Add -snmp-log option.

client/lib/util.go

 package snowflake_client
 
 import (
+	"fmt"
 	"log"
+	"os"
 	"time"
+
+	"github.com/xtaci/kcp-go/v5"
 )
 
 const (
@@ -14,6 +18,10 @@ type bytesLogger interface {
 	addInbound(int64)
 }
 
+var SNMPRunID [8]byte
+var SNMPLogFile *os.File
+var SNMPRecordCounter int64
+
 // Default bytesLogger does nothing.
 type bytesNullLogger struct{}
 
@@ -52,6 +60,13 @@ func (b *bytesSyncLogger) log() {
 			outEvents = 0
 			inbound = 0
 			inEvents = 0
+			if SNMPLogFile != nil {
+				err := logSNMP(SNMPLogFile, SNMPRunID, SNMPRecordCounter)
+				SNMPRecordCounter++
+				if err != nil {
+					log.Printf("error logging SNMP: %v", err)
+				}
+			}
 		case amount := <-b.outboundChan:
 			outbound += amount
 			outEvents++
@@ -69,3 +84,19 @@ func (b *bytesSyncLogger) addOutbound(amount int64) {
 func (b *bytesSyncLogger) addInbound(amount int64) {
 	b.inboundChan <- amount
 }
+
+func logSNMP(f *os.File, runID [8]byte, counter int64) error {
+	_, err := fmt.Fprintf(f, "%x,%d,%s,%s\n", runID, counter, "Date", time.Now().UTC().Format(time.RFC3339))
+	if err != nil {
+		return err
+	}
+	labels := kcp.DefaultSnmp.Header()
+	values := kcp.DefaultSnmp.ToSlice()
+	for i := 0; i < len(labels) && i < len(values); i++ {
+		_, err := fmt.Fprintf(f, "%x,%d,%s,%s\n", runID, counter, labels[i], values[i])
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}

client/snowflake.go

@@ -2,6 +2,7 @@
 package main
 
 import (
+	"crypto/rand"
 	"flag"
 	"fmt"
 	"io"
@@ -160,6 +161,7 @@ func main() {
 	max := flag.Int("max", DefaultSnowflakeCapacity,
 		"capacity for number of multiplexed WebRTC peers")
 	versionFlag := flag.Bool("version", false, "display version info to stderr and quit")
+	snmpLogFilename := flag.String("snmp-log", "", "name of kcp-go SNMP log file")
 
 	// Deprecated
 	oldLogToStateDir := flag.Bool("logToStateDir", false, "use -log-to-state-dir instead")
@@ -203,6 +205,20 @@ func main() {
 		log.SetOutput(&safelog.LogScrubber{Output: logOutput})
 	}
 
+	if *snmpLogFilename != "" {
+		var err error
+		sf.SNMPLogFile, err = os.OpenFile(*snmpLogFilename,
+			os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0600)
+		if err != nil {
+			log.Fatal(err)
+		}
+		_, err = rand.Read(sf.SNMPRunID[:])
+		if err != nil {
+			log.Fatal(err)
+		}
+		defer sf.SNMPLogFile.Close()
+	}
+
 	log.Printf("snowflake-client %s\n", version.GetVersion())
 
 	iceAddresses := strings.Split(strings.TrimSpace(*iceServersCommas), ",")