Re: Found infinite looping in libCurl version 7.55.1

On Mon, 20 Jan 2020, Uma Shunmugan via curl-library wrote:

> It might not be a coincidence, but when this occurred, I noticed that a time
> value (timeval) returned by GetTickCount() and set in the "key" for some
> node in the Curl_tree passed into Curl_splay() had just wrapped around (due
> to the 49.7 days limitation). Is this a known issue, or is it possible that
> this could have caused Curl_splay() to get stuck in a loop?

It is not a known issue but having the time wrap and start over at zero sounds
like something that could be problematic.

> If so, is there a fix for it?

Current libcurl doesn't use GetTickCount() if you run on Vista or later so it
should already be avoided. For older systems there's no fix as far as I can
see.

> And is there any test program that I could run against libcurl to reproduce
> this infinite loop issue?

Not to my knowledge.

> BTW, I see in the libCurl changlog that high resolution timestamps are used
> on Windows starting from version libcurl 7.64.0. Was this change done to
> avoid similar issues as the one I have seen?

No.

> Would you recommend me to upgrade to this version?

If you're going to upgrade, I would recommend going to the latest version
while you're at it.

> Now, I've checked timeval.c in 7.55.1, and realized that GetTickcount64()
> would have been used instead, if _WIN32_WINNT and _WIN32_WINNT_VISTA had
> been defined to the correct values. It's not clear to me where/how these
> macros are to be defined, though. Is there a configuration option for these
> in the build? If not, could I simply define these in config-win32.h? FYI,
> I had compiled libcurl on Window 2008 using Visual Studio 2005, and
> obviously these macros were not defined at all.

I don't remember what 7.55.1 did.

> If this issue could not be due to time value rolling over problem, is there
> any other known issues that would explain this infinite looping? What else
> could I do to debug this further?

I'm not aware of any infinite looping bug mentioned in recent years until your
mail here.

To debug it, I would first try hard to reproduce (possibly by writing a mock
version of GetTickCount() for curl). Then when reproduced, see if a current
libcurl is likely to have similar logic that can be tricked in the same or
similar ways.

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