需求

项目中Android 板通过有线连接poe摄像头， android app通过wifi跟外部通讯。采用的Android 8.1的代码。

网上搜索发现有不少实现该功能的文章，不过文章都有一些差异，对于不了解这些模块的人来说会不知道应该修改哪个。这里只简单记录下我的调试记录，还没深究

现象

这边照着网上几篇文章修改后，出现的现象是：eth0 处于Running的状态时， 去重连wifi， wifi只会显示saved，不会继续走configure流程

调试

1. 最常见的的方法就是通过打印去了解信息，把涉及到NetworkFactory 和ConnectivityService的打印都打开

• 没有连接eth0时点击wifi连接的打印

09-03 01:59:40.998   465   561 D WifiStateMachine: connectToUserSelectNetwork netId 3, uid 1000, forceReconnect = false
09-03 01:59:41.033   465   561 D WifiStateMachine: CMD_START_CONNECT sup state DisconnectedState my state DisconnectedState nid=3 roam=false
09-03 01:59:43.300   465   561 D WifiStateMachine: CMD_START_CONNECT sup state ScanState my state DisconnectedState nid=3 roam=false
09-03 01:59:45.650   465   561 E WifiStateMachine: L2ConnectedState enter

• eth0处于running时，点击wifi连接的打印

09-03 02:02:47.526   465   561 D WifiStateMachine: connectToUserSelectNetwork netId 4, uid 1000, forceReconnect = false
09-03 02:02:47.564   465   561 E WifiStateMachine: CMD_START_CONNECT but no requests and not connected, bailing

由打印的差异 跟踪到代码
frameworks/opt/net/wifi/service/java/com/android/server/wifi/WifiStateMachine.java

 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()) {
                            loge("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;
                            }
                        }
                    }

                    config = mWifiConfigManager.getConfiguredNetworkWithPassword(netId);
                    logd("CMD_START_CONNECT sup state "
                            + mSupplicantStateTracker.getSupplicantStateName()
                            + " my state " + getCurrentState().getName()
                            + " nid=" + Integer.toString(netId)
                            + " roam=" + Boolean.toString(mIsAutoRoaming));
                    if (config == null) {
                        loge("CMD_START_CONNECT and no config, bail out...");
                        break;
                    }

   private boolean hasConnectionRequests() {
        return mConnectionReqCount > 0 || mUntrustedReqCount > 0;
    }

从打印和代码分析，两个流程的差异主要在hasConnectionRequests这个函数

2. 接下来主要跟踪hasConnectionRequests
   从代码查到主要问题在mConnectionReqCount这个变量，所以查找修改这个变量的地方，还好只有两处：

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

        @Override
        protected void releaseNetworkFor(NetworkRequest networkRequest) {
            synchronized (mWifiReqCountLock) {
                loge("releaseNetworkFor mConnectionReqCount="+ mConnectionReqCount);
                Exception e = new Exception("log");
                e.fillInStackTrace();
                loge("Called: " , e);
                if (--mConnectionReqCount == 0) {
                    if (mWifiConnectivityManager != null && mUntrustedReqCount == 0) {
                        mWifiConnectivityManager.enable(false);
                    }
                }
            }
        }

为了能知道对这个变量的调用流程，一个简单的方法就是利用Exception打印出堆栈信息
Exception e = new Exception("log");
e.fillInStackTrace();
loge("Called: " , e);

3. 堆栈打印信息忘记记下来了，这里只记下最后修改的地方
   frameworks/base/core/java/android/net/NetworkFactory.java

    private void evalRequest(NetworkRequestInfo n) {
        if (VDBG) log("evalRequest");
        Log.e("NetworkFactory", "evalRequest n.score:" + n.score + ", mScore:" + mScore);
        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");
        }
    }

将下面两行注释掉
//releaseNetworkFor(n.request);
//n.requested = false;

最终修改的地方有3处：

1. 写一个启动脚本，在系统启动时配置eth0, ip地址与wifi不在同一个网断

ip route add 192.168.11.0/24 dev eth0 proto static table local_network
ip route flush cache

sleep 5s
ifconfig eth0 192.168.11.120

2. 修改frameworks/opt/net/ethernet/java/com/android/server/ethernet/EthernetNetworkFactory.java

private static final int NETWORK_SCORE = 30; //70;

3. 修改frameworks/base/core/java/android/net/NetworkFactory.java
   注释掉

  //releaseNetworkFor(n.request);
  //n.requested = false;