src/main/java/org/jivesoftware/smack/Connection.java
protected void firePacketInterceptors(Packet packet) {
        if (packet != null) {
            for (InterceptorWrapper interceptorWrapper : interceptors.values()) {
                interceptorWrapper.notifyListener(packet);
            }
        }
    }
protected void firePacketInterceptors(Packet packet) {
        if (packet != null) {
            for (InterceptorWrapper interceptorWrapper : interceptors.values()) {
                interceptorWrapper.notifyListener(packet);
            }
        }
    }
Process interceptors. Interceptors may modify the packet that is about to
be sent. Since the thread that requested to send the packet will invoke
all interceptors, it is important that interceptors perform their work as
soon as possible so that the thread does not remain blocked for a long
period.

@param packet
the packet that is going to be sent to the server