netdev - Re: [PATCH net-next] ipv6: Export nd_tbl to allow modules to support IPv6

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Date:	Thu, 06 Sep 2012 13:47:38 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	tgraf@...g.ch
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next] ipv6: Export nd_tbl to allow modules to
 support IPv6

From: Thomas Graf <tgraf@...g.ch>
Date: Thu, 6 Sep 2012 04:51:02 -0400

> On Wed, Sep 05, 2012 at 01:06:36PM -0400, David Miller wrote:
>> So if one of our goals is to move towards a situation where all neigh
>> accesses are refcount'less, having those external users makes that
>> nearly impossible.
>> 
>> Instead, I'd rather see patches that mark arp_tbl as being exported
>> only for internal usage inside of the tree, so that we can reach that
>> goal.
>> 
>> I'm not applying this, sorry.
> 
> Fair enough
> 
> Does that mean you dismiss neighbour lookups by external users in
> general in order to get rid of the refcnt?
> 
> Assuming that lookups would still be ok, would an ipv6 version of
> __ipv4_neigh_lookup() be an acceptable API for external users?
> (Yes there is __ipv6_neigh_lookup() already but unlike the ipv4 version
> it takes the table as first argument)

Right now we're in a transition period where ipv4 is mostly refcount'less
and ipv6 is not.

This is part of the reason I don't want to expose these things, the
calling convention and locking requirements are going to be fluid for
any interface you might propose.

arp_tbl was exported only for in-tree users, and I therefore say that
we should only export nd_tbl for in-tree users as well, since that's
the only way we can audit and update all the referencing callers as
the semantics radically change.


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