gpo: add min gas tip, crosscheck against txpool's min gas tip

cmd/opera/launcher/config.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"errors"
 	"fmt"
+	"math/big"
 	"os"
 	"path"
 	"path/filepath"
@@ -540,6 +541,13 @@ func mayMakeAllConfigs(ctx *cli.Context) (*config, error) {
 
 	// Process DBs defaults in the end because they are applied only in absence of config or flags
 	cfg = setDBConfigDefault(cfg, cacheRatio)
+	// Sanitize GPO config
+	if cfg.Opera.GPO.MinGasTip == nil || cfg.Opera.GPO.MinGasTip.Sign() == 0 {
+		cfg.Opera.GPO.MinGasTip = new(big.Int).SetUint64(cfg.TxPool.PriceLimit)
+	}
+	if cfg.Opera.GPO.MinGasTip.Cmp(new(big.Int).SetUint64(cfg.TxPool.PriceLimit)) < 0 {
+		log.Warn(fmt.Sprintf("GPO minimum gas tip (Opera.GPO.MinGasTip=%s) is lower than txpool minimum gas tip (TxPool.PriceLimit=%d)", cfg.Opera.GPO.MinGasTip.String(), cfg.TxPool.PriceLimit))
+	}
 
 	if err := cfg.Opera.Validate(); err != nil {
 		return nil, err

gossip/config.go

@@ -213,6 +213,7 @@ func DefaultConfig(scale cachescale.Func) Config {
 		GPO: gasprice.Config{
 			MaxGasPrice:      gasprice.DefaultMaxGasPrice,
 			MinGasPrice:      new(big.Int),
+			MinGasTip:        new(big.Int),
 			DefaultCertainty: 0.5 * gasprice.DecimalUnit,
 		},
 

gossip/gasprice/gasprice.go

@@ -49,6 +49,7 @@ const (
 type Config struct {
 	MaxGasPrice      *big.Int `toml:",omitempty"`
 	MinGasPrice      *big.Int `toml:",omitempty"`
+	MinGasTip        *big.Int `toml:",omitempty"`
 	DefaultCertainty uint64   `toml:",omitempty"`
 }
 
@@ -107,7 +108,8 @@ func sanitizeBigInt(val, min, max, _default *big.Int, name string) *big.Int {
 // gasprice for newly created transaction.
 func NewOracle(params Config) *Oracle {
 	params.MaxGasPrice = sanitizeBigInt(params.MaxGasPrice, nil, nil, DefaultMaxGasPrice, "MaxGasPrice")
-	params.MinGasPrice = sanitizeBigInt(params.MinGasPrice, nil, nil, new(big.Int), "MinGasPrice")
+	params.MinGasPrice = sanitizeBigInt(params.MinGasPrice, nil, params.MaxGasPrice, new(big.Int), "MinGasPrice")
+	params.MinGasTip = sanitizeBigInt(params.MinGasTip, nil, new(big.Int).Sub(params.MaxGasPrice, params.MinGasPrice), new(big.Int), "MinGasTip")
 	params.DefaultCertainty = sanitizeBigInt(new(big.Int).SetUint64(params.DefaultCertainty), big.NewInt(0), DecimalUnitBn, big.NewInt(DecimalUnit/2), "DefaultCertainty").Uint64()
 	tCache, _ := lru.New(100)
 	return &Oracle{
@@ -148,8 +150,8 @@ func (gpo *Oracle) suggestTip(certainty uint64) *big.Int {
 	}
 
 	tip := new(big.Int).Sub(combined, minPrice)
-	if tip.Sign() < 0 {
-		return new(big.Int)
+	if tip.Cmp(gpo.cfg.MinGasTip) < 0 {
+		return new(big.Int).Set(gpo.cfg.MinGasTip)
 	}
 	return tip
 }