Add Flag for SSZ Encoding (#3256)

* add flag and enum

* change help message

* linter

* add flag

* add comment

* one more comment

* fix panic

* preston's comments

* add panic

beacon-chain/main.go

@@ -39,6 +39,7 @@ var appFlags = []cli.Flag{
 	cmd.P2PMaxPeers,
 	cmd.P2PPrivKey,
 	cmd.P2PWhitelist,
+	cmd.P2PEncoding,
 	cmd.DataDirFlag,
 	cmd.VerbosityFlag,
 	cmd.EnableTracingFlag,

beacon-chain/node/node.go

@@ -215,6 +215,7 @@ func (b *BeaconNode) registerP2P(ctx *cli.Context) error {
 			MaxPeers:          ctx.GlobalUint(cmd.P2PMaxPeers.Name),
 			WhitelistCIDR:     ctx.GlobalString(cmd.P2PWhitelist.Name),
 			EnableUPnP:        ctx.GlobalBool(cmd.EnableUPnPFlag.Name),
+			Encoding:          ctx.GlobalString(cmd.P2PEncoding.Name),
 		})
 		if err != nil {
 			return err

beacon-chain/p2p/broadcaster_test.go

@@ -25,6 +25,9 @@ func TestService_Broadcast(t *testing.T) {
 	p := &Service{
 		host:   p1.Host,
 		pubsub: p1.PubSub(),
+		cfg: &Config{
+			Encoding: "ssz",
+		},
 	}
 
 	msg := &testpb.TestSimpleMessage{

beacon-chain/p2p/config.go

@@ -14,4 +14,5 @@ type Config struct {
 	MaxPeers          uint
 	WhitelistCIDR     string
 	EnableUPnP        bool
+	Encoding          string
 }

beacon-chain/p2p/encoder/network_encoding.go

@@ -6,6 +6,12 @@ import (
 	"github.com/gogo/protobuf/proto"
 )
 
+// Defines the different encoding formats
+const (
+	SSZ       = "ssz"        // SSZ is SSZ only.
+	SSZSnappy = "ssz-snappy" // SSZSnappy is SSZ with snappy compression.
+)
+
 // NetworkEncoding represents an encoder compatible with Ethereum 2.0 p2p.
 type NetworkEncoding interface {
 	// Decode reads bytes from the reader and decodes it to the provided message.

beacon-chain/p2p/service.go

@@ -105,8 +105,15 @@ func (s *Service) Status() error {
 
 // Encoding returns the configured networking encoding.
 func (s *Service) Encoding() encoder.NetworkEncoding {
-	// TODO(3147): Return based on flag value
-	return &encoder.SszNetworkEncoder{}
+	encoding := s.cfg.Encoding
+	switch encoding {
+	case encoder.SSZ:
+		return &encoder.SszNetworkEncoder{}
+	case encoder.SSZSnappy:
+		return &encoder.SszNetworkEncoder{UseSnappyCompression: true}
+	default:
+		panic("Invalid Network Encoding Flag Provided")
+	}
 }
 
 // PubSub returns the p2p pubsub framework.

beacon-chain/usage.go

@@ -94,6 +94,7 @@ var appHelpFlagGroups = []flagGroup{
 			cmd.P2PWhitelist,
 			cmd.StaticPeers,
 			cmd.EnableUPnPFlag,
+			cmd.P2PEncoding,
 		},
 	},
 	{

shared/cmd/flags.go

@@ -107,6 +107,12 @@ var (
 			"would whitelist connections to peers on your local network only. The default " +
 			"is to accept all connections.",
 	}
+	// P2PEncoding defines the encoding format for p2p messages.
+	P2PEncoding = cli.StringFlag{
+		Name:  "p2p-encoding",
+		Usage: "The encoding format of messages sent over the wire. The default is 0, which represents ssz",
+		Value: "ssz",
+	}
 	// ClearDB tells the beacon node to remove any previously stored data at the data directory.
 	ClearDB = cli.BoolFlag{
 		Name:  "clear-db",