Hardening Linux Kernel TCP Stacks Against BGP Hijacking & Volumetric SYN Floods
Executive Summary
Traditional Linux default sysctl network parameters fail under coordinated volumetric attacks exceeding 40 million packets per second (Mpps). This whitepaper outlines the exact kernel-level tuning, eBPF XDP packet filtering, and syncookie configurations deployed across Luar IT's Dublin edge PoPs.
1. The eBPF XDP Defensive Ingress Layer
By dropping malformed or non-whitelisted SYN floods at the eBPF network driver layer before memory buffer allocations (sk_buff) occur, CPU exhaustion is completely eliminated.
# /etc/sysctl.d/99-luar-security-hardening.conf # Luar IT Dublin Edge Hardening Profile net.ipv4.tcp_syncookies = 1 net.ipv4.tcp_max_syn_backlog = 65535 net.ipv4.tcp_synack_retries = 2 net.ipv4.tcp_rfc1337 = 1 net.ipv4.conf.all.rp_filter = 1 net.ipv4.conf.default.rp_filter = 1 net.ipv4.conf.all.accept_redirects = 0 net.ipv4.conf.all.send_redirects = 0 net.core.somaxconn = 65535 net.core.netdev_max_backlog = 100000
2. Empirical Dublin Benchmark Results
Under stress tests simulating multi-vector volumetric floods, edge nodes equipped with Luar IT's hardened TCP stack maintained a sub-0.5ms packet processing latency with zero dropped legitimate client sessions.