Re: bug #1 in draft-ietf-sip-outbound-16 grammar

Hi Florian,

I think the intent of RFC3261 should have been to allow optional  
whitespace at the end of a quoted-string:

Currently in RFC 3261:
quoted-string = SWS DQUOTE *(qdtext / quoted-pair ) DQUOTE

Probably should have been in RFC 3261:
quoted-string = LDQUOT *(qdtext / quoted-pair ) RDQUOT

However, that is water under the bridge, so I have no objection  
changing the c-p-instance production to look like this:

c-p-instance = "+sip.instance" EQUAL DQUOTE "<" instance-val ">" DQUOTE

If you are responsible for an implementation however, I urge you to be  
generous in what you receive in this regard. Please ignore extraneous  
whitespace unless the spec gives it some special semantic meaning (ex:  
inside a quoted string).

thanks,
-rohan



On Apr 13, 2009, at 1:50 PM, Florian Zumbiehl wrote:
> Hi,
>
> in case you've read my bug report concerning draft-ietf-sip-gruu-15
> from this morning, the short version: draft-ietf-sip-outbound-16 is
> affected by the same problem.
>
> The complete version:
>
> draft-ietf-sip-outbound-16 contains (amongst others) these ABNF rules:
>
> | contact-params =/ c-p-reg / c-p-instance
> | c-p-instance   =  "+sip.instance" EQUAL
> |                   LDQUOT "<" instance-val ">" RDQUOT
>
> which, when adding them to the grammar from RFC 3261, would produce
> from <Contact> a language that's a superset of the language that would
> be produced by <Contact> from RFC 3261-only.
>
> In particular, the language produced by <foo> is a subset of the
> "outbound extended" language, but not of the RFC 3261-only one:
>
> | foo = "m: <sip:[email protected]>;+sip.instance=" DQUOTE "x" DQUOTE SP CRLF
>
> To put it in more practical terms: the <RDQUOT> in <c-p-instance>
> allows for trailing <LWS>, which <contact-extension> does not,
> so an implementation conforming to draft-ietf-sip-outbound-16 could
> produce a Contact header that potentially could not be parsable
> (except as an <extension-header>) by an implementation conforming
> to RFC 3261.
>
> Thus, I would suggest to replace the rules quoted above by:
>
> | contact-params =/ c-p-reg / c-p-instance
> | c-p-instance   =  "+sip.instance" EQUAL
> |                   LDQUOT "<" instance-val ">" DQUOTE
>
> This produces the same language, maybe it's a more consistent
> replacement:
>
> | contact-params =/ c-p-reg / c-p-instance
> | c-p-instance   =  "+sip.instance" EQUAL
> |                   DQUOTE "<" instance-val ">" DQUOTE
>
> Florian

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