1 .\" $OpenBSD: enc.4,v 1.22 2006/05/26 08:51:29 jmc Exp $
3 .\" Copyright (c) 1999 Angelos D. Keromytis
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39 .Nd Encapsulating Interface
41 To compile this driver into the kernel,
42 place the following line in your
43 kernel configuration file:
44 .Bd -ragged -offset indent
48 Alternatively, to load the driver as a
49 module at boot time, place the following line in
51 .Bd -literal -offset indent
57 interface is a software loopback mechanism that allows hosts or
60 traffic using any firewall package that hooks in via the
66 interface allows an administrator to see incoming and outgoing packets
67 before and after they will be or have been processed by
74 interface inherits all IPsec traffic.
75 Thus all IPsec traffic can be filtered based on
77 and all IPsec traffic could be seen by invoking
85 and what will be passed on to the firewalls via the
87 framework can be independently controlled using the following
90 .Bl -column net.enc.out.ipsec_filter_mask 0x00000000 0x00000000
91 .It Sy "Name Defaults Suggested"
92 .It "net.enc.out.ipsec_bpf_mask 0x00000003 0x00000001"
93 .It "net.enc.out.ipsec_filter_mask 0x00000001 0x00000001"
94 .It "net.enc.in.ipsec_bpf_mask 0x00000001 0x00000002"
95 .It "net.enc.in.ipsec_filter_mask 0x00000001 0x00000002"
98 For the incoming path a value of
101 .Dq Li before stripping off the outer header
105 .Dq Li after stripping off the outer header .
106 For the outgoing path
109 .Dq Li with only the inner header
113 .Dq Li with outer and inner headers .
115 incoming path |------|
116 ---- IPsec processing ---- (before) ---- (after) ----> | |
118 <--- IPsec processing ---- (after) ----- (before) ---- | |
119 outgoing path |------|
122 Most people will want to run with the suggested defaults for
123 .Cm ipsec_filter_mask
124 and rely on the security policy database for the outer headers.
126 Note that packets are captured by BPF before firewall processing.
127 The special value 0x4 can be configured in the
129 and packets will be also captured after firewall processing.
131 To see the packets the processed via
135 variables according to your need and run:
137 .Dl "tcpdump -i enc0"