I assume your question pertains to verifying Curl_ipvalid function. This function does check if IPv6 stack is there or not. However, it checks the IPv6 stack only if conn->ip_version == CURL_IPRESOLVE_V6, otherwise it just returns TRUE. For cases where CURL_IPRESOLVE_* option is not set by application the default conn->ip_version is to CURL_IPRESOLVE_WHATEVER.

So, for default cases the libcurl is not checking if IPv6 stack is there or not and that is what we are seeing.

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** [bugs:#1274] IPv6 DNS requests were sent out from Android Handsets even if the IPv6 stack is not present on the device.**
**Status:** pending-needsinfo
**Labels:** dns ipv6 
**Created:** Tue Sep 03, 2013 09:36 PM UTC by Rajiv Dwivedi
**Last Updated:** Sun Sep 15, 2013 06:41 PM UTC
**Owner:** Daniel Stenberg
Observation:
IPv6 DNS requests were sent out from Android Handsets even if the IPv6 stack is not present on the device.
Expected Result:
If there is no IPv6 stack on the device/machine, the IPv6 request should not be sent from the device.
Workaround:
Using option "CURL_IPRESOLVE_V4", disables sending IPv6 DNS queries.
Libcurl details:
OS: Linux - Android
version: 7.32.0
link: http://curl.haxx.se/download.html
Attachments:
Wireshark log ( which displays both Ipv$ and IPv6 records)
Verbose output using libcurl (captured while making HTTP requests)
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