implement a RTTGenerator for generating random RTTs for the UDP Proxy

ref #233

integrationtests/drop_test.go

@@ -32,7 +32,7 @@ var _ = Describe("Drop Proxy", func() {
 
 		iPort, _ := strconv.Atoi(port)
 		var err error
-		dropproxy, err = proxy.NewUDPProxy(proxyPort, "localhost", iPort, incomingPacketDropper, outgoingPacketDropper, 0)
+		dropproxy, err = proxy.NewUDPProxy(proxyPort, "localhost", iPort, incomingPacketDropper, outgoingPacketDropper, 0, 0)
 		Expect(err).ToNot(HaveOccurred())
 
 		command := exec.Command(

integrationtests/proxy/rtt_generator.go

@@ -0,0 +1,31 @@
+package proxy
+
+import (
+	"math/rand"
+	"time"
+)
+
+type rttGenerator struct {
+	min time.Duration
+	max time.Duration
+}
+
+func newRttGenerator(min, max time.Duration) rttGenerator {
+	rand.Seed(time.Now().UnixNano())
+	return rttGenerator{
+		min: min,
+		max: max,
+	}
+}
+
+func (s *rttGenerator) getRTT() time.Duration {
+	if s.min == s.max {
+		return s.min
+	}
+
+	minns := s.min.Nanoseconds()
+	maxns := s.max.Nanoseconds()
+	rttns := rand.Int63n(maxns-minns) + minns
+
+	return time.Duration(rttns) * time.Nanosecond
+}

integrationtests/proxy/rtt_generator_test.go

@@ -0,0 +1,56 @@
+package proxy
+
+import (
+	"time"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("RTT settings", func() {
+	Context("no variance", func() {
+		It("always gets the same value", func() {
+			rttGen := newRttGenerator(10*time.Millisecond, 10*time.Millisecond)
+			for i := 0; i < 100; i++ {
+				Expect(rttGen.getRTT()).To(Equal(10 * time.Millisecond))
+			}
+		})
+	})
+
+	Context("random RTT", func() {
+		var rttGen rttGenerator
+
+		BeforeEach(func() {
+			rttGen = newRttGenerator(10*time.Millisecond, 30*time.Millisecond)
+		})
+
+		It("has the right mean value", func() {
+			var rttSum time.Duration
+			rep := 1000
+			for i := 0; i < rep; i++ {
+				rttSum += rttGen.getRTT()
+			}
+			averageRTT := rttSum.Nanoseconds() / 1000 / int64(rep) // in microseconds
+			Expect(averageRTT).To(BeNumerically("~", 20000, 1000)) // between 19 and 21 microseconds
+		})
+
+		It("covers the whole interval", func() {
+			var max time.Duration
+			min := time.Hour
+
+			rep := 1000
+			for i := 0; i < rep; i++ {
+				rtt := rttGen.getRTT()
+				if rtt > max {
+					max = rtt
+				}
+				if rtt < min {
+					min = rtt
+				}
+			}
+
+			Expect(min.Nanoseconds() / 1000).To(BeNumerically("<", 11000))
+			Expect(max.Nanoseconds() / 1000).To(BeNumerically(">", 29000))
+		})
+	})
+})

integrationtests/proxy/udp_proxy.go

@@ -31,14 +31,14 @@ type UDPProxy struct {
 	proxyConn          *net.UDPConn
 	dropIncomingPacket DropCallback
 	dropOutgoingPacket DropCallback
-	rtt                time.Duration
+	rttGen             rttGenerator
 
 	// Mapping from client addresses (as host:port) to connection
 	clientDict map[string]*connection
 }
 
 // NewUDPProxy creates a new UDP proxy
-func NewUDPProxy(proxyPort int, serverAddress string, serverPort int, dropIncomingPacket, dropOutgoingPacket DropCallback, rtt time.Duration) (*UDPProxy, error) {
+func NewUDPProxy(proxyPort int, serverAddress string, serverPort int, dropIncomingPacket, dropOutgoingPacket DropCallback, rttMin time.Duration, rttMax time.Duration) (*UDPProxy, error) {
 	dontDrop := func(p PacketNumber) bool {
 		return false
 	}
@@ -54,7 +54,7 @@ func NewUDPProxy(proxyPort int, serverAddress string, serverPort int, dropIncomi
 		clientDict:         make(map[string]*connection),
 		dropIncomingPacket: dropIncomingPacket,
 		dropOutgoingPacket: dropOutgoingPacket,
-		rtt:                rtt,
+		rttGen:             newRttGenerator(rttMin, rttMax),
 	}
 
 	saddr, err := net.ResolveUDPAddr("udp", ":"+strconv.Itoa(proxyPort))
@@ -126,7 +126,7 @@ func (p *UDPProxy) runProxy() error {
 		if !p.dropIncomingPacket(conn.incomingPacketCounter) {
 			// Relay to server
 			go func() {
-				time.Sleep(p.rtt / 2)
+				time.Sleep(p.rttGen.getRTT() / 2)
 				conn.ServerConn.Write(buffer[0:n])
 			}()
 		}
@@ -147,7 +147,7 @@ func (p *UDPProxy) runConnection(conn *connection) error {
 		if !p.dropOutgoingPacket(conn.outgoingPacketCounter) {
 			// Relay it to client
 			go func() {
-				time.Sleep(p.rtt / 2)
+				time.Sleep(p.rttGen.getRTT() / 2)
 				p.proxyConn.WriteToUDP(buffer[0:n], conn.ClientAddr)
 			}()
 		}

integrationtests/proxy/udp_proxy_test.go

@@ -19,7 +19,7 @@ var _ = Describe("UDP Proxy", func() {
 	})
 
 	It("sets up the UDPProxy", func() {
-		proxy, err := NewUDPProxy(13370, "localhost", serverPort, nil, nil, 0)
+		proxy, err := NewUDPProxy(13370, "localhost", serverPort, nil, nil, 0, 0)
 		Expect(err).ToNot(HaveOccurred())
 		Expect(proxy.clientDict).To(HaveLen(0))
 
@@ -34,7 +34,7 @@ var _ = Describe("UDP Proxy", func() {
 	})
 
 	It("stops the UDPProxy", func() {
-		proxy, err := NewUDPProxy(13371, "localhost", serverPort, nil, nil, 0)
+		proxy, err := NewUDPProxy(13371, "localhost", serverPort, nil, nil, 0, 0)
 		Expect(err).ToNot(HaveOccurred())
 		proxy.Stop()
 
@@ -102,7 +102,7 @@ var _ = Describe("UDP Proxy", func() {
 			BeforeEach(func() {
 				// setup the proxy
 				var err error
-				proxy, err = NewUDPProxy(10001, "localhost", serverPort, nil, nil, 0)
+				proxy, err = NewUDPProxy(10001, "localhost", serverPort, nil, nil, 0, 0)
 				Expect(err).ToNot(HaveOccurred())
 			})
 
@@ -175,7 +175,7 @@ var _ = Describe("UDP Proxy", func() {
 				}
 
 				var err error
-				proxy, err = NewUDPProxy(10001, "localhost", serverPort, dropper, nil, 0)
+				proxy, err = NewUDPProxy(10001, "localhost", serverPort, dropper, nil, 0, 0)
 				Expect(err).ToNot(HaveOccurred())
 
 				for i := 1; i <= 6; i++ {
@@ -195,7 +195,7 @@ var _ = Describe("UDP Proxy", func() {
 				}
 
 				var err error
-				proxy, err = NewUDPProxy(10001, "localhost", serverPort, nil, dropper, 0)
+				proxy, err = NewUDPProxy(10001, "localhost", serverPort, nil, dropper, 0, 0)
 				Expect(err).ToNot(HaveOccurred())
 
 				for i := 1; i <= 6; i++ {

integrationtests/rtt_test.go

@@ -18,7 +18,7 @@ import (
 	. "github.com/onsi/gomega/gexec"
 )
 
-var _ = Describe("RTT", func() {
+var _ = Describe("non-zero RTT", func() {
 	var rttProxy *proxy.UDPProxy
 
 	runRTTTest := func(rtt time.Duration, version protocol.VersionNumber) {
@@ -32,7 +32,7 @@ var _ = Describe("RTT", func() {
 
 		iPort, _ := strconv.Atoi(port)
 		var err error
-		rttProxy, err = proxy.NewUDPProxy(proxyPort, "localhost", iPort, nil, nil, rtt)
+		rttProxy, err = proxy.NewUDPProxy(proxyPort, "localhost", iPort, nil, nil, rtt, rtt)
 		Expect(err).ToNot(HaveOccurred())
 
 		command := exec.Command(