config root man

.\"	$OpenBSD: enc.4,v 1.22 2006/05/26 08:51:29 jmc Exp $
.\"
.\" Copyright (c) 1999 Angelos D. Keromytis
.\" All rights reserved.
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.\"    must display the following acknowledgement:
.\"	This product includes software developed by Angelos D. Keromytis.
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.\" $FreeBSD: release/9.1.0/share/man/man4/enc.4 211406 2010-08-16 21:26:47Z joel $
.\"
.Dd November 28, 2007
.Dt ENC 4
.Os
.Sh NAME
.Nm enc
.Nd Encapsulating Interface
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following line in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device enc"
.Ed
.Sh DESCRIPTION
The
.Nm
interface is a software loopback mechanism that allows hosts or
firewalls to filter
.Xr ipsec 4
traffic using any firewall package that hooks in via the
.Xr pfil 9
framework.
.Pp
The
.Nm
interface allows an administrator to see incoming and outgoing packets
before and after they will be or have been processed by
.Xr ipsec 4
via
.Xr tcpdump 1 .
.Pp
The
.Dq Li enc0
interface inherits all IPsec traffic.
Thus all IPsec traffic can be filtered based on
.Dq Li enc0 ,
and all IPsec traffic could be seen by invoking
.Xr tcpdump 1
on the
.Dq Li enc0
interface.
.Pp
What can be seen with
.Xr tcpdump 1
and what will be passed on to the firewalls via the
.Xr pfil 9
framework can be independently controlled using the following
.Xr sysctl 8
variables:
.Bl -column net.enc.out.ipsec_filter_mask 0x00000000 0x00000000
.It Sy "Name	Defaults	Suggested"
.It "net.enc.out.ipsec_bpf_mask	0x00000003	0x00000001"
.It "net.enc.out.ipsec_filter_mask	0x00000001	0x00000001"
.It "net.enc.in.ipsec_bpf_mask	0x00000001	0x00000002"
.It "net.enc.in.ipsec_filter_mask	0x00000001	0x00000002"
.El
.Pp
For the incoming path a value of
.Li 0x1
means
.Dq Li before stripping off the outer header
and
.Li 0x2
means
.Dq Li after stripping off the outer header .
For the outgoing path
.Li 0x1
means
.Dq Li with only the inner header
and
.Li 0x2
means
.Dq Li with outer and inner headers .
.Bd -literal
incoming path                                          |------|
---- IPsec processing ---- (before) ---- (after) ----> |      |
                                                       | Host |
<--- IPsec processing ---- (after) ----- (before) ---- |      |
outgoing path                                          |------|
.Ed
.Pp
Most people will want to run with the suggested defaults for
.Cm ipsec_filter_mask
and rely on the security policy database for the outer headers.
.Sh EXAMPLES
To see the packets the processed via
.Xr ipsec 4 ,
adjust the
.Xr sysctl 8
variables according to your need and run:
.Pp
.Dl "tcpdump -i enc0"
.Sh SEE ALSO
.Xr tcpdump 1 ,
.Xr bpf 4 ,
.Xr ipf 4 ,
.Xr ipfw 4 ,
.Xr ipsec 4 ,
.Xr pf 4 ,
.Xr tcpdump 8