path: root/sbin/pfctl/pfctl.8

.\" $OpenBSD: pfctl.8,v 1.34 2001/10/11 00:53:21 dhartmei Exp $
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.Dd June 24, 2001
.Dt PFCTL 8
.Os
.Sh NAME
.Nm pfctl
.Nd control the packet filter and NAT subsystems
.Sh SYNOPSIS
.Nm pfctl
.Op Fl dehnqv
.Op Fl F Ar modifier
.Op Fl l Ar interface
.Op Fl N Ar file
.Op Fl O Ar level
.Op Fl R Ar file
.Op Fl s Ar modifier
.Op Fl t Ar modifier
.Op Fl x Ar level
.Sh DESCRIPTION
The
.Nm
utility communicates with the packet filter system using the
ioctl interface described in
.Xr pf 4 .
.Pp
Packet filtering lets you restrict packets entering or leaving
your host; packets can be specified in a variety of ways including
by protocol, by port number, and by address.
Network Address Translation lets you map a series of internal
host IP numbers to a single external address.
The NAT code also has provisions for redirecting a
range of connections to a different host and/or port number.
Taken together this provides a powerful basic firewall mechanism.
.Pp
The
.Nm
command is normally invoked automatically at system initialization
time to start and load the packet filter,
but can also be used when the filter or translation rules change.
.Pp
.Nm
requires the
.Xr pf 4
pseudo-device driver.
Forwarding packets, by using NAT, also requires specifying
.Li net.inet.ip.forwarding=1
in the file
.Pa /etc/sysctl.conf .
.Pp
The
.Nm
utility provides several commands.
The options are as follows:
.Bl -tag -width Ds
.It Fl d
Disable the packet filter.
.It Fl e
Enable the packet filter.
.It Fl F Ar modifier
Flush one of the following.
Modifier name may be abbreviated:
.Bl -tag -width "F rules " -compact
.It Fl F Ar nat
Flush the NAT rules.
.It Fl F Ar rules
Flush the filter rules.
.It Fl F Ar state
Flush the state table (NAT and filter).
.It Fl F Ar info
Flush the filter information (statistics and counters).
.It Fl F Ar all
Flush all of the above.
.El
.It Fl h
Help.
.It Fl l Ar interface
Enable collection of packet and byte count statistics for interface named
.Ar interface .
These statistics can be viewed with the
.Fl s Ar info
option.
.It Fl n
Do not actually load rules.
.It Fl N Ar file
Load a NAT rules file.
.It Fl O Ar modifier
Optimize the engine to one of the following network topographies or
environments:
.Bl -tag -width "O high-latency " -compact
.It Fl O Ar default
A normal network environment.  Suitable for almost all networks.
.It Fl O Ar normal
Alias for
.Em default
.It Fl O Ar high-latency
A high-latency environment (such as a satellite connection)
.It Fl O Ar satellite
Alias for
.Em high-latency
.It Fl O Ar aggressive
Aggressively expire connections when they are likely no longer valid.  This
can greatly reduce the memory usage of the firewall at the cost of dropping
idle connections early.
.It Fl O Ar conservative
Extremely conservative settings.  Pains will be taken to avoid dropping
legitimate connections at the expense of greater memory utilization (possibly
much greater on a busy network) and slightly increased processor utilization.
.El
Currently the optimizations only encompass the state table timeouts but much
more is planned in future revisions of the finite state machines (FSMs).
.It Fl q
Only print errors and warnings.
.It Fl R Ar file
Load a filter rules file into the filter.
.It Fl s Ar modifier
Show filter parameters. Modifier names may be abbreviated:
.Bl -tag -width "s rules " -compact
.It Fl s Ar nat
Show the currently loaded NAT rules.
.It Fl s Ar rules
Show the currently loaded packet filter rules.
When used together with -v, the per-rule statistics (number of evaluations,
packets and bytes) are also shown. Note that the 'skip step' optimization
done automatically by the kernel will skip evaluation of rules where
redundant. Packets passed statefully are counted in the rule that created
the state (even though the rule isn't evaluated more than once for the
entire connection).
.It Fl s Ar state
Show the contents of the state table.
.It Fl s Ar info
Show filter information (statistics and counters).
.It Fl s Ar all
Show all of the above.
.El
.It Fl t Ar modifier
Get a timeout or interval value.  Any of the modifiers may be set,
with the exception of
.Em all ,
by appending =<seconds> to the modifier without any whitespace seperating
the modifier, the equals and the number of seconds.
.Bl -tag -width "t interval " -compact
.It Fl t Ar all
Display all timeouts and intervals.
.It Fl t Ar interval
Interval between purging expired states and fragments.
.It Fl t Ar frag
Seconds before an unassembled fragment is expired.
.El
.Pp
When a packet matches a stateful connection, the seconds to live of the
connection will be updated to that of the proto.modifier which corresponds
to the connection state.  Each packet which matches this state will increase
the TTL.  It is permissible to set the TTL for a particular state to zero
if you do not want packets matching a particular state to prolong the life
of the state.  Tuning these values may improve the performance of the
firewall at the risk of dropping valid idled connections.

.Bl -tag -width "t tcp.established " -compact
.It Fl t Ar tcp.first
The state after the first packet.
.It Fl t Ar tcp.opening
The state before the destination host ever sends a packet.
.It Fl t Ar tcp.established
The fully established state.
.It Fl t Ar tcp.closing
The state after the first FIN has been sent.
.It Fl t Ar tcp.finwait
The state after both FINs have been exchanged and the connection is closed.
If you see lots of blocked packets coming back from web servers (notably
Solaris), increase this value and possibly tcp.closing.
.It Fl t Ar tcp.closed
The state after one endpoint sends a RST.
.El
.Pp
ICMP and UDP are handled in a similar fashion to TCP but with a much more
limited set of states.
.Bl -tag -width "t udp.multiple " -compact
.It Fl t Ar udp.first
The state after the first packet.
.It Fl t Ar udp.single
The state if the source host sends more than one packet but the destination
host has never sent one back.
.It Fl t Ar udp.multiple
The state if both hosts have sent packets.
.It Fl t Ar icmp.first
The state after the first packet.
.It Fl t Ar icmp.error
The state after an icmp error came back in response to an icmp packet.
.El
.Pp
.Bd -literal
Example:
    # Timeout established connections after an hour of inactivity
    pfctl -t tcp.established=3600

    # Display the current established idle timeout
    pfctl -t tcp.established
.Ed

.It Fl v
Produce more verbose output.
.It Fl x Ar level
Set the debug level to one of the following.
Level names may be abbreviated:
.Bl -tag -width "x urgent " -compact
.It Fl x Ar none
Don't generate debug messages.
.It Fl x Ar urgent
Generate debug messages only for serious errors.
.It Fl x Ar misc
Generate debug messages for various errors.
.El
.Sh FILES
.Bl -tag -width "/etc/nat.conf" -compact
.It Pa /etc/pf.conf
Packet filter rules file.
.It Pa /etc/nat.conf
Rules for Network Address Translation.
.El
.Sh SEE ALSO
.Xr pf 4 , 
.Xr nat.conf 5 ,
.Xr pf.conf 5 ,
.Xr ftp-proxy 8 ,
.Xr rc 8
.Sh AUTHORS
Daniel Hartmeier wrote the program and the underlying mechanism.
.Sh HISTORY
The
.Nm
program and the 
.Xr pf 4
filter mechanism first appeared in
.Ox 3.0 .
.Sh BUGS
Probably.