Home | History | Annotate | Download | only in dhcp 
      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.Inet4Address;
     20 import java.nio.ByteBuffer;
     21 
     22 /**
     23  * This class implements the DHCP-OFFER packet.
     24  */
     25 class DhcpOfferPacket extends DhcpPacket {
     26     /**
     27      * The IP address of the server which sent this packet.
     28      */
     29     private final Inet4Address mSrcIp;
     30 
     31     /**
     32      * Generates a OFFER packet with the specified parameters.
     33      */
     34     DhcpOfferPacket(int transId, short secs, boolean broadcast, Inet4Address serverAddress,
     35                     Inet4Address clientIp, Inet4Address yourIp, byte[] clientMac) {
     36         super(transId, secs, clientIp, yourIp, INADDR_ANY, INADDR_ANY, clientMac, broadcast);
     37         mSrcIp = serverAddress;
     38     }
     39 
     40     public String toString() {
     41         String s = super.toString();
     42         String dnsServers = ", DNS servers: ";
     43 
     44         if (mDnsServers != null) {
     45             for (Inet4Address dnsServer: mDnsServers) {
     46                 dnsServers += dnsServer + " ";
     47             }
     48         }
     49 
     50         return s + " OFFER, ip " + mYourIp + ", mask " + mSubnetMask +
     51                 dnsServers + ", gateways " + mGateways +
     52                 " lease time " + mLeaseTime + ", domain " + mDomainName;
     53     }
     54 
     55     /**
     56      * Fills in a packet with the specified OFFER attributes.
     57      */
     58     public ByteBuffer buildPacket(int encap, short destUdp, short srcUdp) {
     59         ByteBuffer result = ByteBuffer.allocate(MAX_LENGTH);
     60         Inet4Address destIp = mBroadcast ? INADDR_BROADCAST : mYourIp;
     61         Inet4Address srcIp = mBroadcast ? INADDR_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 server-generated OFFER packet.
     71      */
     72     void finishPacket(ByteBuffer buffer) {
     73         addTlv(buffer, DHCP_MESSAGE_TYPE, DHCP_MESSAGE_TYPE_OFFER);
     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, mGateways);
     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