Internet-Draft GRASP API June 2020
Carpenter, et al. Expires 14 December 2020 [Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-ietf-anima-grasp-api-06
Published:
Intended Status:
Informational
Expires:
Authors:
B. E. Carpenter
Univ. of Auckland
B. Liu, Ed.
Huawei Technologies
W. Wang
BUPT University
X. Gong
BUPT University

Generic Autonomic Signaling Protocol Application Program Interface (GRASP API)

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 to the support for asynchronicity in various languages and operating systems.

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 14 December 2020.

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Table of Contents

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, a GRASP implementation 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 contains some extended functions based upon GRASP basic protocol. For example, [I-D.liu-anima-grasp-distribution] describes a possible extended function.

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 module will therefore be split into two layers. The top layer is a library that provides the API and communicates directly with ASAs. The lower layer 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) mechanism. The details of this are system-dependent.

 +--------------+          +--------------+
 |     ASAs     |          |     ASAs     |
 +--------------+          +--------------+
   |          |                    |
   |          | GRASP Function     |
   |          | API                |
   | +------------------+          |GRASP API
   | | GRASP Extended   |          |
   | | Function Modules |          |
   | +------------------+          |
   |          |                    |
+------------------------------------------+
|                   GRASP API Library      |
|  GRASP Modules - - - - - - - - - - - - - |
|                   GRASP Core (Daemon)    |
+------------------------------------------+

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 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 GRASP 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 any Autonomic Service Agent (ASA) needs to call a GRASP module. 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 module 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:

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:

2.2. Asynchronous Operations

GRASP depends on asynchronous operations and wait states, and 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 three main techniques for such parallel operations: multi-threading, an event loop structure using polling, and an event loop structure using callback functions.

  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 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. In an event loop implementation with callbacks, the ASA programmer would provide a callback function for each asynchronous operation, e.g. discovery_received(). This would be called asynchronously when a reply is received or a failure such as a timeout occurs.

The following calls involve waiting for a remote operation, so they could use a polling or callback mechanism. In a threaded mechanism, they will usually require to be called in a separate thread:

  • discover() whose callback would be discovery_received().
  • request_negotiate() whose callback would be negotiate_step_received().
  • 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().

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.

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 an ASA managing a resource may need to conduct multiple parallel negotiations, possibly with the same peer. 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 negotiate_step_received(), 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. This is why the GRASP design includes a session identifier. Thus, when necessary, a 'session_nonce' parameter 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

In calls where it is used, the 'session_nonce' is an opaque read/write parameter. On the first call, it is set to a null value, and the API returns a non-null 'session_nonce' value based on the GRASP session identifier. This value must be used in all subsequent calls for the same session, and will be provided as a parameter in the callback functions. By this mechanism, multiple overlapping sessions can be distinguished, both in the ASA and in the GRASP core. The value of the 'session_nonce" is opaque to the ASA.

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_nonce 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.

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_nonce parameter exposes this aspect of the implementation.

2.3. API definition

2.3.1. Parameters and data structures

This section describes parameters and data structures used 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 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.

2.3.1.2. 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:

  • 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 a language such as C the preferred implementation may be to represent the Boolean flags as bits in a single byte.
  • loop_count (integer) - Limit on negotiation steps etc. (default GRASP_DEF_LOOPCT, see [I-D.ietf-anima-grasp])

  • 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, assuming the use of a particular CBOR library, is:

     typedef struct {
    char *name;
    uint8_t flags;            // flag bits as defined by GRASP
    int loop_count;
    int 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 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 = 0      # Place holder; any valid Python object
2.3.1.4. ASA_locator

An 'ASA_locator' parameter is a data structure with the following contents:

  • locator - The actual locator, either an IP address or an ASCII string.
  • ifi (integer) - The interface identifier index via which this was discovered - probably no use to a normal ASA
  • 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
  • diverted (Boolean) - True if the locator was discovered via a Divert option
  • protocol (integer) - Applicable transport protocol (IPPROTO_TCP or IPPROTO_UDP)
  • port (integer) - Applicable port number
2.3.1.5. Tagged_objective

A 'tagged_objective' parameter is a data structure with the following contents:

  • objective - An objective
  • locator - The ASA_locator associated with the objective, or a null value.
2.3.1.6. Asa_nonce

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 nonce that, although not cryptographically protected, would be difficult for a third party to predict. The ASA must present this nonce 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_nonce' parameter is required. It is generated when an ASA first registers with GRASP, and the ASA must then store the asa_nonce and use it in every subsequent GRASP call. 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.

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, these API calls would need to be modified accordingly.

  • 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.

  • deregister_asa()

    • Input parameters:

      asa_nonce (integer)
      name of the ASA (UTF-8 string)

    • Return parameter:

      errorcode (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 crashes.
    • Note - the ASA name is strictly speaking redundant in this call, but is present for clarity.

  • 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 for "read-only" operations, i.e., the ASA only wants to receive synchronization or flooded 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 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.
    • 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_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

  • discover()

    • Input parameters:

      asa_nonce (integer)
      objective (structure)
      timeout (integer)
      age_limit (integer)

    • Return parameters:

      errorcode (integer)
      locator_list (structure)
    • This returns a list of discovered 'ASA_locator's for the given objective. Note that this structure includes all the fields described in Section 2.3.1.4.
    • If the parameter 'age_limit' is greater than zero, any locally cached locators for the objective whose remaining lifetime in milliseconds is less than or equal to 'age_limit' are deleted first. Thus 'age_limit' = 0 will flush all entries.
    • 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 'age_limit' 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.

    • Asynchronous Mechanisms:

      • 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. A callback may be used in the case of a non-zero tiemout.

2.3.4. Negotiation

  • 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 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 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.

    • 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.

    • Asynchronous Mechanisms:

      • 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.
    • 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_nonce' data structure, which is opaque to normal ASAs.

  • listen_negotiate()

    • Input parameters:

      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, as mentioned under register_objective() in Section 2.3.2.

    • Asynchronous Mechanisms:

      • Threaded implementation: It will block waiting for an incoming request, so should be called in a separate thread if asynchronous operation is required. If the ASA supports multiple simultaneous transactions, a new thread must be spawned for each new session.
      • Event loop implementation: A read/write 'session_nonce' parameter is used. If the ASA supports multiple simultaneous transactions, a new event must be inserted in the event loop for each new session.
    • 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.

  • stop_listen_negotiate()

    • Input parameters:

      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'.

    • Asynchronous Mechanisms:

      • Threaded implementation: Must be called from a different thread than 'listen_negotiate'.
      • Event loop implementation: no special considerations.

  • 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.

    • Asynchronous Mechanisms:

      • 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'.

  • negotiate_wait()

    • Input parameters:

      asa_nonce (integer)
      session_nonce (structure)
      timeout (integer)

    • Return parameters:

      errorcode (integer)
    • Delay negotiation session by 'timeout' milliseconds, thereby extending the original timeout. This function simply triggers a GRASP Confirm Waiting message.

    • Asynchronous Mechanisms:

      • 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'.

  • 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.

    • Asynchronous Mechanisms:

      • 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'.

2.3.5. Synchronization and Flooding

  • 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, unless an authorization model is added to GRASP in future. Therefore the API checks that the ASA is registered, but the objective does not 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.

    • Asynchronous Mechanisms:

      • Threaded implementation: Call in a separate thread if asynchronous operation is required.
      • Event loop implementation: An additional read/write 'session_nonce' parameter is used.
    • 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.

  • 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, as mentioned under register_objective() in Section 2.3.2.
    • This call is non-blocking and may be repeated whenever the value changes.

  • 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.

  • flood()

    • Input parameters:

      asa_nonce (integer)
      ttl (integer)
      tagged_objective_list (structure)

    • Return parameters:

      errorcode (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()

    • Input parameters:

      asa_nonce (integer)
      objective (structure)

    • Return parameters:

      errorcode (integer)
      tagged_objective_list (structure) (if successful)
    • This call instructs GRASP to return the given synchronization objective if it has been flooded and its lifetime has not expired.
    • 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.
    • 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()

    • Input parameters:

      asa_nonce (integer)
      tagged_objective (structure)

    • Return parameters:

      errorcode (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.
    • The 'tagged_objective' parameter is the one to be expired.

2.3.6. Invalid Message Function

  • send_invalid()

    • Input parameters:

      asa_nonce (integer)
      session_nonce (structure)
      info (bytes)

    • Return parameters:

      errorcode (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. 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 issues for the GRASP protocol are discussed in [I-D.ietf-anima-grasp]. Authorization of ASAs is a subject for future study.

The 'asa_nonce' parameter is used in the API as a first line of defence against a malware process attempting to imitate a legitimately registered ASA. The 'session_nonce' parameter is used in the API as a first line of defence against a malware process attempting to hijack a GRASP session.

5. IANA Considerations

This document makes no request of the IANA.

6. Acknowledgements

Excellent suggestions were made by Ignas Bagdonas, Laurent Ciavaglia, Toerless Eckert, Guangpeng Li, Michael Richardson, and other participants in the ANIMA WG.

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, , <https://tools.ietf.org/html/draft-ietf-anima-grasp-15>.

7.2. Informative References

[I-D.ietf-anima-autonomic-control-plane]
Eckert, T., Behringer, M., and S. Bjarnason, "An Autonomic Control Plane (ACP)", Work in Progress, Internet-Draft, draft-ietf-anima-autonomic-control-plane-24, , <https://tools.ietf.org/html/draft-ietf-anima-autonomic-control-plane-24>.
[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-41, , <https://tools.ietf.org/html/draft-ietf-anima-bootstrapping-keyinfra-41>.
[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, , <https://tools.ietf.org/html/draft-ietf-anima-reference-model-10>.
[I-D.liu-anima-grasp-distribution]
Liu, B., Xiao, X., Hecker, A., Jiang, S., and Z. Despotovic, "Information Distribution in Autonomic Networking", Work in Progress, Internet-Draft, draft-liu-anima-grasp-distribution-13, , <https://tools.ietf.org/html/draft-liu-anima-grasp-distribution-13>.

Appendix A. Error Codes

This Appendix lists the error codes defined so far, 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.

ok               0 "OK"
declined         1 "Declined"
noReply          2 "No reply"
unspec           3 "Unspecified error"
ASAfull          4 "ASA registry full"
dupASA           5 "Duplicate ASA name"
noASA            6 "ASA not registered"
notYourASA       7 "ASA registered but not by you"
notBoth          8 "Objective cannot support both negotiation
                    and synchronization"
notDry           9 "Dry-run allowed only with negotiation"
notOverlap      10 "Overlap not supported by this implementation"
objFull         11 "Objective registry full"
objReg          12 "Objective already registered"
notYourObj      13 "Objective not registered by this ASA"
notObj          14 "Objective not found"
notNeg          15 "Objective not negotiable"
noSecurity      16 "No security"
noDiscReply     17 "No reply to discovery"
sockErrNegRq    18 "Socket error sending negotiation request"
noSession       19 "No session"
noSocket        20 "No socket"
loopExhausted   21 "Loop count exhausted"
sockErrNegStep  22 "Socket error sending negotiation step"
noPeer          23 "No negotiation peer"
CBORfail        24 "CBOR decode failure"
invalidNeg      25 "Invalid Negotiate message"
invalidEnd      26 "Invalid end message"
noNegReply      27 "No reply to negotiation step"
noValidStep     28 "No valid reply to negotiation step"
sockErrWait     29 "Socket error sending wait message"
sockErrEnd      30 "Socket error sending end message"
IDclash         31 "Incoming request Session ID clash"
notSynch        32 "Not a synchronization objective"
notFloodDisc    33 "Not flooded and no reply to discovery"
sockErrSynRq    34 "Socket error sending synch request"
noListener      35 "No synch listener"
noSynchReply    36 "No reply to synchronization request"
noValidSynch    37 "No valid reply to synchronization request"
invalidLoc      38 "Invalid locator"

Appendix B. Change log [RFC Editor: Please remove]

draft-ietf-anima-grasp-api-06, 2020-06-07:

draft-ietf-anima-grasp-api-05, 2020-05-08:

draft-ietf-anima-grasp-api-04, 2019-10-07:

draft-ietf-anima-grasp-api-03, 2019-01-21:

draft-ietf-anima-grasp-api-02, 2018-06-30:

draft-ietf-anima-grasp-api-01, 2018-03-03:

draft-ietf-anima-grasp-api-00, 2017-12-23:

draft-liu-anima-grasp-api-06, 2017-11-24:

draft-liu-anima-grasp-api-05, 2017-10-02:

draft-liu-anima-grasp-api-04, 2017-06-30:

draft-liu-anima-grasp-api-03, 2017-02-13:

draft-liu-anima-grasp-api-02, 2016-12-17:

draft-liu-anima-grasp-api-02, 2016-09-30:

draft-liu-anima-grasp-api-01, 2016-06-24:

draft-liu-anima-grasp-api-00, 2016-04-04:

Authors' Addresses

Brian Carpenter
School of Computer Science
University of Auckland
PB 92019
Auckland 1142
New Zealand
Bing Liu (editor)
Huawei Technologies
Q14, Huawei Campus
No.156 Beiqing Road
Hai-Dian District, Beijing
100095
P.R. China
Wendong Wang
BUPT University
Beijing University of Posts & Telecom.
No.10 Xitucheng Road
Hai-Dian District, Beijing 100876
P.R. China
Xiangyang Gong
BUPT University
Beijing University of Posts & Telecom.
No.10 Xitucheng Road
Hai-Dian District, Beijing 100876
P.R. China