prysm-pulse/beacon-chain/blockchain/process_attestation_helpers.go

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package blockchain
import (
"context"
"fmt"
"strconv"
"github.com/pkg/errors"
types "github.com/prysmaticlabs/eth2-types"
"github.com/prysmaticlabs/prysm/beacon-chain/core"
"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
"github.com/prysmaticlabs/prysm/beacon-chain/core/transition"
"github.com/prysmaticlabs/prysm/beacon-chain/state"
ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
"github.com/prysmaticlabs/prysm/shared/bytesutil"
"github.com/prysmaticlabs/prysm/shared/mputil"
"github.com/prysmaticlabs/prysm/shared/params"
)
// getAttPreState retrieves the att pre state by either from the cache or the DB.
func (s *Service) getAttPreState(ctx context.Context, c *ethpb.Checkpoint) (state.BeaconState, error) {
// Use a multilock to allow scoped holding of a mutex by a checkpoint root + epoch
// allowing us to behave smarter in terms of how this function is used concurrently.
epochKey := strconv.FormatUint(uint64(c.Epoch), 10 /* base 10 */)
lock := mputil.NewMultilock(string(c.Root) + epochKey)
lock.Lock()
defer lock.Unlock()
cachedState, err := s.checkpointStateCache.StateByCheckpoint(c)
if err != nil {
return nil, errors.Wrap(err, "could not get cached checkpoint state")
}
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if cachedState != nil && !cachedState.IsNil() {
return cachedState, nil
}
baseState, err := s.cfg.StateGen.StateByRoot(ctx, bytesutil.ToBytes32(c.Root))
if err != nil {
return nil, errors.Wrapf(err, "could not get pre state for epoch %d", c.Epoch)
}
epochStartSlot, err := core.StartSlot(c.Epoch)
if err != nil {
return nil, err
}
if epochStartSlot > baseState.Slot() {
baseState, err = transition.ProcessSlots(ctx, baseState, epochStartSlot)
if err != nil {
return nil, errors.Wrapf(err, "could not process slots up to epoch %d", c.Epoch)
}
}
// Sharing the same state across caches is perfectly fine here, the fetching
// of attestation prestate is by far the most accessed state fetching pattern in
// the beacon node. An extra state instance cached isn't an issue in the bigger
// picture.
if err := s.checkpointStateCache.AddCheckpointState(c, baseState); err != nil {
return nil, errors.Wrap(err, "could not save checkpoint state to cache")
}
return baseState, nil
}
// verifyAttTargetEpoch validates attestation is from the current or previous epoch.
func (s *Service) verifyAttTargetEpoch(_ context.Context, genesisTime, nowTime uint64, c *ethpb.Checkpoint) error {
currentSlot := types.Slot((nowTime - genesisTime) / params.BeaconConfig().SecondsPerSlot)
currentEpoch := core.SlotToEpoch(currentSlot)
var prevEpoch types.Epoch
// Prevents previous epoch under flow
if currentEpoch > 1 {
prevEpoch = currentEpoch - 1
}
if c.Epoch != prevEpoch && c.Epoch != currentEpoch {
return fmt.Errorf("target epoch %d does not match current epoch %d or prev epoch %d", c.Epoch, currentEpoch, prevEpoch)
}
return nil
}
// verifyBeaconBlock verifies beacon head block is known and not from the future.
func (s *Service) verifyBeaconBlock(ctx context.Context, data *ethpb.AttestationData) error {
r := bytesutil.ToBytes32(data.BeaconBlockRoot)
b, err := s.cfg.BeaconDB.Block(ctx, r)
if err != nil {
return err
}
// If the block does not exist in db, check again if block exists in initial sync block cache.
// This could happen as the node first syncs to head.
if (b == nil || b.IsNil()) && s.hasInitSyncBlock(r) {
b = s.getInitSyncBlock(r)
}
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if err := helpers.VerifyNilBeaconBlock(b); err != nil {
return err
}
if b.Block().Slot() > data.Slot {
return fmt.Errorf("could not process attestation for future block, block.Slot=%d > attestation.Data.Slot=%d", b.Block().Slot(), data.Slot)
}
return nil
}