On 2/9/2021 3:48 PM, usdutt@xxxxxxxxxxxxxx wrote:
On 2020-12-23 21:59, usdutt@xxxxxxxxxxxxxx wrote:On 2020-12-14 14:55, Arend van Spriel wrote:On 09-12-2020 16:36, Johannes Berg wrote:Hi,Multi-link support is introduced in 802.11be specification.[...] I'll definitely have to take a closer look at this and the spec and think about it - but a couple of quick comments below.Thanks for your comments. Please allow me to address your comments in the subsequent patches. Our main intention through this RFC is to get the view on the proposal to introduce a new NL80211_IFTYPE for an MLO Link. Please suggest on this.Did not get my hands on the spec yet, but just firing random thoughts. This multi-link support sounds a bit like bonding. Could that be leveraged for wireless? I wonder why there is a need for a non-netdev interface. Does networking layer need to be aware of the multi-link for scheduling traffic to it? Is there one driver per multi-link or per radio?The following is what the Bonding driver / interface does for the multiple network interfaces. 1. Bonding driver aggregates multiple network interfaces into a single logical bonded interface. 2. Each network interface is called as a slave in the bonding driver.3. It’s the Bonding driver that schedules the traffic across these slaves.4. Bonding interface operates on one of the following modes ( mentioning for a quick reference ). balance-rr : Round-robin policy: Transmit packets in sequential order from the first available slave through the last. active-backup : Only one slave in the bond is active. A different slave becomes active if, and only if, the active slave fails. balance-xor : Transmit based on the selected transmit hash policy. balance-tlb : channel bonding that does not require any special switch support. The outgoing traffic is distributed according to the current load balance-alb : includes balance-tlb plus receive load balancing. 5. With the above modes, the scheduling of the traffic is determined with in the kernel / bonding driver and have the host driver / firmware follow it. The following are the factors for not considering the MLO Link as a bonding interface and further to propose this RFC (new NL80211_IF_TYPE -> NL80211_IFTYPE_MLO_LINK_DEVICE). 1. For MLO, our intention is to allow the traffic scheduling (among the MLO links) to be closer to the lower layers in the driver/firmware, etc, unlike the bonding driver where kernel schedules the traffic. 2. If MLO Link has to use a bonding interface, each MLO link has to be associated with a network interface and thus eachof the MLO link has to be of NL80211_IF_TYPE -> NL80211_IFTYPE_STATION.3. This further means that NL80211_CONNECT / NL80211_ASSOCIATE needs to get triggered on each of this MLO Link of the MLO connection. 4. Our intention is to consider the MLO station as a single network interface . More specifically, have a single NL80211_CONNECT / NL80211_CMD_ASSOCIATE triggered for each MLO connection ( MLD + MLO Links). 5. The reason we had to introduce a new NL80211_IF_TYPE -> NL80211_IFTYPE_MLO_LINK_DEVICE is to have the corresponding link connection specific information ( e.g., Connection State, Connected BSS Info, Connection Frequency/properties, etc), for each wdev / MLO Link and at the same time have a single connect / association request to the driver / AP. 6. Further, these NL80211_IFTYPE_MLO_LINK_DEVICE link devices shall represent an MLO Link and attribute to a network interface ( MLD ) of an MLO connection. 7. The current proposal to introduce a new NL80211_IF_TYPE should support the architectures of MLO links across the multiple wiphy interfaces or on the same wiphy interface. These wiphy interfaces can be from different drivers too. Please review the above.[...]struct sk_buff *msg; void *hdr; + struct nlattr *nested, *nested_mlo_links; + struct cfg80211_mlo_link_device_params *mlo_link; + int i = 0; msg = nlmsg_new(100 + cr->req_ie_len + cr->resp_ie_len + cr->fils.kek_len + cr->fils.pmk_len + - (cr->fils.pmkid ? WLAN_PMKID_LEN : 0), gfp); + (cr->fils.pmkid ? WLAN_PMKID_LEN : 0) + + (cr->n_mlo_links ? cr->n_mlo_links * 32 : 0), gfp);32 probably should be some NLA_SIZE or something constant?Probably sizeof(*mlo_link) ?There's also no point in the ternary operator since 0 * 32 is 0 :)/* Consumes bss object one way or another */ @@ -833,7 +849,9 @@ void cfg80211_connect_done(struct net_device *dev, ev = kzalloc(sizeof(*ev) + (params->bssid ? ETH_ALEN : 0) + params->req_ie_len + params->resp_ie_len + params->fils.kek_len + params->fils.pmk_len + - (params->fils.pmkid ? WLAN_PMKID_LEN : 0), gfp); + (params->fils.pmkid ? WLAN_PMKID_LEN : 0) + + (params->n_mlo_links ? params->n_mlo_links *+ sizeof(struct cfg80211_mlo_link_device_params) : 0), gfp);same here, no need for the ternary It feels strangely asymmetric to have stop and no start ... but I guess that's the part where I need to think about it and look a bit at how it all works :)Had the same feeling in my gutt (wherever that is ;-)Sure. Will take this point. In fact, this was documented in the commit message to consider the start (say start_mlo_link), but do not want the drivers to depend on this trigger for starting the MLO link. For example, the host drivers with SME can as well start the MLO Link after getting the Assoc response for MLO links from the AP.Regards, ArendHi, Can you please provide your comments on the proposal. We wanted to hear your feedback on the following points.Represent MLO link of an MLO connection by a wdev of type NL80211_IFTYPE_MLO_LINK_DEVICE. MLO link wdev does not have an active netdev associated to it but will be similar to that of NL80211_IFTYPE_STATION, w.r.t maintaining link’s connection information ( connected channel , BSSID, etc). MLD interface of an MLO connection will be a station interface (NL80211_IFTYPE_STATION wdev) This station interface shall link the wdev’s of all the MLO link wdev’s part of the MLO connection. Cfg80211 layer shall link all such wdev’s. Such MLO Link wdev’s shall be part of the same wiphy or different wiphy (if host driver's register a single wiphy for each supported band/MAC/PHY). MLO link wdev (NL80211_IFTYPE_MLO_LINK_DEVICE) is created by the user space prior the MLO connection.
From your explanation earlier it makes more sense to me now.
User space can as well change the interface type among NL80211_IFTYPE_STATION wdev To NL80211_IFTYPE_MLO_LINK_DEVICE wdev. To support the use case where an existing STA wdev can change to a MLO wdev and vice versa.
This seems complicated especially for the "vice versa" scenario where wdevs may be linked to it across different wiphy instances. btw. would that also mean different drivers. I suspect it does, right?
Your explanation seems to focus on the station side of the MLO link, but I think on the AP side one would also setup a MLO link. Would the MLD interface be an AP interface in that case?
Actually, if I am not too confused here then what you call an "MLO link" device is called MLD in the spec.:
"""multi-link device (MLD): A device that is a logical entity and has more than one affiliated station (STA) and has a single medium access control (MAC) service access point (SAP) to logical link control (LLC), which includes one MAC data service.
""" The spec refers to AP MLD and non-AP MLD. Regards, Arend --This electronic communication and the information and any files transmitted with it, or attached to it, are confidential and are intended solely for the use of the individual or entity to whom it is addressed and may contain information that is confidential, legally privileged, protected by privacy laws, or otherwise restricted from disclosure to anyone else. If you are not the intended recipient or the person responsible for delivering the e-mail to the intended recipient, you are hereby notified that any use, copying, distributing, dissemination, forwarding, printing, or copying of this e-mail is strictly prohibited. If you received this e-mail in error, please return the e-mail to the sender, delete it from your computer, and destroy any printed copy of it.
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