[PATCH v3] net/sched: dualpi2: clear stale classification on filter miss
From: Samuel Moelius
Date: Sun Jun 28 2026 - 09:50:35 EST
DualPI2 leaves previous classification state attached to an skb when
filter classification returns no match. The enqueue path can then act
on stale state from an earlier classification attempt.
A filter miss should fall back to the default class without reusing old
per-packet classification data.
Initialize the classification result to CLASSIC before running the
classifier. Explicit L4S, priority, and successful filter
classification can still override that default.
Fixes: 8f9516daedd6 ("sched: Add enqueue/dequeue of dualpi2 qdisc")
Assisted-by: Codex:gpt-5.5-cyber-preview
Signed-off-by: Samuel Moelius <sam.moelius@xxxxxxxxxxxxxxx>
---
Changes in v3:
- Improve readability
Changes in v2:
- Add fixes tag
net/sched/sch_dualpi2.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/sched/sch_dualpi2.c b/net/sched/sch_dualpi2.c
index 5434df6ca8ef..27088760eff4 100644
--- a/net/sched/sch_dualpi2.c
+++ b/net/sched/sch_dualpi2.c
@@ -346,6 +346,8 @@ static int dualpi2_skb_classify(struct dualpi2_sched_data *q,
struct tcf_proto *fl;
int result;
+ cb->classified = DUALPI2_C_CLASSIC;
+
dualpi2_read_ect(skb);
if (cb->ect & q->ecn_mask) {
cb->classified = DUALPI2_C_L4S;
@@ -359,10 +361,8 @@ static int dualpi2_skb_classify(struct dualpi2_sched_data *q,
}
fl = rcu_dereference_bh(q->tcf_filters);
- if (!fl) {
- cb->classified = DUALPI2_C_CLASSIC;
+ if (!fl)
return NET_XMIT_SUCCESS;
- }
result = tcf_classify(skb, NULL, fl, &res, false);
if (result >= 0) {
--
2.43.0