max_rx_pkt_len issues with i40e dpdk SRIOV driver net_i40e_vf.

https://bugs.dpdk.org/show_bug.cgi?id=296

            Bug ID: 296
           Summary: max_rx_pkt_len issues with i40e dpdk SRIOV driver
                    net_i40e_vf.
           Product: DPDK
           Version: 18.02
          Hardware: x86
                OS: All
            Status: CONFIRMED
          Severity: major
          Priority: Normal
         Component: ethdev
          Assignee: [email protected]
          Reporter: [email protected]
                CC: [email protected]

Target Milestone: ---
CC: [email protected]

When deployed an SRIOV setup with Intel® Ethernet 700 Series 40GB NIC, we noticed the traffic with default mtu (1500) is not working. The maximum MSS which was worked is 1456 ( instead of the default value 1460).

On debugging, it is found that the driver is actually setting the dev_data->dev_conf.rxmode.max_rx_pkt_len to 1518(ETHER_MAX_LEN) which is wrong.

The max len is not including the vlan tag len( also not including QinQ). The ETH Overhead is defined as below

#define I40E_ETH_OVERHEAD \
        (ETHER_HDR_LEN + ETHER_CRC_LEN + I40E_VLAN_TAG_SIZE * 2)    

which is equal to 26

So for supporting an MTU size of 1500, the max_rx_pkt_len should be 1526 instead of 1518.

The i40evf_dev_mtu_set API also wrongly checking the framesize against ETHER_MAX_LEN(1518) to set the jumbo_frame mode.

The attached patch resolved the issue for our testing. Please verify and fix the issue.

Thanks and Regards,
Lava

--- Comment #1 from Xiao Zhang ([email protected]) --- Hi Lava,

I did not see the patch, can you upstream your patch to the community?

Thanks,
Xiao

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