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 April 4, 2010 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. 115(The methods supplied via 116.Fa dtab 117take priority over those implemented in NSS modules in the event 118of a conflict.) 119.Pp 120.Va defaults 121contains a list of default sources to try if 122.Xr nsswitch.conf 5 123is missing or corrupted, or if there is no relevant entry for 124.Va database . 125It is an array of 126.Va ns_src 127structures, which have the following format: 128.Bd -literal -offset indent 129typedef struct _ns_src { 130 const char *src; 131 uint32_t flags; 132} ns_src; 133.Ed 134.Pp 135The 136.Fa defaults 137array should consist of one entry for each source to be configured by 138default indicated by 139.Va src , 140and 141.Va flags 142set to the criterion desired 143(usually 144.Dv NS_SUCCESS ; 145refer to 146.Sx Method return values 147for more information). 148The last entry in 149.Va defaults 150should have 151.Va src 152set to 153.Dv NULL 154and 155.Va flags 156set to 0. 157.Pp 158For convenience, a global variable defined as: 159.Pp 160.Dl extern const ns_src __nsdefaultsrc[]; 161.Pp 162exists which contains a single default entry for the source 163.Sq files 164that may be used by callers which do not require complicated default 165rules. 166.Pp 167.Sq Va ... 168are optional extra arguments, which are passed to the appropriate method 169as a variable argument list of the type 170.Vt va_list . 171.Ss Valid source types 172While there is support for arbitrary sources, the following 173#defines for commonly implemented sources are available: 174.Bl -column NSSRC_COMPAT compat -offset indent 175.It Sy "#define value" 176.It Dv NSSRC_FILES Ta \&"files\&" 177.It Dv NSSRC_DB Ta \&"db\&" 178.It Dv NSSRC_DNS Ta \&"dns\&" 179.It Dv NSSRC_NIS Ta \&"nis\&" 180.It Dv NSSRC_COMPAT Ta \&"compat\&" 181.El 182.Pp 183Refer to 184.Xr nsswitch.conf 5 185for a complete description of what each source type is. 186.Ss Method return values 187The 188.Vt nss_method 189functions must return one of the following values depending upon status 190of the lookup: 191.Bl -column "Return value" "Status code" 192.It Sy "Return value Status code" 193.It Dv NS_SUCCESS Ta success 194.It Dv NS_NOTFOUND Ta notfound 195.It Dv NS_UNAVAIL Ta unavail 196.It Dv NS_TRYAGAIN Ta tryagain 197.It Dv NS_RETURN Ta -none- 198.El 199.Pp 200Refer to 201.Xr nsswitch.conf 5 202for a complete description of each status code. 203.Pp 204The 205.Fn nsdispatch 206function returns the value of the method that caused the dispatcher to 207terminate, or 208.Dv NS_NOTFOUND 209otherwise. 210.Sh NOTES 211.Fx Ns 's 212.Lb libc 213provides stubs for compatibility with NSS modules 214written for the 215.Tn GNU 216C Library 217.Nm nsswitch 218interface. 219However, these stubs only support the use of the 220.Dq Li passwd 221and 222.Dq Li group 223databases. 224.Sh SEE ALSO 225.Xr hesiod 3 , 226.Xr stdarg 3 , 227.Xr nsswitch.conf 5 , 228.Xr yp 8 229.Sh HISTORY 230The 231.Fn nsdispatch 232function first appeared in 233.Fx 5.0 . 234It was imported from the 235.Nx 236Project, 237where it appeared first in 238.Nx 1.4 . 239Support for NSS modules first appeared in 240.Fx 5.1 . 241.Sh AUTHORS 242.An Luke Mewburn Aq Mt lukem@netbsd.org 243wrote this freely-distributable name-service switch implementation, 244using ideas from the 245.Tn ULTRIX 246svc.conf(5) 247and 248.Tn Solaris 249nsswitch.conf(4) 250manual pages. 251The 252.Fx 253Project 254added the support for threads and NSS modules, and normalized the uses 255of 256.Fn nsdispatch 257within the standard C library. 258