Re: [NSE] ASN

[David Fifield <david () bamsoftware com>]

On Sun, Sep 07, 2008 at 04:14:00AM +0100, jah wrote:
> On 06/09/2008 06:09, David Fifield wrote:
> > One other thing. The DNS queries in ASN.nse don't work with the caching
> > DNS server in my DSL modem. If I use a script arg and use the DNS server
> > the modem is using it works fine. But without it there's a timeout of 40
> > seconds (4 times 10 seconds I guess) per host. Maybe the script could
> > bail out if the first query times out, and mark that it has done so in
> > the registry so other instances of the script don't waste their time?
> Attached is an update which makes the following changes:
>
> When no dns servers could be found by dns.lua, or if no response was
> obtained from any dns server, then a debug message is printed, an entry
> is made in the registry to signal all threads and no further queries are
> attempted.  Very interested to know if this is satisfactory for your
> fussy resolver David.

Yes, the revised script gives up quickly.

The DSL modem is an Actiontec M1000. According to
http://opensource.actiontec.com/ it runs dproxy-nexgen
(http://dproxy.sourceforge.net/) as a caching name server. A Wireshark
trace shows that no response is received to the TXT query. Script
debugging says

SCRIPT ENGINE DEBUG: AS Numbers Failed to send dns query.  Response from dns.query(): nil

> Outputs "No Such Name" when this message is received.  I'd decided not
> to show this message, but for now at least, it's helpful to know that we
> got an answer we can understand rather than wondering if the query failed.

I didn't get the "No Such Name" message.

This script (actually the revised one you posted in a reply) is a great
improvement and I have committed it. I thought I had gotten it into an
infinite loop but then I couldn't reproduce it, so maybe I didn't wait
long enough.

David Fifield

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