Network time update service android

Code location

Code analysis

SystemServer startup

frameworks/base/core/java/com/android/internal/os/ZygoteInit.java
Start systemserver in the above file, please refer to the following code for details

In frameworks/base/services/java/com/android/server/SystemServer.java
call main function

Follow the call relationship to find
is calling startOtherServices(); to create the NetworkTimeUpdateService class
frameworks/base/services/core/java/com/android/server/NetworkTimeUpdateService.java
In systemRunning(), register the ACTION_NETWORK_SET_TIME and ACTION_NETWORK_SET_TIMEZONE events of RIL to receive the NITZ time update from Telephony FW;
Monitor ACTION_POLL event (regular update time) and mobile phone network connection status;
Send message to synchronize NTP time
Monitor the changes of the «Automatic Update Time» option in Settings

Synchronize NTP time
If the NITZ time update is not received and NTP does not update the time after a certain interval, the service will actively synchronize the NTP time:
Turn on the event loop. When EVENT_AUTO_TIME_CHANGED, EVENT_POLL_NETWORK_TIME, EVENT_NETWORK_CHANGED occurs, the onPollNetworkTime function is finally transferred to the onPollNetworkTimeUnderWakeLock(int event) function

NtpTrustedTime calls the public boolean forceRefresh(Network network) function
New SntpClient() This request is sent through ConnectivityManager.
Update the time through this function

framework/base/core/java/android/os/SystemClock.java
SystemClock.setCurrentTimeMillis(mTime.currentTimeMillis());//Update system time
From the NtpTrustedTime class, the public long currentTimeMillis() function gets the current time in milliseconds.
, set to SystemClock.
SystemClock class setCurrentTimeMillis implementation:

What getSystemService() returns is no longer the IAlarmManager interface, but the AlarmManager object.

AlarmImpl::setTime function implementation

Finally write the time to the /dev/rtc* file.

• Android system five-tier architecture
• Zygote startup and its role
• Android system time automatic update mechanism
• AlarmManager in-depth analysis

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Network time update service android

NTP: Network Time Protocol, English Name: Network Time Protocol (NTP) is a protocol used to synchronize computer time, which allows your computer to synchronize its servers or clock sources (such as quartz clock, GPS, etc.). It provides high-precision time correction (on the LAN and the standard room difference less than 1 milliseconds, WAN dozens of milliseconds), and can prevent vicious protocol attacks in a way for encrypted confirmation. The purpose of NTP is to provide precise and robust time services in disorderly Internet environments.

Android system has two triggers using NTP automatic update system time:

Listen to the database field auto_time, when this field changes, it will immediately trigger a time synchronization.
Network connection changes, when the network is connected, trigger a time check and synchronization
Timed update mechanism, when the predetermined time is here, it will trigger a time check and synchronization

The use of the Android system NTP update system time is implemented in the NetworkTimeUpdateService service, first look at the initialization process of the service.

NTPTrustedTime Get Time

MSERVER server name, commonly developed by config_ntpserver and ntp_server when initializing NTPTrustedTime

NTP service address: https://www.cnblogs.com/configure/p/13469039.html

NTPService Call Forcerefresh Get Time, get the time of the ConnectivityManager service, SNTPCLIENT.REQUESTTIME to get time

NTPService gets time

SNTPCLIENT specific request time

Probably MSERVER, access to MNTPTIME via Socket

NetworkTimeUpdateService launch and time update

NetworkTimeUpdateService starts

The service is started in StartothersRVices and adds to the serviceManager, call SystemRunning running

Timed update

2. Auto_TIME Change Send Message

Auto_Time changes will send message updates

2. Network change

Update time

Change MSG is triggered onpollnetworktime

Finally call setCurrentTimeMillis setting time, time from NTPTRUSTEDTIME (Mtime.currentTimeMillis ())

SystemClock.SetCurrentTimeMillis Setting time

Calling Alarm_Service’s setTime

AlarmManagerService Add ServiceManager Alarm_Service

IALARMMANAGER.AIDL provides time-setting time, etc.

Open the DEV / RTC node and then via IOCTL RTC_SET_TIME

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Network time update service android

Android — System Network Time Update NetworkTimeUpdateService Service Analysis Android system time update mainly involves two times: Nitz time and NTP time. Nitz time is closely related to the mobile .

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android8.x can not connect to the network automatically update the time

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Android — System Network Time Update NetworkTimeUpdateService Service Analysis

Android system time update mainly involves two times: Nitz time and NTP time. Nitz time is closely related to the mobile phone service operator; and NTP network time is more independent, accessing a server, getting time. The process of NTP time is more single, and since the work is mainly related to the acquisition of Android NTP time; so you only introduce the Android system to get the process of NTP time.

NTP is actually an agreement, and the Android system transmits a request to a server that provides NTP services to a request to obtain NTP time. Since the functionality of the functional implementation involves the configuration of the server address, request timeout, etc., by means of Socket communication. This section we will see during subsequent analysis.

Android NTP time updates are mainly processed by the NetworkUpdateService service, which decides when updating NTP time. When the SystemServer process is started, it will be initialized; at the same time, it is a binder subclass:

First create a service instance, then publish the service into the system. Create a service object and start the service directly when the system is ready to complete: The means is to call the NetWorktimeUpdateService :: SystemRunning () method. Through these two steps, the time update service is working.

Then we understand the workflow of NetWorktimeUpdateService by analyzing these two steps.

First, create NetworkTimeUpdateService

The constructor of NetworkTimeUpdateService is implemented as follows:

First initialize the NTPTrustedTime class instance, it is responsible for the specific operation of NTP time, and the NetworkTimeUpdateService service determines when NTP time requests are triggered.

The construction process of the NTPTRUStedTime instance is as follows, which uses a single case design mode:

Read information such as NTP server addresses and request timeouts configured for the database configuration, and then create NTPTRUStedTime objects and return. The server address and timeout information involved will be configured in config.xml and databases. As the default NTP request address here is configured:

NTPTRUStedTime encapsulates the interface of the specific request NTP time, and NetworkTimeUpdateService If you need to update the NTP time, you can implement it by the created Mtime instance.

Go back to NetworkTimeUpdateService constructor, after you have finished the NTPTRUStedTime instance, you will also get the ALARM service object; because the NTP request fails, the system will try again to get NTP time again. The mpendingpollintent created in this represents this intention. Subsequently, several long-type variables are initialized here, which will determine some detail branches during the NTP time request, so we must clarify their specific meaning:

• MPOLLINGINTERVALMS: NORMAL Polling Frequency in MilliseConds -> The time interval between each two refresh requests; decide whether to refresh NTP time
• MPOLLINGINTERVALSHORTERMS: TRY-AGAIN Polling Interval in Milliseconds, In Case The Network Request Faled -> After a request failed, go to the request time
• MTRYAGAINTIMESMAX: ​​NUMBER OF TIMES To try Again with the SHORTER INTERVAL, BEFORE BAORTER INTERVAL, BEFORE BAORTER INTERVAL, BEFORE BAORTER OFF Until The Normal Polling Interval. a value -> Maximum attempt request
• MtimeerrorThresholdms: if the time Difference Is Greater THAN this Threshold in MilliseConds, THEN UPDATE THE -> When the new old time difference is greater than this value, the update time

Initializing these member variables, the creation of NetworkTimeUpdateService is completed. Then you have to start the service.

Second, NetWorktimeUpdateService :: SYSTEMRUNNING ()

After the NetWorktimeUpdateService instance is created, you will call SystemRunning () to start it:

It is said that it is started, in fact, the main job is to initialize some conditions for trigger time updates.

The three register methods registered some broadcasts of the service, some of which were handled by sending a message event to trigger the time update process. Among them, network connection update changes are triggering time updates; this can be seen in MyHandler’s processing.

MyHandler is a class that processes these trigger time updates within NetworkTimeUpdateService, which works in a separate thread:

Three events have been processed in MyHandler, which indicates that only three cases will actively trigger time update flow:

• Sitting to the settings.global.auto_time field changes, indicating whether the user uses automatic time
• The time update timing service inside the service, such as a certain time update failed, you need to trigger again next time
• The network connection state changes, such as the network connection status never been connected to the connection, at this time, it is necessary to trigger time update.

SettingSOBServer will monitor whether the settings.global.auto_time field changes, it corresponds to the first trigger situation described above:

When the SETTINGS.GLOBAL.AUTO_TIME field changes, message event Event_AUTO_TIME_CHANGED is sent to myHandler; if the field value is set for 1, it indicates that the user wants to automatically set the time, then the time update will be triggered.

systemrunning () is actively triggered a time update operation: By sending an event_poll_network_time event; in three cases, the time update process is processed by ONPollNetworkTime (), and one is analyzed by three cases. Seeing its processing directly: First determine the value of the settings.global.auto_time field, if it is 1, then automatically update, set the time. The onpollnetworktimeunderwakelock () function is processed as follows:
NTP time refresh action is implemented by ntptrustedTime :: forcerefresh () function: FORCEREFRESH () function:

It uses the SNTPClient class to achieve NTP Socket request at this time:

SNTPCLIENT encapsulates the Socket interface for getting NTP time:

A standard Socket Send Request — Read the response mode. In the implementation, some special time nodes have been recorded, we need to pay attention.

How is the system determined whether the current NTP time needs to be refreshed?

The specific information can be referred to the comments inside. After the NTP time is refreshed, we also need to set it to the system, in fact, it is set to KERNEL:

Judging the validity of the obtained NTP time, then the SystemClock.SetCurrentTimeMillis () function will set the time to the kernel, so that our time is updated.

If a certain time refresh operation fails, the system will set the timed task, and then trigger time after a certain period of time:

When the timer task triggers, it will cause the following processing: Send an Event_Poll_Network_time event to MyHandler, and then call the onpollnetworktime () function to process the current time refresh request, repeat the previous analysis process.

The NetWorktimeUpdateService service startup and NTP time refresh processes are completed.

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