Re: MAC address set requires decision

[Hemant Agrawal]

On 22-Feb-23 11:25 PM, Honnappa Nagarahalli wrote:
-----Original Message-----
From: Richardson, Bruce<bruce.richard...@intel.com>
Sent: Thursday, February 16, 2023 9:05 AM
To: Ferruh Yigit<ferruh.yi...@amd.com>;techbo...@dpdk.org
Cc: Huisong Li<lihuis...@huawei.com>; Chengwen Feng
<fengcheng...@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.yi...@amd.com>
Sent: Thursday, February 16, 2023 2:44 PM
To:techbo...@dpdk.org
Cc: Huisong Li<lihuis...@huawei.com>; Chengwen Feng
<fengcheng...@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-
lihuis...@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