1.\" $NetBSD: nsdispatch.3,v 1.8 1999/03/22 19:44:53 garbled Exp $ 2.\" 3.\" Copyright (c) 1997, 1998, 1999 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Luke Mewburn. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 4. Neither the name of The NetBSD Foundation nor the names of its 18.\" contributors may be used to endorse or promote products derived 19.\" from this software without specific prior written permission. 20.\" 21.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 22.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 23.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 24.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 25.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 26.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 27.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 28.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 29.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 30.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 31.\" POSSIBILITY OF SUCH DAMAGE. 32.\" 33.\" $FreeBSD$ 34.\" 35.Dd January 22, 2007 36.Dt NSDISPATCH 3 37.Os 38.Sh NAME 39.Nm nsdispatch 40.Nd name-service switch dispatcher routine 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In sys/types.h 45.In stdarg.h 46.In nsswitch.h 47.Ft int 48.Fo nsdispatch 49.Fa "void *retval" 50.Fa "const ns_dtab dtab[]" 51.Fa "const char *database" 52.Fa "const char *method_name" 53.Fa "const ns_src defaults[]" 54.Fa "..." 55.Fc 56.Sh DESCRIPTION 57The 58.Fn nsdispatch 59function invokes the methods specified in 60.Va dtab 61in the order given by 62.Xr nsswitch.conf 5 63for the database 64.Va database 65until a successful entry is found. 66.Pp 67.Va retval 68is passed to each method to modify as necessary, to pass back results to 69the caller of 70.Fn nsdispatch . 71.Pp 72Each method has the function signature described by the typedef: 73.Pp 74.Ft typedef int 75.Fn \*(lp*nss_method\*(rp "void *retval" "void *mdata" "va_list *ap" ; 76.Pp 77.Va dtab 78is an array of 79.Va ns_dtab 80structures, which have the following format: 81.Bd -literal -offset indent 82typedef struct _ns_dtab { 83 const char *src; 84 nss_method method; 85 void *mdata; 86} ns_dtab; 87.Ed 88.Pp 89.Bd -ragged -offset indent 90The 91.Fa dtab 92array should consist of one entry for each source type that is 93implemented, with 94.Va src 95as the name of the source, 96.Va method 97as a function which handles that source, and 98.Va mdata 99as a handle on arbitrary data to be passed to the method. 100The last entry in 101.Va dtab 102should contain 103.Dv NULL 104values for 105.Va src , 106.Va method , 107and 108.Va mdata . 109.Ed 110.Pp 111Additionally, methods may be implemented in NSS modules, in 112which case they are selected using the 113.Fa database 114and 115.Fa method_name 116arguments along with the configured source. 117(The methods supplied via 118.Fa dtab 119take priority over those implemented in NSS modules in the event 120of a conflict.) 121.Pp 122.Va defaults 123contains a list of default sources to try if 124.Xr nsswitch.conf 5 125is missing or corrupted, or if there is no relevant entry for 126.Va database . 127It is an array of 128.Va ns_src 129structures, which have the following format: 130.Bd -literal -offset indent 131typedef struct _ns_src { 132 const char *src; 133 u_int32_t flags; 134} ns_src; 135.Ed 136.Pp 137.Bd -ragged -offset indent 138The 139.Fa defaults 140array should consist of one entry for each source to be configured by 141default indicated by 142.Va src , 143and 144.Va flags 145set to the criterion desired 146(usually 147.Dv NS_SUCCESS ; 148refer to 149.Sx Method return values 150for more information). 151The last entry in 152.Va defaults 153should have 154.Va src 155set to 156.Dv NULL 157and 158.Va flags 159set to 0. 160.Pp 161For convenience, a global variable defined as: 162.Dl extern const ns_src __nsdefaultsrc[]; 163exists which contains a single default entry for the source 164.Sq files 165that may be used by callers which do not require complicated default 166rules. 167.Ed 168.Pp 169.Sq Va ... 170are optional extra arguments, which are passed to the appropriate method 171as a variable argument list of the type 172.Vt va_list . 173.Ss Valid source types 174While there is support for arbitrary sources, the following 175#defines for commonly implemented sources are available: 176.Bl -column NSSRC_COMPAT compat -offset indent 177.It Sy "#define value" 178.It Dv NSSRC_FILES Ta """files"" 179.It Dv NSSRC_DNS Ta """dns"" 180.It Dv NSSRC_NIS Ta """nis"" 181.It Dv NSSRC_COMPAT Ta """compat"" 182.El 183.Pp 184Refer to 185.Xr nsswitch.conf 5 186for a complete description of what each source type is. 187.Pp 188.Ss Method return values 189The 190.Vt nss_method 191functions must return one of the following values depending upon status 192of the lookup: 193.Bl -column "Return value" "Status code" 194.It Sy "Return value Status code" 195.It Dv NS_SUCCESS Ta success 196.It Dv NS_NOTFOUND Ta notfound 197.It Dv NS_UNAVAIL Ta unavail 198.It Dv NS_TRYAGAIN Ta tryagain 199.It Dv NS_RETURN Ta -none- 200.El 201.Pp 202Refer to 203.Xr nsswitch.conf 5 204for a complete description of each status code. 205.Pp 206The 207.Fn nsdispatch 208function returns the value of the method that caused the dispatcher to 209terminate, or 210.Dv NS_NOTFOUND 211otherwise. 212.Sh NOTES 213.Fx Ns 's 214.Lb libc 215provides stubs for compatibility with NSS modules 216written for the 217.Tn GNU 218C Library 219.Nm nsswitch 220interface. 221However, these stubs only support the use of the 222.Dq Li passwd 223and 224.Dq Li group 225databases. 226.Sh SEE ALSO 227.Xr hesiod 3 , 228.Xr stdarg 3 , 229.Xr nsswitch.conf 5 , 230.Xr yp 8 231.Sh HISTORY 232The 233.Fn nsdispatch 234function first appeared in 235.Fx 5.0 . 236It was imported from the 237.Nx 238Project, 239where it appeared first in 240.Nx 1.4 . 241Support for NSS modules first appeared in 242.Fx 5.1 . 243.Sh AUTHORS 244Luke Mewburn 245.Aq lukem@netbsd.org 246wrote this freely-distributable name-service switch implementation, 247using ideas from the 248.Tn ULTRIX 249svc.conf(5) 250and 251.Tn Solaris 252nsswitch.conf(4) 253manual pages. 254The 255.Fx 256Project 257added the support for threads and NSS modules, and normalized the uses 258of 259.Fn nsdispatch 260within the standard C library. 261