Add option for autounmount

Even though filesystem notifications aren't implemented for FUSE, I decided to
try my hand at implementing the autounmount feature (#128). I based it on the
EncFS autounmount code, which records filesystem accesses and checks every X
seconds whether it's idled long enough to unmount.

I've tested the feature locally, but I haven't added any tests for this flag.
I also haven't worked with Go before. So please let me know if there's
anything that should be done differently.

One particular concern: I worked from the assumption that the open files table
is unique per-filesystem. If that's not true, I'll need to add an open file
count and associated lock to the Filesystem type instead.

https://github.com/rfjakob/gocryptfs/pull/265

1 files changed, 12 insertions, 0 deletions

diff --git a/cli_args.go b/cli_args.go
index dd00658..c073958 100644
--- a/cli_args.go
+++ b/cli_args.go
@@ -7,6 +7,7 @@ import (
 	"os"
 	"strconv"
 	"strings"
+	"time"
 
 	"github.com/hanwen/go-fuse/fuse"
 	"github.com/rfjakob/gocryptfs/internal/configfile"
@@ -33,6 +34,8 @@ type argContainer struct {
 	// Configuration file name override
 	config             string
 	notifypid, scryptn int
+	// Idle time before autounmount
+	idle time.Duration
 	// Helper variables that are NOT cli options all start with an underscore
 	// _configCustom is true when the user sets a custom config file name.
 	_configCustom bool
@@ -187,6 +190,11 @@ func parseCliOpts() (args argContainer) {
 		"successful mount - used internally for daemonization")
 	flagSet.IntVar(&args.scryptn, "scryptn", configfile.ScryptDefaultLogN, "scrypt cost parameter logN. Possible values: 10-28. "+
 		"A lower value speeds up mounting and reduces its memory needs, but makes the password susceptible to brute-force attacks")
+
+	flagSet.DurationVar(&args.idle, "i", 0, "Alias for -idle")
+	flagSet.DurationVar(&args.idle, "idle", 0, "Auto-unmount after specified idle duration (ignored in reverse mode). "+
+		"Durations are specified like \"500s\" or \"2h45m\". 0 means stay mounted indefinitely.")
+
 	var dummyString string
 	flagSet.StringVar(&dummyString, "o", "", "For compatibility with mount(1), options can be also passed as a comma-separated list to -o on the end.")
 	// Actual parsing
@@ -247,6 +255,10 @@ func parseCliOpts() (args argContainer) {
 		tlog.Fatal.Printf("The options -extpass and -trezor cannot be used at the same time")
 		os.Exit(exitcodes.Usage)
 	}
+	if args.idle < 0 {
+		tlog.Fatal.Printf("Idle timeout cannot be less than 0")
+		os.Exit(exitcodes.Usage)
+	}
 	return args
 }