Add forwarded header in gateway

spring-cloud-function-gateway/src/main/java/org/springframework/cloud/function/gateway/ProxyExchange.java

@@ -366,6 +366,7 @@ public class ProxyExchange<T> {
 		if (sensitive == null) {
 			sensitive = DEFAULT_SENSITIVE;
 		}
+		proxy();
 		for (String name : headers.keySet()) {
 			if (sensitive.contains(name.toLowerCase())) {
 				continue;
@@ -375,6 +376,53 @@ public class ProxyExchange<T> {
 		return builder;
 	}
 
+	private void proxy() {
+		try {
+			URI uri = new URI(webRequest.getNativeRequest(HttpServletRequest.class)
+					.getRequestURL().toString());
+			appendForwarded(uri);
+			appendXForwarded(uri);
+		}
+		catch (URISyntaxException e) {
+			throw new IllegalStateException("Cannot create URI for request: " + webRequest
+					.getNativeRequest(HttpServletRequest.class).getRequestURL());
+		}
+	}
+
+	private void appendXForwarded(URI uri) {
+		// Append the legacy headers if they were already added upstream
+		String host = headers.getFirst("x-forwarded-host");
+		if (host == null) {
+			return;
+		}
+		host = host + ","  + uri.getHost();
+		headers.set("x-forwarded-host", host);
+		String proto = headers.getFirst("x-forwarded-proto");
+		if (proto == null) {
+			return;
+		}
+		proto = proto + ","  + uri.getScheme();
+		headers.set("x-forwarded-proto", proto);
+	}
+
+	private void appendForwarded(URI uri) {
+		String forwarded = headers.getFirst("forwarded");
+		if (forwarded != null) {
+			forwarded = forwarded + ",";
+		} else {
+			forwarded = "";
+		}
+		forwarded = forwarded + forwarded(uri);
+		headers.set("forwarded", forwarded);
+	}
+
+	private String forwarded(URI uri) {
+		if ("http".equals(uri.getScheme())) {
+			return "host=" + uri.getHost();
+		}
+		return String.format("host=%s;proto=%s", uri.getHost(), uri.getScheme());
+	}
+
 	private Object body() {
 		if (body != null) {
 			return body;

spring-cloud-function-gateway/src/test/java/org/springframework/cloud/function/web/gateway/ProductionConfigurationTests.java

@@ -111,7 +111,7 @@ public class ProductionConfigurationTests {
     @Test
     public void post() throws Exception {
         assertThat(rest.postForObject("/proxy/0", Collections.singletonMap("name", "foo"),
-                Bar.class).getName()).isEqualTo("foo");
+                Bar.class).getName()).isEqualTo("host=localhost;foo");
     }
 
     @Test
@@ -186,13 +186,13 @@ public class ProductionConfigurationTests {
                                 "/proxy"))
                 .body(Collections.singletonList(Collections.singletonMap("name", "foo"))),
                 new ParameterizedTypeReference<List<Bar>>() {
-                }).getBody().iterator().next().getName()).isEqualTo("foo");
+                }).getBody().iterator().next().getName()).isEqualTo("host=localhost;foo");
     }
 
     @Test
     public void bodyless() throws Exception {
         assertThat(rest.postForObject("/proxy/0", Collections.singletonMap("name", "foo"),
-                Bar.class).getName()).isEqualTo("foo");
+                Bar.class).getName()).isEqualTo("host=localhost;foo");
     }
 
     @Test
@@ -203,7 +203,7 @@ public class ProductionConfigurationTests {
                                 .expand("/proxy/entity"))
                         .body(Collections.singletonMap("name", "foo")),
                 new ParameterizedTypeReference<List<Bar>>() {
-                }).getBody().iterator().next().getName()).isEqualTo("foo");
+                }).getBody().iterator().next().getName()).isEqualTo("host=localhost;foo");
     }
 
     @Test
@@ -214,21 +214,21 @@ public class ProductionConfigurationTests {
                                 .expand("/proxy/type"))
                         .body(Collections.singletonMap("name", "foo")),
                 new ParameterizedTypeReference<List<Bar>>() {
-                }).getBody().iterator().next().getName()).isEqualTo("foo");
+                }).getBody().iterator().next().getName()).isEqualTo("host=localhost;foo");
     }
 
     @Test
     public void single() throws Exception {
         assertThat(rest.postForObject("/proxy/single",
                 Collections.singletonMap("name", "foobar"), Bar.class).getName())
-                        .isEqualTo("foobar");
+                        .isEqualTo("host=localhost;foobar");
     }
 
     @Test
     public void converter() throws Exception {
         assertThat(rest.postForObject("/proxy/converter",
                 Collections.singletonMap("name", "foobar"), Bar.class).getName())
-                        .isEqualTo("foobar");
+                        .isEqualTo("host=localhost;foobar");
     }
 
     @SpringBootApplication
@@ -394,6 +394,7 @@ public class ProductionConfigurationTests {
                     @RequestHeader HttpHeaders headers) {
                 String custom = headers.getFirst("X-Custom");
                 custom = custom == null ? "" : custom;
+                custom = headers.getFirst("forwarded")==null ? custom : headers.getFirst("forwarded") + ";" + custom;
                 return Arrays.asList(new Bar(custom + foos.iterator().next().getName()));
             }