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.

2 files changed, 70 insertions, 0 deletions

diff --git a/p2p/discover/node.go b/p2p/discover/node.go
index d9cbd9448..fc928a91a 100644
--- a/p2p/discover/node.go
+++ b/p2p/discover/node.go
@@ -225,6 +225,11 @@ func (n *Node) UnmarshalText(text []byte) error {
 // The node identifier is a marshaled elliptic curve public key.
 type NodeID [NodeIDBits / 8]byte
 
+// Bytes returns a byte slice representation of the NodeID
+func (n NodeID) Bytes() []byte {
+	return n[:]
+}
+
 // NodeID prints as a long hexadecimal number.
 func (n NodeID) String() string {
 	return fmt.Sprintf("%x", n[:])
@@ -240,6 +245,41 @@ func (n NodeID) TerminalString() string {
 	return hex.EncodeToString(n[:8])
 }
 
+// MarshalText implements the encoding.TextMarshaler interface.
+func (n NodeID) MarshalText() ([]byte, error) {
+	return []byte(hex.EncodeToString(n[:])), nil
+}
+
+// UnmarshalText implements the encoding.TextUnmarshaler interface.
+func (n *NodeID) UnmarshalText(text []byte) error {
+	id, err := HexID(string(text))
+	if err != nil {
+		return err
+	}
+	*n = id
+	return nil
+}
+
+// BytesID converts a byte slice to a NodeID
+func BytesID(b []byte) (NodeID, error) {
+	var id NodeID
+	if len(b) != len(id) {
+		return id, fmt.Errorf("wrong length, want %d bytes", len(id))
+	}
+	copy(id[:], b)
+	return id, nil
+}
+
+// MustBytesID converts a byte slice to a NodeID.
+// It panics if the byte slice is not a valid NodeID.
+func MustBytesID(b []byte) NodeID {
+	id, err := BytesID(b)
+	if err != nil {
+		panic(err)
+	}
+	return id
+}
+
 // HexID converts a hex string to a NodeID.
 // The string may be prefixed with 0x.
 func HexID(in string) (NodeID, error) {
diff --git a/p2p/discover/node_test.go b/p2p/discover/node_test.go
index 3d1662d0b..ed8db4dc6 100644
--- a/p2p/discover/node_test.go
+++ b/p2p/discover/node_test.go
@@ -17,6 +17,7 @@
 package discover
 
 import (
+	"bytes"
 	"fmt"
 	"math/big"
 	"math/rand"
@@ -192,6 +193,35 @@ func TestHexID(t *testing.T) {
 	}
 }
 
+func TestNodeID_textEncoding(t *testing.T) {
+	ref := NodeID{
+		0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x10,
+		0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x20,
+		0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x30,
+		0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x40,
+		0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x50,
+		0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x60,
+		0x61, 0x62, 0x63, 0x64,
+	}
+	hex := "01020304050607080910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364"
+
+	text, err := ref.MarshalText()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(text, []byte(hex)) {
+		t.Fatalf("text encoding did not match\nexpected: %s\ngot:      %s", hex, text)
+	}
+
+	id := new(NodeID)
+	if err := id.UnmarshalText(text); err != nil {
+		t.Fatal(err)
+	}
+	if *id != ref {
+		t.Fatalf("text decoding did not match\nexpected: %s\ngot:      %s", ref, id)
+	}
+}
+
 func TestNodeID_recover(t *testing.T) {
 	prv := newkey()
 	hash := make([]byte, 32)