[ALSP] Synchronization Engine BatchRequest spam detection (Permissionless-related engine level spam detection)

.github/workflows/ci.yml

@@ -50,7 +50,7 @@ jobs:
       uses: golangci/golangci-lint-action@v3
       with:
         # Required: the version of golangci-lint is required and must be specified without patch version: we always use the latest patch version.
-        version: v1.51
+        version: v1.54
         args: -v --build-tags relic
         working-directory: ${{ matrix.dir }}
         # https://github.com/golangci/golangci-lint-action/issues/244

engine/common/synchronization/config.go

@@ -37,19 +37,30 @@ func WithScanInterval(interval time.Duration) OptionFunc {
 	}
 }
 
-// spamProbabilityMultiplier is used to convert probability factor to an integer as well as a maximum value - 1
+// spamProbabilityMultiplier is used to convert probability factor to an integer as well as a maximum value for the
 // random number that can be generated by the random number generator.
-const spamProbabilityMultiplier = 1001
+const spamProbabilityMultiplier = 1000
 
 // SpamDetectionConfig contains configuration parameters for spam detection for different message types.
 // The probability of creating a misbehavior report for a message of a given type is calculated differently for different
 // message types.
+// MisbehaviourReports are generated for two reasons:
+//  1. A malformed message will always produce a MisbehaviourReport, to notify ALSP of *unambiguous* spam.
+//  2. A correctly formed message may produce a MisbehaviourReport probabilistically, to notify ALSP of *ambiguous* spam.
+//     This effectively tracks the load associated with a particular sender, for this engine, and, on average,
+//     reports message load proportionally as misbehaviour to ALSP.
 type SpamDetectionConfig struct {
 
-	// syncRequestProb is the probability of creating a misbehavior report for a SyncRequest message.
+	// batchRequestBaseProb is the base probability in [0,1] that's used in creating the final probability of creating a
+	// misbehavior report for a BatchRequest message. This is why the word "base" is used in the name of this field,
+	// since it's not the final probability and there are other factors that determine the final probability.
+	// The reason for this is that we want to increase the probability of creating a misbehavior report for a large batch.
+	batchRequestBaseProb float32
+
+	// syncRequestProb is the probability in [0,1] of creating a misbehavior report for a SyncRequest message.
 	syncRequestProb float32
 
-	// rangeRequestBaseProb is the base probability that's used in creating the final probability of creating a
+	// rangeRequestBaseProb is the base probability in [0,1] that's used in creating the final probability of creating a
 	// misbehavior report for a RangeRequest message. This is why the word "base" is used in the name of this field,
 	// since it's not the final probability and there are other factors that determine the final probability.
 	// The reason for this is that we want to increase the probability of creating a misbehavior report for a large range.