netdev - Re: [PATCHv9 bpf-next] samples/bpf: add xdp program on egress for xdp_redirect

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Date:   Thu, 21 Jan 2021 16:05:38 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Hangbin Liu <liuhangbin@...il.com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Yonghong Song <yhs@...com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        brouer@...hat.com
Subject: Re: [PATCHv9 bpf-next] samples/bpf: add xdp program on egress for
 xdp_redirect_map

On Thu, 21 Jan 2021 21:06:42 +0800
Hangbin Liu <liuhangbin@...il.com> wrote:

> This patch add a xdp program on egress to show that we can modify
> the packet on egress. In this sample we will set the pkt's src
> mac to egress's mac address. The xdp_prog will be attached when
> -X option supplied.
> 
> Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
> 
> ---
> v9:
> roll back to just set src mac to egress interface mac on 2nd xdp prog,
> this could avoid packet reorder introduce in patch v6.

I like this V9 much better.

One (hopefully) last nitpick below.

> diff --git a/samples/bpf/xdp_redirect_map_kern.c b/samples/bpf/xdp_redirect_map_kern.c
> index 6489352ab7a4..35ce5e26bbe5 100644
> --- a/samples/bpf/xdp_redirect_map_kern.c
> +++ b/samples/bpf/xdp_redirect_map_kern.c
> -SEC("xdp_redirect_map")
> -int xdp_redirect_map_prog(struct xdp_md *ctx)
> +static int xdp_redirect_map(struct xdp_md *ctx, void *redirect_map)

Can you make this function always inline?

>  {
>  	void *data_end = (void *)(long)ctx->data_end;
>  	void *data = (void *)(long)ctx->data;
>  	struct ethhdr *eth = data;
>  	int rc = XDP_DROP;
> -	int vport, port = 0, m = 0;
>  	long *value;
>  	u32 key = 0;
>  	u64 nh_off;
> +	int vport;
>  
>  	nh_off = sizeof(*eth);
>  	if (data + nh_off > data_end)
> @@ -79,7 +96,40 @@ int xdp_redirect_map_prog(struct xdp_md *ctx)
>  	swap_src_dst_mac(data);
>  
>  	/* send packet out physical port */
> -	return bpf_redirect_map(&tx_port, vport, 0);
> +	return bpf_redirect_map(redirect_map, vport, 0);
> +}
> +
> +SEC("xdp_redirect_general")
> +int xdp_redirect_map_general(struct xdp_md *ctx)
> +{
> +	return xdp_redirect_map(ctx, &tx_port_general);
> +}
> +
> +SEC("xdp_redirect_native")
> +int xdp_redirect_map_native(struct xdp_md *ctx)
> +{
> +	return xdp_redirect_map(ctx, &tx_port_native);
> +}

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer