How to test a patch in resolv/?

[Florian Weimer]

On 10/06/2015 08:38 PM, Stan Shebs wrote:
> Last week at Google, getaddrinfo() blew up in an attention-getting way,
> apparently due to an innocuous internal server change triggering BZ 16754
> (the library version we're using derives from 2.19).

I think that's not the right bug number.

> So while there is a patch for this bug, and it even applies cleanly to our
> version, I'm wondering how to write a test that demonstrates it's an actual
> fix, without depending on masses of internal Google configuration. It seems
> like one ought to be able to build a little mock DNS server, but I don't see
> that anyone has done that to date, and maybe there is some better way
> to do a unit test.

You can use static linking to poke at library internals reliably, if
that helps.

It used to be possible to override the configured name servers by
directly writing to the _res structure.  This would make it possible to
redirect DNS queries to a custom test server (either in another thread
or process).  I don't know if current libresolv versions still support that.

Florian