serenity/Libraries/LibIPC/IClientConnection.h

#pragma once

#include <LibCore/CEvent.h>
#include <LibCore/CEventLoop.h>
#include <LibCore/CIODevice.h>
#include <LibCore/CLocalSocket.h>
#include <LibCore/CNotifier.h>
#include <LibCore/CObject.h>
#include <LibIPC/IEndpoint.h>
#include <LibIPC/IMessage.h>
#include <errno.h>
#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

class IEvent : public CEvent {
public:
    enum Type {
        Invalid = 2000,
        Disconnected,
    };
    IEvent() {}
    explicit IEvent(Type type)
        : CEvent(type)
    {
    }
};

class IDisconnectedEvent : public IEvent {
public:
    explicit IDisconnectedEvent(int client_id)
        : IEvent(Disconnected)
        , m_client_id(client_id)
    {
    }

    int client_id() const { return m_client_id; }

private:
    int m_client_id { 0 };
};

template<typename T, class... Args>
NonnullRefPtr<T> new_client_connection(Args&&... args)
{
    return T::construct(forward<Args>(args)...) /* arghs */;
}

template<typename Endpoint>
class IClientConnection : public CObject {
public:
    IClientConnection(Endpoint& endpoint, CLocalSocket& socket, int client_id)
        : m_endpoint(endpoint)
        , m_socket(socket)
        , m_client_id(client_id)
    {
        add_child(socket);
        m_socket->on_ready_to_read = [this] { drain_messages_from_client(); };
    }

    virtual ~IClientConnection() override
    {
    }

    void post_message(const IMessage& message)
    {
        auto buffer = message.encode();

        int nwritten = write(m_socket->fd(), buffer.data(), (size_t)buffer.size());
        if (nwritten < 0) {
            switch (errno) {
            case EPIPE:
                dbg() << "Connection::post_message: Disconnected from peer";
                shutdown();
                return;
            case EAGAIN:
                dbg() << "Connection::post_message: Client buffer overflowed.";
                did_misbehave();
                return;
            default:
                perror("Connection::post_message write");
                ASSERT_NOT_REACHED();
            }
        }

        ASSERT(nwritten == buffer.size());
    }

    void drain_messages_from_client()
    {
        Vector<u8> bytes;
        for (;;) {
            u8 buffer[4096];
            ssize_t nread = recv(m_socket->fd(), buffer, sizeof(buffer), MSG_DONTWAIT);
            if (nread == 0 || (nread == -1 && errno == EAGAIN)) {
                if (bytes.is_empty()) {
                    CEventLoop::current().post_event(*this, make<IDisconnectedEvent>(client_id()));
                    return;
                }
                break;
            }
            if (nread < 0) {
                perror("recv");
                ASSERT_NOT_REACHED();
            }
            bytes.append(buffer, nread);
        }

        size_t decoded_bytes = 0;
        for (size_t index = 0; index < (size_t)bytes.size(); index += decoded_bytes) {
            auto remaining_bytes = ByteBuffer::wrap(bytes.data() + index, bytes.size() - index);
            auto message = Endpoint::decode_message(remaining_bytes, decoded_bytes);
            if (!message) {
                dbg() << "drain_messages_from_client: Endpoint didn't recognize message";
                did_misbehave();
                return;
            }
            if (auto response = m_endpoint.handle(*message))
                post_message(*response);
            ASSERT(decoded_bytes);
        }
    }

    void did_misbehave()
    {
        dbg() << "Connection{" << this << "} (id=" << m_client_id << ", pid=" << m_client_pid << ") misbehaved, disconnecting.";
        shutdown();
    }

    void did_misbehave(const char* message)
    {
        dbg() << "Connection{" << this << "} (id=" << m_client_id << ", pid=" << m_client_pid << ") misbehaved (" << message << "), disconnecting.";
        shutdown();
    }

    void shutdown()
    {
        m_socket->close();
        die();
    }

    int client_id() const { return m_client_id; }
    pid_t client_pid() const { return m_client_pid; }
    void set_client_pid(pid_t pid) { m_client_pid = pid; }

    virtual void die() = 0;

protected:
    void event(CEvent& event) override
    {
        if (event.type() == IEvent::Disconnected) {
            int client_id = static_cast<const IDisconnectedEvent&>(event).client_id();
            dbgprintf("Connection: Client disconnected: %d\n", client_id);
            die();
            return;
        }

        CObject::event(event);
    }

private:
    Endpoint& m_endpoint;
    RefPtr<CLocalSocket> m_socket;
    int m_client_id { -1 };
    int m_client_pid { -1 };
};