NAME

       pmdaAttribute - informs a PMDA about client connection attributes

C SYNOPSIS

       #include <pcp/pmapi.h>
       #include <pcp/pmda.h>

       int pmdaAttribute(int context, int key, char *value, int length, pmdaExt *pmda);

       cc ... -lpcp_pmda -lpcp

DESCRIPTION

       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  in‐
       formation, 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  pmdaSe‐
       tEndContextCallBack(3) interface, as a result.  The pmdaGetContext(3) interface may be particularly help‐
       ful 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 at‐
       tributes can be found in the headers listed above, all are prefixed by PCP_ATTR.

CAVEAT

       The PMDA must be using PMDA_INTERFACE_6 or later, as specified in the  call  to  pmdaDSO(3)  or  pmdaDae‐
       mon(3).

DIAGNOSTICS

       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.

SEE ALSO

       PMAPI(3), PMDA(3), pmdaDaemon(3), pmdaDSO(3), pmdaMain(3) and pmdaGetContext(3).

Performance Co-Pilot                                   PCP                                      PMDAATTRIBUTE(3)