Count link and syscall failures instead of printing them

counters.go

@@ -1,27 +1,31 @@
 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",
-}
+// Everything the driver counts against a frame the link failed to carry, split
+// by direction of travel so each counter belongs to exactly one direction: the
+// transmitting interface owns the tx fields and the receiving interface the rx
+// ones. Reading both sets off both interfaces would report every drop twice.
+var (
+	nicTxFields = []string{
+		"tx_errors", "tx_dropped", "tx_fifo_errors",
+		"tx_carrier_errors", "tx_aborted_errors", "tx_window_errors",
+		"collisions",
+	}
+	nicRxFields = []string{
+		"rx_errors", "rx_dropped", "rx_crc_errors", "rx_missed_errors",
+		"rx_length_errors", "rx_over_errors", "rx_frame_errors", "rx_fifo_errors",
+	}
+)
 
 type nicCounters struct {
-	stats          map[string]uint64
-	carrierChanges uint64
-	carrierUp      uint64
-	carrierDown    uint64
+	tx          uint64
+	rx          uint64
+	carrierDown uint64
 }
 
 func readUint(path string) (uint64, bool) {
@@ -36,36 +40,22 @@ func readUint(path string) (uint64, bool) {
 	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 {
+func sumFields(base string, fields []string) uint64 {
+	var total uint64
+	for _, f := range fields {
 		if v, ok := readUint(base + "/statistics/" + f); ok {
-			c.stats[f] = v
+			total += v
 		}
 	}
-	c.carrierChanges, _ = readUint(base + "/carrier_changes")
-	c.carrierUp, _ = readUint(base + "/carrier_up_count")
+	return total
+}
+
+func readNIC(ifname string) nicCounters {
+	base := "/sys/class/net/" + ifname
+	c := nicCounters{
+		tx: sumFields(base, nicTxFields),
+		rx: sumFields(base, nicRxFields),
+	}
 	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, " ")
-}