ATS proxy closes the connection "close" even if client sends "keep-alive"

[Ananth Laxminarasimhan (alaxmina)]

I have configured ATS as a web proxy in a NTLM authentication domain; and, have 
a plugin with a function for TS_HTTP_READ_REQUEST_HDR_HOOK say, func_1.
In func_1 which is invoked during the request header, I create a hook for 
TS_HTTP_SEND_RESPONSE_HDR_HOOK (say, func_2) and then do a 
TSHttpTxnReenable(txnp, TS_EVENT_HTTP_ERROR);

Subsequently, when func_2 is invoked during the SEND_RESPONSE_HEADER event, I 
frame a “407 Proxy Auth required” response header along with Proxy-Authenticate 
set to “NTLM” and then do a TSHttpTxnReenable(txnp, TS_EVENT_HTTP_CONTINUE);

Func_1() {
….
…
TSHttpTxnHookAdd(txnp, TS_HTTP_SEND_RESPONSE_HDR_HOOK,
                                 TSContCreate(responseHook, TS_NULL_MUTEX));
            }
            TSHttpTxnReenable(txnp, TS_EVENT_HTTP_ERROR);
….
return;
}

func_2() {

…
TSHttpTxnReenable(txnp, TS_EVENT_HTTP_CONTINUE);
return;
}

What happens is that even though the client sends a “Connection: keep-alive”, 
ATS seems to be returning a “Connection: close” which results in the connection 
getting closed.


> GET http://www.purple.com/ HTTP/1.1
> Host: www.purple.com
> Proxy-Authorization: NTLM TlRMTVNTUAABAAAABoIIAAAAAAAAAAAAAAAAAAAAAAA=
> User-Agent: curl/7.44.0
> Accept: */*
> Proxy-Connection: Keep-Alive
>
< HTTP/1.1 407 Proxy Authentication Required
< Date: Sun, 03 Sep 2017 10:47:24 GMT
< Connection: close
< Via: http/1.1 POD128-CentOS7-01 (ApacheTrafficServer/6.2.1)
< Server: ATS/6.2.1
< Proxy-Authenticate: NTLM
< Content-Length: 15
< Content-Type: text/plain
<
  0    15    0     0    0     0      0      0 --:--:--  0:00:01 --:--:--     0
* Closing connection 7

Why is ATS closing the connection?And, how can I control this behavior?

Thanks,
Ananth