Show detailed error for failed connections in VPN mode

Also change such errors colors from red to orange, as they
are normal during a capture.

Closes #441

app/src/main/java/com/emanuelef/remote_capture/adapters/ConnectionsAdapter.java

@@ -147,6 +147,10 @@ public class ConnectionsAdapter extends RecyclerView.Adapter<ConnectionsAdapter.
             else if((conn.status == ConnectionDescriptor.CONN_STATUS_CLOSED)
                     || (conn.status == ConnectionDescriptor.CONN_STATUS_RESET))
                 color = R.color.statusClosed;
+            else if ((conn.status == ConnectionDescriptor.CONN_STATUS_ERROR)
+                    || ((conn.status == ConnectionDescriptor.CONN_STATUS_SOCKET_ERROR))
+                    || (conn.status == ConnectionDescriptor.CONN_STATUS_UNREACHABLE))
+                color = R.color.warning;
             else
                 color = R.color.statusError;
 

app/src/main/java/com/emanuelef/remote_capture/fragments/ConnectionOverview.java

@@ -25,6 +25,7 @@ import android.content.Context;
 import android.content.Intent;
 import android.net.Uri;
 import android.os.Bundle;
+import android.util.Pair;
 import android.view.LayoutInflater;
 import android.view.Menu;
 import android.view.MenuInflater;
@@ -70,6 +71,9 @@ public class ConnectionOverview extends Fragment implements ConnectionDetailsAct
     private TextView mLastSeen;
     //private TextView mTcpFlags;
     private TextView mError;
+    private TextView mSocketErrno;
+    private View mSocketErrnoRow;
+    private View mSocketErrnoInfo;
     private ImageView mBlacklistedIp;
     private ImageView mBlacklistedHost;
 
@@ -130,6 +134,9 @@ public class ConnectionOverview extends Fragment implements ConnectionDetailsAct
         mLastSeen = view.findViewById(R.id.last_seen);
         //mTcpFlags = view.findViewById(R.id.tcp_flags);
         mError = view.findViewById(R.id.error_msg);
+        mSocketErrno = view.findViewById(R.id.detail_errno);
+        mSocketErrnoRow = view.findViewById(R.id.error_row);
+        mSocketErrnoInfo = view.findViewById(R.id.error_info);
         mBlacklistedIp = view.findViewById(R.id.blacklisted_ip);
         mBlacklistedHost = view.findViewById(R.id.blacklisted_host);
 
@@ -280,6 +287,26 @@ public class ConnectionOverview extends Fragment implements ConnectionDetailsAct
         mBlacklistedIp.setVisibility(mConn.isBlacklistedIp() ? View.VISIBLE : View.GONE);
         mBlacklistedHost.setVisibility(mConn.isBlacklistedHost() ? View.VISIBLE : View.GONE);
 
+        if (mConn.error > 0) {
+            mSocketErrnoRow.setVisibility(View.VISIBLE);
+
+            Pair<Integer, Integer> errnoInfo = getSocketErrnoInfo(mConn.error);
+            mSocketErrno.setText(context.getString(R.string.error_code_with_text,
+                    context.getString((errnoInfo != null) ? errnoInfo.first : R.string.unknown_app),
+                    mConn.error));
+
+            if (errnoInfo != null) {
+                final int msgId = errnoInfo.second;
+
+                mSocketErrnoInfo.setOnClickListener(view -> {
+                    Context ctx = getContext();
+                    if (ctx != null)
+                        Utils.showHelpDialog(ctx, msgId);
+                });
+            } else
+                mSocketErrnoInfo.setVisibility(View.GONE);
+        }
+
         if(mConn.decryption_error != null) {
             mError.setTextColor(ContextCompat.getColor(context, R.color.danger));
             mError.setText(mConn.decryption_error);
@@ -316,4 +343,28 @@ public class ConnectionOverview extends Fragment implements ConnectionDetailsAct
         } else
             mError.setVisibility(View.GONE);
     }
+
+    private Pair<Integer, Integer> getSocketErrnoInfo(int errno) {
+        return switch (errno) {
+            case 32 -> /* EPIPE */
+                    new Pair<>(R.string.errno_epipe, R.string.errno_epipe_msg);
+            case 100 -> /* ENETDOWN */
+                    new Pair<>(R.string.errno_enetdown, R.string.errno_enetdown_msg);
+            case 101 -> /* ENETUNREACH */
+                    new Pair<>(R.string.errno_enetunreach, R.string.errno_enetunreach_msg);
+            case 102 -> /* ENETRESET */
+                    new Pair<>(R.string.errno_enetreset, R.string.errno_enetreset_msg);
+            case 103 -> /* ECONNABORTED */
+                    new Pair<>(R.string.errno_econnaborted, R.string.errno_econnaborted_msg);
+            case 104 -> /* ECONNRESET */
+                    new Pair<>(R.string.errno_econnreset, R.string.errno_econnreset_msg);
+            case 110 -> /* ETIMEDOUT */
+                    new Pair<>(R.string.errno_etimedout, R.string.errno_etimedout_msg);
+            case 111 -> /* ECONNREFUSED */
+                    new Pair<>(R.string.errno_econnrefused, R.string.errno_econnrefused_msg);
+            case 113 -> /* EHOSTUNREACH */
+                    new Pair<>(R.string.errno_ehostunreach, R.string.errno_ehostunreach_msg);
+            default -> null;
+        };
+    }
 }

app/src/main/java/com/emanuelef/remote_capture/model/ConnectionDescriptor.java

@@ -109,6 +109,7 @@ public class ConnectionDescriptor {
     private final boolean mitm_decrypt; // true if the connection is under mitm for TLS decryption
     private boolean internal_decrypt;
     public int status;
+    public int error;
     private int tcp_flags;
     private boolean blacklisted_ip;
     private boolean blacklisted_host;
@@ -160,6 +161,7 @@ public class ConnectionDescriptor {
             rcvd_pkts = update.rcvd_pkts;
             blocked_pkts = update.blocked_pkts;
             status = (update.status & 0x00FF);
+            error = (update.status & 0xFF0000) >> 16;
             port_mapping_applied = (update.status & 0x2000) != 0;
             decryption_ignored = (update.status & 0x1000) != 0;
             netd_block_missed = (update.status & 0x0800) != 0;

app/src/main/jni/core/capture_vpn.c

@@ -334,6 +334,7 @@ static void connection_closed(zdtun_t *zdt, const zdtun_conn_t *conn_info) {
 
     pd_giveup_dpi(pd, data, tuple);
     data->status = zdtun_conn_get_status(conn_info);
+    data->error = zdtun_conn_get_error(conn_info);
     data->to_purge = true;
 }
 
@@ -346,8 +347,10 @@ static void update_conn_status(zdtun_t *zdt, const zdtun_pkt_t *pkt, uint8_t fro
 
     // Update the connection status
     data->status = zdtun_conn_get_status(conn_info);
-    if(data->status >= CONN_STATUS_CLOSED)
+    if(data->status >= CONN_STATUS_CLOSED) {
         data->to_purge = true;
+        data->error = zdtun_conn_get_error(conn_info);
+    }
 }
 
 /* ******************************************************* */

app/src/main/jni/core/jni_impl.c

@@ -169,7 +169,8 @@ static jobject getConnUpdate(pcapdroid_t *pd, const conn_and_tuple_t *conn) {
         (*env)->CallVoidMethod(env, update, mids.connUpdateSetStats, data->last_seen,
                                data->payload_length, data->sent_bytes, data->rcvd_bytes, data->sent_pkts, data->rcvd_pkts, data->blocked_pkts,
                                (data->tcp_flags[0] << 8) | data->tcp_flags[1],
-                               (data->port_mapping_applied << 13) |
+                               (data->error << 16) /* 8 bits are enough for socket errno */ |
+                                    (data->port_mapping_applied << 13) |
                                     (data->decryption_ignored << 12) |
                                     (data->netd_block_missed << 11) |
                                     (blocked << 10) |

app/src/main/jni/core/pcapdroid.h

@@ -105,6 +105,7 @@ typedef struct {
     jint rcvd_pkts;
     jint blocked_pkts;
     zdtun_conn_status_t status;
+    int error;
     char *info;
     jint uid;
     char country_code[3];

app/src/main/res/layout/connection_overview.xml

@@ -177,6 +177,43 @@
                 tools:text="Open" />
         </TableRow>
 
+        <TableRow
+            android:id="@+id/error_row"
+            android:layout_width="match_parent"
+            android:layout_height="0dp"
+            android:layout_marginBottom="4dp"
+            android:visibility="gone"
+            tools:visibility="visible">
+            <TextView
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:layout_weight="0.25"
+                android:textStyle="bold"
+                android:text="@string/error" />
+            <LinearLayout
+                android:layout_width="0dp"
+                android:layout_height="match_parent"
+                android:layout_weight="0.75"
+                android:orientation="horizontal">
+
+                <TextView
+                    android:id="@+id/detail_errno"
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:textIsSelectable="true"
+                    android:textColor="@color/warning"
+                    tools:text="No route to host (error 113)" />
+
+                <ImageView
+                    android:id="@+id/error_info"
+                    android:layout_gravity="center"
+                    android:layout_width="wrap_content"
+                    android:layout_height="match_parent"
+                    android:paddingTop="1sp"
+                    android:src="@drawable/ic_info" />
+            </LinearLayout>
+        </TableRow>
+
         <TableRow
             android:id="@+id/interface_row"
             android:layout_width="match_parent"
@@ -496,6 +533,7 @@
         android:textIsSelectable="true"
         android:layout_marginTop="8dp"
         android:visibility="gone"
+        tools:visibility="visible"
         tools:text="The client may not trust certificate" />
 
 </androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/values/strings.xml

@@ -507,7 +507,7 @@
     <string name="pcap_file_load_aborted">Capture file loading aborted</string>
     <string name="host_resolution_failed">"Could not resolve host %1$s</string>
     <string name="pcapdroid_trailer_notice">To show the actual apps instead of \"%1$s\", be sure to enable the \"%2$s\" option before generating the dump</string>
-    <string name="decryption_info_no_rule">This connection will not be decrypted. Create a decryption rule to decrypt it</string>
+    <string name="decryption_info_no_rule">This connection will not be decrypted. Create a decryption rule to decrypt it (e.g from the left drawer)</string>
     <string name="tls_decryption_no_rules_notice">TLS decryption is only applied to connections that match the configured rules. Do you want to create decryption rules now?</string>
     <string name="active_vpn_detected">Active VPN detected</string>
     <string name="mitm_doze_notice">Battery optimization may interfere with the mitm addon</string>
@@ -533,4 +533,23 @@
     <string name="larger_than">Larger than</string>
     <string name="select_the_pcap_file">Select the PCAP/Pcapng file</string>
     <string name="select_the_keylog_file">Select the SSL keylog file</string>
+    <string name="error_code_with_text">%1$s (error %2$d)</string>
+    <string name="errno_epipe">Broken pipe</string>
+    <string name="errno_epipe_msg">The server unexpectedly closed the connection during the data transfer</string>
+    <string name="errno_enetdown">Network is down</string>
+    <string name="errno_enetdown_msg">The network interface is down or it\'s unable to connect to the network</string>
+    <string name="errno_enetunreach">Network is unreachable</string>
+    <string name="errno_enetunreach_msg">The system cannot find a valid route to the destination network</string>
+    <string name="errno_enetreset">Network reset</string>
+    <string name="errno_enetreset_msg">The network connection was reset by an intermediary device (e.g. router or mobile carrier)</string>
+    <string name="errno_econnaborted">Connection aborted</string>
+    <string name="errno_econnaborted_msg">The connection was aborted, usually due to a network transition</string>
+    <string name="errno_econnreset">Connection reset by peer</string>
+    <string name="errno_econnreset_msg">The server abruptly closed the connection, usually due to a crash or ungraceful shutdown</string>
+    <string name="errno_etimedout">Connection timed out</string>
+    <string name="errno_etimedout_msg">The server took too long to respond, likely due to network delays or a busy server</string>
+    <string name="errno_econnrefused">Connection refused</string>
+    <string name="errno_econnrefused_msg">The server rejected the connection, which may indicate a too busy or malfunctioning server</string>
+    <string name="errno_ehostunreach">No route to host</string>
+    <string name="errno_ehostunreach_msg">The system cannot find a route to the destination host</string>
 </resources>