Add full-duplex raw-Ethernet 10G cable stress tester

counters.go

@@ -0,0 +1,71 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+)
+
+var nicFields = []string{
+	"rx_packets", "tx_packets",
+	"rx_errors", "tx_errors",
+	"rx_dropped", "tx_dropped",
+	"rx_crc_errors", "rx_missed_errors",
+	"rx_length_errors", "rx_over_errors",
+	"rx_frame_errors", "rx_fifo_errors",
+	"collisions",
+}
+
+type nicCounters struct {
+	stats          map[string]uint64
+	carrierChanges uint64
+	carrierUp      uint64
+	carrierDown    uint64
+}
+
+func readUint(path string) (uint64, bool) {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return 0, false
+	}
+	v, err := strconv.ParseUint(strings.TrimSpace(string(b)), 10, 64)
+	if err != nil {
+		return 0, false
+	}
+	return v, true
+}
+
+func readNIC(ifname string) nicCounters {
+	c := nicCounters{stats: make(map[string]uint64, len(nicFields))}
+	base := "/sys/class/net/" + ifname
+	for _, f := range nicFields {
+		if v, ok := readUint(base + "/statistics/" + f); ok {
+			c.stats[f] = v
+		}
+	}
+	c.carrierChanges, _ = readUint(base + "/carrier_changes")
+	c.carrierUp, _ = readUint(base + "/carrier_up_count")
+	c.carrierDown, _ = readUint(base + "/carrier_down_count")
+	return c
+}
+
+func (c nicCounters) diff(prev nicCounters) string {
+	var parts []string
+	for _, f := range nicFields {
+		now, ok := c.stats[f]
+		if !ok {
+			continue
+		}
+		if d := now - prev.stats[f]; d != 0 && !strings.HasSuffix(f, "_packets") {
+			parts = append(parts, fmt.Sprintf("%s=%d", f, d))
+		}
+	}
+	if d := c.carrierChanges - prev.carrierChanges; d != 0 {
+		parts = append(parts, fmt.Sprintf("carrier_changes=%d", d))
+	}
+	if d := c.carrierDown - prev.carrierDown; d != 0 {
+		parts = append(parts, fmt.Sprintf("carrier_down=%d", d))
+	}
+	return strings.Join(parts, " ")
+}