netdev - Re: [PATCH][bpf-next] bpf: return EOPNOTSUPP when invalid map type in __bpf_tx_xdp

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Date:   Wed, 8 Jan 2020 18:17:55 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Li RongQing <lirongqing@...du.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org, brouer@...hat.com
Subject: Re: [PATCH][bpf-next] bpf: return EOPNOTSUPP when invalid map type in
 __bpf_tx_xdp_map

On 1/3/20 7:25 AM, Li RongQing wrote:
> a negative value -EOPNOTSUPP should be returned if map->map_type
> is invalid although that seems unlikely now, then the caller will
> continue to handle buffer, or else the buffer will be leaked
> 
> Signed-off-by: Li RongQing <lirongqing@...du.com>
> ---
>   net/core/filter.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 1cbac34a4e11..40fa5905321c 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -3512,7 +3512,7 @@ static int __bpf_tx_xdp_map(struct net_device *dev_rx, void *fwd,
>   	case BPF_MAP_TYPE_XSKMAP:
>   		return __xsk_map_redirect(fwd, xdp);
>   	default:
> -		break;
> +		return -EOPNOTSUPP;

So in case of generic XDP we return with -EBADRQC in xdp_do_generic_redirect_map().
I would suggest we adapt the same error code here as well, so it's consistent for
the tracepoint output and not to be confused with -EOPNOTSUPP from other locations
like dev_map_enqueue() when ndo_xdp_xmit is missing or such.

>   	}
>   	return 0;
>   }
>