[PATCH RFC] xfrm: fail to create ixgbe offload of IPsec tunnel mode sa

[Antony Antony <antony@phenome.org>]

Based on talks and indirect references ixgbe driver does not
support offloading IPsec tunnel mode. It only support transport mode.
Now explicitly fail to avoid when trying to offload.

Fixes: 63a67fe229ea ("ixgbe: add ipsec offload add and remove SA")
Signed-off-by: Antony Antony <antony@phenome.org>
---
I haven't tested this fix as I have no access to the hardware.
This patch is based on a libreswan bug report.
https://github.com/libreswan/libreswan/issues/252
Is it useful to this bug report in kernel commit message?

 drivers/net/ethernet/intel/ixgbe/ixgbe_ipsec.c | 5 +++++
 drivers/net/ethernet/intel/ixgbevf/ipsec.c     | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_ipsec.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_ipsec.c
index eca73526ac86..e2b978efcc5a 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_ipsec.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_ipsec.c
@@ -575,6 +575,11 @@ static int ixgbe_ipsec_add_sa(struct xfrm_state *xs)
 		return -EINVAL;
 	}
 
+	if (xs->props.mode != XFRM_MODE_TRANSPORT) {
+		netdev_err(dev, "Unsupported mode for ipsec offload\n");
+		return -EINVAL;
+	}
+
 	if (ixgbe_ipsec_check_mgmt_ip(xs)) {
 		netdev_err(dev, "IPsec IP addr clash with mgmt filters\n");
 		return -EINVAL;
diff --git a/drivers/net/ethernet/intel/ixgbevf/ipsec.c b/drivers/net/ethernet/intel/ixgbevf/ipsec.c
index 5170dd9d8705..d11b3f3414ea 100644
--- a/drivers/net/ethernet/intel/ixgbevf/ipsec.c
+++ b/drivers/net/ethernet/intel/ixgbevf/ipsec.c
@@ -272,6 +272,11 @@ static int ixgbevf_ipsec_add_sa(struct xfrm_state *xs)
 		return -EINVAL;
 	}
 
+	if (xs->props.mode != XFRM_MODE_TRANSPORT) {
+		netdev_err(dev, "Unsupported mode for ipsec offload\n");
+		return -EINVAL;
+	}
+
 	if (xs->xso.flags & XFRM_OFFLOAD_INBOUND) {
 		struct rx_sa rsa;
 
-- 
2.21.3