p2p/enode: clean up DNS name support in Node

Remove methods Endpoint and NeedResolve, since they are kind of redundant.
Instead of adding a new constructor with a hostname parameter, provide method
WithHostname to attach a name to any node.

p2p/enode/node.go

@@ -37,11 +37,14 @@ var errMissingPrefix = errors.New("missing 'enr:' prefix for base64-encoded reco
 type Node struct {
 	r  enr.Record
 	id ID
+
+	// hostname tracks the DNS name of the node.
+	hostname string
+
 	// endpoint information
 	ip  netip.Addr
 	udp uint16
 	tcp uint16
-	hostname string
 }
 
 // New wraps a node record. The record must be valid according to the given
@@ -185,20 +188,16 @@ func (n *Node) TCP() int {
 	return int(n.tcp)
 }
 
-// Endpoint returns the hostname of the node if set, otherwise the IP address.
+// WithHostname adds a DNS hostname to the node.
-func (n *Node) Endpoint() string {
+func (n *Node) WithHostname(hostname string) *Node {
-	if n.hostname != "" {
+	cpy := *n
-		return n.hostname
+	cpy.hostname = hostname
-	}
+	return &cpy
-	if n.ip.IsValid() {
-		return n.ip.String()
-	}
-	return ""
 }
 
-// NeedResolve checks if the node requires DNS resolution.
+// Hostname returns the DNS name assigned by WithHostname.
-func (n *Node) NeedResolve() bool {
+func (n *Node) Hostname() string {
-	return n.hostname != "" //TODO: Add check for n.ip.IsValid(), but we need to implement invalidation for the previous resolved IP
+	return n.hostname
 }
 
 // UDPEndpoint returns the announced UDP endpoint.
@@ -246,9 +245,6 @@ func (n *Node) Record() *enr.Record {
 	cpy := n.r
 	return &cpy
 }
-func (n *Node) Hostname() string {
-	return n.hostname
-}
 
 // ValidateComplete checks whether n has a valid IP and UDP port.
 // Deprecated: don't use this method.

p2p/enode/urlv4.go

@@ -100,28 +100,6 @@ func NewV4(pubkey *ecdsa.PublicKey, ip net.IP, tcp, udp int) *Node {
 	return n
 }
 
-func NewV4WithDNS(pubkey *ecdsa.PublicKey, ip net.IP, hostname string, tcp, udp int) *Node {
-	var r enr.Record
-	if tcp != 0 {
-		r.Set(enr.TCP(tcp))
-	}
-	if udp != 0 {
-		r.Set(enr.UDP(udp))
-	}
-	if len(ip) > 0 {
-		r.Set(enr.IP(ip))
-	}
-	signV4Compat(&r, pubkey)
-	n, err := New(v4CompatID{}, &r)
-	if err != nil {
-		panic(err)
-	}
-	n.tcp = uint16(tcp)
-	n.udp = uint16(udp)
-	n.hostname = hostname
-	return n
-}
-
 // isNewV4 returns true for nodes created by NewV4.
 func isNewV4(n *Node) bool {
 	var k s256raw
@@ -132,7 +110,6 @@ func parseComplete(rawurl string) (*Node, error) {
 	var (
 		id               *ecdsa.PublicKey
 		tcpPort, udpPort uint64
-		node             *Node
 	)
 	u, err := url.Parse(rawurl)
 	if err != nil {
@@ -149,15 +126,8 @@ func parseComplete(rawurl string) (*Node, error) {
 		return nil, fmt.Errorf("invalid public key (%v)", err)
 	}
 
-	// Parse the IP address if its one.
+	// Parse the IP and ports.
 	ip := net.ParseIP(u.Hostname())
-	if ip != nil {
-		// Ensure the IP is 4 bytes long for IPv4 addresses.
-		if ipv4 := ip.To4(); ipv4 != nil {
-			ip = ipv4
-		}
-	}
-	// Parse the port numbers.
 	if tcpPort, err = strconv.ParseUint(u.Port(), 10, 16); err != nil {
 		return nil, errors.New("invalid port")
 	}
@@ -170,12 +140,11 @@ func parseComplete(rawurl string) (*Node, error) {
 		}
 	}
 
-	if ip != nil {
+	// Create the node.
-		node = NewV4(id, ip, int(tcpPort), int(udpPort))
+	node := NewV4(id, ip, int(tcpPort), int(udpPort))
-	} else {
+	if ip == nil && u.Hostname() != "" {
-		node = NewV4WithDNS(id, nil, u.Hostname(), int(tcpPort), int(udpPort))
+		node = node.WithHostname(u.Hostname())
 	}
-
 	return node, nil
 }
 
@@ -207,7 +176,7 @@ func (n *Node) URLv4() string {
 	}
 	u := url.URL{Scheme: "enode"}
 	if n.Hostname() != "" {
-		// For DNS nodes: include DNS name, TCP port, and optional UDP port
+		// For nodes with a DNS name: include DNS name, TCP port, and optional UDP port
 		u.User = url.User(nodeid)
 		u.Host = fmt.Sprintf("%s:%d", n.Hostname(), n.TCP())
 		if n.UDP() != n.TCP() {

p2p/enode/urlv4_test.go

@@ -79,13 +79,12 @@ var parseNodeTests = []struct {
 	},
 	{
 		input: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@valid.:3",
-		wantResult: NewV4WithDNS(
+		wantResult: NewV4(
 			hexPubkey("1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
 			nil,
-			"valid.",
 			3,
 			3,
-		),
+		).WithHostname("valid."),
 	},
 	{
 		input: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@[::]:52150",