netdev - Re: [Intel-wired-lan] [PATCH net-next 1/2] igc: AF_XDP zero-copy metadata adjust breaks SKBs on XDP

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Date:   Sun, 21 Nov 2021 12:32:13 +0200
From:   "Kraus, NechamaX" <nechamax.kraus@...ux.intel.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org
Cc:     intel-wired-lan@...ts.osuosl.org, bjorn@...nel.org,
        Jakub Kicinski <kuba@...nel.org>, bpf@...r.kernel.org,
        Daniel Borkmann <borkmann@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>, magnus.karlsson@...el.com
Subject: Re: [Intel-wired-lan] [PATCH net-next 1/2] igc: AF_XDP zero-copy
 metadata adjust breaks SKBs on XDP_PASS

On 11/15/2021 22:36, Jesper Dangaard Brouer wrote:
> Driver already implicitly supports XDP metadata access in AF_XDP
> zero-copy mode, as xsk_buff_pool's xp_alloc() naturally set xdp_buff
> data_meta equal data.
> 
> This works fine for XDP and AF_XDP, but if a BPF-prog adjust via
> bpf_xdp_adjust_meta() and choose to call XDP_PASS, then igc function
> igc_construct_skb_zc() will construct an invalid SKB packet. The
> function correctly include the xdp->data_meta area in the memcpy, but
> forgot to pull header to take metasize into account.
> 
> Fixes: fc9df2a0b520 ("igc: Enable RX via AF_XDP zero-copy")
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
> ---
>   drivers/net/ethernet/intel/igc/igc_main.c |    4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
Tested-by: Nechama Kraus <nechamax.kraus@...ux.intel.com>