76 lines
2.0 KiB
Go
76 lines
2.0 KiB
Go
// Copyright (c) 2016 The btcsuite developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package connmgr
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import (
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"fmt"
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mrand "math/rand"
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"net"
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"strconv"
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"time"
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"github.com/btcsuite/btcd/chaincfg"
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"github.com/btcsuite/btcd/wire"
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)
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const (
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// These constants are used by the DNS seed code to pick a random last
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// seen time.
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secondsIn3Days int32 = 24 * 60 * 60 * 3
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secondsIn4Days int32 = 24 * 60 * 60 * 4
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)
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// OnSeed is the signature of the callback function which is invoked when DNS
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// seeding is succesfull.
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type OnSeed func(addrs []*wire.NetAddress)
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// LookupFunc is the signature of the DNS lookup function.
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type LookupFunc func(string) ([]net.IP, error)
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// SeedFromDNS uses DNS seeding to populate the address manager with peers.
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func SeedFromDNS(chainParams *chaincfg.Params, reqServices wire.ServiceFlag,
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lookupFn LookupFunc, seedFn OnSeed) {
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for _, dnsseed := range chainParams.DNSSeeds {
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var host string
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if !dnsseed.HasFiltering || reqServices == wire.SFNodeNetwork {
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host = dnsseed.Host
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} else {
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host = fmt.Sprintf("x%x.%s", uint64(reqServices), dnsseed.Host)
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}
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go func(host string) {
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randSource := mrand.New(mrand.NewSource(time.Now().UnixNano()))
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seedpeers, err := lookupFn(host)
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if err != nil {
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log.Infof("DNS discovery failed on seed %s: %v", host, err)
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return
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}
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numPeers := len(seedpeers)
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log.Infof("%d addresses found from DNS seed %s", numPeers, host)
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if numPeers == 0 {
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return
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}
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addresses := make([]*wire.NetAddress, len(seedpeers))
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// if this errors then we have *real* problems
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intPort, _ := strconv.Atoi(chainParams.DefaultPort)
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for i, peer := range seedpeers {
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addresses[i] = wire.NewNetAddressTimestamp(
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// bitcoind seeds with addresses from
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// a time randomly selected between 3
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// and 7 days ago.
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time.Now().Add(-1*time.Second*time.Duration(secondsIn3Days+
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randSource.Int31n(secondsIn4Days))),
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0, peer, uint16(intPort))
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}
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seedFn(addresses)
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}(host)
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}
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}
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