[dpdk-dev] [PATCH v8 2/2] doc: annouce deprecation of jumbo frame flag condition

[Ferruh Yigit]

On 11/2/2020 1:18 PM, Andrew Rybchenko wrote:
> On 11/2/20 11:52 AM, SteveX Yang wrote:
>> Annouce to replace 'RTE_ETHER_MAX_LEN' with 'RTE_ETHER_MTU' as type
>> condition of jumbo frame. Involved scopes:
>> - rte_ethdev;
>> - app, e.g.: test-pmd, test-eventdev;
>> - examples, e.g.: ipsec-secgw, l3fwd, vhost;
>> - net PMDs which support VLAN tag(s) within overhead, e.g.: i40e, ixgbe;
>>
>> Signed-off-by: SteveX Yang <stevex.yang at intel.com>
>> ---
>>   doc/guides/rel_notes/deprecation.rst | 12 ++++++++++++
>>   1 file changed, 12 insertions(+)
>>
>> diff --git a/doc/guides/rel_notes/deprecation.rst 
>> b/doc/guides/rel_notes/deprecation.rst
>> index 2e082499b..fae139f01 100644
>> --- a/doc/guides/rel_notes/deprecation.rst
>> +++ b/doc/guides/rel_notes/deprecation.rst
>> @@ -138,6 +138,18 @@ Deprecation Notices
>>     will be limited to maximum 256 queues.
>>     Also compile time flag ``RTE_ETHDEV_QUEUE_STAT_CNTRS`` will be removed.
>> +* ethdev: Offload flag ``DEV_RX_OFFLOAD_JUMBO_FRAME`` will be set according to
>> +  ``RTE_ETHER_MTU`` in next release. Currently, the jumbo frame uses the
>> +  ``RTE_ETHER_MAX_LEN`` as boundary condition. When the MTU (1500) set, the
>> +  frame type of rx packet will be different if used different overhead, it will
>> +  cause the consistency issue. Hence, using fixed value ``RTE_ETHER_MTU`` can
>> +  avoid this issue.
>> +  Following scopes will be changed:
>> +  - ``rte_ethdev``
>> +  - ``app``, e.g.: ``test-pmd``, ``test-eventdev``;
>> +  - ``examples``, e.g.: ``ipsec-secgw``, ``l3fwd``, ``vhost``;
>> +  - net PMDs which support VLAN tag(s) within overhead, e.g.: ``i40e``;
>> +
>>   * cryptodev: support for using IV with all sizes is added, J0 still can
>>     be used but only when IV length in following structs 
>> ``rte_crypto_auth_xform``,
>>     ``rte_crypto_aead_xform`` is set to zero. When IV length is greater or equal
>>
> 
> If so, what's the point to have the offload? May be just deprecate and
> later remove it?
> 

Above just changes the condition of what is called jumbo frame, nothing more.

ethdev assumes max frame size (without jumbo frame support) can be 
'RTE_ETHER_MAX_LEN' (1518)

But a PMD can support double VLAN, and it can have RTE_ETHER_MAX_LEN + 8 bytes 
frame size and still may not support jumbo frame.

In that case ethdev overwrites the frame size as RTE_ETHER_MAX_LEN, and this 
will reduce the supported MTU to 1492 (instead of expected 1500).
Above deprecation notice is to fix this.