Added ipp-usb status command, for troubleshooting

    The `ipp-usb status` command prints actual status of all
    attached 7/1/4 devices. It is designed with a purpose to
    add some visibility in a case of troubleshooting. See also #52

Author: alexpevzner

flock_unix.go

@@ -10,27 +10,55 @@
 
 package main
 
+/*
+#include <errno.h>
+#include <unistd.h>
+
+static inline int do_lockf (int fd, int cmd, off_t len) {
+    int rc = lockf(fd, cmd, len);
+    if (rc < 0) {
+        rc = -errno;
+    }
+    return rc;
+}
+*/
+import "C"
+
 import (
 	"os"
 	"syscall"
 )
 
-// FileLock acquires file lock
-func FileLock(file *os.File, exclusive, wait bool) error {
-	var how int
+// FileLockCmd represents set of possible values for the
+// FileLock argument
+type FileLockCmd C.int
 
-	if exclusive {
-		how = syscall.LOCK_EX
-	} else {
-		how = syscall.LOCK_SH
-	}
+const (
+	// Lock the file; wait if it is busy
+	FileLockWait = C.F_LOCK
+
+	// Lock the file; fail with ErrLockIsBusy if it is busy
+	FileLockNoWait = C.F_TLOCK
+
+	// Test the lock. Return immediately with ErrLockIsBusy
+	// if file is busy or with the nil error, if file is not
+	// busy. File locking state is not affected in both cases
+	FileLockTest = C.F_TEST
+
+	// Unlock the file
+	FileLockUnlock = C.F_ULOCK
+)
 
-	if !wait {
-		how |= syscall.LOCK_NB
+// FileLock manages file lock
+func FileLock(file *os.File, cmd FileLockCmd) error {
+	rc := C.do_lockf(C.int(file.Fd()), C.int(cmd), 0)
+	if rc == 0 {
+		return nil
 	}
 
-	err := syscall.Flock(int(file.Fd()), how)
-	if err == syscall.Errno(syscall.EWOULDBLOCK) {
+	var err error = syscall.Errno(-rc)
+	switch err {
+	case syscall.EACCES, syscall.EAGAIN:
 		err = ErrLockIsBusy
 	}
 
@@ -39,5 +67,5 @@ func FileLock(file *os.File, exclusive, wait bool) error {
 
 // FileUnlock releases file lock
 func FileUnlock(file *os.File) error {
-	return syscall.Flock(int(file.Fd()), syscall.LOCK_UN)
+	return FileLock(file, FileLockUnlock)
 }

flock_windows.go

@@ -25,6 +25,9 @@ logs duplicated on console, \-bg option is ignored
 .TP
 \fBcheck\fR
 check configuration and exit\. It also prints a list of all connected devices
+.TP
+\fBstatus\fR
+print \fBipp\-usb\fR status
 .SS "Options are"
 .TP
 \fB\-bg\fR
@@ -228,6 +231,8 @@ If you found out about your device that it needs a quirk to work properly or it
 .IP "\[ci]" 4
 \fB/var/ipp\-usb/lock/ipp\-usb\.lock\fR: lock file, that helps to prevent multiple copies of daemon to run simultaneously
 .IP "\[ci]" 4
+\fB/var/ipp\-usb/status\fR: per\-device status in a form of a text file (printed by \fBipp\-usb status\fR)
+.IP "\[ci]" 4
 \fB/usr/share/ipp\-usb/quirks/*\.conf\fR: device\-specific quirks (see above)
 .IP "\[ci]" 4
 \fB/etc/ipp\-usb/quirks/*\.conf\fR: device\-specific quirks defined by sysadmin (see above)
@@ -239,4 +244,4 @@ All rights reserved\.
 .P
 This program is licensed under 2\-Clause BSD license\. See LICENSE file for details\.
 .SH "SEE ALSO"
-cups(1)
+\fBcups(1)\fR

ipp-usb.8

@@ -35,6 +35,9 @@ IPP printing, eSCL scanning and web console are fully supported.
      check configuration and exit. It also prints a list
      of all connected devices
 
+   * `status`:
+     print `ipp-usb` status
+
 ### Options are
 
    * `-bg`:
@@ -285,6 +288,9 @@ of such a device.
    * `/var/ipp-usb/lock/ipp-usb.lock`:
      lock file, that helps to prevent multiple copies of daemon to run simultaneously
 
+   * `/var/ipp-usb/status`:
+     per-device status in a form of a text file (printed by `ipp-usb status`)
+
    * `/usr/share/ipp-usb/quirks/*.conf`: device-specific quirks (see above)
 
    * `/etc/ipp-usb/quirks/*.conf`: device-specific quirks defined by sysadmin (see above)
@@ -298,6 +304,6 @@ This program is licensed under 2-Clause BSD license. See LICENSE file for detail
 
 ## SEE ALSO
 
-cups(1)
+**cups(1)**
 
 # vim:ts=8:sw=4:et

ipp-usb.8.md

@@ -11,6 +11,7 @@ package main
 import (
 	"bytes"
 	"fmt"
+	"io/ioutil"
 	"os"
 	"sort"
 )
@@ -26,6 +27,7 @@ Modes are:
     debug       - logs duplicated on console, -bg option is
                   ignored
     check       - check configuration and exit
+    status      - print ipp-usb status and exit
 
 Options are
     -bg         - run in background (ignored in debug mode)
@@ -40,6 +42,7 @@ const (
 	RunUdev
 	RunDebug
 	RunCheck
+	RunStatus
 )
 
 // String returns RunMode name
@@ -55,6 +58,8 @@ func (m RunMode) String() string {
 		return "debug"
 	case RunCheck:
 		return "check"
+	case RunStatus:
+		return "status"
 	}
 
 	return fmt.Sprintf("unknown (%d)", int(m))
@@ -113,6 +118,9 @@ func parseArgv() (params RunParameters) {
 		case "check":
 			params.Mode = RunCheck
 			modes++
+		case "status":
+			params.Mode = RunStatus
+			modes++
 		case "-bg":
 			params.Background = true
 		default:
@@ -131,6 +139,65 @@ func parseArgv() (params RunParameters) {
 	return
 }
 
+// printStatus prints status of running ipp-usb daemon, if any
+func printStatus() {
+	running := false
+
+	// Check if ipp-usb is running
+	lock, err := os.OpenFile(PathLockFile,
+		os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	if err == nil {
+		err = FileLock(lock, FileLockTest)
+		lock.Close()
+	}
+
+	switch err {
+	case nil:
+		InitLog.Info(0, "ipp-usb is not running")
+	case ErrLockIsBusy:
+		InitLog.Info(0, "ipp-usb is running")
+		running = true
+	default:
+		InitLog.Info(0, "%s", err)
+	}
+
+	// Dump ipp-usb status file, if ipp-usb is running
+	if running {
+		var text []byte
+
+		status, err := os.OpenFile(PathStatusFile,
+			os.O_RDWR, 0600)
+		if err == nil {
+			defer status.Close()
+			err = FileLock(status, FileLockWait)
+		}
+		if err == nil {
+			err = FileLock(status, FileLockWait)
+			text, err = ioutil.ReadAll(status)
+		}
+
+		if err == nil {
+			text = bytes.Trim(text, "\n")
+			lines := bytes.Split(text, []byte("\n"))
+
+			for len(lines) > 0 && len(lines[len(lines)-1]) == 0 {
+				lines = lines[0 : len(lines)-1]
+			}
+
+			if len(lines) == 0 {
+				InitLog.Info(0, "per-device status: empty")
+			} else {
+				InitLog.Info(0, "per-device status:")
+				for _, line := range lines {
+					InitLog.Info(0, "%s", line)
+				}
+			}
+		} else {
+			InitLog.Info(0, "per-device status: %s", err)
+		}
+	}
+}
+
 // The main function
 func main() {
 	var err error
@@ -143,7 +210,9 @@ func main() {
 	InitLog.Check(err)
 
 	// Setup logging
-	if params.Mode != RunDebug && params.Mode != RunCheck {
+	if params.Mode != RunDebug &&
+		params.Mode != RunCheck &&
+		params.Mode != RunStatus {
 		Console.ToNowhere()
 	} else if Conf.ColorConsole {
 		Console.ToColorConsole()
@@ -200,8 +269,13 @@ func main() {
 		InitLog.Exit(0, "This program requires root privileges")
 	}
 
-	// If mode is "check", we are done
-	if params.Mode == RunCheck {
+	// In RunStatus mode, print ipp-usb status
+	if params.Mode == RunStatus {
+		printStatus()
+	}
+
+	// If mode is "check" or "status", we are done
+	if params.Mode == RunCheck || params.Mode == RunStatus {
 		os.Exit(0)
 	}
 
@@ -220,7 +294,7 @@ func main() {
 	InitLog.Check(err)
 	defer lock.Close()
 
-	err = FileLock(lock, true, false)
+	err = FileLock(lock, FileLockNoWait)
 	if err == ErrLockIsBusy {
 		if params.Mode == RunUdev {
 			// It's not an error in udev mode
@@ -232,7 +306,7 @@ func main() {
 	InitLog.Check(err)
 
 	// Write to log that we are here
-	if params.Mode != RunCheck {
+	if params.Mode != RunCheck && params.Mode != RunStatus {
 		Log.Info(' ', "===============================")
 		Log.Info(' ', "ipp-usb started in %q mode, pid=%d",
 			params.Mode, os.Getpid())
@@ -269,7 +343,7 @@ func main() {
 			Log.Check(err)
 
 			if UsbCheckIppOverUsbDevices() &&
-				FileLock(lock, true, false) == nil {
+				FileLock(lock, FileLockNoWait) == nil {
 				Log.Info(' ', "New IPP-over-USB device found")
 				continue
 			}

main.go

@@ -27,6 +27,9 @@ const (
 	// PathLockFile defines path to lock file
 	PathLockFile = PathLockDir + "/ipp-usb.lock"
 
+	// PathStatusFile defines path to the status file
+	PathStatusFile = PathProgState + "/status"
+
 	// PathProgStateDev defines path to directory where per-device state
 	// files are saved to
 	PathProgStateDev = PathProgState + "/dev"