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clique.go
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clique.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 clique implements the proof-of-authority consensus engine.
package clique
import (
"bytes"
"context"
"errors"
"fmt"
"math/big"
"math/rand"
"sync"
"time"
"github.com/hashicorp/golang-lru"
"go.opencensus.io/trace"
"github.com/gochain-io/gochain/accounts"
"github.com/gochain-io/gochain/common"
"github.com/gochain-io/gochain/common/hexutil"
"github.com/gochain-io/gochain/consensus"
"github.com/gochain-io/gochain/core/types"
"github.com/gochain-io/gochain/crypto"
"github.com/gochain-io/gochain/crypto/sha3"
"github.com/gochain-io/gochain/ethdb"
"github.com/gochain-io/gochain/log"
"github.com/gochain-io/gochain/params"
"github.com/gochain-io/gochain/rlp"
"github.com/gochain-io/gochain/rpc"
)
const (
checkpointInterval = 1024 // Number of blocks after which to save the vote snapshot to the database
inmemorySnapshots = 128 // Number of recent vote snapshots to keep in memory
inmemorySignatures = 4096 // Number of recent block signatures to keep in memory
wiggleTime = 200 * time.Millisecond // Delay step for out-of-turn signers.
)
// Clique proof-of-authority protocol constants.
var (
signatureLength = 65
extraVanity = 32 // Fixed number of extra-data prefix bytes reserved for signer vanity.
extraPropose = common.AddressLength + 1 // Number of extra-data suffix bytes reserved for a proposal vote.
voterElection byte = 0xff
signerElection byte = 0x00
nonceAuthVote = hexutil.MustDecode("0xffffffffffffffff") // Magic nonce number to vote on adding a new signer
nonceDropVote = hexutil.MustDecode("0x0000000000000000") // Magic nonce number to vote on removing a signer.
uncleHash = types.CalcUncleHash(nil) // Always Keccak256(RLP([])) as uncles are meaningless outside of PoW.
)
// Various error messages to mark blocks invalid. These should be private to
// prevent engine specific errors from being referenced in the remainder of the
// codebase, inherently breaking if the engine is swapped out. Please put common
// error types into the consensus package.
var (
// errUnknownBlock is returned when the list of signers is requested for a block
// that is not part of the local blockchain.
errUnknownBlock = errors.New("unknown block")
// errInvalidCheckpointBeneficiary is returned if a checkpoint/epoch transition
// block has a beneficiary set to non-zeroes.
errInvalidCheckpointBeneficiary = errors.New("beneficiary in checkpoint block non-zero")
// errInvalidVote is returned if a nonce value is something else that the two
// allowed constants of 0x00..0 or 0xff..f.
errInvalidVote = errors.New("vote nonce not 0x00..0 or 0xff..f")
// errInvalidCheckpointVote is returned if a checkpoint/epoch transition block
// has a vote nonce set to non-zeroes.
errInvalidCheckpointVote = errors.New("vote nonce in checkpoint block non-zero")
// errMissingVanity is returned if a block's extra-data section is shorter than
// 32 bytes, which is required to store the signer vanity.
errMissingVanity = errors.New("extra-data 32 byte vanity prefix missing")
// errMissingSignature is returned if a block's signer section doesn't seem
// to contain a 65 byte secp256k1 signature.
errMissingSignature = errors.New("signer signature missing")
// errMissingSigners is returned if a block's signers section is empty
errMissingSigners = errors.New("signers list missing")
// errMissingVoters is returned if a block's voters section is empty
errMissingVoters = errors.New("voters list missing")
// errInvalidCheckpointSigners is returned if a checkpoint block contains an
// invalid list of signers
errInvalidCheckpointSigners = errors.New("invalid signer list on checkpoint block")
// errInvalidCheckpointVoters is returned if a checkpoint block contains an
// invalid list of voters
errInvalidCheckpointVoters = errors.New("invalid voter list on checkpoint block")
// errInvalidMixDigest is returned if a block's mix digest is non-zero.
errInvalidMixDigest = errors.New("non-zero mix digest")
// errInvalidUncleHash is returned if a block contains an non-empty uncle list.
errInvalidUncleHash = errors.New("non empty uncle hash")
// errInvalidDifficulty is returned if the difficulty of a block is missing or 0,
// or if the value does not match the turn of the signer.
errInvalidDifficulty = errors.New("invalid difficulty")
// ErrInvalidTimestamp is returned if the timestamp of a block is lower than
// the previous block's timestamp + the minimum block period.
ErrInvalidTimestamp = errors.New("invalid timestamp")
// errInvalidVotingChain is returned if an authorization list is attempted to
// be modified via out-of-range or non-contiguous headers.
errInvalidVotingChain = errors.New("invalid voting chain")
// errWaitTransactions is returned if an empty block is attempted to be sealed
// on an instant chain (0 second period). It's important to refuse these as the
// block reward is zero, so an empty block just bloats the chain... fast.
errWaitTransactions = errors.New("waiting for transactions")
)
// sigHash returns the hash which is used as input for the proof-of-authority
// signing. It is the hash of the entire header apart from the 65 byte signature
// contained at the end of the extra data.
//
// Note, the method requires the extra data to be at least 65 bytes, otherwise it
// panics. This is done to avoid accidentally using both forms (signature present
// or not), which could be abused to produce different hashes for the same header.
func sigHash(ctx context.Context, header *types.Header) (hash common.Hash) {
hasher := sha3.NewKeccak256SingleSum()
rlp.EncodeCtx(ctx, hasher, []interface{}{
header.ParentHash,
header.UncleHash,
header.Coinbase,
header.Root,
header.TxHash,
header.ReceiptHash,
header.Bloom,
header.Difficulty,
header.Number,
header.GasLimit,
header.GasUsed,
header.Time,
header.Signers,
header.Voters,
header.Extra, // Yes, this will panic if extra is too short
header.MixDigest,
header.Nonce,
})
hasher.Sum(hash[:0])
return hash
}
// ecrecover extracts the Ethereum account address from a signed header.
func ecrecover(ctx context.Context, header *types.Header, sigcache *lru.ARCCache) (common.Address, error) {
// If the signature's already cached, return that
hash := header.Hash()
if address, known := sigcache.Get(hash); known {
return address.(common.Address), nil
}
// Retrieve the signature from the header
if len(header.Signer) < signatureLength {
return common.Address{}, errMissingSignature
}
signature := header.Signer
// Recover the public key and the Ethereum address
pubkey, err := crypto.Ecrecover(sigHash(ctx, header).Bytes(), signature)
if err != nil {
return common.Address{}, err
}
h := crypto.Keccak256Hash(pubkey[1:])
var signer common.Address
copy(signer[:], h[12:])
sigcache.Add(hash, signer)
return signer, nil
}
type propose struct {
Authorize bool
VoterElection bool
}
// Clique is the proof-of-authority consensus engine proposed to support the
// Ethereum testnet following the Ropsten attacks.
type Clique struct {
config *params.CliqueConfig // Consensus engine configuration parameters
db ethdb.Database // Database to store and retrieve snapshot checkpoints
recents *lru.ARCCache // Snapshots for recent block to speed up reorgs
signatures *lru.ARCCache // Signatures of recent blocks to speed up mining
proposals map[common.Address]propose // Current list of proposals we are pushing
signer common.Address // Address of the signing key
signFn consensus.SignerFn // Signer function to authorize hashes with
lock sync.RWMutex // Protects the signer fields
}
// New creates a Clique proof-of-authority consensus engine with the initial
// signers set to the ones provided by the user.
func New(config *params.CliqueConfig, db ethdb.Database) *Clique {
// Set any missing consensus parameters to their defaults
conf := *config
if conf.Epoch == 0 {
conf.Epoch = params.DefaultCliqueEpoch
}
// Allocate the snapshot caches and create the engine
recents, _ := lru.NewARC(inmemorySnapshots)
signatures, _ := lru.NewARC(inmemorySignatures)
return &Clique{
config: &conf,
db: db,
recents: recents,
signatures: signatures,
proposals: make(map[common.Address]propose),
}
}
// Author implements consensus.Engine, returning the address recovered
// from the signature in the header's extra-data section.
func (c *Clique) Author(ctx context.Context, header *types.Header) (common.Address, error) {
return ecrecover(ctx, header, c.signatures)
}
// VerifyHeader checks whether a header conforms to the consensus rules.
func (c *Clique) VerifyHeader(ctx context.Context, chain consensus.ChainReader, header *types.Header) error {
ctx, span := trace.StartSpan(ctx, "Clique.VerifyHeader")
defer span.End()
if err := c.verifyHeader(ctx, chain, header, nil); err != nil {
return err
}
if err := c.verifyCascadingFields(ctx, chain, header, nil); err != nil {
return err
}
return c.verifySeal(ctx, chain, header, nil)
}
// VerifyHeaders is similar to VerifyHeader, but verifies a batch of headers. The
// method returns a quit channel to abort the operations and a results channel to
// retrieve the async verifications (the order is that of the input slice).
func (c *Clique) VerifyHeaders(ctx context.Context, chain consensus.ChainReader, headers []*types.Header) (chan<- struct{}, <-chan error) {
verify := []verifyFn{c.verifyHeader, c.verifyCascadingFields, c.verifySeal}
return c.verifyHeaders(ctx, chain, headers, verify)
}
func (c *Clique) verifyHeaders(ctx context.Context, chain consensus.ChainReader, headers []*types.Header, verify []verifyFn) (chan<- struct{}, <-chan error) {
abort := make(chan struct{})
results := make(chan error, len(headers))
go func() {
ctx, span := trace.StartSpan(context.Background(), "Clique.verifyHeaders")
defer span.End()
defer close(results)
for i, header := range headers {
parents := headers[:i]
var err error
for _, fn := range verify {
err = fn(ctx, chain, header, parents)
if err != nil {
break
}
}
select {
case <-abort:
return
case results <- err:
}
}
}()
return abort, results
}
type verifyFn func(ctx context.Context, chain consensus.ChainReader, header *types.Header, parents []*types.Header) error
// verifyHeader checks whether a header conforms to the consensus rules.The
// caller may optionally pass in a batch of parents (ascending order) to avoid
// looking those up from the database. This is useful for concurrently verifying
// a batch of new headers.
func (c *Clique) verifyHeader(ctx context.Context, chain consensus.ChainReader, header *types.Header, parents []*types.Header) error {
ctx, span := trace.StartSpan(ctx, "Clique.verifyHeader")
defer span.End()
if header.Number == nil {
return errUnknownBlock
}
number := header.Number.Uint64()
// Checkpoint blocks need to enforce zero beneficiary
checkpoint := (number % c.config.Epoch) == 0
if checkpoint && len(header.Extra) > extraVanity {
return errInvalidCheckpointBeneficiary
}
// Nonces must be 0x00..0 or 0xff..f, zeroes enforced on checkpoints
if !bytes.Equal(header.Nonce[:], nonceAuthVote) && !bytes.Equal(header.Nonce[:], nonceDropVote) {
return errInvalidVote
}
if checkpoint && !bytes.Equal(header.Nonce[:], nonceDropVote) {
return errInvalidCheckpointVote
}
// Check that the extra-data contains the vanity
//if len(header.Extra) < extraVanity {
// return errMissingVanity
//}
// Check if header contains signers and voters
if checkpoint {
if len(header.Signers) < 1 {
return errMissingSigners
}
if len(header.Voters) < 1 {
return errMissingVoters
}
}
// Check if block was signed
if len(header.Signer) < signatureLength {
return errMissingSignature
}
// Ensure that the mix digest is zero as we don't have fork protection currently
if header.MixDigest != (common.Hash{}) {
return errInvalidMixDigest
}
// Ensure that the block doesn't contain any uncles which are meaningless in PoA
if header.UncleHash != uncleHash {
return errInvalidUncleHash
}
if number > 0 {
// Ensure that the block's difficulty is meaningful (may not be correct at this point)
if header.Difficulty == nil || header.Difficulty.Uint64() == 0 {
return errInvalidDifficulty
}
}
// If all checks passed, validate any special fields for hard forks
if err := verifyForkHashes(chain.Config(), header); err != nil {
return err
}
return nil
}
// verifyForkHashes verifies that blocks conforming to network hard-forks do have
// the correct hashes, to avoid clients going off on different chains. This is an
// optional feature.
func verifyForkHashes(config *params.ChainConfig, header *types.Header) error {
// If the homestead reprice hash is set, validate it
if config.EIP150Block != nil && config.EIP150Block.Cmp(header.Number) == 0 {
if config.EIP150Hash != (common.Hash{}) && config.EIP150Hash != header.Hash() {
return fmt.Errorf("homestead gas reprice fork: have 0x%x, want 0x%x", header.Hash(), config.EIP150Hash)
}
}
// All ok, return
return nil
}
// verifyCascadingFields verifies all the header fields that are not standalone,
// rather depend on a batch of previous headers. The caller may optionally pass
// in a batch of parents (ascending order) to avoid looking those up from the
// database. This is useful for concurrently verifying a batch of new headers.
func (c *Clique) verifyCascadingFields(ctx context.Context, chain consensus.ChainReader, header *types.Header, parents []*types.Header) error {
ctx, span := trace.StartSpan(ctx, "Clique.verifyCascadingFields")
defer span.End()
// Don't waste time checking blocks from the future
if header.Time.Cmp(big.NewInt(time.Now().Unix())) > 0 {
return consensus.ErrFutureBlock
}
// The genesis block is the always valid dead-end
number := header.Number.Uint64()
if number == 0 {
return nil
}
// Ensure that the block's timestamp isn't too close to it's parent
var parent *types.Header
if len(parents) > 0 {
parent = parents[len(parents)-1]
} else {
parent = chain.GetHeader(header.ParentHash, number-1)
}
if parent == nil || parent.Number.Uint64() != number-1 || parent.Hash() != header.ParentHash {
return consensus.ErrUnknownAncestor
}
if parent.Time.Uint64()+c.config.Period > header.Time.Uint64() {
return ErrInvalidTimestamp
}
// Retrieve the snapshot needed to verify this header and cache it
snap, err := c.snapshot(ctx, chain, number-1, header.ParentHash, parents)
if err != nil {
return err
}
// If the block is a checkpoint block, verify the signer list
if number%c.config.Epoch == 0 {
for i, signer := range snap.signers() {
if signer != header.Signers[i] {
return errInvalidCheckpointSigners
}
}
for i, voter := range snap.voters() {
if voter != header.Voters[i] {
return errInvalidCheckpointVoters
}
}
}
return nil
}
// snapshot retrieves the authorization snapshot at a given point in time.
func (c *Clique) snapshot(ctx context.Context, chain consensus.ChainReader, number uint64, hash common.Hash, parents []*types.Header) (*Snapshot, error) {
ctx, span := trace.StartSpan(ctx, "Clique.snapshot")
defer span.End()
// Search for a snapshot in memory or on disk for checkpoints
var (
headers []*types.Header
snap *Snapshot
)
for snap == nil {
// If an in-memory snapshot was found, use that
if s, ok := c.recents.Get(hash); ok {
snap = s.(*Snapshot)
break
}
// If an on-disk checkpoint snapshot can be found, use that
if number%checkpointInterval == 0 {
if s, err := loadSnapshot(c.config, c.signatures, c.db, hash); err == nil {
log.Trace("Loaded voting snapshot form disk", "number", number, "hash", hash)
snap = s
break
}
}
// If we're at block zero, make a snapshot
if number == 0 {
genesis := chain.GetHeaderByNumber(0)
if err := c.VerifyHeader(ctx, chain, genesis); err != nil {
return nil, err
}
snap = newGenesisSnapshot(c.config, c.signatures, 0, genesis.Hash(), genesis.Signers, genesis.Voters)
if err := snap.store(c.db); err != nil {
return nil, err
}
log.Trace("Stored genesis voting snapshot to disk")
break
}
// No snapshot for this header, gather the header and move backward
var header *types.Header
if len(parents) > 0 {
// If we have explicit parents, pick from there (enforced)
header = parents[len(parents)-1]
if header.Hash() != hash || header.Number.Uint64() != number {
return nil, consensus.ErrUnknownAncestor
}
parents = parents[:len(parents)-1]
} else {
// No explicit parents (or no more left), reach out to the database
header = chain.GetHeader(hash, number)
if header == nil {
return nil, consensus.ErrUnknownAncestor
}
}
headers = append(headers, header)
number, hash = number-1, header.ParentHash
}
// Previous snapshot found, apply any pending headers on top of it
for i := 0; i < len(headers)/2; i++ {
headers[i], headers[len(headers)-1-i] = headers[len(headers)-1-i], headers[i]
}
snap, err := snap.apply(ctx, headers)
if err != nil {
return nil, err
}
c.recents.Add(snap.Hash, snap)
// If we've generated a new checkpoint snapshot, save to disk
if snap.Number%checkpointInterval == 0 && len(headers) > 0 {
if err = snap.store(c.db); err != nil {
return nil, err
}
log.Trace("Stored voting snapshot to disk", "number", snap.Number, "hash", snap.Hash)
}
return snap, err
}
// verifySeal checks whether the signature contained in the header satisfies the
// consensus protocol requirements. The method accepts an optional list of parent
// headers that aren't yet part of the local blockchain to generate the snapshots
// from.
func (c *Clique) verifySeal(ctx context.Context, chain consensus.ChainReader, header *types.Header, parents []*types.Header) error {
ctx, span := trace.StartSpan(ctx, "Clique.verifySeal")
defer span.End()
// The genesis block is the always valid dead-end
number := header.Number.Uint64()
if number == 0 {
return nil
}
// Retrieve the snapshot needed to verify this header and cache it
snap, err := c.snapshot(ctx, chain, number-1, header.ParentHash, parents)
if err != nil {
return err
}
// Resolve the authorization key and check against signers
signer, err := ecrecover(ctx, header, c.signatures)
if err != nil {
return err
}
lastBlockSigned, authorized := snap.Signers[signer]
if !authorized {
return fmt.Errorf("%s not authorized to sign", signer.Hex())
}
if lastBlockSigned > 0 {
if next := snap.nextSignableBlockNumber(lastBlockSigned); number < next {
return fmt.Errorf("%s not authorized to sign %d: signed recently %d, next eligible signature %d", signer.Hex(), number, lastBlockSigned, next)
}
}
if header.Difficulty.Uint64() != CalcDifficulty(snap.Signers, signer) {
return errInvalidDifficulty
}
return nil
}
// Prepare implements consensus.Engine, preparing all the consensus fields of the
// header for running the transactions on top.
func (c *Clique) Prepare(ctx context.Context, chain consensus.ChainReader, header *types.Header) (*time.Time, error) {
ctx, span := trace.StartSpan(ctx, "Clique.Prepare")
defer span.End()
// If the block isn't a checkpoint, cast a random vote (good enough for now)
header.Nonce = types.BlockNonce{}
number := header.Number.Uint64()
// Assemble the voting snapshot to check which votes make sense
snap, err := c.snapshot(ctx, chain, number-1, header.ParentHash, nil)
if err != nil {
return nil, err
}
if c.signer != (common.Address{}) {
// Check that we can sign.
if _, ok := snap.Signers[c.signer]; !ok {
return nil, fmt.Errorf("not authorized to sign: %s", c.signer.Hex())
}
}
// Calculate and validate the difficulty.
diff := CalcDifficulty(snap.Signers, c.signer)
if c.signer != (common.Address{}) && diff == 0 {
return nil, fmt.Errorf("signed too recently: %s", c.signer.Hex())
}
header.Difficulty = new(big.Int).SetUint64(diff)
header.Extra = ExtraEnsureVanity(header.Extra)
//if not checkpoint
if number%c.config.Epoch != 0 {
c.lock.RLock()
// Gather all the proposals that make sense voting on
addresses := make([]common.Address, 0, len(c.proposals))
for address, propose := range c.proposals {
if snap.validVote(address, propose.Authorize, propose.VoterElection) {
addresses = append(addresses, address)
}
}
// If there's pending proposals, cast a vote on them
if len(addresses) > 0 {
candidate := addresses[rand.Intn(len(addresses))]
propose := c.proposals[candidate]
header.Extra = ExtraAppendVote(header.Extra, candidate, propose.VoterElection)
if propose.Authorize {
copy(header.Nonce[:], nonceAuthVote)
} else {
copy(header.Nonce[:], nonceDropVote)
}
log.Info("propose", "Candidate", candidate, "vote", propose.Authorize, "voterElection", propose.VoterElection)
}
c.lock.RUnlock()
}
if number%c.config.Epoch == 0 {
header.Signers = snap.signers()
header.Voters = snap.voters()
}
// Mix digest is reserved for now, set to empty
header.MixDigest = common.Hash{}
// Ensure the timestamp has the correct delay
parent := chain.GetHeader(header.ParentHash, number-1)
if parent == nil {
return nil, consensus.ErrUnknownAncestor
}
header.Time = new(big.Int).Add(parent.Time, new(big.Int).SetUint64(c.config.Period))
if header.Time.Int64() < time.Now().Unix() {
header.Time = big.NewInt(time.Now().Unix())
}
var deadline *time.Time
if c.config.Period != 0 {
t := time.Unix(header.Time.Int64(), 0)
deadline = &t
}
return deadline, nil
}
func (c *Clique) Authorize(signer common.Address, signFn consensus.SignerFn) {
c.lock.Lock()
defer c.lock.Unlock()
c.signer = signer
c.signFn = signFn
}
// Seal implements consensus.Engine, attempting to create a sealed block using
// the local signing credentials.
func (c *Clique) Seal(ctx context.Context, chain consensus.ChainReader, block *types.Block, stop <-chan struct{}) (*types.Block, error) {
ctx, span := trace.StartSpan(ctx, "Clique.Seal")
defer span.End()
header := block.Header()
// Sealing the genesis block is not supported
number := header.Number.Uint64()
if number == 0 {
return nil, errUnknownBlock
}
// For 0-period chains, refuse to seal empty blocks (no reward but would spin sealing)
if c.config.Period == 0 && len(block.Transactions()) == 0 {
return nil, errWaitTransactions
}
// Don't hold the signer fields for the entire sealing procedure
c.lock.RLock()
signer, signFn := c.signer, c.signFn
c.lock.RUnlock()
// Bail out if we're unauthorized to sign a block
snap, err := c.snapshot(ctx, chain, number-1, header.ParentHash, nil)
if err != nil {
return nil, err
}
lastBlockSigned, authorized := snap.Signers[signer]
if !authorized {
return nil, fmt.Errorf("%s not authorized to sign", signer.Hex())
}
if lastBlockSigned > 0 {
if next := snap.nextSignableBlockNumber(lastBlockSigned); number < next {
log.Info("Signed recently, must wait for others", "number", number, "signed", lastBlockSigned, "next", next)
<-stop
return nil, nil
}
}
// The in-turn signer, with difficulty n, will not delay.
var delay time.Duration
n := uint64(len(header.Signers))
if diff := header.Difficulty.Uint64(); diff < n {
// Out-of-turn to sign, delay it a bit.
// Since diff is in the range [n/2+1,n], delay is [wiggleTime,n/2*wiggleTime].
delay = time.Duration(n-diff) * wiggleTime
}
if until := time.Unix(header.Time.Int64(), delay.Nanoseconds()); time.Now().Before(until) {
// Need to wait.
if delay == 0 {
log.Trace("Waiting for slot to sign and propagate", "number", number, "until", header.Time.Int64())
} else {
log.Trace("Out-of-turn signing requested - waiting for slot to sign and propagate after delay",
"number", number, "until", header.Time.Int64(), "delay", common.PrettyDuration(delay))
}
if wait := until.Sub(time.Now()); wait > 0 {
select {
case <-stop:
return nil, nil
case <-time.After(wait):
}
}
}
// Sign all the things!
sighash, err := signFn(accounts.Account{Address: signer}, sigHash(ctx, header).Bytes())
if err != nil {
return nil, err
}
header.Signer = sighash
return block.WithSeal(header), nil
}
// CalcDifficulty returns the difficulty for signer, given all signers and their most recently signed block numbers,
// with 0 meaning 'has not signed'. With n signers, it will always return values from n/2+1 to n, inclusive, or 0.
//
// Difficulty for ineligible signers (too recent) is always 0. For eligible signers, difficulty is defined as 1 plus the
// number of lower priority signers, with more recent signers have lower priority. If multiple signers have not yet
// signed (0), then addresses which lexicographically sort later have lower priority.
func CalcDifficulty(lastSigned map[common.Address]uint64, signer common.Address) uint64 {
last := lastSigned[signer]
difficulty := 1
// Note that signer's entry is implicitly skipped by the condition in both loops, so it never counts itself.
if last > 0 {
for _, n := range lastSigned {
if n > last {
difficulty++
}
}
} else {
// Haven't signed yet. If there are others, fall back to address sort.
for addr, n := range lastSigned {
if n > 0 || bytes.Compare(addr[:], signer[:]) > 0 {
difficulty++
}
}
}
if difficulty <= len(lastSigned)/2 {
// [1,n/2]: Too recent to sign again.
return 0
}
// [n/2+1,n]
return uint64(difficulty)
}
// APIs implements consensus.Engine, returning the user facing RPC API to allow
// controlling the signer voting.
func (c *Clique) APIs(chain consensus.ChainReader) []rpc.API {
return []rpc.API{{
Namespace: "clique",
Version: "1.0",
Service: &API{chain: chain, clique: c},
Public: false,
}}
}
// ExtraEnsureVanity returns a slice of length 32, trimming extra or filling with 0s as necessary.
func ExtraEnsureVanity(extra []byte) []byte {
if len(extra) < extraVanity {
return append(extra, make([]byte, extraVanity-len(extra))...)
}
return extra[:extraVanity]
}
// ExtraVanity returns a slice of the vanity portion of extra (up to 32). It may still contain trailing 0s.
func ExtraVanity(extra []byte) []byte {
if len(extra) < extraVanity {
return extra
}
return extra[:extraVanity]
}
// ExtraAppendVote appends a vote to extra data as 20 bytes of address and a single byte for voter or signer election.
func ExtraAppendVote(extra []byte, candidate common.Address, voter bool) []byte {
extra = append(extra, candidate[:]...)
election := signerElection
if voter {
election = voterElection
}
return append(extra, election)
}
// ExtraHasVote returns true if extra contains a proposal vote.
func ExtraHasVote(extra []byte) bool {
return len(extra) == extraVanity+extraPropose
}
// ExtraCandidate returns the candidate address of the proposal vote, or the zero value if one is not present.
func ExtraCandidate(extra []byte) common.Address {
if len(extra) < extraVanity+common.AddressLength {
return common.Address{}
}
return common.BytesToAddress(extra[extraVanity : extraVanity+common.AddressLength])
}
// IsVoterElection returns true if extra votes on a voter election, or false if it votes on a signer election or does
// not contain a vote.
func ExtraIsVoterElection(extra []byte) bool {
if len(extra) < extraVanity+extraPropose {
return false
}
switch extra[extraVanity+common.AddressLength] {
case voterElection:
return true
case signerElection:
return false
}
return false
}