Bugs item #3412787, was opened at 2011-09-22 12:06
Message generated for change (Comment added) made by akshukla
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Category: name resolving/DNS
Group: bad behaviour
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Akanksha Shukla (akshukla)
Assigned to: Daniel Stenberg (bagder)
Summary: libcurl.so.4 failes to resolve hostname to IPv6 using DNS

Initial Comment:
Problem Description:

We have an application program running on Linux machine. We have one DNS machine which has IPv6 address and in our Linux machine (in /etc/resolv.conf), we have specified the IPv6 address of DNS machine. When we try to make a request from our application (basically GET,POST etc), which uses libcurl api, then the request gets failed. While debugging we found that the libcurl api was failing while executing curl_easy_perform(). On setting the libcurl api in verbose mode we found that the libcurl api couldn't resolve the IPv6 address from the hostname. It gives following error:

* Resolving host timed out: <host-name>
* Closing connection #0
* Couldn't resolve host name

We also found that our libcurl DNS requests were not reaching to the DNS machine. At the time of issue the application was linked to the libcurl.so.4.

When we linked our application to libcurl.so.3, then everthing works fine.

So it seems to us that there is problem with libcurl's new version.

This issue comes only when we specify the IPv6 address of DNS in /etc/resolv.conf file of Unity Server. If we specify the IPv4 address of DNS machine in /etc/resolv.conf file, then everything works fine with libcurl.so.4 version as well.

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>Comment By: Akanksha Shukla (akshukla)
Date: 2011-09-30 13:26

Message:
Hi Daniel,

In request to the query mentioned yesterday, one more thing is there which
i would like to ask:

Is it possible for you to provide patch on 7.19.0 version with the fix of
this issue so that we can use the same in our product rather than upgrading
to the latest one.

Please provide your inputs for both the queries.

Thanks
Akanksha Shukla.

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Comment By: Akanksha Shukla (akshukla)
Date: 2011-09-29 20:11

Message:
Hi Daniel,

Thanks for your help so far. I tried with the latest lib curl version
(7.22.0) and i am not facing issue anymore. But i have one query which i
want to ask from you. Since we are using libcurl.so.4 from quite few years
in our product and we never faced any issue so far except this one. But
this issue became as showstopper for us. Thought latest release has
resolved our problem but upgrading to that release would be a challenge for
us. Since there are lot of bug fixes and features has been added from
7.19.0 to 7.22.0 releases. So, my queries are :
1) Is it possible for you to let us know in which particular release of
lib curl the problem would have been resolved ( i mean later than 7.19.0
but lesser than 7.22.0 because i think you would be familiar about the same
that DNS related changes have been done in which releases and if those
changes might have fixed our issue as well).

Once again thanks for your help.

Waiting for your inputs.

Thanks
Akanksha Shukla.

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Comment By: Daniel Stenberg (bagder)
Date: 2011-09-26 15:12

Message:
(please don't change priority, that's our call)

We've done 18 releases in the 3 years that have passed since 7.19.0 and
we've fixed 491 bugs. Please consider trying a current version and see if
the bug still remains.

You can check which resolver backend is used by interpreting the 'curl -V'
output, the build options or check what curl_version_info() returns.

If you're using c-ares, then your specific c-ares version would also be
interesting info.

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Comment By: Akanksha Shukla (akshukla)
Date: 2011-09-26 11:37

Message:
Hi,

This is in response to your queries asked in last mail:

What's the exact libcurl version you're using? (libcurl.so.4 is just the
ABI name which has been the same for many years)

<AS> The libcurl version used is 7.19.0

What resolver backend in libcurl are you using? (stock, c-ares or
threaded)

<AS> I am not sure which resolver backend is getting called. I simply
called curl_easy_perform() API. Could you please let me know how to check
which resolver backend is getting called? Is there any command to check for
the same.

I assume other services work fine with this DNS server?

<AS> Yes, other services work fine with this DNS server.

Please let me know, in case you need any other information.

Waiting for reply.

Thanks
Akanksha Shukla.

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Comment By: Daniel Stenberg (bagder)
Date: 2011-09-22 12:22

Message:
What's the exact libcurl version you're using? (libcurl.so.4 is just the
ABI name which has been the same for many years)

What resolver backend in libcurl are you using? (stock, c-ares or
threaded)

I assume other services work fine with this DNS server?

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Received on 2011-09-30