[PATCH v2] net/sched: hhf: clear heavy-hitter state on reset

[PATCH v2] net/sched: hhf: clear heavy-hitter state on reset

[Samuel Moelius]

HHF reset does not clear the classifier state used to identify heavy
hitters.  Packets after reset can therefore be scheduled using flow
history from before the reset.

The reset operation should return the qdisc to an empty state.

Clear the heavy-hitter classifier tables when HHF is reset.

Fixes: 10239edf86f1 ("net-qdisc-hhf: Heavy-Hitter Filter (HHF) qdisc")
Assisted-by: Codex:gpt-5.5-cyber-preview
Signed-off-by: Samuel Moelius <sam.moelius@trailofbits.com>
---
Changes in v2:
  - Ensure no NULL dereference when initialization fails

 net/sched/sch_hhf.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/net/sched/sch_hhf.c b/net/sched/sch_hhf.c
index 1e25b75daae2..d85cb0263b67 100644
--- a/net/sched/sch_hhf.c
+++ b/net/sched/sch_hhf.c
@@ -462,12 +462,39 @@ static struct sk_buff *hhf_dequeue(struct Qdisc *sch)
 	return skb;
 }
 
+static void hhf_reset_classifier(struct hhf_sched_data *q)
+{
+	int i;
+
+	if (!q->hh_flows)
+		return;
+
+	for (i = 0; i < HH_FLOWS_CNT; i++) {
+		struct hh_flow_state *flow, *next;
+		struct list_head *head = &q->hh_flows[i];
+
+		list_for_each_entry_safe(flow, next, head, flowchain) {
+			list_del(&flow->flowchain);
+			kfree(flow);
+		}
+	}
+	WRITE_ONCE(q->hh_flows_current_cnt, 0);
+
+	for (i = 0; i < HHF_ARRAYS_CNT; i++) {
+		if (q->hhf_valid_bits[i])
+			bitmap_zero(q->hhf_valid_bits[i], HHF_ARRAYS_LEN);
+	}
+	q->hhf_arrays_reset_timestamp = hhf_time_stamp();
+}
+
 static void hhf_reset(struct Qdisc *sch)
 {
+	struct hhf_sched_data *q = qdisc_priv(sch);
 	struct sk_buff *skb;
 
 	while ((skb = hhf_dequeue(sch)) != NULL)
 		rtnl_kfree_skbs(skb, skb);
+	hhf_reset_classifier(q);
 }
 
 static void hhf_destroy(struct Qdisc *sch)
-- 
2.43.0

Re: [PATCH v2] net/sched: hhf: clear heavy-hitter state on reset

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by David S. Miller <davem@davemloft.net>:

On Mon, 29 Jun 2026 16:44:59 +0000 you wrote:
> HHF reset does not clear the classifier state used to identify heavy
> hitters.  Packets after reset can therefore be scheduled using flow
> history from before the reset.
> 
> The reset operation should return the qdisc to an empty state.
> 
> Clear the heavy-hitter classifier tables when HHF is reset.
> 
> [...]

Here is the summary with links:
  - [v2] net/sched: hhf: clear heavy-hitter state on reset
    https://git.kernel.org/netdev/net/c/a225f8c20712

You are awesome, thank you!
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