netdev - Re: [PATCH xfrm-next v2 4/6] xfrm: add TX datapath support for IPsec full offload mode

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Message-ID: <20220822080454.GF2602992@gauss3.secunet.de>
Date:   Mon, 22 Aug 2022 10:04:54 +0200
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     Leon Romanovsky <leon@...nel.org>
CC:     "David S . Miller" <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        <netdev@...r.kernel.org>, Raed Salem <raeds@...dia.com>,
        ipsec-devel <devel@...ux-ipsec.org>
Subject: Re: [PATCH xfrm-next v2 4/6] xfrm: add TX datapath support for IPsec
 full offload mode

On Thu, Aug 18, 2022 at 04:34:54PM +0300, Leon Romanovsky wrote:
> On Thu, Aug 18, 2022 at 12:24:51PM +0200, Steffen Klassert wrote:
> > On Tue, Aug 16, 2022 at 11:59:25AM +0300, Leon Romanovsky wrote:
> > > From: Leon Romanovsky <leonro@...dia.com>
> > > 
> > > In IPsec full mode, the device is going to encrypt and encapsulate
> > > packets that are associated with offloaded policy. After successful
> > > policy lookup to indicate if packets should be offloaded or not,
> > > the stack forwards packets to the device to do the magic.
> > > 
> > > Signed-off-by: Raed Salem <raeds@...dia.com>
> > > Signed-off-by: Huy Nguyen <huyn@...dia.com>
> > > Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> > > ---
> > >  net/xfrm/xfrm_device.c | 13 +++++++++++++
> > >  net/xfrm/xfrm_output.c | 20 ++++++++++++++++++++
> > >  2 files changed, 33 insertions(+)
> > > 
> > > diff --git a/net/xfrm/xfrm_device.c b/net/xfrm/xfrm_device.c
> > > index 1cc482e9c87d..db5ebd36f68c 100644
> > > --- a/net/xfrm/xfrm_device.c
> > > +++ b/net/xfrm/xfrm_device.c
> > 
> > > @@ -366,6 +376,9 @@ bool xfrm_dev_offload_ok(struct sk_buff *skb, struct xfrm_state *x)
> > >  	struct xfrm_dst *xdst = (struct xfrm_dst *)dst;
> > >  	struct net_device *dev = x->xso.dev;
> > >  
> > > +	if (x->xso.type == XFRM_DEV_OFFLOAD_FULL)
> > > +		goto ok;
> > 
> > You skip the PMTU checks here. I've seen that you check
> > the packet length against the device MTU in one of your
> > mlx5 patches, but that does not help if the PMTU is below.
> 
> If device supports transformation of the packet, this packet
> won't be counted as XFRM anymore. I'm not sure that we need
> to perform XFRM specific checks.

This is not xfrm specific, it makes sure that the packet you
want to send fits into the PMTU.