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Re: #327: Expect syntax

From: Julian Reschke <julian.reschke@gmx.de>
Date: Sat, 17 Dec 2011 22:12:05 +0100
Message-ID: <4EED05A5.7080603@gmx.de>
To: Willy Tarreau <w@1wt.eu>
CC: Alex Rousskov <rousskov@measurement-factory.com>, HTTP Working Group <ietf-http-wg@w3.org>
On 2011-12-17 08:40, Willy Tarreau wrote:
> Hi Julian,
>
> On Sat, Dec 17, 2011 at 01:02:21AM +0100, Julian Reschke wrote:
>> Will those servers process
>>
>>    ,100-continue
>>
>> or
>>
>>    100-continue,
>>
>> ? These were valid before already.
>
> Speaking for haproxy, the second one will work, because it splits header
> values on the commas and trims the spaces. So the first above will be
> considered as an empty expectation followed by a 100-continue (but haproxy
> only considers the first Expect value) and the second one is OK.
>
> Haproxy's processing of Expect is incomplete and almost unused, so it
> should not be seen as a reference implementation at all (!). However
> the semi-colon after 100-continue was not supposed to happen in 2616,
> which is why I think other implementations might get trapped.

That is true, but it *is* an edge case.

The alternative is to make the grammar different from Prefer:; or to 
change Prefer: as well.

In practice, most parsers that understand ";" separated parameters allow 
"empty" parameters (see, for instance, my Content-Disposition test 
cases). We can pretend this is wrong, or we can try to bring a bit more 
sanity to this.

In any case, the fact that existing implementations might trip over 
something that (for Expect!) will only happen in test cases doesn't seem 
to be a big problem to me.

Best regards, Julian
Received on Saturday, 17 December 2011 21:13:21 GMT

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