net/mlx5e: Fix driver's declaration to support GRE offload

Declare GRE offload support with respect to the inner protocol. Add a
list of supported inner protocols on which the driver can offload
checksum and GSO. For other protocols, inform the stack to do the needed
operations. There is no noticeable impact on GRE performance.

Fixes: 27299841 ("net/mlx5e: Support TSO and TX checksum offloads for GRE tunnels")
Signed-off-by: Aya Levin <ayal@mellanox.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/en_main.c

@@ -4226,6 +4226,21 @@ int mlx5e_get_vf_stats(struct net_device *dev,
 }
 #endif
 
+static bool mlx5e_gre_tunnel_inner_proto_offload_supported(struct mlx5_core_dev *mdev,
+							   struct sk_buff *skb)
+{
+	switch (skb->inner_protocol) {
+	case htons(ETH_P_IP):
+	case htons(ETH_P_IPV6):
+	case htons(ETH_P_TEB):
+		return true;
+	case htons(ETH_P_MPLS_UC):
+	case htons(ETH_P_MPLS_MC):
+		return MLX5_CAP_ETH(mdev, tunnel_stateless_mpls_over_gre);
+	}
+	return false;
+}
+
 static netdev_features_t mlx5e_tunnel_features_check(struct mlx5e_priv *priv,
 						     struct sk_buff *skb,
 						     netdev_features_t features)
@@ -4248,7 +4263,9 @@ static netdev_features_t mlx5e_tunnel_features_check(struct mlx5e_priv *priv,
 
 	switch (proto) {
 	case IPPROTO_GRE:
-		return features;
+		if (mlx5e_gre_tunnel_inner_proto_offload_supported(priv->mdev, skb))
+			return features;
+		break;
 	case IPPROTO_IPIP:
 	case IPPROTO_IPV6:
 		if (mlx5e_tunnel_proto_supported(priv->mdev, IPPROTO_IPIP))