8367976: Validate and clamp jdk.httpclient.bufsize

src/java.net.http/share/classes/jdk/internal/net/http/common/Utils.java

@@ -174,15 +174,20 @@ private static boolean hostnameVerificationDisabledValue() {
     public static final int SLICE_THRESHOLD = 32;
 
     /**
-     * Allocated buffer size. Must never be higher than 16K. But can be lower
-     * if smaller allocation units preferred. HTTP/2 mandates that all
-     * implementations support frame payloads of at least 16K.
+     * The capacity of ephemeral {@link ByteBuffer}s allocated to pass data to and from the client.
+     * It is ensured to have a value between 1 and 2^14 (16,384).
      */
-    private static final int DEFAULT_BUFSIZE = 16 * 1024;
-
     public static final int BUFSIZE = getIntegerNetProperty(
-            "jdk.httpclient.bufsize", DEFAULT_BUFSIZE
-    );
+            "jdk.httpclient.bufsize", 1,
+            // We cap at 2^14 (16,384) for two main reasons:
+            // - The initial frame size is 2^14 (RFC 9113)
+            // - SSL record layer fragments data in chunks of 2^14 bytes or less (RFC 5246)
+            1 << 14,
+            // We choose 2^14 (16,384) as the default, because:
+            // 1. It maximizes throughput within the limits described above
+            // 2. It is small enough to not create a GC bottleneck when it is partially filled
+            1 << 14,
+            true);
 
     public static final BiPredicate<String,String> ACCEPT_ALL = (x,y) -> true;
 

src/java.net.http/share/classes/module-info.java

@@ -48,7 +48,9 @@
  * depending on the context. These restrictions cannot be overridden by this property.
  * </li>
  * <li><p><b>{@systemProperty jdk.httpclient.bufsize}</b> (default: 16384 bytes or 16 kB)<br>
- * The size to use for internal allocated buffers in bytes.
+ * The capacity of internal ephemeral buffers allocated to pass data to and from the
+ * client, in bytes. Valid values are in the range [1, 2^14 (16384)].
+ * If an invalid value is provided, the default value is used.
  * </li>
  * <li><p><b>{@systemProperty jdk.httpclient.connectionPoolSize}</b> (default: 0)<br>
  * The maximum number of connections to keep in the HTTP/1.1 keep alive cache. A value of 0

test/jdk/java/net/httpclient/BufferSize1Test.java

@@ -0,0 +1,158 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. 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.httpclient.test.lib.common.HttpServerAdapters;
+import jdk.internal.net.http.common.Utils;
+import jdk.test.lib.net.SimpleSSLContext;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import javax.net.ssl.SSLContext;
+import java.io.IOException;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpClient.Version;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
+
+import static java.net.http.HttpClient.Builder.NO_PROXY;
+import static java.net.http.HttpClient.Version.HTTP_1_1;
+import static java.net.http.HttpClient.Version.HTTP_2;
+import static java.net.http.HttpClient.Version.HTTP_3;
+import static java.net.http.HttpOption.H3_DISCOVERY;
+import static java.net.http.HttpOption.Http3DiscoveryMode.HTTP_3_URI_ONLY;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/*
+ * @test id
+ * @bug 8367976
+ * @summary Verifies that setting the `jdk.httpclient.bufsize` system property
+ *          to its lowest possible value, 1, does not wedge the client
+ * @library /test/jdk/java/net/httpclient/lib
+ *          /test/lib
+ * @run junit/othervm -Djdk.httpclient.bufsize=1 BufferSize1Test
+ */
+
+class BufferSize1Test implements HttpServerAdapters {
+
+    @BeforeAll
+    static void verifyBufferSize() {
+        assertEquals(1, Utils.BUFSIZE);
+    }
+
+    static Object[][] testArgs() {
+        return new Object[][]{
+                {HTTP_1_1, false},
+                {HTTP_1_1, true},
+                {HTTP_2, false},
+                {HTTP_2, true},
+                {HTTP_3, true}
+        };
+    }
+
+    @ParameterizedTest
+    @MethodSource("testArgs")
+    void test(Version version, boolean secure) throws Exception {
+
+        // Create the server
+        var sslContext = secure || HTTP_3.equals(version) ? new SimpleSSLContext().get() : null;
+        try (var server = switch (version) {
+            case HTTP_1_1, HTTP_2 -> HttpTestServer.create(version, sslContext);
+            case HTTP_3 -> HttpTestServer.create(HTTP_3_URI_ONLY, sslContext);
+        }) {
+
+            // Add the handler and start the server
+            var serverHandlerPath = "/" + BufferSize1Test.class.getSimpleName();
+            server.addHandler(new HttpTestEchoHandler(), serverHandlerPath);
+            server.start();
+
+            // Create the client
+            try (var client = createClient(version, sslContext)) {
+
+                // Create the request with body to ensure that `ByteBuffer`s
+                // will be used throughout the entire end-to-end interaction.
+                byte[] requestBodyBytes = "body".repeat(1000).getBytes(StandardCharsets.US_ASCII);
+                var request = createRequest(sslContext, server, serverHandlerPath, version, requestBodyBytes);
+
+                // Execute and verify the request.
+                // Do it twice to cover code paths before and after a protocol upgrade.
+                requestAndVerify(client, request, requestBodyBytes);
+                requestAndVerify(client, request, requestBodyBytes);
+
+            }
+
+        }
+
+    }
+
+    private HttpClient createClient(Version version, SSLContext sslContext) {
+        var clientBuilder = newClientBuilderForH3()
+                .proxy(NO_PROXY)
+                .version(version);
+        if (sslContext != null) {
+            clientBuilder.sslContext(sslContext);
+        }
+        return clientBuilder.build();
+    }
+
+    private static HttpRequest createRequest(
+            SSLContext sslContext,
+            HttpTestServer server,
+            String serverHandlerPath,
+            Version version,
+            byte[] requestBodyBytes) {
+        var requestUri = URI.create(String.format(
+                "%s://%s%s/x",
+                sslContext == null ? "http" : "https",
+                server.serverAuthority(),
+                serverHandlerPath));
+        var requestBuilder = HttpRequest
+                .newBuilder(requestUri)
+                .version(version)
+                .POST(HttpRequest.BodyPublishers.ofByteArray(requestBodyBytes));
+        if (HTTP_3.equals(version)) {
+            requestBuilder.setOption(H3_DISCOVERY, HTTP_3_URI_ONLY);
+        }
+        return requestBuilder.build();
+    }
+
+    private static void requestAndVerify(HttpClient client, HttpRequest request, byte[] requestBodyBytes)
+            throws IOException, InterruptedException {
+        var response = client.send(request, HttpResponse.BodyHandlers.ofByteArray());
+        if (response.statusCode() != 200) {
+            throw new AssertionError("Was expecting status code 200, found: " + response.statusCode());
+        }
+        byte[] responseBodyBytes = response.body();
+        int mismatchIndex = Arrays.mismatch(requestBodyBytes, responseBodyBytes);
+        assertTrue(
+                mismatchIndex < 0,
+                String.format(
+                        "Response body (%s bytes) mismatches the request body (%s bytes) at index %s!",
+                        responseBodyBytes.length, requestBodyBytes.length, mismatchIndex));
+    }
+
+}

test/jdk/java/net/httpclient/BufferSizePropertyClampTest.java

@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. 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.internal.net.http.common.Utils;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import java.text.MessageFormat;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.logging.Handler;
+import java.util.logging.LogRecord;
+import java.util.logging.Logger;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/*
+ * @test
+ * @bug 8367976
+ * @summary Verifies that the `jdk.httpclient.bufsize` system property is
+ *          clamped correctly
+ *
+ * @library /test/lib
+ *
+ * @comment `-Djdk.httpclient.HttpClient.log=errors` is needed to enable
+ *          logging and verify that invalid input gets logged
+ * @run junit/othervm
+ *      -Djdk.httpclient.HttpClient.log=errors
+ *      -Djdk.httpclient.bufsize=-1
+ *      BufferSizePropertyClampTest
+ * @run junit/othervm
+ *      -Djdk.httpclient.HttpClient.log=errors
+ *      -Djdk.httpclient.bufsize=0
+ *      BufferSizePropertyClampTest
+ * @run junit/othervm
+ *      -Djdk.httpclient.HttpClient.log=errors
+ *      -Djdk.httpclient.bufsize=16385
+ *      BufferSizePropertyClampTest
+ */
+
+class BufferSizePropertyClampTest {
+
+    /** Anchor to avoid the {@code Logger} instance get GC'ed */
+    private static final Logger CLIENT_LOGGER =
+            Logger.getLogger("jdk.httpclient.HttpClient");
+
+    private static final List<String> CLIENT_LOGGER_MESSAGES =
+            Collections.synchronizedList(new ArrayList<>());
+
+    @BeforeAll
+    static void registerLoggerHandler() {
+        CLIENT_LOGGER.addHandler(new Handler() {
+
+            @Override
+            public void publish(LogRecord record) {
+                var message = MessageFormat.format(record.getMessage(), record.getParameters());
+                CLIENT_LOGGER_MESSAGES.add(message);
+            }
+
+            @Override
+            public void flush() {
+                // Do nothing
+            }
+
+            @Override
+            public void close() {
+                // Do nothing
+            }
+
+        });
+    }
+
+    @Test
+    void test() {
+        assertEquals(16384, Utils.BUFSIZE);
+        assertEquals(
+                1, CLIENT_LOGGER_MESSAGES.size(),
+                "Unexpected number of logger messages: " + CLIENT_LOGGER_MESSAGES);
+        var expectedMessage = "ERROR: Property value for jdk.httpclient.bufsize=" +
+                System.getProperty("jdk.httpclient.bufsize") +
+                " not in [1..16384]: using default=16384";
+        assertEquals(expectedMessage, CLIENT_LOGGER_MESSAGES.getFirst().replaceAll(",", ""));
+    }
+
+}

test/jdk/java/net/httpclient/HttpRequestBodyPublishers/OfByteArrayTest.java

@@ -43,8 +43,6 @@
  * @run junit OfByteArrayTest
  *
  * @comment Using `main/othervm` to initiate tests that depend on a custom-configured JVM
- * @run main/othervm -Djdk.httpclient.bufsize=-1 OfByteArrayTest testInvalidBufferSize
- * @run main/othervm -Djdk.httpclient.bufsize=0 OfByteArrayTest testInvalidBufferSize
  * @run main/othervm -Djdk.httpclient.bufsize=3 OfByteArrayTest testChunking "" 0 0 ""
  * @run main/othervm -Djdk.httpclient.bufsize=3 OfByteArrayTest testChunking a 0 0 ""
  * @run main/othervm -Djdk.httpclient.bufsize=3 OfByteArrayTest testChunking a 1 0 ""
@@ -88,7 +86,6 @@ void testInvalidOffsetOrLength(String contentText, int offset, int length) {
      */
     public static void main(String[] args) throws InterruptedException {
         switch (args[0]) {
-            case "testInvalidBufferSize" -> testInvalidBufferSize();
             case "testChunking" -> testChunking(
                     parseStringArg(args[1]),
                     Integer.parseInt(args[2]),
@@ -102,10 +99,6 @@ private static String parseStringArg(String arg) {
         return arg == null || arg.trim().equals("\"\"") ? "" : arg;
     }
 
-    private static void testInvalidBufferSize() {
-        assertThrows(IllegalArgumentException.class, () -> HttpRequest.BodyPublishers.ofByteArray(new byte[1]));
-    }
-
     private static void testChunking(
             String contentText, int offset, int length, String expectedBuffersText)
             throws InterruptedException {