Building a Lightning Fast Firewall with Java & eBPF by Mohammed Aboullaite, Johannes Bechberger

eBPF is a technology that makes the Linux kernel programmable by allowing users to run sandboxed programs within the kernel safely

XDP (eXpress Data Path) with eBPF enables high-performance packet filtering and network processing at the kernel level before packets reach the network stack

The eBPF verifier ensures programs are safe to run in the kernel by checking bounds, memory access, and other security constraints

Java developers can now write eBPF programs using Java syntax through Project Panama integration, without needing to write C code directly

eBPF programs are event-driven and must be attached to specific hook points in the kernel like system calls, network interfaces, or kernel functions

Key use cases include networking/firewalls, observability/monitoring, and security tooling

eBPF maps provide bidirectional communication between userspace and kernel space programs, allowing data sharing and configuration

Performance benefits come from processing packets early in the network path and reducing context switches between kernel and userspace

eBPF programs can be dynamically loaded and updated without requiring kernel module compilation or system reboots

The technology is being widely adopted by companies like Meta, Cloudflare and others for production use cases like load balancing and monitoring