net/mlx5e: IPsec: Fix a misuse of the software parser's fields

IPsec crypto offload current Software Parser (SWP) fields settings in
the ethernet segment (eseg) are not aligned with PRM/HW expectations.
Among others in case of IP|ESP|TCP packet, current driver sets the
offsets for inner_l3 and inner_l4 although there is no inner l3/l4
headers relative to ESP header in such packets.

SWP provides the offsets for HW ,so it can be used to find csum fields
to offload the checksum, however these are not necessarily used by HW
and are used as fallback in case HW fails to parse the packet, e.g
when performing IPSec Transport Aware (IP | ESP | TCP) there is no
need to add SW parse on inner packet. So in some cases packets csum
was calculated correctly , whereas in other cases it failed. The later
faced csum errors (caused by wrong packet length calculations) which
led to lots of packet drops hence the low throughput.

Fix by setting the SWP fields as expected in a IP|ESP|TCP packet.

the following describe the expected SWP offsets:
* Tunnel Mode:
* SWP:      OutL3       InL3  InL4
* Pkt: MAC  IP     ESP  IP    L4
*
* Transport Mode:
* SWP:      OutL3       OutL4
* Pkt: MAC  IP     ESP  L4
*
* Tunnel(VXLAN TCP/UDP) over Transport Mode
* SWP:      OutL3                   InL3  InL4
* Pkt: MAC  IP     ESP  UDP  VXLAN  IP    L4

Fixes: f1267798 ("net/mlx5: Fix checksum issue of VXLAN and IPsec crypto offload")
Signed-off-by: Emeel Hakim <ehakim@nvidia.com>
Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/en_accel/ipsec_rxtx.c

@@ -141,8 +141,7 @@ static void mlx5e_ipsec_set_swp(struct sk_buff *skb,
 	 * Pkt: MAC  IP     ESP  IP    L4
 	 *
 	 * Transport Mode:
-	 * SWP:      OutL3       InL4
-	 *           InL3
+	 * SWP:      OutL3       OutL4
 	 * Pkt: MAC  IP     ESP  L4
 	 *
 	 * Tunnel(VXLAN TCP/UDP) over Transport Mode
@@ -171,15 +170,18 @@ static void mlx5e_ipsec_set_swp(struct sk_buff *skb,
 		return;
 
 	if (!xo->inner_ipproto) {
-		eseg->swp_inner_l3_offset = skb_network_offset(skb) / 2;
-		eseg->swp_inner_l4_offset = skb_inner_transport_offset(skb) / 2;
-		if (skb->protocol == htons(ETH_P_IPV6))
-			eseg->swp_flags |= MLX5_ETH_WQE_SWP_INNER_L3_IPV6;
-		if (xo->proto == IPPROTO_UDP)
-			eseg->swp_flags |= MLX5_ETH_WQE_SWP_INNER_L4_UDP;
-		return;
+		switch (xo->proto) {
+		case IPPROTO_UDP:
+			eseg->swp_flags |= MLX5_ETH_WQE_SWP_OUTER_L4_UDP;
+			fallthrough;
+		case IPPROTO_TCP:
+			/* IP | ESP | TCP */
+			eseg->swp_outer_l4_offset = skb_inner_transport_offset(skb) / 2;
+			break;
+		default:
+			break;
 		}
-
+	} else {
 		/* Tunnel(VXLAN TCP/UDP) over Transport Mode */
 		switch (xo->inner_ipproto) {
 		case IPPROTO_UDP:
@@ -187,15 +189,16 @@ static void mlx5e_ipsec_set_swp(struct sk_buff *skb,
 			fallthrough;
 		case IPPROTO_TCP:
 			eseg->swp_inner_l3_offset = skb_inner_network_offset(skb) / 2;
-		eseg->swp_inner_l4_offset = (skb->csum_start + skb->head - skb->data) / 2;
+			eseg->swp_inner_l4_offset =
+				(skb->csum_start + skb->head - skb->data) / 2;
 			if (skb->protocol == htons(ETH_P_IPV6))
 				eseg->swp_flags |= MLX5_ETH_WQE_SWP_INNER_L3_IPV6;
 			break;
 		default:
 			break;
 		}
+	}
 
-	return;
 }
 
 void mlx5e_ipsec_set_iv_esn(struct sk_buff *skb, struct xfrm_state *x,