p2p: add dynamic name resolution for enodes

p2p/dial.go

@@ -77,6 +77,7 @@ var (
 	errRecentlyDialed   = errors.New("recently dialed")
 	errNetRestrict      = errors.New("not contained in netrestrict list")
 	errNoPort           = errors.New("node does not provide TCP port")
+	errNoResolvedIP     = errors.New("node does not provide a resolved IP")
 )
 
 // dialer creates outbound connections and submits them into Server.
@@ -135,7 +136,6 @@ type dialConfig struct {
 	log            log.Logger
 	clock          mclock.Clock
 	rand           *mrand.Rand
-	ttl            time.Duration
 }
 
 func (cfg dialConfig) withDefaults() dialConfig {
@@ -275,15 +275,13 @@ loop:
 		case node := <-d.addStaticCh:
 			id := node.ID()
 			_, exists := d.static[id]
-			d.log.Trace("Adding static node", "id", id, "addr", node.DisplayAddr(), "ip", node.IPAddr(), "added", !exists)
+			d.log.Trace("Adding static node", "id", id, "endpoint", node.Endpoint(), "added", !exists)
 			if exists {
 				continue loop
 			}
 			task := newDialTask(node, staticDialedConn)
 			d.static[id] = task
-			if err := d.checkDial(node); err != nil {
+			if d.checkDial(node) == nil {
-				d.log.Trace("Discarding dial candidate", "id", node.ID(), "addr", node.DisplayAddr(), "ip", node.IPAddr(), "reason", err)
-			} else {
 				d.addToStaticPool(task)
 			}
 
@@ -436,10 +434,42 @@ func (d *dialScheduler) removeFromStaticPool(idx int) {
 	task.staticPoolIndex = -1
 }
 
+func (d *dialScheduler) resolve(n *enode.Node) (*enode.Node, error) {
+	if n.NeedResolve() {
+		d.log.Debug("Attempting DNS resolution", "id", n.ID(), "name", n.Hostname())
+		ips, err := net.LookupIP(n.Hostname())
+		if err != nil {
+			d.log.Debug("DNS resolution failed", "id", n.ID(), "name", n.Hostname(), "err", err)
+			return n, err
+		}
+		d.log.Debug("DNS lookup succeeded", "id", n.ID(), "name", n.Hostname(), "ipcount", len(ips))
+
+		// Try IPv4 first
+		for _, ip := range ips {
+			if ip4 := ip.To4(); ip4 != nil {
+				resolved := enode.NewV4WithDNS(n.Pubkey(), ip4, n.Hostname(), n.TCP(), n.UDP())
+				d.log.Debug("DNS resolved to IPv4", "id", n.ID(), "name", n.Hostname(), "ip", ip4)
+				return resolved, nil
+			}
+		}
+		// Then try IPv6
+		for _, ip := range ips {
+			if ip6 := ip.To16(); ip6 != nil {
+				resolved := enode.NewV4WithDNS(n.Pubkey(), ip6, n.Hostname(), n.TCP(), n.UDP())
+				d.log.Debug("DNS resolved to IPv6", "id", n.ID(), "name", n.Hostname(), "ip", ip6)
+				return resolved, nil
+			}
+		}
+		d.log.Debug("DNS resolution found no usable IPs", "id", n.ID(), "name", n.Hostname())
+		return n, errNoResolvedIP
+	}
+	return n, nil
+}
+
 // startDial runs the given dial task in a separate goroutine.
 func (d *dialScheduler) startDial(task *dialTask) {
 	node := task.dest()
-	d.log.Trace("Starting p2p dial", "id", node.ID(), "addr", node.DisplayAddr(), "ip", node.IPAddr(), "flag", task.flags)
+	d.log.Trace("Starting p2p dial", "id", node.ID(), "endpoint", node.Endpoint(), "flag", task.flags)
 	hkey := string(node.ID().Bytes())
 	d.history.add(hkey, d.clock.Now().Add(dialHistoryExpiration))
 	d.dialing[node.ID()] = task
@@ -476,7 +506,16 @@ func (t *dialTask) dest() *enode.Node {
 }
 
 func (t *dialTask) run(d *dialScheduler) {
-	if !t.resolveIfNeeded(d) {
+	node := t.dest()
+	if node.NeedResolve() {
+		resolved, err := d.resolve(node)
+		if err != nil {
+			return
+		}
+		t.destPtr.Store(resolved)
+	}
+
+	if t.needResolve() && !t.resolve(d) {
 		return
 	}
 
@@ -491,36 +530,8 @@ func (t *dialTask) run(d *dialScheduler) {
 	}
 }
 
-// resolveIfNeeded attempts to resolve the node's IP address if it is invalid.
+func (t *dialTask) needResolve() bool {
-// It returns true if the node's IP address is valid after resolution attempts.
+	return t.flags&staticDialedConn != 0 && !t.dest().IPAddr().IsValid()
-func (t *dialTask) resolveIfNeeded(d *dialScheduler) bool {
-	node := t.dest()
-
-	if t.flags&staticDialedConn != 0 {
-		if t.resolve(d) && node.IPAddr().IsValid() {
-			return true
-		}
-	}
-
-	if node.NeedsDNSResolve() {
-		if t.resolveDNS(d) && node.IPAddr().IsValid() {
-			return true
-		}
-	}
-
-	return false
-}
-
-// resolveDNS attempts to resolve the DNS name of the destination node.
-// It returns true if resolution succeeds.
-func (t *dialTask) resolveDNS(d *dialScheduler) bool {
-	node := t.dest()
-	d.log.Trace("Starting DNS resolution", "id", node.ID(), "addr", node.DisplayAddr())
-	if err := node.RefreshDNS(d.dialConfig.ttl); err != nil {
-		d.log.Trace("DNS resolution failed", "id", node.ID(), "addr", node.DisplayAddr())
-		return false
-	}
-	return true
 }
 
 // resolve attempts to find the current endpoint for the destination
@@ -564,7 +575,8 @@ func (t *dialTask) dial(d *dialScheduler, dest *enode.Node) error {
 	dialMeter.Mark(1)
 	fd, err := d.dialer.Dial(d.ctx, dest)
 	if err != nil {
-		d.log.Trace("Dial error", "id", dest.ID(), "addr", dest.DisplayAddr(), "ip", dest.IPAddr(), "conn", t.flags, "err", cleanupDialErr(err))
+		addr, _ := dest.TCPEndpoint()
+		d.log.Trace("Dial error", "id", dest.ID(), "addr", addr, "conn", t.flags, "err", cleanupDialErr(err))
 		dialConnectionError.Mark(1)
 		return &dialError{err}
 	}

p2p/enode/node.go

@@ -22,14 +22,12 @@ import (
 	"encoding/hex"
 	"errors"
 	"fmt"
+	"github.com/ethereum/go-ethereum/p2p/enr"
+	"github.com/ethereum/go-ethereum/rlp"
 	"math/bits"
 	"net"
 	"net/netip"
 	"strings"
-	"time"
-
-	"github.com/ethereum/go-ethereum/p2p/enr"
-	"github.com/ethereum/go-ethereum/rlp"
 )
 
 var errMissingPrefix = errors.New("missing 'enr:' prefix for base64-encoded record")
@@ -39,13 +37,10 @@ type Node struct {
 	r  enr.Record
 	id ID
 	// endpoint information
-	ip  netip.Addr
+	ip       netip.Addr
-	udp uint16
+	udp      uint16
-	tcp uint16
+	tcp      uint16
-	// dns information
+	hostname string
-	dnsName     string
-	dnsResolved time.Time
-	dnsTTL      time.Duration
 }
 
 // New wraps a node record. The record must be valid according to the given
@@ -189,6 +184,22 @@ func (n *Node) TCP() int {
 	return int(n.tcp)
 }
 
+// Endpoint returns the hostname of the node if set, otherwise the IP address.
+func (n *Node) Endpoint() string {
+	if n.hostname != "" {
+		return n.hostname
+	}
+	if n.ip.IsValid() {
+		return n.ip.String()
+	}
+	return ""
+}
+
+// NeedResolve checks if the node requires DNS resolution.
+func (n *Node) NeedResolve() bool {
+	return n.hostname != "" //TODO: Add check for n.ip.IsValid(), but we need to implement invalidation for the previous resolved IP
+}
+
 // UDPEndpoint returns the announced UDP endpoint.
 func (n *Node) UDPEndpoint() (netip.AddrPort, bool) {
 	if !n.ip.IsValid() || n.ip.IsUnspecified() || n.udp == 0 {
@@ -234,6 +245,9 @@ 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.
@@ -262,84 +276,6 @@ func (n *Node) String() string {
 	return "enr:" + b64
 }
 
-// resolveDNS attempts to resolve a DNS name to an IP address
-func (n *Node) resolveDNS(dnsName string) (netip.Addr, error) {
-	ips, err := net.LookupIP(dnsName)
-	if err != nil {
-		return netip.Addr{}, err
-	}
-	for _, ip := range ips {
-		if ip4 := ip.To4(); ip4 != nil {
-			addr, ok := netip.AddrFromSlice(ip4)
-			if ok {
-				return addr, nil
-			}
-		}
-	}
-	// Fall back to IPv6 if no IPv4 is available
-	for _, ip := range ips {
-		addr, ok := netip.AddrFromSlice(ip)
-		if ok {
-			return addr, nil
-		}
-	}
-
-	return netip.Addr{}, errors.New("no valid IP address found")
-}
-
-// SetDNS sets the DNS name and resolves it to an IP address
-func (n *Node) SetDNS(dnsName string, ttl time.Duration) error {
-	ip, err := n.resolveDNS(dnsName)
-	if err != nil {
-		return err
-	}
-
-	n.dnsName = dnsName
-	n.dnsResolved = time.Now()
-	n.dnsTTL = ttl
-
-	if ip.Is4() {
-		n.setIP4(ip)
-	} else {
-		n.setIP6(ip)
-	}
-	return nil
-}
-
-// DNSName returns the stored DNS name
-func (n *Node) DNSName() string {
-	return n.dnsName
-}
-
-// RefreshDNS updates the IP address from the stored DNS name
-func (n *Node) RefreshDNS(ttl time.Duration) error {
-	if n.dnsName == "" {
-		return errors.New("no DNS name set")
-	}
-	return n.SetDNS(n.dnsName, ttl)
-}
-
-// DisplayAddr returns either "hostname:port" or "ip:port"
-func (n *Node) DisplayAddr() string {
-	addr := n.dnsName
-	if addr == "" {
-		addr = n.ip.String()
-	}
-	return fmt.Sprintf("%s:%d", addr, n.tcp)
-}
-
-// NeedsDNSResolve returns true if the node has a DNS name that needs resolution
-func (n *Node) NeedsDNSResolve() bool {
-	if n.dnsName == "" {
-		return false
-	}
-	return !n.ip.IsValid() || time.Since(n.dnsResolved) > n.dnsTTL
-}
-
-func (n *Node) GetTTL() time.Duration {
-	return n.dnsTTL
-}
-
 // MarshalText implements encoding.TextMarshaler.
 func (n *Node) MarshalText() ([]byte, error) {
 	return []byte(n.String()), nil

p2p/enode/node_test.go

@@ -274,7 +274,7 @@ func TestNodeEndpoints(t *testing.T) {
 			node: func() *Node {
 				var r enr.Record
 				n := SignNull(&r, id)
-				n.dnsName = "example.com"
+				n.hostname = "example.com"
 				n.tcp = 30303
 				n.udp = 30303
 				return n
@@ -283,40 +283,6 @@ func TestNodeEndpoints(t *testing.T) {
 			wantUDP: 30303,
 			wantDNS: "example.com",
 		},
-		{
-			name: "dns-with-ports",
-			node: func() *Node {
-				var r enr.Record
-				r.Set(enr.TCP(9000))
-				r.Set(enr.UDP(9001))
-				n := SignNull(&r, id)
-				n.dnsName = "node.example.org"
-				n.tcp = 9000
-				n.udp = 9001
-				return n
-			}(),
-			wantTCP: 9000,
-			wantUDP: 9001,
-			wantDNS: "node.example.org",
-		},
-		{
-			name: "dns-with-ip-fallback",
-			node: func() *Node {
-				var r enr.Record
-				r.Set(enr.IPv4Addr(netip.MustParseAddr("192.168.1.1")))
-				r.Set(enr.TCP(9000))
-				r.Set(enr.UDP(9000))
-				n := SignNull(&r, id)
-				n.dnsName = "node.example.org"
-				n.tcp = 9000
-				n.udp = 9000
-				return n
-			}(),
-			wantIP:  netip.MustParseAddr("192.168.1.1"),
-			wantTCP: 9000,
-			wantUDP: 9000,
-			wantDNS: "node.example.org",
-		},
 	}
 
 	for _, test := range tests {
@@ -333,8 +299,8 @@ func TestNodeEndpoints(t *testing.T) {
 			if quic, _ := test.node.QUICEndpoint(); test.wantQUIC != int(quic.Port()) {
 				t.Errorf("node has wrong QUIC port %d, want %d", quic.Port(), test.wantQUIC)
 			}
-			if test.wantDNS != test.node.DNSName() {
+			if test.wantDNS != test.node.Hostname() {
-				t.Errorf("node has wrong DNS name %s, want %s", test.node.DNSName(), test.wantDNS)
+				t.Errorf("node has wrong DNS name %s, want %s", test.node.Hostname(), test.wantDNS)
 			}
 		})
 	}

p2p/enode/urlv4.go

@@ -101,17 +101,25 @@ func NewV4(pubkey *ecdsa.PublicKey, ip net.IP, tcp, udp int) *Node {
 	return n
 }
 
-func NewV4WithDNS(pubkey *ecdsa.PublicKey, ip net.IP, dnsName string, tcp, udp int) *Node {
+func NewV4WithDNS(pubkey *ecdsa.PublicKey, ip net.IP, hostname string, tcp, udp int) *Node {
-	n := NewV4(pubkey, ip, tcp, udp)
+	var r enr.Record
-	// Always set TCP/UDP ports regardless of IP
+	if tcp != 0 {
-	// This is to ensure that the node is always
+		r.Set(enr.TCP(tcp))
-	// considered valid even if the IP is not
-	// set.
-	if len(ip) == 0 {
-		n.tcp = uint16(tcp)
-		n.udp = uint16(udp)
 	}
-	n.dnsName = dnsName
+	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
 }
 
@@ -125,6 +133,7 @@ func parseComplete(rawurl string) (*Node, error) {
 	var (
 		id               *ecdsa.PublicKey
 		tcpPort, udpPort uint64
+		node             *Node
 	)
 	u, err := url.Parse(rawurl)
 	if err != nil {
@@ -140,6 +149,16 @@ func parseComplete(rawurl string) (*Node, error) {
 	if id, err = parsePubkey(u.User.String()); err != nil {
 		return nil, fmt.Errorf("invalid public key (%v)", err)
 	}
+
+	// Parse the IP address if its one.
+	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")
 	}
@@ -151,20 +170,14 @@ func parseComplete(rawurl string) (*Node, error) {
 			return nil, errors.New("invalid discport in query")
 		}
 	}
-	// Check if hostname is an IP address and create node accordingly
+
-	hostname := u.Hostname()
+	if ip != nil {
-	ip := net.ParseIP(hostname)
+		node = NewV4(id, ip, int(tcpPort), int(udpPort))
-	if ip == nil {
+	} else {
-		ips, err := lookupIPFunc(hostname)
+		node = NewV4WithDNS(id, nil, u.Hostname(), int(tcpPort), int(udpPort))
-		if err != nil {
-			return NewV4WithDNS(id, nil, hostname, int(tcpPort), int(udpPort)), nil
-		}
-		ip = ips[0]
 	}
-	if ipv4 := ip.To4(); ipv4 != nil {
+
-		ip = ipv4
+	return node, nil
-	}
-	return NewV4(id, ip, int(tcpPort), int(udpPort)), nil
 }
 
 // parsePubkey parses a hex-encoded secp256k1 public key.
@@ -194,19 +207,23 @@ func (n *Node) URLv4() string {
 		nodeid = fmt.Sprintf("%s.%x", scheme, n.id[:])
 	}
 	u := url.URL{Scheme: "enode"}
-	if !n.ip.IsValid() && n.dnsName == "" {
+	if n.NeedResolve() {
-		u.Host = nodeid
+		// For DNS nodes: include DNS name, TCP port, and optional UDP port
-		return u.String()
+		u.User = url.User(nodeid)
-	}
+		u.Host = fmt.Sprintf("%s:%d", n.Hostname(), n.TCP())
-	u.User = url.User(nodeid)
+		if n.UDP() != n.TCP() {
-	if n.dnsName != "" {
+			u.RawQuery = "discport=" + strconv.Itoa(n.UDP())
-		u.Host = fmt.Sprintf("%s:%d", n.dnsName, n.TCP())
+		}
-	} else {
+	} else if n.ip.IsValid() {
+		// For IP-based nodes: include IP address, TCP port, and optional UDP port
 		addr := net.TCPAddr{IP: n.IP(), Port: n.TCP()}
+		u.User = url.User(nodeid)
 		u.Host = addr.String()
-	}
+		if n.UDP() != n.TCP() {
-	if n.UDP() != n.TCP() {
+			u.RawQuery = "discport=" + strconv.Itoa(n.UDP())
-		u.RawQuery = "discport=" + strconv.Itoa(n.UDP())
+		}
+	} else {
+		u.Host = nodeid
 	}
 	return u.String()
 }

p2p/enode/urlv4_test.go

@@ -78,6 +78,15 @@ var parseNodeTests = []struct {
 		input:     "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@127.0.0.1:3?discport=foo",
 		wantError: `invalid discport in query`,
 	},
+	{
+		input: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@127.0.0.1:52150",
+		wantResult: NewV4(
+			hexPubkey("1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
+			net.IP{127, 0, 0, 1},
+			52150,
+			52150,
+		),
+	},
 	{
 		input: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@valid.:3",
 		wantResult: NewV4WithDNS(
@@ -88,15 +97,6 @@ var parseNodeTests = []struct {
 			3,
 		),
 	},
-	{
-		input: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@127.0.0.1:52150",
-		wantResult: NewV4(
-			hexPubkey("1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439"),
-			net.IP{127, 0, 0, 1},
-			52150,
-			52150,
-		),
-	},
 	{
 		input: "enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@[::]:52150",
 		wantResult: NewV4(

p2p/server.go

@@ -64,10 +64,6 @@ const (
 
 	// Maximum amount of time allowed for writing a complete message.
 	frameWriteTimeout = 20 * time.Second
-
-	defaultTTL = 5 * time.Minute
-	minTTL     = 1 * time.Second
-	maxTTL     = 24 * time.Hour
 )
 
 var (
@@ -126,11 +122,6 @@ type Config struct {
 	// allowed to connect, even above the peer limit.
 	TrustedNodes []*enode.Node
 
-	// TTL is the time-to-live for DNS discovery queries
-	// This value is passed to the DNS resolvers when performing name
-	// resolutions.
-	TTL time.Duration `toml:",omitempty"`
-
 	// Connectivity can be restricted to certain IP networks.
 	// If this option is set to a non-nil value, only hosts which match one of the
 	// IP networks contained in the list are considered.
@@ -629,11 +620,6 @@ func (srv *Server) setupDialScheduler() {
 	if config.dialer == nil {
 		config.dialer = tcpDialer{&net.Dialer{Timeout: defaultDialTimeout}}
 	}
-	if srv.TTL >= minTTL && srv.TTL <= maxTTL {
-		config.ttl = srv.TTL
-	} else {
-		config.ttl = defaultTTL
-	}
 	srv.dialsched = newDialScheduler(config, srv.discmix, srv.SetupConn)
 	for _, n := range srv.StaticNodes {
 		srv.dialsched.addStatic(n)