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Re: Is forwarding hop-by-hop headers a MUST-level violation?

From: Alex Rousskov <rousskov@measurement-factory.com>
Date: Mon, 12 Jul 2004 22:53:12 -0600 (MDT)
To: ietf-http-wg@w3.org
Message-ID: <Pine.BSF.4.58.0407122229300.10397@measurement-factory.com>

On Mon, 12 Jul 2004, David Morris wrote:

> If the proxy implementor can't read and understand the RFC notion of
> hop-hop headers,

RFC notion is defined by normative rules in the RFC. Please note that
current normative rules are incomplete and inconsistent.

> how can you have confidence they'll even look at the content header
> and use it to control filtering?

I am confident that most implementations will remain incompliant even
if we fix the spec (compliance is not driven by correct specs).
However, leaving the spec buggy, despite real implementors
questions/concerns, is bad for everybody involved (compliance with
incorrect specs is impossible or meaningless).

On Tue, 2004-07-13 at 07:32, David Morris wrote:

> There should be an exception for ALL headers declared in the
> specification. It is absurd to bloat the size of HTTP headers to
> declare information contained in the RFC.

I would agree 100% if we were talking about changing an Internet Draft.
Unfortunately, we are working in a context of an existing IETF
Standard that needs to be fixed. As developer questions and actual
implementations indicate the "information contained in the RFC [2616]"
is imprecise, inconsistent, or missing, depending on the hop-by-hop
header. Existing implementations may honestly forward some hop-by-hop
headers (while also honoring the Connection header logic). Thus, we
cannot simply reply on [hop-by-hop header] information contained in
the RFC".

If we add explicit hop-by-hop headers to Connection, the above
mentioned implementations will be automatically "fixed" when they
receive messages from newer HTTP agents. I suspect that chances of
breaking an old implementation by listing explicit hop-by-hop headers
are non-zero, but hope that they are negligible.

The proposed new wording does two things:

	1) documents the intent of the original wording in a normative
	and consistent way (proxies MUST NOT forward)

	2) attempts to increase the probability that old and new
	implementations will do the right thing (by listing all
	hop-by-hop headers in the Connection header)

I do not have strong feelings about (2). Adding a few bytes to a few
messages does not bother me much, but I am worried that, in some
corner cases, listing more headers in Connection might expose
currently undetected vulnerabilities in old products.

I did not hear any objections to (1). Can we declare consensus on that
part of the fix?

Thank you,

Received on Tuesday, 13 July 2004 01:02:44 UTC

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