Prevent reverse name lookup when configuring Jetty's address

Previously, the host on Jetty's connector was configured using the
host address of the InetSocketAddress. This could result in reverse
name resolution that could cause Jetty to bind to a different IP
address than was configured.

This commit updates the configuration code to use the host string
when specifically does not perform reverse name resolution.

See spring-projectsgh-11889

spring-boot/src/main/java/org/springframework/boot/context/embedded/jetty/JettyEmbeddedServletContainerFactory.java

@@ -101,6 +101,8 @@
  * @author Eddú Meléndez
  * @author Venil Noronha
  * @author Henri Kerola
+ * @author Henrich Krämer
+ *
  * @see #setPort(int)
  * @see #setConfigurations(Collection)
  * @see JettyEmbeddedServletContainer
@@ -895,7 +897,7 @@ public AbstractConnector createConnector(Server server, InetSocketAddress addres
 				ReflectionUtils.findMethod(connectorClass, "setPort", int.class)
 						.invoke(connector, address.getPort());
 				ReflectionUtils.findMethod(connectorClass, "setHost", String.class)
-						.invoke(connector, address.getHostName());
+						.invoke(connector, address.getHostString());
 				if (acceptors > 0) {
 					ReflectionUtils.findMethod(connectorClass, "setAcceptors", int.class)
 							.invoke(connector, acceptors);
@@ -924,7 +926,7 @@ private static class Jetty9ConnectorFactory implements ConnectorFactory {
 		public AbstractConnector createConnector(Server server, InetSocketAddress address,
 				int acceptors, int selectors) {
 			ServerConnector connector = new ServerConnector(server, acceptors, selectors);
-			connector.setHost(address.getHostName());
+			connector.setHost(address.getHostString());
 			connector.setPort(address.getPort());
 			for (ConnectionFactory connectionFactory : connector
 					.getConnectionFactories()) {

spring-boot/src/test/java/org/springframework/boot/context/embedded/jetty/JettyEmbeddedServletContainerFactoryTests.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.context.embedded.jetty;
 
 import java.io.IOException;
+import java.net.InetAddress;
 import java.nio.charset.Charset;
 import java.util.Arrays;
 import java.util.Locale;
@@ -35,6 +36,8 @@
 import javax.servlet.http.HttpServletResponse;
 
 import org.apache.jasper.servlet.JspServlet;
+import org.eclipse.jetty.server.AbstractNetworkConnector;
+import org.eclipse.jetty.server.Connector;
 import org.eclipse.jetty.server.Handler;
 import org.eclipse.jetty.server.Server;
 import org.eclipse.jetty.server.ServerConnector;
@@ -114,6 +117,32 @@ public void jettyCustomizations() throws Exception {
 		}
 	}
 
+	@Test
+	public void specificIPAddressNotReverseResolved() throws Exception {
+		JettyEmbeddedServletContainerFactory factory = getFactory();
+		final String[] refAncHost = new String[1];
+		refAncHost[0] = "HostNotSetInAbstractNetworkConnector";
+		InetAddress lhAddress = InetAddress.getLocalHost();
+		InetAddress address = InetAddress.getByAddress(lhAddress.getAddress());
+		// the address should have no host name associated with ith
+		String expectedHost = address.getHostAddress();
+		factory.setAddress(address);
+		factory.addServerCustomizers(server -> {
+			for (Connector connector : server.getConnectors()) {
+				if (connector instanceof AbstractNetworkConnector) {
+					@SuppressWarnings("resource")
+					AbstractNetworkConnector anc = (AbstractNetworkConnector) connector;
+					String ancHost = anc.getHost();
+					refAncHost[0] = ancHost;
+					break;
+				}
+			}
+		});
+		this.container = factory
+				.getEmbeddedServletContainer(exampleServletRegistration());
+		assertThat(refAncHost[0]).isEqualTo(expectedHost);
+	}
+
 	@Test
 	public void sessionTimeout() throws Exception {
 		JettyEmbeddedServletContainerFactory factory = getFactory();