[snowflake/master] Set max number of snowflakes in the Tongue

27 Aug 2020

commit cc55481faf7bb886ef3cae99110800189abb0992
Author: Cecylia Bocovich <cohosh@torproject.org>
Date:   Tue Aug 11 13:57:51 2020 -0400

    Set max number of snowflakes in the Tongue
---
 client/lib/interfaces.go |  3 +++
 client/lib/lib_test.go   | 37 ++++++++++++++++++++-----------------
 client/lib/peers.go      | 26 +++++++++++++++-----------
 client/lib/rendezvous.go | 10 +++++++++-
 client/lib/snowflake.go  |  6 ++++--
 client/snowflake.go      |  2 +-
 6 files changed, 52 insertions(+), 32 deletions(-)

diff --git a/client/lib/interfaces.go b/client/lib/interfaces.go
index 71426d6..5378f4a 100644
--- a/client/lib/interfaces.go
+++ b/client/lib/interfaces.go
@@ -7,6 +7,9 @@ import (
 // Interface for catching Snowflakes. (aka the remote dialer)
 type Tongue interface {
 	Catch() (*WebRTCPeer, error)
+
+	// Get the maximum number of snowflakes
+	GetMax() int
 }
 
 // Interface for collecting some number of Snowflakes, for passing along
diff --git a/client/lib/lib_test.go b/client/lib/lib_test.go
index a93943f..5537a52 100644
--- a/client/lib/lib_test.go
+++ b/client/lib/lib_test.go
@@ -27,13 +27,19 @@ func (m *MockTransport) RoundTrip(req *http.Request) (*http.Response, error) {
 	return r, nil
 }
 
-type FakeDialer struct{}
+type FakeDialer struct {
+	max int
+}
 
 func (w FakeDialer) Catch() (*WebRTCPeer, error) {
 	fmt.Println("Caught a dummy snowflake.")
 	return &WebRTCPeer{}, nil
 }
 
+func (w FakeDialer) GetMax() int {
+	return w.max
+}
+
 type FakeSocksConn struct {
 	net.Conn
 	rejected bool
@@ -55,19 +61,19 @@ func TestSnowflakeClient(t *testing.T) {
 
 	Convey("Peers", t, func() {
 		Convey("Can construct", func() {
-			p := NewPeers(1)
-			So(p.capacity, ShouldEqual, 1)
+			d := &FakeDialer{max: 1}
+			p, _ := NewPeers(d)
+			So(p.Tongue.GetMax(), ShouldEqual, 1)
 			So(p.snowflakeChan, ShouldNotBeNil)
 			So(cap(p.snowflakeChan), ShouldEqual, 1)
 		})
 
 		Convey("Collecting a Snowflake requires a Tongue.", func() {
-			p := NewPeers(1)
-			_, err := p.Collect()
+			p, err := NewPeers(nil)
 			So(err, ShouldNotBeNil)
-			So(p.Count(), ShouldEqual, 0)
 			// Set the dialer so that collection is possible.
-			p.Tongue = FakeDialer{}
+			d := &FakeDialer{max: 1}
+			p, err = NewPeers(d)
 			_, err = p.Collect()
 			So(err, ShouldBeNil)
 			So(p.Count(), ShouldEqual, 1)
@@ -77,8 +83,7 @@ func TestSnowflakeClient(t *testing.T) {
 
 		Convey("Collection continues until capacity.", func() {
 			c := 5
-			p := NewPeers(c)
-			p.Tongue = FakeDialer{}
+			p, _ := NewPeers(FakeDialer{max: c})
 			// Fill up to capacity.
 			for i := 0; i < c; i++ {
 				fmt.Println("Adding snowflake ", i)
@@ -104,8 +109,7 @@ func TestSnowflakeClient(t *testing.T) {
 		})
 
 		Convey("Count correctly purges peers marked for deletion.", func() {
-			p := NewPeers(4)
-			p.Tongue = FakeDialer{}
+			p, _ := NewPeers(FakeDialer{max: 5})
 			p.Collect()
 			p.Collect()
 			p.Collect()
@@ -121,7 +125,7 @@ func TestSnowflakeClient(t *testing.T) {
 
 		Convey("End Closes all peers.", func() {
 			cnt := 5
-			p := NewPeers(cnt)
+			p, _ := NewPeers(FakeDialer{max: cnt})
 			for i := 0; i < cnt; i++ {
 				p.activePeers.PushBack(&WebRTCPeer{})
 			}
@@ -132,8 +136,7 @@ func TestSnowflakeClient(t *testing.T) {
 		})
 
 		Convey("Pop skips over closed peers.", func() {
-			p := NewPeers(4)
-			p.Tongue = FakeDialer{}
+			p, _ := NewPeers(FakeDialer{max: 4})
 			wc1, _ := p.Collect()
 			wc2, _ := p.Collect()
 			wc3, _ := p.Collect()
@@ -158,7 +161,7 @@ func TestSnowflakeClient(t *testing.T) {
 		SkipConvey("Handler Grants correctly", func() {
 			socks := &FakeSocksConn{}
 			broker := &BrokerChannel{Host: "test"}
-			d := NewWebRTCDialer(broker, nil)
+			d := NewWebRTCDialer(broker, nil, 1)
 
 			So(socks.rejected, ShouldEqual, false)
 			Handler(socks, d)
@@ -169,14 +172,14 @@ func TestSnowflakeClient(t *testing.T) {
 	Convey("Dialers", t, func() {
 		Convey("Can construct WebRTCDialer.", func() {
 			broker := &BrokerChannel{Host: "test"}
-			d := NewWebRTCDialer(broker, nil)
+			d := NewWebRTCDialer(broker, nil, 1)
 			So(d, ShouldNotBeNil)
 			So(d.BrokerChannel, ShouldNotBeNil)
 			So(d.BrokerChannel.Host, ShouldEqual, "test")
 		})
 		SkipConvey("WebRTCDialer can Catch a snowflake.", func() {
 			broker := &BrokerChannel{Host: "test"}
-			d := NewWebRTCDialer(broker, nil)
+			d := NewWebRTCDialer(broker, nil, 1)
 			conn, err := d.Catch()
 			So(conn, ShouldBeNil)
 			So(err, ShouldNotBeNil)
diff --git a/client/lib/peers.go b/client/lib/peers.go
index f766a66..d864fc8 100644
--- a/client/lib/peers.go
+++ b/client/lib/peers.go
@@ -24,33 +24,37 @@ type Peers struct {
 
 	snowflakeChan chan *WebRTCPeer
 	activePeers   *list.List
-	capacity      int
 
 	melt chan struct{}
 }
 
 // Construct a fresh container of remote peers.
-func NewPeers(max int) *Peers {
-	p := &Peers{capacity: max}
+func NewPeers(tongue Tongue) (*Peers, error) {
+	p := &Peers{}
 	// Use buffered go channel to pass snowflakes onwards to the SOCKS handler.
-	p.snowflakeChan = make(chan *WebRTCPeer, max)
+	if tongue == nil {
+		return nil, errors.New("missing Tongue to catch Snowflakes with")
+	}
+	p.snowflakeChan = make(chan *WebRTCPeer, tongue.GetMax())
 	p.activePeers = list.New()
 	p.melt = make(chan struct{})
-	return p
+	p.Tongue = tongue
+	return p, nil
 }
 
 // As part of |SnowflakeCollector| interface.
 func (p *Peers) Collect() (*WebRTCPeer, error) {
-	cnt := p.Count()
-	s := fmt.Sprintf("Currently at [%d/%d]", cnt, p.capacity)
-	if cnt >= p.capacity {
-		return nil, fmt.Errorf("At capacity [%d/%d]", cnt, p.capacity)
-	}
-	log.Println("WebRTC: Collecting a new Snowflake.", s)
 	// Engage the Snowflake Catching interface, which must be available.
 	if nil == p.Tongue {
 		return nil, errors.New("missing Tongue to catch Snowflakes with")
 	}
+	cnt := p.Count()
+	capacity := p.Tongue.GetMax()
+	s := fmt.Sprintf("Currently at [%d/%d]", cnt, capacity)
+	if cnt >= capacity {
+		return nil, fmt.Errorf("At capacity [%d/%d]", cnt, capacity)
+	}
+	log.Println("WebRTC: Collecting a new Snowflake.", s)
 	// BUG: some broker conflict here.
 	connection, err := p.Tongue.Catch()
 	if nil != err {
diff --git a/client/lib/rendezvous.go b/client/lib/rendezvous.go
index 37ade35..10853a5 100644
--- a/client/lib/rendezvous.go
+++ b/client/lib/rendezvous.go
@@ -155,15 +155,18 @@ func (bc *BrokerChannel) SetNATType(NATType string) {
 type WebRTCDialer struct {
 	*BrokerChannel
 	webrtcConfig *webrtc.Configuration
+	max          int
 }
 
-func NewWebRTCDialer(broker *BrokerChannel, iceServers []webrtc.ICEServer) *WebRTCDialer {
+func NewWebRTCDialer(broker *BrokerChannel, iceServers []webrtc.ICEServer, max int) *WebRTCDialer {
 	config := webrtc.Configuration{
 		ICEServers: iceServers,
 	}
+
 	return &WebRTCDialer{
 		BrokerChannel: broker,
 		webrtcConfig:  &config,
+		max:           max,
 	}
 }
 
@@ -173,3 +176,8 @@ func (w WebRTCDialer) Catch() (*WebRTCPeer, error) {
 	// TODO: [#25596] Consider TURN servers here too.
 	return NewWebRTCPeer(w.webrtcConfig, w.BrokerChannel)
 }
+
+// Returns the maximum number of snowflakes to collect
+func (w WebRTCDialer) GetMax() int {
+	return w.max
+}
diff --git a/client/lib/snowflake.go b/client/lib/snowflake.go
index d08a7bc..0ba5667 100644
--- a/client/lib/snowflake.go
+++ b/client/lib/snowflake.go
@@ -144,8 +144,10 @@ var sessionManager = sessionManager_{}
 // remote peer and exchange traffic.
 func Handler(socks net.Conn, tongue Tongue) error {
 	// Prepare to collect remote WebRTC peers.
-	snowflakes := NewPeers(1)
-	snowflakes.Tongue = tongue
+	snowflakes, err := NewPeers(tongue)
+	if err != nil {
+		return err
+	}
 
 	// Use a real logger to periodically output how much traffic is happening.
 	snowflakes.BytesLogger = NewBytesSyncLogger()
diff --git a/client/snowflake.go b/client/snowflake.go
index a7f5208..a1b97fa 100644
--- a/client/snowflake.go
+++ b/client/snowflake.go
@@ -148,7 +148,7 @@ func main() {
 	go updateNATType(iceServers, broker)
 
 	// Create a new WebRTCDialer to use as the |Tongue| to catch snowflakes
-	dialer := sf.NewWebRTCDialer(broker, iceServers)
+	dialer := sf.NewWebRTCDialer(broker, iceServers, *max)
 
 	// Begin goptlib client process.
 	ptInfo, err := pt.ClientSetup(nil)

    

cohosh＠torproject.org

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