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

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Date:   Thu, 05 Dec 2019 08:10:36 +0000
From:   Mark Gillott <mgillott@...tta.att-mail.com>
To:     nicolas.dichtel@...nd.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

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.

Does that help?

Mark