diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/java.base/share/classes/sun/security/ssl/MaxFragmentLengthExtension.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.base/share/classes/sun/security/ssl/MaxFragmentLengthExtension.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,139 @@
+/*
+ * Copyright (c) 2015, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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.
+ */
+
+package sun.security.ssl;
+
+import java.io.IOException;
+import javax.net.ssl.SSLProtocolException;
+
+/*
+ * [RFC6066] TLS specifies a fixed maximum plaintext fragment length of
+ * 2^14 bytes.  It may be desirable for constrained clients to negotiate
+ * a smaller maximum fragment length due to memory limitations or bandwidth
+ * limitations.
+ *
+ * In order to negotiate smaller maximum fragment lengths, clients MAY
+ * include an extension of type "max_fragment_length" in the (extended)
+ * client hello.  The "extension_data" field of this extension SHALL
+ * contain:
+ *
+ *    enum{
+ *        2^9(1), 2^10(2), 2^11(3), 2^12(4), (255)
+ *    } MaxFragmentLength;
+ *
+ * whose value is the desired maximum fragment length.
+ */
+final class MaxFragmentLengthExtension extends HelloExtension {
+
+    private static final int MAX_FRAGMENT_LENGTH_512  = 1;      // 2^9
+    private static final int MAX_FRAGMENT_LENGTH_1024 = 2;      // 2^10
+    private static final int MAX_FRAGMENT_LENGTH_2048 = 3;      // 2^11
+    private static final int MAX_FRAGMENT_LENGTH_4096 = 4;      // 2^12
+
+    final int maxFragmentLength;
+
+    MaxFragmentLengthExtension(int fragmentSize) {
+        super(ExtensionType.EXT_MAX_FRAGMENT_LENGTH);
+
+        if (fragmentSize < 1024) {
+            maxFragmentLength = MAX_FRAGMENT_LENGTH_512;
+        } else if (fragmentSize < 2048) {
+            maxFragmentLength = MAX_FRAGMENT_LENGTH_1024;
+        } else if (fragmentSize < 4096) {
+            maxFragmentLength = MAX_FRAGMENT_LENGTH_2048;
+        } else {
+            maxFragmentLength = MAX_FRAGMENT_LENGTH_4096;
+        }
+    }
+
+    MaxFragmentLengthExtension(HandshakeInStream s, int len)
+                throws IOException {
+        super(ExtensionType.EXT_MAX_FRAGMENT_LENGTH);
+
+        // check the extension length
+        if (len != 1) {
+            throw new SSLProtocolException("Invalid " + type + " extension");
+        }
+
+        maxFragmentLength = s.getInt8();
+        if ((maxFragmentLength > 4) || (maxFragmentLength < 1)) {
+            throw new SSLProtocolException("Invalid " + type + " extension");
+        }
+    }
+
+    // Length of the encoded extension, including the type and length fields
+    @Override
+    int length() {
+        return 5;               // 4: extension type and length fields
+                                // 1: MaxFragmentLength field
+    }
+
+    @Override
+    void send(HandshakeOutStream s) throws IOException {
+        s.putInt16(type.id);
+        s.putInt16(1);
+        s.putInt8(maxFragmentLength);
+    }
+
+    int getMaxFragLen() {
+        switch (maxFragmentLength) {
+            case MAX_FRAGMENT_LENGTH_512:
+                return 512;
+            case MAX_FRAGMENT_LENGTH_1024:
+                return 1024;
+            case MAX_FRAGMENT_LENGTH_2048:
+                return 2048;
+            case MAX_FRAGMENT_LENGTH_4096:
+                return 4096;
+        }
+
+        // unlikely to happen
+        return -1;
+    }
+
+    static boolean needFragLenNego(int fragmentSize) {
+        return (fragmentSize > 0) && (fragmentSize <= 4096);
+    }
+
+    static int getValidMaxFragLen(int fragmentSize) {
+        if (fragmentSize < 1024) {
+            return 512;
+        } else if (fragmentSize < 2048) {
+            return 1024;
+        } else if (fragmentSize < 4096) {
+            return 2048;
+        } else if (fragmentSize == 4096) {
+            return 4096;
+        } else {
+            return 16384;
+        }
+    }
+
+    @Override
+    public String toString() {
+        return "Extension " + type + ", max_fragment_length: " +
+                "(2^" + (maxFragmentLength + 8) + ")";
+    }
+}