extract from 0.4.0

p2p/net/mock/ratelimiter.go

 package mocknet
 
 import (
+	"sync"
 	"time"
 )
 
 //  A ratelimiter is used by a link to determine how long to wait before sending
 //  data given a bandwidth cap.
 type ratelimiter struct {
+	lock         sync.Mutex
 	bandwidth    float64       // bytes per nanosecond
 	allowance    float64       // in bytes
 	maxAllowance float64       // in bytes
@@ -29,6 +31,8 @@ func NewRatelimiter(bandwidth float64) *ratelimiter {
 
 //  Changes bandwidth of a ratelimiter and resets its allowance
 func (r *ratelimiter) UpdateBandwidth(bandwidth float64) {
+	r.lock.Lock()
+	defer r.lock.Unlock()
 	//  Convert bandwidth from bytes/second to bytes/nanosecond
 	b := bandwidth / float64(time.Second)
 	r.bandwidth = b
@@ -40,6 +44,8 @@ func (r *ratelimiter) UpdateBandwidth(bandwidth float64) {
 
 //  Returns how long to wait before sending data with length 'dataSize' bytes
 func (r *ratelimiter) Limit(dataSize int) time.Duration {
+	r.lock.Lock()
+	defer r.lock.Unlock()
 	//  update time
 	var duration time.Duration = time.Duration(0)
 	if r.bandwidth == 0 {

p2p/net/swarm/addr/addr.go

@@ -3,14 +3,14 @@ package addrutil
 import (
 	"fmt"
 
-	logging "github.com/ipfs/go-ipfs/vendor/go-log-v1.0.0"
+	logging "QmWRypnfEwrgH4k93KEHN5hng7VjKYkWmzDYRuTZeh2Mgh/go-log"
 
-	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
-	manet "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr-net"
-	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
+	ma "github.com/jbenet/go-multiaddr"
+	manet "github.com/jbenet/go-multiaddr-net"
+	context "golang.org/x/net/context"
 )
 
-var log = logging.Logger("p2p/net/swarm/addr")
+var log = logging.Logger("github.com/ipfs/go-libp2p/p2p/net/swarm/addr")
 
 // SupportedTransportStrings is the list of supported transports for the swarm.
 // These are strings of encapsulated multiaddr protocols. E.g.:

p2p/net/swarm/addr/addr_test.go

@@ -3,8 +3,8 @@ package addrutil
 import (
 	"testing"
 
-	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
-	manet "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr-net"
+	ma "github.com/jbenet/go-multiaddr"
+	manet "github.com/jbenet/go-multiaddr-net"
 )
 
 func newMultiaddr(t *testing.T, s string) ma.Multiaddr {

p2p/net/swarm/dial_test.go

@@ -2,6 +2,7 @@ package swarm
 
 import (
 	"net"
+	"sort"
 	"sync"
 	"testing"
 	"time"
@@ -9,12 +10,12 @@ import (
 	addrutil "github.com/ipfs/go-libp2p/p2p/net/swarm/addr"
 	peer "github.com/ipfs/go-libp2p/p2p/peer"
 
-	testutil "github.com/ipfs/go-ipfs/util/testutil"
-	ci "github.com/ipfs/go-ipfs/util/testutil/ci"
+	testutil "util/testutil"
+	ci "util/testutil/ci"
 
-	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
-	manet "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr-net"
-	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
+	ma "github.com/jbenet/go-multiaddr"
+	manet "github.com/jbenet/go-multiaddr-net"
+	context "golang.org/x/net/context"
 )
 
 func acceptAndHang(l net.Listener) {
@@ -419,18 +420,18 @@ func TestDialBackoffClears(t *testing.T) {
 	}
 	s1.peers.AddAddrs(s2.local, ifaceAddrs1, peer.PermanentAddrTTL)
 
-	before = time.Now()
+	if _, err := s1.Dial(ctx, s2.local); err == nil {
+		t.Fatal("should have failed to dial backed off peer")
+	}
+
+	time.Sleep(baseBackoffTime)
+
 	if c, err := s1.Dial(ctx, s2.local); err != nil {
 		t.Fatal(err)
 	} else {
 		c.Close()
 		t.Log("correctly connected")
 	}
-	duration = time.Now().Sub(before)
-
-	if duration >= dt {
-		// t.Error("took too long", duration, dt)
-	}
 
 	if s1.backf.Backoff(s2.local) {
 		t.Error("s2 should no longer be on backoff")
@@ -438,3 +439,38 @@ func TestDialBackoffClears(t *testing.T) {
 		t.Log("correctly cleared backoff")
 	}
 }
+
+func mkAddr(t *testing.T, s string) ma.Multiaddr {
+	a, err := ma.NewMultiaddr(s)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	return a
+}
+
+func TestAddressSorting(t *testing.T) {
+	u1 := mkAddr(t, "/ip4/152.12.23.53/udp/1234/utp")
+	u2l := mkAddr(t, "/ip4/127.0.0.1/udp/1234/utp")
+	local := mkAddr(t, "/ip4/127.0.0.1/tcp/1234")
+	norm := mkAddr(t, "/ip4/6.5.4.3/tcp/1234")
+
+	l := AddrList{local, u1, u2l, norm}
+	sort.Sort(l)
+
+	if !l[0].Equal(u2l) {
+		t.Fatal("expected utp local addr to be sorted first: ", l[0])
+	}
+
+	if !l[1].Equal(u1) {
+		t.Fatal("expected utp addr to be sorted second")
+	}
+
+	if !l[2].Equal(local) {
+		t.Fatal("expected tcp localhost addr thid")
+	}
+
+	if !l[3].Equal(norm) {
+		t.Fatal("expected normal addr last")
+	}
+}

p2p/net/swarm/peers_test.go

@@ -5,8 +5,8 @@ import (
 
 	peer "github.com/ipfs/go-libp2p/p2p/peer"
 
-	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
-	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
+	ma "github.com/jbenet/go-multiaddr"
+	context "golang.org/x/net/context"
 )
 
 func TestPeers(t *testing.T) {

p2p/net/swarm/simul_test.go

 package swarm
 
 import (
+	"runtime"
 	"sync"
 	"testing"
 	"time"
 
-	ci "github.com/ipfs/go-ipfs/util/testutil/ci"
 	peer "github.com/ipfs/go-libp2p/p2p/peer"
+	ci "util/testutil/ci"
 
-	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
-	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
+	ma "github.com/jbenet/go-multiaddr"
+	context "golang.org/x/net/context"
 )
 
 func TestSimultOpen(t *testing.T) {
@@ -49,7 +50,8 @@ func TestSimultOpenMany(t *testing.T) {
 
 	addrs := 20
 	rounds := 10
-	if ci.IsRunning() {
+	if ci.IsRunning() || runtime.GOOS == "darwin" {
+		// osx has a limit of 256 file descriptors
 		addrs = 10
 		rounds = 5
 	}

p2p/net/swarm/swarm.go

@@ -7,22 +7,26 @@ import (
 	"sync"
 	"time"
 
-	logging "github.com/ipfs/go-ipfs/vendor/go-log-v1.0.0"
+	metrics "github.com/ipfs/go-libp2p/p2p/metrics"
+	mconn "github.com/ipfs/go-libp2p/p2p/metrics/conn"
 	inet "github.com/ipfs/go-libp2p/p2p/net"
+	conn "github.com/ipfs/go-libp2p/p2p/net/conn"
 	filter "github.com/ipfs/go-libp2p/p2p/net/filter"
 	addrutil "github.com/ipfs/go-libp2p/p2p/net/swarm/addr"
+	transport "github.com/ipfs/go-libp2p/p2p/net/transport"
 	peer "github.com/ipfs/go-libp2p/p2p/peer"
-	metrics "github.com/ipfs/go-libp2p/util/metrics"
-
-	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
-	ps "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-peerstream"
-	pst "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-stream-muxer"
-	psy "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-stream-muxer/yamux"
-	"github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/goprocess"
-	goprocessctx "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/goprocess/context"
-	prom "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/prometheus/client_golang/prometheus"
-	mafilter "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/whyrusleeping/multiaddr-filter"
-	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
+
+	ma "github.com/jbenet/go-multiaddr"
+	ps "github.com/jbenet/go-peerstream"
+	pst "github.com/jbenet/go-stream-muxer"
+	psmss "github.com/jbenet/go-stream-muxer/multistream"
+	"github.com/jbenet/goprocess"
+	goprocessctx "github.com/jbenet/goprocess/context"
+	prom "github.com/prometheus/client_golang/prometheus"
+	mafilter "github.com/whyrusleeping/multiaddr-filter"
+	context "golang.org/x/net/context"
+
+	logging "QmWRypnfEwrgH4k93KEHN5hng7VjKYkWmzDYRuTZeh2Mgh/go-log"
 )
 
 var log = logging.Logger("swarm2")
@@ -37,9 +41,7 @@ var peersTotal = prom.NewGaugeVec(prom.GaugeOpts{
 }, []string{"peer_id"})
 
 func init() {
-	tpt := *psy.DefaultTransport
-	tpt.MaxStreamWindowSize = 512 * 1024
-	PSTransport = &tpt
+	PSTransport = psmss.NewTransport()
 }
 
 // Swarm is a connection muxer, allowing connections to other peers to
@@ -58,12 +60,19 @@ type Swarm struct {
 	backf dialbackoff
 	dialT time.Duration // mainly for tests
 
+	dialer *conn.Dialer
+
 	notifmu sync.RWMutex
 	notifs  map[inet.Notifiee]ps.Notifiee
 
+	transports []transport.Transport
+
 	// filters for addresses that shouldnt be dialed
 	Filters *filter.Filters
 
+	// file descriptor rate limited
+	fdRateLimit chan struct{}
+
 	proc goprocess.Process
 	ctx  context.Context
 	bwc  metrics.Reporter
@@ -78,6 +87,10 @@ func NewSwarm(ctx context.Context, listenAddrs []ma.Multiaddr,
 		return nil, err
 	}
 
+	wrap := func(c transport.Conn) transport.Conn {
+		return mconn.WrapConn(bwc, c)
+	}
+
 	s := &Swarm{
 		swarm:       ps.NewSwarm(PSTransport),
 		local:       local,
@@ -85,8 +98,11 @@ func NewSwarm(ctx context.Context, listenAddrs []ma.Multiaddr,
 		ctx:         ctx,
 		dialT:       DialTimeout,
 		notifs:      make(map[inet.Notifiee]ps.Notifiee),
+		transports:  []transport.Transport{transport.NewTCPTransport()},
 		bwc:         bwc,
+		fdRateLimit: make(chan struct{}, concurrentFdDials),
 		Filters:     filter.NewFilters(),
+		dialer:      conn.NewDialer(local, peers.PrivKey(local), wrap),
 	}
 
 	// configure Swarm
@@ -97,7 +113,12 @@ func NewSwarm(ctx context.Context, listenAddrs []ma.Multiaddr,
 	prom.MustRegisterOrGet(peersTotal)
 	s.Notify((*metricsNotifiee)(s))
 
-	return s, s.listen(listenAddrs)
+	err = s.setupInterfaces(listenAddrs)
+	if err != nil {
+		return nil, err
+	}
+
+	return s, nil
 }
 
 func (s *Swarm) teardown() error {
@@ -130,7 +151,7 @@ func (s *Swarm) Listen(addrs ...ma.Multiaddr) error {
 		return err
 	}
 
-	return s.listen(addrs)
+	return s.setupInterfaces(addrs)
 }
 
 // Process returns the Process of the swarm

p2p/net/swarm/swarm_addr.go

@@ -4,7 +4,7 @@ import (
 	conn "github.com/ipfs/go-libp2p/p2p/net/conn"
 	addrutil "github.com/ipfs/go-libp2p/p2p/net/swarm/addr"
 
-	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
+	ma "github.com/jbenet/go-multiaddr"
 )
 
 // ListenAddresses returns a list of addresses at which this swarm listens.

p2p/net/swarm/swarm_addr_test.go

@@ -3,13 +3,13 @@ package swarm
 import (
 	"testing"
 
-	testutil "github.com/ipfs/go-ipfs/util/testutil"
+	metrics "github.com/ipfs/go-libp2p/p2p/metrics"
 	addrutil "github.com/ipfs/go-libp2p/p2p/net/swarm/addr"
 	peer "github.com/ipfs/go-libp2p/p2p/peer"
-	metrics "github.com/ipfs/go-libp2p/util/metrics"
+	testutil "util/testutil"
 
-	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
-	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
+	ma "github.com/jbenet/go-multiaddr"
+	context "golang.org/x/net/context"
 )
 
 func TestFilterAddrs(t *testing.T) {

p2p/net/swarm/swarm_conn.go

@@ -8,9 +8,9 @@ import (
 	conn "github.com/ipfs/go-libp2p/p2p/net/conn"
 	peer "github.com/ipfs/go-libp2p/p2p/peer"
 
-	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
-	ps "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-peerstream"
-	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
+	ma "github.com/jbenet/go-multiaddr"
+	ps "github.com/jbenet/go-peerstream"
+	context "golang.org/x/net/context"
 )
 
 // a Conn is a simple wrapper around a ps.Conn that also exposes

p2p/net/swarm/swarm_dial.go

 package swarm
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
-	"math/rand"
-	"net"
+	"sort"
 	"sync"
 	"time"
 
+	"github.com/jbenet/go-multiaddr-net"
 	conn "github.com/ipfs/go-libp2p/p2p/net/conn"
 	addrutil "github.com/ipfs/go-libp2p/p2p/net/swarm/addr"
 	peer "github.com/ipfs/go-libp2p/p2p/peer"
-	lgbl "github.com/ipfs/go-libp2p/util/eventlog/loggables"
-	mconn "github.com/ipfs/go-libp2p/util/metrics/conn"
-
-	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
-	manet "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr-net"
-	process "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/goprocess"
-	processctx "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/goprocess/context"
-	ratelimit "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/goprocess/ratelimit"
-	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
+	lgbl "util/eventlog/loggables"
+
+	ma "github.com/jbenet/go-multiaddr"
+	context "golang.org/x/net/context"
 )
 
 // Diagram of dial sync:
@@ -44,6 +40,9 @@ var (
 // add loop back in Dial(.)
 const dialAttempts = 1
 
+// number of concurrent outbound dials over transports that consume file descriptors
+const concurrentFdDials = 160
+
 // DialTimeout is the amount of time each dial attempt has. We can think about making
 // this larger down the road, or putting more granular timeouts (i.e. within each
 // subcomponent of Dial)
@@ -115,6 +114,7 @@ func (ds *dialsync) Unlock(dst peer.ID) {
 	if !found {
 		panic("called dialDone with no ongoing dials to peer: " + dst.Pretty())
 	}
+
 	delete(ds.ongoing, dst) // remove ongoing dial
 	close(wait)             // release everyone else
 	ds.lock.Unlock()
@@ -145,44 +145,71 @@ func (ds *dialsync) Unlock(dst peer.ID) {
 //  	dialbackoff.Clear(p)
 //  }
 //
+
 type dialbackoff struct {
-	entries map[peer.ID]struct{}
+	entries map[peer.ID]*backoffPeer
 	lock    sync.RWMutex
 }
 
+type backoffPeer struct {
+	tries int
+	until time.Time
+}
+
 func (db *dialbackoff) init() {
 	if db.entries == nil {
-		db.entries = make(map[peer.ID]struct{})
+		db.entries = make(map[peer.ID]*backoffPeer)
 	}
 }
 
 // Backoff returns whether the client should backoff from dialing
-// peeer p
-func (db *dialbackoff) Backoff(p peer.ID) bool {
+// peer p
+func (db *dialbackoff) Backoff(p peer.ID) (backoff bool) {
 	db.lock.Lock()
+	defer db.lock.Unlock()
 	db.init()
-	_, found := db.entries[p]
-	db.lock.Unlock()
-	return found
+	bp, found := db.entries[p]
+	if found && time.Now().Before(bp.until) {
+		return true
+	}
+
+	return false
 }
 
+const baseBackoffTime = time.Second * 5
+const maxBackoffTime = time.Minute * 5
+
 // AddBackoff lets other nodes know that we've entered backoff with
 // peer p, so dialers should not wait unnecessarily. We still will
 // attempt to dial with one goroutine, in case we get through.
 func (db *dialbackoff) AddBackoff(p peer.ID) {
 	db.lock.Lock()
+	defer db.lock.Unlock()
 	db.init()
-	db.entries[p] = struct{}{}
-	db.lock.Unlock()
+	bp, ok := db.entries[p]
+	if !ok {
+		db.entries[p] = &backoffPeer{
+			tries: 1,
+			until: time.Now().Add(baseBackoffTime),
+		}
+		return
+	}
+
+	expTimeAdd := time.Second * time.Duration(bp.tries*bp.tries)
+	if expTimeAdd > maxBackoffTime {
+		expTimeAdd = maxBackoffTime
+	}
+	bp.until = time.Now().Add(baseBackoffTime + expTimeAdd)
+	bp.tries++
 }
 
 // Clear removes a backoff record. Clients should call this after a
 // successful Dial.
 func (db *dialbackoff) Clear(p peer.ID) {
 	db.lock.Lock()
+	defer db.lock.Unlock()
 	db.init()
 	delete(db.entries, p)
-	db.lock.Unlock()
 }
 
 // Dial connects to a peer.
@@ -225,14 +252,20 @@ func (s *Swarm) gatedDialAttempt(ctx context.Context, p peer.ID) (*Conn, error)
 
 	// check if there's an ongoing dial to this peer
 	if ok, wait := s.dsync.Lock(p); ok {
+		defer s.dsync.Unlock(p)
+
+		// if this peer has been backed off, lets get out of here
+		if s.backf.Backoff(p) {
+			log.Event(ctx, "swarmDialBackoff", logdial)
+			return nil, ErrDialBackoff
+		}
+
 		// ok, we have been charged to dial! let's do it.
 		// if it succeeds, dial will add the conn to the swarm itself.
-
 		defer log.EventBegin(ctx, "swarmDialAttemptStart", logdial).Done()
 		ctxT, cancel := context.WithTimeout(ctx, s.dialT)
 		conn, err := s.dial(ctxT, p)
 		cancel()
-		s.dsync.Unlock(p)
 		log.Debugf("dial end %s", conn)
 		if err != nil {
 			log.Event(ctx, "swarmDialBackoffAdd", logdial)
@@ -287,14 +320,6 @@ func (s *Swarm) dial(ctx context.Context, p peer.ID) (*Conn, error) {
 		log.Debug("Dial not given PrivateKey, so WILL NOT SECURE conn.")
 	}
 
-	// get our own addrs. try dialing out from our listener addresses (reusing ports)
-	// Note that using our peerstore's addresses here is incorrect, as that would
-	// include observed addresses. TODO: make peerstore's address book smarter.
-	localAddrs := s.ListenAddresses()
-	if len(localAddrs) == 0 {
-		log.Debug("Dialing out with no local addresses.")
-	}
-
 	// get remote peer addrs
 	remoteAddrs := s.peers.Addrs(p)
 	// make sure we can use the addresses.
@@ -319,23 +344,8 @@ func (s *Swarm) dial(ctx context.Context, p peer.ID) (*Conn, error) {
 		return nil, err
 	}
 
-	// open connection to peer
-	d := &conn.Dialer{
-		Dialer: manet.Dialer{
-			Dialer: net.Dialer{
-				Timeout: s.dialT,
-			},
-		},
-		LocalPeer:  s.local,
-		LocalAddrs: localAddrs,
-		PrivateKey: sk,
-		Wrapper: func(c manet.Conn) manet.Conn {
-			return mconn.WrapConn(s.bwc, c)
-		},
-	}
-
 	// try to get a connection to any addr
-	connC, err := s.dialAddrs(ctx, d, p, remoteAddrs)
+	connC, err := s.dialAddrs(ctx, p, remoteAddrs)
 	if err != nil {
 		logdial["error"] = err
 		return nil, err
@@ -355,7 +365,10 @@ func (s *Swarm) dial(ctx context.Context, p peer.ID) (*Conn, error) {
 	return swarmC, nil
 }
 
-func (s *Swarm) dialAddrs(ctx context.Context, d *conn.Dialer, p peer.ID, remoteAddrs []ma.Multiaddr) (conn.Conn, error) {
+func (s *Swarm) dialAddrs(ctx context.Context, p peer.ID, remoteAddrs []ma.Multiaddr) (conn.Conn, error) {
+
+	// sort addresses so preferred addresses are dialed sooner
+	sort.Sort(AddrList(remoteAddrs))
 
 	// try to connect to one of the peer's known addresses.
 	// we dial concurrently to each of the addresses, which:
@@ -367,78 +380,89 @@ func (s *Swarm) dialAddrs(ctx context.Context, d *conn.Dialer, p peer.ID, remote
 	ctx, cancel := context.WithCancel(ctx)
 	defer cancel() // cancel work when we exit func
 
-	foundConn := make(chan struct{})
-	conns := make(chan conn.Conn, len(remoteAddrs))
+	conns := make(chan conn.Conn)
 	errs := make(chan error, len(remoteAddrs))
 
 	// dialSingleAddr is used in the rate-limited async thing below.
 	dialSingleAddr := func(addr ma.Multiaddr) {
-		connC, err := s.dialAddr(ctx, d, p, addr)
+		// rebind chans in scope so we can nil them out easily
+		connsout := conns
+		errsout := errs
+
+		connC, err := s.dialAddr(ctx, p, addr)
+		if err != nil {
+			connsout = nil
+		} else if connC == nil {
+			// NOTE: this really should never happen
+			log.Errorf("failed to dial %s %s and got no error!", p, addr)
+			err = fmt.Errorf("failed to dial %s %s", p, addr)
+			connsout = nil
+		} else {
+			errsout = nil
+		}
 
 		// check parent still wants our results
 		select {
-		case <-foundConn:
+		case <-ctx.Done():
 			if connC != nil {
 				connC.Close()
 			}
-			return
-		default:
-		}
-
-		if err != nil {
-			errs <- err
-		} else if connC == nil {
-			errs <- fmt.Errorf("failed to dial %s %s", p, addr)
-		} else {
-			conns <- connC
+		case errsout <- err:
+		case connsout <- connC:
 		}
 	}
 
 	// this whole thing is in a goroutine so we can use foundConn
 	// to end early.
 	go func() {
-		// rate limiting just in case. at most 10 addrs at once.
-		limiter := ratelimit.NewRateLimiter(process.Background(), 10)
-		limiter.Go(func(worker process.Process) {
-			// permute addrs so we try different sets first each time.
-			for _, i := range rand.Perm(len(remoteAddrs)) {
+		limiter := make(chan struct{}, 8)
+		for _, addr := range remoteAddrs {
+			// returns whatever ratelimiting is acceptable for workerAddr.
+			// may not rate limit at all.
+			rl := s.addrDialRateLimit(addr)
 			select {
-				case <-foundConn: // if one of them succeeded already
-					break
-				case <-worker.Closing(): // our context was cancelled
-					break
-				default:
+			case <-ctx.Done(): // our context was cancelled
+				return
+			case rl <- struct{}{}:
+				// take the token, move on
 			}
 
-				workerAddr := remoteAddrs[i] // shadow variable to avoid race
-				limiter.LimitedGo(func(worker process.Process) {
-					dialSingleAddr(workerAddr)
-				})
+			select {
+			case <-ctx.Done(): // our context was cancelled
+				return
+			case limiter <- struct{}{}:
+				// take the token, move on
 			}
-		})
 
-		processctx.CloseAfterContext(limiter, ctx)
+			go func(rlc <-chan struct{}, a ma.Multiaddr) {
+				dialSingleAddr(a)
+				<-limiter
+				<-rlc
+			}(rl, addr)
+		}
 	}()
 
-	// wair fot the results.
+	// wair for the results.
 	exitErr := fmt.Errorf("failed to dial %s", p)
-	for i := 0; i < len(remoteAddrs); i++ {
+	for range remoteAddrs {
 		select {
 		case exitErr = <-errs: //
 			log.Debug("dial error: ", exitErr)
 		case connC := <-conns:
 			// take the first + return asap
-			close(foundConn)
 			return connC, nil
+		case <-ctx.Done():
+			// break out and return error
+			break
 		}
 	}
 	return nil, exitErr
 }
 
-func (s *Swarm) dialAddr(ctx context.Context, d *conn.Dialer, p peer.ID, addr ma.Multiaddr) (conn.Conn, error) {
+func (s *Swarm) dialAddr(ctx context.Context, p peer.ID, addr ma.Multiaddr) (conn.Conn, error) {
 	log.Debugf("%s swarm dialing %s %s", s.local, p, addr)
 
-	connC, err := d.Dial(ctx, addr, p)
+	connC, err := s.dialer.Dial(ctx, addr, p)
 	if err != nil {
 		return nil, fmt.Errorf("%s --> %s dial attempt failed: %s", s.local, p, err)
 	}
@@ -491,3 +515,72 @@ func dialConnSetup(ctx context.Context, s *Swarm, connC conn.Conn) (*Conn, error
 
 	return swarmC, err
 }
+
+// addrDialRateLimit returns a ratelimiting channel for dialing transport
+// addrs like a. for example, tcp is fd-ratelimited. utp is not ratelimited.
+func (s *Swarm) addrDialRateLimit(a ma.Multiaddr) chan struct{} {
+	if isFDCostlyTransport(a) {
+		return s.fdRateLimit
+	}
+
+	// do not rate limit it at all
+	return make(chan struct{}, 1)
+}
+
+func isFDCostlyTransport(a ma.Multiaddr) bool {
+	return isTCPMultiaddr(a)
+}
+
+func isTCPMultiaddr(a ma.Multiaddr) bool {
+	p := a.Protocols()
+	return len(p) == 2 && (p[0].Name == "ip4" || p[0].Name == "ip6") && p[1].Name == "tcp"
+}
+
+type AddrList []ma.Multiaddr
+
+func (al AddrList) Len() int {
+	return len(al)
+}
+
+func (al AddrList) Swap(i, j int) {
+	al[i], al[j] = al[j], al[i]
+}
+
+func (al AddrList) Less(i, j int) bool {
+	a := al[i]
+	b := al[j]
+
+	// dial localhost addresses next, they should fail immediately
+	lba := manet.IsIPLoopback(a)
+	lbb := manet.IsIPLoopback(b)
+	if lba {
+		if !lbb {
+			return true
+		}
+	}
+
+	// dial utp and similar 'non-fd-consuming' addresses first
+	fda := isFDCostlyTransport(a)
+	fdb := isFDCostlyTransport(b)
+	if !fda {
+		if fdb {
+			return true
+		}
+
+		// if neither consume fd's, assume equal ordering
+		return false
+	}
+
+	// if 'b' doesnt take a file descriptor
+	if !fdb {
+		return false
+	}
+
+	// if 'b' is loopback and both take file descriptors
+	if lbb {
+		return false
+	}
+
+	// for the rest, just sort by bytes
+	return bytes.Compare(a.Bytes(), b.Bytes()) > 0
+}

p2p/net/swarm/swarm_listen.go

@@ -3,68 +3,81 @@ package swarm
 import (
 	"fmt"
 
+	mconn "github.com/ipfs/go-libp2p/p2p/metrics/conn"
 	inet "github.com/ipfs/go-libp2p/p2p/net"
 	conn "github.com/ipfs/go-libp2p/p2p/net/conn"
-	addrutil "github.com/ipfs/go-libp2p/p2p/net/swarm/addr"
-	lgbl "github.com/ipfs/go-libp2p/util/eventlog/loggables"
-	mconn "github.com/ipfs/go-libp2p/util/metrics/conn"
-
-	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
-	manet "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr-net"
-	ps "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-peerstream"
-	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
-	multierr "github.com/ipfs/go-ipfs/thirdparty/multierr"
-)
+	transport "github.com/ipfs/go-libp2p/p2p/net/transport"
+	lgbl "util/eventlog/loggables"
 
-// Open listeners for each network the swarm should listen on
-func (s *Swarm) listen(addrs []ma.Multiaddr) error {
+	ma "github.com/jbenet/go-multiaddr"
+	ps "github.com/jbenet/go-peerstream"
+	context "golang.org/x/net/context"
+)
 
-	for _, addr := range addrs {
-		if !addrutil.AddrUsable(addr, true) {
-			return fmt.Errorf("cannot use addr: %s", addr)
+// Open listeners and reuse-dialers for the given addresses
+func (s *Swarm) setupInterfaces(addrs []ma.Multiaddr) error {
+	errs := make([]error, len(addrs))
+	var succeeded int
+	for i, a := range addrs {
+		tpt := s.transportForAddr(a)
+		if tpt == nil {
+			errs[i] = fmt.Errorf("no transport for address: %s", a)
+			continue
 		}
+
+		d, err := tpt.Dialer(a, transport.TimeoutOpt(DialTimeout), transport.ReusePorts)
+		if err != nil {
+			errs[i] = err
+			continue
 		}
 
-	retErr := multierr.New()
+		s.dialer.AddDialer(d)
 
-	// listen on every address
-	for i, addr := range addrs {
-		err := s.setupListener(addr)
+		list, err := tpt.Listen(a)
 		if err != nil {
-			if retErr.Errors == nil {
-				retErr.Errors = make([]error, len(addrs))
+			errs[i] = err
+			continue
 		}
-			retErr.Errors[i] = err
-			log.Debugf("Failed to listen on: %s - %s", addr, err)
+
+		err = s.addListener(list)
+		if err != nil {
+			errs[i] = err
+			continue
 		}
+		succeeded++
 	}
 
-	if retErr.Errors != nil {
-		return retErr
+	for i, e := range errs {
+		if e != nil {
+			log.Warning("listen on %s failed: %s", addrs[i], errs[i])
+		}
+	}
+	if succeeded == 0 && len(addrs) > 0 {
+		return fmt.Errorf("failed to listen on any addresses: %s", errs)
 	}
+
 	return nil
 }
 
-// Listen for new connections on the given multiaddr
-func (s *Swarm) setupListener(maddr ma.Multiaddr) error {
+func (s *Swarm) transportForAddr(a ma.Multiaddr) transport.Transport {
+	for _, t := range s.transports {
+		if t.Matches(a) {
+			return t
+		}
+	}
 
-	// TODO rethink how this has to work. (jbenet)
-	//
-	// resolved, err := resolveUnspecifiedAddresses([]ma.Multiaddr{maddr})
-	// if err != nil {
-	// 	return err
-	// }
-	// for _, a := range resolved {
-	// 	s.peers.AddAddr(s.local, a)
-	// }
+	return nil
+}
+
+func (s *Swarm) addListener(tptlist transport.Listener) error {
 
 	sk := s.peers.PrivKey(s.local)
 	if sk == nil {
 		// may be fine for sk to be nil, just log a warning.
 		log.Warning("Listener not given PrivateKey, so WILL NOT SECURE conns.")
 	}
-	log.Debugf("Swarm Listening at %s", maddr)
-	list, err := conn.Listen(s.Context(), maddr, s.local, sk)
+
+	list, err := conn.WrapTransportListener(s.Context(), tptlist, s.local, sk)
 	if err != nil {
 		return err
 	}
@@ -72,11 +85,15 @@ func (s *Swarm) setupListener(maddr ma.Multiaddr) error {
 	list.SetAddrFilters(s.Filters)
 
 	if cw, ok := list.(conn.ListenerConnWrapper); ok {
-		cw.SetConnWrapper(func(c manet.Conn) manet.Conn {
+		cw.SetConnWrapper(func(c transport.Conn) transport.Conn {
 			return mconn.WrapConn(s.bwc, c)
 		})
 	}
 
+	return s.addConnListener(list)
+}
+
+func (s *Swarm) addConnListener(list conn.Listener) error {
 	// AddListener to the peerstream Listener. this will begin accepting connections
 	// and streams!
 	sl, err := s.swarm.AddListener(list)
@@ -85,6 +102,8 @@ func (s *Swarm) setupListener(maddr ma.Multiaddr) error {
 	}
 	log.Debugf("Swarm Listeners at %s", s.ListenAddresses())
 
+	maddr := list.Multiaddr()
+
 	// signal to our notifiees on successful conn.
 	s.notifyAll(func(n inet.Notifiee) {
 		n.Listen((*Network)(s), maddr)
@@ -107,7 +126,7 @@ func (s *Swarm) setupListener(maddr ma.Multiaddr) error {
 				if !more {
 					return
 				}
-				log.Warningf("swarm listener accept error: %s", err)
+				log.Errorf("swarm listener accept error: %s", err)
 			case <-ctx.Done():
 				return
 			}
@@ -138,5 +157,8 @@ func (s *Swarm) connHandler(c *ps.Conn) *Conn {
 		return nil
 	}
 
+	// if a peer dials us, remove from dial backoff.
+	s.backf.Clear(sc.RemotePeer())
+
 	return sc
 }

p2p/net/swarm/swarm_net.go

@@ -5,12 +5,12 @@ import (
 
 	peer "github.com/ipfs/go-libp2p/p2p/peer"
 
+	metrics "github.com/ipfs/go-libp2p/p2p/metrics"
 	inet "github.com/ipfs/go-libp2p/p2p/net"
-	metrics "github.com/ipfs/go-libp2p/util/metrics"
 
-	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
-	"github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/goprocess"
-	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
+	ma "github.com/jbenet/go-multiaddr"
+	"github.com/jbenet/goprocess"
+	context "golang.org/x/net/context"
 )
 
 // Network implements the inet.Network interface.

p2p/net/swarm/swarm_net_test.go

@@ -5,7 +5,7 @@ import (
 	"testing"
 	"time"
 
-	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
+	context "golang.org/x/net/context"
 	inet "github.com/ipfs/go-libp2p/p2p/net"
 	testutil "github.com/ipfs/go-libp2p/p2p/test/util"
 )

p2p/net/swarm/swarm_notif_test.go

@@ -4,8 +4,8 @@ import (
 	"testing"
 	"time"
 
-	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
-	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
+	ma "github.com/jbenet/go-multiaddr"
+	context "golang.org/x/net/context"
 
 	inet "github.com/ipfs/go-libp2p/p2p/net"
 	peer "github.com/ipfs/go-libp2p/p2p/peer"

p2p/net/swarm/swarm_stream.go

@@ -3,7 +3,7 @@ package swarm
 import (
 	inet "github.com/ipfs/go-libp2p/p2p/net"
 
-	ps "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-peerstream"
+	ps "github.com/jbenet/go-peerstream"
 )
 
 // a Stream is a wrapper around a ps.Stream that exposes a way to get

p2p/net/swarm/swarm_test.go

@@ -9,13 +9,13 @@ import (
 	"testing"
 	"time"
 
-	testutil "github.com/ipfs/go-ipfs/util/testutil"
+	metrics "github.com/ipfs/go-libp2p/p2p/metrics"
 	inet "github.com/ipfs/go-libp2p/p2p/net"
 	peer "github.com/ipfs/go-libp2p/p2p/peer"
-	metrics "github.com/ipfs/go-libp2p/util/metrics"
+	testutil "util/testutil"
 
-	ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
-	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
+	ma "github.com/jbenet/go-multiaddr"
+	context "golang.org/x/net/context"
 )
 
 func EchoStreamHandler(stream inet.Stream) {
@@ -237,6 +237,15 @@ func TestSwarm(t *testing.T) {
 	SubtestSwarm(t, swarms, msgs)
 }
 
+func TestBasicSwarm(t *testing.T) {
+	// t.Skip("skipping for another test")
+	t.Parallel()
+
+	msgs := 1
+	swarms := 2
+	SubtestSwarm(t, swarms, msgs)
+}
+
 func TestConnHandler(t *testing.T) {
 	// t.Skip("skipping for another test")
 	t.Parallel()

p2p/net/conn/reuseport.go → p2p/net/transport/reuseport.go

-package conn
+package transport
 
 import (
+	"net"
 	"os"
 	"strings"
+	"syscall"
 
-	reuseport "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-reuseport"
+	reuseport "github.com/jbenet/go-reuseport"
 )
 
 // envReuseport is the env variable name used to turn off reuse port.
@@ -30,6 +32,34 @@ func init() {
 //
 // If this becomes a sought after feature, we could add this to the config.
 // In the end, reuseport is a stop-gap.
-func reuseportIsAvailable() bool {
+func ReuseportIsAvailable() bool {
 	return envReuseportVal && reuseport.Available()
 }
+
+// ReuseErrShouldRetry diagnoses whether to retry after a reuse error.
+// if we failed to bind, we should retry. if bind worked and this is a
+// real dial error (remote end didnt answer) then we should not retry.
+func ReuseErrShouldRetry(err error) bool {
+	if err == nil {
+		return false // hey, it worked! no need to retry.
+	}
+
+	// if it's a network timeout error, it's a legitimate failure.
+	if nerr, ok := err.(net.Error); ok && nerr.Timeout() {
+		return false
+	}
+
+	errno, ok := err.(syscall.Errno)
+	if !ok { // not an errno? who knows what this is. retry.
+		return true
+	}
+
+	switch errno {
+	case syscall.EADDRINUSE, syscall.EADDRNOTAVAIL:
+		return true // failure to bind. retry.
+	case syscall.ECONNREFUSED:
+		return false // real dial error
+	default:
+		return true // optimistically default to retry.
+	}
+}

p2p/net/transport/tcp.go

+package transport
+
+import (
+	"fmt"
+	"net"
+	"sync"
+	"time"
+
+	ma "github.com/jbenet/go-multiaddr"
+	manet "github.com/jbenet/go-multiaddr-net"
+	reuseport "github.com/jbenet/go-reuseport"
+	context "golang.org/x/net/context"
+	lgbl "util/eventlog/loggables"
+)
+
+type TcpTransport struct {
+	dlock   sync.Mutex
+	dialers map[string]Dialer
+
+	llock     sync.Mutex
+	listeners map[string]Listener
+}
+
+func NewTCPTransport() *TcpTransport {
+	return &TcpTransport{
+		dialers:   make(map[string]Dialer),
+		listeners: make(map[string]Listener),
+	}
+}
+
+func (t *TcpTransport) Dialer(laddr ma.Multiaddr, opts ...DialOpt) (Dialer, error) {
+	t.dlock.Lock()
+	defer t.dlock.Unlock()
+	s := laddr.String()
+	d, found := t.dialers[s]
+	if found {
+		return d, nil
+	}
+	var base manet.Dialer
+
+	var doReuse bool
+	for _, o := range opts {
+		switch o := o.(type) {
+		case TimeoutOpt:
+			base.Timeout = time.Duration(o)
+		case ReuseportOpt:
+			doReuse = bool(o)
+		default:
+			return nil, fmt.Errorf("unrecognized option: %#v", o)
+		}
+	}
+
+	tcpd, err := t.newTcpDialer(base, laddr, doReuse)
+	if err != nil {
+		return nil, err
+	}
+
+	t.dialers[s] = tcpd
+	return tcpd, nil
+}
+
+func (t *TcpTransport) Listen(laddr ma.Multiaddr) (Listener, error) {
+	t.llock.Lock()
+	defer t.llock.Unlock()
+	s := laddr.String()
+	l, found := t.listeners[s]
+	if found {
+		return l, nil
+	}
+
+	list, err := manetListen(laddr)
+	if err != nil {
+		return nil, err
+	}
+
+	tlist := &tcpListener{
+		list:      list,
+		transport: t,
+	}
+
+	t.listeners[s] = tlist
+	return tlist, nil
+}
+
+func manetListen(addr ma.Multiaddr) (manet.Listener, error) {
+	network, naddr, err := manet.DialArgs(addr)
+	if err != nil {
+		return nil, err
+	}
+
+	if ReuseportIsAvailable() {
+		nl, err := reuseport.Listen(network, naddr)
+		if err == nil {
+			// hey, it worked!
+			return manet.WrapNetListener(nl)
+		}
+		// reuseport is available, but we failed to listen. log debug, and retry normally.
+		log.Debugf("reuseport available, but failed to listen: %s %s, %s", network, naddr, err)
+	}
+
+	// either reuseport not available, or it failed. try normally.
+	return manet.Listen(addr)
+}
+
+func (t *TcpTransport) Matches(a ma.Multiaddr) bool {
+	return IsTcpMultiaddr(a)
+}
+
+type tcpDialer struct {
+	laddr ma.Multiaddr
+
+	doReuse bool
+
+	rd       reuseport.Dialer
+	madialer manet.Dialer
+
+	transport Transport
+}
+
+func (t *TcpTransport) newTcpDialer(base manet.Dialer, laddr ma.Multiaddr, doReuse bool) (*tcpDialer, error) {
+	// get the local net.Addr manually
+	la, err := manet.ToNetAddr(laddr)
+	if err != nil {
+		return nil, err // something wrong with laddr.
+	}
+
+	if doReuse && ReuseportIsAvailable() {
+		rd := reuseport.Dialer{
+			D: net.Dialer{
+				LocalAddr: la,
+				Timeout:   base.Timeout,
+			},
+		}
+
+		return &tcpDialer{
+			doReuse:   true,
+			laddr:     laddr,
+			rd:        rd,
+			madialer:  base,
+			transport: t,
+		}, nil
+	}
+
+	return &tcpDialer{
+		doReuse:   false,
+		laddr:     laddr,
+		madialer:  base,
+		transport: t,
+	}, nil
+}
+
+func (d *tcpDialer) Dial(raddr ma.Multiaddr) (Conn, error) {
+	var c manet.Conn
+	var err error
+	if d.doReuse {
+		c, err = d.reuseDial(raddr)
+	} else {
+		c, err = d.madialer.Dial(raddr)
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	return &connWrap{
+		Conn:      c,
+		transport: d.transport,
+	}, nil
+}
+
+func (d *tcpDialer) reuseDial(raddr ma.Multiaddr) (manet.Conn, error) {
+	logdial := lgbl.Dial("conn", "", "", d.laddr, raddr)
+	rpev := log.EventBegin(context.TODO(), "tptDialReusePort", logdial)
+
+	network, netraddr, err := manet.DialArgs(raddr)
+	if err != nil {
+		return nil, err
+	}
+
+	con, err := d.rd.Dial(network, netraddr)
+	if err == nil {
+		logdial["reuseport"] = "success"
+		rpev.Done()
+		return manet.WrapNetConn(con)
+	}
+
+	if !ReuseErrShouldRetry(err) {
+		logdial["reuseport"] = "failure"
+		logdial["error"] = err
+		rpev.Done()
+		return nil, err
+	}
+
+	logdial["reuseport"] = "retry"
+	logdial["error"] = err
+	rpev.Done()
+
+	return d.madialer.Dial(raddr)
+}
+
+func (d *tcpDialer) Matches(a ma.Multiaddr) bool {
+	return IsTcpMultiaddr(a)
+}
+
+type tcpListener struct {
+	list      manet.Listener
+	transport Transport
+}
+
+func (d *tcpListener) Accept() (Conn, error) {
+	c, err := d.list.Accept()
+	if err != nil {
+		return nil, err
+	}
+
+	return &connWrap{
+		Conn:      c,
+		transport: d.transport,
+	}, nil
+}
+
+func (d *tcpListener) Addr() net.Addr {
+	return d.list.Addr()
+}
+
+func (t *tcpListener) Multiaddr() ma.Multiaddr {
+	return t.list.Multiaddr()
+}
+
+func (t *tcpListener) NetListener() net.Listener {
+	return t.list.NetListener()
+}
+
+func (d *tcpListener) Close() error {
+	return d.list.Close()
+}

p2p/net/transport/transport.go

+package transport
+
+import (
+	"net"
+	"time"
+
+	logging "QmWRypnfEwrgH4k93KEHN5hng7VjKYkWmzDYRuTZeh2Mgh/go-log"
+	ma "github.com/jbenet/go-multiaddr"
+	manet "github.com/jbenet/go-multiaddr-net"
+)
+
+var log = logging.Logger("transport")
+
+type Conn interface {
+	manet.Conn
+
+	Transport() Transport
+}
+
+type Transport interface {
+	Dialer(laddr ma.Multiaddr, opts ...DialOpt) (Dialer, error)
+	Listen(laddr ma.Multiaddr) (Listener, error)
+	Matches(ma.Multiaddr) bool
+}
+
+type Dialer interface {
+	Dial(raddr ma.Multiaddr) (Conn, error)
+	Matches(ma.Multiaddr) bool
+}
+
+type Listener interface {
+	Accept() (Conn, error)
+	Close() error
+	Addr() net.Addr
+	Multiaddr() ma.Multiaddr
+}
+
+type connWrap struct {
+	manet.Conn
+	transport Transport
+}
+
+func (cw *connWrap) Transport() Transport {
+	return cw.transport
+}
+
+type DialOpt interface{}
+type TimeoutOpt time.Duration
+type ReuseportOpt bool
+
+var ReusePorts ReuseportOpt = true
+
+func IsTcpMultiaddr(a ma.Multiaddr) bool {
+	p := a.Protocols()
+	return len(p) == 2 && (p[0].Name == "ip4" || p[0].Name == "ip6") && p[1].Name == "tcp"
+}
+
+func IsUtpMultiaddr(a ma.Multiaddr) bool {
+	p := a.Protocols()
+	return len(p) == 3 && p[2].Name == "utp"
+}