Re: When using ActiveMode of FTPS on Curl for Windows, it takes polling timeout time (1000msec) to establish DataConnection.

From: Yoshimasa Ohno via curl-library <curl-library_at_lists.haxx.se> Date: Wed, 4 Sep 2024 22:20:49 +0900

----
Here you can see that it is weighted for 1 second
2024年9月4日(水) 20:59 Stefan Eissing <stefan_at_eissing.org>:
>
>
> > Am 04.09.2024 um 13:41 schrieb Yoshimasa Ohno via curl-library <
> curl-library_at_lists.haxx.se>:
> >
> > Thanks for the response!
> >
> > I tried a local build including
> >
> https://github.com/curl/curl/commit/a07ba37b5e88a89bf4bcc6b0c927f7a42d7ea4f2
> > Unfortunately, it did not solve the problem I am experiencing in my
> environment.
> >
> > Even just adding printf debugging.
> > I don't know where the real cause is, because the problem is no longer
> reproduced.
> >
> > One of the conditions for the occurrence of the Dalay problem seems to
> be that the ReceivedServerConnect function exits in the socket
> unestablished state.
> > ReceivedServerConnect function seems to occur when the following,
> unestablished state comes through.
> >
> https://github.com/curl/curl/blob/6a9b71037a441eac28d3c7f629ac5801c01f99e2/lib/ftp.c#L572C1-L573C22
> >   case 0:  /* Server connect is not received yet */
> >     break; /* loop */
> >
> > When a problem occurs, there is a delay of timeout time (standard is 1
> second, extended that way if modified) in the following
> WSAWaitForMultipleEvents.
> >
> https://github.com/curl/curl/blob/6a9b71037a441eac28d3c7f629ac5801c01f99e2/lib/multi.c#L1366
> >     else { /* now wait... if not ready during the pre-check (pollrc ==
> 0) */
> >       WSAWaitForMultipleEvents(1, &multi->wsa_event, FALSE,
> (DWORD)timeout_ms,
> >                                FALSE);
> >     }
> >
> > Is there anything I can try?
>
> Can you produce a log file via 'curl -v --trace-config all' of such a
> situation?
>
> As you describe it, the delay happens when the first check on the
> listening socket does
> not find anything and curl goes POLLing for socket events. The arriving
> server connect
> should then trigger the processing right away, but maybe there is
> something else in play here.
>
> - Stefan
>
> > 2024年9月3日(火) 16:59 Stefan Eissing via curl-library <
> curl-library_at_lists.haxx.se>:
> > I created https://github.com/curl/curl/pull/14766 as a fix for this.
> >
> > The bug was that the socket was not using POLLIN, but POLLOUT. So it
> never
> > triggered an event when the FTP server tried to connect. That led to the
> > connect only being noticed a second later when curl checks on all
> transfers.
> >
> > Hope this works for you.
> >
> >
> > > Am 03.09.2024 um 08:13 schrieb Daniel Stenberg via curl-library <
> curl-library_at_lists.haxx.se>:
> > >
> > > On Sat, 31 Aug 2024, Yoshimasa Ohno via curl-library wrote:
> > >
> > >> I found that the timeout argument of curl_multi_poll, the literal
> 1000, was having an effect. Changing this to 3000 resulted in a 3 second
> wait.
> > >
> > > We believe there might be a bug in the code that sets what socket
> activity curl should wait for when waiting for the connect to happen. (A
> regression)
> > >
> > > Stefan is going to try to get a fix made and submitted soon.
> > >
> > > --
> > >
> > > / daniel.haxx.se
> > > | Commercial curl support up to 24x7 is available!
> > > | Private help, bug fixes, support, ports, new features
> > > | https://curl.se/support.html
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>