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Design Constraints: Aegis Packet Engine

This document outlines the strict guidelines governing all code contributions on the Aegis packet processing path.

1. Hot-Path / Fast-Path Constraints

The hot path includes all functions executed for each packet frame (parsing, dispatching, tracking, rule evaluation, metrics counting, writing).

  • No Heap Allocations: Dynamic memory allocation (malloc, free, new, delete, std::make_shared, std::make_unique) is prohibited.
  • No Mutexes: Mutex locks and standard blocking locks are banned. Synchronization must utilize atomic operators, SPSC queues, or thread-isolation patterns.
  • No Virtual Functions: Virtual function calls and runtime polymorphism are banned to avoid vtable lookups and enable inline optimizations. Use templates or compile-time specialization.
  • No std::string Copies: Do not construct or copy standard strings. Reference characters using std::string_view.
  • No RTTI: Run-Time Type Information (dynamic_cast, typeid) is disabled.
  • No C++ Exceptions: Exceptions are prohibited on the packet loop. Use structured error codes or boolean return states. Keep functions marked noexcept.

2. General Architecture Rules

  • RAII (Resource Acquisition Is Initialization): All resource lifecycles (sockets, files, thread pools) are tied to scope.Destructors must coordinate cleanup.
  • Rule of Zero: Prefers classes that do not declare custom copy/move constructors or destructors, letting the compiler generate them. Where custom resources are managed, implement the Rule of Five.
  • Thread Ownership & Affinity: Thread lifetimes must be explicit. Pinning threads to CPU cores is standard behavior on supported systems (Linux), with safe preprocessor fallbacks.
  • No Shared Mutable State: Worker threads operate on isolated connection tables and statistics counters to avoid cache invalidation between cores.
  • Constexpr Usage: Define all configuration variables, protocol constants, and magic numbers as constexpr to resolve calculations at compile-time.