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 [off-list ref] wrote:

quoted

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@secunet.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.