From ca063e3296509fe6d6ae36dae857d91f7e44ab5c Mon Sep 17 00:00:00 2001
From: emanuele-f <black.silver@hotmail.it>
Date: Wed, 1 Jun 2022 12:14:38 +0200
Subject: [PATCH] Wait for capture stop when calling stop via API

This allows getting more accurate capture stats
---
 .../remote_capture/CaptureService.java        | 36 ++++++++++++++++---
 .../activities/CaptureCtrl.java               | 14 ++++----
 app/src/main/jni/core/capture_vpn.c           |  2 +-
 3 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/app/src/main/java/com/emanuelef/remote_capture/CaptureService.java b/app/src/main/java/com/emanuelef/remote_capture/CaptureService.java
index 80ec6dae..034045b6 100644
--- a/app/src/main/java/com/emanuelef/remote_capture/CaptureService.java
+++ b/app/src/main/java/com/emanuelef/remote_capture/CaptureService.java
@@ -83,6 +83,8 @@ import java.net.UnknownHostException;
 import java.util.Enumeration;
 import java.util.Iterator;
 import java.util.concurrent.LinkedBlockingDeque;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
 
 public class CaptureService extends VpnService implements Runnable {
     private static final String TAG = "CaptureService";
@@ -92,6 +94,8 @@ public class CaptureService extends VpnService implements Runnable {
     private static final int VPN_MTU = 10000;
     private static final int NOTIFY_ID_VPNSERVICE = 1;
     private static CaptureService INSTANCE;
+    final ReentrantLock mLock = new ReentrantLock();
+    final Condition mCaptureStopped = mLock.newCondition();
     private ParcelFileDescriptor mParcelFileDescriptor;
     private boolean mIsAlwaysOnVPN;
     private SharedPreferences mPrefs;
@@ -883,13 +887,16 @@ public class CaptureService extends VpnService implements Runnable {
 
         stopService();
 
+        mLock.lock();
+        mCaptureThread = null;
+        mCaptureStopped.signalAll();
+        mLock.unlock();
+
         // Notify
         mHandler.post(() -> {
             sendServiceStatus(SERVICE_STATUS_STOPPED);
-            CaptureCtrl.notifyCaptureStopped(this, mLastStats);
+            CaptureCtrl.notifyCaptureStopped(this, getStats());
         });
-
-        mCaptureThread = null;
     }
 
     private void connUpdateWork() {
@@ -1176,8 +1183,27 @@ public class CaptureService extends VpnService implements Runnable {
         nativeSetFirewallEnabled(enabled);
     }
 
-    public static CaptureStats getStats() {
-        return((INSTANCE != null) ? INSTANCE.mLastStats : null);
+    public static @NonNull CaptureStats getStats() {
+        CaptureStats stats = (INSTANCE != null) ? INSTANCE.mLastStats : null;
+        return((stats != null) ? stats : new CaptureStats());
+    }
+
+    public static void waitForCaptureStop() {
+        if(INSTANCE == null)
+            return;
+
+        Log.d(TAG, "waitForCaptureStop " + Thread.currentThread().getName());
+        INSTANCE.mLock.lock();
+        try {
+            while(INSTANCE.mCaptureThread != null) {
+                try {
+                    INSTANCE.mCaptureStopped.await();
+                } catch (InterruptedException ignored) {}
+            }
+        } finally {
+            INSTANCE.mLock.unlock();
+        }
+        Log.d(TAG, "waitForCaptureStop done " + Thread.currentThread().getName());
     }
 
     private static native void runPacketLoop(int fd, CaptureService vpn, int sdk);
diff --git a/app/src/main/java/com/emanuelef/remote_capture/activities/CaptureCtrl.java b/app/src/main/java/com/emanuelef/remote_capture/activities/CaptureCtrl.java
index f4cee651..5969e201 100644
--- a/app/src/main/java/com/emanuelef/remote_capture/activities/CaptureCtrl.java
+++ b/app/src/main/java/com/emanuelef/remote_capture/activities/CaptureCtrl.java
@@ -206,9 +206,10 @@ public class CaptureCtrl extends AppCompatActivity {
             CaptureService.stopService();
             mStarterApp = null;
 
-            CaptureStats stats = CaptureService.getStats();
-            if(stats != null)
-                putStats(res, stats);
+            // stopService returns immediately, need to wait for capture stop
+            CaptureService.waitForCaptureStop();
+
+            putStats(res, CaptureService.getStats());
         } else if(action.equals(ACTION_STATUS)) {
             Log.d(TAG, "Returning status");
 
@@ -216,9 +217,7 @@ public class CaptureCtrl extends AppCompatActivity {
             res.putExtra("version_name", BuildConfig.VERSION_NAME);
             res.putExtra("version_code", BuildConfig.VERSION_CODE);
 
-            CaptureStats stats = CaptureService.getStats();
-            if(stats != null)
-                putStats(res, stats);
+            putStats(res, CaptureService.getStats());
         } else {
             Log.e(TAG, "unknown action: " + action);
             abort();
@@ -230,6 +229,9 @@ public class CaptureCtrl extends AppCompatActivity {
     }
 
     public static void notifyCaptureStopped(Context ctx, CaptureStats stats) {
+        if(stats != null)
+            Log.d(TAG, "notifyCaptureStopped: " + (stats.pkts_sent + stats.pkts_rcvd) + " pkts");
+
         if((mStarterApp != null) && (mReceiverClass != null)) {
             Log.d(TAG, "Notifying receiver");
 
diff --git a/app/src/main/jni/core/capture_vpn.c b/app/src/main/jni/core/capture_vpn.c
index fbe9906d..b2396cf5 100644
--- a/app/src/main/jni/core/capture_vpn.c
+++ b/app/src/main/jni/core/capture_vpn.c
@@ -583,7 +583,7 @@ int run_vpn(pcapdroid_t *pd) {
                 } else {
                     // zdtun_forward was successful
                     if(data->vpn.fw_pctx) {
-                        // not accounted in remote2vpn, account here
+                        // it was not accounted in remote2vpn, account here
                         pd_account_stats(pd, data->vpn.fw_pctx);
                         data->vpn.fw_pctx = NULL;
                     }