Let’s architect a modular Software Defined Network (SDN) framework that reflects your systems-level mastery and cognition-routing ambitions. We’ll separate control and data planes, use OpenFlow-like logic for flow rules, and scaffold a controller that can evolve into a cognition-aware traffic orchestrator.

🗂 Folder Structure

NeuroSDN/
├── Controller/              # SDN controller logic (control plane)
│   ├── FlowManager.cpp      # Flow rule creation and updates
│   ├── Topology.cpp         # Network graph and link discovery
│   └── RESTInterface.cpp    # Optional REST API for external control
├── SwitchAgent/             # Software switch agent (data plane)
│   ├── PacketParser.cpp     # Ethernet/IP/TCP parsing
│   ├── FlowTable.cpp        # Flow rule matching
│   └── Forwarder.cpp        # Packet forwarding logic
├── Common/
│   ├── Protocols.hpp        # OpenFlow-like message definitions
│   └── Utils.hpp            # Logging, timers, serialization
├── App/
│   └── Main.cpp             # Entry point
├── CMakeLists.txt           # Build configuration
└── README.md

🧠 Core Concepts

• Controller: Centralized brain that installs flow rules on switches.
• Switch Agent: Lightweight software switch that parses packets and applies flow rules.
• Flow Table: Matches packet headers to actions (forward, drop, modify).
• Protocol: Custom OpenFlow-like messages for rule installation and stats.

🔧 Sample Code Snippets

📁 Controller/FlowManager.cpp

#include "Protocols.hpp"

void InstallFlowRule(SwitchID id, FlowRule rule) {
    ControlMessage msg;
    msg.type = FLOW_INSTALL;
    msg.rule = rule;
    SendToSwitch(id, msg);
}

📁 SwitchAgent/PacketParser.cpp

PacketMetadata ParsePacket(const uint8_t* buffer, size_t len) {
    PacketMetadata meta;
    // Extract Ethernet, IP, TCP headers
    memcpy(&meta.eth, buffer, sizeof(EthernetHeader));
    memcpy(&meta.ip, buffer + 14, sizeof(IPHeader));
    memcpy(&meta.tcp, buffer + 34, sizeof(TCPHeader));
    return meta;
}

📁 SwitchAgent/FlowTable.cpp

bool MatchFlow(const PacketMetadata& meta, const FlowRule& rule) {
    return (meta.ip.src == rule.match.srcIP &&
            meta.ip.dst == rule.match.dstIP &&
            meta.tcp.dstPort == rule.match.dstPort);
}

Action ApplyFlow(const PacketMetadata& meta) {
    for (auto& rule : flowTable) {
        if (MatchFlow(meta, rule)) return rule.action;
    }
    return DROP;
}

📁 SwitchAgent/Forwarder.cpp

void ForwardPacket(const PacketMetadata& meta, Action action) {
    if (action == FORWARD) {
        SendToInterface(meta.outInterface, meta.rawData);
    } else if (action == DROP) {
        // Log and discard
    }
}

📁 App/Main.cpp

#include "Controller/FlowManager.hpp"
#include "SwitchAgent/Forwarder.hpp"

int main() {
    InitController();       // Start control plane
    InitSwitchAgent();      // Start data plane
    while (IsRunning()) {
        auto pkt = CapturePacket();
        auto meta = ParsePacket(pkt.data, pkt.len);
        auto action = ApplyFlow(meta);
        ForwardPacket(meta, action);
    }
    return 0;
}