From a238ddb35a14dbd148add518ce58253ef829a8d8 Mon Sep 17 00:00:00 2001
From: Raghav Gulati <rargulati@users.noreply.github.com>
Date: Mon, 26 Feb 2018 21:50:43 -0800
Subject: [PATCH] discovery: swap mdns lib for grandcat/zeroconf

This commit makes the minimal amount of changes to switch us from
whyrusleeping/mdns to grandcat/zeroconf. Of note, rather than asking the
host.Host which addrs we're available to listen on, we push this to the
zeroconf library (which runs across available ifaces).
---
 p2p/discovery/mdns.go | 87 +++++++++++++++----------------------------
 1 file changed, 30 insertions(+), 57 deletions(-)

diff --git a/p2p/discovery/mdns.go b/p2p/discovery/mdns.go
index a7ec72ab12..4d594b85cf 100644
--- a/p2p/discovery/mdns.go
+++ b/p2p/discovery/mdns.go
@@ -2,21 +2,21 @@ package discovery
 
 import (
 	"context"
-	"errors"
 	"io"
 	"io/ioutil"
 	golog "log"
 	"net"
+	"strings"
 	"sync"
 	"time"
 
+	mdns "github.com/grandcat/zeroconf"
 	logging "github.com/ipfs/go-log"
 	"github.com/libp2p/go-libp2p-host"
 	"github.com/libp2p/go-libp2p-peer"
 	pstore "github.com/libp2p/go-libp2p-peerstore"
 	ma "github.com/multiformats/go-multiaddr"
 	manet "github.com/multiformats/go-multiaddr-net"
-	"github.com/whyrusleeping/mdns"
 )
 
 var log = logging.Logger("mdns")
@@ -34,72 +34,36 @@ type Notifee interface {
 }
 
 type mdnsService struct {
-	server  *mdns.Server
-	service *mdns.MDNSService
-	host    host.Host
-	tag     string
+	server *mdns.Server
+	host   host.Host
+	tag    string
 
 	lk       sync.Mutex
 	notifees []Notifee
 	interval time.Duration
 }
 
-func getDialableListenAddrs(ph host.Host) ([]*net.TCPAddr, error) {
-	var out []*net.TCPAddr
-	for _, addr := range ph.Addrs() {
-		na, err := manet.ToNetAddr(addr)
-		if err != nil {
-			continue
-		}
-		tcp, ok := na.(*net.TCPAddr)
-		if ok {
-			out = append(out, tcp)
-		}
-	}
-	if len(out) == 0 {
-		return nil, errors.New("failed to find good external addr from peerhost")
-	}
-	return out, nil
-}
-
 func NewMdnsService(ctx context.Context, peerhost host.Host, interval time.Duration, serviceTag string) (Service, error) {
 
 	// TODO: dont let mdns use logging...
 	golog.SetOutput(ioutil.Discard)
 
-	var ipaddrs []net.IP
 	port := 4001
-
-	addrs, err := getDialableListenAddrs(peerhost)
-	if err != nil {
-		log.Warning(err)
-	} else {
-		port = addrs[0].Port
-		for _, a := range addrs {
-			ipaddrs = append(ipaddrs, a.IP)
-		}
-	}
-
 	myid := peerhost.ID().Pretty()
 
 	info := []string{myid}
 	if serviceTag == "" {
 		serviceTag = ServiceTag
 	}
-	service, err := mdns.NewMDNSService(myid, serviceTag, "", "", port, ipaddrs, info)
-	if err != nil {
-		return nil, err
-	}
 
 	// Create the mDNS server, defer shutdown
-	server, err := mdns.NewServer(&mdns.Config{Zone: service})
+	server, err := mdns.Register(myid, serviceTag, "", port, info, nil)
 	if err != nil {
 		return nil, err
 	}
 
 	s := &mdnsService{
 		server:   server,
-		service:  service,
 		host:     peerhost,
 		interval: interval,
 		tag:      serviceTag,
@@ -111,34 +75,38 @@ func NewMdnsService(ctx context.Context, peerhost host.Host, interval time.Durat
 }
 
 func (m *mdnsService) Close() error {
-	return m.server.Shutdown()
+	m.server.Shutdown()
+	// grandcat/zerconf swallows error, satisfy interface
+	return nil
 }
 
 func (m *mdnsService) pollForEntries(ctx context.Context) {
 
 	ticker := time.NewTicker(m.interval)
 	for {
+		resolver, err := mdns.NewResolver(nil)
+		if err != nil {
+			log.Error("Failed to initialize resolver:", err)
+		}
+
 		//execute mdns query right away at method call and then with every tick
 		entriesCh := make(chan *mdns.ServiceEntry, 16)
-		go func() {
-			for entry := range entriesCh {
+		go func(results <-chan *mdns.ServiceEntry) {
+			for entry := range results {
 				m.handleEntry(entry)
 			}
-		}()
+		}(entriesCh)
 
 		log.Debug("starting mdns query")
-		qp := &mdns.QueryParam{
-			Domain:  "local",
-			Entries: entriesCh,
-			Service: m.tag,
-			Timeout: time.Second * 5,
-		}
 
-		err := mdns.Query(qp)
-		if err != nil {
+		ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
+		defer cancel()
+
+		if err := resolver.Browse(ctx, m.tag, "local", entriesCh); err != nil {
 			log.Error("mdns lookup error: ", err)
 		}
 		close(entriesCh)
+
 		log.Debug("mdns query complete")
 
 		select {
@@ -152,8 +120,13 @@ func (m *mdnsService) pollForEntries(ctx context.Context) {
 }
 
 func (m *mdnsService) handleEntry(e *mdns.ServiceEntry) {
-	log.Debugf("Handling MDNS entry: %s:%d %s", e.AddrV4, e.Port, e.Info)
-	mpeer, err := peer.IDB58Decode(e.Info)
+	// pull out the txt
+	info := strings.Join(e.Text, "|")
+
+	// addripv4 potential issue
+	log.Debugf("Handling MDNS entry: %s:%d %s", e.AddrIPv4[0], e.Port, info)
+
+	mpeer, err := peer.IDB58Decode(info)
 	if err != nil {
 		log.Warning("Error parsing peer ID from mdns entry: ", err)
 		return
@@ -165,7 +138,7 @@ func (m *mdnsService) handleEntry(e *mdns.ServiceEntry) {
 	}
 
 	maddr, err := manet.FromNetAddr(&net.TCPAddr{
-		IP:   e.AddrV4,
+		IP:   e.AddrIPv4[0],
 		Port: e.Port,
 	})
 	if err != nil {