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[curl:bugs] #1213 Wrong STARTTRANSFER timer accounting for POST requests

From: Daniel Stenberg <bagder_at_users.sf.net>
Date: Mon, 17 Jun 2013 20:53:45 +0000

I'm sorry but I read the code and I can't see the problem. I believe your test case is wrong. readwrite_upload() clearly sets the timer on its first invoke when nothing has been sent before. So, I think libcurl sends the data very early, it is just that your CGI waits so it doesn't receive it until later but your server did...

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** [bugs:#1213] Wrong STARTTRANSFER timer accounting for POST requests**
**Status:** pending-invalid
**Labels:** POST CURLINFO_STARTTRANSFER_TIME 
**Created:** Sat Apr 06, 2013 07:17 PM UTC by Mezon
**Last Updated:** Sat Apr 06, 2013 07:17 PM UTC
**Owner:** Daniel Stenberg
curl 7.28.1 (i686-pc-linux-gnu) libcurl/7.28.1 OpenSSL/0.9.8o zlib/1.2.3.4
Protocols: dict file ftp ftps gopher http https imap imaps pop3 pop3s rtsp smtp smtps telnet tftp 
Features: IPv6 Largefile NTLM NTLM_WB SSL libz 
There is an error in timing accounting at least for STARTTRANSFER timer during POST requests.
Timer works fine with GET requests, but while using POST the time for CURLINFO_STARTTRANSFER_TIME is wrong. While using POST CURLINFO_STARTTRANSFER_TIME minus CURLINFO_PRETRANSFER_TIME is near to zero every time.
Proof of concept:
I've prepared CGI script that sleeps 3 seconds on start, before it returns any data.
While making curl GET request to the script, (CURLINFO_STARTTRANSFER_TIME - CURLINFO_PRETRANSFER_TIME) is ok [~ 3 seconds]. Trying the same thing with POST request, cause the 3 seconds appears in CURLINFO_TOTAL_TIME instead of CURLINFO_STARTTRANSFER_TIME. So with POST it looks like the transfer took 3 seconds instead of waiting for server reply.
IMHO the problem is in ./lib/transfer.c in readwrite_upload() function, where Curl_pgrsTime(data, TIMER_STARTTRANSFER) is called in wrong place. Unfortunately I'm not sure where to replace it to fix the bug. I think it should go somewhere in Curl_readwrite() function, for example here:
~~~~~~
/* We go ahead and do a read if we have a readable socket or if
     the stream was rewound (in which case we have data in a
     buffer) */
if((k->keepon & KEEP_RECV) &&
     ((select_res & CURL_CSELECT_IN) || conn->bits.stream_was_rewound)) {
    result = readwrite_data(data, conn, k, &didwhat, done);
    if(result || *done)
      return result;
  }
  else {
      Curl_pgrsTime(data, TIMER_STARTTRANSFER); // <-- here
  }
~~~~~~
I'm not sure if any other timers are affected.
Best regards,
Mezon
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Received on 2013-06-17

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