Copyright (c) 1997, 1998, 1999 The NetBSD Foundation, Inc.
All rights reserved.
This code is derived from software contributed to The NetBSD Foundation
by Luke Mewburn.
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.
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 FOUNDATION 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.
$FreeBSD: releng/11.0/lib/libc/net/nsdispatch.3 267774 2014-06-23 08:25:03Z bapt $
.Dd April 4, 2010 .Dt NSDISPATCH 3 .Os .Sh NAME .Nm nsdispatch .Nd name-service switch dispatcher routine .Sh LIBRARY .Lb libc .Sh SYNOPSIS n sys/types.h n stdarg.h n nsswitch.h .Ft int .Fo nsdispatch .Fa "void *retval" .Fa "const ns_dtab dtab[]" .Fa "const char *database" .Fa "const char *method_name" .Fa "const ns_src defaults[]" .Fa "..." .Fc .Sh DESCRIPTION The .Fn nsdispatch function invokes the methods specified in .Va dtab in the order given by .Xr nsswitch.conf 5 for the database .Va database until a successful entry is found.
p .Va retval is passed to each method to modify as necessary, to pass back results to the caller of .Fn nsdispatch .
p Each method has the function signature described by the typedef:
p .Ft typedef int .Fn \*(lp*nss_method\*(rp "void *retval" "void *mdata" "va_list *ap" ;
p .Va dtab is an array of .Va ns_dtab structures, which have the following format: d -literal -offset indent typedef struct _ns_dtab { const char *src; nss_method method; void *mdata; } ns_dtab; .Ed
p The .Fa dtab array should consist of one entry for each source type that is implemented, with .Va src as the name of the source, .Va method as a function which handles that source, and .Va mdata as a handle on arbitrary data to be passed to the method. The last entry in .Va dtab should contain .Dv NULL values for .Va src , .Va method , and .Va mdata .
p Additionally, methods may be implemented in NSS modules, in which case they are selected using the .Fa database and .Fa method_name arguments along with the configured source. (The methods supplied via .Fa dtab take priority over those implemented in NSS modules in the event of a conflict.)
p .Va defaults contains a list of default sources to try if .Xr nsswitch.conf 5 is missing or corrupted, or if there is no relevant entry for .Va database . It is an array of .Va ns_src structures, which have the following format: d -literal -offset indent typedef struct _ns_src { const char *src; uint32_t flags; } ns_src; .Ed
p The .Fa defaults array should consist of one entry for each source to be configured by default indicated by .Va src , and .Va flags set to the criterion desired (usually .Dv NS_SUCCESS ; refer to .Sx Method return values for more information). The last entry in .Va defaults should have .Va src set to .Dv NULL and .Va flags set to 0.
p For convenience, a global variable defined as:
p .Dl extern const ns_src __nsdefaultsrc[];
p exists which contains a single default entry for the source .Sq files that may be used by callers which do not require complicated default rules.
p .Sq Va ... are optional extra arguments, which are passed to the appropriate method as a variable argument list of the type .Vt va_list . .Ss Valid source types While there is support for arbitrary sources, the following #defines for commonly implemented sources are available: l -column NSSRC_COMPAT compat -offset indent t Sy "#define value" t Dv NSSRC_FILES Ta "files" t Dv NSSRC_DB Ta "db" t Dv NSSRC_DNS Ta "dns" t Dv NSSRC_NIS Ta "nis" t Dv NSSRC_COMPAT Ta "compat" .El
p Refer to .Xr nsswitch.conf 5 for a complete description of what each source type is. .Ss Method return values The .Vt nss_method functions must return one of the following values depending upon status of the lookup: l -column "Return value" "Status code" t Sy "Return value Status code" t Dv NS_SUCCESS Ta success t Dv NS_NOTFOUND Ta notfound t Dv NS_UNAVAIL Ta unavail t Dv NS_TRYAGAIN Ta tryagain t Dv NS_RETURN Ta -none- .El
p Refer to .Xr nsswitch.conf 5 for a complete description of each status code.
p The .Fn nsdispatch function returns the value of the method that caused the dispatcher to terminate, or .Dv NS_NOTFOUND otherwise. .Sh NOTES .Fx Ns 's .Lb libc provides stubs for compatibility with NSS modules written for the .Tn GNU C Library .Nm nsswitch interface. However, these stubs only support the use of the .Dq Li passwd and .Dq Li group databases. .Sh SEE ALSO .Xr hesiod 3 , .Xr stdarg 3 , .Xr nsswitch.conf 5 , .Xr yp 8 .Sh HISTORY The .Fn nsdispatch function first appeared in .Fx 5.0 . It was imported from the .Nx Project, where it appeared first in .Nx 1.4 . Support for NSS modules first appeared in .Fx 5.1 . .Sh AUTHORS .An Luke Mewburn Aq Mt lukem@netbsd.org wrote this freely-distributable name-service switch implementation, using ideas from the .Tn ULTRIX svc.conf(5) and .Tn Solaris nsswitch.conf(4) manual pages. The .Fx Project added the support for threads and NSS modules, and normalized the uses of .Fn nsdispatch within the standard C library.