[PATCH 05/22] hostapd: MLO: handle auth/assoc on link address

[Aditya Kumar Singh]

On 4/16/24 13:35, Jouni Malinen wrote:
> On Thu, Mar 28, 2024 at 11:46:35PM +0530, Aditya Kumar Singh wrote:
>> Modify authentication and association frames to be always sent with link
>> address as A1 and A3 for ease of Tx status handling.
> 
> It would be nice to get a bit more complete commit message that explains
> why this can be done. Surely there was some reason for the previous more
> complex design..
> 

Okay. So, if we see mlme_event_mgmt_tx_status(), link_id will be only 
filled if the frame was the last transmitted on the whole drv level.
For single MLD this approach is fine. But when considering multiple 
MLDs, there could be cases where multiple packets are sent out by 
various interfaces (BSS) under same drv. Now while handling the Tx 
status, only one interface will get the proper link_id. Rest all will 
get -1, and event will be routed to first BSS always. Now there is a 
possibility of frame getting dropped due to this since it is not routed 
to correct link hapd.

Hence to make it convenient, it is better to pass A1, A3 as link 
address. Since via A3, in get_hapd_bssid(), your hapd->own_addr would 
match and proper link hapd will be selected even when link_id is not 
present.

>> diff --git a/src/ap/ieee802_11.c b/src/ap/ieee802_11.c
> 
>> @@ -444,7 +437,7 @@ static int send_auth_reply(struct hostapd_data *hapd, struct sta_info *sta,
>> -	os_memcpy(reply->bssid, bssid, ETH_ALEN);
>> +	os_memcpy(reply->bssid, sa, ETH_ALEN);
> 
> This removes the only use of bssid in send_auth_reply(). Is that really
> correct for all cases? It might be, but again, this needs more
> justification in the commit message.

As said above, in order to ensure link_address only returns back in A3 
during Tx status, we have to ensure we are filling link address in the 
packet being sent. Hence the above change.

This was the place where issue was there when handling co-hosted MLDs 
hence made changes only here as of now. With more thorough testing, if 
needed will change as other places as well.

> In addition, this should remove the
> bssid argument from this function and potentially in a number of calling
> functions as well since all the would now be unused.

Yeah sure. So if you agree, I will send out a clean up patch separately?