Re: [PATCH bpf-next v4 2/3] bpf: support specifying ingress via xdp_md context in BPF_PROG_TEST_RUN

[Yonghong Song <yhs@fb.com>]

On 6/4/21 3:02 PM, Zvi Effron wrote:
> Support specifying the ingress_ifindex and rx_queue_index of xdp_md
> contexts for BPF_PROG_TEST_RUN.
> 
> The intended use case is to allow testing XDP programs that make decisions
> based on the ingress interface or RX queue.
> 
> If ingress_ifindex is specified, look up the device by the provided index
> in the current namespace and use its xdp_rxq for the xdp_buff. If the
> rx_queue_index is out of range, or is non-zero when the ingress_ifindex is
> 0, return EINVAL.
> 
> Co-developed-by: Cody Haas <chaas@riotgames.com>
> Signed-off-by: Cody Haas <chaas@riotgames.com>
> Co-developed-by: Lisa Watanabe <lwatanabe@riotgames.com>
> Signed-off-by: Lisa Watanabe <lwatanabe@riotgames.com>
> Signed-off-by: Zvi Effron <zeffron@riotgames.com>
> ---
>   net/bpf/test_run.c | 16 +++++++++++++++-
>   1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
> index 698618f2b27e..3916205fc3d4 100644
> --- a/net/bpf/test_run.c
> +++ b/net/bpf/test_run.c
> @@ -690,6 +690,8 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
>   static int xdp_convert_md_to_buff(struct xdp_buff *xdp, struct xdp_md *xdp_md)
>   {
>   	void *data;
> +	struct net_device *device;
> +	struct netdev_rx_queue *rxqueue;

reverse christmas tree?

>   
>   	if (!xdp_md)
>   		return 0;
> @@ -702,9 +704,21 @@ static int xdp_convert_md_to_buff(struct xdp_buff *xdp, struct xdp_md *xdp_md)
>   
>   	xdp->data = xdp->data_meta + xdp_md->data;
>   
> -	if (xdp_md->ingress_ifindex != 0 || xdp_md->rx_queue_index != 0)
> +	if (!xdp_md->ingress_ifindex && xdp_md->rx_queue_index)
>   		return -EINVAL;

xdp_md->ingress_ifindex and xdp_md->rx_queue_index are used three times 
each in this function here. Maybe worthwhile to assign them to
temporary variables?

>   
> +	if (xdp_md->ingress_ifindex) {
> +		device = dev_get_by_index(current->nsproxy->net_ns, xdp_md->ingress_ifindex);
> +		if (!device)
> +			return -EINVAL;
> +
> +		if (xdp_md->rx_queue_index >= device->real_num_rx_queues)
> +			return -EINVAL;
> +
> +		rxqueue = __netif_get_rx_queue(device, xdp_md->rx_queue_index);
> +		xdp->rxq = &rxqueue->xdp_rxq;
> +	}
> +
>   	return 0;
>   }
>   
>