133 lines
4.0 KiB
Groff
133 lines
4.0 KiB
Groff
.\" $OpenBSD: enc.4,v 1.22 2006/05/26 08:51:29 jmc Exp $
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.\"
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.\" Copyright (c) 1999 Angelos D. Keromytis
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\"
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by Angelos D. Keromytis.
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.\" 4. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd November 28, 2007
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.Dt ENC 4
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.Os
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.Sh NAME
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.Nm enc
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.Nd Encapsulating Interface
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.Sh SYNOPSIS
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To compile this driver into the kernel,
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place the following line in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device enc"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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interface is a software loopback mechanism that allows hosts or
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firewalls to filter
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.Xr ipsec 4
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traffic using any firewall package that hooks in via the
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.Xr pfil 9
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framework.
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.Pp
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The
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.Nm
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interface allows an administrator to see incoming and outgoing packets
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before and after they will be or have been processed by
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.Xr ipsec 4
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via
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.Xr tcpdump 1 .
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.Pp
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The
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.Dq Li enc0
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interface inherits all IPsec traffic.
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Thus all IPsec traffic can be filtered based on
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.Dq Li enc0 ,
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and all IPsec traffic could be seen by invoking
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.Xr tcpdump 1
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on the
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.Dq Li enc0
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interface.
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.Pp
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What can be seen with
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.Xr tcpdump 1
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and what will be passed on to the firewalls via the
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.Xr pfil 9
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framework can be independently controlled using the following
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.Xr sysctl 8
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variables:
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.Bl -column net.enc.out.ipsec_filter_mask 0x00000000 0x00000000
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.It Sy "Name Defaults Suggested"
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.It "net.enc.out.ipsec_bpf_mask 0x00000003 0x00000001"
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.It "net.enc.out.ipsec_filter_mask 0x00000001 0x00000001"
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.It "net.enc.in.ipsec_bpf_mask 0x00000001 0x00000002"
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.It "net.enc.in.ipsec_filter_mask 0x00000001 0x00000002"
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.El
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.Pp
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For the incoming path a value of
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.Li 0x1
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means
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.Dq Li before stripping off the outer header
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and
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.Li 0x2
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means
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.Dq Li after stripping off the outer header .
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For the outgoing path
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.Li 0x1
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means
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.Dq Li with only the inner header
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and
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.Li 0x2
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means
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.Dq Li with outer and inner headers .
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.Bd -literal
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incoming path |------|
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---- IPsec processing ---- (before) ---- (after) ----> | |
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| Host |
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<--- IPsec processing ---- (after) ----- (before) ---- | |
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outgoing path |------|
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.Ed
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.Pp
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Most people will want to run with the suggested defaults for
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.Cm ipsec_filter_mask
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and rely on the security policy database for the outer headers.
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.Sh EXAMPLES
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To see the packets the processed via
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.Xr ipsec 4 ,
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adjust the
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.Xr sysctl 8
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variables according to your need and run:
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.Pp
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.Dl "tcpdump -i enc0"
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.Sh SEE ALSO
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.Xr tcpdump 1 ,
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.Xr bpf 4 ,
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.Xr ipf 4 ,
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.Xr ipfw 4 ,
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.Xr ipsec 4 ,
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.Xr pf 4
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