[Feature] Add TCP information (RTT and Cwnd) to Logging

This patch adds support for logging the underlying RTT and Cwnd of the
TCP connection used when doing probes. More work to follow in order to
add support for this information on Windows and Darwin.

1 files changed, 16 insertions, 2 deletions

diff --git a/rpm/rpm.go b/rpm/rpm.go
index 19da8f5..fe8184e 100644
--- a/rpm/rpm.go
+++ b/rpm/rpm.go
@@ -27,6 +27,7 @@ import (
 	"github.com/network-quality/goresponsiveness/constants"
 	"github.com/network-quality/goresponsiveness/datalogger"
 	"github.com/network-quality/goresponsiveness/debug"
+	"github.com/network-quality/goresponsiveness/extendedstats"
 	"github.com/network-quality/goresponsiveness/lgc"
 	"github.com/network-quality/goresponsiveness/ma"
 	"github.com/network-quality/goresponsiveness/stats"
@@ -63,7 +64,9 @@ type ProbeConfiguration struct {
 type ProbeDataPoint struct {
 	Time           time.Time     `Description:"Time of the generation of the data point." Formatter:"Format" FormatterArgument:"01-02-2006-15-04-05.000"`
 	RoundTripCount uint64        `Description:"The number of round trips measured by this data point."`
-	Duration       time.Duration `Description:"The duration for this measurement."`
+	Duration       time.Duration `Description:"The duration for this measurement." Formatter:"Seconds"`
+	TCPRtt         time.Duration `Description:"The underlying connection's RTT at probe time." Formatter:"Seconds"`
+	TCPCwnd        uint32        `Description:"The underlying connection's congestion window at probe time."`
 }
 
 type ThroughputDataPoint struct {
@@ -186,7 +189,18 @@ func Probe(
 			)
 		}
 	}()
-	dataPoint := ProbeDataPoint{Time: time_before_probe, RoundTripCount: roundTripCount, Duration: totalDelay}
+	tcpRtt := time.Duration(0 * time.Second)
+	tcpCwnd := uint32(0)
+	if extendedstats.ExtendedStatsAvailable() {
+		tcpInfo, err := extendedstats.GetTCPInfo(probeTracer.stats.ConnInfo.Conn)
+		if err == nil {
+			tcpRtt = time.Duration(tcpInfo.Rtt) * time.Microsecond
+			tcpCwnd = tcpInfo.Snd_cwnd
+		} else {
+			fmt.Printf("Warning: Could not fetch the extended stats for a probe: %v\n", err)
+		}
+	}
+	dataPoint := ProbeDataPoint{Time: time_before_probe, RoundTripCount: roundTripCount, Duration: totalDelay, TCPRtt: tcpRtt, TCPCwnd: tcpCwnd}
 	if !utilities.IsInterfaceNil(logger) {
 		logger.LogRecord(dataPoint)
 	}