Android Wi-Fi Ethernet新IP获取机制—IpManager(Android 7.0)

1 android N之前 Ethernet旧的ip获取

Android N之前，即android 5.0和android 6.0的IP获取机制都是通过/system/bin下面的dhcpcd的bin档去拿的ip

//EthernetNetworkFactory.java (frameworks\opt\net\ethernet\java\com\android\server\ethernet)

    public void onRequestNetwork() {
        // TODO: Handle DHCP renew.
        Thread dhcpThread = new Thread(new Runnable() {
            public void run() {
                        ...

                    DhcpResults dhcpResults = new DhcpResults();
                    // TODO: Handle DHCP renewals better.
                    // In general runDhcp handles DHCP renewals for us, because
                    // the dhcp client stays running, but if the renewal fails,
                    // we will lose our IP address and connectivity without
                    // noticing.
                    //通过这个函数call到jni之后，最后run /system/bin/dhcpcd
                    if (!NetworkUtils.runDhcp(mIface, dhcpResults)) {
                        Log.e(TAG, "DHCP request error:" + NetworkUtils.getDhcpError());
                        // set our score lower than any network could go
                        // so we get dropped.
                        mFactory.setScoreFilter(-1);
                        return;
                    }

不知道是不是dhcpcd本身的问题，这段code其实不是稳定，超时拿不到ip的现象经常可以遇到。只能在这里多加几次try runDhcp。

2 android N新的拿IP的机制

android N不要了runDhcpcd(),而是通过DhcpClient，这个是android M引入的wifi那边另外一种获得ip的方式，DhcpClient是通过framework发送dhcpcd协议的UDP请求包直接去拿IP，不再使用开源的dhcpcd。在调用DhcpClient的基础之前，google还用了一个状态机IpManager来管理dhcpcd成功还是失败等状态，将ip赋值给IpConfiguration和LinkProperties传递到上层的framework。还有就是加入ipv6的支持，不过ipv6的部分目前还没做好。

//EthernetNetworkFactory.java (frameworks\opt\net\ethernet\java\com\android\server\ethernet)    

        final Thread ipProvisioningThread = new Thread(new Runnable() {
            public void run() {
                if (DBG) {
                    Log.d(TAG, String.format("starting ipProvisioningThread(%s): mNetworkInfo=%s",
                            mIface, mNetworkInfo));
                }

                LinkProperties linkProperties;

                IpConfiguration config = mEthernetManager.getConfiguration();

                if (config.getIpAssignment() == IpAssignment.STATIC) {
                    if (!setStaticIpAddress(config.getStaticIpConfiguration())) {
                        // We've already logged an error.
                        return;
                    }
                    linkProperties = config.getStaticIpConfiguration().toLinkProperties(mIface);
                } else {

                    mNetworkInfo.setDetailedState(DetailedState.OBTAINING_IPADDR, null, mHwAddr);
                    WaitForProvisioningCallback ipmCallback = new WaitForProvisioningCallback() {
                        @Override
                        public void onLinkPropertiesChange(LinkProperties newLp) {
                            synchronized(EthernetNetworkFactory.this) {
                                if (mNetworkAgent != null && mNetworkInfo.isConnected()) {
                                    mLinkProperties = newLp;
                                    mNetworkAgent.sendLinkProperties(newLp);
                                }
                            }
                        }
                    };

                    synchronized(EthernetNetworkFactory.this) {
                        stopIpManagerLocked();
                        //IPManger，用这个代替之前的runDhcpcd（）
                        mIpManager = new IpManager(mContext, mIface, ipmCallback);

                        if (config.getProxySettings() == ProxySettings.STATIC ||
                                config.getProxySettings() == ProxySettings.PAC) {
                            mIpManager.setHttpProxy(config.getHttpProxy());
                        }

                        final String tcpBufferSizes = mContext.getResources().getString(
                                com.android.internal.R.string.config_ethernet_tcp_buffers);
                        if (!TextUtils.isEmpty(tcpBufferSizes)) {
                            mIpManager.setTcpBufferSizes(tcpBufferSizes);
                        }

                        final ProvisioningConfiguration provisioningConfiguration =
                                mIpManager.buildProvisioningConfiguration()
                                        .withProvisioningTimeoutMs(0)
                                        .build();
                        //start
                        mIpManager.startProvisioning(provisioningConfiguration);
                    }
                    //通过callback去拿到新的IP
                    linkProperties = ipmCallback.waitForProvisioning();
                    if (linkProperties == null) {
                        Log.e(TAG, "IP provisioning error");
                        // set our score lower than any network could go
                        // so we get dropped.
                        mFactory.setScoreFilter(-1);
                        synchronized(EthernetNetworkFactory.this) {
                            stopIpManagerLocked();
                        }
                        return;
                    }
                }

IpManager

IpManager，是wifi和Ethernet都会用到。把它定义为获取ip的管理器好了。

2.1 构造函数

    public IpManager(Context context, String ifName, Callback callback)
                throws IllegalArgumentException {
        this(context, ifName, callback, INetworkManagementService.Stub.asInterface(
                ServiceManager.getService(Context.NETWORKMANAGEMENT_SERVICE)));
    }

    /**
     * An expanded constructor, useful for dependency injection.
     */
    public IpManager(Context context, String ifName, Callback callback,
            INetworkManagementService nwService) throws IllegalArgumentException {
        super(IpManager.class.getSimpleName() + "." + ifName);
        mTag = getName();

        mContext = context;
        //网口的名字,eth0 or wlan0
        mInterfaceName = ifName;
        mClatInterfaceName = CLAT_PREFIX + ifName;
        mCallback = new LoggingCallbackWrapper(callback);
        //NetworkManagementService对象，可以对Interface做一些操作
        mNwService = nwService;

        //检测Interface的状态变化
        mNetlinkTracker = new NetlinkTracker(
                mInterfaceName,
                new NetlinkTracker.Callback() {
                    @Override
                    public void update() {
                        sendMessage(EVENT_NETLINK_LINKPROPERTIES_CHANGED);
                    }
                }) {
            @Override
            public void interfaceAdded(String iface) {
                super.interfaceAdded(iface);
                if (mClatInterfaceName.equals(iface)) {
                    mCallback.setNeighborDiscoveryOffload(false);
                }
            }

            @Override
            public void interfaceRemoved(String iface) {
                super.interfaceRemoved(iface);
                if (mClatInterfaceName.equals(iface)) {
                    // TODO: consider sending a message to the IpManager main
                    // StateMachine thread, in case "NDO enabled" state becomes
                    // tied to more things that 464xlat operation.
                    mCallback.setNeighborDiscoveryOffload(true);
                }
            }
        };

        try {
            mNwService.registerObserver(mNetlinkTracker);
        } catch (RemoteException e) {
            Log.e(mTag, "Couldn't register NetlinkTracker: " + e.toString());
        }
        //LinkProperties里面记录着网络相关的ip和dns等信息，这个在connectivityservice中会被使用到
        resetLinkProperties();

        mProvisioningTimeoutAlarm = new WakeupMessage(mContext, getHandler(),
                mTag + ".EVENT_PROVISIONING_TIMEOUT", EVENT_PROVISIONING_TIMEOUT);
        mDhcpActionTimeoutAlarm = new WakeupMessage(mContext, getHandler(),
                mTag + ".EVENT_DHCPACTION_TIMEOUT", EVENT_DHCPACTION_TIMEOUT);

        // Super simple StateMachine.
        //状态机，很简单，才三个状态
        addState(mStoppedState);
        addState(mStartedState);
        addState(mStoppingState);

        setInitialState(mStoppedState);
        mLocalLog = new LocalLog(MAX_LOG_RECORDS);
        super.start();
    }

2.2 ProvisioningConfiguration配置类

前面再IpManager开始之前，会new一个provisioningConfiguration对象，这个configuration就指明，是否enabled ipv6，静态ip的对象是哪个，还有timeout的时间。

final ProvisioningConfiguration provisioningConfiguration = 
mIpManager.buildProvisioningConfiguration() 
.withProvisioningTimeoutMs(0) 
.build();

        public ProvisioningConfiguration() {}

        public ProvisioningConfiguration(ProvisioningConfiguration other) {
            mEnableIPv4 = other.mEnableIPv4;
            mEnableIPv6 = other.mEnableIPv6;
            mUsingIpReachabilityMonitor = other.mUsingIpReachabilityMonitor;
            mRequestedPreDhcpActionMs = other.mRequestedPreDhcpActionMs;
            mStaticIpConfig = other.mStaticIpConfig;
            mApfCapabilities = other.mApfCapabilities;
            mProvisioningTimeoutMs = other.mProvisioningTimeoutMs;
        }

2.3 mIpManager.startProvisioning(provisioningConfiguration)

开始获取IP啦~

    public void startProvisioning(ProvisioningConfiguration req) {
        getNetworkInterface();

        mCallback.setNeighborDiscoveryOffload(true);
        //发送CMD_START出来
        sendMessage(CMD_START, new ProvisioningConfiguration(req));
    }

一开始的状态时在StoppedState中，收到CMD_START跟着就会跳转到mStartedState

    class StoppedState extends State {
        @Override
        public void enter() {
            try {
                mNwService.disableIpv6(mInterfaceName);
                mNwService.clearInterfaceAddresses(mInterfaceName);
            } catch (Exception e) {
                Log.e(mTag, "Failed to clear addresses or disable IPv6" + e);
            }

            resetLinkProperties();
            if (mStartTimeMillis > 0) {
                recordMetric(IpManagerEvent.COMPLETE_LIFECYCLE);
                mStartTimeMillis = 0;
            }
        }

        @Override
        public boolean processMessage(Message msg) {
            switch (msg.what) {
                case CMD_STOP:
                    break;

                case CMD_START:
                    mConfiguration = (ProvisioningConfiguration) msg.obj;
                    transitionTo(mStartedState);
                    break;

先跑StartedState的enter函数

    class StartedState extends State {
        private boolean mDhcpActionInFlight;

        @Override
        public void enter() {
            //开始的时间
            mStartTimeMillis = SystemClock.elapsedRealtime();
            /**
         * For networks that support packet filtering via APF programs, {@code ApfFilter}
         * listens for IPv6 ICMPv6 router advertisements (RAs) and generates APF programs to
         * filter out redundant duplicate ones.
         *
         * Threading model:
         * A collection of RAs we've received is kept in mRas. Generating APF programs uses mRas to
         * know what RAs to filter for, thus generating APF programs is dependent on mRas.
         * mRas can be accessed by multiple threads:
         * - ReceiveThread, which listens for RAs and adds them to mRas, and generates APF programs.
         * - callers of:
         *    - setMulticastFilter(), which can cause an APF program to be generated.
         *    - dump(), which dumps mRas among other things.
         *    - shutdown(), which clears mRas.
         * So access to mRas is synchronized.
         *
         * @hide
         */
            mApfFilter = ApfFilter.maybeCreate(mConfiguration.mApfCapabilities, mNetworkInterface,
                    mCallback, mMulticastFiltering);
            // TODO: investigate the effects of any multicast filtering racing/interfering with the
            // rest of this IP configuration startup.
            if (mApfFilter == null) {
                mCallback.setFallbackMulticastFilter(mMulticastFiltering);
            }

            //如果ipv6如果这么写的话，如果timout会存在卡到ipv4?ipv6和ipv4之间的逻辑关系应该是怎么样的？
            if (mConfiguration.mEnableIPv6) {
                // TODO: Consider transitionTo(mStoppingState) if this fails.
                startIPv6();
            }
            //这个是arp邻居表的检测
            if (mConfiguration.mUsingIpReachabilityMonitor) {
                mIpReachabilityMonitor = new IpReachabilityMonitor(
                        mContext,
                        mInterfaceName,
                        new IpReachabilityMonitor.Callback() {
                            @Override
                            public void notifyLost(InetAddress ip, String logMsg) {
                                mCallback.onReachabilityLost(logMsg);
                            }
                        });
            }
            //启动ipv4
            if (mConfiguration.mEnableIPv4) {
                if (!startIPv4()) {
                    transitionTo(mStoppingState);
                }
            }
        }

startIPv6的部分还没写好，跳过，看ipv4的部分

    private boolean startIPv4() {
        // If we have a StaticIpConfiguration attempt to apply it and
        // handle the result accordingly.
        //如果是静态ip，在这里设置一下
        if (mConfiguration.mStaticIpConfig != null) {
            if (setIPv4Address(mConfiguration.mStaticIpConfig.ipAddress)) {
                handleIPv4Success(new DhcpResults(mConfiguration.mStaticIpConfig));
            } else {
                if (VDBG) { Log.d(mTag, "onProvisioningFailure()"); }
                recordMetric(IpManagerEvent.PROVISIONING_FAIL);
                mCallback.onProvisioningFailure(new LinkProperties(mLinkProperties));
                return false;
            }
        } else {
            // Start DHCPv4.
            //构造DhcpClient对象，发送dhcp client请求
            mDhcpClient = DhcpClient.makeDhcpClient(mContext, IpManager.this, mInterfaceName);
            mDhcpClient.registerForPreDhcpNotification();
            mDhcpClient.sendMessage(DhcpClient.CMD_START_DHCP);

            if (mConfiguration.mProvisioningTimeoutMs > 0) {
                final long alarmTime = SystemClock.elapsedRealtime() +
                        mConfiguration.mProvisioningTimeoutMs;
                 //通过闹钟去叫醒
                 /*
                         mProvisioningTimeoutAlarm = new WakeupMessage(mContext, getHandler(),
                mTag + ".EVENT_PROVISIONING_TIMEOUT", EVENT_PROVISIONING_TIMEOUT);
                 */
                mProvisioningTimeoutAlarm.schedule(alarmTime);
            }
        }

        return true;
    }

2.4 DhcpClient

接收前面发过来的mDhcpClient.sendMessage(DhcpClient.CMD_START_DHCP);, 跟着跳转到DhcpInitState:

    class StoppedState extends LoggingState {
        @Override
        public boolean processMessage(Message message) {
            super.processMessage(message);
            switch (message.what) {
                case CMD_START_DHCP:
                    if (mRegisteredForPreDhcpNotification) {
                        transitionTo(mWaitBeforeStartState);
                    } else {
                        transitionTo(mDhcpInitState);
                    }
                    return HANDLED;
                default:
                    return NOT_HANDLED;
            }
        }
    }

    class DhcpInitState extends PacketRetransmittingState {

        public DhcpInitState() {
            super();
        }

        @Override
        //跑DhcpInitState的父类PacketRetransmittingState的enter
        public void enter() {
            super.enter();
            startNewTransaction();
        }

        protected boolean sendPacket() {
            return sendDiscoverPacket();
        }

        protected void receivePacket(DhcpPacket packet) {
            if (!isValidPacket(packet)) return;
            if (!(packet instanceof DhcpOfferPacket)) return;
            mOffer = packet.toDhcpResults();
            if (mOffer != null) {
                Log.d(TAG, "Got pending lease: " + mOffer);
                transitionTo(mDhcpRequestingState);
            }
        }
    }

重点是这里的CMD_KICK命令，发送这个命令，之后会调用sendPacket()函数，去发送请求包.

    /**
     * Retransmits packets using jittered exponential backoff with an optional timeout. Packet
     * transmission is triggered by CMD_KICK, which is sent by an AlarmManager alarm. If a subclass
     * sets mTimeout to a positive value, then timeout() is called by an AlarmManager alarm mTimeout
     * milliseconds after entering the state. Kicks and timeouts are cancelled when leaving the
     * state.
     *
     * Concrete subclasses must implement sendPacket, which is called when the alarm fires and a
     * packet needs to be transmitted, and receivePacket, which is triggered by CMD_RECEIVED_PACKET
     * sent by the receive thread. They may also set mTimeout and implement timeout.
     */
    abstract class PacketRetransmittingState extends LoggingState {

        private int mTimer;
        protected int mTimeout = 0;

        @Override
        public void enter() {
            super.enter();
            initTimer();
            maybeInitTimeout();
            sendMessage(CMD_KICK);
        }

这里发送的是DHCPDISCOVER dhcp协议的DISCOVER包

    private boolean sendDiscoverPacket() {
        ByteBuffer packet = DhcpPacket.buildDiscoverPacket(
                DhcpPacket.ENCAP_L2, mTransactionId, getSecs(), mHwAddr,
                DO_UNICAST, REQUESTED_PARAMS);
        return transmitPacket(packet, "DHCPDISCOVER", DhcpPacket.ENCAP_L2, INADDR_BROADCAST);
    }

另外一边有一个接收函数，一直在收dhcp server的的数据包。

    class ReceiveThread extends Thread {

        private final byte[] mPacket = new byte[DhcpPacket.MAX_LENGTH];
        private volatile boolean mStopped = false;

        public void halt() {
            mStopped = true;
            closeSockets();  // Interrupts the read() call the thread is blocked in.
        }

        @Override
        public void run() {
            if (DBG) Log.d(TAG, "Receive thread started");
            while (!mStopped) {
                int length = 0;  // Or compiler can't tell it's initialized if a parse error occurs.
                try {
                    length = Os.read(mPacketSock, mPacket, 0, mPacket.length);
                    DhcpPacket packet = null;
                    packet = DhcpPacket.decodeFullPacket(mPacket, length, DhcpPacket.ENCAP_L2);
                    if (DBG) Log.d(TAG, "Received packet: " + packet);
                    //发送CMD_RECEIVED_PACKET，把数据包往上面送
                    sendMessage(CMD_RECEIVED_PACKET, packet);
                } catch (IOException|ErrnoException e) {
                    if (!mStopped) {
                        Log.e(TAG, "Read error", e);
                        DhcpErrorEvent.logReceiveError(mIfaceName);
                    }
                } catch (DhcpPacket.ParseException e) {
                    Log.e(TAG, "Can't parse packet: " + e.getMessage());
                    if (PACKET_DBG) {
                        Log.d(TAG, HexDump.dumpHexString(mPacket, 0, length));
                    }
                    DhcpErrorEvent.logParseError(mIfaceName, e.errorCode);
                }
            }
            if (DBG) Log.d(TAG, "Receive thread stopped");
        }
    }

接收CMD_RECEIVED_PACKET,我们还在PacketRetransmittingState 这个state中，所以他会处理这个CMD

    abstract class PacketRetransmittingState extends LoggingState {

        private int mTimer;
        protected int mTimeout = 0;
        ...
        @Override
        public boolean processMessage(Message message) {
            super.processMessage(message);
            switch (message.what) {
                case CMD_KICK:
                    sendPacket();
                    scheduleKick();
                    return HANDLED;
                case CMD_RECEIVED_PACKET:
                    //这个会call到DhcpInitState的receivePacket函数
                    receivePacket((DhcpPacket) message.obj);
                    return HANDLED;
                case CMD_TIMEOUT:
                    timeout();
                    return HANDLED;
                default:
                    return NOT_HANDLED;
            }
        }

接收的数据在这里被处理，处理完之后，将结果赋值给mOffer，意思是dhcp的offer数据包，里面当然就是存着ip的值，然后跳转到mDhcpRequestingState

        protected void receivePacket(DhcpPacket packet) {
            if (!isValidPacket(packet)) return;
            //判断是不是server 放回的offer包
            if (!(packet instanceof DhcpOfferPacket)) return;
            mOffer = packet.toDhcpResults();
            if (mOffer != null) {
                Log.d(TAG, "Got pending lease: " + mOffer);
                transitionTo(mDhcpRequestingState);
            }
        }

这个DhcpRequestingState 是继承了PacketRetransmittingState ，还记得前面的CMD_KICK吗？scheduleKick()函数的调用，这个CMD_KICK会定时发送,理论上dicover包要发4次。server offer之后，就要跑client发送request了，当跑到这个statemachine里面的时候，就会跑DhcpRequestingState 这个里面的sendPacket()了，google大神真是牛。那这次send的是dhcp协议的什么数据包呢？

    class DhcpRequestingState extends PacketRetransmittingState {
        public DhcpRequestingState() {
            mTimeout = DHCP_TIMEOUT_MS / 2;
        }

        protected boolean sendPacket() {
            return sendRequestPacket(
                    INADDR_ANY,                                    // ciaddr
                    (Inet4Address) mOffer.ipAddress.getAddress(),  // DHCP_REQUESTED_IP
                    (Inet4Address) mOffer.serverAddress,           // DHCP_SERVER_IDENTIFIER
                    INADDR_BROADCAST);                             // packet destination address
        }

        protected void receivePacket(DhcpPacket packet) {
            if (!isValidPacket(packet)) return;
            if ((packet instanceof DhcpAckPacket)) {
                DhcpResults results = packet.toDhcpResults();
                if (results != null) {
                    setDhcpLeaseExpiry(packet);
                    acceptDhcpResults(results, "Confirmed");
                    transitionTo(mConfiguringInterfaceState);
                }
            } else if (packet instanceof DhcpNakPacket) {
                // TODO: Wait a while before returning into INIT state.
                Log.d(TAG, "Received NAK, returning to INIT");
                mOffer = null;
                transitionTo(mDhcpInitState);
            }
        }

        @Override
        protected void timeout() {
            // After sending REQUESTs unsuccessfully for a while, go back to init.
            transitionTo(mDhcpInitState);
        }
    }

DHCPREQUEST ciaddr 知道知道dhcp的协议，就知道发完discover包之后，要再发一个DHCPREQUEST。相当是这个ip我要了，然后等sever的ACK。

DHCP Client会以广播形式向DHCP Server发送DHCPRequest报文来续租IP地址。如果DHCP Client成功收到DHCP Server发送的DHCP ACK报文.

    private boolean sendRequestPacket(
            Inet4Address clientAddress, Inet4Address requestedAddress,
            Inet4Address serverAddress, Inet4Address to) {
        // TODO: should we use the transaction ID from the server?
        final int encap = INADDR_ANY.equals(clientAddress)
                ? DhcpPacket.ENCAP_L2 : DhcpPacket.ENCAP_BOOTP;

        ByteBuffer packet = DhcpPacket.buildRequestPacket(
                encap, mTransactionId, getSecs(), clientAddress,
                DO_UNICAST, mHwAddr, requestedAddress,
                serverAddress, REQUESTED_PARAMS, null);
        String serverStr = (serverAddress != null) ? serverAddress.getHostAddress() : null;
        String description = "DHCPREQUEST ciaddr=" + clientAddress.getHostAddress() +
                             " request=" + requestedAddress.getHostAddress() +
                             " serverid=" + serverStr;
        return transmitPacket(packet, description, encap, to);
    }

sever ack之后，我们再次处理接收包。

        protected void receivePacket(DhcpPacket packet) {
            if (!isValidPacket(packet)) return;
            if ((packet instanceof DhcpAckPacket)) {
                DhcpResults results = packet.toDhcpResults();
                if (results != null) {
                    setDhcpLeaseExpiry(packet);
                    //这里会调用notifySuccess，发送CMD去通知IpManager说，IP拿到了
                    acceptDhcpResults(results, "Confirmed");//①
                    //自己调到mConfiguringInterfaceState
                    transitionTo(mConfiguringInterfaceState);//②
                }
            } else if (packet instanceof DhcpNakPacket) {
                // TODO: Wait a while before returning into INIT state.
                Log.d(TAG, "Received NAK, returning to INIT");
                mOffer = null;
                transitionTo(mDhcpInitState);
            }
        }

①这里调用了notifySuccess()发生CMD去通知IpManager，IP获取成功了。

    private void acceptDhcpResults(DhcpResults results, String msg) {
        mDhcpLease = results;
        mOffer = null;
        Log.d(TAG, msg + " lease: " + mDhcpLease);
        notifySuccess();
    }

这里的mController指的是IpManager里面的接收者，发送CMD_POST_DHCP_ACTION

    private void notifySuccess() {
        mController.sendMessage(
                CMD_POST_DHCP_ACTION, DHCP_SUCCESS, 0, new DhcpResults(mDhcpLease));
    }

   class StartedState extends State {
                ....
                // This message is only received when:
                //
                //     a) initial address acquisition succeeds,
                //     b) renew succeeds or is NAK'd,
                //     c) rebind succeeds or is NAK'd, or
                //     c) the lease expires,
                //
                // but never when initial address acquisition fails. The latter
                // condition is now governed by the provisioning timeout.
                case DhcpClient.CMD_POST_DHCP_ACTION:
                    stopDhcpAction();

                    switch (msg.arg1) {
                        case DhcpClient.DHCP_SUCCESS:
                            handleIPv4Success((DhcpResults) msg.obj);
                            break;
                        case DhcpClient.DHCP_FAILURE:
                            handleIPv4Failure();
                            break;
                        default:
                            Log.e(mTag, "Unknown CMD_POST_DHCP_ACTION status:" + msg.arg1);
                    }
                    break;
          .....
     }

    private void handleIPv4Success(DhcpResults dhcpResults) {
        mDhcpResults = new DhcpResults(dhcpResults);
        final LinkProperties newLp = assembleLinkProperties();
        final ProvisioningChange delta = setLinkProperties(newLp);

        if (VDBG) {
            Log.d(mTag, "onNewDhcpResults(" + Objects.toString(dhcpResults) + ")");
        }
        mCallback.onNewDhcpResults(dhcpResults);
        //这里分发dhcpResults
        dispatchCallback(delta, newLp);
    }

    private void dispatchCallback(ProvisioningChange delta, LinkProperties newLp) {
        switch (delta) {
            case GAINED_PROVISIONING:
                if (VDBG) { Log.d(mTag, "onProvisioningSuccess()"); }
                recordMetric(IpManagerEvent.PROVISIONING_OK);
                mCallback.onProvisioningSuccess(newLp);
                break;

            case LOST_PROVISIONING:
                if (VDBG) { Log.d(mTag, "onProvisioningFailure()"); }
                recordMetric(IpManagerEvent.PROVISIONING_FAIL);
                mCallback.onProvisioningFailure(newLp);
                break;

            default:
                if (VDBG) { Log.d(mTag, "onLinkPropertiesChange()"); }
                mCallback.onLinkPropertiesChange(newLp);
                break;
        }
    }

dispatchCallback的结果最后会作用到WaitForProvisioningCallback ，这个就是前面EthernetNetworkFactory 中 linkProperties = ipmCallback.waitForProvisioning();，等待的结果。

    public static class WaitForProvisioningCallback extends Callback {
        private LinkProperties mCallbackLinkProperties;

        public LinkProperties waitForProvisioning() {
            synchronized (this) {
                try {
                    wait();
                } catch (InterruptedException e) {}
                return mCallbackLinkProperties;
            }
        }

        @Override
        public void onProvisioningSuccess(LinkProperties newLp) {
            synchronized (this) {
                mCallbackLinkProperties = newLp;
                notify();
            }
        }

        @Override
        public void onProvisioningFailure(LinkProperties newLp) {
            synchronized (this) {
                mCallbackLinkProperties = null;
                notify();
            }
        }
    }

②这里跑入enter(),给IpManager发了一个CMD_CONFIGURE_LINKADDRESS 的CMD

    class ConfiguringInterfaceState extends LoggingState {
        @Override
        public void enter() {
            super.enter();
            mController.sendMessage(CMD_CONFIGURE_LINKADDRESS, mDhcpLease.ipAddress);
        }

        @Override
        public boolean processMessage(Message message) {
            super.processMessage(message);
            switch (message.what) {
                case EVENT_LINKADDRESS_CONFIGURED:
                    transitionTo(mDhcpBoundState);
                    return HANDLED;
                default:
                    return NOT_HANDLED;
            }
        }
    }

我们返回到IpManager中去看，在IpManger中，我们还处于StartedState中

   class StartedState extends State {
                ......
                case DhcpClient.CMD_CONFIGURE_LINKADDRESS: {

                    final LinkAddress ipAddress = (LinkAddress) msg.obj;
                    //将IP通过NetworkManagerService写到Interface上面
                    if (setIPv4Address(ipAddress)) {
                        mDhcpClient.sendMessage(DhcpClient.EVENT_LINKADDRESS_CONFIGURED);
                    } else {
                        Log.e(mTag, "Failed to set IPv4 address!");
                        dispatchCallback(ProvisioningChange.LOST_PROVISIONING,
                                new LinkProperties(mLinkProperties));
                        transitionTo(mStoppingState);
                    }
                    break;
                }
                ......
   }

这个setIPv4Address很简单，调用了NetworkManagementService.setInterfaceConfig()

    private boolean setIPv4Address(LinkAddress address) {
        final InterfaceConfiguration ifcg = new InterfaceConfiguration();
        ifcg.setLinkAddress(address);
        try {
            mNwService.setInterfaceConfig(mInterfaceName, ifcg);
            if (VDBG) Log.d(mTag, "IPv4 configuration succeeded");
        } catch (IllegalStateException | RemoteException e) {
            Log.e(mTag, "IPv4 configuration failed: ", e);
            return false;
        }
        return true;
    }

调用Netd，通过Commandlisten.Java去往下跑，这里不跟了。

//NetworkManagementService.java (frameworks\base\services\core\java\com\android\server) 

    @Override
    public void setInterfaceConfig(String iface, InterfaceConfiguration cfg) {
        mContext.enforceCallingOrSelfPermission(CONNECTIVITY_INTERNAL, TAG);
        LinkAddress linkAddr = cfg.getLinkAddress();
        if (linkAddr == null || linkAddr.getAddress() == null) {
            throw new IllegalStateException("Null LinkAddress given");
        }

        final Command cmd = new Command("interface", "setcfg", iface,
                linkAddr.getAddress().getHostAddress(),
                linkAddr.getPrefixLength());
        for (String flag : cfg.getFlags()) {
            cmd.appendArg(flag);
        }

        try {
            mConnector.execute(cmd);
        } catch (NativeDaemonConnectorException e) {
            throw e.rethrowAsParcelableException();
        }
    }

3 总结

不知道google加入的这个IpManager是否又有效，但是从整个框架看下来，为后面ipv6的加入可以说是打好了基础，加速ipv6时代的到来。因为apple已经开始强制要求app support ipv6了，android需要加把劲。