pmdaattribute(3)

NAME

   pmdaAttribute - informs a PMDA about client connection attributes

C SYNOPSIS

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

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.

CAVEAT

   The  PMDA  must  be using PMDA_PROTOCOL_6 or later, as specified in the
   call to pmdaDSO(3) or pmdaDaemon(3).

SEE ALSO

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

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