1 /*
2 * Copyright 2019 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License,
5 * version 2.0 (the "License"); you may not use this file except in compliance
6 * with the License. You may obtain a copy of the License at:
7 *
8 * https://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package io.netty.handler.address;
17
18 import io.netty.channel.ChannelHandlerContext;
19 import io.netty.channel.ChannelOutboundHandler;
20 import io.netty.channel.ChannelOutboundHandlerAdapter;
21 import io.netty.channel.ChannelPromise;
22
23 import java.net.NetworkInterface;
24 import java.net.SocketAddress;
25
26 /**
27 * {@link ChannelOutboundHandler} implementation which allows to dynamically replace the used
28 * {@code remoteAddress} and / or {@code localAddress} when making a connection attempt.
29 * <p>
30 * This can be useful to for example bind to a specific {@link NetworkInterface} based on
31 * the {@code remoteAddress}.
32 */
33 public abstract class DynamicAddressConnectHandler extends ChannelOutboundHandlerAdapter {
34
35 @Override
36 public final void connect(ChannelHandlerContext ctx, SocketAddress remoteAddress,
37 SocketAddress localAddress, ChannelPromise promise) {
38 final SocketAddress remote;
39 final SocketAddress local;
40 try {
41 remote = remoteAddress(remoteAddress, localAddress);
42 local = localAddress(remoteAddress, localAddress);
43 } catch (Exception e) {
44 promise.setFailure(e);
45 return;
46 }
47 ctx.connect(remote, local, promise).addListener(future -> {
48 if (future.isSuccess()) {
49 // We only remove this handler from the pipeline once the connect was successful as otherwise
50 // the user may try to connect again.
51 ctx.pipeline().remove(DynamicAddressConnectHandler.this);
52 }
53 });
54 }
55
56 /**
57 * Returns the local {@link SocketAddress} to use for
58 * {@link ChannelHandlerContext#connect(SocketAddress, SocketAddress)} based on the original {@code remoteAddress}
59 * and {@code localAddress}.
60 * By default, this method returns the given {@code localAddress}.
61 */
62 protected SocketAddress localAddress(
63 @SuppressWarnings("unused") SocketAddress remoteAddress, SocketAddress localAddress) throws Exception {
64 return localAddress;
65 }
66
67 /**
68 * Returns the remote {@link SocketAddress} to use for
69 * {@link ChannelHandlerContext#connect(SocketAddress, SocketAddress)} based on the original {@code remoteAddress}
70 * and {@code localAddress}.
71 * By default, this method returns the given {@code remoteAddress}.
72 */
73 protected SocketAddress remoteAddress(
74 SocketAddress remoteAddress, @SuppressWarnings("unused") SocketAddress localAddress) throws Exception {
75 return remoteAddress;
76 }
77 }