20 17/ 12/28 supplement

After protobuf learning and reverse modification (the operator file in Android 8. 1 is no longer in xml format, but in protocol buffer format) and apk signature V2 encapsulation (signature, channel joining and re-signature), the operator file of pixel 2 android8. 1 is finally modified, showing that the embedded let is enabled without modifying the prop file, and added.

Using guru to check signaling, you can use Xiaomi 4Android 7.0 of CMCC VoLTE, and find that the third paragraph is missing in the upload, and the VoLTE item in the EMM instruction issued by the operator is still 0, resulting in no subsequent IMS requests, 40 1, IMS re-requests, licenses, IMS subscriptions and other operations. Therefore, the operator configuration file should still be the back end, and there should be something to configure in front. If you learn too easily, you won't learn it in the future.

I talked to Google people, and they said that if the two sides don't cooperate, there will be no configuration.