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NAME | SYNOPSIS AND DESCRIPTION | ATTRIBUTES | SEE ALSO | COLOPHON |
RPC(3) Linux Programmer's Manual RPC(3)
rpc - library routines for remote procedure calls
These routines allow C programs to make procedure calls on other
machines across the network. First, the client calls a procedure to
send a data packet to the server. Upon receipt of the packet, the
server calls a dispatch routine to perform the requested service, and
then sends back a reply. Finally, the procedure call returns to the
client.
To take use of these routines, include the header file <rpc/rpc.h>.
The prototypes below make use of the following types:
typedef int bool_t;
typedef bool_t (*xdrproc_t) (XDR *, void *, ...);
typedef bool_t (*resultproc_t) (caddr_t resp,
struct sockaddr_in *raddr);
See the header files for the declarations of the AUTH, CLIENT,
SVCXPRT, and XDR types.
void auth_destroy(AUTH *auth);
A macro that destroys the authentication information
associated with auth. Destruction usually involves
deallocation of private data structures. The use of auth is
undefined after calling auth_destroy().
AUTH *authnone_create(void);
Create and return an RPC authentication handle that passes
nonusable authentication information with each remote
procedure call. This is the default authentication used by
RPC.
AUTH *authunix_create(char *host, int uid, int gid,
int len, int *aup_gids);
Create and return an RPC authentication handle that contains
authentication information. The parameter host is the name of
the machine on which the information was created; uid is the
user's user ID; gid is the user's current group ID; len and
aup_gids refer to a counted array of groups to which the user
belongs. It is easy to impersonate a user.
AUTH *authunix_create_default(void);
Calls authunix_create() with the appropriate parameters.
int callrpc(char *host, unsigned long prognum,
unsigned long versnum, unsigned long procnum,
xdrproc_t inproc, char *in,
xdrproc_t outproc, char *out);
Call the remote procedure associated with prognum, versnum,
and procnum on the machine, host. The parameter in is the
address of the procedure's argument(s), and out is the address
of where to place the result(s); inproc is used to encode the
procedure's parameters, and outproc is used to decode the
procedure's results. This routine returns zero if it
succeeds, or the value of enum clnt_stat cast to an integer if
it fails. The routine clnt_perrno() is handy for translating
failure statuses into messages.
Warning: calling remote procedures with this routine uses
UDP/IP as a transport; see clntudp_create() for restrictions.
You do not have control of timeouts or authentication using
this routine.
enum clnt_stat clnt_broadcast(unsigned long prognum,
unsigned long versnum, unsigned long procnum,
xdrproc_t inproc, char *in,
xdrproc_t outproc, char *out,
resultproc_t eachresult);
Like callrpc(), except the call message is broadcast to all
locally connected broadcast nets. Each time it receives a
response, this routine calls eachresult(), whose form is:
eachresult(char *out, struct sockaddr_in *addr);
where out is the same as out passed to clnt_broadcast(),
except that the remote procedure's output is decoded there;
addr points to the address of the machine that sent the
results. If eachresult() returns zero, clnt_broadcast() waits
for more replies; otherwise it returns with appropriate
status.
Warning: broadcast sockets are limited in size to the maximum
transfer unit of the data link. For ethernet, this value is
1500 bytes.
enum clnt_stat clnt_call(CLIENT *clnt, unsigned long procnum,
xdrproc_t inproc, char *in,
xdrproc_t outproc, char *out,
struct timeval tout);
A macro that calls the remote procedure procnum associated
with the client handle, clnt, which is obtained with an RPC
client creation routine such as clnt_create(). The parameter
in is the address of the procedure's argument(s), and out is
the address of where to place the result(s); inproc is used to
encode the procedure's parameters, and outproc is used to
decode the procedure's results; tout is the time allowed for
results to come back.
clnt_destroy(CLIENT *clnt);
A macro that destroys the client's RPC handle. Destruction
usually involves deallocation of private data structures,
including clnt itself. Use of clnt is undefined after calling
clnt_destroy(). If the RPC library opened the associated
socket, it will close it also. Otherwise, the socket remains
open.
CLIENT *clnt_create(char *host, unsigned long prog,
unsigned long vers, char *proto);
Generic client creation routine. host identifies the name of
the remote host where the server is located. proto indicates
which kind of transport protocol to use. The currently
supported values for this field are “udp” and “tcp”. Default
timeouts are set, but can be modified using clnt_control().
Warning: using UDP has its shortcomings. Since UDP-based RPC
messages can hold only up to 8 Kbytes of encoded data, this
transport cannot be used for procedures that take large
arguments or return huge results.
bool_t clnt_control(CLIENT *cl, int req, char *info);
A macro used to change or retrieve various information about a
client object. req indicates the type of operation, and info
is a pointer to the information. For both UDP and TCP, the
supported values of req and their argument types and what they
do are:
CLSET_TIMEOUT struct timeval // set total timeout
CLGET_TIMEOUT struct timeval // get total timeout
Note: if you set the timeout using clnt_control(), the timeout
parameter passed to clnt_call() will be ignored in all future
calls.
CLGET_SERVER_ADDR struct sockaddr_in // get server's address
The following operations are valid for UDP only:
CLSET_RETRY_TIMEOUT struct timeval // set the retry timeout
CLGET_RETRY_TIMEOUT struct timeval // get the retry timeout
The retry timeout is the time that "UDP RPC" waits for the
server to reply before retransmitting the request.
clnt_freeres(CLIENT * clnt, xdrproc_t outproc, char *out);
A macro that frees any data allocated by the RPC/XDR system
when it decoded the results of an RPC call. The parameter out
is the address of the results, and outproc is the XDR routine
describing the results. This routine returns one if the
results were successfully freed, and zero otherwise.
void clnt_geterr(CLIENT *clnt, struct rpc_err *errp);
A macro that copies the error structure out of the client
handle to the structure at address errp.
void clnt_pcreateerror(char *s);
Print a message to standard error indicating why a client RPC
handle could not be created. The message is prepended with
string s and a colon. Used when a clnt_create(),
clntraw_create(), clnttcp_create(), or clntudp_create() call
fails.
void clnt_perrno(enum clnt_stat stat);
Print a message to standard error corresponding to the
condition indicated by stat. Used after callrpc().
clnt_perror(CLIENT *clnt, char *s);
Print a message to standard error indicating why an RPC call
failed; clnt is the handle used to do the call. The message
is prepended with string s and a colon. Used after
clnt_call().
char *clnt_spcreateerror(char *s);
Like clnt_pcreateerror(), except that it returns a string
instead of printing to the standard error.
Bugs: returns pointer to static data that is overwritten on
each call.
char *clnt_sperrno(enum clnt_stat stat);
Take the same arguments as clnt_perrno(), but instead of
sending a message to the standard error indicating why an RPC
call failed, return a pointer to a string which contains the
message. The string ends with a NEWLINE.
clnt_sperrno() is used instead of clnt_perrno() if the program
does not have a standard error (as a program running as a
server quite likely does not), or if the programmer does not
want the message to be output with printf(3), or if a message
format different than that supported by clnt_perrno() is to be
used. Note: unlike clnt_sperror() and clnt_spcreateerror(),
clnt_sperrno() returns pointer to static data, but the result
will not get overwritten on each call.
char *clnt_sperror(CLIENT *rpch, char *s);
Like clnt_perror(), except that (like clnt_sperrno()) it
returns a string instead of printing to standard error.
Bugs: returns pointer to static data that is overwritten on
each call.
CLIENT *clntraw_create(unsigned long prognum, unsigned long versnum);
This routine creates a toy RPC client for the remote program
prognum, version versnum. The transport used to pass messages
to the service is actually a buffer within the process's
address space, so the corresponding RPC server should live in
the same address space; see svcraw_create(). This allows
simulation of RPC and acquisition of RPC overheads, such as
round trip times, without any kernel interference. This
routine returns NULL if it fails.
CLIENT *clnttcp_create(struct sockaddr_in *addr,
unsigned long prognum, unsigned long versnum,
int *sockp, unsigned int sendsz, unsigned int recvsz);
This routine creates an RPC client for the remote program
prognum, version versnum; the client uses TCP/IP as a
transport. The remote program is located at Internet address
*addr. If addr->sin_port is zero, then it is set to the
actual port that the remote program is listening on (the
remote portmap service is consulted for this information).
The parameter sockp is a socket; if it is RPC_ANYSOCK, then
this routine opens a new one and sets sockp. Since TCP-based
RPC uses buffered I/O, the user may specify the size of the
send and receive buffers with the parameters sendsz and
recvsz; values of zero choose suitable defaults. This routine
returns NULL if it fails.
CLIENT *clntudp_create(struct sockaddr_in *addr,
unsigned long prognum, unsigned long versnum,
struct timeval wait, int *sockp);
This routine creates an RPC client for the remote program
prognum, version versnum; the client uses use UDP/IP as a
transport. The remote program is located at Internet address
addr. If addr->sin_port is zero, then it is set to actual
port that the remote program is listening on (the remote
portmap service is consulted for this information). The
parameter sockp is a socket; if it is RPC_ANYSOCK, then this
routine opens a new one and sets sockp. The UDP transport
resends the call message in intervals of wait time until a
response is received or until the call times out. The total
time for the call to time out is specified by clnt_call().
Warning: since UDP-based RPC messages can hold only up to 8
Kbytes of encoded data, this transport cannot be used for
procedures that take large arguments or return huge results.
CLIENT *clntudp_bufcreate(struct sockaddr_in *addr,
unsigned long prognum, unsigned long versnum,
struct timeval wait, int *sockp,
unsigned int sendsize, unsigned int recosize);
This routine creates an RPC client for the remote program
prognum, on versnum; the client uses use UDP/IP as a
transport. The remote program is located at Internet address
addr. If addr->sin_port is zero, then it is set to actual
port that the remote program is listening on (the remote
portmap service is consulted for this information). The
parameter sockp is a socket; if it is RPC_ANYSOCK, then this
routine opens a new one and sets sockp. The UDP transport
resends the call message in intervals of wait time until a
response is received or until the call times out. The total
time for the call to time out is specified by clnt_call().
This allows the user to specify the maximum packet size for
sending and receiving UDP-based RPC messages.
void get_myaddress(struct sockaddr_in *addr);
Stuff the machine's IP address into *addr, without consulting
the library routines that deal with /etc/hosts. The port
number is always set to htons(PMAPPORT).
struct pmaplist *pmap_getmaps(struct sockaddr_in *addr);
A user interface to the portmap service, which returns a list
of the current RPC program-to-port mappings on the host
located at IP address *addr. This routine can return NULL.
The command rpcinfo -p uses this routine.
unsigned short pmap_getport(struct sockaddr_in *addr,
unsigned long prognum, unsigned long versnum,
unsigned int protocol);
A user interface to the portmap service, which returns the
port number on which waits a service that supports program
number prognum, version versnum, and speaks the transport
protocol associated with protocol. The value of protocol is
most likely IPPROTO_UDP or IPPROTO_TCP. A return value of
zero means that the mapping does not exist or that the RPC
system failed to contact the remote portmap service. In the
latter case, the global variable rpc_createerr contains the
RPC status.
enum clnt_stat pmap_rmtcall(struct sockaddr_in *addr,
unsigned long prognum, unsigned long versnum,
unsigned long procnum,
xdrproc_t inproc, char *in,
xdrproc_t outproc, char *out,
struct timeval tout, unsigned long *portp);
A user interface to the portmap service, which instructs
portmap on the host at IP address *addr to make an RPC call on
your behalf to a procedure on that host. The parameter *portp
will be modified to the program's port number if the procedure
succeeds. The definitions of other parameters are discussed
in callrpc() and clnt_call(). This procedure should be used
for a “ping” and nothing else. See also clnt_broadcast().
bool_t pmap_set(unsigned long prognum, unsigned long versnum,
unsigned int protocol, unsigned short port);
A user interface to the portmap service, which establishes a
mapping between the triple [prognum,versnum,protocol] and port
on the machine's portmap service. The value of protocol is
most likely IPPROTO_UDP or IPPROTO_TCP. This routine returns
one if it succeeds, zero otherwise. Automatically done by
svc_register().
bool_t pmap_unset(unsigned long prognum, unsigned long versnum);
A user interface to the portmap service, which destroys all
mapping between the triple [prognum,versnum,*] and ports on
the machine's portmap service. This routine returns one if it
succeeds, zero otherwise.
int registerrpc(unsigned long prognum, unsigned long versnum,
unsigned long procnum, char *(*procname)(char *),
xdrproc_t inproc, xdrproc_t outproc);
Register procedure procname with the RPC service package. If
a request arrives for program prognum, version versnum, and
procedure procnum, procname is called with a pointer to its
parameter(s); procname should return a pointer to its static
result(s); inproc is used to decode the parameters while
outproc is used to encode the results. This routine returns
zero if the registration succeeded, -1 otherwise.
Warning: remote procedures registered in this form are
accessed using the UDP/IP transport; see svcudp_create() for
restrictions.
struct rpc_createerr rpc_createerr;
A global variable whose value is set by any RPC client
creation routine that does not succeed. Use the routine
clnt_pcreateerror() to print the reason why.
void svc_destroy(SVCXPRT *xprt);
A macro that destroys the RPC service transport handle, xprt.
Destruction usually involves deallocation of private data
structures, including xprt itself. Use of xprt is undefined
after calling this routine.
fd_set svc_fdset;
A global variable reflecting the RPC service side's read file
descriptor bit mask; it is suitable as a parameter to the
select(2) system call. This is of interest only if a service
implementor does their own asynchronous event processing,
instead of calling svc_run(). This variable is read-only (do
not pass its address to select(2)!), yet it may change after
calls to svc_getreqset() or any creation routines.
int svc_fds;
Similar to svc_fdset, but limited to 32 file descriptors.
This interface is obsoleted by svc_fdset.
svc_freeargs(SVCXPRT *xprt, xdrproc_t inproc, char *in);
A macro that frees any data allocated by the RPC/XDR system
when it decoded the arguments to a service procedure using
svc_getargs(). This routine returns 1 if the results were
successfully freed, and zero otherwise.
svc_getargs(SVCXPRT *xprt, xdrproc_t inproc, char *in);
A macro that decodes the arguments of an RPC request
associated with the RPC service transport handle, xprt. The
parameter in is the address where the arguments will be
placed; inproc is the XDR routine used to decode the
arguments. This routine returns one if decoding succeeds, and
zero otherwise.
struct sockaddr_in *svc_getcaller(SVCXPRT *xprt);
The approved way of getting the network address of the caller
of a procedure associated with the RPC service transport
handle, xprt.
void svc_getreqset(fd_set *rdfds);
This routine is of interest only if a service implementor does
not call svc_run(), but instead implements custom asynchronous
event processing. It is called when the select(2) system call
has determined that an RPC request has arrived on some RPC
socket(s); rdfds is the resultant read file descriptor bit
mask. The routine returns when all sockets associated with
the value of rdfds have been serviced.
void svc_getreq(int rdfds);
Similar to svc_getreqset(), but limited to 32 file
descriptors. This interface is obsoleted by svc_getreqset().
bool_t svc_register(SVCXPRT *xprt, unsigned long prognum,
unsigned long versnum,
void (*dispatch)(svc_req *, SVCXPRT *),
unsigned long protocol);
Associates prognum and versnum with the service dispatch
procedure, dispatch. If protocol is zero, the service is not
registered with the portmap service. If protocol is nonzero,
then a mapping of the triple [prognum,versnum,protocol] to
xprt->xp_port is established with the local portmap service
(generally protocol is zero, IPPROTO_UDP or IPPROTO_TCP). The
procedure dispatch has the following form:
dispatch(struct svc_req *request, SVCXPRT *xprt);
The svc_register() routine returns one if it succeeds, and
zero otherwise.
void svc_run(void);
This routine never returns. It waits for RPC requests to
arrive, and calls the appropriate service procedure using
svc_getreq() when one arrives. This procedure is usually
waiting for a select(2) system call to return.
bool_t svc_sendreply(SVCXPRT *xprt, xdrproc_t outproc, char *out);
Called by an RPC service's dispatch routine to send the
results of a remote procedure call. The parameter xprt is the
request's associated transport handle; outproc is the XDR
routine which is used to encode the results; and out is the
address of the results. This routine returns one if it
succeeds, zero otherwise.
void svc_unregister(unsigned long prognum, unsigned long versnum);
Remove all mapping of the double [prognum,versnum] to dispatch
routines, and of the triple [prognum,versnum,*] to port
number.
void svcerr_auth(SVCXPRT *xprt, enum auth_stat why);
Called by a service dispatch routine that refuses to perform a
remote procedure call due to an authentication error.
void svcerr_decode(SVCXPRT *xprt);
Called by a service dispatch routine that cannot successfully
decode its parameters. See also svc_getargs().
void svcerr_noproc(SVCXPRT *xprt);
Called by a service dispatch routine that does not implement
the procedure number that the caller requests.
void svcerr_noprog(SVCXPRT *xprt);
Called when the desired program is not registered with the RPC
package. Service implementors usually do not need this
routine.
void svcerr_progvers(SVCXPRT *xprt);
Called when the desired version of a program is not registered
with the RPC package. Service implementors usually do not
need this routine.
void svcerr_systemerr(SVCXPRT *xprt);
Called by a service dispatch routine when it detects a system
error not covered by any particular protocol. For example, if
a service can no longer allocate storage, it may call this
routine.
void svcerr_weakauth(SVCXPRT *xprt);
Called by a service dispatch routine that refuses to perform a
remote procedure call due to insufficient authentication
parameters. The routine calls svcerr_auth(xprt,
AUTH_TOOWEAK).
SVCXPRT *svcfd_create(int fd, unsigned int sendsize,
unsigned int recvsize);
Create a service on top of any open file descriptor.
Typically, this file descriptor is a connected socket for a
stream protocol such as TCP. sendsize and recvsize indicate
sizes for the send and receive buffers. If they are zero, a
reasonable default is chosen.
SVCXPRT *svcraw_create(void);
This routine creates a toy RPC service transport, to which it
returns a pointer. The transport is really a buffer within
the process's address space, so the corresponding RPC client
should live in the same address space; see clntraw_create().
This routine allows simulation of RPC and acquisition of RPC
overheads (such as round trip times), without any kernel
interference. This routine returns NULL if it fails.
SVCXPRT *svctcp_create(int sock, unsigned int send_buf_size,
unsigned int recv_buf_size);
This routine creates a TCP/IP-based RPC service transport, to
which it returns a pointer. The transport is associated with
the socket sock, which may be RPC_ANYSOCK, in which case a new
socket is created. If the socket is not bound to a local TCP
port, then this routine binds it to an arbitrary port. Upon
completion, xprt->xp_sock is the transport's socket
descriptor, and xprt->xp_port is the transport's port number.
This routine returns NULL if it fails. Since TCP-based RPC
uses buffered I/O, users may specify the size of buffers;
values of zero choose suitable defaults.
SVCXPRT *svcudp_bufcreate(int sock, unsigned int sendsize,
unsigned int recosize);
This routine creates a UDP/IP-based RPC service transport, to
which it returns a pointer. The transport is associated with
the socket sock, which may be RPC_ANYSOCK, in which case a new
socket is created. If the socket is not bound to a local UDP
port, then this routine binds it to an arbitrary port. Upon
completion, xprt->xp_sock is the transport's socket
descriptor, and xprt->xp_port is the transport's port number.
This routine returns NULL if it fails.
This allows the user to specify the maximum packet size for
sending and receiving UDP-based RPC messages.
SVCXPRT *svcudp_create(int sock);
This call is equivalent to svcudp_bufcreate(sock,SZ,SZ) for
some default size SZ.
bool_t xdr_accepted_reply(XDR *xdrs, struct accepted_reply *ar);
Used for encoding RPC reply messages. This routine is useful
for users who wish to generate RPC-style messages without
using the RPC package.
bool_t xdr_authunix_parms(XDR *xdrs, struct authunix_parms *aupp);
Used for describing UNIX credentials. This routine is useful
for users who wish to generate these credentials without using
the RPC authentication package.
void xdr_callhdr(XDR *xdrs, struct rpc_msg *chdr);
Used for describing RPC call header messages. This routine is
useful for users who wish to generate RPC-style messages
without using the RPC package.
bool_t xdr_callmsg(XDR *xdrs, struct rpc_msg *cmsg);
Used for describing RPC call messages. This routine is useful
for users who wish to generate RPC-style messages without
using the RPC package.
bool_t xdr_opaque_auth(XDR *xdrs, struct opaque_auth *ap);
Used for describing RPC authentication information messages.
This routine is useful for users who wish to generate RPC-
style messages without using the RPC package.
bool_t xdr_pmap(XDR *xdrs, struct pmap *regs);
Used for describing parameters to various portmap procedures,
externally. This routine is useful for users who wish to
generate these parameters without using the pmap interface.
bool_t xdr_pmaplist(XDR *xdrs, struct pmaplist **rp);
Used for describing a list of port mappings, externally. This
routine is useful for users who wish to generate these
parameters without using the pmap interface.
bool_t xdr_rejected_reply(XDR *xdrs, struct rejected_reply *rr);
Used for describing RPC reply messages. This routine is
useful for users who wish to generate RPC-style messages
without using the RPC package.
bool_t xdr_replymsg(XDR *xdrs, struct rpc_msg *rmsg);
Used for describing RPC reply messages. This routine is
useful for users who wish to generate RPC style messages
without using the RPC package.
void xprt_register(SVCXPRT *xprt);
After RPC service transport handles are created, they should
register themselves with the RPC service package. This
routine modifies the global variable svc_fds. Service
implementors usually do not need this routine.
void xprt_unregister(SVCXPRT *xprt);
Before an RPC service transport handle is destroyed, it should
unregister itself with the RPC service package. This routine
modifies the global variable svc_fds. Service implementors
usually do not need this routine.
For an explanation of the terms used in this section, see
attributes(7).
┌────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├────────────────────────────────────┼───────────────┼─────────┤
│auth_destroy(), authnone_create(), │ Thread safety │ MT-Safe │
│authunix_create(), │ │ │
│authunix_create_default(), │ │ │
│callrpc(), clnt_broadcast(), │ │ │
│clnt_call(), clnt_destroy(), │ │ │
│clnt_create(), clnt_control(), │ │ │
│clnt_freeres(), clnt_geterr(), │ │ │
│clnt_pcreateerror(), clnt_perrno(), │ │ │
│clnt_perror(), │ │ │
│clnt_spcreateerror(), │ │ │
│clnt_sperrno(), clnt_sperror(), │ │ │
│clntraw_create(), clnttcp_create(), │ │ │
│clntudp_create(), │ │ │
│clntudp_bufcreate(), │ │ │
│get_myaddress(), pmap_getmaps(), │ │ │
│pmap_getport(), pmap_rmtcall(), │ │ │
│pmap_set(), pmap_unset(), │ │ │
│registerrpc(), svc_destroy(), │ │ │
│svc_freeargs(), svc_getargs(), │ │ │
│svc_getcaller(), svc_getreqset(), │ │ │
│svc_getreq(), svc_register(), │ │ │
│svc_run(), svc_sendreply(), │ │ │
│svc_unregister(), svcerr_auth(), │ │ │
│svcerr_decode(), svcerr_noproc(), │ │ │
│svcerr_noprog(), svcerr_progvers(), │ │ │
│svcerr_systemerr(), │ │ │
│svcerr_weakauth(), │ │ │
│svcfd_create(), svcraw_create(), │ │ │
│svctcp_create(), │ │ │
│svcudp_bufcreate(), │ │ │
│svcudp_create(), │ │ │
│xdr_accepted_reply(), │ │ │
│xdr_authunix_parms(), │ │ │
│xdr_callhdr(), │ │ │
│xdr_callmsg(), xdr_opaque_auth(), │ │ │
│xdr_pmap(), xdr_pmaplist(), │ │ │
│xdr_rejected_reply(), │ │ │
│xdr_replymsg(), │ │ │
│xprt_register(), xprt_unregister() │ │ │
└────────────────────────────────────┴───────────────┴─────────┘
xdr(3)
The following manuals:
Remote Procedure Calls: Protocol Specification
Remote Procedure Call Programming Guide
rpcgen Programming Guide
RPC: Remote Procedure Call Protocol Specification, RFC 1050, Sun
Microsystems, Inc., USC-ISI.
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
2016-03-15 RPC(3)
Pages that refer to this page: autofsd-probe(1), xdr(3), rpc.rquotad(8)