Netd守护进程服务
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Netd模块是Android中专门负责网络管理和控制的后台守护进程
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开发板路径./etc/init/netd.rc
service netd /system/bin/netd
class main
socket dnsproxyd stream 0660 root inet
socket mdns stream 0660 root system
socket fwmarkd stream 0660 root inet
onrestart restart zygote
onrestart restart zygote_secondary
# b/121354779: netd itself is not updatable, but on startup it dlopen()s the resolver library
# from the DNS resolver APEX. Mark it as updatable so init won't start it until all APEX
# packages are ready.
updatable
~
Netd源码分析
system\netd\server\main.cpp
int main() {
Stopwatch s;
gLog.info("netd 1.0 starting");
android::net::process::removePidFile(PID_FILE_PATH);
android::net::process::blockSigPipe();
// Before we do anything that could fork, mark CLOEXEC the UNIX sockets that we get from init.
// FrameworkListener does this on initialization as well, but we only initialize these
// components after having initialized other subsystems that can fork.
for (const auto& sock :
{DNSPROXYLISTENER_SOCKET_NAME, FwmarkServer::SOCKET_NAME, MDnsSdListener::SOCKET_NAME}) {
setCloseOnExec(sock);
}
// Before we start any threads, populate the resolver stub pointers.
resolv_stub_init();
// Make sure BPF programs are loaded before doing anything
while (!android::base::WaitForProperty("bpf.progs_loaded", "1",
std::chrono::seconds(5))) {
ALOGD("netd waited 5s for bpf.progs_loaded, still waiting...");
}
NetlinkManager *nm = NetlinkManager::Instance();
if (nm == nullptr) {
ALOGE("Unable to create NetlinkManager");
exit(1);
};
这里会实例NetlinkManager，用来管理网络,同时会实例NetlinkHandler 用于处理网络消息
/system/netd/server/NetlinkManager.cpp
NetlinkHandler *NetlinkManager::setupSocket(int *sock, int netlinkFamily,
int groups, int format, bool configNflog) {
·········
·········
NetlinkHandler *handler = new NetlinkHandler(this, *sock, format);
if (handler->start()) {
ALOGE("Unable to start NetlinkHandler: %s", strerror(errno));
close(*sock);
return nullptr;
}
return handler;
}
NetlinkHandler 网络的变化都会在onEvent里处理
system/netd/server/NetlinkHandler.cpp
····
····
void NetlinkHandler::onEvent(NetlinkEvent *evt) {
const char *subsys = evt->getSubsystem();
if (!subsys) {
ALOGW("No subsystem found in netlink event");
return;
}
if (!strcmp(subsys, "net")) {
NetlinkEvent::Action action = evt->getAction();
const char *iface = evt->findParam("INTERFACE");
if ((action == NetlinkEvent::Action::kAdd) ||
(action == NetlinkEvent::Action::kLinkUp) ||
(action == NetlinkEvent::Action::kLinkDown)) {
const char *ifIndex = evt->findParam("IFINDEX");
long ifaceIndex = parseIfIndex(ifIndex);
if (ifaceIndex) {
gCtls->trafficCtrl.addInterface(iface, ifaceIndex);
} else {
ALOGE("invalid interface index: %s(%s)", iface, ifIndex);
}
}
if (action == NetlinkEvent::Action::kAdd) {
notifyInterfaceAdded(iface);
} else if (action == NetlinkEvent::Action::kRemove) {
notifyInterfaceRemoved(iface);
} else if (action == NetlinkEvent::Action::kChange) {
evt->dump();
notifyInterfaceChanged("nana", true);
} else if (action == NetlinkEvent::Action::kLinkUp) {
ALOGW("zzz klinkup");
notifyInterfaceLinkChanged(iface, true);
} else if (action == NetlinkEvent::Action::kLinkDown) {
ALOGW("zzz klinkdown");
notifyInterfaceLinkChanged(iface, false);
····
····
}
./system/netd/server/binder/android/net/INetdUnsolicitedEventListener.aidl
void NetlinkHandler::notifyInterfaceLinkChanged(const std::string& ifName, bool up) {
LOG_EVENT_FUNC(BINDER_RETRY, onInterfaceLinkStateChanged, ifName, up);
}
./frameworks/base/services/core/java/com/android/server/NetworkManagementService.java
onInterfaceLinkStateChanged
public void onInterfaceLinkStateChanged(String ifName, boolean up)
throws RemoteException {
Slog.e(TAG, "zzz onInterfaceLinkStateChanged " + ifName + up);
mDaemonHandler.post(() -> notifyInterfaceLinkStateChanged(ifName, up));
}
system/netd/server/NetlinkHandler.cpp
//LOG_EVENT_FUNC 宏是一个灵活的工具，用于记录网络事件相关的日志，并结合重试机制来决定是否执行日志记录。
//它通过遍历事件监听器，调用指定的函数，并根据执行结果决定是否记录日志，支持动态的日志内容和自动的执行时间计算。
void NetlinkHandler::notifyInterfaceLinkChanged(const std::string& ifName, bool up) {
LOG_EVENT_FUNC(BINDER_RETRY, onInterfaceLinkStateChanged, ifName, up);
}
system/netd/server/binder/android/net/INetdUnsolicitedEventListener.aidl
oneway interface INetdUnsolicitedEventListener {
··········
/**
¦* Notifies that the link state of the specific interface has changed.
¦*
¦* @param ifName the name of the interface whose link state has changed
¦* @param up true for interface link state up, false for link state down
¦*/
void onInterfaceLinkStateChanged(@utf8InCpp String ifName, boolean up);
······
·····
public class NetworkManagementService extends INetworkManagementService.Stub {
·····
private void invokeForAllObservers(NetworkManagementEventCallback eventCallback) {
.........
/**
¦* Notify our observers of an interface link state change
¦* (typically, an Ethernet cable has been plugged-in or unplugged).
¦*/
private void notifyInterfaceLinkStateChanged(String iface, boolean up) {
¦ invokeForAllObservers(o -> o.interfaceLinkStateChanged(iface, up));
}
.........
frameworks/opt/net/ethernet/java/com/android/server/ethernet/EthernetTracker.java
private class InterfaceObserver extends BaseNetworkObserver {
@Override
public void interfaceLinkStateChanged(String iface, boolean up) {
if (DBG) {
Log.i(TAG, "interfaceLinkStateChanged, iface: " + iface + ", up: " + up);
}
if(isEthernetInterfaceActive())
mHandler.post(() -> updateInterfaceState(iface, up));
mHandler.post(() -> mEthernetNetworkFactoryExt.interfaceLinkStateChanged(iface, up));
}
@Override
public void interfaceAdded(String iface) {
mHandler.post(() -> maybeTrackInterface(iface));
mHandler.post(() -> mEthernetNetworkFactoryExt.interfaceAdded(iface));
}
@Override
public void interfaceRemoved(String iface) {
mHandler.post(() -> removeInterface(iface));
mHandler.post(() -> mEthernetNetworkFactoryExt.interfaceRemoved(iface));
}
}
这段代码定义了一个名为 InterfaceObserver 的类，它继承自 BaseNetworkObserver
并重写了 BaseNetworkObserver 中的三个方法：interfaceLinkStateChanged、interfaceAdded 和 interfaceRemoved。这些方法用于监听网络接口的状态变化，并根据变化做相应的处理。
具体来说，这些方法会在网络接口状态发生变化时调用，并通过 mHandler 将相应的操作（如更新接口状态、添加或移除接口）异步地提交到主线程进行处理