cmd/geth, cmd/utils, eth, p2p: pass and honor a no discovery flag

cmd/geth/main.go

@@ -260,6 +260,7 @@ JavaScript API. See https://github.com/ethereum/go-ethereum/wiki/Javascipt-Conso
 		utils.AutoDAGFlag,
 		utils.NATFlag,
 		utils.NatspecEnabledFlag,
+		utils.NoDiscoverFlag,
 		utils.NodeKeyFileFlag,
 		utils.NodeKeyHexFlag,
 		utils.RPCEnabledFlag,

cmd/utils/flags.go

@@ -235,6 +235,10 @@ var (
 		Usage: "NAT port mapping mechanism (any|none|upnp|pmp|extip:<IP>)",
 		Value: "any",
 	}
+	NoDiscoverFlag = cli.BoolFlag{
+		Name:  "nodiscover",
+		Usage: "Disables the peer discovery mechanism (manual peer addition)",
+	}
 	WhisperEnabledFlag = cli.BoolFlag{
 		Name:  "shh",
 		Usage: "Enable whisper",
@@ -312,6 +316,7 @@ func MakeEthConfig(clientID, version string, ctx *cli.Context) *eth.Config {
 		Port:               ctx.GlobalString(ListenPortFlag.Name),
 		NAT:                GetNAT(ctx),
 		NatSpec:            ctx.GlobalBool(NatspecEnabledFlag.Name),
+		Discovery:          !ctx.GlobalBool(NoDiscoverFlag.Name),
 		NodeKey:            GetNodeKey(ctx),
 		Shh:                ctx.GlobalBool(WhisperEnabledFlag.Name),
 		Dial:               true,
@@ -320,7 +325,6 @@ func MakeEthConfig(clientID, version string, ctx *cli.Context) *eth.Config {
 		SolcPath:           ctx.GlobalString(SolcPathFlag.Name),
 		AutoDAG:            ctx.GlobalBool(AutoDAGFlag.Name) || ctx.GlobalBool(MiningEnabledFlag.Name),
 	}
-
 }
 
 func GetChain(ctx *cli.Context) (*core.ChainManager, common.Database, common.Database) {

eth/backend.go

@@ -72,6 +72,7 @@ type Config struct {
 
 	MaxPeers        int
 	MaxPendingPeers int
+	Discovery       bool
 	Port            string
 
 	// Space-separated list of discovery node URLs
@@ -311,6 +312,7 @@ func New(config *Config) (*Ethereum, error) {
 		Name:            config.Name,
 		MaxPeers:        config.MaxPeers,
 		MaxPendingPeers: config.MaxPendingPeers,
+		Discovery:       config.Discovery,
 		Protocols:       protocols,
 		NAT:             config.NAT,
 		NoDial:          !config.Dial,

p2p/server.go

@@ -55,6 +55,10 @@ type Server struct {
 	// Zero defaults to preset values.
 	MaxPendingPeers int
 
+	// Discovery specifies whether the peer discovery mechanism should be started
+	// or not. Disabling is usually useful for protocol debugging (manual topology).
+	Discovery bool
+
 	// Name sets the node name of this server.
 	// Use common.MakeName to create a name that follows existing conventions.
 	Name string
@@ -240,6 +244,14 @@ func (srv *Server) Self() *discover.Node {
 	if !srv.running {
 		return &discover.Node{IP: net.ParseIP("0.0.0.0")}
 	}
+	if srv.ntab == nil {
+		addr := srv.listener.Addr().(*net.TCPAddr)
+		return &discover.Node{
+			ID:  discover.PubkeyID(&srv.PrivateKey.PublicKey),
+			IP:  addr.IP,
+			TCP: uint16(addr.Port),
+		}
+	}
 	return srv.ntab.Self()
 }
 
@@ -290,15 +302,22 @@ func (srv *Server) Start() (err error) {
 	srv.peerOpDone = make(chan struct{})
 
 	// node table
-	ntab, err := discover.ListenUDP(srv.PrivateKey, srv.ListenAddr, srv.NAT, srv.NodeDatabase)
-	if err != nil {
-		return err
+	if srv.Discovery {
+		ntab, err := discover.ListenUDP(srv.PrivateKey, srv.ListenAddr, srv.NAT, srv.NodeDatabase)
+		if err != nil {
+			return err
+		}
+		srv.ntab = ntab
 	}
-	srv.ntab = ntab
-	dialer := newDialState(srv.StaticNodes, srv.ntab, srv.MaxPeers/2)
+
+	dynPeers := srv.MaxPeers / 2
+	if !srv.Discovery {
+		dynPeers = 0
+	}
+	dialer := newDialState(srv.StaticNodes, srv.ntab, dynPeers)
 
 	// handshake
-	srv.ourHandshake = &protoHandshake{Version: baseProtocolVersion, Name: srv.Name, ID: ntab.Self().ID}
+	srv.ourHandshake = &protoHandshake{Version: baseProtocolVersion, Name: srv.Name, ID: discover.PubkeyID(&srv.PrivateKey.PublicKey)}
 	for _, p := range srv.Protocols {
 		srv.ourHandshake.Caps = append(srv.ourHandshake.Caps, p.cap())
 	}
@@ -454,7 +473,9 @@ running:
 	}
 
 	// Terminate discovery. If there is a running lookup it will terminate soon.
-	srv.ntab.Close()
+	if srv.ntab != nil {
+		srv.ntab.Close()
+	}
 	// Disconnect all peers.
 	for _, p := range peers {
 		p.Disconnect(DiscQuitting)
@@ -486,7 +507,7 @@ func (srv *Server) encHandshakeChecks(peers map[discover.NodeID]*Peer, c *conn)
 		return DiscTooManyPeers
 	case peers[c.id] != nil:
 		return DiscAlreadyConnected
-	case c.id == srv.ntab.Self().ID:
+	case c.id == srv.Self().ID:
 		return DiscSelf
 	default:
 		return nil