On 2014-08-05 at 19:16 -0500, Patrick Landry wrote:
> I have been experimenting with the sortlist directive in /etc/resolv.conf,

Everything around /etc/resolv.conf is fragile, system dependent and
subject to varying interpretations.  From "oops, does 'search' or
'domain' take precedence?" through to availability of options, through
to what the standard system resolver interface is (NetBSD made backwards
incompatible changes to the API if managing resolver objects, etc etc).
It's all a source of misery and pain.

If you must have a particular semantic specification used, pick a DNS
resolver library which supports that and write applications which use
that.  The moment you're relying upon shipped binaries where you don't
get to patch these things, all bets are off.

In this particular case, I have a very vague recollection that some
implementations of getaddrinfo(3) (the multi-stack compatible hostname
resolution API, which is required for IPv6 support) do not support
"sortlist", but I could be wrong.  This is, however, consistent with
"ping" working (IPv4-only) but not apps updated to support IPv6.

Ahah, here you go, the normal Linux libc implementation did not carry
across support for sortlist into getaddrinfo because Ulrich Drepper
felt that an RFC on an appropriate default standard sorting mechanism
overrides any locally set administrative policy:

  https://bugzilla.redhat.com/show_bug.cgi?id=144373

So: on Linux, only works with ancient v4-only applications.
-- 
My employer, Apcera Inc, is hiring sysadmin; primarily San Francisco:
 http://www.apcera.com/jobs/#operations-engineer
(but all the mistakes in this email are made in my personal capacity)
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