Drop compatibility with pre-2024-08 remoting releases

src/main/java/hudson/remoting/Channel.java

@@ -1018,29 +1018,7 @@ public boolean preloadJar(ClassLoader local, URL... jars) throws IOException, In
             jars[i] = url;
             contents[i] = Util.readFully(url.openStream());
         }
-        try {
-            return call(new PreloadJarTask2(jars, contents, local));
-        } catch (IOException ex) {
-            if (ex.getCause() instanceof IllegalAccessError) {
-                logger.log(
-                        Level.FINE,
-                        ex,
-                        () -> "Failed to call PreloadJarTask2 on " + this + ", retrying with PreloadJarTask");
-                // When the agent is running an outdated version of remoting, we cannot access nonpublic classes in the
-                // same package, as PreloadJarTask2 would be loaded from the controller, and hence a different module/
-                // classloader, than the rest of remoting. As a result PreloadJarTask2 will throw IllegalAccessError:
-                //
-                // java.lang.IllegalAccessError: failed to access class hudson.remoting.RemoteClassLoader from class
-                // hudson.remoting.PreloadJarTask2 (hudson.remoting.RemoteClassLoader is in unnamed module of loader
-                // 'app'; hudson.remoting.PreloadJarTask2 is in unnamed module of loader 'Jenkins v${project.version}'
-                // @795f104a)
-                //
-                // Identify this error here and fall back to PreloadJarTask, relying on the restrictive controller-side
-                // implementation of IClassLoader#fetchJar.
-                return call(new PreloadJarTask(jars, local));
-            }
-            throw ex;
-        }
+        return call(new PreloadJarTask2(jars, contents, local));
     }
 
     /**

src/main/java/hudson/remoting/DumbClassLoaderBridge.java

@@ -2,7 +2,6 @@
 
 import edu.umd.cs.findbugs.annotations.NonNull;
 import java.io.IOException;
-import java.net.URL;
 import java.util.Map;
 
 /**
@@ -24,11 +23,6 @@ class DumbClassLoaderBridge implements RemoteClassLoader.IClassLoader {
         this.base = base;
     }
 
-    @Override
-    public byte[] fetchJar(URL url) throws IOException {
-        return base.fetchJar(url);
-    }
-
     @Override
     public byte[] fetch(String className) throws ClassNotFoundException {
         return base.fetch(className);

src/main/java/hudson/remoting/PreloadJarTask2.java

@@ -31,11 +31,7 @@
 
 /**
  * {@link Callable} used to deliver a jar file to {@link RemoteClassLoader}.
- * <p>
- *  This replaces {@link hudson.remoting.PreloadJarTask} and delivers the jar contents as part of the Callable rather
- *  than needing to call {@link hudson.remoting.RemoteClassLoader#prefetch(java.net.URL)}.
- * </p>
  * @since TODO 2024-08
  */
 final class PreloadJarTask2 implements DelegatingCallable<Boolean, IOException> {
     /**

src/main/java/hudson/remoting/RemoteClassLoader.java

@@ -675,33 +675,6 @@ public static void deleteDirectoryOnExit(File dir) {
         Util.deleteDirectoryOnExit(dir);
     }
 
-    /**
-     * Prefetches the jar into this class loader.
-     *
-     * @param jar Jar to be prefetched. Note that this file is an file on the other end,
-     *            and doesn't point to anything meaningful locally.
-     * @return true if the prefetch happened. false if the jar is already prefetched.
-     * @deprecated Only left in for compatibility with pre-2024-08 remoting. Use {@link #prefetch(java.net.URL, byte[])} instead.
-     * @see Channel#preloadJar(Callable, Class[])
-     * @see hudson.remoting.PreloadJarTask
-     * @see hudson.remoting.PreloadJarTask2
-     */
-    @Deprecated
-    /*package*/ boolean prefetch(URL jar) throws IOException {
-        synchronized (prefetchedJars) {
-            if (prefetchedJars.contains(jar)) {
-                return false;
-            }
-
-            String p = jar.getPath().replace('\\', '/');
-            p = Util.getBaseName(p);
-            File localJar = Util.makeResource(p, proxy.fetchJar(jar));
-            addURL(localJar.toURI().toURL());
-            prefetchedJars.add(jar);
-            return true;
-        }
-    }
-
     /**
      * Prefetches the specified jar with the specified content into this classloader.
      * @param jar Jar to be prefetched. Note that this file is an file on the other end,
@@ -873,9 +846,6 @@ public static class ClassFile2 extends ResourceFile {
      * Remoting interface.
      */
     public interface IClassLoader {
-        @Deprecated
-        byte[] fetchJar(URL url) throws IOException;
-
         /**
          * Retrieves the bytecode of a class.
          */
@@ -998,31 +968,6 @@ public ClassLoaderProxy(@NonNull ClassLoader cl, Channel channel) {
             this.channel = channel;
         }
 
-        @Override
-        @SuppressFBWarnings(
-                value = "URLCONNECTION_SSRF_FD",
-                justification = "URL validation is being done through JarURLValidator")
-        public byte[] fetchJar(URL url) throws IOException {
-            final Object o = channel.getProperty(JarURLValidator.class);
-            if (o == null) {
-                final boolean disabled = Boolean.getBoolean(Channel.class.getName() + ".DISABLE_JAR_URL_VALIDATOR");
-                LOGGER.log(Level.FINE, "Default behavior for URL: " + url + " with disabled flag: " + disabled);
-                if (!disabled) {
-                    throw new IOException(
-                            "No hudson.remoting.JarURLValidator has been set for this channel, so all #fetchJar calls are rejected."
-                                    + " This is likely a bug in Jenkins."
-                                    + " As a workaround, try updating the agent.jar file.");
-                }
-            } else {
-                if (o instanceof JarURLValidator) {
-                    ((JarURLValidator) o).validate(url);
-                } else {
-                    throw new IOException("Unexpected channel property hudson.remoting.JarURLValidator value: " + o);
-                }
-            }
-            return Util.readFully(url.openStream());
-        }
-
         @Override
         public byte[] fetch(String className) throws ClassNotFoundException {
             if (!USE_BOOTSTRAP_CLASSLOADER && cl == PSEUDO_BOOTSTRAP) {
@@ -1316,11 +1261,6 @@ private RemoteIClassLoader(int oid, IClassLoader proxy) {
             this.oid = oid;
         }
 
-        @Override
-        public byte[] fetchJar(URL url) throws IOException {
-            return proxy.fetchJar(url);
-        }
-
         @Override
         public byte[] fetch(String className) throws ClassNotFoundException {
             return proxy.fetch(className);
@@ -1398,11 +1338,6 @@ public Map<String, ClassFile2> fetch3(String className) throws ClassNotFoundExce
             throw new ClassNotFoundException(className, cause);
         }
 
-        @Override
-        public byte[] fetchJar(URL url) throws IOException {
-            throw new IOException("Cannot fetch " + url, cause);
-        }
-
         @Override
         public byte[] getResource(String name) throws IOException {
             throw new IOException("Cannot get " + name, cause);