Refactor RPM calculations

Refactor RPM calculations to make them more reusble. Enable (perhaps
temporarily) probe calculations on the saturated connections. This
change is to check whether this makes our RPM calculations match the
ones generated by Apple's native client.

3 files changed, 72 insertions, 48 deletions

diff --git a/lgc/lgc.go b/lgc/lgc.go
index a32bb36..1f6332d 100644
--- a/lgc/lgc.go
+++ b/lgc/lgc.go
@@ -126,6 +126,10 @@ func (lgd *LoadGeneratingConnectionDownload) SetGotConnTimeInfo(
 	now time.Time,
 	gotConnInfo httptrace.GotConnInfo,
 ) {
+	if gotConnInfo.Reused {
+		fmt.Printf("Unexpectedly reusing a connection!\n")
+		panic(!gotConnInfo.Reused)
+	}
 	lgd.stats.GetConnectionDoneTime = now
 	lgd.stats.ConnInfo = gotConnInfo
 	if debug.IsDebug(lgd.debug) {
diff --git a/rpm/rpm.go b/rpm/rpm.go
index e01e2e8..40a7729 100644
--- a/rpm/rpm.go
+++ b/rpm/rpm.go
@@ -252,6 +252,55 @@ func (probe *Probe) SetHttpResponseReadyTime(
 	}
 }
 
+func getLatency(ctx context.Context, probe *Probe, url string, debugLevel debug.DebugLevel) utilities.GetLatency {
+	before := time.Now()
+	c_b_req, err := http.NewRequestWithContext(
+		httptrace.WithClientTrace(ctx, probe.GetTrace()),
+		"GET",
+		url,
+		nil,
+	)
+	if err != nil {
+		return utilities.GetLatency{Delay: 0, RoundTripCount: 0, Err: err}
+	}
+
+	c_b, err := probe.client.Do(c_b_req)
+	if err != nil {
+		return utilities.GetLatency{Delay: 0, RoundTripCount: 0, Err: err}
+	}
+
+	// TODO: Make this interruptable somehow by using _ctx_.
+	_, err = io.ReadAll(c_b.Body)
+	if err != nil {
+		return utilities.GetLatency{Delay: 0, Err: err}
+	}
+	after := time.Now()
+
+	// Depending on whether we think that Close() requires another RTT (via TCP), we
+	// may need to move this before/after capturing the after time.
+	c_b.Body.Close()
+
+	sanity := after.Sub(before)
+
+	tlsAndHttpHeaderDelta := probe.GetTLSAndHttpHeaderDelta() // Constitutes 2 RTT, per the Spec.
+	httpDownloadDelta := probe.GetHttpDownloadDelta(after)    // Constitutes 1 RTT, per the Spec.
+	dnsDelta := probe.GetDnsDelta()                           // Constitutes 1 RTT, per the Spec.
+	tcpDelta := probe.GetTCPDelta()                           // Constitutes 1 RTT, per the Spec.
+	totalDelay := tlsAndHttpHeaderDelta + httpDownloadDelta + dnsDelta + tcpDelta
+
+	if debug.IsDebug(debugLevel) {
+		fmt.Printf(
+			"(Probe %v) sanity vs total: %v vs %v\n",
+			probe.ProbeId(),
+			sanity,
+			totalDelay,
+		)
+	}
+
+	roundTripCount := uint16(5) // According to addition, there are 5 RTTs that we measured.
+	return utilities.GetLatency{Delay: totalDelay, RoundTripCount: roundTripCount, Err: nil}
+}
+
 func CalculateSequentialRTTsTime(
 	ctx context.Context,
 	saturated_rtt_probe *Probe,
@@ -261,8 +310,17 @@ func CalculateSequentialRTTsTime(
 ) chan utilities.GetLatency {
 	responseChannel := make(chan utilities.GetLatency)
 	go func() {
-		before := time.Now()
-		roundTripCount := uint16(0)
+
+		if debug.IsDebug(debugLevel) {
+			fmt.Printf("Beginning saturated RTT probe.\n")
+		}
+		saturated_latency := getLatency(ctx, saturated_rtt_probe, url, debugLevel)
+
+		if saturated_latency.Err != nil {
+			fmt.Printf("Error occurred getting the saturated RTT.\n")
+			responseChannel <- saturated_latency
+			return
+		}
 		/*
 			  TODO: We are not going to measure round-trip times on the load-generating connection
 				right now because we are dealing with a massive amount of buffer bloat on the
@@ -289,54 +347,19 @@ func CalculateSequentialRTTsTime(
 				roundTripCount += 5
 				c_a.Body.Close()
 		*/
-		c_b_req, err := http.NewRequestWithContext(
-			httptrace.WithClientTrace(ctx, new_rtt_probe.GetTrace()),
-			"GET",
-			url,
-			nil,
-		)
-		if err != nil {
-			responseChannel <- utilities.GetLatency{Delay: 0, RoundTripCount: 0, Err: err}
-			return
-		}
-
-		c_b, err := new_rtt_probe.client.Do(c_b_req)
-		if err != nil {
-			responseChannel <- utilities.GetLatency{Delay: 0, RoundTripCount: 0, Err: err}
-			return
+		if debug.IsDebug(debugLevel) {
+			fmt.Printf("Beginning unsaturated RTT probe.\n")
 		}
+		new_rtt_latency := getLatency(ctx, new_rtt_probe, url, debugLevel)
 
-		// TODO: Make this interruptable somehow by using _ctx_.
-		_, err = io.ReadAll(c_b.Body)
-		if err != nil {
-			responseChannel <- utilities.GetLatency{Delay: 0, Err: err}
+		if new_rtt_latency.Err != nil {
+			fmt.Printf("Error occurred getting the unsaturated RTT.\n")
+			responseChannel <- new_rtt_latency
 			return
 		}
-		after := time.Now()
-
-		// Depending on whether we think that Close() requires another RTT (via TCP), we
-		// may need to move this before/after capturing the after time.
-		c_b.Body.Close()
-
-		sanity := after.Sub(before)
-
-		tlsAndHttpHeaderDelta := new_rtt_probe.GetTLSAndHttpHeaderDelta() // Constitutes 2 RTT, per the Spec.
-		httpDownloadDelta := new_rtt_probe.GetHttpDownloadDelta(after)    // Constitutes 1 RTT, per the Spec.
-		dnsDelta := new_rtt_probe.GetDnsDelta()                           // Constitutes 1 RTT, per the Spec.
-		tcpDelta := new_rtt_probe.GetTCPDelta()                           // Constitutes 1 RTT, per the Spec.
-		totalDelay := tlsAndHttpHeaderDelta + httpDownloadDelta + dnsDelta + tcpDelta
-
-		if debug.IsDebug(debugLevel) {
-			fmt.Printf(
-				"(Probe %v) sanity vs total: %v vs %v\n",
-				new_rtt_probe.ProbeId(),
-				sanity,
-				totalDelay,
-			)
-		}
 
-		roundTripCount += 5 // According to addition, there are 5 RTTs that we measured.
-		responseChannel <- utilities.GetLatency{Delay: totalDelay, RoundTripCount: roundTripCount, Err: nil}
+		responseChannel <- utilities.GetLatency{Delay: saturated_latency.Delay + new_rtt_latency.Delay, RoundTripCount: uint16(10), Err: nil}
+		return
 	}()
 	return responseChannel
 }
diff --git a/traceable/traceable.go b/traceable/traceable.go
index 6efc7f7..0d9da21 100644
--- a/traceable/traceable.go
+++ b/traceable/traceable.go
@@ -42,9 +42,6 @@ func GenerateHttpTimingTracer(
 			traceable.SetGetConnTime(time.Now())
 		},
 		GotConn: func(connInfo httptrace.GotConnInfo) {
-			if connInfo.Reused {
-				panic(!connInfo.Reused)
-			}
 			traceable.SetGotConnTimeInfo(time.Now(), connInfo)
 		},
 		TLSHandshakeStart: func() {