Re: Tacking stuff on to VN packets

David Schinazi <dschinazi.ietf@gmail.com> Tue, 11 May 2021 17:18 UTC

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From: David Schinazi <dschinazi.ietf@gmail.com>
Date: Tue, 11 May 2021 10:18:21 -0700
Message-ID: <CAPDSy+7DmR+fUi0K6vVGLW4N09TaBy6CQaJBrAD5==KuSBJ3eA@mail.gmail.com>
Subject: Re: Tacking stuff on to VN packets
To: Martin Duke <martin.h.duke@gmail.com>
Cc: IETF QUIC WG <quic@ietf.org>
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Unfortunately that won't work. Supporting multiple versions of QUIC does
not require supporting any document, apart from the QUIC invariants. And
the invariants don't reserve space for a trailer after the Supported
Versions field. What problem are you trying to solve with this trailer? I
suspect there are easier ways of solving it.

David

On Tue, May 11, 2021 at 10:11 AM Martin Duke <martin.h.duke@gmail.com>
wrote:

> Section 6 of invariants
> <https://quicwg.org/base-drafts/rfc8999.html#name-version-negotiation>
> sayeth:
>
> "Version Negotiation packets do not use integrity or confidentiality
> protection. Specific QUIC versions might include protocol elements that
> allow endpoints to detect modification or corruption in the set of
> supported versions."
>
> I also vaguely remember ekr batting around the idea of tacking some data
> onto the packet  to solve a problem we were discussing.
>
> *Maybe we just don't want to do this at all and we can safely ignore this
> text in invariants.*
>
> If we *do* want to do it, the design is a little problematic. There is no
> length field in VN packets to signal that the supported version list is
> ending and other stuff is beginning.
>
> The only way I can think of to make this work is to use the VN draft to
> reserve a magic version number to mean "this is the end of the supported
> version list". That version is not a real version, MUST be the last one
> listed, and perhaps can be followed by another magic number to indicate the
> content that follows.
>
> Leaving aside legacy stuff negotiating pre-standard versions, which will
> hopefully go away someday, someone supporting multiple versions would be
> REQUIRED to support the VN draft and therefore incorporate this change.
>
> Thoughts?
> Martin
>
>
>