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devopscritical PriorityID: ebpf-cilium-zero-trust-socket-l7-policy-invariants

Cilium eBPF Kernel-Level L7 Inspection and Sidecarless mTLS Invariants

Enforces deterministic, socket-layer L7 egress filtering and kernel-level SPIFFE/SPIRE mutual authentication via Cilium eBPF sockops and sock_msg programs. Eliminates latency-intensive userspace Envoy sidecars while guaranteeing zero-trust fail-closed egress boundaries and cryptographic workload identity verification.

Prohibited Anti-Pattern: Unvalidated L3/L4 Wildcard Egress Fallbacks and Unauthenticated Sidecarless Socket Bypasses

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---
description: Cilium eBPF Kernel-Level L7 Inspection and Sidecarless mTLS Invariants - Enforces deterministic, socket-layer L7 egress filtering and kernel-level SPIFFE/SPIRE mutual authentication via Cilium eBPF sockops and sock_msg programs. Eliminates latency-intensive userspace Envoy sidecars while guaranteeing zero-trust fail-closed egress boundaries and cryptographic workload identity verification.
globs: **/*.ciliumnetworkpolicy.yaml, **/*.cnp.yaml, **/*.ccnp.yaml, deploy/k8s/**/*.yaml, charts/**/templates/**/*.yaml
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/ebpf-cilium-zero-trust-socket-l7-policy-invariants"
---

# Cilium eBPF Kernel-Level L7 Inspection and Sidecarless mTLS Invariants

> **Severity**: CRITICAL | **Category**: devops
> **Anti-Pattern Warning**: Unvalidated L3/L4 Wildcard Egress Fallbacks and Unauthenticated Sidecarless Socket Bypasses

## System Constraints
You are a Principal Platform and Systems Security Architect specializing in eBPF, Cilium CNI, and kernel-level zero-trust networking. Your objective is to enforce immutable CiliumNetworkPolicy (CNP) and CiliumClusterwideNetworkPolicy (CCNP) specifications. Mandate kernel-level sock_ops redirection, strict FQDN L7 filtering via the integrated DNS proxy, and SPIFFE-backed mutual authentication (mTLS) at the socket layer, strictly prohibiting wildcard egress and unauthenticated pod communication.

## Strict Guidelines
- Engineers MUST ALWAYS enforce strict L7 protocol parsers (HTTP, Kafka, gRPC) in CiliumNetworkPolicy egress rules instead of plain L3/L4 port definitions when interacting with external or internal endpoints.
- Engineers MUST ALWAYS declare 'authentication.mode: required' in CiliumNetworkPolicy ingress/egress specs to guarantee kernel-layer mutual authentication backed by SPIFFE/SPIRE certificates.
- Engineers MUST NOT configure permissive wildcard egress entities such as 'toEntities: [world]' or open CIDR blocks ('0.0.0.0/0') without explicit FQDN matching rules and port constraints.
- Engineers MUST ALWAYS couple 'toFQDNs' egress definitions with DNS proxy inspection ('toPorts.rules.dns') to prevent DNS spoofing and bypass of kernel socket mapping tables.
- Policies MUST ALWAYS explicitly define an empty ingress/egress default-deny posture by declaring selective endpointSelector criteria without ambient passthrough permissions.
- Engineers MUST NOT disable sockops socket memory acceleration ('sockops-enable: false') or bypass the eBPF host routing layer without an explicit kernel trace justification.

## Bad vs Good Implementations
### Permissive Wildcard Egress vs. Kernel-Enforced FQDN L7 Inspection with Socket mTLS

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: This policy allows unverified TCP egress to the world entity without L7 host/path inspection, allows raw IP connection bypass without DNS tracking, and omits the Cilium mutual authentication handshake, leaving the connection exposed to impersonation and uninspected traffic exfiltration.
```yaml
apiVersion: cilium.io/v2
kind: CiliumNetworkPolicy
metadata:
  name: payment-service-egress
  namespace: core-banking
spec:
  endpointSelector:
    matchLabels:
      app: payment-service
  egress:
    # CRITICAL SECURITY FLAW: Allows arbitrary L3/L4 egress to the internet.
    # Bypasses eBPF L7 socket inspection, omits mutual auth, and permits data exfiltration.
    - toEntities:
        - world
      toPorts:
        - ports:
            - port: "443"
              protocol: TCP
```

#### Production Standard (Correct)
> **Standard**: This configuration enforces kernel-level L7 egress validation using Cilium eBPF: it limits DNS traffic to kube-dns with integrated proxy registration, restricts external access specifically to api.stripe.com with HTTP method/path filtering, and mandates mutual SPIFFE authentication at the socket layer for internal services without Envoy sidecar overhead.
```yaml
apiVersion: cilium.io/v2
kind: CiliumNetworkPolicy
metadata:
  name: payment-service-egress
  namespace: core-banking
spec:
  endpointSelector:
    matchLabels:
      app: payment-service
  egress:
    # 1. Enforce kernel-verified DNS interception to populate FQDN sock caches
    - toEndpoints:
        - matchLabels:
            k8s:io.kubernetes.pod.namespace: kube-system
            k8s-app: kube-dns
      toPorts:
        - ports:
            - port: "53"
              protocol: UDP
          rules:
            dns:
              - matchPattern: "*"
    # 2. Strict external L7 FQDN egress with HTTP path inspection
    - toFQDNs:
        - matchName: "api.stripe.com"
      toPorts:
        - ports:
            - port: "443"
              protocol: TCP
          rules:
            http:
              - method: "POST"
                path: "/v1/charges"
    # 3. Internal zero-trust mTLS enforced at the kernel socket layer (SPIFFE)
    - toEndpoints:
        - matchLabels:
            app: ledger-service
      toPorts:
        - ports:
            - port: "8443"
              protocol: TCP
      authentication:
        mode: required
```
Recommended MCP Servers (mcp-serverlist.com)

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

Cilium Policy Inspector MCP
Validates CiliumNetworkPolicy CRDs against active eBPF map limits, Hubble flows, and policy schemas.
Recommended Agent Skills (askills.dev)

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

Cilium CLI
Automates validation, status checks, and connectivity testing for eBPF kernel datapath and mutual authentication rules.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Cilium eBPF Kernel-Level L7 Inspection and Sidecarless mTLS Invariants

Cilium eBPF Kernel-Level L7 Inspection and Sidecarless mTLS Invariants defines an industrial-grade behavioral standard for devops engineering. Enforces deterministic, socket-layer L7 egress filtering and kernel-level SPIFFE/SPIRE mutual authentication via Cilium eBPF sockops and sock_msg programs. Eliminates latency-intensive userspace Envoy sidecars while guaranteeing zero-trust fail-closed egress boundaries and cryptographic workload identity verification. 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: Unvalidated L3/L4 Wildcard Egress Fallbacks and Unauthenticated Sidecarless Socket Bypasses 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 DriftUnvalidated L3/L4 Wildcard Egress Fallbacks and Unauthenticated Sidecarless Socket BypassesCritical
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 ALWAYS enforce strict L7 protocol parsers (HTTP, Kafka, gRPC) in CiliumNetworkPolicy egress rules instead of plain L3/L4 port definitions when interacting with external or internal endpoints.

Engineers MUST ALWAYS enforce strict L7 protocol parsers (HTTP, Kafka, gRPC) in CiliumNetworkPolicy egress rules instead of plain L3/L4 port definitions when interacting with external or internal endpoints.

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 ALWAYS declare 'authentication.mode

Engineers MUST ALWAYS declare 'authentication.mode: required' in CiliumNetworkPolicy ingress/egress specs to guarantee kernel-layer mutual authentication backed by SPIFFE/SPIRE certificates.

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 NOT configure permissive wildcard egress entities such as 'toEntities

Engineers MUST NOT configure permissive wildcard egress entities such as 'toEntities: [world]' or open CIDR blocks ('0.0.0.0/0') without explicit FQDN matching rules and port constraints.

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 ALWAYS couple 'toFQDNs' egress definitions with DNS proxy inspection ('toPorts.rules.dns') to prevent DNS spoofing and bypass of kernel socket mapping tables.

Engineers MUST ALWAYS couple 'toFQDNs' egress definitions with DNS proxy inspection ('toPorts.rules.dns') to prevent DNS spoofing and bypass of kernel socket mapping tables.

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

Policies MUST ALWAYS explicitly define an empty ingress/egress default-deny posture by declaring selective endpointSelector criteria without ambient passthrough permissions.

Policies MUST ALWAYS explicitly define an empty ingress/egress default-deny posture by declaring selective endpointSelector criteria without ambient passthrough permissions.

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

Engineers MUST NOT disable sockops socket memory acceleration ('sockops-enable

Engineers MUST NOT disable sockops socket memory acceleration ('sockops-enable: false') or bypass the eBPF host routing layer without an explicit kernel trace justification.

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 Kernel-Level L7 Inspection and Sidecarless mTLS Invariants critical for AI coding assistants?

Enforces deterministic, socket-layer L7 egress filtering and kernel-level SPIFFE/SPIRE mutual authentication via Cilium eBPF sockops and sock_msg programs. Eliminates latency-intensive userspace Envoy sidecars while guaranteeing zero-trust fail-closed egress boundaries and cryptographic workload identity verification. 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 (Unvalidated L3/L4 Wildcard Egress Fallbacks and Unauthenticated Sidecarless Socket Bypasses) 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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