ServerCore/TCPServer.h

#ifndef __TCPServer_h__
# define __TCPServer_h__

# include "Command.h"
# include "CommandList.h"
# include "IPAddressList.h"
# include "Socket.h"
# include "SubscriptionManager.h"
# include "TCPSession.h"
# include "TCPSocket.h"
# include "TLSInfo.h"
# include <mutex>
# include <set>

namespace core {
   
   ///
   /// TCPServer
   ///
   /// Manage a socket connection as a TCP server type. Connections to the socket are processed through
   /// the accept functionality.
   ///
   /// A list of connections is maintained in a vector object.
   ///
   /// This object extends the Command object as well so it can be added to a Console object and
   /// process commands to display status information.
   ///
   
   class TCPServer : public TCPSocket, public Command {
      
    public:
      
      ///
      /// The constructor for the TCPServer object.
      ///
      /// @param ePoll the EPoll instance that manages the socket.
      /// @param url the IP address for the socket to receive connection requests.
      /// @param port the port number that the socket will listen on.
      /// @param commandName the name of the command used to invoke the status display for this object.
      ///
      
      TCPServer(EPoll &ePoll, IPAddress address, TLSInfo *tlsInfo, std::string delimiter = " ", int depth = 10, std::string text = "");
      
      ///
      /// The destructor for this object.
      ///
      
      virtual ~TCPServer();
      
      virtual void sessionErrorHandler(std::string errorString, std::stringstream &out);
      
      ///
      /// getSocketAccept is designed to allow a polymorphic extension of this object to
      /// return a type of object that extends the definition of the server socket.
      /// Returning the appropriate session object that extends from Session provides
      /// the mechanism where the server can select the protocol dialog for the desired
      /// service.
      ///
      
      virtual TCPSession *getSocketAccept(EPoll &epoll);
      
      ///
      /// The list of sessions that are currently open and being maintained by this object.
      ///
      /// This is the one real, strong-owning reference per live session -
      /// see TCPSession::pin()'s own doc comment for the full reasoning.
      /// Every other place that keeps a TCPSession* around (Subscription::
      /// subscribers, a Zephora-specific sessionsByPlayerName map, etc.)
      /// is just a non-owning observer and must pin() before touching the
      /// object. A session stops existing, for real, the instant its
      /// entry here is erased and every other outstanding pin() (if any
      /// thread happened to be mid-call) has released its own reference -
      /// removeFromSessionList() is the only place that ever removes an
      /// entry, and Thread::run() calls it instead of ever calling
      /// `delete` on a TCPSession directly (see its own comment).
      ///

      std::vector<std::shared_ptr<TCPSession>> sessions;
      
      ///
      /// The commands object is a CommandList and is used to store Command objects to be
      /// parsed and run as data comes into the session.
      ///
      
      CommandList commands;
      
      ///
      /// If not NULL the blacklist object can be assigned to this server socket and the server
      /// IP addresses connecting to the server attempting to accept a socket are contained in
      /// this list then the connection is rejected and no accept is granted.
      ///
      
      IPAddressList *blackList;
      
      ///
      /// If not NULL the blacklist object can be assigned to this server socket and the server
      /// IP addresses connecting to the server attempting to accept a socket are contained in
      /// this list then the connection is rejected and no accept is granted.
      ///
      
      IPAddressList *whiteList;
      
      void removeFromSessionList(TCPSession *session);
      
      void output(std::stringstream &out); ///< Output the consoles array to the console.
      
      ///
      ///
      ///
      
      void sendToAll(std::stringstream &out);
      
      ///
      /// Use this sendToAll method to output the contents of the out stream
      /// to all the connections on the server excluding the sender session.
      ///
      
      void sendToAll(std::stringstream &out, TCPSession &sender, SessionFilter filter);
      
      ///
      /// Use this sendToAll method to output the contents of the out stream
      /// to all the connections on the server excluding the sender session
      /// and the entries identified by the passed in filter object.
      ///
      
      void sendToAll(std::stringstream &out, TCPSession &sender);
      
      ///
      /// The Subscription Manager tracks all subscriptions on the server.
      ///
      
      SubscriptionManager subscriptions;
      
      ///
      /// Use the getSessionByAlias to retrieve a session pointer by the value
      /// of the alias pointer. Returns an already-pin()'d shared_ptr (null
      /// if not found) rather than a raw pointer, so callers can't
      /// accidentally hold onto - or use - a reference that isn't actually
      /// keeping the session alive.
      ///

      std::shared_ptr<TCPSession> getSessionByAlias(void *alias);
      
    protected:
      ///
      /// This method is called by the lower socket when a connection request comes into
      /// the listening and bound server port.
      ///

      void connectionRequest() override;

      ///
      /// Drops any session that completed a TCP accept() but has never
      /// had a single byte of real data pass through onDataReceived() -
      /// covers both a TLS handshake that never finishes and a plain
      /// connection that never sends anything - once it's been open
      /// longer than a short grace period. Nothing else in this class
      /// ever revisits an already-accepted session once it stops
      /// generating epoll events (Thread::run()'s dispatch loop only
      /// acts on a session when a real event for it arrives), so a
      /// connection that completes the handshake and then goes
      /// permanently silent - exactly what a port scan/prober looks
      /// like from here, as opposed to a normal scan that just connects
      /// and immediately closes again, which the existing read-hangup
      /// path already cleans up fine - would otherwise sit in `sessions`
      /// forever, one TCPSession + one fd each. Called from
      /// connectionRequest() (see its own call site) so the sweep keeps
      /// pace with however fast new connections are actually arriving,
      /// without needing a dedicated timer/thread of its own; a
      /// legitimate, already-talking client is never at risk, since
      /// hasReceivedData latches true permanently on its first real byte
      /// and is never consulted again after that.
      ///

      void sweepStaleSessions();

      ///
      /// The listening socket itself is never a TLS peer - accepting a
      /// connection on it surfaces as a plain read() failing with ENOTCONN
      /// (see Socket::receiveData(), which is what actually detects and
      /// dispatches to connectionRequest() above). When this server is
      /// TLS-configured, TCPSocket::receiveData()'s normal ctx-based
      /// dispatch would instead route that same event through
      /// TLS::receiveData()/SSL_read() against a listening fd that was
      /// never SSL_accept()-ed at all (real per-connection sessions are
      /// the only sockets TLS applies to) - confirmed via a real crash
      /// (SIGSEGV inside SSL_read, called with `this` pointing at this
      /// server object, not a session). Always using the plain path here,
      /// regardless of whether tlsInfo is set, keeps connection-detection
      /// working the same way with or without TLS configured.
      ///

      void receiveData(coreutils::ZString &buffer) override;
      
      ///
      /// This method is called when the Command associated with this object is requested
      /// because a user has typed in the associated command name on a command entry line.
      ///
      /// @param the session object to write the output to.
      ///
      
      int processCommand(coreutils::ZString &request, TCPSession &session) override;
      
    protected:
      // Was private - ConsoleServer::logSend() (and any other subclass
      // that iterates `sessions`, itself public further up) needs to be
      // able to synchronize against the exact same mutex
      // connectionRequest()/removeFromSessionList() already use, rather
      // than reading a shared_ptr vector with no locking of its own.
      std::mutex lock;

    public:
      ///
      /// A listening TCPServer/ConsoleServer (as opposed to an accepted
      /// TCPSession) is constructed once, directly by main(), and lives
      /// for the whole process - never through the shared_ptr-based
      /// ownership TCPSession::registerLive()/pin() provide (see their
      /// own comments), since nothing ever calls `new` on one of these.
      /// Thread::run()'s epoll dispatch still needs a SAFE way to tell
      /// "this raw pointer is one of those known-immortal listening
      /// sockets, fine to call methods on directly" apart from "this is
      /// an unrecognized/stale pointer that must not be touched at all"
      /// (see TCPSession::tryGet()'s own comment on why dynamic_cast
      /// can't make that distinction safely). Registering `this` once,
      /// in the constructor, into this tiny set is that signal - it's
      /// checked by address only, never dereferenced for the check
      /// itself.
      ///

      static bool isKnownListeningSocket(void *ptr) {
         std::lock_guard<std::mutex> guard(listeningSocketsMutex());
         return listeningSockets().count(ptr) > 0;
      }

    private:
      TCPSession *accept();

      static std::mutex &listeningSocketsMutex() {
         static std::mutex m;
         return m;
      }
      static std::set<void *> &listeningSockets() {
         static std::set<void *> s;
         return s;
      }
   };
   
}

#endif