2878 lines
88 KiB
Groff
2878 lines
88 KiB
Groff
.\" $FreeBSD$
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.\" $OpenBSD: pf.conf.5,v 1.292 2004/02/24 05:44:48 mcbride Exp $
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.\"
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.\" Copyright (c) 2002, Daniel Hartmeier
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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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.\" - 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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.\" - Redistributions in binary form must reproduce the above
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.\" copyright notice, this list of conditions and the following
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.\" disclaimer in the documentation and/or other materials provided
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.\" with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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.\" "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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.\" FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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.\" COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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.\" ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd February 7, 2005
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.Dt PF.CONF 5
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.Os
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.Sh NAME
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.Nm pf.conf
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.Nd packet filter configuration file
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.Sh DESCRIPTION
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The
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.Xr pf 4
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packet filter modifies, drops or passes packets according to rules or
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definitions specified in
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.Nm pf.conf .
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.Sh STATEMENT ORDER
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There are seven types of statements in
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.Nm pf.conf :
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.Bl -tag -width xxxx
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.It Cm Macros
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User-defined variables may be defined and used later, simplifying
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the configuration file.
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Macros must be defined before they are referenced in
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.Nm pf.conf .
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.It Cm Tables
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Tables provide a mechanism for increasing the performance and flexibility of
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rules with large numbers of source or destination addresses.
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.It Cm Options
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Options tune the behaviour of the packet filtering engine.
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.It Cm Traffic Normalization Li (e.g. Em scrub )
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Traffic normalization protects internal machines against inconsistencies
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in Internet protocols and implementations.
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.It Cm Queueing
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Queueing provides rule-based bandwidth control.
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.It Cm Translation Li (Various forms of NAT)
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Translation rules specify how addresses are to be mapped or redirected to
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other addresses.
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.It Cm Packet Filtering
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Stateful and stateless packet filtering provides rule-based blocking or
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passing of packets.
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.El
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.Pp
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With the exception of
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.Cm macros
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and
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.Cm tables ,
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the types of statements should be grouped and appear in
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.Nm pf.conf
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in the order shown above, as this matches the operation of the underlying
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packet filtering engine.
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By default
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.Xr pfctl 8
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enforces this order (see
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.Ar set require-order
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below).
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.Sh MACROS
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Much like
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.Xr cpp 1
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or
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.Xr m4 1 ,
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macros can be defined that will later be expanded in context.
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Macro names must start with a letter, and may contain letters, digits
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and underscores.
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Macro names may not be reserved words (for example
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.Ar pass ,
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.Ar in ,
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.Ar out ) .
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Macros are not expanded inside quotes.
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.Pp
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For example,
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.Bd -literal -offset indent
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ext_if = \&"kue0\&"
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all_ifs = \&"{\&" $ext_if lo0 \&"}\&"
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pass out on $ext_if from any to any keep state
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pass in on $ext_if proto tcp from any to any port 25 keep state
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.Ed
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.Sh TABLES
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Tables are named structures which can hold a collection of addresses and
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networks.
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Lookups against tables in
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.Xr pf 4
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are relatively fast, making a single rule with tables much more efficient,
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in terms of
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processor usage and memory consumption, than a large number of rules which
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differ only in IP address (either created explicitly or automatically by rule
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expansion).
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.Pp
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Tables can be used as the source or destination of filter rules,
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.Ar scrub
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rules
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or
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translation rules such as
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.Ar nat
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or
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.Ar rdr
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(see below for details on the various rule types).
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Tables can also be used for the redirect address of
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.Ar nat
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and
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.Ar rdr
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rules and in the routing options of filter rules, but only for
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.Ar round-robin
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pools.
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.Pp
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Tables can be defined with any of the following
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.Xr pfctl 8
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mechanisms.
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As with macros, reserved words may not be used as table names.
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.Bl -tag -width "manually"
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.It Ar manually
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Persistent tables can be manually created with the
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.Ar add
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or
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.Ar replace
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option of
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.Xr pfctl 8 ,
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before or after the ruleset has been loaded.
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.It Pa pf.conf
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Table definitions can be placed directly in this file, and loaded at the
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same time as other rules are loaded, atomically.
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Table definitions inside
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.Nm pf.conf
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use the
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.Ar table
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statement, and are especially useful to define non-persistent tables.
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The contents of a pre-existing table defined without a list of addresses
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to initialize it is not altered when
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.Nm pf.conf
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is loaded.
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A table initialized with the empty list,
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.Li { } ,
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will be cleared on load.
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.El
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.Pp
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Tables may be defined with the following two attributes:
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.Bl -tag -width persist
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.It Ar persist
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The
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.Ar persist
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flag forces the kernel to keep the table even when no rules refer to it.
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If the flag is not set, the kernel will automatically remove the table
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when the last rule referring to it is flushed.
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.It Ar const
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The
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.Ar const
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flag prevents the user from altering the contents of the table once it
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has been created.
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Without that flag,
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.Xr pfctl 8
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can be used to add or remove addresses from the table at any time, even
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when running with
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.Xr securelevel 7
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= 2.
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.El
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.Pp
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|
For example,
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.Bd -literal -offset indent
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table <private> const { 10/8, 172.16/12, 192.168/16 }
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table <badhosts> persist
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block on fxp0 from { <private>, <badhosts> } to any
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.Ed
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.Pp
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creates a table called private, to hold RFC 1918 private network
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blocks, and a table called badhosts, which is initially empty.
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A filter rule is set up to block all traffic coming from addresses listed in
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either table.
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The private table cannot have its contents changed and the badhosts table
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will exist even when no active filter rules reference it.
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Addresses may later be added to the badhosts table, so that traffic from
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these hosts can be blocked by using
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.Bd -literal -offset indent
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# pfctl -t badhosts -Tadd 204.92.77.111
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.Ed
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.Pp
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A table can also be initialized with an address list specified in one or more
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external files, using the following syntax:
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.Bd -literal -offset indent
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table <spam> persist file \&"/etc/spammers\&" file \&"/etc/openrelays\&"
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block on fxp0 from <spam> to any
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.Ed
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.Pp
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The files
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.Pa /etc/spammers
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and
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.Pa /etc/openrelays
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list IP addresses, one per line.
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Any lines beginning with a # are treated as comments and ignored.
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In addition to being specified by IP address, hosts may also be
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specified by their hostname.
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When the resolver is called to add a hostname to a table,
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.Em all
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resulting IPv4 and IPv6 addresses are placed into the table.
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IP addresses can also be entered in a table by specifying a valid interface
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name or the
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.Em self
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keyword, in which case all addresses assigned to the interface(s) will be
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added to the table.
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.Sh OPTIONS
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.Xr pf 4
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may be tuned for various situations using the
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.Ar set
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command.
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.Bl -tag -width xxxx
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.It Ar set timeout
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.Pp
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.Bl -tag -width "src.track" -compact
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.It Ar interval
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Interval between purging expired states and fragments.
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.It Ar frag
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Seconds before an unassembled fragment is expired.
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.It Ar src.track
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Length of time to retain a source tracking entry after the last state
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expires.
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.El
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.Pp
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|
When a packet matches a stateful connection, the seconds to live for the
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connection will be updated to that of the
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.Ar proto.modifier
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which corresponds to the connection state.
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Each packet which matches this state will reset the TTL.
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Tuning these values may improve the performance of the
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firewall at the risk of dropping valid idle connections.
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.Pp
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.Bl -tag -width xxxx -compact
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.It Ar tcp.first
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The state after the first packet.
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.It Ar tcp.opening
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The state before the destination host ever sends a packet.
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.It Ar tcp.established
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The fully established state.
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.It Ar tcp.closing
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The state after the first FIN has been sent.
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.It Ar tcp.finwait
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The state after both FINs have been exchanged and the connection is closed.
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Some hosts (notably web servers on Solaris) send TCP packets even after closing
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the connection.
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|
Increasing
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.Ar tcp.finwait
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(and possibly
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.Ar tcp.closing )
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can prevent blocking of such packets.
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.It Ar tcp.closed
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The state after one endpoint sends an RST.
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.El
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.Pp
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ICMP and UDP are handled in a fashion similar to TCP, but with a much more
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limited set of states:
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.Pp
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.Bl -tag -width xxxx -compact
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.It Ar udp.first
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The state after the first packet.
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.It Ar udp.single
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The state if the source host sends more than one packet but the destination
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host has never sent one back.
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.It Ar udp.multiple
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The state if both hosts have sent packets.
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.It Ar icmp.first
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The state after the first packet.
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.It Ar icmp.error
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The state after an ICMP error came back in response to an ICMP packet.
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.El
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.Pp
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Other protocols are handled similarly to UDP:
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.Pp
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.Bl -tag -width xxxx -compact
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.It Ar other.first
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.It Ar other.single
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.It Ar other.multiple
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.El
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.Pp
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Timeout values can be reduced adaptively as the number of state table
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entries grows.
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.Pp
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.Bl -tag -width xxxx -compact
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.It Ar adaptive.start
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When the number of state entries exceeds this value, adaptive scaling
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begins.
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|
All timeout values are scaled linearly with factor
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(adaptive.end - number of states) / (adaptive.end - adaptive.start).
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.It Ar adaptive.end
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When reaching this number of state entries, all timeout values become
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zero, effectively purging all state entries immediately.
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This value is used to define the scale factor, it should not actually
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be reached (set a lower state limit, see below).
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.El
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.Pp
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These values can be defined both globally and for each rule.
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When used on a per-rule basis, the values relate to the number of
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states created by the rule, otherwise to the total number of
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states.
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.Pp
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For example:
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.Bd -literal -offset indent
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set timeout tcp.first 120
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set timeout tcp.established 86400
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set timeout { adaptive.start 6000, adaptive.end 12000 }
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set limit states 10000
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.Ed
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.Pp
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With 9000 state table entries, the timeout values are scaled to 50%
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(tcp.first 60, tcp.established 43200).
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.Pp
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.It Ar set loginterface
|
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Enable collection of packet and byte count statistics for the given interface.
|
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These statistics can be viewed using
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.Bd -literal -offset indent
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# pfctl -s info
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.Ed
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.Pp
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In this example
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.Xr pf 4
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collects statistics on the interface named dc0:
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.Bd -literal -offset indent
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set loginterface dc0
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.Ed
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.Pp
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One can disable the loginterface using:
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.Bd -literal -offset indent
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set loginterface none
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.Ed
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.Pp
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.It Ar set limit
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Sets hard limits on the memory pools used by the packet filter.
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See
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.Xr zone 9
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for an explanation of memory pools.
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.Pp
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For example,
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.Bd -literal -offset indent
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set limit states 20000
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.Ed
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.Pp
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sets the maximum number of entries in the memory pool used by state table
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entries (generated by
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.Ar keep state
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rules) to 20000.
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Using
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.Bd -literal -offset indent
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set limit frags 20000
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.Ed
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.Pp
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sets the maximum number of entries in the memory pool used for fragment
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reassembly (generated by
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.Ar scrub
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rules) to 20000.
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Finally,
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.Bd -literal -offset indent
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set limit src-nodes 2000
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.Ed
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.Pp
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sets the maximum number of entries in the memory pool used for tracking
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source IP addresses (generated by the
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.Ar sticky-address
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and
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.Ar source-track
|
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options) to 2000.
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.Pp
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These can be combined:
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.Bd -literal -offset indent
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set limit { states 20000, frags 20000, src-nodes 2000 }
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.Ed
|
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.Pp
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.It Ar set optimization
|
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Optimize the engine for one of the following network environments:
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.Pp
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.Bl -tag -width xxxx -compact
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.It Ar normal
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A normal network environment.
|
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Suitable for almost all networks.
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.It Ar high-latency
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A high-latency environment (such as a satellite connection).
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.It Ar satellite
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Alias for
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|
.Ar high-latency .
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.It Ar aggressive
|
|
Aggressively expire connections.
|
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This can greatly reduce the memory usage of the firewall at the cost of
|
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dropping idle connections early.
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.It Ar conservative
|
|
Extremely conservative settings.
|
|
Avoid dropping legitimate connections at the
|
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expense of greater memory utilization (possibly much greater on a busy
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network) and slightly increased processor utilization.
|
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.El
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|
.Pp
|
|
For example:
|
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.Bd -literal -offset indent
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set optimization aggressive
|
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.Ed
|
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.Pp
|
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.It Ar set block-policy
|
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The
|
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.Ar block-policy
|
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option sets the default behaviour for the packet
|
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.Ar block
|
|
action:
|
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.Pp
|
|
.Bl -tag -width xxxxxxxx -compact
|
|
.It Ar drop
|
|
Packet is silently dropped.
|
|
.It Ar return
|
|
A TCP RST is returned for blocked TCP packets,
|
|
an ICMP UNREACHABLE is returned for blocked UDP packets,
|
|
and all other packets are silently dropped.
|
|
.El
|
|
.Pp
|
|
For example:
|
|
.Bd -literal -offset indent
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set block-policy return
|
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.Ed
|
|
.It Ar set state-policy
|
|
The
|
|
.Ar state-policy
|
|
option sets the default behaviour for states:
|
|
.Pp
|
|
.Bl -tag -width group-bound -compact
|
|
.It Ar if-bound
|
|
States are bound to interface.
|
|
.It Ar group-bound
|
|
States are bound to interface group (i.e. ppp)
|
|
.It Ar floating
|
|
States can match packets on any interfaces (the default).
|
|
.El
|
|
.Pp
|
|
For example:
|
|
.Bd -literal -offset indent
|
|
set state-policy if-bound
|
|
.Ed
|
|
.It Ar set require-order
|
|
By default
|
|
.Xr pfctl 8
|
|
enforces an ordering of the statement types in the ruleset to:
|
|
.Em options ,
|
|
.Em normalization ,
|
|
.Em queueing ,
|
|
.Em translation ,
|
|
.Em filtering .
|
|
Setting this option to
|
|
.Ar no
|
|
disables this enforcement.
|
|
There may be non-trivial and non-obvious implications to an out of
|
|
order ruleset.
|
|
Consider carefully before disabling the order enforcement.
|
|
.It Ar set fingerprints
|
|
Load fingerprints of known operating systems from the given filename.
|
|
By default fingerprints of known operating systems are automatically
|
|
loaded from
|
|
.Xr pf.os 5
|
|
in
|
|
.Pa /etc
|
|
but can be overridden via this option.
|
|
Setting this option may leave a small period of time where the fingerprints
|
|
referenced by the currently active ruleset are inconsistent until the new
|
|
ruleset finishes loading.
|
|
.Pp
|
|
For example:
|
|
.Pp
|
|
.Dl set fingerprints \&"/etc/pf.os.devel\&"
|
|
.Pp
|
|
.It Ar set skip on <ifspec>
|
|
List interfaces for which packets should not be filtered.
|
|
Packets passing in or out on such interfaces are passed as if pf was
|
|
disabled, i.e. pf does not process them in any way.
|
|
This can be useful on loopback and other virtual interfaces, when
|
|
packet filtering is not desired and can have unexpected effects.
|
|
For example:
|
|
.Pp
|
|
.Dl set skip on lo0
|
|
.Pp
|
|
.It Ar set debug
|
|
Set the debug
|
|
.Ar level
|
|
to one of the following:
|
|
.Pp
|
|
.Bl -tag -width xxxxxxxxxxxx -compact
|
|
.It Ar none
|
|
Don't generate debug messages.
|
|
.It Ar urgent
|
|
Generate debug messages only for serious errors.
|
|
.It Ar misc
|
|
Generate debug messages for various errors.
|
|
.It Ar loud
|
|
Generate debug messages for common conditions.
|
|
.El
|
|
.El
|
|
.Sh TRAFFIC NORMALIZATION
|
|
Traffic normalization is used to sanitize packet content in such
|
|
a way that there are no ambiguities in packet interpretation on
|
|
the receiving side.
|
|
The normalizer does IP fragment reassembly to prevent attacks
|
|
that confuse intrusion detection systems by sending overlapping
|
|
IP fragments.
|
|
Packet normalization is invoked with the
|
|
.Ar scrub
|
|
directive.
|
|
.Pp
|
|
.Ar scrub
|
|
has the following options:
|
|
.Bl -tag -width xxxx
|
|
.It Ar no-df
|
|
Clears the
|
|
.Ar dont-fragment
|
|
bit from a matching IP packet.
|
|
Some operating systems are known to generate fragmented packets with the
|
|
.Ar dont-fragment
|
|
bit set.
|
|
This is particularly true with NFS.
|
|
.Ar Scrub
|
|
will drop such fragmented
|
|
.Ar dont-fragment
|
|
packets unless
|
|
.Ar no-df
|
|
is specified.
|
|
.Pp
|
|
Unfortunately some operating systems also generate their
|
|
.Ar dont-fragment
|
|
packets with a zero IP identification field.
|
|
Clearing the
|
|
.Ar dont-fragment
|
|
bit on packets with a zero IP ID may cause deleterious results if an
|
|
upstream router later fragments the packet.
|
|
Using the
|
|
.Ar random-id
|
|
modifier (see below) is recommended in combination with the
|
|
.Ar no-df
|
|
modifier to ensure unique IP identifiers.
|
|
.It Ar min-ttl <number>
|
|
Enforces a minimum TTL for matching IP packets.
|
|
.It Ar max-mss <number>
|
|
Enforces a maximum MSS for matching TCP packets.
|
|
.It Ar random-id
|
|
Replaces the IP identification field with random values to compensate
|
|
for predictable values generated by many hosts.
|
|
This option only applies to packets that are not fragmented
|
|
after the optional fragment reassembly.
|
|
.It Ar fragment reassemble
|
|
Using
|
|
.Ar scrub
|
|
rules, fragments can be reassembled by normalization.
|
|
In this case, fragments are buffered until they form a complete
|
|
packet, and only the completed packet is passed on to the filter.
|
|
The advantage is that filter rules have to deal only with complete
|
|
packets, and can ignore fragments.
|
|
The drawback of caching fragments is the additional memory cost.
|
|
But the full reassembly method is the only method that currently works
|
|
with NAT.
|
|
This is the default behavior of a
|
|
.Ar scrub
|
|
rule if no fragmentation modifier is supplied.
|
|
.It Ar fragment crop
|
|
The default fragment reassembly method is expensive, hence the option
|
|
to crop is provided.
|
|
In this case,
|
|
.Xr pf 4
|
|
will track the fragments and cache a small range descriptor.
|
|
Duplicate fragments are dropped and overlaps are cropped.
|
|
Thus data will only occur once on the wire with ambiguities resolving to
|
|
the first occurrence.
|
|
Unlike the
|
|
.Ar fragment reassemble
|
|
modifier, fragments are not buffered, they are passed as soon as they
|
|
are received.
|
|
The
|
|
.Ar fragment crop
|
|
reassembly mechanism does not yet work with NAT.
|
|
.Pp
|
|
.It Ar fragment drop-ovl
|
|
This option is similar to the
|
|
.Ar fragment crop
|
|
modifier except that all overlapping or duplicate fragments will be
|
|
dropped, and all further corresponding fragments will be
|
|
dropped as well.
|
|
.It Ar reassemble tcp
|
|
Statefully normalizes TCP connections.
|
|
.Ar scrub reassemble tcp
|
|
rules may not have the direction (in/out) specified.
|
|
.Ar reassemble tcp
|
|
performs the following normalizations:
|
|
.Pp
|
|
.Bl -tag -width timeout -compact
|
|
.It ttl
|
|
Neither side of the connection is allowed to reduce their IP TTL.
|
|
An attacker may send a packet such that it reaches the firewall, affects
|
|
the firewall state, and expires before reaching the destination host.
|
|
.Ar reassemble tcp
|
|
will raise the TTL of all packets back up to the highest value seen on
|
|
the connection.
|
|
.It timestamp modulation
|
|
Modern TCP stacks will send a timestamp on every TCP packet and echo
|
|
the other endpoint's timestamp back to them.
|
|
Many operating systems will merely start the timestamp at zero when
|
|
first booted, and increment it several times a second.
|
|
The uptime of the host can be deduced by reading the timestamp and multiplying
|
|
by a constant.
|
|
Also observing several different timestamps can be used to count hosts
|
|
behind a NAT device.
|
|
And spoofing TCP packets into a connection requires knowing or guessing
|
|
valid timestamps.
|
|
Timestamps merely need to be monotonically increasing and not derived off a
|
|
guessable base time.
|
|
.Ar reassemble tcp
|
|
will cause
|
|
.Ar scrub
|
|
to modulate the TCP timestamps with a random number.
|
|
.It extended PAWS checks
|
|
There is a problem with TCP on long fat pipes, in that a packet might get
|
|
delayed for longer than it takes the connection to wrap its 32-bit sequence
|
|
space.
|
|
In such an occurrence, the old packet would be indistinguishable from a
|
|
new packet and would be accepted as such.
|
|
The solution to this is called PAWS: Protection Against Wrapped Sequence
|
|
numbers.
|
|
It protects against it by making sure the timestamp on each packet does
|
|
not go backwards.
|
|
.Ar reassemble tcp
|
|
also makes sure the timestamp on the packet does not go forward more
|
|
than the RFC allows.
|
|
By doing this,
|
|
.Xr pf 4
|
|
artificially extends the security of TCP sequence numbers by 10 to 18
|
|
bits when the host uses appropriately randomized timestamps, since a
|
|
blind attacker would have to guess the timestamp as well.
|
|
.El
|
|
.El
|
|
.Pp
|
|
For example,
|
|
.Bd -literal -offset indent
|
|
scrub in on $ext_if all fragment reassemble
|
|
.Ed
|
|
.Pp
|
|
The
|
|
.Ar no
|
|
option prefixed to a scrub rule causes matching packets to remain unscrubbed,
|
|
much in the same way as
|
|
.Ar drop quick
|
|
works in the packet filter (see below).
|
|
This mechanism should be used when it is necessary to exclude specific packets
|
|
from broader scrub rules.
|
|
.Sh QUEUEING/ALTQ
|
|
The ALTQ system is currently not available in the GENERIC kernel nor as
|
|
loadable modules.
|
|
In order to use the herein after called queueing options one has to use a
|
|
custom built kernel.
|
|
Please refer to
|
|
.Xr altq 4
|
|
to learn about the related kernel options.
|
|
.Pp
|
|
Packets can be assigned to queues for the purpose of bandwidth
|
|
control.
|
|
At least two declarations are required to configure queues, and later
|
|
any packet filtering rule can reference the defined queues by name.
|
|
During the filtering component of
|
|
.Nm pf.conf ,
|
|
the last referenced
|
|
.Ar queue
|
|
name is where any packets from
|
|
.Ar pass
|
|
rules will be queued, while for
|
|
.Ar block
|
|
rules it specifies where any resulting ICMP or TCP RST
|
|
packets should be queued.
|
|
The
|
|
.Ar scheduler
|
|
defines the algorithm used to decide which packets get delayed, dropped, or
|
|
sent out immediately.
|
|
There are three
|
|
.Ar schedulers
|
|
currently supported.
|
|
.Bl -tag -width xxxx
|
|
.It Ar cbq
|
|
Class Based Queueing.
|
|
.Ar Queues
|
|
attached to an interface build a tree, thus each
|
|
.Ar queue
|
|
can have further child
|
|
.Ar queues .
|
|
Each queue can have a
|
|
.Ar priority
|
|
and a
|
|
.Ar bandwidth
|
|
assigned.
|
|
.Ar Priority
|
|
mainly controls the time packets take to get sent out, while
|
|
.Ar bandwidth
|
|
has primarily effects on throughput.
|
|
.Ar cbq
|
|
achieves both partitioning and sharing of link bandwidth
|
|
by hierarchically structured classes.
|
|
Each class has its own
|
|
.Ar queue
|
|
and is assigned its share of
|
|
.Ar bandwidth .
|
|
A child class can borrow bandwidth from its parent class
|
|
as long as excess bandwidth is available
|
|
(see the option
|
|
.Ar borrow ,
|
|
below).
|
|
.It Ar priq
|
|
Priority Queueing.
|
|
.Ar Queues
|
|
are flat attached to the interface, thus,
|
|
.Ar queues
|
|
cannot have further child
|
|
.Ar queues .
|
|
Each
|
|
.Ar queue
|
|
has a unique
|
|
.Ar priority
|
|
assigned, ranging from 0 to 15.
|
|
Packets in the
|
|
.Ar queue
|
|
with the highest
|
|
.Ar priority
|
|
are processed first.
|
|
.It Ar hfsc
|
|
Hierarchical Fair Service Curve.
|
|
.Ar Queues
|
|
attached to an interface build a tree, thus each
|
|
.Ar queue
|
|
can have further child
|
|
.Ar queues .
|
|
Each queue can have a
|
|
.Ar priority
|
|
and a
|
|
.Ar bandwidth
|
|
assigned.
|
|
.Ar Priority
|
|
mainly controls the time packets take to get sent out, while
|
|
.Ar bandwidth
|
|
has primarily effects on throughput.
|
|
.Ar hfsc
|
|
supports both link-sharing and guaranteed real-time services.
|
|
It employs a service curve based QoS model,
|
|
and its unique feature is an ability to decouple
|
|
.Ar delay
|
|
and
|
|
.Ar bandwidth
|
|
allocation.
|
|
.El
|
|
.Pp
|
|
The interfaces on which queueing should be activated are declared using
|
|
the
|
|
.Ar altq on
|
|
declaration.
|
|
.Ar altq on
|
|
has the following keywords:
|
|
.Bl -tag -width xxxx
|
|
.It Ar <interface>
|
|
Queueing is enabled on the named interface.
|
|
.It Ar <scheduler>
|
|
Specifies which queueing scheduler to use.
|
|
Currently supported values
|
|
are
|
|
.Ar cbq
|
|
for Class Based Queueing,
|
|
.Ar priq
|
|
for Priority Queueing and
|
|
.Ar hfsc
|
|
for the Hierarchical Fair Service Curve scheduler.
|
|
.It Ar bandwidth <bw>
|
|
The maximum bitrate for all queues on an
|
|
interface may be specified using the
|
|
.Ar bandwidth
|
|
keyword.
|
|
The value can be specified as an absolute value or as a
|
|
percentage of the interface bandwidth.
|
|
When using an absolute value, the suffixes
|
|
.Ar b ,
|
|
.Ar Kb ,
|
|
.Ar Mb ,
|
|
and
|
|
.Ar Gb
|
|
are used to represent bits, kilobits, megabits, and
|
|
gigabits per second, respectively.
|
|
The value must not exceed the interface bandwidth.
|
|
If
|
|
.Ar bandwidth
|
|
is not specified, the interface bandwidth is used.
|
|
.It Ar qlimit <limit>
|
|
The maximum number of packets held in the queue.
|
|
The default is 50.
|
|
.It Ar tbrsize <size>
|
|
Adjusts the size, in bytes, of the token bucket regulator.
|
|
If not specified, heuristics based on the
|
|
interface bandwidth are used to determine the size.
|
|
.It Ar queue <list>
|
|
Defines a list of subqueues to create on an interface.
|
|
.El
|
|
.Pp
|
|
In the following example, the interface dc0
|
|
should queue up to 5 Mbit/s in four second-level queues using
|
|
Class Based Queueing.
|
|
Those four queues will be shown in a later example.
|
|
.Bd -literal -offset indent
|
|
altq on dc0 cbq bandwidth 5Mb queue { std, http, mail, ssh }
|
|
.Ed
|
|
.Pp
|
|
Once interfaces are activated for queueing using the
|
|
.Ar altq
|
|
directive, a sequence of
|
|
.Ar queue
|
|
directives may be defined.
|
|
The name associated with a
|
|
.Ar queue
|
|
must match a queue defined in the
|
|
.Ar altq
|
|
directive (e.g. mail), or, except for the
|
|
.Ar priq
|
|
.Ar scheduler ,
|
|
in a parent
|
|
.Ar queue
|
|
declaration.
|
|
The following keywords can be used:
|
|
.Bl -tag -width xxxx
|
|
.It Ar on <interface>
|
|
Specifies the interface the queue operates on.
|
|
If not given, it operates on all matching interfaces.
|
|
.It Ar bandwidth <bw>
|
|
Specifies the maximum bitrate to be processed by the queue.
|
|
This value must not exceed the value of the parent
|
|
.Ar queue
|
|
and can be specified as an absolute value or a percentage of the parent
|
|
queue's bandwidth.
|
|
If not specified, defaults to 100% of the parent queue's bandwidth.
|
|
The
|
|
.Ar priq
|
|
scheduler does not support bandwidth specification.
|
|
.It Ar priority <level>
|
|
Between queues a priority level can be set.
|
|
For
|
|
.Ar cbq
|
|
and
|
|
.Ar hfsc ,
|
|
the range is 0 to 7 and for
|
|
.Ar priq ,
|
|
the range is 0 to 15.
|
|
The default for all is 1.
|
|
.Ar Priq
|
|
queues with a higher priority are always served first.
|
|
.Ar Cbq
|
|
and
|
|
.Ar Hfsc
|
|
queues with a higher priority are preferred in the case of overload.
|
|
.It Ar qlimit <limit>
|
|
The maximum number of packets held in the queue.
|
|
The default is 50.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Ar scheduler
|
|
can get additional parameters with
|
|
.Ar <scheduler> Ns Li (\& Ar <parameters> No ) .
|
|
Parameters are as follows:
|
|
.Bl -tag -width Fl
|
|
.It Ar default
|
|
Packets not matched by another queue are assigned to this one.
|
|
Exactly one default queue is required.
|
|
.It Ar red
|
|
Enable RED (Random Early Detection) on this queue.
|
|
RED drops packets with a probability proportional to the average
|
|
queue length.
|
|
.It Ar rio
|
|
Enables RIO on this queue.
|
|
RIO is RED with IN/OUT, thus running
|
|
RED two times more than RIO would achieve the same effect.
|
|
RIO is currently not supported in the GENERIC kernel.
|
|
.It Ar ecn
|
|
Enables ECN (Explicit Congestion Notification) on this queue.
|
|
ECN implies RED.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Ar cbq
|
|
.Ar scheduler
|
|
supports an additional option:
|
|
.Bl -tag -width Fl
|
|
.It Ar borrow
|
|
The queue can borrow bandwidth from the parent.
|
|
.El
|
|
.Pp
|
|
The
|
|
.Ar hfsc
|
|
.Ar scheduler
|
|
supports some additional options:
|
|
.Bl -tag -width Fl
|
|
.It Ar realtime <sc>
|
|
The minimum required bandwidth for the queue.
|
|
.It Ar upperlimit <sc>
|
|
The maximum allowed bandwidth for the queue.
|
|
.It Ar linkshare <sc>
|
|
The bandwidth share of a backlogged queue.
|
|
.El
|
|
.Pp
|
|
<sc> is an acronym for
|
|
.Ar service curve .
|
|
.Pp
|
|
The format for service curve specifications is
|
|
.Ar ( m1 , d , m2 ) .
|
|
.Ar m2
|
|
controls the bandwidth assigned to the queue.
|
|
.Ar m1
|
|
and
|
|
.Ar d
|
|
are optional and can be used to control the initial bandwidth assignment.
|
|
For the first
|
|
.Ar d
|
|
milliseconds the queue gets the bandwidth given as
|
|
.Ar m1 ,
|
|
afterwards the value given in
|
|
.Ar m2 .
|
|
.Pp
|
|
Furthermore, with
|
|
.Ar cbq
|
|
and
|
|
.Ar hfsc ,
|
|
child queues can be specified as in an
|
|
.Ar altq
|
|
declaration, thus building a tree of queues using a part of
|
|
their parent's bandwidth.
|
|
.Pp
|
|
Packets can be assigned to queues based on filter rules by using the
|
|
.Ar queue
|
|
keyword.
|
|
Normally only one
|
|
.Ar queue
|
|
is specified; when a second one is specified it will instead be used for
|
|
packets which have a
|
|
.Em TOS
|
|
of
|
|
.Em lowdelay
|
|
and for TCP ACKs with no data payload.
|
|
.Pp
|
|
To continue the previous example, the examples below would specify the
|
|
four referenced
|
|
queues, plus a few child queues.
|
|
Interactive
|
|
.Xr ssh 1
|
|
sessions get priority over bulk transfers like
|
|
.Xr scp 1
|
|
and
|
|
.Xr sftp 1 .
|
|
The queues may then be referenced by filtering rules (see
|
|
.Sx PACKET FILTERING
|
|
below).
|
|
.Bd -literal
|
|
queue std bandwidth 10% cbq(default)
|
|
queue http bandwidth 60% priority 2 cbq(borrow red) \e
|
|
{ employees, developers }
|
|
queue developers bandwidth 75% cbq(borrow)
|
|
queue employees bandwidth 15%
|
|
queue mail bandwidth 10% priority 0 cbq(borrow ecn)
|
|
queue ssh bandwidth 20% cbq(borrow) { ssh_interactive, ssh_bulk }
|
|
queue ssh_interactive bandwidth 50% priority 7 cbq(borrow)
|
|
queue ssh_bulk bandwidth 50% priority 0 cbq(borrow)
|
|
|
|
block return out on dc0 inet all queue std
|
|
pass out on dc0 inet proto tcp from $developerhosts to any port 80 \e
|
|
keep state queue developers
|
|
pass out on dc0 inet proto tcp from $employeehosts to any port 80 \e
|
|
keep state queue employees
|
|
pass out on dc0 inet proto tcp from any to any port 22 \e
|
|
keep state queue(ssh_bulk, ssh_interactive)
|
|
pass out on dc0 inet proto tcp from any to any port 25 \e
|
|
keep state queue mail
|
|
.Ed
|
|
.Sh TRANSLATION
|
|
Translation rules modify either the source or destination address of the
|
|
packets associated with a stateful connection.
|
|
A stateful connection is automatically created to track packets matching
|
|
such a rule as long as they are not blocked by the filtering section of
|
|
.Nm pf.conf .
|
|
The translation engine modifies the specified address and/or port in the
|
|
packet, recalculates IP, TCP and UDP checksums as necessary, and passes it to
|
|
the packet filter for evaluation.
|
|
.Pp
|
|
Since translation occurs before filtering the filter
|
|
engine will see packets as they look after any
|
|
addresses and ports have been translated.
|
|
Filter rules will therefore have to filter based on the translated
|
|
address and port number.
|
|
Packets that match a translation rule are only automatically passed if
|
|
the
|
|
.Ar pass
|
|
modifier is given, otherwise they are
|
|
still subject to
|
|
.Ar block
|
|
and
|
|
.Ar pass
|
|
rules.
|
|
.Pp
|
|
The state entry created permits
|
|
.Xr pf 4
|
|
to keep track of the original address for traffic associated with that state
|
|
and correctly direct return traffic for that connection.
|
|
.Pp
|
|
Various types of translation are possible with pf:
|
|
.Bl -tag -width xxxx
|
|
.It Ar binat
|
|
A
|
|
.Ar binat
|
|
rule specifies a bidirectional mapping between an external IP netblock
|
|
and an internal IP netblock.
|
|
.It Ar nat
|
|
A
|
|
.Ar nat
|
|
rule specifies that IP addresses are to be changed as the packet
|
|
traverses the given interface.
|
|
This technique allows one or more IP addresses
|
|
on the translating host to support network traffic for a larger range of
|
|
machines on an "inside" network.
|
|
Although in theory any IP address can be used on the inside, it is strongly
|
|
recommended that one of the address ranges defined by RFC 1918 be used.
|
|
These netblocks are:
|
|
.Bd -literal
|
|
10.0.0.0 - 10.255.255.255 (all of net 10, i.e., 10/8)
|
|
172.16.0.0 - 172.31.255.255 (i.e., 172.16/12)
|
|
192.168.0.0 - 192.168.255.255 (i.e., 192.168/16)
|
|
.Ed
|
|
.It Pa rdr
|
|
The packet is redirected to another destination and possibly a
|
|
different port.
|
|
.Ar rdr
|
|
rules can optionally specify port ranges instead of single ports.
|
|
rdr ... port 2000:2999 -> ... port 4000
|
|
redirects ports 2000 to 2999 (inclusive) to port 4000.
|
|
rdr ... port 2000:2999 -> ... port 4000:*
|
|
redirects port 2000 to 4000, 2001 to 4001, ..., 2999 to 4999.
|
|
.El
|
|
.Pp
|
|
In addition to modifying the address, some translation rules may modify
|
|
source or destination ports for
|
|
.Xr tcp 4
|
|
or
|
|
.Xr udp 4
|
|
connections; implicitly in the case of
|
|
.Ar nat
|
|
rules and explicitly in the case of
|
|
.Ar rdr
|
|
rules.
|
|
Port numbers are never translated with a
|
|
.Ar binat
|
|
rule.
|
|
.Pp
|
|
For each packet processed by the translator, the translation rules are
|
|
evaluated in sequential order, from first to last.
|
|
The first matching rule decides what action is taken.
|
|
.Pp
|
|
The
|
|
.Ar no
|
|
option prefixed to a translation rule causes packets to remain untranslated,
|
|
much in the same way as
|
|
.Ar drop quick
|
|
works in the packet filter (see below).
|
|
If no rule matches the packet it is passed to the filter engine unmodified.
|
|
.Pp
|
|
Translation rules apply only to packets that pass through
|
|
the specified interface, and if no interface is specified,
|
|
translation is applied to packets on all interfaces.
|
|
For instance, redirecting port 80 on an external interface to an internal
|
|
web server will only work for connections originating from the outside.
|
|
Connections to the address of the external interface from local hosts will
|
|
not be redirected, since such packets do not actually pass through the
|
|
external interface.
|
|
Redirections cannot reflect packets back through the interface they arrive
|
|
on, they can only be redirected to hosts connected to different interfaces
|
|
or to the firewall itself.
|
|
.Pp
|
|
Note that redirecting external incoming connections to the loopback
|
|
address, as in
|
|
.Bd -literal -offset indent
|
|
rdr on ne3 inet proto tcp to port 8025 -> 127.0.0.1 port 25
|
|
.Ed
|
|
.Pp
|
|
will effectively allow an external host to connect to daemons
|
|
bound solely to the loopback address, circumventing the traditional
|
|
blocking of such connections on a real interface.
|
|
Unless this effect is desired, any of the local non-loopback addresses
|
|
should be used as redirection target instead, which allows external
|
|
connections only to daemons bound to this address or not bound to
|
|
any address.
|
|
.Pp
|
|
See
|
|
.Sx TRANSLATION EXAMPLES
|
|
below.
|
|
.Sh PACKET FILTERING
|
|
.Xr pf 4
|
|
has the ability to
|
|
.Ar block
|
|
and
|
|
.Ar pass
|
|
packets based on attributes of their layer 3 (see
|
|
.Xr ip 4
|
|
and
|
|
.Xr ip6 4 )
|
|
and layer 4 (see
|
|
.Xr icmp 4 ,
|
|
.Xr icmp6 4 ,
|
|
.Xr tcp 4 ,
|
|
.Xr udp 4 )
|
|
headers.
|
|
In addition, packets may also be
|
|
assigned to queues for the purpose of bandwidth control.
|
|
.Pp
|
|
For each packet processed by the packet filter, the filter rules are
|
|
evaluated in sequential order, from first to last.
|
|
The last matching rule decides what action is taken.
|
|
.Pp
|
|
The following actions can be used in the filter:
|
|
.Bl -tag -width xxxx
|
|
.It Ar block
|
|
The packet is blocked.
|
|
There are a number of ways in which a
|
|
.Ar block
|
|
rule can behave when blocking a packet.
|
|
The default behaviour is to
|
|
.Ar drop
|
|
packets silently, however this can be overridden or made
|
|
explicit either globally, by setting the
|
|
.Ar block-policy
|
|
option, or on a per-rule basis with one of the following options:
|
|
.Pp
|
|
.Bl -tag -width xxxx -compact
|
|
.It Ar drop
|
|
The packet is silently dropped.
|
|
.It Ar return-rst
|
|
This applies only to
|
|
.Xr tcp 4
|
|
packets, and issues a TCP RST which closes the
|
|
connection.
|
|
.It Ar return-icmp
|
|
.It Ar return-icmp6
|
|
This causes ICMP messages to be returned for packets which match the rule.
|
|
By default this is an ICMP UNREACHABLE message, however this
|
|
can be overridden by specifying a message as a code or number.
|
|
.It Ar return
|
|
This causes a TCP RST to be returned for
|
|
.Xr tcp 4
|
|
packets and an ICMP UNREACHABLE for UDP and other packets.
|
|
.El
|
|
.Pp
|
|
Options returning ICMP packets currently have no effect if
|
|
.Xr pf 4
|
|
operates on a
|
|
.Xr if_bridge 4 ,
|
|
as the code to support this feature has not yet been implemented.
|
|
.It Ar pass
|
|
The packet is passed.
|
|
.El
|
|
.Pp
|
|
If no rule matches the packet, the default action is
|
|
.Ar pass .
|
|
.Pp
|
|
To block everything by default and only pass packets
|
|
that match explicit rules, one uses
|
|
.Bd -literal -offset indent
|
|
block all
|
|
.Ed
|
|
.Pp
|
|
as the first filter rule.
|
|
.Pp
|
|
See
|
|
.Sx FILTER EXAMPLES
|
|
below.
|
|
.Sh PARAMETERS
|
|
The rule parameters specify the packets to which a rule applies.
|
|
A packet always comes in on, or goes out through, one interface.
|
|
Most parameters are optional.
|
|
If a parameter is specified, the rule only applies to packets with
|
|
matching attributes.
|
|
Certain parameters can be expressed as lists, in which case
|
|
.Xr pfctl 8
|
|
generates all needed rule combinations.
|
|
.Bl -tag -width xxxx
|
|
.It Ar in No or Ar out
|
|
This rule applies to incoming or outgoing packets.
|
|
If neither
|
|
.Ar in
|
|
nor
|
|
.Ar out
|
|
are specified, the rule will match packets in both directions.
|
|
.It Ar log
|
|
In addition to the action specified, a log message is generated.
|
|
All packets for that connection are logged, unless the
|
|
.Ar keep state ,
|
|
.Ar modulate state
|
|
or
|
|
.Ar synproxy state
|
|
options are specified, in which case only the
|
|
packet that establishes the state is logged.
|
|
(See
|
|
.Ar keep state ,
|
|
.Ar modulate state
|
|
and
|
|
.Ar synproxy state
|
|
below).
|
|
The logged packets are sent to the
|
|
.Xr pflog 4
|
|
interface.
|
|
This interface is monitored by the
|
|
.Xr pflogd 8
|
|
logging daemon, which dumps the logged packets to the file
|
|
.Pa /var/log/pflog
|
|
in
|
|
.Xr pcap 3
|
|
binary format.
|
|
.It Ar log-all
|
|
Used with
|
|
.Ar keep state ,
|
|
.Ar modulate state
|
|
or
|
|
.Ar synproxy state
|
|
rules to force logging of all packets for a connection.
|
|
As with
|
|
.Ar log ,
|
|
packets are logged to
|
|
.Xr pflog 4 .
|
|
.It Ar quick
|
|
If a packet matches a rule which has the
|
|
.Ar quick
|
|
option set, this rule
|
|
is considered the last matching rule, and evaluation of subsequent rules
|
|
is skipped.
|
|
.It Ar on <interface>
|
|
This rule applies only to packets coming in on, or going out through, this
|
|
particular interface.
|
|
It is also possible to simply give the interface driver name, like ppp or fxp,
|
|
to make the rule match packets flowing through a group of interfaces.
|
|
.It Ar <af>
|
|
This rule applies only to packets of this address family.
|
|
Supported values are
|
|
.Ar inet
|
|
and
|
|
.Ar inet6 .
|
|
.It Ar proto <protocol>
|
|
This rule applies only to packets of this protocol.
|
|
Common protocols are
|
|
.Xr icmp 4 ,
|
|
.Xr icmp6 4 ,
|
|
.Xr tcp 4 ,
|
|
and
|
|
.Xr udp 4 .
|
|
For a list of all the protocol name to number mappings used by
|
|
.Xr pfctl 8 ,
|
|
see the file
|
|
.Em /etc/protocols .
|
|
.It Xo
|
|
.Ar from <source> port <source> os <source>
|
|
.Ar to <dest> port <dest>
|
|
.Xc
|
|
This rule applies only to packets with the specified source and destination
|
|
addresses and ports.
|
|
.Pp
|
|
Addresses can be specified in CIDR notation (matching netblocks), as
|
|
symbolic host names or interface names, or as any of the following keywords:
|
|
.Pp
|
|
.Bl -tag -width xxxxxxxxxxxxxx -compact
|
|
.It Ar any
|
|
Any address.
|
|
.It Ar route <label>
|
|
Any address whose associated route has label
|
|
.Ar <label> .
|
|
See
|
|
.Xr route 4
|
|
and
|
|
.Xr route 8 .
|
|
.It Ar no-route
|
|
Any address which is not currently routable.
|
|
.It Ar <table>
|
|
Any address that matches the given table.
|
|
.El
|
|
.Pp
|
|
Interface names can have modifiers appended:
|
|
.Pp
|
|
.Bl -tag -width xxxxxxxxxxxx -compact
|
|
.It Ar :network
|
|
Translates to the network(s) attached to the interface.
|
|
.It Ar :broadcast
|
|
Translates to the interface's broadcast address(es).
|
|
.It Ar :peer
|
|
Translates to the point to point interface's peer address(es).
|
|
.It Ar :0
|
|
Do not include interface aliases.
|
|
.El
|
|
.Pp
|
|
Host names may also have the
|
|
.Ar :0
|
|
option appended to restrict the name resolution to the first of each
|
|
v4 and v6 address found.
|
|
.Pp
|
|
Host name resolution and interface to address translation are done at
|
|
ruleset load-time.
|
|
When the address of an interface (or host name) changes (under DHCP or PPP,
|
|
for instance), the ruleset must be reloaded for the change to be reflected
|
|
in the kernel.
|
|
Surrounding the interface name (and optional modifiers) in parentheses
|
|
changes this behaviour.
|
|
When the interface name is surrounded by parentheses, the rule is
|
|
automatically updated whenever the interface changes its address.
|
|
The ruleset does not need to be reloaded.
|
|
This is especially useful with
|
|
.Ar nat .
|
|
.Pp
|
|
Ports can be specified either by number or by name.
|
|
For example, port 80 can be specified as
|
|
.Em www .
|
|
For a list of all port name to number mappings used by
|
|
.Xr pfctl 8 ,
|
|
see the file
|
|
.Pa /etc/services .
|
|
.Pp
|
|
Ports and ranges of ports are specified by using these operators:
|
|
.Bd -literal -offset indent
|
|
= (equal)
|
|
!= (unequal)
|
|
< (less than)
|
|
<= (less than or equal)
|
|
> (greater than)
|
|
>= (greater than or equal)
|
|
: (range including boundaries)
|
|
>< (range excluding boundaries)
|
|
<> (except range)
|
|
.Ed
|
|
.Pp
|
|
><, <> and :
|
|
are binary operators (they take two arguments).
|
|
For instance:
|
|
.Bl -tag -width Fl
|
|
.It Ar port 2000:2004
|
|
means
|
|
.Sq all ports >= 2000 and <= 2004 ,
|
|
hence ports 2000, 2001, 2002, 2003 and 2004.
|
|
.It Ar port 2000 >< 2004
|
|
means
|
|
.Sq all ports > 2000 and < 2004 ,
|
|
hence ports 2001, 2002 and 2003.
|
|
.It Ar port 2000 <> 2004
|
|
means
|
|
.Sq all ports < 2000 or > 2004 ,
|
|
hence ports 1-1999 and 2005-65535.
|
|
.El
|
|
.Pp
|
|
The operating system of the source host can be specified in the case of TCP
|
|
rules with the
|
|
.Ar OS
|
|
modifier.
|
|
See the
|
|
.Sx OPERATING SYSTEM FINGERPRINTING
|
|
section for more information.
|
|
.Pp
|
|
The host, port and OS specifications are optional, as in the following examples:
|
|
.Bd -literal -offset indent
|
|
pass in all
|
|
pass in from any to any
|
|
pass in proto tcp from any port <= 1024 to any
|
|
pass in proto tcp from any to any port 25
|
|
pass in proto tcp from 10.0.0.0/8 port > 1024 \e
|
|
to ! 10.1.2.3 port != ssh
|
|
pass in proto tcp from any os "OpenBSD" flags S/SA
|
|
pass in proto tcp from route "DTAG"
|
|
.Ed
|
|
.It Ar all
|
|
This is equivalent to "from any to any".
|
|
.It Ar group <group>
|
|
Similar to
|
|
.Ar user ,
|
|
this rule only applies to packets of sockets owned by the specified group.
|
|
.Pp
|
|
The use of
|
|
.Ar group
|
|
or
|
|
.Ar user
|
|
in
|
|
.Va debug.mpsafenet Ns = Ns 1
|
|
environments may result in a deadlock.
|
|
Please see the
|
|
.Sx BUGS
|
|
section for details.
|
|
.It Ar user <user>
|
|
This rule only applies to packets of sockets owned by the specified user.
|
|
For outgoing connections initiated from the firewall, this is the user
|
|
that opened the connection.
|
|
For incoming connections to the firewall itself, this is the user that
|
|
listens on the destination port.
|
|
For forwarded connections, where the firewall is not a connection endpoint,
|
|
the user and group are
|
|
.Em unknown .
|
|
.Pp
|
|
All packets, both outgoing and incoming, of one connection are associated
|
|
with the same user and group.
|
|
Only TCP and UDP packets can be associated with users; for other protocols
|
|
these parameters are ignored.
|
|
.Pp
|
|
User and group refer to the effective (as opposed to the real) IDs, in
|
|
case the socket is created by a setuid/setgid process.
|
|
User and group IDs are stored when a socket is created;
|
|
when a process creates a listening socket as root (for instance, by
|
|
binding to a privileged port) and subsequently changes to another
|
|
user ID (to drop privileges), the credentials will remain root.
|
|
.Pp
|
|
User and group IDs can be specified as either numbers or names.
|
|
The syntax is similar to the one for ports.
|
|
The value
|
|
.Em unknown
|
|
matches packets of forwarded connections.
|
|
.Em unknown
|
|
can only be used with the operators
|
|
.Cm =
|
|
and
|
|
.Cm != .
|
|
Other constructs like
|
|
.Cm user >= unknown
|
|
are invalid.
|
|
Forwarded packets with unknown user and group ID match only rules
|
|
that explicitly compare against
|
|
.Em unknown
|
|
with the operators
|
|
.Cm =
|
|
or
|
|
.Cm != .
|
|
For instance
|
|
.Cm user >= 0
|
|
does not match forwarded packets.
|
|
The following example allows only selected users to open outgoing
|
|
connections:
|
|
.Bd -literal -offset indent
|
|
block out proto { tcp, udp } all
|
|
pass out proto { tcp, udp } all \e
|
|
user { < 1000, dhartmei } keep state
|
|
.Ed
|
|
.It Ar flags <a>/<b> | /<b>
|
|
This rule only applies to TCP packets that have the flags
|
|
.Ar <a>
|
|
set out of set
|
|
.Ar <b> .
|
|
Flags not specified in
|
|
.Ar <b>
|
|
are ignored.
|
|
The flags are: (F)IN, (S)YN, (R)ST, (P)USH, (A)CK, (U)RG, (E)CE, and C(W)R.
|
|
.Bl -tag -width Fl
|
|
.It Ar flags S/S
|
|
Flag SYN is set.
|
|
The other flags are ignored.
|
|
.It Ar flags S/SA
|
|
Out of SYN and ACK, exactly SYN may be set.
|
|
SYN, SYN+PSH and SYN+RST match, but SYN+ACK, ACK and ACK+RST do not.
|
|
This is more restrictive than the previous example.
|
|
.It Ar flags /SFRA
|
|
If the first set is not specified, it defaults to none.
|
|
All of SYN, FIN, RST and ACK must be unset.
|
|
.El
|
|
.It Ar icmp-type <type> code <code>
|
|
.It Ar icmp6-type <type> code <code>
|
|
This rule only applies to ICMP or ICMPv6 packets with the specified type
|
|
and code.
|
|
Text names for ICMP types and codes are listed in
|
|
.Xr icmp 4
|
|
and
|
|
.Xr icmp6 4 .
|
|
This parameter is only valid for rules that cover protocols ICMP or
|
|
ICMP6.
|
|
The protocol and the ICMP type indicator
|
|
.Po
|
|
.Ar icmp-type
|
|
or
|
|
.Ar icmp6-type
|
|
.Pc
|
|
must match.
|
|
.It Ar allow-opts
|
|
By default, packets which contain IP options are blocked.
|
|
When
|
|
.Ar allow-opts
|
|
is specified for a
|
|
.Ar pass
|
|
rule, packets that pass the filter based on that rule (last matching)
|
|
do so even if they contain IP options.
|
|
For packets that match state, the rule that initially created the
|
|
state is used.
|
|
The implicit
|
|
.Ar pass
|
|
rule that is used when a packet does not match any rules does not
|
|
allow IP options.
|
|
.It Ar label <string>
|
|
Adds a label (name) to the rule, which can be used to identify the rule.
|
|
For instance,
|
|
pfctl -s labels
|
|
shows per-rule statistics for rules that have labels.
|
|
.Pp
|
|
The following macros can be used in labels:
|
|
.Pp
|
|
.Bl -tag -width $srcaddr -compact -offset indent
|
|
.It Ar $if
|
|
The interface.
|
|
.It Ar $srcaddr
|
|
The source IP address.
|
|
.It Ar $dstaddr
|
|
The destination IP address.
|
|
.It Ar $srcport
|
|
The source port specification.
|
|
.It Ar $dstport
|
|
The destination port specification.
|
|
.It Ar $proto
|
|
The protocol name.
|
|
.It Ar $nr
|
|
The rule number.
|
|
.El
|
|
.Pp
|
|
For example:
|
|
.Bd -literal -offset indent
|
|
ips = \&"{ 1.2.3.4, 1.2.3.5 }\&"
|
|
pass in proto tcp from any to $ips \e
|
|
port > 1023 label \&"$dstaddr:$dstport\&"
|
|
.Ed
|
|
.Pp
|
|
expands to
|
|
.Bd -literal -offset indent
|
|
pass in inet proto tcp from any to 1.2.3.4 \e
|
|
port > 1023 label \&"1.2.3.4:>1023\&"
|
|
pass in inet proto tcp from any to 1.2.3.5 \e
|
|
port > 1023 label \&"1.2.3.5:>1023\&"
|
|
.Ed
|
|
.Pp
|
|
The macro expansion for the
|
|
.Ar label
|
|
directive occurs only at configuration file parse time, not during runtime.
|
|
.It Ar queue <queue> | ( <queue> , <queue> )
|
|
Packets matching this rule will be assigned to the specified queue.
|
|
If two queues are given, packets which have a
|
|
.Em tos
|
|
of
|
|
.Em lowdelay
|
|
and TCP ACKs with no data payload will be assigned to the second one.
|
|
See
|
|
.Sx QUEUEING/ALTQ
|
|
for setup details.
|
|
.Pp
|
|
For example:
|
|
.Bd -literal -offset indent
|
|
pass in proto tcp to port 25 queue mail
|
|
pass in proto tcp to port 22 queue(ssh_bulk, ssh_prio)
|
|
.Ed
|
|
.It Ar tag <string>
|
|
Packets matching this rule will be tagged with the
|
|
specified string.
|
|
The tag acts as an internal marker that can be used to
|
|
identify these packets later on.
|
|
This can be used, for example, to provide trust between
|
|
interfaces and to determine if packets have been
|
|
processed by translation rules.
|
|
Tags are
|
|
.Qq sticky ,
|
|
meaning that the packet will be tagged even if the rule
|
|
is not the last matching rule.
|
|
Further matching rules can replace the tag with a
|
|
new one but will not remove a previously applied tag.
|
|
A packet is only ever assigned one tag at a time.
|
|
.Ar pass
|
|
rules that use the
|
|
.Ar tag
|
|
keyword must also use
|
|
.Ar keep state ,
|
|
.Ar modulate state
|
|
or
|
|
.Ar synproxy state .
|
|
Packet tagging can be done during
|
|
.Ar nat ,
|
|
.Ar rdr ,
|
|
or
|
|
.Ar binat
|
|
rules in addition to filter rules.
|
|
Tags take the same macros as labels (see above).
|
|
.It Ar tagged <string>
|
|
Used with filter or translation rules to specify that packets must already
|
|
be tagged with the given tag in order to match the rule.
|
|
Inverse tag matching can also be done
|
|
by specifying the
|
|
.Cm !\&
|
|
operator before the
|
|
.Ar tagged
|
|
keyword.
|
|
.It Ar probability <number>
|
|
A probability attribute can be attached to a rule, with a value set between
|
|
0 and 1, bounds not included.
|
|
In that case, the rule will be honoured using the given probability value
|
|
only.
|
|
For example, the following rule will drop 20% of incoming ICMP packets:
|
|
.Bd -literal -offset indent
|
|
block in proto icmp probability 20%
|
|
.Ed
|
|
.El
|
|
.Sh ROUTING
|
|
If a packet matches a rule with a route option set, the packet filter will
|
|
route the packet according to the type of route option.
|
|
When such a rule creates state, the route option is also applied to all
|
|
packets matching the same connection.
|
|
.Bl -tag -width xxxx
|
|
.It Ar fastroute
|
|
The
|
|
.Ar fastroute
|
|
option does a normal route lookup to find the next hop for the packet.
|
|
.It Ar route-to
|
|
The
|
|
.Ar route-to
|
|
option routes the packet to the specified interface with an optional address
|
|
for the next hop.
|
|
When a
|
|
.Ar route-to
|
|
rule creates state, only packets that pass in the same direction as the
|
|
filter rule specifies will be routed in this way.
|
|
Packets passing in the opposite direction (replies) are not affected
|
|
and are routed normally.
|
|
.It Ar reply-to
|
|
The
|
|
.Ar reply-to
|
|
option is similar to
|
|
.Ar route-to ,
|
|
but routes packets that pass in the opposite direction (replies) to the
|
|
specified interface.
|
|
Opposite direction is only defined in the context of a state entry, and
|
|
.Ar reply-to
|
|
is useful only in rules that create state.
|
|
It can be used on systems with multiple external connections to
|
|
route all outgoing packets of a connection through the interface
|
|
the incoming connection arrived through (symmetric routing enforcement).
|
|
.It Ar dup-to
|
|
The
|
|
.Ar dup-to
|
|
option creates a duplicate of the packet and routes it like
|
|
.Ar route-to .
|
|
The original packet gets routed as it normally would.
|
|
.El
|
|
.Sh POOL OPTIONS
|
|
For
|
|
.Ar nat
|
|
and
|
|
.Ar rdr
|
|
rules, (as well as for the
|
|
.Ar route-to ,
|
|
.Ar reply-to
|
|
and
|
|
.Ar dup-to
|
|
rule options) for which there is a single redirection address which has a
|
|
subnet mask smaller than 32 for IPv4 or 128 for IPv6 (more than one IP
|
|
address), a variety of different methods for assigning this address can be
|
|
used:
|
|
.Bl -tag -width xxxx
|
|
.It Ar bitmask
|
|
The
|
|
.Ar bitmask
|
|
option applies the network portion of the redirection address to the address
|
|
to be modified (source with
|
|
.Ar nat ,
|
|
destination with
|
|
.Ar rdr ) .
|
|
.It Ar random
|
|
The
|
|
.Ar random
|
|
option selects an address at random within the defined block of addresses.
|
|
.It Ar source-hash
|
|
The
|
|
.Ar source-hash
|
|
option uses a hash of the source address to determine the redirection address,
|
|
ensuring that the redirection address is always the same for a given source.
|
|
An optional key can be specified after this keyword either in hex or as a
|
|
string; by default
|
|
.Xr pfctl 8
|
|
randomly generates a key for source-hash every time the
|
|
ruleset is reloaded.
|
|
.It Ar round-robin
|
|
The
|
|
.Ar round-robin
|
|
option loops through the redirection address(es).
|
|
.Pp
|
|
When more than one redirection address is specified,
|
|
.Ar round-robin
|
|
is the only permitted pool type.
|
|
.It Ar static-port
|
|
With
|
|
.Ar nat
|
|
rules, the
|
|
.Ar static-port
|
|
option prevents
|
|
.Xr pf 4
|
|
from modifying the source port on TCP and UDP packets.
|
|
.El
|
|
.Pp
|
|
Additionally, the
|
|
.Ar sticky-address
|
|
option can be specified to help ensure that multiple connections from the
|
|
same source are mapped to the same redirection address.
|
|
This option can be used with the
|
|
.Ar random
|
|
and
|
|
.Ar round-robin
|
|
pool options.
|
|
Note that by default these associations are destroyed as soon as there are
|
|
no longer states which refer to them; in order to make the mappings last
|
|
beyond the lifetime of the states, increase the global options with
|
|
.Ar set timeout source-track
|
|
See
|
|
.Sx STATEFUL TRACKING OPTIONS
|
|
for more ways to control the source tracking.
|
|
.Sh STATEFUL INSPECTION
|
|
.Xr pf 4
|
|
is a stateful packet filter, which means it can track the state of
|
|
a connection.
|
|
Instead of passing all traffic to port 25, for instance, it is possible
|
|
to pass only the initial packet, and then begin to keep state.
|
|
Subsequent traffic will flow because the filter is aware of the connection.
|
|
.Pp
|
|
If a packet matches a
|
|
.Ar pass ... keep state
|
|
rule, the filter creates a state for this connection and automatically
|
|
lets pass all subsequent packets of that connection.
|
|
.Pp
|
|
Before any rules are evaluated, the filter checks whether the packet
|
|
matches any state.
|
|
If it does, the packet is passed without evaluation of any rules.
|
|
.Pp
|
|
States are removed after the connection is closed or has timed out.
|
|
.Pp
|
|
This has several advantages.
|
|
Comparing a packet to a state involves checking its sequence numbers.
|
|
If the sequence numbers are outside the narrow windows of expected
|
|
values, the packet is dropped.
|
|
This prevents spoofing attacks, such as when an attacker sends packets with
|
|
a fake source address/port but does not know the connection's sequence
|
|
numbers.
|
|
.Pp
|
|
Also, looking up states is usually faster than evaluating rules.
|
|
If there are 50 rules, all of them are evaluated sequentially in O(n).
|
|
Even with 50000 states, only 16 comparisons are needed to match a
|
|
state, since states are stored in a binary search tree that allows
|
|
searches in O(log2 n).
|
|
.Pp
|
|
For instance:
|
|
.Bd -literal -offset indent
|
|
block all
|
|
pass out proto tcp from any to any flags S/SA keep state
|
|
pass in proto tcp from any to any port 25 flags S/SA keep state
|
|
.Ed
|
|
.Pp
|
|
This ruleset blocks everything by default.
|
|
Only outgoing connections and incoming connections to port 25 are allowed.
|
|
The initial packet of each connection has the SYN
|
|
flag set, will be passed and creates state.
|
|
All further packets of these connections are passed if they match a state.
|
|
.Pp
|
|
By default, packets coming in and out of any interface can match a state,
|
|
but it is also possible to change that behaviour by assigning states to a
|
|
single interface or a group of interfaces.
|
|
.Pp
|
|
The default policy is specified by the
|
|
.Ar state-policy
|
|
global option, but this can be adjusted on a per-rule basis by adding one
|
|
of the
|
|
.Ar if-bound ,
|
|
.Ar group-bound
|
|
or
|
|
.Ar floating
|
|
keywords to the
|
|
.Ar keep state
|
|
option.
|
|
For example, if a rule is defined as:
|
|
.Bd -literal -offset indent
|
|
pass out on ppp from any to 10.12/16 keep state (group-bound)
|
|
.Ed
|
|
.Pp
|
|
A state created on ppp0 would match packets an all PPP interfaces,
|
|
but not packets flowing through fxp0 or any other interface.
|
|
.Pp
|
|
Keeping rules
|
|
.Ar floating
|
|
is the more flexible option when the firewall is in a dynamic routing
|
|
environment.
|
|
However, this has some security implications since a state created by one
|
|
trusted network could allow potentially hostile packets coming in from other
|
|
interfaces.
|
|
.Pp
|
|
Specifying
|
|
.Ar flags S/SA
|
|
restricts state creation to the initial SYN
|
|
packet of the TCP handshake.
|
|
One can also be less restrictive, and allow state creation from
|
|
intermediate
|
|
.Pq non-SYN
|
|
packets.
|
|
This will cause
|
|
.Xr pf 4
|
|
to synchronize to existing connections, for instance
|
|
if one flushes the state table.
|
|
.Pp
|
|
For UDP, which is stateless by nature,
|
|
.Ar keep state
|
|
will create state as well.
|
|
UDP packets are matched to states using only host addresses and ports.
|
|
.Pp
|
|
ICMP messages fall into two categories: ICMP error messages, which always
|
|
refer to a TCP or UDP packet, are matched against the referred to connection.
|
|
If one keeps state on a TCP connection, and an ICMP source quench message
|
|
referring to this TCP connection arrives, it will be matched to the right
|
|
state and get passed.
|
|
.Pp
|
|
For ICMP queries,
|
|
.Ar keep state
|
|
creates an ICMP state, and
|
|
.Xr pf 4
|
|
knows how to match ICMP replies to states.
|
|
For example,
|
|
.Bd -literal -offset indent
|
|
pass out inet proto icmp all icmp-type echoreq keep state
|
|
.Ed
|
|
.Pp
|
|
allows echo requests (such as those created by
|
|
.Xr ping 8 )
|
|
out, creates state, and matches incoming echo replies correctly to states.
|
|
.Pp
|
|
Note:
|
|
.Ar nat , binat No and Ar rdr
|
|
rules implicitly create state for connections.
|
|
.Sh STATE MODULATION
|
|
Much of the security derived from TCP is attributable to how well the
|
|
initial sequence numbers (ISNs) are chosen.
|
|
Some popular stack implementations choose
|
|
.Em very
|
|
poor ISNs and thus are normally susceptible to ISN prediction exploits.
|
|
By applying a
|
|
.Ar modulate state
|
|
rule to a TCP connection,
|
|
.Xr pf 4
|
|
will create a high quality random sequence number for each connection
|
|
endpoint.
|
|
.Pp
|
|
The
|
|
.Ar modulate state
|
|
directive implicitly keeps state on the rule and is
|
|
only applicable to TCP connections.
|
|
.Pp
|
|
For instance:
|
|
.Bd -literal -offset indent
|
|
block all
|
|
pass out proto tcp from any to any modulate state
|
|
pass in proto tcp from any to any port 25 flags S/SA modulate state
|
|
.Ed
|
|
.Pp
|
|
There are two caveats associated with state modulation:
|
|
A
|
|
.Ar modulate state
|
|
rule can not be applied to a pre-existing but unmodulated connection.
|
|
Such an application would desynchronize TCP's strict
|
|
sequencing between the two endpoints.
|
|
Instead,
|
|
.Xr pf 4
|
|
will treat the
|
|
.Ar modulate state
|
|
modifier as a
|
|
.Ar keep state
|
|
modifier and the pre-existing connection will be inferred without
|
|
the protection conferred by modulation.
|
|
.Pp
|
|
The other caveat affects currently modulated states when the state table
|
|
is lost (firewall reboot, flushing the state table, etc...).
|
|
.Xr pf 4
|
|
will not be able to infer a connection again after the state table flushes
|
|
the connection's modulator.
|
|
When the state is lost, the connection may be left dangling until the
|
|
respective endpoints time out the connection.
|
|
It is possible on a fast local network for the endpoints to start an ACK
|
|
storm while trying to resynchronize after the loss of the modulator.
|
|
Using a
|
|
.Ar flags S/SA
|
|
modifier on
|
|
.Ar modulate state
|
|
rules between fast networks is suggested to prevent ACK storms.
|
|
.Sh SYN PROXY
|
|
By default,
|
|
.Xr pf 4
|
|
passes packets that are part of a
|
|
.Xr tcp 4
|
|
handshake between the endpoints.
|
|
The
|
|
.Ar synproxy state
|
|
option can be used to cause
|
|
.Xr pf 4
|
|
itself to complete the handshake with the active endpoint, perform a handshake
|
|
with the passive endpoint, and then forward packets between the endpoints.
|
|
.Pp
|
|
No packets are sent to the passive endpoint before the active endpoint has
|
|
completed the handshake, hence so-called SYN floods with spoofed source
|
|
addresses will not reach the passive endpoint, as the sender can't complete the
|
|
handshake.
|
|
.Pp
|
|
The proxy is transparent to both endpoints, they each see a single
|
|
connection from/to the other endpoint.
|
|
.Xr pf 4
|
|
chooses random initial sequence numbers for both handshakes.
|
|
Once the handshakes are completed, the sequence number modulators
|
|
(see previous section) are used to translate further packets of the
|
|
connection.
|
|
Hence,
|
|
.Ar synproxy state
|
|
includes
|
|
.Ar modulate state
|
|
and
|
|
.Ar keep state .
|
|
.Pp
|
|
Rules with
|
|
.Ar synproxy
|
|
will not work if
|
|
.Xr pf 4
|
|
operates on a
|
|
.Xr if_bridge 4 .
|
|
.Pp
|
|
Example:
|
|
.Bd -literal -offset indent
|
|
pass in proto tcp from any to any port www flags S/SA synproxy state
|
|
.Ed
|
|
.Sh STATEFUL TRACKING OPTIONS
|
|
All three of
|
|
.Ar keep state ,
|
|
.Ar modulate state
|
|
and
|
|
.Ar synproxy state
|
|
support the following options:
|
|
.Pp
|
|
.Bl -tag -width xxxx -compact
|
|
.It Ar max <number>
|
|
Limits the number of concurrent states the rule may create.
|
|
When this limit is reached, further packets matching the rule that would
|
|
create state are dropped, until existing states time out.
|
|
.It Ar no-sync
|
|
Prevent state changes for states created by this rule from appearing on the
|
|
.Xr pfsync 4
|
|
interface.
|
|
.It Ar <timeout> <seconds>
|
|
Changes the timeout values used for states created by this rule.
|
|
For a list of all valid timeout names, see
|
|
.Sx OPTIONS
|
|
above.
|
|
.El
|
|
.Pp
|
|
Multiple options can be specified, separated by commas:
|
|
.Bd -literal -offset indent
|
|
pass in proto tcp from any to any \e
|
|
port www flags S/SA keep state \e
|
|
(max 100, source-track rule, max-src-nodes 75, \e
|
|
max-src-states 3, tcp.established 60, tcp.closing 5)
|
|
.Ed
|
|
.Pp
|
|
When the
|
|
.Ar source-track
|
|
keyword is specified, the number of states per source IP is tracked.
|
|
.Pp
|
|
.Bl -tag -width xxxx -compact
|
|
.It Ar source-track rule
|
|
The maximum number of states created by this rule is limited by the rule's
|
|
.Ar max-src-nodes
|
|
and
|
|
.Ar max-src-state
|
|
options.
|
|
Only state entries created by this particular rule count toward the rule's
|
|
limits.
|
|
.It Ar source-track global
|
|
The number of states created by all rules that use this option is limited.
|
|
Each rule can specify different
|
|
.Ar max-src-nodes
|
|
and
|
|
.Ar max-src-states
|
|
options, however state entries created by any participating rule count towards
|
|
each individual rule's limits.
|
|
.El
|
|
.Pp
|
|
The following limits can be set:
|
|
.Pp
|
|
.Bl -tag -width xxxx -compact
|
|
.It Ar max-src-nodes <number>
|
|
Limits the maximum number of source addresses which can simultaneously
|
|
have state table entries.
|
|
.It Ar max-src-states <number>
|
|
Limits the maximum number of simultaneous state entries that a single
|
|
source address can create with this rule.
|
|
.El
|
|
.Pp
|
|
For stateful TCP connections, limits on established connections (connections
|
|
which have completed the TCP 3-way handshake) can also be enforced
|
|
per source IP.
|
|
.Pp
|
|
.Bl -tag -width xxxx -compact
|
|
.It Ar max-src-conn <number>
|
|
Limits the maximum number of simultaneous TCP connections which have
|
|
completed the 3-way handshake that a single host can make.
|
|
.It Ar max-src-conn-rate <number> / <seconds>
|
|
Limit the rate of new connections over a time interval.
|
|
The connection rate is an approximation calculated as a moving average.
|
|
.El
|
|
.Pp
|
|
Because the 3-way handshake ensures that the source address is not being
|
|
spoofed, more aggressive action can be taken based on these limits.
|
|
With the
|
|
.Ar overload <table>
|
|
state option, source IP addresses which hit either of the limits on
|
|
established connections will be added to the named table.
|
|
This table can be used in the ruleset to block further activity from
|
|
the offending host, redirect it to a tarpit process, or restrict its
|
|
bandwidth.
|
|
.Pp
|
|
The optional
|
|
.Ar flush
|
|
keyword kills all states created by the matching rule which originate
|
|
from the host which exceeds these limits.
|
|
The
|
|
.Ar global
|
|
modifier to the flush command kills all states originating from the
|
|
offending host, regardless of which rule created the state.
|
|
.Pp
|
|
For example, the following rules will protect the webserver against
|
|
hosts making more than 100 connections in 10 seconds.
|
|
Any host which connects faster than this rate will have its address added
|
|
to the <bad_hosts> table and have all states originating from it flushed.
|
|
Any new packets arriving from this host will be dropped unconditionally
|
|
by the block rule.
|
|
.Bd -literal -offset indent
|
|
block quick from <bad_hosts>
|
|
pass in on $ext_if proto tcp to $webserver port www flags S/SA keep state \e
|
|
(max-src-conn-rate 100/10, overload <bad_hosts> flush global)
|
|
.Ed
|
|
.Sh OPERATING SYSTEM FINGERPRINTING
|
|
Passive OS Fingerprinting is a mechanism to inspect nuances of a TCP
|
|
connection's initial SYN packet and guess at the host's operating system.
|
|
Unfortunately these nuances are easily spoofed by an attacker so the
|
|
fingerprint is not useful in making security decisions.
|
|
But the fingerprint is typically accurate enough to make policy decisions
|
|
upon.
|
|
.Pp
|
|
The fingerprints may be specified by operating system class, by
|
|
version, or by subtype/patchlevel.
|
|
The class of an operating system is typically the vendor or genre
|
|
and would be OpenBSD for the
|
|
.Xr pf 4
|
|
firewall itself.
|
|
The version of the oldest available OpenBSD release on the main ftp site
|
|
would be 2.6 and the fingerprint would be written
|
|
.Pp
|
|
.Dl \&"OpenBSD 2.6\&"
|
|
.Pp
|
|
The subtype of an operating system is typically used to describe the
|
|
patchlevel if that patch led to changes in the TCP stack behavior.
|
|
In the case of OpenBSD, the only subtype is for a fingerprint that was
|
|
normalized by the
|
|
.Ar no-df
|
|
scrub option and would be specified as
|
|
.Pp
|
|
.Dl \&"OpenBSD 3.3 no-df\&"
|
|
.Pp
|
|
Fingerprints for most popular operating systems are provided by
|
|
.Xr pf.os 5 .
|
|
Once
|
|
.Xr pf 4
|
|
is running, a complete list of known operating system fingerprints may
|
|
be listed by running:
|
|
.Pp
|
|
.Dl # pfctl -so
|
|
.Pp
|
|
Filter rules can enforce policy at any level of operating system specification
|
|
assuming a fingerprint is present.
|
|
Policy could limit traffic to approved operating systems or even ban traffic
|
|
from hosts that aren't at the latest service pack.
|
|
.Pp
|
|
The
|
|
.Ar unknown
|
|
class can also be used as the fingerprint which will match packets for
|
|
which no operating system fingerprint is known.
|
|
.Pp
|
|
Examples:
|
|
.Bd -literal -offset indent
|
|
pass out proto tcp from any os OpenBSD keep state
|
|
block out proto tcp from any os Doors
|
|
block out proto tcp from any os "Doors PT"
|
|
block out proto tcp from any os "Doors PT SP3"
|
|
block out from any os "unknown"
|
|
pass on lo0 proto tcp from any os "OpenBSD 3.3 lo0" keep state
|
|
.Ed
|
|
.Pp
|
|
Operating system fingerprinting is limited only to the TCP SYN packet.
|
|
This means that it will not work on other protocols and will not match
|
|
a currently established connection.
|
|
.Pp
|
|
Caveat: operating system fingerprints are occasionally wrong.
|
|
There are three problems: an attacker can trivially craft his packets to
|
|
appear as any operating system he chooses;
|
|
an operating system patch could change the stack behavior and no fingerprints
|
|
will match it until the database is updated;
|
|
and multiple operating systems may have the same fingerprint.
|
|
.Sh BLOCKING SPOOFED TRAFFIC
|
|
"Spoofing" is the faking of IP addresses, typically for malicious
|
|
purposes.
|
|
The
|
|
.Ar antispoof
|
|
directive expands to a set of filter rules which will block all
|
|
traffic with a source IP from the network(s) directly connected
|
|
to the specified interface(s) from entering the system through
|
|
any other interface.
|
|
.Pp
|
|
For example, the line
|
|
.Bd -literal -offset indent
|
|
antispoof for lo0
|
|
.Ed
|
|
.Pp
|
|
expands to
|
|
.Bd -literal -offset indent
|
|
block drop in on ! lo0 inet from 127.0.0.1/8 to any
|
|
block drop in on ! lo0 inet6 from ::1 to any
|
|
.Ed
|
|
.Pp
|
|
For non-loopback interfaces, there are additional rules to block incoming
|
|
packets with a source IP address identical to the interface's IP(s).
|
|
For example, assuming the interface wi0 had an IP address of 10.0.0.1 and a
|
|
netmask of 255.255.255.0,
|
|
the line
|
|
.Bd -literal -offset indent
|
|
antispoof for wi0 inet
|
|
.Ed
|
|
.Pp
|
|
expands to
|
|
.Bd -literal -offset indent
|
|
block drop in on ! wi0 inet from 10.0.0.0/24 to any
|
|
block drop in inet from 10.0.0.1 to any
|
|
.Ed
|
|
.Pp
|
|
Caveat: Rules created by the
|
|
.Ar antispoof
|
|
directive interfere with packets sent over loopback interfaces
|
|
to local addresses.
|
|
One should pass these explicitly.
|
|
.Sh FRAGMENT HANDLING
|
|
The size of IP datagrams (packets) can be significantly larger than the
|
|
maximum transmission unit (MTU) of the network.
|
|
In cases when it is necessary or more efficient to send such large packets,
|
|
the large packet will be fragmented into many smaller packets that will each
|
|
fit onto the wire.
|
|
Unfortunately for a firewalling device, only the first logical fragment will
|
|
contain the necessary header information for the subprotocol that allows
|
|
.Xr pf 4
|
|
to filter on things such as TCP ports or to perform NAT.
|
|
.Pp
|
|
Besides the use of
|
|
.Ar scrub
|
|
rules as described in
|
|
.Sx TRAFFIC NORMALIZATION
|
|
above, there are three options for handling fragments in the packet filter.
|
|
.Pp
|
|
One alternative is to filter individual fragments with filter rules.
|
|
If no
|
|
.Ar scrub
|
|
rule applies to a fragment, it is passed to the filter.
|
|
Filter rules with matching IP header parameters decide whether the
|
|
fragment is passed or blocked, in the same way as complete packets
|
|
are filtered.
|
|
Without reassembly, fragments can only be filtered based on IP header
|
|
fields (source/destination address, protocol), since subprotocol header
|
|
fields are not available (TCP/UDP port numbers, ICMP code/type).
|
|
The
|
|
.Ar fragment
|
|
option can be used to restrict filter rules to apply only to
|
|
fragments, but not complete packets.
|
|
Filter rules without the
|
|
.Ar fragment
|
|
option still apply to fragments, if they only specify IP header fields.
|
|
For instance, the rule
|
|
.Bd -literal -offset indent
|
|
pass in proto tcp from any to any port 80
|
|
.Ed
|
|
.Pp
|
|
never applies to a fragment, even if the fragment is part of a TCP
|
|
packet with destination port 80, because without reassembly this information
|
|
is not available for each fragment.
|
|
This also means that fragments cannot create new or match existing
|
|
state table entries, which makes stateful filtering and address
|
|
translation (NAT, redirection) for fragments impossible.
|
|
.Pp
|
|
It's also possible to reassemble only certain fragments by specifying
|
|
source or destination addresses or protocols as parameters in
|
|
.Ar scrub
|
|
rules.
|
|
.Pp
|
|
In most cases, the benefits of reassembly outweigh the additional
|
|
memory cost, and it's recommended to use
|
|
.Ar scrub
|
|
rules to reassemble
|
|
all fragments via the
|
|
.Ar fragment reassemble
|
|
modifier.
|
|
.Pp
|
|
The memory allocated for fragment caching can be limited using
|
|
.Xr pfctl 8 .
|
|
Once this limit is reached, fragments that would have to be cached
|
|
are dropped until other entries time out.
|
|
The timeout value can also be adjusted.
|
|
.Pp
|
|
Currently, only IPv4 fragments are supported and IPv6 fragments
|
|
are blocked unconditionally.
|
|
.Sh ANCHORS
|
|
Besides the main ruleset,
|
|
.Xr pfctl 8
|
|
can load rulesets into
|
|
.Ar anchor
|
|
attachment points.
|
|
An
|
|
.Ar anchor
|
|
is a container that can hold rules, address tables, and other anchors.
|
|
.Pp
|
|
An
|
|
.Ar anchor
|
|
has a name which specifies the path where
|
|
.Xr pfctl 8
|
|
can be used to access the anchor to perform operations on it, such as
|
|
attaching child anchors to it or loading rules into it.
|
|
Anchors may be nested, with components separated by
|
|
.Sq /
|
|
characters, similar to how file system hierarchies are laid out.
|
|
The main ruleset is actually the default anchor, so filter and
|
|
translation rules, for example, may also be contained in any anchor.
|
|
.Pp
|
|
An anchor can reference another
|
|
.Ar anchor
|
|
attachment point
|
|
using the following kinds
|
|
of rules:
|
|
.Bl -tag -width xxxx
|
|
.It Ar nat-anchor <name>
|
|
Evaluates the
|
|
.Ar nat
|
|
rules in the specified
|
|
.Ar anchor .
|
|
.It Ar rdr-anchor <name>
|
|
Evaluates the
|
|
.Ar rdr
|
|
rules in the specified
|
|
.Ar anchor .
|
|
.It Ar binat-anchor <name>
|
|
Evaluates the
|
|
.Ar binat
|
|
rules in the specified
|
|
.Ar anchor .
|
|
.It Ar anchor <name>
|
|
Evaluates the filter rules in the specified
|
|
.Ar anchor .
|
|
.It Ar load anchor <name> from <file>
|
|
Loads the rules from the specified file into the
|
|
anchor
|
|
.Ar name .
|
|
.El
|
|
.Pp
|
|
When evaluation of the main ruleset reaches an
|
|
.Ar anchor
|
|
rule,
|
|
.Xr pf 4
|
|
will proceed to evaluate all rules specified in that anchor.
|
|
.Pp
|
|
Matching filter and translation rules in anchors with the
|
|
.Ar quick
|
|
option are final and abort the evaluation of the rules in other
|
|
anchors
|
|
and the main ruleset.
|
|
.Pp
|
|
.Ar anchor
|
|
rules are evaluated relative to the anchor in which they are contained.
|
|
For example, all
|
|
.Ar anchor
|
|
rules specified in the main ruleset will reference anchor
|
|
attachment points underneath the main ruleset, and
|
|
.Ar anchor
|
|
rules specified in a file loaded from a
|
|
.Ar load anchor
|
|
rule will be attached under that anchor point.
|
|
.Pp
|
|
Rules may be contained in
|
|
.Ar anchor
|
|
attachment points which do not contain any rules when the main ruleset
|
|
is loaded, and later such anchors can be manipulated through
|
|
.Xr pfctl 8
|
|
without reloading the main ruleset or other anchors.
|
|
For example,
|
|
.Bd -literal -offset indent
|
|
ext_if = \&"kue0\&"
|
|
block on $ext_if all
|
|
anchor spam
|
|
pass out on $ext_if all keep state
|
|
pass in on $ext_if proto tcp from any \e
|
|
to $ext_if port smtp keep state
|
|
.Ed
|
|
.Pp
|
|
blocks all packets on the external interface by default, then evaluates
|
|
all rules in the
|
|
.Ar anchor
|
|
named "spam", and finally passes all outgoing connections and
|
|
incoming connections to port 25.
|
|
.Bd -literal -offset indent
|
|
# echo \&"block in quick from 1.2.3.4 to any\&" \&| \e
|
|
pfctl -a spam -f -
|
|
.Ed
|
|
.Pp
|
|
This loads a single rule into the
|
|
.Ar anchor ,
|
|
which blocks all packets from a specific address.
|
|
.Pp
|
|
The anchor can also be populated by adding a
|
|
.Ar load anchor
|
|
rule after the
|
|
.Ar anchor
|
|
rule:
|
|
.Bd -literal -offset indent
|
|
anchor spam
|
|
load anchor spam from "/etc/pf-spam.conf"
|
|
.Ed
|
|
.Pp
|
|
When
|
|
.Xr pfctl 8
|
|
loads
|
|
.Nm pf.conf ,
|
|
it will also load all the rules from the file
|
|
.Pa /etc/pf-spam.conf
|
|
into the anchor.
|
|
.Pp
|
|
Optionally,
|
|
.Ar anchor
|
|
rules can specify the parameter's
|
|
direction, interface, address family, protocol and source/destination
|
|
address/port
|
|
using the same syntax as filter rules.
|
|
When parameters are used, the
|
|
.Ar anchor
|
|
rule is only evaluated for matching packets.
|
|
This allows conditional evaluation of anchors, like:
|
|
.Bd -literal -offset indent
|
|
block on $ext_if all
|
|
anchor spam proto tcp from any to any port smtp
|
|
pass out on $ext_if all keep state
|
|
pass in on $ext_if proto tcp from any to $ext_if port smtp keep state
|
|
.Ed
|
|
.Pp
|
|
The rules inside
|
|
.Ar anchor
|
|
spam are only evaluated for
|
|
.Ar tcp
|
|
packets with destination port 25.
|
|
Hence,
|
|
.Bd -literal -offset indent
|
|
# echo \&"block in quick from 1.2.3.4 to any" \&| \e
|
|
pfctl -a spam -f -
|
|
.Ed
|
|
.Pp
|
|
will only block connections from 1.2.3.4 to port 25.
|
|
.Pp
|
|
Anchors may end with the asterisk
|
|
.Pq Sq *
|
|
character, which signifies that all anchors attached at that point
|
|
should be evaluated in the alphabetical ordering of their anchor name.
|
|
For example,
|
|
.Bd -literal -offset indent
|
|
anchor "spam/*"
|
|
.Ed
|
|
.Pp
|
|
will evaluate each rule in each anchor attached to the
|
|
.Li spam
|
|
anchor.
|
|
Note that it will only evaluate anchors that are directly attached to the
|
|
.Li spam
|
|
anchor, and will not descend to evaluate anchors recursively.
|
|
.Pp
|
|
Since anchors are evaluated relative to the anchor in which they are
|
|
contained, there is a mechanism for accessing the parent and ancestor
|
|
anchors of a given anchor.
|
|
Similar to file system path name resolution, if the sequence
|
|
.Dq ..
|
|
appears as an anchor path component, the parent anchor of the current
|
|
anchor in the path evaluation at that point will become the new current
|
|
anchor.
|
|
As an example, consider the following:
|
|
.Bd -literal -offset indent
|
|
# echo ' anchor "spam/allowed" ' | pfctl -f -
|
|
# echo -e ' anchor "../banned" \en pass' | \e
|
|
pfctl -a spam/allowed -f -
|
|
.Ed
|
|
.Pp
|
|
Evaluation of the main ruleset will lead into the
|
|
.Li spam/allowed
|
|
anchor, which will evaluate the rules in the
|
|
.Li spam/banned
|
|
anchor, if any, before finally evaluating the
|
|
.Ar pass
|
|
rule.
|
|
.Pp
|
|
Since the parser specification for anchor names is a string, any
|
|
reference to an anchor name containing solidus
|
|
.Pq Sq /
|
|
characters will require double quote
|
|
.Pq Sq \&"
|
|
characters around the anchor name.
|
|
.Sh TRANSLATION EXAMPLES
|
|
This example maps incoming requests on port 80 to port 8080, on
|
|
which a daemon is running (because, for example, it is not run as root,
|
|
and therefore lacks permission to bind to port 80).
|
|
.Bd -literal
|
|
# use a macro for the interface name, so it can be changed easily
|
|
ext_if = \&"ne3\&"
|
|
|
|
# map daemon on 8080 to appear to be on 80
|
|
rdr on $ext_if proto tcp from any to any port 80 -> 127.0.0.1 port 8080
|
|
.Ed
|
|
.Pp
|
|
If the
|
|
.Ar pass
|
|
modifier is given, packets matching the translation rule are passed without
|
|
inspecting the filter rules:
|
|
.Bd -literal
|
|
rdr pass on $ext_if proto tcp from any to any port 80 -> 127.0.0.1 \e
|
|
port 8080
|
|
.Ed
|
|
.Pp
|
|
In the example below, vlan12 is configured as 192.168.168.1;
|
|
the machine translates all packets coming from 192.168.168.0/24 to 204.92.77.111
|
|
when they are going out any interface except vlan12.
|
|
This has the net effect of making traffic from the 192.168.168.0/24
|
|
network appear as though it is the Internet routable address
|
|
204.92.77.111 to nodes behind any interface on the router except
|
|
for the nodes on vlan12.
|
|
(Thus, 192.168.168.1 can talk to the 192.168.168.0/24 nodes.)
|
|
.Bd -literal
|
|
nat on ! vlan12 from 192.168.168.0/24 to any -> 204.92.77.111
|
|
.Ed
|
|
.Pp
|
|
In the example below, the machine sits between a fake internal 144.19.74.*
|
|
network, and a routable external IP of 204.92.77.100.
|
|
The
|
|
.Ar no nat
|
|
rule excludes protocol AH from being translated.
|
|
.Bd -literal
|
|
# NO NAT
|
|
no nat on $ext_if proto ah from 144.19.74.0/24 to any
|
|
nat on $ext_if from 144.19.74.0/24 to any -> 204.92.77.100
|
|
.Ed
|
|
.Pp
|
|
In the example below, packets bound for one specific server, as well as those
|
|
generated by the sysadmins are not proxied; all other connections are.
|
|
.Bd -literal
|
|
# NO RDR
|
|
no rdr on $int_if proto { tcp, udp } from any to $server port 80
|
|
no rdr on $int_if proto { tcp, udp } from $sysadmins to any port 80
|
|
rdr on $int_if proto { tcp, udp } from any to any port 80 -> 127.0.0.1 \e
|
|
port 80
|
|
.Ed
|
|
.Pp
|
|
This longer example uses both a NAT and a redirection.
|
|
The external interface has the address 157.161.48.183.
|
|
On the internal interface, we are running
|
|
.Xr ftp-proxy 8 ,
|
|
listening for outbound ftp sessions captured to port 8021.
|
|
.Bd -literal
|
|
# NAT
|
|
# Translate outgoing packets' source addresses (any protocol).
|
|
# In this case, any address but the gateway's external address is mapped.
|
|
nat on $ext_if inet from ! ($ext_if) to any -> ($ext_if)
|
|
|
|
# NAT PROXYING
|
|
# Map outgoing packets' source port to an assigned proxy port instead of
|
|
# an arbitrary port.
|
|
# In this case, proxy outgoing isakmp with port 500 on the gateway.
|
|
nat on $ext_if inet proto udp from any port = isakmp to any -> ($ext_if) \e
|
|
port 500
|
|
|
|
# BINAT
|
|
# Translate outgoing packets' source address (any protocol).
|
|
# Translate incoming packets' destination address to an internal machine
|
|
# (bidirectional).
|
|
binat on $ext_if from 10.1.2.150 to any -> $ext_if
|
|
|
|
# RDR
|
|
# Translate incoming packets' destination addresses.
|
|
# As an example, redirect a TCP and UDP port to an internal machine.
|
|
rdr on $ext_if inet proto tcp from any to ($ext_if) port 8080 \e
|
|
-> 10.1.2.151 port 22
|
|
rdr on $ext_if inet proto udp from any to ($ext_if) port 8080 \e
|
|
-> 10.1.2.151 port 53
|
|
|
|
# RDR
|
|
# Translate outgoing ftp control connections to send them to localhost
|
|
# for proxying with ftp-proxy(8) running on port 8021.
|
|
rdr on $int_if proto tcp from any to any port 21 -> 127.0.0.1 port 8021
|
|
.Ed
|
|
.Pp
|
|
In this example, a NAT gateway is set up to translate internal addresses
|
|
using a pool of public addresses (192.0.2.16/28) and to redirect
|
|
incoming web server connections to a group of web servers on the internal
|
|
network.
|
|
.Bd -literal
|
|
# NAT LOAD BALANCE
|
|
# Translate outgoing packets' source addresses using an address pool.
|
|
# A given source address is always translated to the same pool address by
|
|
# using the source-hash keyword.
|
|
nat on $ext_if inet from any to any -> 192.0.2.16/28 source-hash
|
|
|
|
# RDR ROUND ROBIN
|
|
# Translate incoming web server connections to a group of web servers on
|
|
# the internal network.
|
|
rdr on $ext_if proto tcp from any to any port 80 \e
|
|
-> { 10.1.2.155, 10.1.2.160, 10.1.2.161 } round-robin
|
|
.Ed
|
|
.Sh FILTER EXAMPLES
|
|
.Bd -literal
|
|
# The external interface is kue0
|
|
# (157.161.48.183, the only routable address)
|
|
# and the private network is 10.0.0.0/8, for which we are doing NAT.
|
|
|
|
# use a macro for the interface name, so it can be changed easily
|
|
ext_if = \&"kue0\&"
|
|
|
|
# normalize all incoming traffic
|
|
scrub in on $ext_if all fragment reassemble
|
|
|
|
# block and log everything by default
|
|
block return log on $ext_if all
|
|
|
|
# block anything coming from source we have no back routes for
|
|
block in from no-route to any
|
|
|
|
# block and log outgoing packets that do not have our address as source,
|
|
# they are either spoofed or something is misconfigured (NAT disabled,
|
|
# for instance), we want to be nice and do not send out garbage.
|
|
block out log quick on $ext_if from ! 157.161.48.183 to any
|
|
|
|
# silently drop broadcasts (cable modem noise)
|
|
block in quick on $ext_if from any to 255.255.255.255
|
|
|
|
# block and log incoming packets from reserved address space and invalid
|
|
# addresses, they are either spoofed or misconfigured, we cannot reply to
|
|
# them anyway (hence, no return-rst).
|
|
block in log quick on $ext_if from { 10.0.0.0/8, 172.16.0.0/12, \e
|
|
192.168.0.0/16, 255.255.255.255/32 } to any
|
|
|
|
# ICMP
|
|
|
|
# pass out/in certain ICMP queries and keep state (ping)
|
|
# state matching is done on host addresses and ICMP id (not type/code),
|
|
# so replies (like 0/0 for 8/0) will match queries
|
|
# ICMP error messages (which always refer to a TCP/UDP packet) are
|
|
# handled by the TCP/UDP states
|
|
pass on $ext_if inet proto icmp all icmp-type 8 code 0 keep state
|
|
|
|
# UDP
|
|
|
|
# pass out all UDP connections and keep state
|
|
pass out on $ext_if proto udp all keep state
|
|
|
|
# pass in certain UDP connections and keep state (DNS)
|
|
pass in on $ext_if proto udp from any to any port domain keep state
|
|
|
|
# TCP
|
|
|
|
# pass out all TCP connections and modulate state
|
|
pass out on $ext_if proto tcp all modulate state
|
|
|
|
# pass in certain TCP connections and keep state (SSH, SMTP, DNS, IDENT)
|
|
pass in on $ext_if proto tcp from any to any port { ssh, smtp, domain, \e
|
|
auth } flags S/SA keep state
|
|
|
|
# pass in data mode connections for ftp-proxy running on this host.
|
|
# (see ftp-proxy(8) for details)
|
|
pass in on $ext_if proto tcp from any to 157.161.48.183 port >= 49152 \e
|
|
flags S/SA keep state
|
|
|
|
# Do not allow Windows 9x SMTP connections since they are typically
|
|
# a viral worm. Alternately we could limit these OSes to 1 connection each.
|
|
block in on $ext_if proto tcp from any os {"Windows 95", "Windows 98"} \e
|
|
to any port smtp
|
|
|
|
# Packet Tagging
|
|
|
|
# three interfaces: $int_if, $ext_if, and $wifi_if (wireless). NAT is
|
|
# being done on $ext_if for all outgoing packets. tag packets in on
|
|
# $int_if and pass those tagged packets out on $ext_if. all other
|
|
# outgoing packets (i.e., packets from the wireless network) are only
|
|
# permitted to access port 80.
|
|
|
|
pass in on $int_if from any to any tag INTNET keep state
|
|
pass in on $wifi_if from any to any keep state
|
|
|
|
block out on $ext_if from any to any
|
|
pass out quick on $ext_if tagged INTNET keep state
|
|
pass out on $ext_if proto tcp from any to any port 80 keep state
|
|
|
|
# tag incoming packets as they are redirected to spamd(8). use the tag
|
|
# to pass those packets through the packet filter.
|
|
|
|
rdr on $ext_if inet proto tcp from <spammers> to port smtp \e
|
|
tag SPAMD -> 127.0.0.1 port spamd
|
|
|
|
block in on $ext_if
|
|
pass in on $ext_if inet proto tcp tagged SPAMD keep state
|
|
.Ed
|
|
.Sh GRAMMAR
|
|
Syntax for
|
|
.Nm
|
|
in BNF:
|
|
.Bd -literal
|
|
line = ( option | pf-rule | nat-rule | binat-rule | rdr-rule |
|
|
antispoof-rule | altq-rule | queue-rule | anchor-rule |
|
|
trans-anchors | load-anchors | table-rule )
|
|
|
|
option = "set" ( [ "timeout" ( timeout | "{" timeout-list "}" ) ] |
|
|
[ "optimization" [ "default" | "normal" |
|
|
"high-latency" | "satellite" |
|
|
"aggressive" | "conservative" ] ]
|
|
[ "limit" ( limit-item | "{" limit-list "}" ) ] |
|
|
[ "loginterface" ( interface-name | "none" ) ] |
|
|
[ "block-policy" ( "drop" | "return" ) ] |
|
|
[ "state-policy" ( "if-bound" | "group-bound" |
|
|
"floating" ) ]
|
|
[ "require-order" ( "yes" | "no" ) ]
|
|
[ "fingerprints" filename ] |
|
|
[ "debug" ( "none" | "urgent" | "misc" | "loud" ) ] )
|
|
|
|
pf-rule = action [ ( "in" | "out" ) ]
|
|
[ "log" | "log-all" ] [ "quick" ]
|
|
[ "on" ifspec ] [ route ] [ af ] [ protospec ]
|
|
hosts [ filteropt-list ]
|
|
|
|
filteropt-list = filteropt-list filteropt | filteropt
|
|
filteropt = user | group | flags | icmp-type | icmp6-type | tos |
|
|
( "keep" | "modulate" | "synproxy" ) "state"
|
|
[ "(" state-opts ")" ] |
|
|
"fragment" | "no-df" | "min-ttl" number |
|
|
"max-mss" number | "random-id" | "reassemble tcp" |
|
|
fragmentation | "allow-opts" |
|
|
"label" string | "tag" string | [ ! ] "tagged" string
|
|
"queue" ( string | "(" string [ [ "," ] string ] ")" ) |
|
|
"probability" number"%"
|
|
|
|
nat-rule = [ "no" ] "nat" [ "pass" ] [ "on" ifspec ] [ af ]
|
|
[ protospec ] hosts [ "tag" string ] [ "tagged" string ]
|
|
[ "->" ( redirhost | "{" redirhost-list "}" )
|
|
[ portspec ] [ pooltype ] [ "static-port" ] ]
|
|
|
|
binat-rule = [ "no" ] "binat" [ "pass" ] [ "on" interface-name ]
|
|
[ af ] [ "proto" ( proto-name | proto-number ) ]
|
|
"from" address [ "/" mask-bits ] "to" ipspec
|
|
[ "tag" string ] [ "tagged" string ]
|
|
[ "->" address [ "/" mask-bits ] ]
|
|
|
|
rdr-rule = [ "no" ] "rdr" [ "pass" ] [ "on" ifspec ] [ af ]
|
|
[ protospec ] hosts [ "tag" string ] [ "tagged" string ]
|
|
[ "->" ( redirhost | "{" redirhost-list "}" )
|
|
[ portspec ] [ pooltype ] ]
|
|
|
|
antispoof-rule = "antispoof" [ "log" ] [ "quick" ]
|
|
"for" ( interface-name | "{" interface-list "}" )
|
|
[ af ] [ "label" string ]
|
|
|
|
table-rule = "table" "<" string ">" [ tableopts-list ]
|
|
tableopts-list = tableopts-list tableopts | tableopts
|
|
tableopts = "persist" | "const" | "file" string |
|
|
"{" [ tableaddr-list ] "}"
|
|
tableaddr-list = tableaddr-list [ "," ] tableaddr-spec | tableaddr-spec
|
|
tableaddr-spec = [ "!" ] tableaddr [ "/" mask-bits ]
|
|
tableaddr = hostname | ipv4-dotted-quad | ipv6-coloned-hex |
|
|
interface-name | "self"
|
|
|
|
altq-rule = "altq on" interface-name queueopts-list
|
|
"queue" subqueue
|
|
queue-rule = "queue" string [ "on" interface-name ] queueopts-list
|
|
subqueue
|
|
|
|
anchor-rule = "anchor" string [ ( "in" | "out" ) ] [ "on" ifspec ]
|
|
[ af ] [ "proto" ] [ protospec ] [ hosts ]
|
|
|
|
trans-anchors = ( "nat-anchor" | "rdr-anchor" | "binat-anchor" ) string
|
|
[ "on" ifspec ] [ af ] [ "proto" ] [ protospec ] [ hosts ]
|
|
|
|
load-anchor = "load anchor" string "from" filename
|
|
|
|
queueopts-list = queueopts-list queueopts | queueopts
|
|
queueopts = [ "bandwidth" bandwidth-spec ] |
|
|
[ "qlimit" number ] | [ "tbrsize" number ] |
|
|
[ "priority" number ] | [ schedulers ]
|
|
schedulers = ( cbq-def | priq-def | hfsc-def )
|
|
bandwidth-spec = "number" ( "b" | "Kb" | "Mb" | "Gb" | "%" )
|
|
|
|
action = "pass" | "block" [ return ] | [ "no" ] "scrub"
|
|
return = "drop" | "return" | "return-rst" [ "( ttl" number ")" ] |
|
|
"return-icmp" [ "(" icmpcode ["," icmp6code ] ")" ] |
|
|
"return-icmp6" [ "(" icmp6code ")" ]
|
|
icmpcode = ( icmp-code-name | icmp-code-number )
|
|
icmp6code = ( icmp6-code-name | icmp6-code-number )
|
|
|
|
ifspec = ( [ "!" ] interface-name ) | "{" interface-list "}"
|
|
interface-list = [ "!" ] interface-name [ [ "," ] interface-list ]
|
|
route = "fastroute" |
|
|
( "route-to" | "reply-to" | "dup-to" )
|
|
( routehost | "{" routehost-list "}" )
|
|
[ pooltype ]
|
|
af = "inet" | "inet6"
|
|
|
|
protospec = "proto" ( proto-name | proto-number |
|
|
"{" proto-list "}" )
|
|
proto-list = ( proto-name | proto-number ) [ [ "," ] proto-list ]
|
|
|
|
hosts = "all" |
|
|
"from" ( "any" | "no-route" | "self" | host |
|
|
"{" host-list "}" | "route" string ) [ port ] [ os ]
|
|
"to" ( "any" | "no-route" | "self" | host |
|
|
"{" host-list "}" | "route" string ) [ port ]
|
|
|
|
ipspec = "any" | host | "{" host-list "}"
|
|
host = [ "!" ] ( address [ "/" mask-bits ] | "<" string ">" )
|
|
redirhost = address [ "/" mask-bits ]
|
|
routehost = ( interface-name [ address [ "/" mask-bits ] ] )
|
|
address = ( interface-name | "(" interface-name ")" | hostname |
|
|
ipv4-dotted-quad | ipv6-coloned-hex )
|
|
host-list = host [ [ "," ] host-list ]
|
|
redirhost-list = redirhost [ [ "," ] redirhost-list ]
|
|
routehost-list = routehost [ [ "," ] routehost-list ]
|
|
|
|
port = "port" ( unary-op | binary-op | "{" op-list "}" )
|
|
portspec = "port" ( number | name ) [ ":" ( "*" | number | name ) ]
|
|
os = "os" ( os-name | "{" os-list "}" )
|
|
user = "user" ( unary-op | binary-op | "{" op-list "}" )
|
|
group = "group" ( unary-op | binary-op | "{" op-list "}" )
|
|
|
|
unary-op = [ "=" | "!=" | "<" | "<=" | ">" | ">=" ]
|
|
( name | number )
|
|
binary-op = number ( "<>" | "><" | ":" ) number
|
|
op-list = ( unary-op | binary-op ) [ [ "," ] op-list ]
|
|
|
|
os-name = operating-system-name
|
|
os-list = os-name [ [ "," ] os-list ]
|
|
|
|
flags = "flags" [ flag-set ] "/" flag-set
|
|
flag-set = [ "F" ] [ "S" ] [ "R" ] [ "P" ] [ "A" ] [ "U" ] [ "E" ]
|
|
[ "W" ]
|
|
|
|
icmp-type = "icmp-type" ( icmp-type-code | "{" icmp-list "}" )
|
|
icmp6-type = "icmp6-type" ( icmp-type-code | "{" icmp-list "}" )
|
|
icmp-type-code = ( icmp-type-name | icmp-type-number )
|
|
[ "code" ( icmp-code-name | icmp-code-number ) ]
|
|
icmp-list = icmp-type-code [ [ "," ] icmp-list ]
|
|
|
|
tos = "tos" ( "lowdelay" | "throughput" | "reliability" |
|
|
[ "0x" ] number )
|
|
|
|
state-opts = state-opt [ [ "," ] state-opts ]
|
|
state-opt = ( "max" number | "no-sync" | timeout |
|
|
"source-track" [ ( "rule" | "global" ) ] |
|
|
"max-src-nodes" number | "max-src-states" number |
|
|
"max-src-conn" number |
|
|
"max-src-conn-rate" number "/" number |
|
|
"overload" "<" string ">" [ "flush" ] |
|
|
"if-bound" | "group-bound" | "floating" )
|
|
|
|
fragmentation = [ "fragment reassemble" | "fragment crop" |
|
|
"fragment drop-ovl" ]
|
|
|
|
timeout-list = timeout [ [ "," ] timeout-list ]
|
|
timeout = ( "tcp.first" | "tcp.opening" | "tcp.established" |
|
|
"tcp.closing" | "tcp.finwait" | "tcp.closed" |
|
|
"udp.first" | "udp.single" | "udp.multiple" |
|
|
"icmp.first" | "icmp.error" |
|
|
"other.first" | "other.single" | "other.multiple" |
|
|
"frag" | "interval" | "src.track" |
|
|
"adaptive.start" | "adaptive.end" ) number
|
|
|
|
limit-list = limit-item [ [ "," ] limit-list ]
|
|
limit-item = ( "states" | "frags" | "src-nodes" ) number
|
|
|
|
pooltype = ( "bitmask" | "random" |
|
|
"source-hash" [ ( hex-key | string-key ) ] |
|
|
"round-robin" ) [ sticky-address ]
|
|
|
|
subqueue = string | "{" queue-list "}"
|
|
queue-list = string [ [ "," ] string ]
|
|
cbq-def = "cbq" [ "(" cbq-opt [ [ "," ] cbq-opt ] ")" ]
|
|
priq-def = "priq" [ "(" priq-opt [ [ "," ] priq-opt ] ")" ]
|
|
hfsc-def = "hfsc" [ "(" hfsc-opt [ [ "," ] hfsc-opt ] ")" ]
|
|
cbq-opt = ( "default" | "borrow" | "red" | "ecn" | "rio" )
|
|
priq-opt = ( "default" | "red" | "ecn" | "rio" )
|
|
hfsc-opt = ( "default" | "red" | "ecn" | "rio" |
|
|
linkshare-sc | realtime-sc | upperlimit-sc )
|
|
linkshare-sc = "linkshare" sc-spec
|
|
realtime-sc = "realtime" sc-spec
|
|
upperlimit-sc = "upperlimit" sc-spec
|
|
sc-spec = ( bandwidth-spec |
|
|
"(" bandwidth-spec number bandwidth-spec ")" )
|
|
.Ed
|
|
.Sh FILES
|
|
.Bl -tag -width "/usr/share/examples/pf" -compact
|
|
.It Pa /etc/hosts
|
|
Host name database.
|
|
.It Pa /etc/pf.conf
|
|
Default location of the ruleset file.
|
|
.It Pa /etc/pf.os
|
|
Default location of OS fingerprints.
|
|
.It Pa /etc/protocols
|
|
Protocol name database.
|
|
.It Pa /etc/services
|
|
Service name database.
|
|
.It Pa /usr/share/examples/pf
|
|
Example rulesets.
|
|
.El
|
|
.Sh BUGS
|
|
Due to a lock order reversal (LOR) with the socket layer, the use of the
|
|
.Ar group
|
|
and
|
|
.Ar user
|
|
filter parameter in conjuction with a Giant-free netstack
|
|
can result in a deadlock.
|
|
If you have to use
|
|
.Ar group
|
|
or
|
|
.Ar user
|
|
you must set
|
|
.Va debug.mpsafenet
|
|
to
|
|
.Dq 0
|
|
from the
|
|
.Xr loader 8 ,
|
|
for the moment.
|
|
This workaround will still produce the LOR, but Giant will protect from the
|
|
deadlock.
|
|
.Sh SEE ALSO
|
|
.Xr altq 4 ,
|
|
.Xr icmp 4 ,
|
|
.Xr icmp6 4 ,
|
|
.Xr ip 4 ,
|
|
.Xr ip6 4 ,
|
|
.Xr pf 4 ,
|
|
.Xr pfsync 4 ,
|
|
.Xr route 4 ,
|
|
.Xr tcp 4 ,
|
|
.Xr udp 4 ,
|
|
.Xr hosts 5 ,
|
|
.Xr pf.os 5 ,
|
|
.Xr protocols 5 ,
|
|
.Xr services 5 ,
|
|
.Xr ftp-proxy 8 ,
|
|
.Xr pfctl 8 ,
|
|
.Xr pflogd 8 ,
|
|
.Xr route 8
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
file format first appeared in
|
|
.Ox 3.0 .
|