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Commit 86bff867 authored by Lorenzo Colitti's avatar Lorenzo Colitti
Browse files

DHCP: glue code. 

1. Add a method to make a DhcpResults object from a DHCP packet.
2. Add a method to fetch the client MAC from the packet. This is
   needed to check that the message is for us (lots of DHCP
   messages are broadcast).
3. Add a length argument to the method that parses DHCP packets,
   so the caller can use the same MTU-sized array all the time
   instead of having to pass in a new array for every packet.

Bug: 19704592
Change-Id: I58223f5ec90fb5c762bc2934649e02f9122018b2
parent 7f7cc611

services/net/java/android/net/dhcp/DhcpPacket.java

+58 −3
Original line number Diff line number Diff line 
package android.net.dhcp;



import android.net.DhcpResults;

import android.net.LinkAddress;

import android.net.NetworkUtils;

import android.os.Build;

import android.os.SystemProperties;

import android.system.OsConstants;



import java.net.Inet4Address;
@@ -27,6 +32,8 @@ abstract class DhcpPacket { 
            (byte) 0xff, (byte) 0xff, (byte) 0xff,

            (byte) 0xff, (byte) 0xff, (byte) 0xff,

    };

    // Minimum length of a DHCP packet w/o options: Ethernet header, IP header, fixed bootp format.

    public static final int MIN_PACKET_LENGTH_L2 = 14 + 20 + 300;



    /**

     * Packet encapsulations.
@@ -179,6 +186,7 @@ abstract class DhcpPacket { 
     * DHCP Optional Type: Vendor Class Identifier

     */

    protected static final byte DHCP_VENDOR_CLASS_ID = 60;

    protected String mVendorId;



    /**

     * DHCP Optional Type: DHCP Client Identifier
@@ -242,6 +250,13 @@ abstract class DhcpPacket { 
        return mTransId;

    }



    /**

     * Returns the client MAC.

     */

    public byte[] getClientMac() {

        return mClientMac;

    }



    /**

     * Creates a new L3 packet (including IP header) containing the

     * DHCP udp packet.  This method relies upon the delegated method
@@ -820,18 +835,58 @@ abstract class DhcpPacket { 
        newPacket.mRequestedParams = expectedParams;

        newPacket.mServerIdentifier = serverIdentifier;

        newPacket.mSubnetMask = netMask;

        newPacket.mVendorId = vendorId;

        return newPacket;

    }



    /**

     * Parse a packet from an array of bytes.

     * Parse a packet from an array of bytes, stopping at the given length.

     */

    public static DhcpPacket decodeFullPacket(byte[] packet, int pktType)

    public static DhcpPacket decodeFullPacket(byte[] packet, int length, int pktType)

    {

        ByteBuffer buffer = ByteBuffer.wrap(packet).order(ByteOrder.BIG_ENDIAN);

        ByteBuffer buffer = ByteBuffer.wrap(packet, 0, length).order(ByteOrder.BIG_ENDIAN);

        return decodeFullPacket(buffer, pktType);

    }



    /**

     *  Construct a DhcpResults object from a DHCP reply packet.

     */

    public DhcpResults toDhcpResults() {

        Inet4Address ipAddress = mYourIp;

        if (ipAddress == Inet4Address.ANY) {

            ipAddress = mClientIp;

            if (ipAddress == Inet4Address.ANY) {

                return null;

            }

        }



        int prefixLength;

        if (mSubnetMask != null) {

            try {

                prefixLength = NetworkUtils.netmaskToPrefixLength(mSubnetMask);

            } catch (IllegalArgumentException e) {

                // Non-contiguous netmask.

                return null;

            }

        } else {

            prefixLength = NetworkUtils.getImplicitNetmask(ipAddress);

        }



        DhcpResults results = new DhcpResults();

        try {

            results.ipAddress = new LinkAddress(ipAddress, prefixLength);

        } catch (IllegalArgumentException e) {

            return null;

        }

        results.gateway = mGateway;

        results.dnsServers.addAll(mDnsServers);

        results.domains = mDomainName;

        results.serverAddress = mServerIdentifier;

        results.vendorInfo = mVendorId;

        results.leaseDuration = mLeaseTime;

        return results;

    }



    /**

     * Builds a DHCP-DISCOVER packet from the required specified

     * parameters.