Add round trip time measurement to candidate pair (#731)

* Add round trip time measurement to candidate pair

Use the round trip time measurement to populate RTT fields in
CandidatePairStats.

Atomic and tests

* Use int64 nanosecnods to make atomic easier

agent.go

@@ -973,16 +973,16 @@ func (a *Agent) invalidatePendingBindingRequests(filterTime time.Time) {
 
 // Assert that the passed TransactionID is in our pendingBindingRequests and returns the destination
 // If the bindingRequest was valid remove it from our pending cache
-func (a *Agent) handleInboundBindingSuccess(id [stun.TransactionIDSize]byte) (bool, *bindingRequest) {
+func (a *Agent) handleInboundBindingSuccess(id [stun.TransactionIDSize]byte) (bool, *bindingRequest, time.Duration) {
 	a.invalidatePendingBindingRequests(time.Now())
 	for i := range a.pendingBindingRequests {
 		if a.pendingBindingRequests[i].transactionID == id {
 			validBindingRequest := a.pendingBindingRequests[i]
 			a.pendingBindingRequests = append(a.pendingBindingRequests[:i], a.pendingBindingRequests[i+1:]...)
-			return true, &validBindingRequest
+			return true, &validBindingRequest, time.Since(validBindingRequest.timestamp)
 		}
 	}
-	return false, nil
+	return false, nil, 0
 }
 
 // handleInbound processes STUN traffic from a remote candidate

agent_stats.go

@@ -29,14 +29,14 @@ func (a *Agent) GetCandidatePairsStats() []CandidatePairStats {
 				// FirstRequestTimestamp time.Time
 				// LastRequestTimestamp time.Time
 				// LastResponseTimestamp time.Time
-				// TotalRoundTripTime float64
-				// CurrentRoundTripTime float64
+				TotalRoundTripTime:   cp.TotalRoundTripTime(),
+				CurrentRoundTripTime: cp.CurrentRoundTripTime(),
 				// AvailableOutgoingBitrate float64
 				// AvailableIncomingBitrate float64
 				// CircuitBreakerTriggerCount uint32
 				// RequestsReceived uint64
 				// RequestsSent uint64
-				// ResponsesReceived uint64
+				ResponsesReceived: cp.ResponsesReceived(),
 				// ResponsesSent uint64
 				// RetransmissionsReceived uint64
 				// RetransmissionsSent uint64

agent_test.go

@@ -721,6 +721,10 @@ func TestCandidatePairStats(t *testing.T) {
 	p := a.findPair(hostLocal, prflxRemote)
 	p.state = CandidatePairStateFailed
 
+	for i := 0; i < 10; i++ {
+		p.UpdateRoundTripTime(time.Duration(i+1) * time.Second)
+	}
+
 	stats := a.GetCandidatePairsStats()
 	if len(stats) != 4 {
 		t.Fatal("expected 4 candidate pairs stats")
@@ -766,6 +770,23 @@ func TestCandidatePairStats(t *testing.T) {
 		t.Fatalf("expected host-prflx pair to have state failed, it has state %s instead",
 			prflxPairStat.State.String())
 	}
+
+	expectedCurrentRoundTripTime := time.Duration(10) * time.Second
+	if prflxPairStat.CurrentRoundTripTime != expectedCurrentRoundTripTime.Seconds() {
+		t.Fatalf("expected current round trip time to be %f, it is %f instead",
+			expectedCurrentRoundTripTime.Seconds(), prflxPairStat.CurrentRoundTripTime)
+	}
+
+	expectedTotalRoundTripTime := time.Duration(55) * time.Second
+	if prflxPairStat.TotalRoundTripTime != expectedTotalRoundTripTime.Seconds() {
+		t.Fatalf("expected total round trip time to be %f, it is %f instead",
+			expectedTotalRoundTripTime.Seconds(), prflxPairStat.TotalRoundTripTime)
+	}
+
+	if prflxPairStat.ResponsesReceived != 10 {
+		t.Fatalf("expected responses received to be 10, it is %d instead",
+			prflxPairStat.ResponsesReceived)
+	}
 }
 
 func TestLocalCandidateStats(t *testing.T) {

candidatepair.go

@@ -5,6 +5,8 @@ package ice
 
 import (
 	"fmt"
+	"sync/atomic"
+	"time"
 
 	"github.com/pion/stun/v3"
 )
@@ -28,6 +30,11 @@ type CandidatePair struct {
 	state                    CandidatePairState
 	nominated                bool
 	nominateOnBindingSuccess bool
+
+	// stats
+	currentRoundTripTime int64 // in ns
+	totalRoundTripTime   int64 // in ns
+	responsesReceived    uint64
 }
 
 func (p *CandidatePair) String() string {
@@ -100,3 +107,30 @@ func (a *Agent) sendSTUN(msg *stun.Message, local, remote Candidate) {
 		a.log.Tracef("Failed to send STUN message: %s", err)
 	}
 }
+
+// UpdateRoundTripTime sets the current round time of this pair and
+// accumulates total round trip time and responses received
+func (p *CandidatePair) UpdateRoundTripTime(rtt time.Duration) {
+	rttNs := rtt.Nanoseconds()
+	atomic.StoreInt64(&p.currentRoundTripTime, rttNs)
+	atomic.AddInt64(&p.totalRoundTripTime, rttNs)
+	atomic.AddUint64(&p.responsesReceived, 1)
+}
+
+// CurrentRoundTripTime returns the current round trip time in seconds
+// https://www.w3.org/TR/webrtc-stats/#dom-rtcicecandidatepairstats-currentroundtriptime
+func (p *CandidatePair) CurrentRoundTripTime() float64 {
+	return time.Duration(atomic.LoadInt64(&p.currentRoundTripTime)).Seconds()
+}
+
+// TotalRoundTripTime returns the current round trip time in seconds
+// https://www.w3.org/TR/webrtc-stats/#dom-rtcicecandidatepairstats-totalroundtriptime
+func (p *CandidatePair) TotalRoundTripTime() float64 {
+	return time.Duration(atomic.LoadInt64(&p.totalRoundTripTime)).Seconds()
+}
+
+// ResponsesReceived returns the total number of connectivity responses received
+// https://www.w3.org/TR/webrtc-stats/#dom-rtcicecandidatepairstats-responsesreceived
+func (p *CandidatePair) ResponsesReceived() uint64 {
+	return atomic.LoadUint64(&p.responsesReceived)
+}

selection.go

@@ -120,7 +120,7 @@ func (s *controllingSelector) HandleBindingRequest(m *stun.Message, local, remot
 }
 
 func (s *controllingSelector) HandleSuccessResponse(m *stun.Message, local, remote Candidate, remoteAddr net.Addr) {
-	ok, pendingRequest := s.agent.handleInboundBindingSuccess(m.TransactionID)
+	ok, pendingRequest, rtt := s.agent.handleInboundBindingSuccess(m.TransactionID)
 	if !ok {
 		s.log.Warnf("Discard message from (%s), unknown TransactionID 0x%x", remote, m.TransactionID)
 		return
@@ -149,6 +149,8 @@ func (s *controllingSelector) HandleSuccessResponse(m *stun.Message, local, remo
 	if pendingRequest.isUseCandidate && s.agent.getSelectedPair() == nil {
 		s.agent.setSelectedPair(p)
 	}
+
+	p.UpdateRoundTripTime(rtt)
 }
 
 func (s *controllingSelector) PingCandidate(local, remote Candidate) {
@@ -211,7 +213,7 @@ func (s *controlledSelector) HandleSuccessResponse(m *stun.Message, local, remot
 	// request with an appropriate error code response (e.g., 400)
 	// [RFC5389].
 
-	ok, pendingRequest := s.agent.handleInboundBindingSuccess(m.TransactionID)
+	ok, pendingRequest, rtt := s.agent.handleInboundBindingSuccess(m.TransactionID)
 	if !ok {
 		s.log.Warnf("Discard message from (%s), unknown TransactionID 0x%x", remote, m.TransactionID)
 		return
@@ -245,6 +247,8 @@ func (s *controlledSelector) HandleSuccessResponse(m *stun.Message, local, remot
 			s.log.Tracef("Ignore nominate new pair %s, already nominated pair %s", p, selectedPair)
 		}
 	}
+
+	p.UpdateRoundTripTime(rtt)
 }
 
 func (s *controlledSelector) HandleBindingRequest(m *stun.Message, local, remote Candidate) {