netdev - Re: [PATCH net 0/6] net/sched: Fix packet loops in mirred and netem

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Message-ID: <CAM_iQpXXiOj=+jbZbmcth06-46LoU_XQd5-NuusaRdJn-80_HQ@mail.gmail.com>
Date: Tue, 13 Jan 2026 12:10:12 -0800
From: Cong Wang <xiyou.wangcong@...il.com>
To: Jamal Hadi Salim <jhs@...atatu.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, horms@...nel.org, andrew+netdev@...n.ch, 
	netdev@...r.kernel.org, jiri@...nulli.us, victor@...atatu.com, 
	dcaratti@...hat.com, lariel@...dia.com, daniel@...earbox.net, 
	pablo@...filter.org, kadlec@...filter.org, fw@...len.de, phil@....cc, 
	netfilter-devel@...r.kernel.org, coreteam@...filter.org, 
	zyc199902@...omail.cn, lrGerlinde@...lfence.com, jschung2@...ton.me
Subject: Re: [PATCH net 0/6] net/sched: Fix packet loops in mirred and netem

On Sun, Jan 11, 2026 at 8:40 AM Jamal Hadi Salim <jhs@...atatu.com> wrote:
>
>
> We introduce a 2-bit global skb->ttl counter.Patch #1 describes how we puti
> together those bits. Patches #2 and patch #5 use these bits.
> I added Fixes tags to patch #1 in case it is useful for backporting.
> Patch #3 and #4 revert William's earlier netem commits. Patch #6 introduces
> tdc test cases.

3 reasons why this patchset should be rejected:

1) It increases sk_buff size potentially by 1 byte with minimal config

2) Infinite loop is the symptom caused by enqueuing to the root qdisc,
fixing the infinite loop itself is fixing the symptom and covering up the
root cause deeper.

3) Using skb->ttl makes netem duplication behavior less predictable
for users. With a TTL-based approach, the duplication depth is limited
by a kernel-internal constant that is invisible to userspace. Users
configuring nested netem hierarchies cannot determine from tc
commands alone whether their packets will be duplicated at each
stage or silently pass through when TTL is exhausted.

NACKed-by: Cong Wang <xiyou.wangcong@...il.com>

(I hope I am still better than your AI.)

Regards,
Cong