netdev - RE: [PATCH net v2 2/3] xfrm: Add an activate() offload dev op

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Date:   Sun, 3 Dec 2017 21:09:36 +0000
From:   Yossi Kuperman <yossiku@...lanox.com>
To:     Shannon Nelson <shannon.nelson@...cle.com>,
        Steffen Klassert <steffen.klassert@...unet.com>
CC:     Aviv Heller <avivh@...lanox.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Boris Pismenny <borisp@...lanox.com>,
        "Yevgeny Kliteynik" <kliteyn@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH net v2 2/3] xfrm: Add an activate() offload dev op



> -----Original Message-----
> From: Shannon Nelson [mailto:shannon.nelson@...cle.com]
> Sent: Sunday, December 3, 2017 2:38 AM
> To: Yossi Kuperman <yossiku@...lanox.com>; Steffen Klassert
> <steffen.klassert@...unet.com>
> Cc: Aviv Heller <avivh@...lanox.com>; Herbert Xu
> <herbert@...dor.apana.org.au>; Boris Pismenny <borisp@...lanox.com>;
> Yevgeny Kliteynik <kliteyn@...lanox.com>; netdev@...r.kernel.org
> Subject: Re: [PATCH net v2 2/3] xfrm: Add an activate() offload dev op
> 
> On 12/2/2017 2:33 PM, Yossi Kuperman wrote:
> >
> >
> >>> On 1 Dec 2017, at 9:09, Steffen Klassert <steffen.klassert@...unet.com>
> wrote:
> >>>
> >>> On Tue, Nov 28, 2017 at 07:55:41PM +0200, avivh@...lanox.com wrote:
> >>> From: Aviv Heller <avivh@...lanox.com>
> >>>
> >>> Adding the state to the offload device prior to replay init in
> >>> xfrm_state_construct() will result in NULL dereference if a matching
> >>> ESP packet is received in between.
> >>>
> >>> In order to inhibit driver offload logic from processing the state's
> >>> packets prior to the xfrm_state object being completely initialized
> >>> and added to the SADBs, a new activate() operation was added to
> >>> inform the driver the aforementioned conditions have been met.
> >>
> >> We discussed this already some time ago, and I still think that we
> >> should fix this by setting XFRM_STATE_VALID only after the state is
> >> fully initialized.
> >
> > An upcoming patch will refactor the if statement (encap_type < 0) in
> xfrm_input, in order to support crypto offload with GRO disabled. Currently it
> doesn’t work. This entails yet another check for the validity of the state.
> Resulting in total of 3 copies: 1) for normal traffic, 2) GRO and 3) crypto offload.
> >
> > Anyway, IMO it is not right that we (the driver) allow an incoming packet to be
> delivered while the SA is not yet ready. Rather than checking for an invalid input I
> prefer to make sure that such a case won’t happen in the first place.
> >
> > To complete the picture, there is another patch to the driver which simply drop
> incoming packets that underwent successful decryption and haven’t been
> activated yet. Active state merely means that the SA is present in the driver’s
> hash table.
> >
> > We can make a separate patch to set the state to valid once it is fully
> initialized, it make sense on its own.
> >
> > What do you think?
> >
> 
> If the SA isn't ready, just don't tell the driver about it.  Please don't add yet
> another state for the driver to track.  This should be as simple as possible, and
> shouldn't be any more complex than the model already used by
> ndo_vlan_rx_add_vid and ndo_vlan_rx_kill_vid.

It is not something new, the driver already "tracks" any SA that uses crypto offload, we just
do it in two phases; please see other answers.

Anyway it is symmetric with xdo_dev_state_delete and xdo_dev_state_free, J

> 
> sln