eth, eth/downloader: handle header requests, table driven proto tests

cmd/geth/main.go

@@ -283,6 +283,7 @@ JavaScript API. See https://github.com/ethereum/go-ethereum/wiki/Javascipt-Conso
 		utils.DataDirFlag,
 		utils.BlockchainVersionFlag,
 		utils.OlympicFlag,
+		utils.EthVersionFlag,
 		utils.CacheFlag,
 		utils.JSpathFlag,
 		utils.ListenPortFlag,
@@ -333,6 +334,7 @@ JavaScript API. See https://github.com/ethereum/go-ethereum/wiki/Javascipt-Conso
 	app.Before = func(ctx *cli.Context) error {
 		utils.SetupLogger(ctx)
 		utils.SetupVM(ctx)
+		utils.SetupEth(ctx)
 		if ctx.GlobalBool(utils.PProfEanbledFlag.Name) {
 			utils.StartPProf(ctx)
 		}

cmd/utils/flags.go

@@ -138,6 +138,11 @@ var (
 		Name:  "olympic",
 		Usage: "Use olympic style protocol",
 	}
+	EthVersionFlag = cli.IntFlag{
+		Name:  "eth",
+		Value: 61,
+		Usage: "Highest eth protocol to advertise (temporary, dev option)",
+	}
 
 	// miner settings
 	MinerThreadsFlag = cli.IntFlag{
@@ -459,6 +464,18 @@ func SetupVM(ctx *cli.Context) {
 	vm.SetJITCacheSize(ctx.GlobalInt(VMJitCacheFlag.Name))
 }
 
+// SetupEth configures the eth packages global settings
+func SetupEth(ctx *cli.Context) {
+	version := ctx.GlobalInt(EthVersionFlag.Name)
+	for len(eth.ProtocolVersions) > 0 && eth.ProtocolVersions[0] > uint(version) {
+		eth.ProtocolVersions = eth.ProtocolVersions[1:]
+		eth.ProtocolLengths = eth.ProtocolLengths[1:]
+	}
+	if len(eth.ProtocolVersions) == 0 {
+		Fatalf("No valid eth protocols remaining")
+	}
+}
+
 // MakeChain creates a chain manager from set command line flags.
 func MakeChain(ctx *cli.Context) (chain *core.ChainManager, chainDb common.Database) {
 	datadir := ctx.GlobalString(DataDirFlag.Name)