1.7.3 - root zone transfer and resolving SLD of delegated TLD

Wouter Wijngaards wouter at nlnetlabs.nl
Thu Nov 29 08:42:35 UTC 2018


On 11/28/18 6:18 PM, ѽ҉ᶬḳ℠ via Unbound-users wrote:
> I can appreciate if you are tired of, and thus refrain from, responding
> further in light of my continued ignorance.

We make our tools for knowledgeable users, also because the education
part is very hard.  There are other places, and people, to get
information about how it all really works.  But let me still try to
answer the questions.  Probably in ways that make you ask more ... :-)

> What I am not understanding is that forward and recursing are
> conflicting since I would have considered forwarding being part of
> recursing.

The difference is that forward is: send full query, get the answer.
For full-recursion: send parts, get referrals to other authoritative
servers, ask again there, until there is an answer.

If you enabled both, and unbound would perform full lookups to its
internal copy of the root zone.  This then results in a list of TLD
servers to contact.  But then it ignores that list, because, for TLDs,
it sends the full query to your configured DoT upstream forward server.
 Then that upstream forward query would be the full query.  Just like it
would have sent without the local copy of the root.

So your solution to turn off the local copy of the root, seems to have
resulted in the behaviour you want from enabling both.  Unbound sends
the full query to the upstream DoT server.  And then uses that answer.

The local copy of the root is useful for full recursion, not forwarding,
setups, where the first referral lookups to the root servers are omitted
with a local copy.  This is both faster and has privacy benefits.

Best regards, Wouter

> The issue to me as simple user seems rather that the forward-zone name
> is limited to . and therein somehow conflicting with auth-zone name .
> Or else forward-zone name being a domain name but it can hardly be
> expected having to list every TLD there is such as .com .net .gov and so
> forth ("Define them for other names, and that should work for those
> subzones.")
> Perhaps if there was instead a logic for forward-zone name: .* it would
> solve the matter comprehensively for all TLD and subdomains.
> I do appreciate all the effort being put into unbound and I am happy
> with deploying the application just in this case of the “hyperlocal”
> concept its usability does not appeal really.
> Having to chose between complicating matters with stub-zone and DoT I
> have opted for the latter and dropped the idea of hyperlocal (auth-zone
> name: .).
> On 28.11.2018 17:15, Wouter via Unbound-users wrote:
>> Hi,
>> So to summarize, another user also had this problem.  And the issue
>> was he enabled both a forward-zone with the new DoT.  And RFC7706
>> local copy of the root.  But that is both forward and do full
>> recursion at the same time, conflicting.  You have to pick one.
>> That query can get TLSed and sent to an upstream forwarder.  Or it can
>> take a referral from an RFC7706 copy of the root and then do full
>> recursion.  But not really both at the same time.  Hence, a bug,
>> previously, and now it prints errors.  But you ran into that error.
>> Unbound can actually also do DoT with stub-zones too, if you
>> configured it in unbound.conf, but there are no upstreams or method to
>> find any.  Anyway, that was not what you tried to do.
>> Best regards, Wouter
>> On 28/11/2018 16:56, Wouter Wijngaards via Unbound-users wrote:
>>> Hi,
>>> Yes the RFC7706 functionality needs you to not have a forward-zone
>>> clause and then an auth-zone for the root.  With for-downstream: no
>>> and for-upstream: yes (and the RFC recommends the fallback enabled, I
>>> think).  Unbound uses the auth-zone as a repository of data that is
>>> accessed instead of the  upstream, this is why the forward-zone and
>>> stub-zone definitions are still used, because they regulate how that
>>> local-copy of the upstream is accessed.
>>> If you want DoT upstreams, you can define them.  Just not for the "."
>>> zone whilst doing the auth-zone for the root.  Define them for other
>>> names, and that should work for those subzones.
>>> There is an example in the example.conf for RFC7706 functionality for
>>> the root.  You keep turning the options wrong?
>>> The servfail is because you instructed unbound to act as a forwarder
>>> to a root server, whose content is locally cached in an auth-zone. 
>>> The root server has very little data, itself, hence the servfails. 
>>> It needs to not have that forwarder clause.  Then it uses the
>>> referrals from the local copy to continue the full recursion.  And
>>> you could have gotten non SERVFAIL answers, if only you asked for the
>>> data that the local copy actually has, the root SOA record.  That
>>> would be answered and then a forwarder configuration works, giving
>>> the SOA record answer.  But for RFC7706 it wants the referrals
>>> followed, so not the forwarder configuration.
>>> The auth zone, when configured as for-downstream:no and for-upstream:
>>> yes is a quick method to get a reply from the upstream.  By having a
>>> local copy of the data to fill in the upstream reply.  Unbound then
>>> still needs to have the configuration on how to contact upstreams.
>>> And for a local root copy mirror that means a configuration where it
>>> will use the referral answer.  Using the referral answer needs a
>>> stub-zone (or the absence of a forward-zone).
>>> Looks like the architecture of the system and its configuration
>>> settings is complicated, if you end up figureing out where the
>>> understanding issue is, I mean how to fix documentation that would be
>>> nice.  Unbound is using both stub/forward decls to feed into an
>>> upstream selection, using auth-zone copies.   With for-downstream:
>>> yes the auth-zone moves closer and overtakes the stub/forward zones
>>> to provide the answer directly, something that is useful for giving
>>> authority answers to downstreams.
>>> Best regards, Wouter
>>> On 28/11/2018 16:01, ѽ҉ᶬḳ℠ via Unbound-users wrote:
>>>> I am not sure where my understanding is going awry here. What I want
>>>> to achieve seems to be called “hyperlocal” concept - a local copy
>>>> (AXFR/IXFR) of the root zone (to be served) by unbound to its
>>>> clients. Something like:
>>>>   * https://tools.ietf.org/html/rfc7706
>>>>   * https://tools.ietf.org/html/draft-ietf-dnsop-7706bis-00
>>>>   * https://localroot.isi.edu/about/
>>>> Thus far my understanding is that is (zone transfer) best to be
>>>> achieved via auth-zone and sub-zone rather to be utilized for
>>>> company-local data or private  zones (authoritative data  that
>>>> cannot be accessed using the public internet servers), which the
>>>> root zone is not. And stub-zone does not provide for zone transfer,
>>>> as far as I understand.
>>>> If the forward-zone definition is removed than I cannot utilise DoT
>>>> with selected upstream resolvers.
>>>> What I not get is the servfail on the referrals/delegation from the
>>>> root zone. Is unbound not suited for this “hyperlocal” concept thence?
>>>> On 28.11.2018 14:42, Wouter via Unbound-users wrote:
>>>>> Hi,
>>>>> On 28/11/2018 13:46, ѽ҉ᶬḳ℠ via Unbound-users wrote:
>>>>>> Hi Wouter,
>>>>>> thanks for looking into it and the response. Unfortunately with
>>>>>> the below setting the /second-level domain does not resolve/
>>>>> It is configured to forward to the root zone that you have
>>>>> mirrored.  The root zone only contains delegations, so you get
>>>>> servfail or referrals out of that.  What you want is that it
>>>>> performs full recursion with the copy of the root zone, that is the
>>>>> stub-zone behaviour.  You should change your config to have
>>>>> stub-zone for the name: "." zone and not a forward-zone for that;
>>>>> or remove the forward-zone definition.
>>>>> These two log lines contained the info:
>>>>> debug: forwarder, ignoring referral from auth zone
>>>>> debug: auth zone lookup failed, no fallback, servfail

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: OpenPGP digital signature
URL: <http://lists.nlnetlabs.nl/pipermail/unbound-users/attachments/20181129/735b95cd/attachment.bin>

More information about the Unbound-users mailing list