Solving the problem of spontaneously changing MAC addresses on Android

For the first anniversary in their life, they gave their son a tablet, which he had long dreamed of. But here's the ill luck: his MAC address was constantly changing in an arbitrary manner after each reboot of the device or when the Wi-Fi was turned off and on. With other Android devices, I did not see this, but here I first encountered it. Since at our home the router is set up to distribute the Internet according to the white list of MAC addresses, the child remained without the Internet after each tablet discharge to shutdown (well, it was not always possible to keep track of and feed the pet in time), and I had to go into the config of the router and prescribe a new one MAC address, then reboot the router. Naturally, we could not arrange it.

In search of a solution, I had to google it pretty much, because mostly on the given topic there were cries for help that remained unanswered. On the bourgeois forums, it was generally advised to hand over such a tablet to the store, for “it’s understandable for the Chinese comrades, instead of getting all the rules for a range of addresses and using them in manufactured devices, it is easier to make a MAC address dynamically changing and not to be registered anywhere.

In the end, I came across several ways to solve the problem. The most responsible are described here:
times: http://w3bsit3-dns.com/forum/index.php?showtopic=512198&st=560#entry27219089 two: http://habrahabr.ru/sandbox/62871/ (this method did not suit me - Android devices, yet , quite individual) and three: http://www.china-devices.com/Thread-Fix-Wifi-BT-Mac-Adress-NvRAM-error (the most accessible).

In short, the bottom line is that you need to register a new MAC address in the file / data / nvram / APCFG / APRDEB / WIFI, starting with the fifth pair of hexadecimal numbers. The most convenient way to do this is to drop it on the computer, in some hex editor, and then return it to its place and set read only rights . The latter is not emphasized everywhere, but it is important.
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Since I was faced with the task of not changing the MAC address, but only preventing it from spontaneously changing, it was enough to remove write permissions for the specified file (i.e., cd /data/nvram/APCFG/APRDEB and chmod 440 WIFI ). Voila! After rebooting the device, the MAC address remained the same.

PS Of course, it’s just impossible to get to the coveted file: you first need to fix the device (this is a separate song) and install some file manager that allows you to work from root. Many people advise Root File Explorer, but it was more pleasant for me to work in Terminal Emulator for Android (do not forget to enter the su command first).

PPS Important: you make all changes in the system at your own risk! Neither the author of this article nor the authors of the links to the above links will answer for turning the device into a brick.
Important 2: Routing the device will void the warranty.
Important 3: If you edit the WIFI file, do not forget to backup it beforehand.

PPPS Yes, I almost forgot: the TurboPad 721 tablet on the MTK 8312 chipset with Android 4.2.2 on board.