🐝 tinyfilter

eBPF (XDP) packet filter for the layer 2, 3 and 4.

The filtering mechanism is inspired by Berkeley packet filters but in a simpler way.

📖 Build and run

You only need the following requirements (packages):

• llvm
• clang
• make
• libxdp

Debian / Ubuntu

apt install -y llvm clang make libxdp-dev

RHEL / Fedora

dnf install -y llvm clang make libxdp-devel

You should also have bpftool if you need to debug.

To build, run the following command.

make

Then you can run.

./tinyfilter help

🤝 Contribute

If you want to help the project, you can follow the guidelines in CONTRIBUTING.md.

📏 Filters

There are multiple available filters, addresse and port can be source or/and dest.

• Layer 2
  • Ethernet (adresses)
• Layer 3
  • IPv4 (adresses)
  • IPv6 (adresses)
• Layer 4
  • TCP (ports)
  • UDP (ports)
  • ICMP (type)

⭐ Use cases

To test the program, I have created two Linux network namespaces (both reachable by each other) following this steps.

# Creates namespaces
ip netns add ns1
ip netns add ns2

# Creates two wirtual network interface peered
ip link add veth1 type veth peer name veth2

# Assigns virtual interface to the namespaces
ip link set veth1 netns ns1
ip link set veth2 netns ns2

# Assigns IP addresses to the virtual interfaces inside the namespaces
ip netns exec ns1 ip addr add 10.10.0.2/24 dev veth1
ip netns exec ns2 ip addr add 10.10.0.3/24 dev veth2

# Enables the virtual interfaces inside the namespaces
ip netns exec ns1 ip link set dev veth1 up
ip netns exec ns2 ip link set dev veth2 up

Now everything is setup, you can run the XDP program inside the first network namespace and play with filters.

📎 Some examples

Load the XDP program

./tinyfilter load -i veth1

If you this error libxdp: No bpffs found at /sys/fs/bpf, you can mount the filesystem using the following command.

mount -t bpf bpf /sys/fs/bpf/

Load the XDP program with the XDP_PASS return value

./tinyfilter load -i veth1 -b ./src/tinyfilter_pass.bpf.o

Filter for TCP from port 10001 to 10002

./tinyfilter port add -i veth1 --src 10001 --dst 10002 -p tcp

Filter for SSH port

./tinyfilter port add -i veth1 --dst 22 -p tcp

Filter for IPv6 address fe80::9c0c:93ff:fe18:7d1d

./tinyfilter ip6 add -i veth1 --src fe80::9c0c:93ff:fe18:7d1d

🎉 Tasks

• Resolve layer 4 protocols strings
• Implement ICMP filters
• Two programs for two default policy (allow / drop)
• Unpin maps at unload by network interface name