Re: [spfbis] Revisit: Issue #36: RFC 2119 key words

[Scott Kitterman <[e-mail]>]

On Friday, February 08, 2013 04:57:05 PM Barry Leiba wrote:
> >> -- Section 4.6.4 --
> >> In the second paragraph, why are you mixing "MX resource records" in
> >> the first sentence with "A resource records" in the second sentence?
> >> Is this a typo, or intentional?  If it's intentional, I would re-word
> >> it, which will probably correct the odd "MUST".
> > 
> > What I was trying to communicate there is something like the following
> >
> > sequence:
> >  - Do mx lookup for the domain.
> >  - One or more a records returned
> >  - If the number of a records is =< 10, then do a lookups to find the
> >relevant>
> > IP addresses
> >
> >  - If the number of a records is > 10, don't do any lookups and return a
> >
> > permerror.
> > 
> > When I look at it, I think it says that, but obviously it's not clear.
> > Wording suggestions appreciated.
> 
> Right, but you start by talking about how many MX lookups there are.
> What you say in your explanation above is that there's one, and the
> issue is how many A records that expands to.
> 
> As written, it seems to say that you can do up to 10 MX lookups, and
> each of those can result in up to 10 A lookups, for a total of 110 DNS
> lookups.  Is that what you mean?

Yes.  This is the basis for the infamous 111 DNS lookups.

> Are you trying to limit the total number of lookups in an SPF-record
> evaluation?  Or just the total number from any one clause?

For a single term (clause).

> Maybe this is enough to help you with wording... or maybe when you
> answer the questions above, I can take a stab.

Please do.

Scott K