[9fans] dns, cs, and smtp

[9fans] dns, cs, and smtp

[David Presotto]

I updated dns, cs, and smtp to better handle the situation
of some chunk of the dns tree being unreachable.  Before the
changes, smtp would often return mail prematurely if we
couldn't reach part of the dns tree.  Now it just leaves the
mail queued to try again later.

A side effect of this change is to make cs and dns return
better error messages.

I also fixed a problem with inherited dns domain's.  When I
added caching of negative replies, I broke the handling of
inherited dns domain's.  For example, if you had in your /lib/ndb/local
file something like:

ipnet=mh-astro ip=135.104.0.0
	dnsdomain=cs.bell-labs.com
	dnsdomain=research.bell-labs.com
	dnsdomain=x.bell-labs.com
	dnsdomain=bell-labs.com
	...

any attempt to access an undistiguished domain name 'x' should
have tried x.cs.bell-labs.com, then x.research.bell-labs.com,
then x.x.bell-labs.com, then x.bell-labs.com.  Unfortunately,
when I added the negative cached entries, the first domain that
returned a negative reply would cause the search to stop.  Its
fixed now.  It was broken for over a year and I don't recall
anyone complaining.  I just happened to notice it this weekend
when I was testing the other stuff.

Also, I fixed a few nits in dnsdebug.

I've been running the code for a few days without ill effects here.

Tell me ASAP if you have any problems with it.

Re: [9fans] dns, cs, and smtp

[Lucio De Re]

On Tue, Apr 01, 2003 at 09:21:39PM -0500, David Presotto wrote:
>
> I updated dns, cs, and smtp to better handle the situation
> of some chunk of the dns tree being unreachable.  Before the
> changes, smtp would often return mail prematurely if we
> couldn't reach part of the dns tree.  Now it just leaves the
> mail queued to try again later.
>
I've been meaning to ask for a while:  the man pages are not very
clear (to the extent that I have been digging) about the format of
reverse DNS resolution.

Perhaps an example will help?  I haven't had much success with
experimentation and reading the source is always a little daunting.

++L

Re: [9fans] dns, cs, and smtp

[David Presotto]

[-- Attachment #1: Type: text/plain, Size: 439 bytes --]

You mean like:

% ndb/dnsquery
> yahoo.com mx
yahoo.com mx	1 mx2.mail.yahoo.com
yahoo.com mx	5 mx4.mail.yahoo.com
yahoo.com mx	1 mx1.mail.yahoo.com
> mx1.mail.yahoo.com
mx1.mail.yahoo.com ip	64.157.4.84
mx1.mail.yahoo.com ip	64.157.4.83
mx1.mail.yahoo.com ip	64.156.215.5
mx1.mail.yahoo.com ip	64.157.4.82
> 64.157.4.84
84.4.157.64.in-addr.arpa ptr	mta-v14.level3.mail.yahoo.com(0)
>

Or do you want a program that does it?

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From: Lucio De Re <lucio@proxima.alt.za>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] dns, cs, and smtp
Date: Wed, 2 Apr 2003 16:07:27 +0200
Message-ID: <20030402160726.I11994@cackle.proxima.alt.za>

On Tue, Apr 01, 2003 at 09:21:39PM -0500, David Presotto wrote:
>
> I updated dns, cs, and smtp to better handle the situation
> of some chunk of the dns tree being unreachable.  Before the
> changes, smtp would often return mail prematurely if we
> couldn't reach part of the dns tree.  Now it just leaves the
> mail queued to try again later.
>
I've been meaning to ask for a while:  the man pages are not very
clear (to the extent that I have been digging) about the format of
reverse DNS resolution.

Perhaps an example will help?  I haven't had much success with
experimentation and reading the source is always a little daunting.

++L

Re: [9fans] dns, cs, and smtp

[Lucio De Re]

On Wed, Apr 02, 2003 at 09:20:40AM -0500, David Presotto wrote:
>
> You mean like:
>
> % ndb/dnsquery
> > yahoo.com mx
> yahoo.com mx	1 mx2.mail.yahoo.com
> yahoo.com mx	5 mx4.mail.yahoo.com
> yahoo.com mx	1 mx1.mail.yahoo.com
> > mx1.mail.yahoo.com
> mx1.mail.yahoo.com ip	64.157.4.84
> mx1.mail.yahoo.com ip	64.157.4.83
> mx1.mail.yahoo.com ip	64.156.215.5
> mx1.mail.yahoo.com ip	64.157.4.82
> > 64.157.4.84
> 84.4.157.64.in-addr.arpa ptr	mta-v14.level3.mail.yahoo.com(0)
> >
>
> Or do you want a program that does it?

Oops, sorry, again.  What I meant is that the ndb file format is not
self-explanatory.  A zone file for in-addr.arpa _is_ analogous to any
other forward-lookup zone, but Plan 9 has a somewhat different
approach and I can't seem to glean the full scope from the man pages.

I think it needs to be clarified at the possible cost of repetition,
if only for my benefit.

++L

Re: [9fans] dns, cs, and smtp

[David Presotto]

dom=jones.null.com ip=111.11.75.3 sys=jones

Generates both the forward and reverse resource records.  We don't
separate the records.  That means that you can't have the forward
and reverse entries not map to each other.  Sorry if that's what you
want.

Re: [9fans] dns, cs, and smtp

[Lucio De Re]

On Wed, Apr 02, 2003 at 09:56:20AM -0500, David Presotto wrote:
>
> dom=jones.null.com ip=111.11.75.3 sys=jones
>
> Generates both the forward and reverse resource records.  We don't
> separate the records.  That means that you can't have the forward
> and reverse entries not map to each other.  Sorry if that's what you
> want.

That's what IBM would call a "feature".  I assumed as much, but
somehow could not get the "ptr" queries to work.  Maybe it's just
the SOA record I have trouble with (that is, defining the "zone",
which from the above I assume is largely implicit) or, more likely,
the actual way delegations take place.

It's all quite muddled in my mind.  I'll see if I can rephrase my
problem more clearly.  As I'm about to rearrange my network, this
is a good time for me to get more familiar with the network database.

++L

Re: [9fans] dns, cs, and smtp

[George Michaelson]

On Thu, 3 Apr 2003 08:43:58 +0200 Lucio De Re <lucio@proxima.alt.za> wrote:

> On Wed, Apr 02, 2003 at 09:56:20AM -0500, David Presotto wrote:
> >
> > dom=jones.null.com ip=111.11.75.3 sys=jones
> >
> > Generates both the forward and reverse resource records.  We don't
> > separate the records.  That means that you can't have the forward
> > and reverse entries not map to each other.  Sorry if that's what you
> > want.


How do you handle multiple A bindings to different names? (only one PTR can
exist)

-George

Re: [9fans] dns, cs, and smtp

[David Presotto]

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We will return PTR records for all names bound to an IP address.  From
RFC2181:

10.2. PTR records

   Confusion about canonical names has lead to a belief that a PTR
   record should have exactly one RR in its RRSet.  This is incorrect,
   the relevant section of RFC1034 (section 3.6.2) indicates that the
   value of a PTR record should be a canonical name.  That is, it should
   not be an alias.  There is no implication in that section that only
   one PTR record is permitted for a name.  No such restriction should
   be inferred.

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From: George Michaelson <ggm@apnic.net>
To: 9fans@cse.psu.edu
Cc: lucio@proxima.alt.za
Subject: Re: [9fans] dns, cs, and smtp
Date: Thu, 3 Apr 2003 16:50:49 +1000
Message-ID: <20030403165049.63877fba.ggm@apnic.net>

On Thu, 3 Apr 2003 08:43:58 +0200 Lucio De Re <lucio@proxima.alt.za> wrote:

> On Wed, Apr 02, 2003 at 09:56:20AM -0500, David Presotto wrote:
> >
> > dom=jones.null.com ip=111.11.75.3 sys=jones
> >
> > Generates both the forward and reverse resource records.  We don't
> > separate the records.  That means that you can't have the forward
> > and reverse entries not map to each other.  Sorry if that's what you
> > want.


How do you handle multiple A bindings to different names? (only one PTR can
exist)

-George