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devopscritical PriorityID: cilium-ebpf-host-routing-wireguard-encryption

Cilium eBPF Host-Routing & Sidecarless WireGuard Transparent Encryption Invariants

Enforces kernel-level eBPF host routing alongside transparent WireGuard pod-to-pod encryption while eliminating user-space sidecar proxies. Mandates strict MTU clamping, socket-layer enforcement, and native routing mode to prevent TCP segmentation packet drops, proxy memory bloat, and iptables traversal bottlenecks.

Prohibited Anti-Pattern: Injecting user-space sidecars and defaulting to generic overlay iptables without MTU clamping and eBPF host routing

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---
description: Cilium eBPF Host-Routing & Sidecarless WireGuard Transparent Encryption Invariants - Enforces kernel-level eBPF host routing alongside transparent WireGuard pod-to-pod encryption while eliminating user-space sidecar proxies. Mandates strict MTU clamping, socket-layer enforcement, and native routing mode to prevent TCP segmentation packet drops, proxy memory bloat, and iptables traversal bottlenecks.
globs: charts/**/values.yaml, deploy/cilium/**/*.yaml, infrastructure/terraform/**/*.tf, k8s/**/*.yaml, manifests/**/*.yaml
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/cilium-ebpf-host-routing-wireguard-encryption"
---

# Cilium eBPF Host-Routing & Sidecarless WireGuard Transparent Encryption Invariants

> **Severity**: CRITICAL | **Category**: devops
> **Anti-Pattern Warning**: Injecting user-space sidecars and defaulting to generic overlay iptables without MTU clamping and eBPF host routing

## System Constraints
You are a Principal Cloud-Native Networking Architect enforcing Cilium eBPF Host-Routing and Transparent WireGuard Encryption. You must strictly reject user-space sidecar proxy injection, disable kube-proxy iptables duplication, mandate eBPF host-routing mode, and ensure dynamic WireGuard interface MTU reduction to eliminate kernel packet drop risks and maintain line-rate throughput.

## Strict Guidelines
- Engineers MUST configure `encryption.type: wireguard` and set `bpf.hostRouting: true` in Cilium Helm values to bypass iptables overhead.
- Engineers MUST set `kubeProxyReplacement: true` and fully remove `kube-proxy` DaemonSets from nodes to prevent netfilter rule conflicts.
- Engineers MUST explicitly reduce pod network MTU by at least 60 bytes (IPv4) or 80 bytes (IPv6) relative to node MTU to accommodate WireGuard headers (typically 1420 on standard 1500 MTU fabrics).
- Engineers MUST NOT inject Envoy sidecars for L3/L4 zero-trust encryption; WireGuard transparent node-to-node and pod-to-pod mesh must handle encryption at the kernel level.
- Deployments MUST enforce `routingMode: native` with appropriate CIDR allocations or ensure strict direct routing to avoid double-encapsulation when WireGuard is active.

## Bad vs Good Implementations
### Cilium Helm Configuration for eBPF Host Routing and WireGuard Encryption

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Fails to enable kernel-level encryption, relies on high-overhead user-space proxies (Envoy sidecars), leaves kube-proxy iptables running, and does not configure WireGuard or MTU compensation.
```yaml
# Anti-Pattern: Retaining iptables kube-proxy, sidecar proxies, and unadjusted MTU with VXLAN encapsulation
kubeProxyReplacement: "false"
routingMode: "tunnel"
tunnelProtocol: "vxlan"
enryption:
  enabled: false
# Pod-level sidecars injected for MTLS; default 1500 MTU causes silent IP packet drops
```

#### Production Standard (Correct)
> **Standard**: Enables wire-speed zero-trust transport encryption via kernel WireGuard, leverages eBPF direct host routing to skip netfilter chains, disables sidecar overhead, and prevents PMTU blackholes by explicitly clamping MTU to 1420.
```yaml
# Production Standard: Transparent WireGuard, native eBPF host routing, strict MTU adjustment
kubeProxyReplacement: true
bpf:
  hostRouting: true
  masquerade: true
routingMode: "native"
ipv4NativeRoutingCIDR: "10.244.0.0/16"
enryption:
  enabled: true
  type: wireguard
  wireguard:
    userspaceFallback: false
mtu: 1420 # 1500 byte host MTU minus 80 bytes for WireGuard/eBPF headroom
socketLB:
  enabled: true
  hostNamespaceOnly: false
```
Recommended MCP Servers (mcp-serverlist.com)

Equip agent with system tools to verify code for this stack.

Kubernetes Cluster Controller MCP
Validates live Cilium DaemonSet states, eBPF maps, and CiliumNetworkPolicy resources directly on the cluster.
Recommended Agent Skills (askills.dev)

Ready-to-use executable skill functions tailored to this stack.

Cilium CLI Diagnostic Suite
Executes cilium status, cilium bpf tunnel list, and cilium encrypt status to verify WireGuard kernel peers and MTU integrity.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Cilium eBPF Host-Routing & Sidecarless WireGuard Transparent Encryption Invariants

Cilium eBPF Host-Routing & Sidecarless WireGuard Transparent Encryption Invariants defines an industrial-grade behavioral standard for devops engineering. Enforces kernel-level eBPF host routing alongside transparent WireGuard pod-to-pod encryption while eliminating user-space sidecar proxies. Mandates strict MTU clamping, socket-layer enforcement, and native routing mode to prevent TCP segmentation packet drops, proxy memory bloat, and iptables traversal bottlenecks. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: Injecting user-space sidecars and defaulting to generic overlay iptables without MTU clamping and eBPF host routing Without an explicit system instruction file, developers spend hours debugging silent failures.
Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure ModeAI Symptom (The Anti-Pattern)SeverityProduction Impact & Remedy
AI Hallucination & Deprecation DriftInjecting user-space sidecars and defaulting to generic overlay iptables without MTU clamping and eBPF host routingCritical
Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production.
Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture InconsistencyAI assistants produce mixed paradigms across files, creating fragmented codebase conventions.Medium
Increases cognitive load during code reviews and leads to maintenance debt across engineering teams.
Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.
Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

1

Engineers MUST configure `encryption.type

Engineers MUST configure `encryption.type: wireguard` and set `bpf.hostRouting: true` in Cilium Helm values to bypass iptables overhead.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
2

Engineers MUST set `kubeProxyReplacement

Engineers MUST set `kubeProxyReplacement: true` and fully remove `kube-proxy` DaemonSets from nodes to prevent netfilter rule conflicts.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
3

Engineers MUST explicitly reduce pod network MTU by at least 60 bytes (IPv4) or 80 bytes (IPv6) relative to node MTU to accommodate WireGuard headers (typically 1420 on standard 1500 MTU fabrics).

Engineers MUST explicitly reduce pod network MTU by at least 60 bytes (IPv4) or 80 bytes (IPv6) relative to node MTU to accommodate WireGuard headers (typically 1420 on standard 1500 MTU fabrics).

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
4

Engineers MUST NOT inject Envoy sidecars for L3/L4 zero-trust encryption

Engineers MUST NOT inject Envoy sidecars for L3/L4 zero-trust encryption; WireGuard transparent node-to-node and pod-to-pod mesh must handle encryption at the kernel level.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
5

Deployments MUST enforce `routingMode

Deployments MUST enforce `routingMode: native` with appropriate CIDR allocations or ensure strict direct routing to avoid double-encapsulation when WireGuard is active.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
Technical Questions & Answers

Frequently Asked Technical Questions

Common questions developers face when configuring AI coding assistants for this stack:

Q:Why is Cilium eBPF Host-Routing & Sidecarless WireGuard Transparent Encryption Invariants critical for AI coding assistants?

Enforces kernel-level eBPF host routing alongside transparent WireGuard pod-to-pod encryption while eliminating user-space sidecar proxies. Mandates strict MTU clamping, socket-layer enforcement, and native routing mode to prevent TCP segmentation packet drops, proxy memory bloat, and iptables traversal bottlenecks. Without explicit behavioral boundaries, AI coding assistants (Cursor, Claude Code, Windsurf, Codex) rely on training data averages, which frequently produce deprecated, inefficient, or vulnerable code patterns.

Q:How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (Injecting user-space sidecars and defaulting to generic overlay iptables without MTU clamping and eBPF host routing) and prescribes verified positive examples. Grounding the LLM with negative and positive pairs eliminates guesswork.

Q:Which AI coding environments are supported?

This specification is multi-platform compatible: Cursor (.cursor/rules/*.mdc & .cursorrules), Anthropic Claude Code (CLAUDE.md), Windsurf (.windsurfrules), Codex / Cline (AGENTS.md), and GitHub Copilot (.github/copilot-instructions.md).

Q:Can I combine this rule with other technology stacks?

Yes. Use the Interactive Stack Builder or download an Agent Pack to merge this rule with other frontend, backend, database, security, and DevOps rules without syntax collision.

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