Re: dig trace and 'dig: Too many lookups'

8 msg	Dynamic update of virtual hosting domains
3 msg	Primary name server updates propagating to seco...
2 msg	can't find error message meaning
3 msg	Bad zone transfer request
14 msg	Leases on Dynamic Updates?
2 msg	exclude domain from logging
4 msg	bind port problems
4 msg	Configure DNS to provide translation for best r...
7 msg	forwarding options?
8 msg	Too many timeouts resolving / disabling EDNS me...
7 msg	pure DNS forwarder
5 msg	Help with views plz, letting internal users vie...
2 msg	SERVFAIL after ipv6 query
8 msg	BIND9 and probleme receiving pop emails
3 msg	What is the simple and safe way to make onw dyn...
8 msg	Problem with powerdns(master) -> bind(slave)
3 msg	HTTP SRV Records
3 msg	Bind is crashing? How to troubleshoot?
2 msg	Failing to load zone file after upgrade to 9.4.2

dig trace and 'dig: Too many lookups'
\ Jeremy C. Reed (16 Jan 2008)
. \ Mark Andrews (17 Jan 2008)

Subject:	Re: dig trace and 'dig: Too many lookups'
Group:	Bind-users
From:	Mark Andrews
Date:	17 Jan 2008

> Our ns1 was down and a customer using an outsourced monitoring service
> forwarded me a report from DiG 9.3.1 doing a +trace. The ns2 (as far as I
> saw) was working fine.
>
> I don't know the dig command that was used but I am guessing:
>
> dig site.example.com +trace @some.root-servers.net
>
> since the output started with the root-servers.
>
> It has the same lookup repeated near 90 times. It looked like this:
>
> example.com 170877 IN NS ns1.example.net.
> example.com 170877 IN NS ns2.example.net.
> ;; Received 124 bytes from 65.77.130.5#53(ns2.example.net) in 79 ms
>
> example.com 170876 IN NS ns2.example.net.
> example.com 170876 IN NS ns1.example.net.
> ;; Recedig: Too many lookups
> ived 124 bytes from 65.77.130.5#53(ns2.example.net) in 80 ms
>
>
> The above "Recedig: Too many lookups" was in the report forwarded to me.
> The "dig: Too many lookups" was in the middle of the "Received 124 bytes
> ..." message.
>
> It had that a few times:
>
> ;; Receivedig: too many lookups
> ...
> ;; Recedig: Too many lookups
> ...
> ;; Recedig: Too many lookups
>
>
> I know this doesn't provide much details and the problem was from sixteen
> hours ago so I can't see it myself.
>
>
> Anyone seen this before? Any ideas what it means?
>
> Thanks!
>
>
> Jeremy C. Reed
>
> p.s. Hope it is okay I replaced the domain names above.

fatal("too many lookups"); -> stderr
printf(";; Received %u bytes from %s(%s) in %d ms\n\n", -> stdout

stdout was not flushed before before the stderr was output.
As a result part of the dtdout stream was before the message
to stderr and part after.

"dig +trace" does not try to track which servers it has
talked too, unlike a full iterative resolver which does
track this information. As a result it can easily loop
forever so there is a lookup limit which stop the lookup
when it starts to loop.

Mark

--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: Mark_Andrews