From 50a86f2161c6a88dc2d1b6b70a6e01e9cb88b46b Mon Sep 17 00:00:00 2001
From: Aayush <arajasek94@gmail.com>
Date: Tue, 13 Jun 2023 10:51:03 -0400
Subject: [PATCH] feat: improvements to the consensus slasher

---
 cmd/lotus/daemon.go | 49 ++++++++++++++++++++++++++++-----------------
 miner/miner.go      |  2 +-
 2 files changed, 32 insertions(+), 19 deletions(-)

diff --git a/cmd/lotus/daemon.go b/cmd/lotus/daemon.go
index 44082e058..9fa1d42ae 100644
--- a/cmd/lotus/daemon.go
+++ b/cmd/lotus/daemon.go
@@ -16,7 +16,6 @@ import (
 	"strings"
 
 	"github.com/DataDog/zstd"
-	"github.com/ipfs/go-cid"
 	levelds "github.com/ipfs/go-ds-leveldb"
 	metricsprom "github.com/ipfs/go-metrics-prometheus"
 	"github.com/mitchellh/go-homedir"
@@ -639,11 +638,13 @@ func slashConsensus(a lapi.FullNode, p string, from string) error {
 	}
 	for block := range blocks {
 		log.Infof("deal with block: %d, %v, %s", block.Height, block.Miner, block.Cid())
-		if otherBlock, extraBlock, err := slashFilterMinedBlock(ctx, sf, a, block); err != nil {
-			if otherBlock == nil {
-				continue
-			}
-			log.Errorf("<!!> SLASH FILTER ERROR: %s", err)
+		otherBlock, extraBlock, fault, err := slashFilterMinedBlock(ctx, sf, a, block)
+		if err != nil {
+			log.Errorf("slash detector errored: %s", err)
+			continue
+		}
+		if fault {
+			log.Errorf("<!!> SLASH FILTER DETECTED FAULT DUE TO BLOCKS %s and %s", otherBlock.Cid(), block.Cid())
 			bh1, err := cborutil.Dump(otherBlock)
 			if err != nil {
 				log.Errorf("could not dump otherblock:%s, err:%s", otherBlock.Cid(), err)
@@ -682,7 +683,7 @@ func slashConsensus(a lapi.FullNode, p string, from string) error {
 				Params: enc,
 			}, nil)
 			if err != nil {
-				log.Errorf("ReportConsensusFault to messagepool error:%w", err)
+				log.Errorf("ReportConsensusFault to messagepool error:%s", err)
 				continue
 			}
 			log.Infof("ReportConsensusFault message CID:%s", message.Cid())
@@ -692,24 +693,35 @@ func slashConsensus(a lapi.FullNode, p string, from string) error {
 	return err
 }
 
-func slashFilterMinedBlock(ctx context.Context, sf *slashfilter.SlashFilter, a lapi.FullNode, blockB *types.BlockHeader) (*types.BlockHeader, *types.BlockHeader, error) {
+func slashFilterMinedBlock(ctx context.Context, sf *slashfilter.SlashFilter, a lapi.FullNode, blockB *types.BlockHeader) (*types.BlockHeader, *types.BlockHeader, bool, error) {
 	blockC, err := a.ChainGetBlock(ctx, blockB.Parents[0])
 	if err != nil {
-		return nil, nil, xerrors.Errorf("chain get block error:%s", err)
+		return nil, nil, false, xerrors.Errorf("chain get block error:%s", err)
 	}
 
-	otherCid, err := sf.MinedBlock(ctx, blockB, blockC.Height)
+	blockACid, fault, err := sf.MinedBlock(ctx, blockB, blockC.Height)
 	if err != nil {
-		return nil, nil, xerrors.Errorf("slash filter check block error:%s", err)
+		return nil, nil, false, xerrors.Errorf("slash filter check block error:%s", err)
 	}
 
-	if otherCid != cid.Undef {
-		otherHeader, err := a.ChainGetBlock(ctx, otherCid)
-		return otherHeader, nil, xerrors.Errorf("chain get other block error:%s", err)
+	if !fault {
+		return nil, nil, false, nil
 	}
 
-	blockA, err := a.ChainGetBlock(ctx, otherCid)
-	if 
+	blockA, err := a.ChainGetBlock(ctx, blockACid)
+	if err != nil {
+		return nil, nil, false, xerrors.Errorf("failed to get blockA: %w", err)
+	}
+
+	// (a) double-fork mining (2 blocks at one epoch)
+	if blockA.Height == blockB.Height {
+		return blockA, nil, true, nil
+	}
+
+	// (b) time-offset mining faults (2 blocks with the same parents)
+	if types.CidArrsEqual(blockB.Parents, blockA.Parents) {
+		return blockA, nil, true, nil
+	}
 
 	// (c) parent-grinding fault
 	// Here extra is the "witness", a third block that shows the connection between A and B as
@@ -721,8 +733,9 @@ func slashFilterMinedBlock(ctx context.Context, sf *slashfilter.SlashFilter, a l
 	//  [A, C]
 	if types.CidArrsEqual(blockA.Parents, blockC.Parents) && blockA.Height == blockC.Height &&
 		types.CidArrsContains(blockB.Parents, blockC.Cid()) && !types.CidArrsContains(blockB.Parents, blockA.Cid()) {
-		return blockA, blockC, xerrors.Errorf("chain get other block error:%s", err)
+		return blockA, blockC, true, nil
 	}
 
-	return nil, nil, nil
+	log.Error("unexpectedly reached end of slashFilterMinedBlock despite fault being reported!")
+	return nil, nil, false, nil
 }
diff --git a/miner/miner.go b/miner/miner.go
index 1caaade96..9281854d7 100644
--- a/miner/miner.go
+++ b/miner/miner.go
@@ -333,7 +333,7 @@ minerLoop:
 				}
 
 				if fault {
-					log.Errorf("<!!> SLASH FILTER DETECTED FAULT due to witness %s", witness)
+					log.Errorf("<!!> SLASH FILTER DETECTED FAULT due to blocks %s and %s", b.Header.Cid(), witness)
 					continue
 				}
 			}