i40e: incorrect byte counters

https://bugs.dpdk.org/show_bug.cgi?id=521

            Bug ID: 521
           Summary: i40e: incorrect byte counters
           Product: DPDK
           Version: 18.11
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: ethdev
          Assignee: [email protected]
          Reporter: [email protected]

Target Milestone: ---

After running under 10G traffic over 3 days, the X710 card starts showing incorrect RX/TX bytes statistics.

The problem seems to happen because of the following code in i40e_update_vsi_stats:

        /* exclude CRC bytes */
        nes->rx_bytes -= (nes->rx_unicast + nes->rx_multicast +
                nes->rx_broadcast) * ETHER_CRC_LEN;

The rx_bytes counter in X710 cards is 48-bit long, so it takes around 3 days to overflow. When it overflows, it becomes less than (rx_pkts * ETHER_CRC_LEN), and the substruction makes it a negative number, or, to be more precise, a very big positive number, as it's uint64_t.

For XL710 40G cards, it will take less than one day to face the issue.

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