From: Christophe Gouault <christophe.gouault@6wind•com>
To: netdev@vger•kernel.org
Subject: Re: IPsec: Why do pfkey_getspi and xfrm_alloc_userspi call xfrm_find_acq_byseq?
Date: Thu, 19 Aug 2010 14:55:21 +0200 [thread overview]
Message-ID: <4C6D29B9.5070403@6wind.com> (raw)
Dear netdev developers,
The call to xfrm_find_acq_byseq() by the pfkey_getspi() and
xfrm_alloc_userspi() functions is quite costly and proves to entail
scalability issues when performing thousands of IKE negotiations with
racoon (from ipsec-tools distribution) or charon (from strongswan
distribution).
Removing this call in the kernel drastically accelerates the processing
and does not seem to entail functional problems.
For now, I don't see the point of this call. I need to understand its
purpose, because I'm highly tempted to simply remove it.
Regards,
Christophe
> Dear netdev developers,
>
> I would like to understand why the pfkey_getspi and xfrm_alloc_userspi
> functions call xfrm_find_acq_byseq() and try to find an reuse an SA in
> state XFRM_STATE_ACQ with the same sequence number and destination
> address as the GETSPI request.
>
> As far as I understand, SAs in state XFRM_STATE_ACQ can only be created
> as a result of a user call to GETSPI or a kernel ACQUIRE message.
> - GETSPI is invoked by an application in order to create a temporary SA
> with a unique SPI, typically during an IKE negotiation, to create the
> inbound SA of the pair. No later GETSPI will be done on this SA.
> - An acquire message is triggered by the kernel and creates a temporary
> outbound SA whose SPI will be chosen by the remote IKE peer.
> No later GETSPI will be done on this SA.
>
> In which case can GETSPI find and reuse an SA that matches the message
> sequence number and destination address?
> A second lookup is done just after, with xfrm_find_acq (this function
> uses a hash table). Wouldn't this lookup find this SA too?
>
> The call to xfrm_find_acq_byseq is quite costly (the whole SAD is looked
> up every time GETSPI is called), so I'd like to understand what its
> purpose is.
>
> Thanks in advance,
>
> Christophe
next reply other threads:[~2010-08-19 12:57 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-19 12:55 Christophe Gouault [this message]
2010-08-22 7:53 ` IPsec: Why do pfkey_getspi and xfrm_alloc_userspi call xfrm_find_acq_byseq? David Miller
2010-08-23 13:30 ` Christophe Gouault
2010-08-23 14:47 ` Christophe Gouault
2010-09-12 18:47 ` David Miller
-- strict thread matches above, loose matches on Subject: below --
2010-08-17 8:46 Christophe Gouault
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