From 062e86e21894965ba78905e305ad8abae63a2529 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Tue, 2 Sep 2014 14:05:22 -0700
Subject: [PATCH 1/3] packer/rpc: MuxBroker

---
 packer/rpc/mux_broker.go      | 160 ++++++++++++++++++++++++++++++++++
 packer/rpc/mux_broker_test.go |  82 +++++++++++++++++
 2 files changed, 242 insertions(+)
 create mode 100644 packer/rpc/mux_broker.go
 create mode 100644 packer/rpc/mux_broker_test.go

diff --git a/packer/rpc/mux_broker.go b/packer/rpc/mux_broker.go
new file mode 100644
index 000000000..2e1061c9d
--- /dev/null
+++ b/packer/rpc/mux_broker.go
@@ -0,0 +1,160 @@
+package rpc
+
+import (
+	"encoding/binary"
+	"fmt"
+	"net"
+	"sync"
+	"time"
+
+	"github.com/hashicorp/yamux"
+)
+
+// muxBroker is responsible for brokering multiplexed connections by unique ID.
+//
+// This allows a plugin to request a channel with a specific ID to connect to
+// or accept a connection from, and the broker handles the details of
+// holding these channels open while they're being negotiated.
+type muxBroker struct {
+	session *yamux.Session
+	streams map[uint32]*muxBrokerPending
+
+	sync.Mutex
+}
+
+type muxBrokerPending struct {
+	ch     chan net.Conn
+	doneCh chan struct{}
+}
+
+func newMuxBroker(s *yamux.Session) *muxBroker {
+	return &muxBroker{
+		session: s,
+		streams: make(map[uint32]*muxBrokerPending),
+	}
+}
+
+// Accept accepts a connection by ID.
+//
+// This should not be called multiple times with the same ID at one time.
+func (m *muxBroker) Accept(id uint32) (net.Conn, error) {
+	var c net.Conn
+	p := m.getStream(id)
+	select {
+	case c = <-p.ch:
+		close(p.doneCh)
+	case <-time.After(5 * time.Second):
+		m.Lock()
+		defer m.Unlock()
+		delete(m.streams, id)
+
+		return nil, fmt.Errorf("timeout waiting for accept")
+	}
+
+	// Ack our connection
+	if err := binary.Write(c, binary.LittleEndian, id); err != nil {
+		c.Close()
+		return nil, err
+	}
+
+	return c, nil
+}
+
+// Dial opens a connection by ID.
+func (m *muxBroker) Dial(id uint32) (net.Conn, error) {
+	// Open the stream
+	stream, err := m.session.OpenStream()
+	if err != nil {
+		return nil, err
+	}
+
+	// Write the stream ID onto the wire.
+	if err := binary.Write(stream, binary.LittleEndian, id); err != nil {
+		stream.Close()
+		return nil, err
+	}
+
+	// Read the ack that we connected. Then we're off!
+	var ack uint32
+	if err := binary.Read(stream, binary.LittleEndian, &ack); err != nil {
+		stream.Close()
+		return nil, err
+	}
+	if ack != id {
+		stream.Close()
+		return nil, fmt.Errorf("bad ack: %d (expected %d)", ack, id)
+	}
+
+	return stream, nil
+}
+
+// Run starts the brokering and should be executed in a goroutine, since it
+// blocks forever, or until the session closes.
+func (m *muxBroker) Run() {
+	for {
+		stream, err := m.session.AcceptStream()
+		if err != nil {
+			// Once we receive an error, just exit
+			break
+		}
+
+		// Read the stream ID from the stream
+		var id uint32
+		if err := binary.Read(stream, binary.LittleEndian, &id); err != nil {
+			stream.Close()
+			continue
+		}
+
+		// Initialize the waiter
+		p := m.getStream(id)
+		select {
+		case p.ch <- stream:
+		default:
+		}
+
+		// Wait for a timeout
+		go m.timeoutWait(id, p)
+	}
+}
+
+func (m *muxBroker) getStream(id uint32) *muxBrokerPending {
+	m.Lock()
+	defer m.Unlock()
+
+	p, ok := m.streams[id]
+	if ok {
+		return p
+	}
+
+	m.streams[id] = &muxBrokerPending{
+		ch:     make(chan net.Conn, 1),
+		doneCh: make(chan struct{}),
+	}
+	return m.streams[id]
+}
+
+func (m *muxBroker) timeoutWait(id uint32, p *muxBrokerPending) {
+	// Wait for the stream to either be picked up and connected, or
+	// for a timeout.
+	timeout := false
+	select {
+	case <-p.doneCh:
+	case <-time.After(5 * time.Second):
+		timeout = true
+	}
+
+	m.Lock()
+	defer m.Unlock()
+
+	// Delete the stream so no one else can grab it
+	delete(m.streams, id)
+
+	// If we timed out, then check if we have a channel in the buffer,
+	// and if so, close it.
+	if timeout {
+		select {
+		case s := <-p.ch:
+			s.Close()
+		}
+	}
+}
diff --git a/packer/rpc/mux_broker_test.go b/packer/rpc/mux_broker_test.go
new file mode 100644
index 000000000..88739a0ff
--- /dev/null
+++ b/packer/rpc/mux_broker_test.go
@@ -0,0 +1,82 @@
+package rpc
+
+import (
+	"net"
+	"testing"
+
+	"github.com/hashicorp/yamux"
+)
+
+func TestMuxBroker(t *testing.T) {
+	c, s := testYamux(t)
+	defer c.Close()
+	defer s.Close()
+
+	bc := newMuxBroker(c)
+	bs := newMuxBroker(s)
+	go bc.Run()
+	go bs.Run()
+
+	go func() {
+		c, err := bc.Dial(5)
+		if err != nil {
+			t.Fatalf("err: %s", err)
+		}
+
+		if _, err := c.Write([]byte{42}); err != nil {
+			t.Fatalf("err: %s", err)
+		}
+	}()
+
+	client, err := bs.Accept(5)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	var data [1]byte
+	if _, err := client.Read(data[:]); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if data[0] != 42 {
+		t.Fatalf("bad: %d", data[0])
+	}
+}
+
+func testYamux(t *testing.T) (client *yamux.Session, server *yamux.Session) {
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// Server side
+	doneCh := make(chan struct{})
+	go func() {
+		defer close(doneCh)
+		conn, err := l.Accept()
+		l.Close()
+		if err != nil {
+			t.Fatalf("err: %s", err)
+		}
+
+		server, err = yamux.Server(conn, nil)
+		if err != nil {
+			t.Fatalf("err: %s", err)
+		}
+	}()
+
+	// Client side
+	conn, err := net.Dial("tcp", l.Addr().String())
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	client, err = yamux.Client(conn, nil)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// Wait for the server
+	<-doneCh
+
+	return
+}

From 9ffa0b8e25dfc4b0b68de681c08ab40b010d0318 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Tue, 2 Sep 2014 14:23:06 -0700
Subject: [PATCH 2/3] packer/rpc: no more muxconn

---
 packer/rpc/build.go          |   4 +-
 packer/rpc/builder.go        |   4 +-
 packer/rpc/client.go         |  13 +-
 packer/rpc/command.go        |   4 +-
 packer/rpc/communicator.go   |   6 +-
 packer/rpc/environment.go    |   4 +-
 packer/rpc/hook.go           |   4 +-
 packer/rpc/mux_broker.go     |  31 ++
 packer/rpc/muxconn.go        | 605 -----------------------------------
 packer/rpc/muxconn_test.go   | 311 ------------------
 packer/rpc/post_processor.go |   4 +-
 packer/rpc/provisioner.go    |   4 +-
 packer/rpc/server.go         |  10 +-
 13 files changed, 64 insertions(+), 940 deletions(-)
 delete mode 100644 packer/rpc/muxconn.go
 delete mode 100644 packer/rpc/muxconn_test.go

diff --git a/packer/rpc/build.go b/packer/rpc/build.go
index c2e6dceca..4d0b7edf4 100644
--- a/packer/rpc/build.go
+++ b/packer/rpc/build.go
@@ -9,14 +9,14 @@ import (
 // over an RPC connection.
 type build struct {
 	client *rpc.Client
-	mux    *MuxConn
+	mux    *muxBroker
 }
 
 // BuildServer wraps a packer.Build implementation and makes it exportable
 // as part of a Golang RPC server.
 type BuildServer struct {
 	build packer.Build
-	mux   *MuxConn
+	mux   *muxBroker
 }
 
 type BuildPrepareResponse struct {
diff --git a/packer/rpc/builder.go b/packer/rpc/builder.go
index 5e3f429b5..0e2464bd7 100644
--- a/packer/rpc/builder.go
+++ b/packer/rpc/builder.go
@@ -10,14 +10,14 @@ import (
 // over an RPC connection.
 type builder struct {
 	client *rpc.Client
-	mux    *MuxConn
+	mux    *muxBroker
 }
 
 // BuilderServer wraps a packer.Builder implementation and makes it exportable
 // as part of a Golang RPC server.
 type BuilderServer struct {
 	builder packer.Builder
-	mux     *MuxConn
+	mux     *muxBroker
 }
 
 type BuilderPrepareArgs struct {
diff --git a/packer/rpc/client.go b/packer/rpc/client.go
index 0cc8fc869..7e2ff00fc 100644
--- a/packer/rpc/client.go
+++ b/packer/rpc/client.go
@@ -12,22 +12,29 @@ import (
 // Establishing a connection is up to the user, the Client can just
 // communicate over any ReadWriteCloser.
 type Client struct {
-	mux      *MuxConn
+	mux      *muxBroker
 	client   *rpc.Client
 	closeMux bool
 }
 
 func NewClient(rwc io.ReadWriteCloser) (*Client, error) {
-	result, err := newClientWithMux(NewMuxConn(rwc), 0)
+	mux, err := newMuxBrokerClient(rwc)
 	if err != nil {
 		return nil, err
 	}
+	go mux.Run()
+
+	result, err := newClientWithMux(mux, 0)
+	if err != nil {
+		mux.Close()
+		return nil, err
+	}
 
 	result.closeMux = true
 	return result, err
 }
 
-func newClientWithMux(mux *MuxConn, streamId uint32) (*Client, error) {
+func newClientWithMux(mux *muxBroker, streamId uint32) (*Client, error) {
 	clientConn, err := mux.Dial(streamId)
 	if err != nil {
 		return nil, err
diff --git a/packer/rpc/command.go b/packer/rpc/command.go
index 1484e5225..b5e5ccd52 100644
--- a/packer/rpc/command.go
+++ b/packer/rpc/command.go
@@ -9,14 +9,14 @@ import (
 // command is actually executed over an RPC connection.
 type command struct {
 	client *rpc.Client
-	mux    *MuxConn
+	mux    *muxBroker
 }
 
 // A CommandServer wraps a packer.Command and makes it exportable as part
 // of a Golang RPC server.
 type CommandServer struct {
 	command packer.Command
-	mux     *MuxConn
+	mux     *muxBroker
 }
 
 type CommandRunArgs struct {
diff --git a/packer/rpc/communicator.go b/packer/rpc/communicator.go
index 9ac539323..e1d6cb649 100644
--- a/packer/rpc/communicator.go
+++ b/packer/rpc/communicator.go
@@ -12,14 +12,14 @@ import (
 // executed over an RPC connection.
 type communicator struct {
 	client *rpc.Client
-	mux    *MuxConn
+	mux    *muxBroker
 }
 
 // CommunicatorServer wraps a packer.Communicator implementation and makes
 // it exportable as part of a Golang RPC server.
 type CommunicatorServer struct {
 	c   packer.Communicator
-	mux *MuxConn
+	mux *muxBroker
 }
 
 type CommandFinished struct {
@@ -252,7 +252,7 @@ func (c *CommunicatorServer) Download(args *CommunicatorDownloadArgs, reply *int
 	return
 }
 
-func serveSingleCopy(name string, mux *MuxConn, id uint32, dst io.Writer, src io.Reader) {
+func serveSingleCopy(name string, mux *muxBroker, id uint32, dst io.Writer, src io.Reader) {
 	conn, err := mux.Accept(id)
 	if err != nil {
 		log.Printf("[ERR] '%s' accept error: %s", name, err)
diff --git a/packer/rpc/environment.go b/packer/rpc/environment.go
index 644807bc4..5048b54ea 100644
--- a/packer/rpc/environment.go
+++ b/packer/rpc/environment.go
@@ -10,14 +10,14 @@ import (
 // where the actual environment is executed over an RPC connection.
 type Environment struct {
 	client *rpc.Client
-	mux    *MuxConn
+	mux    *muxBroker
 }
 
 // A EnvironmentServer wraps a packer.Environment and makes it exportable
 // as part of a Golang RPC server.
 type EnvironmentServer struct {
 	env packer.Environment
-	mux *MuxConn
+	mux *muxBroker
 }
 
 type EnvironmentCliArgs struct {
diff --git a/packer/rpc/hook.go b/packer/rpc/hook.go
index 6f149d41a..4aa7d75bc 100644
--- a/packer/rpc/hook.go
+++ b/packer/rpc/hook.go
@@ -10,14 +10,14 @@ import (
 // over an RPC connection.
 type hook struct {
 	client *rpc.Client
-	mux    *MuxConn
+	mux    *muxBroker
 }
 
 // HookServer wraps a packer.Hook implementation and makes it exportable
 // as part of a Golang RPC server.
 type HookServer struct {
 	hook packer.Hook
-	mux  *MuxConn
+	mux  *muxBroker
 }
 
 type HookRunArgs struct {
diff --git a/packer/rpc/mux_broker.go b/packer/rpc/mux_broker.go
index 2e1061c9d..7af76f640 100644
--- a/packer/rpc/mux_broker.go
+++ b/packer/rpc/mux_broker.go
@@ -3,8 +3,10 @@ package rpc
 import (
 	"encoding/binary"
 	"fmt"
+	"io"
 	"net"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/hashicorp/yamux"
@@ -16,6 +18,7 @@ import (
 // or accept a connection from, and the broker handles the details of
 // holding these channels open while they're being negotiated.
 type muxBroker struct {
+	nextId  uint32
 	session *yamux.Session
 	streams map[uint32]*muxBrokerPending
 
@@ -34,6 +37,24 @@ func newMuxBroker(s *yamux.Session) *muxBroker {
 	}
 }
 
+func newMuxBrokerClient(rwc io.ReadWriteCloser) (*muxBroker, error) {
+	s, err := yamux.Client(rwc, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return newMuxBroker(s), nil
+}
+
+func newMuxBrokerServer(rwc io.ReadWriteCloser) (*muxBroker, error) {
+	s, err := yamux.Server(rwc, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return newMuxBroker(s), nil
+}
+
 // Accept accepts a connection by ID.
 //
 // This should not be called multiple times with the same ID at one time.
@@ -60,6 +81,11 @@ func (m *muxBroker) Accept(id uint32) (net.Conn, error) {
 	return c, nil
 }
 
+// Close closes the connection and all sub-connections.
+func (m *muxBroker) Close() error {
+	return m.session.Close()
+}
+
 // Dial opens a connection by ID.
 func (m *muxBroker) Dial(id uint32) (net.Conn, error) {
 	// Open the stream
@@ -88,6 +114,11 @@ func (m *muxBroker) Dial(id uint32) (net.Conn, error) {
 	return stream, nil
 }
 
+// NextId returns a unique ID to use next.
+func (m *muxBroker) NextId() uint32 {
+	return atomic.AddUint32(&m.nextId, 1)
+}
+
 // Run starts the brokering and should be executed in a goroutine, since it
 // blocks forever, or until the session closes.
 func (m *muxBroker) Run() {
diff --git a/packer/rpc/muxconn.go b/packer/rpc/muxconn.go
deleted file mode 100644
index bc9de8e72..000000000
--- a/packer/rpc/muxconn.go
+++ /dev/null
@@ -1,605 +0,0 @@
-package rpc
-
-import (
-	"encoding/binary"
-	"fmt"
-	"io"
-	"log"
-	"sync"
-	"time"
-)
-
-// MuxConn is able to multiplex multiple streams on top of any
-// io.ReadWriteCloser. These streams act like TCP connections (Dial, Accept,
-// Close, full duplex, etc.).
-//
-// The underlying io.ReadWriteCloser is expected to guarantee delivery
-// and ordering, such as TCP. Congestion control and such aren't implemented
-// by the streams, so that is also up to the underlying connection.
-//
-// MuxConn works using a fairly dumb multiplexing technique of simply
-// framing every piece of data sent into a prefix + data format. Streams
-// are established using a subset of the TCP protocol. Only a subset is
-// necessary since we assume ordering on the underlying RWC.
-type MuxConn struct {
-	curId         uint32
-	rwc           io.ReadWriteCloser
-	streamsAccept map[uint32]*Stream
-	streamsDial   map[uint32]*Stream
-	muAccept      sync.RWMutex
-	muDial        sync.RWMutex
-	wlock         sync.Mutex
-	doneCh        chan struct{}
-}
-
-type muxPacketFrom byte
-type muxPacketType byte
-
-const (
-	muxPacketFromAccept muxPacketFrom = iota
-	muxPacketFromDial
-)
-
-const (
-	muxPacketSyn muxPacketType = iota
-	muxPacketSynAck
-	muxPacketAck
-	muxPacketFin
-	muxPacketData
-)
-
-func (f muxPacketFrom) String() string {
-	switch f {
-	case muxPacketFromAccept:
-		return "accept"
-	case muxPacketFromDial:
-		return "dial"
-	default:
-		panic("unknown from type")
-	}
-}
-
-// Create a new MuxConn around any io.ReadWriteCloser.
-func NewMuxConn(rwc io.ReadWriteCloser) *MuxConn {
-	m := &MuxConn{
-		rwc:           rwc,
-		streamsAccept: make(map[uint32]*Stream),
-		streamsDial:   make(map[uint32]*Stream),
-		doneCh:        make(chan struct{}),
-	}
-
-	go m.cleaner()
-	go m.loop()
-
-	return m
-}
-
-// Close closes the underlying io.ReadWriteCloser. This will also close
-// all streams that are open.
-func (m *MuxConn) Close() error {
-	m.muAccept.Lock()
-	m.muDial.Lock()
-	defer m.muAccept.Unlock()
-	defer m.muDial.Unlock()
-
-	// Close all the streams
-	for _, w := range m.streamsAccept {
-		w.Close()
-	}
-	for _, w := range m.streamsDial {
-		w.Close()
-	}
-	m.streamsAccept = make(map[uint32]*Stream)
-	m.streamsDial = make(map[uint32]*Stream)
-
-	// Close the actual connection. This will also force the loop
-	// to end since it'll read EOF or closed connection.
-	return m.rwc.Close()
-}
-
-// Accept accepts a multiplexed connection with the given ID. This
-// will block until a request is made to connect.
-func (m *MuxConn) Accept(id uint32) (io.ReadWriteCloser, error) {
-	//log.Printf("[TRACE] %p: Accept on stream ID: %d", m, id)
-
-	// Get the stream. It is okay if it is already in the list of streams
-	// because we may have prematurely received a syn for it.
-	m.muAccept.Lock()
-	stream, ok := m.streamsAccept[id]
-	if !ok {
-		stream = newStream(muxPacketFromAccept, id, m)
-		m.streamsAccept[id] = stream
-	}
-	m.muAccept.Unlock()
-
-	stream.mu.Lock()
-	defer stream.mu.Unlock()
-
-	// If the stream isn't closed, then it is already open somehow
-	if stream.state != streamStateSynRecv && stream.state != streamStateClosed {
-		panic(fmt.Sprintf(
-			"Stream %d already open in bad state: %d", id, stream.state))
-	}
-
-	if stream.state == streamStateClosed {
-		// Go into the listening state and wait for a syn
-		stream.setState(streamStateListen)
-		if err := stream.waitState(streamStateSynRecv); err != nil {
-			return nil, err
-		}
-	}
-
-	if stream.state == streamStateSynRecv {
-		// Send a syn-ack
-		if _, err := stream.write(muxPacketSynAck, nil); err != nil {
-			return nil, err
-		}
-	}
-
-	if err := stream.waitState(streamStateEstablished); err != nil {
-		return nil, err
-	}
-
-	return stream, nil
-}
-
-// Dial opens a connection to the remote end using the given stream ID.
-// An Accept on the remote end will only work with if the IDs match.
-func (m *MuxConn) Dial(id uint32) (io.ReadWriteCloser, error) {
-	//log.Printf("[TRACE] %p: Dial on stream ID: %d", m, id)
-
-	m.muDial.Lock()
-
-	// If we have any streams with this ID, then it is a failure. The
-	// reaper should clear out old streams once in awhile.
-	if stream, ok := m.streamsDial[id]; ok {
-		m.muDial.Unlock()
-		panic(fmt.Sprintf(
-			"Stream %d already open for dial. State: %d",
-			id, stream.state))
-	}
-
-	// Create the new stream and put it in our list. We can then
-	// unlock because dialing will no longer be allowed on that ID.
-	stream := newStream(muxPacketFromDial, id, m)
-	m.streamsDial[id] = stream
-
-	// Don't let anyone else mess with this stream
-	stream.mu.Lock()
-	defer stream.mu.Unlock()
-
-	m.muDial.Unlock()
-
-	// Open a connection
-	if _, err := stream.write(muxPacketSyn, nil); err != nil {
-		return nil, err
-	}
-
-	// It is safe to set the state after the write above because
-	// we hold the stream lock.
-	stream.setState(streamStateSynSent)
-
-	if err := stream.waitState(streamStateEstablished); err != nil {
-		return nil, err
-	}
-
-	stream.write(muxPacketAck, nil)
-	return stream, nil
-}
-
-// NextId returns the next available listen stream ID that isn't currently
-// taken.
-func (m *MuxConn) NextId() uint32 {
-	m.muAccept.Lock()
-	defer m.muAccept.Unlock()
-
-	for {
-		// We never use stream ID 0 because 0 is the zero value of a uint32
-		// and we want to reserve that for "not in use"
-		if m.curId == 0 {
-			m.curId = 1
-		}
-
-		result := m.curId
-		m.curId += 1
-		if _, ok := m.streamsAccept[result]; !ok {
-			return result
-		}
-	}
-}
-
-func (m *MuxConn) cleaner() {
-	checks := []struct {
-		Map  *map[uint32]*Stream
-		Lock *sync.RWMutex
-	}{
-		{&m.streamsAccept, &m.muAccept},
-		{&m.streamsDial, &m.muDial},
-	}
-
-	for {
-		done := false
-		select {
-		case <-time.After(500 * time.Millisecond):
-		case <-m.doneCh:
-			done = true
-		}
-
-		for _, check := range checks {
-			check.Lock.Lock()
-			for id, s := range *check.Map {
-				s.mu.Lock()
-
-				if done && s.state != streamStateClosed {
-					s.closeWriter()
-				}
-
-				if s.state == streamStateClosed {
-					// Only clean up the streams that have been closed
-					// for a certain amount of time.
-					since := time.Now().UTC().Sub(s.stateUpdated)
-					if since > 2*time.Second {
-						delete(*check.Map, id)
-					}
-				}
-
-				s.mu.Unlock()
-			}
-			check.Lock.Unlock()
-		}
-
-		if done {
-			return
-		}
-	}
-}
-
-func (m *MuxConn) loop() {
-	// Force close every stream that we know about when we exit so
-	// that they all read EOF and don't block forever.
-	defer func() {
-		log.Printf("[INFO] Mux connection loop exiting")
-		close(m.doneCh)
-	}()
-
-	var from muxPacketFrom
-	var id uint32
-	var packetType muxPacketType
-	var length int32
-	for {
-		if err := binary.Read(m.rwc, binary.BigEndian, &from); err != nil {
-			log.Printf("[ERR] Error reading stream direction: %s", err)
-			return
-		}
-		if err := binary.Read(m.rwc, binary.BigEndian, &id); err != nil {
-			log.Printf("[ERR] Error reading stream ID: %s", err)
-			return
-		}
-		if err := binary.Read(m.rwc, binary.BigEndian, &packetType); err != nil {
-			log.Printf("[ERR] Error reading packet type: %s", err)
-			return
-		}
-		if err := binary.Read(m.rwc, binary.BigEndian, &length); err != nil {
-			log.Printf("[ERR] Error reading length: %s", err)
-			return
-		}
-
-		// TODO(mitchellh): probably would be better to re-use a buffer...
-		data := make([]byte, length)
-		n := 0
-		for n < int(length) {
-			if n2, err := m.rwc.Read(data[n:]); err != nil {
-				log.Printf("[ERR] Error reading data: %s", err)
-				return
-			} else {
-				n += n2
-			}
-		}
-
-		// Get the proper stream. Note that the map we look into is
-		// opposite the "from" because if the dial side is talking to
-		// us, we need to look into the accept map, and so on.
-		//
-		// Note: we also switch the "from" value so that logging
-		// below is correct.
-		var stream *Stream
-		switch from {
-		case muxPacketFromDial:
-			m.muAccept.Lock()
-			stream = m.streamsAccept[id]
-			m.muAccept.Unlock()
-
-			from = muxPacketFromAccept
-		case muxPacketFromAccept:
-			m.muDial.Lock()
-			stream = m.streamsDial[id]
-			m.muDial.Unlock()
-
-			from = muxPacketFromDial
-		default:
-			panic(fmt.Sprintf("Unknown stream direction: %d", from))
-		}
-
-		if stream == nil && packetType != muxPacketSyn {
-			log.Printf(
-				"[WARN] %p: Non-existent stream %d (%s) received packer %d",
-				m, id, from, packetType)
-			continue
-		}
-
-		//log.Printf("[TRACE] %p: Stream %d (%s) received packet %d", m, id, from, packetType)
-		switch packetType {
-		case muxPacketSyn:
-			// If the stream is nil, this is the only case where we'll
-			// automatically create the stream struct.
-			if stream == nil {
-				var ok bool
-
-				m.muAccept.Lock()
-				stream, ok = m.streamsAccept[id]
-				if !ok {
-					stream = newStream(muxPacketFromAccept, id, m)
-					m.streamsAccept[id] = stream
-				}
-				m.muAccept.Unlock()
-			}
-
-			stream.mu.Lock()
-			switch stream.state {
-			case streamStateClosed:
-				fallthrough
-			case streamStateListen:
-				stream.setState(streamStateSynRecv)
-			default:
-				log.Printf("[ERR] Syn received for stream in state: %d", stream.state)
-			}
-			stream.mu.Unlock()
-		case muxPacketAck:
-			stream.mu.Lock()
-			switch stream.state {
-			case streamStateSynRecv:
-				stream.setState(streamStateEstablished)
-			case streamStateFinWait1:
-				stream.setState(streamStateFinWait2)
-			case streamStateLastAck:
-				stream.closeWriter()
-				fallthrough
-			case streamStateClosing:
-				stream.setState(streamStateClosed)
-			default:
-				log.Printf("[ERR] Ack received for stream in state: %d", stream.state)
-			}
-			stream.mu.Unlock()
-		case muxPacketSynAck:
-			stream.mu.Lock()
-			switch stream.state {
-			case streamStateSynSent:
-				stream.setState(streamStateEstablished)
-			default:
-				log.Printf("[ERR] SynAck received for stream in state: %d", stream.state)
-			}
-			stream.mu.Unlock()
-		case muxPacketFin:
-			stream.mu.Lock()
-			switch stream.state {
-			case streamStateEstablished:
-				stream.closeWriter()
-				stream.setState(streamStateCloseWait)
-				stream.write(muxPacketAck, nil)
-			case streamStateFinWait2:
-				stream.closeWriter()
-				stream.setState(streamStateClosed)
-				stream.write(muxPacketAck, nil)
-			case streamStateFinWait1:
-				stream.closeWriter()
-				stream.setState(streamStateClosing)
-				stream.write(muxPacketAck, nil)
-			default:
-				log.Printf("[ERR] Fin received for stream %d in state: %d", id, stream.state)
-			}
-			stream.mu.Unlock()
-
-		case muxPacketData:
-			stream.mu.Lock()
-			switch stream.state {
-			case streamStateFinWait1:
-				fallthrough
-			case streamStateFinWait2:
-				fallthrough
-			case streamStateEstablished:
-				if len(data) > 0 && stream.writeCh != nil {
-					//log.Printf("[TRACE] %p: Stream %d (%s) WRITE-START", m, id, from)
-					stream.writeCh <- data
-					//log.Printf("[TRACE] %p: Stream %d (%s) WRITE-END", m, id, from)
-				}
-			default:
-				log.Printf("[ERR] Data received for stream in state: %d", stream.state)
-			}
-			stream.mu.Unlock()
-		}
-	}
-}
-
-func (m *MuxConn) write(from muxPacketFrom, id uint32, dataType muxPacketType, p []byte) (int, error) {
-	m.wlock.Lock()
-	defer m.wlock.Unlock()
-
-	if err := binary.Write(m.rwc, binary.BigEndian, from); err != nil {
-		return 0, err
-	}
-	if err := binary.Write(m.rwc, binary.BigEndian, id); err != nil {
-		return 0, err
-	}
-	if err := binary.Write(m.rwc, binary.BigEndian, byte(dataType)); err != nil {
-		return 0, err
-	}
-	if err := binary.Write(m.rwc, binary.BigEndian, int32(len(p))); err != nil {
-		return 0, err
-	}
-
-	// Write all the bytes. If we don't write all the bytes, report an error
-	var err error = nil
-	n := 0
-	for n < len(p) {
-		var n2 int
-		n2, err = m.rwc.Write(p[n:])
-		n += n2
-		if err != nil {
-			log.Printf("[ERR] %p: Stream %d (%s) write error: %s", m, id, from, err)
-			break
-		}
-	}
-
-	return n, err
-}
-
-// Stream is a single stream of data and implements io.ReadWriteCloser.
-// A Stream is full-duplex so you can write data as well as read data.
-type Stream struct {
-	from         muxPacketFrom
-	id           uint32
-	mux          *MuxConn
-	reader       io.Reader
-	state        streamState
-	stateChange  map[chan<- streamState]struct{}
-	stateUpdated time.Time
-	mu           sync.Mutex
-	writeCh      chan<- []byte
-}
-
-type streamState byte
-
-const (
-	streamStateClosed streamState = iota
-	streamStateListen
-	streamStateSynRecv
-	streamStateSynSent
-	streamStateEstablished
-	streamStateFinWait1
-	streamStateFinWait2
-	streamStateCloseWait
-	streamStateClosing
-	streamStateLastAck
-)
-
-func newStream(from muxPacketFrom, id uint32, m *MuxConn) *Stream {
-	// Create the stream object and channel where data will be sent to
-	dataR, dataW := io.Pipe()
-	writeCh := make(chan []byte, 4096)
-
-	// Set the data channel so we can write to it.
-	stream := &Stream{
-		from:        from,
-		id:          id,
-		mux:         m,
-		reader:      dataR,
-		writeCh:     writeCh,
-		stateChange: make(map[chan<- streamState]struct{}),
-	}
-	stream.setState(streamStateClosed)
-
-	// Start the goroutine that will read from the queue and write
-	// data out.
-	go func() {
-		defer dataW.Close()
-
-		drain := false
-		for {
-			data := <-writeCh
-			if data == nil {
-				// A nil is a tombstone letting us know we're done
-				// accepting data.
-				return
-			}
-
-			if drain {
-				// We're draining, meaning we're just waiting for the
-				// write channel to close.
-				continue
-			}
-
-			if _, err := dataW.Write(data); err != nil {
-				drain = true
-			}
-		}
-	}()
-
-	return stream
-}
-
-func (s *Stream) Close() error {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-
-	if s.state != streamStateEstablished && s.state != streamStateCloseWait {
-		return fmt.Errorf("Stream in bad state: %d", s.state)
-	}
-
-	if s.state == streamStateEstablished {
-		s.setState(streamStateFinWait1)
-	} else {
-		s.setState(streamStateLastAck)
-	}
-
-	s.write(muxPacketFin, nil)
-	return nil
-}
-
-func (s *Stream) Read(p []byte) (int, error) {
-	return s.reader.Read(p)
-}
-
-func (s *Stream) Write(p []byte) (int, error) {
-	s.mu.Lock()
-	state := s.state
-	s.mu.Unlock()
-
-	if state != streamStateEstablished && state != streamStateCloseWait {
-		return 0, fmt.Errorf("Stream %d in bad state to send: %d", s.id, state)
-	}
-
-	return s.write(muxPacketData, p)
-}
-
-func (s *Stream) closeWriter() {
-	if s.writeCh != nil {
-		s.writeCh <- nil
-		s.writeCh = nil
-	}
-}
-
-func (s *Stream) setState(state streamState) {
-	//log.Printf("[TRACE] %p: Stream %d (%s) went to state %d", s.mux, s.id, s.from, state)
-	s.state = state
-	s.stateUpdated = time.Now().UTC()
-	for ch, _ := range s.stateChange {
-		select {
-		case ch <- state:
-		default:
-		}
-	}
-}
-
-func (s *Stream) waitState(target streamState) error {
-	// Register a state change listener to wait for changes
-	stateCh := make(chan streamState, 10)
-	s.stateChange[stateCh] = struct{}{}
-	s.mu.Unlock()
-
-	defer func() {
-		s.mu.Lock()
-		delete(s.stateChange, stateCh)
-	}()
-
-	//log.Printf("[TRACE] %p: Stream %d (%s) waiting for state: %d", s.mux, s.id, s.from, target)
-	state := <-stateCh
-	if state == target {
-		return nil
-	} else {
-		return fmt.Errorf("Stream %d went to bad state: %d", s.id, state)
-	}
-}
-
-func (s *Stream) write(dataType muxPacketType, p []byte) (int, error) {
-	return s.mux.write(s.from, s.id, dataType, p)
-}
diff --git a/packer/rpc/muxconn_test.go b/packer/rpc/muxconn_test.go
deleted file mode 100644
index 27a77fb46..000000000
--- a/packer/rpc/muxconn_test.go
+++ /dev/null
@@ -1,311 +0,0 @@
-package rpc
-
-import (
-	"io"
-	"net"
-	"sync"
-	"testing"
-)
-
-func readStream(t *testing.T, s io.Reader) string {
-	var data [1024]byte
-	n, err := s.Read(data[:])
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	return string(data[0:n])
-}
-
-func testMux(t *testing.T) (client *MuxConn, server *MuxConn) {
-	l, err := net.Listen("tcp", "127.0.0.1:0")
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	// Server side
-	doneCh := make(chan struct{})
-	go func() {
-		defer close(doneCh)
-		conn, err := l.Accept()
-		l.Close()
-		if err != nil {
-			t.Fatalf("err: %s", err)
-		}
-
-		server = NewMuxConn(conn)
-	}()
-
-	// Client side
-	conn, err := net.Dial("tcp", l.Addr().String())
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-	client = NewMuxConn(conn)
-
-	// Wait for the server
-	<-doneCh
-
-	return
-}
-
-func TestMuxConn(t *testing.T) {
-	client, server := testMux(t)
-	defer client.Close()
-	defer server.Close()
-
-	// When the server is done
-	doneCh := make(chan struct{})
-
-	// The server side
-	go func() {
-		defer close(doneCh)
-
-		s0, err := server.Accept(0)
-		if err != nil {
-			t.Fatalf("err: %s", err)
-		}
-
-		s1, err := server.Dial(1)
-		if err != nil {
-			t.Fatalf("err: %s", err)
-		}
-
-		var wg sync.WaitGroup
-		wg.Add(2)
-
-		go func() {
-			defer wg.Done()
-			defer s1.Close()
-			data := readStream(t, s1)
-			if data != "another" {
-				t.Fatalf("bad: %#v", data)
-			}
-		}()
-
-		go func() {
-			defer wg.Done()
-			defer s0.Close()
-			data := readStream(t, s0)
-			if data != "hello" {
-				t.Fatalf("bad: %#v", data)
-			}
-		}()
-
-		wg.Wait()
-	}()
-
-	s0, err := client.Dial(0)
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	s1, err := client.Accept(1)
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	if _, err := s0.Write([]byte("hello")); err != nil {
-		t.Fatalf("err: %s", err)
-	}
-	if _, err := s1.Write([]byte("another")); err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	s0.Close()
-	s1.Close()
-
-	// Wait for the server to be done
-	<-doneCh
-}
-
-func TestMuxConn_lotsOfData(t *testing.T) {
-	client, server := testMux(t)
-	defer client.Close()
-	defer server.Close()
-
-	// When the server is done
-	doneCh := make(chan struct{})
-
-	// The server side
-	go func() {
-		defer close(doneCh)
-
-		s0, err := server.Accept(0)
-		if err != nil {
-			t.Fatalf("err: %s", err)
-		}
-
-		var data [1024]byte
-		for {
-			n, err := s0.Read(data[:])
-			if err == io.EOF {
-				break
-			}
-
-			dataString := string(data[0:n])
-			if dataString != "hello" {
-				t.Fatalf("bad: %#v", dataString)
-			}
-		}
-
-		s0.Close()
-	}()
-
-	s0, err := client.Dial(0)
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	for i := 0; i < 4096*4; i++ {
-		if _, err := s0.Write([]byte("hello")); err != nil {
-			t.Fatalf("err: %s", err)
-		}
-	}
-
-	if err := s0.Close(); err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	// Wait for the server to be done
-	<-doneCh
-}
-
-// This tests that even when the client end is closed, data can be
-// read from the server.
-func TestMuxConn_clientCloseRead(t *testing.T) {
-	client, server := testMux(t)
-	defer client.Close()
-	defer server.Close()
-
-	// This channel will be closed when we close
-	waitCh := make(chan struct{})
-
-	go func() {
-		conn, err := server.Accept(0)
-		if err != nil {
-			t.Fatalf("err: %s", err)
-		}
-
-		<-waitCh
-
-		_, err = conn.Write([]byte("foo"))
-		if err != nil {
-			t.Fatalf("err: %s", err)
-		}
-
-		conn.Close()
-	}()
-
-	s0, err := client.Dial(0)
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	if err := s0.Close(); err != nil {
-		t.Fatalf("bad: %s", err)
-	}
-
-	// Close this to continue on on the server-side
-	close(waitCh)
-
-	var data [1024]byte
-	n, err := s0.Read(data[:])
-	if string(data[:n]) != "foo" {
-		t.Fatalf("bad: %#v", string(data[:n]))
-	}
-}
-
-func TestMuxConn_socketClose(t *testing.T) {
-	client, server := testMux(t)
-	defer client.Close()
-	defer server.Close()
-
-	go func() {
-		_, err := server.Accept(0)
-		if err != nil {
-			t.Fatalf("err: %s", err)
-		}
-
-		server.rwc.Close()
-	}()
-
-	s0, err := client.Dial(0)
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	var data [1024]byte
-	_, err = s0.Read(data[:])
-	if err != io.EOF {
-		t.Fatalf("err: %s", err)
-	}
-}
-
-func TestMuxConn_clientClosesStreams(t *testing.T) {
-	client, server := testMux(t)
-	defer client.Close()
-	defer server.Close()
-
-	go func() {
-		conn, err := server.Accept(0)
-		if err != nil {
-			t.Fatalf("err: %s", err)
-		}
-		conn.Close()
-	}()
-
-	s0, err := client.Dial(0)
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	var data [1024]byte
-	_, err = s0.Read(data[:])
-	if err != io.EOF {
-		t.Fatalf("err: %s", err)
-	}
-}
-
-func TestMuxConn_serverClosesStreams(t *testing.T) {
-	client, server := testMux(t)
-	defer client.Close()
-	defer server.Close()
-	go server.Accept(0)
-
-	s0, err := client.Dial(0)
-	if err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	if err := server.Close(); err != nil {
-		t.Fatalf("err: %s", err)
-	}
-
-	// This should block forever since we never write onto this stream.
-	var data [1024]byte
-	_, err = s0.Read(data[:])
-	if err != io.EOF {
-		t.Fatalf("err: %s", err)
-	}
-}
-
-func TestMuxConnNextId(t *testing.T) {
-	client, server := testMux(t)
-	defer client.Close()
-	defer server.Close()
-
-	a := client.NextId()
-	b := client.NextId()
-
-	if a != 1 || b != 2 {
-		t.Fatalf("IDs should increment")
-	}
-
-	a = server.NextId()
-	b = server.NextId()
-
-	if a != 1 || b != 2 {
-		t.Fatalf("IDs should increment: %d %d", a, b)
-	}
-}
diff --git a/packer/rpc/post_processor.go b/packer/rpc/post_processor.go
index 3a22c1a8a..b183780b9 100644
--- a/packer/rpc/post_processor.go
+++ b/packer/rpc/post_processor.go
@@ -9,14 +9,14 @@ import (
 // executed over an RPC connection.
 type postProcessor struct {
 	client *rpc.Client
-	mux    *MuxConn
+	mux    *muxBroker
 }
 
 // PostProcessorServer wraps a packer.PostProcessor implementation and makes it
 // exportable as part of a Golang RPC server.
 type PostProcessorServer struct {
 	client *rpc.Client
-	mux    *MuxConn
+	mux    *muxBroker
 	p      packer.PostProcessor
 }
 
diff --git a/packer/rpc/provisioner.go b/packer/rpc/provisioner.go
index e2346cd21..08d31700a 100644
--- a/packer/rpc/provisioner.go
+++ b/packer/rpc/provisioner.go
@@ -10,14 +10,14 @@ import (
 // executed over an RPC connection.
 type provisioner struct {
 	client *rpc.Client
-	mux    *MuxConn
+	mux    *muxBroker
 }
 
 // ProvisionerServer wraps a packer.Provisioner implementation and makes it
 // exportable as part of a Golang RPC server.
 type ProvisionerServer struct {
 	p   packer.Provisioner
-	mux *MuxConn
+	mux *muxBroker
 }
 
 type ProvisionerPrepareArgs struct {
diff --git a/packer/rpc/server.go b/packer/rpc/server.go
index df50f48ad..ca9691870 100644
--- a/packer/rpc/server.go
+++ b/packer/rpc/server.go
@@ -29,7 +29,7 @@ const (
 // Server represents an RPC server for Packer. This must be paired on
 // the other side with a Client.
 type Server struct {
-	mux      *MuxConn
+	mux      *muxBroker
 	streamId uint32
 	server   *rpc.Server
 	closeMux bool
@@ -37,12 +37,14 @@ type Server struct {
 
 // NewServer returns a new Packer RPC server.
 func NewServer(conn io.ReadWriteCloser) *Server {
-	result := newServerWithMux(NewMuxConn(conn), 0)
+	mux, _ := newMuxBrokerServer(conn)
+	result := newServerWithMux(mux, 0)
 	result.closeMux = true
+	go mux.Run()
 	return result
 }
 
-func newServerWithMux(mux *MuxConn, streamId uint32) *Server {
+func newServerWithMux(mux *muxBroker, streamId uint32) *Server {
 	return &Server{
 		mux:      mux,
 		streamId: streamId,
@@ -140,11 +142,11 @@ func (s *Server) Serve() {
 	// Accept a connection on stream ID 0, which is always used for
 	// normal client to server connections.
 	stream, err := s.mux.Accept(s.streamId)
-	defer stream.Close()
 	if err != nil {
 		log.Printf("[ERR] Error retrieving stream for serving: %s", err)
 		return
 	}
+	defer stream.Close()
 
 	var h codec.MsgpackHandle
 	rpcCodec := codec.GoRpc.ServerCodec(stream, &h)

From b7c604795ed6b07c4391d128d131d3569214343b Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Tue, 2 Sep 2014 14:28:21 -0700
Subject: [PATCH 3/3] packer/plugin: increase version for Yamux

---
 packer/plugin/server.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packer/plugin/server.go b/packer/plugin/server.go
index a36f8beda..83292c320 100644
--- a/packer/plugin/server.go
+++ b/packer/plugin/server.go
@@ -33,7 +33,7 @@ const MagicCookieValue = "d602bf8f470bc67ca7faa0386276bbdd4330efaf76d1a219cb4d69
 // The APIVersion is outputted along with the RPC address. The plugin
 // client validates this API version and will show an error if it doesn't
 // know how to speak it.
-const APIVersion = "3"
+const APIVersion = "4"
 
 // Server waits for a connection to this plugin and returns a Packer
 // RPC server that you can use to register components and serve them.