Subject: Re: [PATCH RFC xfrm-next v3 4/8] xfrm: add TX datapath support for IPsec full offload mode

From: Leon Romanovsky <[email-masked]>
Date: Mon, 26 Sep 2022 09:06:48 +0300

On Sun, Sep 25, 2022 at 11:16:03AM +0200, Steffen Klassert wrote:
> On Sun, Sep 04, 2022 at 04:15:38PM +0300, Leon Romanovsky wrote:
> > From: Leon Romanovsky <[email-masked]>
> > 
> > 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 <[email-masked]>
> > Signed-off-by: Huy Nguyen <[email-masked]>
> > Signed-off-by: Leon Romanovsky <[email-masked]>
> > ---
> >  net/xfrm/xfrm_device.c | 15 +++++++++++++--
> >  net/xfrm/xfrm_output.c | 12 +++++++++++-
> >  2 files changed, 24 insertions(+), 3 deletions(-)
> > 
> > diff --git a/net/xfrm/xfrm_device.c b/net/xfrm/xfrm_device.c
> > index 1cc482e9c87d..2d37bb86914a 100644
> > --- a/net/xfrm/xfrm_device.c
> > +++ b/net/xfrm/xfrm_device.c
> > @@ -120,6 +120,16 @@ struct sk_buff *validate_xmit_xfrm(struct sk_buff *skb, netdev_features_t featur
> >  	if (xo->flags & XFRM_GRO || x->xso.dir == XFRM_DEV_OFFLOAD_IN)
> >  		return skb;
> >  
> > +	/* The packet was sent to HW IPsec full offload engine,
> > +	 * but to wrong device. Drop the packet, so it won't skip
> > +	 * XFRM stack.
> > +	 */
> > +	if (x->xso.type == XFRM_DEV_OFFLOAD_FULL && x->xso.dev != dev) {
> > +		kfree_skb(skb);
> > +		dev_core_stats_tx_dropped_inc(dev);
> > +		return NULL;
> > +	}
> > +
> >  	/* This skb was already validated on the upper/virtual dev */
> >  	if ((x->xso.dev != dev) && (x->xso.real_dev == dev))
> >  		return skb;
> > @@ -369,8 +379,9 @@ bool xfrm_dev_offload_ok(struct sk_buff *skb, struct xfrm_state *x)
> >  	if (!x->type_offload || x->encap)
> >  		return false;
> >  
> > -	if ((!dev || (dev == xfrm_dst_path(dst)->dev)) &&
> > -	    (!xdst->child->xfrm)) {
> > +	if (x->xso.type == XFRM_DEV_OFFLOAD_FULL ||
> > +	    ((!dev || (dev == xfrm_dst_path(dst)->dev)) &&
> > +	     !xdst->child->xfrm)) {
> >  		mtu = xfrm_state_mtu(x, xdst->child_mtu_cached);
> >  		if (skb->len <= mtu)
> >  			goto ok;
> > diff --git a/net/xfrm/xfrm_output.c b/net/xfrm/xfrm_output.c
> > index 9a5e79a38c67..dde009be8463 100644
> > --- a/net/xfrm/xfrm_output.c
> > +++ b/net/xfrm/xfrm_output.c
> > @@ -494,7 +494,7 @@ static int xfrm_output_one(struct sk_buff *skb, int err)
> >  	struct xfrm_state *x = dst->xfrm;
> >  	struct net *net = xs_net(x);
> >  
> > -	if (err <= 0)
> > +	if (err <= 0 || x->xso.type == XFRM_DEV_OFFLOAD_FULL)
> >  		goto resume;
> 
> You check here that the state is marked as 'full offload' before
> you skip the SW xfrm handling, but I don't see where you check
> that the policy that led to this state is offloaded too. Also,
> we have to make sure that both, policy and state is offloaded to
> the same device. Looks like this part is missing.

In SW flow, users are not required to configure policy. If they don't
have policy, the packet will be encrypted and sent anyway.

The full offload follows same semantic. The missing offloaded policy is
equal to no policy at all.

I don't think that extra checks are needed.

Thanks