# Milestone 412: Cross-Language IPC, Shared Memory, and Fuzzing (Rust-like Rigor)

[TOC]

## Objective
To guarantee that the Perl UPB implementation is as rock-solid and rigorous as languages like Rust are famous for. This milestone focuses on testing the library in live, unpredictable environments against other language runtimes, specifically handling malicious, undefined, or misunderstood protocols gracefully without crashing. It also introduces a high-performance, secure local IPC mechanism tailored for Protobuf.

## High-Performance Shared Memory IPC (tmpfs + SELinux)
*   [x] Design an IPC harness that leverages a memory-backed filesystem (`tmpfs`, e.g., `/dev/shm`) to pass serialized Protobuf messages.
*   [x] Implement a lightweight signaling mechanism (e.g., Unix domain sockets) to notify peers.
*   [ ] **Auth-Aware Isolation:** Configure POSIX permissions and SELinux contexts:
    *   [ ] TODO: Implement POSIX `chmod`/`chown` for `tmpfs` IPC segments. (Difficulty: 2/10)
    *   [ ] TODO: Define SELinux policy module for Perl-to-C++ IPC isolation. (Difficulty: 3/10)
    *   [ ] TODO: Verify access denial for unauthorized UIDs attempting IPC access. (Difficulty: 2/10)
*   [x] Spawn two concurrent processes: one using the **Perl** UPB runtime, and another peer.
*   [x] Verify absolute 1:1 agreement on the structure and content of messages transferred via the `tmpfs` pool.
*   [x] Review and update perl/doc/architecture/advanced/01-tmpfs-ipc-design.md documents.

## Robustness and Fuzzing (Undefined Situations)
*   [ ] Write tests that intentionally exercise "undefined situations" (e.g., malformed headers). (Difficulty: 5/10).
*   [ ] **Graceful Degradation:** Implement fail-safe logic (croak) when parsing malicious data:
    *   [ ] TODO: Implement C-level validation for wire-format consistency. (Difficulty: 3/10)
    *   [ ] TODO: Map `upb_DecodeStatus` to descriptive Perl `croak` messages. (Difficulty: 2/10)
    *   [ ] TODO: Verify arena cleanup after failed parse attempts. (Difficulty: 2/10)
*   [x] **Connection/State Reset:** Cleanly reset connection and ensure no leaks on corruption.
*   [ ] Ensure the Perl interpreter survives all Fuzzing attempts (leveraging ASan):
    *   [ ] TODO: Integrate `libFuzzer` with Perl XS extension. (Difficulty: 3/10)
    *   [ ] TODO: Create corpus of valid/invalid Protobuf messages for fuzzer seed. (Difficulty: 2/10)
    *   [ ] TODO: Run fuzzer under ASan for 24h and resolve identified leaks/crashes. (Difficulty: 3/10)

*   **Engineering Excellence (Reach for More):**
    *   [ ] TODO: Implement Zero-Copy IPC Transport Layer via direct memory mapping:
        *   [ ] TODO: Implement `mmap` wrapping for shared memory `upb_Arena`. (Difficulty: 3/10)
        *   [ ] TODO: Create relative-pointer (offset) system for cross-process address space. (Difficulty: 3/10)
        *   [ ] TODO: Implement synchronization primitives (mutex/cond) in shared memory. (Difficulty: 3/10)
    *   [ ] TODO: Implement SELinux-Aware Shared Memory Isolation for production security:
        *   [ ] TODO: Implement `seclabel` support for shared memory segments. (Difficulty: 3/10)
        *   [ ] TODO: Create audit logs for SELinux violations during IPC. (Difficulty: 2/10)
        *   [ ] TODO: Verify policy enforcement in Enforcing mode. (Difficulty: 2/10)
    *   [ ] TODO: Implement Chaos Allocation Engine (IPC Stress) for non-deterministic pressure:
        *   [ ] TODO: Implement randomized allocation/deallocation in shared arena. (Difficulty: 3/10)
        *   [ ] TODO: Create "chaos worker" that interrupts IPC transfers. (Difficulty: 2/10)
        *   [ ] TODO: Verify system recovery from partial/corrupted IPC state. (Difficulty: 2/10)
    *   [ ] TODO: Implement Cross-Language Fuzzing Suite (Perl/Python/C++):
        *   [ ] TODO: Design universal fuzzer harness for multiple language runtimes. (Difficulty: 3/10)
        *   [ ] TODO: Implement cross-language message validation bridge. (Difficulty: 3/10)
        *   [ ] TODO: Create automated triage system for cross-language inconsistencies. (Difficulty: 3/10)

*Note: This code hardens the API and proves the viability of ultra-fast local IPC for modern Perl microservice architectures.*