netdev - Re: [PATCH ipsec] xfrm: Provide private skb extensions for segmented and hw offloaded ESP packets

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Date:   Thu, 25 Mar 2021 09:46:07 +0100
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     Florian Westphal <fw@...len.de>
CC:     <netdev@...r.kernel.org>
Subject: Re: [PATCH ipsec] xfrm: Provide private skb extensions for segmented
 and hw offloaded ESP packets

On Tue, Mar 23, 2021 at 01:02:35PM +0100, Florian Westphal wrote:
> Steffen Klassert <steffen.klassert@...unet.com> wrote:
> > Commit 94579ac3f6d0 ("xfrm: Fix double ESP trailer insertion in IPsec
> > crypto offload.") added a XFRM_XMIT flag to avoid duplicate ESP trailer
> > insertion on HW offload. This flag is set on the secpath that is shared
> > amongst segments. This lead to a situation where some segments are
> > not transformed correctly when segmentation happens at layer 3.
> > 
> > Fix this by using private skb extensions for segmented and hw offloaded
> > ESP packets.
> > 
> > Fixes: 94579ac3f6d0 ("xfrm: Fix double ESP trailer insertion in IPsec crypto offload.")
> > Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
> > ---
> >  include/linux/skbuff.h  |  1 +
> >  net/core/skbuff.c       | 23 ++++++++++++++++++-----
> >  net/ipv4/esp4_offload.c | 16 +++++++++++++++-
> >  net/ipv6/esp6_offload.c | 16 +++++++++++++++-
> >  net/xfrm/xfrm_device.c  |  2 --
> >  5 files changed, 49 insertions(+), 9 deletions(-)
> > 
> > -	if (hw_offload)
> > +	if (hw_offload) {
> > +		ext = skb_ext_cow(skb->extensions, skb->active_extensions);
> 
> It should be possible to do
> 
> 	if (hw_offload) {
> 		if (!skb_ext_add(skb, SKB_EXT_SECPATH);
> 			return -ENOMEM;
> 
> 		xo = xfrm_offload(skb);
> 		....
> 
> without need for a new 'cow' function.
> skb_ext_add() will auto-COW if the extension area has a refcount > 1.

Good point, thanks! Will do a v2.