NAME | SYNOPSIS AND DESCRIPTION | SEE ALSO | COLOPHON

RPC(3)                    Linux Programmer's Manual                   RPC(3)

NAME         top

       rpc - library routines for remote procedure calls

SYNOPSIS AND DESCRIPTION         top

       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_spcreaterror(),
              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); progname 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 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 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 descriptor.  Typically,
              this 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.

SEE ALSO         top

       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.

COLOPHON         top

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       description of the project, information about reporting bugs, and the
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                                 2013-09-26                           RPC(3)