cmd/geth: added --mainnet flag (#21932)

* cmd/geth: added --mainnet flag

* cmd/utils: set default genesis if --mainnet is specified

* cmd/utils: addressed comments

Author: MariusVanDerWijden

cmd/geth/chaincmd.go

@@ -159,6 +159,7 @@ The export-preimages command export hash preimages to an RLP encoded stream`,
 			utils.CacheFlag,
 			utils.SyncModeFlag,
 			utils.FakePoWFlag,
+			utils.MainnetFlag,
 			utils.RopstenFlag,
 			utils.RinkebyFlag,
 			utils.TxLookupLimitFlag,
@@ -210,6 +211,7 @@ Use "ethereum dump 0" to dump the genesis block.`,
 			utils.DataDirFlag,
 			utils.AncientFlag,
 			utils.CacheFlag,
+			utils.MainnetFlag,
 			utils.RopstenFlag,
 			utils.RinkebyFlag,
 			utils.GoerliFlag,

cmd/geth/main.go

@@ -140,6 +140,7 @@ var (
 		utils.NodeKeyFileFlag,
 		utils.NodeKeyHexFlag,
 		utils.DNSDiscoveryFlag,
+		utils.MainnetFlag,
 		utils.DeveloperFlag,
 		utils.DeveloperPeriodFlag,
 		utils.LegacyTestnetFlag,

cmd/geth/usage.go

@@ -40,6 +40,7 @@ var AppHelpFlagGroups = []flags.FlagGroup{
 			utils.USBFlag,
 			utils.SmartCardDaemonPathFlag,
 			utils.NetworkIdFlag,
+			utils.MainnetFlag,
 			utils.GoerliFlag,
 			utils.RinkebyFlag,
 			utils.YoloV2Flag,

cmd/utils/flags.go

@@ -135,6 +135,10 @@ var (
 		Usage: "Explicitly set network id (integer)(For testnets: use --ropsten, --rinkeby, --goerli instead)",
 		Value: eth.DefaultConfig.NetworkId,
 	}
+	MainnetFlag = cli.BoolFlag{
+		Name:  "mainnet",
+		Usage: "Ethereum mainnet",
+	}
 	GoerliFlag = cli.BoolFlag{
 		Name:  "goerli",
 		Usage: "Görli network: pre-configured proof-of-authority test network",
@@ -1494,7 +1498,7 @@ func SetShhConfig(ctx *cli.Context, stack *node.Node) {
 // SetEthConfig applies eth-related command line flags to the config.
 func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *eth.Config) {
 	// Avoid conflicting network flags
-	CheckExclusive(ctx, DeveloperFlag, LegacyTestnetFlag, RopstenFlag, RinkebyFlag, GoerliFlag, YoloV2Flag)
+	CheckExclusive(ctx, MainnetFlag, DeveloperFlag, LegacyTestnetFlag, RopstenFlag, RinkebyFlag, GoerliFlag, YoloV2Flag)
 	CheckExclusive(ctx, LegacyLightServFlag, LightServeFlag, SyncModeFlag, "light")
 	CheckExclusive(ctx, DeveloperFlag, ExternalSignerFlag) // Can't use both ephemeral unlocked and external signer
 	CheckExclusive(ctx, GCModeFlag, "archive", TxLookupLimitFlag)
@@ -1608,6 +1612,12 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *eth.Config) {
 	}
 	// Override any default configs for hard coded networks.
 	switch {
+	case ctx.GlobalBool(MainnetFlag.Name):
+		if !ctx.GlobalIsSet(NetworkIdFlag.Name) {
+			cfg.NetworkId = 1
+		}
+		cfg.Genesis = core.DefaultGenesisBlock()
+		SetDNSDiscoveryDefaults(cfg, params.MainnetGenesisHash)
 	case ctx.GlobalBool(LegacyTestnetFlag.Name) || ctx.GlobalBool(RopstenFlag.Name):
 		if !ctx.GlobalIsSet(NetworkIdFlag.Name) {
 			cfg.NetworkId = 3