net: don't touch dev->stats in BPF redirect paths

PATCH Applied Jakub Kicinski 3 participants 3 messages Jan 30 – Jan 31

Subsystems (4)

Networking Network drivers BPF BPF networking

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Jakub Kicinski

author maintainer

2026-01-30 03:38 UTC #0 lore raw

PATCH v2 1/1 net: don't touch dev->stats in BPF redirect paths

Gal reports that BPF redirect increments dev->stats.tx_errors on failure. This is not correct, most modern drivers completely ignore dev->stats so these drops will be invisible to the user. Core code should use the dedicated core stats which are folded into device stats in dev_get_stats().

Note that we're switching from tx_errors to tx_dropped. Core only has tx_dropped, hence presumably users already expect that counter to increment for "stack" Tx issues.

Acked-by Martin KaFai Lau <[email protected]>

Acked-by Daniel Borkmann <[email protected]>

Reported-by Gal Pressman <[email protected]>

Link https://lore.kernel.org/[email protected] open here

Fixes b4ab31414970 ("bpf: Add redirect_neigh helper as redirect drop-in")

Signed-off-by Jakub Kicinski <[email protected]>

---
v2:
- add note on tx_dropped to the commit msg
v1: https://lore.kernel.org/[email protected]

CC [email protected]

---
 net/core/filter.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

net/core/filter.c +4 -4

index 616e0520a0bb..2c21735798a5 100644
@@ -2289,12 +2289,12 @@ static int __bpf_redirect_neigh_v6(struct sk_buff *skb, struct net_device *dev,
 
 	err = bpf_out_neigh_v6(net, skb, dev, nh);
 	if (unlikely(net_xmit_eval(err)))
-		DEV_STATS_INC(dev, tx_errors);
+		dev_core_stats_tx_dropped_inc(dev);
 	else
 		ret = NET_XMIT_SUCCESS;
 	goto out_xmit;
 out_drop:
-	DEV_STATS_INC(dev, tx_errors);
+	dev_core_stats_tx_dropped_inc(dev);
 	kfree_skb(skb);
 out_xmit:
 	return ret;

@@ -2396,12 +2396,12 @@ static int __bpf_redirect_neigh_v4(struct sk_buff *skb, struct net_device *dev,
 
 	err = bpf_out_neigh_v4(net, skb, dev, nh);
 	if (unlikely(net_xmit_eval(err)))
-		DEV_STATS_INC(dev, tx_errors);
+		dev_core_stats_tx_dropped_inc(dev);
 	else
 		ret = NET_XMIT_SUCCESS;
 	goto out_xmit;
 out_drop:
-	DEV_STATS_INC(dev, tx_errors);
+	dev_core_stats_tx_dropped_inc(dev);
 	kfree_skb(skb);
 out_xmit:
 	return ret;

Signature · 1 line

2.52.0

Eric Dumazet

Reviewed-by on v2 1/1

2026-01-30 18:55 UTC #1 lore raw

Quoted 10 lines · Jakub Kicinski

Gal reports that BPF redirect increments dev->stats.tx_errors on failure. This is not correct, most modern drivers completely ignore dev->stats so these drops will be invisible to the user. Core code should use the dedicated core stats which are folded into device stats in dev_get_stats().
Note that we're switching from tx_errors to tx_dropped. Core only has tx_dropped, hence presumably users already expect that counter to increment for "stack" Tx issues.

Reviewed-by Eric Dumazet <[email protected]>

[email protected]

CI Applied

2026-01-31 21:20 UTC #2 lore raw

In reply to Jakub Kicinski

This patch was applied to netdev/net.git (main) by Jakub Kicinski <[email protected]>:

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <[email protected]>:

Quoted 11 lines · On Thu, 29 Jan 2026 19:38:27 -0800 you wrote:

Gal reports that BPF redirect increments dev->stats.tx_errors on failure. This is not correct, most modern drivers completely ignore dev->stats so these drops will be invisible to the user. Core code should use the dedicated core stats which are folded into device stats in dev_get_stats().
Note that we're switching from tx_errors to tx_dropped. Core only has tx_dropped, hence presumably users already expect that counter to increment for "stack" Tx issues.
[...]

Here is the summary with links:
- [net,v2] net: don't touch dev->stats in BPF redirect paths

    https://git.kernel.org/netdev/net/c/fdf3f6800be3

You are awesome, thank you!

Signature · 2 lines

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