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DHCP: glue code.

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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
This commit is contained in:
Lorenzo Colitti
2015-03-11 01:16:18 +09:00
parent 15204d50b4
commit 29cb944bef
1 changed files with 58 additions and 3 deletions
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61
services/net/java/android/net/dhcp/DhcpPacket.java
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@@ -1,5 +1,10 @@
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.