dhcpcd-discuss

Roy,

thank you very much for your clear and concise answer! That helps me 
alot, since I don't need to worry about handling SLAs as 
integers/offsets, but instead know that I simply need to tack on the 
SLA/subnet bits. That makes things easier for me.

Best regards,
Harald


Am 30.05.2017 um 22:09 schrieb Roy Marples:
> Hi
>
>
> On 30/05/17 21:01, Harald Albrecht wrote:
> > Hi,
> >
> > anothwr discussion here reminded me of a question I alsways had in my 
> > mind about assigning prefixes from a delegated prefix block: is the 
> > "SLA" a bitfield that gets added to the delegated prefix or is it an 
> > integer that gets added to the prefix (base)?
>
> It's a bitmask. Code here:
> https://dev.marples.name/source/dhcpcd/browse/master/src/ipv6.c;f58a7db77fd3dfec7f0d5c3630ecf906f300e9c1$484 
>
> > For example, let's ask for a /63 prefix delegation, and the 
> > delegating router hands out 2001:db8:0:ff ... for whatever reason, 
> > that where it has space for two prefixes. Or is this already an 
> > invalid assumption, so delegating routers never allocate on 
> > "unaligned" boundaries?
>
> It's an invalid assumption, because anything beyond the prefix mask is 
> ours to play with as we choose.
>
> > Would then the second prefix 2001:db8:0:ff::PLUS 0:0:0:1:: or is this 
> > wrong, because the prefix block needs to be 2001:db8:0:fe:: OR 0:0:0:1?
>
> Because it's /63 you were really delegated 2001:db8:0:fe
>
> Hope this helps
>
> Roy