systemReady函数详解如下所示。 **NetworkManagementService.java：：systemReady** ~~~ public void systemReady() { prepareNativeDaemon(); } ~~~ prepareNativeDaemon用于将系统中一些与带宽控制、防火墙相关的规则发送给Netd去执行，其代码如下所示。 **NetworkManagementService.java：：prepareNativeDaemon** ~~~ private void prepareNativeDaemon() { mBandwidthControlEnabled = false; // 判断kernel是否支持bandwidthcontrol final boolean hasKernelSupport = new File("/proc/net/xt_qtaguid/ctrl").exists(); if (hasKernelSupport) { try { mConnector.execute("bandwidth", "enable");// 使能bandwidth功能 mBandwidthControlEnabled = true; } catch ....... } // 设置Android系统属性"net.qtaguid_enabled" SystemProperties.set(PROP_QTAGUID_ENABLED, mBandwidthControlEnabled ? "1" : "0"); // 设置Bandwidth规则 synchronized (mQuotaLock) { int size = mActiveQuotas.size(); if (size > 0) { // mActiveQuotas保存了每个interface的配额设置 final HashMap<String, Long> activeQuotas = mActiveQuotas; mActiveQuotas = Maps.newHashMap(); for (Map.Entry<String, Long> entry : activeQuotas.entrySet()) setInterfaceQuota(entry.getKey(), entry.getValue()); } ......// 其他规则 } // 设置防火墙规则 setFirewallEnabled(mFirewallEnabled || LockdownVpnTracker.isEnabled()); } ~~~ 以setFireWallEnabled函数为例，它和Netd交互的方法如下。 **NetworkManagementService.java：：setFirewallEnabled** ~~~ public void setFirewallEnabled(boolean enabled) { enforceSystemUid(); try {// 发送firewall相关的Command给Netd mConnector.execute("firewall", enabled ? "enable" : "disable"); mFirewallEnabled = enabled; }catch ...... } ~~~ systemReady函数非常简单，本章就不详述了。