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INTERNET-DRAFT Kurt D. Zeilenga
Intended Category: Standards Track OpenLDAP Foundation
Extends: draft-ietf-ldapext-ldap-c-api-03.txt
Expires: 28 March 2000
28 September 1999
LDAP C API Concurrency Extensions
<draft-zeilenga-ldap-c-api-concurrency-00.txt>
1. Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
This draft document will be submitted to the RFC Editor as a Standards
Track document. Distribution of this memo is unlimited. Technical
discussion of this document will take place on the IETF LDAP Extension
Working Group mailing list <ietf-ldapext@netscape.com>. Please send
editorial comments directly to the author <Kurt@OpenLDAP.org>.
Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Copyright 1999, The Internet Society. All Rights Reserved.
Please see the Copyright section near the end of this document for
more information.
2. Abstract
This document defines extensions to the LDAP C API to support use in
concurrent execution environments. The document describes and defines
Zeilenga [Page 1]
INTERNET-DRAFT LDAP C API Concurrency Extensions 28 September 1999
requirements for multiple concurrency levels: thread safe, session
thread safe, and operation thread safe.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", and "MAY" in this document are
to be interpreted as described in RFC 2119 [KEYW].
3. Introduction
This document extends the LDAP C API [CAPI] specification to support
use in concurrent execution environments. The extensions add powerful
concurrent processing capabilities to the simple to use CAPI. This
document provides an overview of different levels of concurrent
execution support and offers a number of CAPI "features" to provide
capabilities at these levels.
The remainder of this section describes three levels of concurrent
execution: thread safe, session thread safe, operation thread safe
APIs.
3.1. Thread Safe
An implementation which allows applications to safely execute in
concurrent execution environments where the application provides
necessary synchronization to ensure serialization of CAPI usage is
considered to be "thread safe." Applications may execute non-CAPI
calls in concurrent execution contexts when using thread safe
implementations.
3.2. Session Thread Safe
A "thread safe" implementation which allows CAPI calls associated with
different LDAP sessions to proceed asychronously is considered to be
"session thread safe."
3.3. Operation Thread Safe
A "session thread safe" implementation which allows CAPI calls
associated with different LDAP operations to proceed asychronously is
considered to be "operation thread safe".
4. Basic Thread Safe Feature
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This section details requirements for the thread safe CAPI feature.
Implementations fulfilling these requirements are said to support the
LDAP_API_FEATURE_THREAD_SAFE feature and SHOULD advertise this support
as detailed below. This feature SHOULD be provided by
implementations.
Implementations of this feature MUST implement the LDAP error handling
extension [ERRNO].
Implementations of this feature MUST allow non-CAPI calls to proceed
asynchronously.
Implementations of this feature MUST NOT use any non-thread safe call
or mechanism provided by C environment or operating system. An
example of non-reentrant calls is the UNIX strtok() function. Example
of a non-reentrant mechanism is global (i.e.: non-thread specific)
errno.
5. Session Thread Safe Feature
This section details requirements for the session thread safe CAPI
feature. Implementations fulfilling these requirements are said to
support the LDAP_API_FEATURE_SESSION_THREAD_SAFE feature and SHOULD
advertise this support as detailed below. This feature is
RECOMMENDED.
5.1. Prerequisite Features
Implementations providing this feature MUST provide and advertise both
LDAP_API_FEATURE_CONTEXT_SPECIFIC_ERRNO [ERRNO] and
LDAP_API_FEATURE_THREAD_SAFE.
5.2. Atomic Session Handles
Implementations providing this feature SHOULD ensure that operations
upon a given session handle are atomic. Implementations which provide
atomic session handles SHOULD advertise the feature
LDAP_API_FEATURE_ATOMIC_SESSION_HANDLES.
5.3. Concurrency Requirements
Implementations providing this feature MUST not restrict CAPI calls
acting upon a given LDAP session to a particular execution context.
Applications MAY use a session handle on any thread. Applications
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MUST NOT assume that operations upon a session are atomic.
Implementations providing this feature MUST allow CAPI calls acting
upon different LDAP sessions to safely proceed asynchronously.
Implementations providing this feature MUST allow CAPI calls not
acting upon an LDAP session to safely proceed asynchronously.
6. Operation Thread Safe Feature
This section details requirements for the operation thread safe CAPI
feature based upon a duplicate session handles mechanism.
Implementations fulfilling these requirements are said to support the
LDAP_API_FEATURE_DUPLICATE_SESSION_HANDLES feature and SHOULD
advertise this support as detailed below. This feature is OPTIONAL.
6.1. Prerequisite Features
Implementations of this feature MUST provide and advertise
LDAP_API_FEATURE_CONTEXT_SPECIFIC_ERRNO [ERRNO],
LDAP_API_FEATURE_THREAD_SAFE, LDAP_API_FEATURE_SESSION_THREAD_SAFE,
and LDAP_API_FEATURE_ATOMIC_SESSION_HANDLES.
6.2. Duplicated Session Handles
Implementations of this feature MUST support duplicated session
handles.
As defined in CAPI, a session handle refers to an LDAP session
encompassing connections with one or more servers, associated message
results, a set of properties (options), and state information. This
feature provides a mechanism for a handle to be duplicated. A session
handle and its duplicates are considered siblings. Each sibling
session handle refers to the same LDAP session and message results.
Some properties and state are specific to a handle and others shared
between siblings as detailed below.
CAPI calls made on a handle are atomic. Calls made on sibling (or
other) handles MAY proceed asynchronously.
Session handles are duplicated using ldap_dup() and destroyed using
ldap_destroy(). Use of duplicated session handles with CAPI calls
have the following semantics detailed in the sections below.
Zeilenga [Page 4]
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6.2.1. Creating and Destroying duplicated sessions
Implementations of this feature are required to provide two new
routines: LDAP *ldap_dup( ld ); int ldap_destroy( ld );
Parameters are: ld The session handle
The ldap_dup() function returns a duplicate of a session handle. The
returned session handle may be used concurrently with the original
session handle as described below. ldap_dup returns NULL if it is not
able to duplicate the session handle and sets LDAP_OPT_ERROR_NUMBER
and ldap_errno indicating the nature of the failure.
The ldap_destroy() function destroys the session handle. If the
session handle has no siblings, ldap_destroy behaves exactly like
ldap_unbind. If the session handle has siblings, the resources
assocated with the handle are released and the siblings remain valid.
ldap_destroy() returns LDAP_SUCCESS or an error number indicating the
nature of failure. Regardless of returned value, the handle SHOULD be
considered invalid and MUST not be used in subsequent calls. Attempts
to use a destroyed session handle MUST NOT result in
LDAP_INVALID_SESSION error being reported. Implementations SHOULD
report LDAP_PARAM_ERROR in such cases.
6.2.2. ldap_unbind and siblings
When ldap_unbind() is called on a session handle with siblings, the
siblings become invalid. The siblings must be destroyed using
ldap_destroy(). All attempts to obtain the siblings'
LDAP_OPT_ERROR_NUMBER will return LDAP_INVALID_SESSION. Any use other
than ldap_destroy() or reading LDAP_OPT_ERROR_NUMBER will fail with an
LDAP_INVALID_SESSION error being reported.
6.2.3. ldap_result()
Message queues are shared between siblings. Results of operations on
a duplicated session handles are accessible to all sibling session
handles.
Applications desiring results associated with a specific operation
SHOULD provide the appropriate msgid to ldap_result(). Applications
SHOULD avoid calling ldap_result() with LDAP_RES_ANY as such may
"steal" and return results which an operation on a sibling requires to
complete.
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6.2.4. Session Options
The following CAPI options access values shared between siblings:
LDAP_OPT_API_INFO LDAP_OPT_DESC LDAP_OPT_REFERRALS
LDAP_OPT_PROTOCOL_VERSION LDAP_OPT_API_FEATURE_INFO
LDAP_OPT_HOST_NAME
The following CAPI options access values specific to a sibling:
LDAP_OPT_DEREF LDAP_OPT_SIZELIMIT LDAP_OPT_TIMELIMIT
LDAP_OPT_RESTART LDAP_OPT_CLIENT_CONTROLS
LDAP_OPT_SERVER_CONTROLS LDAP_OPT_ERROR_NUMBER
LDAP_OPT_ERROR_STRING LDAP_OPT_MATCHED_DN
6.2.4.1. LDAP_OPT_SESSION_REFCNT
In addition, implementations MUST provide the READ-ONLY, shared
LDAP_OPT_SESSION_REFCNT option. LDAP_OPT_SESSION_REFCNT returns the
reference count associated with the supplied session handle argument.
The session handle argument is required. The outvalue argument should
be a pointer to an integer. Example use:
int refcount(LDAP *ld) {
#ifdef LDAP_OPT_SESSION_REFCNT
if(ld != NULL) {
int refcnt, rc;
rc = ldap_get_option(ld,
LDAP_OPT_SESSION_REFCNT, &refcnt);
if(rc == LDAP_OPT_SUCCESS) {
return refcnt;
}
}
#endif
return -1;
}
7. Advertising Features
This document REQUIRES that supported features with the name in the
form LDAP_API_FEATURE_x be advertised to consumers of the CAPI as
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follows:
SHOULD provide the macro LDAP_API_FEATURE_x with the value
of 1000 + revision number of this draft (i.e.: 1000+0 for
this 0 revision of the draft).
MUST provide the CAPI extension "x" when returning API
information upon LDAP_OPT_API_INFO option access, and
MUST provide feature info for "x" via LDAP_OPT_FEATURE_INFO
option mechanism. The feature version provided MUST match
the value LDAP_API_FEATURE_x macro
where x is replaced appropriately.
As implementations may not provide macros for all features,
applications SHOULD use LDAP_OPT_API_INFO to determine which features
are provided by a given implementation.
8. Changes to the C API specification
8.1. New Symbols
This extension introduces the following macros:
LDAP_API_FEATURE_ATOMIC_SESSION_HANDLES
LDAP_API_FEATURE_DUPLICATE_SESSION_HANDLES
LDAP_API_FEATURE_SESSION_THREAD_SAFE
LDAP_API_FEATURE_THREAD_SAFE
LDAP_API_FEATURE_OPERATION_THREAD_SAFE LDAP_INVALID_SESSION
LDAP_OPT_SESSION_REFCNT
This extension introduces these new functions:
ldap_destroy() ldap_dup()
This extension introduces no new typedefs nor structure names.
8.2. Duplicated Session Handles
This extension introduces duplicated session handles and requirements
for handling duplicated session handles. Semantics of non-duplicated
session handles are not affected by this introduction. However, the
semantics of calls upon duplicate session handles differs as described
in the extension.
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9. Security Considerations
None taken, none given.
10. Copyright
Copyright 1999, The Internet Society. All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be followed,
or as required to translate it into languages other than English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE AUTHORS, THE INTERNET SOCIETY, AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
11. Bibliography
[CAPI] M. Smith, T. Howes, A. Herron, M. Wahl, A. Anantha, "The
C LDAP Application Program Interface", INTERNET-DRAFT, <draft-
ietf-ldapext-ldap-c-api-03.txt> + LDAPext discussions, June 1999.
[ERRNO] K. Zeilenga, "LDAP C API Error Reporting Extension",
INTERNET-DRAFT, <draft-zeilenga-ldap-c-api-errno-00.txt>,
June 1999.
[KEYW] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
Zeilenga [Page 8]
INTERNET-DRAFT LDAP C API Concurrency Extensions 28 September 1999
[LDAP] M. Wahl, T. Howes, S. Kille, "Lightweight Directory
Access Protocol (v3)", RFC 2251, December 1997.
13. Author's Address
Kurt D. Zeilenga
OpenLDAP Foundation
<Kurt@OpenLDAP.org>
This document expires on 28 March 2000.
Zeilenga [Page 9]
---------------------------------------------------------------------
INTERNET-DRAFT Kurt D. Zeilenga
Intended Category: Standards Track OpenLDAP Foundation
Extends: draft-ietf-ldapext-ldap-c-api-03.txt
Expires: 28 March 2000
28 September 1999
LDAP C API Error Reporting Extension
<draft-zeilenga-ldap-c-api-errno-00.txt>
1. Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
This draft document will be submitted to the RFC Editor as a Standards
Track document. Distribution of this memo is unlimited. Technical
discussion of this document will take place on the IETF LDAP Extension
Working Group mailing list <ietf-ldapext@netscape.com>. Please send
editorial comments directly to the author <Kurt@OpenLDAP.org>.
Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
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.''
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Copyright 1999, The Internet Society. All Rights Reserved.
Please see the Copyright section near the end of this document for
more information.
2. Abstract
This document defines a manatory extension to the LDAP C API to
provide error reporting for all API calls. The mechanism is
nonintrusive and can, optionally, support concurrent execution
environments.
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INTERNET-DRAFT LDAP C API Error Reporting Extension 28 September 1999
The key words ``MUST'', ``MUST NOT'', ``REQUIRED'', ``SHALL'', ``SHALL
NOT'', ``SHOULD'', ``SHOULD NOT'', ``RECOMMENDED'', and ``MAY'' in
this document are to be interpreted as described in RFC 2119 [KEYW].
3. Background and Intent of Use
The LDAP [LDAP] C API [CAPI] provides an interface which (due to
legacy compatibiity issues) does not provide a consistent mechanism
for reporting errors. A large number of the calls within the
specification have no mechanism to indicate the nature of a failure.
The usefulness of a CAPI without a consistent, easy to use, error
reporting mechanism is limited.
This document defines an mandatory extension to the CAPI. All
implementations of the CAPI MUST provide this extension.
The extension details additional requirements for error reporting.
Implementations MUST fulfill all other CAPI error reporting
requirements.
4. Error Handling Extension
This extension provides a mechanism that applications MAY use to
obtain an LDAP error number indicating the nature of the failure
associated with the last failed CAPI call.
Implementations MUST provide access to an LDAP error number (CAPI,
Section 9) resulting from the last failed CAPI call via the symbol
ldap_errno. The last failed CAPI call may be within the global
context or within the current execution context.
The ldap_errno MUST evaluate to a modifiable lvalue that has type
'int', the value of which is set to a LDAP error number. It is
unspecified whether ldap_errno is a macro or an identifier declared
with external linkage. If a macro definition is suppressed in order
to access an actual object, or a program defines an identifier with
the name ldap_errno, the behavior is undefined.
Applications MUST access ldap_errno within the same concurrent
execution context, commonly a thread, in which the failure occurred.
The value of ldap_errno is LDAP_SUCCESS (0) if no API failure has
occurred within the supported context and the user has not assigned a
value within the supported context.
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INTERNET-DRAFT LDAP C API Error Reporting Extension 28 September 1999
Implementations SHALL NOT update the ldap_errno value upon successful
CAPI call completion.
Implementations providing a current execution context specific
ldap_errno MUST advertise the feature LDAP_API_CONTEXT_SPECIFIC_ERRNO
as described in Section 6. Implementation of
LDAP_API_CONTEXT_SPECIFIC_ERRNO is RECOMMENDED.
4.1. Reporting Server Errors
It is not a CAPI failure for a server to return an error number.
Implementations SHALL NOT assign error results returned by servers to
ldap_errno.
4.2. Implementation Specific Reporting
The CAPI specification stated that the caller may obtain an indication
of failure of certain calls (see listed below) using implementation
specific and/or operating system specific requirements.
Implementations are NOT REQUIRED to support any implementation
specific and/or operating system mechanism for ANY call detailed by
the CAPI specification or its extensions.
Affected calls include ldap_init(), ldap_open(), and ber_*().
4.3. Example
The following is an example showing how an application may obtain the
error information resulting from a failed CAPI calls:
int msgid;
LDAP *ld = ldap_init("localhost", 389);
if(ld == NULL) {
printf("ldap_init failed, ldap_errno=%d (%s)\n",
ldap_errno, ldap_err2string(ldap_errno));
printf("unable to initialize LDAP session\n");
return -1;
}
msgid = ldap_simple_bind(ld, NULL, NULL);
if(msgid == -1) {
int err = ldap_errno;
if (err != LDAP_SUCCESS ) {
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INTERNET-DRAFT LDAP C API Error Reporting Extension 28 September 1999
/* API failure */
printf("ldap_simple_bind failure: ldap_errno=%d (%s)\n",
err, ldap_err2string(err));
} else {
int lderr, rc;
printf("ldap_simple_bind failed\n");
rc = ldap_get_option(ld,
LDAP_OPT_ERROR_NUMBER, &lderr);
if(rc == LDAP_OPT_SUCCESS) {
printf(" reason=%d (%s)\n",
lderr, ldap_err2string(lderr));
} else {
printf("ldap_get_option failed, ldap_errno=%d (%s)\n",
ldap_errno, ldap_err2string(ldap_errno)); }
}
goto unbind;
}
/* ... */
unbind: if(ldap_unbind(ld) != 0) {
printf("ldap_unbind failed, ldap_errno=%d (%s)\n",
ldap_errno, ldap_error2str(ldap_errno));
return -1;
}
return 0;
5. Advertising Features
This document REQUIRES that supported features with the name in the
form LDAP_API_FEATURE_x be advertised to consumers of the CAPI as
follows:
SHOULD provide the macro LDAP_API_FEATURE_x with the value
of 1000 + revision number of this draft (i.e.: 1000+0 for
this 0 revision of the draft).
MUST provide the CAPI extension "x" when returning API
information upon LDAP_OPT_API_INFO option access, and
Zeilenga [Page 4]
INTERNET-DRAFT LDAP C API Error Reporting Extension 28 September 1999
MUST provide feature info for "x" via LDAP_OPT_FEATURE_INFO
option mechanism. The feature version provided MUST match
the value LDAP_API_FEATURE_x macro
where x is replaced appropriately.
As implementations may not provide macros for all features,
applications SHOULD use LDAP_OPT_API_INFO to determine which features
are provided by a given implementation.
6. Changes to the LDAP C API
This section provides a summary of changes to the CAPI specification.
6.1. LDAP_API_VERSION
LDAP_API_VERSION should be set to the RFC number of this extension if
and when it is published as a Standards Track RFC. (see purpose of
this draft above).
Until such time as this document is published as an RFC,
implementations should use the value specified by CAPI plus 100 + 10 *
the number of this draft.
For the third draft of CAPI and this 0 revision of draft, the value of
2103 ((2000+3) + (100+10*0)) should be used.
6.2. New Symbols
This extension introduces two new symbols:
LDAP_API_FEATURE_CONTEXT_SPECIFIC_ERRNO ldap_errno
LDAP_API_FEATURE_CONTEXT_SPECIFIC_ERRNO is a macro. ldap_errno MAY be
a MACRO.
This extension indroductes no new functions, typedefs, or structure
names.
6.3. Implementation/System Specific Error Handling
This extensions removes any requirements that implementations to use
implementation and/or operating system specific error reporting
mechanisms.
Zeilenga [Page 5]
INTERNET-DRAFT LDAP C API Error Reporting Extension 28 September 1999
7. Security Considerations
None taken, none given.
8. Copyright
Copyright 1999, The Internet Society. All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be followed,
or as required to translate it into languages other than English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE AUTHORS, THE INTERNET SOCIETY, AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
9. Bibliography
[CAPI] M. Smith, T. Howes, A. Herron, M. Wahl, A. Anantha,
"The C LDAP Application Program Interface", INTERNET-DRAFT,
<draft-ietf-ldapext-ldap-c-api-03.txt> + LDAPext discussions,
June 1999.
[KEYW] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[LDAP] M. Wahl, T. Howes, S. Kille, "Lightweight Directory
Access Protocol (v3)", RFC 2251, December 1997.
Zeilenga [Page 6]
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10. Author's Address
Kurt D. Zeilenga
OpenLDAP Foundation
<Kurt@OpenLDAP.org>
This document expires on 28 March 2000.
Zeilenga [Page 7]
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