p2p/discover/dht/dns_seeds.go

   1 package dht
   2
   3 import (
   4         "net"
   5         "time"
   6
   7         log "github.com/sirupsen/logrus"
   8
   9         "github.com/bytom/vapor/consensus"
  10         "github.com/bytom/vapor/errors"
  11 )
  12
  13 var (
  14         errInvalidIP     = errors.New("invalid ip address")
  15         errDNSTimeout    = errors.New("get dns seed timeout")
  16         errDNSSeedsEmpty = errors.New("dns seeds is empty")
  17
  18         dnsTimeout = 5 * time.Second
  19 )
  20
  21 // QueryDNSSeeds Query the DNS seeds.
  22 func QueryDNSSeeds(lookupHost func(host string) (addrs []string, err error)) ([]string, error) {
  23         if len(consensus.ActiveNetParams.DNSSeeds) == 0 {
  24                 return nil, errDNSSeedsEmpty
  25         }
  26
  27         resultCh := make(chan *[]string, 1)
  28         for _, dnsSeed := range consensus.ActiveNetParams.DNSSeeds {
  29                 go queryDNSSeeds(lookupHost, resultCh, dnsSeed, consensus.ActiveNetParams.DefaultPort)
  30         }
  31
  32         select {
  33         case result := <-resultCh:
  34                 return *result, nil
  35         case <-time.After(dnsTimeout):
  36                 return nil, errDNSTimeout
  37         }
  38 }
  39
  40 func queryDNSSeeds(lookupHost func(host string) (addrs []string, err error), resultCh chan *[]string, dnsSeed, port string) {
  41         var seeds []string
  42
  43         //TODO add proxy
  44         addrs, err := lookupHost(dnsSeed)
  45         if err != nil {
  46                 log.WithFields(log.Fields{"module": logModule, "err": err, "dnsSeed": dnsSeed}).Error("fail on look up host")
  47                 return
  48         }
  49
  50         for _, addr := range addrs {
  51                 if ip := net.ParseIP(addr); ip == nil {
  52                         log.WithFields(log.Fields{"module": logModule, "err": errInvalidIP, "dnsSeed": dnsSeed}).Error("fail on parse IP")
  53                         return
  54                 }
  55
  56                 seeds = append(seeds, net.JoinHostPort(addr, port))
  57         }
  58         if len(seeds) == 0 {
  59                 return
  60         }
  61         //if channel is full, drop it
  62         select {
  63         case resultCh <- &seeds:
  64         default:
  65         }
  66 }