Re: about violation of standards

Le 22/04/2019 à 18:37, Yucel Guven a écrit :
[...]
> On Thu, Apr 18, 2019 at 11:03 PM 神明達哉 <jinmei@wide.ad.jp 
> <mailto:jinmei@wide.ad.jp>> wrote:
> 
> On Thu, Apr 18, 2019 at 11:59 AM Alexandre Petrescu 
> <alexandre.petrescu@gmail.com <mailto:alexandre.petrescu@gmail.com>> 
> wrote:
> 
>> In private conversation this debate happened:
[...]
Tauya said:
> Regarding Linux, I'd note that link-local addresses are
> automatically generated by the system, and the generated address
> conforms to the format specified in Section 2.5.6 of RFC4291.

YEs, RFC4291.  As a side not they are not privacy addresses, probably
risking to be discarded in conversation.

> More specifically, its intermediate 54 bits are all set to 0.

YEs.

> Plus, as far as I know, the vast majority of people never bother to 
> change the auto-generated link-local addresses.

Do these people ping on CLIs w/o mice? (use ping command on a Command
Line Interface without having access to mouse top copy paste long IIDs;
like in a car, or in some position where kbd is available but not the
mouse).

> In that sense the use of addresses like "fe80:1::2" are not really
> widely used,

Agreed.  It is a matter of saying what is widely used and what not.

Probably only a few people type ifconfig fe80:1::1.  But I think I have 
heard some people on the mailist list doing so, and in private too. 
True, it was based on my request.

In my setting, it would be advantageous to do it.

BTW, I do not think anybody on linux uses fe80::1 on lo, right?

> even if the implementation that allows its users to
> manually configure such addresses is widely used.

YEs, that is how to say it: the implementation that allows its users to 
manually configure such addresses is widely used.

I would like to add something else: the implementation that does _not_ 
allow the users to add fe80:1::1 (BSD) does not complain about it.  It 
silently refuses.

> Almost any implementation has some weapon that allows its user to 
> shoot their feet, often violating protocol standards.  An extreme 
> case is a tool like bpf, with which you can send out almost any 
> broken packets to the wire. 

:-)

> BPF is widely used tools, but as far as
>  I know no one uses the existence of that tool to justify the 
> violation of the standard.
> 
> Now, I'm open to the discussion of possibly updating RFC4291 to
> allow non-0 value in the intermediate 54-bit field, starting from the
> fact that it currently violates the standard.  But I don't buy an
> argument that a behavior against the current standard is not a
> violation simply because there's a system utility of a widely used OS
> that allows that particular behavior.

I understand.

Alex

> 
> -- JINMEI, Tatuya 
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