oxdpus is a toy tool that demonstrates some of the super powers of XDP - a high performance packet processing path built into the kernel.

To build oxdpus you have to satisify the following requirements:

• have a modern Linux kernel (>4.12) that supports XDP
• linux headers
• clang
• LLVM
• Go >1.12
• gobindata (to embed XDP bytecode inside Go binary)

This repository ships with a Makefile to facilitate the build process. The make xdp command compiles the XDP program and generates Go source code to reference the resulting bytecode. Once the XDP ELF object is produced, you can build the Go binary with make go. After compilation is done, the binary will be availalbe in cmd/oxdpus/oxdpus.

If your mere intention is to just build the Go binary without requiring modifications in the XDP program, then you'll only need the Go compiler since the XDP bytecode is already baked into the binary.

To see available CLI options, run oxdpus --help:

oxdpus --help
A toy tool that leverages the super powers of XDP to bring in-kernel IP filtering

Usage:
  oxdpus [command]

Available Commands:
  add         Appends a new IP address to the blacklist
  attach      Attaches the XDP program on the specified device
  detach      Removes the XDP program from the specified device
  help        Help about any command
  list        Shows all IP addresses registered in the blacklist
  remove      Removes an IP address from the blacklist

Flags:
  -h, --help   help for oxdpus

Use "oxdpus [command] --help" for more information about a command.

To attach the XDP program to the network interface:

$ oxdpus attach --dev=vethbd33820
INFO XDP program successfully attached to vethbd33820 device

The magic happens after you add a couple of IP addresses to the blacklist:

$ oxdpus add --ip=172.17.0.2
INFO 172.17.0.2 address added to the blacklist
$ oxdpus list
* 172.17.0.2
$ curl -v 172.17.0.2:80
*   Trying 172.17.0.2...
* TCP_NODELAY set
curl: (7) Failed to connect to 172.17.0.2 port 80: No route to host

You can remove the IP from the blacklist or even completely unload the program:

$ oxdpus remove --ip=172.17.0.2
INFO 172.17.0.2 address removed from the blacklist
$ oxdpus detach --dev=vethbd33820
INFO XDP program successfully unloaded from vethbd33820 device

If you get an error such as FATA error while loading map "maps/blacklist": too many open files, you're likely running on low file descriptor limits. Run the following commands to bump the limt:

echo "fs.file-max = 4194304" >> /etc/sysctl.d/local.conf
echo "fs.nr_open = 4194304" >> /etc/sysctl.d/local.conf
sysctl -p /etc/sysctl.d/local.conf
ulimit -n 4194304
ulimit -l unlimited
sed -i "s/# End of file//" /etc/security/limits.conf
printf "\n* - nofile 4194304\nroot - nofile 4194304\n" >> /etc/security/limits.conf
printf "\n* - memlock unlimited\nroot - memlock unlimited\n" >> /etc/security/limits.conf
printf "\nulimit -n 4194304\nulimit -l unlimited\n" >> ~/.bashrc

To read more, check out the tutorial I wrote about Processing Packets at Bare-metal Speed.