[Dibbler] dibbler-client and pd

Jyrki Soini Jyrki.Soini at iki.fi
Fri Mar 29 22:22:55 CET 2013


> 2. Someone told me that for the stateless autoconf to work, exactly /64
> prefix is needed and for larger (/63 or less) prefixes some devices
> won't work. If that is the case, there probably should be a switch in
> dibbler-client to force the client to split prefixes exactly to /64. For
> example, if client receives a /48 prefix and has 2 interfaces, it would
> use only two /64 prefixes. This is potentially very wasteful approach,
> so it should not be the default. Let me know if you're interested in
> this. I can help with adding extra directive to the parser.

Wouldn't it be better to have /64 for each interface as a default?
That would maintain easy addition of new interfaces/vllans in case
the router configuration changes later. If the prefix is allocated in
the beginning to (nearly) same size parts, additional interfaces/vlans
would require change of other prefixes as well.

Unused parts of the prefix may be routed to bit bucket. i-e. packets
to them discarded.
--
Jyrki


On Fri, Mar 29, 2013 at 11:29 AM, Tomasz Mrugalski <thomson at klub.com.pl>wrote:

> On 27.03.2013 16:30, Jean-Jacques Sarton wrote:
> > Hello,
> >
> > Am 27.03.2013 13:13, schrieb Jean-Jacques Sarton:
> >> Hello,
> >>
> >> If I request a prefix delegation from my CPE I get a /62 prefix.
> >> I have foreseen 2 interfaces. If I look to the route assigned
> >> via dibbler-client I see that the first /64 is used for both
> >> interfaces:
> >> 2001:db8:dead:fc:800::/70  on if 1
> >> 2001:db8:dead:fc:1000::/70 on if 2
> This code could use some improvement. I chose the easy (or lazy if you
> prefer) way and thought that typically you'd get /56 or /48, so I just
> make the prefix longer by 8 bits. This is clearly not the way to go.
>
> >>
> >> It will be nice to have:
> >> 2001:db8:dead:fc::/64  on if 1
> >> 2001:db8:dead:fd::/64  on if 2
> >> or
> >> 2001:db8:dead:fc::/61  on if 1
> >> 2001:db8:dead:fd::/61  on if 2
> >>
> > Sorry I had mean /63
> >> Is it possible to arrange the client in order to get such results ?
> Not with the current code, but I'd be very interested in the code you're
> developing to remedy this issue. :-)
>
> > I have commenced to rearrange the file ClntIfaceMgr/ClntIfaceMgr.cpp
> > With my actual modification I will have the following:
> > if the number of subnets is >= the number of interfaces and the prefix
> > length is less than 64 the route for the concerned interface will be
> > set to /64, /63, ... according to number of possible subnets per
> > interfaces.
> >
> > If the preliminary condidions is not meet or only one interface is
> > stated the routing will be set as this what is done actually.
> >
> > Example the client.conf file contain downlink-prefix-ifaces eth1 eth2
> > and the delegated prefix is 2001:db8:cafe:fc::/62
> > We will set the route to 2001:db8:cafe:fc::/63 for eth1 and
> > 2001:db8:cafe:fe::/63 for eth2.
> > If We want 3 subnets for eth1 and one for eth2 we can put
> > downlink-prefix-ifaces eth1, eth1, eth1, eth0
> > to the client.conf file.
> >
> > If we have 3 interface defined (eth1, eth2 and eth1) we will
> > see one /64 subnet for each interface, the last subnet will
> > not be subject to a route.
> >
> > Any kind of interess for this ?
> Sure. Do you want to develop this code? I think this should more or less
> look like following:
>
> 1. find out how many interfaces are in need of a prefix
> 2. calculate how many bits are needed to cover them
> 3. calculate prefix for each interface
>
> There are 2 extra things in this areas that may be improved as well:
>
> 1. downlink-prefix-ifaces command does not handle vlans (see bug #265).
> This may be tricky to fix, because it is possible that the whole dibbler
> framework do not support vlans. This may require hacking some low level
> C code around Port-linux/lowlevel-linux.c in if_list_get().
>
> 2. Someone told me that for the stateless autoconf to work, exactly /64
> prefix is needed and for larger (/63 or less) prefixes some devices
> won't work. If that is the case, there probably should be a switch in
> dibbler-client to force the client to split prefixes exactly to /64. For
> example, if client receives a /48 prefix and has 2 interfaces, it would
> use only two /64 prefixes. This is potentially very wasteful approach,
> so it should not be the default. Let me know if you're interested in
> this. I can help with adding extra directive to the parser.
>
> Cheers,
> Tomek
>
>
> _______________________________________________
> http://klub.com.pl/cgi-bin/mailman/listinfo/dibbler
>
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