1 /* 2 * Copyright 2017 The gRPC Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://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, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package io.grpc; 18 19 import java.io.IOException; 20 import java.net.SocketAddress; 21 import javax.annotation.Nullable; 22 23 /** 24 * A utility class to detect which proxy, if any, should be used for a given 25 * {@link java.net.SocketAddress}. This class performs network requests to resolve address names, 26 * and should only be used in places that are expected to do IO such as the 27 * {@link io.grpc.NameResolver}. 28 * 29 * <h1>How Proxies work in gRPC</h1> 30 * 31 * <p>In order for gRPC to use a proxy, {@link NameResolver}, {@link ProxyDetector} and the 32 * underlying transport need to work together. 33 * 34 * <p>The {@link NameResolver} should invoke the {@link ProxyDetector} retrieved from the {@link 35 * NameResolver.Args#getProxyDetector}, and pass the returned {@link ProxiedSocketAddress} to 36 * {@link NameResolver.Listener#onAddresses}. The DNS name resolver shipped with gRPC is already 37 * doing so. 38 * 39 * <p>The default {@code ProxyDetector} uses Java's standard {@link java.net.ProxySelector} and 40 * {@link java.net.Authenticator} to detect proxies and authentication credentials and produce 41 * {@link HttpConnectProxiedSocketAddress}, which is for using an HTTP CONNECT proxy. A custom 42 * {@code ProxyDetector} can be passed to {@link ManagedChannelBuilder#proxyDetector}. 43 * 44 * <p>The {@link ProxiedSocketAddress} is then handled by the transport. The transport needs to 45 * support whatever type of {@code ProxiedSocketAddress} returned by {@link ProxyDetector}. The 46 * Netty transport and the OkHttp transport currently only support {@link 47 * HttpConnectProxiedSocketAddress} which is returned by the default {@code ProxyDetector}. 48 */ 49 public interface ProxyDetector { 50 /** 51 * Given a target address, returns a proxied address if a proxy should be used. If no proxy should 52 * be used, then return value will be {@code null}. 53 * 54 * <p>If the returned {@code ProxiedSocketAddress} contains any address that needs to be resolved 55 * locally, it should be resolved before it's returned, and this method throws if unable to 56 * resolve it. 57 * 58 * @param targetServerAddress the target address, which is generally unresolved, because the proxy 59 * will resolve it. 60 */ 61 @Nullable proxyFor(SocketAddress targetServerAddress)62 ProxiedSocketAddress proxyFor(SocketAddress targetServerAddress) throws IOException; 63 } 64