github.com/zhiqiangxu/go-ethereum@v1.9.16-0.20210824055606-be91cfdebc48/eth/discovery.go (about)

     1  // Copyright 2019 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package eth
    18  
    19  import (
    20  	"github.com/zhiqiangxu/go-ethereum/core"
    21  	"github.com/zhiqiangxu/go-ethereum/core/forkid"
    22  	"github.com/zhiqiangxu/go-ethereum/p2p"
    23  	"github.com/zhiqiangxu/go-ethereum/p2p/dnsdisc"
    24  	"github.com/zhiqiangxu/go-ethereum/p2p/enode"
    25  	"github.com/zhiqiangxu/go-ethereum/rlp"
    26  )
    27  
    28  // ethEntry is the "eth" ENR entry which advertises eth protocol
    29  // on the discovery network.
    30  type ethEntry struct {
    31  	ForkID forkid.ID // Fork identifier per EIP-2124
    32  
    33  	// Ignore additional fields (for forward compatibility).
    34  	Rest []rlp.RawValue `rlp:"tail"`
    35  }
    36  
    37  // ENRKey implements enr.Entry.
    38  func (e ethEntry) ENRKey() string {
    39  	return "eth"
    40  }
    41  
    42  // startEthEntryUpdate starts the ENR updater loop.
    43  func (eth *Ethereum) startEthEntryUpdate(ln *enode.LocalNode) {
    44  	var newHead = make(chan core.ChainHeadEvent, 10)
    45  	sub := eth.blockchain.SubscribeChainHeadEvent(newHead)
    46  
    47  	go func() {
    48  		defer sub.Unsubscribe()
    49  		for {
    50  			select {
    51  			case <-newHead:
    52  				ln.Set(eth.currentEthEntry())
    53  			case <-sub.Err():
    54  				// Would be nice to sync with eth.Stop, but there is no
    55  				// good way to do that.
    56  				return
    57  			}
    58  		}
    59  	}()
    60  }
    61  
    62  func (eth *Ethereum) currentEthEntry() *ethEntry {
    63  	return &ethEntry{ForkID: forkid.NewID(eth.blockchain)}
    64  }
    65  
    66  // setupDiscovery creates the node discovery source for the eth protocol.
    67  func (eth *Ethereum) setupDiscovery(cfg *p2p.Config) (enode.Iterator, error) {
    68  	if cfg.NoDiscovery || len(eth.config.DiscoveryURLs) == 0 {
    69  		return nil, nil
    70  	}
    71  	client := dnsdisc.NewClient(dnsdisc.Config{})
    72  	return client.NewIterator(eth.config.DiscoveryURLs...)
    73  }