[Development] DNS resolver docs for Linux/OSX

Mandeep Sandhu mandeepsandhu.chd at gmail.com
Tue Oct 15 10:38:38 CEST 2013


> However, I wanted to know more about the main "struct __res_state" used in
> these functions. Google hasn't thrown up much.
>
> Basically, I wanted to know the usage of 2 of the fields used in this struct
> - "nssocks[MAXNS]" and "nsmap[MAXNS]". What values are these supposed to
> hold?

Answering my own question. The nsmap[] array is supposed to be used to
tell the resolver which entry in the nsaddrs[] array holds an IPv6
address.

Dug up this info from this old thread:
https://sourceware.org/ml/libc-hacker/2002-05/msg00035.html

There's more info about the resolver in this thread:
https://sourceware.org/ml/libc-hacker/2000-07/msg00487.html

Though this message is old (posted around Jul 2000), one stmt here has
me a little worried:

"You cannot change the address of an IPv6 nameserver dynamically in
your program though"

I'm not sure why he's saying so as I've tested programatically setting
a IPv6 nameserver and it's working.

Regards,
-mandeep



>
> Thanks,
> -mandeep
>
>



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