feat: introduce different diff for senior

consensus/clique/api.go

@@ -162,7 +162,7 @@ func (api *API) Status() (*status, error) {
 		if h == nil {
 			return nil, fmt.Errorf("missing block %d", n)
 		}
-		if h.Difficulty.Cmp(diffInTurn) == 0 {
+		if h.Difficulty.Cmp(diffInTurnSenior) == 0 || h.Difficulty.Cmp(diffInTurnSubordinate) == 0 {
 			optimals++
 		}
 		diff += h.Difficulty.Uint64()

consensus/clique/clique.go

@@ -68,8 +68,9 @@ var (
 
 	uncleHash = types.CalcUncleHash(nil) // Always Keccak256(RLP([])) as uncles are meaningless outside of PoW.
 
-	diffInTurn = big.NewInt(2) // Block difficulty for in-turn signatures
-	diffNoTurn = big.NewInt(1) // Block difficulty for out-of-turn signatures
+	diffInTurnSenior      = big.NewInt(7) // Block difficulty for in-turn signatures
+	diffInTurnSubordinate = big.NewInt(2) // Block difficulty for in-turn signatures
+	diffNoTurn            = big.NewInt(1) // Block difficulty for out-of-turn signatures
 
 	blockSizeGaugeName = "clique/block_size_in_bytes"
 	gasUsedInBlock     = "clique/gas_used_in_block"
@@ -296,7 +297,7 @@ func (c *Clique) verifyHeader(chain consensus.ChainHeaderReader, header *types.H
 	}
 	// Ensure that the block's difficulty is meaningful (may not be correct at this point)
 	if number > 0 {
-		if header.Difficulty == nil || (header.Difficulty.Cmp(diffInTurn) != 0 && header.Difficulty.Cmp(diffNoTurn) != 0) {
+		if header.Difficulty == nil || (header.Difficulty.Cmp(diffInTurnSenior) != 0 && header.Difficulty.Cmp(diffInTurnSenior) != 0 && header.Difficulty.Cmp(diffInTurnSubordinate) != 0) {
 			return errInvalidDifficulty
 		}
 	}
@@ -505,7 +506,7 @@ func (c *Clique) verifySeal(snap *Snapshot, header *types.Header, parents []*typ
 	// Ensure that the difficulty corresponds to the turn-ness of the signer
 	if !c.fakeDiff {
 		inturn := snap.inturn(header.Number.Uint64(), signer)
-		if inturn && header.Difficulty.Cmp(diffInTurn) != 0 {
+		if inturn && (header.Difficulty.Cmp(diffInTurnSenior) != 0 || header.Difficulty.Cmp(diffInTurnSubordinate) != 0) {
 			return errWrongDifficulty
 		}
 		if !inturn && header.Difficulty.Cmp(diffNoTurn) != 0 {
@@ -710,7 +711,10 @@ func (c *Clique) CalcDifficulty(chain consensus.ChainHeaderReader, time uint64,
 
 func calcDifficulty(snap *Snapshot, signer common.Address) *big.Int {
 	if snap.inturn(snap.Number+1, signer) {
-		return new(big.Int).Set(diffInTurn)
+		if snap.isSenior(signer) {
+			return new(big.Int).Set(diffInTurnSenior)
+		}
+		return new(big.Int).Set(diffInTurnSubordinate)
 	}
 	return new(big.Int).Set(diffNoTurn)
 }

consensus/clique/clique_test.go

@@ -61,7 +61,7 @@ func TestReimportMirroredState(t *testing.T) {
 	_, blocks, _ := core.GenerateChainWithGenesis(genspec, engine, 3, func(i int, block *core.BlockGen) {
 		// The chain maker doesn't have access to a chain, so the difficulty will be
 		// lets unset (nil). Set it here to the correct value.
-		block.SetDifficulty(diffInTurn)
+		block.SetDifficulty(diffInTurnSenior)
 
 		// We want to simulate an empty middle block, having the same state as the
 		// first one. The last is needs a state change again to force a reorg.
@@ -79,7 +79,7 @@ func TestReimportMirroredState(t *testing.T) {
 			header.ParentHash = blocks[i-1].Hash()
 		}
 		header.Extra = make([]byte, extraVanity+extraSeal)
-		header.Difficulty = diffInTurn
+		header.Difficulty = diffInTurnSenior
 
 		sig, _ := crypto.Sign(SealHash(header).Bytes(), key)
 		copy(header.Extra[len(header.Extra)-extraSeal:], sig)

consensus/clique/snapshot.go

@@ -19,6 +19,7 @@ package clique
 import (
 	"bytes"
 	"encoding/json"
+	"sort"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -60,6 +61,7 @@ type Snapshot struct {
 	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
+	Seniors map[common.Address]struct{} `json:"seniors"` // Set of senior signers
 }
 
 // newSnapshot creates a new snapshot with the specified startup parameters. This
@@ -74,10 +76,21 @@ func newSnapshot(config *params.CliqueConfig, sigcache *sigLRU, number uint64, h
 		Signers:  make(map[common.Address]struct{}),
 		Recents:  make(map[uint64]common.Address),
 		Tally:    make(map[common.Address]Tally),
+		Seniors:  make(map[common.Address]struct{}),
 	}
 	for _, signer := range signers {
 		snap.Signers[signer] = struct{}{}
 	}
+	sortedSigners := make([]common.Address, 0, len(snap.Signers))
+	for signer := range snap.Signers {
+		sortedSigners = append(sortedSigners, signer)
+	}
+	sort.Slice(sortedSigners, func(i, j int) bool {
+		return bytes.Compare(sortedSigners[i].Bytes(), sortedSigners[j].Bytes()) < 0
+	})
+	if len(sortedSigners) > 0 {
+		snap.Seniors[sortedSigners[0]] = struct{}{}
+	}
 	return snap
 }
 
@@ -312,6 +325,12 @@ func (s *Snapshot) signers() []common.Address {
 	return sigs
 }
 
+// isSenior checks if the given address is a senior signer.
+func (s *Snapshot) isSenior(address common.Address) bool {
+	_, senior := s.Seniors[address]
+	return senior
+}
+
 // 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

consensus/clique/snapshot_test.go

@@ -443,7 +443,7 @@ func (tt *cliqueTest) run(t *testing.T) {
 			header.Extra = make([]byte, extraVanity+len(auths)*common.AddressLength+extraSeal)
 			accounts.checkpoint(header, auths)
 		}
-		header.Difficulty = diffInTurn // Ignored, we just need a valid number
+		header.Difficulty = diffInTurnSenior // Ignored, we just need a valid number
 
 		// Generate the signature, embed it into the header and the block
 		accounts.sign(header, tt.votes[j].signer)