// 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 clique
import (
"bytes"
"encoding/json"
"sort"
"time"
"github.com/ava-labs/coreth/core/types"
"github.com/ava-labs/coreth/params"
"github.com/ava-labs/go-ethereum/common"
"github.com/ava-labs/go-ethereum/ethdb"
"github.com/ava-labs/go-ethereum/log"
lru "github.com/hashicorp/golang-lru"
)
// Vote represents a single vote that an authorized signer made to modify the
// list of authorizations.
type Vote struct {
Signer common.Address `json:"signer"` // Authorized signer that cast this vote
Block uint64 `json:"block"` // Block number the vote was cast in (expire old votes)
Address common.Address `json:"address"` // Account being voted on to change its authorization
Authorize bool `json:"authorize"` // Whether to authorize or deauthorize the voted account
}
// Tally is a simple vote tally to keep the current score of votes. Votes that
// go against the proposal aren't counted since it's equivalent to not voting.
type Tally struct {
Authorize bool `json:"authorize"` // Whether the vote is about authorizing or kicking someone
Votes int `json:"votes"` // Number of votes until now wanting to pass the proposal
}
// Snapshot is the state of the authorization voting at a given point in time.
type Snapshot struct {
config *params.CliqueConfig // 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
Signers map[common.Address]struct{} `json:"signers"` // Set of authorized signers at this moment
Recents map[uint64]common.Address `json:"recents"` // Set of recent signers for spam protections
Votes []*Vote `json:"votes"` // List of votes cast in chronological order
Tally map[common.Address]Tally `json:"tally"` // Current vote tally to avoid recalculating
}
// signersAscending implements the sort interface to allow sorting a list of addresses
type signersAscending []common.Address
func (s signersAscending) Len() int { return len(s) }
func (s signersAscending) Less(i, j int) bool { return bytes.Compare(s[i][:], s[j][:]) < 0 }
func (s signersAscending) 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 signers, so only ever use if for
// the genesis block.
func newSnapshot(config *params.CliqueConfig, sigcache *lru.ARCCache, number uint64, hash common.Hash, signers []common.Address) *Snapshot {
snap := &Snapshot{
config: config,
sigcache: sigcache,
Number: number,
Hash: hash,
Signers: make(map[common.Address]struct{}),
Recents: make(map[uint64]common.Address),
Tally: make(map[common.Address]Tally),
}
for _, signer := range signers {
snap.Signers[signer] = struct{}{}
}
return snap
}
// loadSnapshot loads an existing snapshot from the database.
func loadSnapshot(config *params.CliqueConfig, sigcache *lru.ARCCache, db ethdb.Database, hash common.Hash) (*Snapshot, error) {
blob, err := db.Get(append([]byte("clique-"), 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("clique-"), 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,
Signers: make(map[common.Address]struct{}),
Recents: make(map[uint64]common.Address),
Votes: make([]*Vote, len(s.Votes)),
Tally: make(map[common.Address]Tally),
}
for signer := range s.Signers {
cpy.Signers[signer] = struct{}{}
}
for block, signer := range s.Recents {
cpy.Recents[block] = signer
}
for address, tally := range s.Tally {
cpy.Tally[address] = tally
}
copy(cpy.Votes, s.Votes)
return cpy
}
// validVote returns whether it makes sense to cast the specified vote in the
// given snapshot context (e.g. don't try to add an already authorized signer).
func (s *Snapshot) validVote(address common.Address, authorize bool) bool {
_, signer := s.Signers[address]
return (signer && !authorize) || (!signer && authorize)
}
// cast adds a new vote into the tally.
func (s *Snapshot) cast(address common.Address, authorize bool) bool {
// Ensure the vote is meaningful
if !s.validVote(address, authorize) {
return false
}
// Cast the vote into an existing or new tally
if old, ok := s.Tally[address]; ok {
old.Votes++
s.Tally[address] = old
} else {
s.Tally[address] = Tally{Authorize: authorize, Votes: 1}
}
return true
}
// uncast removes a previously cast vote from the tally.
func (s *Snapshot) uncast(address common.Address, authorize bool) bool {
// If there's no tally, it's a dangling vote, just drop
tally, ok := s.Tally[address]
if !ok {
return false
}
// Ensure we only revert counted votes
if tally.Authorize != authorize {
return false
}
// Otherwise revert the vote
if tally.Votes > 1 {
tally.Votes--
s.Tally[address] = tally
} else {
delete(s.Tally, address)
}
return true
}
// apply creates a new authorization snapshot by applying the given headers to
// the original one.
func (s *Snapshot) apply(headers []*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()
var (
start = time.Now()
logged = time.Now()
)
for i, header := range headers {
// Remove any votes on checkpoint blocks
number := header.Number.Uint64()
if number%s.config.Epoch == 0 {
snap.Votes = nil
snap.Tally = make(map[common.Address]Tally)
}
// Delete the oldest signer from the recent list to allow it signing again
if limit := uint64(len(snap.Signers)/2 + 1); number >= limit {
delete(snap.Recents, number-limit)
}
// Resolve the authorization key and check against signers
signer, err := ecrecover(header, s.sigcache)
if err != nil {
return nil, err
}
if _, ok := snap.Signers[signer]; !ok {
return nil, errUnauthorizedSigner
}
for _, recent := range snap.Recents {
if recent == signer {
return nil, errRecentlySigned
}
}
snap.Recents[number] = signer
// Header authorized, discard any previous votes from the signer
for i, vote := range snap.Votes {
if vote.Signer == signer && vote.Address == header.Coinbase {
// Uncast the vote from the cached tally
snap.uncast(vote.Address, vote.Authorize)
// Uncast the vote from the chronological list
snap.Votes = append(snap.Votes[:i], snap.Votes[i+1:]...)
break // only one vote allowed
}
}
// Tally up the new vote from the signer
var authorize bool
switch {
case bytes.Equal(header.Nonce[:], nonceAuthVote):
authorize = true
case bytes.Equal(header.Nonce[:], nonceDropVote):
authorize = false
default:
return nil, errInvalidVote
}
if snap.cast(header.Coinbase, authorize) {
snap.Votes = append(snap.Votes, &Vote{
Signer: signer,
Block: number,
Address: header.Coinbase,
Authorize: authorize,
})
}
// If the vote passed, update the list of signers
if tally := snap.Tally[header.Coinbase]; tally.Votes > len(snap.Signers)/2 {
if tally.Authorize {
snap.Signers[header.Coinbase] = struct{}{}
} else {
delete(snap.Signers, header.Coinbase)
// Signer list shrunk, delete any leftover recent caches
if limit := uint64(len(snap.Signers)/2 + 1); number >= limit {
delete(snap.Recents, number-limit)
}
// Discard any previous votes the deauthorized signer cast
for i := 0; i < len(snap.Votes); i++ {
if snap.Votes[i].Signer == header.Coinbase {
// Uncast the vote from the cached tally
snap.uncast(snap.Votes[i].Address, snap.Votes[i].Authorize)
// Uncast the vote from the chronological list
snap.Votes = append(snap.Votes[:i], snap.Votes[i+1:]...)
i--
}
}
}
// Discard any previous votes around the just changed account
for i := 0; i < len(snap.Votes); i++ {
if snap.Votes[i].Address == header.Coinbase {
snap.Votes = append(snap.Votes[:i], snap.Votes[i+1:]...)
i--
}
}
delete(snap.Tally, header.Coinbase)
}
// If we're taking too much time (ecrecover), notify the user once a while
if time.Since(logged) > 8*time.Second {
log.Info("Reconstructing voting history", "processed", i, "total", len(headers), "elapsed", common.PrettyDuration(time.Since(start)))
logged = time.Now()
}
}
if time.Since(start) > 8*time.Second {
log.Info("Reconstructed voting history", "processed", len(headers), "elapsed", common.PrettyDuration(time.Since(start)))
}
snap.Number += uint64(len(headers))
snap.Hash = headers[len(headers)-1].Hash()
return snap, nil
}
// signers retrieves the list of authorized signers in ascending order.
func (s *Snapshot) signers() []common.Address {
sigs := make([]common.Address, 0, len(s.Signers))
for sig := range s.Signers {
sigs = append(sigs, sig)
}
sort.Sort(signersAscending(sigs))
return sigs
}
// inturn returns if a signer at a given block height is in-turn or not.
func (s *Snapshot) inturn(number uint64, signer common.Address) bool {
signers, offset := s.signers(), 0
for offset < len(signers) && signers[offset] != signer {
offset++
}
return (number % uint64(len(signers))) == uint64(offset)
}