Refine TFO

src/main/scala/com/github/shadowsocks/ShadowsocksApplication.scala

@@ -112,12 +112,7 @@ class ShadowsocksApplication extends Application {
     }
     pending.setResultCallback(callback, 2, TimeUnit.SECONDS)
 
-    // TFO
-    val tfo = settings.getBoolean(Key.tfo, false)
-    if (tfo && !TcpFastOpen.isEnabled)
-    {
-      TcpFastOpen.enabled(true)
-    }
+    TcpFastOpen.enabled(settings.getBoolean(Key.tfo, false))
   }
 
   def refreshContainerHolder {

src/main/scala/com/github/shadowsocks/ShadowsocksNatService.scala

@@ -105,7 +105,7 @@ class ShadowsocksNatService extends BaseService {
 
     if (profile.auth) cmd += "-A"
 
-    if (TcpFastOpen.isEnabled) cmd += "--fast-open"
+    if (TcpFastOpen.sendEnabled) cmd += "--fast-open"
 
     if (profile.route != Route.ALL) {
       cmd += "--acl"

src/main/scala/com/github/shadowsocks/ShadowsocksSettings.scala

@@ -155,17 +155,14 @@ class ShadowsocksSettings extends PreferenceFragment with OnSharedPreferenceChan
     }
     switch.setChecked(BootReceiver.getEnabled(activity))
 
-    if (getPreferenceManager.getSharedPreferences.getBoolean(Key.tfo, false) && !TcpFastOpen.isEnabled) {
-      TcpFastOpen.enabled(true)
-    }
     val tfo = findPreference(Key.tfo).asInstanceOf[SwitchPreference]
-    tfo.setChecked(TcpFastOpen.isEnabled)
+    tfo.setChecked(TcpFastOpen.sendEnabled)
     tfo.setOnPreferenceChangeListener((_, v) => {
       val value = v.asInstanceOf[Boolean]
       val result = TcpFastOpen.enabled(value)
       if (result != null && result != "Success.")
         Snackbar.make(activity.findViewById(android.R.id.content), result, Snackbar.LENGTH_LONG).show()
-      value == TcpFastOpen.isEnabled
+      value == TcpFastOpen.sendEnabled
     })
     if (!TcpFastOpen.supported) {
       tfo.setEnabled(false)

src/main/scala/com/github/shadowsocks/ShadowsocksVpnService.scala

@@ -266,7 +266,7 @@ class ShadowsocksVpnService extends VpnService with BaseService {
       cmd += (getApplicationInfo.dataDir + "/acl.list")
     }
 
-    if (TcpFastOpen.isEnabled) cmd += "--fast-open"
+    if (TcpFastOpen.sendEnabled) cmd += "--fast-open"
 
     if (BuildConfig.DEBUG) Log.d(TAG, cmd.mkString(" "))
 

src/main/scala/com/github/shadowsocks/utils/TcpFastOpen.scala

@@ -23,12 +23,12 @@ object TcpFastOpen {
     case _ => false
   }
 
-  def isEnabled = {
+  def sendEnabled = {
     val file = new File("/proc/sys/net/ipv4/tcp_fastopen")
     file.canRead && (Utils.readAllLines(file).toInt & 1) > 0
   }
 
-  def enabled(value: Boolean): String = {
+  def enabled(value: Boolean): String = if (sendEnabled != value) {
     val res = Shell.run("su", Array(
       "if echo " + (if (value) 3 else 0) + " > /proc/sys/net/ipv4/tcp_fastopen; then",
       "  echo Success.",
@@ -36,5 +36,5 @@ object TcpFastOpen {
       "  echo Failed.",
       "fi"), null, true)
     if (res != null) res.asScala.mkString("\n") else null
-  }
+  } else null
 }