From 052a0da4f748eff9392a0dbd41fc5948f7da4cb1 Mon Sep 17 00:00:00 2001
From: Lorenzo Colitti <lorenzo@google.com>
Date: Wed, 22 Apr 2015 15:38:01 +0900
Subject: [PATCH] Always send the DHCP client identifier.

Currently we send it only in request packets, but not in discover
packets. This might confuse servers because they might think that
the discover and the request come from different clients.

Also reorder the options in the request packet to match the order
used by the legacy DHCP client.

While I'm at it, fix the generation code for inform and decline
packets, which we do not use.

Bug: 19704592
Bug: 20335221
Change-Id: I1d45306e76dbd5da9cc4611e6df84a9f67346b2c
---
 .../net/java/android/net/dhcp/DhcpDeclinePacket.java   |  5 ++++-
 .../net/java/android/net/dhcp/DhcpDiscoverPacket.java  |  1 +
 .../net/java/android/net/dhcp/DhcpInformPacket.java    |  9 +++------
 services/net/java/android/net/dhcp/DhcpPacket.java     | 10 ++++++++++
 .../net/java/android/net/dhcp/DhcpRequestPacket.java   |  8 +-------
 5 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/services/net/java/android/net/dhcp/DhcpDeclinePacket.java b/services/net/java/android/net/dhcp/DhcpDeclinePacket.java
index d0a3d34f4a93a..7ecdea7b89da2 100644
--- a/services/net/java/android/net/dhcp/DhcpDeclinePacket.java
+++ b/services/net/java/android/net/dhcp/DhcpDeclinePacket.java
@@ -53,6 +53,9 @@ class DhcpDeclinePacket extends DhcpPacket {
      * Adds optional parameters to the DECLINE packet.
      */
     void finishPacket(ByteBuffer buffer) {
-        // None needed
+        addTlv(buffer, DHCP_MESSAGE_TYPE, DHCP_MESSAGE_TYPE_DECLINE);
+        addTlv(buffer, DHCP_CLIENT_IDENTIFIER, getClientId());
+        // RFC 2131 says we MUST NOT include our common client TLVs or the parameter request list.
+        addTlvEnd(buffer);
     }
 }
diff --git a/services/net/java/android/net/dhcp/DhcpDiscoverPacket.java b/services/net/java/android/net/dhcp/DhcpDiscoverPacket.java
index 4676d44f713e5..91e6bd6469d80 100644
--- a/services/net/java/android/net/dhcp/DhcpDiscoverPacket.java
+++ b/services/net/java/android/net/dhcp/DhcpDiscoverPacket.java
@@ -52,6 +52,7 @@ class DhcpDiscoverPacket extends DhcpPacket {
      */
     void finishPacket(ByteBuffer buffer) {
         addTlv(buffer, DHCP_MESSAGE_TYPE, DHCP_MESSAGE_TYPE_DISCOVER);
+        addTlv(buffer, DHCP_CLIENT_IDENTIFIER, getClientId());
         addCommonClientTlvs(buffer);
         addTlv(buffer, DHCP_PARAMETER_LIST, mRequestedParams);
         addTlvEnd(buffer);
diff --git a/services/net/java/android/net/dhcp/DhcpInformPacket.java b/services/net/java/android/net/dhcp/DhcpInformPacket.java
index 6d8d09c6c564b..7a83466c6e054 100644
--- a/services/net/java/android/net/dhcp/DhcpInformPacket.java
+++ b/services/net/java/android/net/dhcp/DhcpInformPacket.java
@@ -53,12 +53,9 @@ class DhcpInformPacket extends DhcpPacket {
      * Adds additional parameters to the INFORM packet.
      */
     void finishPacket(ByteBuffer buffer) {
-        byte[] clientId = new byte[7];
-
-        clientId[0] = CLIENT_ID_ETHER;
-        System.arraycopy(mClientMac, 0, clientId, 1, 6);
-
-        addTlv(buffer, DHCP_MESSAGE_TYPE, DHCP_MESSAGE_TYPE_REQUEST);
+        addTlv(buffer, DHCP_MESSAGE_TYPE, DHCP_MESSAGE_TYPE_INFORM);
+        addTlv(buffer, DHCP_CLIENT_IDENTIFIER, getClientId());
+        addCommonClientTlvs(buffer);
         addTlv(buffer, DHCP_PARAMETER_LIST, mRequestedParams);
         addTlvEnd(buffer);
     }
diff --git a/services/net/java/android/net/dhcp/DhcpPacket.java b/services/net/java/android/net/dhcp/DhcpPacket.java
index 0c51ef8ecaed5..b923b1bf25fb6 100644
--- a/services/net/java/android/net/dhcp/DhcpPacket.java
+++ b/services/net/java/android/net/dhcp/DhcpPacket.java
@@ -290,6 +290,16 @@ abstract class DhcpPacket {
         return mClientMac;
     }
 
+    /**
+     * Returns the client ID. This follows RFC 2132 and is based on the hardware address.
+     */
+    public byte[] getClientId() {
+        byte[] clientId = new byte[mClientMac.length + 1];
+        clientId[0] = CLIENT_ID_ETHER;
+        System.arraycopy(mClientMac, 0, clientId, 1, mClientMac.length);
+        return clientId;
+    }
+
     /**
      * Creates a new L3 packet (including IP header) containing the
      * DHCP udp packet.  This method relies upon the delegated method
diff --git a/services/net/java/android/net/dhcp/DhcpRequestPacket.java b/services/net/java/android/net/dhcp/DhcpRequestPacket.java
index 5611476d4a25f..4f9aa01151ca2 100644
--- a/services/net/java/android/net/dhcp/DhcpRequestPacket.java
+++ b/services/net/java/android/net/dhcp/DhcpRequestPacket.java
@@ -56,20 +56,14 @@ class DhcpRequestPacket extends DhcpPacket {
      * Adds the optional parameters to the client-generated REQUEST packet.
      */
     void finishPacket(ByteBuffer buffer) {
-        byte[] clientId = new byte[7];
-
-        // assemble client identifier
-        clientId[0] = CLIENT_ID_ETHER;
-        System.arraycopy(mClientMac, 0, clientId, 1, 6);
-
         addTlv(buffer, DHCP_MESSAGE_TYPE, DHCP_MESSAGE_TYPE_REQUEST);
+        addTlv(buffer, DHCP_CLIENT_IDENTIFIER, getClientId());
         if (!INADDR_ANY.equals(mRequestedIp)) {
             addTlv(buffer, DHCP_REQUESTED_IP, mRequestedIp);
         }
         if (!INADDR_ANY.equals(mServerIdentifier)) {
             addTlv(buffer, DHCP_SERVER_IDENTIFIER, mServerIdentifier);
         }
-        addTlv(buffer, DHCP_CLIENT_IDENTIFIER, clientId);
         addCommonClientTlvs(buffer);
         addTlv(buffer, DHCP_PARAMETER_LIST, mRequestedParams);
         addTlvEnd(buffer);