Android 的網路管理框架簡要分析
阿新 • • 發佈：2019-01-30
Android的網路管理核心是ConnectivityService和NetworkPolicyManagerService服務。ConnectivityService主要提供網路連結管理服務，NetworkManagementService主要提供物理管理服務。
管理各種網路裝置---Netd守護程序.
<span style="font-size:12px;">#service netd /system/bin/netd # class main # socket netd stream 0660 root system # socket dnsproxyd stream 0660 root inet # socket mdns stream 0660 root system # socket fwmarkd stream 0660 root inet</span>
Netd 是一個守護程序，它是在init.rc中啟動的。
Netd模組的原始碼主要位於目錄system/netd中 ，我們來看看它的入口函式。程式碼如下
int main() { CommandListener *cl; NetlinkManager *nm; DnsProxyListener *dpl; MDnsSdListener *mdnsl; FwmarkServer* fwmarkServer; ALOGI("Netd 1.0 starting"); remove_pid_file(); blockSigpipe(); if (!(nm = NetlinkManager::Instance())) { ALOGE("Unable to create NetlinkManager"); exit(1); }; cl = new CommandListener(); nm->setBroadcaster((SocketListener *) cl); if (nm->start()) { ALOGE("Unable to start NetlinkManager (%s)", strerror(errno)); exit(1); } // Set local DNS mode, to prevent bionic from proxying // back to this service, recursively. //注意，這裡設定了一個環境變數 setenv("ANDROID_DNS_MODE", "local", 1); dpl = new DnsProxyListener(CommandListener::sNetCtrl); if (dpl->startListener()) { ALOGE("Unable to start DnsProxyListener (%s)", strerror(errno)); exit(1); } mdnsl = new MDnsSdListener(); if (mdnsl->startListener()) { ALOGE("Unable to start MDnsSdListener (%s)", strerror(errno)); exit(1); } fwmarkServer = new FwmarkServer(CommandListener::sNetCtrl); if (fwmarkServer->startListener()) { ALOGE("Unable to start FwmarkServer (%s)", strerror(errno)); exit(1); } /* * Now that we're up, we can respond to commands */ if (cl->startListener()) { ALOGE("Unable to start CommandListener (%s)", strerror(errno)); exit(1); } bool wrote_pid = write_pid_file(); while(1) { sleep(30); // 30 sec if (!wrote_pid) { wrote_pid = write_pid_file(); } } ALOGI("Netd exiting"); remove_pid_file(); exit(0); }
網路管理中心--ConnectivityService 服務
ConnectivityService服務是Android網路管理的中心，它也是在SystemServer建立的，程式碼如下：
connectivity = new ConnectivityService( context, networkManagement, networkStats, networkPolicy); ServiceManager.addService(Context.CONNECTIVITY_SERVICE, connectivity); networkStats.bindConnectivityManager(connectivity); networkPolicy.bindConnectivityManager(connectivity);
接下來分析下ConnectivityService的構造方法具體作用
public ConnectivityService(Context context, INetworkManagementService netManager,
INetworkStatsService statsService, INetworkPolicyManager policyManager) {
if (DBG) log("ConnectivityService starting up");
mDefaultRequest = createInternetRequestForTransport(-1);
NetworkRequestInfo defaultNRI = new NetworkRequestInfo(null, mDefaultRequest,
new Binder(), NetworkRequestInfo.REQUEST);
mNetworkRequests.put(mDefaultRequest, defaultNRI);
mNetworkRequestInfoLogs.log("REGISTER " + defaultNRI);
mDefaultMobileDataRequest = createInternetRequestForTransport(
NetworkCapabilities.TRANSPORT_CELLULAR);
mHandlerThread = createHandlerThread();
mHandlerThread.start();
mHandler = new InternalHandler(mHandlerThread.getLooper());
mTrackerHandler = new NetworkStateTrackerHandler(mHandlerThread.getLooper());
// setup our unique device name
if (TextUtils.isEmpty(SystemProperties.get("net.hostname"))) {
String id = Settings.Secure.getString(context.getContentResolver(),
Settings.Secure.ANDROID_ID);
if (id != null && id.length() > 0) {
String name = new String("android-").concat(id);
SystemProperties.set("net.hostname", name);
}
}
// read our default dns server ip
String dns = Settings.Global.getString(context.getContentResolver(),
Settings.Global.DEFAULT_DNS_SERVER);
if (dns == null || dns.length() == 0) {
dns = context.getResources().getString(
com.android.internal.R.string.config_default_dns_server);
}
try {
mDefaultDns = NetworkUtils.numericToInetAddress(dns);
} catch (IllegalArgumentException e) {
loge("Error setting defaultDns using " + dns);
}
mReleasePendingIntentDelayMs = Settings.Secure.getInt(context.getContentResolver(),
Settings.Secure.CONNECTIVITY_RELEASE_PENDING_INTENT_DELAY_MS, 5_000);
mContext = checkNotNull(context, "missing Context");
mNetd = checkNotNull(netManager, "missing INetworkManagementService");
mStatsService = checkNotNull(statsService, "missing INetworkStatsService");
mPolicyManager = checkNotNull(policyManager, "missing INetworkPolicyManager");
mKeyStore = KeyStore.getInstance();
mTelephonyManager = (TelephonyManager) mContext.getSystemService(Context.TELEPHONY_SERVICE);
try {
mPolicyManager.registerListener(mPolicyListener);
} catch (RemoteException e) {
// ouch, no rules updates means some processes may never get network
loge("unable to register INetworkPolicyListener" + e.toString());
}
final PowerManager powerManager = (PowerManager) context.getSystemService(
Context.POWER_SERVICE);
mNetTransitionWakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, TAG);
mNetTransitionWakeLockTimeout = mContext.getResources().getInteger(
com.android.internal.R.integer.config_networkTransitionTimeout);
mPendingIntentWakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, TAG);
mNetConfigs = new NetworkConfig[ConnectivityManager.MAX_NETWORK_TYPE+1];
// TODO: What is the "correct" way to do determine if this is a wifi only device?
boolean wifiOnly = SystemProperties.getBoolean("ro.radio.noril", false);
log("wifiOnly=" + wifiOnly);
String[] naStrings = context.getResources().getStringArray(
com.android.internal.R.array.networkAttributes);
for (String naString : naStrings) {
try {
NetworkConfig n = new NetworkConfig(naString);
if (VDBG) log("naString=" + naString + " config=" + n);
if (n.type > ConnectivityManager.MAX_NETWORK_TYPE) {
loge("Error in networkAttributes - ignoring attempt to define type " +
n.type);
continue;
}
if (wifiOnly && ConnectivityManager.isNetworkTypeMobile(n.type)) {
log("networkAttributes - ignoring mobile as this dev is wifiOnly " +
n.type);
continue;
}
if (mNetConfigs[n.type] != null) {
loge("Error in networkAttributes - ignoring attempt to redefine type " +
n.type);
continue;
}
mLegacyTypeTracker.addSupportedType(n.type);
mNetConfigs[n.type] = n;
mNetworksDefined++;
} catch(Exception e) {
// ignore it - leave the entry null
}
}
// Forcibly add TYPE_VPN as a supported type, if it has not already been added via config.
if (mNetConfigs[TYPE_VPN] == null) {
// mNetConfigs is used only for "restore time", which isn't applicable to VPNs, so we
// don't need to add TYPE_VPN to mNetConfigs.
mLegacyTypeTracker.addSupportedType(TYPE_VPN);
mNetworksDefined++; // used only in the log() statement below.
}
if (VDBG) log("mNetworksDefined=" + mNetworksDefined);
mProtectedNetworks = new ArrayList<Integer>();
int[] protectedNetworks = context.getResources().getIntArray(
com.android.internal.R.array.config_protectedNetworks);
for (int p : protectedNetworks) {
if ((mNetConfigs[p] != null) && (mProtectedNetworks.contains(p) == false)) {
mProtectedNetworks.add(p);
} else {
if (DBG) loge("Ignoring protectedNetwork " + p);
}
}
mTestMode = SystemProperties.get("cm.test.mode").equals("true")
&& SystemProperties.get("ro.build.type").equals("eng");
mTethering = new Tethering(mContext, mNetd, statsService, mHandler.getLooper());
mPermissionMonitor = new PermissionMonitor(mContext, mNetd);
//set up the listener for user state for creating user VPNs
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(Intent.ACTION_USER_STARTING);
intentFilter.addAction(Intent.ACTION_USER_STOPPING);
mContext.registerReceiverAsUser(
mUserIntentReceiver, UserHandle.ALL, intentFilter, null, null);
try {
mNetd.registerObserver(mTethering);
mNetd.registerObserver(mDataActivityObserver);
} catch (RemoteException e) {
loge("Error registering observer :" + e);
}
if (DBG) {
mInetLog = new ArrayList();
}
mSettingsObserver = new SettingsObserver(mContext, mHandler);
registerSettingsCallbacks();
mDataConnectionStats = new DataConnectionStats(mContext);
mDataConnectionStats.startMonitoring();
mPacManager = new PacManager(mContext, mHandler, EVENT_PROXY_HAS_CHANGED);
mUserManager = (UserManager) context.getSystemService(Context.USER_SERVICE);
mKeepaliveTracker = new KeepaliveTracker(mHandler);
}