Re: Ambiguity on HTTP/3 HEADERS and QUIC STREAM FIN requirement

Willy Tarreau <w@1wt.eu> Fri, 17 June 2022 17:50 UTC

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Date: Fri, 17 Jun 2022 19:49:51 +0200
From: Willy Tarreau <w@1wt.eu>
To: Lucas Pardue <lucaspardue.24.7@gmail.com>
Cc: David Schinazi <dschinazi.ietf@gmail.com>, Martin Thomson <mt@lowentropy.net>, HTTP Working Group <ietf-http-wg@w3.org>
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Subject: Re: Ambiguity on HTTP/3 HEADERS and QUIC STREAM FIN requirement
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On Fri, Jun 17, 2022 at 06:41:56PM +0100, Lucas Pardue wrote:
> On Fri, 17 Jun 2022, 18:31 David Schinazi, <dschinazi.ietf@gmail.com> wrote:
> 
> > Since it's Friday and we're exploring crazy thoughts, instead of
> > ":no-content" why not simply content-length=0?
> > David
> >
> 
> My thinking is that for an H2-to-H2, H3-to-H3 gateway (or some variant),
> that  the content-length is optional and explicit declaration of chunked
> T-E cannot be relied upon to guess if there's content coming. So a
> pseudo-header fills the gap between ndicating an end to request after the
> current flight, without having to wait for ES or FIN. Pseudo-headers are
> also a property of the frame, so don't risk affecting the end-to-end
> message semantic.

For the long term a pseudo header is a nice evolution, but it will be
hard to get anyone to agree on it if it's not part of the spec. An
interoperability recommendation, however can easily be added as an
errata to the existing document in one paragraph and get the job done
without any difficult protocol element for those who don't control the
whole chain. It's even imaginable that some applications would explicitly
add C-L:0 above the H3 layer if they're aware of trouble in the H3 layer.

Willy