1 files changed, 77 insertions, 0 deletions
diff --git a/core/java/android/net/NattKeepalivePacketData.java b/core/java/android/net/NattKeepalivePacketData.java
new file mode 100644
index 000000000000..dd2b108cdbfd
--- /dev/null
+++ b/core/java/android/net/NattKeepalivePacketData.java
@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.net;
+
+import android.net.SocketKeepalive.InvalidPacketException;
+import android.net.util.IpUtils;
+import android.system.OsConstants;
+
+import java.net.Inet4Address;
+import java.net.InetAddress;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+
+/** @hide */
+public final class NattKeepalivePacketData extends KeepalivePacketData {
+
+    // This should only be constructed via static factory methods, such as
+    // nattKeepalivePacket
+    private NattKeepalivePacketData(InetAddress srcAddress, int srcPort,
+            InetAddress dstAddress, int dstPort, byte[] data) throws
+            InvalidPacketException {
+        super(srcAddress, srcPort, dstAddress, dstPort, data);
+    }
+
+    /**
+     * Factory method to create Nat-T keepalive packet structure.
+     */
+    public static NattKeepalivePacketData nattKeepalivePacket(
+            InetAddress srcAddress, int srcPort, InetAddress dstAddress, int dstPort)
+            throws InvalidPacketException {
+
+        if (!(srcAddress instanceof Inet4Address) || !(dstAddress instanceof Inet4Address)) {
+            throw new InvalidPacketException(SocketKeepalive.ERROR_INVALID_IP_ADDRESS);
+        }
+
+        if (dstPort != NattSocketKeepalive.NATT_PORT) {
+            throw new InvalidPacketException(SocketKeepalive.ERROR_INVALID_PORT);
+        }
+
+        int length = IPV4_HEADER_LENGTH + UDP_HEADER_LENGTH + 1;
+        ByteBuffer buf = ByteBuffer.allocate(length);
+        buf.order(ByteOrder.BIG_ENDIAN);
+        buf.putShort((short) 0x4500);             // IP version and TOS
+        buf.putShort((short) length);
+        buf.putInt(0);                            // ID, flags, offset
+        buf.put((byte) 64);                       // TTL
+        buf.put((byte) OsConstants.IPPROTO_UDP);
+        int ipChecksumOffset = buf.position();
+        buf.putShort((short) 0);                  // IP checksum
+        buf.put(srcAddress.getAddress());
+        buf.put(dstAddress.getAddress());
+        buf.putShort((short) srcPort);
+        buf.putShort((short) dstPort);
+        buf.putShort((short) (length - 20));      // UDP length
+        int udpChecksumOffset = buf.position();
+        buf.putShort((short) 0);                  // UDP checksum
+        buf.put((byte) 0xff);                     // NAT-T keepalive
+        buf.putShort(ipChecksumOffset, IpUtils.ipChecksum(buf, 0));
+        buf.putShort(udpChecksumOffset, IpUtils.udpChecksum(buf, 0, IPV4_HEADER_LENGTH));
+
+        return new NattKeepalivePacketData(srcAddress, srcPort, dstAddress, dstPort, buf.array());
+    }
+}