Re: [PATCH bpf-next V2 0/7] xdp: Allow BPF to set RX hints for XDP_REDIRECTed packets
From: Martin KaFai Lau <martin.lau@linux.dev>
Date: 2025-08-13 03:00:10
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bpf
On 8/7/25 12:07 PM, Jesper Dangaard Brouer wrote:
Yan and I have previously[1] (Oct 2024) explored adding a common callback to XDP drivers, which have access to both the xdp_buff and SKB in the function call. (Ignore the GRO disable bit, focus on callback) We named the functions: xdp_buff_fixup_skb_offloading() and xdp_frame_fixup_skb_offloading() We implemented the driver changes for [bnxt], [mlx5], [ice] and [veth]. What do you think of the idea of adding a BPF-hook, at this callback, which have access to both the XDP and SKB pointer. That would allow us to implement your idea, right? [1] https://lore.kernel.org/all/cover.1718919473.git.yan@cloudflare.com/#r (local) [bnxt] https://lore.kernel.org/all/ f804c22ca168ec3aedb0ee754bfbee71764eb894.1718919473.git.yan@cloudflare.com/ [mlx5] https://lore.kernel.org/ all/17595a278ee72964b83c0bd0b502152aa025f600.1718919473.git.yan@cloudflare.com/ [ice] https://lore.kernel.org/all/ a9eba425bfd3bfac7e7be38fe86ad5dbff3ae01f.1718919473.git.yan@cloudflare.com/ [veth] https://lore.kernel.org/all/ b7c75daecca9c4e36ef79af683d288653a9b5b82.1718919473.git.yan@cloudflare.com/
It should not need a new BPF-hook to consume info produced by an earlier xdp prog. Instead, the same and existing xdp prog can call a kfunc to directly create the skb and update the skb fields. The kfunc could be driver specific, like the current .xmo_rx_xxx.