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diff --git a/lib/librpc/doc/rpc.prog.ms b/lib/librpc/doc/rpc.prog.ms deleted file mode 100644 index 3b02447..0000000 --- a/lib/librpc/doc/rpc.prog.ms +++ /dev/null @@ -1,2684 +0,0 @@ -.\" -.\" Must use -- tbl and pic -- with this one -.\" -.\" @(#)rpc.prog.ms 2.3 88/08/11 4.0 RPCSRC -.de BT -.if \\n%=1 .tl ''- % -'' -.. -.IX "Network Programming" "" "" "" PAGE MAJOR -.nr OF 0 -.ND -.\" prevent excess underlining in nroff -.if n .fp 2 R -.OH 'Remote Procedure Call Programming Guide''Page %' -.EH 'Page %''Remote Procedure Call Programming Guide' -.SH -\&Remote Procedure Call Programming Guide -.nr OF 1 -.IX "RPC Programming Guide" -.LP -This document assumes a working knowledge of network theory. It is -intended for programmers who wish to write network applications using -remote procedure calls (explained below), and who want to understand -the RPC mechanisms usually hidden by the -.I rpcgen(1) -protocol compiler. -.I rpcgen -is described in detail in the previous chapter, the -.I "\fBrpcgen\fP \fIProgramming Guide\fP". -.SH -Note: -.I -.IX rpcgen "" \fIrpcgen\fP -Before attempting to write a network application, or to convert an -existing non-network application to run over the network, you may want to -understand the material in this chapter. However, for most applications, -you can circumvent the need to cope with the details presented here by using -.I rpcgen . -The -.I "Generating XDR Routines" -section of that chapter contains the complete source for a working RPC -service\(ema remote directory listing service which uses -.I rpcgen -to generate XDR routines as well as client and server stubs. -.LP -.LP -What are remote procedure calls? Simply put, they are the high-level -communications paradigm used in the operating system. -RPC presumes the existence of -low-level networking mechanisms (such as TCP/IP and UDP/IP), and upon them -it implements a logical client to server communications system designed -specifically for the support of network applications. With RPC, the client -makes a procedure call to send a data packet to the server. When the -packet arrives, the server calls a dispatch routine, performs whatever -service is requested, sends back the reply, and the procedure call returns -to the client. -.NH 0 -\&Layers of RPC -.IX "layers of RPC" -.IX "RPC" "layers" -.LP -The RPC interface can be seen as being divided into three layers.\** -.FS -For a complete specification of the routines in the remote procedure -call Library, see the -.I rpc(3N) -manual page. -.FE -.LP -.I "The Highest Layer:" -.IX RPC "The Highest Layer" -The highest layer is totally transparent to the operating system, -machine and network upon which is is run. It's probably best to -think of this level as a way of -.I using -RPC, rather than as -a \fIpart of\fP RPC proper. Programmers who write RPC routines -should (almost) always make this layer available to others by way -of a simple C front end that entirely hides the networking. -.LP -To illustrate, at this level a program can simply make a call to -.I rnusers (), -a C routine which returns the number of users on a remote machine. -The user is not explicitly aware of using RPC \(em they simply -call a procedure, just as they would call -.I malloc() . -.LP -.I "The Middle Layer:" -.IX RPC "The Middle Layer" -The middle layer is really \*QRPC proper.\*U Here, the user doesn't -need to consider details about sockets, the UNIX system, or other low-level -implementation mechanisms. They simply make remote procedure calls -to routines on other machines. The selling point here is simplicity. -It's this layer that allows RPC to pass the \*Qhello world\*U test \(em -simple things should be simple. The middle-layer routines are used -for most applications. -.LP -RPC calls are made with the system routines -.I registerrpc() -.I callrpc() -and -.I svc_run (). -The first two of these are the most fundamental: -.I registerrpc() -obtains a unique system-wide procedure-identification number, and -.I callrpc() -actually executes a remote procedure call. At the middle level, a -call to -.I rnusers() -is implemented by way of these two routines. -.LP -The middle layer is unfortunately rarely used in serious programming -due to its inflexibility (simplicity). It does not allow timeout -specifications or the choice of transport. It allows no UNIX -process control or flexibility in case of errors. It doesn't support -multiple kinds of call authentication. The programmer rarely needs -all these kinds of control, but one or two of them is often necessary. -.LP -.I "The Lowest Layer:" -.IX RPC "The Lowest Layer" -The lowest layer does allow these details to be controlled by the -programmer, and for that reason it is often necessary. Programs -written at this level are also most efficient, but this is rarely a -real issue \(em since RPC clients and servers rarely generate -heavy network loads. -.LP -Although this document only discusses the interface to C, -remote procedure calls can be made from any language. -Even though this document discusses RPC -when it is used to communicate -between processes on different machines, -it works just as well for communication -between different processes on the same machine. -.br -.KS -.NH 2 -\&The RPC Paradigm -.IX RPC paradigm -.LP -Here is a diagram of the RPC paradigm: -.LP -\fBFigure 1-1\fI Network Communication with the Remote Reocedure Call\fR -.LP -.PS -L1: arrow down 1i "client " rjust "program " rjust -L2: line right 1.5i "\fIcallrpc\fP" "function" -move up 1.5i; line dotted down 6i; move up 4.5i -arrow right 1i -L3: arrow down 1i "invoke " rjust "service " rjust -L4: arrow right 1.5i "call" "service" -L5: arrow down 1i " service" ljust " executes" ljust -L6: arrow left 1.5i "\fIreturn\fP" "answer" -L7: arrow down 1i "request " rjust "completed " rjust -L8: line left 1i -arrow left 1.5i "\fIreturn\fP" "reply" -L9: arrow down 1i "program " rjust "continues " rjust -line dashed down from L2 to L9 -line dashed down from L4 to L7 -line dashed up 1i from L3 "service " rjust "daemon " rjust -arrow dashed down 1i from L8 -move right 1i from L3 -box invis "Machine B" -move left 1.2i from L2; move down -box invis "Machine A" -.PE -.KE -.KS -.NH 1 -\&Higher Layers of RPC -.NH 2 -\&Highest Layer -.IX "highest layer of RPC" -.IX RPC "highest layer" -.LP -Imagine you're writing a program that needs to know -how many users are logged into a remote machine. -You can do this by calling the RPC library routine -.I rnusers() -as illustrated below: -.ie t .DS -.el .DS L -.ft CW -#include <stdio.h> - -main(argc, argv) - int argc; - char **argv; -{ - int num; - - if (argc != 2) { - fprintf(stderr, "usage: rnusers hostname\en"); - exit(1); - } - if ((num = rnusers(argv[1])) < 0) { - fprintf(stderr, "error: rnusers\en"); - exit(-1); - } - printf("%d users on %s\en", num, argv[1]); - exit(0); -} -.DE -.KE -RPC library routines such as -.I rnusers() -are in the RPC services library -.I librpcsvc.a -Thus, the program above should be compiled with -.DS -.ft CW -% cc \fIprogram.c -lrpcsvc\fP -.DE -.I rnusers (), -like the other RPC library routines, is documented in section 3R -of the -.I "System Interface Manual for the Sun Workstation" , -the same section which documents the standard Sun RPC services. -.IX "RPC Services" -See the -.I intro(3R) -manual page for an explanation of the documentation strategy -for these services and their RPC protocols. -.LP -Here are some of the RPC service library routines available to the -C programmer: -.LP -\fBTable 3-3\fI RPC Service Library Routines\RP -.TS -box tab (&) ; -cfI cfI -lfL l . -Routine&Description -_ -.sp.5 -rnusers&Return number of users on remote machine -rusers&Return information about users on remote machine -havedisk&Determine if remote machine has disk -rstats&Get performance data from remote kernel -rwall&Write to specified remote machines -yppasswd&Update user password in Yellow Pages -.TE -.LP -Other RPC services \(em for example -.I ether() -.I mount -.I rquota() -and -.I spray -\(em are not available to the C programmer as library routines. -They do, however, -have RPC program numbers so they can be invoked with -.I callrpc() -which will be discussed in the next section. Most of them also -have compilable -.I rpcgen(1) -protocol description files. (The -.I rpcgen -protocol compiler radically simplifies the process of developing -network applications. -See the \fBrpcgen\fI Programming Guide\fR -for detailed information about -.I rpcgen -and -.I rpcgen -protocol description files). -.KS -.NH 2 -\&Intermediate Layer -.IX "intermediate layer of RPC" -.IX "RPC" "intermediate layer" -.LP -The simplest interface, which explicitly makes RPC calls, uses the -functions -.I callrpc() -and -.I registerrpc() -Using this method, the number of remote users can be gotten as follows: -.ie t .DS -.el .DS L -#include <stdio.h> -#include <rpc/rpc.h> -#include <utmp.h> -#include <rpcsvc/rusers.h> - -main(argc, argv) - int argc; - char **argv; -{ - unsigned long nusers; - int stat; - - if (argc != 2) { - fprintf(stderr, "usage: nusers hostname\en"); - exit(-1); - } - if (stat = callrpc(argv[1], - RUSERSPROG, RUSERSVERS, RUSERSPROC_NUM, - xdr_void, 0, xdr_u_long, &nusers) != 0) { - clnt_perrno(stat); - exit(1); - } - printf("%d users on %s\en", nusers, argv[1]); - exit(0); -} -.DE -.KE -Each RPC procedure is uniquely defined by a program number, -version number, and procedure number. The program number -specifies a group of related remote procedures, each of -which has a different procedure number. Each program also -has a version number, so when a minor change is made to a -remote service (adding a new procedure, for example), a new -program number doesn't have to be assigned. When you want -to call a procedure to find the number of remote users, you -look up the appropriate program, version and procedure numbers -in a manual, just as you look up the name of a memory allocator -when you want to allocate memory. -.LP -The simplest way of making remote procedure calls is with the the RPC -library routine -.I callrpc() -It has eight parameters. The first is the name of the remote server -machine. The next three parameters are the program, version, and procedure -numbers\(emtogether they identify the procedure to be called. -The fifth and sixth parameters are an XDR filter and an argument to -be encoded and passed to the remote procedure. -The final two parameters are a filter for decoding the results -returned by the remote procedure and a pointer to the place where -the procedure's results are to be stored. Multiple arguments and -results are handled by embedding them in structures. If -.I callrpc() -completes successfully, it returns zero; else it returns a nonzero -value. The return codes (of type -.IX "enum clnt_stat (in RPC programming)" "" "\fIenum clnt_stat\fP (in RPC programming)" -cast into an integer) are found in -.I <rpc/clnt.h> . -.LP -Since data types may be represented differently on different machines, -.I callrpc() -needs both the type of the RPC argument, as well as -a pointer to the argument itself (and similarly for the result). For -.I RUSERSPROC_NUM , -the return value is an -.I "unsigned long" -so -.I callrpc() -has -.I xdr_u_long() -as its first return parameter, which says -that the result is of type -.I "unsigned long" -and -.I &nusers -as its second return parameter, -which is a pointer to where the long result will be placed. Since -.I RUSERSPROC_NUM -takes no argument, the argument parameter of -.I callrpc() -is -.I xdr_void (). -.LP -After trying several times to deliver a message, if -.I callrpc() -gets no answer, it returns with an error code. -The delivery mechanism is UDP, -which stands for User Datagram Protocol. -Methods for adjusting the number of retries -or for using a different protocol require you to use the lower -layer of the RPC library, discussed later in this document. -The remote server procedure -corresponding to the above might look like this: -.ie t .DS -.el .DS L -.ft CW -.ft CW -char * -nuser(indata) - char *indata; -{ - unsigned long nusers; - -.ft I - /* - * Code here to compute the number of users - * and place result in variable \fInusers\fP. - */ -.ft CW - return((char *)&nusers); -} -.DE -.LP -It takes one argument, which is a pointer to the input -of the remote procedure call (ignored in our example), -and it returns a pointer to the result. -In the current version of C, -character pointers are the generic pointers, -so both the input argument and the return value are cast to -.I "char *" . -.LP -Normally, a server registers all of the RPC calls it plans -to handle, and then goes into an infinite loop waiting to service requests. -In this example, there is only a single procedure -to register, so the main body of the server would look like this: -.ie t .DS -.el .DS L -.ft CW -#include <stdio.h> -#include <rpc/rpc.h> -#include <utmp.h> -#include <rpcsvc/rusers.h> - -char *nuser(); - -main() -{ - registerrpc(RUSERSPROG, RUSERSVERS, RUSERSPROC_NUM, - nuser, xdr_void, xdr_u_long); - svc_run(); /* \fINever returns\fP */ - fprintf(stderr, "Error: svc_run returned!\en"); - exit(1); -} -.DE -.LP -The -.I registerrpc() -routine registers a C procedure as corresponding to a -given RPC procedure number. The first three parameters, -.I RUSERPROG , -.I RUSERSVERS , -and -.I RUSERSPROC_NUM -are the program, version, and procedure numbers -of the remote procedure to be registered; -.I nuser() -is the name of the local procedure that implements the remote -procedure; and -.I xdr_void() -and -.I xdr_u_long() -are the XDR filters for the remote procedure's arguments and -results, respectively. (Multiple arguments or multiple results -are passed as structures). -.LP -Only the UDP transport mechanism can use -.I registerrpc() -thus, it is always safe in conjunction with calls generated by -.I callrpc() . -.SH -.IX "UDP 8K warning" -Warning: the UDP transport mechanism can only deal with -arguments and results less than 8K bytes in length. -.LP -.LP -After registering the local procedure, the server program's -main procedure calls -.I svc_run (), -the RPC library's remote procedure dispatcher. It is this -function that calls the remote procedures in response to RPC -call messages. Note that the dispatcher takes care of decoding -remote procedure arguments and encoding results, using the XDR -filters specified when the remote procedure was registered. -.NH 2 -\&Assigning Program Numbers -.IX "program number assignment" -.IX "assigning program numbers" -.LP -Program numbers are assigned in groups of -.I 0x20000000 -according to the following chart: -.DS -.ft CW - 0x0 - 0x1fffffff \fRDefined by Sun\fP -0x20000000 - 0x3fffffff \fRDefined by user\fP -0x40000000 - 0x5fffffff \fRTransient\fP -0x60000000 - 0x7fffffff \fRReserved\fP -0x80000000 - 0x9fffffff \fRReserved\fP -0xa0000000 - 0xbfffffff \fRReserved\fP -0xc0000000 - 0xdfffffff \fRReserved\fP -0xe0000000 - 0xffffffff \fRReserved\fP -.ft R -.DE -Sun Microsystems administers the first group of numbers, which -should be identical for all Sun customers. If a customer -develops an application that might be of general interest, that -application should be given an assigned number in the first -range. The second group of numbers is reserved for specific -customer applications. This range is intended primarily for -debugging new programs. The third group is reserved for -applications that generate program numbers dynamically. The -final groups are reserved for future use, and should not be -used. -.LP -To register a protocol specification, send a request by network -mail to -.I rpc@sun -or write to: -.DS -RPC Administrator -Sun Microsystems -2550 Garcia Ave. -Mountain View, CA 94043 -.DE -Please include a compilable -.I rpcgen -\*Q.x\*U file describing your protocol. -You will be given a unique program number in return. -.IX RPC administration -.IX administration "of RPC" -.LP -The RPC program numbers and protocol specifications -of standard Sun RPC services can be -found in the include files in -.I "/usr/include/rpcsvc" . -These services, however, constitute only a small subset -of those which have been registered. The complete list of -registered programs, as of the time when this manual was -printed, is: -.LP -\fBTable 3-2\fI RPC Registered Programs\fR -.TS H -box tab (&) ; -lfBI lfBI lfBI -lfL lfL lfI . -RPC Number&Program&Description -_ -.TH -.sp.5 -100000&PMAPPROG&portmapper -100001&RSTATPROG&remote stats -100002&RUSERSPROG&remote users -100003&NFSPROG&nfs -100004&YPPROG&Yellow Pages -100005&MOUNTPROG&mount demon -100006&DBXPROG&remote dbx -100007&YPBINDPROG&yp binder -100008&WALLPROG&shutdown msg -100009&YPPASSWDPROG&yppasswd server -100010ÐERSTATPROGðer stats -100011&RQUOTAPROG&disk quotas -100012&SPRAYPROG&spray packets -100013&IBM3270PROG&3270 mapper -100014&IBMRJEPROG&RJE mapper -100015&SELNSVCPROG&selection service -100016&RDATABASEPROG&remote database access -100017&REXECPROG&remote execution -100018&ALICEPROG&Alice Office Automation -100019&SCHEDPROG&scheduling service -100020&LOCKPROG&local lock manager -100021&NETLOCKPROG&network lock manager -100022&X25PROG&x.25 inr protocol -100023&STATMON1PROG&status monitor 1 -100024&STATMON2PROG&status monitor 2 -100025&SELNLIBPROG&selection library -100026&BOOTPARAMPROG&boot parameters service -100027&MAZEPROG&mazewars game -100028&YPUPDATEPROG&yp update -100029&KEYSERVEPROG&key server -100030&SECURECMDPROG&secure login -100031&NETFWDIPROG&nfs net forwarder init -100032&NETFWDTPROG&nfs net forwarder trans -100033&SUNLINKMAP_PROG&sunlink MAP -100034&NETMONPROG&network monitor -100035&DBASEPROG&lightweight database -100036&PWDAUTHPROG&password authorization -100037&TFSPROG&translucent file svc -100038&NSEPROG&nse server -100039&NSE_ACTIVATE_PROG&nse activate daemon -.sp .2i -150001&PCNFSDPROG&pc passwd authorization -.sp .2i -200000&PYRAMIDLOCKINGPROG&Pyramid-locking -200001&PYRAMIDSYS5&Pyramid-sys5 -200002&CADDS_IMAGE&CV cadds_image -.sp .2i -300001&ADT_RFLOCKPROG&ADT file locking -.TE -.NH 2 -\&Passing Arbitrary Data Types -.IX "arbitrary data types" -.LP -In the previous example, the RPC call passes a single -.I "unsigned long" -RPC can handle arbitrary data structures, regardless of -different machines' byte orders or structure layout conventions, -by always converting them to a network standard called -.I "External Data Representation" -(XDR) before -sending them over the wire. -The process of converting from a particular machine representation -to XDR format is called -.I serializing , -and the reverse process is called -.I deserializing . -The type field parameters of -.I callrpc() -and -.I registerrpc() -can be a built-in procedure like -.I xdr_u_long() -in the previous example, or a user supplied one. -XDR has these built-in type routines: -.IX RPC "built-in routines" -.DS -.ft CW -xdr_int() xdr_u_int() xdr_enum() -xdr_long() xdr_u_long() xdr_bool() -xdr_short() xdr_u_short() xdr_wrapstring() -xdr_char() xdr_u_char() -.DE -Note that the routine -.I xdr_string() -exists, but cannot be used with -.I callrpc() -and -.I registerrpc (), -which only pass two parameters to their XDR routines. -.I xdr_wrapstring() -has only two parameters, and is thus OK. It calls -.I xdr_string (). -.LP -As an example of a user-defined type routine, -if you wanted to send the structure -.DS -.ft CW -struct simple { - int a; - short b; -} simple; -.DE -then you would call -.I callrpc() -as -.DS -.ft CW -callrpc(hostname, PROGNUM, VERSNUM, PROCNUM, - xdr_simple, &simple ...); -.DE -where -.I xdr_simple() -is written as: -.ie t .DS -.el .DS L -.ft CW -#include <rpc/rpc.h> - -xdr_simple(xdrsp, simplep) - XDR *xdrsp; - struct simple *simplep; -{ - if (!xdr_int(xdrsp, &simplep->a)) - return (0); - if (!xdr_short(xdrsp, &simplep->b)) - return (0); - return (1); -} -.DE -.LP -An XDR routine returns nonzero (true in the sense of C) if it -completes successfully, and zero otherwise. -A complete description of XDR is in the -.I "XDR Protocol Specification" -section of this manual, only few implementation examples are -given here. -.LP -In addition to the built-in primitives, -there are also the prefabricated building blocks: -.DS -.ft CW -xdr_array() xdr_bytes() xdr_reference() -xdr_vector() xdr_union() xdr_pointer() -xdr_string() xdr_opaque() -.DE -To send a variable array of integers, -you might package them up as a structure like this -.DS -.ft CW -struct varintarr { - int *data; - int arrlnth; -} arr; -.DE -and make an RPC call such as -.DS -.ft CW -callrpc(hostname, PROGNUM, VERSNUM, PROCNUM, - xdr_varintarr, &arr...); -.DE -with -.I xdr_varintarr() -defined as: -.ie t .DS -.el .DS L -.ft CW -xdr_varintarr(xdrsp, arrp) - XDR *xdrsp; - struct varintarr *arrp; -{ - return (xdr_array(xdrsp, &arrp->data, &arrp->arrlnth, - MAXLEN, sizeof(int), xdr_int)); -} -.DE -This routine takes as parameters the XDR handle, -a pointer to the array, a pointer to the size of the array, -the maximum allowable array size, -the size of each array element, -and an XDR routine for handling each array element. -.KS -.LP -If the size of the array is known in advance, one can use -.I xdr_vector (), -which serializes fixed-length arrays. -.ie t .DS -.el .DS L -.ft CW -int intarr[SIZE]; - -xdr_intarr(xdrsp, intarr) - XDR *xdrsp; - int intarr[]; -{ - int i; - - return (xdr_vector(xdrsp, intarr, SIZE, sizeof(int), - xdr_int)); -} -.DE -.KE -.LP -XDR always converts quantities to 4-byte multiples when serializing. -Thus, if either of the examples above involved characters -instead of integers, each character would occupy 32 bits. -That is the reason for the XDR routine -.I xdr_bytes() -which is like -.I xdr_array() -except that it packs characters; -.I xdr_bytes() -has four parameters, similar to the first four parameters of -.I xdr_array (). -For null-terminated strings, there is also the -.I xdr_string() -routine, which is the same as -.I xdr_bytes() -without the length parameter. -On serializing it gets the string length from -.I strlen (), -and on deserializing it creates a null-terminated string. -.LP -Here is a final example that calls the previously written -.I xdr_simple() -as well as the built-in functions -.I xdr_string() -and -.I xdr_reference (), -which chases pointers: -.ie t .DS -.el .DS L -.ft CW -struct finalexample { - char *string; - struct simple *simplep; -} finalexample; - -xdr_finalexample(xdrsp, finalp) - XDR *xdrsp; - struct finalexample *finalp; -{ - - if (!xdr_string(xdrsp, &finalp->string, MAXSTRLEN)) - return (0); - if (!xdr_reference(xdrsp, &finalp->simplep, - sizeof(struct simple), xdr_simple); - return (0); - return (1); -} -.DE -Note that we could as easily call -.I xdr_simple() -here instead of -.I xdr_reference (). -.NH 1 -\&Lowest Layer of RPC -.IX "lowest layer of RPC" -.IX "RPC" "lowest layer" -.LP -In the examples given so far, -RPC takes care of many details automatically for you. -In this section, we'll show you how you can change the defaults -by using lower layers of the RPC library. -It is assumed that you are familiar with sockets -and the system calls for dealing with them. -.LP -There are several occasions when you may need to use lower layers of -RPC. First, you may need to use TCP, since the higher layer uses UDP, -which restricts RPC calls to 8K bytes of data. Using TCP permits calls -to send long streams of data. -For an example, see the -.I TCP -section below. Second, you may want to allocate and free memory -while serializing or deserializing with XDR routines. -There is no call at the higher level to let -you free memory explicitly. -For more explanation, see the -.I "Memory Allocation with XDR" -section below. -Third, you may need to perform authentication -on either the client or server side, by supplying -credentials or verifying them. -See the explanation in the -.I Authentication -section below. -.NH 2 -\&More on the Server Side -.IX RPC "server side" -.LP -The server for the -.I nusers() -program shown below does the same thing as the one using -.I registerrpc() -above, but is written using a lower layer of the RPC package: -.ie t .DS -.el .DS L -.ft CW -#include <stdio.h> -#include <rpc/rpc.h> -#include <utmp.h> -#include <rpcsvc/rusers.h> - -main() -{ - SVCXPRT *transp; - int nuser(); - - transp = svcudp_create(RPC_ANYSOCK); - if (transp == NULL){ - fprintf(stderr, "can't create an RPC server\en"); - exit(1); - } - pmap_unset(RUSERSPROG, RUSERSVERS); - if (!svc_register(transp, RUSERSPROG, RUSERSVERS, - nuser, IPPROTO_UDP)) { - fprintf(stderr, "can't register RUSER service\en"); - exit(1); - } - svc_run(); /* \fINever returns\fP */ - fprintf(stderr, "should never reach this point\en"); -} - -nuser(rqstp, transp) - struct svc_req *rqstp; - SVCXPRT *transp; -{ - unsigned long nusers; - - switch (rqstp->rq_proc) { - case NULLPROC: - if (!svc_sendreply(transp, xdr_void, 0)) - fprintf(stderr, "can't reply to RPC call\en"); - return; - case RUSERSPROC_NUM: -.ft I - /* - * Code here to compute the number of users - * and assign it to the variable \fInusers\fP - */ -.ft CW - if (!svc_sendreply(transp, xdr_u_long, &nusers)) - fprintf(stderr, "can't reply to RPC call\en"); - return; - default: - svcerr_noproc(transp); - return; - } -} -.DE -.LP -First, the server gets a transport handle, which is used -for receiving and replying to RPC messages. -.I registerrpc() -uses -.I svcudp_create() -to get a UDP handle. -If you require a more reliable protocol, call -.I svctcp_create() -instead. -If the argument to -.I svcudp_create() -is -.I RPC_ANYSOCK -the RPC library creates a socket -on which to receive and reply to RPC calls. Otherwise, -.I svcudp_create() -expects its argument to be a valid socket number. -If you specify your own socket, it can be bound or unbound. -If it is bound to a port by the user, the port numbers of -.I svcudp_create() -and -.I clnttcp_create() -(the low-level client routine) must match. -.LP -If the user specifies the -.I RPC_ANYSOCK -argument, the RPC library routines will open sockets. -Otherwise they will expect the user to do so. The routines -.I svcudp_create() -and -.I clntudp_create() -will cause the RPC library routines to -.I bind() -their socket if it is not bound already. -.LP -A service may choose to register its port number with the -local portmapper service. This is done is done by specifying -a non-zero protocol number in -.I svc_register (). -Incidently, a client can discover the server's port number by -consulting the portmapper on their server's machine. This can -be done automatically by specifying a zero port number in -.I clntudp_create() -or -.I clnttcp_create (). -.LP -After creating an -.I SVCXPRT , -the next step is to call -.I pmap_unset() -so that if the -.I nusers() -server crashed earlier, -any previous trace of it is erased before restarting. -More precisely, -.I pmap_unset() -erases the entry for -.I RUSERSPROG -from the port mapper's tables. -.LP -Finally, we associate the program number for -.I nusers() -with the procedure -.I nuser (). -The final argument to -.I svc_register() -is normally the protocol being used, -which, in this case, is -.I IPPROTO_UDP -Notice that unlike -.I registerrpc (), -there are no XDR routines involved -in the registration process. -Also, registration is done on the program, -rather than procedure, level. -.LP -The user routine -.I nuser() -must call and dispatch the appropriate XDR routines -based on the procedure number. -Note that -two things are handled by -.I nuser() -that -.I registerrpc() -handles automatically. -The first is that procedure -.I NULLPROC -(currently zero) returns with no results. -This can be used as a simple test -for detecting if a remote program is running. -Second, there is a check for invalid procedure numbers. -If one is detected, -.I svcerr_noproc() -is called to handle the error. -.KS -.LP -The user service routine serializes the results and returns -them to the RPC caller via -.I svc_sendreply() -Its first parameter is the -.I SVCXPRT -handle, the second is the XDR routine, -and the third is a pointer to the data to be returned. -Not illustrated above is how a server -handles an RPC program that receives data. -As an example, we can add a procedure -.I RUSERSPROC_BOOL -which has an argument -.I nusers (), -and returns -.I TRUE -or -.I FALSE -depending on whether there are nusers logged on. -It would look like this: -.ie t .DS -.el .DS L -.ft CW -case RUSERSPROC_BOOL: { - int bool; - unsigned nuserquery; - - if (!svc_getargs(transp, xdr_u_int, &nuserquery) { - svcerr_decode(transp); - return; - } -.ft I - /* - * Code to set \fInusers\fP = number of users - */ -.ft CW - if (nuserquery == nusers) - bool = TRUE; - else - bool = FALSE; - if (!svc_sendreply(transp, xdr_bool, &bool)) { - fprintf(stderr, "can't reply to RPC call\en"); - return (1); - } - return; -} -.DE -.KE -.LP -The relevant routine is -.I svc_getargs() -which takes an -.I SVCXPRT -handle, the XDR routine, -and a pointer to where the input is to be placed as arguments. -.NH 2 -\&Memory Allocation with XDR -.IX "memory allocation with XDR" -.IX XDR "memory allocation" -.LP -XDR routines not only do input and output, -they also do memory allocation. -This is why the second parameter of -.I xdr_array() -is a pointer to an array, rather than the array itself. -If it is -.I NULL , -then -.I xdr_array() -allocates space for the array and returns a pointer to it, -putting the size of the array in the third argument. -As an example, consider the following XDR routine -.I xdr_chararr1() -which deals with a fixed array of bytes with length -.I SIZE . -.ie t .DS -.el .DS L -.ft CW -xdr_chararr1(xdrsp, chararr) - XDR *xdrsp; - char chararr[]; -{ - char *p; - int len; - - p = chararr; - len = SIZE; - return (xdr_bytes(xdrsp, &p, &len, SIZE)); -} -.DE -If space has already been allocated in -.I chararr , -it can be called from a server like this: -.ie t .DS -.el .DS L -.ft CW -char chararr[SIZE]; - -svc_getargs(transp, xdr_chararr1, chararr); -.DE -If you want XDR to do the allocation, -you would have to rewrite this routine in the following way: -.ie t .DS -.el .DS L -.ft CW -xdr_chararr2(xdrsp, chararrp) - XDR *xdrsp; - char **chararrp; -{ - int len; - - len = SIZE; - return (xdr_bytes(xdrsp, charrarrp, &len, SIZE)); -} -.DE -Then the RPC call might look like this: -.ie t .DS -.el .DS L -.ft CW -char *arrptr; - -arrptr = NULL; -svc_getargs(transp, xdr_chararr2, &arrptr); -.ft I -/* - * Use the result here - */ -.ft CW -svc_freeargs(transp, xdr_chararr2, &arrptr); -.DE -Note that, after being used, the character array can be freed with -.I svc_freeargs() -.I svc_freeargs() -will not attempt to free any memory if the variable indicating it -is NULL. For example, in the the routine -.I xdr_finalexample (), -given earlier, if -.I finalp->string -was NULL, then it would not be freed. The same is true for -.I finalp->simplep . -.LP -To summarize, each XDR routine is responsible -for serializing, deserializing, and freeing memory. -When an XDR routine is called from -.I callrpc() -the serializing part is used. -When called from -.I svc_getargs() -the deserializer is used. -And when called from -.I svc_freeargs() -the memory deallocator is used. When building simple examples like those -in this section, a user doesn't have to worry -about the three modes. -See the -.I "External Data Representation: Sun Technical Notes" -for examples of more sophisticated XDR routines that determine -which of the three modes they are in and adjust their behavior accordingly. -.KS -.NH 2 -\&The Calling Side -.IX RPC "calling side" -.LP -When you use -.I callrpc() -you have no control over the RPC delivery -mechanism or the socket used to transport the data. -To illustrate the layer of RPC that lets you adjust these -parameters, consider the following code to call the -.I nusers -service: -.ie t .DS -.el .DS L -.ft CW -.vs 11 -#include <stdio.h> -#include <rpc/rpc.h> -#include <utmp.h> -#include <rpcsvc/rusers.h> -#include <sys/socket.h> -#include <sys/time.h> -#include <netdb.h> - -main(argc, argv) - int argc; - char **argv; -{ - struct hostent *hp; - struct timeval pertry_timeout, total_timeout; - struct sockaddr_in server_addr; - int sock = RPC_ANYSOCK; - register CLIENT *client; - enum clnt_stat clnt_stat; - unsigned long nusers; - - if (argc != 2) { - fprintf(stderr, "usage: nusers hostname\en"); - exit(-1); - } - if ((hp = gethostbyname(argv[1])) == NULL) { - fprintf(stderr, "can't get addr for %s\en",argv[1]); - exit(-1); - } - pertry_timeout.tv_sec = 3; - pertry_timeout.tv_usec = 0; - bcopy(hp->h_addr, (caddr_t)&server_addr.sin_addr, - hp->h_length); - server_addr.sin_family = AF_INET; - server_addr.sin_port = 0; - if ((client = clntudp_create(&server_addr, RUSERSPROG, - RUSERSVERS, pertry_timeout, &sock)) == NULL) { - clnt_pcreateerror("clntudp_create"); - exit(-1); - } - total_timeout.tv_sec = 20; - total_timeout.tv_usec = 0; - clnt_stat = clnt_call(client, RUSERSPROC_NUM, xdr_void, - 0, xdr_u_long, &nusers, total_timeout); - if (clnt_stat != RPC_SUCCESS) { - clnt_perror(client, "rpc"); - exit(-1); - } - clnt_destroy(client); - close(sock); - exit(0); -} -.vs -.DE -.KE -The low-level version of -.I callrpc() -is -.I clnt_call() -which takes a -.I CLIENT -pointer rather than a host name. The parameters to -.I clnt_call() -are a -.I CLIENT -pointer, the procedure number, -the XDR routine for serializing the argument, -a pointer to the argument, -the XDR routine for deserializing the return value, -a pointer to where the return value will be placed, -and the time in seconds to wait for a reply. -.LP -The -.I CLIENT -pointer is encoded with the transport mechanism. -.I callrpc() -uses UDP, thus it calls -.I clntudp_create() -to get a -.I CLIENT -pointer. To get TCP (Transmission Control Protocol), you would use -.I clnttcp_create() . -.LP -The parameters to -.I clntudp_create() -are the server address, the program number, the version number, -a timeout value (between tries), and a pointer to a socket. -The final argument to -.I clnt_call() -is the total time to wait for a response. -Thus, the number of tries is the -.I clnt_call() -timeout divided by the -.I clntudp_create() -timeout. -.LP -Note that the -.I clnt_destroy() -call -always deallocates the space associated with the -.I CLIENT -handle. It closes the socket associated with the -.I CLIENT -handle, however, only if the RPC library opened it. It the -socket was opened by the user, it stays open. This makes it -possible, in cases where there are multiple client handles -using the same socket, to destroy one handle without closing -the socket that other handles are using. -.LP -To make a stream connection, the call to -.I clntudp_create() -is replaced with a call to -.I clnttcp_create() . -.DS -.ft CW -clnttcp_create(&server_addr, prognum, versnum, &sock, - inputsize, outputsize); -.DE -There is no timeout argument; instead, the receive and send buffer -sizes must be specified. When the -.I clnttcp_create() -call is made, a TCP connection is established. -All RPC calls using that -.I CLIENT -handle would use this connection. -The server side of an RPC call using TCP has -.I svcudp_create() -replaced by -.I svctcp_create() . -.DS -.ft CW -transp = svctcp_create(RPC_ANYSOCK, 0, 0); -.DE -The last two arguments to -.I svctcp_create() -are send and receive sizes respectively. If `0' is specified for -either of these, the system chooses a reasonable default. -.KS -.NH 1 -\&Other RPC Features -.IX "RPC" "miscellaneous features" -.IX "miscellaneous RPC features" -.LP -This section discusses some other aspects of RPC -that are occasionally useful. -.NH 2 -\&Select on the Server Side -.IX RPC select() RPC \fIselect()\fP -.IX select() "" \fIselect()\fP "on the server side" -.LP -Suppose a process is processing RPC requests -while performing some other activity. -If the other activity involves periodically updating a data structure, -the process can set an alarm signal before calling -.I svc_run() -But if the other activity -involves waiting on a a file descriptor, the -.I svc_run() -call won't work. -The code for -.I svc_run() -is as follows: -.ie t .DS -.el .DS L -.ft CW -.vs 11 -void -svc_run() -{ - fd_set readfds; - int dtbsz = getdtablesize(); - - for (;;) { - readfds = svc_fds; - switch (select(dtbsz, &readfds, NULL,NULL,NULL)) { - - case -1: - if (errno == EINTR) - continue; - perror("select"); - return; - case 0: - break; - default: - svc_getreqset(&readfds); - } - } -} -.vs -.DE -.KE -.LP -You can bypass -.I svc_run() -and call -.I svc_getreqset() -yourself. -All you need to know are the file descriptors -of the socket(s) associated with the programs you are waiting on. -Thus you can have your own -.I select() -.IX select() "" \fIselect()\fP -that waits on both the RPC socket, -and your own descriptors. Note that -.I svc_fds() -is a bit mask of all the file descriptors that RPC is using for -services. It can change everytime that -.I any -RPC library routine is called, because descriptors are constantly -being opened and closed, for example for TCP connections. -.NH 2 -\&Broadcast RPC -.IX "broadcast RPC" -.IX RPC "broadcast" -.LP -The -.I portmapper -is a daemon that converts RPC program numbers -into DARPA protocol port numbers; see the -.I portmap -man page. You can't do broadcast RPC without the portmapper. -Here are the main differences between -broadcast RPC and normal RPC calls: -.IP 1. -Normal RPC expects one answer, whereas -broadcast RPC expects many answers -(one or more answer from each responding machine). -.IP 2. -Broadcast RPC can only be supported by packet-oriented (connectionless) -transport protocols like UPD/IP. -.IP 3. -The implementation of broadcast RPC -treats all unsuccessful responses as garbage by filtering them out. -Thus, if there is a version mismatch between the -broadcaster and a remote service, -the user of broadcast RPC never knows. -.IP 4. -All broadcast messages are sent to the portmap port. -Thus, only services that register themselves with their portmapper -are accessible via the broadcast RPC mechanism. -.IP 5. -Broadcast requests are limited in size to the MTU (Maximum Transfer -Unit) of the local network. For Ethernet, the MTU is 1500 bytes. -.KS -.NH 3 -\&Broadcast RPC Synopsis -.IX "broadcast RPC" synopsis -.IX "RPC" "broadcast synopsis" -.ie t .DS -.el .DS L -.ft CW -#include <rpc/pmap_clnt.h> - . . . -enum clnt_stat clnt_stat; - . . . -clnt_stat = clnt_broadcast(prognum, versnum, procnum, - inproc, in, outproc, out, eachresult) - u_long prognum; /* \fIprogram number\fP */ - u_long versnum; /* \fIversion number\fP */ - u_long procnum; /* \fIprocedure number\fP */ - xdrproc_t inproc; /* \fIxdr routine for args\fP */ - caddr_t in; /* \fIpointer to args\fP */ - xdrproc_t outproc; /* \fIxdr routine for results\fP */ - caddr_t out; /* \fIpointer to results\fP */ - bool_t (*eachresult)();/* \fIcall with each result gotten\fP */ -.DE -.KE -The procedure -.I eachresult() -is called each time a valid result is obtained. -It returns a boolean that indicates -whether or not the user wants more responses. -.ie t .DS -.el .DS L -.ft CW -bool_t done; - . . . -done = eachresult(resultsp, raddr) - caddr_t resultsp; - struct sockaddr_in *raddr; /* \fIAddr of responding machine\fP */ -.DE -If -.I done -is -.I TRUE , -then broadcasting stops and -.I clnt_broadcast() -returns successfully. -Otherwise, the routine waits for another response. -The request is rebroadcast -after a few seconds of waiting. -If no responses come back, -the routine returns with -.I RPC_TIMEDOUT . -.NH 2 -\&Batching -.IX "batching" -.IX RPC "batching" -.LP -The RPC architecture is designed so that clients send a call message, -and wait for servers to reply that the call succeeded. -This implies that clients do not compute -while servers are processing a call. -This is inefficient if the client does not want or need -an acknowledgement for every message sent. -It is possible for clients to continue computing -while waiting for a response, -using RPC batch facilities. -.LP -RPC messages can be placed in a \*Qpipeline\*U of calls -to a desired server; this is called batching. -Batching assumes that: -1) each RPC call in the pipeline requires no response from the server, -and the server does not send a response message; and -2) the pipeline of calls is transported on a reliable -byte stream transport such as TCP/IP. -Since the server does not respond to every call, -the client can generate new calls in parallel -with the server executing previous calls. -Furthermore, the TCP/IP implementation can buffer up -many call messages, and send them to the server in one -.I write() -system call. This overlapped execution -greatly decreases the interprocess communication overhead of -the client and server processes, -and the total elapsed time of a series of calls. -.LP -Since the batched calls are buffered, -the client should eventually do a nonbatched call -in order to flush the pipeline. -.LP -A contrived example of batching follows. -Assume a string rendering service (like a window system) -has two similar calls: one renders a string and returns void results, -while the other renders a string and remains silent. -The service (using the TCP/IP transport) may look like: -.ie t .DS -.el .DS L -.ft CW -#include <stdio.h> -#include <rpc/rpc.h> -#include <suntool/windows.h> - -void windowdispatch(); - -main() -{ - SVCXPRT *transp; - - transp = svctcp_create(RPC_ANYSOCK, 0, 0); - if (transp == NULL){ - fprintf(stderr, "can't create an RPC server\en"); - exit(1); - } - pmap_unset(WINDOWPROG, WINDOWVERS); - if (!svc_register(transp, WINDOWPROG, WINDOWVERS, - windowdispatch, IPPROTO_TCP)) { - fprintf(stderr, "can't register WINDOW service\en"); - exit(1); - } - svc_run(); /* \fINever returns\fP */ - fprintf(stderr, "should never reach this point\en"); -} - -void -windowdispatch(rqstp, transp) - struct svc_req *rqstp; - SVCXPRT *transp; -{ - char *s = NULL; - - switch (rqstp->rq_proc) { - case NULLPROC: - if (!svc_sendreply(transp, xdr_void, 0)) - fprintf(stderr, "can't reply to RPC call\en"); - return; - case RENDERSTRING: - if (!svc_getargs(transp, xdr_wrapstring, &s)) { - fprintf(stderr, "can't decode arguments\en"); -.ft I - /* - * Tell caller he screwed up - */ -.ft CW - svcerr_decode(transp); - break; - } -.ft I - /* - * Code here to render the string \fIs\fP - */ -.ft CW - if (!svc_sendreply(transp, xdr_void, NULL)) - fprintf(stderr, "can't reply to RPC call\en"); - break; - case RENDERSTRING_BATCHED: - if (!svc_getargs(transp, xdr_wrapstring, &s)) { - fprintf(stderr, "can't decode arguments\en"); -.ft I - /* - * We are silent in the face of protocol errors - */ -.ft CW - break; - } -.ft I - /* - * Code here to render string s, but send no reply! - */ -.ft CW - break; - default: - svcerr_noproc(transp); - return; - } -.ft I - /* - * Now free string allocated while decoding arguments - */ -.ft CW - svc_freeargs(transp, xdr_wrapstring, &s); -} -.DE -Of course the service could have one procedure -that takes the string and a boolean -to indicate whether or not the procedure should respond. -.LP -In order for a client to take advantage of batching, -the client must perform RPC calls on a TCP-based transport -and the actual calls must have the following attributes: -1) the result's XDR routine must be zero -.I NULL ), -and 2) the RPC call's timeout must be zero. -.KS -.LP -Here is an example of a client that uses batching to render a -bunch of strings; the batching is flushed when the client gets -a null string (EOF): -.ie t .DS -.el .DS L -.ft CW -.vs 11 -#include <stdio.h> -#include <rpc/rpc.h> -#include <sys/socket.h> -#include <sys/time.h> -#include <netdb.h> -#include <suntool/windows.h> - -main(argc, argv) - int argc; - char **argv; -{ - struct hostent *hp; - struct timeval pertry_timeout, total_timeout; - struct sockaddr_in server_addr; - int sock = RPC_ANYSOCK; - register CLIENT *client; - enum clnt_stat clnt_stat; - char buf[1000], *s = buf; - - if ((client = clnttcp_create(&server_addr, - WINDOWPROG, WINDOWVERS, &sock, 0, 0)) == NULL) { - perror("clnttcp_create"); - exit(-1); - } - total_timeout.tv_sec = 0; - total_timeout.tv_usec = 0; - while (scanf("%s", s) != EOF) { - clnt_stat = clnt_call(client, RENDERSTRING_BATCHED, - xdr_wrapstring, &s, NULL, NULL, total_timeout); - if (clnt_stat != RPC_SUCCESS) { - clnt_perror(client, "batched rpc"); - exit(-1); - } - } - - /* \fINow flush the pipeline\fP */ - - total_timeout.tv_sec = 20; - clnt_stat = clnt_call(client, NULLPROC, xdr_void, NULL, - xdr_void, NULL, total_timeout); - if (clnt_stat != RPC_SUCCESS) { - clnt_perror(client, "rpc"); - exit(-1); - } - clnt_destroy(client); - exit(0); -} -.vs -.DE -.KE -Since the server sends no message, -the clients cannot be notified of any of the failures that may occur. -Therefore, clients are on their own when it comes to handling errors. -.LP -The above example was completed to render -all of the (2000) lines in the file -.I /etc/termcap . -The rendering service did nothing but throw the lines away. -The example was run in the following four configurations: -1) machine to itself, regular RPC; -2) machine to itself, batched RPC; -3) machine to another, regular RPC; and -4) machine to another, batched RPC. -The results are as follows: -1) 50 seconds; -2) 16 seconds; -3) 52 seconds; -4) 10 seconds. -Running -.I fscanf() -on -.I /etc/termcap -only requires six seconds. -These timings show the advantage of protocols -that allow for overlapped execution, -though these protocols are often hard to design. -.NH 2 -\&Authentication -.IX "authentication" -.IX "RPC" "authentication" -.LP -In the examples presented so far, -the caller never identified itself to the server, -and the server never required an ID from the caller. -Clearly, some network services, such as a network filesystem, -require stronger security than what has been presented so far. -.LP -In reality, every RPC call is authenticated by -the RPC package on the server, and similarly, -the RPC client package generates and sends authentication parameters. -Just as different transports (TCP/IP or UDP/IP) -can be used when creating RPC clients and servers, -different forms of authentication can be associated with RPC clients; -the default authentication type used as a default is type -.I none . -.LP -The authentication subsystem of the RPC package is open ended. -That is, numerous types of authentication are easy to support. -.NH 3 -\&UNIX Authentication -.IX "UNIX Authentication" -.IP "\fIThe Client Side\fP" -.LP -When a caller creates a new RPC client handle as in: -.DS -.ft CW -clnt = clntudp_create(address, prognum, versnum, - wait, sockp) -.DE -the appropriate transport instance defaults -the associate authentication handle to be -.DS -.ft CW -clnt->cl_auth = authnone_create(); -.DE -The RPC client can choose to use -.I UNIX -style authentication by setting -.I clnt\->cl_auth -after creating the RPC client handle: -.DS -.ft CW -clnt->cl_auth = authunix_create_default(); -.DE -This causes each RPC call associated with -.I clnt -to carry with it the following authentication credentials structure: -.ie t .DS -.el .DS L -.ft I -/* - * UNIX style credentials. - */ -.ft CW -struct authunix_parms { - u_long aup_time; /* \fIcredentials creation time\fP */ - char *aup_machname; /* \fIhost name where client is\fP */ - int aup_uid; /* \fIclient's UNIX effective uid\fP */ - int aup_gid; /* \fIclient's current group id\fP */ - u_int aup_len; /* \fIelement length of aup_gids\fP */ - int *aup_gids; /* \fIarray of groups user is in\fP */ -}; -.DE -These fields are set by -.I authunix_create_default() -by invoking the appropriate system calls. -Since the RPC user created this new style of authentication, -the user is responsible for destroying it with: -.DS -.ft CW -auth_destroy(clnt->cl_auth); -.DE -This should be done in all cases, to conserve memory. -.sp -.IP "\fIThe Server Side\fP" -.LP -Service implementors have a harder time dealing with authentication issues -since the RPC package passes the service dispatch routine a request -that has an arbitrary authentication style associated with it. -Consider the fields of a request handle passed to a service dispatch routine: -.ie t .DS -.el .DS L -.ft I -/* - * An RPC Service request - */ -.ft CW -struct svc_req { - u_long rq_prog; /* \fIservice program number\fP */ - u_long rq_vers; /* \fIservice protocol vers num\fP */ - u_long rq_proc; /* \fIdesired procedure number\fP */ - struct opaque_auth rq_cred; /* \fIraw credentials from wire\fP */ - caddr_t rq_clntcred; /* \fIcredentials (read only)\fP */ -}; -.DE -The -.I rq_cred -is mostly opaque, except for one field of interest: -the style or flavor of authentication credentials: -.ie t .DS -.el .DS L -.ft I -/* - * Authentication info. Mostly opaque to the programmer. - */ -.ft CW -struct opaque_auth { - enum_t oa_flavor; /* \fIstyle of credentials\fP */ - caddr_t oa_base; /* \fIaddress of more auth stuff\fP */ - u_int oa_length; /* \fInot to exceed \fIMAX_AUTH_BYTES */ -}; -.DE -.IX RPC guarantees -The RPC package guarantees the following -to the service dispatch routine: -.IP 1. -That the request's -.I rq_cred -is well formed. Thus the service implementor may inspect the request's -.I rq_cred.oa_flavor -to determine which style of authentication the caller used. -The service implementor may also wish to inspect the other fields of -.I rq_cred -if the style is not one of the styles supported by the RPC package. -.IP 2. -That the request's -.I rq_clntcred -field is either -.I NULL -or points to a well formed structure -that corresponds to a supported style of authentication credentials. -Remember that only -.I unix -style is currently supported, so (currently) -.I rq_clntcred -could be cast to a pointer to an -.I authunix_parms -structure. If -.I rq_clntcred -is -.I NULL , -the service implementor may wish to inspect the other (opaque) fields of -.I rq_cred -in case the service knows about a new type of authentication -that the RPC package does not know about. -.LP -Our remote users service example can be extended so that -it computes results for all users except UID 16: -.ie t .DS -.el .DS L -.ft CW -.vs 11 -nuser(rqstp, transp) - struct svc_req *rqstp; - SVCXPRT *transp; -{ - struct authunix_parms *unix_cred; - int uid; - unsigned long nusers; - -.ft I - /* - * we don't care about authentication for null proc - */ -.ft CW - if (rqstp->rq_proc == NULLPROC) { - if (!svc_sendreply(transp, xdr_void, 0)) { - fprintf(stderr, "can't reply to RPC call\en"); - return (1); - } - return; - } -.ft I - /* - * now get the uid - */ -.ft CW - switch (rqstp->rq_cred.oa_flavor) { - case AUTH_UNIX: - unix_cred = - (struct authunix_parms *)rqstp->rq_clntcred; - uid = unix_cred->aup_uid; - break; - case AUTH_NULL: - default: - svcerr_weakauth(transp); - return; - } - switch (rqstp->rq_proc) { - case RUSERSPROC_NUM: -.ft I - /* - * make sure caller is allowed to call this proc - */ -.ft CW - if (uid == 16) { - svcerr_systemerr(transp); - return; - } -.ft I - /* - * Code here to compute the number of users - * and assign it to the variable \fInusers\fP - */ -.ft CW - if (!svc_sendreply(transp, xdr_u_long, &nusers)) { - fprintf(stderr, "can't reply to RPC call\en"); - return (1); - } - return; - default: - svcerr_noproc(transp); - return; - } -} -.vs -.DE -A few things should be noted here. -First, it is customary not to check -the authentication parameters associated with the -.I NULLPROC -(procedure number zero). -Second, if the authentication parameter's type is not suitable -for your service, you should call -.I svcerr_weakauth() . -And finally, the service protocol itself should return status -for access denied; in the case of our example, the protocol -does not have such a status, so we call the service primitive -.I svcerr_systemerr() -instead. -.LP -The last point underscores the relation between -the RPC authentication package and the services; -RPC deals only with -.I authentication -and not with individual services' -.I "access control" . -The services themselves must implement their own access control policies -and reflect these policies as return statuses in their protocols. -.NH 2 -\&DES Authentication -.IX RPC DES -.IX RPC authentication -.LP -UNIX authentication is quite easy to defeat. Instead of using -.I authunix_create_default (), -one can call -.I authunix_create() -and then modify the RPC authentication handle it returns by filling in -whatever user ID and hostname they wish the server to think they have. -DES authentication is thus recommended for people who want more security -than UNIX authentication offers. -.LP -The details of the DES authentication protocol are complicated and -are not explained here. -See -.I "Remote Procedure Calls: Protocol Specification" -for the details. -.LP -In order for DES authentication to work, the -.I keyserv(8c) -daemon must be running on both the server and client machines. The -users on these machines need public keys assigned by the network -administrator in the -.I publickey(5) -database. And, they need to have decrypted their secret keys -using their login password. This automatically happens when one -logs in using -.I login(1) , -or can be done manually using -.I keylogin(1) . -The -.I "Network Services" -chapter -./" XXX -explains more how to setup secure networking. -.sp -.IP "\fIClient Side\fP" -.LP -If a client wishes to use DES authentication, it must set its -authentication handle appropriately. Here is an example: -.DS -cl->cl_auth = - authdes_create(servername, 60, &server_addr, NULL); -.DE -The first argument is the network name or \*Qnetname\*U of the owner of -the server process. Typically, server processes are root processes -and their netname can be derived using the following call: -.DS -char servername[MAXNETNAMELEN]; - -host2netname(servername, rhostname, NULL); -.DE -Here, -.I rhostname -is the hostname of the machine the server process is running on. -.I host2netname() -fills in -.I servername -to contain this root process's netname. If the -server process was run by a regular user, one could use the call -.I user2netname() -instead. Here is an example for a server process with the same user -ID as the client: -.DS -char servername[MAXNETNAMELEN]; - -user2netname(servername, getuid(), NULL); -.DE -The last argument to both of these calls, -.I user2netname() -and -.I host2netname (), -is the name of the naming domain where the server is located. The -.I NULL -used here means \*Quse the local domain name.\*U -.LP -The second argument to -.I authdes_create() -is a lifetime for the credential. Here it is set to sixty -seconds. What that means is that the credential will expire 60 -seconds from now. If some mischievous user tries to reuse the -credential, the server RPC subsystem will recognize that it has -expired and not grant any requests. If the same mischievous user -tries to reuse the credential within the sixty second lifetime, -he will still be rejected because the server RPC subsystem -remembers which credentials it has already seen in the near past, -and will not grant requests to duplicates. -.LP -The third argument to -.I authdes_create() -is the address of the host to synchronize with. In order for DES -authentication to work, the server and client must agree upon the -time. Here we pass the address of the server itself, so the -client and server will both be using the same time: the server's -time. The argument can be -.I NULL , -which means \*Qdon't bother synchronizing.\*U You should only do this -if you are sure the client and server are already synchronized. -.LP -The final argument to -.I authdes_create() -is the address of a DES encryption key to use for encrypting -timestamps and data. If this argument is -.I NULL , -as it is in this example, a random key will be chosen. The client -may find out the encryption key being used by consulting the -.I ah_key -field of the authentication handle. -.sp -.IP "\fIServer Side\fP" -.LP -The server side is a lot simpler than the client side. Here is the -previous example rewritten to use -.I AUTH_DES -instead of -.I AUTH_UNIX : -.ie t .DS -.el .DS L -.ft CW -.vs 11 -#include <sys/time.h> -#include <rpc/auth_des.h> - . . . - . . . -nuser(rqstp, transp) - struct svc_req *rqstp; - SVCXPRT *transp; -{ - struct authdes_cred *des_cred; - int uid; - int gid; - int gidlen; - int gidlist[10]; -.ft I - /* - * we don't care about authentication for null proc - */ -.ft CW - - if (rqstp->rq_proc == NULLPROC) { - /* \fIsame as before\fP */ - } - -.ft I - /* - * now get the uid - */ -.ft CW - switch (rqstp->rq_cred.oa_flavor) { - case AUTH_DES: - des_cred = - (struct authdes_cred *) rqstp->rq_clntcred; - if (! netname2user(des_cred->adc_fullname.name, - &uid, &gid, &gidlen, gidlist)) - { - fprintf(stderr, "unknown user: %s\n", - des_cred->adc_fullname.name); - svcerr_systemerr(transp); - return; - } - break; - case AUTH_NULL: - default: - svcerr_weakauth(transp); - return; - } - -.ft I - /* - * The rest is the same as before - */ -.ft CW -.vs -.DE -Note the use of the routine -.I netname2user (), -the inverse of -.I user2netname (): -it takes a network ID and converts to a unix ID. -.I netname2user () -also supplies the group IDs which we don't use in this example, -but which may be useful to other UNIX programs. -.NH 2 -\&Using Inetd -.IX inetd "" "using \fIinetd\fP" -.LP -An RPC server can be started from -.I inetd -The only difference from the usual code is that the service -creation routine should be called in the following form: -.ie t .DS -.el .DS L -.ft CW -transp = svcudp_create(0); /* \fIFor UDP\fP */ -transp = svctcp_create(0,0,0); /* \fIFor listener TCP sockets\fP */ -transp = svcfd_create(0,0,0); /* \fIFor connected TCP sockets\fP */ -.DE -since -.I inet -passes a socket as file descriptor 0. -Also, -.I svc_register() -should be called as -.ie t .DS -.el .DS L -.ft CW -svc_register(transp, PROGNUM, VERSNUM, service, 0); -.DE -with the final flag as 0, -since the program would already be registered by -.I inetd -Remember that if you want to exit -from the server process and return control to -.I inet -you need to explicitly exit, since -.I svc_run() -never returns. -.LP -The format of entries in -.I /etc/inetd.conf -for RPC services is in one of the following two forms: -.ie t .DS -.el .DS L -.ft CW -p_name/version dgram rpc/udp wait/nowait user server args -p_name/version stream rpc/tcp wait/nowait user server args -.DE -where -.I p_name -is the symbolic name of the program as it appears in -.I rpc(5) , -.I server -is the program implementing the server, -and -.I program -and -.I version -are the program and version numbers of the service. -For more information, see -.I inetd.conf(5) . -.LP -If the same program handles multiple versions, -then the version number can be a range, -as in this example: -.ie t .DS -.el .DS L -.ft CW -rstatd/1-2 dgram rpc/udp wait root /usr/etc/rpc.rstatd -.DE -.NH 1 -\&More Examples -.sp 1 -.NH 2 -\&Versions -.IX "versions" -.IX "RPC" "versions" -.LP -By convention, the first version number of program -.I PROG -is -.I PROGVERS_ORIG -and the most recent version is -.I PROGVERS -Suppose there is a new version of the -.I user -program that returns an -.I "unsigned short" -rather than a -.I long . -If we name this version -.I RUSERSVERS_SHORT -then a server that wants to support both versions -would do a double register. -.ie t .DS -.el .DS L -.ft CW -if (!svc_register(transp, RUSERSPROG, RUSERSVERS_ORIG, - nuser, IPPROTO_TCP)) { - fprintf(stderr, "can't register RUSER service\en"); - exit(1); -} -if (!svc_register(transp, RUSERSPROG, RUSERSVERS_SHORT, - nuser, IPPROTO_TCP)) { - fprintf(stderr, "can't register RUSER service\en"); - exit(1); -} -.DE -Both versions can be handled by the same C procedure: -.ie t .DS -.el .DS L -.ft CW -.vs 11 -nuser(rqstp, transp) - struct svc_req *rqstp; - SVCXPRT *transp; -{ - unsigned long nusers; - unsigned short nusers2; - - switch (rqstp->rq_proc) { - case NULLPROC: - if (!svc_sendreply(transp, xdr_void, 0)) { - fprintf(stderr, "can't reply to RPC call\en"); - return (1); - } - return; - case RUSERSPROC_NUM: -.ft I - /* - * Code here to compute the number of users - * and assign it to the variable \fInusers\fP - */ -.ft CW - nusers2 = nusers; - switch (rqstp->rq_vers) { - case RUSERSVERS_ORIG: - if (!svc_sendreply(transp, xdr_u_long, - &nusers)) { - fprintf(stderr,"can't reply to RPC call\en"); - } - break; - case RUSERSVERS_SHORT: - if (!svc_sendreply(transp, xdr_u_short, - &nusers2)) { - fprintf(stderr,"can't reply to RPC call\en"); - } - break; - } - default: - svcerr_noproc(transp); - return; - } -} -.vs -.DE -.KS -.NH 2 -\&TCP -.IX "TCP" -.LP -Here is an example that is essentially -.I rcp. -The initiator of the RPC -.I snd -call takes its standard input and sends it to the server -.I rcv -which prints it on standard output. -The RPC call uses TCP. -This also illustrates an XDR procedure that behaves differently -on serialization than on deserialization. -.ie t .DS -.el .DS L -.vs 11 -.ft I -/* - * The xdr routine: - * on decode, read from wire, write onto fp - * on encode, read from fp, write onto wire - */ -.ft CW -#include <stdio.h> -#include <rpc/rpc.h> - -xdr_rcp(xdrs, fp) - XDR *xdrs; - FILE *fp; -{ - unsigned long size; - char buf[BUFSIZ], *p; - - if (xdrs->x_op == XDR_FREE)/* nothing to free */ - return 1; - while (1) { - if (xdrs->x_op == XDR_ENCODE) { - if ((size = fread(buf, sizeof(char), BUFSIZ, - fp)) == 0 && ferror(fp)) { - fprintf(stderr, "can't fread\en"); - return (1); - } - } - p = buf; - if (!xdr_bytes(xdrs, &p, &size, BUFSIZ)) - return 0; - if (size == 0) - return 1; - if (xdrs->x_op == XDR_DECODE) { - if (fwrite(buf, sizeof(char), size, - fp) != size) { - fprintf(stderr, "can't fwrite\en"); - return (1); - } - } - } -} -.vs -.DE -.KE -.ie t .DS -.el .DS L -.vs 11 -.ft I -/* - * The sender routines - */ -.ft CW -#include <stdio.h> -#include <netdb.h> -#include <rpc/rpc.h> -#include <sys/socket.h> -#include <sys/time.h> - -main(argc, argv) - int argc; - char **argv; -{ - int xdr_rcp(); - int err; - - if (argc < 2) { - fprintf(stderr, "usage: %s servername\en", argv[0]); - exit(-1); - } - if ((err = callrpctcp(argv[1], RCPPROG, RCPPROC, - RCPVERS, xdr_rcp, stdin, xdr_void, 0) != 0)) { - clnt_perrno(err); - fprintf(stderr, "can't make RPC call\en"); - exit(1); - } - exit(0); -} - -callrpctcp(host, prognum, procnum, versnum, - inproc, in, outproc, out) - char *host, *in, *out; - xdrproc_t inproc, outproc; -{ - struct sockaddr_in server_addr; - int socket = RPC_ANYSOCK; - enum clnt_stat clnt_stat; - struct hostent *hp; - register CLIENT *client; - struct timeval total_timeout; - - if ((hp = gethostbyname(host)) == NULL) { - fprintf(stderr, "can't get addr for '%s'\en", host); - return (-1); - } - bcopy(hp->h_addr, (caddr_t)&server_addr.sin_addr, - hp->h_length); - server_addr.sin_family = AF_INET; - server_addr.sin_port = 0; - if ((client = clnttcp_create(&server_addr, prognum, - versnum, &socket, BUFSIZ, BUFSIZ)) == NULL) { - perror("rpctcp_create"); - return (-1); - } - total_timeout.tv_sec = 20; - total_timeout.tv_usec = 0; - clnt_stat = clnt_call(client, procnum, - inproc, in, outproc, out, total_timeout); - clnt_destroy(client); - return (int)clnt_stat; -} -.vs -.DE -.ie t .DS -.el .DS L -.vs 11 -.ft I -/* - * The receiving routines - */ -.ft CW -#include <stdio.h> -#include <rpc/rpc.h> - -main() -{ - register SVCXPRT *transp; - int rcp_service(), xdr_rcp(); - - if ((transp = svctcp_create(RPC_ANYSOCK, - BUFSIZ, BUFSIZ)) == NULL) { - fprintf("svctcp_create: error\en"); - exit(1); - } - pmap_unset(RCPPROG, RCPVERS); - if (!svc_register(transp, - RCPPROG, RCPVERS, rcp_service, IPPROTO_TCP)) { - fprintf(stderr, "svc_register: error\en"); - exit(1); - } - svc_run(); /* \fInever returns\fP */ - fprintf(stderr, "svc_run should never return\en"); -} - -rcp_service(rqstp, transp) - register struct svc_req *rqstp; - register SVCXPRT *transp; -{ - switch (rqstp->rq_proc) { - case NULLPROC: - if (svc_sendreply(transp, xdr_void, 0) == 0) { - fprintf(stderr, "err: rcp_service"); - return (1); - } - return; - case RCPPROC_FP: - if (!svc_getargs(transp, xdr_rcp, stdout)) { - svcerr_decode(transp); - return; - } - if (!svc_sendreply(transp, xdr_void, 0)) { - fprintf(stderr, "can't reply\en"); - return; - } - return (0); - default: - svcerr_noproc(transp); - return; - } -} -.vs -.DE -.NH 2 -\&Callback Procedures -.IX RPC "callback procedures" -.LP -Occasionally, it is useful to have a server become a client, -and make an RPC call back to the process which is its client. -An example is remote debugging, -where the client is a window system program, -and the server is a debugger running on the remote machine. -Most of the time, -the user clicks a mouse button at the debugging window, -which converts this to a debugger command, -and then makes an RPC call to the server -(where the debugger is actually running), -telling it to execute that command. -However, when the debugger hits a breakpoint, the roles are reversed, -and the debugger wants to make an rpc call to the window program, -so that it can inform the user that a breakpoint has been reached. -.LP -In order to do an RPC callback, -you need a program number to make the RPC call on. -Since this will be a dynamically generated program number, -it should be in the transient range, -.I "0x40000000 - 0x5fffffff" . -The routine -.I gettransient() -returns a valid program number in the transient range, -and registers it with the portmapper. -It only talks to the portmapper running on the same machine as the -.I gettransient() -routine itself. The call to -.I pmap_set() -is a test and set operation, -in that it indivisibly tests whether a program number -has already been registered, -and if it has not, then reserves it. On return, the -.I sockp -argument will contain a socket that can be used -as the argument to an -.I svcudp_create() -or -.I svctcp_create() -call. -.ie t .DS -.el .DS L -.ft CW -.vs 11 -#include <stdio.h> -#include <rpc/rpc.h> -#include <sys/socket.h> - -gettransient(proto, vers, sockp) - int proto, vers, *sockp; -{ - static int prognum = 0x40000000; - int s, len, socktype; - struct sockaddr_in addr; - - switch(proto) { - case IPPROTO_UDP: - socktype = SOCK_DGRAM; - break; - case IPPROTO_TCP: - socktype = SOCK_STREAM; - break; - default: - fprintf(stderr, "unknown protocol type\en"); - return 0; - } - if (*sockp == RPC_ANYSOCK) { - if ((s = socket(AF_INET, socktype, 0)) < 0) { - perror("socket"); - return (0); - } - *sockp = s; - } - else - s = *sockp; - addr.sin_addr.s_addr = 0; - addr.sin_family = AF_INET; - addr.sin_port = 0; - len = sizeof(addr); -.ft I - /* - * may be already bound, so don't check for error - */ -.ft CW - bind(s, &addr, len); - if (getsockname(s, &addr, &len)< 0) { - perror("getsockname"); - return (0); - } - while (!pmap_set(prognum++, vers, proto, - ntohs(addr.sin_port))) continue; - return (prognum-1); -} -.vs -.DE -.SH -Note: -.I -The call to -.I ntohs() -is necessary to ensure that the port number in -.I "addr.sin_port" , -which is in -.I network -byte order, is passed in -.I host -byte order (as -.I pmap_set() -expects). See the -.I byteorder(3N) -man page for more details on the conversion of network -addresses from network to host byte order. -.KS -.LP -The following pair of programs illustrate how to use the -.I gettransient() -routine. -The client makes an RPC call to the server, -passing it a transient program number. -Then the client waits around to receive a callback -from the server at that program number. -The server registers the program -.I EXAMPLEPROG -so that it can receive the RPC call -informing it of the callback program number. -Then at some random time (on receiving an -.I ALRM -signal in this example), it sends a callback RPC call, -using the program number it received earlier. -.ie t .DS -.el .DS L -.vs 11 -.ft I -/* - * client - */ -.ft CW -#include <stdio.h> -#include <rpc/rpc.h> - -int callback(); -char hostname[256]; - -main() -{ - int x, ans, s; - SVCXPRT *xprt; - - gethostname(hostname, sizeof(hostname)); - s = RPC_ANYSOCK; - x = gettransient(IPPROTO_UDP, 1, &s); - fprintf(stderr, "client gets prognum %d\en", x); - if ((xprt = svcudp_create(s)) == NULL) { - fprintf(stderr, "rpc_server: svcudp_create\en"); - exit(1); - } -.ft I - /* protocol is 0 - gettransient does registering - */ -.ft CW - (void)svc_register(xprt, x, 1, callback, 0); - ans = callrpc(hostname, EXAMPLEPROG, EXAMPLEVERS, - EXAMPLEPROC_CALLBACK, xdr_int, &x, xdr_void, 0); - if ((enum clnt_stat) ans != RPC_SUCCESS) { - fprintf(stderr, "call: "); - clnt_perrno(ans); - fprintf(stderr, "\en"); - } - svc_run(); - fprintf(stderr, "Error: svc_run shouldn't return\en"); -} - -callback(rqstp, transp) - register struct svc_req *rqstp; - register SVCXPRT *transp; -{ - switch (rqstp->rq_proc) { - case 0: - if (!svc_sendreply(transp, xdr_void, 0)) { - fprintf(stderr, "err: exampleprog\en"); - return (1); - } - return (0); - case 1: - if (!svc_getargs(transp, xdr_void, 0)) { - svcerr_decode(transp); - return (1); - } - fprintf(stderr, "client got callback\en"); - if (!svc_sendreply(transp, xdr_void, 0)) { - fprintf(stderr, "err: exampleprog"); - return (1); - } - } -} -.vs -.DE -.KE -.ie t .DS -.el .DS L -.vs 11 -.ft I -/* - * server - */ -.ft CW -#include <stdio.h> -#include <rpc/rpc.h> -#include <sys/signal.h> - -char *getnewprog(); -char hostname[256]; -int docallback(); -int pnum; /* \fIprogram number for callback routine\fP */ - -main() -{ - gethostname(hostname, sizeof(hostname)); - registerrpc(EXAMPLEPROG, EXAMPLEVERS, - EXAMPLEPROC_CALLBACK, getnewprog, xdr_int, xdr_void); - fprintf(stderr, "server going into svc_run\en"); - signal(SIGALRM, docallback); - alarm(10); - svc_run(); - fprintf(stderr, "Error: svc_run shouldn't return\en"); -} - -char * -getnewprog(pnump) - char *pnump; -{ - pnum = *(int *)pnump; - return NULL; -} - -docallback() -{ - int ans; - - ans = callrpc(hostname, pnum, 1, 1, xdr_void, 0, - xdr_void, 0); - if (ans != 0) { - fprintf(stderr, "server: "); - clnt_perrno(ans); - fprintf(stderr, "\en"); - } -} -.vs -.DE |
