[KA03] Support tcp keepalive offload

When offload is starting, socket will be switched to repair
mode. Read and write on the socket will not be allowed until
repair mode is turned off. If remote packet arrives, repair
mode will be turned off automatically and a callback will
be raised to indicate that socket is ready to read from.

Bug: 114151147
Test: -atest FrameworksNetTests
      -manual

Change-Id: I0c335865912e183e7ad32a8ea12188f02ccde5fd

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
--- /dev/null
+++ 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];
+                }
+            };
+}