feat: add eth/62 handshake support for XDC

- Added StatusPacket62 without ForkID field
- Added handshake62() function for eth/62, eth/63, XDPOS2
- Added readStatus62() for reading XDC status messages

Note: Peer connection still fails due to XDC's custom discovery
protocol using pingXDC (type 5) instead of standard ping (type 1).
This requires modification to p2p/discover layer.

eth/protocols/eth/handshake.go

@@ -19,6 +19,7 @@ package eth
 import (
 	"errors"
 	"fmt"
+	"math/big"
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -41,11 +42,59 @@ func (p *Peer) Handshake(networkID uint64, chain forkid.Blockchain, rangeMsg Blo
 		return p.handshake69(networkID, chain, rangeMsg)
 	case ETH68:
 		return p.handshake68(networkID, chain)
+	case ETH62, ETH63, XDPOS2:
+		// XDC uses eth/62, eth/63, and xdpos2 without ForkID
+		return p.handshake62(networkID, chain)
 	default:
 		return errors.New("unsupported protocol version")
 	}
 }
 
+// handshake62 performs the eth/62 handshake without ForkID (used by XDC)
+func (p *Peer) handshake62(networkID uint64, chain forkid.Blockchain) error {
+	var (
+		genesis = chain.Genesis()
+		latest  = chain.CurrentHeader()
+		// XDC is pre-merge, so TD is relevant. Use a placeholder TD based on block number.
+		// In a proper implementation, this should come from the chain's state.
+		td = new(big.Int).SetUint64(latest.Number.Uint64())
+	)
+	errc := make(chan error, 2)
+	go func() {
+		pkt := &StatusPacket62{
+			ProtocolVersion: uint32(p.version),
+			NetworkID:       networkID,
+			TD:              td,
+			Head:            latest.Hash(),
+			Genesis:         genesis.Hash(),
+		}
+		errc <- p2p.Send(p.rw, StatusMsg, pkt)
+	}()
+	var status StatusPacket62 // safe to read after two values have been received from errc
+	go func() {
+		errc <- p.readStatus62(networkID, &status, genesis.Hash())
+	}()
+
+	return waitForHandshake(errc, p)
+}
+
+func (p *Peer) readStatus62(networkID uint64, status *StatusPacket62, genesis common.Hash) error {
+	if err := p.readStatusMsg(status); err != nil {
+		return err
+	}
+	if status.NetworkID != networkID {
+		return fmt.Errorf("%w: %d (!= %d)", errNetworkIDMismatch, status.NetworkID, networkID)
+	}
+	if uint(status.ProtocolVersion) != p.version {
+		return fmt.Errorf("%w: %d (!= %d)", errProtocolVersionMismatch, status.ProtocolVersion, p.version)
+	}
+	if status.Genesis != genesis {
+		return fmt.Errorf("%w: %x (!= %x)", errGenesisMismatch, status.Genesis, genesis)
+	}
+	// No ForkID check for eth/62
+	return nil
+}
+
 func (p *Peer) handshake68(networkID uint64, chain forkid.Blockchain) error {
 	var (
 		genesis    = chain.Genesis()

eth/protocols/eth/protocol.go

@@ -111,6 +111,16 @@ type Packet interface {
 	Kind() byte   // Kind returns the message type.
 }
 
+// StatusPacket62 is the network packet for the status message in eth/62 and eth/63.
+// XDC uses this format without ForkID.
+type StatusPacket62 struct {
+	ProtocolVersion uint32
+	NetworkID       uint64
+	TD              *big.Int
+	Head            common.Hash
+	Genesis         common.Hash
+}
+
 // StatusPacket is the network packet for the status message.
 type StatusPacket68 struct {
 	ProtocolVersion uint32
@@ -361,6 +371,9 @@ type BlockRangeUpdatePacket struct {
 	LatestBlockHash common.Hash
 }
 
+func (*StatusPacket62) Name() string { return "Status" }
+func (*StatusPacket62) Kind() byte   { return StatusMsg }
+
 func (*StatusPacket68) Name() string { return "Status" }
 func (*StatusPacket68) Kind() byte   { return StatusMsg }