dnsjava · ibauersachs · Oct 26, 2021 · Oct 24, 2021
diff --git a/src/main/java/org/xbill/DNS/config/AndroidResolverConfigProvider.java b/src/main/java/org/xbill/DNS/config/AndroidResolverConfigProvider.java
@@ -31,6 +31,7 @@ public static void setContext(Context ctx) {
 
   @Override
   public void initialize() throws InitializationException {
+    reset();
     if (context == null) {
       throw new InitializationException("Context must be initialized by calling setContext");
     }

diff --git a/src/main/java/org/xbill/DNS/config/BaseResolverConfigProvider.java b/src/main/java/org/xbill/DNS/config/BaseResolverConfigProvider.java
@@ -24,8 +24,15 @@ public abstract class BaseResolverConfigProvider implements ResolverConfigProvid
   private static final boolean ipv6first = Boolean.getBoolean("java.net.preferIPv6Addresses");
 
   private final List<InetSocketAddress> nameservers = new ArrayList<>(3);
-  final Logger log = LoggerFactory.getLogger(getClass());
-  List<Name> searchlist = new ArrayList<>(1);
+
+  protected final Logger log = LoggerFactory.getLogger(getClass());
+  protected final List<Name> searchlist = new ArrayList<>(1);
+
+  protected final void reset() {
+    // TODO v4: make a final void initialize() that clears and then calls abstract doInit()
+    nameservers.clear();
+    searchlist.clear();
+  }
 
   protected void parseSearchPathList(String search, String delimiter) {
     if (search != null) {

diff --git a/src/main/java/org/xbill/DNS/config/JndiContextResolverConfigProvider.java b/src/main/java/org/xbill/DNS/config/JndiContextResolverConfigProvider.java
@@ -43,6 +43,7 @@ private static final class InnerJndiContextResolverConfigProvider
 
     @Override
     public void initialize() {
+      reset();
       Hashtable<String, String> env = new Hashtable<>();
       env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.dns.DnsContextFactory");
       // http://mail.openjdk.java.net/pipermail/net-dev/2017-March/010695.html

diff --git a/src/main/java/org/xbill/DNS/config/PropertyResolverConfigProvider.java b/src/main/java/org/xbill/DNS/config/PropertyResolverConfigProvider.java
@@ -34,6 +34,7 @@ public void initialize() {
    * @since 3.2
    */
   protected void initialize(String serverName, String searchName, String ndotsName) {
+    reset();
     String servers = System.getProperty(serverName);
     if (servers != null) {
       StringTokenizer st = new StringTokenizer(servers, ",");

diff --git a/src/main/java/org/xbill/DNS/config/ResolvConfResolverConfigProvider.java b/src/main/java/org/xbill/DNS/config/ResolvConfResolverConfigProvider.java
@@ -17,6 +17,7 @@ public class ResolvConfResolverConfigProvider extends BaseResolverConfigProvider
 
   @Override
   public void initialize() {
+    reset();
     // first try the default unix config path
     if (!tryParseResolveConf("/etc/resolv.conf")) {
       // then fallback to netware

diff --git a/src/main/java/org/xbill/DNS/config/SunJvmResolverConfigProvider.java b/src/main/java/org/xbill/DNS/config/SunJvmResolverConfigProvider.java
@@ -20,6 +20,7 @@
 public class SunJvmResolverConfigProvider extends BaseResolverConfigProvider {
   @Override
   public void initialize() throws InitializationException {
+    reset();
     try {
       Class<?> resConfClass = Class.forName("sun.net.dns.ResolverConfiguration");
       Method open = resConfClass.getDeclaredMethod("open");

diff --git a/src/main/java/org/xbill/DNS/config/WindowsResolverConfigProvider.java b/src/main/java/org/xbill/DNS/config/WindowsResolverConfigProvider.java
@@ -57,9 +57,10 @@ private static final class InnerWindowsResolverConfigProvider extends BaseResolv
 
     @Override
     public void initialize() throws InitializationException {
+      reset();
       // The recommended method of calling the GetAdaptersAddresses function is to pre-allocate a
       // 15KB working buffer
-      Memory buffer = new Memory(15 * 1024);
+      Memory buffer = new Memory(15 * 1024L);
       IntByReference size = new IntByReference(0);
       int flags =
           GAA_FLAG_SKIP_UNICAST

diff --git a/src/test/java/org/xbill/DNS/ResolverConfigTest.java b/src/test/java/org/xbill/DNS/ResolverConfigTest.java
@@ -41,12 +41,13 @@ void testSkipInit() throws Exception {
 
   @Test
   void properties() {
-    String[] dnsServers = {"192.168.1.1", "192.168.1.2", "192.168.1.1"};
+    String[] dnsServers1 = {"192.168.1.1", "192.168.1.2", "192.168.1.1"};
+    String[] dnsServers2 = {"192.168.1.3"};
     // intentionally adding duplicate search entries for testing
     String[] dnsSearch = {"dnsjava.org", "example.com", "dnsjava.org"};
     Name[] searchPath =
         Arrays.stream(dnsSearch).map(s -> Name.fromConstantString(s + ".")).toArray(Name[]::new);
-    System.setProperty(DNS_SERVER_PROP, String.join(",", dnsServers));
+    System.setProperty(DNS_SERVER_PROP, String.join(",", dnsServers1));
     System.setProperty(DNS_SEARCH_PROP, String.join(",", dnsSearch));
     System.setProperty(DNS_NDOTS_PROP, String.valueOf(5));
     try {
@@ -55,7 +56,12 @@ void properties() {
       rc.initialize();
 
       assertEquals(2, rc.servers().size());
-      assertEquals(dnsServers[0], rc.servers().get(0).getAddress().getHostAddress());
+      assertEquals(dnsServers1[0], rc.servers().get(0).getAddress().getHostAddress());
+
+      // must remove no longer present servers
+      System.setProperty(DNS_SERVER_PROP, String.join(",", dnsServers2));
+      rc.initialize();
+      assertEquals(1, rc.servers().size());
 
       // any duplicate suffixes should be excluded
       assertEquals(2, rc.searchPaths().size());