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<table class="title-block">
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<td><table class="title-block">
<tr>
<td><font size="+3"><b>The NARP protocol specification
</b></font></td>
</tr>
</table><table class="title-block">
<tr>
<td><font size="+1"><b>A Generic Recursive Communication Protocol for
Networked Applications</b></font></td>
</tr>
</table></td>
</tr>
</table>
<p>
In this document we explain the purpose and provide a draft
specification for the NARP protocol, a general-purpose networking
protocol destined to be used in many layers of a new operating system
and networking system.
</p>
<h2 id="auto-1">1<span style="margin-left: 1em"></span>Introduction</h2>
<p>
We begin by remarking that a basic operation in all computer operation
processes consists in naming objects and providing acces to these named
objects. Here are a few examples of naming in real use cases:
</p>
<ul>
<li>
<p>
Naming of files on a local or distant file system
</p>
</li>
<li>
<p>
Naming of devices in the <tt class="verbatim">/dev</tt> virtual filesystem on
Unix machines
</p>
</li>
<li>
<p>
Naming of networked machines (with IP adresses and DNS records)
</p>
</li>
<li>
<p>
Naming of internet ressources over protocols such as HTTP, IMAP,
IRC, specfic web services, …
</p>
</li>
</ul>
<p>
We propose here a novel architecture with the purpose of unifying all
the naming happening at all levels of the system, with two base concepts
: <em>objects</em> and <em>service</em>.
</p>
<ul>
<li>
<p>
<em>objects</em> are ressources that may implement different
semantics : bidirectionnal communication (such as sockets) ;
unidirectionnal communication (FIFO-like) ; file semantics ; etc.
</p>
</li>
<li>
<p>
<em>services</em> are a way of naming objects, querying the
interfaces they implement, and multiplexing communications with them
</p>
</li>
</ul>
<p>
We suggest that a NARP service may be provided on any bidirectionnal
channel of communication supporting the (reliable) sending and recieving
of messages. In addition, NARP objects may implement such a send/recieve
interface ; therefore a NARP service can be channeled into an object.
Such a construction of using a NARP object to access a NARP service is a
fundamental operation that we call <em>recursive multiplexing</em>, or
just <em>multiplexing</em>.
</p>
<p>
The NARP protocol is a client/server protocol meant to include a variety
of different operations that may or may not be implemented by a specific
NARP server.
</p>
<h2 id="auto-2">2<span style="margin-left: 1em"></span>High-level overview</h2>
<h3 id="auto-3">2.1<span style="margin-left: 1em"></span>The basic operations on services and
objects</h3>
<p>
A NARP service is basically any object that implements the following
operations:
</p>
<ul>
<li>
<p>
<em>query</em> : get information on a ressource identified by name
</p>
</li>
<li>
<p>
<em>list</em> : know the names of ressources presented by the
service (possibly in a specific sub-path)
</p>
</li>
<li>
<p>
<em>attach</em> : get an object interface for accessing a ressource,
identified by name
</p>
</li>
</ul>
<p>
A NARP object is basically any object that implements the following
operations :
</p>
<ul>
<li>
<p>
<em>send</em> : send a message (an arbitrary byte string) to the
object
</p>
</li>
<li>
<p>
<em>recieve</em> : recieve a message from the object (this may be
done asynchronously with handler functions)
</p>
</li>
<li>
<p>
<em>detach</em> : delete object connection
</p>
</li>
</ul>
<h3 id="auto-4">2.2<span style="margin-left: 1em"></span>The basics of the NARP protocol</h3>
<p>
Given any interface with send/recieve capabilities considered as an
assymetric (client/server) configuration, the following client messages
consitute the basics of the NARP protocol for providing a NARP service
on the interface:
</p>
<ul>
<li>
<p>
<tt class="verbatim">hello</tt> : initialize a connection, check version
information, …
</p>
</li>
<li>
<p>
<tt class="verbatim">authenticate</tt> and appropriate response messages : use
credentials (user/password or access token) to gain acces to some
ressources provided by the server (the protocol is thus statefull)
</p>
</li>
<li>
<p>
<tt class="verbatim">walk</tt>, <tt class="verbatim">list</tt> and appropriate response
messages : get information about the available ressources
</p>
</li>
<li>
<p>
<tt class="verbatim">attach</tt> and appropriate response messages : give an
identifier (a descriptor) to a ressource in order to communicate
with it
</p>
</li>
<li>
<p>
<tt class="verbatim">send</tt> and appropriate response messages : send a
message to an attached ressource, identified by its descriptor
</p>
</li>
<li>
<p>
<tt class="verbatim">detach</tt> : close a descriptor and detach from a
ressource
</p>
</li>
<li>
<p>
<tt class="verbatim">create</tt>, <tt class="verbatim">delete</tt>, <tt class="verbatim">rename</tt>,
<tt class="verbatim">link</tt> : requests the creation or modification of a
ressource in the namespace
</p>
</li>
</ul>
<p>
The server may also at any moment send a message, including:
</p>
<ul>
<li>
<p>
a response to a query
</p>
</li>
<li>
<p>
<tt class="verbatim">recieve</tt> : a notification of a message sent from the
object to the client
</p>
</li>
<li>
<p>
<tt class="verbatim">detached</tt> : the connection to the object has been
terminated by the object server
</p>
</li>
</ul>
<h3 id="auto-5">2.3<span style="margin-left: 1em"></span>Recursion</h3>
<p>
If an object is a NARP server, the messages sent to it and recieved from
it are messages of the NARP protocol. Otherwise, they are arbitrary.
</p>
<h3 id="auto-6"><a id="rev-sock"></a>2.4<span style="margin-left: 1em"></span>Reverse object</h3>
<p>
Some NARP servers may support reverse object serving: the client creates
an object on the server and handles all the requests arriving to this
object (therefore the initial NARP server only serves as a relay between
the new server and its clients
<p>
<font size="-1"><div align="justify">
<div style="margin-left: 0px">
<div style="margin-right: 0px">
<class style="font-style: normal"><p>
1. Research is to be done on shortcutting mechanisms in
specific situations where too many levels of recursion cause a
performance issue.
</p></class>
</div>
</div>
</div></font>
</p>
<span style="margin-left: 0em"></span>
<a id="footnr-1"></a>
<sup><class style="font-style: normal"><a href="#footnote-1">1</a></class></sup>
). A client wishing to act as a reverse object server may use the
following commands:
</p>
<ul>
<li>
<p>
<tt class="verbatim">serve</tt> : listen for attach requests on a servable
(empty) object created in the server namespace (if authorized)
</p>
</li>
<li>
<p>
<tt class="verbatim">accept</tt> and <tt class="verbatim">reject</tt> : accept (or
reject) an attach request to the object
</p>
</li>
<li>
<p>
<tt class="verbatim">detach</tt> : close connection between object and client
(this is the same detach message as in standard communications)
</p>
</li>
<li>
<p>
<tt class="verbatim">unserve</tt> : stop serving for the object. Attached
clients continue to be attached.
</p>
</li>
</ul>
<p>
The server may in turn send the following messages concerning the server
object:
</p>
<ul>
<li>
<p>
<tt class="verbatim">attach_request</tt> : a client is willing to attach to
the object. A descriptor is already associated to the connection to
be established, but the server may reject it.
</p>
</li>
</ul>
<p>
Once a client is attached to the object, a classical send/recieved
interface is provided.
</p>
<p>
Typically, the protocol exchanged over the object is NARP protocol,
therefore enabling the reverse server to provide its own namespace and
other functionnality.
</p>
<h3 id="auto-7">2.5<span style="margin-left: 1em"></span>Specific object types and associated
messages</h3>
<h4 id="auto-8">2.5.1<span style="margin-left: 1em"></span>Objects are sockets</h4>
<p>
Sockets are the basis of the NARP protocol : attaching to an objects
opens a socket connection to the process serving the object, and when
the connection is accepted, basic send/recieve functionnality is
provided. See also the reverse object protocol described in section <a
href="#rev-sock">2.4</a>.
</p>
<h4 id="auto-9">2.5.2<span style="margin-left: 1em"></span>File objects</h4>
<p>
Small files may implement the following interface:
</p>
<ul>
<li>
<p>
<tt class="verbatim">put</tt> : erase the whole file and put the transmitted
content
</p>
</li>
<li>
<p>
<tt class="verbatim">get</tt> : retrieve the whole file content
</p>
</li>
</ul>
<p>
Big files may implement the following interface:
</p>
<ul>
<li>
<p>
<tt class="verbatim">write</tt> : write a portion of the file at a given
offset
</p>
</li>
<li>
<p>
<tt class="verbatim">read</tt> : read a portion of the file at a given offset
</p>
</li>
</ul>
<h4 id="auto-10">2.5.3<span style="margin-left: 1em"></span>User IO (terminals…)</h4>
<p>
Virtual terminals can be seen as objects implementing a simple
send/recieve semantic, where the data transmitted is unstructured (or
structured given a specific terminal data structure). More specific
interfaces can be defined for advanced terminals and GUIs.
</p>
<h4 id="auto-11">2.5.4<span style="margin-left: 1em"></span>Specific applications</h4>
<p>
Specific applications may define custom messages. Examples include:
</p>
<ul>
<li>
<p>
e-mail
</p>
</li>
<li>
<p>
instant messaging
</p>
</li>
<li>
<p>
collaborative editing of text-based documents
</p>
</li>
</ul>
<p>
and many other applications yet to be invented.
</p>
<h3 id="auto-12">2.6<span style="margin-left: 1em"></span>Big messages</h3>
<p>
The message size in the NARP protocol is limited to 64kb, and
recommended not to exceed 4kb+header (4kb is the size of a memory page
on many machines). Therefore a possibility would be for the NARP
protocol to include a way to transmit big messages by fragmenting them
into small messages. Optionnal error correction may be included. This
can be useful for example when using <tt class="verbatim">put</tt> or <tt class="verbatim">get</tt>
on large files, or <tt class="verbatim">read</tt>s and <tt class="verbatim">write</tt>s of
big file portions. The recieving of a large fragmented message may have
a specific implementation allowing the reciever to work with the partial
data as soon as it starts arriving and not having to wait for the whole
message to be transmitted and buffered. Research is yet to be done on
this specific subject.
</p>
<h3 id="auto-13">2.7<span style="margin-left: 1em"></span>Permissions</h3>
<p>
For each attached client the server may keep track of associated
permissions, and accept or reject requests according to those
permissions. The client may use an authentication command to gain
supplementary privileges on the server's ressources. The client may
request a token to delegate it's privileges on a given object to another
client. Advanced right management functionnalities are to be discussed.
</p>
<h3 id="auto-14">2.8<span style="margin-left: 1em"></span>Reliability concerns</h3>
<p>
The NARP protocol relies on the fact that when transmitting a message,
the other end will recieve it. It is nevertheless recommended that NARP
implementations support the repeating of messages if an expected
acknowlegment has not arrived after a given delay.
</p>
<h3 id="auto-15">2.9<span style="margin-left: 1em"></span>Example NARP servers</h3>
<h4 id="auto-16">2.9.1<span style="margin-left: 1em"></span>Virtual NARP server (i.e. NARP
router)</h4>
<p>
This server implements a namespace where any client may create an empty
object and serve connections to it. Additionnaly, the server may
implement the possibility to create virtual files, virtual directories,
FIFO queues, etc.
</p>
<p>
This server may be connected to other virtual NARP servers in order to
provide a global namespace accessible to all. Each virtual NARP server
acts as an endpoint into the network and may have functionnality for
routing the communications to objects to the clients that serve them.
</p>
<h4 id="auto-17">2.9.2<span style="margin-left: 1em"></span>NARP file server</h4>
<p>
This server simply implements access to a filesystem : listed ressources
are the same as the files present in a served directory, each of these
implements the filing protocol (served directly by the file server), and
the creation of files/directories may also be implemented.
</p>
<h4 id="auto-18">2.9.3<span style="margin-left: 1em"></span>NARP terminal/GUI server</h4>
<p>
Clients may create objects on the server ; each of these objects
correspond to a GUI window. Two interfaces may be implemented : text IO
(terminal) and graphical interaction. Advanced terminal interaction
features may be implemented at the protocol level, such as
auto-completion of commands or of text being edited…
</p>
<p>
Suggestion for a third kind of window : the data sent by the client
corresponds to a description of the scene in a given markup language and
the server does the rendering. The client can also subscribed to events
such as clicking on an item or entering text. This possibility is to be
explored.
</p>
<h4 id="auto-19">2.9.4<span style="margin-left: 1em"></span>NARP e-mail and newsgroup server</h4>
<p>
Several features to be implemented:
</p>
<ul>
<li>
<p>
user login and private user mailboxes
</p>
</li>
<li>
<p>
bridge to standard SMTP/POP3/IMAP services
</p>
</li>
<li>
<p>
private threads of conversation with access rights (the users don't
each have a copy of the thread)
</p>
</li>
<li>
<p>
synchronization between many servers
</p>
</li>
<li>
<p>
public discussion forums
</p>
</li>
</ul>
<h4 id="auto-20">2.9.5<span style="margin-left: 1em"></span>NARP chat server</h4>
<ul>
<li>
<p>
user login and status notification
</p>
</li>
<li>
<p>
online and offline private messaging
</p>
</li>
<li>
<p>
public chat rooms, chat room logging independently of user being
online or offline
</p>
</li>
<li>
<p>
bridging and synchronization between many servers
</p>
</li>
</ul>
<h4 id="auto-21">2.9.6<span style="margin-left: 1em"></span>NARP applicative server</h4>
<p>
TODO…
</p>
<h2 id="auto-22">3<span style="margin-left: 1em"></span>Specifics of the NARP protocol</h2>
<h3 id="auto-23">3.1<span style="margin-left: 1em"></span>Protocol description format</h3>
<p>
A protocol message is given in the following form:
</p>
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid">element type</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">element type</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">…</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">element type</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">element description</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">element description</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">…</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">element description</td>
</tr></tbody>
</table>
<p>
The following element types apply:
</p>
<ul>
<li>
<p>
int16, int32, int64 : 16-bit, 32-bit or 64-bit little-endian
integers
</p>
</li>
<li>
<p>
str : a string, prefixed by a 16-bit length header
</p>
</li>
<li>
<p>
arr(<var>T</var>) : an array of <var>T</var>'s (where <var>T</var>
is another element type), prefixed by a 16-bit length header
</p>
</li>
<li>
<p>
* (for the last element) : consider all the rest of the message as a
byte string
</p>
</li>
</ul>
<h3 id="auto-24">3.2<span style="margin-left: 1em"></span>Basic message format</h3>
<p>
The basic format of a message is :
</p>
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid">int16</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int16</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">*</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">message size</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">message type</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">payload</td>
</tr></tbody>
</table>
<p>
We will abbreviate by “header” the first 32 bits (4 bytes)
of the message. The list of message types is given in section <a href="#type-nums">3.7.1</a>.
</p>
<p>
Messages for communication with an attached ressource will have the
following format :
</p>
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid">int16</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int16</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">*</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">message size</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">message type</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">ressource descriptor (handle)</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">payload</td>
</tr></tbody>
</table>
<p>
Many client messages awating a response will have a message ID included
; this message ID is an arbitrary number generated by the client and
used by the server when giving its response. The header then looks like
this:
</p>
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid">int16</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int16</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">*</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">message size</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">message type</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">message ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">payload</td>
</tr></tbody>
</table>
<h3 id="auto-25">3.3<span style="margin-left: 1em"></span>Message list for core NARP protocol</h3>
<p>
Client messages have an up arrow (<var>↑</var>) next to their name,
while server messages have a down arrow (<var>↓</var>).
</p>
<p>
The core NARP protocol is meant for small size and rapidity (so that
many layers can be encapsulated with minimal overhead), therefore no
acknowlegment is to be sent for recursive send/recieve messages. Other
messages usually imply some kind of action or getting of information,
therefore an acknowlegment or an error is usually sent as a response.
</p>
<p>
<a id="auto-26"></a><h5>Hello<var>↑</var><var>↓</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<p>
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">arr(int32)</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">version</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">list of needed/provided interfaces</td>
</tr></tbody>
</table>
</p>
</div>
<div style="margin-left: 35.145870328812px">
<p>
When a NARP connection is established, the client is always the
first to send a <strong>Hello</strong> message. The object may then
respond either with a <strong>Hello</strong> message indicating that
the requested interfaces can be provided, or with an
<strong>Error</strong> message. The two common error causes are
<em>interface not implemented</em> and <em>incompatible
versions</em>.
</p>
</div>
<div style="margin-left: 35.145870328812px">
<p>
For interface numbers : see table in section <a href="#interface-nums">3.7.3</a>.
</p>
</div>
</p>
<p>
<a id="auto-27"></a><h5>Error<var>↓</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<p>
Generic error response message for any operation.
</p>
</div>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">error ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">error string</td>
</tr></tbody>
</table>
</div>
<div style="margin-left: 35.145870328812px">
<p>
Common error IDs are specified in section <a href="#error-nums">3.7.2</a>.
</p>
</div>
</p>
<p>
<a id="auto-28"></a><h5>Ack<var>↓</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
</tr></tbody>
</table>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<p>
Generic acknowlegment message for commands that require it. An
acknowlege implies the command has been sucessfully executed
(otherwise an error message is sent).
</p>
</div>
</p>
<p>
<a id="auto-29"></a><h5>Stat<var>↑</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">filename</td>
</tr></tbody>
</table>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<p>
The request ID is an ID decided by the client so that it can
identify the answer.
</p>
</div>
</p>
<p>
<a id="auto-30"></a><h5>StatR<var>↓</var></h5>Response to the
<strong>Stat</strong> message.
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">arr(int32)</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">implemented interface</td>
</tr></tbody>
</table>
</div>
<div style="margin-left: 35.145870328812px">
<p>
Common interface numbers are to be found in section <a href="#interface-nums">3.7.3</a>.
</p>
<p>
If a <strong>Stat</strong> query on an object gives a certain list
of interfaces, then when connecting to the object at least all these
interfaces must be included in the server's <strong>Hello</strong>
message as supported interfaces.
</p>
</div>
<div style="margin-left: 35.145870328812px">
<p>
Note that some interface numbers correspond to actions that can be
done on the object from the connection where the object exists (e.g.
: symbolic link, directory), and others correspond to actions that
can be performed after attaching to the object (e.g. file, terminal,
…)
</p>
</div>
</p>
<p>
<a id="auto-31"></a><h5>List<var>↑</var></h5>
</p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">first entry number</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">number of entries requested</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">base path string</td>
</tr></tbody>
</table>
</div>
<p>
<a id="auto-32"></a><h5>ListR<var>↓</var></h5>Response to the
<strong>List</strong> message.
</p>
<p>
<div style="margin-left: 35.145870328812px">
<p>
One message is passed for each entry in the requested range:
</p>
</div>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">entry number</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">entry name</td>
</tr></tbody>
</table>
</div>
<div style="margin-left: 35.145870328812px">
<p>
After the directory has finished being enumerated, a supplementary
entry is given with entry number the last valid entry number plus
one and an empty entry name. This supplementary entry is only given
if its (ficious) entry number is included in the range requested by
the client.
</p>
</div>
</p>
<p>
Possible extension : combine List and Stat so that when the answer to
List is given, information is also given on the object's implemented
interfaces.
</p>
<p>
<a id="auto-33"></a><h5>Attach<var>↑</var></h5>
</p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">filename</td>
</tr></tbody>
</table>
</div>
<p>
<a id="auto-34"></a><h5>Attached<var>↓</var></h5>Response to the
<strong>Attach</strong> command.
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">handle</td>
</tr></tbody>
</table>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<p>
(the handle, ie the ressource descriptor, is attributed by the
server)
</p>
</div>
</p>
<p>
<a id="auto-35"></a><h5>Send<var>↑</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">*</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">handle</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">payload</td>
</tr></tbody>
</table>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<p>
This message does not expect a response.
</p>
</div>
</p>
<p>
<a id="auto-36"></a><h5>Recieve<var>↓</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<p>
Spontaneous server message indicating some data is sent by an
attached ressource. This message does not expect a response.
</p>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">*</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">handle</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">payload</td>
</tr></tbody>
</table>
</div>
</p>
<p>
<a id="auto-37"></a><h5>Detach<var>↑</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">handle</td>
</tr></tbody>
</table>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<p>
This message does not expect a response.
</p>
</div>
</p>
<p>
<a id="auto-38"></a><h5>Detached<var>↓</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<p>
Spontaneous server message indicating the object has been detached.
</p>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">handle</td>
</tr></tbody>
</table>
</div>
</p>
<p>
<a id="auto-39"></a><h5><strong>Create<var>↑</var></strong></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">arr(int32)</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">needed interfaces</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">path</td>
</tr></tbody>
</table>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<p>
A create request is accompanied with a list of needed interfaces
that direct the server into creating the corresponding type of
object (e.g. an empty object to be served, a directory, a file,
…)
</p>
</div>
</p>
<p>
<a id="auto-40"></a><h5>Created<var>↓</var></h5>Response to the
<strong>Create</strong> command.
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">arr(int32)</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">implemented interfaces</td>
</tr></tbody>
</table>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<p>
Signals that the object has been created, and has corresponding
interfaces associated to it.
</p>
</div>
</p>
<p>
<a id="auto-41"></a><h5>Delete<var>↑</var><tt class="verbatim"></tt></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">path</td>
</tr></tbody>
</table>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<p>
This message expects a standard <strong>Ack</strong> response
message.
</p>
</div>
</p>
<p>
<a id="auto-42"></a><h5>Link<var>↑</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">destination path</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">link path</td>
</tr></tbody>
</table>
</div>
<div style="margin-left: 35.145870328812px">
<p>
This message expects a standard <strong>Ack</strong> response
message.
</p>
<p>
Semantics of the link object:
</p>
</div>
<div style="margin-left: 35.145870328812px">
<ul>
<li>
<p>
attaching or serving on this objects corresponds to resolving
the linked path and attaching/serving on the linked object
</p>
</li>
<li>
<p>
stating the link will stat the linked object and add as an
implemented interface the “this is a symlink”
information
</p>
</li>
<li>
<p>
directory listings follow links
</p>
</li>
<li>
<p>
deleting the link will not delete the original file but only the
link
</p>
</li>
</ul>
</div>
</p>
<p>
<a id="auto-43"></a><h5>ReadLink<var>↑</var></h5>
</p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">path</td>
</tr></tbody>
</table>
</div>
<p>
<a id="auto-44"></a><h5>ReadLinkR<var>↓</var></h5>Response to the
<strong>ReadLink</strong> message.
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">link description</td>
</tr></tbody>
</table>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<p>
This will only return the first level of linking, ie the link data
directly associated to the link object.
</p>
</div>
</p>
<p>
<a id="auto-45"></a><h5>Rename<var>↑</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">original path</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">new path</td>
</tr></tbody>
</table>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<p>
This message expects a standard <strong>Ack</strong> response
message.
</p>
</div>
</p>
<p>
<a id="auto-46"></a><h5>Serve<var>↑</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">array(int32)</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">path</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">announced interfaces</td>
</tr></tbody>
</table>
</div>
<div style="margin-left: 35.145870328812px">
<p>
This message is a request for the client to be a reverse server to
an object. The response message to this message is an
<strong>Attached</strong> message. The handle attributed to the
served object is known as the <em>server handle</em> and is used in
the <strong>Incoming</strong> and <strong>Detach</strong> messages.
</p>
<p>
To stop serving an object, the client simply sends a
<strong>Detach</strong> command on the server handle. The semantics
is that all connections that have been openned through the
reverse-served object are preserved when the object stops being
served, and an individual <strong>Detach</strong> message must be
sent to all of them if we want to close them.
</p>
</div>
<div style="margin-left: 35.145870328812px">
<p>
The <em>announced interfaces</em> serves to answer
<strong>Stat</strong> messages on the object while we are serving
it.
</p>
</div>
</p>
<p>
<a id="auto-47"></a><h5>Incoming<var>↓</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">server handle</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">client hande</td>
</tr></tbody>
</table>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<p>
This message is sent by the server when another client wishes to
attach to an object reverse-served by this client. The server handle
is the one given as a response to the <strong>Serve</strong>
message. The client handle is a handle associated to the connection.
The reverse server may reject the connection by issuing a
<strong>Detach</strong> command on the client handle, or may accept
it using the <strong>Accept</strong> message given below.
</p>
</div>
</p>
<p>
<a id="auto-48"></a><h5>Accept<var>↑</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">client handle</td>
</tr></tbody>
</table>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<p>
Once a connection has been accepted, the reverse server may at any
moment close it by sending a <strong>Detach</strong> command on the
corresponding client handle.
</p>
</div>
</p>
<p>
<a id="auto-49"></a><h5>Unbox<var>↑</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">outer handle</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">inner handle</td>
</tr></tbody>
</table>
</div>
<div style="margin-left: 35.145870328812px">
<p>
Consider the handle <em>outer handle</em> as a NARP protocol
service, and associate a handle in the outer layer to the handle of
the inner layer with handle <em>inner handle</em>.
</p>
<p>
Example : in connection A we have a connection open on handle 5
which contains NARP data that we will call B, and in connection B we
have another connection open on handle 7. Issuing a Unbox(id, 5, 7)
request on A will lead to the server creating a handle (say 12)
where sending corresponds to sending a message to handle 7 on
connection B, and such that all messages recieved on handle 5 (ie on
connection B) are filtered and messages whose destination is handle
7 on connection B are removed from the stream and issued on handle
12 of connection A instead.
</p>
<p>
The answer to such a request is an <strong>Attached</strong>
response giving a handle to the unboxed connection.
</p>
</div>
<div style="margin-left: 35.145870328812px">
<p>
Systematically unboxing open connections may lead in some cases to
the network infrastructure being able to do simplifications in the
interconnections. In other cases it may result to useless overhead
on the server side : in such a case the server may refuse an unbox
request.
</p>
</div>
</p>
<p>
<a id="auto-50"></a><h5>Plug<var>↑</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">handle A</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">handle B</td>
</tr></tbody>
</table>
</div>
<div style="margin-left: 35.145870328812px">
<p>
Ask the server to redirect all messages recieved on handle A to
handle B and all mesages recieved on handle B to handle A. The
messages recieved on either handle are not sent to the client
anymore.
</p>
</div>
<div style="margin-left: 35.145870328812px">
<p>
The answer messages are standard
<strong>Ack</strong>/<strong>Error</strong> messages.
</p>
</div>
</p>
<p>
<a id="auto-51"></a><h5>Unplug<var>↑</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">request ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">handle A</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">handle B</td>
</tr></tbody>
</table>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<p>
Undoes a plugging.
</p>
</div>
</p>
<h3 id="auto-52">3.4<span style="margin-left: 1em"></span>Big message protocol</h3>
<p>
To be defined. Is it really usefull? What role exactly does it have? Can
it implement repetition in the case where the message hasn't been
acknowledge? …
</p>
<h3 id="auto-53">3.5<span style="margin-left: 1em"></span>Authentification and rights managment
commands</h3>
<p>
<a id="auto-54"></a><h5>Authenticate<var>↑</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">*</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">message ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">authentification method</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">authentification data</td>
</tr></tbody>
</table>
</div>
<div style="margin-left: 35.145870328812px">
<p>
Used to gain access using credentials (user/password, token,
…). Response messages are standard <strong>Ack</strong> on
success or <strong>Error</strong> on failure. Autentification
methods include :
</p>
</div>
<div style="margin-left: 35.145870328812px">
<ul>
<li>
<p>
1 : user + password
</p>
</li>
<li>
<p>
2 : token
</p>
</li>
</ul>
</div>
</p>
<p>
<a id="auto-55"></a><h5>NewToken<var>↑</var></h5>
</p>
<p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">message ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">path</td>
</tr></tbody>
</table>
</div>
<p>
</p>
<div style="margin-left: 35.145870328812px">
<p>
Requests the server to create an authentication token for accessing
a given object with the privileges of the connected client. Once the
token has been returned, it may be transmitted to another client so
that that client will use it to gain same access to the object.
</p>
</div>
</p>
<p>
<a id="auto-56"></a><h5>NewTokenR<var>↓</var></h5>Response to the
<strong>NewToken</strong> message.
</p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.1em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">int32</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-top: 1px solid">str</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center; border-left: 1px solid">header</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">message ID</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; text-align: center">token</td>
</tr></tbody>
</table>
</div>
<p>
TODO : request account creation, manage user groups and ACLs, …
</p>
<h3 id="auto-57">3.6<span style="margin-left: 1em"></span>TODO</h3>
<ul>
<li>
<p>
file protocol
</p>
<p>
</p>
</li>
<li>
<p>
system protocols (see section on OS design using NARP)
</p>
</li>
<li>
<p>
UI protocols (terminal, GUI)
</p>
</li>
<li>
<p>
communication protocols (mail, IM)
</p>
</li>
</ul>
<h3 id="auto-58">3.7<span style="margin-left: 1em"></span>Table of IDs</h3>
<p>
The tables presented in this section give the number associated to the
message types. These tables are the reference on the subject ; any
information found somewhere else is wrong if it is not the same as found
here. This is for protocol version 1.
</p>
<h4 id="auto-59"><a id="type-nums"></a>3.7.1<span style="margin-left: 1em"></span>Message types</h4>
<p>
<a id="auto-60"></a><h5>Base protocol</h5>
</p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -6.6em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid; border-top: 1px solid">message</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 1px solid"><var>↑</var> id</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 1px solid"><var>↓</var> id</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 0 solid; border-bottom: 0 solid; border-top: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 1px solid">message</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 1px solid"><var>↑</var> id</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 1px solid"><var>↓</var> id</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"><strong>Hello</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">0</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">10000</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 0 solid; border-bottom: 0 solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"><strong>Stat</strong> / <strong>StatR</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">10</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">10010</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"><strong>Error</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">10001</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 0 solid; border-bottom: 0 solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"><strong>List</strong> / <strong>ListR</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">11</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">10011</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"><strong>Ack</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">10002</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 0 solid; border-bottom: 0 solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"><strong>Create</strong> / <strong>Created</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">12</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">10012</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 0 solid; border-bottom: 0 solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"><strong>Delete</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">13</td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"><strong>Attach</strong> / <strong>Attached</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">5</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">10005</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 0 solid; border-bottom: 0 solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"><strong>Rename</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">14</td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"><strong>Send</strong> / <strong>Recieve</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">6</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">10006</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 0 solid; border-bottom: 0 solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"><strong>Link</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">15</td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"><strong>Detach</strong> / <strong>Detached</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">7</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">10007</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 0 solid; border-bottom: 0 solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"><strong>ReadLink</strong> /
<strong>ReadLinkR</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">16</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">10016</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"><strong>Serve</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">8</td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 0 solid; border-bottom: 0 solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"><strong>Incoming</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">10008</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 0 solid; border-bottom: 0 solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"><strong>Unbox</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">20</td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"><strong>Accept</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">9</td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 0 solid; border-bottom: 0 solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"><strong>Plug</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">21</td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 0 solid; border-bottom: 0 solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"><strong>Unplug</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">22</td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
</tr></tbody>
</table>
</div>
<p>
<a id="auto-61"></a><h5>Authentication & privileges</h5>
</p>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -1.65em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid; border-top: 1px solid">message</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 1px solid"><var>↑</var> id</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 1px solid"><var>↓</var> id</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"><strong>Authenticate</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">30</td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"><strong>NewToken</strong> /
<strong>NewTokenR</strong></td>
<td style="border-right: 1px solid; border-bottom: 1px solid">31</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">10031</td>
</tr></tbody>
</table>
</div>
<h4 id="auto-62"><a id="error-nums"></a>3.7.2<span style="margin-left: 1em"></span>Error messages</h4>
<div style="margin-left: 35.145870328812px">
<table style="display: inline; vertical-align: -6.05em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid; border-top: 1px solid">id</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 1px solid">cause</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">1</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">Incompatible versions</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">2</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">Command/interface not implemented</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">3</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">Invalid request (e.g. : out of bounds)</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">4</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">Invalid handle</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">5</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">Attach request rejected</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">6</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">Action impossible because object is in use (cannot
delete, …)</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">7</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">No such object (invalid path)</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">8</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">Could not resolve link</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">9</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">Incorrect credentials</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">10</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">Unauthorized</td>
</tr></tbody>
</table>
</div>
<h4 id="auto-63">3.7.3<span style="margin-left: 1em"></span>Object interfaces<a id="interface-nums"></a></h4>
<div style="margin-left: 35.145870328812px">
<p>
<table style="display: inline; vertical-align: -7.15em">
<tbody><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid; border-top: 1px solid">id</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 1px solid">name</td>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-top: 1px solid">must implement messages</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">0</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">servable</td>
<td style="border-right: 1px solid; border-bottom: 1px solid"><strong>Serve</strong>, <strong>Accept</strong>,
<strong>Incoming</strong></td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">1</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">enumerable</td>
<td style="border-right: 1px solid; border-bottom: 1px solid"><strong>List</strong>, <strong>ListR</strong></td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">2</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">is symlink</td>
<td style="border-right: 1px solid; border-bottom: 1px solid"><strong>ReadLink</strong>,
<strong>ReadLinkR</strong></td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">9</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">non-NARP inside</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">once attached, inside data is arbitrary</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">10</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">NARP service</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">once attached, inside data is a NARP service (ie has
objects, …)</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">11</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">NARP unbox</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">once attached, <strong>Unbox</strong> command
supported</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">12</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">NARP plug</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">once attached, <strong>Plug</strong> and
<strong>Unplug</strong> commands supported</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
<td style="border-right: 1px solid; border-bottom: 1px solid"></td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">20</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">file</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">once attached, file semantics</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">21</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">terminal</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">once attached, terminal semantics</td>
</tr><tr>
<td style="border-right: 1px solid; border-bottom: 1px solid; border-left: 1px solid">22</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">graphics window</td>
<td style="border-right: 1px solid; border-bottom: 1px solid">once attached, GUI semantics</td>
</tr></tbody>
</table>
</p>
</div>
<p>
<a id="auto-64"></a><h5>Servable</h5>This interface specifies that the object is
currently an empty object waiting for someone to issue a
<strong>Serve</strong> command on it, providing it with an
implementation of some interfaces.
</p>
<p>
<a id="auto-65"></a><h5>non-NARP inside</h5>This interfaces indicates that once
attached to the object, the messages sent/recieved to it are not
supposed to be NARP format but any arbitrary format. If this interface
is not specified, then it is expected that the messages transmitted will
follow the general NARP protocol (message format, standard
hello/ack/error messages).
</p>
<p>
<a id="auto-66"></a><h5>NARP service</h5>This interface indicates that once
attached to the object, one can have access to a new NARP namespace
where at least the following operations are supported :
<strong>Stat</strong>, <strong>Attach</strong>, <strong>Send</strong>,
<strong>Recieve</strong>, <strong>Detach</strong>. Additionnal messages
may or may not be supported.
</p>
<h2 id="auto-67">4<span style="margin-left: 1em"></span>Architecture of a NARP implementation in
OCaml or Haskell</h2>
<p>
An asynchronous implementation can be easily programmed in functionnal
languages such as OCaml or Haskell, using closures as continuations for
<em>what to do when a (response) message arrives</em>.
</p>
<p>
TODO
</p>
<h2 id="auto-68">5<span style="margin-left: 1em"></span>Using NARP to design an Operating System</h2>
<p>
When designing the NARP protocol, we had in mind that it would be
possible to use it in a new operating system design at many levels :
access to devices, process management, memory management, filesystems,
IPC, GUI, …
</p>
<p>
Kernel helpers could be developped so that a part of the NARP
multiplexing and demultiplexing takes place in kernel land, before
messages are passed to userspace. For instance, this would allow the
simplification of useless mux-demux chains taking place on the same
machine. The mux-demux helper can be implemented via the
<strong>Unbox</strong> protocol message, handled at the level of the
root stream of NARP communication with the kernel. Another possible
helper would be to map a virtual memory region to a NARP ressource
implementing a standard filing protocol, much like memory mapped files
in standard OSes (only this would work with arbitrary ressources).
</p>
<p>
In this section we will develop on a concrete proposal for a NARP-based
operating system.
</p>
<h3 id="auto-69">5.1<span style="margin-left: 1em"></span>Architecture of the OS</h3>
<p>
The basic primitive of the system being message-passing, the system
looks a lot like a micro-kernel. Only the message format has a complex
semantic and the communication layer is not really “simple”.
Furthermore, the system has device drivers, file system and networking
running as kernel-mode processes, making the kernel more monolithic (but
still having a micro-kernel spirit). It should be easy to make any user
mode process run as a kernel mode process instead, for the sake of
performance (eg : graphical server & compositor).
</p>
<p>
The kernel land is divided in three major parts, with strict dependency
order:
</p>
<ul>
<li>
<p>
Level 0 : System ressource managment : physical memory, virtual
memory, hardware interaction (IRQ, v86), debug output
</p>
</li>
<li>
<p>
Level 1 : Scheduler, IPC & NARP core server : builds on top of
level 0, adds support for processes and communication between them
restricted to NARP protocol data.
</p>
</li>
<li>
<p>
Level 2 : System processes : hardware, file systems, network,
… (may access level 0 and level 1 features)
</p>
</li>
</ul>
<p>
User processes are restricted to syscalls that call level 1 primitives.
</p>
<p>
Here are a few basic principles for the design of these three levels :
</p>
<ul>
<li>
<p>
Level 2 processes may not communicate directly nor share memory :
they must go through level 0 and level 1 primitives to achieve such
a goal. Each level 2 process has a separate heap, which is
completely freed when the process dies. Level 2 processes do not use
separate virtual memory spaces : since the kernel memory space is
mapped in all page directories, a level 2 process may run with any
page directory.
</p>
<p>
Benefits : critical system parts are restricted to level 0 and level
1. Level 2 components may leak or crash with less consequences.
</p>
</li>
<li>
<p>
All synchronization & locking is handle by level 1, except for
level 0 that must implement its own locking devices (since it cannot
rely on level 1).
</p>
<p>
Benefits : no complex synchronization in most of the code (which is
either level 2 or userland), only simple message passing and waiting
for stuff to happen
</p>
</li>
<li>
<p>
No concept of “threads” : system processes are actually
kernel threads, but we call them processes since they use separate
parts of memory. Userlands processes cannot spawn multiple threads
of execution either : they must fork and communicate through NARP if
they want to do so (eg: launching an expensive communication in the
background).
</p>
<p>
(since fork is a complicated system call, and features such as
copy-on-write depend on processes using different paging
directories, the fork system call is accessible only to userland
processes : level 2 processes may not fork, but only create new
processes)
</p>
</li>
<li>
<p>
Level 1 also has a memory heap ; it is used with <tt class="verbatim">core_malloc/core_free</tt>.
Level 2 proceses use standard <tt class="verbatim">malloc/free</tt>, which are
modified to act on the heap of the current process.
</p>
</li>
<li>
<p>
Each process (system or user) has a <em>mailbox</em>, ie a queue of
incoming NARP messages waiting to be transferred. The mailbox has a
maximum <em>size</em> (buffer size), and a <em>send</em> call may
fail with a <em>no space left in queue</em> error. This is the only
possible failure for a <em>send</em> call.
</p>
<p>
System processes (level 2) spend most of their time in <em>waiting
mode</em> ; they may be waked up by either recieving a NARP messsage
or by a hardware event. Therefore the <em>wait_for_event</em>
function that composes the main loop may return either : <em>a
message was recieved</em> or <em>a system event happenned</em>. If
the reason is <em>a message was recieved</em>, the process is free
not to read the message immediately.
</p>
<p>
On the other hand, user processes can wait for only one thing :
recieving a NARP message. Each user process has a <em>message
zone</em> in its memory space, and the <em>wait for message</em>
function just copies the first message of the mailbox into this zone
(overwriting whatever was there before) and returns control to the
process (returning the length of the message).
</p>
</li>
<li>
<p>
Handling of IRQs : some hardware stuff requires action as soon as
the interrupt is fired, therefore a specifi IRQ handler may be used.
Such a handler must do as little as possible, and when it is done
signal level 1 that an IRQ has happenned (it may add specific data
to the “IRQ happenned” message). Level 1 adds a message
to the queue of the recipient process (if there is one) and returns
immediately : the IRQ handler must leave as soon as possible. An IRQ
is handled on whatever stack is currently used, and the IF flag is
constantly off while the IRQ handler is running. The timer IRQ is
the only one that behaves differently, since it has to trigger a
task switch.
</p>
</li>
</ul>
<h3 id="auto-70">5.2<span style="margin-left: 1em"></span>Steps of the developpment of the OS</h3>
<ol>
<li>
<p>
Develop level 0 completely and with cleanest possible design
</p>
</li>
<li>
<p>
Develop level 1 with only basic funcionnality
</p>
</li>
<li>
<p>
Develop some basic applications in level 2 : display, keyboard, mini
kernel shell, mini file system, …
</p>
</li>
<li>
<p>
Improve level 1 with more complex stuff ; try to quickly attain a
complete level 1
</p>
</li>
<li>
<p>
Work on the rest of the stuff
</p>
</li>
</ol>
</body>
</html>
