On Thu, Nov 26, 2020 at 11:51:19AM +0100, Jesper Dangaard Brouer wrote:
> On Thu, 26 Nov 2020 16:43:25 +0800
> Hangbin Liu <liuhang...@gmail.com> wrote:
>
> > Current sample test xdp_redirect_map only count pkts on ingress. But we
> > can't know whether the pkts are redirected or dropped. So add a counter
> > on egress interface so we could know how many pkts are redirect in fact.
>
> This is not true.
>
> The 2nd devmap XDP-prog will run in the same RX-context, so it doesn't
> tell us if the redirect was successful. I looked up the code, and the
> 2nd XDP-prog is even allowed to run when the egress driver doesn't
> support the NDO to xmit (dev->netdev_ops->ndo_xdp_xmit), which is very
> misleading, if you place a output counter here.
>
> --
> Best regards,
> Jesper Dangaard Brouer
> MSc.CS, Principal Kernel Engineer at Red Hat
> LinkedIn: http://www.linkedin.com/in/brouer
>
>
> static inline int __xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
> struct net_device *dev_rx)
> {
> struct xdp_frame *xdpf;
> int err;
>
> if (!dev->netdev_ops->ndo_xdp_xmit)
> return -EOPNOTSUPP;
>
Err... You are right. I didn't read this part carefully.
Based on Toke's suggestion, maybe edit the src mac address to the egress
iface's mac address is a better example. WDYT?
And does it make any sense to run perf test for 2nd xdp program
for xdp_redirect_map?
Thanks
Hangbin
> err = xdp_ok_fwd_dev(dev, xdp->data_end - xdp->data);
> if (unlikely(err))
> return err;
>
> xdpf = xdp_convert_buff_to_frame(xdp);
> if (unlikely(!xdpf))
> return -EOVERFLOW;
>
> bq_enqueue(dev, xdpf, dev_rx);
> return 0;
> }
>
>
> int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
> struct net_device *dev_rx)
> {
> struct net_device *dev = dst->dev;
>
> if (dst->xdp_prog) {
> xdp = dev_map_run_prog(dev, xdp, dst->xdp_prog);
> if (!xdp)
> return 0;
> }
> return __xdp_enqueue(dev, xdp, dev_rx);
> }
>
