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From: "Gaul, Maximilian" <maximilian.gaul@hm.edu>
Subject: Intel 10G 2P X520 Adapter doesn't receive anything with AF XDP
Date: Thu, 4 Jun 2020 19:25:23 +0000
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To: Xdp <xdp-newbies@vger.kernel.org>

Sorry to ask another question but I don't get this working.

I have this AF_XDP test program which creates an ordinary SOCK_RAW socket a=
nd adds a multicast address to it via IP_ADD_MEMBERSHIP.
Then it loads a BPF program and launches an AF_XDP socket which then proces=
ses packets of that multicast.

This works fine on my Mellanox ConnectX5 card, but it doesn't work on my In=
tel 10G 2P X520 (Kernel 5.6.0 and driver ixgbe 5.1.0-k).
I have an array map in the BPF program which counts the amount of packets r=
eceived on each RX-Queue:

=09=09SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx) {

=09=09=09const void *data =3D (void*)(unsigned long)ctx->data;
=09=09=09const void *data_end =3D (void*)(unsigned long)ctx->data_end;
=09=09=09const int rx_queue_idx =3D ctx->rx_queue_index;

=09=09=09const struct ethhdr *eth =3D (struct ethhdr*)(data);

=09=09=09unsigned long *idx_counter =3D bpf_map_lookup_elem(&rx_queue_pckt_=
counter_map, &rx_queue_idx);
=09=09=09if(idx_counter !=3D NULL) {
=09=09=09=09*idx_counter +=3D 1;
=09=09=09}

I can then look at this map via bpftool. What I found is that almost no pac=
kets are received: only like 4 packets on RX-Queues 1, 2, 3, 4 which I assu=
me are random pings in the network or something but nothing significant (th=
e multicast stream would have a packet rate of 270k pps).

The strange thing now is that everything works fine if I just use that gene=
ric Linux socket to receive the packets (without any XDP / AF_XDP / BPF inv=
olved).

Any ideas why that is?

Best regards

Max