igb: take VLAN double header into account

Increase the packet header padding to include double VLAN tagging.
This patch uses a macro for this.

Fixes: 9cbc948b ("igb: add XDP support")
Suggested-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Sven Auhagen <sven.auhagen@voleatech.de>
Tested-by: Sandeep Penigalapati <sandeep.penigalapati@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/igb/igb.h

@@ -138,6 +138,8 @@ struct vf_mac_filter {
 /* this is the size past which hardware will drop packets when setting LPE=0 */
 #define MAXIMUM_ETHERNET_VLAN_SIZE 1522
 
+#define IGB_ETH_PKT_HDR_PAD	(ETH_HLEN + ETH_FCS_LEN + (VLAN_HLEN * 2))
+
 /* Supported Rx Buffer Sizes */
 #define IGB_RXBUFFER_256	256
 #define IGB_RXBUFFER_1536	1536
@@ -247,6 +249,9 @@ enum igb_tx_flags {
 #define IGB_SFF_ADDRESSING_MODE		0x4
 #define IGB_SFF_8472_UNSUP		0x00
 
+/* TX resources are shared between XDP and netstack
+ * and we need to tag the buffer type to distinguish them
+ */
 enum igb_tx_buf_type {
 	IGB_TYPE_SKB = 0,
 	IGB_TYPE_XDP,

drivers/net/ethernet/intel/igb/igb_main.c

@@ -2826,7 +2826,7 @@ static int igb_setup_tc(struct net_device *dev, enum tc_setup_type type,
 
 static int igb_xdp_setup(struct net_device *dev, struct bpf_prog *prog)
 {
-	int i, frame_size = dev->mtu + ETH_HLEN + ETH_FCS_LEN + VLAN_HLEN;
+	int i, frame_size = dev->mtu + IGB_ETH_PKT_HDR_PAD;
 	struct igb_adapter *adapter = netdev_priv(dev);
 	bool running = netif_running(dev);
 	struct bpf_prog *old_prog;
@@ -3950,8 +3950,7 @@ static int igb_sw_init(struct igb_adapter *adapter)
 	/* set default work limits */
 	adapter->tx_work_limit = IGB_DEFAULT_TX_WORK;
 
-	adapter->max_frame_size = netdev->mtu + ETH_HLEN + ETH_FCS_LEN +
-				  VLAN_HLEN;
+	adapter->max_frame_size = netdev->mtu + IGB_ETH_PKT_HDR_PAD;
 	adapter->min_frame_size = ETH_ZLEN + ETH_FCS_LEN;
 
 	spin_lock_init(&adapter->nfc_lock);
@@ -6491,7 +6490,7 @@ static void igb_get_stats64(struct net_device *netdev,
 static int igb_change_mtu(struct net_device *netdev, int new_mtu)
 {
 	struct igb_adapter *adapter = netdev_priv(netdev);
-	int max_frame = new_mtu + ETH_HLEN + ETH_FCS_LEN + VLAN_HLEN;
+	int max_frame = new_mtu + IGB_ETH_PKT_HDR_PAD;
 
 	if (adapter->xdp_prog) {
 		int i;