[Bug network/14415] AI_V4MAPPED is useless with AI_UNSPEC but they're used together as defaults when hints=NULL

["psimerda at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=14415

--- Comment #5 from Pavel Åimerda <psimerda at redhat dot com> 2013-01-03 14:53:57 UTC ---
Created attachment 6794
  --> http://sourceware.org/bugzilla/attachment.cgi?id=6794
getaddrinfo: use zero ai_flags by default

    According to POSIX1-2008, AI_V4MAPPED flag shall be ignored unless
ai_family
    equals AF_INET6. In the default hints, ai_family is AF_UNSPEC. Therefore
    AI_V4MAPPED is redundant.

    AI_ADDRCONFIG can potentially be beneficial to applications that use
    getaddrinfo() results to immediately call connect(), sendto() and
    similar functions to avoid querying redundant DNS records according
    to the current address configuration.

    Those applications will also need to specify ai_socktype and/or
    ai_protocol and therefore will not use hints=NULL. As AI_DEFAULT is not
    a part of the public API, such applications will not be able to use the
    default flags at all.

    Please note that POSIX1-2008 doesn't define any default flags at all.

    Resolves: #14415, #14965

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