Re: [PATCH v7 0/5] netem: bug fixes

Simon Horman
2026-04-17T16:02:11Z

On Wed, Apr 15, 2026 at 07:27:03AM -0700, Stephen Hemminger wrote:
> These bugs were found when doing AI assisted review of sch_netem.c
> during investigation of the packet duplication recursion problem
> addressed in Jamal's series.
>
> The fixes cover:
>
> - probability gaps in the 4-state Markov loss model
> - queue limit not accounting for reordered packets
> - PRNG reseeded on every tc change, breaking reproducibility
> - slot delay configuration not validated for inverted ranges
> - slot delay arithmetic overflow for ranges above ~2.1 seconds
>
> v7 - queue limit check Fixes: goes back further to earlier change
> - use NL_SET_ERR_MSG_ATTR
>
> Stephen Hemminger (5):
> net/sched: netem: fix probability gaps in 4-state loss model
> net/sched: netem: fix queue limit check to include reordered packets
> net/sched: netem: only reseed PRNG when seed is explicitly provided
> net/sched: netem: check for invalid slot range
> net/sched: netem: fix slot delay calculation overflow

To the maintainers: I'd like to ask for more time to complete review of this.