1.\" $NetBSD: nsdispatch.3,v 1.29 2009/10/14 17:24:03 joerg Exp $ 2.\" 3.\" Copyright (c) 1997, 1998, 1999, 2004, 2005, 2008 4.\" The NetBSD Foundation, Inc. 5.\" All rights reserved. 6.\" 7.\" This code is derived from software contributed to The NetBSD Foundation 8.\" by Luke Mewburn; and by Jason R. Thorpe. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29.\" POSSIBILITY OF SUCH DAMAGE. 30.\" 31.Dd May 8, 2008 32.Dt NSDISPATCH 3 33.Os 34.Sh NAME 35.Nm nsdispatch 36.Nd name-service switch dispatcher routine 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In nsswitch.h 41.Ft int 42.Fo nsdispatch 43.Fa "void *nsdrv" 44.Fa "const ns_dtab dtab[]" 45.Fa "const char *database" 46.Fa "const char *name" 47.Fa "const ns_src defaults[]" 48.Fa "..." 49.Fc 50.Sh DESCRIPTION 51The 52.Fn nsdispatch 53function invokes the callback functions specified in 54.Fa dtab 55in the order given in 56.Pa /etc/nsswitch.conf 57for the database 58.Fa database 59until the action criteria for a source of that database is fulfilled. 60.Pp 61.Fa nsdrv 62is passed to each callback function to use as necessary 63(to pass back to the caller of 64.Fn nsdispatch ) . 65.Pp 66.Fa dtab 67is an array of 68.Fa ns_dtab 69structures, which have the following format: 70.Bl -item -offset indent 71.It 72.Bd -literal 73typedef struct { 74 const char *src; 75 nss_method cb; 76 void *cb_data; 77} ns_dtab; 78.Ed 79.It 80The 81.Fa dtab 82array should consist of one entry for each source type that has a 83static implementation, 84with 85.Fa src 86as the name of the source, 87.Fa cb 88as a callback function which handles that source, and 89.Fa cb_data 90as a pointer to arbitrary data to be passed to the callback function. 91The last entry in 92.Fa dtab 93should contain 94.Dv NULL 95values for 96.Fa src , 97.Fa cb , 98and 99.Fa cb_data . 100.It 101The callback function signature is described by the typedef: 102.Bd -ragged -offset indent 103.Ft typedef int 104.Fo \*(lp*nss_method\*(rp 105.Fa "void *cbrv" 106.Fa "void *cbdata" 107.Fa "va_list ap" 108.Fc ; 109.Bl -tag -width cbdata 110.It Fa cbrv 111The 112.Fa nsdrv 113that 114.Fn nsdispatch 115was invoked with. 116.It Fa cbdata 117The 118.Fa cb_data 119member of the array entry for the source that this 120callback function implements in the 121.Fa dtab 122argument of 123.Fn nsdispatch . 124.It Fa ap 125The 126.Fa ... 127arguments to 128.Fn nsdispatch , 129converted to a 130.Ft va_list . 131.El 132.Ed 133.El 134.Pp 135.Fa database 136and 137.Fa name 138are used to select methods from optional per-source 139dynamically-loaded modules. 140.Fa name 141is usually the name of the function calling 142.Fn nsdispatch . 143Note that the callback functions provided by 144.Fa dtab 145take priority over those implemented in dynamically-loaded modules in the 146event of a conflict. 147.Pp 148.Fa defaults 149contains a list of default sources to try in the case of 150a missing or corrupt 151.Xr nsswitch.conf 5 , 152or if there isn't a relevant entry for 153.Fa database . 154It is an array of 155.Fa ns_src 156structures, which have the following format: 157.Bl -item -offset indent 158.It 159.Bd -literal 160typedef struct { 161 const char *src; 162 uint32_t flags; 163} ns_src; 164.Ed 165.It 166The 167.Fa defaults 168array should consist of one entry for each source to consult by default 169indicated by 170.Fa src , 171and 172.Fa flags 173set to the desired behavior 174(usually 175.Dv NS_SUCCESS ; 176refer to 177.Sx Callback function return values 178for more information). 179The last entry in 180.Fa defaults 181should have 182.Fa src 183set to 184.Dv NULL 185and 186.Fa flags 187set to 0. 188.It 189Some invokers of 190.Fn nsdispatch 191(such as 192.Xr setgrent 3 ) 193need to force all callback functions to be invoked, 194irrespective of the action criteria listed in 195.Xr nsswitch.conf 5 . 196This can be achieved by adding 197.Dv NS_FORCEALL 198to 199.Fa defaults[0].flags 200before invoking 201.Fn nsdispatch . 202The return value of 203.Fn nsdispatch 204will be the result of the final callback function invoked. 205.It 206For convenience, a global variable defined as: 207.Dl extern const ns_src __nsdefaultsrc[]; 208exists which contains a single default entry for 209.Sq files 210for use by callers which don't require complicated default rules. 211.El 212.Pp 213.Fa ... 214are optional extra arguments, which 215are passed to the appropriate callback function as a 216.Xr stdarg 3 217variable argument 218list of the type 219.Fa va_list . 220.Pp 221.Nm 222returns the value of the callback function that caused the dispatcher 223to finish, or 224.Dv NS_NOTFOUND 225otherwise. 226.\" 227.Ss Dynamically-loaded module interface 228The 229.Fn nsdispatch 230function loads callback functions from the run-time link-editor's search 231path using the following naming convention: 232.Bl -item -offset indent 233.It 234.Bd -literal 235nss_\*[Lt]source\*[Gt].so.\*[Lt]version\*[Gt] 236.Ed 237.Bl -tag -width XversionX 238.It Aq source 239The source that the module implements. 240.It Aq version 241The 242.Nm nsdispatch 243module interface version, which is defined by the integer 244.Dv NSS_MODULE_INTERFACE_VERSION , 245which has the value 0. 246.El 247.El 248.Pp 249When a module is loaded, 250.Fn nsdispatch 251looks for and calls the following function in the module: 252.Pp 253.Bd -ragged -offset indent 254.Ft ns_mtab * 255.Fo nss_module_register 256.Fa "const char *source" 257.Fa "u_int *nelems" 258.Fa "nss_module_unregister_fn *unreg" 259.Fc ; 260.Pp 261.Bl -tag -width source 262.It Fa source 263The name of the source that the module implements, as used by 264.Fn nsdispatch 265to construct the module's name. 266.It Fa nelems 267A pointer to an unsigned integer that 268.Fn nss_module_register 269should set to the number of elements in the 270.Ft ns_mtab 271array returned by 272.Fn nss_module_register , 273or 274.Dv 0 275if there was a failure. 276.It Fa unreg 277A pointer to a function pointer that 278.Fn nss_module_register 279can optionally set to an unregister function to be invoked when the module is 280unloaded, or 281.Dv NULL 282if there isn't one. 283.El 284.Ed 285.Pp 286The unregister function signature is described by the typedef: 287.Pp 288.Bd -ragged -offset indent 289.Ft typedef void 290.Fo \*(lp*nss_module_unregister_fn\*(rp 291.Fa "ns_mtab *mtab" 292.Fa "u_int nelems" 293.Fc ; 294.Pp 295.Bl -tag -width nelems 296.It Fa mtab 297The array of 298.Ft ns_mtab 299structures returned by 300.Fn nss_module_register . 301.It Fa nelems 302The 303.Fa *nelems 304value set by 305.Fn nss_module_register . 306.El 307.Ed 308.Pp 309.Fn nss_module_register 310returns an array of 311.Ft ns_mtab 312structures 313(with 314.Fa *nelems 315entries), or 316.Dv NULL 317if there was a failure. 318The 319.Ft ns_mtab 320structures have the following format: 321.Bl -item -offset indent 322.It 323.Bd -literal 324typedef struct { 325 const char *database; 326 const char *name; 327 nss_method method; 328 void *mdata; 329} ns_mtab; 330.Ed 331.It 332The 333.Fa mtab 334array should consist of one entry for each callback function (method) 335that is implemented, 336with 337.Fa database 338as the name of the database, 339.Fa name 340as the name of the callback function, 341.Fa method 342as the 343.Ft nss_method 344callback function that implements the method, and 345.Fa mdata 346as a pointer to arbitrary data to be passed to the callback function as its 347.Fa cbdata 348argument. 349.El 350.\" 351.Ss Valid source types 352While there is support for arbitrary sources, the following 353#defines for commonly implemented sources are provided: 354.Bl -column NSSRC_COMPAT COMPAT -offset indent 355.It Sy #define Value 356.It NSSRC_FILES "files" 357.It NSSRC_DNS "dns" 358.It NSSRC_NIS "nis" 359.It NSSRC_COMPAT "compat" 360.El 361.Pp 362Refer to 363.Xr nsswitch.conf 5 364for a complete description of what each source type is. 365.\" 366.Ss Valid database types 367While there is support for arbitrary databases, the following 368#defines for currently implemented system databases are provided: 369.Bl -column NSDB_PASSWD_COMPAT PASSWD_COMPAT -offset indent 370.It Sy #define Value 371.It NSDB_HOSTS "hosts" 372.It NSDB_GROUP "group" 373.It NSDB_GROUP_COMPAT "group_compat" 374.It NSDB_NETGROUP "netgroup" 375.It NSDB_NETWORKS "networks" 376.It NSDB_PASSWD "passwd" 377.It NSDB_PASSWD_COMPAT "passwd_compat" 378.It NSDB_SHELLS "shells" 379.El 380.Pp 381Refer to 382.Xr nsswitch.conf 5 383for a complete description of what each database is. 384.\" 385.Ss Callback function return values 386The callback functions should return one of the following values 387depending upon status of the lookup: 388.Bl -column NS_NOTFOUND -offset indent 389.It Sy "Return value" Status code 390.It NS_SUCCESS The requested entry was found. 391.It NS_NOTFOUND The entry is not present at this source. 392.It NS_TRYAGAIN The source is busy, and may respond to retries. 393.It NS_UNAVAIL The source is not responding, or entry is corrupt. 394.El 395.\" 396.Sh CALLBACK FUNCTION API FOR STANDARD DATABASES 397The organization of the 398.Fa ap 399argument for an 400.Fn nss_method 401callback function for a standard method in a standard database is: 402.Bl -enum -offset indent -compact 403.It 404Pointer to return value of the standard function. 405.It 406First argument of the standard function. 407.It 408(etc.) 409.El 410.Pp 411For example, given the standard function 412.Xr getgrnam 3 : 413.Bd -ragged -offset indent -compact 414.Ft struct group * 415.Fn getgrnam "const char *name" 416.Ed 417the 418.Fa ap 419organization used by the callback functions is: 420.Bl -enum -offset indent -compact 421.It 422.Ft "struct group **" 423.It 424.Ft "const char *" 425.El 426.Pp 427.Sy NOTE: 428Not all standard databases are using this calling convention yet; 429those that aren't are noted below. 430These will be changed in the future. 431.Pp 432The callback function names and 433.Ft va_list 434organization for various standard database callback functions are: 435.\" 436.Ss Methods for hosts database 437.Sy NOTE: 438The method APIs for this database will be changing in the near future. 439.Bl -tag -width 3n 440.It Sy getaddrinfo 441.Ft "char *name" , 442.Ft "const struct addrinfo *pai" 443.Pp 444Returns 445.Ft "struct addrinfo *" 446via 447.Ft "void *cbrv" . 448.It Sy gethostbyaddr 449.Ft "unsigned char *addr" , 450.Ft "int addrlen" , 451.Ft "int af" 452.Pp 453Returns 454.Ft "struct hostent *" 455via 456.Ft "void *cbrv" . 457.It Sy gethostbyname 458.Ft "char *name" , 459.Ft "int namelen" , 460.Ft "int af" 461.Pp 462Returns 463.Ft "struct hostent *" 464via 465.Ft "void *cbrv" . 466.El 467.\" 468.Ss Methods for group and group_compat databases 469.Bl -tag -width 3n 470.It Sy endgrent 471Empty 472.Fa ap . 473.Pp 474All methods for all sources are invoked for this method name. 475.It Sy getgrent 476.Ft "struct group **retval" 477.Pp 478.Fa *retval 479should be set to a pointer to an internal static 480.Ft "struct group" 481on success, 482.Dv NULL otherwise. 483.Pp 484.Xr getgrent 3 485returns 486.Fa *retval 487if 488.Fn nsdispatch 489returns 490.Dv NS_SUCCESS , 491.Dv NULL 492otherwise. 493.It Sy getgrent_r 494.Ft "int *retval" , 495.Ft "struct group *grp" , 496.Ft "char *buffer" , 497.Ft "size_t buflen" , 498.Ft "struct group **result" 499.Pp 500.Fa *retval 501should be set to an appropriate 502.Xr errno 2 503on failure. 504.Pp 505.Xr getgrent_r 3 506returns 0 507if 508.Fn nsdispatch 509returns 510.Dv NS_SUCCESS 511or 512.Dv NS_NOTFOUND , 513and 514.Fa *retval 515otherwise. 516.It Sy getgrgid 517.Ft "struct group **retval" , 518.Ft "gid_t gid" 519.Pp 520.Fa *retval 521should be set to a pointer to an internal static 522.Ft "struct group" 523on success, 524.Dv NULL otherwise. 525.Pp 526.Xr getgrgid 3 527returns 528.Fa *retval 529if 530.Fn nsdispatch 531returns 532.Dv NS_SUCCESS , 533.Dv NULL 534otherwise. 535.It Sy getgrgid_r 536.Ft "int *retval" , 537.Ft "gid_t gid" , 538.Ft "struct group *grp" , 539.Ft "char *buffer" , 540.Ft "size_t buflen" , 541.Ft "struct group **result" 542.Pp 543.Fa *retval 544should be set to an appropriate 545.Xr errno 2 546on failure. 547.Pp 548.Xr getgrgid_r 3 549returns 0 550if 551.Fn nsdispatch 552returns 553.Dv NS_SUCCESS 554or 555.Dv NS_NOTFOUND , 556and 557.Fa *retval 558otherwise. 559.It Sy getgrnam 560.Ft "struct group **retval" , 561.Ft "const char *name" 562.Pp 563.Fa *retval 564should be set to a pointer to an internal static 565.Ft "struct group" 566on success, 567.Dv NULL otherwise. 568.Pp 569.Xr getgrnam 3 570returns 571.Fa *retval 572if 573.Fn nsdispatch 574returns 575.Dv NS_SUCCESS , 576.Dv NULL 577otherwise. 578.It Sy getgrnam_r 579.Ft "int *retval" , 580.Ft "const char *name" , 581.Ft "struct group *grp" , 582.Ft "char *buffer" , 583.Ft "size_t buflen" , 584.Ft "struct group **result" 585.Pp 586.Fa *retval 587should be set to an appropriate 588.Xr errno 2 589on failure. 590.Pp 591.Xr getgrnam_r 3 592returns 0 593if 594.Fn nsdispatch 595returns 596.Dv NS_SUCCESS 597or 598.Dv NS_NOTFOUND , 599and 600.Fa *retval 601otherwise. 602.It Sy getgroupmembership 603.Ft "int *retval" , 604.Ft "const char *name" , 605.Ft "gid_t basegid" , 606.Ft "gid_t *groups" , 607.Ft "int maxgrp" , 608.Ft "int *groupc" 609.Pp 610.Fa retval 611is unused. 612.Pp 613Lookups for 614.Sy group_compat 615are also stopped if 616.Dv NS_SUCCESS 617was returned to prevent multiple 618.Dq "+:" 619compat entries from being expanded. 620.Pp 621.Xr getgroupmembership 3 622returns 623is -1 if 624.Fa *groupc 625is greater than to 626.Fa maxgrp , 627and 0 otherwise. 628.It Sy setgroupent 629.Ft "int *retval" , 630.Ft "int stayopen" 631.Pp 632.Fa retval 633should be set to 0 on failure and 1 on success. 634.Pp 635All methods for all sources are invoked for this method name. 636.It Sy setgrent 637Empty 638.Fa ap . 639.Pp 640All methods for all sources are invoked for this method name. 641.El 642.\" 643.Ss Methods for netgroup database 644.Sy NOTE: 645The method APIs for this database will be changing in the near future. 646.Bl -tag -width 3n 647.It Sy endnetgrent 648Empty 649.Fa ap . 650.It Sy lookup 651.Ft "char *name" , 652.Ft "char **line" , 653.Ft "int bywhat" 654.Pp 655Find the given 656.Fa name 657and return its value in 658.Fa line . 659.Fa bywhat 660is one of 661.Dv _NG_KEYBYNAME , 662.Dv _NG_KEYBYUSER , 663or 664.Dv _NG_KEYBYHOST . 665.It Sy getnetgrent 666.Ft "int *retval" , 667.Ft "const char **host" , 668.Ft "const char **user" , 669.Ft "const char **domain" 670.Pp 671.Fa *retval 672should be set to 0 for no more netgroup members and 1 otherwise. 673.Pp 674.Xr getnetgrent 3 675returns 676.Fa *retval 677if 678.Fn nsdispatch 679returns 680.Dv NS_SUCCESS , 6810 otherwise. 682.It Sy innetgr 683.Ft "int *retval" , 684.Ft "const char *grp" , 685.Ft "const char *host" , 686.Ft "const char *user" , 687.Ft "const char *domain" 688.Pp 689.Fa *retval 690should be set to 1 for a successful match and 0 otherwise. 691.It Sy setnetgrent 692.Ft "const char *netgroup" 693.El 694.\" 695.Ss Methods for networks database 696.Bl -tag -width 3n 697.It Sy getnetbyaddr 698.Ft "struct netent **retval" , 699.Ft "uint32_t net" , 700.Ft "int type" 701.Pp 702.Fa *retval 703should be set to a pointer to an internal static 704.Ft "struct netent" 705on success, 706.Dv NULL otherwise. 707.Pp 708.Xr getnetbyaddr 3 709returns 710.Fa *retval 711if 712.Fn nsdispatch 713returns 714.Dv NS_SUCCESS , 715.Dv NULL 716otherwise. 717.It Sy getnetbyname 718.Ft "struct netent **retval" , 719.Ft "const char *name" 720.Pp 721.Fa *retval 722should be set to a pointer to an internal static 723.Ft "struct netent" 724on success, 725.Dv NULL otherwise. 726.Pp 727.Xr getnetbyname 3 728returns 729.Fa *retval 730if 731.Fn nsdispatch 732returns 733.Dv NS_SUCCESS , 734.Dv NULL 735otherwise. 736.El 737.\" 738.Ss Methods for passwd and passwd_compat databases 739.Bl -tag -width 3n 740.It Sy endpwent 741Empty 742.Fa ap . 743.Pp 744All methods for all sources are invoked for this method name. 745.It Sy getpwent 746.Ft "struct passwd **retval" 747.Pp 748.Fa *retval 749should be set to a pointer to an internal static 750.Ft "struct passwd" 751on success, 752.Dv NULL otherwise. 753.Pp 754.Xr getpwent 3 755returns 756.Fa *retval 757if 758.Fn nsdispatch 759returns 760.Dv NS_SUCCESS , 761.Dv NULL 762otherwise. 763.It Sy getpwent_r 764.Ft "int *retval" , 765.Ft "struct passwd *pw" , 766.Ft "char *buffer" , 767.Ft "size_t buflen" , 768.Ft "struct passwd **result" 769.Pp 770.Fa *retval 771should be set to an appropriate 772.Xr errno 2 773on failure. 774.Pp 775.Xr getpwent_r 3 776returns 0 777if 778.Fn nsdispatch 779returns 780.Dv NS_SUCCESS 781or 782.Dv NS_NOTFOUND , 783and 784.Fa *retval 785otherwise. 786.It Sy getpwnam 787.Ft "struct passwd **retval" , 788.Ft "const char *name" 789.Pp 790.Fa *retval 791should be set to a pointer to an internal static 792.Ft "struct passwd" 793on success, 794.Dv NULL otherwise. 795.Pp 796.Xr getpwnam 3 797returns 798.Fa *retval 799if 800.Fn nsdispatch 801returns 802.Dv NS_SUCCESS , 803.Dv NULL 804otherwise. 805.It Sy getpwnam_r 806.Ft "int *retval" , 807.Ft "const char *name" , 808.Ft "struct passwd *pw" , 809.Ft "char *buffer" , 810.Ft "size_t buflen" , 811.Ft "struct passwd **result" 812.Pp 813.Fa *retval 814should be set to an appropriate 815.Xr errno 2 816on failure. 817.Pp 818.Xr getpwnam_r 3 819returns 0 820if 821.Fn nsdispatch 822returns 823.Dv NS_SUCCESS 824or 825.Dv NS_NOTFOUND , 826and 827.Fa *retval 828otherwise. 829.It Sy getpwuid 830.Ft "struct passwd **retval" , 831.Ft "uid_t uid" 832.Pp 833.Fa *retval 834should be set to a pointer to an internal static 835.Ft "struct passwd" 836on success, 837.Dv NULL otherwise. 838.Pp 839.Xr getpwuid 3 840returns 841.Fa *retval 842if 843.Fn nsdispatch 844returns 845.Dv NS_SUCCESS , 846.Dv NULL 847otherwise. 848.It Sy getpwuid_r 849.Ft "int *retval" , 850.Ft "uid_t uid" , 851.Ft "struct passwd *pw" , 852.Ft "char *buffer" , 853.Ft "size_t buflen" , 854.Ft "struct passwd **result" 855.Pp 856.Fa *retval 857should be set to an appropriate 858.Xr errno 2 859on failure. 860.Pp 861.Xr getpwuid_r 862returns 0 863if 864.Fn nsdispatch 865returns 866.Dv NS_SUCCESS 867or 868.Dv NS_NOTFOUND , 869and 870.Fa *retval 871otherwise. 872.It Sy setpassent 873.Ft "int *retval" , 874.Ft "int stayopen" 875.Pp 876.Fa retval 877should be set to 0 on failure and 1 on success. 878.Pp 879All methods for all sources are invoked for this method name. 880.It Sy setpwent 881Empty 882.Fa ap . 883.Pp 884All methods for all sources are invoked for this method name. 885.El 886.\" 887.Ss Methods for shells database 888.Bl -tag -width 3n 889.It Sy endusershell 890Empty 891.Fa ap . 892.Pp 893All methods for all sources are invoked for this method name. 894.It Sy getusershell 895.Ft "char **retval" 896.Pp 897.Xr getusershell 3 898returns 899.Fa *retval 900if 901.Fn nsdispatch 902returns 903.Dv NS_SUCCESS , 904and 0 otherwise. 905.It Sy setusershell 906Empty 907.Fa ap . 908.Pp 909All methods for all sources are invoked for this method name. 910.El 911.\" 912.Sh SEE ALSO 913.Xr ld.elf_so 1 , 914.Xr hesiod 3 , 915.Xr stdarg 3 , 916.Xr ypclnt 3 , 917.Xr nsswitch.conf 5 918.Sh HISTORY 919The 920.Nm 921routines first appeared in 922.Nx 1.4 . 923Support for dynamically-loaded modules first appeared in 924.Nx 3.0 . 925.Sh AUTHORS 926Luke Mewburn 927.Aq lukem@NetBSD.org 928wrote this freely distributable name-service switch implementation, 929using ideas from the 930.Tn ULTRIX 931.Xr svc.conf 5 932and 933.Tn Solaris 934.Xr nsswitch.conf 4 935manual pages. 936Support for dynamically-loaded modules was added by Jason Thorpe 937.Aq thorpej@NetBSD.org , 938based on code developed by the 939.Fx 940Project. 941