netdev - Re: IPsec: Why do pfkey_getspi and xfrm_alloc_userspi call xfrm_find_acq

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <4C6D29B9.5070403@6wind.com>
Date:	Thu, 19 Aug 2010 14:55:21 +0200
From:	Christophe Gouault <christophe.gouault@...nd.com>
To:	netdev@...r.kernel.org
Subject: Re: IPsec: Why do pfkey_getspi and xfrm_alloc_userspi call xfrm_find_acq_byseq?

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
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html