NAME
rpc - library routines for remote procedure calls SYNOPSIS AND DESCRIPTION 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
. The prototypes below make use of the following types: typedef int boolt; typedef boolt (*xdrproct) (XDR *, void *, ...); typedef boolt (*resultproct) (caddrt resp, struct sockaddrin *raddr); See the header files for the declarations of the AUTH, CLIENT, SVCXPRT, and XDR types. void authdestroy(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 authdestroy(). AUTH *authnonecreate(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 *authunixcreate(char *host, int uid, int gid, int len, int *aupgids); 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 aupgids refer to a counted array of groups to which the user belongs. It is easy to impersonate a user. AUTH *authunixcreatedefault(void); Calls authunixcreate() with the appropriate parameters. int callrpc(char *host, unsigned long prognum, unsigned long versnum, unsigned long procnum, xdrproct inproc, char *in, xdrproct 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 clntstat cast to an integer if it fails. The routine clntperrno() is handy for translating failure statuses into messages. Warning: calling remote procedures with this routine uses UDP/IP as a transport; see clntudpcreate() for restrictions. You do not have control of timeouts or authentication using this rou‐ tine. enum clntstat clntbroadcast(unsigned long prognum, unsigned long versnum, unsigned long procnum, xdrproct inproc, char *in, xdrproct outproc, char *out, resultproct 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 sockaddrin *addr); where out is the same as out passed to clntbroadcast(), except that the remote procedure's output is decoded there; addr points to the address of the machine that sent the results. If eachre‐ sult() returns zero, clntbroadcast() 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 clntstat clntcall(CLIENT *clnt, unsigned long procnum, xdrproct inproc, char *in, xdrproct 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 clntcreate(). 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 proce‐ dure's results; tout is the time allowed for results to come back. clntdestroy(CLIENT *clnt); A macro that destroys the client's RPC handle. Destruction usu‐ ally involves deallocation of private data structures, including clnt itself. Use of clnt is undefined after calling clntdestroy(). If the RPC library opened the associated socket, it will close it also. Otherwise, the socket remains open. CLIENT *clntcreate(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 sup‐ ported values for this field are “udp” and “tcp”. Default time‐ outs are set, but can be modified using clntcontrol(). 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 argu‐ ments or return huge results. boolt clntcontrol(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 sup‐ ported values of req and their argument types and what they do are: CLSETTIMEOUT struct timeval // set total timeout CLGETTIMEOUT struct timeval // get total timeout Note: if you set the timeout using clntcontrol(), the timeout parameter passed to clntcall() will be ignored in all future calls. CLGETSERVERADDR struct sockaddrin // get server's address The following operations are valid for UDP only: CLSETRETRYTIMEOUT struct timeval // set the retry timeout CLGETRETRYTIMEOUT 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. clntfreeres(CLIENT * clnt, xdrproct 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 describ‐ ing the results. This routine returns one if the results were successfully freed, and zero otherwise. void clntgeterr(CLIENT *clnt, struct rpcerr *errp); A macro that copies the error structure out of the client handle to the structure at address errp. void clntpcreateerror(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 clntcreate(), clntrawcre‐ ate(), clnttcpcreate(), or clntudpcreate() call fails. void clntperrno(enum clntstat stat); Print a message to standard error corresponding to the condition indicated by stat. Used after callrpc(). clntperror(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 clntcall(). char *clntspcreateerror(char *s); Like clntpcreateerror(), 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 *clntsperrno(enum clntstat stat); Take the same arguments as clntperrno(), 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. clntsperrno() is used instead of clntperrno() 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 dif‐ ferent than that supported by clntperrno() is to be used. Note: unlike clntsperror() and clntspcreaterror(), clntsper‐ rno() returns pointer to static data, but the result will not get overwritten on each call. char *clntsperror(CLIENT *rpch, char *s); Like clntperror(), except that (like clntsperrno()) it returns a string instead of printing to standard error. Bugs: returns pointer to static data that is overwritten on each call. CLIENT *clntrawcreate(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 svcrawcreate(). 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 *clnttcpcreate(struct sockaddrin *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->sinport 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 RPCANYSOCK, 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 *clntudpcreate(struct sockaddrin *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 trans‐ port. The remote program is located at Internet address addr.
If addr->sinport 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 RPCANYSOCK, 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 clntcall().
Warning: since UDP-based RPC messages can hold only up to 8 Kbytes of encoded data, this transport cannot be used for proce‐ dures that take large arguments or return huge results. CLIENT *clntudpbufcreate(struct sockaddrin *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->sinport 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 RPCANYSOCK, 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 clntcall(). This allows the user to specify the maximum packet size for
sending and receiving UDP-based RPC messages. void getmyaddress(struct sockaddrin *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 *pmapgetmaps(struct sockaddrin *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 pmapgetport(struct sockaddrin *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 IPPROTOUDP or IPPROTOTCP. A return value of zero means that the mapping does not exist or that the RPC system failed to con‐ tact the remote portmap service. In the latter case, the global variable rpccreateerr contains the RPC status. enum clntstat pmaprmtcall(struct sockaddrin *addr, unsigned long prognum, unsigned long versnum, unsigned long procnum, xdrproct inproc, char *in, xdrproct 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 suc‐ ceeds. The definitions of other parameters are discussed in callrpc() and clntcall(). This procedure should be used for a “ping” and nothing else. See also clntbroadcast(). boolt pmapset(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 IPPROTOUDP or IPPROTOTCP. This routine returns one if it succeeds, zero otherwise. Automatically done by svcregis‐ ter(). boolt pmapunset(unsigned long prognum, unsigned long versnum); A user interface to the portmap service, which destroys all map‐ ping between the triple [prognum,versnum,*] and ports on the machine's portmap service. This routine returns one if it suc‐ ceeds, zero otherwise. int registerrpc(unsigned long prognum, unsigned long versnum, unsigned long procnum, char *(*procname)(char *), xdrproct inproc, xdrproct outproc); Register procedure procname with the RPC service package. If a request arrives for program prognum, version versnum, and proce‐ dure procnum, procname is called with a pointer to its parame‐ ter(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 svcudpcreate() for restric‐ tions. struct rpccreateerr rpccreateerr; A global variable whose value is set by any RPC client creation routine that does not succeed. Use the routine clntpcreateer‐ ror() to print the reason why. void svcdestroy(SVCXPRT *xprt); A macro that destroys the RPC service transport handle, xprt. Destruction usually involves deallocation of private data struc‐ tures, including xprt itself. Use of xprt is undefined after calling this routine. fdset svcfdset; 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 not call svcrun(), but rather does his own
asynchronous event processing. This variable is read-only (do not pass its address to select(2)!), yet it may change after calls to svcgetreqset() or any creation routines. int svcfds; Similar to svcfdset, but limited to 32 descriptors. This interface is obsoleted by svcfdset. svcfreeargs(SVCXPRT *xprt, xdrproct 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 svcgetargs(). This routine returns 1 if the results were suc‐ cessfully freed, and zero otherwise. svcgetargs(SVCXPRT *xprt, xdrproct 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 sockaddrin *svcgetcaller(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 svcgetreqset(fdset *rdfds); This routine is of interest only if a service implementor does not call svcrun(), 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 svcgetreq(int rdfds); Similar to svcgetreqset(), but limited to 32 descriptors. This interface is obsoleted by svcgetreqset(). boolt svcregister(SVCXPRT *xprt, unsigned long prognum, unsigned long versnum, void (*dispatch)(svcreq *, SVCXPRT *), unsigned long protocol); Associates prognum and versnum with the service dispatch proce‐ dure, dispatch. If protocol is zero, the service is not regis‐ tered with the portmap service. If protocol is nonzero, then a mapping of the triple [prognum,versnum,protocol] to
xprt->xpport is established with the local portmap service (generally protocol is zero, IPPROTOUDP or IPPROTOTCP). The procedure dispatch has the following form: dispatch(struct svcreq *request, SVCXPRT *xprt); The svcregister() routine returns one if it succeeds, and zero otherwise. void svcrun(void); This routine never returns. It waits for RPC requests to arrive, and calls the appropriate service procedure using svcgetreq() when one arrives. This procedure is usually wait‐ ing for a select(2) system call to return. boolt svcsendreply(SVCXPRT *xprt, xdrproct 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 other‐ wise. void svcunregister(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 svcerrauth(SVCXPRT *xprt, enum authstat why); Called by a service dispatch routine that refuses to perform a remote procedure call due to an authentication error. void svcerrdecode(SVCXPRT *xprt); Called by a service dispatch routine that cannot successfully decode its parameters. See also svcgetargs(). void svcerrnoproc(SVCXPRT *xprt); Called by a service dispatch routine that does not implement the procedure number that the caller requests. void svcerrnoprog(SVCXPRT *xprt); Called when the desired program is not registered with the RPC package. Service implementors usually do not need this routine. void svcerrprogvers(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 svcerrsystemerr(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 rou‐ tine. void svcerrweakauth(SVCXPRT *xprt); Called by a service dispatch routine that refuses to perform a remote procedure call due to insufficient authentication parame‐ ters. The routine calls svcerrauth(xprt, AUTHTOOWEAK). SVCXPRT *svcfdcreate(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 cho‐ sen. SVCXPRT *svcrawcreate(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 clntrawcreate(). This rou‐ tine 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 *svctcpcreate(int sock, unsigned int sendbufsize, unsigned int recvbufsize);
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 RPCANYSOCK, 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->xpsock is the transport's socket descriptor,
and xprt->xpport 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 *svcudpbufcreate(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 RPCANYSOCK, 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->xpsock is the transport's socket descriptor,
and xprt->xpport 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 *svcudpcreate(int sock); This call is equivalent to svcudpbufcreate(sock,SZ,SZ) for some default size SZ. boolt xdracceptedreply(XDR *xdrs, struct acceptedreply *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. boolt xdrauthunixparms(XDR *xdrs, struct authunixparms *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 xdrcallhdr(XDR *xdrs, struct rpcmsg *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. boolt xdrcallmsg(XDR *xdrs, struct rpcmsg *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. boolt xdropaqueauth(XDR *xdrs, struct opaqueauth *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. boolt xdrpmap(XDR *xdrs, struct pmap *regs); Used for describing parameters to various portmap procedures, externally. This routine is useful for users who wish to gener‐ ate these parameters without using the pmap interface. boolt xdrpmaplist(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 parame‐ ters without using the pmap interface. boolt xdrrejectedreply(XDR *xdrs, struct rejectedreply *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. boolt xdrreplymsg(XDR *xdrs, struct rpcmsg *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 xprtregister(SVCXPRT *xprt); After RPC service transport handles are created, they should register themselves with the RPC service package. This routine modifies the global variable svcfds. Service implementors usu‐ ally do not need this routine. void xprtunregister(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 svcfds. Service implementors usu‐ ally do not need this routine. SEE ALSO 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
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2008-07-17 RPC(3)