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

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Message-ID: <20250708131822.GJ452973@horms.kernel.org>
Date: Tue, 8 Jul 2025 14:18:22 +0100
From: Simon Horman <horms@...nel.org>
To: Cong Wang <xiyou.wangcong@...il.com>
Cc: netdev@...r.kernel.org, jhs@...atatu.com, will@...lsroot.io,
	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 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>