[PATCH v3] net/ice: fix L2TPv2 outer MAC in training packet

[Shaiq Wani]

In ice_fdir_get_gen_prgm_pkt() there are two pointers into the
training-packet buffer:

pkt  – start of the full packet (outer Ethernet header, offset 0)
loc  – start of the current protocol segment; equals pkt for
       non-tunnel flows but points past the tunnel header for
       tunnel flows

The L2TPv2 cases wrote the outer source and destination MAC addresses
through loc.  For non-tunnel L2TPv2, loc == pkt so this happened to
work, but it is semantically wrong: outer Ethernet fields must always
be written relative to pkt so the code remains correct regardless of
the tunnel/non-tunnel path taken.

Replace loc with pkt in the four L2TPv2 MAC-insertion case blocks
(IPv4 control, IPv4 data/PPP, IPv6 control, IPv6 data/PPP)

Fixes: bf662653976e ("net/ice/base: support L2TPv2 flow rule")
Signed-off-by: Shaiq Wani <shaiq.wani at intel.com>
---
v3:
- Fixed checkpatch issue.
- Moved comment after all declarations.
v2:
- Split from combined outer-MAC patch into separate fix.
- Add comment documenting difference between pkt vs loc pointers.

 drivers/net/intel/ice/base/ice_fdir.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/net/intel/ice/base/ice_fdir.c b/drivers/net/intel/ice/base/ice_fdir.c
index 2c0cb99854..1846fbc515 100644
--- a/drivers/net/intel/ice/base/ice_fdir.c
+++ b/drivers/net/intel/ice/base/ice_fdir.c
@@ -3835,6 +3835,12 @@ ice_fdir_get_gen_prgm_pkt(struct ice_hw *hw, struct ice_fdir_fltr *input,
 	u16 pos;
 	u16 offset;
 
+	/* pkt  = start of full packet buffer (outer Ethernet header, offset 0).
+	 * loc  = start of current protocol segment; equals pkt for non-tunnel
+	 *        flows, but points past the tunnel header for tunnel flows.
+	 * Use pkt for outer L2 fields, loc for the active segment.
+	 */
+
 	if (input->flow_type == ICE_FLTR_PTYPE_NONF_IPV4_OTHER) {
 		switch (input->ip.v4.proto) {
 		case ICE_IP_PROTO_TCP:
@@ -4599,16 +4605,16 @@ ice_fdir_get_gen_prgm_pkt(struct ice_hw *hw, struct ice_fdir_fltr *input,
 				     input->ip.v6.tc);
 		break;
 	case ICE_FLTR_PTYPE_NONF_IPV4_L2TPV2_CONTROL:
-		ice_pkt_insert_mac_addr(loc, input->ext_data_outer.dst_mac);
-		ice_pkt_insert_mac_addr(loc + ETH_ALEN,
+		ice_pkt_insert_mac_addr(pkt, input->ext_data_outer.dst_mac);
+		ice_pkt_insert_mac_addr(pkt + ETH_ALEN,
 					input->ext_data_outer.src_mac);
 		ice_pkt_insert_u16(loc, ICE_IPV4_L2TPV2_LEN_SESS_ID_OFFSET,
 				   input->l2tpv2_data.session_id);
 		break;
 	case ICE_FLTR_PTYPE_NONF_IPV4_L2TPV2:
 	case ICE_FLTR_PTYPE_NONF_IPV4_L2TPV2_PPP:
-		ice_pkt_insert_mac_addr(loc, input->ext_data_outer.dst_mac);
-		ice_pkt_insert_mac_addr(loc + ETH_ALEN,
+		ice_pkt_insert_mac_addr(pkt, input->ext_data_outer.dst_mac);
+		ice_pkt_insert_mac_addr(pkt + ETH_ALEN,
 					input->ext_data_outer.src_mac);
 		flags_version = BE16_TO_CPU(input->l2tpv2_data.flags_version);
 		if (flags_version & ICE_L2TPV2_FLAGS_LEN) {
@@ -4622,16 +4628,16 @@ ice_fdir_get_gen_prgm_pkt(struct ice_hw *hw, struct ice_fdir_fltr *input,
 		}
 		break;
 	case ICE_FLTR_PTYPE_NONF_IPV6_L2TPV2_CONTROL:
-		ice_pkt_insert_mac_addr(loc, input->ext_data_outer.dst_mac);
-		ice_pkt_insert_mac_addr(loc + ETH_ALEN,
+		ice_pkt_insert_mac_addr(pkt, input->ext_data_outer.dst_mac);
+		ice_pkt_insert_mac_addr(pkt + ETH_ALEN,
 					input->ext_data_outer.src_mac);
 		ice_pkt_insert_u16(loc, ICE_IPV6_L2TPV2_LEN_SESS_ID_OFFSET,
 				   input->l2tpv2_data.session_id);
 		break;
 	case ICE_FLTR_PTYPE_NONF_IPV6_L2TPV2:
 	case ICE_FLTR_PTYPE_NONF_IPV6_L2TPV2_PPP:
-		ice_pkt_insert_mac_addr(loc, input->ext_data_outer.dst_mac);
-		ice_pkt_insert_mac_addr(loc + ETH_ALEN,
+		ice_pkt_insert_mac_addr(pkt, input->ext_data_outer.dst_mac);
+		ice_pkt_insert_mac_addr(pkt + ETH_ALEN,
 					input->ext_data_outer.src_mac);
 		flags_version = BE16_TO_CPU(input->l2tpv2_data.flags_version);
 		if (flags_version & ICE_L2TPV2_FLAGS_LEN) {
-- 
2.43.0