Official Go implementation of the Ethereum protocol
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go-ethereum/eth/discovery.go

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2.3 KiB

// Copyright 2019 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package eth
import (
"github.com/ethereum/go-ethereum/core"
"github.com/ethereum/go-ethereum/core/forkid"
"github.com/ethereum/go-ethereum/p2p"
"github.com/ethereum/go-ethereum/p2p/dnsdisc"
"github.com/ethereum/go-ethereum/p2p/enode"
"github.com/ethereum/go-ethereum/rlp"
)
// ethEntry is the "eth" ENR entry which advertises eth protocol
// on the discovery network.
type ethEntry struct {
ForkID forkid.ID // Fork identifier per EIP-2124
// Ignore additional fields (for forward compatibility).
Rest []rlp.RawValue `rlp:"tail"`
}
// ENRKey implements enr.Entry.
func (e ethEntry) ENRKey() string {
return "eth"
}
// startEthEntryUpdate starts the ENR updater loop.
func (eth *Ethereum) startEthEntryUpdate(ln *enode.LocalNode) {
var newHead = make(chan core.ChainHeadEvent, 10)
sub := eth.blockchain.SubscribeChainHeadEvent(newHead)
go func() {
defer sub.Unsubscribe()
for {
select {
case <-newHead:
ln.Set(eth.currentEthEntry())
case <-sub.Err():
// Would be nice to sync with eth.Stop, but there is no
// good way to do that.
return
}
}
}()
}
func (eth *Ethereum) currentEthEntry() *ethEntry {
return &ethEntry{ForkID: forkid.NewID(eth.blockchain)}
}
// setupDiscovery creates the node discovery source for the eth protocol.
func (eth *Ethereum) setupDiscovery(cfg *p2p.Config) (enode.Iterator, error) {
if cfg.NoDiscovery || len(eth.config.DiscoveryURLs) == 0 {
return nil, nil
}
client := dnsdisc.NewClient(dnsdisc.Config{})
return client.NewIterator(eth.config.DiscoveryURLs...)
}