Building a Custom eBPF Network Monitor on Linux
eBPF has revolutionized Linux network observability. In this post, we build a lightweight network traffic monitor using XDP (eXpress Data Path) programs that can process packets at line rate without impacting system performance.
What is eBPF?
eBPF (extended Berkeley Packet Filter) allows running sandboxed programs in the Linux kernel without modifying kernel source code. XDP programs run at the earliest point in the network stack, making them ideal for high-performance packet processing.
Getting Started
We'll use the libbpf library with C to write our XDP program. The kernel BPF verifier ensures our program is safe to run in kernel context.
#include
#include
SEC("xdp")
int xdp_monitor(struct xdp_md *ctx) {
void *data = (void *)(long)ctx->data;
void *data_end = (void *)(long)ctx->data_end;
// Process packet headers here
return XDP_PASS;
}