Reset cumulative error counts on space

input.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+// Delivers a value every time space is pressed. Puts the terminal in
+// non-canonical mode so the keypress arrives without waiting for a newline,
+// and returns a function that restores the original settings.
+func watchSpace() (<-chan struct{}, func()) {
+	ch := make(chan struct{}, 1)
+	restore := func() {}
+	fd := int(os.Stdin.Fd())
+
+	if orig, err := unix.IoctlGetTermios(fd, unix.TCGETS); err == nil {
+		saved := *orig
+		raw := *orig
+		raw.Lflag &^= unix.ICANON | unix.ECHO
+		raw.Cc[unix.VMIN] = 1
+		raw.Cc[unix.VTIME] = 0
+		if unix.IoctlSetTermios(fd, unix.TCSETS, &raw) == nil {
+			restore = func() { unix.IoctlSetTermios(fd, unix.TCSETS, &saved) }
+		}
+	}
+
+	go func() {
+		buf := make([]byte, 64)
+		for {
+			n, err := os.Stdin.Read(buf)
+			if err != nil {
+				return
+			}
+			for _, b := range buf[:n] {
+				if b != ' ' {
+					continue
+				}
+				select {
+				case ch <- struct{}{}:
+				default:
+				}
+			}
+		}
+	}()
+
+	return ch, restore
+}

main.go

@@ -45,10 +45,12 @@ type direction struct {
 	rxFDs   []int
 	reports chan string
 
-	prev  sample
-	drops uint64
-	nicTX nicCounters
-	nicRX nicCounters
+	prev     sample
+	drops    uint64
+	errBase  sample
+	dropBase uint64
+	nicTX    nicCounters
+	nicRX    nicCounters
 }
 
 type sample struct {
@@ -121,6 +123,14 @@ func (d *direction) snapshot() sample {
 	return s
 }
 
+// Counters keep climbing in the workers, so resetting just moves the origin
+// the display subtracts from.
+func (d *direction) resetErrors() {
+	d.sampleDrops()
+	d.errBase = d.snapshot()
+	d.dropBase = d.drops
+}
+
 func (d *direction) sampleDrops() {
 	for _, fd := range d.rxFDs {
 		d.drops += packetDrops(fd)
@@ -157,7 +167,13 @@ func (d *direction) intervalRow(elapsed time.Duration, secs, target float64) []s
 	rxB := now.rxBytes - p.rxBytes
 
 	d.sampleDrops()
-	total := now.lost + now.crcErr + now.badMagic + now.badLen + d.drops
+	b := d.errBase
+	lost := now.lost - b.lost
+	late := now.late - b.late
+	crc := now.crcErr - b.crcErr
+	badMagic := now.badMagic - b.badMagic
+	badLen := now.badLen - b.badLen
+	drops := d.drops - d.dropBase
 
 	return []string{
 		uptime(elapsed),
@@ -166,12 +182,12 @@ func (d *direction) intervalRow(elapsed time.Duration, secs, target float64) []s
 		rateCell(gbps(txB, txF, secs), target),
 		commas(uint64(float64(rxF) / secs)),
 		rateCell(gbps(rxB, rxF, secs), target),
-		statusCell(now.lost),
-		statusCell(now.late),
-		statusCell(now.crcErr),
-		statusCell(now.badMagic),
-		statusCell(d.drops),
-		statusCell(total),
+		statusCell(lost),
+		statusCell(late),
+		statusCell(crc),
+		statusCell(badMagic),
+		statusCell(drops),
+		statusCell(lost + crc + badMagic + badLen + drops),
 	}
 }
 
@@ -405,7 +421,7 @@ func run(aName, bName, sizesArg, patArg string,
 				humanBytes(uint64(sockBufSize(dirs[0].txFDs[0], unix.SO_SNDBUF))),
 				humanBytes(uint64(sockBufSize(dirs[0].rxFDs[0], unix.SO_RCVBUF))))},
 		}))
-	fmt.Println(paint("rates are per interval; error counts are cumulative since start", cDim))
+	fmt.Println(paint("rates are per interval; error counts are cumulative, press space to reset them", cDim))
 	fmt.Println()
 
 	var doneTx, doneRx atomic.Bool
@@ -423,6 +439,9 @@ func run(aName, bName, sizesArg, patArg string,
 	sig := make(chan os.Signal, 1)
 	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
 
+	space, restoreTerm := watchSpace()
+	defer restoreTerm()
+
 	start := time.Now()
 	close(startTx)
 	tick := time.NewTicker(reportInterval)
@@ -437,6 +456,12 @@ func run(aName, bName, sizesArg, patArg string,
 			doneRx.Store(true)
 			wg.Wait()
 			return nil
+		case <-space:
+			for _, d := range dirs {
+				d.resetErrors()
+			}
+			stats.sinceHeader = 0
+			fmt.Println(paint("error counts reset", cDim))
 		case now := <-tick.C:
 			secs := now.Sub(last).Seconds()
 			last = now