Re: [BUG] Enforcing IPv6 forwarding in radvd startup script breaks some use cases

[Emmanuel Thierry <ml@sekil.fr>]

Hello,

Le 8 mars 2013 à 03:36, YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org> a écrit :

> Emmanuel Thierry wrote:
> 
>> The RFC is consistent with this behaviour. It states that a node may send Router Advertisements while having its forwarding capabilities disabled, as soon as it sets the Router Lifetime field (AdvDefaultLifetime) to zero.
>> RFC 4861 section 6.2.5:
>>>   Note that system management may disable a router's IP forwarding
>>>   capability (i.e., changing the system from being a router to being a
>>>   host), a step that does not necessarily imply that the router's
>>>   interfaces stop being advertising interfaces.  In such cases,
>>>   subsequent Router Advertisements MUST set the Router Lifetime field
>>>   to zero.
>> 
>> 
>> As a conclusion, i kindly ask you to consider relaxing the constraint of having net.ipv6.conf.all.forwarding enabled. It breaks some use cases were disabling forwarding is intended and legal.
> 
> Maybe 6.2.3:
>   A router might want to send Router Advertisements without advertising
>   itself as a default router.  For instance, a router might advertise
>   prefixes for stateless address autoconfiguration while not wishing to
>   forward packets.  Such a router sets the Router Lifetime field in
>   outgoing advertisements to zero.
> 
> I think it is better to send feedback to radvd upstream.
> 
> --yoshfuji

I don't think radvd itself is in fault.
If you bypass the Debian init.d script constraint and you launch radvd without ipv6 forwarding, it works as expected. Radvd just complains in syslog that forwarding is disabled but i consider it acceptable. Radvd itself doesn't enforces ipv6 forwarding, but the init.d script provided by debian does.

Regards.
Emmanuel Thierry