Linux Game Server Anti-DDoS & Kernel Hardening Generator

Generate tuned Linux kernel sysctl network parameters, nftables defense rules, iptables hashlimit rate-limits, and eBPF/XDP drop filters. Protect Counter-Strike 2, Minecraft, DayZ, and Unreal Engine servers against UDP reflection and A2S query floods.

KERNEL HARDENING XDP / eBPF WARDEN COMPATIBLE

Game Engine Defense Archetypes Active: Source Engine (CS2 / TF2 / GMod)

Socket Buffer Window rmem / wmem

32 MB

Prevents socket buffer packet drops during burst spikes

Network Backlog Queue Cap

100,000 pkts

netdev_max_backlog input ring buffer capacity

Defense Rating 8 layers

HIGH-RESILIENCE (GRADE A)

Multi-layer kernel, firewall, and eBPF protection

Conntrack Mode OPTIMAL

NOTRACK

Bypasses Netfilter table lockup

Target Configuration

Interface: eth0

NIC Device Name

Buffer Capacity Tier

Game Daemon Port

27015 port

Query Daemon Port

27015 port

RCON Admin Port

27015 port

Query Packet Rate Limit

30 pkts/s

Game Packet Rate Limit

250 pkts/s

Kernel Defense Modules Google BBR Congestion Control & Fair Queueing (fq) TCP SYN Cookies (tcp_syncookies = 1) Netfilter Raw NOTRACK Conntrack Bypass (UDP Only) Strict Reverse Path Filtering (rp_filter = 1) ICMP Echo Rate-Limit & Broadcast Shield

Target Path: /etc/sysctl.d/99-gameserver.conf Linux kernel network socket buffers and backlogs

# =============================================================================
# DustBowl Warden // Linux Kernel Network Hardening Configuration
# Engine Profile : Source Engine (CS2 / TF2 / GMod)
# Target Interface : eth0
# Generated on : 2026-11-05 17:21:01 UTC
# Apply via: sudo sysctl --system (or write to /etc/sysctl.d/99-gameserver.conf)
# =============================================================================

# --- Socket Buffer Sizing (Absorb Volumetric Micro-Bursts) ---
net.core.rmem_max = 33554432
net.core.wmem_max = 33554432
net.core.rmem_default = 16777216
net.core.wmem_default = 16777216
net.core.optmem_max = 4194304

# --- Network Device Queues & Socket Backlogs ---
net.core.netdev_max_backlog = 100000
net.core.somaxconn = 65535
net.core.netdev_budget = 600
net.core.netdev_budget_usecs = 4000

# --- UDP Buffer Allocations ---
net.ipv4.udp_rmem_min = 16384
net.ipv4.udp_wmem_min = 16384

# --- TCP SYN Flood & Connection Hardening ---
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_max_syn_backlog = 16384
net.ipv4.tcp_synack_retries = 2
net.ipv4.tcp_syn_retries = 3
net.ipv4.tcp_fin_timeout = 15
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_max_tw_buckets = 2000000

# --- Congestion Control (BBR + Fair Queueing) ---
net.core.default_qdisc = fq
net.ipv4.tcp_congestion_control = bbr

# --- IP Spoofing & Route Validation ---
net.ipv4.conf.all.rp_filter = 2
net.ipv4.conf.default.rp_filter = 2
net.ipv4.conf.eth0.rp_filter = 2
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0

# --- ICMP Flood & Broadcast Shield ---
net.ipv4.icmp_echo_ignore_broadcasts = 1
net.ipv4.icmp_ignore_bogus_error_responses = 1
net.ipv4.icmp_ratelimit = 100
net.ipv4.icmp_ratemask = 8808

# --- Virtual Memory Overcommit & Swap Tuning ---
vm.swappiness = 10
vm.dirty_ratio = 15
vm.dirty_background_ratio = 5

Verified Defense Invariants

[OK] Expanded socket receive & send buffers to 32 MB to absorb micro-bursts without packet loss
[OK] Increased kernel network backlog queue to 100,000 packets to prevent NIC overrun
[OK] Configured strict per-source rate-limiting on Query port (30 pkts/s)
[OK] Configured per-source packet rate-limiting on Game port (250 pkts/s)
[OK] Bypassed Linux Netfilter connection tracking (NOTRACK) for UDP game packets to prevent conntrack table exhaustion
[OK] Enabled TCP SYN cookies (syncookies=1) with 16,384 SYN backlog queue to neutralize SYN flood attacks
[OK] Configured Google BBR congestion control and Fair Queueing (fq) for low-latency TCP packet pacing
[OK] Enforced ICMP broadcast drop and rate-limited ping echo replies to 100/sec

Linux Game Server Networking & Anti-DDoS Architecture

Why Default Linux Sockets Fail Game Servers

Default Linux kernel distributions are configured for general web workloads with modest UDP socket receive buffers (typically 208 KB). When a game server experiences a 10,000 PPS burst of queries or player packets, the socket buffer fills instantly, causing the kernel to drop legitimate player packets before the game daemon can read them via recvfrom.

Steam A2S Query Amplification Mitigation

Attackers exploit game servers by forging source IPs and sending A2S_INFO or A2S_PLAYER query packets, turning the server into a reflection amplifier against external targets. Rate-limiting query ports with nftables dynamic meters or iptables hashlimit caps query processing to 25 to 35 packets per second per IP without degrading server browser listings.

Netfilter Conntrack Table Exhaustion

Linux Netfilter state tracking records every unique UDP 4-tuple in memory. During spoofed UDP floods, the nf_conntrack table fills completely (often at 65,536 entries), causing the kernel to reject new connections. Bypassing conntrack with NOTRACK in the RAW table allows game packets to pass directly to user space without state overhead.

DustBowl Warden High-Rate eBPF/XDP Scrubbing

In DustBowl Warden, edge scrubbing nodes execute eBPF/XDP filters directly inside the network driver before Linux memory allocation (sk_buff) takes place. This allows single-node servers to discard 10+ million malicious packets per second with minimal CPU overhead.