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.\" 3. 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 October 15, 2018 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 89The 90.Fa dtab 91array should consist of one entry for each source type that is 92implemented, with 93.Va src 94as the name of the source, 95.Va method 96as a function which handles that source, and 97.Va mdata 98as a handle on arbitrary data to be passed to the method. 99The last entry in 100.Va dtab 101should contain 102.Dv NULL 103values for 104.Va src , 105.Va method , 106and 107.Va mdata . 108.Pp 109Additionally, methods may be implemented in NSS modules, in 110which case they are selected using the 111.Fa database 112and 113.Fa method_name 114arguments along with the configured source. 115Modules must use source names different from the built-in ones. 116.Pp 117.Va defaults 118contains a list of default sources to try if 119.Xr nsswitch.conf 5 120is missing or corrupted, or if there is no relevant entry for 121.Va database . 122It is an array of 123.Va ns_src 124structures, which have the following format: 125.Bd -literal -offset indent 126typedef struct _ns_src { 127 const char *src; 128 uint32_t flags; 129} ns_src; 130.Ed 131.Pp 132The 133.Fa defaults 134array should consist of one entry for each source to be configured by 135default indicated by 136.Va src , 137and 138.Va flags 139set to the criterion desired 140(usually 141.Dv NS_SUCCESS ; 142refer to 143.Sx Method return values 144for more information). 145The last entry in 146.Va defaults 147should have 148.Va src 149set to 150.Dv NULL 151and 152.Va flags 153set to 0. 154.Pp 155For convenience, a global variable defined as: 156.Pp 157.Dl extern const ns_src __nsdefaultsrc[]; 158.Pp 159exists which contains a single default entry for the source 160.Sq files 161that may be used by callers which do not require complicated default 162rules. 163.Pp 164.Sq Va ... 165are optional extra arguments, which are passed to the appropriate method 166as a variable argument list of the type 167.Vt va_list . 168.Ss Valid source types 169While there is support for arbitrary sources, the following 170#defines for commonly implemented sources are available: 171.Bl -column NSSRC_COMPAT compat -offset indent 172.It Sy "#define value" 173.It Dv NSSRC_FILES Ta \&"files\&" 174.It Dv NSSRC_DB Ta \&"db\&" 175.It Dv NSSRC_DNS Ta \&"dns\&" 176.It Dv NSSRC_NIS Ta \&"nis\&" 177.It Dv NSSRC_COMPAT Ta \&"compat\&" 178.El 179.Pp 180Refer to 181.Xr nsswitch.conf 5 182for a complete description of what each source type is. 183.Ss Method return values 184The 185.Vt nss_method 186functions must return one of the following values depending upon status 187of the lookup: 188.Bl -column "Return value" "Status code" 189.It Sy "Return value Status code" 190.It Dv NS_SUCCESS Ta success 191.It Dv NS_NOTFOUND Ta notfound 192.It Dv NS_UNAVAIL Ta unavail 193.It Dv NS_TRYAGAIN Ta tryagain 194.It Dv NS_RETURN Ta -none- 195.El 196.Pp 197Refer to 198.Xr nsswitch.conf 5 199for a complete description of each status code. 200.Pp 201The 202.Fn nsdispatch 203function returns the value of the method that caused the dispatcher to 204terminate, or 205.Dv NS_NOTFOUND 206otherwise. 207.Sh NOTES 208.Fx Ns 's 209.Lb libc 210provides stubs for compatibility with NSS modules 211written for the 212.Tn GNU 213C Library 214.Nm nsswitch 215interface. 216However, these stubs only support the use of the 217.Dq Li passwd 218and 219.Dq Li group 220databases. 221.Sh SEE ALSO 222.Xr hesiod 3 , 223.Xr stdarg 3 , 224.Xr nsswitch.conf 5 , 225.Xr yp 8 226.Sh HISTORY 227The 228.Fn nsdispatch 229function first appeared in 230.Fx 5.0 . 231It was imported from the 232.Nx 233Project, 234where it appeared first in 235.Nx 1.4 . 236Support for NSS modules first appeared in 237.Fx 5.1 . 238.Sh AUTHORS 239.An Luke Mewburn Aq Mt lukem@netbsd.org 240wrote this freely-distributable name-service switch implementation, 241using ideas from the 242.Tn ULTRIX 243svc.conf(5) 244and 245.Tn Solaris 246nsswitch.conf(4) 247manual pages. 248The 249.Fx 250Project 251added the support for threads and NSS modules, and normalized the uses 252of 253.Fn nsdispatch 254within the standard C library. 255