[Dibbler] Question concerning preferred and valid lifetime

Tomasz Mrugalski thomson at klub.com.pl
Fri Mar 18 16:53:01 CET 2005


On Fri, 18 Mar 2005 somebody known as Harald Schwier wrote:

> Hallo,
> hmmm... seams that there is a Problem concerning
> preferred and valid lifetime. After the DHCPv6 Client has requested an IA,
> the DHCPv6 Server sends an IA-Address with:
> preferred lifetime: 1800s
> valid lifetime :      3600s
>
> Everthing works fine, but i am a little astonished that the Client
> shows an invalid lifetime
>
> 2: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
>    inet6 fda5:b08e:dbb0:1::ca/128 scope global
>       valid_lft forever preferred_lft forever
>
> RFC3315 says on page 77  "the client MUST use the values in the preferred and valid
>   lifetime fields for the preferred and valid lifetimes."
>
> Is this a Problem with dibbler (Cool name) or have i misunderstod something?
Yeah, it's a bug, but you have sent this bug report to the wrong project. 
Contact Linus Torvalds :)
Seriously, there is currently no way to add dynamic address with finite 
lifetimes in linux kernels. Address aging mechanism is implemented in 
linux kernel, but there is no API to take advantage of it. Interesting 
note: when host recevied Router Advertisement, address with decreasing 
preferred/valid lifetime is added to the interface.

I have checked it serveral months ago, and I'm trying to look at changelog 
each time new kernel is released, but there seems nothing new in this 
matter. I'm not very experienced with low level kernel programming, so I 
can't fix this myself... yet. Of course, there's possibility that I'm 
wrong and this thing can be done. If that is so, I'd like to take a look 
and some code which adds a dynamic IPv6 address.

Take note that Dibbler should remove address it valid lifetime has 
expired. Think of it as a userspace workaround for bug in kernelspace.

-- 
Tomasz Mrugalski,              | " Talk is cheap. Show me the code."  |
thomson(at)klub(dot)com(dot)pl |                     Linus Torvalds   |



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