af_xdp tests for Linux 4.19

First of all, please install 4.19 kernel for your Ubuntu machine this way

I will use Ubuntu 18.04.

In this guide I will build example AF_XDP application without using any bundled make files from kernel to get more understanding what's going on inside.

We need compilers:

sudo apt-get update 
sudo apt-get install -y clang llvm gcc make

Pull source code:

cd
wget https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.19.tar.xz
tar -xf linux-4.19.tar.xz
cd linux-4.19

Build bpf library:

sudo apt-get install -y libelf-dev
cd /root/linux-4.19/tools/lib/bpf
make
mkdir /opt/libbpf
cp libbpf.so libbpf.a /opt/libbpf
mkdir -p /opt/libbpf/include/bpf
cp bpf.h libbpf.h /opt/libbpf/include/bpf

I use this unpretty way for fixing compilation errors because I can't use include from new kernel due to minor make-kpkg bug:

cp ~/linux-4.19/include/uapi/linux/if_xdp.h /usr/include/linux/if_xdp.h
cp ~/linux-4.19/include/uapi/linux/if_link.h /usr/include/linux/if_link.h
cp  ~/linux-4.19/include/uapi/linux/bpf.h  /usr/include/linux/bpf.h

And finally build main example for AF_XDP from developers:

cd /root/linux-4.19/samples/bpf
gcc xdpsock_user.c -o xdpsock_user -lpthread -L/opt/libbpf -lbpf -lelf  -I/opt/libbpf/include -I/root/linux-4.19/tools/testing/selftests/bpf

Build BPF tool (keep your mind sane! Build command has huge number of tricky things, I copy'n'pasted it from official examples):

clang -c  xdpsock_kern.c  -I/root/linux-4.19/include -I/root/linux-4.19/tools/testing/selftests/bpf -D__KERNEL__ -D__BPF_TRACING__ -Wno-unused-value -Wno-pointer-sign  -Wno-compare-distinct-pointer-types -Wno-gnu-variable-sized-type-not-at-end -Wno-address-of-packed-member -Wno-tautological-compare   -Wno-unknown-warning-option  -O2 -emit-llvm -c -o -| llc -march=bpf -filetype=obj  -o xdpsock_user_kern.o

Also, you must change this structure, first 16 bytes should specify ethernet addresses (MAC destination / MAC source):

static const char pkt_data[] =
        "\xec\x0d\x9a\x84\x40\xb6\xec\x0d\x9a\x84\x40\xda\x08\x00\x45\x00"
        "\x00\x2e\x00\x00\x00\x00\x40\x11\x88\x97\x05\x08\x07\x08\xc8\x14"
        "\x1e\x04\x10\x92\x10\x92\x00\x1a\x6d\xa3\x34\x33\x1f\x69\x40\x6b"
        "\x54\x59\xb6\x14\x2d\x11\x44\xbf\xaf\xd9\xbe\xaa";

To implement processing properly, you must target all traffic to queue 16 using flow director (I used Mellanox CX-4 and you can use ixgbe also):

ethtool -N enP9p144s0f0 flow-type udp4 src-port 4242 dst-port 4242           action 16

Run receiver tool:

LD_LIBRARY_PATH=/opt/libbpf ./xdpsock_user --rxdrop --interface enP9p144s0f0 --queue=16

Traffic generation command:

LD_LIBRARY_PATH=/opt/libbpf ./xdpsock_user --txonly --interface enP9p144s0f0

Expected output for traffic generator:

 sock0@enP9p144s0f0:0 txonly 	
                pps         pkts        0.10       
rx              0           0          
tx              0           292,352,353

Receiver side:

 sock0@enP9p144s0f0:16 rxdrop 	
                pps         pkts        0.23       
rx              0           297,753,014
tx              0           0