P4-Kataran

p4c-ebpf --arch psa -o OUTPUT.c test.p4

TODO specify difference between with and without --xdp

Compilation

You can compile a P4-16 PSA program for eBPF in a single step using:

make -f backends/ebpf/runtime/kernel.mk BPFOBJ=out.o P4FILE=<P4-PROGRAM>.p4 P4C=p4c-ebpf psa

You can also perform compilation step by step:

TODO at the moment is not working fine, investigate.

$ p4c-ebpf --arch psa --target kernel -o out.c main.p4
$ clang -Ibackends/ebpf/runtime -Ibackends/ebpf/runtime/usr/include -O2 -g -c -emit-llvm -o out.bc out.c
$ llc -march=bpf -mcpu=generic -filetype=obj -o out.o out.bc

TODO Note about relative path that make sense to clang otherwise https://github.com/NIKSS-vSwitch/nikss/issues/101#issue-1724077656 solution https://github.com/NIKSS-vSwitch/nikss/issues/101#issuecomment-1564308258

Note that you can use -mcpu flag to define the eBPF instruction set. Visit this blog post to learn more about eBPF instruction sets.

The above steps generate out.o BPF object file that can be loaded to the kernel.

NIKSS API and nikss-ctl

To load eBPF programs generated by P4-eBPF compiler run:

$ nikss-ctl pipeline load id <PIPELINE-ID> out.o

Note you migth need to use sudo

PIPELINE-ID is a user-defined value used to uniquely identify PSA-eBPF pipeline (we are going to support for multiple PSA-eBPF pipelines running in parallel). In the next step, for each interface that should be attached to PSA-eBPF run:

$ nikss-ctl add-port pipe <PIPELINE-ID> dev <INTF>

Note you migth need to use sudo

Troubleshooting

The PSA implementation for eBPF backend generates standard BPF objects that can be inspected using bpftool.

To troubleshoot PSA-eBPF program you will probably need bpftool. Follow the steps below to install it.

You should be able to see bpftool help:

$ bpftool help
  Usage: bpftool [OPTIONS] OBJECT { COMMAND | help }
         bpftool batch file FILE
         bpftool version

         OBJECT := { prog | map | link | cgroup | perf | net | feature | btf | gen | struct_ops | iter }
         OPTIONS := { {-j|--json} [{-p|--pretty}] | {-f|--bpffs} |
                      {-m|--mapcompat} | {-n|--nomount} }

You can install it via:

sudo apt install linux-tools-common

Refer to the bpftool guide for more examples how to use it.