class ConnectHookInterface {
    /**
     * Runs optional validation logic on an isMaster reply from a remote host.
     * If a non-OK Status is returned, a the ErrorCode 
     * XXXTemporaryNamePHostValidationFailedXXXTemporaryName will be passed to     
     * the command handler associated with the request that caused this       
     * connection to be created. This will be called once for each new   
     * connection that is established 
     * - even if we have previously connected a host with the same   HostAndPort.
     */
    virtual Status validateHost(const HostAndPort&, const BSONObj& isMasterReply) = 0;

    /**
     * Generates a command to run on the remote host immediately after        
     * connecting to it. This will be run after socket setup, SSL handshake,          
     * authentication and wire protocol detection occurs.
     */
    virtual RemoteCommandRequest makeRequest(const HostAndPort& remote) = 0;

    /**
     * Handles the server's reply to the command generated with makeCommand.
     */
    virtual Status handleReply(StatusWith<RemoteCommandResponse>&& reply) = 0;
};  

/**
 * Sets a connect hook for this NetworkInterface. This method can only be  
 * called once, and must be called before startup() - otherwise the result 
 * is undefined.
 */
void NetworkInterfaceASIO::setConnectHook(std::unique_ptr<ConnectionHookInterface> hook);