vmxnet3: limit number of TXDs used for TSO packet

Currently, vmxnet3 does not have a limit on number of descriptors
used for a TSO packet. However, with UPT, for hardware performance
reasons, this patch limits the number of transmit descriptors to 24
for a TSO packet.
Signed-off-by: Ronak Doshi <doshir@vmware.com>
Acked-by: Guolin Yang <gyang@vmware.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/vmxnet3/vmxnet3_defs.h

@@ -400,6 +400,8 @@ union Vmxnet3_GenericDesc {
 
 /* max # of tx descs for a non-tso pkt */
 #define VMXNET3_MAX_TXD_PER_PKT 16
+/* max # of tx descs for a tso pkt */
+#define VMXNET3_MAX_TSO_TXD_PER_PKT 24
 
 /* Max size of a single rx buffer */
 #define VMXNET3_MAX_RX_BUF_SIZE  ((1 << 14) - 1)

drivers/net/vmxnet3/vmxnet3_drv.c

@@ -1061,6 +1061,23 @@ vmxnet3_tq_xmit(struct sk_buff *skb, struct vmxnet3_tx_queue *tq,
 			}
 			tq->stats.copy_skb_header++;
 		}
+		if (unlikely(count > VMXNET3_MAX_TSO_TXD_PER_PKT)) {
+			/* tso pkts must not use more than
+			 * VMXNET3_MAX_TSO_TXD_PER_PKT entries
+			 */
+			if (skb_linearize(skb) != 0) {
+				tq->stats.drop_too_many_frags++;
+				goto drop_pkt;
+			}
+			tq->stats.linearized++;
+
+			/* recalculate the # of descriptors to use */
+			count = VMXNET3_TXD_NEEDED(skb_headlen(skb)) + 1;
+			if (unlikely(count > VMXNET3_MAX_TSO_TXD_PER_PKT)) {
+				tq->stats.drop_too_many_frags++;
+				goto drop_pkt;
+			}
+		}
 		if (skb->encapsulation) {
 			vmxnet3_prepare_inner_tso(skb, &ctx);
 		} else {