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|
// +build darwin dragonfly freebsd linux netbsd openbsd plan9 solaris
package daemon
import (
"encoding/json"
"fmt"
"os"
"path/filepath"
"syscall"
)
// A Context describes daemon context.
type Context struct {
// If PidFileName is non-empty, parent process will try to create and lock
// pid file with given name. Child process writes process id to file.
PidFileName string
// Permissions for new pid file.
PidFilePerm os.FileMode
// If LogFileName is non-empty, parent process will create file with given name
// and will link to fd 2 (stderr) for child process.
LogFileName string
// Permissions for new log file.
LogFilePerm os.FileMode
// If WorkDir is non-empty, the child changes into the directory before
// creating the process.
WorkDir string
// If Chroot is non-empty, the child changes root directory
Chroot string
// If Env is non-nil, it gives the environment variables for the
// daemon-process in the form returned by os.Environ.
// If it is nil, the result of os.Environ will be used.
Env []string
// If Args is non-nil, it gives the command-line args for the
// daemon-process. If it is nil, the result of os.Args will be used.
Args []string
// Credential holds user and group identities to be assumed by a daemon-process.
Credential *syscall.Credential
// If Umask is non-zero, the daemon-process call Umask() func with given value.
Umask int
// Struct contains only serializable public fields (!!!)
abspath string
pidFile *LockFile
logFile *os.File
nullFile *os.File
rpipe, wpipe *os.File
}
func (d *Context) reborn() (child *os.Process, err error) {
if !WasReborn() {
child, err = d.parent()
} else {
err = d.child()
}
return
}
func (d *Context) search() (daemon *os.Process, err error) {
if len(d.PidFileName) > 0 {
var pid int
if pid, err = ReadPidFile(d.PidFileName); err != nil {
return
}
daemon, err = os.FindProcess(pid)
}
return
}
func (d *Context) parent() (child *os.Process, err error) {
if err = d.prepareEnv(); err != nil {
return
}
defer d.closeFiles()
if err = d.openFiles(); err != nil {
return
}
attr := &os.ProcAttr{
Dir: d.WorkDir,
Env: d.Env,
Files: d.files(),
Sys: &syscall.SysProcAttr{
//Chroot: d.Chroot,
Credential: d.Credential,
Setsid: true,
},
}
if child, err = os.StartProcess(d.abspath, d.Args, attr); err != nil {
if d.pidFile != nil {
d.pidFile.Remove()
}
return
}
d.rpipe.Close()
encoder := json.NewEncoder(d.wpipe)
if err = encoder.Encode(d); err != nil {
return
}
_, err = fmt.Fprint(d.wpipe, "\n\n")
return
}
func (d *Context) openFiles() (err error) {
if d.PidFilePerm == 0 {
d.PidFilePerm = FILE_PERM
}
if d.LogFilePerm == 0 {
d.LogFilePerm = FILE_PERM
}
if d.nullFile, err = os.Open(os.DevNull); err != nil {
return
}
if len(d.PidFileName) > 0 {
if d.PidFileName, err = filepath.Abs(d.PidFileName); err != nil {
return err
}
if d.pidFile, err = OpenLockFile(d.PidFileName, d.PidFilePerm); err != nil {
return
}
if err = d.pidFile.Lock(); err != nil {
return
}
if len(d.Chroot) > 0 {
// Calculate PID-file absolute path in child's environment
if d.PidFileName, err = filepath.Rel(d.Chroot, d.PidFileName); err != nil {
return err
}
d.PidFileName = "/" + d.PidFileName
}
}
if len(d.LogFileName) > 0 {
if d.logFile, err = os.OpenFile(d.LogFileName,
os.O_WRONLY|os.O_CREATE|os.O_APPEND, d.LogFilePerm); err != nil {
return
}
}
d.rpipe, d.wpipe, err = os.Pipe()
return
}
func (d *Context) closeFiles() (err error) {
cl := func(file **os.File) {
if *file != nil {
(*file).Close()
*file = nil
}
}
cl(&d.rpipe)
cl(&d.wpipe)
cl(&d.logFile)
cl(&d.nullFile)
if d.pidFile != nil {
d.pidFile.Close()
d.pidFile = nil
}
return
}
func (d *Context) prepareEnv() (err error) {
if d.abspath, err = osExecutable(); err != nil {
return
}
if len(d.Args) == 0 {
d.Args = os.Args
}
mark := fmt.Sprintf("%s=%s", MARK_NAME, MARK_VALUE)
if len(d.Env) == 0 {
d.Env = os.Environ()
}
d.Env = append(d.Env, mark)
return
}
func (d *Context) files() (f []*os.File) {
log := d.nullFile
if d.logFile != nil {
log = d.logFile
}
f = []*os.File{
d.rpipe, // (0) stdin
log, // (1) stdout
log, // (2) stderr
d.nullFile, // (3) dup on fd 0 after initialization
}
if d.pidFile != nil {
f = append(f, d.pidFile.File) // (4) pid file
}
return
}
var initialized = false
func (d *Context) child() (err error) {
if initialized {
return os.ErrInvalid
}
initialized = true
decoder := json.NewDecoder(os.Stdin)
if err = decoder.Decode(d); err != nil {
return
}
// create PID file after context decoding to know PID file full path.
if len(d.PidFileName) > 0 {
d.pidFile = NewLockFile(os.NewFile(4, d.PidFileName))
if err = d.pidFile.WritePid(); err != nil {
return
}
defer func() {
if err != nil {
d.pidFile.Remove()
}
}()
}
if err = syscallDup(3, 0); err != nil {
return
}
if d.Umask != 0 {
syscall.Umask(int(d.Umask))
}
if len(d.Chroot) > 0 {
err = syscall.Chroot(d.Chroot)
if err != nil {
return
}
}
return
}
func (d *Context) release() (err error) {
if !initialized {
return
}
if d.pidFile != nil {
err = d.pidFile.Remove()
}
return
}
|
