/
snapshot.go
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/
snapshot.go
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// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package congress
import (
"bytes"
"encoding/json"
"sort"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/consensus"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/params"
lru "github.com/hashicorp/golang-lru"
)
// Snapshot is the state of the authorization voting at a given point in time.
type Snapshot struct {
config *params.CongressConfig // Consensus engine parameters to fine tune behavior
sigcache *lru.ARCCache // Cache of recent block signatures to speed up ecrecover
Number uint64 `json:"number"` // Block number where the snapshot was created
Hash common.Hash `json:"hash"` // Block hash where the snapshot was created
Validators map[common.Address]struct{} `json:"validators"` // Set of authorized validators at this moment
Recents map[uint64]common.Address `json:"recents"` // Set of recent validators for spam protections
}
// validatorsAscending implements the sort interface to allow sorting a list of addresses
type validatorsAscending []common.Address
func (s validatorsAscending) Len() int { return len(s) }
func (s validatorsAscending) Less(i, j int) bool { return bytes.Compare(s[i][:], s[j][:]) < 0 }
func (s validatorsAscending) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
// newSnapshot creates a new snapshot with the specified startup parameters. This
// method does not initialize the set of recent validators, so only ever use if for
// the genesis block.
func newSnapshot(config *params.CongressConfig, sigcache *lru.ARCCache, number uint64, hash common.Hash, validators []common.Address) *Snapshot {
snap := &Snapshot{
config: config,
sigcache: sigcache,
Number: number,
Hash: hash,
Validators: make(map[common.Address]struct{}),
Recents: make(map[uint64]common.Address),
}
for _, validator := range validators {
snap.Validators[validator] = struct{}{}
}
return snap
}
// loadSnapshot loads an existing snapshot from the database.
func loadSnapshot(config *params.CongressConfig, sigcache *lru.ARCCache, db ethdb.Database, hash common.Hash) (*Snapshot, error) {
blob, err := db.Get(append([]byte("congress-"), hash[:]...))
if err != nil {
return nil, err
}
snap := new(Snapshot)
if err := json.Unmarshal(blob, snap); err != nil {
return nil, err
}
snap.config = config
snap.sigcache = sigcache
return snap, nil
}
// store inserts the snapshot into the database.
func (s *Snapshot) store(db ethdb.Database) error {
blob, err := json.Marshal(s)
if err != nil {
return err
}
return db.Put(append([]byte("congress-"), s.Hash[:]...), blob)
}
// copy creates a deep copy of the snapshot, though not the individual votes.
func (s *Snapshot) copy() *Snapshot {
cpy := &Snapshot{
config: s.config,
sigcache: s.sigcache,
Number: s.Number,
Hash: s.Hash,
Validators: make(map[common.Address]struct{}),
Recents: make(map[uint64]common.Address),
}
for validator := range s.Validators {
cpy.Validators[validator] = struct{}{}
}
for block, validator := range s.Recents {
cpy.Recents[block] = validator
}
return cpy
}
// apply creates a new authorization snapshot by applying the given headers to
// the original one.
func (s *Snapshot) apply(headers []*types.Header, chain consensus.ChainHeaderReader, parents []*types.Header) (*Snapshot, error) {
// Allow passing in no headers for cleaner code
if len(headers) == 0 {
return s, nil
}
// Sanity check that the headers can be applied
for i := 0; i < len(headers)-1; i++ {
if headers[i+1].Number.Uint64() != headers[i].Number.Uint64()+1 {
return nil, errInvalidVotingChain
}
}
if headers[0].Number.Uint64() != s.Number+1 {
return nil, errInvalidVotingChain
}
// Iterate through the headers and create a new snapshot
snap := s.copy()
for _, header := range headers {
// Remove any votes on checkpoint blocks
number := header.Number.Uint64()
// Delete the oldest validator from the recent list to allow it signing again
if limit := uint64(len(snap.Validators)/2 + 1); number >= limit {
delete(snap.Recents, number-limit)
}
// Resolve the authorization key and check against validators
validator, err := ecrecover(header, s.sigcache)
if err != nil {
return nil, err
}
if _, ok := snap.Validators[validator]; !ok {
return nil, errUnauthorizedValidator
}
for _, recent := range snap.Recents {
if recent == validator {
return nil, errRecentlySigned
}
}
snap.Recents[number] = validator
// update validators at the first block at epoch
if number > 0 && number%s.config.Epoch == 0 {
checkpointHeader := header
// get validators from headers and use that for new validator set
validators := make([]common.Address, (len(checkpointHeader.Extra)-extraVanity-extraSeal)/common.AddressLength)
for i := 0; i < len(validators); i++ {
copy(validators[i][:], checkpointHeader.Extra[extraVanity+i*common.AddressLength:])
}
newValidators := make(map[common.Address]struct{})
for _, validator := range validators {
newValidators[validator] = struct{}{}
}
// need to delete recorded recent seen blocks if necessary, it may pause whole chain when validators length
// decreases.
limit := uint64(len(newValidators)/2 + 1)
for i := 0; i < len(snap.Validators)/2-len(newValidators)/2; i++ {
delete(snap.Recents, number-limit-uint64(i))
}
snap.Validators = newValidators
}
}
snap.Number += uint64(len(headers))
snap.Hash = headers[len(headers)-1].Hash()
return snap, nil
}
// validators retrieves the list of authorized validators in ascending order.
func (s *Snapshot) validators() []common.Address {
sigs := make([]common.Address, 0, len(s.Validators))
for sig := range s.Validators {
sigs = append(sigs, sig)
}
sort.Sort(validatorsAscending(sigs))
return sigs
}
// inturn returns if a validator at a given block height is in-turn or not.
func (s *Snapshot) inturn(number uint64, validator common.Address) bool {
validators, offset := s.validators(), 0
for offset < len(validators) && validators[offset] != validator {
offset++
}
return (number % uint64(len(validators))) == uint64(offset)
}