[discuss] about genrating evt of packetloss

[dzy176]

Hi, I see in packetloss, if sth is wrong in GetSymsByStack() , the evt won't be sent to the sink because we continue to skip the next steps :

	stacks, err := bpfutil.GetSymsByStack(uint32(event.StackId), p.objs.InspPlStack)
	if err != nil {
		log.Warnf("%s failed get sym by stack, err: %v", probeName, err)
		continue
	}

It means we finaly miss record this event. Actually in my production env, I do encounter this problem, I get some packetloss metric but no event.
So how about not continue,

	stacks, err := bpfutil.GetSymsByStack(uint32(event.StackId), p.objs.InspPlStack)
	if err != nil {
		log.Warnf("%s failed get sym by stack, err: %v", probeName, err)
		// continue
                evt.Message = "unknown"
	} else {
	  var strs []string
	  for _, sym := range stacks {
		  if _, ok := ignoreSymbolList[sym.GetName()]; ok {
			  goto anotherLoop
		  }
		  strs = append(strs, sym.GetExpr())
	  }
	  evt.Message = strings.Join(strs, "\n") 
        }

[jzwlqx]

Stop on failing getting kernel symbol to avoid too many meaningless drop event (drop event on tcp closing e.g.).

I understand user do need the event regardless of whether symbol was resolved. Should we add a config for packetloss probe to specify the behaviour when cannot resolve symbol