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: 8
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: 2011-09-26 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 2011-09-26