lbcd/connmgr/seed.go

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