[dpdk-dev] [PATCH v2 6/7] net/e1000: set min and max MTU for igb devices

[Ian Stokes <ian.stokes@intel.com>]

This commit sets the min and max supported MTU values for igb devices
via the eth_igb_info_get() function. Min MTU supported is set to
ETHER_MIN_MTU and max mtu is calculated as the max packet length
supported minus the transport overhead. To aid in these calculations
a new MACRO 'E1000_ETH_OVERHEAD' has been introduced to consolidate
overhead calculation and avoid duplication.

Signed-off-by: Ian Stokes <ian.stokes@intel.com>
---
 drivers/net/e1000/e1000_ethdev.h | 6 ++++++
 drivers/net/e1000/igb_ethdev.c   | 7 +++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/net/e1000/e1000_ethdev.h b/drivers/net/e1000/e1000_ethdev.h
index 94edff08e..3e74cd8fe 100644
--- a/drivers/net/e1000/e1000_ethdev.h
+++ b/drivers/net/e1000/e1000_ethdev.h
@@ -89,6 +89,12 @@
 	ETH_RSS_IPV6_UDP_EX)
 
 /*
+ * The overhead from MTU to max frame size.
+ * Considering VLAN so a tag needs to be counted.
+ */
+#define E1000_ETH_OVERHEAD (ETHER_HDR_LEN + ETHER_CRC_LEN + VLAN_TAG_SIZE)
+
+/*
  * Maximum number of Ring Descriptors.
  *
  * Since RDLEN/TDLEN should be multiple of 128 bytes, the number of ring
diff --git a/drivers/net/e1000/igb_ethdev.c b/drivers/net/e1000/igb_ethdev.c
index 87c9aedf2..b897e8ad4 100644
--- a/drivers/net/e1000/igb_ethdev.c
+++ b/drivers/net/e1000/igb_ethdev.c
@@ -2283,6 +2283,10 @@ eth_igb_infos_get(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
 	dev_info->speed_capa = ETH_LINK_SPEED_10M_HD | ETH_LINK_SPEED_10M |
 			ETH_LINK_SPEED_100M_HD | ETH_LINK_SPEED_100M |
 			ETH_LINK_SPEED_1G;
+
+	dev_info->max_mtu = dev_info->max_rx_pktlen - E1000_ETH_OVERHEAD;
+	dev_info->min_mtu = ETHER_MIN_MTU;
+
 }
 
 static const uint32_t *
@@ -4466,8 +4470,7 @@ eth_igb_mtu_set(struct rte_eth_dev *dev, uint16_t mtu)
 	uint32_t rctl;
 	struct e1000_hw *hw;
 	struct rte_eth_dev_info dev_info;
-	uint32_t frame_size = mtu + (ETHER_HDR_LEN + ETHER_CRC_LEN +
-				     VLAN_TAG_SIZE);
+	uint32_t frame_size = mtu + E1000_ETH_OVERHEAD;
 
 	hw = E1000_DEV_PRIVATE_TO_HW(dev->data->dev_private);
 
-- 
2.13.6