minix/lib/libc/rpc/rpc_clnt_create.3

.\" @(#)rpc_clnt_create.3n 1.36 93/08/31 SMI; from SVr4
.\" Copyright 1989 AT&T
.\" @(#)rpc_clnt_create 1.5 89/07/24 SMI;
.\" Copyright (c) 1988 Sun Microsystems, Inc. - All Rights Reserved.
.\"	$NetBSD: rpc_clnt_create.3,v 1.11 2009/05/23 18:57:25 christos Exp $
.Dd May 23, 2009
.Dt RPC_CLNT_CREATE 3
.Os
.Sh NAME
.Nm rpc_clnt_create ,
.Nm clnt_control ,
.Nm clnt_create ,
.Nm clnt_create_vers ,
.Nm clnt_destroy ,
.Nm clnt_dg_create ,
.Nm clnt_pcreateerror ,
.Nm clnt_raw_create ,
.Nm clnt_spcreateerror ,
.Nm clnt_tli_create ,
.Nm clnt_tp_create ,
.Nm clnt_vc_create ,
.Nm rpc_createerr
.Nd "library routines for dealing with creation and manipulation of CLIENT handles"
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In rpc/rpc.h
.Ft bool_t
.Fn clnt_control "CLIENT *clnt" "const u_int req" "char *info"
.Ft "CLIENT *"
.Fn clnt_create "const char * host" "const rpcprog_t prognum" "const rpcvers_t versnum" "const char *nettype"
.Ft "CLIENT *"
.Fn clnt_create_vers "const char * host" "const rpcprog_t prognum" "rpcvers_t *vers_outp" "const rpcvers_t vers_low" "const rpcvers_t vers_high" "char *nettype"
.Ft void
.Fn clnt_destroy "CLIENT * clnt"
.Ft "CLIENT *"
.Fn clnt_dg_create "const int fildes" "const struct netbuf *svcaddr" "const rpcprog_t prognum" "const rpcvers_t versnum" "const u_int sendsz" "const u_int recvsz"
.Ft void
.Fn clnt_pcreateerror "const char *s"
.Ft "char *"
.Fn clnt_spcreateerror "const char *s"
.Ft "CLIENT *"
.Fn clnt_raw_create "const rpcprog_t prognum" "const rpcvers_t versnum"
.Ft "CLIENT *"
.Fn clnt_tli_create "const int fildes" "const struct netconfig *netconf" "const struct netbuf *svcaddr" "const rpcprog_t prognum" "const rpcvers_t versnum" "const u_int sendsz" "const u_int recvsz"
.Ft "CLIENT *"
.Fn clnt_tp_create "const char * host" "const rpcprog_t prognum" "const rpcvers_t versnum" "const struct netconfig *netconf"
.Ft "CLIENT *"
.Fn clnt_vc_create "const int fildes" "const struct netbuf *svcaddr" "const rpcprog_t prognum" "const rpcvers_t versnum" "const u_int sendsz" "const u_int recvsz"
.Sh DESCRIPTION
RPC library routines allow C language programs to make procedure
calls on other machines across the network.
First a
.Dv CLIENT
handle is created and then the client calls a procedure to send a
request to the server.
On receipt of the request, the server calls a dispatch routine
to perform the requested service, and then sends a reply.
.Sh ROUTINES
.Bl -tag -width YYYYYYY
.It Fn clnt_control
A function macro to change or retrieve various information
about a client object.
.Fa req
indicates the type of operation, and
.Fa info
is a pointer to the information.
For both connectionless and connection-oriented transports,
the supported values of
.Fa req
and their argument types and what they do are:
.Bl -column "CLSET_FD_NCLOSE" "struct timeval *" "set total timeout"
.It Dv CLSET_TIMEOUT Ta "struct timeval *" Ta "set total timeout"
.It Dv CLGET_TIMEOUT Ta "struct timeval *" Ta "get total timeout"
.El
.Pp
Note:
if you set the timeout using
.Fn clnt_control ,
the timeout argument passed by
.Fn clnt_call
is ignored in all subsequent calls.
.Pp
Note:
If you set the timeout value to 0
.Fn clnt_control
immediately returns an error (
.Dv RPC_TIMEDOUT ) .
Set the timeout parameter to 0 for batching calls.
.Bl -column CLSET_FD_NCLOSE "struct timeval *" "do not close fd on destroy"
.It Dv CLGET_SVC_ADDR Ta "struct netbuf *" Ta "get servers address"
.It Dv CLGET_FD Ta "int *" Ta "get fd from handle"
.It Dv CLSET_FD_CLOSE Ta "void" Ta "close fd on destroy"
.It Dv CLSET_FD_NCLOSE Ta void Ta "don't close fd on destroy"
.It Dv CLGET_VERS Ta "unsigned long *" Ta "get RPC program version"
.It Dv CLSET_VERS Ta "unsigned long *" Ta "set RPC program version"
.It Dv CLGET_XID Ta "unsigned long *" Ta "get XID of previous call"
.It Dv CLSET_XID Ta "unsigned long *" Ta "set XID of next call"
.El
.Pp
The following operations are valid for connectionless transports only:
.Bl -column CLSET_RETRY_TIMEOUT "struct timeval *" "set total timeout"
.It Dv CLSET_RETRY_TIMEOUT Ta "struct timeval *" Ta "set the retry timeout"
.It Dv CLGET_RETRY_TIMEOUT Ta "struct timeval *" Ta "get the retry timeout"
.El
.Pp
The retry timeout is the time that RPC
waits for the server to reply before retransmitting the request.
.Fn clnt_control
returns
.Dv TRUE
on success and
.Dv FALSE
on failure.
.Pp
.It Fn clnt_create
Generic client creation routine for program
.Fa prognum
and version
.Fa versnum .
.Fa host
identifies the name of the remote host where the server
is located.
.Fa nettype
indicates the class of transport protocol to use.
The transports are tried in left to right order in
.Ev NETPATH
environment variable or in top to bottom order in
the netconfig database.
.Fn clnt_create
tries all the transports of the
.Fa nettype
class available from the
.Ev NETPATH
environment variable and the netconfig database,
and chooses the first successful one.
A default timeout is set and can be modified using
.Fn clnt_control .
This routine returns
.Dv NULL
if it fails.
The
.Fn clnt_pcreateerror
routine can be used to print the reason for failure.
.Pp
Note:
.Fn clnt_create
returns a valid client handle even
if the particular version number supplied to
.Fn clnt_create
is not registered with the
.Xr rpcbind 8
service.
This mismatch will be discovered by a
.Fn clnt_call
later (see
.Xr rpc_clnt_calls 3 ) .
.Pp
.It Fn clnt_create_vers
Generic client creation routine which is similar to
.Fn clnt_create
but which also checks for the
version availability.
.Fa host
identifies the name of the remote host where the server
is located.
.Fa nettype
indicates the class transport protocols to be used.
If the routine is successful it returns a client handle created for
the highest version between
.Fa vers_low
and
.Fa vers_high
that is supported by the server.
.Fa vers_outp
is set to this value.
That is, after a successful return
.Fa vers_low
\*[Le]
.Fa *vers_outp
\*[Le]
.Fa vers_high .
If no version between
.Fa vers_low
and
.Fa vers_high
is supported by the server then the routine fails and returns
.Dv NULL .
A default timeout is set and can be modified using
.Fn clnt_control .
This routine returns
.Dv NULL
if it fails.
The
.Fn clnt_pcreateerror
routine can be used to print the reason for failure.
Note:
.Fn clnt_create
returns a valid client handle even
if the particular version number supplied to
.Fn clnt_create
is not registered with the
.Xr rpcbind 8
service.
This mismatch will be discovered by a
.Fn clnt_call
later (see
.Xr rpc_clnt_calls 3 ) .
However,
.Fn clnt_create_vers
does this for you and returns a valid handle
only if a version within
the range supplied is supported by the server.
.Pp
.It Fn clnt_destroy
A function macro that destroys the client's RPC handle.
Destruction usually involves deallocation
of private data structures, including
.Fa clnt
itself.
Use of
.Fa clnt
is undefined after calling
.Fn clnt_destroy .
If the RPC library opened the associated file descriptor, or
.Dv CLSET_FD_CLOSE
was set using
.Fn clnt_control ,
the file descriptor will be closed.
The caller should call
.Fn auth_destroy "clnt-\*[Gt]cl_auth"
(before calling
.Fn clnt_destroy )
to destroy the associated
.Dv AUTH
structure (see
.Xr rpc_clnt_auth 3 ) .
.Pp
.It Fn clnt_dg_create
This routine creates an RPC client for the remote program
.Fa prognum
and version
.Fa versnum ;
the client uses a connectionless transport.
The remote program is located at address
.Fa svcaddr .
The parameter
.Fa fildes
is an open and bound file descriptor.
This routine will resend the call message in intervals of
15 seconds until a response is received or until the
call times out.
The total time for the call to time out is specified by
.Fn clnt_call
(see
.Fn clnt_call
in
.Xr rpc_clnt_calls 3 ) .
The retry time out and the total time out periods can
be changed using
.Fn clnt_control .
The user may set the size of the send and receive
buffers with the parameters
.Fa sendsz
and
.Fa recvsz ;
values of 0 choose suitable defaults.
This routine returns
.Dv NULL
if it fails.
.Pp
.It Fn clnt_pcreateerror
Print a message to standard error indicating
why a client RPC handle could not be created.
The message is prepended with the string
.Fa s
and a colon, and appended with a newline.
.Pp
.It Fn clnt_spcreateerror
Like
.Fn clnt_pcreateerror ,
except that it returns a string
instead of printing to the standard error.
A newline is not appended to the message in this case.
Warning:
returns a pointer to a buffer that is overwritten
on each call.
.Pp
.It Fn clnt_raw_create
This routine creates an RPC
client handle for the remote program
.Fa prognum
and version
.Fa versnum .
The transport used to pass messages to the service is
a buffer within the process's address space,
so the corresponding RPC
server should live in the same address space;
(see
.Fn svc_raw_create
in
.Xr rpc_svc_create 3 ) .
This allows simulation of RPC and measurement of
RPC overheads, such as round trip times,
without any kernel or networking interference.
This routine returns
.Dv NULL
if it fails.
.Fn clnt_raw_create
should be called after
.Fn svc_raw_create .
.Pp
.It Fn clnt_tli_create
This routine creates an RPC
client handle for the remote program
.Fa prognum
and version
.Fa versnum .
The remote program is located at address
.Fa svcaddr .
If
.Fa svcaddr
is
.Dv NULL
and it is connection-oriented, it is assumed that the file descriptor
is connected.
For connectionless transports, if
.Fa svcaddr
is
.Dv NULL ,
.Dv RPC_UNKNOWNADDR
error is set.
.Fa fildes
is a file descriptor which may be open, bound and connected.
If it is
.Dv RPC_ANYFD ,
it opens a file descriptor on the transport specified by
.Fa netconf .
If
.Fa fildes
is
.Dv RPC_ANYFD
and
.Fa netconf
is
.Dv NULL ,
a
.Dv RPC_UNKNOWNPROTO
error is set.
If
.Fa fildes
is unbound, then it will attempt to bind the descriptor.
The user may specify the size of the buffers with the parameters
.Fa sendsz
and
.Fa recvsz ;
values of 0 choose suitable defaults.
Depending upon the type of the transport (connection-oriented
or connectionless),
.Fn clnt_tli_create
calls appropriate client creation routines.
This routine returns
.Dv NULL
if it fails.
The
.Fn clnt_pcreateerror
routine can be used to print the reason for failure.
The remote rpcbind
service (see
.Xr rpcbind 8 )
is not consulted for the address of the remote
service.
.Pp
.It Fn clnt_tp_create
Like
.Fn clnt_create
except
.Fn clnt_tp_create
tries only one transport specified through
.Fa netconf .
.Fn clnt_tp_create
creates a client handle for the program
.Fa prognum ,
the version
.Fa versnum ,
and for the transport specified by
.Fa netconf .
Default options are set,
which can be changed using
.Fn clnt_control
calls.
The remote rpcbind service on the host
.Fa host
is consulted for the address of the remote service.
This routine returns
.Dv NULL
if it fails.
The
.Fn clnt_pcreateerror
routine can be used to print the reason for failure.
.Pp
.It Fn clnt_vc_create
This routine creates an RPC
client for the remote program
.Fa prognum
and version
.Fa versnum ;
the client uses a connection-oriented transport.
The remote program is located at address
.Fa svcaddr .
The parameter
.Fa fildes
is an open and bound file descriptor.
The user may specify the size of the send and receive buffers
with the parameters
.Fa sendsz
and
.Fa recvsz ;
values of 0 choose suitable defaults.
This routine returns
.Dv NULL
if it fails.
The address
.Fa svcaddr
should not be
.Dv NULL
and should point to the actual address of the remote program.
.Fn clnt_vc_create
does not consult the remote rpcbind service for this information.
.Pp
.It struct rpc_createerr rpc_createerr;
A global variable whose value is set by any RPC
client handle creation routine
that fails.
It is used by the routine
.Fn clnt_pcreateerror
to print the reason for the failure.
.El
.Sh SEE ALSO
.Xr rpc 3 ,
.Xr rpc_clnt_auth 3 ,
.Xr rpc_clnt_calls 3 ,
.Xr rpcbind 8