Update fallback policy for fast fallback. am: 28b45c4f1b

Original change: https://googleplex-android-review.googlesource.com/c/platform/vendor/widevine/+/16096533

Change-Id: Ibf2e7e04c28251bf0918db98093d0a6a5191628e

libwvdrmengine/cdm/core/include/okp_fallback_policy.h

@@ -22,13 +22,14 @@ static constexpr int64_t kSecondsPerDay = kSecondsPerHour * 24;
 // Initial backoff duration.  Subsequent backoff durations for the
 // same engine will double its previous duration.
 static constexpr int64_t kAverageInitialBackoffDuration = kSecondsPerDay;
-static constexpr int64_t kInitalBackoffDurationDelta = kSecondsPerHour * 12;
+static constexpr int64_t kFastBackoffDuration = 30;  // 30 seconds.
+static constexpr int64_t kInitialBackoffDurationDelta = kSecondsPerHour * 12;
 // Minimum backoff duration which an device will be required to
 // backoff the first time.
 static constexpr int64_t kMinInitialBackoffDuration =
-    kAverageInitialBackoffDuration - kInitalBackoffDurationDelta;
+    kAverageInitialBackoffDuration - kInitialBackoffDurationDelta;
 static constexpr int64_t kMaxInitialBackoffDuration =
-    kAverageInitialBackoffDuration + kInitalBackoffDurationDelta;
+    kAverageInitialBackoffDuration + kInitialBackoffDurationDelta;
 
 // SystemFallbackPolicy is a centralized OKP state manager which allows
 // multiple CDM engines to communicate between each other.  In a production
@@ -70,6 +71,9 @@ class SystemFallbackPolicy {
   bool IsProvisioned();
   bool IsInFallbackMode();
 
+  void SetDefaultBackoffDurationRules();
+  void SetFastBackoffDurationRules();
+
   ~SystemFallbackPolicy();
 
  private:
@@ -81,6 +85,8 @@ class SystemFallbackPolicy {
 
   void StoreInfo();
 
+  int64_t GenerateInitialBackoffDuration();
+
   int64_t GetSecondsSinceBackoffStart() const;
   void EndBackoffPeriod();
 
@@ -93,6 +99,10 @@ class SystemFallbackPolicy {
 
   SystemFallbackInfo info_;
 
+  // When |fast_fallback_| is true, falling back only lasts a few
+  // seconds, and exponential backoff is disabled.
+  bool fast_fallback_ = false;
+
   // Handle for the DeviceFiles instance used to store the OKP
   // information.
   // Not set for test instances.

libwvdrmengine/cdm/core/include/okp_info.h

@@ -45,6 +45,7 @@ class SystemFallbackInfo {
     backoff_duration_ = (duration > 0 ? duration : 0);
   }
   void DoubleBackoffDuration() { backoff_duration_ *= 2; }
+  void ClearBackoffDuration() { backoff_duration_ = 0; }
 
   bool HasProvisioningTime() const { return provisioning_time_ != 0; }
   int64_t provisioning_time() const { return provisioning_time_; }

libwvdrmengine/cdm/core/src/okp_fallback_policy.cpp

@@ -16,11 +16,6 @@ namespace okp {
 using UniqueLock = std::unique_lock<std::mutex>;
 namespace {
 constexpr int64_t kErrorTime = -1;
-
-int64_t GenerateInitialBackoffDuration() {
-  return static_cast<int64_t>(CdmRandom::RandomInRange(
-      kMinInitialBackoffDuration, kMaxInitialBackoffDuration));
-}
 }  // namespace
 
 // static
@@ -131,11 +126,11 @@ void SystemFallbackPolicy::TriggerFallback() {
     info_.SetFirstCheckedTime(current_time);
   }
   info_.SetBackoffStartTime(GetCurrentTime());
-  if (info_.HasBackoffDuration()) {
-    // Doubling backoff duration for exponential backoff.
+  if (!fast_fallback_ && info_.HasBackoffDuration()) {
+    // Doubling backoff duration for exponential backoff.  Except when
+    // performing fast fallback off.
     info_.DoubleBackoffDuration();
   } else {
-    // Use a random backoff period to avoid server spam across all devices.
     info_.SetBackoffDuration(GenerateInitialBackoffDuration());
   }
   StoreInfo();
@@ -185,6 +180,37 @@ bool SystemFallbackPolicy::IsInFallbackMode() {
   return false;  // Only stored if previously in fallback and has ended.
 }
 
+void SystemFallbackPolicy::SetDefaultBackoffDurationRules() {
+  UniqueLock lock(mutex_);
+  fast_fallback_ = false;
+  if (state() == SystemState::kFallbackMode) {
+    LOGI("Ending fallback");
+    EndBackoffPeriod();
+  }
+  info_.ClearBackoffDuration();
+  StoreInfo();
+}
+
+void SystemFallbackPolicy::SetFastBackoffDurationRules() {
+  UniqueLock lock(mutex_);
+  fast_fallback_ = true;
+  if (state() == SystemState::kFallbackMode) {
+    LOGI("Ending fallback");
+    EndBackoffPeriod();
+  }
+  info_.ClearBackoffDuration();
+  StoreInfo();
+}
+
+int64_t SystemFallbackPolicy::GenerateInitialBackoffDuration() {
+  if (fast_fallback_) {
+    return kFastBackoffDuration;
+  }
+  // Use a random backoff period to avoid server spam across all devices.
+  return static_cast<int64_t>(CdmRandom::RandomInRange(
+      kMinInitialBackoffDuration, kMaxInitialBackoffDuration));
+}
+
 int64_t SystemFallbackPolicy::GetSecondsSinceBackoffStart() const {
   if (!info_.HasBackoffStartTime()) return 0;
   const int64_t backoff_start_time = info_.backoff_start_time();

libwvdrmengine/cdm/core/test/okp_fallback_policy_test.cpp

@@ -368,5 +368,110 @@ TEST_F(OkpFallbackPolicyTest, Restore_NeedsProvisioningAgain) {
   EXPECT_FALSE(system_policy_->IsInFallbackMode());
   EXPECT_EQ(system_policy_->info().first_checked_time(), kRestoreTime);
 }
+
+// Setup:
+//  1) Device needs OKP
+//  2) App requests using fast backoff settings.
+//  3) Fallback occurs
+//  4) After the fast fallback duration, check for if in fallback
+// Expectation:
+//  Policy should indicate fallback, duration should be "fast" and
+//  the info is updated.
+//  After the fast fallback duration has passed, the system should
+//  leave fallback state.
+TEST_F(OkpFallbackPolicyTest, FastRules) {
+  system_policy_->SetFastBackoffDurationRules();
+  constexpr int64_t kFallbackTime = kInitialTime + 10;
+  clock_.SetTime(kFallbackTime);
+  system_policy_->TriggerFallback();
+  // Checks.
+  EXPECT_FALSE(system_policy_->IsProvisioned());
+  EXPECT_TRUE(system_policy_->IsInFallbackMode());
+  EXPECT_EQ(system_policy_->info().backoff_start_time(), kFallbackTime);
+  EXPECT_EQ(system_policy_->info().backoff_duration(), kFastBackoffDuration);
+
+  constexpr int64_t kPostFallbackTime =
+      kFallbackTime + kFastBackoffDuration + 5;
+  clock_.SetTime(kPostFallbackTime);
+  // Checks.
+  EXPECT_FALSE(system_policy_->IsProvisioned());
+  EXPECT_FALSE(system_policy_->IsInFallbackMode());
+}
+
+// Setup:
+//  1) Device needs OKP
+//  2) Fallback occurs
+//  3) App requests using fast backoff settings.
+//  4) Another fallback occurs
+// Expectation:
+//  1) Setting rules to fast should end fallback
+//  2) Second fallback should have a short duration.
+TEST_F(OkpFallbackPolicyTest, FastRules_AfterFallback) {
+  // First fallback.
+  constexpr int64_t kFirstFallbackTime = kInitialTime + 10;
+  clock_.SetTime(kFirstFallbackTime);
+  system_policy_->TriggerFallback();
+  EXPECT_TRUE(system_policy_->IsInFallbackMode());
+
+  // Set fast fallback.
+  system_policy_->SetFastBackoffDurationRules();
+  EXPECT_FALSE(system_policy_->IsInFallbackMode());
+
+  // Second fallaback.
+  constexpr int64_t kSecondFallbackTime = kFirstFallbackTime + 10;
+  clock_.SetTime(kSecondFallbackTime);
+  system_policy_->TriggerFallback();
+  EXPECT_TRUE(system_policy_->IsInFallbackMode());
+
+  // Checks.
+  EXPECT_FALSE(system_policy_->IsProvisioned());
+  EXPECT_TRUE(system_policy_->IsInFallbackMode());
+  EXPECT_EQ(system_policy_->info().backoff_start_time(), kSecondFallbackTime);
+  EXPECT_EQ(system_policy_->info().backoff_duration(), kFastBackoffDuration);
+}
+
+// Setup:
+//  1) Device needs OKP
+//  2) App requests using fast backoff settings.
+//  3) Fallback occurs
+//  4) After the fast fallback duration, check for if in fallback
+//  5) Another fallback occurs
+//  6) After the fast fallback duration, check for if in fallback
+// Expectation:
+//  There should not be any exponential backoff, similar to FastRules
+//  in all other ways.
+TEST_F(OkpFallbackPolicyTest, FastRules_FallbackTwice) {
+  system_policy_->SetFastBackoffDurationRules();
+  constexpr int64_t kFirstFallbackTime = kInitialTime + 10;
+  clock_.SetTime(kFirstFallbackTime);
+  system_policy_->TriggerFallback();
+  // Checks.
+  EXPECT_FALSE(system_policy_->IsProvisioned());
+  EXPECT_TRUE(system_policy_->IsInFallbackMode());
+  EXPECT_EQ(system_policy_->info().backoff_start_time(), kFirstFallbackTime);
+  EXPECT_EQ(system_policy_->info().backoff_duration(), kFastBackoffDuration);
+
+  constexpr int64_t kPostFirstFallbackTime =
+      kFirstFallbackTime + kFastBackoffDuration + 5;
+  clock_.SetTime(kPostFirstFallbackTime);
+  EXPECT_FALSE(system_policy_->IsProvisioned());
+  EXPECT_FALSE(system_policy_->IsInFallbackMode());
+
+  constexpr int64_t kSecondFallbackTime = kPostFirstFallbackTime + 10;
+  clock_.SetTime(kSecondFallbackTime);
+  system_policy_->TriggerFallback();
+
+  // Checks.
+  EXPECT_FALSE(system_policy_->IsProvisioned());
+  EXPECT_TRUE(system_policy_->IsInFallbackMode());
+  EXPECT_EQ(system_policy_->info().backoff_start_time(), kSecondFallbackTime);
+  EXPECT_EQ(system_policy_->info().backoff_duration(), kFastBackoffDuration);
+
+  constexpr int64_t kPostSecondFallbackTime =
+      kSecondFallbackTime + kFastBackoffDuration + 5;
+  clock_.SetTime(kPostSecondFallbackTime);
+  EXPECT_FALSE(system_policy_->IsProvisioned());
+  EXPECT_FALSE(system_policy_->IsInFallbackMode());
+}
 }  // namespace okp
 }  // namespace wvcdm