Re: appropriate length of fe80:: prefix and new IP-over-foo drafts

[Alexandre Petrescu <[e-mail]>]

Le 31/01/2019 à 18:43, 神明達哉 a écrit :
> At Thu, 31 Jan 2019 14:00:04 +0100,
> Alexandre Petrescu <[e-mail] 
> <mailto:[e-mail]>> wrote:
> 
>  > >> Ah?  according to which spec do the BSD implementers put bits in the
>  > >> range 16-64?
>  > >
>  > > They don't send those bits on the wire. But they do use those bits as
>  > > described. -- According to no spec. If the link-local prefix is assumed
>  > > to be /64, then you're free to use those bits *internally* as you wish.
>  > > That's what BSDs do. Jinmei is quite likely in a better position ot
>  > > comment on this.
>  >
>  > I would like to kindly ask Jinmei to make sure to keep that internal
>  > such that to not forbid the end user to ifconfig add fe80:1::1/63
> 
> I don't think it's up to me anymore, but just to explain the current
> state of art:
> - an end user of a BSD box can't use fe80:1::1 as a "link-local" address
> - BSD hosts generally drop incoming packets whose source or
>    destination address matches fe80::/10 and contains a non-0 value in
>    bits 15-31 (like fe80:1::1)
> 
> Basically it doesn't allow an IPv6 address that matches fe80::/10
> unless it conforms to following format specified in RFC4291:
> 
> 2.5.6.  Link-Local IPv6 Unicast Addresses
> 
>     Link-Local addresses are for use on a single link.  Link-Local
>     addresses have the following format:
> 
>     |   10     |
>     |  bits    |         54 bits         |          64 bits           |
>     +----------+-------------------------+----------------------------+
>     |1111111010|           0             |       interface ID         |
>     +----------+-------------------------+----------------------------+
> 
> The BSD implementation conforms to the RFC.  If someone wants to
> violate the standard, they can freely do so, but they cannot assume
> it's interoperable with other standard-compliant implementations.
> That's a consequence of violating the standard.
> 
> I previously stated I was already done with this discussion, so I'll
> stop here.  Anyone can freely hate this specification, but if it's not
> even about an attempt of updating that specification (which is my
> understanding of the previous cycle of this discussion), I don't think
> it's a productive way of using my time to participate in it.

jinmei,

Thank you very much for the clarification.  I appreciate it.  Now I 
understand very much of our earlier discussions.

This situation is extremely worth considering.

In linux I must use fe80:1::1.  In BSD I cant.

Let us see how we can see further beyond the blocking situation.

Alex
> 
> --
> jinmei