From bdf366bd867c4565b535a5825df7ddcb4773fc28 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Thu, 16 Feb 2023 00:46:31 +0200 Subject: [PATCH] net/sched: taprio: don't allow dynamic max_sdu to go negative after stab adjustment The overhead specified in the size table comes from the user. With small time intervals (or gates always closed), the overhead can be larger than the max interval for that traffic class, and their difference is negative. What we want to happen is for max_sdu_dynamic to have the smallest non-zero value possible (1) which means that all packets on that traffic class are dropped on enqueue. However, since max_sdu_dynamic is u32, a negative is represented as a large value and oversized dropping never happens. Use max_t with int to force a truncation of max_frm_len to no smaller than dev->hard_header_len + 1, which in turn makes max_sdu_dynamic no smaller than 1. Fixes: fed87cc6718a ("net/sched: taprio: automatically calculate queueMaxSDU based on TC gate durations") Signed-off-by: Vladimir Oltean Reviewed-by: Kurt Kanzenbach Signed-off-by: Paolo Abeni --- net/sched/sch_taprio.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c index 556e72e..53ba4d6 100644 --- a/net/sched/sch_taprio.c +++ b/net/sched/sch_taprio.c @@ -279,8 +279,14 @@ static void taprio_update_queue_max_sdu(struct taprio_sched *q, u32 max_frm_len; max_frm_len = duration_to_length(q, sched->max_open_gate_duration[tc]); - if (stab) + /* Compensate for L1 overhead from size table, + * but don't let the frame size go negative + */ + if (stab) { max_frm_len -= stab->szopts.overhead; + max_frm_len = max_t(int, max_frm_len, + dev->hard_header_len + 1); + } max_sdu_dynamic = max_frm_len - dev->hard_header_len; } -- 2.7.4