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Contribute

Know-How

You will need:

  • Docker for the build-dependencies (or install Go and the dependencies locally..)
  • Some knowledge about how eBPF works

Docs

Build

DEV Build: bash scripts/build_dev.sh <SRC-DIR>

Full Build: make build_all or bash scripts/build_all.sh

We use docker to build the binaries as this provides a clean and reproducible build-environment.

We use cilium/ebpf bpf2go to cross-compile the sources.

This is what happens in the build-process:

  1. We build the docker-image from docker/Dockerfile_build
  2. Using the bpftool we generate the build/vmlinux.h file
  3. Download go dependencies
  4. Using the bpf2go tool we generate the src/bpf_bpfe[b|l].[o|go] files (see: //go:generate in main.go)
  5. Then we build the binaries into build/

Debug

You can use bpf_trace_printk(fmt, sizeof(fmt)); to temporarily enable debug-output. See: eBPF Docs

You can read it via: sudo cat /sys/kernel/tracing/trace | grep BPF (if you add prefix like [eBPF] to the message)

NOTE: bpf_trace_printk can only take 3 format-parameters.

Examples:

  • Format IPv4

    const char log_ip4[] = "[eBPF] IP4: %pI4\n";
bpf_trace_printk(log_ip4, sizeof(log_ip4), &ip4->saddr);
// bpf_trace_printk: [eBPF] IP4: 127.0.0.1

  • Format IPv6

    const char log_ip6[] = "[eBPF] IP6: %pI6\n";
bpf_trace_printk(log_ip6, sizeof(log_ip6), &ip6->saddr);
// bpf_trace_printk: [eBPF] IP6: fe80:0000:0000:0000:c87f:acff:fe69:287a

  • Write hex of bytes

    const char log_ip6_p1[] = "[eBPF] IP6: Parts 1+2 (0x%x 0x%x)\n";
bpf_trace_printk(log_ip6_p1, sizeof(log_ip6_p1), bpf_ntohl(ip6o.addr[0]), bpf_ntohl(ip6o.addr[1]));
const char log_ip6_p2[] = "[eBPF] IP6: Parts 3+4 (0x%x 0x%x)\n";
bpf_trace_printk(log_ip6_p2, sizeof(log_ip6_p2), bpf_ntohl(ip6o.addr[2]), bpf_ntohl(ip6o.addr[3]));
// bpf_trace_printk: [eBPF] IP6: Parts 1+2 (0xfe800000 0x0)
// bpf_trace_printk: [eBPF] IP6: Parts 3+4 (0xc87facff 0xfe69287a)