PFCTL(8)

System Manager's Manual

PFCTL(8)

NAME

pfctl — control the packet filter (PF) and network address translation (NAT) device

SYNOPSIS

pfctl

[-AdeghmNnOqRrvz] [-a anchor] [-D macro= value] [-F modifier] [-f file] [-i interface] [-K host | network] [-k host | network] [-o level] [-p device] [-s modifier] [-t table -T command [address ...]] [-x level]

DESCRIPTION

The pfctl utility communicates with the packet filter device using the ioctl interface described in pf(4). It allows ruleset and parameter configuration and retrieval of status information from the packet filter.

Packet filtering restricts the types of packets that pass through network interfaces entering or leaving the host based on filter rules as described in pf.conf(5). The packet filter can also replace addresses and ports of packets. Replacing source addresses and ports of outgoing packets is called NAT (Network Address Translation) and is used to connect an internal network (usually reserved address space) to an external one (the Internet) by making all connections to external hosts appear to come from the gateway. Replacing destination addresses and ports of incoming packets is used to redirect connections to different hosts and/or ports. A combination of both translations, bidirectional NAT, is also supported. Translation rules are described in pf.conf(5).

When the variable pf is set to YES in rc.conf(5), the rule file specified with the variable pf_rules is loaded automatically by the rc(8) scripts and the packet filter is enabled.

The packet filter does not itself forward packets between interfaces. Forwarding can be enabled by setting the sysctl(8) variables net.inet.ip.forwarding and/or net.inet6.ip6.forwarding to 1. Set them permanently in /etc/sysctl.conf.

The pfctl utility provides several commands. The options are as follows:

-A

Load only the queue rules present in the rule file. Other rules and options are ignored.

-a anchor

Apply flags -f, -F, and -s only to the rules in the specified anchor. In addition to the main ruleset, pfctl can load and manipulate additional rulesets by name, called anchors. The main ruleset is the default anchor.

Anchors are referenced by name and may be nested, with the various components of the anchor path separated by ‘/' characters, similar to how file system hierarchies are laid out. The last component of the anchor path is where ruleset operations are performed.

Evaluation of anchor rules from the main ruleset is described in pf.conf(5).

For example, the following will show all filter rules (see the -s flag below) inside the anchor “authpf/smith(1234)”, which would have been created for user “smith” by authpf(8), PID 1234:

# pfctl -a "authpf/smith(1234)" -s rules

Private tables can also be put inside anchors, either by having table statements in the pf.conf(5) file that is loaded in the anchor, or by using regular table commands, as in:

# pfctl -a foo/bar -t mytable -T add 1.2.3.4 5.6.7.8

When a rule referring to a table is loaded in an anchor, the rule will use the private table if one is defined, and then fall back to the table defined in the main ruleset, if there is one. This is similar to C rules for variable scope. It is possible to create distinct tables with the same name in the global ruleset and in an anchor, but this is often bad design and a warning will be issued in that case.

By default, recursive inline printing of anchors applies only to unnamed anchors specified inline in the ruleset. If the anchor name is terminated with a ‘*' character, the -s flag will recursively print all anchors in a brace delimited block. For example the following will print the “authpf” ruleset recursively:

# pfctl -a 'authpf/*' -sr

To print the main ruleset recursively, specify only ‘*' as the anchor name:

# pfctl -a '*' -sr

-D macro=value

Define macro to be set to value on the command line. Overrides the definition of macro in the ruleset.

-d

Disable the packet filter.

-e

Enable the packet filter.

-F modifier

Flush the filter parameters specified by modifier (may be abbreviated):

-f file

Load the rules contained in file. This file may contain macros, tables, options, and normalization, queueing, translation, and filtering rules. With the exception of macros and tables, the statements must appear in that order.

-g

Include output helpful for debugging.

-h

Help.

-i interface

Restrict the operation to the given interface.

-K host | network

Kill all of the source tracking entries originating from the specified host or network. A second -K host or -K network option may be specified, which will kill all the source tracking entries from the first host/network to the second.

-k host | network

Kill all of the state entries originating from the specified host or network. A second -k host or -k network option may be specified, which will kill all the state entries from the first host/network to the second. For example, to kill all of the state entries originating from “host”:

# pfctl -k host

To kill all of the state entries from “host1” to “host2”:

# pfctl -k host1 -k host2

To kill all states originating from 192.168.1.0/24 to 172.16.0.0/16:

# pfctl -k 192.168.1.0/24 -k 172.16.0.0/16

A network prefix length of 0 can be used as a wildcard. To kill all states with the target “host2”:

# pfctl -k 0.0.0.0/0 -k host2

-m

Merge in explicitly given options without resetting those which are omitted. Allows single options to be modified without disturbing the others:

# echo "set loginterface fxp0" | pfctl -mf -

-N

Load only the NAT rules present in the rule file. Other rules and options are ignored.

-n

Do not actually load rules, just parse them.

-O

Load only the options present in the rule file. Other rules and options are ignored.

-o level

Control the ruleset optimizer, overriding any rule file settings.

For further information on the ruleset optimizer, see pf.conf(5).

-p device

Use the device file device instead of the default /dev/pf.

-q

Only print errors and warnings.

-R

Load only the filter rules present in the rule file. Other rules and options are ignored.

-r

Perform reverse DNS lookups on states when displaying them.

-s modifier

Show the filter parameters specified by modifier (may be abbreviated):

-T command [address ...]

Specify the command (may be abbreviated) to apply to the table. Commands include:

For the add, delete, replace, and test commands, the list of addresses can be specified either directly on the command line and/or in an unformatted text file, using the -f flag. Comments starting with a ‘#' are allowed in the text file. With these commands, the -v flag can also be used once or twice, in which case pfctl will print the detailed result of the operation for each individual address, prefixed by one of the following letters:

Each table maintains a set of counters that can be retrieved using the -v flag of pfctl. For example, the following commands define a wide open firewall which will keep track of packets going to or coming from the OpenBSD FTP server. The following commands configure the firewall and send 10 pings to the FTP server:

# printf "table <test> { ftp.NetBSD.org }\n \ 
    pass out to <test>\n" | pfctl -f- 
# ping -qc10 ftp.NetBSD.org

We can now use the table show command to output, for each address and packet direction, the number of packets and bytes that are being passed or blocked by rules referencing the table. The time at which the current accounting started is also shown with the “Cleared” line.

# pfctl -t test -vTshow 
   129.128.5.191 
    Cleared:     Thu Feb 13 18:55:18 2003 
    In/Block:    [ Packets: 0        Bytes: 0        ] 
    In/Pass:     [ Packets: 10       Bytes: 840      ] 
    Out/Block:   [ Packets: 0        Bytes: 0        ] 
    Out/Pass:    [ Packets: 10       Bytes: 840      ]

Similarly, it is possible to view global information about the tables by using the -v modifier twice and the -s Tables command. This will display the number of addresses on each table, the number of rules which reference the table, and the global packet statistics for the whole table:

# pfctl -vvsTables 
--a-r-  test 
    Addresses:   1 
    Cleared:     Thu Feb 13 18:55:18 2003 
    References:  [ Anchors: 0        Rules: 1        ] 
    Evaluations: [ NoMatch: 3496     Match: 1        ] 
    In/Block:    [ Packets: 0        Bytes: 0        ] 
    In/Pass:     [ Packets: 10       Bytes: 840      ] 
    In/XPass:    [ Packets: 0        Bytes: 0        ] 
    Out/Block:   [ Packets: 0        Bytes: 0        ] 
    Out/Pass:    [ Packets: 10       Bytes: 840      ] 
    Out/XPass:   [ Packets: 0        Bytes: 0        ]

As we can see here, only one packet - the initial ping request - matched the table, but all packets passing as the result of the state are correctly accounted for. Reloading the table(s) or ruleset will not affect packet accounting in any way. The two “XPass” counters are incremented instead of the “Pass” counters when a “stateful” packet is passed but doesn't match the table anymore. This will happen in our example if someone flushes the table while the ping(8) command is running.

When used with a single -v, pfctl will only display the first line containing the table flags and name. The flags are defined as follows:

-t table

Specify the name of the table.

-v

Produce more verbose output. A second use of -v will produce even more verbose output including ruleset warnings. See the previous section for its effect on table commands.

-x level

Set the debug level (may be abbreviated) to one of the following:

-z

Clear per-rule statistics.

FILES

HISTORY

The pfctl program and the pf(4) filter mechanism first appeared in OpenBSD 3.0.

May 31, 2007

NetBSD 6.1

NAME

SYNOPSIS

DESCRIPTION

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SEE ALSO

HISTORY