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GetAddrInfo fails with error 11001 when there was a previous call for the AF_INET6 family in Windows

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This article addresses an issue in which you receive a WSAHOST_NOT_FOUND error when the GetAddrInfo is called after another call for the AF_INET6 family.

Applies to:   Windows 10 - all editions
Original KB number:   4057932

Symptoms

Consider the following scenario:

  • You use a flat name without any suffixes to run a query for a host name.
  • You have a suffix search list, and this host name is resolvable through one of these suffixes other than the last suffix in the list.
  • You run GetAddrInfo for the AF_INET6 family first, and then you run that command for the AF_INET family.

In this scenario, the function can't resolve the provided host name, and you receive the " WSAHOST_NOT_FOUND (11001)" error message.

For example, you have the following environment:

  • Suffix Search List: contoso.com, foo.contoso.com, bar.contoso.com
  • Host name trying to be resolved: test
  • Host DNS A record present in: foo.contoso.com

When you try to run the following sample code, the calls fail with the 11001 error.

hints.ai_socktype = SOCK_STREAM;
                hints.ai_protocol = IPPROTO_TCP;
                hints.ai_flags = 0;
                hints.ai_family = AF_INET6;
getaddrinfo("test", NULL, &hints, &res)
hints.ai_family = AF_INET;
getaddrinfo("test", NULL, &hints, &res)

Workaround

This issue can be avoided by using the following methods. The issue will not occur if you:

  • Use AF_UNSPEC for the family and let our code determine the A/AAAA results for you.
  • Put the suffix with the matching host A record as the last entry in the suffix search list.
  • Disable negative caching on the DNS client.
  • Pass the fully qualified host name to be resolved.

The first option is the recommended method, as there's usually no need to do the calls on a per family basis, and Windows is much better optimized to return the best possible set of results for both families.