Re: [PATCH 24/27] wifi: mac80211: implement link switching

[Wen Gong <quic_wgong@quicinc.com>]

On 9/2/2022 10:12 PM, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@intel.com>
>
> Implement an API function and debugfs file to switch
> active links.
>
> Also provide an async version of the API so drivers
> can call it in arbitrary contexts, e.g. while in the
> authorized callback.
>
> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
> ---
>   include/net/mac80211.h        |  41 ++++++++
>   net/mac80211/debugfs_netdev.c |  26 ++++++
>   net/mac80211/ieee80211_i.h    |   4 +
>   net/mac80211/iface.c          |  12 +++
>   net/mac80211/key.c            |  34 +++++++
>   net/mac80211/key.h            |   3 +
>   net/mac80211/link.c           | 171 ++++++++++++++++++++++++++++++++++
>   7 files changed, 291 insertions(+)
>
> ...
> +static int _ieee80211_set_active_links(struct ieee80211_sub_if_data *sdata,
> +				       u16 active_links)
> +{
> +	struct ieee80211_bss_conf *link_confs[IEEE80211_MLD_MAX_NUM_LINKS];
> +	struct ieee80211_local *local = sdata->local;
> +	u16 old_active = sdata->vif.active_links;
> +	unsigned long rem = old_active & ~active_links;
> +	unsigned long add = active_links & ~old_active;
> +	struct sta_info *sta;
> +	unsigned int link_id;
> +	int ret, i;
> +
> +	if (!ieee80211_sdata_running(sdata))
> +		return -ENETDOWN;
> +
> +	if (sdata->vif.type != NL80211_IFTYPE_STATION)
> +		return -EINVAL;
> +
> +	/* cannot activate links that don't exist */
> +	if (active_links & ~sdata->vif.valid_links)
> +		return -EINVAL;
> +
> +	/* nothing to do */
> +	if (old_active == active_links)
> +		return 0;
> +
> +	for (i = 0; i < IEEE80211_MLD_MAX_NUM_LINKS; i++)
> +		link_confs[i] = sdata_dereference(sdata->vif.link_conf[i],
> +						  sdata);
> +
> +	if (add) {
> +		sdata->vif.active_links |= active_links;
> +		ret = drv_change_vif_links(local, sdata,
> +					   old_active,
> +					   sdata->vif.active_links,
> +					   link_confs);
> +		if (ret) {
> +			sdata->vif.active_links = old_active;
> +			return ret;
> +		}
> +	}
> +
> +	for_each_set_bit(link_id, &rem, IEEE80211_MLD_MAX_NUM_LINKS) {
> +		struct ieee80211_link_data *link;
> +
> +		link = sdata_dereference(sdata->link[link_id], sdata);
> +
> +		/* FIXME: kill TDLS connections on the link */
> +
> +		ieee80211_link_release_channel(link);
> +	}
> +
> +	list_for_each_entry(sta, &local->sta_list, list) {
> +		if (sdata != sta->sdata)
> +			continue;
> +		ret = drv_change_sta_links(local, sdata, &sta->sta,
> +					   old_active,
> +					   old_active | active_links);
> +		WARN_ON_ONCE(ret);
> +	}
> +
> +	ret = ieee80211_key_switch_links(sdata, rem, add);

I see ieee80211_key_switch_link() only handler the per-link(link_id >= 
0) keys,

So I think lower driver also install the pairwise keys(link_id = -1) for 
the added links at this moment?

> +	WARN_ON_ONCE(ret);
> +
> +	list_for_each_entry(sta, &local->sta_list, list) {
> +		if (sdata != sta->sdata)
> +			continue;
> +		ret = drv_change_sta_links(local, sdata, &sta->sta,
> +					   old_active | active_links,
> +					   active_links);
> +		WARN_ON_ONCE(ret);
> +	}
> +

I see 2 times to call drv_change_sta_link() above, and with sequence  
old_active->old_active | active_links->active_links

May I know is it has some design here?

> +	for_each_set_bit(link_id, &add, IEEE80211_MLD_MAX_NUM_LINKS) {
> +		struct ieee80211_link_data *link;
> +
> +		link = sdata_dereference(sdata->link[link_id], sdata);
> +
> +		ret = ieee80211_link_use_channel(link, &link->conf->chandef,
> +						 IEEE80211_CHANCTX_SHARED);

For the 1st link of MLO connection/NON-MLO connetion, ieee80211_link_use_channel() is called before drv_change_sta_link(),
And now it is after drv_change_sta_link(), May I know is it also has some design here?

Also I see commit(8fb7e2ef4bab mac80211_hwsim: always activate all links) and ieee80211_if_parse_active_links()
will use ieee80211_set_active_links(), so I think ieee80211_set_active_links() has passed test case with some type lower driver/chip?

> +		WARN_ON_ONCE(ret);
> +
> +		ieee80211_link_info_change_notify(sdata, link,
> +						  BSS_CHANGED_ERP_CTS_PROT |
> +						  BSS_CHANGED_ERP_PREAMBLE |
> +						  BSS_CHANGED_ERP_SLOT |
> +						  BSS_CHANGED_HT |
> +						  BSS_CHANGED_BASIC_RATES |
> +						  BSS_CHANGED_BSSID |
> +						  BSS_CHANGED_CQM |
> +						  BSS_CHANGED_QOS |
> +						  BSS_CHANGED_TXPOWER |
> +						  BSS_CHANGED_BANDWIDTH |
> +						  BSS_CHANGED_TWT |
> +						  BSS_CHANGED_HE_OBSS_PD |
> +						  BSS_CHANGED_HE_BSS_COLOR);
> +		ieee80211_mgd_set_link_qos_params(link);
> +	}
> +
> +	old_active = sdata->vif.active_links;
> +	sdata->vif.active_links = active_links;
> +
> +	if (rem) {
> +		ret = drv_change_vif_links(local, sdata, old_active,
> +					   active_links, link_confs);
> +		WARN_ON_ONCE(ret);
> +	}
> +
> +	return 0;
> +}
> +
...