mac802154: Handle basic beaconing

Implement the core hooks in order to provide the softMAC layer support
for sending beacons. Coordinators may be requested to send beacons in a
beacon enabled PAN in order for the other devices around to self
discover the available PANs automatically.

Changing the channels is prohibited while a beacon operation is
ongoing.

The implementation uses a workqueue triggered at a certain interval
depending on the symbol duration for the current channel and the
interval order provided.

Sending beacons in response to a BEACON_REQ frame (ie. answering active
scans) is not yet supported.

This initial patchset has no security support (llsec).

Co-developed-by: David Girault <[e-mail]>
Signed-off-by: David Girault <[e-mail]>
Signed-off-by: Miquel Raynal <[e-mail]>
Acked-by: Alexander Aring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Stefan Schmidt <[e-mail]>

include/net/ieee802154_netdev.h

···
 	IEEE802154_MULTIPURPOSE_STD = IEEE802154_2003_STD,
 };
 
+enum ieee802154_addressing_mode {
+	IEEE802154_NO_ADDRESSING,
+	IEEE802154_RESERVED,
+	IEEE802154_SHORT_ADDRESSING,
+	IEEE802154_EXTENDED_ADDRESSING,
+};
+
 struct ieee802154_hdr {
 	struct ieee802154_hdr_fc fc;
 	u8 seq;
 	struct ieee802154_addr source;
 	struct ieee802154_addr dest;
 	struct ieee802154_sechdr sec;
+};
+
+struct ieee802154_beacon_frame {
+	struct ieee802154_hdr mhr;
+	struct ieee802154_beacon_hdr mac_pl;
 };
 
 /* pushes hdr onto the skb. fields of hdr->fc that can be calculated from
···
  * header_ops.parse
  */
 int ieee802154_hdr_peek(const struct sk_buff *skb, struct ieee802154_hdr *hdr);
+
+/* pushes a beacon frame into an skb */
+int ieee802154_beacon_push(struct sk_buff *skb,
+			   struct ieee802154_beacon_frame *beacon);
 
 int ieee802154_max_payload(const struct ieee802154_hdr *hdr);
 

net/ieee802154/header_ops.c

···
 }
 EXPORT_SYMBOL_GPL(ieee802154_hdr_push);
 
+int ieee802154_beacon_push(struct sk_buff *skb,
+			   struct ieee802154_beacon_frame *beacon)
+{
+	struct ieee802154_beacon_hdr *mac_pl = &beacon->mac_pl;
+	struct ieee802154_hdr *mhr = &beacon->mhr;
+	int ret;
+
+	skb_reserve(skb, sizeof(*mhr));
+	ret = ieee802154_hdr_push(skb, mhr);
+	if (ret < 0)
+		return ret;
+
+	skb_reset_mac_header(skb);
+	skb->mac_len = ret;
+
+	skb_put_data(skb, mac_pl, sizeof(*mac_pl));
+
+	if (mac_pl->pend_short_addr_count || mac_pl->pend_ext_addr_count)
+		return -EOPNOTSUPP;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ieee802154_beacon_push);
+
 static int
 ieee802154_hdr_get_addr(const u8 *buf, int mode, bool omit_pan,
 			struct ieee802154_addr *addr)

net/mac802154/cfg.c

···
 	    wpan_phy->current_channel == channel)
 		return 0;
 
-	/* Refuse to change channels during a scanning operation */
-	if (mac802154_is_scanning(local))
+	/* Refuse to change channels during scanning or beaconing */
+	if (mac802154_is_scanning(local) || mac802154_is_beaconing(local))
 		return -EBUSY;
 
 	ret = drv_set_channel(local, page, channel);
···
 	ASSERT_RTNL();
 
 	return mac802154_abort_scan_locked(local, sdata);
+}
+
+static int mac802154_send_beacons(struct wpan_phy *wpan_phy,
+				  struct cfg802154_beacon_request *request)
+{
+	struct ieee802154_sub_if_data *sdata;
+
+	sdata = IEEE802154_WPAN_DEV_TO_SUB_IF(request->wpan_dev);
+
+	ASSERT_RTNL();
+
+	return mac802154_send_beacons_locked(sdata, request);
+}
+
+static int mac802154_stop_beacons(struct wpan_phy *wpan_phy,
+				  struct wpan_dev *wpan_dev)
+{
+	struct ieee802154_local *local = wpan_phy_priv(wpan_phy);
+	struct ieee802154_sub_if_data *sdata;
+
+	sdata = IEEE802154_WPAN_DEV_TO_SUB_IF(wpan_dev);
+
+	ASSERT_RTNL();
+
+	return mac802154_stop_beacons_locked(local, sdata);
 }
 
 #ifdef CONFIG_IEEE802154_NL802154_EXPERIMENTAL
···
 	.set_ackreq_default = ieee802154_set_ackreq_default,
 	.trigger_scan = mac802154_trigger_scan,
 	.abort_scan = mac802154_abort_scan,
+	.send_beacons = mac802154_send_beacons,
+	.stop_beacons = mac802154_stop_beacons,
 #ifdef CONFIG_IEEE802154_NL802154_EXPERIMENTAL
 	.get_llsec_table = ieee802154_get_llsec_table,
 	.lock_llsec_table = ieee802154_lock_llsec_table,

net/mac802154/ieee802154_i.h

···
 
 enum ieee802154_ongoing {
 	IEEE802154_IS_SCANNING = BIT(0),
+	IEEE802154_IS_BEACONING = BIT(1),
 };
 
 /* mac802154 device private data */
···
 	u8 scan_channel;
 	struct cfg802154_scan_request __rcu *scan_req;
 	struct delayed_work scan_work;
+
+	/* Beaconing */
+	unsigned int beacon_interval;
+	struct ieee802154_beacon_frame beacon;
+	struct cfg802154_beacon_request __rcu *beacon_req;
+	struct delayed_work beacon_work;
 
 	/* Asynchronous tasks */
 	struct list_head rx_beacon_list;
···
 static inline bool mac802154_is_scanning(struct ieee802154_local *local)
 {
 	return test_bit(IEEE802154_IS_SCANNING, &local->ongoing);
+}
+
+void mac802154_beacon_worker(struct work_struct *work);
+int mac802154_send_beacons_locked(struct ieee802154_sub_if_data *sdata,
+				  struct cfg802154_beacon_request *request);
+int mac802154_stop_beacons_locked(struct ieee802154_local *local,
+				  struct ieee802154_sub_if_data *sdata);
+
+static inline bool mac802154_is_beaconing(struct ieee802154_local *local)
+{
+	return test_bit(IEEE802154_IS_BEACONING, &local->ongoing);
 }
 
 /* interface handling */

net/mac802154/iface.c

···
 	if (mac802154_is_scanning(local))
 		mac802154_abort_scan_locked(local, sdata);
 
+	if (mac802154_is_beaconing(local))
+		mac802154_stop_beacons_locked(local, sdata);
+
 	netif_stop_queue(dev);
 	local->open_count--;
 

net/mac802154/llsec.c

···
 
 	hlen = ieee802154_hdr_pull(skb, &hdr);
 
-	if (hlen < 0 || hdr.fc.type != IEEE802154_FC_TYPE_DATA)
+	/* TODO: control frames security support */
+	if (hlen < 0 ||
+	    (hdr.fc.type != IEEE802154_FC_TYPE_DATA &&
+	     hdr.fc.type != IEEE802154_FC_TYPE_BEACON))
 		return -EINVAL;
 
 	if (!hdr.fc.security_enabled ||

net/mac802154/main.c

···
 	INIT_WORK(&local->sync_tx_work, ieee802154_xmit_sync_worker);
 	INIT_DELAYED_WORK(&local->scan_work, mac802154_scan_worker);
 	INIT_WORK(&local->rx_beacon_work, mac802154_rx_beacon_worker);
+	INIT_DELAYED_WORK(&local->beacon_work, mac802154_beacon_worker);
 
 	/* init supported flags with 802.15.4 default ranges */
 	phy->supported.max_minbe = 8;

net/mac802154/scan.c

···
 #include "driver-ops.h"
 #include "../ieee802154/nl802154.h"
 
+#define IEEE802154_BEACON_MHR_SZ 13
+#define IEEE802154_BEACON_PL_SZ 4
+#define IEEE802154_BEACON_SKB_SZ (IEEE802154_BEACON_MHR_SZ + \
+				  IEEE802154_BEACON_PL_SZ)
+
 /* mac802154_scan_cleanup_locked() must be called upon scan completion or abort.
  * - Completions are asynchronous, not locked by the rtnl and decided by the
  *   scan worker.
···
 	if (likely(scan_req))
 		nl802154_scan_event(scan_req->wpan_phy, scan_req->wpan_dev, &desc);
 	rcu_read_unlock();
+
+	return 0;
+}
+
+static int mac802154_transmit_beacon(struct ieee802154_local *local,
+				     struct wpan_dev *wpan_dev)
+{
+	struct cfg802154_beacon_request *beacon_req;
+	struct ieee802154_sub_if_data *sdata;
+	struct sk_buff *skb;
+	int ret;
+
+	/* Update the sequence number */
+	local->beacon.mhr.seq = atomic_inc_return(&wpan_dev->bsn) & 0xFF;
+
+	skb = alloc_skb(IEEE802154_BEACON_SKB_SZ, GFP_KERNEL);
+	if (!skb)
+		return -ENOBUFS;
+
+	rcu_read_lock();
+	beacon_req = rcu_dereference(local->beacon_req);
+	if (unlikely(!beacon_req)) {
+		rcu_read_unlock();
+		kfree_skb(skb);
+		return -EINVAL;
+	}
+
+	sdata = IEEE802154_WPAN_DEV_TO_SUB_IF(beacon_req->wpan_dev);
+	skb->dev = sdata->dev;
+
+	rcu_read_unlock();
+
+	ret = ieee802154_beacon_push(skb, &local->beacon);
+	if (ret) {
+		kfree_skb(skb);
+		return ret;
+	}
+
+	return ieee802154_subif_start_xmit(skb, sdata->dev);
+}
+
+void mac802154_beacon_worker(struct work_struct *work)
+{
+	struct ieee802154_local *local =
+		container_of(work, struct ieee802154_local, beacon_work.work);
+	struct cfg802154_beacon_request *beacon_req;
+	struct ieee802154_sub_if_data *sdata;
+	struct wpan_dev *wpan_dev;
+	int ret;
+
+	rcu_read_lock();
+	beacon_req = rcu_dereference(local->beacon_req);
+	if (unlikely(!beacon_req)) {
+		rcu_read_unlock();
+		return;
+	}
+
+	sdata = IEEE802154_WPAN_DEV_TO_SUB_IF(beacon_req->wpan_dev);
+
+	/* Wait an arbitrary amount of time in case we cannot use the device */
+	if (local->suspended || !ieee802154_sdata_running(sdata)) {
+		rcu_read_unlock();
+		queue_delayed_work(local->mac_wq, &local->beacon_work,
+				   msecs_to_jiffies(1000));
+		return;
+	}
+
+	wpan_dev = beacon_req->wpan_dev;
+
+	rcu_read_unlock();
+
+	dev_dbg(&sdata->dev->dev, "Sending beacon\n");
+	ret = mac802154_transmit_beacon(local, wpan_dev);
+	if (ret)
+		dev_err(&sdata->dev->dev,
+			"Beacon could not be transmitted (%d)\n", ret);
+
+	if (local->beacon_interval >= 0)
+		queue_delayed_work(local->mac_wq, &local->beacon_work,
+				   local->beacon_interval);
+}
+
+int mac802154_stop_beacons_locked(struct ieee802154_local *local,
+				  struct ieee802154_sub_if_data *sdata)
+{
+	struct wpan_dev *wpan_dev = &sdata->wpan_dev;
+	struct cfg802154_beacon_request *request;
+
+	ASSERT_RTNL();
+
+	if (!mac802154_is_beaconing(local))
+		return -ESRCH;
+
+	clear_bit(IEEE802154_IS_BEACONING, &local->ongoing);
+	cancel_delayed_work(&local->beacon_work);
+	request = rcu_replace_pointer(local->beacon_req, NULL, 1);
+	if (!request)
+		return 0;
+	kfree_rcu(request);
+
+	nl802154_beaconing_done(wpan_dev);
+
+	return 0;
+}
+
+int mac802154_send_beacons_locked(struct ieee802154_sub_if_data *sdata,
+				  struct cfg802154_beacon_request *request)
+{
+	struct ieee802154_local *local = sdata->local;
+
+	ASSERT_RTNL();
+
+	if (mac802154_is_beaconing(local))
+		mac802154_stop_beacons_locked(local, sdata);
+
+	/* Store beaconing parameters */
+	rcu_assign_pointer(local->beacon_req, request);
+
+	set_bit(IEEE802154_IS_BEACONING, &local->ongoing);
+
+	memset(&local->beacon, 0, sizeof(local->beacon));
+	local->beacon.mhr.fc.type = IEEE802154_FC_TYPE_BEACON;
+	local->beacon.mhr.fc.security_enabled = 0;
+	local->beacon.mhr.fc.frame_pending = 0;
+	local->beacon.mhr.fc.ack_request = 0;
+	local->beacon.mhr.fc.intra_pan = 0;
+	local->beacon.mhr.fc.dest_addr_mode = IEEE802154_NO_ADDRESSING;
+	local->beacon.mhr.fc.version = IEEE802154_2003_STD;
+	local->beacon.mhr.fc.source_addr_mode = IEEE802154_EXTENDED_ADDRESSING;
+	atomic_set(&request->wpan_dev->bsn, -1);
+	local->beacon.mhr.source.mode = IEEE802154_ADDR_LONG;
+	local->beacon.mhr.source.pan_id = cpu_to_le16(request->wpan_dev->pan_id);
+	local->beacon.mhr.source.extended_addr = cpu_to_le64(request->wpan_dev->extended_addr);
+	local->beacon.mac_pl.beacon_order = request->interval;
+	local->beacon.mac_pl.superframe_order = request->interval;
+	local->beacon.mac_pl.final_cap_slot = 0xf;
+	local->beacon.mac_pl.battery_life_ext = 0;
+	/* TODO: Fill this field depending on the coordinator capacity */
+	local->beacon.mac_pl.pan_coordinator = 1;
+	local->beacon.mac_pl.assoc_permit = 1;
+
+	/* Start the beacon work */
+	local->beacon_interval =
+		mac802154_scan_get_channel_time(request->interval,
+						request->wpan_phy->symbol_duration);
+	queue_delayed_work(local->mac_wq, &local->beacon_work, 0);
 
 	return 0;
 }