On Thu, Apr 28, 2022 at 02:36:26PM +0200, Johannes Berg wrote: > However, I'm starting to have second thoughts on this. > > I do understand the concern that Jouni mentioned, that the device might > roam by itself, and change the underlying links, and you'd have races if > you identify only by the link ID, and that just changed, and so now > you're referring to something else. His suggestion was that we might > need to include the BSSID or the address of the AP MLD, or such, in some > cases. [1] > > However, if e.g. roaming is offloaded but the supplicant isn't, then we > really do need the ability to refer to the link ID, e.g. to set the per > link GTK/IGTK/BIGTK after the 4-way-HS (or later 2-way-HS). > > So now I'm wondering what we're achieving by having a mapping, if every > component in the system needs to be aware of the mapping? There are use cases where over-the-air Link ID is used and other cases where it is more appropriate to identify the local link based on the band (or subband, etc.) in a manner that is valid over one or multiple associations. It might actually make more sense to come up with two nl80211 attributes for identifying a link based on either the over-the-air Link ID (which is valid only during an association and can change whenever roaming occurs) or the internal identifier for a link. This would allow nl80211 commands to use only one of the possible ways of identifying link so that user space components would not need to know or care about the mapping and would just use the variant that is easier for the particular case. For nl80211 event messages, both attributes could be included since the driver and/or cfg80211 would know the mapping and could fill in both options so that the user space components would not need to be aware of the full mapping. In addition, there seems to still be some open discussion on how various Management frames are targeting specific links and that might even result in there being a protocol mechanism for targeting a subset of the available links, i.e., not all of MLD but one or more links. I'm not sure whether this would need anything particular in nl80211 since we could always send multiple copies of the command/event (one per link), but it might also be convenient to be able to use an array of the over-the-air and/or internal identifiers for the links. -- Jouni Malinen PGP id EFC895FA
