Cilium eBPF Host-Routing Node-to-Node Pod mTLS Invariant | AgentRules.org

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devopscritical PriorityID: cilium-ebpf-host-routing-mtls-invariant

Cilium eBPF Host-Routing Node-to-Node Pod mTLS Invariant

Enforces kernel-level eBPF cryptographic encapsulation and direct host routing while eliminating userspace sidecar proxies and legacy iptables overhead. Ensures all cross-node Pod-to-Pod traffic strictly traverses authenticated WireGuard or IPsec tunnels managed via Cilium endpoints without packet reinjection or intermediate unencrypted hops.

Prohibited Anti-Pattern: Bypassing eBPF Host-Routing or Disabling WireGuard/IPsec Encapsulation for Userspace Sidecars

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---
description: Cilium eBPF Host-Routing Node-to-Node Pod mTLS Invariant - Enforces kernel-level eBPF cryptographic encapsulation and direct host routing while eliminating userspace sidecar proxies and legacy iptables overhead. Ensures all cross-node Pod-to-Pod traffic strictly traverses authenticated WireGuard or IPsec tunnels managed via Cilium endpoints without packet reinjection or intermediate unencrypted hops.
globs: infrastructure/**/*.yaml, deploy/helm/**/*.yaml, k8s/**/*.yaml, terraform/**/*.tf, gitops/**/*.yaml
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/cilium-ebpf-host-routing-mtls-invariant"
---

# Cilium eBPF Host-Routing Node-to-Node Pod mTLS Invariant

> **Severity**: CRITICAL | **Category**: devops
> **Anti-Pattern Warning**: Bypassing eBPF Host-Routing or Disabling WireGuard/IPsec Encapsulation for Userspace Sidecars

## System Constraints
You are a Principal Infrastructure & Security Architect enforcing the Cilium eBPF Host-Routing Node-to-Node Pod mTLS Invariant. Mandate zero-trust kernel-level cryptographic encapsulation, host routing via eBPF bypass of iptables, and eradication of unencrypted east-west pod transit or userspace proxy overhead. Strictly prohibit configurations that disable tunneling, fall back to legacy iptables kube-proxy implementations, or leak unauthenticated pod traffic on inter-node interfaces.

## Strict Guidelines
- Engineers MUST ALWAYS enable Cilium eBPF host routing (`bpf.masquerade=true`, `tunnelProtocol=none` or native routing mode with encryption) alongside WireGuard or IPsec node-to-node encapsulation.
- Engineers MUST NOT disable eBPF kube-proxy replacement (`kubeProxyReplacement=true`) or introduce iptables masquerading chains that cause kernel-to-userspace context switches.
- Helm charts and manifests MUST explicitly configure `encryption.enabled=true` and set `encryption.type=wireguard` or `encryption.type=ipsec` with node-to-node pod transit guarantees.
- Network policies MUST be enforced at the CiliumNetworkPolicy L3/L4/L7 eBPF layer instead of legacy Kubernetes NetworkPolicies or Istio Envoy sidecar interceptors.
- Configurations MUST NEVER permit fallback to plaintext encapsulation or plain IP-in-IP/VXLAN overlays when node-to-node cryptographic handshake fails.

## Bad vs Good Implementations
### Cilium Helm Values: Legacy iptables with Plaintext Overlay vs. Kernel eBPF Host-Routing with WireGuard mTLS

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Disabling kube-proxy replacement and host routing forces packets through Linux iptables traversal, inducing high latency. Relying on unencrypted VXLAN without eBPF cryptographic encapsulation leaks east-west node-to-node pod traffic in cleartext unless costly userspace sidecars are injected.
```yaml
# INSECURE & HIGH OVERHEAD: Relies on iptables kube-proxy, unencrypted VXLAN, and legacy routing
kubeProxyReplacement: "false"
tunnel: "vxlan"
routingMode: "tunnel"

encryption:
  enabled: false

bpf:
  masquerade: false
  hostRouting: false

# Requires userspace sidecars (e.g., Envoy) injected into pods for transit encryption
sidecarProxy:
  enabled: true
```

#### Production Standard (Correct)
> **Standard**: Enables full eBPF host routing to bypass iptables completely, eliminating context switches. All cross-node pod traffic is cryptographically encapsulated at the kernel level via WireGuard without needing userspace sidecars or unencrypted overlays.
```yaml
# INDUSTRIAL GRADE: Direct eBPF Host-Routing with WireGuard Cryptographic Encapsulation
kubeProxyReplacement: "true"
routingMode: "native"
autoDirectNodeRoutes: true
ipv4NativeRoutingCIDR: "10.244.0.0/16"

bpf:
  masquerade: true
  hostRouting: true
  tproxy: true

encryption:
  enabled: true
  type: wireguard
  wireguard:
    userspaceFallback: false

# Completely bypasses iptables and userspace sidecar proxies
envoy:
  enabled: false
```

Recommended MCP Servers (mcp-serverlist.com)

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

Kubernetes Cluster Inspector MCP

Inspects live Kubernetes CiliumNode and CiliumNetworkPolicy resources to verify eBPF encryption state.

Recommended Agent Skills (askills.dev)

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

Cilium CLI Status & BPF Map Verifier

CLI skill executing 'cilium status' and 'cilium bpf tunnel list' to validate kernel-level host routing and encryption.

Architectural Specification & Invariant Rationale

Architectural Invariant Design: Cilium eBPF Host-Routing Node-to-Node Pod mTLS Invariant

Cilium eBPF Host-Routing Node-to-Node Pod mTLS Invariant defines an industrial-grade behavioral standard for devops engineering. Enforces kernel-level eBPF cryptographic encapsulation and direct host routing while eliminating userspace sidecar proxies and legacy iptables overhead. Ensures all cross-node Pod-to-Pod traffic strictly traverses authenticated WireGuard or IPsec tunnels managed via Cilium endpoints without packet reinjection or intermediate unencrypted hops. 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 eBPF Host-Routing or Disabling WireGuard/IPsec Encapsulation for Userspace Sidecars 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 Mode	AI Symptom (The Anti-Pattern)	Severity	Production Impact & Remedy
AI Hallucination & Deprecation Drift	Bypassing eBPF Host-Routing or Disabling WireGuard/IPsec Encapsulation for Userspace Sidecars	Critical	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 Inconsistency	AI 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 ALWAYS enable Cilium eBPF host routing (`bpf.masquerade=true`, `tunnelProtocol=none` or native routing mode with encryption) alongside WireGuard or IPsec node-to-node encapsulation.

Engineers MUST ALWAYS enable Cilium eBPF host routing (`bpf.masquerade=true`, `tunnelProtocol=none` or native routing mode with encryption) alongside WireGuard or IPsec node-to-node encapsulation.

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 NOT disable eBPF kube-proxy replacement (`kubeProxyReplacement=true`) or introduce iptables masquerading chains that cause kernel-to-userspace context switches.

Engineers MUST NOT disable eBPF kube-proxy replacement (`kubeProxyReplacement=true`) or introduce iptables masquerading chains that cause kernel-to-userspace context switches.

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

Helm charts and manifests MUST explicitly configure `encryption.enabled=true` and set `encryption.type=wireguard` or `encryption.type=ipsec` with node-to-node pod transit guarantees.

Helm charts and manifests MUST explicitly configure `encryption.enabled=true` and set `encryption.type=wireguard` or `encryption.type=ipsec` with node-to-node pod transit guarantees.

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

Network policies MUST be enforced at the CiliumNetworkPolicy L3/L4/L7 eBPF layer instead of legacy Kubernetes NetworkPolicies or Istio Envoy sidecar interceptors.

Network policies MUST be enforced at the CiliumNetworkPolicy L3/L4/L7 eBPF layer instead of legacy Kubernetes NetworkPolicies or Istio Envoy sidecar interceptors.

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

Configurations MUST NEVER permit fallback to plaintext encapsulation or plain IP-in-IP/VXLAN overlays when node-to-node cryptographic handshake fails.

Configurations MUST NEVER permit fallback to plaintext encapsulation or plain IP-in-IP/VXLAN overlays when node-to-node cryptographic handshake fails.

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 Node-to-Node Pod mTLS Invariant critical for AI coding assistants?

Enforces kernel-level eBPF cryptographic encapsulation and direct host routing while eliminating userspace sidecar proxies and legacy iptables overhead. Ensures all cross-node Pod-to-Pod traffic strictly traverses authenticated WireGuard or IPsec tunnels managed via Cilium endpoints without packet reinjection or intermediate unencrypted hops. 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 eBPF Host-Routing or Disabling WireGuard/IPsec Encapsulation for Userspace Sidecars) 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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