[src/trunk]: src/lib/libc/net PR/48379: mention kqueue functionality

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/9a056c43c021
branches:  trunk
changeset: 791342:9a056c43c021
user:      christos <christos%NetBSD.org@localhost>
date:      Wed Nov 13 23:58:51 2013 +0000

description:
PR/48379: mention kqueue functionality

diffstat:

 lib/libc/net/resolver.3 |  24 ++++++++++++++++++++++--
 1 files changed, 22 insertions(+), 2 deletions(-)

diffs (45 lines):

diff -r e5bc77beb872 -r 9a056c43c021 lib/libc/net/resolver.3
--- a/lib/libc/net/resolver.3   Wed Nov 13 22:11:52 2013 +0000
+++ b/lib/libc/net/resolver.3   Wed Nov 13 23:58:51 2013 +0000
@@ -1,4 +1,4 @@
-.\"    $NetBSD: resolver.3,v 1.26 2013/05/08 18:18:32 wiz Exp $
+.\"    $NetBSD: resolver.3,v 1.27 2013/11/13 23:58:51 christos Exp $
 .\" Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 .\"
 .\" Permission to use, copy, modify, and distribute this software for any
@@ -33,7 +33,7 @@
 .\"    @(#)resolver.3  6.5 (Berkeley) 6/23/90
 .\"    Id: resolver.man3,v 1.2 2009/01/21 00:12:34 each Exp
 .\"
-.Dd May 8, 2013
+.Dd November 13, 2013
 .Dt RESOLVER 3
 .Os
 .Sh NAME
@@ -364,6 +364,26 @@
 Initialization normally occurs on the first call
 to one of the other resolver routines.
 .Pp
+In
+.Nx
+the initialization code also sets up a
+.Xr kqueue 2
+and creates a
+.Xr kevent 2
+watching a file descriptor that points to the resolver file.
+Every resolver function, calls the internal function
+.Fn __res_check
+which checks for a new
+.Xr kevent 2
+related to the
+.Xr resolv.conf 5
+file, and reloads the file if necessary.
+This does not work if the file is accessed through a symlink and the symlink
+changes to point to a different file.
+To fix the symlink issue one could add a system call per resolver call to
+get the current time, and reload every so often.
+This is not done currently, but it is under consideration.
+.Pp
 The memory referred to by
 .Ft statp
 must be set to all zeros prior to the first call to