Re: [DNSOP] SVCB and the specialness of _
Ben Schwartz <bemasc@google.com> Wed, 07 October 2020 19:27 UTC
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From: Ben Schwartz <bemasc@google.com>
Date: Wed, 07 Oct 2020 15:26:56 -0400
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To: Brian Dickson <brian.peter.dickson@gmail.com>
Cc: dnsop <dnsop@ietf.org>
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Subject: Re: [DNSOP] SVCB and the specialness of _
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On Wed, Oct 7, 2020 at 3:20 PM Brian Dickson <brian.peter.dickson@gmail.com> wrote: > > > On Tue, Oct 6, 2020 at 6:10 PM Ben Schwartz <bemasc@google.com> wrote: > >> On Tue, Oct 6, 2020 at 8:51 PM Brian Dickson < >> brian.peter.dickson@gmail.com> wrote: >> >>> >>> Other than the syntactic brevity, is there any functional difference to >>> the client between a TargetName of "." versus a TargetName of "$HOSTNAME" >>> in the description above? >>> >> >> Currently, "." means $HOSTNAME for the HTTPS record (when no prefixes are >> applied). With the proposed change, "." would always mean $HOSTNAME when a >> ServiceMode record is returned directly for the original query. However, >> if the ServiceMode record is reached via a CNAME or AliasMode record, then >> "." does not correspond to (the original) $HOSTNAME. >> > > This presents two significant problems. > > First, this (what you write above) means that "." will not be guaranteed > 100% of the time to result in the "correct" value, if I understand > correctly. > I'm not sure what you mean by "correct". With or without this proposal, the expanded name for "." is well-defined. Second, the use of "." by whoever creates the ServiceMode record may not be > aware of how it is reached (e.g. by CNAME or AliasMode records not under > their control or that they are aware of or which may be added later). > The expanded name does not depend on how the record was reached. I'm merely trying to point out that, after an alias has been followed, any information about "$HOSTNAME" has been lost. ... > As you note below, "@" is available, and while perhaps not as elegant, is > handled in the authority server's loading of zone files, and never results > in dynamic processing or additional handling requirements. I.e. it achieves > maybe 90% of the intended "happy" result, but does so with 100% > interoperability after the zone itself is constructed and loaded. > My impression is that "@" is always, or nearly always, a zone apex. I expect that the majority of HTTPS and SVCB records will not be for the zone apex. Setting a ServiceMode TargetName of @ would instruct those records to use the A/AAAA records for the apex name. This strikes me as an unlikely configuration. > >> >> First, is the use of the standard zone file construct of "@", which only >>> exists within the zone master file, and gets substituted on import with >>> whatever $ORIGIN is. >>> >> >> Yes, the syntax already supports "@" and relative names when writing out >> a TargetName in the zone file. This is useful, but I don't think it has >> the effect of guiding users toward a good configuration. >> > > Brian >
- [DNSOP] SVCB and the specialness of _ Ben Schwartz
- Re: [DNSOP] SVCB and the specialness of _ Brian Dickson
- Re: [DNSOP] SVCB and the specialness of _ Ben Schwartz
- Re: [DNSOP] SVCB and the specialness of _ Tommy Pauly
- Re: [DNSOP] SVCB and the specialness of _ Brian Dickson
- Re: [DNSOP] SVCB and the specialness of _ Ben Schwartz
- Re: [DNSOP] SVCB and the specialness of _ Tommy Pauly