Re: MAC address set requires decision

[Hemant Agrawal <hemant.agrawal@oss.nxp.com>]

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On 22-Feb-23 11:25 PM, Honnappa Nagarahalli wrote:
> -----Original Message-----
>> From: Richardson, Bruce<bruce.richardson@intel.com>
>> Sent: Thursday, February 16, 2023 9:05 AM
>> To: Ferruh Yigit<ferruh.yigit@amd.com>;techboard@dpdk.org
>> Cc: Huisong Li<lihuisong@huawei.com>; Chengwen Feng
>> <fengchengwen@huawei.com>
>> Subject: RE: MAC address set requires decision
>>
>> Alternative suggestions:
>>
>> 1. Don't allow "set" of mac address to value already in the list. The user must
>> delete the entry manually first before adding it. Similarly, "add" fails if no
>> default mac address is set. This ensures consistency by enforcing strict
>> separation between the default mac address and the extra mac addresses.
>> You can't have extra addresses without a default, and you can't have
>> duplicates.
>>
>> 2. Always enforce overlap between the two lists - once default mac address is
>> set (automatically adding it to the mac addresses list), you can only replace
>> the default mac address by using an already-added one to the list. In this
>> case, the default address is only really an index into the address list, and no
>> deletion ever occurs.
>>
>> All the solutions below seem rather mixed to me, I'd rather see either strict
>> overlap, or strict non-overlap. Both these cases make it that you need more
>> calls to do certain tasks, e.g. with #2 to just replace mac address, you need to
>> add, set, then delete, but we can always add new, clearly named APIs, to do
>> these compound ops. On the plus side, with #2 we could make things doubly
>> clear by changing the parameter type of "set" to be an index, rather than
>> explicit mac, to make it clear what is happening, that you are choosing a
>> default mac from a list of pre-configured options.
>>
>> Regards,
>> /Bruce

Both of the above option seems good.The option #1 above is safe, where 
you are making the mac address set as independent of mac filtering. Also 
making sure that mac filter are not messed up. However, the application 
needs to add error handling now to delete and set.

In the option #2,Iassume, it will provide full backward compatibility 
i.e. the ethernet library can take care of the logic and application 
need not to implement anything extra ? If that is the case, it seems to 
be best.

Regards

Hemant


>>> -----Original Message-----
>>> From: Ferruh Yigit<ferruh.yigit@amd.com>
>>> Sent: Thursday, February 16, 2023 2:44 PM
>>> To:techboard@dpdk.org
>>> Cc: Huisong Li<lihuisong@huawei.com>; Chengwen Feng
>>> <fengchengwen@huawei.com>
>>> Subject: MAC address set requires decision
>>>
>>> Hi Board,
>>>
>>> We need a decision on how MAC address set works in DPDK, is it
>>> possible to vote offline so we can proceed with the patch for this release?
>>>
>>>
>>> Can you please select one of:
>>> a) Keep current implementation
>>> b) Proposal 1
>>> c) Proposal 2
>>>
>>> Details below, @Huisong feel free to add/correct if needed.
>>>
>>>
>>>
>>> Background:
>>> DPDK supports multiple MAC address for MAC filtering. MAC addresses
>>> are kept in a list, and index 0 is default MAC address.
>>>
>>> `rte_eth_dev_default_mac_addr_set()` -> sets default MAC [ set() ]
>>> `rte_eth_dev_mac_addr_add()` -> adds MAC to list, if no default MAC
>>> set this adds to index 0 [ add() ] `rte_eth_dev_mac_addr_remove()` ->
>>> remove MAC from list [ del() ]
>>>
>>>
>>> Problem:
>>> When a MAC address is already in the list, if set() called, what will
>>> be the behavior? Like:
>>>
>>> add(MAC1) => MAC1
>>> add(MAC2) => MAC1, MAC2
>>> add(MAC3) => MAC1, MAC2, MAC3
>>> set(MAC2) => ???
>>>
>>>
>>>
>>> Current code behavior:
>>> add(MAC1) => MAC1
>>> add(MAC2) => MAC1, MAC2
>>> add(MAC3) => MAC1, MAC2, MAC3
>>> set(MAC2) => MAC2, MAC2, MAC3
>>>
>>> Problem with current behavior:
>>> - A MAC address is duplicated in list (MAC2), and this leads different
>>> implementation for different PMDs. Some removes MAC2 filter some not.
>>> - Can't delete duplicate, because del() tries to delete first MAC it
>>> finds and since it first finds default MAC address, fails to delete.
>>> (We can fix del() if desicion to keep this implementation.)
>>>
>>>
>>>
>>> Proposal 1 (in the patchwork):
>>> https://patches.dpdk.org/project/dpdk/patch/20230202123625.14975-1-
>>> lihuisong@huawei.com/
>>>
>>> set(MAC) deletes MAC if it is in the list:
>>>
>>> add(MAC1) => MAC1
>>> add(MAC2) => MAC1, MAC2
>>> add(MAC3) => MAC1, MAC2, MAC3
>>> set(MAC2) => MAC2, MAC3
>>> set(MAC3) => MAC3
>>>
>>>
>>> Disagreement on this proposal:
>>> - It causes implicit delete of MAC addresses in the list, so MAC list
>>> may shrink with multiple set() calls, this may be confusing
>>>
>>>
>>>
>>> Proposal 2 (suggested alternative):
>>> set(MAC) {
>>>      if only_default_mac_exist
>>>          replace_default_mac
>>>
>>>      if MAC exists in list
>>> 	swap MAC and list[0]
>>>      else
>>> 	replace_default_mac
>>> }
>>>
>>> Intention here is to prevent implicit delete, swap is just a way to
>>> keep MAC address in the list, like:
>>> add(MAC1) => MAC1
>>> add(MAC2) => MAC1, MAC2
>>> add(MAC3) => MAC1, MAC2, MAC3
>>> set(MAC2) => MAC2, MAC1, MAC3
>>> set(MAC3) => MAC3, MAC1, MAC2
>>>
>>> Disagreement on this proposal:
>>> - It is not clear user expects to keep swapped MAC address.
>>>
>>>
>>> Thanks,
>>> Ferruh

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