Add new properties to customize InetUtils.

Added useOnlySiteLocalInterfaces and preferredNetworks properties to
InetUtils. The preferredNetworks property allows for a whitelist of
networks. The useOnlySiteLocalInterfaces allows InetAddresses where
isSiteLocalAddress is true.

Fixes gh-114

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

@@ -404,3 +404,25 @@ spring:
         - docker0
         - veth.*
 ----
+
+You can also force to use only specified network addresses using list of regular expressions:
+
+.application.yml
+----
+spring:
+  cloud:
+    inetutils:
+      preferredNetworks:
+        - 192.168
+        - 10.0
+----
+
+You can also force to use only site local addresses. See https://docs.oracle.com/javase/8/docs/api/java/net/Inet4Address.html#isSiteLocalAddress--[Inet4Address.html.isSiteLocalAddress()] for more details what is site local address.
+
+.application.yml
+----
+spring:
+  cloud:
+    inetutils:
+      useOnlySiteLocalInterfaces: true
+----

spring-cloud-commons/src/main/java/org/springframework/cloud/commons/util/InetUtils.java

@@ -98,7 +98,8 @@ public class InetUtils implements Closeable {
 								.getInetAddresses(); addrs.hasMoreElements();) {
 							InetAddress address = addrs.nextElement();
 							if (address instanceof Inet4Address
-									&& !address.isLoopbackAddress()) {
+									&& !address.isLoopbackAddress()
+									&& !ignoreAddress(address)) {
 								log.trace("Found non-loopback interface: "
 										+ ifc.getDisplayName());
 								result = address;
@@ -127,7 +128,23 @@ public class InetUtils implements Closeable {
 		return null;
 	}
 
-	boolean ignoreInterface(String interfaceName) {
+	/** for testing */ boolean ignoreAddress(InetAddress address) {
+
+		if (this.properties.isUseOnlySiteLocalInterfaces() && !address.isSiteLocalAddress()) {
+			log.trace("Ignoring address: " + address.getHostAddress());
+			return true;
+		}
+	
+		for (String regex : this.properties.getPreferredNetworks()) {
+		if (!address.getHostAddress().matches(regex) && !address.getHostAddress().startsWith(regex)) {
+			log.trace("Ignoring address: " + address.getHostAddress());
+				return true;
+			}
+		}
+		return false;
+	}
+
+	/** for testing */ boolean ignoreInterface(String interfaceName) {
 		for (String regex : this.properties.getIgnoredInterfaces()) {
 			if (interfaceName.matches(regex)) {
 				log.trace("Ignoring interface: " + interfaceName);

spring-cloud-commons/src/main/java/org/springframework/cloud/commons/util/InetUtilsProperties.java

@@ -1,5 +1,6 @@
 package org.springframework.cloud.commons.util;
 
+import java.net.InetAddress;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -36,4 +37,14 @@ public class InetUtilsProperties {
 	 * List of Java regex expressions for network interfaces that will be ignored.
 	 */
 	private List<String> ignoredInterfaces = new ArrayList<>();
+	
+	/**
+	 * Use only interfaces with site local addresses. See {@link InetAddress#isSiteLocalAddress()} for more details.
+	 */
+	private boolean useOnlySiteLocalInterfaces = false;
+	
+	/**
+	 * List of Java regex expressions for network addresses that will be ignored.
+	 */
+	private List<String> preferredNetworks = new ArrayList<>();
 }

spring-cloud-commons/src/test/java/org/springframework/cloud/commons/util/InetUtilsTests.java

@@ -86,4 +86,36 @@ public class InetUtilsTests {
 		}
 	}
 
+	@Test
+	public void testSiteLocalAddresses() throws Exception {
+		InetUtilsProperties properties = new InetUtilsProperties();
+		properties.setUseOnlySiteLocalInterfaces(true);
+
+		try (InetUtils utils = new InetUtils(properties)) {
+			assertFalse(utils.ignoreAddress(InetAddress.getByName("192.168.0.1")));
+			assertTrue(utils.ignoreAddress(InetAddress.getByName("5.5.8.1")));
+		}
+	}
+	
+	@Test
+	public void testPrefferedNetworksRegex() throws Exception {
+		InetUtilsProperties properties = new InetUtilsProperties();
+		properties.setPreferredNetworks(Arrays.asList("192.168.*"));
+
+		try (InetUtils utils = new InetUtils(properties)) {
+			assertFalse(utils.ignoreAddress(InetAddress.getByName("192.168.0.1")));
+			assertTrue(utils.ignoreAddress(InetAddress.getByName("5.5.8.1")));
+		}
+	}
+	
+	@Test
+	public void testPrefferedNetworksSimple() throws Exception {
+		InetUtilsProperties properties = new InetUtilsProperties();
+		properties.setPreferredNetworks(Arrays.asList("192"));
+		
+		try (InetUtils utils = new InetUtils(properties)) {
+			assertFalse(utils.ignoreAddress(InetAddress.getByName("192.168.0.1")));
+			assertTrue(utils.ignoreAddress(InetAddress.getByName("5.5.8.1")));
+		}
+	}
 }