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Date: Sat, 4 Apr 2015 13:49:28 +0200
From: Pablo Neira Ayuso <pablo@...filter.org>
To: David Miller <davem@...emloft.net>
Cc: netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
hannes@...essinduktion.org, jiri@...nulli.us
Subject: Re: [PATCH 0/9] netfilter: Compress hook function signatures.
On Fri, Apr 03, 2015 at 10:07:34PM -0400, David Miller wrote:
>
> Currently netfilter hooks have a function signature that is huge and
> has many arguments. This propagates from the hook entry points down
> into the individual hook implementations themselves.
>
> This means that if, for example, we want to change the type of one of
> these arguments then we have to touch hundreds of locations.
>
> The main initial motivation behind this is that we'd like to change
> the signature of "okfn" so that a socket pointer can be passed in (and
> reference counted properly) for the sake of using the proper socket
> context in the case of tunnels whilst not releasing the top level user
> socket from skb->sk (and thus releasing it's socket memory quota
> usage) in order to accomodate this.
>
> This also makes it clear who actually uses 'okfn', nf_queue(). It is
> absolutely critical to make this obvious because any user of 'okfn'
> down in these hook chains have the be strictly audited for
> escapability. Specifically, escapability of references to objects
> outside of the packet processing path. And that's exactly what
> nf_queue() does via it's packet reinjection framework.
>
> In fact this points out a bug in Jiri's original attempt to push the
> socket pointer down through netfilter's okfn. It didn't grab and drop
> a reference to the socket in net/netfilter/nf_queue.c as needed.
>
> Furthermore, so many code paths are simplified, and should in fact be
> more efficient because we aren't passing in arguments that often are
> simply not used by the netfilter hook at all.
>
> Further simplifications are probably possible, but this series takes
> care of the main cases.
>
> Unfortunately I couldn't convert ebt_do_table() because ebtables is
> complete and utter crap and uses ebt_do_table() outside of the hook
> call chains. But that should not be news to anyone.
>
> Signed-off-by: David S. Miller <davem@...emloft.net>
Nice series. If you route them through net-next, please add:
Acked-by: Pablo Neira Ayuso <pablo@...filter.org>
or I can place them in nf-next, your call.
Regarding Jiri's okfn() signature changes, please let me know on those
patches, they will simplify a patchset I'll submit soon. And count on
me to help on that change too, of course.
Thanks a lot David!
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