netdev - Re: [net-next 0/6] move CAN skb headroom content to skb extensions

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Message-ID: <20260127174937.4c5fc226@kernel.org>
Date: Tue, 27 Jan 2026 17:49:37 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Oliver Hartkopp <socketcan@...tkopp.net>
Cc: netdev@...r.kernel.org, linux-can@...r.kernel.org
Subject: Re: [net-next 0/6] move CAN skb headroom content to skb extensions

On Sun, 25 Jan 2026 21:15:55 +0100 Oliver Hartkopp wrote:
> CAN bus related skbuffs (ETH_P_CAN/ETH_P_CANFD/ETH_P_CANXL) simply contain
> CAN frame structs for CAN CC/FD/XL of skb->len length at skb->data.
> Those CAN skbs do not have network/mac/transport headers nor other such
> references for encapsulated protocols like ethernet/IP protocols.
> 
> To store data for CAN specific use-cases all CAN bus related skbuffs are
> created with a 16 byte private skb headroom (struct can_skb_priv).
> Using the skb headroom and accessing skb->head for this private data
> led to several problems in the past likely due to "The struct can_skb_priv
> business is highly unconventional for the networking stack." [1]
> 
> This patch set aims to remove the unconventional skb headroom usage for
> CAN bus related skbuffs and use the common skb extensions instead.

This is fine. Wish we could make md_dst work, since skb_ext still burns
a bit in the skb (last extension bit in fact, next user will have to
bump the filed size). And you very much do not route these frames, 
so dst would work perfectly fine. But whatever.

lore never received patch 6, tho, you'll need to repost.
-- 
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