improvement(broker): don't reject unrestricted client if there are no restricted proxies

I.e. match it with an unrestricted proxy (if there is one).

The old behavior exists since the inception of the restricted vs
unrestricted feature, i.e. 0052c0e10c

broker/ipc.go

@@ -234,22 +234,19 @@ func (i *IPC) ClientOffers(arg messages.Arg, response *[]byte) error {
 }
 
 func (i *IPC) matchSnowflake(natType string) *Snowflake {
-	// Only hand out known restricted snowflakes to unrestricted clients
-	var snowflakeHeap *SnowflakeHeap
-	if natType == NATUnrestricted {
-		snowflakeHeap = i.ctx.restrictedSnowflakes
-	} else {
-		snowflakeHeap = i.ctx.snowflakes
-	}
-
 	i.ctx.snowflakeLock.Lock()
 	defer i.ctx.snowflakeLock.Unlock()
 
-	if snowflakeHeap.Len() > 0 {
+	// Proiritize known restricted snowflakes for unrestricted clients
-		return heap.Pop(snowflakeHeap).(*Snowflake)
+	if natType == NATUnrestricted && i.ctx.restrictedSnowflakes.Len() > 0 {
-	} else {
+		return heap.Pop(i.ctx.restrictedSnowflakes).(*Snowflake)
-		return nil
 	}
+
+	if i.ctx.snowflakes.Len() > 0 {
+		return heap.Pop(i.ctx.snowflakes).(*Snowflake)
+	}
+
+	return nil
 }
 
 func (i *IPC) ProxyAnswers(arg messages.Arg, response *[]byte) error {

broker/snowflake-broker_test.go

@@ -167,6 +167,30 @@ func TestBroker(t *testing.T) {
 				So(w.Code, ShouldEqual, http.StatusOK)
 			})
 
+			Convey("with unrestricted proxy to unrestricted client if there are no restricted proxies", func() {
+				snowflake := ctx.AddSnowflake("test", "", NATUnrestricted, 0)
+				offerData, err := createClientOffer(sdp, NATUnrestricted, "")
+				So(err, ShouldBeNil)
+				r, err := http.NewRequest("POST", "snowflake.broker/client", offerData)
+
+				done := make(chan bool)
+				go func() {
+					clientOffers(i, w, r)
+					done <- true
+				}()
+
+				select {
+				case <-snowflake.offerChannel:
+				case <-time.After(250 * time.Millisecond):
+					So(false, ShouldBeTrue)
+					return
+				}
+				snowflake.answerChannel <- "test answer"
+
+				<-done
+				So(w.Body.String(), ShouldEqual, `{"answer":"test answer"}`)
+			})
+
 			Convey("Times out when no proxy responds.", func() {
 				if testing.Short() {
 					return