net: fec: correct queue selection

The old implementation extracted VLAN TCI info from the payload
before the VLAN tag has been pushed in the payload.

Another problem was that the VLAN TCI was extracted even if the
packet did not have VLAN protocol header.

This resulted in invalid VLAN TCI and as a consequence a random
queue was computed.

This patch fixes the above issues and use the VLAN TCI from the
skb if it is present or VLAN TCI from payload if present. If no
VLAN header is present queue 0 is selected.

Fixes: 52c4a1a ("net: fec: add ndo_select_queue to fix TX bandwidth fluctuations")
Signed-off-by: Radu Bulie <[email protected]>
Signed-off-by: Wei Fang <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: Radu Bulie

drivers/net/ethernet/freescale/fec_main.c

@@ -3731,31 +3731,26 @@ static int fec_set_features(struct net_device *netdev,
 	return 0;
 }
 
-static u16 fec_enet_get_raw_vlan_tci(struct sk_buff *skb)
-{
-	struct vlan_ethhdr *vhdr;
-	unsigned short vlan_TCI = 0;
-
-	if (skb->protocol == htons(ETH_P_ALL)) {
-		vhdr = (struct vlan_ethhdr *)(skb->data);
-		vlan_TCI = ntohs(vhdr->h_vlan_TCI);
-	}
-
-	return vlan_TCI;
-}
-
 static u16 fec_enet_select_queue(struct net_device *ndev, struct sk_buff *skb,
 				 struct net_device *sb_dev)
 {
 	struct fec_enet_private *fep = netdev_priv(ndev);
-	u16 vlan_tag;
+	u16 vlan_tag = 0;
 
 	if (!(fep->quirks & FEC_QUIRK_HAS_AVB))
 		return netdev_pick_tx(ndev, skb, NULL);
 
-	vlan_tag = fec_enet_get_raw_vlan_tci(skb);
-	if (!vlan_tag)
+	/* VLAN is present in the payload.*/
+	if (eth_type_vlan(skb->protocol)) {
+		struct vlan_ethhdr *vhdr = skb_vlan_eth_hdr(skb);
+
+		vlan_tag = ntohs(vhdr->h_vlan_TCI);
+	/*  VLAN is present in the skb but not yet pushed in the payload.*/
+	} else if (skb_vlan_tag_present(skb)) {
+		vlan_tag = skb->vlan_tci;
+	} else {
 		return vlan_tag;
+	}
 
 	return fec_enet_vlan_pri_to_queue[vlan_tag >> 13];
 }