Installation

Prerequisites

Linux kernel ≥ 5.15 (recommended ≥ 6.10 for full feature set)
4 GB RAM (v2.16+; smaller hosts: lower maps.ban_max / maps.ip_stats_max after install — the installer warns you)
CONFIG_DEBUG_INFO_BTF=y in kernel config
XDP-capable NIC driver (native mode) or any NIC (generic/skb mode)
clang ≥ 12, llvm, bpftool, libbpf-dev
Go ≥ 1.21

Check BTF

bash

ls /sys/kernel/btf/vmlinux

If this file doesn't exist, your kernel was compiled without BTF support. Rebuild with CONFIG_DEBUG_INFO_BTF=y.

Kernel feature gates

OpenShield-XDP automatically detects available kernel features at load time and silently disables features your kernel doesn't support. For example:

Bloom filter maps require kernel 5.16+ — if unavailable, the LRU hashmap whitelist is used instead
freplace requires kernel 5.15+ — if unavailable, all BPF logic runs in the main program (no hot-patching)
BPF timers require kernel 5.15+ — connection tracking uses a simpler mechanism without them

Run openshield status after loading to see which features are active on your kernel.

bash