p2p: add network simulation framework (#14982)

This commit introduces a network simulation framework which
can be used to run simulated networks of devp2p nodes. The
intention is to use this for testing protocols, performing
benchmarks and visualising emergent network behaviour.

1 files changed, 215 insertions, 0 deletions

diff --git a/p2p/simulations/adapters/types.go b/p2p/simulations/adapters/types.go
new file mode 100644
index 000000000..ed6cfc504
--- /dev/null
+++ b/p2p/simulations/adapters/types.go
@@ -0,0 +1,215 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package adapters
+
+import (
+	"crypto/ecdsa"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"net"
+	"os"
+
+	"github.com/docker/docker/pkg/reexec"
+	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/ethereum/go-ethereum/node"
+	"github.com/ethereum/go-ethereum/p2p"
+	"github.com/ethereum/go-ethereum/p2p/discover"
+	"github.com/ethereum/go-ethereum/rpc"
+)
+
+// Node represents a node in a simulation network which is created by a
+// NodeAdapter, for example:
+//
+// * SimNode    - An in-memory node
+// * ExecNode   - A child process node
+// * DockerNode - A Docker container node
+//
+type Node interface {
+	// Addr returns the node's address (e.g. an Enode URL)
+	Addr() []byte
+
+	// Client returns the RPC client which is created once the node is
+	// up and running
+	Client() (*rpc.Client, error)
+
+	// ServeRPC serves RPC requests over the given connection
+	ServeRPC(net.Conn) error
+
+	// Start starts the node with the given snapshots
+	Start(snapshots map[string][]byte) error
+
+	// Stop stops the node
+	Stop() error
+
+	// NodeInfo returns information about the node
+	NodeInfo() *p2p.NodeInfo
+
+	// Snapshots creates snapshots of the running services
+	Snapshots() (map[string][]byte, error)
+}
+
+// NodeAdapter is used to create Nodes in a simulation network
+type NodeAdapter interface {
+	// Name returns the name of the adapter for logging purposes
+	Name() string
+
+	// NewNode creates a new node with the given configuration
+	NewNode(config *NodeConfig) (Node, error)
+}
+
+// NodeConfig is the configuration used to start a node in a simulation
+// network
+type NodeConfig struct {
+	// ID is the node's ID which is used to identify the node in the
+	// simulation network
+	ID discover.NodeID
+
+	// PrivateKey is the node's private key which is used by the devp2p
+	// stack to encrypt communications
+	PrivateKey *ecdsa.PrivateKey
+
+	// Name is a human friendly name for the node like "node01"
+	Name string
+
+	// Services are the names of the services which should be run when
+	// starting the node (for SimNodes it should be the names of services
+	// contained in SimAdapter.services, for other nodes it should be
+	// services registered by calling the RegisterService function)
+	Services []string
+}
+
+// nodeConfigJSON is used to encode and decode NodeConfig as JSON by encoding
+// all fields as strings
+type nodeConfigJSON struct {
+	ID         string   `json:"id"`
+	PrivateKey string   `json:"private_key"`
+	Name       string   `json:"name"`
+	Services   []string `json:"services"`
+}
+
+// MarshalJSON implements the json.Marshaler interface by encoding the config
+// fields as strings
+func (n *NodeConfig) MarshalJSON() ([]byte, error) {
+	confJSON := nodeConfigJSON{
+		ID:       n.ID.String(),
+		Name:     n.Name,
+		Services: n.Services,
+	}
+	if n.PrivateKey != nil {
+		confJSON.PrivateKey = hex.EncodeToString(crypto.FromECDSA(n.PrivateKey))
+	}
+	return json.Marshal(confJSON)
+}
+
+// UnmarshalJSON implements the json.Unmarshaler interface by decoding the json
+// string values into the config fields
+func (n *NodeConfig) UnmarshalJSON(data []byte) error {
+	var confJSON nodeConfigJSON
+	if err := json.Unmarshal(data, &confJSON); err != nil {
+		return err
+	}
+
+	if confJSON.ID != "" {
+		nodeID, err := discover.HexID(confJSON.ID)
+		if err != nil {
+			return err
+		}
+		n.ID = nodeID
+	}
+
+	if confJSON.PrivateKey != "" {
+		key, err := hex.DecodeString(confJSON.PrivateKey)
+		if err != nil {
+			return err
+		}
+		privKey, err := crypto.ToECDSA(key)
+		if err != nil {
+			return err
+		}
+		n.PrivateKey = privKey
+	}
+
+	n.Name = confJSON.Name
+	n.Services = confJSON.Services
+
+	return nil
+}
+
+// RandomNodeConfig returns node configuration with a randomly generated ID and
+// PrivateKey
+func RandomNodeConfig() *NodeConfig {
+	key, err := crypto.GenerateKey()
+	if err != nil {
+		panic("unable to generate key")
+	}
+	var id discover.NodeID
+	pubkey := crypto.FromECDSAPub(&key.PublicKey)
+	copy(id[:], pubkey[1:])
+	return &NodeConfig{
+		ID:         id,
+		PrivateKey: key,
+	}
+}
+
+// ServiceContext is a collection of options and methods which can be utilised
+// when starting services
+type ServiceContext struct {
+	RPCDialer
+
+	NodeContext *node.ServiceContext
+	Config      *NodeConfig
+	Snapshot    []byte
+}
+
+// RPCDialer is used when initialising services which need to connect to
+// other nodes in the network (for example a simulated Swarm node which needs
+// to connect to a Geth node to resolve ENS names)
+type RPCDialer interface {
+	DialRPC(id discover.NodeID) (*rpc.Client, error)
+}
+
+// Services is a collection of services which can be run in a simulation
+type Services map[string]ServiceFunc
+
+// ServiceFunc returns a node.Service which can be used to boot a devp2p node
+type ServiceFunc func(ctx *ServiceContext) (node.Service, error)
+
+// serviceFuncs is a map of registered services which are used to boot devp2p
+// nodes
+var serviceFuncs = make(Services)
+
+// RegisterServices registers the given Services which can then be used to
+// start devp2p nodes using either the Exec or Docker adapters.
+//
+// It should be called in an init function so that it has the opportunity to
+// execute the services before main() is called.
+func RegisterServices(services Services) {
+	for name, f := range services {
+		if _, exists := serviceFuncs[name]; exists {
+			panic(fmt.Sprintf("node service already exists: %q", name))
+		}
+		serviceFuncs[name] = f
+	}
+
+	// now we have registered the services, run reexec.Init() which will
+	// potentially start one of the services if the current binary has
+	// been exec'd with argv[0] set to "p2p-node"
+	if reexec.Init() {
+		os.Exit(0)
+	}
+}