netdev - Re: [Patch v3 net 1/4] net_sched: Implement the right netem duplication behavior

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Message-ID: <20250713151220.772882ab@hermes.local>
Date: Sun, 13 Jul 2025 15:12:20 -0700
From: Stephen Hemminger <stephen@...workplumber.org>
To: Cong Wang <xiyou.wangcong@...il.com>
Cc: netdev@...r.kernel.org, jhs@...atatu.com, will@...lsroot.io, Savino
 Dicanosa <savy@...t3mfailure.io>
Subject: Re: [Patch v3 net 1/4] net_sched: Implement the right netem
 duplication behavior

On Sun, 13 Jul 2025 14:47:45 -0700
Cong Wang <xiyou.wangcong@...il.com> wrote:

> +	if (q->duplicate) {
> +		bool dup = true;
> +
> +		if (netem_skb_cb(skb)->duplicate) {
> +			netem_skb_cb(skb)->duplicate = 0;
> +			dup = false;
> +		}
> +		if (dup && q->duplicate >= get_crandom(&q->dup_cor, &q->prng))
> +			++count;
> +	}

Doesn't look ideal.

Why do yo need the temporary variable here?
And you risk having bug where first duplicate sets the flag then second clears it
and a third layer would do duplicate and reset it.