Re: Slow name-resolution of very large target list

[Fyodor <fyodor () insecure org>]

On Thu, May 22, 2008 at 09:23:24PM +0000, Brandon Enright wrote:
> I'm working on cooking up a perl script to use the adns library.  I'm
> not sure how portable adns is but perhaps we could either look into
> using it or look into extending Doug's rDNS system to support
> forward-lookups too.  We could have the --system-dns fall back on
> gethostbyname().
>
> Perhaps it is rare enough for someone to be doing what I'm doing that
> it isn't worth the effort?

Well, I'm not opposed to Nmap doing its own forward DNS if the patch
is reasonbly small (no need to use adns -- we don't use that for rdns)
and it is also very reliable.  Even if we just do them one at a time
as they are encountered in TargetGroup.cc, it could speed things up
quite a bit because you don't have to wait 30 seconds or a minute or
whatever rediculous amount of time gethostbyname() waits for
resolution before it gives up.  Or maybe there are environmental
variables we could set on Linux or other ways to speed up
gethostbyname()?

Cheers,
-F


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