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net/enic: fix max MTU calculation

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The maximum packet length (max_pkt_len) from the firmware does not
include CRC, so do not subtract 4 when deriving the max MTU. This
change effectively increases the max MTU by 4B. Apps often assume max
MTU = max_rx_pkt_len - 14 (ethernet header), and attempt to set the
MTU to that value (i.e. set MTU to max HW value). This change
incidentally allows such apps to change MTU to max value successfully.

Fixes: bb34ffb848a0 ("net/enic: determine max egress packet size and max MTU")
Cc: stable@dpdk.org

Signed-off-by: Hyong Youb Kim <hyonkim@cisco.com>
Reviewed-by: John Daley <johndale@cisco.com>
This commit is contained in:
Hyong Youb Kim 2019-03-14 04:05:32 -07:00 committed by Ferruh Yigit
parent e00a5eaab2
commit c09eb93529
2 changed files with 4 additions and 5 deletions
drivers/net/enic
enic.henic_res.c

4
drivers/net/enic/enic.h

@ -203,8 +203,8 @@ struct enic {
/* Compute ethdev's max packet size from MTU */
static inline uint32_t enic_mtu_to_max_rx_pktlen(uint32_t mtu)
{
/* ethdev max size includes eth and crc whereas NIC MTU does not */
return mtu + ETHER_HDR_LEN + ETHER_CRC_LEN;
/* ethdev max size includes eth whereas NIC MTU does not */
return mtu + ETHER_HDR_LEN;
}
/* Get the CQ index from a Start of Packet(SOP) RQ index */

5
drivers/net/enic/enic_res.c

@ -61,10 +61,9 @@ int enic_get_vnic_config(struct enic *enic)
* and will be 0 for legacy firmware and VICs
*/
if (c->max_pkt_size > ENIC_DEFAULT_RX_MAX_PKT_SIZE)
enic->max_mtu = c->max_pkt_size - (ETHER_HDR_LEN + 4);
enic->max_mtu = c->max_pkt_size - ETHER_HDR_LEN;
else
enic->max_mtu = ENIC_DEFAULT_RX_MAX_PKT_SIZE
- (ETHER_HDR_LEN + 4);
enic->max_mtu = ENIC_DEFAULT_RX_MAX_PKT_SIZE - ETHER_HDR_LEN;
if (c->mtu == 0)
c->mtu = 1500;