Subject: Re: [PATCH net-next 0/6] net/sched: netem: cleanups and improvements

From: Stephen Hemminger <[email-masked]>
Date: Mon, 30 Mar 2026 07:49:23 -0700

On Mon, 30 Mar 2026 10:16:21 +0200
Paolo Abeni <[email-masked]> wrote:

> On 3/28/26 7:26 PM, Stephen Hemminger wrote:
> > Cleanup and improvement patches for netem, done as follow-on
> > to the bug fix series found during AI-assisted review.
> > 
> > - replace pr_info() with netlink extack error reporting
> > - validate slot min/max delay range on configuration
> > - fix slot delay calculation overflow for large ranges
> > - remove unused loss model struct fields
> > - remove stale VERSION string
> > - add per-impairment extended statistics (delayed, dropped,
> >   corrupted, duplicated, reordered, ecn_marked)
> > 
> > The xstats patch requires a corresponding iproute2 change
> > to display the new counters in tc -s qdisc show. This will go
> > as separate patch after this.
> > 
> > Stephen Hemminger (6):
> >   net/sched: netem: replace pr_info with netlink extack error messages
> >   net/sched: netem: check for invalid slot range
> >   net/sched: netem: fix slot delay calculation overflow
> >   net/sched: netem: remove unused loss model fields
> >   net/sched: netem: remove useless VERSION
> >   net/sched: netem: add per-impairment extended statistics
> > 
> >  include/uapi/linux/pkt_sched.h |   9 +++
> >  net/sched/sch_netem.c          | 120 ++++++++++++++++++++++-----------
> >  2 files changed, 89 insertions(+), 40 deletions(-)  
> 
> I wild guess this is causing TDC failures:
> 
> # not ok 364 8c17 - Test netem's recursive duplicate
> # Value doesn't match: bytes: 294 != 196
> # Matching against output: {'kind': 'netem', 'handle': '1:', 'root':
> True, 'refcnt': 2, 'options': {'limit': 1, 'duplicate': {'duplicate': 1,
> 'correlation': 0}, 'seed': 6495514880116664183, 'ecn': False, 'gap': 0},
> 'bytes': 196, 'packets': 2, 'drops': 1, 'overlimits': 0, 'requeues': 0,
> 'backlog': 0, 'qlen': 0}
> 
> Possibly patch 6/6 needs to update the expected netem output accordingly?!?
> 
> Also there are a is a checkpatch issue on patch 2/6 (empty line between
> fixes tag and SoB). Tentatively set this revision to 'changes requested'.
> 
> /P
> 

The other patches from Jamal should go in that fix the duplicate loop
stuff.