[OASIS Issue Tracker] (MQTT-216) Explore the downgrade of MUST level requirements to check UTF-8 encodings

[OASIS Issues Tracker <workgroup_mailer@lists.oasis-open.org>]

    [ https://issues.oasis-open.org/browse/MQTT-216?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=59142#comment-59142 ] 

Richard Coppen commented on MQTT-216:
-------------------------------------

Comment added on behalf of David Kemper:

Given the bit-pattern rules of UTF-8, it’s easy to test for ASCII characters in the stream. You could, for example, scan for the separator and wildcards and make early matching decisions. While testing shows you can perform validation quickly, it’s even faster not to.


We were interested in more leeway to support targeted use cases where each nanosecond is important. However, if more complete UTF-8 scanning is a requirement, so be it.


> Explore the downgrade of MUST level requirements to check UTF-8 encodings
> -------------------------------------------------------------------------
>
>                 Key: MQTT-216
>                 URL: https://issues.oasis-open.org/browse/MQTT-216
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: Improvement
>          Components: futures
>    Affects Versions: 3.1.1
>            Reporter: Richard Coppen
>
> Following on from David Kemper's mqtt-comment on CSPRD02 the TC agreed to open this Jira to explore the relaxing of the MUST level requirements surround UTF-8 checking 
> Servers are required to scan the UTF-8 content of all strings in all packets. Since the strings themselves are bounded by a length prefix, is it possible that the following MUST level clauses could downgraded to SHOULD / SHOULD NOT to promote lower-latency solutions?
> [MQTT-1.5.3-1] The character data in a UTF-8 encoded string MUST be well-formed UTF-8 as defined by the Unicode specification [Unicode] and restated in RFC 3629[RFC3629]. In particular this data MUST NOT include encodings of code points between U+D800 and U+DFFF. If a Server or Client receives a Control Packet containing ill-formed UTF-8 it MUST close the Network Connection.
> [MQTT-1.5.3-2] A UTF-8 encoded string MUST NOT include an encoding of the null character U+0000. If a receiver (Server or Client) receives a Control Packet containing U+0000 it MUST close the Network Connection.



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