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draft-liu-anima-grasp-api-06.txt
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Network Working Group B. Carpenter
Internet-Draft Univ. of Auckland
Intended status: Informational B. Liu, Ed.
Expires: May 28, 2018 Huawei Technologies
W. Wang
X. Gong
BUPT University
November 24, 2017
Generic Autonomic Signaling Protocol Application Program Interface
(GRASP API)
draft-liu-anima-grasp-api-06
Abstract
This document is a conceptual outline of the application programming
interface (API) of the Generic Autonomic Signaling Protocol (GRASP).
Such an API is needed for Autonomic Service Agents (ASA) calling the
GRASP protocol module to exchange autonomic network messages with
other ASAs.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 28, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. GRASP API for ASA . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Design Principles . . . . . . . . . . . . . . . . . . . . 3
2.2. Asynchronous Operations . . . . . . . . . . . . . . . . . 4
2.3. API definition . . . . . . . . . . . . . . . . . . . . . 6
2.3.1. Parameters and data structures . . . . . . . . . . . 6
2.3.2. Registration . . . . . . . . . . . . . . . . . . . . 9
2.3.3. Discovery . . . . . . . . . . . . . . . . . . . . . . 11
2.3.4. Negotiation . . . . . . . . . . . . . . . . . . . . . 12
2.3.5. Synchronization and Flooding . . . . . . . . . . . . 17
2.3.6. Invalid Message Function . . . . . . . . . . . . . . 20
3. Example Logic Flows . . . . . . . . . . . . . . . . . . . . . 21
4. Security Considerations . . . . . . . . . . . . . . . . . . . 21
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.1. Normative References . . . . . . . . . . . . . . . . . . 21
7.2. Informative References . . . . . . . . . . . . . . . . . 22
Appendix A. Error Codes . . . . . . . . . . . . . . . . . . . . 22
Appendix B. Change log [RFC Editor: Please remove] . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction
As defined in [I-D.ietf-anima-reference-model], the Autonomic Service
Agent (ASA) is the atomic entity of an autonomic function; and it is
instantiated on autonomic nodes. When ASAs communicate with each
other, they should use the Generic Autonomic Signaling Protocol
(GRASP) [I-D.ietf-anima-grasp].
As the following figure shows, GRASP could contain two major sub-
layers. The bottom is the GRASP base protocol module, which is only
responsible for sending and receiving GRASP messages and maintaining
shared data structures. The upper layer is some extended functions
based upon GRASP basic protocol. For example,
[I-D.liu-anima-grasp-distribution] describes a possible extended
function.
It is desirable that ASAs can be designed as portable user-space
programs using a portable API. In many operating systems, the GRASP
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module will therefore be split into two layers, one being a library
that provides the API and the other being core code containing common
components such as multicast handling and the discovery cache. The
details of this are system-dependent. In particular, the GRASP
library might need to communicate with the GRASP core via an inter-
process communication (IPC) mechanism.
+----+ +----+
|ASAs| |ASAs|
+----+ +----+
| |
| GRASP Function API |
| |
+------------------+ |GRASP API
| GRASP Extended | |
| Function Modules | |
+------------------+ |
+------------------------------------------+
| GRASP Library |
| GRASP Module - - - - - - - - - - - - - -|
| GRASP Core |
+------------------------------------------+
Both the GRASP library and the extended function modules should be
available to the ASAs. Thus, there needs to be two sub-sets of API.
However, since the extended functions are expected to be added in an
incremental manner, it is inappropriate to define the function APIs
in a single document. This document only defines the base GRASP API.
Note that a very simple autonomic node might contain only a single
ASA in addition to the autonomic infrastructure components described
in [I-D.ietf-anima-bootstrapping-keyinfra] and
[I-D.ietf-anima-autonomic-control-plane]. Such a node might directly
integrate GRASP in its autonomic code and therefore not require this
API to be installed.
This document gives a conceptual outline of the API. It is not a
formal specification for any particular programming language or
operating system, and it is expected that details will be clarified
in individual implementations.
2. GRASP API for ASA
2.1. Design Principles
The assumption of this document is that any Autonomic Service Agent
(ASA) needs to call a GRASP module that handles protocol details
(security, sending and listening for GRASP messages, waiting, caching
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discovery results, negotiation looping, sending and receiving
sychronization data, etc.) but understands nothing about individual
objectives. So this is a high level abstract API for use by ASAs.
Individual language bindings should be defined in separate documents.
An assumption of this API is that ASAs may fall into various classes:
o ASAs that only use GRASP for discovery purposes.
o ASAs that use GRASP negotiation but only as an initiator (client).
o ASAs that use GRASP negotiation but only as a responder.
o ASAs that use GRASP negotiation as an initiator or responder.
o ASAs that use GRASP synchronization but only as an initiator
(recipient).
o ASAs that use GRASP synchronization but only as a responder and/or
flooder.
o ASAs that use GRASP synchronization as an initiator, responder
and/or flooder.
The API also assumes that one ASA may support multiple objectives.
Nothing prevents an ASA from supporting some objectives for
synchronization and others for negotiation.
The API design assumes that the operating system and programming
language provide a mechanism for simultaneous asynchronous
operations. This is discussed in detail in Section 2.2.
This is a preliminary version. A few gaps exist:
o Authorization of ASAs is out of scope.
o User-supplied explicit locators for an objective are not
supported.
o The Rapid mode of GRASP is not supported.
2.2. Asynchronous Operations
GRASP includes asynchronous operations and wait states. Most ASAs
will need to support several simultaneous operations; for example an
ASA might need to negotiate one objective with a peer while
discovering and synchronizing a different objective with a different
peer. Alternatively, an ASA which acts as a resource manager might
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need to run simultaneous negotiations for a given objective with
multiple different peers. Thus, both the GRASP core and most ASAs
need to support asynchronous operations. Depending on both the
operating system and the programming language in use, there are two
main techniques for such parallel operations: multi-threading, or a
polling or 'event loop' structure.
In multi-threading, the operating system and language will provide
the necessary support for asynchronous operations, including creation
of new threads, context switching between threads, queues, locks, and
implicit wait states. In this case, all API calls can be treated
naturally as synchronous, even if they include wait states, blocking
and queueing.
In an event loop implementation, synchronous blocking calls are not
acceptable. Therefore all calls must be non-blocking, and the main
loop will support multiple GRASP sessions in parallel by repeatedly
checking each one for a change of state. To facilitate this, the API
implementation will provide non-blocking versions of all the
functions that otherwise involve blocking and queueing. In these
calls, a 'noReply' code will be returned by each call instead of
blocking, until such time as the event for which it is waiting has
occurred. Thus, for example, discover() would return "noReply"
instead of waiting until discovery has succeeded or timed out. The
discover() call would be repeated in every cycle of the main loop
until it completes. A 'session_nonce' parameter (described below) is
used to distinguish simultaneous GRASP sessions from each other, so
that any number of sessions may proceed in parallel.
The following calls involve waiting for a remote operation, so they
use this mechanism:
discover()
request_negotiate()
negotiate_step()
listen_negotiate()
synchronize()
In all these calls, the 'session_nonce' is a read/write parameter.
On the first call, it is set to a null value, and the API returns the
'noReply' code and a non-null value. This value must be used in all
subsequent calls. By this mechanism, multiple overlapping sessions
can be distinguished.
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2.3. API definition
2.3.1. Parameters and data structures
This section describes parameters and data structures uaed in
multiple API calls.
2.3.1.1. Errorcode
All functions in the API have an unsigned 'errorcode' integer as
their return value (the first returned value in languages that allow
multiple returned parameters). An errorcode of zero indicates
success. Any other value indicates failure of some kind. The first
three errorcodes have special importance:
1. Declined: used to indicate that the other end has sent a GRASP
Negotiation End message (M_END) with a Decline option
(O_DECLINE).
2. No reply: used in non-blocking calls to indicate that the other
end has sent no reply so far (see Section 2.2).
3. Unspecified error: used when no more specific error code applies.
Appendix A gives a full list of currently defined error codes.
2.3.1.2. Timeout
Wherever a 'timeout' parameter appears, it is an integer expressed in
milliseconds. If it is zero, the GRASP default timeout
(GRASP_DEF_TIMEOUT, see [I-D.ietf-anima-grasp]) will apply. If no
response is received before the timeout expires, the call will fail
unless otherwise noted.
2.3.1.3. Objective
An 'objective' parameter is a data structure with the following
components:
o name (UTF-8 string) - the objective's name
o neg (Boolean flag) - True if objective supports negotiation
(default False)
o synch (Boolean flag) - True if objective supports synchronization
(default False)
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o dry (Boolean flag) - True if objective supports dry-run
synchronization (default False)
* Note 1: All objectives are assumed to support discovery, so
there is no Boolean for that.
* Note 2: Only one of 'synch' or 'neg' may be True.
* Note 3: 'dry' must not be True unless 'neg' is also True.
o loop_count (integer) - Limit on negotiation steps etc. (default
GRASP_DEF_LOOPCT, see [I-D.ietf-anima-grasp])
o value - a specific data structure expressing the value of the
objective. The format is language dependent, with the constraint
that it can be validly represented in CBOR (default integer = 0).
An essential requirement for all language mappings and all
implementations is that, regardless of what other options exist
for a language-specific represenation of the value, there is
always an option to use a CBOR byte string as the value. The API
will then wrap this byte string in CBOR Tag 24 for transmission
via GRASP, and unwrap it after reception.
An example data structure definition for an objective in the C
language is:
typedef struct {
char *name;
uint8_t flags; // flag bits as defined by GRASP
int loop_count;
int value_size; // size of value
uint8_t cbor_value[]; // CBOR bytestring of value
} objective;
An example data structure definition for an objective in the
Python language is:
class objective:
"""A GRASP objective"""
def __init__(self, name):
self.name = name #Unique name, string
self.neg = False #True if objective supports negotiation
self.dry = False #True if objective supports dry-run negotiation
self.synch = False #True if objective supports synch
self.loop_count = GRASP_DEF_LOOPCT #Default starting value
self.value = 0 #Place holder; any valid Python object
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2.3.1.4. ASA_locator
An 'ASA_locator' parameter is a data structure with the following
contents:
o locator - The actual locator, either an IP address or an ASCII
string.
o ifi (integer) - The interface identifier index via which this was
discovered - probably no use to a normal ASA
o expire (system dependent type) - The time on the local system
clock when this locator will expire from the cache
o is_ipaddress (Boolean) - True if the locator is an IP address
o is_fqdn (Boolean) - True if the locator is an FQDN
o is_uri (Boolean) - True if the locator is a URI
o diverted (Boolean) - True if the locator was discovered via a
Divert option
o protocol (integer) - Applicable transport protocol (IPPROTO_TCP or
IPPROTO_UDP)
o port (integer) - Applicable port number
2.3.1.5. Tagged_objective
A 'tagged_objective' parameter is a data structure with the following
contents:
o objective - An objective
o locator - The ASA_locator associated with the objective, or a null
value.
2.3.1.6. Asa_nonce
In most calls, an 'asa_nonce' parameter is required. It is generated
when an ASA registers with GRASP, and any call in which an invalid
nonce is presented will fail. It is an up to 32-bit opaque value
(for example represented as a uint32_t, depending on the language).
It should be unpredictable; a possible implementation is to use the
same mechanism that GRASP uses to generate Session IDs
[I-D.ietf-anima-grasp]. Another possible implementation is to hash
the name of the ASA with a locally defined secret key.
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2.3.1.7. Session_nonce
In some calls, a 'session_nonce' parameter is required. This is an
opaque data structure as far as the ASA is concerned, used to
identify calls to the API as belonging to a specific GRASP session
(see Section 2.2). In fully threaded implementations this parameter
might not be needed, but it is included to act as a session handle if
necessary. It will also allow GRASP to detect and ignore malicious
calls or calls from timed-out sessions. A possible implementation is
to form the nonce from the underlying GRASP Session ID and the source
address of the session.
2.3.2. Registration
These functions are used to register an ASA and the objectives that
it supports with the GRASP module. If an authorization model is
added to GRASP, it would be added here.
o register_asa()
Input parameter:
name of the ASA (UTF-8 string)
Return parameters:
errorcode (integer)
asa_nonce (integer) (if successful)
This initialises state in the GRASP module for the calling
entity (the ASA). In the case of success, an 'asa_nonce' is
returned which the ASA must present in all subsequent calls.
In the case of failure, the ASA has not been authorized and
cannot operate.
o deregister_asa()
Input parameters:
asa_nonce (integer)
name of the ASA (UTF-8 string)
Return parameter:
errorcode (integer)
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This removes all state in the GRASP module for the calling
entity (the ASA), and deregisters any objectives it has
registered. Note that these actions must also happen
automatically if an ASA crashes.
Note - the ASA name is strictly speaking redundant in this
call, but is present for clarity.
o register_objective()
Input parameters:
asa_nonce (integer)
objective (structure)
ttl (integer - default GRASP_DEF_TIMEOUT)
discoverable (Boolean - default False)
overlap (Boolean - default False)
local (Boolean - default False)
Return parameter:
errorcode (integer)
This registers an objective that this ASA supports and may
modify. The 'objective' becomes a candidate for discovery.
However, discovery responses should not be enabled until the
ASA calls listen_negotiate() or listen_synchronize(), showing
that it is able to act as a responder. The ASA may negotiate
the objective or send synchronization or flood data.
Registration is not needed if the ASA only wants to receive
synchronization or flood data for the objective concerned.
The 'ttl' parameter is the valid lifetime (time to live) in
milliseconds of any discovery response for this objective. The
default value should be the GRASP default timeout
(GRASP_DEF_TIMEOUT, see [I-D.ietf-anima-grasp]).
If the optional parameter 'discoverable' is True, the objective
is immediately discoverable. This is intended for objectives
that are only defined for GRASP discovery, and which do not
support negotiation or synchronization.
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If the optional parameter 'overlap' is True, more than one ASA
may register this objective in the same GRASP instance.
If the optional parameter 'local' is True, discovery must
return a link-local address. This feature is for objectives
that must be restricted to the local link.
This call may be repeated for multiple objectives.
o deregister_objective()
Input parameters:
asa_nonce (integer)
objective (structure)
Return parameter:
errorcode (integer)
The 'objective' must have been registered by the calling ASA;
if not, this call fails. Otherwise, it removes all state in
the GRASP module for the given objective.
2.3.3. Discovery
o discover()
Input parameters:
asa_nonce (integer)
objective (structure)
timeout (integer)
flush (Boolean - default False)
Return parameters:
errorcode (integer)
locator_list (structure)
This returns a list of discovered 'ASA_locator's for the given
objective. If the optional parameter 'flush' is True, any
locally cached locators for the objective are deleted first.
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Otherwise, they are returned immediately. If not, GRASP
discovery is performed, and all results obtained before the
timeout expires are returned. If no results are obtained, an
empty list is returned after the timeout. That is not an error
condition.
Threaded implementation: This should be called in a separate
thread if asynchronous operation is required.
Event loop implementation: An additional read/write
'session_nonce' parameter is used.
2.3.4. Negotiation
o request_negotiate()
Input parameters:
asa_nonce (integer)
objective (structure)
peer (ASA_locator)
timeout (integer)
Return parameters:
errorcode (integer)
session_nonce (structure) (if successful)
proffered_objective (structure) (if successful)
reason (string) (if negotiation declined)
This function opens a negotiation session. The 'objective'
parameter must include the requested value, and its loop count
should be set to a suitable value by the ASA. If not, the
GRASP default will apply.
Note that a given negotiation session may or may not be a dry-
run negotiation; the two modes must not be mixed in a single
session.
The 'peer' parameter is the target node; it must be an
'ASA_locator' as returned by discover(). If the peer is null,
GRASP discovery is performed first.
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If the 'errorcode' return parameter is 0, the negotiation has
successfully started. There are then two cases:
1. The 'session_nonce' parameter is null. In this case the
negotiation has succeeded (the peer has accepted the
request). The returned 'proffered_objective' contains the
value accepted by the peer.
2. The 'session_nonce' parameter is not null. In this case
negotiation must continue. The returned
'proffered_objective' contains the first value proffered by
the negotiation peer. Note that this instance of the
objective must be used in the subsequent negotiation call
because it also contains the current loop count. The
'session_nonce' must be presented in all subsequent
negotiation steps.
This function must be followed by calls to 'negotiate_step'
and/or 'negotiate_wait' and/or 'end_negotiate' until the
negotiation ends. 'request_negotiate' may then be called
again to start a new negotation.
If the 'errorcode' parameter has the value 1 ('declined'), the
negotiation has been declined by the peer (M_END and O_DECLINE
features of GRASP). The 'reason' string is then available for
information and diagnostic use, but it may be a null string.
For this and any other error code, an exponential backoff is
recommended before any retry.
Threaded implementation: This should be called in a separate
thread if asynchronous operation is required.
Event loop implementation: The 'session_nonce' parameter is
used in read/write mode.
Special note for the ACP infrastructure ASA: It is likely that
this ASA will need to discover and negotiate with its peers in
each of its on-link neighbors. It will therefore need to know
not only the link-local IP address but also the physical
interface and transport port for connecting to each neighbor.
One implementation approach to this is to include these details
in the 'session_nonce' data structure, which is opaque to
normal ASAs.
o listen_negotiate()
Input parameters:
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asa_nonce (integer)
objective (structure)
Return parameters:
errorcode (integer)
session_nonce (structure) (if successful)
requested_objective (structure) (if successful)
This function instructs GRASP to listen for negotiation
requests for the given 'objective'. It also enables discovery
responses for the objective.
Threaded implementation: It will block waiting for an incoming
request, so should be called in a separate thread if
asynchronous operation is required.
Event loop implementation: A read/write 'session_nonce'
parameter is used.
Unless there is an unexpected failure, this call only returns
after an incoming negotiation request. When it does so,
'requested_objective' contains the first value requested by the
negotiation peer. Note that this instance of the objective
must be used in the subsequent negotiation call because it also
contains the current loop count. The 'session_nonce' must be
presented in all subsequent negotiation steps.
This function must be followed by calls to 'negotiate_step'
and/or 'negotiate_wait' and/or 'end_negotiate' until the
negotiation ends. 'listen_negotiate' may then be called again
to await a new negotation.
If an ASA is capable of handling multiple negotiations
simultaneously, it may call 'listen_negotiate' simultaneously
from multiple threads. The API and GRASP implementation must
support re-entrant use of the listening state and the
negotiation calls. Simultaneous sessions will be distinguished
by the threads themselves, the GRASP Session IDs, and the
underlying unicast transport sockets.
o stop_listen_negotiate()
Input parameters:
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asa_nonce (integer)
objective (structure)
Return parameter:
errorcode (integer)
Instructs GRASP to stop listening for negotiation requests for
the given objective, i.e., cancels 'listen_negotiate'.
Threaded implementation: Must be called from a different thread
than 'listen_negotiate'.
Event loop implementation: no special considerations.
o negotiate_step()
Input parameters:
asa_nonce (integer)
session_nonce (structure)
objective (structure)
timeout (integer)
Return parameters:
Exactly as for 'request_negotiate'
Executes the next negotation step with the peer. The
'objective' parameter contains the next value being proffered
by the ASA in this step.
Threaded implementation: Called in the same thread as the
preceding 'request_negotiate' or 'listen_negotiate', with the
same value of 'session_nonce'.
Event loop implementation: Must use the same value of
'session_nonce' returned by the preceding 'request_negotiate'
or 'listen_negotiate'.
o negotiate_wait()
Input parameters:
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asa_nonce (integer)
session_nonce (structure)
timeout (integer)
Return parameters:
errorcode (integer)
Delay negotiation session by 'timeout' milliseconds.
Threaded implementation: Called in the same thread as the
preceding 'request_negotiate' or 'listen_negotiate', with the
same value of 'session_nonce'.
Event loop implementation: Must use the same value of
'session_nonce' returned by the preceding 'request_negotiate'
or 'listen_negotiate'.
o end_negotiate()
Input parameters:
asa_nonce (integer)
session_nonce (structure)
reply (Boolean)
reason (UTF-8 string)
Return parameters:
errorcode (integer)
End the negotiation session.
'reply' = True for accept (successful negotiation), False for
decline (failed negotiation).
'reason' = optional string describing reason for decline.
Threaded implementation: Called in the same thread as the
preceding 'request_negotiate' or 'listen_negotiate', with the
same value of 'session_nonce'.
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Event loop implementation: Must use the same value of
'session_nonce' returned by the preceding 'request_negotiate'
or 'listen_negotiate'.
2.3.5. Synchronization and Flooding
o synchronize()
Input parameters:
asa_nonce (integer)
objective (structure)
peer (ASA_locator)
timeout (integer)
Return parameters:
errorcode (integer)
objective (structure) (if successful)
This call requests the synchronized value of the given
'objective'.
Since this is essentially a read operation, any ASA can do it.
Therefore the API checks that the ASA is registered but the
objective doesn't need to be registered by the calling ASA.
If the objective was already flooded, the flooded value is
returned immediately in the 'result' parameter. In this case,
the 'source' and 'timeout' are ignored.
Otherwise, synchronization with a discovered ASA is performed.
The 'peer' parameter is an 'ASA_locator' as returned by
discover(). If 'peer' is null, GRASP discovery is performed
first.
This call should be repeated whenever the latest value is
needed.
Threaded implementation: Call in a separate thread if
asynchronous operation is required.
Event loop implementation: An additional read/write
'session_nonce' parameter is used.
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Since this is essentially a read operation, any ASA can use it.
Therefore GRASP checks that the calling ASA is registered but
the objective doesn't need to be registered by the calling ASA.
In the case of failure, an exponential backoff is recommended
before retrying.
o listen_synchronize()
Input parameters:
asa_nonce (integer)
objective (structure)
Return parameters:
errorcode (integer)
This instructs GRASP to listen for synchronization requests for
the given objective, and to respond with the value given in the
'objective' parameter. It also enables discovery responses for
the objective.
This call is non-blocking and may be repeated whenever the
value changes.
o stop_listen_synchronize()
Input parameters:
asa_nonce (integer)
objective (structure)
Return parameters:
errorcode (integer)
This call instructs GRASP to stop listening for synchronization
requests for the given 'objective', i.e. it cancels a previous
listen_synchronize.
o flood()