1 files changed, 202 insertions, 0 deletions
diff --git a/core/java/android/net/TcpKeepalivePacketData.java b/core/java/android/net/TcpKeepalivePacketData.java
new file mode 100644
index 000000000000..aba4989e0bf3
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+++ b/core/java/android/net/TcpKeepalivePacketData.java
@@ -0,0 +1,202 @@
+/*
+ * 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 static android.net.SocketKeepalive.ERROR_INVALID_IP_ADDRESS;
+
+import android.annotation.Nullable;
+import android.net.SocketKeepalive.InvalidPacketException;
+import android.net.util.IpUtils;
+import android.os.Parcel;
+import android.os.Parcelable;
+import android.system.OsConstants;
+
+import java.net.Inet4Address;
+import java.net.InetAddress;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.util.Objects;
+
+/**
+ * Represents the actual tcp keep alive packets which will be used for hardware offload.
+ * @hide
+ */
+public class TcpKeepalivePacketData extends KeepalivePacketData implements Parcelable {
+    private static final String TAG = "TcpKeepalivePacketData";
+
+     /** TCP sequence number. */
+    public final int tcpSeq;
+
+    /** TCP ACK number. */
+    public final int tcpAck;
+
+    /** TCP RCV window. */
+    public final int tcpWnd;
+
+    /** TCP RCV window scale. */
+    public final int tcpWndScale;
+
+    private static final int IPV4_HEADER_LENGTH = 20;
+    private static final int IPV6_HEADER_LENGTH = 40;
+    private static final int TCP_HEADER_LENGTH = 20;
+
+    // This should only be constructed via static factory methods, such as
+    // tcpKeepalivePacket.
+    private TcpKeepalivePacketData(TcpSocketInfo tcpDetails, byte[] data)
+            throws InvalidPacketException {
+        super(tcpDetails.srcAddress, tcpDetails.srcPort, tcpDetails.dstAddress,
+                tcpDetails.dstPort, data);
+        tcpSeq = tcpDetails.seq;
+        tcpAck = tcpDetails.ack;
+        // In the packet, the window is shifted right by the window scale.
+        tcpWnd = tcpDetails.rcvWnd;
+        tcpWndScale = tcpDetails.rcvWndScale;
+    }
+
+    /**
+     * Factory method to create tcp keepalive packet structure.
+     */
+    public static TcpKeepalivePacketData tcpKeepalivePacket(
+            TcpSocketInfo tcpDetails) throws InvalidPacketException {
+        final byte[] packet;
+        if ((tcpDetails.srcAddress instanceof Inet4Address)
+                && (tcpDetails.dstAddress instanceof Inet4Address)) {
+            packet = buildV4Packet(tcpDetails);
+        } else {
+            // TODO: support ipv6
+            throw new InvalidPacketException(ERROR_INVALID_IP_ADDRESS);
+        }
+
+        return new TcpKeepalivePacketData(tcpDetails, packet);
+    }
+
+    /**
+     * Build ipv4 tcp keepalive packet, not including the link-layer header.
+     */
+    // TODO : if this code is ever moved to the network stack, factorize constants with the ones
+    // over there.
+    private static byte[] buildV4Packet(TcpSocketInfo tcpDetails) {
+        final int length = IPV4_HEADER_LENGTH + TCP_HEADER_LENGTH;
+        ByteBuffer buf = ByteBuffer.allocate(length);
+        buf.order(ByteOrder.BIG_ENDIAN);
+        // IP version and TOS. TODO : fetch this from getsockopt(SOL_IP, IP_TOS)
+        buf.putShort((short) 0x4500);
+        buf.putShort((short) length);
+        buf.putInt(0x4000);                         // ID, flags=DF, offset
+        // TODO : fetch TTL from getsockopt(SOL_IP, IP_TTL)
+        buf.put((byte) 64);
+        buf.put((byte) OsConstants.IPPROTO_TCP);
+        final int ipChecksumOffset = buf.position();
+        buf.putShort((short) 0);                    // IP checksum
+        buf.put(tcpDetails.srcAddress.getAddress());
+        buf.put(tcpDetails.dstAddress.getAddress());
+        buf.putShort((short) tcpDetails.srcPort);
+        buf.putShort((short) tcpDetails.dstPort);
+        buf.putInt(tcpDetails.seq);                 // Sequence Number
+        buf.putInt(tcpDetails.ack);                 // ACK
+        buf.putShort((short) 0x5010);               // TCP length=5, flags=ACK
+        buf.putShort((short) (tcpDetails.rcvWnd >> tcpDetails.rcvWndScale));   // Window size
+        final int tcpChecksumOffset = buf.position();
+        buf.putShort((short) 0);                    // TCP checksum
+        // URG is not set therefore the urgent pointer is not included
+        buf.putShort(ipChecksumOffset, IpUtils.ipChecksum(buf, 0));
+        buf.putShort(tcpChecksumOffset, IpUtils.tcpChecksum(
+                buf, 0, IPV4_HEADER_LENGTH, TCP_HEADER_LENGTH));
+
+        return buf.array();
+    }
+
+    // TODO: add buildV6Packet.
+
+    /** Represents tcp/ip information. */
+    public static class TcpSocketInfo {
+        public final InetAddress srcAddress;
+        public final InetAddress dstAddress;
+        public final int srcPort;
+        public final int dstPort;
+        public final int seq;
+        public final int ack;
+        public final int rcvWnd;
+        public final int rcvWndScale;
+
+        public TcpSocketInfo(InetAddress sAddr, int sPort, InetAddress dAddr,
+                int dPort, int writeSeq, int readSeq, int rWnd, int rWndScale) {
+            srcAddress = sAddr;
+            dstAddress = dAddr;
+            srcPort = sPort;
+            dstPort = dPort;
+            seq = writeSeq;
+            ack = readSeq;
+            rcvWnd = rWnd;
+            rcvWndScale = rWndScale;
+        }
+    }
+
+    @Override
+    public boolean equals(@Nullable final Object o) {
+        if (!(o instanceof TcpKeepalivePacketData)) return false;
+        final TcpKeepalivePacketData other = (TcpKeepalivePacketData) o;
+        return this.srcAddress.equals(other.srcAddress)
+                && this.dstAddress.equals(other.dstAddress)
+                && this.srcPort == other.srcPort
+                && this.dstPort == other.dstPort
+                && this.tcpAck == other.tcpAck
+                && this.tcpSeq == other.tcpSeq
+                && this.tcpWnd == other.tcpWnd
+                && this.tcpWndScale == other.tcpWndScale;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(srcAddress, dstAddress, srcPort, dstPort, tcpAck, tcpSeq, tcpWnd,
+                tcpWndScale);
+    }
+
+    /* Parcelable Implementation. */
+    /** No special parcel contents. */
+    public int describeContents() {
+        return 0;
+    }
+
+    /** Write to parcel. */
+    public void writeToParcel(Parcel out, int flags) {
+        super.writeToParcel(out, flags);
+        out.writeInt(tcpSeq);
+        out.writeInt(tcpAck);
+        out.writeInt(tcpWnd);
+        out.writeInt(tcpWndScale);
+    }
+
+    private TcpKeepalivePacketData(Parcel in) {
+        super(in);
+        tcpSeq = in.readInt();
+        tcpAck = in.readInt();
+        tcpWnd = in.readInt();
+        tcpWndScale = in.readInt();
+    }
+
+    /** Parcelable Creator. */
+    public static final Parcelable.Creator<TcpKeepalivePacketData> CREATOR =
+            new Parcelable.Creator<TcpKeepalivePacketData>() {
+                public TcpKeepalivePacketData createFromParcel(Parcel in) {
+                    return new TcpKeepalivePacketData(in);
+                }
+
+                public TcpKeepalivePacketData[] newArray(int size) {
+                    return new TcpKeepalivePacketData[size];
+                }
+            };
+}