How to refused connections when upstream is unavailable?

Networking
1

When upstream is starting and the service port is unavailable, request will be refused like after without inject istio-proxy.

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But after inject with istio-proxy, the request changes to 503, this will affect the behavior of the clients.

*   Trying 10.32.5.131:8080...
* TCP_NODELAY set
* Connected to 10.32.5.131 (10.32.5.131) port 8080 (#0)
> GET /ping HTTP/1.1
> Host: 10.32.5.131:8080
> User-Agent: curl/7.68.0
> Accept: */*
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 503 Service Unavailable
< content-length: 145
< content-type: text/plain
< date: Wed, 21 Sep 2022 09:40:25 GMT
< server: istio-envoy
< 
* Connection #0 to host 10.32.5.131 left intact
upstream connect error or disconnect/reset before headers. reset reason: connection failure, transport failure reason: delayed connect error: 111

so, How to refused connections when upstream is unavailable?