p2p/discover: add config option for discv5 protocol ID (#26041)

This option is occasionally useful for advanced uses of the discv5 protocol.
Co-authored-by: Felix Lange <fjl@twurst.com>

cmd/devp2p/internal/v5test/framework.go

@@ -86,7 +86,7 @@ func newConn(dest *enode.Node, log logger) *conn {
 		localNode:  ln,
 		remote:     dest,
 		remoteAddr: &net.UDPAddr{IP: dest.IP(), Port: dest.UDP()},
-		codec:      v5wire.NewCodec(ln, key, mclock.System{}),
+		codec:      v5wire.NewCodec(ln, key, mclock.System{}, nil),
 		log:        log,
 	}
 }

p2p/discover/common.go

@@ -35,6 +35,10 @@ type UDPConn interface {
 	LocalAddr() net.Addr
 }
 
+type V5Config struct {
+	ProtocolID *[6]byte
+}
+
 // Config holds settings for the discovery listener.
 type Config struct {
 	// These settings are required and configure the UDP listener:
@@ -45,6 +49,10 @@ type Config struct {
 	Bootnodes   []*enode.Node     // list of bootstrap nodes
 	Unhandled   chan<- ReadPacket // unhandled packets are sent on this channel
 	Log         log.Logger        // if set, log messages go here
+
+	// V5ProtocolID configures the discv5 protocol identifier.
+	V5ProtocolID *[6]byte
+
 	ValidSchemes enr.IdentityScheme // allowed identity schemes
 	Clock        mclock.Clock
 }

p2p/discover/v5_udp.go

@@ -154,7 +154,7 @@ func newUDPv5(conn UDPConn, ln *enode.LocalNode, cfg Config) (*UDPv5, error) {
 		callDoneCh:    make(chan *callV5),
 		respTimeoutCh: make(chan *callTimeout),
 		// state of dispatch
-		codec:            v5wire.NewCodec(ln, cfg.PrivateKey, cfg.Clock),
+		codec:            v5wire.NewCodec(ln, cfg.PrivateKey, cfg.Clock, cfg.V5ProtocolID),
 		activeCallByNode: make(map[enode.ID]*callV5),
 		activeCallByAuth: make(map[v5wire.Nonce]*callV5),
 		callQueue:        make(map[enode.ID][]*callV5),

p2p/discover/v5wire/encoding.go

@@ -98,7 +98,7 @@ const (
 	randomPacketMsgSize = 20
 )
 
-var protocolID = [6]byte{'d', 'i', 's', 'c', 'v', '5'}
+var DefaultProtocolID = [6]byte{'d', 'i', 's', 'c', 'v', '5'}
 
 // Errors.
 var (
@@ -138,6 +138,7 @@ type Codec struct {
 	localnode  *enode.LocalNode
 	privkey    *ecdsa.PrivateKey
 	sc         *SessionCache
+	protocolID [6]byte
 
 	// encoder buffers
 	buf      bytes.Buffer // whole packet
@@ -150,12 +151,16 @@ type Codec struct {
 }
 
 // NewCodec creates a wire codec.
-func NewCodec(ln *enode.LocalNode, key *ecdsa.PrivateKey, clock mclock.Clock) *Codec {
+func NewCodec(ln *enode.LocalNode, key *ecdsa.PrivateKey, clock mclock.Clock, protocolID *[6]byte) *Codec {
 	c := &Codec{
 		sha256:     sha256.New(),
 		localnode:  ln,
 		privkey:    key,
 		sc:         NewSessionCache(1024, clock),
+		protocolID: DefaultProtocolID,
+	}
+	if protocolID != nil {
+		c.protocolID = *protocolID
 	}
 	return c
 }
@@ -255,7 +260,7 @@ func (c *Codec) makeHeader(toID enode.ID, flag byte, authsizeExtra int) Header {
 	}
 	return Header{
 		StaticHeader: StaticHeader{
-			ProtocolID: protocolID,
+			ProtocolID: c.protocolID,
 			Version:    version,
 			Flag:       flag,
 			AuthSize:   uint16(authsize),
@@ -434,7 +439,7 @@ func (c *Codec) Decode(input []byte, addr string) (src enode.ID, n *enode.Node,
 	c.reader.Reset(staticHeader)
 	binary.Read(&c.reader, binary.BigEndian, &head.StaticHeader)
 	remainingInput := len(input) - sizeofStaticPacketData
-	if err := head.checkValid(remainingInput); err != nil {
+	if err := head.checkValid(remainingInput, c.protocolID); err != nil {
 		return enode.ID{}, nil, nil, err
 	}
 
@@ -621,7 +626,7 @@ func (c *Codec) decryptMessage(input, nonce, headerData, readKey []byte) (Packet
 
 // checkValid performs some basic validity checks on the header.
 // The packetLen here is the length remaining after the static header.
-func (h *StaticHeader) checkValid(packetLen int) error {
+func (h *StaticHeader) checkValid(packetLen int, protocolID [6]byte) error {
 	if h.ProtocolID != protocolID {
 		return errInvalidHeader
 	}

p2p/discover/v5wire/encoding_test.go

@@ -504,8 +504,8 @@ type handshakeTestNode struct {
 
 func newHandshakeTest() *handshakeTest {
 	t := new(handshakeTest)
-	t.nodeA.init(testKeyA, net.IP{127, 0, 0, 1}, &t.clock)
-	t.nodeB.init(testKeyB, net.IP{127, 0, 0, 1}, &t.clock)
+	t.nodeA.init(testKeyA, net.IP{127, 0, 0, 1}, &t.clock, DefaultProtocolID)
+	t.nodeB.init(testKeyB, net.IP{127, 0, 0, 1}, &t.clock, DefaultProtocolID)
 	return t
 }
 
@@ -514,11 +514,11 @@ func (t *handshakeTest) close() {
 	t.nodeB.ln.Database().Close()
 }
 
-func (n *handshakeTestNode) init(key *ecdsa.PrivateKey, ip net.IP, clock mclock.Clock) {
+func (n *handshakeTestNode) init(key *ecdsa.PrivateKey, ip net.IP, clock mclock.Clock, protocolID [6]byte) {
 	db, _ := enode.OpenDB("")
 	n.ln = enode.NewLocalNode(db, key)
 	n.ln.SetStaticIP(ip)
-	n.c = NewCodec(n.ln, key, clock)
+	n.c = NewCodec(n.ln, key, clock, nil)
 }
 
 func (n *handshakeTestNode) encode(t testing.TB, to handshakeTestNode, p Packet) ([]byte, Nonce) {