| Message ID | 1383684854-21663-2-git-send-email-luciano.coelho@intel.com (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On Tue, 2013-11-05 at 22:54 +0200, Luciano Coelho wrote: > With a CSA count of 0, we won't transmit any CSA beacons, because the > switch will happen before the next TBTT. To avoid extra work and > potential confusion in the drivers, complete the CSA immediately, > instead of waiting for the driver to call ieee80211_csa_finish(). Does it make sense to go to the workqueue rather than do it inline? Maybe we should just reject this? I'm a bit worried that this might confuse drivers that expect a certain order of calls? johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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On Wed, 2013-11-06 at 11:28 +0000, Coelho, Luciano wrote: > In terms of the order of calls, the difference is that in the past we > had this: > > 1. Set CSA beacon; > 2. When count reaches 1, the driver calls ieee80211_csa_finish(); > 3. We call drv_change_chanctx(); > 4. Set new channel beacon. > > (This continues to be the case with my patch when count > 1) > > With my patch, if count <= 1, we do this instead: > > 1. Call drv_change_chanctx(); > 2. Set new channel beacon. > > The main problem without my patch is that the driver shouldn't beacon > with the CSA element when the count starts <= 1, so it won't have a > chance to check if the count reached 1 to call ieee80211_csa_finish(). I think the other difference is that one calls drv_channel_switch_beacon()? The driver might do some channel preparations there, though I guess you can audit all the drivers (well, one ...) :) But that'd need some more documentation, otherwise I'd guess people would start to rely on drv_channel_switch_beacon() and it would mostly work - hence my question of whether it makes sense to refuse it at all in the case of <=1. johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hey Luca, > With a CSA count of 0, we won't transmit any CSA beacons, because the > switch will happen before the next TBTT. To avoid extra work and > potential confusion in the drivers, complete the CSA immediately, > instead of waiting for the driver to call ieee80211_csa_finish(). > > To keep things simpler, we also switch immediately when the CSA count > is 1, while in theory we should delay the switch until just before the > next TBTT. > > Additionally, move the ieee80211_csa_finish() function to cfg.c, > where it makes more sense (and since we call it from cfg.c now). > > Cc: Simon Wunderlich <sw@simonwunderlich.de> > Signed-off-by: Luciano Coelho <luciano.coelho@intel.com> > --- > Simon, I think with this we won't need any changes in ath9k, right? I think you still need to change ieee80211_ibss_process_chanswitch() which also calls ieee80211_ibss_csa_beacon() and drv_channel_switch_beacon(). Also, I don't think that this is sufficient for IBSS mode - changing immediately without sending any action frame will just split the IBSS network. Action frames are currently set in ieee80211_ibss_csa_beacon() as well, with this change we should probably move that to another position. Even if we don't allow count <=1 from userspace as Johannes suggested, we still have to fix the CSA handling from other STAs in IBSS. Cheers, Simon -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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On Wed, 2013-11-06 at 11:52 +0000, Coelho, Luciano wrote: > Right. I actually added this to the documentation, but I accidentally > sent it as part of patch 1/2: > > > +++ b/include/net/mac80211.h > > @@ -2676,11 +2676,13 @@ enum ieee80211_roc_type { > > * @channel_switch_beacon: Starts a channel switch to a new channel. > [...] > > + * If the CSA count starts as zero or 1, this function will not be called, > > + * since there won't be any time to beacon before the switch anyway. > > This change should be in patch 2/2 (actually these two patches should > probably be squashed, I just kept them separate so that reviewing my v2 > would be easier). > > I can elaborate more in the documentation if you think it's necessary. Ah, ok, I guess that's fine. johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, 2013-11-06 at 12:03 +0000, Coelho, Luciano wrote: > > Even if we don't allow count <=1 from userspace as Johannes suggested, > > Ah, I had misunderstood Johannes. I thought he meant to reject the > patch. :P > > Rejecting count <= 1 could be a temporary solution until we implement > the action frames properly. Unless we decide that the action frames > should be handled in userspace as you proposed. Well even then - the question is who would ever want to use and test count<=1? johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, 2013-11-06 at 13:06 +0100, Johannes Berg wrote: > On Wed, 2013-11-06 at 12:03 +0000, Coelho, Luciano wrote: > > > > Even if we don't allow count <=1 from userspace as Johannes suggested, > > > > Ah, I had misunderstood Johannes. I thought he meant to reject the > > patch. :P > > > > Rejecting count <= 1 could be a temporary solution until we implement > > the action frames properly. Unless we decide that the action frames > > should be handled in userspace as you proposed. > > Well even then - the question is who would ever want to use and test > count<=1? I guess the reason to have this is when you must evacuate the channel immediately, so you transmit the action frame and jump out. If your beacon interval is long (for whatever reason), waiting for the next TBTT to announce the CSA may take longer than the time required to stop transmitting. Also, in a "stop transmitting immediately" scenario, using an action frame with count <= 1 helps reduce data hiccups that would happen if count > 1 and the channel switch mode is "don't transmit". -- Luca.
On Wed, 2013-11-06 at 12:22 +0000, Coelho, Luciano wrote: > > Well even then - the question is who would ever want to use and test > > count<=1? > > I guess the reason to have this is when you must evacuate the channel > immediately, so you transmit the action frame and jump out. If your > beacon interval is long (for whatever reason), waiting for the next TBTT > to announce the CSA may take longer than the time required to stop > transmitting. Fair point, so I guess we'd want to also test that :) johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c index b0a651c..fe5de2c 100644 --- a/net/mac80211/cfg.c +++ b/net/mac80211/cfg.c @@ -2854,6 +2854,15 @@ cfg80211_beacon_dup(struct cfg80211_beacon_data *beacon) return new_beacon; } +void ieee80211_csa_finish(struct ieee80211_vif *vif) +{ + struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif); + + ieee80211_queue_work(&sdata->local->hw, + &sdata->csa_finalize_work); +} +EXPORT_SYMBOL(ieee80211_csa_finish); + void ieee80211_csa_finalize_work(struct work_struct *work) { struct ieee80211_sub_if_data *sdata = @@ -2912,7 +2921,7 @@ static int ieee80211_channel_switch(struct wiphy *wiphy, struct net_device *dev, struct ieee80211_local *local = sdata->local; struct ieee80211_chanctx_conf *chanctx_conf; struct ieee80211_chanctx *chanctx; - int err, num_chanctx; + int err, num_chanctx, changed = 0; if (!list_empty(&local->roc_list) || local->scanning) return -EBUSY; @@ -2951,19 +2960,42 @@ static int ieee80211_channel_switch(struct wiphy *wiphy, struct net_device *dev, switch (sdata->vif.type) { case NL80211_IFTYPE_AP: - sdata->csa_counter_offset_beacon = - params->counter_offset_beacon; - sdata->csa_counter_offset_presp = params->counter_offset_presp; sdata->u.ap.next_beacon = cfg80211_beacon_dup(¶ms->beacon_after); if (!sdata->u.ap.next_beacon) return -ENOMEM; + /* + * With a count of 0, we don't have to wait for any + * TBTT before switching, so complete the CSA + * immediately. In theory, with a count == 1 we + * should delay the switch until just before the next + * TBTT, but that would complicate things so we switch + * immediately too. If we would delay the switch + * until the next TBTT, we would have to set the probe + * response here. + * + * TODO: A channel switch with count <= 1 without + * sending a CSA action frame is kind of useless, + * because the clients won't know we're changing + * channels. The action frame must be implemented + * either here or in the userspace. + */ + if (params->count <= 1) { + ieee80211_csa_finish(&sdata->vif); + break; + } + + sdata->csa_counter_offset_beacon = + params->counter_offset_beacon; + sdata->csa_counter_offset_presp = params->counter_offset_presp; err = ieee80211_assign_beacon(sdata, ¶ms->beacon_csa); if (err < 0) { kfree(sdata->u.ap.next_beacon); return err; } + changed |= err; + break; case NL80211_IFTYPE_ADHOC: if (!sdata->vif.bss_conf.ibss_joined) @@ -2991,9 +3023,17 @@ static int ieee80211_channel_switch(struct wiphy *wiphy, struct net_device *dev, params->chandef.chan->band) return -EINVAL; + /* see comments and TODO in the NL80211_IFTYPE_AP block */ + if (params->count <= 1) { + ieee80211_csa_finish(&sdata->vif); + break; + } + err = ieee80211_ibss_csa_beacon(sdata, params); if (err < 0) return err; + changed |= err; + break; default: return -EOPNOTSUPP; @@ -3009,8 +3049,10 @@ static int ieee80211_channel_switch(struct wiphy *wiphy, struct net_device *dev, local->csa_chandef = params->chandef; sdata->vif.csa_active = true; - ieee80211_bss_info_change_notify(sdata, err); - drv_channel_switch_beacon(sdata, ¶ms->chandef); + ieee80211_bss_info_change_notify(sdata, changed); + + if (params->count > 1) + drv_channel_switch_beacon(sdata, ¶ms->chandef); return 0; } diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c index 1e0d40f..ac4b79f 100644 --- a/net/mac80211/tx.c +++ b/net/mac80211/tx.c @@ -2343,15 +2343,6 @@ static int ieee80211_beacon_add_tim(struct ieee80211_sub_if_data *sdata, return 0; } -void ieee80211_csa_finish(struct ieee80211_vif *vif) -{ - struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif); - - ieee80211_queue_work(&sdata->local->hw, - &sdata->csa_finalize_work); -} -EXPORT_SYMBOL(ieee80211_csa_finish); - static void ieee80211_update_csa(struct ieee80211_sub_if_data *sdata, struct beacon_data *beacon) {
With a CSA count of 0, we won't transmit any CSA beacons, because the switch will happen before the next TBTT. To avoid extra work and potential confusion in the drivers, complete the CSA immediately, instead of waiting for the driver to call ieee80211_csa_finish(). To keep things simpler, we also switch immediately when the CSA count is 1, while in theory we should delay the switch until just before the next TBTT. Additionally, move the ieee80211_csa_finish() function to cfg.c, where it makes more sense (and since we call it from cfg.c now). Cc: Simon Wunderlich <sw@simonwunderlich.de> Signed-off-by: Luciano Coelho <luciano.coelho@intel.com> --- Simon, I think with this we won't need any changes in ath9k, right? --- net/mac80211/cfg.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++------ net/mac80211/tx.c | 9 --------- 2 files changed, 48 insertions(+), 15 deletions(-)