netdev - Re: [PATCH v19 bpf-next 23/23] xdp: disable XDP

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Date:   Mon, 6 Dec 2021 18:11:43 +0100
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>, bpf@...r.kernel.org,
        netdev@...r.kernel.org
Cc:     brouer@...hat.com, lorenzo.bianconi@...hat.com,
        davem@...emloft.net, kuba@...nel.org, ast@...nel.org,
        daniel@...earbox.net, shayagr@...zon.com, john.fastabend@...il.com,
        dsahern@...nel.org, echaudro@...hat.com, jasowang@...hat.com,
        alexander.duyck@...il.com, saeed@...nel.org,
        maciej.fijalkowski@...el.com, magnus.karlsson@...el.com,
        tirthendu.sarkar@...el.com, toke@...hat.com
Subject: Re: [PATCH v19 bpf-next 23/23] xdp: disable XDP_REDIRECT for xdp
 multi-buff

On 30/11/2021 12.53, Lorenzo Bianconi wrote:
> XDP_REDIRECT is not fully supported yet for xdp multi-buff since not
> all XDP capable drivers can map non-linear xdp_frame in ndo_xdp_xmit
> so disable it for the moment.
> 
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---
>   net/core/filter.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/net/core/filter.c b/net/core/filter.c
> index b70725313442..a87d835d1122 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -4189,6 +4189,13 @@ int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
>   	struct bpf_map *map;
>   	int err;
>   
> +	/* XDP_REDIRECT is not fully supported yet for xdp multi-buff since
> +	 * not all XDP capable drivers can map non-linear xdp_frame in
> +	 * ndo_xdp_xmit.
> +	 */
> +	if (unlikely(xdp_buff_is_mb(xdp)))
> +		return -EOPNOTSUPP;
> +

This approach also exclude 'cpumap' use-case, which you AFAIK have added 
MB support for in this patchset.

Generally this check is hopefully something we can remove again, once 
drivers add MB ndo_xdp_xmit support.


>   	ri->map_id = 0; /* Valid map id idr range: [1,INT_MAX[ */
>   	ri->map_type = BPF_MAP_TYPE_UNSPEC;
>   
>