feat: drand: refactor round verification

Author: arajasek

chain/beacon/beacon.go

@@ -79,11 +79,21 @@ func ValidateBlockValues(bSchedule Schedule, nv network.Version, h *types.BlockH
 		return xerrors.Errorf("expected to have beacon entries in this block, but didn't find any")
 	}
 
+	// Verify that the last beacon entry's round corresponds to the round we expect
 	last := h.BeaconEntries[len(h.BeaconEntries)-1]
 	if last.Round != maxRound {
 		return xerrors.Errorf("expected final beacon entry in block to be at round %d, got %d", maxRound, last.Round)
 	}
 
+	// Verify that all other entries' rounds are as expected for the epochs in between parentEpoch and h.Height
+	for i, e := range h.BeaconEntries {
+		correctRound := b.MaxBeaconRoundForEpoch(nv, parentEpoch+abi.ChainEpoch(i)+1)
+		if e.Round != correctRound {
+			return xerrors.Errorf("unexpected beacon round %d, expected %d for epoch %d", e.Round, correctRound, parentEpoch+abi.ChainEpoch(i))
+		}
+	}
+
+	// Verify the beacon entries themselves
 	for i, e := range h.BeaconEntries {
 		if err := b.VerifyEntry(e, prevEntry); err != nil {
 			return xerrors.Errorf("beacon entry %d (%d - %x (%d)) was invalid: %w", i, e.Round, e.Data, len(e.Data), err)
@@ -132,18 +142,17 @@ func BeaconEntriesForBlock(ctx context.Context, bSchedule Schedule, nv network.V
 		prev.Round = maxRound - 1
 	}
 
-	cur := maxRound
 	var out []types.BeaconEntry
-	for cur > prev.Round {
-		rch := beacon.Entry(ctx, cur)
+	for currEpoch := epoch; currEpoch > parentEpoch; currEpoch-- {
+		currRound := beacon.MaxBeaconRoundForEpoch(nv, currEpoch)
+		rch := beacon.Entry(ctx, currRound)
 		select {
 		case resp := <-rch:
 			if resp.Err != nil {
 				return nil, xerrors.Errorf("beacon entry request returned error: %w", resp.Err)
 			}
 
 			out = append(out, resp.Entry)
-			cur = resp.Entry.Round - 1
 		case <-ctx.Done():
 			return nil, xerrors.Errorf("context timed out waiting on beacon entry to come back for epoch %d: %w", epoch, ctx.Err())
 		}

chain/beacon/drand/drand.go

@@ -170,10 +170,6 @@ func (db *DrandBeacon) VerifyEntry(curr types.BeaconEntry, prev types.BeaconEntr
 		return nil
 	}
 
-	if curr.Round != prev.Round+1 {
-		return xerrors.Errorf("invalid beacon entry: cur (%d) != prev (%d) + 1", curr.Round, prev.Round)
-	}
-
 	if be := db.getCachedValue(curr.Round); be != nil {
 		if !bytes.Equal(curr.Data, be.Data) {
 			return xerrors.New("invalid beacon value, does not match cached good value")
@@ -190,7 +186,8 @@ func (db *DrandBeacon) VerifyEntry(curr types.BeaconEntry, prev types.BeaconEntr
 	if err == nil {
 		db.cacheValue(curr)
 	}
-	return err
+
+	return nil
 }
 
 func (db *DrandBeacon) MaxBeaconRoundForEpoch(nv network.Version, filEpoch abi.ChainEpoch) uint64 {

chain/sync.go

@@ -704,25 +704,25 @@ func (syncer *Syncer) collectHeaders(ctx context.Context, incoming *types.TipSet
 	}
 
 	{
-		// ensure consistency of beacon entires
+		// ensure consistency of beacon entries
 		targetBE := incoming.Blocks()[0].BeaconEntries
 		sorted := sort.SliceIsSorted(targetBE, func(i, j int) bool {
 			return targetBE[i].Round < targetBE[j].Round
 		})
 		if !sorted {
-			syncer.bad.Add(incoming.Cids()[0], NewBadBlockReason(incoming.Cids(), "wrong order of beacon entires"))
-			return nil, xerrors.Errorf("wrong order of beacon entires")
+			syncer.bad.Add(incoming.Cids()[0], NewBadBlockReason(incoming.Cids(), "wrong order of beacon entries"))
+			return nil, xerrors.Errorf("wrong order of beacon entries")
 		}
 
 		for _, bh := range incoming.Blocks()[1:] {
 			if len(targetBE) != len(bh.BeaconEntries) {
 				// cannot mark bad, I think @Kubuxu
-				return nil, xerrors.Errorf("tipset contained different number for beacon entires")
+				return nil, xerrors.Errorf("tipset contained different number for beacon entries")
 			}
 			for i, be := range bh.BeaconEntries {
 				if targetBE[i].Round != be.Round || !bytes.Equal(targetBE[i].Data, be.Data) {
 					// cannot mark bad, I think @Kubuxu
-					return nil, xerrors.Errorf("tipset contained different beacon entires")
+					return nil, xerrors.Errorf("tipset contained different beacon entries")
 				}
 			}