.\" $OpenBSD: ypclnt.3,v 1.16 2003/07/07 15:46:37 jmc Exp $ .\" .\" Copyright (c) 1996 The NetBSD Foundation, Inc. .\" All rights reserved. .\" .\" This code is derived from software contributed to The NetBSD Foundation .\" by Jason R. Thorpe. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the NetBSD .\" Foundation, Inc. and its contributors. .\" 4. Neither the name of The NetBSD Foundation nor the names of its .\" contributors may be used to endorse or promote products derived .\" from this software without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED .\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE .\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS .\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN .\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE .\" POSSIBILITY OF SUCH DAMAGE. .\" .Dd October 26, 1994 .Dt YPCLNT 3 .Os .Sh NAME .Nm yp_all , .Nm yp_bind , .Nm yp_first , .Nm yp_get_default_domain , .Nm yp_master , .Nm yp_match , .Nm yp_next , .Nm yp_order , .Nm yp_unbind , .Nm yperr_string , .Nm ypprot_err .Nd Interface to the YP subsystem .Sh SYNOPSIS .Fd #include .Fd #include .Fd #include .Fd #include .Ft int .Fn yp_all "char *indomain" "char *inmap" "struct ypall_callback *incallback" .Ft int .Fn yp_bind "char *dom" .Ft int .Fn yp_first "char *indomain" "char *inmap" "char **outkey" "int *outkeylen" "char **outval" "int *outvallen" .Ft int .Fn yp_get_default_domain "char **domp" .Ft int .Fn yp_master "char *indomain" "char *inmap" "char **outname" .Ft int .Fn yp_match "char *indomain" "char *inmap" "const char *inkey" "int inkeylen" "char **outval" "int *outvallen" .Ft int .Fn yp_next "char *indomain" "char *inmap" "char *inkey" "int inkeylen" "char **outkey" "int *outkeylen" "char **outval" "int *outvallen" .Ft int .Fn yp_order "char *indomain" "char *inmap" "char *outorder" .Ft void .Fn yp_unbind "char *dom" .Ft char * .Fn yperr_string "int incode" .Ft int .Fn ypprot_err "unsigned int incode" .Sh DESCRIPTION The .Nm ypclnt suite provides an interface to the YP subsystem. For a general description of the YP subsystem, see .Xr yp 8 . .Pp For all functions, input values begin with .Pa in and output values begin with .Pa out . Any output values of type .Em char ** should be the addresses of uninitialized character pointers. Memory will be allocated by the YP client routines using .Fn malloc . This memory can later be freed by the user if there is no additional need for the data stored there. For .Pa outkey and .Pa outval , two extra bytes of memory are allocated for a .Ql \en and .Ql \e0 , which are not reflected in the values of .Pa outkeylen or .Pa outvallen . All occurrences of .Pa indomain and .Pa inmap must be non-null, NUL-terminated strings. All input strings which also have a corresponding length parameter cannot be null unless the corresponding length value is zero. Such strings need not be NUL-terminated. .Pp All YP lookup calls (the functions .Fn yp_all , .Fn yp_first , .Fn yp_master , .Fn yp_match , .Fn yp_next , .Fn yp_order ) require a YP domain name and a YP map name. The default domain name may be obtained by calling .Fn yp_get_default_domain , and should thus be used before all other YP calls in a client program. The value it places .Pa outdomain is suitable for use as the .Pa indomain parameter to all subsequent YP calls. .Pp In order for YP lookup calls to succeed, the client process must be bound to a YP server process. The client process need not explicitly bind to the server, as it happens automatically whenever a lookup occurs. The function .Fn yp_bind is provided for a backup strategy, e.g., a local file, when a YP server process is not available. Each binding uses one socket descriptor on the client process, which may be explicitly freed using .Fn yp_unbind , which frees all per-process and per-node resources to bind the domain and marks the domain unbound. .Pp If, during a YP lookup, an RPC failure occurs, the domain used in the lookup is automatically marked unbound and the .Nm ypclnt layer retries the lookup as long as .Xr ypbind 8 is running and either the client process cannot bind to a server for the domain specified in the lookup, or RPC requests to the YP server process fail. If an error is not RPC-related, one of the YP error codes described below is returned and control given back to the user code. .Pp The .Nm ypclnt suite provides the following functionality: .Bl -tag -width "yperr_string()" .It Fn yp_match Provides the value associated with the given key. .It Fn yp_first Provides the first key-value pair from the given map in the named domain. .It Fn yp_next Provides the next key-value pair in the given map. To obtain the second pair, the .Pa inkey value should be the .Pa outkey value provided by the initial call to .Fn yp_first . In the general case, the next key-value pair may be obtained by using the .Pa outkey value from the previous call to .Fn yp_next as the value for .Pa inkey . .Pp Of course, the notions of .Dq first and .Dq next are particular to the type of YP map being accessed, and thus there is no guarantee of lexical order. The only guarantees provided with .Fn yp_first and .Fn yp_next , providing that the same map on the same server is polled repeatedly until .Fn yp_next returns YPERR_NOMORE, are that all key-value pairs in that map will be accessed exactly once, and if the entire procedure is repeated, the order will be the same. .Pp If the server is heavily loaded or the server fails for some reason, the domain being used may become unbound. If this happens, and the client process re-binds, the retrieval rules will break: some entries may be seen twice, and others not at all. For this reason, the function .Fn yp_all provides a better solution for reading all of the entries in a particular map. .It Fn yp_all This function provides a way to transfer an entire map from the server to the client process with a single request. This transfer uses TCP, unlike all other functions in the .Nm ypclnt suite, which use UDP. The entire transaction occurs in a single RPC request-response. The third argument to this function provides a way to supply the name of a function to process each key-value pair in the map. .Fn yp_all returns after the entire transaction is complete, or the .Pa foreach function decides that it does not want any more key-value pairs. The third argument to .Fn yp_all is: .Bd -literal -offset indent struct ypall_callback *incallback { int (*foreach)(); char *data; }; .Ed .Pp The .Em char *data argument is an opaque pointer for use by the callback function. The .Pa foreach function should return non-zero when it no longer wishes to process key-value pairs, at which time .Fn yp_all returns a value of 0, and is called with the following arguments: .Bd -literal -offset indent int foreach ( int instatus, char *inkey, int inkeylen, char *inval, int invallen, char *indata ); .Ed .Pp Where: .Bl -tag -width "inkey, inval" .It Fa instatus Holds one of the return status values described in .Aq Pa rpcsvc/yp_prot.h : see .Fn ypprot_err below for a function that will translate YP protocol errors into a .Nm ypclnt layer error code as described in .Aq Pa rpcsvc/ypclnt.h . .It Fa inkey, inval The key and value arguments are somewhat different here than described above. In this case, the memory pointed to by .Fa inkey and .Fa inval is private to .Fn yp_all , and is overwritten with each subsequent key-value pair; therefore, the .Pa foreach function should do something useful with the contents of that memory during each iteration. If the key-value pairs are not terminated with either .Ql \en or .Ql \e0 in the map, then they will not be terminated as such when given to the .Pa foreach function, either. .It Fa indata This is the contents of the .Pa incallback->data element of the callback structure. It is provided as a means to share state between the .Pa foreach function and the user code. Its use is completely optional: cast it to something useful or simply ignore it. .El .It Fn yp_order Returns the order number for a map. .It Fn yp_master Returns the hostname for the machine on which the master YP server process for a map is running. .It Fn yperr_string Returns a pointer to a NUL-terminated error string that does not contain a .Ql \&. or .Ql \en . .It Fn ypprot_err Converts a YP protocol error code to a .Nm ypclnt error code suitable for .Fn yperr_string . .El .Sh RETURN VALUES All functions in the .Nm ypclnt suite which are of type .Em int return 0 upon success or one of the following error codes upon failure: .Bl -tag -width "YPERR_BADARGS " .It Bq Er YPERR_BADARGS The passed arguments to the function are invalid. .It Bq Er YPERR_BADDB The YP map that was polled is defective. .It Bq Er YPERR_DOMAIN Client process cannot bind to server on this YP domain. .It Bq Er YPERR_KEY The key passed does not exist. .It Bq Er YPERR_MAP There is no such map in the server's domain. .It Bq Er YPERR_DOM The local YP domain is not set. .It Bq Er YPERR_NOMORE There are no more records in the queried map. .It Bq Er YPERR_PMAP Cannot communicate with portmap. .It Bq Er YPERR_RESRC A resource allocation failure occurred. .It Bq Er YPERR_RPC An RPC failure has occurred. The domain has been marked unbound. .It Bq Er YPERR_VERS Client/server version mismatch. If the server is running version 1 of the YP protocol, .Fn yp_all functionality does not exist. .It Bq Er YPERR_BIND Cannot communicate with .Xr ypbind 8 . .It Bq Er YPERR_YPERR An internal server or client error has occurred. .It Bq Er YPERR_YPSERV The client cannot communicate with the YP server process. .El .Sh SEE ALSO .Xr malloc 3 , .Xr yp 8 , .Xr ypbind 8 , .Xr ypserv 8 .Sh AUTHORS Theo De Raadt