XDP Program for protecting a FiveM Server

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XDP Program for Protecting a FiveM Server
This XDP program protects a FiveM server by filtering out non-FiveM traffic. The program inspects incoming packets and drops any packets that are not UDP packets destined for the FiveM server IP address and port. Additionally, it includes rate-limiting and safety checks to prevent legitimate traffic from being inadvertently dropped.

Download Here (Github Repo)
Requirements
Linux based kernel only with XDP support enabled. (Windows not supported)
Clang compiler for compiling the XDP program.
Basic knowledge of Linux networking and handling interfaces.
Installation
Step 1: Modify the XDP Program
Before compiling the program, update the FIVEM_SERVER_IP and FIVEM_SERVER_PORT macros in the XDP script to match your FiveM server’s IP address and port.

Open the xdp_program.c file.
Modify the following macros:
#define FIVEM_SERVER_IP 0x7F000001 // Replace with your server's IP in hex format (e.g., 192.168.1.1 -> 0xC0A80101 or 0x7F000001 for 172.0.0.1 (Localhost)
#define FIVEM_SERVER_PORT 30120 // Replace with your server's port if different
Note: Changing the default FiveM port (30120) to something else is recommended for better security!

Step 2: Compile the XDP Program
Use the clang compiler to compile the XDP program for your system:

clang -O2 -target bpf -c xdp_program.c -o xdp_program.o
This will produce the xdp_program.o object file that you can load into your network interface.

Step 3: Load the XDP Program
Load the compiled XDP program into the network interface that your FiveM server uses. Replace <interface> with the name of your network interface (e.g., eth0):

ip link set dev <interface> xdp obj xdp_program.o sec xdp_program
Step 4: Verify the XDP Program
Test the XDP program by generating traffic to your FiveM server on the configured port (default: 30120). Ensure that non-FiveM traffic is being dropped and legitimate FiveM traffic is allowed to pass through.

You can use packet-capturing tools like tcpdump to verify traffic behavior:

tcpdump -i <interface>
Step 5: Monitor Packet Counts
The program includes logging for tracking how many packets are dropped or passed. Use bpftool to check the statistics:

bpftool map dump name packet_count_map
Unloading the XDP Program
If you need to unload the XDP program from the interface, run the following command:

ip link set dev <interface> xdp off
License
This XDP program is released under the MIT license. See the LICENSE file for more information.