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.

node/api.go

@@ -17,6 +17,7 @@
 package node
 
 import (
+	"context"
 	"fmt"
 	"strings"
 	"time"
@@ -25,6 +26,7 @@ import (
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/p2p"
 	"github.com/ethereum/go-ethereum/p2p/discover"
+	"github.com/ethereum/go-ethereum/rpc"
 	"github.com/rcrowley/go-metrics"
 )
 
@@ -73,6 +75,44 @@ func (api *PrivateAdminAPI) RemovePeer(url string) (bool, error) {
 	return true, nil
 }
 
+// PeerEvents creates an RPC subscription which receives peer events from the
+// node's p2p.Server
+func (api *PrivateAdminAPI) PeerEvents(ctx context.Context) (*rpc.Subscription, error) {
+	// Make sure the server is running, fail otherwise
+	server := api.node.Server()
+	if server == nil {
+		return nil, ErrNodeStopped
+	}
+
+	// Create the subscription
+	notifier, supported := rpc.NotifierFromContext(ctx)
+	if !supported {
+		return nil, rpc.ErrNotificationsUnsupported
+	}
+	rpcSub := notifier.CreateSubscription()
+
+	go func() {
+		events := make(chan *p2p.PeerEvent)
+		sub := server.SubscribeEvents(events)
+		defer sub.Unsubscribe()
+
+		for {
+			select {
+			case event := <-events:
+				notifier.Notify(rpcSub.ID, event)
+			case <-sub.Err():
+				return
+			case <-rpcSub.Err():
+				return
+			case <-notifier.Closed():
+				return
+			}
+		}
+	}()
+
+	return rpcSub, nil
+}
+
 // StartRPC starts the HTTP RPC API server.
 func (api *PrivateAdminAPI) StartRPC(host *string, port *int, cors *string, apis *string) (bool, error) {
 	api.node.lock.Lock()
@@ -163,7 +203,7 @@ func (api *PrivateAdminAPI) StartWS(host *string, port *int, allowedOrigins *str
 		}
 	}
 
-	if err := api.node.startWS(fmt.Sprintf("%s:%d", *host, *port), api.node.rpcAPIs, modules, origins); err != nil {
+	if err := api.node.startWS(fmt.Sprintf("%s:%d", *host, *port), api.node.rpcAPIs, modules, origins, api.node.config.WSExposeAll); err != nil {
 		return false, err
 	}
 	return true, nil