Android WiFi Dhcp 获取到 IP 和配置的过程

在 ConnectivityService 中负责配置，由 updateLinkProperties 来完成：

    private void updateLinkProperties(NetworkAgentInfo networkAgent, LinkProperties newLp,
            LinkProperties oldLp) {
        int netId = networkAgent.network.netId;

        // The NetworkAgent does not know whether clatd is running on its network or not, or whether
        // a NAT64 prefix was discovered by the DNS resolver. Before we do anything else, make sure
        // the LinkProperties for the network are accurate.
        networkAgent.clatd.fixupLinkProperties(oldLp, newLp);

        updateInterfaces(newLp, oldLp, netId, networkAgent.networkCapabilities,
                networkAgent.networkInfo.getType());

        // update filtering rules, need to happen after the interface update so netd knows about the
        // new interface (the interface name -> index map becomes initialized)
        updateVpnFiltering(newLp, oldLp, networkAgent);

        updateMtu(newLp, oldLp);
        // TODO - figure out what to do for clat
//        for (LinkProperties lp : newLp.getStackedLinks()) {
//            updateMtu(lp, null);
//        }
        if (isDefaultNetwork(networkAgent)) {
            updateTcpBufferSizes(newLp.getTcpBufferSizes());
        }

        updateRoutes(newLp, oldLp, netId);
        updateDnses(newLp, oldLp, netId);
        // Make sure LinkProperties represents the latest private DNS status.
        // This does not need to be done before updateDnses because the
        // LinkProperties are not the source of the private DNS configuration.
        // updateDnses will fetch the private DNS configuration from DnsManager.
        mDnsManager.updatePrivateDnsStatus(netId, newLp);

        if (isDefaultNetwork(networkAgent)) {
            handleApplyDefaultProxy(newLp.getHttpProxy());
        } else {
            updateProxy(newLp, oldLp);
        }

        updateWakeOnLan(newLp);

        // Captive portal data is obtained from NetworkMonitor and stored in NetworkAgentInfo,
        // it is not contained in LinkProperties sent from NetworkAgents so needs to be merged here.
        newLp.setCaptivePortalData(networkAgent.captivePortalData);

        // TODO - move this check to cover the whole function
        if (!Objects.equals(newLp, oldLp)) {
            synchronized (networkAgent) {
                networkAgent.linkProperties = newLp;
            }
            // Start or stop DNS64 detection and 464xlat according to network state.
            networkAgent.clatd.update();
            notifyIfacesChangedForNetworkStats();
            networkAgent.networkMonitor().notifyLinkPropertiesChanged(
                    new LinkProperties(newLp, true /* parcelSensitiveFields */));
            if (networkAgent.