I found etc/rc.d/ipsec reads this, so add some documentation.

OK'd by Itojun.

share/man/man5/ipsec.conf.5

@@ -0,0 +1,72 @@
+.\"	$NetBSD: ipsec.conf.5,v 1.1 2001/02/23 02:32:27 hubertf Exp $
+.\"
+.\" Copyright (c) 2001 The NetBSD Foundation, Inc.
+.\" All rights reserved.
+.\"
+.\" This document is derived from works contributed to The NetBSD Foundation
+.\" by Hubert Feyrer.
+.\"
+.\" 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.
+.\" 3. The name of the author may not be used to endorse or promote products
+.\"    derived from this software without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 February 19, 2001
+.Dt IPSEC.CONF 5
+.Os
+.Sh NAME
+.Nm ipsec.conf
+.Nd static IPsec configuration read at system startup
+.Sh DESCRIPTION
+The
+.Nm
+file is read at system startup time if 
+.Sy ipsec
+is set to 
+.Dq yes
+in 
+.Xr rc.conf 5 .
+.Xr setkey 8
+is run with the
+.Fl f
+option to load in IPsec manual keys and policies from
+.Pa /etc/ipsec.conf
+at boot time, before any interfaces are configured.
+.Pp
+Please see the 
+.Xr setkey 8
+manpage for all the commands available.
+.Sh FILES
+.Bl -tag -width /etc/ipsec.conf -compact
+.It Pa /etc/ipsec.conf
+The file
+.Nm
+resides in
+.Pa /etc .
+.El
+.Sh SEE ALSO
+.Xr setkey 8 ,
+.Xr ipsec 4
+.Sh HISTORY
+The
+.Nm
+file appeared in
+.Nx 1.5 .