netdev - [PATCH wpan-next v2 11/11] net: mac802154: Add a warning in the slow path

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Date:   Thu, 12 May 2022 16:33:14 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Alexander Aring <alex.aring@...il.com>,
        Stefan Schmidt <stefan@...enfreihafen.org>,
        linux-wpan@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        David Girault <david.girault@...vo.com>,
        Romuald Despres <romuald.despres@...vo.com>,
        Frederic Blain <frederic.blain@...vo.com>,
        Nicolas Schodet <nico@...fr.eu.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Subject: [PATCH wpan-next v2 11/11] net: mac802154: Add a warning in the slow path

In order to be able to detect possible conflicts between the net
interface core and the ieee802154 core, let's add a warning in the slow
path: we want to be sure that whenever we start an asynchronous MLME
transmission (which can be fully asynchronous) the net core somehow
agrees that this transmission is possible, ie. the device was not
stopped. Warning in this case would allow us to track down more easily
possible issues with the MLME logic if we ever get reports.

Unlike in the hot path, such a situation cannot be handled.

Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
---
 net/mac802154/tx.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/net/mac802154/tx.c b/net/mac802154/tx.c
index a3c9f194c025..d61b076239c3 100644
--- a/net/mac802154/tx.c
+++ b/net/mac802154/tx.c
@@ -132,6 +132,25 @@ int ieee802154_sync_and_hold_queue(struct ieee802154_local *local)
 	return ret;
 }
 
+static bool ieee802154_netif_is_down(struct ieee802154_local *local)
+{
+	struct ieee802154_sub_if_data *sdata;
+	bool is_down = false;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(sdata, &local->interfaces, list) {
+		if (!sdata->dev)
+			continue;
+
+		is_down = !(sdata->dev->flags & IFF_UP);
+		if (is_down)
+			break;
+	}
+	rcu_read_unlock();
+
+	return is_down;
+}
+
 int ieee802154_mlme_tx(struct ieee802154_local *local, struct sk_buff *skb)
 {
 	int ret;
@@ -145,6 +164,12 @@ int ieee802154_mlme_tx(struct ieee802154_local *local, struct sk_buff *skb)
 	if (!local->open_count)
 		return -EBUSY;
 
+	/* Warn if the ieee802154 core thinks MLME frames can be sent while the
+	 * net interface expects this cannot happen.
+	 */
+	if (WARN_ON_ONCE(ieee802154_netif_is_down(local)))
+		return -EHOSTDOWN;
+
 	ieee802154_sync_and_hold_queue(local);
 
 	ieee802154_tx(local, skb);
-- 
2.27.0