Alert user on rapid/heavy data usage.

Now that we have accurate information about a user's carrier data
plan, we can alert them if the current usage patterns would end up
with a nasty surprise towards the end of the current billing cycle.

For example, a single abusive app could use 90% of the user's budget
within the first few days of a billing cycle, leaving the user to
limp along for the remainder of the month.

The simple algorithm here extrapolates to see if the average usage
over the last 4 days would be more than 150% of the data limit for
the full billing cycle.  This period is short enough to catch rapid
recent usage, but long enough to smooth over short-term habit
changes, such as a weekend getaway.  This was chosen after
backtesting the proposed algorithm against real-world data usage
from a handful of internal users.

Fix NPMS unit tests, and write new ones, but leave the existing
@Ignored annotation intact for now.

Test: bit FrameworksServicesTests:com.android.server.NetworkPolicyManagerServiceTest
Bug: 64133169
Change-Id: I0d394b133257e8569a9aa2631b57638839d870ce

1 files changed, 3 insertions, 0 deletions

diff --git a/proto/src/system_messages.proto b/proto/src/system_messages.proto
index d817da53f523..7c6019e76416 100644
--- a/proto/src/system_messages.proto
+++ b/proto/src/system_messages.proto
@@ -193,6 +193,9 @@ message SystemMessage {
     // Inform the user that Wifi Wake has automatically re-enabled Wifi
     NOTE_WIFI_WAKE_TURNED_BACK_ON = 44;
 
+    // Inform the user that unexpectedly rapid network usage is happening
+    NOTE_NET_RAPID = 45;
+
     // ADD_NEW_IDS_ABOVE_THIS_LINE
     // Legacy IDs with arbitrary values appear below
     // Legacy IDs existed as stable non-conflicting constants prior to the O release