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Re: draft-ietf-httpbis-header-structure: handling multiple field values

Ian Clelland <iclelland@google.com> Tue, 12 May 2020 17:41 UTC

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From: Ian Clelland <iclelland@google.com>
Date: Tue, 12 May 2020 13:39:18 -0400
Message-ID: <CAK_TSXJ3o7F9x63MSYyEhr7de0vO1Yu2s8JnjkhT7n4BQiQp+A@mail.gmail.com>
To: Willy Tarreau <w@1wt.eu>
Cc: Julian Reschke <julian.reschke@gmx.de>, HTTP Working Group <ietf-http-wg@w3.org>
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Subject: Re: draft-ietf-httpbis-header-structure: handling multiple field values
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This is mentioned in
https://httpwg.org/http-extensions/draft-ietf-httpbis-header-structure.html#rfc.section.4.2
--
"parsers MUST combine all lines in the same section (header or trailer)
that case-insensitively match the field name into one comma-separated
field-value", (with the warning given that strings split across multiple
field values will have "unpredictable results") -- So I don't think you're
allowed to parse them separately. If both exist in the same message, they
must be combined before parsing.

On Tue, May 12, 2020 at 1:27 PM Willy Tarreau <w@1wt.eu> wrote:

> Hi Julian,
>
> On Tue, May 12, 2020 at 06:53:40PM +0200, Julian Reschke wrote:
> > Hi there,
> >
> > while working on an implementation I encountered the following question.
> >
> > Consider something defined as "sh-list". If a value is received spread
> > over multiple field instances, recipients *can* recombine the value
> > before processing. So for
> >
> >   Foo: "1
> >   Foo: 2"
> >
> > ...the parser would see the string "1,2" (or maybe "1, 2").
> >
> > What's not totally clear to me is whether recipients are *allowed* to
> > process the field values separately, in which case parsing would fail.
>
> Note that they might not be aware that these were two values
> because the folding might have been performed by an upstream
> gateway.
>
> Regards,
> Willy
>
>

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