[Bug 1111] i40e: buffer size fields may overflow in Rx descriptors

[bugzilla at dpdk.org]

https://bugs.dpdk.org/show_bug.cgi?id=1111

            Bug ID: 1111
           Summary: i40e: buffer size fields may overflow in Rx
                    descriptors
           Product: DPDK
           Version: unspecified
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: ethdev
          Assignee: dev at dpdk.org
          Reporter: ivan.malov at oktetlabs.ru
  Target Milestone: ---

Created attachment 226
  --> https://bugs.dpdk.org/attachment.cgi?id=226&action=edit
probable-fix

It appears that opensource ethdev tests [1] have detected a bug in
i40e PMD: by the looks of it, Rx descriptor fill-out is not robust
against overflow in data buffer size field, which happens when the
user provides a mempool with excessively large objects on Rx setup.

A test log example can be found at [2]. In it, a mempool with mbuf
data size of 32900 B is used. The test sends one packet to the NIC,
but the PMD sees 5 packets which have no payload. Manual debugging
indicates that, in the driver, round-up gives the value of 32768 B,
which then gives the value of 256 to use in 7-bit "dbuff" field of
an Rx descriptor ([3]). The value overflows, hence the test result.

A probable fix is attached to the ticket.

[1] http://mails.dpdk.org/archives/dev/2022-October/251663.html
[2] https://ts-factory.io/bublik/v2/log/123183?focusId=123879&mode=treeAndlog
[3]
https://github.com/DPDK/dpdk/blob/main/drivers/net/i40e/base/i40e_lan_hmc.c#L709

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