[PATCHv2 0/3] add IBSS-DFS support

[PATCHv2 0/3] add IBSS-DFS support

[Simon Wunderlich]

This patchset adds DFS support for the IBSS mode. It builds on top of
the previously sent AP DFS mode and channel switch announcement support.

Changes to the previous patchset:
 * describe userspace requirements better in doc and commit message 
   (suggested by Johannes)
 * change variable/attribute names
 * first patch has already been merged, dropped from this patchset
 * safeguard as suggested by Johannes (to protect from crashed/hanging
   userspace) has NOT yet been implemented. I'll probably send a patch for
   this later, as this might be useful for AP mode as well.

The implementation differs from the DFS support as described in IEEE 802.11.
It does not implement the DFS owner service or uses IBSS DFS elements as
described in IEEE 802.11-2012 10.9.8.3. The DFS owner service has various
shortcomings:

 * it requires synchronization to find one central IBSS owner
 * citation: "The potential for hidden nodes within an IBSS means that the
   IBSS channel switch protocol is best effort."
 * the mechanism does not provide any way to handle big adhoc cells like
   mesh networks (which is a major target).

Therefore, a stripped down approach is implemented:

 * userspace must announce that it wants support for DFS and will handle
   events using a flag for the ibss_join command.
 * if a radar is detected, inform userspace. Userspace should then select
   a channel (e.g. decide on it with the peers on higher level protocols
   before, or wait a random backoff time) and start a channel switch process.
 * if a channel switch announcement from another peeris received, adopt it
   and re-transmit it (this has been implemented in the IBSS-CSA patchset
   before)
 * channel switch announcements on DFS channels are interpreted as
   radar signals and will mark the channel as unusable.

As always, any comments are appreciated.

Cheers,
        Simon


Simon Wunderlich (3):
  nl80211/cfg80211: enable DFS for IBSS mode
  mac80211: enable DFS for IBSS mode
  ath9k: enable DFS for IBSS mode

 drivers/net/wireless/ath/ath9k/init.c |    3 +-
 include/net/cfg80211.h                |    6 ++++
 include/uapi/linux/nl80211.h          |    9 ++++++
 net/mac80211/ibss.c                   |   49 +++++++++++++++++++++++++++++----
 net/mac80211/ieee80211_i.h            |    1 +
 net/wireless/chan.c                   |    3 +-
 net/wireless/ibss.c                   |   24 +++++++++++++---
 net/wireless/nl80211.c                |    8 ++++--
 net/wireless/util.c                   |   11 ++++++--
 9 files changed, 99 insertions(+), 15 deletions(-)

-- 
1.7.10.4

[PATCHv2 1/3] nl80211/cfg80211: enable DFS for IBSS mode

[Simon Wunderlich]

To use DFS in IBSS mode, userspace is required to react to radar events.
It can inform nl80211 that it is capable of doing so by adding a
NL80211_ATTR_DFS_CAPABLE attribute when joining the IBSS.

This attribute is supplied to let the kernelspace know that the
userspace application can and will handle radar events, e.g. by
intiating channel switches to a valid channel. DFS channels may
only be used if this attribute is supplied and the driver supports
it. Driver support will be checked even if a channel without DFS
will be initially joined, as a DFS channel may be chosen later.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
---
Changes to PATCHv1:
 * rename NL80211_ATTR_CONTROL_PORT_DFS to NL80211_ATTR_DFS_CAPABLE
   and the if_ibss variable accordingly
 * rework commit message and nl80211.h kerneldoc to describe
   requirements better.
---
 include/net/cfg80211.h       |    6 ++++++
 include/uapi/linux/nl80211.h |    9 +++++++++
 net/wireless/chan.c          |    3 ++-
 net/wireless/ibss.c          |   24 ++++++++++++++++++++----
 net/wireless/nl80211.c       |    8 ++++++--
 net/wireless/util.c          |   11 +++++++++--
 6 files changed, 52 insertions(+), 9 deletions(-)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 12e4a14..0bcdb3c 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -1656,6 +1656,9 @@ struct cfg80211_disassoc_request {
  *	sets/clears %NL80211_STA_FLAG_AUTHORIZED. If true, the driver is
  *	required to assume that the port is unauthorized until authorized by
  *	user space. Otherwise, port is marked authorized by default.
+ * @userspace_handles_dfs: whether user space controls DFS operation, i.e.
+ *	changes the channel when a radar is detected. This is required
+ *	to operate on DFS channels.
  * @basic_rates: bitmap of basic rates to use when creating the IBSS
  * @mcast_rate: per-band multicast rate index + 1 (0: disabled)
  * @ht_capa:  HT Capabilities over-rides.  Values set in ht_capa_mask
@@ -1673,6 +1676,7 @@ struct cfg80211_ibss_params {
 	bool channel_fixed;
 	bool privacy;
 	bool control_port;
+	bool userspace_handles_dfs;
 	int mcast_rate[IEEE80211_NUM_BANDS];
 	struct ieee80211_ht_cap ht_capa;
 	struct ieee80211_ht_cap ht_capa_mask;
@@ -3053,6 +3057,7 @@ struct cfg80211_cached_keys;
  * @conn: (private) cfg80211 software SME connection state machine data
  * @connect_keys: (private) keys to set after connection is established
  * @ibss_fixed: (private) IBSS is using fixed BSSID
+ * @ibss_dfs_possible: (private) IBSS may change to a DFS channel
  * @event_list: (private) list for internal event processing
  * @event_lock: (private) lock for event list
  */
@@ -3091,6 +3096,7 @@ struct wireless_dev {
 	struct ieee80211_channel *channel;
 
 	bool ibss_fixed;
+	bool ibss_dfs_possible;
 
 	bool ps;
 	int ps_timeout;
diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h
index fde2c02..e1cff4e 100644
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -1496,6 +1496,13 @@ enum nl80211_commands {
  * @NL80211_ATTR_RXMGMT_FLAGS: flags for nl80211_send_mgmt(), u32.
  *	As specified in the &enum nl80211_rxmgmt_flags.
  *
+ * @NL80211_ATTR_HANDLE_DFS: A flag indicating whether user space
+ *	controls DFS operation in IBSS mode. If the flag is included in
+ *	%NL80211_CMD_JOIN_IBSS request, the driver will allow use of DFS
+ *	channels and reports radar events to userspace. Userspace is required
+ *	to react to radar events, e.g. initiate a channel switch or leave the
+ *	IBSS network.
+ *
  * @NL80211_ATTR_MAX: highest attribute number currently defined
  * @__NL80211_ATTR_AFTER_LAST: internal use
  */
@@ -1806,6 +1813,8 @@ enum nl80211_attrs {
 
 	NL80211_ATTR_RXMGMT_FLAGS,
 
+	NL80211_ATTR_HANDLE_DFS,
+
 	/* add attributes here, update the policy in nl80211.c */
 
 	__NL80211_ATTR_AFTER_LAST,
diff --git a/net/wireless/chan.c b/net/wireless/chan.c
index 80504e6..92cf75f 100644
--- a/net/wireless/chan.c
+++ b/net/wireless/chan.c
@@ -504,7 +504,8 @@ cfg80211_get_chan_state(struct wireless_dev *wdev,
 	case NL80211_IFTYPE_ADHOC:
 		if (wdev->current_bss) {
 			*chan = wdev->current_bss->pub.channel;
-			*chanmode = wdev->ibss_fixed
+			*chanmode = (wdev->ibss_fixed &&
+				     !wdev->ibss_dfs_possible)
 				  ? CHAN_MODE_SHARED
 				  : CHAN_MODE_EXCLUSIVE;
 			return;
diff --git a/net/wireless/ibss.c b/net/wireless/ibss.c
index 39bff7d..fa7461b 100644
--- a/net/wireless/ibss.c
+++ b/net/wireless/ibss.c
@@ -83,6 +83,8 @@ int __cfg80211_join_ibss(struct cfg80211_registered_device *rdev,
 			 struct cfg80211_cached_keys *connkeys)
 {
 	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct ieee80211_channel *check_chan;
+	u8 radar_detect_width = 0;
 	int err;
 
 	ASSERT_WDEV_LOCK(wdev);
@@ -114,14 +116,28 @@ int __cfg80211_join_ibss(struct cfg80211_registered_device *rdev,
 	wdev->connect_keys = connkeys;
 
 	wdev->ibss_fixed = params->channel_fixed;
+	wdev->ibss_dfs_possible = params->userspace_handles_dfs;
 #ifdef CONFIG_CFG80211_WEXT
 	wdev->wext.ibss.chandef = params->chandef;
 #endif
+	check_chan = params->chandef.chan;
+	if (params->userspace_handles_dfs) {
+		/* use channel NULL to check for radar even if the current
+		 * channel is not a radar channel - it might decide to change
+		 * to DFS channel later.
+		 */
+		radar_detect_width = BIT(params->chandef.width);
+		check_chan = NULL;
+	}
+
+	err = cfg80211_can_use_iftype_chan(rdev, wdev, wdev->iftype,
+					   check_chan,
+					   (params->channel_fixed &&
+					    !radar_detect_width)
+					   ? CHAN_MODE_SHARED
+					   : CHAN_MODE_EXCLUSIVE,
+					   radar_detect_width);
 
-	err = cfg80211_can_use_chan(rdev, wdev, params->chandef.chan,
-				    params->channel_fixed
-				    ? CHAN_MODE_SHARED
-				    : CHAN_MODE_EXCLUSIVE);
 	if (err) {
 		wdev->connect_keys = NULL;
 		return err;
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 2838206..38618ee 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -354,6 +354,7 @@ static const struct nla_policy nl80211_policy[NL80211_ATTR_MAX+1] = {
 	[NL80211_ATTR_CSA_IES] = { .type = NLA_NESTED },
 	[NL80211_ATTR_CSA_C_OFF_BEACON] = { .type = NLA_U16 },
 	[NL80211_ATTR_CSA_C_OFF_PRESP] = { .type = NLA_U16 },
+	[NL80211_ATTR_HANDLE_DFS] = { .type = NLA_FLAG },
 };
 
 /* policy for the key attributes */
@@ -5722,9 +5723,9 @@ skip_beacons:
 	if (!cfg80211_reg_can_beacon(&rdev->wiphy, &params.chandef))
 		return -EINVAL;
 
-	/* DFS channels are only supported for AP/P2P GO ... for now. */
 	if (dev->ieee80211_ptr->iftype == NL80211_IFTYPE_AP ||
-	    dev->ieee80211_ptr->iftype == NL80211_IFTYPE_P2P_GO) {
+	    dev->ieee80211_ptr->iftype == NL80211_IFTYPE_P2P_GO ||
+	    dev->ieee80211_ptr->iftype == NL80211_IFTYPE_ADHOC) {
 		err = cfg80211_chandef_dfs_required(wdev->wiphy,
 						    &params.chandef);
 		if (err < 0) {
@@ -6556,6 +6557,9 @@ static int nl80211_join_ibss(struct sk_buff *skb, struct genl_info *info)
 	ibss.control_port =
 		nla_get_flag(info->attrs[NL80211_ATTR_CONTROL_PORT]);
 
+	ibss.userspace_handles_dfs =
+		nla_get_flag(info->attrs[NL80211_ATTR_HANDLE_DFS]);
+
 	err = cfg80211_join_ibss(rdev, dev, &ibss, connkeys);
 	if (err)
 		kfree(connkeys);
diff --git a/net/wireless/util.c b/net/wireless/util.c
index 3c8be61..6b027df 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -1264,8 +1264,15 @@ int cfg80211_can_use_iftype_chan(struct cfg80211_registered_device *rdev,
 	case NL80211_IFTYPE_MESH_POINT:
 	case NL80211_IFTYPE_P2P_GO:
 	case NL80211_IFTYPE_WDS:
-		radar_required = !!(chan &&
-				    (chan->flags & IEEE80211_CHAN_RADAR));
+		/* if the interface could potentially choose a DFS channel,
+		 * then mark DFS as required.
+		 */
+		if (!chan) {
+			if (chanmode != CHAN_MODE_UNDEFINED && radar_detect)
+				radar_required = true;
+			break;
+		}
+		radar_required = !!(chan->flags & IEEE80211_CHAN_RADAR);
 		break;
 	case NL80211_IFTYPE_P2P_CLIENT:
 	case NL80211_IFTYPE_STATION:
-- 
1.7.10.4

[PATCHv2 2/3] mac80211: enable DFS for IBSS mode

[Simon Wunderlich]

Allow changing to DFS channels if the channel is available for
beaconing and userspace controls DFS operation.

Channel switch announcement from other stations on DFS channels will
be interpreted as radar event. These channels will then be marked as
unvailable.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
---
Changes to PATCHv1:
 * rename control_port_dfs to userspace_handles_dfs
---
 net/mac80211/ibss.c        |   49 +++++++++++++++++++++++++++++++++++++++-----
 net/mac80211/ieee80211_i.h |    1 +
 2 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
index 21a0b88..275bbb2 100644
--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -229,6 +229,7 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
 	struct beacon_data *presp;
 	enum nl80211_bss_scan_width scan_width;
 	bool have_higher_than_11mbit;
+	bool radar_required = false;
 	int err;
 
 	sdata_assert_lock(sdata);
@@ -273,6 +274,23 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
 		}
 		chandef.width = NL80211_CHAN_WIDTH_20;
 		chandef.center_freq1 = chan->center_freq;
+		/* check again for downgraded chandef */
+		if (!cfg80211_reg_can_beacon(local->hw.wiphy, &chandef)) {
+			sdata_info(sdata,
+				   "Failed to join IBSS, beacons forbidden\n");
+			return;
+		}
+	}
+
+	err = cfg80211_chandef_dfs_required(sdata->local->hw.wiphy,
+					    &chandef);
+	if (err > 0) {
+		if (!ifibss->userspace_handles_dfs) {
+			sdata_info(sdata,
+				   "Failed to join IBSS, DFS channel without control program\n");
+			return;
+		}
+		radar_required = true;
 	}
 
 	ieee80211_vif_release_channel(sdata);
@@ -297,6 +315,7 @@ static void __ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
 	rcu_assign_pointer(ifibss->presp, presp);
 	mgmt = (void *)presp->head;
 
+	sdata->radar_required = radar_required;
 	sdata->vif.bss_conf.enable_beacon = true;
 	sdata->vif.bss_conf.beacon_int = beacon_int;
 	sdata->vif.bss_conf.basic_rates = basic_rates;
@@ -796,6 +815,21 @@ static void ieee80211_csa_connection_drop_work(struct work_struct *work)
 	ieee80211_queue_work(&sdata->local->hw, &sdata->work);
 }
 
+static void ieee80211_ibss_csa_mark_radar(struct ieee80211_sub_if_data *sdata)
+{
+	struct ieee80211_if_ibss *ifibss = &sdata->u.ibss;
+	int err;
+
+	/* if the current channel is a DFS channel, mark the channel as
+	 * unavailable.
+	 */
+	err = cfg80211_chandef_dfs_required(sdata->local->hw.wiphy,
+					    &ifibss->chandef);
+	if (err > 0)
+		cfg80211_radar_event(sdata->local->hw.wiphy, &ifibss->chandef,
+				     GFP_ATOMIC);
+}
+
 static bool
 ieee80211_ibss_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 				  struct ieee802_11_elems *elems,
@@ -880,8 +914,7 @@ ieee80211_ibss_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 		goto disconnect;
 	}
 
-	if (!cfg80211_chandef_usable(sdata->local->hw.wiphy, &params.chandef,
-				     IEEE80211_CHAN_DISABLED)) {
+	if (!cfg80211_reg_can_beacon(sdata->local->hw.wiphy, &params.chandef)) {
 		sdata_info(sdata,
 			   "IBSS %pM switches to unsupported channel (%d MHz, width:%d, CF1/2: %d/%d MHz), disconnecting\n",
 			   ifibss->bssid,
@@ -897,10 +930,11 @@ ieee80211_ibss_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 	if (err < 0)
 		goto disconnect;
 	if (err) {
+		/* IBSS-DFS only allowed with a control program */
+		if (!ifibss->userspace_handles_dfs)
+			goto disconnect;
+
 		params.radar_required = true;
-
-		/* TODO: IBSS-DFS not (yet) supported, disconnect. */
-		goto disconnect;
 	}
 
 	rcu_read_lock();
@@ -947,12 +981,16 @@ ieee80211_ibss_process_chanswitch(struct ieee80211_sub_if_data *sdata,
 	ieee80211_bss_info_change_notify(sdata, err);
 	drv_channel_switch_beacon(sdata, &params.chandef);
 
+	ieee80211_ibss_csa_mark_radar(sdata);
+
 	return true;
 disconnect:
 	ibss_dbg(sdata, "Can't handle channel switch, disconnect\n");
 	ieee80211_queue_work(&sdata->local->hw,
 			     &ifibss->csa_connection_drop_work);
 
+	ieee80211_ibss_csa_mark_radar(sdata);
+
 	return true;
 }
 
@@ -1688,6 +1726,7 @@ int ieee80211_ibss_join(struct ieee80211_sub_if_data *sdata,
 
 	sdata->u.ibss.privacy = params->privacy;
 	sdata->u.ibss.control_port = params->control_port;
+	sdata->u.ibss.userspace_handles_dfs = params->userspace_handles_dfs;
 	sdata->u.ibss.basic_rates = params->basic_rates;
 
 	/* fix basic_rates if channel does not support these rates */
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 3a87c89..9752567 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -497,6 +497,7 @@ struct ieee80211_if_ibss {
 	bool privacy;
 
 	bool control_port;
+	bool userspace_handles_dfs;
 
 	u8 bssid[ETH_ALEN] __aligned(2);
 	u8 ssid[IEEE80211_MAX_SSID_LEN];
-- 
1.7.10.4

[PATCHv2 3/3] ath9k: enable DFS for IBSS mode

[Simon Wunderlich]

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
---
 drivers/net/wireless/ath/ath9k/init.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath9k/init.c b/drivers/net/wireless/ath/ath9k/init.c
index 9a1f349..bcc5698 100644
--- a/drivers/net/wireless/ath/ath9k/init.c
+++ b/drivers/net/wireless/ath/ath9k/init.c
@@ -791,7 +791,8 @@ static const struct ieee80211_iface_limit if_limits[] = {
 
 
 static const struct ieee80211_iface_limit if_dfs_limits[] = {
-	{ .max = 1,	.types = BIT(NL80211_IFTYPE_AP) },
+	{ .max = 1,	.types = BIT(NL80211_IFTYPE_AP) |
+				 BIT(NL80211_IFTYPE_ADHOC) },
 };
 
 static const struct ieee80211_iface_combination if_comb[] = {
-- 
1.7.10.4

Re: [PATCHv2 1/3] nl80211/cfg80211: enable DFS for IBSS mode

[Johannes Berg]

On Mon, 2013-10-07 at 18:41 +0200, Simon Wunderlich wrote:
> To use DFS in IBSS mode, userspace is required to react to radar events.
> It can inform nl80211 that it is capable of doing so by adding a
> NL80211_ATTR_DFS_CAPABLE attribute when joining the IBSS.
> 
> This attribute is supplied to let the kernelspace know that the
> userspace application can and will handle radar events, e.g. by
> intiating channel switches to a valid channel. DFS channels may
> only be used if this attribute is supplied and the driver supports
> it. Driver support will be checked even if a channel without DFS
> will be initially joined, as a DFS channel may be chosen later.

Applied, fixed the attribute name above.

johannes

Re: [PATCHv2 2/3] mac80211: enable DFS for IBSS mode

[Johannes Berg]

On Mon, 2013-10-07 at 18:41 +0200, Simon Wunderlich wrote:
> Allow changing to DFS channels if the channel is available for
> beaconing and userspace controls DFS operation.
> 
> Channel switch announcement from other stations on DFS channels will
> be interpreted as radar event. These channels will then be marked as
> unvailable.

Applied

johannes