Speeding up nscd

[Florian Weimer]

On 12/26/2012 08:47 PM, Russ Allbery wrote:

> Also, the original Solaris nscd and I believe early glibc verisons
> completely ignored DNS TTLs. [...]

> Per Urlich at http://udrepper.livejournal.com/16362.html this bug has been
> fixed in glibc since late 2004, but having had that debugging experience,
> I have to say that it's... memorable.  I suspect that many people just
> haven't gotten the message that this was fixed long ago,

I dimly remember subsequent bugs about negative caching and some bad 
interactions between A and AAAA lookups.

Looking at the code (and experimenting with Fedora 17 and glibc 2.15), 
nscd still turns a NODATA response into a NXDOMAIN response.

Here's a getaddrinfo test without nscd:

error: name lookup failure for enyo.de/80: No address associated with 
hostname

But with nscd, I get:

error: name lookup failure for enyo.de/80: Name or service not known

These are the strings returned from gai_strerror, and the constants are 
probably EAI_NODATA and EAI_NONAME.

-- 
Florian Weimer / Red Hat Product Security Team