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IETF RFC 1833
Binding Protocols for ONC RPC Version 2
Last modified on Tuesday, August 8th, 1995
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Network Working Group R. Srinivasan
Request for Comments: 1833 Sun Microsystems
Category: Standards Track August 1995
Binding Protocols for ONC RPC Version 2
 Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract
This document describes the binding protocols used in conjunction
with the ONC Remote Procedure Call (ONC RPC Version 2) protocols.
TABLE OF CONTENTS
1. Introduction 1
2. RPCBIND Program Protocol 2
2.1 RPCBIND Protocol Specification (in RPC Language) 3
2.2 RPCBIND Operation 9
2.2.1 RPCBIND Version 3 9
2.2.2 RPCBIND, Version 4 10
3. Port Mapper Program Protocol 11
3.1 Port Mapper Protocol Specification (in RPC Language) 11
3.2 Port Mapper Operation 13
References 14
Security Considerations 14
Author's Address 14
1. Introduction
This document specifies the binding protocols used in conjunction
with ONC RPC Version 2. As a prerequisite, the reader is expected to
be familiar with [1] and [2] which describe the ONC RPC Version 2 and
XDR (eXternal Data Representation) protocols.
An RPC service is identified by its RPC program number, version
number, and the transport address where it may be reached. The
transport address, in turn, consists of a network address and a
transport selector. In the case of a service available over TCP/IP
or UDP/IP, the network address will be an IP address, and the
transport selector will be a TCP or UDP port number.
Srinivasan Standards Track PAGE 1 
RFC 1833 Binding Protocols for ONC RPC Version 2 August 1995
A client program needs to know the RPC program number, version
number, and the transport address corresponding to a service in order
to utilize the service. Of these, the RPC program number and version
number are usually built into the client program, as part of the
service definition. The network address component of the transport
address is usually available in a name service, or is given as a
parameter to the client program. The transport selector (ie., the
TCP or UDP port) is usually determined dynamically, and varies with
each invocation of the service. Server programs allocate a transport
address, and register it with a well-known lookup service (well-known
because it uses a fixed transport selector, and resides at the same
network address as the server). Client programs consult the lookup
service in order to obtain the server's transport address.
Such a lookup service is very desirable because the range of well-
known transport selectors is very small for some transports and the
number of services is potentially very large. By running only the
lookup service on a well-known transport selector, the transport
addresses of other remote programs can be ascertained by querying the
lookup service.
This document describes three versions of a lookup service, all of
which use the same RPC program number (100000). They all use port
111 over TCP and UDP transports. Versions 3 and 4 are described in
Section 2 ("RPCBIND Program Protocol"). Version 2 is described in
Section 3 ("Port Mapper Program Protocol").
The distinguishing characteristic of RPCBIND (versions 3 and 4) is
that this protocol uses a transport-independent format for the
transport address, known as the universal address format. An address
in universal address format is an ASCII string representation of the
transport dependent address. String representation of addresses
corresponding to a transport are defined by the addressing authority
for the transport. The RPCBIND protocol can be used for binding ONC
RPC clients and servers over any transport.
The Port Mapper (version 2), on the other hand, is an older protocol
that is specific to TCP and UDP. It handles TCP and UDP ports
directly.
2. RPCBIND Program Protocol
The RPCBIND program maps RPC program and version numbers to universal
addresses, thus making dynamic binding of remote programs possible.
The RPCBIND program is bound to a well-known address of each
supported transport, and other programs register their dynamically
allocated transport address with it. The RPCBIND program then makes
Srinivasan Standards Track PAGE 2
RFC 1833 Binding Protocols for ONC RPC Version 2 August 1995
those addresses publicly available.
The RPCBIND program also aids in broadcast RPC. A given RPC program
will usually have different transport address bindings on different
machines, so there is no way to directly broadcast to all of these
programs. The RPCBIND program, however, does have a well-known
address. So, to broadcast to a given program, the client actually
sends its message to the RPCBIND program located at the broadcast
address. Each instance of the RPCBIND program that picks up the
broadcast then calls the local service specified by the client. When
the RPCBIND program gets the reply from the local service, it sends
the reply back to the client.
2.1 RPCBIND Protocol Specification (in RPC Language)
/*
* rpcb_prot.x
* rpcbind protocol, versions 3 and 4, in RPC Language
*/
/*
* rpcbind address for TCP/UDP
*/
const RPCB_PORT = 111;
/*
* A mapping of (program, version, network ID) to address
*
* The network identifier (r_netid):
* This is a string that represents a local identification for a
* network. This is defined by a system administrator based on local
* conventions, and cannot be depended on to have the same value on
* every system.
*/
struct rpcb {
unsigned long r_prog; /* program number */
unsigned long r_vers; /* version number */
string r_netid<>; /* network id */
string r_addr<>; /* universal address */
string r_owner<>; /* owner of this service */
};
struct rp__list {
rpcb rpcb_map;
struct rp__list *rpcb_next;
};
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RFC 1833 Binding Protocols for ONC RPC Version 2 August 1995
typedef rp__list *rpcblist_ptr; /* results of RPCBPROC_DUMP */
/*
* Arguments of remote calls
*/
struct rpcb_rmtcallargs {
unsigned long prog; /* program number */
unsigned long vers; /* version number */
unsigned long proc; /* procedure number */
opaque args<>; /* argument */
};
/*
* Results of the remote call
*/
struct rpcb_rmtcallres {
string addr<>; /* remote universal address */
opaque results<>; /* result */
};
/*
* rpcb_entry contains a merged address of a service on a particular
* transport, plus associated netconfig information. A list of
* rpcb_entry items is returned by RPCBPROC_GETADDRLIST. The meanings
* and values used for the r_nc_* fields are given below.
*
* The network identifier (r_nc_netid):
* This is a string that represents a local identification for a
* network. This is defined by a system administrator based on
* local conventions, and cannot be depended on to have the same
* value on every system.
*
* Transport semantics (r_nc_semantics):
* This represents the type of transport, and has the following values:
* NC_TPI_CLTS (1) Connectionless
* NC_TPI_COTS (2) Connection oriented
* NC_TPI_COTS_ORD (3) Connection oriented with graceful close
* NC_TPI_RAW (4) Raw transport
*
* Protocol family (r_nc_protofmly):
* This identifies the family to which the protocol belongs. The
* following values are defined:
* NC_NOPROTOFMLY "-"
* NC_LOOPBACK "loopback"
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RFC 1833 Binding Protocols for ONC RPC Version 2 August 1995
* NC_INET "inet"
* NC_IMPLINK "implink"
* NC_PUP "pup"
* NC_CHAOS "chaos"
* NC_NS "ns"
* NC_NBS "nbs"
* NC_ECMA "ecma"
* NC_DATAKIT "datakit"
* NC_CCITT "ccitt"
* NC_SNA "sna"
* NC_DECNET "decnet"
* NC_DLI "dli"
* NC_LAT "lat"
* NC_HYLINK "hylink"
* NC_APPLETALK "appletalk"
* NC_NIT "nit"
* NC_IEEE802 "ieee802"
* NC_OSI "osi"
* NC_X25 "x25"
* NC_OSINET "osinet"
* NC_GOSIP "gosip"
*
* Protocol name (r_nc_proto):
* This identifies a protocol within a family. The following are
* currently defined:
* NC_NOPROTO "-"
* NC_TCP "tcp"
* NC_UDP "udp"
* NC_ICMP "icmp"
*/
struct rpcb_entry {
string r_maddr<>; /* merged address of service */
string r_nc_netid<>; /* netid field */
unsigned long r_nc_semantics; /* semantics of transport */
string r_nc_protofmly<>; /* protocol family */
string r_nc_proto<>; /* protocol name */
};
/*
* A list of addresses supported by a service.
*/
struct rpcb_entry_list {
rpcb_entry rpcb_entry_map;
struct rpcb_entry_list *rpcb_entry_next;
};
typedef rpcb_entry_list *rpcb_entry_list_ptr;
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RFC 1833 Binding Protocols for ONC RPC Version 2 August 1995
/*
* rpcbind statistics
*/
const rpcb_highproc_2 = RPCBPROC_CALLIT;
const rpcb_highproc_3 = RPCBPROC_TADDR2UADDR;
const rpcb_highproc_4 = RPCBPROC_GETSTAT;
const RPCBSTAT_HIGHPROC = 13; /* # of procs in rpcbind V4 plus one */
const RPCBVERS_STAT = 3; /* provide only for rpcbind V2, V3 and V4 */
const RPCBVERS_4_STAT = 2;
const RPCBVERS_3_STAT = 1;
const RPCBVERS_2_STAT = 0;
/* Link list of all the stats about getport and getaddr */
struct rpcbs_addrlist {
unsigned long prog;
unsigned long vers;
int success;
int failure;
string netid<>;
struct rpcbs_addrlist *next;
};
/* Link list of all the stats about rmtcall */
struct rpcbs_rmtcalllist {
unsigned long prog;
unsigned long vers;
unsigned long proc;
int success;
int failure;
int indirect; /* whether callit or indirect */
string netid<>;
struct rpcbs_rmtcalllist *next;
};
typedef int rpcbs_proc[RPCBSTAT_HIGHPROC];
typedef rpcbs_addrlist *rpcbs_addrlist_ptr;
typedef rpcbs_rmtcalllist *rpcbs_rmtcalllist_ptr;
struct rpcb_stat {
rpcbs_proc info;
int setinfo;
int unsetinfo;
rpcbs_addrlist_ptr addrinfo;
rpcbs_rmtcalllist_ptr rmtinfo;
};
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RFC 1833 Binding Protocols for ONC RPC Version 2 August 1995
/*
* One rpcb_stat structure is returned for each version of rpcbind
* being monitored.
*/
typedef rpcb_stat rpcb_stat_byvers[RPCBVERS_STAT];
/*
* netbuf structure, used to store the transport specific form of
* a universal transport address.
*/
struct netbuf {
unsigned int maxlen;
opaque buf<>;
};
/*
* rpcbind procedures
*/
program RPCBPROG {
version RPCBVERS {
bool
RPCBPROC_SET(rpcb) = 1;
bool
RPCBPROC_UNSET(rpcb) = 2;
string
RPCBPROC_GETADDR(rpcb) = 3;
rpcblist_ptr
RPCBPROC_DUMP(void) = 4;
rpcb_rmtcallres
RPCBPROC_CALLIT(rpcb_rmtcallargs) = 5;
unsigned int
RPCBPROC_GETTIME(void) = 6;
netbuf
RPCBPROC_UADDR2TADDR(string) = 7;
string
RPCBPROC_TADDR2UADDR(netbuf) = 8;
} = 3;
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RFC 1833 Binding Protocols for ONC RPC Version 2 August 1995
version RPCBVERS4 {
bool
RPCBPROC_SET(rpcb) = 1;
bool
RPCBPROC_UNSET(rpcb) = 2;
string
RPCBPROC_GETADDR(rpcb) = 3;
rpcblist_ptr
RPCBPROC_DUMP(void) = 4;
/*
* NOTE: RPCBPROC_BCAST has the same functionality as CALLIT;
* the new name is intended to indicate that this
* procedure should be used for broadcast RPC, and
* RPCBPROC_INDIRECT should be used for indirect calls.
*/
rpcb_rmtcallres
RPCBPROC_BCAST(rpcb_rmtcallargs) = RPCBPROC_CALLIT;
unsigned int
RPCBPROC_GETTIME(void) = 6;
netbuf
RPCBPROC_UADDR2TADDR(string) = 7;
string
RPCBPROC_TADDR2UADDR(netbuf) = 8;
string
RPCBPROC_GETVERSADDR(rpcb) = 9;
rpcb_rmtcallres
RPCBPROC_INDIRECT(rpcb_rmtcallargs) = 10;
rpcb_entry_list_ptr
RPCBPROC_GETADDRLIST(rpcb) = 11;
rpcb_stat_byvers
RPCBPROC_GETSTAT(void) = 12;
} = 4;
} = 100000;
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RFC 1833 Binding Protocols for ONC RPC Version 2 August 1995
2.2 RPCBIND Operation
RPCBIND is contacted by way of an assigned address specific to the
transport being used. For TCP/IP and UDP/IP, for example, it is port
number 111. Each transport has such an assigned, well-known address.
The following is a description of each of the procedures supported by
RPCBIND.
2.2.1 RPCBIND Version 3
RPCBPROC_SET:
When a program first becomes available on a machine, it registers
itself with RPCBIND running on the same machine. The program passes
its program number "r_prog", version number "r_vers", network
identifier "r_netid", universal address "r_addr", and the owner of
the service "r_owner". The procedure returns a boolean response
whose value is TRUE if the procedure successfully established the
mapping and FALSE otherwise. The procedure refuses to establish a
mapping if one already exists for the ordered set ("r_prog",
"r_vers", "r_netid"). Note that neither "r_netid" nor "r_addr" can
be NULL, and that "r_netid" should be a valid network identifier on
the machine making the call.
RPCBPROC_UNSET:
When a program becomes unavailable, it should unregister itself with
the RPCBIND program on the same machine. The parameters and results
have meanings identical to those of RPCBPROC_SET. The mapping of the
("r_prog", "r_vers", "r_netid") tuple with "r_addr" is deleted. If
"r_netid" is NULL, all mappings specified by the ordered set
("r_prog", "r_vers", *) and the corresponding universal addresses are
deleted. Only the owner of the service or the super-user is allowed
to unset a service.
RPCBPROC_GETADDR:
Given a program number "r_prog", version number "r_vers", and network
identifier "r_netid", this procedure returns the universal address
on which the program is awaiting call requests. The "r_netid" field
of the argument is ignored and the "r_netid" is inferred from the
network identifier of the transport on which the request came in.
RPCBPROC_DUMP:
This procedure lists all entries in RPCBIND's database. The
procedure takes no parameters and returns a list of program, version,
network identifier, and universal addresses.
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RFC 1833 Binding Protocols for ONC RPC Version 2 August 1995
RPCBPROC_CALLIT:
This procedure allows a caller to call another remote procedure on
the same machine without knowing the remote procedure's universal
address. It is intended for supporting broadcasts to arbitrary
remote programs via RPCBIND's universal address. The parameters
"prog", "vers", "proc", and args are the program number, version
number, procedure number, and parameters of the remote procedure.
Note - This procedure only sends a response if the procedure was
successfully executed and is silent (no response) otherwise.
The procedure returns the remote program's universal address, and the
results of the remote procedure.
RPCBPROC_GETTIME:
This procedure returns the local time on its own machine in seconds
since the midnight of the First day of January, 1970.
RPCBPROC_UADDR2TADDR:
This procedure converts universal addresses to transport specific
addresses.
RPCBPROC_TADDR2UADDR:
This procedure converts transport specific addresses to universal
addresses.
2.2.2 RPCBIND, Version 4
Version 4 of the RPCBIND protocol includes all of the above
procedures, and adds several additional ones.
RPCBPROC_BCAST:
This procedure is identical to the version 3 RPCBPROC_CALLIT
procedure. The new name indicates that the procedure should be used
for broadcast RPCs only. RPCBPROC_INDIRECT, defined below, should be
used for indirect RPC calls.
RPCBPROC_GETVERSADDR:
This procedure is similar to RPCBPROC_GETADDR. The difference is the
"r_vers" field of the rpcb structure can be used to specify the
version of interest. If that version is not registered, no address
is returned.
Srinivasan Standards Track PAGE 10
RFC 1833 Binding Protocols for ONC RPC Version 2 August 1995
RPCBPROC_INDIRECT:
Similar to RPCBPROC_CALLIT. Instead of being silent about errors
(such as the program not being registered on the system), this
procedure returns an indication of the error. This procedure should
not be used for broadcast RPC. It is intended to be used with
indirect RPC calls only.
RPCBPROC_GETADDRLIST:
This procedure returns a list of addresses for the given rpcb entry.
The client may be able use the results to determine alternate
transports that it can use to communicate with the server.
RPCBPROC_GETSTAT:
This procedure returns statistics on the activity of the RPCBIND
server. The information lists the number and kind of requests the
server has received.
Note - All procedures except RPCBPROC_SET and RPCBPROC_UNSET can be
called by clients running on a machine other than a machine on which
RPCBIND is running. RPCBIND only accepts RPCBPROC_SET and
RPCBPROC_UNSET requests by clients running on the same machine as the
RPCBIND program.
3. Port Mapper Program Protocol
The port mapper program maps RPC program and version numbers to
transport- specific port numbers. This program makes dynamic binding
of remote programs possible. The port mapper protocol differs from
the newer RPCBIND protocols in that it is transport specific in its
address handling.
3.1 Port Mapper Protocol Specification (in RPC Language)
const PMAP_PORT = 111; /* portmapper port number */
A mapping of (program, version, protocol) to port number:
struct mapping {
unsigned int prog;
unsigned int vers;
unsigned int prot;
unsigned int port;
};
Srinivasan Standards Track PAGE 11
RFC 1833 Binding Protocols for ONC RPC Version 2 August 1995
Supported values for the "prot" field:
const IPPROTO_TCP = 6; /* protocol number for TCP/IP */
const IPPROTO_UDP = 17; /* protocol number for UDP/IP */
A list of mappings:
struct *pmaplist {
mapping map;
pmaplist next;
};
Arguments to callit:
struct call_args {
unsigned int prog;
unsigned int vers;
unsigned int proc;
opaque args<>;
};
Results of callit:
struct call_result {
unsigned int port;
opaque res<>;
};
Port mapper procedures:
program PMAP_PROG {
version PMAP_VERS {
void
PMAPPROC_NULL(void) = 0;
bool
PMAPPROC_SET(mapping) = 1;
bool
PMAPPROC_UNSET(mapping) = 2;
unsigned int
PMAPPROC_GETPORT(mapping) = 3;
pmaplist
PMAPPROC_DUMP(void) = 4;
call_result
Srinivasan Standards Track PAGE 12
RFC 1833 Binding Protocols for ONC RPC Version 2 August 1995
PMAPPROC_CALLIT(call_args) = 5;
} = 2;
} = 100000;
3.2 Port Mapper Operation
The portmapper program currently supports two protocols (UDP and
TCP). The portmapper is contacted by talking to it on assigned port
number 111 (SUNRPC) on either of these protocols.
The following is a description of each of the portmapper procedures:
PMAPPROC_NULL:
This procedure does no work. By convention, procedure zero of any
protocol takes no parameters and returns no results.
PMAPPROC_SET:
When a program first becomes available on a machine, it registers
itself with the port mapper program on the same machine. The program
passes its program number "prog", version number "vers", transport
protocol number "prot", and the port "port" on which it awaits
service request. The procedure returns a boolean reply whose value
is "TRUE" if the procedure successfully established the mapping and
"FALSE" otherwise. The procedure refuses to establish a mapping if
one already exists for the tuple "(prog, vers, prot)".
PMAPPROC_UNSET:
When a program becomes unavailable, it should unregister itself with
the port mapper program on the same machine. The parameters and
results have meanings identical to those of "PMAPPROC_SET". The
protocol and port number fields of the argument are ignored.
PMAPPROC_GETPORT:
Given a program number "prog", version number "vers", and transport
protocol number "prot", this procedure returns the port number on
which the program is awaiting call requests. A port value of zeros
means the program has not been registered. The "port" field of the
argument is ignored.
PMAPPROC_DUMP:
This procedure enumerates all entries in the port mapper's database.
The procedure takes no parameters and returns a list of program,
version, protocol, and port values.
Srinivasan Standards Track PAGE 13
RFC 1833 Binding Protocols for ONC RPC Version 2 August 1995
PMAPPROC_CALLIT:
This procedure allows a client to call another remote procedure on
the same machine without knowing the remote procedure's port number.
It is intended for supporting broadcasts to arbitrary remote programs
via the well-known port mapper's port. The parameters "prog",
"vers", "proc", and the bytes of "args" are the program number,
version number, procedure number, and parameters of the remote
procedure. Note:
(1) This procedure only sends a reply if the procedure was
successfully executed and is silent (no reply) otherwise.
(2) The port mapper communicates with the remote program using UDP
only.
The procedure returns the remote program's port number, and the reply
is the reply of the remote procedure.
References
[1] Srinivasan, R., "Remote Procedure Call Protocol Version 2",
RFC 1831, Sun Microsystems, Inc., August 1995.
[2] Srinivasan, R., "XDR: External Data Representation Standard",
RFC 1832, Sun Microsystems, Inc., August 1995.
Security Considerations
Security issues are not discussed in this memo.
Author's Address
Raj Srinivasan
Sun Microsystems, Inc.
ONC Technologies
2550 Garcia Avenue
M/S MTV-5-40
Mountain View, CA 94043
USA
Phone: 415-336-2478
Fax: 415-336-6015
EMail: raj@eng.sun.com
Srinivasan Standards Track PAGE 14
Binding Protocols for ONC RPC Version 2
RFC TOTAL SIZE: 24449 bytes
PUBLICATION DATE: Tuesday, August 8th, 1995
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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