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Date: Wed, 26 Aug 2026 23:25:54 +0200
From: Florian Westphal <fw@strlen.de>
To: Jakub Sitnicki <jakub@cloudflare.com>
Cc: netdev@vger.kernel.org, Steffen Klassert <steffen.klassert@secunet.com>,
	kernel-team@cloudflare.com
Subject: Re: [PATCH RFC net-next] net: Use fixed slots for skb extensions
Message-ID: <ao9Z4vK-_pzu03uu@strlen.de>
References: <20260825-rfc-skb-ext-fixed-offsets-v1-1-8050ff33bec9@cloudflare.com>
 <ao9UV9S7rUkyQ8jv@strlen.de>
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In-Reply-To: <ao9UV9S7rUkyQ8jv@strlen.de>

Florian Westphal <fw@strlen.de> wrote:
> (or maybe use &= so as to flag something as active
>  that was never enabled).
> 
> Regarding skb_ext_maybe_cow() in above function: Why not ..
> 
> - Fix skb_ext_put_mctp to be safe against double-put.

Should be done in any case.  __skb_ext_del() also lacks
SKB_EXT_MCTP handling.

Once thats fixed, skb_ext_scrub() could look like this, no?

static int __skb_ext_scrub(struct sk_buff *skb, unsigned int keep)
{
	int i;

	for (i = 0; i < SKB_EXT_NUM; i++) {
		if (((i << 1) & keep) == 0)
			skb_ext_del(skb, i);
	}
}

AFAICS that handles all cases, also, doing skb_ext_del() for
all active extensions is supposed to be equal to skb_ext_reset().