Internet DRAFT - draft-ietf-anima-grasp-api
draft-ietf-anima-grasp-api
Network Working Group B. E. Carpenter
Internet-Draft Univ. of Auckland
Intended status: Informational B. Liu, Ed.
Expires: 8 July 2021 Huawei Technologies
W. Wang
X. Gong
BUPT University
4 January 2021
Generic Autonomic Signaling Protocol Application Program Interface
(GRASP API)
draft-ietf-anima-grasp-api-10
Abstract
This document is a conceptual outline of an application programming
interface (API) for 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. Since GRASP is designed to support asynchronous
operations, the API will need to be adapted according to the support
for asynchronicity in various programming languages and operating
systems.
Status of This Memo
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This Internet-Draft will expire on 8 July 2021.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. GRASP API for ASA . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Design Assumptions . . . . . . . . . . . . . . . . . . . 5
2.2. Asynchronous Operations . . . . . . . . . . . . . . . . . 6
2.2.1. Alternative Asynchronous Mechanisms . . . . . . . . . 6
2.2.2. Multiple Negotiation Scenario . . . . . . . . . . . . 7
2.2.3. Overlapping Sessions and Operations . . . . . . . . . 8
2.2.4. Session Termination . . . . . . . . . . . . . . . . . 9
2.3. API definition . . . . . . . . . . . . . . . . . . . . . 9
2.3.1. Overview of Functions . . . . . . . . . . . . . . . . 9
2.3.2. Parameters and data structures . . . . . . . . . . . 10
2.3.3. Registration . . . . . . . . . . . . . . . . . . . . 15
2.3.4. Discovery . . . . . . . . . . . . . . . . . . . . . . 17
2.3.5. Negotiation . . . . . . . . . . . . . . . . . . . . . 19
2.3.6. Synchronization and Flooding . . . . . . . . . . . . 26
2.3.7. Invalid Message Function . . . . . . . . . . . . . . 31
3. Implementation Status [RFC Editor: please remove] . . . . . . 31
4. Security Considerations . . . . . . . . . . . . . . . . . . . 31
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 33
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 33
7.1. Normative References . . . . . . . . . . . . . . . . . . 33
7.2. Informative References . . . . . . . . . . . . . . . . . 33
Appendix A. Error Codes . . . . . . . . . . . . . . . . . . . . 34
Appendix B. Change log [RFC Editor: Please remove] . . . . . . . 36
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39
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. These nodes are members of a secure
Autonomic Control Plane (ACP) such as defined by
[I-D.ietf-anima-autonomic-control-plane].
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When ASAs communicate with each other, they should use the Generic
Autonomic Signaling Protocol (GRASP) [I-D.ietf-anima-grasp]. GRASP
relies on the message confidentiality and integrity provided by the
ACP, with the consequence that all nodes in a given autonomic network
share the same trust boundary, i.e., the boundary of the ACP. Nodes
that have not successfully joined the ACP cannot send, receive or
intercept GRASP messages via the ACP, and cannot usurp ACP addresses.
An ASA runs in an ACP node and therefore benefits from the node's
security properties when transmitting over the ACP, i.e., message
integrity, message confidentiality and the fact that unauthorized
nodes cannot join the ACP. All ASAs within a given autonomic network
therefore trust each other's messages. For these reasons, the API
defined in this document has no explicit security features.
An important feature of GRASP is the concept of a GRASP objective.
This is a data structure encoded, like all GRASP messages, in CBOR
[RFC8949]. Its main contents are a name and a value, explained at
more length in the 'Terminology' section of [I-D.ietf-anima-grasp].
When an objective is passed from one ASA to another using GRASP, its
value is either conveyed in one direction (by a process of
synchronization or flooding), or negotiated bilaterally. The
semantics of the value are opaque to GRASP and therefore to the API.
Each objective must be accurately specified in a dedicated
specification, as discussed in the 'Objective Options' section of
[I-D.ietf-anima-grasp]. In particular, the specification will define
the syntax and semantics of the value of the objective, whether and
how it supports a negotiation process, whether it supports a dry run
mode, and any other details needed for interoperability. The use of
CBOR, with CDDL [RFC8610] as the data definition language, allows the
value to be passed between ASAs regardless of the programming
languages in use. Data storage and consistency during negotiation
are the responsibility of the ASAs involved. Additionally, GRASP
needs to cache the latest values of objectives that are received by
flooding.
As Figure 1 shows, a GRASP implementation could contain several sub-
layers. The bottom layer is the GRASP base protocol module, which is
only responsible for sending and receiving GRASP messages and
maintaining shared data structures. Above that is the basic API
described in this document. The upper layer contains some extended
API functions based upon GRASP basic protocol. For example,
[I-D.ietf-anima-grasp-distribution] describes a possible extended
function.
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+--------------+ +--------------+
| ASAs | | ASAs |
+--------------+ +--------------+
| | |
| +------------------+ |
| | GRASP Extended | |
| | Function API | |
| +------------------+ |
| | |
+------------------------------------------+
| Basic GRASP API Library |
+------------------------------------------+
|
IPC or system call
|
+------------------------------------------+
| GRASP Core |
| (functions, data structures, daemon(s)) |
+------------------------------------------+
Figure 1: Software layout
Multiple ASAs in a single node will share the same instance of GRASP,
much as multiple applications share a single TCP/IP stack. This
aspect is hidden from individual ASAs by the API, and is not further
discussed here.
It is desirable that ASAs can be designed as portable user-space
programs using a system-independent API. In many implementations,
the GRASP code will therefore be split between user space and kernel
space. In user space, library functions provide the API and
communicate directly with ASAs. In kernel space is a daemon, or a
set of sub-services, providing GRASP core functions that are
independent of specific ASAs, such as multicast handling and
relaying, and common data structures such as the discovery cache.
The GRASP API library would need to communicate with the GRASP core
via an inter-process communication (IPC) or system call mechanism.
The details of this are system-dependent.
Both the GRASP library and the extended function modules should be
available to the ASAs. However, since the extended functions are
expected to be added in an incremental manner, they will be the
subject of future documents. This document only describes the basic
GRASP API.
The functions provided by the API do not map one-to-one onto GRASP
messages. Rather, they are intended to offer convenient support for
message sequences (such as a discovery request followed by responses
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from several peers, or a negotiation request followed by various
possible responses). This choice was made to assist ASA programmers
in writing code based on their application requirements rather than
needing to understand protocol details.
Note that a simple autonomic node might contain very few ASAs 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 a GRASP protocol stack in its code and therefore not
require this API to be installed. However, the programmer would then
need a deeper understanding of the GRASP protocol than is needed to
use the API.
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 Assumptions
The assumption of this document is that an Autonomic Service Agent
(ASA) needs to call a separate GRASP implementation. The latter
handles protocol details (security, sending and listening for GRASP
messages, waiting, caching discovery results, negotiation looping,
sending and receiving sychronization data, etc.) but understands
nothing about individual GRASP objectives (Section 2.10 of
[I-D.ietf-anima-grasp]). The semantics of objectives are unknown to
the GRASP protocol and are handled only by the ASAs. Thus, this is
an abstract API for use by ASAs. Individual language bindings should
be defined in separate documents.
Different ASAs may make different use of GRASP features, such as:
* Use GRASP only for discovery purposes.
* Use GRASP negotiation but only as an initiator (client).
* Use GRASP negotiation but only as a responder.
* Use GRASP negotiation as an initiator or responder.
* Use GRASP synchronization but only as an initiator (recipient).
* Use GRASP synchronization but only as a responder and/or flooder.
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* 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.
A few items are out of scope in this version, since practical
experience is required before including them:
* Authorization of ASAs is not defined as part of GRASP and is a
subject for future study.
* User-supplied explicit locators for an objective are not
supported. The GRASP core will supply the locator, using the IP
address of the node concerned.
* The Rapid mode of GRASP (Section 2.5.4 of [I-D.ietf-anima-grasp])
is not supported.
2.2. Asynchronous Operations
GRASP depends on asynchronous operations and wait states, and some of
its messages are not idempotent, meaning that repeating a message may
cause repeated changes of state in the recipient ASA. Many ASAs will
need to support several concurrent 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 need to
run simultaneous negotiations for a given objective with multiple
different peers. Such an ASA will probably need to support
uninterruptible atomic changes to its internal data structures, using
a mechanism provided by the operating system and programming language
in use.
2.2.1. Alternative Asynchronous Mechanisms
Thus, some ASAs need to support asynchronous operations, and
therefore the GRASP core must do so. Depending on both the operating
system and the programming language in use, there are various
techniques for such parallel operations, three of which we consider
here: multi-threading, an event loop structure using polling, and an
event loop structure using callback functions.
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1. 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,
API calls can be treated as simple synchronous function calls
within their own thread, even if the function includes wait
states, blocking and queueing. Concurrent operations will each
run in their own threads. For example, the discover() call may
not return until discovery results have arrived or a timeout has
occurred. If the ASA has other work to do, the discover() call
must be in a thread of its own.
2. In an event loop implementation with polling, blocking calls are
not acceptable. Therefore all calls must be non-blocking, and
the main loop could support multiple GRASP sessions in parallel
by repeatedly polling each one for a change of state. To
facilitate this, the API implementation would 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 (or a failure) 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. Effectively, it becomes a polling call.
3. It was noted earlier that some GRASP messages are not idempotent;
in particular this applies to each step in a negotiation session
- sending the same message twice might produce unintended side
effects. This is not affected by event loop polling: repeating a
call after a 'noReply' does not repeat a message; it simply
checks whether a reply has been received.
4. In an event loop implementation with callbacks, the ASA
programmer would provide a callback function for each
asynchronous operation. This would be called asynchronously when
a reply is received or a failure such as a timeout occurs.
2.2.2. Multiple Negotiation Scenario
The design of GRASP allows the following scenario. Consider an ASA
"A" that acts as a resource allocator for some objective. An ASA "B"
launches a negotiation with "A" to obtain or release a quantity of
the resource. While this negotatition is under way, "B" chooses to
launch a second simultaneous negotiation with "A" for a different
quantity of the same resource. "A" must therefore conduct two
separate negotiation sessions at the same time with the same peer,
and must not mix them up.
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Note that ASAs could be designed to avoid such a scenario, i.e.
restricted to exactly one negotiation session at a time for a given
objective, but this would be a voluntary restriction not required by
the GRASP protocol. In fact it is an assumption of GRASP that any
ASA managing a resource may need to conduct multiple parallel
negotiations, possibly with the same peer. Communication patterns
could be very complex, with a group of ASAs overlapping negotiations
among themselves, as described in [I-D.ciavaglia-anima-coordination].
Therefore, the API design allows for such scenarios.
In the callback model, for the scenario just described, the ASAs "A"
and "B" will each provide two instances of the callback function, one
for each session. For this reason, each ASA must be able to
distinguish the two sessions, and the peer's IP address is not
sufficient for this. It is also not safe to rely on transport port
numbers for this, since future variants of GRASP might use shared
ports rather than a separate port per session. Hence the GRASP
design includes a session identifier. Thus, when necessary, a
session handle (see next section) is used in the API to distinguish
simultaneous GRASP sessions from each other, so that any number of
sessions may proceed asynchronously in parallel.
2.2.3. Overlapping Sessions and Operations
A GRASP session consists of a finite sequence of messages (for
discovery, synchronization, or negotiation) between two ASAs. It is
uniquely identified on the wire by a pseudo-random session identifier
plus the IP address of the initiator of the session. Further details
are given in the section 'Session Identifier' of
[I-D.ietf-anima-grasp].
On the first call in a new GRASP session, the API returns a
'session_handle' handle that uniquely identifies the session within
the API, so that multiple overlapping sessions can be distinguished.
A likely implementation is to form the handle from the underlying
GRASP Session ID and IP address. This handle must be used in all
subsequent calls for the same session. Also see Section 2.3.2.8.
An additional mechanism that might increase efficiency for polling
implementations is to add a general call, say notify(), which would
check the status of all outstanding operations for the calling ASA
and return the session_handle values for all sessions that have
changed state. This would eliminate the need for repeated calls to
the individual functions returning a 'noReply'. This call is not
described below as the details are likely to be implementation-
specific.
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An implication of the above for all GRASP implementations is that the
GRASP core must keep state for each GRASP operation in progress, most
likely keyed by the GRASP Session ID and the GRASP source address of
the session initiator. Even in a threaded implementation, the GRASP
core will need such state internally. The session_handle parameter
exposes this aspect of the implementation.
2.2.4. Session Termination
GRASP sessions may terminate for numerous reasons. A session ends
when discovery succeeds or times out, when negotiation succeeds or
fails, when a synchronization result is delivered, when the other end
fails to respond before a timeout expires, when a loop count expires,
or when a network socket error occurs. Note that a timeout at one
end of a session might result in a timeout or a socket error at the
other end, since GRASP does not send error messages in this case. In
all cases, the API will return an appropriate code to the caller,
which should then release any reserved resources. After failure
cases, the GRASP specification recommends an exponential backoff
before retrying.
2.3. API definition
2.3.1. Overview of Functions
The functions provided by the API fall into several groups:
* Registration. These functions allow an ASA to register itself
with the GRASP core, and allow a registered ASA to register the
GRASP objectives that it will manipulate.
* Discovery. This function allows an ASA that needs to initiate
negotiation or synchronization of a particular objective to
discover a peer willing to respond.
* Negotiation. These functions allow an ASA to act as an initiator
(requester) or responder (listener) for a GRASP negotiation
session. After initiation, negotiation is a symmetric process, so
most of the functions can be used by either party.
* Synchronization. These functions allow an ASA to to act as an
initiator (requester) or responder (listener and data source) for
a GRASP synchronization session.
* Flooding. These functions allow an ASA to send and receive an
objective that is flooded to all nodes of the ACP.
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Some example logic flows for a resource management ASA are given in
[I-D.ietf-anima-asa-guidelines], which may be of help in
understanding the following descriptions. The next section describes
parameters and data structures used in multiple API calls. The
following sections describe various groups of function APIs. Those
APIs that do not list asynchronous mechanisms are implicitly
synchronous in their behaviour.
2.3.2. Parameters and data structures
2.3.2.1. Integers
In this API, integers are assumed to be 32 bit unsigned integers
(uint32_t) unless otherwise indicated.
2.3.2.2. Errorcode
All functions in the API have an unsigned 'errorcode' integer as
their return value (the first return value in languages that allow
multiple return values). 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 suggested error codes,
based on implementation experience. While there is no absolute
requirement for all implementations to use the same error codes, this
is highly recommended for portability of applications.
2.3.2.3. Timeout
Wherever a 'timeout' parameter appears, it is an unsigned integer
expressed in milliseconds. Except for the discover() function, 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.
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2.3.2.4. Objective
An 'objective' parameter is a data structure with the following
components:
* name (UTF-8 string) - the objective's name
* neg (Boolean flag) - True if objective supports negotiation
(default False)
* synch (Boolean flag) - True if objective supports synchronization
(default False)
* dry (Boolean flag) - True if objective supports dry-run
negotiation (default False)
- Note 1: Only one of 'synch' or 'neg' may be True.
- Note 2: 'dry' must not be True unless 'neg' is also True.
- Note 3: In some programming languages the preferred
implementation may be to represent the Boolean flags as bits in
a single byte, which is how they are encoded in GRASP messages.
In other languages an enumeration might be preferable.
* loop_count (unsigned integer, uint8_t) - Limit on negotiation
steps etc. (default GRASP_DEF_LOOPCT, see [I-D.ietf-anima-grasp])
The 'loop_count' is set to a suitable value by the initiator of a
negotiation, to prevent indefinite loops. It is also used to
limit the propagation of discovery and flood messages.
* 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 [RFC8949].
An important advantage of CBOR is that the value of an objective
can be completely opaque to the GRASP core yet pass transparently
through it to and from the ASA. Although the GRASP core must
validate the format and syntax of GRASP messages, it cannot
validate the value of an objective; all it can do is detect
malformed CBOR. The handling of decoding errors depends on the
CBOR library in use, but a corresponding error code ('CBORfail')
is defined in the API and will be returned to the ASA if a faulty
message can be assigned to a current GRASP session. However, it
is the responsibility of each ASA to validate the value of a
received objective, as discussed in Section 5.3 of [RFC8949]. If
the programming language in use is suitably object-oriented, the
GRASP API may deserialize the value and present it to the ASA as
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an object. If not, it will be presented as a CBOR data item. In
all cases, the syntax and semantics of the objective value are the
responsibility of the ASA.
A requirement for all language mappings and all API
implementations is that, regardless of what other options exist
for a language-specific representation of the value, there is
always an option to use a raw CBOR data item as the value. The
API will then wrap this with CBOR Tag 24 as an encoded CBOR data
item for transmission via GRASP, and unwrap it after reception.
By this means, ASAs will be able to communicate regardless of
programming language.
The 'name' and 'value' fields are of variable length. GRASP does not
set a maximum length for these fields, but only for the total length
of a GRASP message. Implementations might impose length limits.
An example data structure definition for an objective in the C
language, using at least the C99 version, and assuming the use of a
particular CBOR library [libcbor], is:
typedef struct {
unsigned char *name;
uint8_t flags; // flag bits as defined by GRASP
uint8_t loop_count;
uint32_t value_size; // size of value in bytes
cbor_mutable_data cbor_value;
// CBOR bytestring (libcbor/cbor/data.h)
} objective;
An example data structure definition for an objective in the Python
language (version 3.4 or later) is:
class objective:
"""A GRASP objective"""
def __init__(self, name):
self.name = name #Unique name (string)
self.negotiate = False #True if objective supports negotiation
self.dryrun = False #True if objective supports dry-run neg.
self.synch = False #True if objective supports synch
self.loop_count = GRASP_DEF_LOOPCT # Default starting value
self.value = None #Place holder; any valid Python object
2.3.2.5. ASA_locator
An 'ASA_locator' parameter is a data structure with the following
contents:
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* locator - The actual locator, either an IP address or an ASCII
string.
* ifi (unsigned integer) - The interface identifier index via which
this was discovered (of limited use to most ASAs).
* expire (system dependent type) - The time on the local system
clock when this locator will expire from the cache
* The following cover all locator types currently supported by
GRASP:
- is_ipaddress (Boolean) - True if the locator is an IP address
- is_fqdn (Boolean) - True if the locator is an FQDN
- is_uri (Boolean) - True if the locator is a URI
- These options are mutually exclusive. Depending on the
programming language, they could be represented as a bit
pattern or an enumeration.
* diverted (Boolean) - True if the locator was discovered via a
Divert option
* protocol (unsigned integer) - Applicable transport protocol
(IPPROTO_TCP or IPPROTO_UDP). These constants are defined in the
CDDL specification of GRASP [I-D.ietf-anima-grasp].
* port (unsigned integer) - Applicable port number
The 'locator' field is of variable length in the case of an FQDN or a
URI. GRASP does not set a maximum length for this field, but only
for the total length of a GRASP message. Implementations might
impose length limits.
It should be noted that when one ASA discovers the ASA_locator of
another, there is no explicit authentication mechanism. In
accordance with the trust model provided by the secure ACP, ASAs are
presumed to provide correct locators in response to discovery. See
the section 'Locator Options' of [I-D.ietf-anima-grasp] for further
details.
2.3.2.6. Tagged_objective
A 'tagged_objective' parameter is a data structure with the following
contents:
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* objective - An objective
* locator - The ASA_locator associated with the objective, or a null
value.
2.3.2.7. Asa_handle
Although an authentication and authorization scheme for ASAs has not
been defined, the API provides a very simple hook for such a scheme.
When an ASA starts up, it registers itself with the GRASP core, which
provides it with an opaque handle that, although not
cryptographically protected, would be difficult for a third party to
predict. The ASA must present this handle in future calls. This
mechanism will prevent some elementary errors or trivial attacks such
as an ASA manipulating an objective it has not registered to use.
Thus, in most calls, an 'asa_handle' parameter is required. It is
generated when an ASA first registers with GRASP, and the ASA must
then store the asa_handle and use it in every subsequent GRASP call.
Any call in which an invalid handle is presented will fail. It is an
up to 32-bit opaque value (for example represented as a uint32_t,
depending on the language). Since it is only used locally, not in
GRASP messages, it is only required to be unique within the local
GRASP instance. It is valid until the ASA terminates. It should be
unpredictable; a possible implementation is to use the same mechanism
that GRASP uses to generate Session Identifiers (see
Section 2.3.2.8).
2.3.2.8. Session_handle and Callbacks
In some calls, a 'session_handle' 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 2.2.3). It will be provided as a parameter in callback
functions. As well as distinguishing calls from different sessions,
it also allows GRASP to detect and ignore calls from non-existent or
timed-out sessions.
In an event loop implementation, callback functions (Section 2.2.1)
may be supported for all API functions that involve waiting for a
remote operation:
discover() whose callback would be discovery_received().
request_negotiate() whose callback would be
negotiate_step_received().
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negotiate_step() whose callback would be
negotiate_step_received().
listen_negotiate() whose callback would be
negotiate_step_received().
synchronize() whose callback would be synchronization_received().
Further details of callbacks are implementation-dependent.
2.3.3. Registration
These functions are used to register an ASA, and the objectives that
it modifies, with the GRASP module. In the absence of an
authorization model, these functions are very simple but they will
avoid multiple ASAs choosing the same name, and will prevent multiple
ASAs manipulating the same objective. If an authorization model is
added to GRASP, these API calls would need to be modified
accordingly.
* register_asa()
All ASAs must use this call before issuing any other API calls.
- Input parameter:
name of the ASA (UTF-8 string)
- Return value:
errorcode (unsigned integer)
asa_handle (unsigned integer)
- This initialises state in the GRASP module for the calling
entity (the ASA). In the case of success, an 'asa_handle' 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. The 'asa_handle' value is undefined.
* deregister_asa()
- Input parameters:
asa_handle (unsigned integer)
name of the ASA (UTF-8 string)
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- Return value:
errorcode (unsigned integer)
- 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 exits.
- Note - the ASA name is strictly speaking redundant in this
call, but is present to detect and reject erroneous
deregistrations.
* register_objective()
ASAs must use this call for any objective whose value they need to
transmit by negotiation, synchronization or flooding.
- Input parameters:
asa_handle (unsigned integer)
objective (structure)
ttl (unsigned integer - default GRASP_DEF_TIMEOUT)
discoverable (Boolean - default False)
overlap (Boolean - default False)
local (Boolean - default False)
- Return value:
errorcode (unsigned integer)
- This registers an objective that this ASA may modify and
transmit to other ASAs by flooding or negotiation. It is not
necessary to register an objective that is only received by
GRASP synchronization or flooding. 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 for
"read-only" operations, i.e., the ASA only wants to receive
synchronization or flooded data for the objective concerned.
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- The 'ttl' parameter is the valid lifetime (time to live) in
milliseconds of any discovery response generated for this
objective. The default value should be the GRASP default
timeout (GRASP_DEF_TIMEOUT, see [I-D.ietf-anima-grasp]).
- If the 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.
- If the parameter 'overlap' is True, more than one ASA may
register this objective in the same GRASP instance. This is of
value for life cycle management of ASAs
[I-D.ietf-anima-asa-guidelines] and must be used consistently
for a given objective (always True or always False).
- If the 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.
* deregister_objective()
- Input parameters:
asa_handle (unsigned integer)
objective (structure)
- Return value:
errorcode (unsigned 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.
2.3.4. Discovery
* discover()
This function may be used by any ASA to discover peers handling a
given objective.
- Input parameters:
asa_handle (unsigned integer)
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objective (structure)
timeout (unsigned integer)
minimum_TTL (unsigned integer)
- Return values:
errorcode (unsigned integer)
locator_list (structure)
- This returns a list of discovered 'ASA_locator's for the given
objective. An empty list means that no locators were
discovered within the timeout. Note that this structure
includes all the fields described in Section 2.3.2.5.
- The parameter 'minimum_TTL' must be greater than or equal to
zero. Any locally cached locators for the objective whose
remaining time to live in milliseconds is less than or equal to
'minimum_TTL' are deleted first. Thus 'minimum_TTL' = 0 will
flush all entries. Note that this will not affect sessions
already in progress using the deleted locators.
- If the parameter 'timeout' is zero, any remaining locally
cached locators for the objective are returned immediately and
no other action is taken. (Thus, a call with 'minimum_TTL' and
'timeout' both equal to zero is pointless.)
- If the parameter 'timeout' is greater than zero, GRASP
discovery is performed, and all results obtained before the
timeout in milliseconds expires are returned. If no results
are obtained, an empty list is returned after the timeout.
That is not an error condition. GRASP discovery is not a
deterministic process. If there are multiple nodes handling an
objective, none, some or all of them will be discovered before
the timeout expires.
- Asynchronous Mechanisms:
o Threaded implementation: This should be called in a separate
thread if asynchronous operation is required.
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o Event loop implementation: An additional in/out
'session_handle' parameter is used. If the 'errorcode'
parameter has the value 2 ('noReply'), no response has been
received so far. The 'session_handle' parameter must be
presented in subsequent calls. A callback may be used in
the case of a non-zero timeout.
2.3.5. Negotiation
Since the negotiation mechanism is different from a typical client/
server exchange, Figure 2 illustrates the sequence of calls and GRASP
messages in a negotiation. Note that after the first protocol
exchange, the process is symmetrical, with negotiating steps strictly
alternating between the two sides. Either side can end the
negotiation. Also, the side that is due to respond next can insert a
delay at any time, to extend the other side's timeout. This would be
used, for example, if an ASA needed to negotiate with a third party
before continuing with the current negotiation.
The loop count embedded in the objective that is the subject of
negotiation is initialised by the ASA that starts a negotiation, and
then decremented by the GRASP core at each step, prior to sending
each M_NEGOTIATE message. If it reaches zero, the negotiation will
fail and each side will receive an error code.
Initiator Responder
--------- ---------
listen_negotiate() \ Await request
request_negotiate()
M_REQ_NEG -> negotiate_step() \ Open session,
<- M_NEGOTIATE / start negotiation
negotiate_step()
M_NEGOTIATE -> negotiate_step() \ Continue
<- M_NEGOTIATE / negotiation
...
negotiate_wait() \ Insert
M_WAIT -> / delay
negotiate_step()
M_NEGOTIATE -> negotiate_step() \ Continue
<- M_NEGOTIATE / negotiation
negotiate_step()
M_NEGOTIATE -> end_negotiate() \ End
<- M_END / negotiation
\ Process results
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Figure 2: Negotiation sequence
As the negotiation proceeds, each side will update the value of the
objective in accordance with its particular semantics, defined in the
specification of the objective. Although many objectives will have
values that can be ordered, so that negotiation can be a simple
bidding process, this is not a requirement.
Failure to agree, a timeout, or loop count exhaustion may all end a
negotiation session, but none of these cases is a protocol failure.
* request_negotiate()
This function is used by any ASA to initiate negotiation of a
GRASP objective as a requester (client).
- Input parameters:
asa_handle (unsigned integer)
objective (structure)
peer (ASA_locator)
timeout (unsigned integer)
- Return values:
errorcode (unsigned integer)
session_handle (structure) (undefined unless successful)
proffered_objective (structure) (undefined unless
successful)
reason (string) (empty unless negotiation declined)
- This function opens a negotiation session between two ASAs.
Note that GRASP currently does not support multi-party
negotiation, which would need to be added as an extended
function.
- The 'objective' parameter must include the requested value, and
its loop count should be set to a suitable starting value by
the ASA. If not, the GRASP default will apply.
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- 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 'peer' is null,
GRASP discovery is automatically performed first to find a
suitable peer (i.e., any node that supports the objective in
question).
- The 'timeout' parameter is described in Section 2.3.2.3.
- If the 'errorcode' return value is 0, the negotiation has
successfully started. There are then two cases:
1. The 'session_handle' parameter is null. In this case the
negotiation has succeeded with one exchange of messages and
the peer has accepted the request. The returned
'proffered_objective' contains the value accepted by the
peer, which is therefore equal to the value in the
requested 'objective'. For this reason, no session handle
is needed, since the session has ended.
2. The 'session_handle' parameter is not null. In this case
negotiation must continue. The 'session_handle' must be
presented in all subsequent negotiation steps. The
returned 'proffered_objective' contains the first value
proffered by the negotiation peer in the first exchange of
messages; in other words it is a counter-offer. The
contents of this instance of the objective must be used to
prepare the next negotiation step (see negotiate_step()
below) because it contains the updated loop count, sent by
the negotiation peer. The GRASP code automatically
decrements the loop count by 1 at each step, and returns an
error if it becomes zero. Since this terminates the
negotiation, the other end will experience a timeout, which
will terminate the other end of the session.
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 negotiation.
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- 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 (see Section 4).
- Asynchronous Mechanisms:
o Threaded implementation: This should be called in a separate
thread if asynchronous operation is required.
o Event loop implementation: The 'session_handle' parameter is
used to distinguish multiple simultaneous sessions. If the
'errorcode' parameter has the value 2 ('noReply'), no
response has been received so far. The 'session_handle'
parameter must be presented in subsequent calls.
- Use of dry run mode: This must be consistent within a GRASP
session. The state of the 'dry' flag in the initial
request_negotiate() call must be the same in all subsequent
negotiation steps of the same session. The semantics of the
dry run mode are built into the ASA; GRASP merely carries the
flag bit.
- 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_handle' data structure, which is opaque to
normal ASAs.
* listen_negotiate()
This function is used by an ASA to start acting as a negotiation
responder (listener) for a given GRASP objective.
- Input parameters:
asa_handle (unsigned integer)
objective (structure)
- Return values:
errorcode (unsigned integer)
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session_handle (structure) (undefined unless successful)
requested_objective (structure) (undefined unless
successful)
- This function instructs GRASP to listen for negotiation
requests for the given 'objective'. It also enables discovery
responses for the objective, as mentioned under
register_objective() in Section 2.3.3.
- Asynchronous Mechanisms:
o Threaded implementation: It will block waiting for an
incoming request, so should be called in a separate thread
if asynchronous operation is required. Unless there is an
unexpected failure, this call only returns after an incoming
negotiation request. If the ASA supports multiple
simultaneous transactions, a new sub-thread must be spawned
for each new session, so that listen_negotiate() can be
called again immediately.
o Event loop implementation: A 'session_handle' parameter is
used to distinguish individual sessions. If the ASA
supports multiple simultaneous transactions, a new event
must be inserted in the event loop for each new session, so
that listen_negotiate() can be reactivated immediately.
- This call only returns (threaded model) or triggers (event
loop) after an incoming negotiation request. When this occurs,
'requested_objective' contains the first value requested by the
negotiation peer. The contents of this instance of the
objective must be used in the subsequent negotiation call
because it contains the loop count sent by the negotiation
peer. The 'session_handle' 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.
- If an ASA is capable of handling multiple negotiations
simultaneously, it may call 'listen_negotiate' simultaneously
from multiple threads, or insert multiple events. 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 or events
themselves, the GRASP session handles, and the underlying
unicast transport sockets.
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* stop_listen_negotiate()
This function is used by an ASA to stop acting as a responder
(listener) for a given GRASP objective.
- Input parameters:
asa_handle (unsigned integer)
objective (structure)
- Return value:
errorcode (unsigned integer)
- Instructs GRASP to stop listening for negotiation requests for
the given objective, i.e., cancels 'listen_negotiate'.
- Asynchronous Mechanisms:
o Threaded implementation: Must be called from a different
thread than 'listen_negotiate'.
o Event loop implementation: no special considerations.
* negotiate_step()
This function is used by either ASA in a negotiation session to
make the next step in negotiation.
- Input parameters:
asa_handle (unsigned integer)
session_handle (structure)
objective (structure)
timeout (unsigned integer) as described in Section 2.3.2.3
- Return values:
Exactly as for 'request_negotiate'
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- Executes the next negotation step with the peer. The
'objective' parameter contains the next value being proffered
by the ASA in this step. It must also contain the latest
'loop_count' value received from request_negotiate() or
negotiate_step().
- Asynchronous Mechanisms:
o Threaded implementation: Usually called in the same thread
as the preceding 'request_negotiate' or 'listen_negotiate',
with the same value of 'session_handle'.
o Event loop implementation: Must use the same value of
'session_handle' returned by the preceding
'request_negotiate' or 'listen_negotiate'.
* negotiate_wait()
This function is used by either ASA in a negotiation session to
delay the next step in negotiation.
- Input parameters:
asa_handle (unsigned integer)
session_handle (structure)
timeout (unsigned integer)
- Return value:
errorcode (unsigned integer)
- Requests the remote peer to delay the negotiation session by
'timeout' milliseconds, thereby extending the original timeout.
This function simply triggers a GRASP Confirm Waiting message
(see [I-D.ietf-anima-grasp] for details).
- Asynchronous Mechanisms:
o Threaded implementation: Called in the same thread as the
preceding 'request_negotiate' or 'listen_negotiate', with
the same value of 'session_handle'.
o Event loop implementation: Must use the same value of
'session_handle' returned by the preceding
'request_negotiate' or 'listen_negotiate'.
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* end_negotiate()
This function is used by either ASA in a negotiation session to
end a negotiation.
- Input parameters:
asa_handle (unsigned integer)
session_handle (structure)
result (Boolean)
reason (UTF-8 string)
- Return value:
errorcode (unsigned integer)
- End the negotiation session.
'result' = True for accept (successful negotiation), False for
decline (failed negotiation).
'reason' = string describing reason for decline (may be null;
ignored if accept).
- Asynchronous Mechanisms:
o Threaded implementation: Called in the same thread as the
preceding 'request_negotiate' or 'listen_negotiate', with
the same value of 'session_handle'.
o Event loop implementation: Must use the same value of
'session_handle' returned by the preceding
'request_negotiate' or 'listen_negotiate'.
2.3.6. Synchronization and Flooding
* synchronize()
This function is used by any ASA to cause synchronization of a
GRASP objective as a requester (client).
- Input parameters:
asa_handle (unsigned integer)
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objective (structure)
peer (ASA_locator)
timeout (unsigned integer)
- Return values:
errorcode (unsigned integer)
result (structure) (undefined unless successful)
- This call requests the synchronized value of the given
'objective'.
- If the 'peer' parameter is null, and the objective is already
available in the local cache, the flooded objective is returned
immediately in the 'result' parameter. In this case, the
'timeout' is ignored.
- If the 'peer' parameter is not null, or a cached value is not
available, synchronization with a discovered ASA is performed.
If successful, the retrieved objective is returned in the
'result' value.
- The 'peer' parameter is an 'ASA_locator' as returned by
discover(). If 'peer' is null, GRASP discovery is
automatically performed first to find a suitable peer (i.e.,
any node that supports the objective in question).
- The 'timeout' parameter is described in Section 2.3.2.3.
- This call should be repeated whenever the latest value is
needed.
- Asynchronous Mechanisms:
o Threaded implementation: Call in a separate thread if
asynchronous operation is required.
o Event loop implementation: An additional in/out
'session_handle' parameter is used, as in
request_negotiate(). If the 'errorcode' parameter has the
value 2 ('noReply'), no response has been received so far.
The 'session_handle' parameter must be presented in
subsequent calls.
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- In the case of failure, an exponential backoff is recommended
before retrying (Section 4).
* listen_synchronize()
This function is used by an ASA to start acting as a
synchronization responder (listener) for a given GRASP objective.
- Input parameters:
asa_handle (unsigned integer)
objective (structure)
- Return value:
errorcode (unsigned 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, as mentioned under register_objective() in
Section 2.3.3.
- This call is non-blocking and may be repeated whenever the
value changes.
* stop_listen_synchronize()
This function is used by an ASA to stop acting as a
synchronization responder (listener) for a given GRASP objective.
- Input parameters:
asa_handle (unsigned integer)
objective (structure)
- Return value:
errorcode (unsigned integer)
- This call instructs GRASP to stop listening for synchronization
requests for the given 'objective', i.e. it cancels a previous
listen_synchronize.
* flood()
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This function is used by an ASA to flood one or more GRASP
objectives throughout the autonomic network.
Note that each GRASP node caches all flooded objectives that it
receives, until each one's time-to-live expires. Cached
objectives are tagged with their origin as well as an expiry time,
so multiple copies of the same objective may be cached
simultaneously. Further details are given in the section 'Flood
Synchronization Message' of [I-D.ietf-anima-grasp]
- Input parameters:
asa_handle (unsigned integer)
ttl (unsigned integer)
tagged_objective_list (structure)
- Return value:
errorcode (unsigned integer)
- This call instructs GRASP to flood the given synchronization
objective(s) and their value(s) and associated locator(s) to
all GRASP nodes.
- The 'ttl' parameter is the valid lifetime (time to live) of the
flooded data in milliseconds (0 = infinity)
- The 'tagged_objective_list' parameter is a list of one or more
'tagged_objective' couplets. The 'locator' parameter that tags
each objective is normally null but may be a valid
'ASA_locator'. Infrastructure ASAs needing to flood an
{address, protocol, port} 3-tuple with an objective create an
ASA_locator object to do so. If the IP address in that locator
is the unspecified address ('::') it is replaced by the link-
local address of the sending node in each copy of the flood
multicast, which will be forced to have a loop count of 1.
This feature is for objectives that must be restricted to the
local link.
- The function checks that the ASA registered each objective.
- This call may be repeated whenever any value changes.
* get_flood()
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This function is used by any ASA to obtain the current value of a
flooded GRASP objective.
- Input parameters:
asa_handle (unsigned integer)
objective (structure)
- Return values:
errorcode (unsigned integer)
tagged_objective_list (structure) (undefined unless
successful)
- This call instructs GRASP to return the given synchronization
objective if it has been flooded and its lifetime has not
expired.
- The 'tagged_objective_list' parameter is a list of
'tagged_objective' couplets, each one being a copy of the
flooded objective and a coresponding locator. Thus if the same
objective has been flooded by multiple ASAs, the recipient can
distinguish the copies.
- Note that this call is for advanced ASAs. In a simple case, an
ASA can simply call synchronize() in order to get a valid
flooded objective.
* expire_flood()
This function may be used by an ASA to expire specific entries in
the local GRASP flood cache.
- Input parameters:
asa_handle (unsigned integer)
tagged_objective (structure)
- Return value:
errorcode (unsigned integer)
- This is a call that can only be used after a preceding call to
get_flood() by an ASA that is capable of deciding that the
flooded value is stale or invalid. Use with care.
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- The 'tagged_objective' parameter is the one to be expired.
2.3.7. Invalid Message Function
* send_invalid()
This function may be used by any ASA to stop an ongoing GRASP
session.
- Input parameters:
asa_handle (unsigned integer)
session_handle (structure)
info (bytes)
- Return value:
errorcode (unsigned integer)
- Sends a GRASP Invalid Message (M_INVALID) message, as described
in [I-D.ietf-anima-grasp]. Should not be used if
end_negotiate() would be sufficient. Note that this message
may be used in response to any unicast GRASP message that the
receiver cannot interpret correctly. In most cases this
message will be generated internally by a GRASP implementation.
'info' = optional diagnostic data supplied by the ASA. May be
raw bytes from the invalid message.
3. Implementation Status [RFC Editor: please remove]
A prototype open source Python implementation of GRASP, including an
API similar to this document, has been used to verify the concepts
for the threaded model. It may be found at
https://github.com/becarpenter/graspy with associated documentation
and demonstration ASAs.
4. Security Considerations
Security considerations for the GRASP protocol are discussed in
[I-D.ietf-anima-grasp]. These include denial of service issues, even
though these are considered a low risk in the ACP. In various places
GRASP recommends an exponential backoff. An ASA using the API should
use exponential backoff after failed discover(), req_negotiate() or
synchronize() operations. The timescale for such backoffs depends on
the semantics of the GRASP objective concerned. Additionally, a
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flood() operation should not be repeated at shorter intervals than is
useful. The appropriate interval depends on the semantics of the
GRASP objective concerned. These precautions are intended to assist
the detection of denial of service attacks.
As a general precaution, all ASAs able to handle multiple negotiation
or synchronization requests in parallel may protect themselves
against a denial of service attack by limiting the number of requests
they handle simultaneously and silently discarding excess requests.
It might also be useful for the GRASP core to limit the number of
objectives registered by a given ASA, the total number of ASAs
registered, and the total number of simultaneous sessions, to protect
system resources. During times of high autonomic activity, such as
recovery from widespread faults, ASAs may experience many GRASP
session failures. Guidance on making ASAs suitably robust is given
in [I-D.ietf-anima-asa-guidelines].
As noted earlier, the trust model is that all ASAs in a given
autonomic network communicate via a secure autonomic control plane
and therefore trust each other's messages. Specific authorization of
ASAs to use particular GRASP objectives is a subject for future
study, also briefly discussed in [I-D.ietf-anima-grasp].
The careful reader will observe that a malicious ASA could extend a
negotiation session indefinitely by use of the negotiate_wait()
function or by manipulating the loop count of an objective. A
robustly implemented ASA could detect such behavior by a peer and
break off negotiation.
The 'asa_handle' is used in the API as a first line of defence
against a malware process attempting to imitate a legitimately
registered ASA. The 'session_handle' is used in the API as a first
line of defence against a malware process attempting to hijack a
GRASP session. Both these handles are likely to be created using
GRASP's 32-bit pseudo-random session ID. By construction, GRASP
avoids the risk of session ID collisions (see the section 'Session
Identifier' of [I-D.ietf-anima-grasp]). There remains a finite
probability that an attacker could guess a session ID,
session_handle, or asa_handle. However, this would only be of value
to an attacker that had already penetrated the ACP, which would allow
many other simpler forms of attack than hijacking GRASP sessions.
5. IANA Considerations
This document makes no request of the IANA.
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6. Acknowledgements
Excellent suggestions were made by Ignas Bagdonas, Carsten Bormann,
Laurent Ciavaglia, Roman Danyliw, Toerless Eckert, Benjamin Kaduk
Erik Kline, Murray Kucherawy, Paul Kyzivat, Guangpeng Li, Michael
Richardson, Joseph Salowey, Eric Vyncke, Magnus Westerlund, Rob
Wilton, and other participants in the ANIMA WG and the IESG.
7. References
7.1. Normative References
[I-D.ietf-anima-grasp]
Bormann, C., Carpenter, B., and B. Liu, "A Generic
Autonomic Signaling Protocol (GRASP)", Work in Progress,
Internet-Draft, draft-ietf-anima-grasp-15, 13 July 2017,
<https://tools.ietf.org/html/draft-ietf-anima-grasp-15>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/info/rfc8610>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/info/rfc8949>.
7.2. Informative References
[I-D.ciavaglia-anima-coordination]
Ciavaglia, L. and P. Peloso, "Autonomic Functions
Coordination", Work in Progress, Internet-Draft, draft-
ciavaglia-anima-coordination-01, 21 March 2016,
<https://tools.ietf.org/html/draft-ciavaglia-anima-
coordination-01>.
[I-D.ietf-anima-asa-guidelines]
Carpenter, B., Ciavaglia, L., Jiang, S., and P. Pierre,
"Guidelines for Autonomic Service Agents", Work in
Progress, Internet-Draft, draft-ietf-anima-asa-guidelines-
00, 14 November 2020, <https://tools.ietf.org/html/draft-
ietf-anima-asa-guidelines-00>.
[I-D.ietf-anima-autonomic-control-plane]
Eckert, T., Behringer, M., and S. Bjarnason, "An Autonomic
Control Plane (ACP)", Work in Progress, Internet-Draft,
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draft-ietf-anima-autonomic-control-plane-30, 30 October
2020, <https://tools.ietf.org/html/draft-ietf-anima-
autonomic-control-plane-30>.
[I-D.ietf-anima-bootstrapping-keyinfra]
Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructures (BRSKI)", Work in Progress, Internet-
Draft, draft-ietf-anima-bootstrapping-keyinfra-45, 11
November 2020, <https://tools.ietf.org/html/draft-ietf-
anima-bootstrapping-keyinfra-45>.
[I-D.ietf-anima-grasp-distribution]
Liu, B., Xiao, X., Hecker, A., Jiang, S., Despotovic, Z.,
and B. Carpenter, "Information Distribution over GRASP",
Work in Progress, Internet-Draft, draft-ietf-anima-grasp-
distribution-01, 1 September 2020,
<https://tools.ietf.org/html/draft-ietf-anima-grasp-
distribution-01>.
[I-D.ietf-anima-reference-model]
Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L.,
and J. Nobre, "A Reference Model for Autonomic
Networking", Work in Progress, Internet-Draft, draft-ietf-
anima-reference-model-10, 22 November 2018,
<https://tools.ietf.org/html/draft-ietf-anima-reference-
model-10>.
[libcbor] Kalvoda, P., "libcbor - Documentation", December 2020,
<https://libcbor.readthedocs.io/>.
Appendix A. Error Codes
This Appendix lists the error codes defined so far on the basis of
implementation experience, with suggested symbolic names and
corresponding descriptive strings in English. It is expected that
complete API implementations will provide for localisation of these
descriptive strings, and that additional error codes will be needed
according to implementation details.
The error codes that may only be returned by one or two functions are
annotated accordingly, and the others may be returned by numerous
functions. The 'noSecurity' error will be returned to most calls if
GRASP is running in an insecure mode (i.e., with no secure substrate
such as the ACP), except for the specific DULL usage mode described
in the section 'Discovery Unsolicited Link-Local' of
[I-D.ietf-anima-grasp].
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ok 0 "OK"
declined 1 "Declined" (req_negotiate, negotiate_step)
noReply 2 "No reply" (indicates waiting state in
event loop calls)
unspec 3 "Unspecified error"
ASAfull 4 "ASA registry full" (register_asa)
dupASA 5 "Duplicate ASA name" (register_asa)
noASA 6 "ASA not registered"
notYourASA 7 "ASA registered but not by you"
(deregister_asa)
notBoth 8 "Objective cannot support both negotiation
and synchronization" (register_obj)
notDry 9 "Dry-run allowed only with negotiation"
(register_obj)
notOverlap 10 "Overlap not supported by this implementation"
(register_obj)
objFull 11 "Objective registry full"
(register_obj)
objReg 12 "Objective already registered"
(register_obj)
notYourObj 13 "Objective not registered by this ASA"
notObj 14 "Objective not found"
notNeg 15 "Objective not negotiable"
(req_negotiate, listen_negotiate)
noSecurity 16 "No security"
noDiscReply 17 "No reply to discovery"
(req_negotiate)
sockErrNegRq 18 "Socket error sending negotiation request"
(req_negotiate)
noSession 19 "No session"
noSocket 20 "No socket"
loopExhausted 21 "Loop count exhausted" (negotiate_step)
sockErrNegStep 22 "Socket error sending negotiation step"
(negotiate_step)
noPeer 23 "No negotiation peer"
(req_negotiate, negotiate_step)
CBORfail 24 "CBOR decode failure"
(req_negotiate, negotiate_step, synchronize)
invalidNeg 25 "Invalid Negotiate message"
(req_negotiate, negotiate_step)
invalidEnd 26 "Invalid end message"
(req_negotiate, negotiate_step)
noNegReply 27 "No reply to negotiation step"
(req_negotiate, negotiate_step)
noValidStep 28 "No valid reply to negotiation step"
(req_negotiate, negotiate_step)
sockErrWait 29 "Socket error sending wait message"
(negotiate_wait)
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sockErrEnd 30 "Socket error sending end message"
(end_negotiate, send_invalid)
IDclash 31 "Incoming request Session ID clash"
(listen_negotiate)
notSynch 32 "Not a synchronization objective"
(synchronize, get_flood)
notFloodDisc 33 "Not flooded and no reply to discovery"
(synchronize)
sockErrSynRq 34 "Socket error sending synch request"
(synchronize)
noListener 35 "No synch listener"
(synchronize)
noSynchReply 36 "No reply to synchronization request"
(synchronize)
noValidSynch 37 "No valid reply to synchronization request"
(synchronize)
invalidLoc 38 "Invalid locator" (flood)
Appendix B. Change log [RFC Editor: Please remove]
draft-ietf-anima-grasp-api-10, 2021-01:
* Closed two final IESG comments
draft-ietf-anima-grasp-api-09, 2020-12:
* Added short discussions of CBOR usage and verification.
* Added section on session termination.
* Clarified that integers are uint32 or uint8.
* Minor technical correction to timeout specification.
* Clarified sequencing of negotiation messages.
* Minor technical addition to request_negotiate() and synchronize()
in event loop model.
* Expanded several points in Security Considerations, including
precautions against resource exhaustion.
* Other clarifications and minor reorganizations; removed some
duplicated text.
* Updated references.
draft-ietf-anima-grasp-api-08, 2020-11:
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* Clarified trust model
* Added explanations of GRASP objectives and sessions
* Added note about non-idempotent messages
* Added overview of API functions, and annotated each function with
a brief description
* Added protocol diagram for negotiation session
* Clarified (absence of) authorization model
* Changed precise semantics of synchronize() for flooded objectives
* Clarified caching of flooded objectives
* Changed 'age_limit' to 'minimum_TTL'
* Improved security considerations, including DOS precautions
* Annotated error codes to indicate which functions generate which
errors
* Other clarifications from Last Call reviews
draft-ietf-anima-grasp-api-07, 2020-10-13:
* Improved diagram and its description
* Added pointer to example logic flows
* Added note on variable length parameters
* Clarified that API decrements loop count automatically
* Other corrections and clarifications from AD review
draft-ietf-anima-grasp-api-06, 2020-06-07:
* Improved diagram
* Numerous clarifications and layout changes
draft-ietf-anima-grasp-api-05, 2020-05-08:
* Converted to xml2rfc v3
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* Editorial fixes.
draft-ietf-anima-grasp-api-04, 2019-10-07:
* Improved discussion of layering, mentioned daemon.
* Added callbacks and improved description of asynchronous
operations.
* Described use case for 'session_handle'.
* More explanation of 'asa_handle'.
* Change 'discover' to use 'age_limit' instead of 'flush'.
* Clarified use of 'dry run'.
* Editorial improvements.
draft-ietf-anima-grasp-api-03, 2019-01-21:
* Replaced empty "logic flows" section by "implementation status".
* Minor clarifications.
* Editorial improvements.
draft-ietf-anima-grasp-api-02, 2018-06-30:
* Additional suggestion for event-loop API.
* Discussion of error code values.
draft-ietf-anima-grasp-api-01, 2018-03-03:
* Editorial updates
draft-ietf-anima-grasp-api-00, 2017-12-23:
* WG adoption
* Editorial improvements.
draft-liu-anima-grasp-api-06, 2017-11-24:
* Improved description of event-loop model.
* Changed intended status to Informational.
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* Editorial improvements.
draft-liu-anima-grasp-api-05, 2017-10-02:
* Added send_invalid()
draft-liu-anima-grasp-api-04, 2017-06-30:
* Noted that simple nodes might not include the API.
* Minor clarifications.
draft-liu-anima-grasp-api-03, 2017-02-13:
* Changed error return to integers.
* Required all implementations to accept objective values in CBOR.
* Added non-blocking alternatives.
draft-liu-anima-grasp-api-02, 2016-12-17:
* Updated for draft-ietf-anima-grasp-09
draft-liu-anima-grasp-api-02, 2016-09-30:
* Added items for draft-ietf-anima-grasp-07
* Editorial corrections
draft-liu-anima-grasp-api-01, 2016-06-24:
* Updated for draft-ietf-anima-grasp-05
* Editorial corrections
draft-liu-anima-grasp-api-00, 2016-04-04:
* Initial version
Authors' Addresses
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Brian Carpenter
School of Computer Science
University of Auckland
PB 92019
Auckland 1142
New Zealand
Email: brian.e.carpenter@gmail.com
Bing Liu (editor)
Huawei Technologies
Q14, Huawei Campus
No.156 Beiqing Road
Hai-Dian District, Beijing
100095
P.R. China
Email: leo.liubing@huawei.com
Wendong Wang
BUPT University
Beijing University of Posts & Telecom.
No.10 Xitucheng Road
Hai-Dian District, Beijing 100876
P.R. China
Email: wdwang@bupt.edu.cn
Xiangyang Gong
BUPT University
Beijing University of Posts & Telecom.
No.10 Xitucheng Road
Hai-Dian District, Beijing 100876
P.R. China
Email: xygong@bupt.edu.cn
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