From: Iyappan Subramanian <redacted>
Date: Mon, 16 Jun 2014 17:18:46 -0700

+static netdev_tx_t xgene_enet_start_xmit(struct sk_buff *skb,
+					 struct net_device *ndev)
+{
+	struct xgene_enet_pdata *pdata = netdev_priv(ndev);
+	struct xgene_enet_desc_ring *tx_ring = pdata->tx_ring;
+	struct xgene_enet_desc_ring *cp_ring = tx_ring->cp_ring;
+	u32 tx_level, cq_level;
+
+	tx_level = xgene_enet_ring_len(tx_ring);
+	cq_level = xgene_enet_ring_len(cp_ring);
+	if (unlikely(tx_level > pdata->tx_qcnt_hi ||
+		     cq_level > pdata->cp_qcnt_hi)) {
+		netif_stop_queue(ndev);
+		return NETDEV_TX_BUSY;
+	}
+
+	if (xgene_enet_setup_tx_desc(tx_ring, skb))
+		return NETDEV_TX_OK;

If you return NETDEV_TX_OK, it is your responsibility to deal with the
SKB, because you own it.

In particular, you have to free the packet.