From 5512745e3a0dd92942a13663a83cb4ff4dab5ff8 Mon Sep 17 00:00:00 2001
From: Xin LI <delphij@FreeBSD.org>
Date: Fri, 29 May 2009 07:55:44 +0000
Subject: [PATCH] Document how to enable strict RFC 1034 enforcements.

PR:		kern/129477
---
 lib/libc/net/resolver.3 | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/lib/libc/net/resolver.3 b/lib/libc/net/resolver.3
index e35a5450ccb5..c1a37b3a24c8 100644
--- a/lib/libc/net/resolver.3
+++ b/lib/libc/net/resolver.3
@@ -28,7 +28,7 @@
 .\"     @(#)resolver.3	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd November 4, 2006
+.Dd May 29, 2009
 .Dt RESOLVER 3
 .Os
 .Sh NAME
@@ -401,6 +401,19 @@ function properly if the programmer attempts to declare his or her own
 .Va _res
 structure in an attempt to replace the per-thread version referred to
 by that macro.
+.Pp
+The following compile-time option can be specified to change the default
+behavior of resolver routines when necessary.
+.Bl -tag -width RES_ENFORCE_RFC1034
+.It Dv RES_ENFORCE_RFC1034
+If this symbol is defined during compile-time,
+.Fn res_search
+will enforce RFC 1034 check, namely, disallow using of underscore character
+within host names.
+This is used by the standard host lookup routines like
+.Xr gethostbyname 3 .
+For compatibility reasons this option is not enabled by default.
+.El
 .Sh RETURN VALUES
 The
 .Fn res_init