Merge branch 'net-add-skb_drop_reason_recursion_limit'

Eric Dumazet says:

====================
net: add SKB_DROP_REASON_RECURSION_LIMIT

Add a new drop reason : SKB_DROP_REASON_RECURSION_LIMIT

Used for packets dropped in a too deep virtual device chain,
from tunnels and __dev_queue_xmit()

__dev_queue_xmit() can also return SKB_DROP_REASON_DEV_READY
====================

Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

include/net/dropreason-core.h

···
 	FN(PFMEMALLOC)	\
 	FN(PSP_INPUT)			\
 	FN(PSP_OUTPUT)			\
+	FN(RECURSION_LIMIT)		\
 	FNe(MAX)
 
 /**
···
 	SKB_DROP_REASON_PSP_INPUT,
 	/** @SKB_DROP_REASON_PSP_OUTPUT: PSP output checks failed */
 	SKB_DROP_REASON_PSP_OUTPUT,
+	/** @SKB_DROP_REASON_RECURSION_LIMIT: Dead loop on virtual device. */
+	SKB_DROP_REASON_RECURSION_LIMIT,
 	/**
 	 * @SKB_DROP_REASON_MAX: the maximum of core drop reasons, which
 	 * shouldn't be used as a real 'reason' - only for tracing code gen

include/net/ip6_tunnel.h

···
 					     dev->name);
 			DEV_STATS_INC(dev, tx_errors);
 		}
-		kfree_skb(skb);
+		kfree_skb_reason(skb, SKB_DROP_REASON_RECURSION_LIMIT);
 		return;
 	}
 

net/core/dev.c

···
 {
 	struct net_device *dev = skb->dev;
 	struct netdev_queue *txq = NULL;
-	struct Qdisc *q;
-	int rc = -ENOMEM;
+	enum skb_drop_reason reason;
+	int cpu, rc = -ENOMEM;
 	bool again = false;
+	struct Qdisc *q;
 
 	skb_reset_mac_header(skb);
 	skb_assert_len(skb);
···
 	 * Check this and shot the lock. It is not prone from deadlocks.
 	 *Either shot noqueue qdisc, it is even simpler 8)
 	 */
-	if (dev->flags & IFF_UP) {
-		int cpu = smp_processor_id(); /* ok because BHs are off */
-
-		if (!netif_tx_owned(txq, cpu)) {
-			bool is_list = false;
-
-			if (dev_xmit_recursion())
-				goto recursion_alert;
-
-			skb = validate_xmit_skb(skb, dev, &again);
-			if (!skb)
-				goto out;
-
-			HARD_TX_LOCK(dev, txq, cpu);
-
-			if (!netif_xmit_stopped(txq)) {
-				is_list = !!skb->next;
-
-				dev_xmit_recursion_inc();
-				skb = dev_hard_start_xmit(skb, dev, txq, &rc);
-				dev_xmit_recursion_dec();
-
-				/* GSO segments a single SKB into
-				 * a list of frames. TCP expects error
-				 * to mean none of the data was sent.
-				 */
-				if (is_list)
-					rc = NETDEV_TX_OK;
-			}
-			HARD_TX_UNLOCK(dev, txq);
-			if (!skb) /* xmit completed */
-				goto out;
-
-			net_crit_ratelimited("Virtual device %s asks to queue packet!\n",
-					     dev->name);
-			/* NETDEV_TX_BUSY or queue was stopped */
-			if (!is_list)
-				rc = -ENETDOWN;
-		} else {
-			/* Recursion is detected! It is possible,
-			 * unfortunately
-			 */
-recursion_alert:
-			net_crit_ratelimited("Dead loop on virtual device %s, fix it urgently!\n",
-					     dev->name);
-			rc = -ENETDOWN;
-		}
+	if (unlikely(!(dev->flags & IFF_UP))) {
+		reason = SKB_DROP_REASON_DEV_READY;
+		goto drop;
 	}
 
+	cpu = smp_processor_id(); /* ok because BHs are off */
+
+	if (likely(!netif_tx_owned(txq, cpu))) {
+		bool is_list = false;
+
+		if (dev_xmit_recursion())
+			goto recursion_alert;
+
+		skb = validate_xmit_skb(skb, dev, &again);
+		if (!skb)
+			goto out;
+
+		HARD_TX_LOCK(dev, txq, cpu);
+
+		if (!netif_xmit_stopped(txq)) {
+			is_list = !!skb->next;
+
+			dev_xmit_recursion_inc();
+			skb = dev_hard_start_xmit(skb, dev, txq, &rc);
+			dev_xmit_recursion_dec();
+
+			/* GSO segments a single SKB into a list of frames.
+			 * TCP expects error to mean none of the data was sent.
+			 */
+			if (is_list)
+				rc = NETDEV_TX_OK;
+		}
+		HARD_TX_UNLOCK(dev, txq);
+		if (!skb) /* xmit completed */
+			goto out;
+
+		net_crit_ratelimited("Virtual device %s asks to queue packet!\n",
+				     dev->name);
+		/* NETDEV_TX_BUSY or queue was stopped */
+		if (!is_list)
+			rc = -ENETDOWN;
+	} else {
+		/* Recursion is detected! It is possible unfortunately. */
+recursion_alert:
+		net_crit_ratelimited("Dead loop on virtual device %s, fix it urgently!\n",
+				     dev->name);
+		rc = -ENETDOWN;
+	}
+
+	reason = SKB_DROP_REASON_RECURSION_LIMIT;
+drop:
 	rcu_read_unlock_bh();
 
 	dev_core_stats_tx_dropped_inc(dev);
-	kfree_skb_list(skb);
+	kfree_skb_list_reason(skb, reason);
 	return rc;
 out:
 	rcu_read_unlock_bh();

net/ipv4/ip_tunnel_core.c

···
 			DEV_STATS_INC(dev, tx_errors);
 		}
 		ip_rt_put(rt);
-		kfree_skb(skb);
+		kfree_skb_reason(skb, SKB_DROP_REASON_RECURSION_LIMIT);
 		return;
 	}