A question about "WARNING: attempt to domain_add(xyz) after domainfinalize()"

[Julian Elischer]

On 1/12/11 5:26 AM, Svatopluk Kraus wrote:
> Hi,
>
> I'd like to add a new network domain into kernel (and never remove it)
> from loadable module. In fact, I did it, but I got following warning
> from domain_add(): "WARNING: attempt to domain_add(xyz) after
> domainfinalize()". Now, I try to figure out what is behind the
> warning, which seems to become KASSERT (now, in notyet section part of
> code, which is 6 years old).
>

just ignore that message, everyone else does :-)

teh problem is that the idea of domainfinalize() is incompatible with 
having the ability
to add domains from modules.
Luckily domain finalize doesn't actually do anything that stops your 
new domain
from working so it doesn't matter.

you'll get the same message if you add netgraph.ko as an object.


> I found a few iteration on domains list and each domain protosw table,
> which are not protected by any lock. OK, it is problem but when I only
> add a domain (it's added at the head of domains list) and never remove
> it then that could be safe. Moreover, it seems that without any
> limits, it is possible to add a new protocol into domain on reserved
> place labeled as PROTO_SPACER by pf_proto_register() function. Well,
> it's not a list so it's a different case (but a copy into spacer isn't
> atomic operation).
>
> I found two global variables (max_hdr,max_datalen) which are evaluated
> in each domain_init() from other variables (max_linkhdr,max_protohdr)
> and a global variable (max_keylen) which is evaluated from all known
> domains (dom_maxrtkey entry). The variables are used in other parts of
> kernel. Futher, I know about 'dom_ifattach' and 'dom_ifdetach'
> pointers to functions defined on each domain, which are responsible
> for 'if_afdata' entry on ifnet structure.
>
> Is there something more I didn't find in current kernel?
> Will be there something more in future kernels, what legitimize
> KASSERT in domain_add()?
>
> My network domain doesn't influence any mentioned global variables,
> doesn't define dom_ifattach() and dom_ifdetach() functions, and should
> be only added from loadable module and never removed. So, I think it's
> safe. But I'm a little bit nervous because of planned KASSERT in
> domain_add().
>
> Well, I can implement an empty domain with some spacers for protocols,
> link it into kernel (thus shut down the warning), and make loadable
> module in which I only register protocols I want on already added
> domain, but why should I do it in that (for me good-for-nothing) way?
>
>   Thanks for any response, Svata
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