Adds PreserveHostHeader filter

This filter sets a request attribute to true. The NettyRoutingFilter
then inspects this attribute and resets the host header, overwritting
the value set by the netty http client.

fixes gh-133

docs/src/main/asciidoc/spring-cloud-gateway.adoc

@@ -349,6 +349,25 @@ spring:
 
 This will prefix `/mypath` to the path of all matching requests. So a request to `/hello`, would be sent to `/mypath/hello`.
 
+=== PreserveHostHeader GatewayFilter Factory
+The PreserveHostHeader GatewayFilter Factory has not parameters. This filter, sets a request attribute that the routing filter will inspect to determine if the original host header should be sent, rather than the host header determined by the http client.
+
+.application.yml
+[source,yaml]
+----
+spring:
+  cloud:
+    gateway:
+      routes:
+      # =====================================
+      - id: preserve_host_route
+        uri: http://example.org
+        filters:
+        - PreserveHostHeader
+----
+
+This will prefix `/mypath` to the path of all matching requests. So a request to `/hello`, would be sent to `/mypath/hello`.
+
 === RequestRateLimiter GatewayFilter Factory
 
 The RequestRateLimiter GatewayFilter Factory takes three parameters: `replenishRate`, `burstCapacity` & `keyResolverName`.

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java

@@ -44,6 +44,7 @@ import org.springframework.cloud.gateway.filter.factory.AddResponseHeaderGateway
 import org.springframework.cloud.gateway.filter.factory.GatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.HystrixGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.PrefixPathGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.PreserveHostHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RedirectToGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RemoveNonProxyHeadersGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RemoveRequestHeaderGatewayFilterFactory;
@@ -322,6 +323,11 @@ public class GatewayAutoConfiguration {
 		return new PrefixPathGatewayFilterFactory();
 	}
 
+	@Bean
+	public PreserveHostHeaderGatewayFilterFactory preserveHostHeaderGatewayFilterFactory() {
+		return new PreserveHostHeaderGatewayFilterFactory();
+	}
+
 	@Bean
 	public RedirectToGatewayFilterFactory redirectToGatewayFilterFactory() {
 		return new RedirectToGatewayFilterFactory();

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/NettyRoutingFilter.java

@@ -27,7 +27,11 @@ import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.http.server.reactive.ServerHttpResponse;
 import org.springframework.web.server.ServerWebExchange;
 
-import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.*;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.CLIENT_RESPONSE_ATTR;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.PRESERVE_HOST_HEADER_ATTRIBUTE;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.isAlreadyRouted;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.setAlreadyRouted;
 
 import io.netty.buffer.Unpooled;
 import io.netty.handler.codec.http.DefaultHttpHeaders;
@@ -71,11 +75,18 @@ public class NettyRoutingFilter implements GlobalFilter, Ordered {
 		final DefaultHttpHeaders httpHeaders = new DefaultHttpHeaders();
 		request.getHeaders().forEach(httpHeaders::set);
 
+		boolean preserveHost = exchange.getAttributeOrDefault(PRESERVE_HOST_HEADER_ATTRIBUTE, false);
+
 		return this.httpClient.request(method, url, req -> {
 			final HttpClientRequest proxyRequest = req.options(NettyPipeline.SendOptions::flushOnEach)
 					.failOnClientError(false)
 					.headers(httpHeaders);
 
+			if (preserveHost) {
+				String host = request.getHeaders().getFirst(HttpHeaders.HOST);
+				proxyRequest.header(HttpHeaders.HOST, host);
+			}
+
 			return proxyRequest.sendHeaders() //I shouldn't need this
 					.send(request.getBody()
 							.map(DataBuffer::asByteBuffer)

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/WebClientHttpRoutingFilter.java

@@ -65,14 +65,13 @@ public class WebClientHttpRoutingFilter implements GlobalFilter, Ordered {
 
 		ServerHttpRequest request = exchange.getRequest();
 
-		//TODO: support forms
-
 		HttpMethod method = request.getMethod();
 
 		RequestBodySpec bodySpec = this.webClient.method(method)
 				.uri(requestUrl)
 				.headers(httpHeaders -> {
 					httpHeaders.addAll(request.getHeaders());
+					//TODO: can this support preserviceHostHeader?
 					httpHeaders.remove(HttpHeaders.HOST);
 				});
 

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/factory/PreserveHostHeaderGatewayFilterFactory.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2013-2017 the original author or authors.
+ *
+ * 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 org.springframework.cloud.gateway.filter.factory;
+
+import org.springframework.cloud.gateway.filter.GatewayFilter;
+import org.springframework.tuple.Tuple;
+
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.PRESERVE_HOST_HEADER_ATTRIBUTE;
+
+/**
+ * @author Spencer Gibb
+ */
+public class PreserveHostHeaderGatewayFilterFactory implements GatewayFilterFactory {
+
+	@Override
+	public GatewayFilter apply(Tuple args) {
+		return apply();
+	}
+
+	public GatewayFilter apply() {
+		return (exchange, chain) -> {
+			exchange.getAttributes().put(PRESERVE_HOST_HEADER_ATTRIBUTE, true);
+			return chain.filter(exchange);
+		};
+	}
+}

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/route/builder/GatewayFilterSpec.java

@@ -30,6 +30,7 @@ import org.springframework.cloud.gateway.filter.factory.AddRequestParameterGatew
 import org.springframework.cloud.gateway.filter.factory.AddResponseHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.HystrixGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.PrefixPathGatewayFilterFactory;
+import org.springframework.cloud.gateway.filter.factory.PreserveHostHeaderGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RedirectToGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RemoveNonProxyHeadersGatewayFilterFactory;
 import org.springframework.cloud.gateway.filter.factory.RemoveRequestHeaderGatewayFilterFactory;
@@ -106,6 +107,10 @@ public class GatewayFilterSpec extends UriSpec {
 		return filter(getBean(PrefixPathGatewayFilterFactory.class).apply(prefix));
 	}
 
+	public GatewayFilterSpec preserveHostHeader() {
+		return filter(getBean(PreserveHostHeaderGatewayFilterFactory.class).apply());
+	}
+
 	public GatewayFilterSpec redirect(int status, URI url) {
 		return redirect(String.valueOf(status), url.toString());
 	}

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/support/ServerWebExchangeUtils.java

@@ -32,6 +32,7 @@ public class ServerWebExchangeUtils {
 
 	private static final Log logger = LogFactory.getLog(ServerWebExchangeUtils.class);
 
+	public static final String PRESERVE_HOST_HEADER_ATTRIBUTE = qualify("preserveHostHeader");
 	public static final String URI_TEMPLATE_VARIABLES_ATTRIBUTE = qualify("uriTemplateVariables");
 
 	public static final String CLIENT_RESPONSE_ATTR = qualify("webHandlerClientResponse");

spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/filter/factory/PreserveHostHeaderGatewayFilterFactoryTests.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright 2013-2017 the original author or authors.
+ *
+ * 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 org.springframework.cloud.gateway.filter.factory;
+
+import java.util.Map;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.cloud.gateway.route.RouteLocator;
+import org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder;
+import org.springframework.cloud.gateway.test.BaseWebClientTests;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Import;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.boot.test.context.SpringBootTest.WebEnvironment.RANDOM_PORT;
+import static org.springframework.cloud.gateway.test.TestUtils.getMap;
+
+
+/**
+ * @author Spencer Gibb
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = RANDOM_PORT)
+@DirtiesContext
+public class PreserveHostHeaderGatewayFilterFactoryTests extends BaseWebClientTests {
+
+	@Test
+	public void setRequestHeaderFilterWorks() {
+		testClient.get().uri("/headers")
+				.header("Host", "www.preservehostheader.org")
+				.exchange()
+				.expectStatus().isOk()
+				.expectBody(Map.class)
+				.consumeWith(result -> {
+					Map<String, Object> headers = getMap(result.getResponseBody(), "headers");
+					assertThat(headers).containsEntry("Host", "myhost.net");
+				});
+	}
+
+	@EnableAutoConfiguration
+	@SpringBootConfiguration
+	@Import(DefaultTestConfig.class)
+	public static class TestConfig {
+		@Value("${test.uri}")
+		String uri;
+
+		@Bean
+		public RouteLocator testRouteLocator(RouteLocatorBuilder builder) {
+			return builder.routes().route("test_preserve_host_header",
+                r -> r.order(-1)
+					.host("**.preservehostheader.org")
+					.prefixPath("/httpbin")
+					.preserveHostHeader()
+					.setRequestHeader("Host", "myhost.net")
+					.uri(uri))
+					.build();
+		}
+	}
+
+}