netdev - Re: [Patch v2 net 1/2] netem: Fix skb duplication logic to prevent infinite loops

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Message-ID: <3SdBpUCGSDH5s1aiYafxKcMPi9-g1hKh11zkNKSudHgduTFQn2w_2biBrtFijTuZgfZFAvx__KRdXywmsN6BYUkFg9AaaZXMlxTG0cwzBHA=@willsroot.io>
Date: Tue, 08 Jul 2025 15:56:29 +0000
From: William Liu <will@...lsroot.io>
To: Simon Horman <horms@...nel.org>
Cc: Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org, jhs@...atatu.com, stephen@...workplumber.org, Savino Dicanosa <savy@...t3mfailure.io>
Subject: Re: [Patch v2 net 1/2] netem: Fix skb duplication logic to prevent infinite loops






On Tuesday, July 8th, 2025 at 1:18 PM, Simon Horman <horms@...nel.org> wrote:

> 
> 
> On Mon, Jul 07, 2025 at 12:50:14PM -0700, Cong Wang wrote:
> 
> > This patch refines the packet duplication handling in netem_enqueue() to ensure
> > that only newly cloned skbs are marked as duplicates. This prevents scenarios
> > where nested netem qdiscs with 100% duplication could cause infinite loops of
> > skb duplication.
> > 
> > By ensuring the duplicate flag is properly managed, this patch maintains skb
> > integrity and avoids excessive packet duplication in complex qdisc setups.
> > 
> > Now we could also get rid of the ugly temporary overwrite of
> > q->duplicate.
> > 
> > Fixes: 0afb51e72855 ("[PKT_SCHED]: netem: reinsert for duplication")
> > Reported-by: William Liu will@...lsroot.io
> > Reported-by: Savino Dicanosa savy@...t3mfailure.io
> > Signed-off-by: Cong Wang xiyou.wangcong@...il.com
> 
> 
> Reviewed-by: Simon Horman horms@...nel.org

>From what Jakub and Jamal suggested, the patch for review is now https://patchwork.kernel.org/project/netdevbpf/list/?series=976473&state=*

It was marked for "Changes Requested" about a week ago but I don't recall any specific changes people wanted for v4 of that patch, other than the attempt at this alternative approach in this patchset thread.