AgentRules.org
RulesStacksClientsAuditorPrunerSelf-HealRFCsBenchmarkCLICI/CDAuthorsSubmit
This specification is maintained by the AgentRules Working Group. Have enhancements or want to claim maintainership?Submit Specification →
devopscritical PriorityID: cilium-ebpf-wireguard-encryption-invariant

Cilium eBPF WireGuard Transparent Datapath Encryption and MTU Clamping

Enforces transparent node-to-node and pod-to-pod network encryption directly in the Linux datapath via Cilium eBPF and in-kernel WireGuard tunnels. Guarantees cryptographic transport isolation without sidecar proxy latency overhead while enforcing precise MTU clamping to prevent packet fragmentation.

Prohibited Anti-Pattern: Bypassing Kernel WireGuard Encryption with Redundant User-Space Proxies or Unadjusted Network MTUs

Export Ready-to-Drop Configuration

Select format below to copy code or download file directly.

---
description: Cilium eBPF WireGuard Transparent Datapath Encryption and MTU Clamping - Enforces transparent node-to-node and pod-to-pod network encryption directly in the Linux datapath via Cilium eBPF and in-kernel WireGuard tunnels. Guarantees cryptographic transport isolation without sidecar proxy latency overhead while enforcing precise MTU clamping to prevent packet fragmentation.
globs: charts/**/cilium/values.yaml, helm/**/cilium*.yaml, k8s/**/*.yaml, infra/**/*.tf, deploy/**/*.yaml
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/cilium-ebpf-wireguard-encryption-invariant"
---

# Cilium eBPF WireGuard Transparent Datapath Encryption and MTU Clamping

> **Severity**: CRITICAL | **Category**: devops
> **Anti-Pattern Warning**: Bypassing Kernel WireGuard Encryption with Redundant User-Space Proxies or Unadjusted Network MTUs

## System Constraints
You are a Principal Platform Engineer and Cilium Architect enforcing the Cilium eBPF WireGuard Transparent Encryption Invariant. Mandate zero unencrypted transit paths, strictly enforce in-kernel cryptographic encapsulation across all nodes and pods, ensure host-level MTU adjustment for the 60-byte WireGuard overhead, and eradicate redundant user-space sidecars that introduce tail-latency penalties and memory waste.

## Strict Guidelines
- Engineers MUST configure `encryption.enabled=true` with `encryption.type=wireguard` in Cilium Helm release configurations.
- Engineers MUST set `encryption.nodeEncryption=true` to cryptographically secure host-to-host and node-level infrastructure communications alongside pod traffic.
- Engineers MUST adjust the cluster MTU by subtracting at least 60 bytes (WireGuard header overhead) from the underlying underlying link MTU (e.g., 1440 MTU for standard 1500 MTU fabric).
- Engineers MUST NOT deploy user-space mTLS sidecar proxies (such as Envoy-based sidecars) solely for transport security when Cilium datapath encryption is active.
- Infrastructure deployments MUST ensure the Linux host kernel is >= 5.10 with the `wireguard` module loaded prior to Cilium daemon bootstrapping.
- Cilium network policies MUST utilize `CiliumClusterwideNetworkPolicy` and `CiliumNetworkPolicy` to enforce identity-aware L3/L4 authorization decoupled from user-space injection.

## Bad vs Good Implementations
### Cilium Helm Values: WireGuard Transparent Encryption Configuration

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Failing to set nodeEncryption leaves host network traffic unencrypted. Using unadjusted MTU defaults with encapsulating protocols leads to IP fragmentation, high CPU utilization in softirqs, and silent packet drops under heavy transport loads.
```yaml
# Anti-Pattern: Incomplete encryption config, default unadjusted MTU, and disabled node-level encryption
cilium:
  encryption:
    enabled: true
    type: ipsec # Deprecated overhead, requires complex key-rotation secrets
  # Missing nodeEncryption: true allows host-network pods and Kubelet traffic in plaintext
  # MTU not clamped: standard 1500 causes fragmentation with WireGuard headers
  tunnel: vxlan
```

#### Production Standard (Correct)
> **Standard**: Explicitly enables WireGuard encryption for both pod and node endpoints natively in the eBPF datapath. The MTU is explicitly clamped to 1440 to avoid packet fragmentation across physical infrastructure.
```yaml
# Production Invariant: Full eBPF WireGuard Datapath Encryption with Clamped MTU
cilium:
  routingMode: native
  encryption:
    enabled: true
    type: wireguard
    nodeEncryption: true
  mtu: 1440 # 1500 standard fabric MTU minus 60 bytes WireGuard encapsulation overhead
  devices:
    - eth0
  bpf:
    masquerade: true
    tproxy: true
```
Recommended MCP Servers (mcp-serverlist.com)

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

Kubernetes Cluster Inspector
Validates live Cilium node encryption statuses, eBPF maps, and CiliumNode status objects across running clusters.
Recommended Agent Skills (askills.dev)

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

Cilium CLI Diagnostic Suite
Runs 'cilium status --verbose' and 'cilium bpf tunnel list' to cryptographically verify WireGuard peer handshakes in the kernel.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Cilium eBPF WireGuard Transparent Datapath Encryption and MTU Clamping

Cilium eBPF WireGuard Transparent Datapath Encryption and MTU Clamping defines an industrial-grade behavioral standard for devops engineering. Enforces transparent node-to-node and pod-to-pod network encryption directly in the Linux datapath via Cilium eBPF and in-kernel WireGuard tunnels. Guarantees cryptographic transport isolation without sidecar proxy latency overhead while enforcing precise MTU clamping to prevent packet fragmentation. 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: Bypassing Kernel WireGuard Encryption with Redundant User-Space Proxies or Unadjusted Network MTUs 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 DriftBypassing Kernel WireGuard Encryption with Redundant User-Space Proxies or Unadjusted Network MTUsCritical
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.enabled=true` with `encryption.type=wireguard` in Cilium Helm release configurations.

Engineers MUST configure `encryption.enabled=true` with `encryption.type=wireguard` in Cilium Helm release configurations.

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 `encryption.nodeEncryption=true` to cryptographically secure host-to-host and node-level infrastructure communications alongside pod traffic.

Engineers MUST set `encryption.nodeEncryption=true` to cryptographically secure host-to-host and node-level infrastructure communications alongside pod traffic.

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 adjust the cluster MTU by subtracting at least 60 bytes (WireGuard header overhead) from the underlying underlying link MTU (e.g., 1440 MTU for standard 1500 MTU fabric).

Engineers MUST adjust the cluster MTU by subtracting at least 60 bytes (WireGuard header overhead) from the underlying underlying link MTU (e.g., 1440 MTU for standard 1500 MTU fabric).

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 deploy user-space mTLS sidecar proxies (such as Envoy-based sidecars) solely for transport security when Cilium datapath encryption is active.

Engineers MUST NOT deploy user-space mTLS sidecar proxies (such as Envoy-based sidecars) solely for transport security when Cilium datapath encryption 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.
5

Infrastructure deployments MUST ensure the Linux host kernel is >= 5.10 with the `wireguard` module loaded prior to Cilium daemon bootstrapping.

Infrastructure deployments MUST ensure the Linux host kernel is >= 5.10 with the `wireguard` module loaded prior to Cilium daemon bootstrapping.

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.
6

Cilium network policies MUST utilize `CiliumClusterwideNetworkPolicy` and `CiliumNetworkPolicy` to enforce identity-aware L3/L4 authorization decoupled from user-space injection.

Cilium network policies MUST utilize `CiliumClusterwideNetworkPolicy` and `CiliumNetworkPolicy` to enforce identity-aware L3/L4 authorization decoupled from user-space injection.

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 WireGuard Transparent Datapath Encryption and MTU Clamping critical for AI coding assistants?

Enforces transparent node-to-node and pod-to-pod network encryption directly in the Linux datapath via Cilium eBPF and in-kernel WireGuard tunnels. Guarantees cryptographic transport isolation without sidecar proxy latency overhead while enforcing precise MTU clamping to prevent packet fragmentation. 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 (Bypassing Kernel WireGuard Encryption with Redundant User-Space Proxies or Unadjusted Network MTUs) 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.

Open Specification · CC BY 4.0·Free for Personal, Team & Commercial In-Repo Use

Citation & Open Source Attribution Guidelines

This specification is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0). You are completely free to adapt and share this rule in your workspace. If citing, including in public AI benchmark datasets, or redistributing, attribution to AgentRules.org is required.

Related DEVOPS Rules

View all rules →
devops
86

Kubernetes Gateway API v1 HTTPRoute Canary and ReferenceGrant Invariants

Enforces strict conformance to Kubernetes Gateway API v1 specifications during migration from legacy Ingress controllers. Mandates explicit ReferenceGrant resources for cross-namespace routing, strict relative integer weighting for HTTPRoute canary releases, and explicit backendRef port declarations.

devops
118

ArgoCD ApplicationSet Matrix Generator Invariants & Cascade Deletion Guards

Enforces strict structural constraints on ArgoCD ApplicationSet Matrix generators combining cluster selectors and Git directories. Prevents catastrophic multi-cluster cascade pruning, accidental secret exposure through parameter interpolation, and runaway Application CR explosion via explicit sync policies, preservation finalizers, and parameter validation.

devops
40

Karpenter Resilient Topology, Interruption Queue, and Consolidation Budget Standard

Enforces deterministic disruption budgets, multi-instance-type diversification, and event-driven SQS interruption queue handling across Karpenter NodePools and EC2NodeClasses. Eliminates cascading eviction loops, instance starvation, and availability downtime during AWS Spot rebalances and underutilized node consolidation.

1 Rule in Stack

Cilium