[PATCH v2] examples/l3fwd: fix jumbo packet drop issue

[rohit.raj at nxp.com]

From: Rohit Raj <rohit.raj at nxp.com>

l3fwd uses mbufs with 2KB data size. If we enable jumbo packets, it is
not able to store packets with size greater than 2KB, hence these
packets are dropped.

This patch fixes this issue by enabling scatter for jumbo packet, if
it is supported by NIC.

If scatter is not supported by NIC and max packet length is greater
than default mbuf data size, then application exits with proper error
message.

Fixes: f68aad7904f ("examples/l3fwd: update")

Signed-off-by: Rohit Raj <rohit.raj at nxp.com>
Signed-off-by: Sachin Saxena <sachin.saxena at nxp.com>
Signed-off-by: Vanshika Shukla <vanshika.shukla at nxp.com>
---

v2:
* Improved the check to not enable Rx scatter when packets fits into
  buffer.
* Check if jumbo packet is enabled using max_rx_pktlen instead of
  jumbo packet flag.

 examples/l3fwd/main.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/examples/l3fwd/main.c b/examples/l3fwd/main.c
index d69373f881..61448c759c 100644
--- a/examples/l3fwd/main.c
+++ b/examples/l3fwd/main.c
@@ -1109,6 +1109,19 @@ l3fwd_poll_resource_setup(void)
 				"Invalid max packet length: %u (port %u)\n",
 				max_pkt_len, portid);
 
+		/* Enable Receive side SCATTER, if supported by NIC,
+		 * when jumbo packet is enabled.
+		 */
+		if (dev_info.max_rx_pktlen > RTE_MBUF_DEFAULT_DATAROOM) {
+			if (dev_info.rx_offload_capa &
+			    RTE_ETH_RX_OFFLOAD_SCATTER)
+				local_port_conf.rxmode.offloads |=
+						RTE_ETH_RX_OFFLOAD_SCATTER;
+			else
+				rte_exit(EXIT_FAILURE,
+					 "Max packet length greater than default MBUF size\n");
+		}
+
 		if (dev_info.tx_offload_capa & RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE)
 			local_port_conf.txmode.offloads |=
 				RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE;
-- 
2.17.1