DNS cache maintenance

Reviewed-by: akozlov

src/java.base/share/classes/java/net/InetAddress.java

@@ -46,8 +46,12 @@
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.Arrays;
 
+import jdk.crac.Context;
+import jdk.crac.Resource;
+import jdk.internal.crac.Core;
 import jdk.internal.access.JavaNetInetAddressAccess;
 import jdk.internal.access.SharedSecrets;
+import jdk.internal.crac.JDKResource;
 import sun.security.action.*;
 import sun.net.InetAddressCachePolicy;
 import sun.net.util.IPAddressUtil;
@@ -301,6 +305,9 @@ InetAddressHolder holder() {
     @java.io.Serial
     private static final long serialVersionUID = 3286316764910316507L;
 
+    /* Resource registration uses weak references; we need to keep it locally. */
+    private static final JDKResource checkpointListener;
+
     /*
      * Load net library into runtime, and perform initializations.
      */
@@ -341,6 +348,25 @@ public byte[] addressBytes(Inet6Address inet6Address) {
                 }
         );
         init();
+        // DNS cache is cleared before the checkpoint; application restored at a later point
+        // or in a different environment should query DNS again.
+        checkpointListener = new JDKResource() {
+            @Override
+            public Priority getPriority() {
+                return Priority.NORMAL;
+            }
+
+            @Override
+            public void beforeCheckpoint(Context<? extends Resource> context) throws Exception {
+                cache.clear();
+                expirySet.clear();
+            }
+
+            @Override
+            public void afterRestore(Context<? extends Resource> context) throws Exception {
+            }
+        };
+        Core.getJDKContext().register(checkpointListener);
     }
 
     /**

test/jdk/jdk/crac/java/net/InetAddress/ResolveInetAddress.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2023, Azul Systems, Inc. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+public class ResolveInetAddress {
+    public static void main(String[] args) {
+        if (args.length < 2) {
+            System.err.println("Args: <ip address> <check file path>");
+            return;
+        }
+        printAddress(args[0]);
+        while (!Files.exists(Path.of(args[1]))) {
+            try {
+                //noinspection BusyWait
+                Thread.sleep(100);
+            } catch (InterruptedException e) {
+                System.err.println("Interrupted!");
+                return;
+            }
+        }
+        printAddress(args[0]);
+    }
+
+    private static void printAddress(String hostname) {
+        try {
+            InetAddress address = InetAddress.getByName(hostname);
+            // we will assume IPv4 address
+            byte[] bytes = address.getAddress();
+            System.out.print(bytes[0] & 0xFF);
+            for (int i = 1; i < bytes.length; ++i) {
+                System.out.print('.');
+                System.out.print(bytes[i] & 0xFF);
+            }
+            System.out.println();
+        } catch (UnknownHostException e) {
+            System.out.println();
+        }
+    }
+}

test/jdk/jdk/crac/java/net/InetAddress/ResolveTest.java

@@ -0,0 +1,163 @@
+/*
+ * Copyright (c) 2023, Azul Systems, Inc. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import jdk.test.lib.Container;
+import jdk.test.lib.Utils;
+import jdk.test.lib.containers.docker.Common;
+import jdk.test.lib.containers.docker.DockerRunOptions;
+import jdk.test.lib.containers.docker.DockerTestUtils;
+import jdk.test.lib.process.StreamPumper;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.*;
+import java.util.function.Consumer;
+
+/*
+ * @test
+ * @summary Test if InetAddress cache is flushed after checkpoint/restore
+ * @requires docker.support
+ * @library /test/lib
+ * @modules java.base/jdk.crac
+ * @build ResolveInetAddress
+ * @run main/timeout=360 ResolveTest
+ */
+public class ResolveTest {
+    private static final String imageName = Common.imageName("inet-address");
+    public static final String TEST_HOSTNAME = "some.test.hostname.example.com";
+    public static final String CONTAINER_NAME = "test-inet-address";
+    public static final String CRAC_CRIU_PATH;
+
+    static {
+        String path = System.getenv("CRAC_CRIU_PATH");
+        if (path == null) {
+            path = Utils.TEST_JDK + "/lib/criu";
+        }
+        CRAC_CRIU_PATH = path;
+    }
+
+    public static void main(String[] args) throws Exception {
+        if (!DockerTestUtils.canTestDocker()) {
+            return;
+        }
+        if (!Files.exists(Path.of(CRAC_CRIU_PATH))) {
+            throw new RuntimeException("criu cannot be found in " + CRAC_CRIU_PATH);
+        }
+        DockerTestUtils.buildJdkDockerImage(imageName, "Dockerfile-is-ignored", "jdk-docker");
+        try {
+            Future<?> completed = startTestProcess();
+            checkpointTestProcess();
+            completed.get(5, TimeUnit.SECONDS);
+            startRestoredProcess();
+        } finally {
+            ensureContainerDead();
+            DockerTestUtils.removeDockerImage(imageName);
+        }
+    }
+
+    private static Future<?> startTestProcess() throws Exception {
+        ensureContainerDead();
+
+        List<String> cmd = new ArrayList<>();
+        cmd.add(Container.ENGINE_COMMAND);
+        cmd.addAll(Arrays.asList("run", "--rm", "--add-host", TEST_HOSTNAME + ":192.168.12.34"));
+        cmd.addAll(Arrays.asList("--volume", Utils.TEST_CLASSES + ":/test-classes/"));
+        cmd.addAll(Arrays.asList("--volume", "cr:/cr"));
+        cmd.addAll(Arrays.asList("--volume", CRAC_CRIU_PATH + ":/criu"));
+        cmd.addAll(Arrays.asList("--env", "CRAC_CRIU_PATH=/criu"));
+        cmd.addAll(Arrays.asList("--entrypoint", "bash"));
+        // checkpoint-restore does not work without this: TODO fine-grained --cap-add
+        cmd.add("--privileged");
+        cmd.addAll(Arrays.asList("--name", CONTAINER_NAME));
+        cmd.add(imageName);
+        // Checkpointing does not work for PID 1, therefore we add an intermediary bash process
+        List<String> javaCmd = new ArrayList<>();
+        javaCmd.addAll(Arrays.asList("/jdk/bin/java", "-cp /test-classes/", "-XX:CRaCCheckpointTo=/cr"));
+        javaCmd.addAll(Arrays.asList(Utils.getTestJavaOpts()));
+        javaCmd.addAll(Arrays.asList("ResolveInetAddress", TEST_HOSTNAME, "/second-run"));
+        cmd.addAll(Arrays.asList("-c", String.join(" ", javaCmd) + "; echo i-am-here-to-force-child-process"));
+
+        System.err.println("Running: " + String.join(" ", cmd));
+
+        CompletableFuture<?> firstOutputFuture = new CompletableFuture<Void>();
+        Future<?> completed = executeWatching(cmd, line -> {
+            System.out.println("OUTPUT: " + line);
+            if (line.equals("192.168.12.34")) {
+                firstOutputFuture.complete(null);
+            }
+        }, error -> {
+            System.err.println("ERROR: " + error);
+            firstOutputFuture.cancel(false);
+        });
+        firstOutputFuture.get(10, TimeUnit.SECONDS);
+        return completed;
+    }
+
+    private static void ensureContainerDead() throws Exception {
+        // ensure the container is not running, ignore if not present
+        DockerTestUtils.execute("docker", "kill", CONTAINER_NAME).getExitValue();
+    }
+
+    private static void checkpointTestProcess() throws Exception {
+        DockerTestUtils.execute("docker", "exec", CONTAINER_NAME,
+                        "/jdk/bin/jcmd", ResolveInetAddress.class.getName(), "JDK.checkpoint")
+                .shouldHaveExitValue(0);
+    }
+
+    private static Future<Void> executeWatching(List<String> command, Consumer<String> outputConsumer, Consumer<String> errorConsumer) throws IOException, ExecutionException, InterruptedException, TimeoutException {
+        ProcessBuilder pb = new ProcessBuilder(command);
+        Process p = pb.start();
+        Future<Void> outputPumper = pump(p.getInputStream(), outputConsumer);
+        Future<Void> errorPumper = pump(p.getErrorStream(), errorConsumer);
+        return outputPumper;
+    }
+
+    private static Future<Void> pump(InputStream stream, Consumer<String> consumer) {
+        return new StreamPumper(stream).addPump(new StreamPumper.LinePump() {
+            @Override
+            protected void processLine(String line) {
+                consumer.accept(line);
+            }
+        }).process();
+    }
+
+    private static void startRestoredProcess() throws Exception {
+        DockerRunOptions opts = new DockerRunOptions(imageName, "/jdk/bin/java", "ResolveInetAddress");
+        opts.addDockerOpts("--volume", Utils.TEST_CLASSES + ":/test-classes/");
+        opts.addDockerOpts("--volume", "cr:/cr");
+        opts.addDockerOpts("--volume", Utils.TEST_CLASSES + ":/second-run"); // any file suffices
+        opts.addDockerOpts("--volume", CRAC_CRIU_PATH + ":/criu");
+        opts.addDockerOpts("--env", "CRAC_CRIU_PATH=/criu");
+        opts.addDockerOpts("--add-host", TEST_HOSTNAME + ":192.168.56.78");
+        opts.addDockerOpts("--privileged");
+        opts.addJavaOpts("-XX:CRaCRestoreFrom=/cr");
+        DockerTestUtils.dockerRunJava(opts)
+                .shouldHaveExitValue(0)
+                .shouldContain("192.168.56.78");
+    }
+}