Hi,
So I've looked at this patch a few times, but it just confuses me ...
On Thu, 2022-12-22 at 17:13 +0800, Michael Lee wrote:
> When the link fails to use the channel, chandef's bandwidth will be
> downgraded without checking the control channel.
> The issue happens when the STA of an extender with limited channel
> context associates with a root AP operating on a different channel.
>
> Below is an example:
>
> ______________ ________________
> | RootAP(ch36) | | Extender(ch44) |
> | | (ASSOC) | AP |
> | AP <-------------------- STA |
> |______________| |________________|
>
> - RootAP is operating on channel 36, while Extender is operating
> on channel 44
What does this matter? The extended is just a STA, no? Or are you saying
it's important that the extender has a concurrent AP interface that's on
channel 44?
And if you say "ch36" or "ch44" that's just the control channel (I
guess), but what's the actual complete channel configuration?
> - When associating with RootAP, Extender-STA downgrades the
> chandef's bandwidth to be compatible with any channels on the phy
What do you mean by "on the phy" here? That's not mac80211 terminology,
so not sure.
> - Finally, chandef's bandwidth is downgraded to 20MHz and
> the association fails
>
> In this patch, a control channel checking is added to avoid unnecessary
> bandwidth downgrading
>
> Signed-off-by: Michael Lee <michael-cy.lee@xxxxxxxxxxxx>
> ---
> net/mac80211/mlme.c | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
> index 0aee2392dd29..bc435e8508e2 100644
> --- a/net/mac80211/mlme.c
> +++ b/net/mac80211/mlme.c
> @@ -4616,6 +4616,27 @@ ieee80211_verify_sta_he_mcs_support(struct ieee80211_sub_if_data *sdata,
> return false;
> }
>
> +static bool
> +ieee80211_check_same_ctrl_channel(struct ieee80211_sub_if_data *sdata,
> + const struct cfg80211_chan_def *chandef)
> +{
> + struct ieee80211_local *local = sdata->local;
> + struct ieee80211_chanctx *ctx;
> +
> + mutex_lock(&local->chanctx_mtx);
> + list_for_each_entry(ctx, &local->chanctx_list, list) {
> + if (ctx->replace_state == IEEE80211_CHANCTX_WILL_BE_REPLACED)
> + continue;
> + if (ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE)
> + continue;
> + if (chandef->chan == ctx->conf.def.chan)
> + return true;
> + }
> +
> + mutex_unlock(&local->chanctx_mtx);
> + return false;
> +}
> +
> static int ieee80211_prep_channel(struct ieee80211_sub_if_data *sdata,
> struct ieee80211_link_data *link,
> struct cfg80211_bss *cbss,
> @@ -4842,6 +4863,9 @@ static int ieee80211_prep_channel(struct ieee80211_sub_if_data *sdata,
> chandef.width == NL80211_CHAN_WIDTH_10)
> goto out;
>
> + if (!ret || !ieee80211_check_same_ctrl_channel(sdata, &chandef))
> + goto out;
Not sure I get how this is any different - you're describing a case
where "ret != 0" (because if ret == 0 nothing happens in the while
loop), so then you fail _anyway_? So what's the point?
johannes
