Ebpf Xdp Networking

eBPF & XDP Networking

Core Mechanics

Extended Berkeley Packet Filter (eBPF) allows running sandboxed programs in a privileged context such as the Linux operating system kernel, without changing kernel source code or loading kernel modules.

1. eXpress Data Path (XDP)

XDP is a specific eBPF hook that attaches directly to the Network Interface Card (NIC) driver. It intercepts network packets before the Linux kernel's networking stack even sees them.

• Used for ultra-fast DDoS mitigation (Cloudflare), Load Balancing, and Firewalls.
• Can return XDP_DROP (discard immediately) or XDP_PASS (send to kernel).

2. The eBPF Verifier

To prevent a custom script from crashing the kernel, the eBPF Verifier analyzes the bytecode before loading. It ensures:

• No infinite loops.
• No out-of-bounds memory access.
• The program terminates safely.

eBPF/XDP Architecture Map

%%{init: {"theme": "default", "flowchart": {"useMaxWidth": true}}}%%
flowchart TD
    subgraph UserSpace ["User Space"]
        A["eBPF Program (C/Rust)"]
        B["Clang/LLVM Compiler"]
        C["eBPF Bytecode"]
    end
    
    subgraph KernelSpace ["Linux Kernel"]
        D["eBPF Verifier"]
        E["JIT Compiler"]
        F["eBPF Map (Shared Memory)"]
    end
    
    subgraph Hardware ["NIC Driver (XDP Hook)"]
        G["Incoming Packet"]
        H{"Run eBPF Logic"}
        I["XDP_DROP"]
        J["XDP_PASS"]
    end
    
    A --> B
    B --> C
    C -->|"bpf() syscall"| D
    D -->|"Safe"| E
    E -->|"Attach"| H
    G --> H
    H -->|"Malicious"| I
    H -->|"Valid"| J
    J -->|"To Kernel TCP/IP Stack"| K["Standard Network Stack"]
    H <-->|"Read/Write"| F