Add method for checking whether contact supports transport.

bramble-api/src/main/java/org/briarproject/bramble/api/plugin/file/RemovableDriveManager.java

@@ -39,6 +39,12 @@ public interface RemovableDriveManager {
 	 */
 	RemovableDriveTask startWriterTask(ContactId c, TransportProperties p);
 
+	/**
+	 * Returns true if the given contact has indicated support for the
+	 * removable drive transport.
+	 */
+	boolean isTransportSupportedByContact(ContactId c) throws DbException;
+
 	/**
 	 * Returns true if there is anything to send to the given contact.
 	 */

bramble-core/src/main/java/org/briarproject/bramble/plugin/file/RemovableDriveManagerImpl.java

@@ -8,6 +8,7 @@ import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.plugin.file.RemovableDriveManager;
 import org.briarproject.bramble.api.plugin.file.RemovableDriveTask;
 import org.briarproject.bramble.api.properties.TransportProperties;
+import org.briarproject.bramble.api.properties.TransportPropertyManager;
 
 import java.util.concurrent.Executor;
 
@@ -16,6 +17,8 @@ import javax.annotation.concurrent.GuardedBy;
 import javax.annotation.concurrent.ThreadSafe;
 import javax.inject.Inject;
 
+import static org.briarproject.bramble.api.plugin.file.RemovableDriveConstants.ID;
+import static org.briarproject.bramble.api.plugin.file.RemovableDriveConstants.PROP_SUPPORTED;
 import static org.briarproject.bramble.plugin.file.RemovableDrivePluginFactory.MAX_LATENCY;
 
 @ThreadSafe
@@ -25,6 +28,7 @@ class RemovableDriveManagerImpl
 
 	private final Executor ioExecutor;
 	private final DatabaseComponent db;
+	private final TransportPropertyManager transportPropertyManager;
 	private final RemovableDriveTaskFactory taskFactory;
 	private final Object lock = new Object();
 
@@ -34,10 +38,14 @@ class RemovableDriveManagerImpl
 	private RemovableDriveTask writer = null;
 
 	@Inject
-	RemovableDriveManagerImpl(@IoExecutor Executor ioExecutor,
-			DatabaseComponent db, RemovableDriveTaskFactory taskFactory) {
+	RemovableDriveManagerImpl(
+			@IoExecutor Executor ioExecutor,
+			DatabaseComponent db,
+			TransportPropertyManager transportPropertyManager,
+			RemovableDriveTaskFactory taskFactory) {
 		this.ioExecutor = ioExecutor;
 		this.db = db;
+		this.transportPropertyManager = transportPropertyManager;
 		this.taskFactory = taskFactory;
 	}
 
@@ -80,6 +88,14 @@ class RemovableDriveManagerImpl
 		return created;
 	}
 
+	@Override
+	public boolean isTransportSupportedByContact(ContactId c)
+			throws DbException {
+		TransportProperties p =
+				transportPropertyManager.getRemoteProperties(c, ID);
+		return "true".equals(p.get(PROP_SUPPORTED));
+	}
+
 	@Override
 	public boolean isWriterTaskNeeded(ContactId c) throws DbException {
 		return db.transactionWithResult(true, txn ->