAttr{
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// setsid (https://linux.die.net/man/2/setsid) in the child process will reset
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// its process group id (PGID) to its PID thus detaching it from parent.
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// This would make autofs fail because it detects mounting process by its PGID.
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Setsid: false,
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}
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attr := &os.ProcAttr{
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Env: env,
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Files: files,
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Sys: sysAttr,
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}
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daemon, err := os.StartProcess(me, args, attr)
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if err != nil {
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return nil, err
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}
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return daemon, nil
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}
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// Processed command line flags of mount helper have simple structure:
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// `--flag` or `--flag=value` but never `--flag value` or `-x`
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// so we can easily pass them as environment variables.
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func argsToEnv(origArgs, origEnv []string) (args, env []string) {
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env = origEnv
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if len(origArgs) == 0 {
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return
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}
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args = []string{origArgs[0]}
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for _, arg := range origArgs[1:] {
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if !strings.HasPrefix(arg, "--") {
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args = append(args, arg)
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continue
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}
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arg = arg[2:]
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key, val := arg, "true"
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if idx := strings.Index(arg, "="); idx != -1 {
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key, val = arg[:idx], arg[idx+1:]
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}
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name := "RCLONE_" + strings.ToUpper(strings.ReplaceAll(key, "-", "_"))
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pref := name + "="
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line := name + "=" + val
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found := false
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for i, s := range env {
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if strings.HasPrefix(s, pref) {
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env[i] = line
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found = true
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}
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}
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if !found {
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env = append(env, line)
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}
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}
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return
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}
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