[dpdk-dev] [RFC] ethdev: add min/max MTU to device info

[Stephen Hemminger <stephen@networkplumber.org>]

This addresses the usability issue raised by OVS at DPDK Userspace
summit. It adds general min/max mtu into device info. For compatiablity,
and to save space, it fits in a hole in existing structure.

The initial version sets max mtu to normal Ethernet, it is up to
PMD to set larger value if it supports Jumbo frames.

Fixing the drivers to use this is trivial and can be done by 18.11.
Already have some of the patches done.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/librte_ethdev/rte_ethdev.c | 7 +++++++
 lib/librte_ethdev/rte_ethdev.h | 2 ++
 2 files changed, 9 insertions(+)

diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
index 4c320250589a..df0c7536a7c4 100644
--- a/lib/librte_ethdev/rte_ethdev.c
+++ b/lib/librte_ethdev/rte_ethdev.c
@@ -2408,6 +2408,8 @@ rte_eth_dev_info_get(uint16_t port_id, struct rte_eth_dev_info *dev_info)
 	dev_info->rx_desc_lim = lim;
 	dev_info->tx_desc_lim = lim;
 	dev_info->device = dev->device;
+	dev_info->min_mtu = ETHER_MIN_MTU;
+	dev_info->max_mtu = ETHER_MTU;
 
 	RTE_FUNC_PTR_OR_RET(*dev->dev_ops->dev_infos_get);
 	(*dev->dev_ops->dev_infos_get)(dev, dev_info);
@@ -2471,12 +2473,17 @@ int
 rte_eth_dev_set_mtu(uint16_t port_id, uint16_t mtu)
 {
 	int ret;
+	struct rte_eth_dev_info dev_info;
 	struct rte_eth_dev *dev;
 
 	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
 	dev = &rte_eth_devices[port_id];
 	RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->mtu_set, -ENOTSUP);
 
+	rte_eth_dev_info_get(port_id, &dev_info);
+	if (mtu < dev_info.min_mtu || mtu > dev_info.max_mtu)
+		return -EINVAL;
+
 	ret = (*dev->dev_ops->mtu_set)(dev, mtu);
 	if (!ret)
 		dev->data->mtu = mtu;
diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h
index 7070e9ab408f..5171a9083288 100644
--- a/lib/librte_ethdev/rte_ethdev.h
+++ b/lib/librte_ethdev/rte_ethdev.h
@@ -1015,6 +1015,8 @@ struct rte_eth_dev_info {
 	const char *driver_name; /**< Device Driver name. */
 	unsigned int if_index; /**< Index to bound host interface, or 0 if none.
 		Use if_indextoname() to translate into an interface name. */
+	uint16_t min_mtu;	/**< Minimum MTU allowed */
+	uint16_t max_mtu;	/**< Maximum MTU allowed */
 	const uint32_t *dev_flags; /**< Device flags */
 	uint32_t min_rx_bufsize; /**< Minimum size of RX buffer. */
 	uint32_t max_rx_pktlen; /**< Maximum configurable length of RX pkt. */
-- 
2.17.1