Add packet capture debug stats

Also remove potentially sensitive memstat and cmdargs from /debug/vars endopint

capture/capture.go

@@ -3,6 +3,7 @@ package capture
 import (
 	"context"
 	"errors"
+	"expvar"
 	"fmt"
 	"io"
 	"log"
@@ -22,9 +23,20 @@ import (
 	"github.com/google/gopacket/pcap"
 )
 
+var stats *expvar.Map
+
+func init() {
+	stats = expvar.NewMap("raw")
+	stats.Init()
+}
+
 // PacketHandler is a function that is used to handle packets
 type PacketHandler func(*tcp.Packet)
 
+type PcapStatProvider interface {
+	Stats() (*pcap.Stats, error)
+}
+
 // PcapOptions options that can be set on a pcap capture handle,
 // these options take effect on inactive pcap handles
 type PcapOptions struct {
@@ -339,10 +351,19 @@ func (l *Listener) read(handler PacketHandler) {
 				}
 			}
 
+			timer := time.NewTicker(1 * time.Second)
+
 			for {
 				select {
 				case <-l.quit:
 					return
+				case <-timer.C:
+					if h, ok := hndl.handler.(PcapStatProvider); ok {
+						s, _ := h.Stats()
+						stats.Add("packets_received", int64(s.PacketsReceived))
+						stats.Add("packets_dropped", int64(s.PacketsDropped))
+						stats.Add("packets_if_dropped", int64(s.PacketsIfDropped))
+					}
 				default:
 					data, ci, err := hndl.handler.ReadPacketData()
 					if err == nil {

gor.go

@@ -3,12 +3,13 @@
 package main
 
 import (
-	_ "expvar"
+	"expvar"
 	"flag"
+	"fmt"
 	"log"
 	"net/http"
 	"net/http/httputil"
-	_ "net/http/pprof"
+	httppptof "net/http/pprof"
 	"os"
 	"os/signal"
 	"runtime"
@@ -22,6 +23,35 @@ var (
 	memprofile = flag.String("memprofile", "", "write memory profile to this file")
 )
 
+func init() {
+	var defaultServeMux http.ServeMux
+	http.DefaultServeMux = &defaultServeMux
+
+	http.HandleFunc("/debug/vars", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		fmt.Fprintf(w, "{\n")
+		first := true
+		expvar.Do(func(kv expvar.KeyValue) {
+			if kv.Key == "memstats" || kv.Key == "cmdline" {
+				return
+			}
+
+			if !first {
+				fmt.Fprintf(w, ",\n")
+			}
+			first = false
+			fmt.Fprintf(w, "%q: %s", kv.Key, kv.Value)
+		})
+		fmt.Fprintf(w, "\n}\n")
+	})
+
+	http.HandleFunc("/debug/pprof/", httppptof.Index)
+	http.HandleFunc("/debug/pprof/cmdline", httppptof.Cmdline)
+	http.HandleFunc("/debug/pprof/profile", httppptof.Profile)
+	http.HandleFunc("/debug/pprof/symbol", httppptof.Symbol)
+	http.HandleFunc("/debug/pprof/trace", httppptof.Trace)
+}
+
 func loggingMiddleware(addr string, next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if r.URL.Path == "/loop" {