diff options
Diffstat (limited to 'common/device')
-rw-r--r-- | common/device/com/android/net/module/util/arp/ArpPacket.java | 171 |
1 files changed, 171 insertions, 0 deletions
diff --git a/common/device/com/android/net/module/util/arp/ArpPacket.java b/common/device/com/android/net/module/util/arp/ArpPacket.java new file mode 100644 index 00000000..dab9694b --- /dev/null +++ b/common/device/com/android/net/module/util/arp/ArpPacket.java @@ -0,0 +1,171 @@ +/* + * 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 com.android.net.module.util.arp; + +import static android.system.OsConstants.ETH_P_ARP; +import static android.system.OsConstants.ETH_P_IP; + +import static com.android.net.module.util.NetworkStackConstants.ARP_ETHER_IPV4_LEN; +import static com.android.net.module.util.NetworkStackConstants.ARP_HWTYPE_ETHER; +import static com.android.net.module.util.NetworkStackConstants.ARP_REPLY; +import static com.android.net.module.util.NetworkStackConstants.ARP_REQUEST; +import static com.android.net.module.util.NetworkStackConstants.ETHER_ADDR_LEN; +import static com.android.net.module.util.NetworkStackConstants.IPV4_ADDR_LEN; + +import android.net.MacAddress; + +import com.android.internal.annotations.VisibleForTesting; + +import java.net.Inet4Address; +import java.net.InetAddress; +import java.net.UnknownHostException; +import java.nio.BufferUnderflowException; +import java.nio.ByteBuffer; + +/** + * Defines basic data and operations needed to build and parse packets for the + * ARP protocol. + * + * @hide + */ +public class ArpPacket { + private static final String TAG = "ArpPacket"; + + public final short opCode; + public final Inet4Address senderIp; + public final Inet4Address targetIp; + public final MacAddress senderHwAddress; + public final MacAddress targetHwAddress; + + ArpPacket(short opCode, MacAddress senderHwAddress, Inet4Address senderIp, + MacAddress targetHwAddress, Inet4Address targetIp) { + this.opCode = opCode; + this.senderHwAddress = senderHwAddress; + this.senderIp = senderIp; + this.targetHwAddress = targetHwAddress; + this.targetIp = targetIp; + } + + /** + * Build an ARP packet from the required specified parameters. + */ + @VisibleForTesting + public static ByteBuffer buildArpPacket(final byte[] dstMac, final byte[] srcMac, + final byte[] targetIp, final byte[] targetHwAddress, byte[] senderIp, + final short opCode) { + final ByteBuffer buf = ByteBuffer.allocate(ARP_ETHER_IPV4_LEN); + + // Ether header + buf.put(dstMac); + buf.put(srcMac); + buf.putShort((short) ETH_P_ARP); + + // ARP header + buf.putShort((short) ARP_HWTYPE_ETHER); // hrd + buf.putShort((short) ETH_P_IP); // pro + buf.put((byte) ETHER_ADDR_LEN); // hln + buf.put((byte) IPV4_ADDR_LEN); // pln + buf.putShort(opCode); // op + buf.put(srcMac); // sha + buf.put(senderIp); // spa + buf.put(targetHwAddress); // tha + buf.put(targetIp); // tpa + buf.flip(); + return buf; + } + + /** + * Parse an ARP packet from a ByteBuffer object. + */ + @VisibleForTesting + public static ArpPacket parseArpPacket(final byte[] recvbuf, final int length) + throws ParseException { + try { + if (length < ARP_ETHER_IPV4_LEN || recvbuf.length < length) { + throw new ParseException("Invalid packet length: " + length); + } + + final ByteBuffer buffer = ByteBuffer.wrap(recvbuf, 0, length); + byte[] l2dst = new byte[ETHER_ADDR_LEN]; + byte[] l2src = new byte[ETHER_ADDR_LEN]; + buffer.get(l2dst); + buffer.get(l2src); + + final short etherType = buffer.getShort(); + if (etherType != ETH_P_ARP) { + throw new ParseException("Incorrect Ether Type: " + etherType); + } + + final short hwType = buffer.getShort(); + if (hwType != ARP_HWTYPE_ETHER) { + throw new ParseException("Incorrect HW Type: " + hwType); + } + + final short protoType = buffer.getShort(); + if (protoType != ETH_P_IP) { + throw new ParseException("Incorrect Protocol Type: " + protoType); + } + + final byte hwAddrLength = buffer.get(); + if (hwAddrLength != ETHER_ADDR_LEN) { + throw new ParseException("Incorrect HW address length: " + hwAddrLength); + } + + final byte ipAddrLength = buffer.get(); + if (ipAddrLength != IPV4_ADDR_LEN) { + throw new ParseException("Incorrect Protocol address length: " + ipAddrLength); + } + + final short opCode = buffer.getShort(); + if (opCode != ARP_REQUEST && opCode != ARP_REPLY) { + throw new ParseException("Incorrect opCode: " + opCode); + } + + byte[] senderHwAddress = new byte[ETHER_ADDR_LEN]; + byte[] senderIp = new byte[IPV4_ADDR_LEN]; + buffer.get(senderHwAddress); + buffer.get(senderIp); + + byte[] targetHwAddress = new byte[ETHER_ADDR_LEN]; + byte[] targetIp = new byte[IPV4_ADDR_LEN]; + buffer.get(targetHwAddress); + buffer.get(targetIp); + + return new ArpPacket(opCode, MacAddress.fromBytes(senderHwAddress), + (Inet4Address) InetAddress.getByAddress(senderIp), + MacAddress.fromBytes(targetHwAddress), + (Inet4Address) InetAddress.getByAddress(targetIp)); + } catch (IndexOutOfBoundsException e) { + throw new ParseException("Invalid index when wrapping a byte array into a buffer"); + } catch (BufferUnderflowException e) { + throw new ParseException("Invalid buffer position"); + } catch (IllegalArgumentException e) { + throw new ParseException("Invalid MAC address representation"); + } catch (UnknownHostException e) { + throw new ParseException("Invalid IP address of Host"); + } + } + + /** + * Thrown when parsing ARP packet failed. + */ + public static class ParseException extends Exception { + ParseException(String message) { + super(message); + } + } +} |