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, 20 insertions, 3 deletions

diff --git a/p2p/dial.go b/p2p/dial.go
index b77971396..2d9e3a0ed 100644
--- a/p2p/dial.go
+++ b/p2p/dial.go
@@ -47,6 +47,24 @@ const (
 	maxResolveDelay     = time.Hour
 )
 
+// NodeDialer is used to connect to nodes in the network, typically by using
+// an underlying net.Dialer but also using net.Pipe in tests
+type NodeDialer interface {
+	Dial(*discover.Node) (net.Conn, error)
+}
+
+// TCPDialer implements the NodeDialer interface by using a net.Dialer to
+// create TCP connections to nodes in the network
+type TCPDialer struct {
+	*net.Dialer
+}
+
+// Dial creates a TCP connection to the node
+func (t TCPDialer) Dial(dest *discover.Node) (net.Conn, error) {
+	addr := &net.TCPAddr{IP: dest.IP, Port: int(dest.TCP)}
+	return t.Dialer.Dial("tcp", addr.String())
+}
+
 // dialstate schedules dials and discovery lookups.
 // it get's a chance to compute new tasks on every iteration
 // of the main loop in Server.run.
@@ -318,14 +336,13 @@ func (t *dialTask) resolve(srv *Server) bool {
 
 // dial performs the actual connection attempt.
 func (t *dialTask) dial(srv *Server, dest *discover.Node) bool {
-	addr := &net.TCPAddr{IP: dest.IP, Port: int(dest.TCP)}
-	fd, err := srv.Dialer.Dial("tcp", addr.String())
+	fd, err := srv.Dialer.Dial(dest)
 	if err != nil {
 		log.Trace("Dial error", "task", t, "err", err)
 		return false
 	}
 	mfd := newMeteredConn(fd, false)
-	srv.setupConn(mfd, t.flags, dest)
+	srv.SetupConn(mfd, t.flags, dest)
 	return true
 }