（一百六十一）Android P WifiStateMachine中的NetworkFactory

 

目录

1.回顾

2. NetworkFactory简介

2.1 构造函数

2.2 setScoreFilter

2.3 register

2.4 看下NetworkRequests哪里来的

2.5 evalRequest

3.总结

---

1.回顾

                case CMD_START_CONNECT:
                    /* connect command coming from auto-join */
                    netId = message.arg1;
                    int uid = message.arg2;
                    bssid = (String) message.obj;

                    synchronized (mWifiReqCountLock) {
                        if (!hasConnectionRequests()) {
                            if (mNetworkAgent == null) {
                                loge("CMD_START_CONNECT but no requests and not connected,"
                                        + " bailing");
                                break;
                            } else if (!mWifiPermissionsUtil.checkNetworkSettingsPermission(uid)) {
                                loge("CMD_START_CONNECT but no requests and connected, but app "
                                        + "does not have sufficient permissions, bailing");
                                break;
                            }
                        }
                    }

在WiFi进行连接的时候会判断一下当前是否有连接请求

    /**
     * Check if there is any connection request for WiFi network.
     * Note, caller of this helper function must acquire mWifiReqCountLock.
     */
    private boolean hasConnectionRequests() {
        return mConnectionReqCount > 0 || mUntrustedReqCount > 0;
    }

看下mConnectionReqCount在哪里进行赋值

    @GuardedBy("mWifiReqCountLock")
    private int mConnectionReqCount = 0;

初始化为0，使用时需要锁mWifiReqCountLock

    private class WifiNetworkFactory extends NetworkFactory {
        public WifiNetworkFactory(Looper l, Context c, String TAG, NetworkCapabilities f) {
            super(l, c, TAG, f);
        }

        @Override
        protected void needNetworkFor(NetworkRequest networkRequest, int score) {
            synchronized (mWifiReqCountLock) {
                if (++mConnectionReqCount == 1) {
                    if (mWifiConnectivityManager != null && mUntrustedReqCount == 0) {
                        mWifiConnectivityManager.enable(true);
                    }
                }
            }
        }

        @Override
        protected void releaseNetworkFor(NetworkRequest networkRequest) {
            synchronized (mWifiReqCountLock) {
                if (--mConnectionReqCount == 0) {
                    if (mWifiConnectivityManager != null && mUntrustedReqCount == 0) {
                        mWifiConnectivityManager.enable(false);
                    }
                }
            }
        }

        @Override
        public void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
            pw.println("mConnectionReqCount " + mConnectionReqCount);
        }

    }

WifiNetworkFactory中会对mConnectionReqCount进行自增和自减的操作，区别在于是needNetworkFor还是releaseNetworkFor.

需要看下NetworkFactory是什么？主要有什么用途？needNetworkFor和releaseNetworkFor是做什么用的？

    void maybeRegisterNetworkFactory() {
        if (mNetworkFactory == null) {
            checkAndSetConnectivityInstance();
            if (mCm != null) {
                mNetworkFactory = new WifiNetworkFactory(getHandler().getLooper(), mContext,
                        NETWORKTYPE, mNetworkCapabilitiesFilter);
                mNetworkFactory.setScoreFilter(60);
                mNetworkFactory.register();

                // We can't filter untrusted network in the capabilities filter because a trusted
                // network would still satisfy a request that accepts untrusted ones.
                mUntrustedNetworkFactory = new UntrustedWifiNetworkFactory(getHandler().getLooper(),
                        mContext, NETWORKTYPE_UNTRUSTED, mNetworkCapabilitiesFilter);
                mUntrustedNetworkFactory.setScoreFilter(Integer.MAX_VALUE);
                mUntrustedNetworkFactory.register();
            }
        }
    }

初始化很简单，就是new出来一个对象，然后设置一下ScoreFilter并注册了一下。

 

2. NetworkFactory简介

/**
 * A NetworkFactory is an entity that creates NetworkAgent objects.
 * The bearers register with ConnectivityService using {@link #register} and
 * their factory will start receiving scored NetworkRequests.  NetworkRequests
 * can be filtered 3 ways: by NetworkCapabilities, by score and more complexly by
 * overridden function.  All of these can be dynamic - changing NetworkCapabilities
 * or score forces re-evaluation of all current requests.
 *
 * If any requests pass the filter some overrideable functions will be called.
 * If the bearer only cares about very simple start/stopNetwork callbacks, those
 * functions can be overridden.  If the bearer needs more interaction, it can
 * override addNetworkRequest and removeNetworkRequest which will give it each
 * request that passes their current filters.
 * @hide
 **/
public class NetworkFactory extends Handler {

NetworkFactory是创建NetworkAgent对象的类

使用了ConnectivityService的register方法，然后工厂就可以收到scored networkRequests

NetworkRequest可以用3种途径过滤：NetworkCapabilites/score和重载方法

改变NetworkCapabilities和score会强制触发所有requests的重新评估

当重载addNetworkRequest和removeNetworkRequest，可以获取通过filters的每个request来获取更多操作可能

2.1 构造函数

    public NetworkFactory(Looper looper, Context context, String logTag,
            NetworkCapabilities filter) {
        super(looper);
        LOG_TAG = logTag;
        mContext = context;
        mCapabilityFilter = filter;
    }

构造函数除了NetworkCapabilities没什么特别的

/**
 * Representation of the capabilities of an active network. Instances are
 * typically obtained through
 * {@link NetworkCallback#onCapabilitiesChanged(Network, NetworkCapabilities)}
 * or {@link ConnectivityManager#getNetworkCapabilities(Network)}.
 * 

 * This replaces the old {@link ConnectivityManager#TYPE_MOBILE} method of
 * network selection. Rather than indicate a need for Wi-Fi because an
 * application needs high bandwidth and risk obsolescence when a new, fast
 * network appears (like LTE), the application should specify it needs high
 * bandwidth. Similarly if an application needs an unmetered network for a bulk
 * transfer it can specify that rather than assuming all cellular based
 * connections are metered and all Wi-Fi based connections are not.
 */
public final class NetworkCapabilities implements Parcelable {

看下WifiStateMachine传递来的NetworkCapabilities有什么特殊的

    // Used to filter out requests we couldn't possibly satisfy.
    private final NetworkCapabilities mNetworkCapabilitiesFilter = new NetworkCapabilities();

        mNetworkCapabilitiesFilter.addTransportType(NetworkCapabilities.TRANSPORT_WIFI);
        mNetworkCapabilitiesFilter.addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
        mNetworkCapabilitiesFilter.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_METERED);
        mNetworkCapabilitiesFilter.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_ROAMING);
        mNetworkCapabilitiesFilter.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_CONGESTED);
        mNetworkCapabilitiesFilter.addCapability(NetworkCapabilities.NET_CAPABILITY_NOT_RESTRICTED);
        mNetworkCapabilitiesFilter.setLinkUpstreamBandwidthKbps(1024 * 1024);
        mNetworkCapabilitiesFilter.setLinkDownstreamBandwidthKbps(1024 * 1024);

暂时还不知道这个filter具体有什么用。

 

2.2 setScoreFilter

    public void setScoreFilter(int score) {
        sendMessage(obtainMessage(CMD_SET_SCORE, score, 0));
    }

看下怎么处理的

    /**
     * Internally used to set our best-guess score.
     * msg.arg1 = new score
     */
    private static final int CMD_SET_SCORE = BASE + 2;

            case CMD_SET_SCORE: {
                handleSetScore(msg.arg1);
                break;
            }

    private void handleSetScore(int score) {
        mScore = score;
        evalRequests();
    }


    private void evalRequests() {
        for (int i = 0; i < mNetworkRequests.size(); i++) {
            NetworkRequestInfo n = mNetworkRequests.valueAt(i);

            evalRequest(n);
        }
    }

需要看下NetworkRequests是哪里初始化的，后面需要再看下evalRequest是怎么评估request的

 

2.3 register

    public void register() {
        if (DBG) log("Registering NetworkFactory");
        if (mMessenger == null) {
            mMessenger = new Messenger(this);
            ConnectivityManager.from(mContext).registerNetworkFactory(mMessenger, LOG_TAG);
        }
    }

这个 register看起来就是和ConnectivityService建立了AsyncChannel通信通道

具体看下

ConnectivityManager

    /** {@hide} */
    public static ConnectivityManager from(Context context) {
        return (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    }

 

   /** {@hide} */
    public void registerNetworkFactory(Messenger messenger, String name) {
        try {
            mService.registerNetworkFactory(messenger, name);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

ConnectivityService

    @Override
    public void registerNetworkFactory(Messenger messenger, String name) {
        enforceConnectivityInternalPermission();
        NetworkFactoryInfo nfi = new NetworkFactoryInfo(name, messenger, new AsyncChannel());
        mHandler.sendMessage(mHandler.obtainMessage(EVENT_REGISTER_NETWORK_FACTORY, nfi));
    }


    /**
     * used internally when registering NetworkFactories
     * obj = NetworkFactoryInfo
     */
    private static final int EVENT_REGISTER_NETWORK_FACTORY = 17;

                case EVENT_REGISTER_NETWORK_FACTORY: {
                    handleRegisterNetworkFactory((NetworkFactoryInfo)msg.obj);
                    break;
                }

看下具体处理逻辑

    private void handleRegisterNetworkFactory(NetworkFactoryInfo nfi) {
        if (DBG) log("Got NetworkFactory Messenger for " + nfi.name);
        mNetworkFactoryInfos.put(nfi.messenger, nfi);
        nfi.asyncChannel.connect(mContext, mTrackerHandler, nfi.messenger);
    }

一堆注册其实就是将ConnectivityService和NetworkFactory之间通过AsyncChannel建立了跨进程通信

 

2.4 看下NetworkRequests哪里来的

NetworkFactory

    public void addNetworkRequest(NetworkRequest networkRequest, int score) {
        sendMessage(obtainMessage(CMD_REQUEST_NETWORK,
                new NetworkRequestInfo(networkRequest, score)));
    }


    /**
     * Pass a network request to the bearer.  If the bearer believes it can
     * satisfy the request it should connect to the network and create a
     * NetworkAgent.  Once the NetworkAgent is fully functional it will
     * register itself with ConnectivityService using registerNetworkAgent.
     * If the bearer cannot immediately satisfy the request (no network,
     * user disabled the radio, lower-scored network) it should remember
     * any NetworkRequests it may be able to satisfy in the future.  It may
     * disregard any that it will never be able to service, for example
     * those requiring a different bearer.
     * msg.obj = NetworkRequest
     * msg.arg1 = score - the score of the any network currently satisfying this
     *            request.  If this bearer knows in advance it cannot
     *            exceed this score it should not try to connect, holding the request
     *            for the future.
     *            Note that subsequent events may give a different (lower
     *            or higher) score for this request, transmitted to each
     *            NetworkFactory through additional CMD_REQUEST_NETWORK msgs
     *            with the same NetworkRequest but an updated score.
     *            Also, network conditions may change for this bearer
     *            allowing for a better score in the future.
     */
    public static final int CMD_REQUEST_NETWORK = BASE;

            case CMD_REQUEST_NETWORK: {
                handleAddRequest((NetworkRequest)msg.obj, msg.arg1);
                break;
            }

 

   @VisibleForTesting
    protected void handleAddRequest(NetworkRequest request, int score) {
        NetworkRequestInfo n = mNetworkRequests.get(request.requestId);
        if (n == null) {
            if (DBG) log("got request " + request + " with score " + score);
            n = new NetworkRequestInfo(request, score);
            mNetworkRequests.put(n.request.requestId, n);
        } else {
            if (VDBG) log("new score " + score + " for exisiting request " + request);
            n.score = score;
        }
        if (VDBG) log("  my score=" + mScore + ", my filter=" + mCapabilityFilter);

        evalRequest(n);
    }

搜了framework下没有直接调用addNetworkRequest的，但是有通过AsyncChannel发送CMD_REQUEST_NETWORK消息的

 

ConnectivityService

    private void handleRegisterNetworkFactory(NetworkFactoryInfo nfi) {
        if (DBG) log("Got NetworkFactory Messenger for " + nfi.name);
        mNetworkFactoryInfos.put(nfi.messenger, nfi);
        nfi.asyncChannel.connect(mContext, mTrackerHandler, nfi.messenger);
    }



    // must be stateless - things change under us.
    private class NetworkStateTrackerHandler extends Handler {
        public NetworkStateTrackerHandler(Looper looper) {
            super(looper);
        }

        private boolean maybeHandleAsyncChannelMessage(Message msg) {
            switch (msg.what) {
                default:
                    return false;
                case AsyncChannel.CMD_CHANNEL_HALF_CONNECTED: {
                    handleAsyncChannelHalfConnect(msg);
                    break;
                }

刚才有说道NetworkFactory和ConnectivityService通过AsyncChannel建立了通信通道，其实是ConnectivityService到NetworkFactory的单向通信通道，这时会调用handleAsyncChannelHalfConnect

    private void handleAsyncChannelHalfConnect(Message msg) {
        AsyncChannel ac = (AsyncChannel) msg.obj;
        if (mNetworkFactoryInfos.containsKey(msg.replyTo)) {
            if (msg.arg1 == AsyncChannel.STATUS_SUCCESSFUL) {
                if (VDBG) log("NetworkFactory connected");
                // A network factory has connected.  Send it all current NetworkRequests.
                for (NetworkRequestInfo nri : mNetworkRequests.values()) {
                    if (nri.request.isListen()) continue;
                    NetworkAgentInfo nai = getNetworkForRequest(nri.request.requestId);
                    ac.sendMessage(android.net.NetworkFactory.CMD_REQUEST_NETWORK,
                            (nai != null ? nai.getCurrentScore() : 0), 0, nri.request);
                }
            } else {
                loge("Error connecting NetworkFactory");
                mNetworkFactoryInfos.remove(msg.obj);
            }
        } 

handleAsyncChannelHalfConnect将ConnectivityService保存的所有mNetworkRequests都传递给了NetworkFactory

而ConnectivityService的NetworkRequest是通过两个api加载的

ConnectivityManager

    /**
     * Helper function to request a network with a particular legacy type.
     *
     * This is temporarily public @hide so it can be called by system code that uses the
     * NetworkRequest API to request networks but relies on CONNECTIVITY_ACTION broadcasts for
     * instead network notifications.
     *
     * TODO: update said system code to rely on NetworkCallbacks and make this method private.
     *
     * @hide
     */
    public void requestNetwork(NetworkRequest request, NetworkCallback networkCallback,
            int timeoutMs, int legacyType, Handler handler) {
        CallbackHandler cbHandler = new CallbackHandler(handler);
        NetworkCapabilities nc = request.networkCapabilities;
        sendRequestForNetwork(nc, networkCallback, timeoutMs, REQUEST, legacyType, cbHandler);
    }

    /**
     * Registers a PendingIntent to be sent when a network is available which satisfies the given
     * {@link NetworkRequest}.
     *
     * This function behaves identically to the version that takes a NetworkCallback, but instead
     * of {@link NetworkCallback} a {@link PendingIntent} is used.  This means
     * the request may outlive the calling application and get called back when a suitable
     * network is found.
     * 

     * The operation is an Intent broadcast that goes to a broadcast receiver that
     * you registered with {@link Context#registerReceiver} or through the
     * <receiver> tag in an AndroidManifest.xml file
     * 

     * The operation Intent is delivered with two extras, a {@link Network} typed
     * extra called {@link #EXTRA_NETWORK} and a {@link NetworkRequest}
     * typed extra called {@link #EXTRA_NETWORK_REQUEST} containing
     * the original requests parameters.
     * 

     * If there is already a request for this Intent registered (with the equality of
     * two Intents defined by {@link Intent#filterEquals}), then it will be removed and
     * replaced by this one, effectively releasing the previous {@link NetworkRequest}.
     * 

     * The request may be released normally by calling
     * {@link #unregisterNetworkCallback(android.app.PendingIntent)}.
     * @param request {@link NetworkRequest} describing this request.
     * @param operation Action to perform when the network is available (corresponds
     *                  to the {@link NetworkCallback#onAvailable} call.  Typically
     *                  comes from {@link PendingIntent#getBroadcast}. Cannot be null.
     */
    @RequiresPermission(android.Manifest.permission.ACCESS_NETWORK_STATE)
    public void registerNetworkCallback(NetworkRequest request, PendingIntent operation) {
        checkPendingIntentNotNull(operation);
        try {
            mService.pendingListenForNetwork(request.networkCapabilities, operation);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        } catch (ServiceSpecificException e) {
            throw convertServiceException(e);
        }
    }

 

2.5 evalRequest

    private void evalRequest(NetworkRequestInfo n) {
        if (VDBG) log("evalRequest");
        if (n.requested == false && n.score < mScore &&
                n.request.networkCapabilities.satisfiedByNetworkCapabilities(
                mCapabilityFilter) && acceptRequest(n.request, n.score)) {
            if (VDBG) log("  needNetworkFor");
            needNetworkFor(n.request, n.score);
            n.requested = true;
        } else if (n.requested == true &&
                (n.score > mScore || n.request.networkCapabilities.satisfiedByNetworkCapabilities(
                mCapabilityFilter) == false || acceptRequest(n.request, n.score) == false)) {
            if (VDBG) log("  releaseNetworkFor");
            releaseNetworkFor(n.request);
            n.requested = false;
        } else {
            if (VDBG) log("  done");
        }
    }

看起来就是当前NetworkFactory满足请求方设置的条件话就设置网络，否则释放网络。

看下条件

• 未被requested
• 请求分比当前分低，WiFi是60分
• satisfiedByNetworkCapabilities
• acceptRequest

看下satisfiedByNetworkCapabilities

    /**
     * Check if our requirements are satisfied by the given {@code NetworkCapabilities}.
     *
     * @param nc the {@code NetworkCapabilities} that may or may not satisfy our requirements.
     * @param onlyImmutable if {@code true}, do not consider mutable requirements such as link
     *         bandwidth, signal strength, or validation / captive portal status.
     *
     * @hide
     */
    private boolean satisfiedByNetworkCapabilities(NetworkCapabilities nc, boolean onlyImmutable) {
        return (nc != null
                && satisfiedByNetCapabilities(nc, onlyImmutable)
                && satisfiedByTransportTypes(nc)
                && (onlyImmutable || satisfiedByLinkBandwidths(nc))
                && satisfiedBySpecifier(nc)
                && (onlyImmutable || satisfiedBySignalStrength(nc))
                && (onlyImmutable || satisfiedByUids(nc))
                && (onlyImmutable || satisfiedBySSID(nc)));
    }

再看下acceptRequest

    /**
     * Overridable function to provide complex filtering.
     * Called for every request every time a new NetworkRequest is seen
     * and whenever the filterScore or filterNetworkCapabilities change.
     *
     * acceptRequest can be overriden to provide complex filter behavior
     * for the incoming requests
     *
     * For output, this class will call {@link #needNetworkFor} and
     * {@link #releaseNetworkFor} for every request that passes the filters.
     * If you don't need to see every request, you can leave the base
     * implementations of those two functions and instead override
     * {@link #startNetwork} and {@link #stopNetwork}.
     *
     * If you want to see every score fluctuation on every request, set
     * your score filter to a very high number and watch {@link #needNetworkFor}.
     *
     * @return {@code true} to accept the request.
     */
    public boolean acceptRequest(NetworkRequest request, int score) {
        return true;
    }

网络过滤的可重载的比较复杂的条件

 

3.总结

NetworkFactory看起来就像是网络（WiFi/lte/...)用来存储“app层发送给ConnectivityService再发给NetworkFactory的NetworkRequest”，

并实时对NetworkRequest进行评估，对于WiFi而言，若可以满足app需要，则可以进行连接操作，否则无法进行连接。（因为既然都无法满足app的网络需求，那连接也是毫无意义的）