* [PATCH net-next 1/2] net: dropreason: add SKB_DROP_REASON_RECURSION_LIMIT
2026-03-12 20:18 [PATCH net-next 0/2] net: add SKB_DROP_REASON_RECURSION_LIMIT Eric Dumazet
@ 2026-03-12 20:18 ` Eric Dumazet
2026-03-13 20:14 ` Joe Damato
2026-03-12 20:18 ` [PATCH net-next 2/2] net: plumb drop reasons to __dev_queue_xmit() Eric Dumazet
2026-03-14 16:00 ` [PATCH net-next 0/2] net: add SKB_DROP_REASON_RECURSION_LIMIT patchwork-bot+netdevbpf
2 siblings, 1 reply; 6+ messages in thread
From: Eric Dumazet @ 2026-03-12 20:18 UTC (permalink / raw)
To: David S . Miller, Jakub Kicinski, Paolo Abeni
Cc: Simon Horman, netdev, eric.dumazet, Eric Dumazet
ip[6]tunnel_xmit() can drop packets if a too deep recursion level
is detected.
Add SKB_DROP_REASON_RECURSION_LIMIT drop reason.
We will use this reason later in __dev_queue_xmit().
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
include/net/dropreason-core.h | 3 +++
include/net/ip6_tunnel.h | 2 +-
net/ipv4/ip_tunnel_core.c | 2 +-
3 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index 5c8c2eb3d2c5b038683b78952106e374cf3b68d1..de61dd5dbfd9dc7d91d22d79a510d42fb69eb60a 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -123,6 +123,7 @@
FN(PFMEMALLOC) \
FN(PSP_INPUT) \
FN(PSP_OUTPUT) \
+ FN(RECURSION_LIMIT) \
FNe(MAX)
/**
@@ -582,6 +583,8 @@ enum skb_drop_reason {
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
diff --git a/include/net/ip6_tunnel.h b/include/net/ip6_tunnel.h
index 359b595f1df93663b3e32c006d936427e8c8b20c..b99805ee2fd14bef6c7bc4daa6e8dfbc34984e4e 100644
--- a/include/net/ip6_tunnel.h
+++ b/include/net/ip6_tunnel.h
@@ -162,7 +162,7 @@ static inline void ip6tunnel_xmit(struct sock *sk, struct sk_buff *skb,
dev->name);
DEV_STATS_INC(dev, tx_errors);
}
- kfree_skb(skb);
+ kfree_skb_reason(skb, SKB_DROP_REASON_RECURSION_LIMIT);
return;
}
diff --git a/net/ipv4/ip_tunnel_core.c b/net/ipv4/ip_tunnel_core.c
index 5683c328990f49df2954af9d890b5f24150caeb2..f430d6f0463e7ab5761e98047a866d304a49abb2 100644
--- a/net/ipv4/ip_tunnel_core.c
+++ b/net/ipv4/ip_tunnel_core.c
@@ -65,7 +65,7 @@ void iptunnel_xmit(struct sock *sk, struct rtable *rt, struct sk_buff *skb,
DEV_STATS_INC(dev, tx_errors);
}
ip_rt_put(rt);
- kfree_skb(skb);
+ kfree_skb_reason(skb, SKB_DROP_REASON_RECURSION_LIMIT);
return;
}
--
2.53.0.880.g73c4285caa-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH net-next 2/2] net: plumb drop reasons to __dev_queue_xmit()
2026-03-12 20:18 [PATCH net-next 0/2] net: add SKB_DROP_REASON_RECURSION_LIMIT Eric Dumazet
2026-03-12 20:18 ` [PATCH net-next 1/2] net: dropreason: " Eric Dumazet
@ 2026-03-12 20:18 ` Eric Dumazet
2026-03-13 20:18 ` Joe Damato
2026-03-14 16:00 ` [PATCH net-next 0/2] net: add SKB_DROP_REASON_RECURSION_LIMIT patchwork-bot+netdevbpf
2 siblings, 1 reply; 6+ messages in thread
From: Eric Dumazet @ 2026-03-12 20:18 UTC (permalink / raw)
To: David S . Miller, Jakub Kicinski, Paolo Abeni
Cc: Simon Horman, netdev, eric.dumazet, Eric Dumazet
Add drop reasons to __dev_queue_xmit():
- SKB_DROP_REASON_DEV_READY : device is not UP.
- SKB_DROP_REASON_RECURSION_LIMIT : recursion limit on virtual device is hit.
Also add an unlikely() for the SKB_DROP_REASON_DEV_READY case,
and reduce indentation level.
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
net/core/dev.c | 83 ++++++++++++++++++++++++++------------------------
1 file changed, 43 insertions(+), 40 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index f48dc299e4b270f2fedba11e669d4940e73f0d4d..200d44883fc130dcc80afa1ddccce68bf3ff592c 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4745,9 +4745,10 @@ int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
{
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);
@@ -4816,59 +4817,61 @@ int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
* 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 (unlikely(!(dev->flags & IFF_UP))) {
+ reason = SKB_DROP_REASON_DEV_READY;
+ goto drop;
+ }
- if (!netif_tx_owned(txq, cpu)) {
- bool is_list = false;
+ cpu = smp_processor_id(); /* ok because BHs are off */
- if (dev_xmit_recursion())
- goto recursion_alert;
+ if (likely(!netif_tx_owned(txq, cpu))) {
+ bool is_list = false;
- skb = validate_xmit_skb(skb, dev, &again);
- if (!skb)
- goto out;
+ if (dev_xmit_recursion())
+ goto recursion_alert;
- HARD_TX_LOCK(dev, txq, cpu);
+ skb = validate_xmit_skb(skb, dev, &again);
+ if (!skb)
+ goto out;
- if (!netif_xmit_stopped(txq)) {
- is_list = !!skb->next;
+ HARD_TX_LOCK(dev, txq, cpu);
- dev_xmit_recursion_inc();
- skb = dev_hard_start_xmit(skb, dev, txq, &rc);
- dev_xmit_recursion_dec();
+ if (!netif_xmit_stopped(txq)) {
+ is_list = !!skb->next;
- /* 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;
+ dev_xmit_recursion_inc();
+ skb = dev_hard_start_xmit(skb, dev, txq, &rc);
+ dev_xmit_recursion_dec();
- 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
+ /* GSO segments a single SKB into a list of frames.
+ * TCP expects error to mean none of the data was sent.
*/
-recursion_alert:
- net_crit_ratelimited("Dead loop on virtual device %s, fix it urgently!\n",
- dev->name);
- rc = -ENETDOWN;
+ 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();
--
2.53.0.880.g73c4285caa-goog
^ permalink raw reply related [flat|nested] 6+ messages in thread