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handshake.go
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handshake.go
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package ent
import (
"fmt"
"github.com/entropyio/go-entropy/blockchain/forkid"
"github.com/entropyio/go-entropy/common"
"github.com/entropyio/go-entropy/server/p2p"
"math/big"
"time"
)
const (
// handshakeTimeout is the maximum allowed time for the `eth` handshake to
// complete before dropping the connection.= as malicious.
handshakeTimeout = 5 * time.Second
)
// Handshake executes the eth protocol handshake, negotiating version number,
// network IDs, difficulties, head and genesis blocks.
func (p *Peer) Handshake(network uint64, td *big.Int, head common.Hash, genesis common.Hash, forkID forkid.ID, forkFilter forkid.Filter) error {
// Send out own handshake in a new thread
errc := make(chan error, 2)
var status StatusPacket // safe to read after two values have been received from errc
go func() {
errc <- p2p.Send(p.rw, StatusMsg, &StatusPacket{
ProtocolVersion: uint32(p.version),
NetworkID: network,
TD: td,
Head: head,
Genesis: genesis,
ForkID: forkID,
})
}()
go func() {
errc <- p.readStatus(network, &status, genesis, forkFilter)
}()
timeout := time.NewTimer(handshakeTimeout)
defer timeout.Stop()
for i := 0; i < 2; i++ {
select {
case err := <-errc:
if err != nil {
return err
}
case <-timeout.C:
return p2p.DiscReadTimeout
}
}
p.td, p.head = status.TD, status.Head
// TD at mainnet block #7753254 is 76 bits. If it becomes 100 million times
// larger, it will still fit within 100 bits
if tdlen := p.td.BitLen(); tdlen > 100 {
return fmt.Errorf("too large total difficulty: bitlen %d", tdlen)
}
return nil
}
// readStatus reads the remote handshake message.
func (p *Peer) readStatus(network uint64, status *StatusPacket, genesis common.Hash, forkFilter forkid.Filter) error {
msg, err := p.rw.ReadMsg()
if err != nil {
return err
}
if msg.Code != StatusMsg {
return fmt.Errorf("%w: first msg has code %x (!= %x)", errNoStatusMsg, msg.Code, StatusMsg)
}
if msg.Size > maxMessageSize {
return fmt.Errorf("%w: %v > %v", errMsgTooLarge, msg.Size, maxMessageSize)
}
// Decode the handshake and make sure everything matches
if err := msg.Decode(&status); err != nil {
return fmt.Errorf("%w: message %v: %v", errDecode, msg, err)
}
if status.NetworkID != network {
return fmt.Errorf("%w: %d (!= %d)", errNetworkIDMismatch, status.NetworkID, network)
}
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)
}
if err := forkFilter(status.ForkID); err != nil {
return fmt.Errorf("%w: %v", errForkIDRejected, err)
}
return nil
}