| /* |
| * Copyright (C) 2019 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package com.android.internal.net.ipsec.ike.utils; |
| |
| import static com.android.internal.net.ipsec.ike.IkeSessionStateMachine.CMD_RETRANSMIT; |
| |
| import android.os.Handler; |
| |
| import com.android.internal.annotations.VisibleForTesting; |
| import com.android.internal.net.ipsec.ike.message.IkeMessage; |
| |
| /** |
| * Retransmitter represents a class that will send a message and trigger delayed retransmissions |
| * |
| * <p>The Retransmitter class will queue retransmission signals on the provided handler. The owner |
| * of this retransmitter instance is expected to wait for the signal, and call retransmit() on the |
| * instance of this class. |
| */ |
| public abstract class Retransmitter { |
| private static IBackoffTimeoutCalculator sBackoffTimeoutCalculator = |
| new BackoffTimeoutCalculator(); |
| |
| /* |
| * Retransmit parameters |
| * |
| * (Re)transmission count | Relative timeout | Absolute timeout |
| * -------------------------+-------------------+------------------ |
| * 0 | 500ms | 500ms |
| * 1 | 1s | 1.5s |
| * 2 | 2s | 3.5s |
| * 3 | 4s | 7.5s |
| * 4 | 8s | 15.5s |
| * 5 | 16s | 31.5s |
| * |
| * TODO: Add retransmitter configurability |
| */ |
| static final double RETRANSMIT_BACKOFF_FACTOR = 2.0; |
| static final long RETRANSMIT_TIMEOUT_MS = 500L; |
| static final int RETRANSMIT_MAX_ATTEMPTS = 5; |
| |
| private final Handler mHandler; |
| private final IkeMessage mRetransmitMsg; |
| private int mRetransmitCount = 0; |
| |
| public Retransmitter(Handler handler, IkeMessage msg) { |
| mHandler = handler; |
| mRetransmitMsg = msg; |
| } |
| |
| /** |
| * Triggers a (re)transmission. Will enqueue a future retransmission signal on the given handler |
| */ |
| public void retransmit() { |
| if (mRetransmitMsg == null) { |
| return; |
| } |
| |
| // If the failed iteration is beyond the max attempts, clean up and shut down. |
| if (mRetransmitCount > RETRANSMIT_MAX_ATTEMPTS) { |
| handleRetransmissionFailure(); |
| return; |
| } |
| |
| send(mRetransmitMsg); |
| |
| long timeout = sBackoffTimeoutCalculator.getExponentialBackoffTimeout(mRetransmitCount++); |
| mHandler.sendMessageDelayed(mHandler.obtainMessage(CMD_RETRANSMIT, this), timeout); |
| } |
| |
| /** Cancels any future retransmissions */ |
| public void stopRetransmitting() { |
| mHandler.removeMessages(CMD_RETRANSMIT, this); |
| } |
| |
| /** Retrieves the message this retransmitter is tracking */ |
| public IkeMessage getMessage() { |
| return mRetransmitMsg; |
| } |
| |
| /** |
| * Implementation-provided sender |
| * |
| * <p>For Retransmitter-internal use only. |
| * |
| * @param msg the message to be sent |
| */ |
| protected abstract void send(IkeMessage msg); |
| |
| /** |
| * Callback for implementations to be informed that we have reached the max retransmissions. |
| * |
| * <p>For Retransmitter-internal use only. |
| */ |
| protected abstract void handleRetransmissionFailure(); |
| |
| /** |
| * IBackoffTimeoutCalculator provides interface for calculating retransmission backoff timeout. |
| * |
| * <p>IBackoffTimeoutCalculator exists so that the interface is injectable for testing. |
| */ |
| @VisibleForTesting |
| public interface IBackoffTimeoutCalculator { |
| /** Calculate retransmission backoff timeout */ |
| long getExponentialBackoffTimeout(int retransmitCount); |
| } |
| |
| private static final class BackoffTimeoutCalculator implements IBackoffTimeoutCalculator { |
| @Override |
| public long getExponentialBackoffTimeout(int retransmitCount) { |
| double expBackoffFactor = Math.pow(RETRANSMIT_BACKOFF_FACTOR, retransmitCount); |
| return (long) (RETRANSMIT_TIMEOUT_MS * expBackoffFactor); |
| } |
| } |
| |
| /** Sets IBackoffTimeoutCalculator */ |
| @VisibleForTesting |
| public static void setBackoffTimeoutCalculator(IBackoffTimeoutCalculator calculator) { |
| sBackoffTimeoutCalculator = calculator; |
| } |
| |
| /** Resets BackoffTimeoutCalculator of retransmitter */ |
| @VisibleForTesting |
| public static void resetBackoffTimeoutCalculator() { |
| sBackoffTimeoutCalculator = new BackoffTimeoutCalculator(); |
| } |
| } |