prysm-pulse/beacon-chain/sync/validate_voluntary_exit.go

package sync

import (
	"context"
	"fmt"
	"time"

	"github.com/gogo/protobuf/proto"
	"github.com/karlseguin/ccache"
	"github.com/prysmaticlabs/prysm/beacon-chain/core/blocks"
	"github.com/prysmaticlabs/prysm/beacon-chain/p2p"
	ethpb "github.com/prysmaticlabs/prysm/proto/eth/v1alpha1"
)

// seenExits tracks exits we've already seen to prevent feedback loop.
var seenExits = ccache.New(ccache.Configure())

func exitCacheKey(exit *ethpb.VoluntaryExit) string {
	return fmt.Sprintf("%d-%d", exit.Epoch, exit.ValidatorIndex)
}

// Clients who receive a voluntary exit on this topic MUST validate the conditions within process_voluntary_exit before
// forwarding it across the network.
func (r *RegularSync) validateVoluntaryExit(ctx context.Context, msg proto.Message, p p2p.Broadcaster) bool {
	exit := msg.(*ethpb.VoluntaryExit)
	if seenExits.Get(exitCacheKey(exit)) != nil {
		return false
	}

	state, err := r.db.HeadState(ctx)
	if err != nil {
		log.WithError(err).Error("Failed to get head state")
		return false
	}
	if err := blocks.VerifyExit(state, exit); err != nil {
		log.WithError(err).Warn("Received invalid voluntary exit")
		return false
	}
	seenExits.Set(exitCacheKey(exit), true /*value*/, 365*24*time.Hour /*TTL*/)

	if err := p.Broadcast(exit); err != nil {
		log.WithError(err).Error("Failed to propagate voluntary exit")
	}
	return true
}