On June 28, 2026 2:23:39 PM GMT+01:00, Roy Marples <[email protected]>
wrote:
>From: Samuel Thibault <[email protected]>
>To: "Joan Lledó"<[email protected]>
>Cc: <[email protected]>, <[email protected]>, <[email protected]>, 
>"Joan Lledó"<[email protected]>
>Date: Sat, 27 Jun 2026 23:15:01 +0100
>Subject: Re: [PATCH 2/4] lwip: clean up IPv6 address handling in init_ifs and 
>inquire_device
> >  
> > >     - and set prefix_len based on whether the 
> > >       address is static (64) or autoconf (128) instead of always 64. 
> >  
> > ? 
> >  
> > Even autoconf addresses usually do have a non-128 prefix len, to be
> > able 
> > to reach neighbours. 
>
>I agree with Samuel. Please don't do this.
>
>Router Advertisements advertise a Prefix from which an address *may* be
>derived based on length (64) and flags (make an autoconf address).
>
>DHCPv6 addresses are always /128 because they are not directly tied to a
>Prefix.
>
>It is impossible to infer a Prefix Length from any address.
>
>Roy
>
>
>

Agreed, it's definitely not a great idea to infer one.

Thanks!

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