Subject: Re: [PATCH net] net: consume xmit errors of GSO frames

From: Jakub Kicinski <[email-masked]>
Date: Fri, 20 Feb 2026 10:32:54 -0800

On Fri, 20 Feb 2026 18:17:14 +0100 Eric Dumazet wrote:
> This rings a bell.
> 
> I sent back in October something in the same vein.
> 
> https://www.spinics.net/lists/netdev/msg1131452.html

Yes, I had a recollection of you explaining this problem in the past.
Otherwise I would have never thought of this path! :) 

If we want to cover the BUSY case maybe the patch below? Too messy?

diff --git a/net/core/dev.c b/net/core/dev.c
index 096b3ff13f6b..65b7c54e1bef 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4822,6 +4822,8 @@ int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
 		 * to -1 or to their cpu id, but not to our id.
 		 */
 		if (READ_ONCE(txq->xmit_lock_owner) != cpu) {
+			bool is_list = false, completed = false;
+
 			if (dev_xmit_recursion())
 				goto recursion_alert;
 
@@ -4832,17 +4834,27 @@ int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
 			HARD_TX_LOCK(dev, txq, cpu);
 
 			if (!netif_xmit_stopped(txq)) {
+				/* GSO segments a single SKB into
+				 * a list of frames. TCP expects error
+				 * to mean none of the data was sent.
+				 */
+				is_list = !!skb->next;
+
 				dev_xmit_recursion_inc();
 				skb = dev_hard_start_xmit(skb, dev, txq, &rc);
 				dev_xmit_recursion_dec();
-				if (dev_xmit_complete(rc)) {
-					HARD_TX_UNLOCK(dev, txq);
-					goto out;
-				}
+				completed = dev_xmit_complete(rc);
+				if (is_list)
+					rc = NETDEV_TX_OK;
 			}
 			HARD_TX_UNLOCK(dev, txq);
+			if (completed)
+				goto out;
+
 			net_crit_ratelimited("Virtual device %s asks to queue packet!\n",
 					     dev->name);
+			if (!is_list)
+				rc = -ENETDOWN;
 		} else {
 			/* Recursion is detected! It is possible,
 			 * unfortunately
@@ -4850,10 +4862,10 @@ int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
 recursion_alert:
 			net_crit_ratelimited("Dead loop on virtual device %s, fix it urgently!\n",
 					     dev->name);
+			rc = -ENETDOWN;
 		}
 	}
 
-	rc = -ENETDOWN;
 	rcu_read_unlock_bh();
 
 	dev_core_stats_tx_dropped_inc(dev);