As part of the Performance Metrics Domain Agent (PMDA) API (see
PMDA(3)), pmdaAttribute is the generic callback for responding to
client connection attributes. These attributes include client
credential information, such as user ID and group ID.
A PMDA that supports connection attributes will provide a private
pmdaAttribute callback by assignment to version.six.attribute of the
pmdaInterface structure, and implement custom logic for any of the
attribute key-value pairs of interest to it.
All attributes are associated with a specific client context, and
these can be uniquely identified using the ctx first argument. The
PMDA should track client connections, and disconnections using the
pmdaSetEndContextCallBack(3) interface, as a result. The
pmdaGetContext(3) interface may be particularly helpful also.
All attributes are passed as key-value pairs and the value is always
passed as a null-terminated string of given length. This includes
numeric attributes like the user ID.
The most commonly used attributes would be PCP_ATTR_USERID and
PCP_ATTR_GROUPID but others may also be optionally passed (such as
PCP_ATTR_USERNAME) if they are available. Some attributes will be
consumed by pmcd and never through passed to PMDAs, such as
PCP_ATTR_PASSWORD. A complete list of all possible attributes can be
found in the headers listed above, all are prefixed by PCP_ATTR.
pmdaAttribute should return either zero on success, or a negative
return code to indicate an error in handling the attribute. This
return code cannot be used to indicate a client should be disallowed
access - such functionality must be performed by the agent in
response to callbacks for the client in question (using
PM_ERR_PERMISSION for those specific callbacks, for that specific
client. In other words, errors will be be passed to PMCD but there
is no guarantee made that the error will be return to the client and
result in termination of the client, for example.
This page is part of the PCP (Performance Co-Pilot) project.
Information about the project can be found at ⟨http://www.pcp.io/⟩.
If you have a bug report for this manual page, send it to
email@example.com. This page was obtained from the project's upstream
Git repository ⟨git://git.pcp.io/pcp⟩ on 2017-03-13. If you discover
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you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
Performance Co-Pilot PCP PMDAATTRIBUTE(3)