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protocol.go
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protocol.go
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package hare3
import (
"bytes"
"fmt"
"slices"
"sync"
"go.uber.org/zap/zapcore"
"golang.org/x/exp/maps"
"github.com/spacemeshos/go-spacemesh/common/types"
"github.com/spacemeshos/go-spacemesh/log"
)
type grade uint8
const (
grade0 grade = iota
grade1
grade2
grade3
grade4
grade5
)
func isSubset(s, v []types.ProposalID) bool {
set := map[types.ProposalID]struct{}{}
for _, id := range v {
set[id] = struct{}{}
}
for _, id := range s {
if _, exist := set[id]; !exist {
return false
}
}
return true
}
func toHash(proposals []types.ProposalID) types.Hash32 {
return types.CalcProposalHash32Presorted(proposals, nil)
}
type messageKey struct {
IterRound
Sender types.NodeID
}
type input struct {
*Message
atxgrade grade
malicious bool
msgHash types.Hash32
}
func (i *input) MarshalLogObject(encoder zapcore.ObjectEncoder) error {
if i.Message != nil {
i.Message.MarshalLogObject(encoder)
}
encoder.AddUint8("atxgrade", uint8(i.atxgrade))
encoder.AddBool("malicious", i.malicious)
encoder.AddString("hash", i.msgHash.ShortString())
return nil
}
type output struct {
coin *bool // set based on preround messages right after preround completes in 0 iter
result []types.ProposalID // set based on notify messages at the start of next iter
terminated bool // protocol participates in one more iteration after outputing result
message *Message
}
func (o *output) MarshalLogObject(encoder zapcore.ObjectEncoder) error {
encoder.AddBool("terminated", o.terminated)
if o.coin != nil {
encoder.AddBool("coin", *o.coin)
}
if o.result != nil {
encoder.AddArray("result", zapcore.ArrayMarshalerFunc(func(encoder log.ArrayEncoder) error {
for _, id := range o.result {
encoder.AppendString(types.Hash20(id).ShortString())
}
return nil
}))
}
if o.message != nil {
encoder.AddObject("msg", o.message)
}
return nil
}
func newProtocol(threshold uint16) *protocol {
return &protocol{
validProposals: map[types.Hash32][]types.ProposalID{},
gossip: gossip{threshold: threshold, state: map[messageKey]*gossipInput{}},
}
}
type protocol struct {
mu sync.Mutex
IterRound
coinout bool
coin *types.VrfSignature // smallest vrf from preround messages. not a part of paper
initial []types.ProposalID // Si
result *types.Hash32 // set after waiting for notify messages. Case 1
locked *types.Hash32 // Li
hardLocked bool
validProposals map[types.Hash32][]types.ProposalID // Ti
gossip gossip
}
func (p *protocol) OnInitial(proposals []types.ProposalID) {
p.mu.Lock()
defer p.mu.Unlock()
p.initial = proposals
}
func (p *protocol) OnInput(msg *input) (bool, *types.HareProof) {
p.mu.Lock()
defer p.mu.Unlock()
gossip, equivocation := p.gossip.receive(p.IterRound, msg)
if !gossip {
return false, equivocation
}
if msg.Round == preround &&
(p.coin == nil || (p.coin != nil && msg.Eligibility.Proof.Cmp(p.coin) == -1)) {
p.coin = &msg.Eligibility.Proof
}
return gossip, equivocation
}
func (p *protocol) thresholdProposals(ir IterRound, grade grade) (*types.Hash32, []types.ProposalID) {
for _, ref := range p.gossip.thresholdGossipRef(ir, grade) {
valid, exist := p.validProposals[ref]
if exist {
return &ref, valid
}
}
return nil, nil
}
func (p *protocol) commitExists(iter uint8, match types.Hash32, grade grade) bool {
for _, ref := range p.gossip.thresholdGossipRef(IterRound{Iter: iter, Round: commit}, grade) {
if ref == match {
return true
}
}
return false
}
func (p *protocol) execution(out *output) {
// 4.3 Protocol Execution
switch p.Round {
case preround:
out.message = &Message{Body: Body{
IterRound: p.IterRound,
Value: Value{Proposals: p.initial},
}}
case hardlock:
if p.Iter > 0 {
if p.result != nil {
out.terminated = true
}
ref, values := p.thresholdProposals(IterRound{Iter: p.Iter - 1, Round: notify}, grade5)
if ref != nil && p.result == nil {
p.result = ref
out.result = values
if values == nil {
// receiver expects non-nil result
out.result = []types.ProposalID{}
}
}
if ref, _ := p.thresholdProposals(IterRound{Iter: p.Iter - 1, Round: commit}, grade4); ref != nil {
p.locked = ref
p.hardLocked = true
} else {
p.locked = nil
p.hardLocked = false
}
}
case softlock:
if p.Iter > 0 && !p.hardLocked {
if ref, _ := p.thresholdProposals(IterRound{Iter: p.Iter - 1, Round: commit}, grade3); ref != nil {
p.locked = ref
} else {
p.locked = nil
}
}
case propose:
values := p.gossip.thresholdGossip(IterRound{Round: preround}, grade4)
if p.Iter > 0 {
ref, overwrite := p.thresholdProposals(IterRound{Iter: p.Iter - 1, Round: commit}, grade2)
if ref != nil {
values = overwrite
}
}
out.message = &Message{Body: Body{
IterRound: p.IterRound,
Value: Value{Proposals: values},
}}
case commit:
// condition (d) is realized by ordering proposals by vrf
proposed := p.gossip.gradecast(IterRound{Iter: p.Iter, Round: propose})
g2values := p.gossip.thresholdGossip(IterRound{Round: preround}, grade2)
for _, graded := range proposed {
// condition (a) and (b)
// grade0 proposals are not added to the set
if !isSubset(graded.values, g2values) {
continue
}
p.validProposals[toHash(graded.values)] = graded.values
}
if p.hardLocked && p.locked != nil {
out.message = &Message{Body: Body{
IterRound: p.IterRound,
Value: Value{Reference: p.locked},
}}
} else {
g3values := p.gossip.thresholdGossip(IterRound{Round: preround}, grade3)
g5values := p.gossip.thresholdGossip(IterRound{Round: preround}, grade5)
for _, graded := range proposed {
id := toHash(graded.values)
// condition (c)
if _, exist := p.validProposals[id]; !exist {
continue
}
// condition (e)
if graded.grade != grade2 {
continue
}
// condition (f)
if !isSubset(graded.values, g3values) {
continue
}
// condition (g)
if !isSubset(g5values, graded.values) && !p.commitExists(p.Iter-1, id, grade1) {
continue
}
// condition (h)
if p.locked != nil && *p.locked != id {
continue
}
out.message = &Message{Body: Body{
IterRound: p.IterRound,
Value: Value{Reference: &id},
}}
break
}
}
case notify:
ref := p.result
if ref == nil {
ref, _ = p.thresholdProposals(IterRound{Iter: p.Iter, Round: commit}, grade5)
}
if ref != nil {
out.message = &Message{Body: Body{
IterRound: p.IterRound,
Value: Value{Reference: ref},
}}
}
}
}
func (p *protocol) Next() output {
p.mu.Lock()
defer p.mu.Unlock()
out := output{}
p.execution(&out)
if p.Round >= softlock && p.coin != nil && !p.coinout {
coin := p.coin.LSB() != 0
out.coin = &coin
p.coinout = true
}
if p.Round == preround && p.Iter == 0 {
// skips hardlock unlike softlock in the paper.
// this makes no practical difference from correctness.
// but allows to simplify assignment in validValues
p.Round = softlock
} else if p.Round == notify {
p.Round = hardlock
p.Iter++
} else {
p.Round++
}
return out
}
func (p *protocol) Stats() *stats {
p.mu.Lock()
defer p.mu.Unlock()
s := &stats{
iter: p.Iter - 1,
threshold: p.gossip.threshold,
}
// preround messages that are received after the very first iteration
// has no impact on protocol
if s.iter == 0 {
for grade := grade1; grade <= grade5; grade++ {
s.preround = append(s.preround, preroundStats{
grade: grade,
tallies: maps.Values(
thresholdTallies(p.gossip.state, IterRound{Round: preround}, grade, tallyProposals),
),
})
}
}
proposals := p.gossip.gradecast(IterRound{Iter: p.Iter - 1, Round: propose})
for _, graded := range proposals {
s.propose = append(s.propose, proposeStats{
grade: graded.grade,
ref: toHash(graded.values),
proposals: graded.values,
})
}
// stats are collected at the start of current iteration (p.Iter)
// we expect 2 network delays to pass since commit messages were broadcasted
for grade := grade4; grade <= grade5; grade++ {
s.commit = append(s.commit, commitStats{
grade: grade,
tallies: maps.Values(
thresholdTallies(p.gossip.state, IterRound{Iter: p.Iter - 1, Round: commit}, grade, tallyRefs),
),
})
}
// we are not interested in any other grade for notify message as they have no impact on protocol execution
s.notify = append(s.notify, notifyStats{
grade: grade5,
tallies: maps.Values(
thresholdTallies(p.gossip.state, IterRound{Iter: p.Iter - 1, Round: notify}, grade5, tallyRefs),
),
})
return s
}
type gossipInput struct {
*input
received IterRound
otherReceived *IterRound
}
// Protocol 1. graded-gossip. page 10.
type gossip struct {
threshold uint16
state map[messageKey]*gossipInput
}
func (g *gossip) receive(current IterRound, input *input) (bool, *types.HareProof) {
// Case 1: will be discarded earlier
other, exist := g.state[input.key()]
if exist {
if other.msgHash != input.msgHash && !other.malicious {
// Protocol 3. thresh-gossip. keep one with the maximal grade.
if input.atxgrade > other.atxgrade {
input.malicious = true
g.state[input.key()] = &gossipInput{
input: input,
received: current,
otherReceived: &other.received,
}
} else {
// Case 3
other.malicious = true
other.otherReceived = ¤t
}
return true, &types.HareProof{Messages: [2]types.HareProofMsg{
other.ToMalfeasanceProof(), input.ToMalfeasanceProof(),
}}
}
// Case 2. but also we filter duplicates from p2p layer here
return false, nil
}
// Case 4
g.state[input.key()] = &gossipInput{input: input, received: current}
return true, nil
}
type gset struct {
values []types.ProposalID
grade grade
smallest types.VrfSignature
}
// Protocol 2. gradecast. page 13.
func (g *gossip) gradecast(target IterRound) []gset {
// unlike paper we use 5-graded gossip for gradecast as well
var rst []gset
for key, value := range g.state {
if key.IterRound == target && (!value.malicious || value.otherReceived != nil) {
if value.atxgrade == grade5 && value.received.Delay(target) <= 1 &&
// 2 (a)
(value.otherReceived == nil || value.otherReceived.Delay(target) > 3) {
// 2 (b)
rst = append(rst, gset{
grade: grade2,
values: value.Value.Proposals,
smallest: value.Eligibility.Proof,
})
} else if value.atxgrade >= grade4 && value.received.Delay(target) <= 2 &&
// 3 (a)
(value.otherReceived == nil || value.otherReceived.Delay(target) > 2) {
// 3 (b)
rst = append(rst, gset{
grade: grade1,
values: value.Value.Proposals,
smallest: value.Eligibility.Proof,
})
}
}
}
// hare expects to receive multiple proposals. expected number of leaders is set to 5.
// we need to choose the same one for commit across the cluster.
// we do that by ordering them by vrf value, and picking one that passes other checks (see commit in execution).
// in hare3 paper look for p-Weak leader election property.
slices.SortFunc(rst, func(i, j gset) int {
return i.smallest.Cmp(&j.smallest)
})
return rst
}
func tallyProposals(all map[types.ProposalID]proposalTally, inp *gossipInput) {
for _, id := range inp.Value.Proposals {
tally, exist := all[id]
if !exist {
tally = proposalTally{id: id}
}
tally.total += inp.Eligibility.Count
if !inp.malicious {
tally.valid += inp.Eligibility.Count
}
all[id] = tally
}
}
// Protocol 3. thresh-gossip. Page 15.
// output returns union of sorted proposals received
// in the given round with minimal specified grade.
func (g *gossip) thresholdGossip(filter IterRound, grade grade) []types.ProposalID {
rst := thresholdGossip(thresholdTallies(g.state, filter, grade, tallyProposals), g.threshold)
slices.SortFunc(rst, func(i, j types.ProposalID) int {
return bytes.Compare(i.Bytes(), j.Bytes())
})
return rst
}
func tallyRefs(all map[types.Hash32]refTally, inp *gossipInput) {
tally, exist := all[*inp.Value.Reference]
if !exist {
tally = refTally{id: *inp.Value.Reference}
}
tally.total += inp.Eligibility.Count
if !inp.malicious {
tally.valid += inp.Eligibility.Count
}
all[*inp.Value.Reference] = tally
}
// thresholdGossipRef returns all references to proposals in the given round with minimal grade.
func (g *gossip) thresholdGossipRef(filter IterRound, grade grade) []types.Hash32 {
return thresholdGossip(thresholdTallies(g.state, filter, grade, tallyRefs), g.threshold)
}
func thresholdGossip[T interface {
comparable
fmt.Stringer
}](
tallies map[T]tallyStats[T], threshold uint16,
) []T {
rst := []T{}
for _, item := range tallies {
// valid > 0 and total >= f
// atleast one non-equivocating vote and crossed committee/2 + 1
if item.total >= threshold && item.valid > 0 {
rst = append(rst, item.id)
}
}
return rst
}
func thresholdTallies[T interface {
comparable
fmt.Stringer
}](
state map[messageKey]*gossipInput, filter IterRound, msgGrade grade,
tally func(tally map[T]tallyStats[T], inp *gossipInput),
) map[T]tallyStats[T] {
all := map[T]tallyStats[T]{}
min := grade5
// pick min atx grade from non equivocating identity.
for key, value := range state {
if key.IterRound == filter && value.atxgrade < min && !value.malicious &&
value.received.Grade(filter) >= msgGrade {
min = value.atxgrade
}
}
// tally votes for valid and malicious messages
for key, value := range state {
if key.IterRound == filter && value.atxgrade >= min && value.received.Grade(filter) >= msgGrade {
tally(all, value)
}
}
return all
}
type preroundStats struct {
grade grade
tallies []proposalTally
}
func (s *preroundStats) MarshalLogObject(encoder zapcore.ObjectEncoder) error {
encoder.AddUint16("grade", uint16(s.grade))
encoder.AddArray("tallies", zapcore.ArrayMarshalerFunc(func(enc zapcore.ArrayEncoder) error {
for _, tally := range s.tallies {
enc.AppendObject(&tally)
}
return nil
}))
return nil
}
type tallyStats[T fmt.Stringer] struct {
id T
total uint16
valid uint16
}
func (s *tallyStats[T]) MarshalLogObject(encoder zapcore.ObjectEncoder) error {
encoder.AddUint16("total", s.total)
encoder.AddUint16("valid", s.valid)
encoder.AddString("id", s.id.String())
return nil
}
type (
proposalTally = tallyStats[types.ProposalID]
refTally = tallyStats[types.Hash32]
)
type proposeStats struct {
grade grade
ref types.Hash32
proposals []types.ProposalID
}
func (s *proposeStats) MarshalLogObject(encoder zapcore.ObjectEncoder) error {
encoder.AddString("ref", s.ref.ShortString())
encoder.AddUint16("grade", uint16(s.grade))
encoder.AddArray("proposals", zapcore.ArrayMarshalerFunc(func(encoder zapcore.ArrayEncoder) error {
for _, id := range s.proposals {
encoder.AppendString(id.String())
}
return nil
}))
return nil
}
type commitStats struct {
grade grade
tallies []refTally
}
func (s *commitStats) MarshalLogObject(encoder zapcore.ObjectEncoder) error {
encoder.AddUint16("grade", uint16(s.grade))
encoder.AddArray("tallies", zapcore.ArrayMarshalerFunc(func(encoder zapcore.ArrayEncoder) error {
for _, tally := range s.tallies {
encoder.AppendObject(&tally)
}
return nil
}))
return nil
}
type notifyStats struct {
grade grade
tallies []refTally
}
func (n *notifyStats) MarshalLogObject(encoder zapcore.ObjectEncoder) error {
encoder.AddUint16("grade", uint16(n.grade))
encoder.AddArray("tallies", zapcore.ArrayMarshalerFunc(func(encoder zapcore.ArrayEncoder) error {
for _, tally := range n.tallies {
encoder.AppendObject(&tally)
}
return nil
}))
return nil
}
type stats struct {
iter uint8
threshold uint16
preround []preroundStats
propose []proposeStats
commit []commitStats
notify []notifyStats
}
func (s *stats) MarshalLogObject(encoder zapcore.ObjectEncoder) error {
encoder.AddUint8("iter", s.iter)
encoder.AddUint16("threshold", s.threshold)
encoder.AddArray("preround", zapcore.ArrayMarshalerFunc(func(encoder zapcore.ArrayEncoder) error {
for _, stat := range s.preround {
encoder.AppendObject(&stat)
}
return nil
}))
encoder.AddArray("propose", zapcore.ArrayMarshalerFunc(func(encoder zapcore.ArrayEncoder) error {
for _, stat := range s.propose {
encoder.AppendObject(&stat)
}
return nil
}))
encoder.AddArray("commit", zapcore.ArrayMarshalerFunc(func(encoder zapcore.ArrayEncoder) error {
for _, stat := range s.commit {
encoder.AppendObject(&stat)
}
return nil
}))
encoder.AddArray("notify", zapcore.ArrayMarshalerFunc(func(encoder zapcore.ArrayEncoder) error {
for _, stat := range s.notify {
encoder.AppendObject(&stat)
}
return nil
}))
return nil
}