mac802154: Handle passive scanning

Implement the core hooks in order to provide the softMAC layer support
for passive scans. Scans are requested by the user and can be aborted.

Changing channels manually is prohibited during scans.

The implementation uses a workqueue triggered at a certain interval
depending on the symbol duration for the current channel and the
duration order provided. More advanced drivers with internal scheduling
capabilities might require additional care but there is none mainline
yet.

Received beacons during a passive scan are processed in a work queue and
their result forwarded to the upper layer.

Active scanning is not supported yet.

Co-developed-by: David Girault <david.girault@qorvo.com>
Signed-off-by: David Girault <david.girault@qorvo.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20230103165644.432209-7-miquel.raynal@bootlin.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

1 files changed, 288 insertions, 0 deletions

diff --git a/net/mac802154/scan.c b/net/mac802154/scan.c
new file mode 100644
index 000000000000..56056b9c93c1
--- /dev/null
+++ b/net/mac802154/scan.c
@@ -0,0 +1,288 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * IEEE 802.15.4 scanning management
+ *
+ * Copyright (C) 2021 Qorvo US, Inc
+ * Authors:
+ *   - David Girault <david.girault@qorvo.com>
+ *   - Miquel Raynal <miquel.raynal@bootlin.com>
+ */
+
+#include <linux/module.h>
+#include <linux/rtnetlink.h>
+#include <net/mac802154.h>
+
+#include "ieee802154_i.h"
+#include "driver-ops.h"
+#include "../ieee802154/nl802154.h"
+
+/* 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.
+ * - Aborts are decided by userspace, and locked by the rtnl.
+ *
+ * Concurrent modifications to the PHY, the interfaces or the hardware is in
+ * general prevented by the rtnl. So in most cases we don't need additional
+ * protection.
+ *
+ * However, the scan worker get's triggered without anybody noticing and thus we
+ * must ensure the presence of the devices as well as data consistency:
+ * - The sub-interface and device driver module get both their reference
+ *   counters incremented whenever we start a scan, so they cannot disappear
+ *   during operation.
+ * - Data consistency is achieved by the use of rcu protected pointers.
+ */
+static int mac802154_scan_cleanup_locked(struct ieee802154_local *local,
+					 struct ieee802154_sub_if_data *sdata,
+					 bool aborted)
+{
+	struct wpan_dev *wpan_dev = &sdata->wpan_dev;
+	struct wpan_phy *wpan_phy = local->phy;
+	struct cfg802154_scan_request *request;
+	u8 arg;
+
+	/* Prevent any further use of the scan request */
+	clear_bit(IEEE802154_IS_SCANNING, &local->ongoing);
+	cancel_delayed_work(&local->scan_work);
+	request = rcu_replace_pointer(local->scan_req, NULL, 1);
+	if (!request)
+		return 0;
+	kfree_rcu(request);
+
+	/* Advertize first, while we know the devices cannot be removed */
+	if (aborted)
+		arg = NL802154_SCAN_DONE_REASON_ABORTED;
+	else
+		arg = NL802154_SCAN_DONE_REASON_FINISHED;
+	nl802154_scan_done(wpan_phy, wpan_dev, arg);
+
+	/* Cleanup software stack */
+	ieee802154_mlme_op_post(local);
+
+	/* Set the hardware back in its original state */
+	drv_set_channel(local, wpan_phy->current_page,
+			wpan_phy->current_channel);
+	ieee802154_configure_durations(wpan_phy, wpan_phy->current_page,
+				       wpan_phy->current_channel);
+	drv_stop(local);
+	synchronize_net();
+	sdata->required_filtering = sdata->iface_default_filtering;
+	drv_start(local, sdata->required_filtering, &local->addr_filt);
+
+	return 0;
+}
+
+int mac802154_abort_scan_locked(struct ieee802154_local *local,
+				struct ieee802154_sub_if_data *sdata)
+{
+	ASSERT_RTNL();
+
+	if (!mac802154_is_scanning(local))
+		return -ESRCH;
+
+	return mac802154_scan_cleanup_locked(local, sdata, true);
+}
+
+static unsigned int mac802154_scan_get_channel_time(u8 duration_order,
+						    u8 symbol_duration)
+{
+	u64 base_super_frame_duration = (u64)symbol_duration *
+		IEEE802154_SUPERFRAME_PERIOD * IEEE802154_SLOT_PERIOD;
+
+	return usecs_to_jiffies(base_super_frame_duration *
+				(BIT(duration_order) + 1));
+}
+
+static void mac802154_flush_queued_beacons(struct ieee802154_local *local)
+{
+	struct cfg802154_mac_pkt *mac_pkt, *tmp;
+
+	list_for_each_entry_safe(mac_pkt, tmp, &local->rx_beacon_list, node) {
+		list_del(&mac_pkt->node);
+		kfree_skb(mac_pkt->skb);
+		kfree(mac_pkt);
+	}
+}
+
+static void
+mac802154_scan_get_next_channel(struct ieee802154_local *local,
+				struct cfg802154_scan_request *scan_req,
+				u8 *channel)
+{
+	(*channel)++;
+	*channel = find_next_bit((const unsigned long *)&scan_req->channels,
+				 IEEE802154_MAX_CHANNEL + 1,
+				 *channel);
+}
+
+static int mac802154_scan_find_next_chan(struct ieee802154_local *local,
+					 struct cfg802154_scan_request *scan_req,
+					 u8 page, u8 *channel)
+{
+	mac802154_scan_get_next_channel(local, scan_req, channel);
+	if (*channel > IEEE802154_MAX_CHANNEL)
+		return -EINVAL;
+
+	return 0;
+}
+
+void mac802154_scan_worker(struct work_struct *work)
+{
+	struct ieee802154_local *local =
+		container_of(work, struct ieee802154_local, scan_work.work);
+	struct cfg802154_scan_request *scan_req;
+	struct ieee802154_sub_if_data *sdata;
+	unsigned int scan_duration = 0;
+	struct wpan_phy *wpan_phy;
+	u8 scan_req_duration;
+	u8 page, channel;
+	int ret;
+
+	/* Ensure the device receiver is turned off when changing channels
+	 * because there is no atomic way to change the channel and know on
+	 * which one a beacon might have been received.
+	 */
+	drv_stop(local);
+	synchronize_net();
+	mac802154_flush_queued_beacons(local);
+
+	rcu_read_lock();
+	scan_req = rcu_dereference(local->scan_req);
+	if (unlikely(!scan_req)) {
+		rcu_read_unlock();
+		return;
+	}
+
+	sdata = IEEE802154_WPAN_DEV_TO_SUB_IF(scan_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->scan_work,
+				   msecs_to_jiffies(1000));
+		return;
+	}
+
+	wpan_phy = scan_req->wpan_phy;
+	scan_req_duration = scan_req->duration;
+
+	/* Look for the next valid chan */
+	page = local->scan_page;
+	channel = local->scan_channel;
+	do {
+		ret = mac802154_scan_find_next_chan(local, scan_req, page, &channel);
+		if (ret) {
+			rcu_read_unlock();
+			goto end_scan;
+		}
+	} while (!ieee802154_chan_is_valid(scan_req->wpan_phy, page, channel));
+
+	rcu_read_unlock();
+
+	/* Bypass the stack on purpose when changing the channel */
+	rtnl_lock();
+	ret = drv_set_channel(local, page, channel);
+	rtnl_unlock();
+	if (ret) {
+		dev_err(&sdata->dev->dev,
+			"Channel change failure during scan, aborting (%d)\n", ret);
+		goto end_scan;
+	}
+
+	local->scan_page = page;
+	local->scan_channel = channel;
+
+	rtnl_lock();
+	ret = drv_start(local, IEEE802154_FILTERING_3_SCAN, &local->addr_filt);
+	rtnl_unlock();
+	if (ret) {
+		dev_err(&sdata->dev->dev,
+			"Restarting failure after channel change, aborting (%d)\n", ret);
+		goto end_scan;
+	}
+
+	ieee802154_configure_durations(wpan_phy, page, channel);
+	scan_duration = mac802154_scan_get_channel_time(scan_req_duration,
+							wpan_phy->symbol_duration);
+	dev_dbg(&sdata->dev->dev,
+		"Scan page %u channel %u for %ums\n",
+		page, channel, jiffies_to_msecs(scan_duration));
+	queue_delayed_work(local->mac_wq, &local->scan_work, scan_duration);
+	return;
+
+end_scan:
+	rtnl_lock();
+	mac802154_scan_cleanup_locked(local, sdata, false);
+	rtnl_unlock();
+}
+
+int mac802154_trigger_scan_locked(struct ieee802154_sub_if_data *sdata,
+				  struct cfg802154_scan_request *request)
+{
+	struct ieee802154_local *local = sdata->local;
+
+	ASSERT_RTNL();
+
+	if (mac802154_is_scanning(local))
+		return -EBUSY;
+
+	/* TODO: support other scanning type */
+	if (request->type != NL802154_SCAN_PASSIVE)
+		return -EOPNOTSUPP;
+
+	/* Store scanning parameters */
+	rcu_assign_pointer(local->scan_req, request);
+
+	/* Software scanning requires to set promiscuous mode, so we need to
+	 * pause the Tx queue during the entire operation.
+	 */
+	ieee802154_mlme_op_pre(local);
+
+	sdata->required_filtering = IEEE802154_FILTERING_3_SCAN;
+	local->scan_page = request->page;
+	local->scan_channel = -1;
+	set_bit(IEEE802154_IS_SCANNING, &local->ongoing);
+
+	nl802154_scan_started(request->wpan_phy, request->wpan_dev);
+
+	queue_delayed_work(local->mac_wq, &local->scan_work, 0);
+
+	return 0;
+}
+
+int mac802154_process_beacon(struct ieee802154_local *local,
+			     struct sk_buff *skb,
+			     u8 page, u8 channel)
+{
+	struct ieee802154_beacon_hdr *bh = (void *)skb->data;
+	struct ieee802154_addr *src = &mac_cb(skb)->source;
+	struct cfg802154_scan_request *scan_req;
+	struct ieee802154_coord_desc desc;
+
+	if (skb->len != sizeof(*bh))
+		return -EINVAL;
+
+	if (unlikely(src->mode == IEEE802154_ADDR_NONE))
+		return -EINVAL;
+
+	dev_dbg(&skb->dev->dev,
+		"BEACON received on page %u channel %u\n",
+		page, channel);
+
+	memcpy(&desc.addr, src, sizeof(desc.addr));
+	desc.page = page;
+	desc.channel = channel;
+	desc.link_quality = mac_cb(skb)->lqi;
+	desc.superframe_spec = get_unaligned_le16(skb->data);
+	desc.gts_permit = bh->gts_permit;
+
+	trace_802154_scan_event(&desc);
+
+	rcu_read_lock();
+	scan_req = rcu_dereference(local->scan_req);
+	if (likely(scan_req))
+		nl802154_scan_event(scan_req->wpan_phy, scan_req->wpan_dev, &desc);
+	rcu_read_unlock();
+
+	return 0;
+}