netdev - Re: [PATCH ipsec] xfrm: check DST_NOPOLICY as well as DST

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Date:   Thu, 5 Dec 2019 09:52:21 +0100
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:     Mark Gillott <mgillott@...tta.att-mail.com>, netdev@...r.kernel.org
Cc:     steffen.klassert@...unet.com, herbert@...dor.apana.org.au
Subject: Re: [PATCH ipsec] xfrm: check DST_NOPOLICY as well as DST_NOXFRM

Le 05/12/2019 à 09:10, Mark Gillott a écrit :
> On Wed, 2019-12-04 at 17:57 +0100, Nicolas Dichtel wrote:
>> Le 04/12/2019 à 16:17, Mark Gillott a écrit :
>>> Before performing a policy bundle lookup, check the DST_NOPOLICY
>>> option, as well as DST_NOXFRM. That is, skip further processing if
>>> either of the disable_policy or disable_xfrm sysctl attributes are
>>> set.
>>
>> Can you elaborate why this change is needed?
> 
> We have a separate DPDK-based dataplane that is responsible for all
> IPsec processing - policy handing/encryption/decryption. Consequently
> we set the net.ipv[4|6].conf.<if>.disable_policy sysctl to 1 for all
> "interesting" interfaces. That is we want the kernel to ignore any
> IPsec policies.
> 
> Despite the above & depending on configuration, we found that
> originating traffic was ending up deep inside XFRM where it would get
> dropped because of a route lookup problem.
And why don't you set disable_xfrm to thoses interfaces also?
disable_policy means no xfrm policy lookup on output, disable_xfrm means no xfrm
policy check on input.

Nicolas