Re: [PATCH] resolv: Do not copy IPv4 addresses to IPv6 address array

[Carlos O'Donell <carlos at redhat dot com>]

On 07/04/2017 05:47 AM, Florian Weimer wrote:
> On 07/03/2017 10:40 PM, Andreas Schwab wrote:
>> On Jun 29 2017, Florian Weimer <fweimer@redhat.com> wrote:
>>
>>> Andreas, if I recall correctly, you wrote get_nsaddr.
>>
>> Yes, the BIND resolver in FreeBSD has the same function.
> 
> What do you think about the patch I posted?
> 
>> Their way to extend _res for IPv6 is worth looking at.
> 
> They put pointers to malloc'ed state directly into _res.  We could od as
> well, but it will cause problems if applications copy _res, so I went
> for the more complex approach.

A design that puts malloc'd pointers directly into _res is not a good idea
for the reasons you note. I agree with your solution.

Several kinds of "handle" interfaces have internal mapping constructs that
let you go from a "handle" (index XOR magic in this case) to a much more
complicated structure that can have reference counts and other data. This
is much more flexible than just a pointer to the data. In some cases it is
more costly than the simple interface, but in this case I think it's worth
the added complexity given what you're trying to achieve.

-- 
Cheers,
Carlos.