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.Dd October 15, 2018 34.Dt NSDISPATCH 3 35.Os 36.Sh NAME 37.Nm nsdispatch 38.Nd name-service switch dispatcher routine 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In sys/types.h 43.In stdarg.h 44.In nsswitch.h 45.Ft int 46.Fo nsdispatch 47.Fa "void *retval" 48.Fa "const ns_dtab dtab[]" 49.Fa "const char *database" 50.Fa "const char *method_name" 51.Fa "const ns_src defaults[]" 52.Fa "..." 53.Fc 54.Sh DESCRIPTION 55The 56.Fn nsdispatch 57function invokes the methods specified in 58.Va dtab 59in the order given by 60.Xr nsswitch.conf 5 61for the database 62.Va database 63until a successful entry is found. 64.Pp 65.Va retval 66is passed to each method to modify as necessary, to pass back results to 67the caller of 68.Fn nsdispatch . 69.Pp 70Each method has the function signature described by the typedef: 71.Pp 72.Ft typedef int 73.Fn \*(lp*nss_method\*(rp "void *retval" "void *mdata" "va_list *ap" ; 74.Pp 75.Va dtab 76is an array of 77.Va ns_dtab 78structures, which have the following format: 79.Bd -literal -offset indent 80typedef struct _ns_dtab { 81 const char *src; 82 nss_method method; 83 void *mdata; 84} ns_dtab; 85.Ed 86.Pp 87The 88.Fa dtab 89array should consist of one entry for each source type that is 90implemented, with 91.Va src 92as the name of the source, 93.Va method 94as a function which handles that source, and 95.Va mdata 96as a handle on arbitrary data to be passed to the method. 97The last entry in 98.Va dtab 99should contain 100.Dv NULL 101values for 102.Va src , 103.Va method , 104and 105.Va mdata . 106.Pp 107Additionally, methods may be implemented in NSS modules, in 108which case they are selected using the 109.Fa database 110and 111.Fa method_name 112arguments along with the configured source. 113Modules must use source names different from the built-in ones. 114.Pp 115.Va defaults 116contains a list of default sources to try if 117.Xr nsswitch.conf 5 118is missing or corrupted, or if there is no relevant entry for 119.Va database . 120It is an array of 121.Va ns_src 122structures, which have the following format: 123.Bd -literal -offset indent 124typedef struct _ns_src { 125 const char *src; 126 uint32_t flags; 127} ns_src; 128.Ed 129.Pp 130The 131.Fa defaults 132array should consist of one entry for each source to be configured by 133default indicated by 134.Va src , 135and 136.Va flags 137set to the criterion desired 138(usually 139.Dv NS_SUCCESS ; 140refer to 141.Sx Method return values 142for more information). 143The last entry in 144.Va defaults 145should have 146.Va src 147set to 148.Dv NULL 149and 150.Va flags 151set to 0. 152.Pp 153For convenience, a global variable defined as: 154.Pp 155.Dl extern const ns_src __nsdefaultsrc[]; 156.Pp 157exists which contains a single default entry for the source 158.Sq files 159that may be used by callers which do not require complicated default 160rules. 161.Pp 162.Sq Va ... 163are optional extra arguments, which are passed to the appropriate method 164as a variable argument list of the type 165.Vt va_list . 166.Ss Valid source types 167While there is support for arbitrary sources, the following 168#defines for commonly implemented sources are available: 169.Bl -column NSSRC_COMPAT compat -offset indent 170.It Sy "#define value" 171.It Dv NSSRC_FILES Ta \&"files\&" 172.It Dv NSSRC_DB Ta \&"db\&" 173.It Dv NSSRC_DNS Ta \&"dns\&" 174.It Dv NSSRC_NIS Ta \&"nis\&" 175.It Dv NSSRC_COMPAT Ta \&"compat\&" 176.El 177.Pp 178Refer to 179.Xr nsswitch.conf 5 180for a complete description of what each source type is. 181.Ss Method return values 182The 183.Vt nss_method 184functions must return one of the following values depending upon status 185of the lookup: 186.Bl -column "Return value" "Status code" 187.It Sy "Return value Status code" 188.It Dv NS_SUCCESS Ta success 189.It Dv NS_NOTFOUND Ta notfound 190.It Dv NS_UNAVAIL Ta unavail 191.It Dv NS_TRYAGAIN Ta tryagain 192.It Dv NS_RETURN Ta -none- 193.El 194.Pp 195Refer to 196.Xr nsswitch.conf 5 197for a complete description of each status code. 198.Pp 199The 200.Fn nsdispatch 201function returns the value of the method that caused the dispatcher to 202terminate, or 203.Dv NS_NOTFOUND 204otherwise. 205.Sh NOTES 206.Fx Ns 's 207.Lb libc 208provides stubs for compatibility with NSS modules 209written for the 210.Tn GNU 211C Library 212.Nm nsswitch 213interface. 214However, these stubs only support the use of the 215.Dq Li passwd 216and 217.Dq Li group 218databases. 219.Sh SEE ALSO 220.Xr hesiod 3 , 221.Xr stdarg 3 , 222.Xr nsswitch.conf 5 , 223.Xr yp 8 224.Sh HISTORY 225The 226.Fn nsdispatch 227function first appeared in 228.Fx 5.0 . 229It was imported from the 230.Nx 231Project, 232where it appeared first in 233.Nx 1.4 . 234Support for NSS modules first appeared in 235.Fx 5.1 . 236.Sh AUTHORS 237.An Luke Mewburn Aq Mt lukem@netbsd.org 238wrote this freely-distributable name-service switch implementation, 239using ideas from the 240.Tn ULTRIX 241svc.conf(5) 242and 243.Tn Solaris 244nsswitch.conf(4) 245manual pages. 246The 247.Fx 248Project 249added the support for threads and NSS modules, and normalized the uses 250of 251.Fn nsdispatch 252within the standard C library. 253