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protocol.go
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protocol.go
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package hare3
import (
"sort"
"sync"
"go.uber.org/zap/zapcore"
"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
validValues [grade5 + 1][]types.ProposalID // Vi
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) (*types.Hash32, []types.ProposalID) {
for _, ref := range p.gossip.thresholdGossipRef(ir) {
valid, exist := p.validProposals[ref]
if exist {
return &ref, valid
}
}
return nil, nil
}
func (p *protocol) commitExists(iter uint8, match types.Hash32) bool {
for _, ref := range p.gossip.thresholdGossipRef(IterRound{Iter: iter, Round: commit}) {
if ref == match {
return true
}
}
return false
}
func (p *protocol) execution(out *output, active bool) {
// 4.3 Protocol Execution
if p.Iter == 0 && p.Round >= softlock && p.Round <= wait2 {
// -1 - skipped hardlock round in iter 0
// -1 - implementation rounds starts from 0
g := grade5 - grade(p.Round-2)
p.validValues[g] = p.gossip.thresholdGossip(IterRound{Round: preround})
}
if p.Round == preround && active {
out.message = &Message{Body: Body{
IterRound: p.IterRound,
Value: Value{Proposals: p.initial},
}}
} else if p.Round == hardlock && p.Iter > 0 {
if p.result != nil {
out.terminated = true
}
ref, values := p.thresholdProposals(IterRound{Iter: p.Iter - 1, Round: notify})
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}); ref != nil {
p.locked = ref
p.hardLocked = true
} else {
p.locked = nil
p.hardLocked = false
}
} else if p.Round == softlock && p.Iter > 0 && !p.hardLocked {
if ref, _ := p.thresholdProposals(IterRound{Iter: p.Iter - 1, Round: commit}); ref != nil {
p.locked = ref
} else {
p.locked = nil
}
} else if p.Round == propose && active {
values := p.validValues[grade4]
if p.Iter > 0 {
ref, overwrite := p.thresholdProposals(IterRound{Iter: p.Iter - 1, Round: commit})
if ref != nil {
values = overwrite
}
}
out.message = &Message{Body: Body{
IterRound: p.IterRound,
Value: Value{Proposals: values},
}}
} else if p.Round == commit {
// condition (d) is realized by ordering proposals by vrf
proposed := p.gossip.gradecast(IterRound{Iter: p.Iter, Round: propose})
for _, graded := range proposed {
// condition (a) and (b)
if graded.grade < grade1 || !isSubset(graded.values, p.validValues[grade2]) {
continue
}
p.validProposals[toHash(graded.values)] = graded.values
}
if active {
var ref *types.Hash32
if p.hardLocked && p.locked != nil {
ref = p.locked
} else {
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, p.validValues[grade3]) {
continue
}
// condition (g)
if !isSubset(p.validValues[grade5], graded.values) &&
!p.commitExists(p.Iter-1, id) {
continue
}
// condition (h)
if p.locked != nil && *p.locked != id {
continue
}
ref = &id
break
}
}
if ref != nil {
out.message = &Message{Body: Body{
IterRound: p.IterRound,
Value: Value{Reference: ref},
}}
}
}
} else if p.Round == notify && active {
ref := p.result
if ref == nil {
ref, _ = p.thresholdProposals(IterRound{Iter: p.Iter, Round: commit})
}
if ref != nil {
out.message = &Message{Body: Body{
IterRound: p.IterRound,
Value: Value{Reference: ref},
}}
}
}
}
func (p *protocol) Next(active bool) output {
p.mu.Lock()
defer p.mu.Unlock()
out := output{}
p.execution(&out, active)
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
}
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) {
g := grade0
if value.atxgrade == grade5 && value.received.Delay(target) <= 1 &&
// 2 (a)
(value.otherReceived == nil || value.otherReceived.Delay(target) > 3) {
// 2 (b)
g = grade2
} else if value.atxgrade >= grade4 && value.received.Delay(target) <= 2 &&
// 3 (a)
(value.otherReceived == nil || value.otherReceived.Delay(target) > 2) {
// 3 (b)
g = grade1
}
if g > grade0 {
rst = append(rst, gset{
grade: g,
values: value.Value.Proposals,
smallest: value.Eligibility.Proof,
})
}
}
}
// it satisfies p-Weak leader election
// inconsistent order of proposals may cause participants to commit on different proposals
sort.Slice(rst, func(i, j int) bool {
return rst[i].smallest.Cmp(&rst[j].smallest) == -1
})
return rst
}
// 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) []types.ProposalID {
rst := thresholdGossip(g.state, g.threshold, filter,
func(total map[types.ProposalID]uint16, valid map[types.ProposalID]struct{}, inp *gossipInput) {
for _, id := range inp.Value.Proposals {
total[id] += inp.Eligibility.Count
if !inp.malicious {
valid[id] = struct{}{}
}
}
})
return types.SortProposalIDs(rst)
}
// thresholdGossipRef returns all references to proposals in the given round with minimal grade.
func (g *gossip) thresholdGossipRef(filter IterRound) []types.Hash32 {
return thresholdGossip(g.state, g.threshold, filter,
func(total map[types.Hash32]uint16, valid map[types.Hash32]struct{}, inp *gossipInput) {
total[*inp.Value.Reference] += inp.Eligibility.Count
if !inp.malicious {
valid[*inp.Value.Reference] = struct{}{}
}
})
}
func thresholdGossip[T comparable](
state map[messageKey]*gossipInput, threshold uint16, filter IterRound,
tally func(all map[T]uint16, good map[T]struct{}, inp *gossipInput),
) []T {
total := map[T]uint16{}
valid := map[T]struct{}{}
min := grade5
// pick min atx grade from non equivocating identity.
for key, value := range state {
if key.IterRound == filter && value.atxgrade < min && !value.malicious {
min = value.atxgrade
}
}
// tally votes for valid and malicious messages
for key, value := range state {
if key.IterRound == filter && value.atxgrade >= min {
tally(total, valid, value)
}
}
rst := []T{}
// valid > 0 and total >= f
// atleast one non-equivocating vote and crossed committee/2 + 1
for id := range valid {
if total[id] >= threshold {
rst = append(rst, id)
}
}
return rst
}