Remove cold-start latency from the VPN by blocking

Previously, if there was no data available the VPN would pause
for 100ms, because the connection was non-blocking. This adds
~50ms to request startup whenever the connection goes quiet,
which is pretty noticeable! This tiny change and that goes
away (ping over wifi is now ~10ms vs 4ms direct).

Author: pimterry

app/src/main/java/tech/httptoolkit/android/ProxyVpnRunnable.kt

@@ -84,7 +84,7 @@ class ProxyVpnRunnable(
                 packet.clear()
             } else {
                 try {
-                    Thread.sleep(100)
+                    Thread.sleep(10)
                 } catch (e: InterruptedException) {
                     Log.d(TAG, "Failed to sleep: " + e.message)
                 }

app/src/main/java/tech/httptoolkit/android/ProxyVpnService.kt

@@ -148,6 +148,7 @@ class ProxyVpnService : VpnService(), IProtectSocket {
             vpnInterface = Builder()
                 .addAddress(VPN_IP_ADDRESS, 32)
                 .addRoute(ALL_ROUTES, 0)
+                .setBlocking(true) // We use a blocking loop to read this in ProxyVpnRunnable
                 .apply {
                     // We exclude ourselves from interception, so we can still make network requests
                     // separately, primarily because otherwise pinging with isReachable is recursive.