.\"	$NetBSD: nsdispatch.3,v 1.34 2017/07/03 21:32:49 wiz Exp $
.\"
.\" Copyright (c) 1997, 1998, 1999, 2004, 2005, 2008
.\" The NetBSD Foundation, Inc.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Luke Mewburn; and by Jason R. Thorpe.
.\"
.\" 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.
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.\" 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.
.\"
.Dd January 4, 2015
.Dt NSDISPATCH 3
.Os
.Sh NAME
.Nm nsdispatch
.Nd name-service switch dispatcher routine
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In nsswitch.h
.Ft int
.Fo nsdispatch
.Fa "void *nsdrv"
.Fa "const ns_dtab dtab[]"
.Fa "const char *database"
.Fa "const char *name"
.Fa "const ns_src defaults[]"
.Fa "..."
.Fc
.Sh DESCRIPTION
The
.Fn nsdispatch
function invokes the callback functions specified in
.Fa dtab
in the order given in
.Pa /etc/nsswitch.conf
for the database
.Fa database
until the action criteria for a source of that database is fulfilled.
.Pp
.Fa nsdrv
is passed to each callback function to use as necessary
(to pass back to the caller of
.Fn nsdispatch ) .
.Pp
.Fa dtab
is an array of
.Fa ns_dtab
structures, which have the following format:
.Bl -item -offset indent
.It
.Bd -literal
typedef struct {
	const char *src;
	nss_method cb;
	void *cb_data;
} ns_dtab;
.Ed
.It
The
.Fa dtab
array should consist of one entry for each source type that has a
static implementation,
with
.Fa src
as the name of the source,
.Fa cb
as a callback function which handles that source, and
.Fa cb_data
as a pointer to arbitrary data to be passed to the callback function.
The last entry in
.Fa dtab
should contain
.Dv NULL
values for
.Fa src ,
.Fa cb ,
and
.Fa cb_data .
.It
The callback function signature is described by the typedef:
.Bd -ragged -offset indent
.Ft typedef int
.Fo \*(lp*nss_method\*(rp
.Fa "void *cbrv"
.Fa "void *cbdata"
.Fa "va_list ap"
.Fc ;
.Bl -tag -width cbdata
.It Fa cbrv
The
.Fa nsdrv
that
.Fn nsdispatch
was invoked with.
.It Fa cbdata
The
.Fa cb_data
member of the array entry for the source that this
callback function implements in the
.Fa dtab
argument of
.Fn nsdispatch .
.It Fa ap
The
.Fa ...
arguments to
.Fn nsdispatch ,
converted to a
.Ft va_list .
.El
.Ed
.El
.Pp
.Fa database
and
.Fa name
are used to select methods from optional per-source
dynamically-loaded modules.
.Fa name
is usually the name of the function calling
.Fn nsdispatch .
Note that the callback functions provided by
.Fa dtab
take priority over those implemented in dynamically-loaded modules in the
event of a conflict.
.Pp
.Fa defaults
contains a list of default sources to try in the case of
a missing or corrupt
.Xr nsswitch.conf 5 ,
or if there isn't a relevant entry for
.Fa database .
It is an array of
.Fa ns_src
structures, which have the following format:
.Bl -item -offset indent
.It
.Bd -literal
typedef struct {
	const char *src;
	uint32_t flags;
} ns_src;
.Ed
.It
The
.Fa defaults
array should consist of one entry for each source to consult by default
indicated by
.Fa src ,
and
.Fa flags
set to the desired behavior
(usually
.Dv NS_SUCCESS ;
refer to
.Sx Callback function return values
for more information).
The last entry in
.Fa defaults
should have
.Fa src
set to
.Dv NULL
and
.Fa flags
set to 0.
.It
Some invokers of
.Fn nsdispatch
(such as
.Xr setgrent 3 )
need to force all callback functions to be invoked,
irrespective of the action criteria listed in
.Xr nsswitch.conf 5 .
This can be achieved by adding
.Dv NS_FORCEALL
to
.Fa defaults[0].flags
before invoking
.Fn nsdispatch .
The return value of
.Fn nsdispatch
will be the result of the final callback function invoked.
.It
For convenience, a global variable defined as:
.Dl extern const ns_src __nsdefaultsrc[];
exists which contains a single default entry for
.Sq files
for use by callers which don't require complicated default rules.
.El
.Pp
.Fa ...
are optional extra arguments, which
are passed to the appropriate callback function as a
.Xr stdarg 3
variable argument
list of the type
.Fa va_list .
.Pp
.Nm
returns the value of the callback function that caused the dispatcher
to finish, or
.Dv NS_NOTFOUND
otherwise.
.\"
.Ss Dynamically-loaded module interface
The
.Fn nsdispatch
function loads callback functions from the run-time link-editor's search
path using the following naming convention:
.Bl -item -offset indent
.It
.Bd -literal
nss_<source>.so.<version>
.Ed
.Bl -tag -width XversionX
.It Aq source
The source that the module implements.
.It Aq version
The
.Nm nsdispatch
module interface version, which is defined by the integer
.Dv NSS_MODULE_INTERFACE_VERSION ,
which has the value 0.
.El
.El
.Pp
When a module is loaded,
.Fn nsdispatch
looks for and calls the following function in the module:
.Pp
.Bd -ragged -offset indent
.Ft ns_mtab *
.Fo nss_module_register
.Fa "const char *source"
.Fa "u_int *nelems"
.Fa "nss_module_unregister_fn *unreg"
.Fc ;
.Pp
.Bl -tag -width source
.It Fa source
The name of the source that the module implements, as used by
.Fn nsdispatch
to construct the module's name.
.It Fa nelems
A pointer to an unsigned integer that
.Fn nss_module_register
should set to the number of elements in the
.Ft ns_mtab
array returned by
.Fn nss_module_register ,
or
.Dv 0
if there was a failure.
.It Fa unreg
A pointer to a function pointer that
.Fn nss_module_register
can optionally set to an unregister function to be invoked when the module is
unloaded, or
.Dv NULL
if there isn't one.
.El
.Ed
.Pp
The unregister function signature is described by the typedef:
.Pp
.Bd -ragged -offset indent
.Ft typedef void
.Fo \*(lp*nss_module_unregister_fn\*(rp
.Fa "ns_mtab *mtab"
.Fa "u_int nelems"
.Fc ;
.Pp
.Bl -tag -width nelems
.It Fa mtab
The array of
.Ft ns_mtab
structures returned by
.Fn nss_module_register .
.It Fa nelems
The
.Fa *nelems
value set by
.Fn nss_module_register .
.El
.Ed
.Pp
.Fn nss_module_register
returns an array of
.Ft ns_mtab
structures
(with
.Fa *nelems
entries), or
.Dv NULL
if there was a failure.
The
.Ft ns_mtab
structures have the following format:
.Bl -item -offset indent
.It
.Bd -literal
typedef struct {
	const char *database;
	const char *name;
	nss_method method;
	void *mdata;
} ns_mtab;
.Ed
.It
The
.Fa mtab
array should consist of one entry for each callback function (method)
that is implemented,
with
.Fa database
as the name of the database,
.Fa name
as the name of the callback function,
.Fa method
as the
.Ft nss_method
callback function that implements the method, and
.Fa mdata
as a pointer to arbitrary data to be passed to the callback function as its
.Fa cbdata
argument.
.El
.\"
.Ss Valid source types
While there is support for arbitrary sources, the following
#defines for commonly implemented sources are provided:
.Bl -column NSSRC_COMPAT COMPAT -offset indent
.It Sy #define	Value
.It NSSRC_FILES	"files"
.It NSSRC_DNS	"dns"
.It NSSRC_NIS	"nis"
.It NSSRC_COMPAT	"compat"
.El
.Pp
Refer to
.Xr nsswitch.conf 5
for a complete description of what each source type is.
.\"
.Ss Valid database types
While there is support for arbitrary databases, the following
#defines for currently implemented system databases are provided:
.Bl -column NSDB_PASSWD_COMPAT PASSWD_COMPAT -offset indent
.It Sy #define	Value
.It NSDB_HOSTS	"hosts"
.It NSDB_GROUP	"group"
.It NSDB_GROUP_COMPAT	"group_compat"
.It NSDB_NETGROUP	"netgroup"
.It NSDB_NETWORKS	"networks"
.It NSDB_PASSWD	"passwd"
.It NSDB_PASSWD_COMPAT	"passwd_compat"
.It NSDB_SHELLS	"shells"
.El
.Pp
Refer to
.Xr nsswitch.conf 5
for a complete description of what each database is.
.\"
.Ss Callback function return values
The callback functions should return one of the following values
depending upon status of the lookup:
.Bl -column NS_NOTFOUND -offset indent
.It Sy "Return value"	Status code
.It NS_SUCCESS	The requested entry was found.
.It NS_NOTFOUND	The entry is not present at this source.
.It NS_TRYAGAIN	The source is busy, and may respond to retries.
.It NS_UNAVAIL	The source is not responding, or entry is corrupt.
.El
.\"
.Sh CALLBACK FUNCTION API FOR STANDARD DATABASES
The organization of the
.Fa ap
argument for an
.Fn nss_method
callback function for a standard method in a standard database is:
.Bl -enum -offset indent -compact
.It
Pointer to return value of the standard function.
.It
First argument of the standard function.
.It
(etc.)
.El
.Pp
For example, given the standard function
.Xr getgrnam 3 :
.Bd -ragged -offset indent -compact
.Ft struct group *
.Fn getgrnam "const char *name"
.Ed
the
.Fa ap
organization used by the callback functions is:
.Bl -enum -offset indent -compact
.It
.Ft "struct group **"
.It
.Ft "const char *"
.El
.Pp
.Sy NOTE:
Not all standard databases are using this calling convention yet;
those that aren't are noted below.
These will be changed in the future.
.Pp
The callback function names and
.Ft va_list
organization for various standard database callback functions are:
.\"
.Ss Methods for hosts database
.Bl -tag -width 3n
.It Sy getaddrinfo
.Ft "char *name" ,
.Ft "const struct addrinfo *pai"
.Pp
Returns
.Ft "struct addrinfo *"
via
.Ft "void *cbrv" .
.It Sy gethostbyaddr
.Ft "unsigned char *addr" ,
.Ft "int addrlen" ,
.Ft "int af"
.Pp
Returns
.Ft "struct getnamaddr *"
via
.Ft "void *cbrv" .
.It Sy gethostbyname
.Ft "char *name" ,
.Ft "int namelen" ,
.Ft "int af"
.Pp
Returns
.Ft "struct getnamaddr *"
via
.Ft "void *cbrv" .
.El
.Pp
The
.Ft "struct getnamaddr"
is defined internally in libc as:
.Bd -literal
struct getnamaddr { 
        struct hostent *hp;
        char *buf; 
        size_t buflen;
        int *he; 
}; 
.Ed
.\"
.Ss Methods for group and group_compat databases
.Bl -tag -width 3n
.It Sy endgrent
Empty
.Fa ap .
.Pp
All methods for all sources are invoked for this method name.
.It Sy getgrent
.Ft "struct group **retval"
.Pp
.Fa *retval
should be set to a pointer to an internal static
.Ft "struct group"
on success,
.Dv NULL
otherwise.
.Pp
.Xr getgrent 3
returns
.Fa *retval
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS ,
.Dv NULL
otherwise.
.It Sy getgrent_r
.Ft "int *retval" ,
.Ft "struct group *grp" ,
.Ft "char *buffer" ,
.Ft "size_t buflen" ,
.Ft "struct group **result"
.Pp
.Fa *retval
should be set to an appropriate
.Xr errno 2
on failure.
.Pp
.Xr getgrent_r 3
returns 0
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS
or
.Dv NS_NOTFOUND ,
and
.Fa *retval
otherwise.
.It Sy getgrgid
.Ft "struct group **retval" ,
.Ft "gid_t gid"
.Pp
.Fa *retval
should be set to a pointer to an internal static
.Ft "struct group"
on success,
.Dv NULL
otherwise.
.Pp
.Xr getgrgid 3
returns
.Fa *retval
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS ,
.Dv NULL
otherwise.
.It Sy getgrgid_r
.Ft "int *retval" ,
.Ft "gid_t gid" ,
.Ft "struct group *grp" ,
.Ft "char *buffer" ,
.Ft "size_t buflen" ,
.Ft "struct group **result"
.Pp
.Fa *retval
should be set to an appropriate
.Xr errno 2
on failure.
.Pp
.Xr getgrgid_r 3
returns 0
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS
or
.Dv NS_NOTFOUND ,
and
.Fa *retval
otherwise.
.It Sy getgrnam
.Ft "struct group **retval" ,
.Ft "const char *name"
.Pp
.Fa *retval
should be set to a pointer to an internal static
.Ft "struct group"
on success,
.Dv NULL
otherwise.
.Pp
.Xr getgrnam 3
returns
.Fa *retval
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS ,
.Dv NULL
otherwise.
.It Sy getgrnam_r
.Ft "int *retval" ,
.Ft "const char *name" ,
.Ft "struct group *grp" ,
.Ft "char *buffer" ,
.Ft "size_t buflen" ,
.Ft "struct group **result"
.Pp
.Fa *retval
should be set to an appropriate
.Xr errno 2
on failure.
.Pp
.Xr getgrnam_r 3
returns 0
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS
or
.Dv NS_NOTFOUND ,
and
.Fa *retval
otherwise.
.It Sy getgroupmembership
.Ft "int *retval" ,
.Ft "const char *name" ,
.Ft "gid_t basegid" ,
.Ft "gid_t *groups" ,
.Ft "int maxgrp" ,
.Ft "int *groupc"
.Pp
.Fa retval
is unused.
.Pp
Lookups for
.Sy group_compat
are also stopped if
.Dv NS_SUCCESS
was returned to prevent multiple
.Dq "+:"
compat entries from being expanded.
.Pp
.Xr getgroupmembership 3
returns
is -1 if
.Fa *groupc
is greater than to
.Fa maxgrp ,
and 0 otherwise.
.It Sy setgroupent
.Ft "int *retval" ,
.Ft "int stayopen"
.Pp
.Fa retval
should be set to 0 on failure and 1 on success.
.Pp
All methods for all sources are invoked for this method name.
.It Sy setgrent
Empty
.Fa ap .
.Pp
All methods for all sources are invoked for this method name.
.El
.\"
.Ss Methods for netgroup database
.Sy NOTE:
The method APIs for this database will be changing in the near future.
.Bl -tag -width 3n
.It Sy endnetgrent
Empty
.Fa ap .
.It Sy lookup
.Ft "char *name" ,
.Ft "char **line" ,
.Ft "int bywhat"
.Pp
Find the given
.Fa name
and return its value in
.Fa line .
.Fa bywhat
is one of
.Dv _NG_KEYBYNAME ,
.Dv _NG_KEYBYUSER ,
or
.Dv _NG_KEYBYHOST .
.It Sy getnetgrent
.Ft "int *retval" ,
.Ft "const char **host" ,
.Ft "const char **user" ,
.Ft "const char **domain"
.Pp
.Fa *retval
should be set to 0 for no more netgroup members and 1 otherwise.
.Pp
.Xr getnetgrent 3
returns
.Fa *retval
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS ,
0 otherwise.
.It Sy innetgr
.Ft "int *retval" ,
.Ft "const char *grp" ,
.Ft "const char *host" ,
.Ft "const char *user" ,
.Ft "const char *domain"
.Pp
.Fa *retval
should be set to 1 for a successful match and 0 otherwise.
.It Sy setnetgrent
.Ft "const char *netgroup"
.El
.\"
.Ss Methods for networks database
.Bl -tag -width 3n
.It Sy getnetbyaddr
.Ft "struct netent **retval" ,
.Ft "uint32_t net" ,
.Ft "int type"
.Pp
.Fa *retval
should be set to a pointer to an internal static
.Ft "struct netent"
on success,
.Dv NULL
otherwise.
.Pp
.Xr getnetbyaddr 3
returns
.Fa *retval
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS ,
.Dv NULL
otherwise.
.It Sy getnetbyname
.Ft "struct netent **retval" ,
.Ft "const char *name"
.Pp
.Fa *retval
should be set to a pointer to an internal static
.Ft "struct netent"
on success,
.Dv NULL
otherwise.
.Pp
.Xr getnetbyname 3
returns
.Fa *retval
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS ,
.Dv NULL
otherwise.
.El
.\"
.Ss Methods for passwd and passwd_compat databases
.Bl -tag -width 3n
.It Sy endpwent
Empty
.Fa ap .
.Pp
All methods for all sources are invoked for this method name.
.It Sy getpwent
.Ft "struct passwd **retval"
.Pp
.Fa *retval
should be set to a pointer to an internal static
.Ft "struct passwd"
on success,
.Dv NULL
otherwise.
.Pp
.Xr getpwent 3
returns
.Fa *retval
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS ,
.Dv NULL
otherwise.
.It Sy getpwent_r
.Ft "int *retval" ,
.Ft "struct passwd *pw" ,
.Ft "char *buffer" ,
.Ft "size_t buflen" ,
.Ft "struct passwd **result"
.Pp
.Fa *retval
should be set to an appropriate
.Xr errno 2
on failure.
.Pp
.Xr getpwent_r 3
returns 0
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS
or
.Dv NS_NOTFOUND ,
and
.Fa *retval
otherwise.
.It Sy getpwnam
.Ft "struct passwd **retval" ,
.Ft "const char *name"
.Pp
.Fa *retval
should be set to a pointer to an internal static
.Ft "struct passwd"
on success,
.Dv NULL
otherwise.
.Pp
.Xr getpwnam 3
returns
.Fa *retval
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS ,
.Dv NULL
otherwise.
.It Sy getpwnam_r
.Ft "int *retval" ,
.Ft "const char *name" ,
.Ft "struct passwd *pw" ,
.Ft "char *buffer" ,
.Ft "size_t buflen" ,
.Ft "struct passwd **result"
.Pp
.Fa *retval
should be set to an appropriate
.Xr errno 2
on failure.
.Pp
.Xr getpwnam_r 3
returns 0
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS
or
.Dv NS_NOTFOUND ,
and
.Fa *retval
otherwise.
.It Sy getpwuid
.Ft "struct passwd **retval" ,
.Ft "uid_t uid"
.Pp
.Fa *retval
should be set to a pointer to an internal static
.Ft "struct passwd"
on success,
.Dv NULL
otherwise.
.Pp
.Xr getpwuid 3
returns
.Fa *retval
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS ,
.Dv NULL
otherwise.
.It Sy getpwuid_r
.Ft "int *retval" ,
.Ft "uid_t uid" ,
.Ft "struct passwd *pw" ,
.Ft "char *buffer" ,
.Ft "size_t buflen" ,
.Ft "struct passwd **result"
.Pp
.Fa *retval
should be set to an appropriate
.Xr errno 2
on failure.
.Pp
.Xr getpwuid_r 3
returns 0
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS
or
.Dv NS_NOTFOUND ,
and
.Fa *retval
otherwise.
.It Sy setpassent
.Ft "int *retval" ,
.Ft "int stayopen"
.Pp
.Fa retval
should be set to 0 on failure and 1 on success.
.Pp
All methods for all sources are invoked for this method name.
.It Sy setpwent
Empty
.Fa ap .
.Pp
All methods for all sources are invoked for this method name.
.El
.\"
.Ss Methods for shells database
.Bl -tag -width 3n
.It Sy endusershell
Empty
.Fa ap .
.Pp
All methods for all sources are invoked for this method name.
.It Sy getusershell
.Ft "char **retval"
.Pp
.Xr getusershell 3
returns
.Fa *retval
if
.Fn nsdispatch
returns
.Dv NS_SUCCESS ,
and 0 otherwise.
.It Sy setusershell
Empty
.Fa ap .
.Pp
All methods for all sources are invoked for this method name.
.El
.\"
.Sh SEE ALSO
.Xr ld.elf_so 1 ,
.Xr hesiod 3 ,
.Xr stdarg 3 ,
.Xr ypclnt 3 ,
.Xr nsswitch.conf 5
.Sh HISTORY
The
.Nm
routines first appeared in
.Nx 1.4 .
Support for dynamically-loaded modules first appeared in
.Nx 3.0 .
.Sh AUTHORS
.An Luke Mewburn
.Aq Mt lukem@NetBSD.org
wrote this freely distributable name-service switch implementation,
using ideas from the
.Tn ULTRIX
.Xr svc.conf 5
and
.Tn Solaris
.Xr nsswitch.conf 4
manual pages.
Support for dynamically-loaded modules was added by
.An Jason Thorpe
.Aq Mt thorpej@NetBSD.org ,
based on code developed by the
.Fx
Project.