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process_block_helpers.go
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process_block_helpers.go
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package blockchain
import (
"bytes"
"context"
"fmt"
"time"
"github.com/pkg/errors"
ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
"github.com/prysmaticlabs/go-ssz"
"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
"github.com/prysmaticlabs/prysm/beacon-chain/db/filters"
stateTrie "github.com/prysmaticlabs/prysm/beacon-chain/state"
"github.com/prysmaticlabs/prysm/shared/bytesutil"
"github.com/prysmaticlabs/prysm/shared/featureconfig"
"github.com/prysmaticlabs/prysm/shared/params"
"github.com/prysmaticlabs/prysm/shared/traceutil"
"github.com/sirupsen/logrus"
"go.opencensus.io/trace"
)
// CurrentSlot returns the current slot based on time.
func (s *Service) CurrentSlot() uint64 {
return uint64(time.Now().Unix()-s.genesisTime.Unix()) / params.BeaconConfig().SecondsPerSlot
}
// getBlockPreState returns the pre state of an incoming block. It uses the parent root of the block
// to retrieve the state in DB. It verifies the pre state's validity and the incoming block
// is in the correct time window.
func (s *Service) getBlockPreState(ctx context.Context, b *ethpb.BeaconBlock) (*stateTrie.BeaconState, error) {
ctx, span := trace.StartSpan(ctx, "forkchoice.getBlockPreState")
defer span.End()
// Verify incoming block has a valid pre state.
preState, err := s.verifyBlkPreState(ctx, b)
if err != nil {
return nil, err
}
// Verify block slot time is not from the feature.
if err := helpers.VerifySlotTime(preState.GenesisTime(), b.Slot); err != nil {
return nil, err
}
// Verify block is a descendent of a finalized block.
if err := s.verifyBlkDescendant(ctx, bytesutil.ToBytes32(b.ParentRoot), b.Slot); err != nil {
return nil, err
}
// Verify block is later than the finalized epoch slot.
if err := s.verifyBlkFinalizedSlot(b); err != nil {
return nil, err
}
return preState, nil
}
// verifyBlkPreState validates input block has a valid pre-state.
func (s *Service) verifyBlkPreState(ctx context.Context, b *ethpb.BeaconBlock) (*stateTrie.BeaconState, error) {
if featureconfig.Get().InitSyncCacheState {
preState := s.initSyncState[bytesutil.ToBytes32(b.ParentRoot)]
var err error
if preState == nil {
preState, err = s.beaconDB.State(ctx, bytesutil.ToBytes32(b.ParentRoot))
if err != nil {
return nil, errors.Wrapf(err, "could not get pre state for slot %d", b.Slot)
}
if preState == nil {
return nil, fmt.Errorf("pre state of slot %d does not exist", b.Slot)
}
return preState, nil // No copy needed from newly hydrated DB object.
}
return preState.Copy(), nil
}
preState, err := s.beaconDB.State(ctx, bytesutil.ToBytes32(b.ParentRoot))
if err != nil {
return nil, errors.Wrapf(err, "could not get pre state for slot %d", b.Slot)
}
if preState == nil {
return nil, fmt.Errorf("pre state of slot %d does not exist", b.Slot)
}
return preState, nil
}
// verifyBlkDescendant validates input block root is a descendant of the
// current finalized block root.
func (s *Service) verifyBlkDescendant(ctx context.Context, root [32]byte, slot uint64) error {
ctx, span := trace.StartSpan(ctx, "forkchoice.verifyBlkDescendant")
defer span.End()
finalizedBlkSigned, err := s.beaconDB.Block(ctx, bytesutil.ToBytes32(s.finalizedCheckpt.Root))
if err != nil || finalizedBlkSigned == nil || finalizedBlkSigned.Block == nil {
return errors.Wrap(err, "could not get finalized block")
}
finalizedBlk := finalizedBlkSigned.Block
bFinalizedRoot, err := s.ancestor(ctx, root[:], finalizedBlk.Slot)
if err != nil {
return errors.Wrap(err, "could not get finalized block root")
}
if !bytes.Equal(bFinalizedRoot, s.finalizedCheckpt.Root) {
err := fmt.Errorf("block from slot %d is not a descendent of the current finalized block slot %d, %#x != %#x",
slot, finalizedBlk.Slot, bytesutil.Trunc(bFinalizedRoot), bytesutil.Trunc(s.finalizedCheckpt.Root))
traceutil.AnnotateError(span, err)
return err
}
return nil
}
// verifyBlkFinalizedSlot validates input block is not less than or equal
// to current finalized slot.
func (s *Service) verifyBlkFinalizedSlot(b *ethpb.BeaconBlock) error {
finalizedSlot := helpers.StartSlot(s.finalizedCheckpt.Epoch)
if finalizedSlot >= b.Slot {
return fmt.Errorf("block is equal or earlier than finalized block, slot %d < slot %d", b.Slot, finalizedSlot)
}
return nil
}
// saveNewValidators saves newly added validator indices from the state to db.
// Does nothing if validator count has not changed.
func (s *Service) saveNewValidators(ctx context.Context, preStateValidatorCount int, postState *stateTrie.BeaconState) error {
postStateValidatorCount := postState.NumValidators()
if preStateValidatorCount != postStateValidatorCount {
indices := make([]uint64, 0)
pubKeys := make([][48]byte, 0)
for i := preStateValidatorCount; i < postStateValidatorCount; i++ {
indices = append(indices, uint64(i))
pubKeys = append(pubKeys, postState.PubkeyAtIndex(uint64(i)))
}
if err := s.beaconDB.SaveValidatorIndices(ctx, pubKeys, indices); err != nil {
return errors.Wrapf(err, "could not save activated validators: %v", indices)
}
log.WithFields(logrus.Fields{
"indices": indices,
"totalValidatorCount": postStateValidatorCount - preStateValidatorCount,
}).Trace("Validator indices saved in DB")
}
return nil
}
// rmStatesOlderThanLastFinalized deletes the states in db since last finalized check point.
func (s *Service) rmStatesOlderThanLastFinalized(ctx context.Context, startSlot uint64, endSlot uint64) error {
ctx, span := trace.StartSpan(ctx, "forkchoice.rmStatesBySlots")
defer span.End()
// Make sure start slot is not a skipped slot
for i := startSlot; i > 0; i-- {
filter := filters.NewFilter().SetStartSlot(i).SetEndSlot(i)
b, err := s.beaconDB.Blocks(ctx, filter)
if err != nil {
return err
}
if len(b) > 0 {
startSlot = i
break
}
}
// Make sure finalized slot is not a skipped slot.
for i := endSlot; i > 0; i-- {
filter := filters.NewFilter().SetStartSlot(i).SetEndSlot(i)
b, err := s.beaconDB.Blocks(ctx, filter)
if err != nil {
return err
}
if len(b) > 0 {
endSlot = i - 1
break
}
}
// Do not remove genesis state
if startSlot == 0 {
startSlot++
}
// If end slot comes less than start slot
if endSlot < startSlot {
endSlot = startSlot
}
filter := filters.NewFilter().SetStartSlot(startSlot).SetEndSlot(endSlot)
roots, err := s.beaconDB.BlockRoots(ctx, filter)
if err != nil {
return err
}
roots, err = s.filterBlockRoots(ctx, roots)
if err != nil {
return err
}
if err := s.beaconDB.DeleteStates(ctx, roots); err != nil {
return err
}
return nil
}
// shouldUpdateCurrentJustified prevents bouncing attack, by only update conflicting justified
// checkpoints in the fork choice if in the early slots of the epoch.
// Otherwise, delay incorporation of new justified checkpoint until next epoch boundary.
// See https://ethresear.ch/t/prevention-of-bouncing-attack-on-ffg/6114 for more detailed analysis and discussion.
func (s *Service) shouldUpdateCurrentJustified(ctx context.Context, newJustifiedCheckpt *ethpb.Checkpoint) (bool, error) {
if helpers.SlotsSinceEpochStarts(s.CurrentSlot()) < params.BeaconConfig().SafeSlotsToUpdateJustified {
return true, nil
}
newJustifiedBlockSigned, err := s.beaconDB.Block(ctx, bytesutil.ToBytes32(newJustifiedCheckpt.Root))
if err != nil {
return false, err
}
if newJustifiedBlockSigned == nil || newJustifiedBlockSigned.Block == nil {
return false, errors.New("nil new justified block")
}
newJustifiedBlock := newJustifiedBlockSigned.Block
if newJustifiedBlock.Slot <= helpers.StartSlot(s.justifiedCheckpt.Epoch) {
return false, nil
}
justifiedBlockSigned, err := s.beaconDB.Block(ctx, bytesutil.ToBytes32(s.justifiedCheckpt.Root))
if err != nil {
return false, err
}
if justifiedBlockSigned == nil || justifiedBlockSigned.Block == nil {
return false, errors.New("nil justified block")
}
justifiedBlock := justifiedBlockSigned.Block
b, err := s.ancestor(ctx, newJustifiedCheckpt.Root, justifiedBlock.Slot)
if err != nil {
return false, err
}
if !bytes.Equal(b, s.justifiedCheckpt.Root) {
return false, nil
}
return true, nil
}
func (s *Service) updateJustified(ctx context.Context, state *stateTrie.BeaconState) error {
cpt := state.CurrentJustifiedCheckpoint()
if cpt.Epoch > s.bestJustifiedCheckpt.Epoch {
s.bestJustifiedCheckpt = cpt
}
canUpdate, err := s.shouldUpdateCurrentJustified(ctx, cpt)
if err != nil {
return err
}
if canUpdate {
s.justifiedCheckpt = cpt
}
if featureconfig.Get().InitSyncCacheState {
justifiedRoot := bytesutil.ToBytes32(cpt.Root)
justifiedState := s.initSyncState[justifiedRoot]
// If justified state is nil, resume back to normal syncing process and save
// justified check point.
if justifiedState == nil {
return s.beaconDB.SaveJustifiedCheckpoint(ctx, cpt)
}
if err := s.beaconDB.SaveState(ctx, justifiedState, justifiedRoot); err != nil {
return errors.Wrap(err, "could not save justified state")
}
}
return s.beaconDB.SaveJustifiedCheckpoint(ctx, cpt)
}
// This saves every finalized state in DB during initial sync, needed as part of optimization to
// use cache state during initial sync in case of restart.
func (s *Service) saveInitState(ctx context.Context, state *stateTrie.BeaconState) error {
if !featureconfig.Get().InitSyncCacheState {
return nil
}
cpt := state.FinalizedCheckpoint()
finalizedRoot := bytesutil.ToBytes32(cpt.Root)
fs := s.initSyncState[finalizedRoot]
if fs == nil {
// This might happen if the client was in sync and is now re-syncing for whatever reason.
log.Warn("Initial sync cache did not have finalized state root cached")
return nil
}
if err := s.beaconDB.SaveState(ctx, fs, finalizedRoot); err != nil {
return errors.Wrap(err, "could not save state")
}
for r, oldState := range s.initSyncState {
if oldState.Slot() < cpt.Epoch*params.BeaconConfig().SlotsPerEpoch {
delete(s.initSyncState, r)
}
}
return nil
}
// This filters block roots that are not known as head root and finalized root in DB.
// It serves as the last line of defence before we prune states.
func (s *Service) filterBlockRoots(ctx context.Context, roots [][32]byte) ([][32]byte, error) {
f, err := s.beaconDB.FinalizedCheckpoint(ctx)
if err != nil {
return nil, err
}
fRoot := f.Root
h, err := s.beaconDB.HeadBlock(ctx)
if err != nil {
return nil, err
}
hRoot, err := ssz.HashTreeRoot(h.Block)
if err != nil {
return nil, err
}
filtered := make([][32]byte, 0, len(roots))
for _, root := range roots {
if bytes.Equal(root[:], fRoot[:]) || bytes.Equal(root[:], hRoot[:]) {
continue
}
filtered = append(filtered, root)
}
return filtered, nil
}
// ancestor returns the block root of an ancestry block from the input block root.
//
// Spec pseudocode definition:
// def get_ancestor(store: Store, root: Hash, slot: Slot) -> Hash:
// block = store.blocks[root]
// if block.slot > slot:
// return get_ancestor(store, block.parent_root, slot)
// elif block.slot == slot:
// return root
// else:
// return Bytes32() # root is older than queried slot: no results.
func (s *Service) ancestor(ctx context.Context, root []byte, slot uint64) ([]byte, error) {
ctx, span := trace.StartSpan(ctx, "forkchoice.ancestor")
defer span.End()
// Stop recursive ancestry lookup if context is cancelled.
if ctx.Err() != nil {
return nil, ctx.Err()
}
signed, err := s.beaconDB.Block(ctx, bytesutil.ToBytes32(root))
if err != nil {
return nil, errors.Wrap(err, "could not get ancestor block")
}
if signed == nil || signed.Block == nil {
return nil, errors.New("nil block")
}
b := signed.Block
// If we dont have the ancestor in the DB, simply return nil so rest of fork choice
// operation can proceed. This is not an error condition.
if b == nil || b.Slot < slot {
return nil, nil
}
if b.Slot == slot {
return root, nil
}
return s.ancestor(ctx, b.ParentRoot, slot)
}
// This updates justified check point in store, if the new justified is later than stored justified or
// the store's justified is not in chain with finalized check point.
//
// Spec definition:
// if (
// state.current_justified_checkpoint.epoch > store.justified_checkpoint.epoch
// or get_ancestor(store, store.justified_checkpoint.root, finalized_slot) != store.finalized_checkpoint.root
// ):
// store.justified_checkpoint = state.current_justified_checkpoint
func (s *Service) finalizedImpliesNewJustified(ctx context.Context, state *stateTrie.BeaconState) error {
finalizedBlkSigned, err := s.beaconDB.Block(ctx, bytesutil.ToBytes32(s.finalizedCheckpt.Root))
if err != nil || finalizedBlkSigned == nil || finalizedBlkSigned.Block == nil {
return errors.Wrap(err, "could not get finalized block")
}
finalizedBlk := finalizedBlkSigned.Block
anc, err := s.ancestor(ctx, s.justifiedCheckpt.Root, finalizedBlk.Slot)
if err != nil {
return err
}
// Either the new justified is later than stored justified or not in chain with finalized check pint.
if cpt := state.CurrentJustifiedCheckpoint(); cpt != nil && cpt.Epoch > s.justifiedCheckpt.Epoch || !bytes.Equal(anc, s.finalizedCheckpt.Root) {
s.justifiedCheckpt = state.CurrentJustifiedCheckpoint()
}
return nil
}
// This retrieves missing blocks from DB (ie. the blocks that couldn't received over sync) and inserts them to fork choice store.
// This is useful for block tree visualizer and additional vote accounting.
func (s *Service) fillInForkChoiceMissingBlocks(ctx context.Context, blk *ethpb.BeaconBlock, state *stateTrie.BeaconState) error {
pendingNodes := make([]*ethpb.BeaconBlock, 0)
parentRoot := bytesutil.ToBytes32(blk.ParentRoot)
slot := blk.Slot
// Fork choice only matters from last finalized slot.
higherThanFinalized := slot > helpers.StartSlot(s.finalizedCheckpt.Epoch)
// As long as parent node is not in fork choice store, and parent node is in DB.
for !s.forkChoiceStore.HasNode(parentRoot) && s.beaconDB.HasBlock(ctx, parentRoot) && higherThanFinalized {
b, err := s.beaconDB.Block(ctx, parentRoot)
if err != nil {
return err
}
pendingNodes = append(pendingNodes, b.Block)
parentRoot = bytesutil.ToBytes32(b.Block.ParentRoot)
slot = b.Block.Slot
higherThanFinalized = slot > helpers.StartSlot(s.finalizedCheckpt.Epoch)
}
// Insert parent nodes to fork choice store in reverse order.
// Lower slots should be at the end of the list.
for i := len(pendingNodes) - 1; i >= 0; i-- {
b := pendingNodes[i]
r, err := ssz.HashTreeRoot(b)
if err != nil {
return err
}
if err := s.forkChoiceStore.ProcessBlock(ctx,
b.Slot, r, bytesutil.ToBytes32(b.ParentRoot),
state.CurrentJustifiedCheckpoint().Epoch,
state.FinalizedCheckpointEpoch()); err != nil {
return errors.Wrap(err, "could not process block for proto array fork choice")
}
}
return nil
}
// The deletes input attestations from the attestation pool, so proposers don't include them in a block for the future.
func (s *Service) deletePoolAtts(atts []*ethpb.Attestation) error {
for _, att := range atts {
if helpers.IsAggregated(att) {
if err := s.attPool.DeleteAggregatedAttestation(att); err != nil {
return err
}
} else {
if err := s.attPool.DeleteUnaggregatedAttestation(att); err != nil {
return err
}
}
}
return nil
}