[Bug 1125] i40e: Tx offload for outer UDP checksum is advertised but in fact unsupported

[Bug 1125] i40e: Tx offload for outer UDP checksum is advertised but in fact unsupported

[bugzilla]

https://bugs.dpdk.org/show_bug.cgi?id=1125

            Bug ID: 1125
           Summary: i40e: Tx offload for outer UDP checksum is advertised
                    but in fact unsupported
           Product: DPDK
           Version: unspecified
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: ethdev
          Assignee: dev@dpdk.org
          Reporter: ivan.malov@oktetlabs.ru
  Target Milestone: ---

In the opensource ethdev verification suite [1], there is a test,
xmit/one_packet, which is tailored specifically for Tx offload checks. In the
case of i40e, the test finds a bug in encap. TSO support.

As shown in [2], a VXLAN packet with TSO request is transmitted, and resulting
packets mismatch because of the wrong checksum in the outer UDP header (it is
the same as the one in the original superframe). However, since the test sees
capability bit TX_OFFLOAD_OUTER_UDP_CKSUM in device info, the checksum is
expected to be offloaded.

According to Intel(R) Ethernet Controller X710/ XXV710/XL710 Datasheet, section
8.4.4.2, "Tunneling UDP headers and GRE header are not offloaded while the
X710/XXV710/XL710 leaves their checksum field as is". That means the i40e PMD
shall not advertise TX_OFFLOAD_OUTER_UDP_CKSUM capability via device info API.

[1] https://mails.dpdk.org/archives/dev/2022-October/251663.html
[2] https://ts-factory.io/bublik/v2/log/163204?focusId=165783&mode=treeAndlog

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