Re: [v6ops] Scope of Unique Local IPv6 Unicast Addresses (Fwd: New Version Notification for draft-gont-6man-ipv6-ula-scope-00.txt)

[Brian E Carpenter <[e-mail]>]

On 14-Feb-21 09:33, Fernando Gont wrote:
> Hi, Brian,
> 
> On 13/2/21 17:18, Brian E Carpenter wrote:
> [....]
>>> ---- cut here ----
>>> 5.1.  Address Attributes in Programming Languages
>>>
>>>      Python's ipaddress library [Python-ipaddr] defines 'IPv6Address'
>>>      objects that have a number of attributes, including:
>>>
>>>      o  'True' if the address is allocated for private networks.
>>>
>>>      o  'True' if the address is allocated for public networks.
>>>
>>>      For ULAs, the is_private attribute is 'True', while the is_global
>>>      attribute is 'False'.  This contradicts the definition of ULAs as
>>>      having "global scope" [RFC4291] [RFC4193], but is in line with the
>>>      specification update performed by this document (see Section 6).
>>> ---- cut here ----
>>>
>>> (this one is documented in our draft, but credit goes to Brian for
>>> spotting it).
>>
>> The fact is that I spotted it due to an issue with running code.
>> Just for fun, here is the test for ULAness according to the Python
>> ipaddress module's semantics:
>>
>> def is_ula(a):
>>      """Test for ULA"""
>>      return (a.is_private and not a.is_link_local
>>               and not a.is_loopback
>>               and not a.is_unspecified)
> 
> IIRC, I don't remember seeing a "is_ula" attribute. -- will recheck.

No, there isn't. But I needed it in my code, so I wrote the function.
(It was a bit purist to write it that way rather than using the fc00::/7 mask)

   Brian

> 
> 
> 
>>> Are the is_private and is_global attributes employed by such library
>>> correct? Do they match our specs? Do they match the obvious
>>> interpretation of such attributes?  Should they be changed? Why, or why not?
>>
>> A bit off topic, but I think the .is_private attribute is a very poor
>> choice, because it might be misunderstood as implying privacy properties.
> 
> I believe the name attribute is borrowed from the IPv4 world (i.e., 
> RFC1918).
> 
> Thanks,
>