path: root/core/agreement.go

// Copyright 2018 The dexon-consensus-core Authors
// This file is part of the dexon-consensus-core library.
//
// The dexon-consensus-core 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 dexon-consensus-core 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 dexon-consensus-core library. If not, see
// <http://www.gnu.org/licenses/>.

package core

import (
    "fmt"
    "sync"
    "sync/atomic"

    "github.com/dexon-foundation/dexon-consensus-core/common"
    "github.com/dexon-foundation/dexon-consensus-core/core/types"
    "github.com/dexon-foundation/dexon-consensus-core/crypto"
)

// Errors for agreement module.
var (
    ErrNotValidator           = fmt.Errorf("not a validaotr")
    ErrIncorrectVoteSignature = fmt.Errorf("incorrect vote signature")
    ErrForkVote               = fmt.Errorf("fork vote")
)

// ErrFork for fork error in agreement.
type ErrFork struct {
    vID      types.ValidatorID
    old, new common.Hash
}

func (e *ErrFork) Error() string {
    return fmt.Sprintf("fork is found for %s, old %s, new %s",
        e.vID.String(), e.old, e.new)
}

type blockProposerFn func() *types.Block

func newVoteListMap() []map[types.ValidatorID]*types.Vote {
    listMap := make([]map[types.ValidatorID]*types.Vote, types.MaxVoteType)
    for idx := range listMap {
        listMap[idx] = make(map[types.ValidatorID]*types.Vote)
    }
    return listMap
}

// agreementReceiver is the interface receiving agreement event.
type agreementReceiver interface {
    proposeVote(vote *types.Vote)
    proposeBlock(common.Hash)
    confirmBlock(common.Hash)
}

// position is the current round of the agreement.
type position struct {
    ShardID uint64
    ChainID uint64
    Height  uint64
}

// agreementData is the data for agreementState.
type agreementData struct {
    recv agreementReceiver

    ID            types.ValidatorID
    leader        *leaderSelector
    defaultBlock  common.Hash
    period        uint64
    requiredVote  int
    votes         map[uint64][]map[types.ValidatorID]*types.Vote
    votesLock     sync.RWMutex
    blocks        map[types.ValidatorID]*types.Block
    blockProposer blockProposerFn
}

// agreement is the agreement protocal describe in the Crypto Shuffle Algorithm.
type agreement struct {
    state      agreementState
    data       *agreementData
    aID        *atomic.Value
    validators map[types.ValidatorID]struct{}
    sigToPub   SigToPubFn
    hasOutput  bool
}

// newAgreement creates a agreement instance.
func newAgreement(
    ID types.ValidatorID,
    recv agreementReceiver,
    validators types.ValidatorIDs,
    leader *leaderSelector,
    sigToPub SigToPubFn,
    blockProposer blockProposerFn) *agreement {
    agreement := &agreement{
        data: &agreementData{
            recv:          recv,
            ID:            ID,
            leader:        leader,
            blockProposer: blockProposer,
        },
        aID:      &atomic.Value{},
        sigToPub: sigToPub,
    }
    agreement.restart(validators)
    return agreement
}

// terminate the current running state.
func (a *agreement) terminate() {
    if a.state != nil {
        a.state.terminate()
    }
}

// restart the agreement
func (a *agreement) restart(validators types.ValidatorIDs) {
    a.data.votesLock.Lock()
    defer a.data.votesLock.Unlock()
    a.data.votes = make(map[uint64][]map[types.ValidatorID]*types.Vote)
    a.data.votes[1] = newVoteListMap()
    a.data.period = 1
    a.data.blocks = make(map[types.ValidatorID]*types.Block)
    a.data.requiredVote = len(validators)/3*2 + 1
    a.hasOutput = false
    a.state = newPrepareState(a.data)
    a.validators = make(map[types.ValidatorID]struct{})
    for _, v := range validators {
        a.validators[v] = struct{}{}
    }
}

// clocks returns how many time this state is required.
func (a *agreement) clocks() int {
    return a.state.clocks()
}

// agreementID returns the current agreementID.
func (a *agreement) agreementID() position {
    return a.aID.Load().(position)
}

// setAgreementID sets the current agreementID.
func (a *agreement) setAgreementID(ID position) {
    a.aID.Store(ID)
}

// nextState is called at the spcifi clock time.
func (a *agreement) nextState() (err error) {
    a.state, err = a.state.nextState()
    return
}

func (a *agreement) sanityCheck(vote *types.Vote) error {
    if _, exist := a.validators[vote.ProposerID]; !exist {
        return ErrNotValidator
    }
    ok, err := verifyVoteSignature(vote, a.sigToPub)
    if err != nil {
        return err
    }
    if !ok {
        return ErrIncorrectVoteSignature
    }
    if _, exist := a.data.votes[vote.Period]; exist {
        if oldVote, exist :=
            a.data.votes[vote.Period][vote.Type][vote.ProposerID]; exist {
            if vote.BlockHash != oldVote.BlockHash {
                return ErrForkVote
            }
        }
    }
    return nil
}

// prepareVote prepares a vote.
func (a *agreement) prepareVote(vote *types.Vote, prv crypto.PrivateKey) (
    err error) {
    hash := hashVote(vote)
    vote.Signature, err = prv.Sign(hash)
    return
}

// processVote is the entry point for processing Vote.
func (a *agreement) processVote(vote *types.Vote) error {
    vote = vote.Clone()
    if err := a.sanityCheck(vote); err != nil {
        return err
    }
    if func() bool {
        a.data.votesLock.Lock()
        defer a.data.votesLock.Unlock()
        if _, exist := a.data.votes[vote.Period]; !exist {
            a.data.votes[vote.Period] = newVoteListMap()
        }
        a.data.votes[vote.Period][vote.Type][vote.ProposerID] = vote
        if !a.hasOutput && vote.Type == types.VoteConfirm {
            if len(a.data.votes[vote.Period][types.VoteConfirm]) >=
                a.data.requiredVote {
                a.hasOutput = true
                a.data.recv.confirmBlock(vote.BlockHash)
            }
        }
        return true
    }() {
        return a.state.receiveVote()
    }
    return nil
}

// processBlock is the entry point for processing Block.
func (a *agreement) processBlock(block *types.Block) error {
    if b, exist := a.data.blocks[block.ProposerID]; exist {
        if b.Hash != block.Hash {
            return &ErrFork{block.ProposerID, b.Hash, block.Hash}
        }
        return nil
    }
    a.data.blocks[block.ProposerID] = block
    if err := a.data.leader.processBlock(block); err != nil {
        return err
    }
    return nil
}

func (a *agreementData) countVote(period uint64, voteType types.VoteType) (
    blockHash common.Hash, ok bool) {
    a.votesLock.RLock()
    defer a.votesLock.RUnlock()
    votes, exist := a.votes[period]
    if !exist {
        return
    }
    candidate := make(map[common.Hash]int)
    for _, vote := range votes[voteType] {
        if _, exist := candidate[vote.BlockHash]; !exist {
            candidate[vote.BlockHash] = 0
        }
        candidate[vote.BlockHash]++
    }
    for candidateHash, votes := range candidate {
        if votes >= a.requiredVote {
            blockHash = candidateHash
            ok = true
            return
        }
    }
    return
}