Removing RFC Editor <[email protected]>
See in-line.
On 18 Jan 2017, at 14:55, Martin Bjorklund <[email protected]> wrote:
RFC Errata System <[email protected]> wrote:
The following errata report has been submitted for RFC6020,
"YANG - A Data Modeling Language for the Network Configuration
Protocol (NETCONF)".
--------------------------------------
You may review the report below and at:
http://www.rfc-editor.org/errata_search.php?rfc=6020&eid=4911
--------------------------------------
Type: Technical
Reported by: Ladislav Lhotka <[email protected]>
Section: 6.1.3
Original Text
-------------
Within a double-quoted string (enclosed within " "), a backslash
character introduces a special character, which depends on the
character that immediately follows the backslash:
\n new line
\t a tab character
\" a double quote
\ a single backslash
Corrected Text
--------------
Within a double-quoted string (enclosed within " "), a backslash
character introduces a special character, which depends on the
character that immediately follows the backslash:
\n new line
\t a tab character
\" a double quote
\ a single backslash
The backslash MUST NOT be followed by any other character.
Notes
-----
The text doesn't state whether other characters may follow the
backslash, and if yes, what it means. Existing implementations have
used three approaches:
1. report an error if another character follows the backslash
2. keep only the character following the backslash, i.e., for example,
"\x" is the same as "x".
3. keep both the backslash and the character following it.
This ambiguity is undesirable and YANG 1.1 [RFC 7950] explicitly
adopted option #1. However, many modules are still being written using
YANG version 1.0, so it is important to clarify this issue in RFC 6020
as well.
I don't think this errata should be accepted. As stated, the spec is
unclear, and YANG 1.1 has fixed this problem. But it is not clear
that the original intention when RFC 6020 was written was #1.
Accepting this errata now would make existing implementations and
modules invalid.
The problem is that the spec is clearly ambiguous and it is impossible to
decide whether such a module is valid or not and, if it is, what the other
backslash-escaped characters mean. Existing implementations can already reject
such modules - the fact that pyang (and probably other tail-f tools) adopted
one interpretation doesn't mean that everybody does the same.
The solution moving forward is to use YANG 1.1.
YANG 1.0 modules continue to be written, and I think it is important to stop
this problem from spreading further. I think tools should at least issue a
warning because otherwise future upgrades to YANG 1.1 may become a nightmare -
modules will suddenly break in unexpected places.
Now two good news.
First, pyang now includes a warning for YANG 1.0 modules:
$ pyang [email protected]
[email protected]:259: warning: the escape sequence
"\S" is unsafe in double quoted strings - pass the flag
--lax-quote-checks to avoid this warning
Thanks Martin for the speedy update. Note that this error message it was
already present for YANG 1.1, as this is covered by RFC 7950.
Second, I ran all my scripts with the new pyang version, and no IETF
YANG 1.0 modules face that issue
(http://www.claise.be/IETFYANGPageCompilation.html)
However, we observed that some proprietary YANG 1.0 modules face this
issue.
If this erratum is rejected, what is the basis for accepting erratum #4909 that
started this discussion?
Exact same question on my side.
Regards, Benoit
Lada
/martin
--
Ladislav Lhotka, CZ.NIC Labs
PGP Key ID: 0xB8F92B08A9F76C67
.
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