netdev - Re: [PATCH net-next v4 0/6] move CAN skb headroom content to skb extensions

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Message-ID: <20260128174137.65929694@kernel.org>
Date: Wed, 28 Jan 2026 17:41:37 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Oliver Hartkopp via B4 Relay <devnull+socketcan.hartkopp.net@...nel.org>
Cc: socketcan@...tkopp.net, netdev@...r.kernel.org,
 linux-can@...r.kernel.org, Marc Kleine-Budde <mkl@...gutronix.de>
Subject: Re: [PATCH net-next v4 0/6] move CAN skb headroom content to skb
 extensions

On Wed, 28 Jan 2026 23:43:39 +0100 Oliver Hartkopp via B4 Relay 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.

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