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Chapter 6: Packet filtering with Raw Sockets

  • A full description of this example can be found in Chapter 6.
  • Please remember that the examples here are tested in the Vagrant machine. Please read more in README.md.
  • Make sure to change the example accordingly if you wish to build somewhere else, open an issue if you have problems doing so!
  • All the dependencies are already handled if you followed the instructions in the main README.md.

In the machine:

Enter into this example folder:

cd ~/linux-observability-with-bpf/code/chapter-6/packet-filtering-raw-sockets

Compile the loader

./build-loader.sh /kernel-src

It will create a binary file named loader-bin

Compile the program

./build-bpf-program.sh

It will create a BPF ELF named bpf-program.o

Execute the program using the loader:

sudo ./loader-bin bpf_program.o

It will show something like this, ten results, one every second for ten seconds:

TCP 0 UDP 0 ICMP 0 packets
TCP 0 UDP 0 ICMP 0 packets
TCP 0 UDP 0 ICMP 0 packets
TCP 0 UDP 0 ICMP 0 packets
TCP 0 UDP 0 ICMP 4 packets
TCP 0 UDP 0 ICMP 8 packets
TCP 0 UDP 0 ICMP 12 packets
TCP 0 UDP 0 ICMP 16 packets
TCP 0 UDP 0 ICMP 16 packets
TCP 0 UDP 0 ICMP 16 packets

Since the program is attached to the loopback interface lo (see loader.c line 30) we need to generate traffic on that interface to show the packets flow.

You can simply do a ping to localhost in the VM while the program is running.

ping 127.0.0.1