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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package android.net.dhcp;
     18 
     19 import java.net.InetAddress;
     20 import java.net.Inet4Address;
     21 import java.nio.ByteBuffer;
     22 
     23 /**
     24  * This class implements the DHCP-ACK packet.
     25  */
     26 class DhcpAckPacket extends DhcpPacket {
     27 
     28     /**
     29      * The address of the server which sent this packet.
     30      */
     31     private final InetAddress mSrcIp;
     32 
     33     DhcpAckPacket(int transId, boolean broadcast, InetAddress serverAddress,
     34                   InetAddress clientIp, byte[] clientMac) {
     35         super(transId, Inet4Address.ANY, clientIp, serverAddress,
     36             Inet4Address.ANY, clientMac, broadcast);
     37         mBroadcast = broadcast;
     38         mSrcIp = serverAddress;
     39     }
     40 
     41     public String toString() {
     42         String s = super.toString();
     43         String dnsServers = " DNS servers: ";
     44 
     45         for (InetAddress dnsServer: mDnsServers) {
     46             dnsServers += dnsServer.toString() + " ";
     47         }
     48 
     49         return s + " ACK: your new IP " + mYourIp +
     50                 ", netmask " + mSubnetMask +
     51                 ", gateway " + mGateway + dnsServers +
     52                 ", lease time " + mLeaseTime;
     53     }
     54 
     55     /**
     56      * Fills in a packet with the requested ACK parameters.
     57      */
     58     public ByteBuffer buildPacket(int encap, short destUdp, short srcUdp) {
     59         ByteBuffer result = ByteBuffer.allocate(MAX_LENGTH);
     60         InetAddress destIp = mBroadcast ? Inet4Address.ALL : mYourIp;
     61         InetAddress srcIp = mBroadcast ? Inet4Address.ANY : mSrcIp;
     62 
     63         fillInPacket(encap, destIp, srcIp, destUdp, srcUdp, result,
     64             DHCP_BOOTREPLY, mBroadcast);
     65         result.flip();
     66         return result;
     67     }
     68 
     69     /**
     70      * Adds the optional parameters to the client-generated ACK packet.
     71      */
     72     void finishPacket(ByteBuffer buffer) {
     73         addTlv(buffer, DHCP_MESSAGE_TYPE, DHCP_MESSAGE_TYPE_ACK);
     74         addTlv(buffer, DHCP_SERVER_IDENTIFIER, mServerIdentifier);
     75         addTlv(buffer, DHCP_LEASE_TIME, mLeaseTime);
     76 
     77         // the client should renew at 1/2 the lease-expiry interval
     78         if (mLeaseTime != null) {
     79             addTlv(buffer, DHCP_RENEWAL_TIME,
     80                 Integer.valueOf(mLeaseTime.intValue() / 2));
     81         }
     82 
     83         addTlv(buffer, DHCP_SUBNET_MASK, mSubnetMask);
     84         addTlv(buffer, DHCP_ROUTER, mGateway);
     85         addTlv(buffer, DHCP_DOMAIN_NAME, mDomainName);
     86         addTlv(buffer, DHCP_BROADCAST_ADDRESS, mBroadcastAddress);
     87         addTlv(buffer, DHCP_DNS_SERVER, mDnsServers);
     88         addTlvEnd(buffer);
     89     }
     90 
     91     /**
     92      * Un-boxes an Integer, returning 0 if a null reference is supplied.
     93      */
     94     private static final int getInt(Integer v) {
     95         if (v == null) {
     96             return 0;
     97         } else {
     98             return v.intValue();
     99         }
    100     }
    101 
    102     /**
    103      * Notifies the specified state machine of the ACK packet parameters.
    104      */
    105     public void doNextOp(DhcpStateMachine machine) {
    106         machine.onAckReceived(mYourIp, mSubnetMask, mGateway, mDnsServers,
    107             mServerIdentifier, getInt(mLeaseTime));
    108     }
    109 }
    110