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35 .Nd packet filter configuration file
39 packet filter modifies, drops or passes packets according to rules or
40 definitions specified in
43 There are seven types of statements in
47 User-defined variables may be defined and used later, simplifying
48 the configuration file.
49 Macros must be defined before they are referenced in
52 Tables provide a mechanism for increasing the performance and flexibility of
53 rules with large numbers of source or destination addresses.
55 Options tune the behaviour of the packet filtering engine.
56 .It Cm Traffic Normalization Li (e.g.\& Em scrub )
57 Traffic normalization protects internal machines against inconsistencies
58 in Internet protocols and implementations.
60 Queueing provides rule-based bandwidth control.
61 .It Cm Translation Li (Various forms of NAT)
62 Translation rules specify how addresses are to be mapped or redirected to
64 .It Cm Packet Filtering
65 Packet filtering provides rule-based blocking or passing of packets.
72 the types of statements should be grouped and appear in
74 in the order shown above, as this matches the operation of the underlying
75 packet filtering engine.
78 enforces this order (see
82 Comments can be put anywhere in the file using a hash mark
84 and extend to the end of the current line.
86 Additional configuration files can be included with the
89 .Bd -literal -offset indent
90 include "/etc/pf/sub.filter.conf"
93 Macros can be defined that will later be expanded in context.
94 Macro names must start with a letter, and may contain letters, digits
96 Macro names may not be reserved words (for example
100 Macros are not expanded inside quotes.
103 .Bd -literal -offset indent
105 all_ifs = \&"{\&" $ext_if lo0 \&"}\&"
106 pass out on $ext_if from any to any
107 pass in on $ext_if proto tcp from any to any port 25
110 Tables are named structures which can hold a collection of addresses and
112 Lookups against tables in
114 are relatively fast, making a single rule with tables much more efficient,
116 processor usage and memory consumption, than a large number of rules which
117 differ only in IP address (either created explicitly or automatically by rule
120 Tables can be used as the source or destination of filter rules,
124 translation rules such as
128 (see below for details on the various rule types).
129 Tables can also be used for the redirect address of
133 rules and in the routing options of filter rules, but only for
137 Tables can be defined with any of the following
140 As with macros, reserved words may not be used as table names.
141 .Bl -tag -width "manually"
143 Persistent tables can be manually created with the
149 before or after the ruleset has been loaded.
151 Table definitions can be placed directly in this file, and loaded at the
152 same time as other rules are loaded, atomically.
153 Table definitions inside
157 statement, and are especially useful to define non-persistent tables.
158 The contents of a pre-existing table defined without a list of addresses
159 to initialize it is not altered when
162 A table initialized with the empty list,
164 will be cleared on load.
167 Tables may be defined with the following two attributes:
168 .Bl -tag -width persist
172 flag forces the kernel to keep the table even when no rules refer to it.
173 If the flag is not set, the kernel will automatically remove the table
174 when the last rule referring to it is flushed.
178 flag prevents the user from altering the contents of the table once it
182 can be used to add or remove addresses from the table at any time, even
189 flag enables per-address packet and byte counters which can be displayed with
194 .Bd -literal -offset indent
195 table \*(Ltprivate\*(Gt const { 10/8, 172.16/12, 192.168/16 }
196 table \*(Ltbadhosts\*(Gt persist
197 block on fxp0 from { \*(Ltprivate\*(Gt, \*(Ltbadhosts\*(Gt } to any
200 creates a table called private, to hold RFC 1918 private network
201 blocks, and a table called badhosts, which is initially empty.
202 A filter rule is set up to block all traffic coming from addresses listed in
204 The private table cannot have its contents changed and the badhosts table
205 will exist even when no active filter rules reference it.
206 Addresses may later be added to the badhosts table, so that traffic from
207 these hosts can be blocked by using
208 .Bd -literal -offset indent
209 # pfctl -t badhosts -Tadd 204.92.77.111
212 A table can also be initialized with an address list specified in one or more
213 external files, using the following syntax:
214 .Bd -literal -offset indent
215 table \*(Ltspam\*(Gt persist file \&"/etc/spammers\&" file \&"/etc/openrelays\&"
216 block on fxp0 from \*(Ltspam\*(Gt to any
223 list IP addresses, one per line.
224 Any lines beginning with a # are treated as comments and ignored.
225 In addition to being specified by IP address, hosts may also be
226 specified by their hostname.
227 When the resolver is called to add a hostname to a table,
229 resulting IPv4 and IPv6 addresses are placed into the table.
230 IP addresses can also be entered in a table by specifying a valid interface
233 keyword, in which case all addresses assigned to the interface will be
237 may be tuned for various situations using the
243 .Bl -tag -width "src.track" -compact
245 Interval between purging expired states and fragments.
247 Seconds before an unassembled fragment is expired.
249 Length of time to retain a source tracking entry after the last state
253 When a packet matches a stateful connection, the seconds to live for the
254 connection will be updated to that of the
256 which corresponds to the connection state.
257 Each packet which matches this state will reset the TTL.
258 Tuning these values may improve the performance of the
259 firewall at the risk of dropping valid idle connections.
261 .Bl -tag -width xxxx -compact
263 The state after the first packet.
265 The state before the destination host ever sends a packet.
266 .It Ar tcp.established
267 The fully established state.
269 The state after the first FIN has been sent.
271 The state after both FINs have been exchanged and the connection is closed.
272 Some hosts (notably web servers on Solaris) send TCP packets even after closing
278 can prevent blocking of such packets.
280 The state after one endpoint sends an RST.
283 ICMP and UDP are handled in a fashion similar to TCP, but with a much more
284 limited set of states:
286 .Bl -tag -width xxxx -compact
288 The state after the first packet.
290 The state if the source host sends more than one packet but the destination
291 host has never sent one back.
293 The state if both hosts have sent packets.
295 The state after the first packet.
297 The state after an ICMP error came back in response to an ICMP packet.
300 Other protocols are handled similarly to UDP:
302 .Bl -tag -width xxxx -compact
305 .It Ar other.multiple
308 Timeout values can be reduced adaptively as the number of state table
311 .Bl -tag -width xxxx -compact
312 .It Ar adaptive.start
313 When the number of state entries exceeds this value, adaptive scaling
315 All timeout values are scaled linearly with factor
316 (adaptive.end - number of states) / (adaptive.end - adaptive.start).
318 When reaching this number of state entries, all timeout values become
319 zero, effectively purging all state entries immediately.
320 This value is used to define the scale factor, it should not actually
321 be reached (set a lower state limit, see below).
324 Adaptive timeouts are enabled by default, with an adaptive.start value
325 equal to 60% of the state limit, and an adaptive.end value equal to
326 120% of the state limit.
327 They can be disabled by setting both adaptive.start and adaptive.end to 0.
329 The adaptive timeout values can be defined both globally and for each rule.
330 When used on a per-rule basis, the values relate to the number of
331 states created by the rule, otherwise to the total number of
335 .Bd -literal -offset indent
336 set timeout tcp.first 120
337 set timeout tcp.established 86400
338 set timeout { adaptive.start 6000, adaptive.end 12000 }
339 set limit states 10000
342 With 9000 state table entries, the timeout values are scaled to 50%
343 (tcp.first 60, tcp.established 43200).
345 .It Ar set loginterface
346 Enable collection of packet and byte count statistics for the given interface.
347 These statistics can be viewed using
348 .Bd -literal -offset indent
354 collects statistics on the interface named dc0:
355 .Bd -literal -offset indent
359 One can disable the loginterface using:
360 .Bd -literal -offset indent
361 set loginterface none
365 Sets hard limits on the memory zones used by the packet filter.
368 for an explanation of memory zones.
371 .Bd -literal -offset indent
372 set limit states 20000
375 sets the maximum number of entries in the memory pool used by state table
376 entries (generated by
378 rules which do not specify
382 .Bd -literal -offset indent
383 set limit frags 20000
386 sets the maximum number of entries in the memory pool used for fragment
387 reassembly (generated by
391 .Bd -literal -offset indent
392 set limit src-nodes 2000
395 sets the maximum number of entries in the memory pool used for tracking
396 source IP addresses (generated by the
402 sets limits on the memory pools used by tables.
403 The first limits the number of tables that can exist to 1000.
404 The second limits the overall number of addresses that can be stored
407 Various limits can be combined on a single line:
408 .Bd -literal -offset indent
409 set limit { states 20000, frags 20000, src-nodes 2000 }
412 .It Ar set ruleset-optimization
413 .Bl -tag -width xxxxxxxx -compact
415 Disable the ruleset optimizer.
417 Enable basic ruleset optimization.
418 This is the default behaviour.
419 Basic ruleset optimization does four things to improve the
420 performance of ruleset evaluations:
424 remove duplicate rules
426 remove rules that are a subset of another rule
428 combine multiple rules into a table when advantageous
430 re-order the rules to improve evaluation performance
434 Uses the currently loaded ruleset as a feedback profile to tailor the
435 ordering of quick rules to actual network traffic.
438 It is important to note that the ruleset optimizer will modify the ruleset
439 to improve performance.
440 A side effect of the ruleset modification is that per-rule accounting
441 statistics will have different meanings than before.
442 If per-rule accounting is important for billing purposes or whatnot,
443 either the ruleset optimizer should not be used or a label field should
444 be added to all of the accounting rules to act as optimization barriers.
446 Optimization can also be set as a command-line argument to
448 overriding the settings in
450 .It Ar set optimization
451 Optimize state timeouts for one of the following network environments:
453 .Bl -tag -width xxxx -compact
455 A normal network environment.
456 Suitable for almost all networks.
458 A high-latency environment (such as a satellite connection).
463 Aggressively expire connections.
464 This can greatly reduce the memory usage of the firewall at the cost of
465 dropping idle connections early.
467 Extremely conservative settings.
468 Avoid dropping legitimate connections at the
469 expense of greater memory utilization (possibly much greater on a busy
470 network) and slightly increased processor utilization.
474 .Bd -literal -offset indent
475 set optimization aggressive
478 .It Ar set keep-policy keep_rule
481 option sets the default state retention policy for all
485 .Sx STATEFUL TRACKING OPTIONS
491 .Ar no Ns / Ns Ar keep Ns / Ns Ar modulate Ns / Ns Ar synproxy state
494 rule will override the default.
496 .Bd -literal -offset indent
497 set keep-policy keep state (pickups)
500 .It Ar set block-policy
503 option sets the default behaviour for the packet
507 .Bl -tag -width xxxxxxxx -compact
509 Packet is silently dropped.
511 A TCP RST is returned for blocked TCP packets,
512 an ICMP UNREACHABLE is returned for blocked UDP packets,
513 and all other packets are silently dropped.
517 .Bd -literal -offset indent
518 set block-policy return
520 .It Ar set state-policy
523 option sets the default behaviour for states:
525 .Bl -tag -width if-bound -compact
527 States are bound to interface.
529 States can match packets on any interfaces (the default).
533 .Bd -literal -offset indent
534 set state-policy if-bound
539 identifies this firewall's state table entries to other firewalls
543 By default the hostid is set to a pseudo-random value, however it may be
544 desirable to manually configure it, for example to more easily identify the
545 source of state table entries.
546 .Bd -literal -offset indent
550 The hostid may be specified in either decimal or hexadecimal.
551 .It Ar set require-order
554 enforces an ordering of the statement types in the ruleset to:
560 Setting this option to
562 disables this enforcement.
563 There may be non-trivial and non-obvious implications to an out of
565 Consider carefully before disabling the order enforcement.
566 .It Ar set fingerprints
567 Load fingerprints of known operating systems from the given filename.
568 By default fingerprints of known operating systems are automatically
573 but can be overridden via this option.
574 Setting this option may leave a small period of time where the fingerprints
575 referenced by the currently active ruleset are inconsistent until the new
576 ruleset finishes loading.
580 .Dl set fingerprints \&"/etc/pf.os.devel\&"
582 .It Ar set skip on Aq Ar ifspec
583 List interfaces for which packets should not be filtered.
584 Packets passing in or out on such interfaces are passed as if pf was
585 disabled, i.e. pf does not process them in any way.
586 This can be useful on loopback and other virtual interfaces, when
587 packet filtering is not desired and can have unexpected effects.
595 to one of the following:
597 .Bl -tag -width xxxxxxxxxxxx -compact
599 Don't generate debug messages.
601 Generate debug messages only for serious errors.
603 Generate debug messages for various errors.
605 Generate debug messages for common conditions.
608 .Sh TRAFFIC NORMALIZATION
609 Traffic normalization is used to sanitize packet content in such
610 a way that there are no ambiguities in packet interpretation on
612 The normalizer does IP fragment reassembly to prevent attacks
613 that confuse intrusion detection systems by sending overlapping
615 Packet normalization is invoked with the
620 has the following options:
625 bit from a matching IP packet.
626 Some operating systems are known to generate fragmented packets with the
629 This is particularly true with NFS.
631 will drop such fragmented
637 Unfortunately some operating systems also generate their
639 packets with a zero IP identification field.
642 bit on packets with a zero IP ID may cause deleterious results if an
643 upstream router later fragments the packet.
646 modifier (see below) is recommended in combination with the
648 modifier to ensure unique IP identifiers.
649 .It Ar min-ttl Aq Ar number
650 Enforces a minimum TTL for matching IP packets.
651 .It Ar max-mss Aq Ar number
652 Enforces a maximum MSS for matching TCP packets.
653 .It Xo Ar set-tos Aq Ar string
654 .No \*(Ba Aq Ar number
658 for matching IP packets.
665 or as either hex or decimal.
667 Replaces the IP identification field with random values to compensate
668 for predictable values generated by many hosts.
669 This option only applies to packets that are not fragmented
670 after the optional fragment reassembly.
671 .It Ar fragment reassemble
674 rules, fragments can be reassembled by normalization.
675 In this case, fragments are buffered until they form a complete
676 packet, and only the completed packet is passed on to the filter.
677 The advantage is that filter rules have to deal only with complete
678 packets, and can ignore fragments.
679 The drawback of caching fragments is the additional memory cost.
680 But the full reassembly method is the only method that currently works
682 This is the default behavior of a
684 rule if no fragmentation modifier is supplied.
686 The default fragment reassembly method is expensive, hence the option
690 will track the fragments and cache a small range descriptor.
691 Duplicate fragments are dropped and overlaps are cropped.
692 Thus data will only occur once on the wire with ambiguities resolving to
693 the first occurrence.
695 .Ar fragment reassemble
696 modifier, fragments are not buffered, they are passed as soon as they
700 reassembly mechanism does not yet work with NAT.
702 .It Ar fragment drop-ovl
703 This option is similar to the
705 modifier except that all overlapping or duplicate fragments will be
706 dropped, and all further corresponding fragments will be
708 .It Ar reassemble tcp
709 Statefully normalizes TCP connections.
710 .Ar scrub reassemble tcp
711 rules may not have the direction (in/out) specified.
713 performs the following normalizations:
715 .Bl -tag -width timeout -compact
717 Neither side of the connection is allowed to reduce their IP TTL.
718 An attacker may send a packet such that it reaches the firewall, affects
719 the firewall state, and expires before reaching the destination host.
721 will raise the TTL of all packets back up to the highest value seen on
723 .It timestamp modulation
724 Modern TCP stacks will send a timestamp on every TCP packet and echo
725 the other endpoint's timestamp back to them.
726 Many operating systems will merely start the timestamp at zero when
727 first booted, and increment it several times a second.
728 The uptime of the host can be deduced by reading the timestamp and multiplying
730 Also observing several different timestamps can be used to count hosts
732 And spoofing TCP packets into a connection requires knowing or guessing
734 Timestamps merely need to be monotonically increasing and not derived off a
739 to modulate the TCP timestamps with a random number.
740 .It extended PAWS checks
741 There is a problem with TCP on long fat pipes, in that a packet might get
742 delayed for longer than it takes the connection to wrap its 32-bit sequence
744 In such an occurrence, the old packet would be indistinguishable from a
745 new packet and would be accepted as such.
746 The solution to this is called PAWS: Protection Against Wrapped Sequence
748 It protects against it by making sure the timestamp on each packet does
751 also makes sure the timestamp on the packet does not go forward more
755 artificially extends the security of TCP sequence numbers by 10 to 18
756 bits when the host uses appropriately randomized timestamps, since a
757 blind attacker would have to guess the timestamp as well.
762 .Bd -literal -offset indent
763 scrub in on $ext_if all fragment reassemble
768 option prefixed to a scrub rule causes matching packets to remain unscrubbed,
769 much in the same way as
771 works in the packet filter (see below).
772 This mechanism should be used when it is necessary to exclude specific packets
773 from broader scrub rules.
775 Packets can be assigned to queues for the purpose of bandwidth
777 At least two declarations are required to configure queues, and later
778 any packet filtering rule can reference the defined queues by name.
779 During the filtering component of
783 name is where any packets from
785 rules will be queued, while for
787 rules it specifies where any resulting ICMP or TCP RST
788 packets should be queued.
791 defines the algorithm used to decide which packets get delayed, dropped, or
792 sent out immediately.
796 .Bl -tag -width ".Ar fairq"
798 Class Based Queueing.
800 attached to an interface build a tree, thus each
802 can have further child
804 Each queue can have a
810 mainly controls the time packets take to get sent out, while
812 has primarily effects on throughput.
814 achieves both partitioning and sharing of link bandwidth
815 by hierarchically structured classes.
816 Each class has its own
818 and is assigned its share of
820 A child class can borrow bandwidth from its parent class
821 as long as excess bandwidth is available
828 are flat attached to the interface, thus,
830 cannot have further child
836 assigned, ranging from 0 to 15.
843 Hierarchical Fair Service Curve.
845 attached to an interface build a tree, thus each
847 can have further child
849 Each queue can have a
855 mainly controls the time packets take to get sent out, while
857 primarily affects throughput.
859 supports both link-sharing and guaranteed real-time services.
860 It employs a service curve based QoS model,
861 and its unique feature is an ability to decouple
869 are flat attached to the interface, thus,
871 cannot have further child
873 Each queue must be given a unique
875 and one must be marked
876 as the default queue.
877 Each queue implements a number of
879 (default 256) which sorts the
880 traffic based on a hash key generated by the
885 Each bucket contains a list of packets controlled by
889 to function properly,
891 must be enabled on most of the rule sets that route packets to the queue.
892 Any rules for which keep state is not enabled are added to the end of the
894 If you do not wish keep state to do TCP sequence space checks use
895 .Ar "keep state (no-pickups)"
897 .Ar "keep state (hash-only)" .
899 Packet selection operates as follows:
900 The queues are scanned from highest priority to lowest priority.
901 If a queue has pending packets and has not reached its bandwidth limit the
902 scan stops and a packet is selected from that queue.
903 If a queue has reached its bandwidth limit the scan continues searching for
904 other, lower priority queues which have not.
905 If no queue is found to be
906 suitable then the highest priority queue with pending packets is used
907 regardless of whether it has reached its bandwidth limit or not.
911 round robins between its
913 extracting one packet from each bucket.
914 This essentially prevents large backlogs of packets from high volume
915 connections from destroying the interactive response of other connections.
921 is guaranteed minimum and more will be used if no higher priority traffic is
923 Creating a queue with one bucket as a catch-all for
925 rules not characterized by
928 Such a queue serves as a basic priority queue with a bandwidth specification.
931 The interfaces on which queueing should be activated are declared using
936 has the following keywords:
939 Queueing is enabled on the named interface.
941 Specifies which queueing scheduler to use.
942 Currently supported values
945 for Class Based Queueing,
947 for Priority Queueing,
949 for the Hierarchical Fair Service Curve scheduler, and
951 for the Fair Queueing.
952 .It Ar bandwidth <bw>
953 The maximum bitrate for all queues on an
954 interface may be specified using the
957 The value can be specified as an absolute value or as a
958 percentage of the interface bandwidth.
959 When using an absolute value, the suffixes
965 are used to represent bits, kilobits, megabits, and
966 gigabits per second, respectively.
967 The value must not exceed the interface bandwidth.
970 is not specified, the interface bandwidth is used
971 (but take note that some interfaces do not know their bandwidth,
972 or can adapt their bandwidth rates).
977 specifies a guaranteed minimum but the fairq is allowed to exceed it.
978 .It Ar qlimit <limit>
979 The maximum number of packets held in the queue.
981 .It Ar tbrsize Aq Ar size
982 Adjusts the size, in bytes, of the token bucket regulator.
983 If not specified, heuristics based on the
984 interface bandwidth are used to determine the size.
985 .It Ar queue Aq Ar list
986 Defines a list of subqueues to create on an interface.
989 In the following example, the interface dc0
990 should queue up to 5 Mbit/s in four second-level queues using
991 Class Based Queueing.
992 Those four queues will be shown in a later example.
993 .Bd -literal -offset indent
994 altq on dc0 cbq bandwidth 5Mb queue { std, http, mail, ssh }
997 Once interfaces are activated for queueing using the
999 directive, a sequence of
1001 directives may be defined.
1002 The name associated with a
1004 must match a queue defined in the
1006 directive (e.g.\& mail), or, except for the
1014 The following keywords can be used:
1015 .Bl -tag -width xxxx
1016 .It Ar on Aq Ar interface
1017 Specifies the interface the queue operates on.
1018 If not given, it operates on all matching interfaces.
1019 .It Ar bandwidth Aq Ar bw
1020 Specifies the maximum bitrate to be processed by the queue.
1021 This value must not exceed the value of the parent
1023 and can be specified as an absolute value or a percentage of the parent
1025 If not specified, defaults to 100% of the parent queue's bandwidth.
1028 scheduler does not support bandwidth specification.
1031 scheduler uses the bandwidth specification as a guaranteed minimum and
1033 .It Ar priority Aq Ar level
1034 Between queues a priority level can be set.
1040 the range is 0 to 7 and for
1042 the range is 0 to 15.
1043 The default for all is 1.
1045 queues with a higher priority are always served first.
1047 queues with a higher priority are served first unless they exceed their
1048 bandwidth specification.
1052 queues with a higher priority are preferred in the case of overload.
1053 .It Ar qlimit Aq Ar limit
1054 The maximum number of packets held in the queue.
1058 this specified the maximum number of packets held per bucket.
1063 can get additional parameters with
1065 .Pf ( Aq Ar parameters ) .
1067 Parameters are as follows:
1070 Packets not matched by another queue are assigned to this one.
1071 Exactly one default queue is required.
1073 Enable RED (Random Early Detection) on this queue.
1074 RED drops packets with a probability proportional to the average
1077 Enables RIO on this queue.
1078 RIO is RED with IN/OUT, thus running
1079 RED two times more than RIO would achieve the same effect.
1081 Enables ECN (Explicit Congestion Notification) on this queue.
1088 supports the following additional options:
1090 .It Ar buckets <number>
1091 Specify the number of buckets, from 1 to 2048 in powers of 2.
1092 A bucket size of 1 causes a
1094 to essentially degenerate into a priority queue.
1095 .It Ar linkshare <sc>
1096 The bandwidth share of a backlogged queue.
1097 This option is parsed but not yet supported.
1098 .It Ar hogs <bandwidth>
1099 This option allows low bandwidth connections to burst up to the specified
1100 bandwidth by not advancing the round robin when taking packets out of
1102 When using this option a small value no greater than 1/20 available interface
1103 bandwidth is recommended.
1109 supports an additional option:
1112 The queue can borrow bandwidth from the parent.
1118 supports some additional options:
1120 .It Ar realtime Aq Ar sc
1121 The minimum required bandwidth for the queue.
1122 .It Ar upperlimit Aq Ar sc
1123 The maximum allowed bandwidth for the queue.
1124 .It Ar linkshare Aq Ar sc
1125 The bandwidth share of a backlogged queue.
1132 The format for service curve specifications is
1137 controls the bandwidth assigned to the queue.
1141 are optional and can be used to control the initial bandwidth assignment.
1144 milliseconds the queue gets the bandwidth given as
1146 afterwards the value given in
1153 child queues can be specified as in an
1155 declaration, thus building a tree of queues using a part of
1156 their parent's bandwidth.
1158 Packets can be assigned to queues based on filter rules by using the
1163 is specified; when a second one is specified it will instead be used for
1164 packets which have a
1168 and for TCP ACKs with no data payload.
1170 To continue the previous example, the examples below would specify the
1172 queues, plus a few child queues.
1175 sessions get priority over bulk transfers like
1179 The queues may then be referenced by filtering rules (see
1180 .Sx PACKET FILTERING
1183 queue std bandwidth 10% cbq(default)
1184 queue http bandwidth 60% priority 2 cbq(borrow red) \e
1185 { employees, developers }
1186 queue developers bandwidth 75% cbq(borrow)
1187 queue employees bandwidth 15%
1188 queue mail bandwidth 10% priority 0 cbq(borrow ecn)
1189 queue ssh bandwidth 20% cbq(borrow) { ssh_interactive, ssh_bulk }
1190 queue ssh_interactive bandwidth 50% priority 7 cbq(borrow)
1191 queue ssh_bulk bandwidth 50% priority 0 cbq(borrow)
1193 block return out on dc0 inet all queue std
1194 pass out on dc0 inet proto tcp from $developerhosts to any port 80 \e
1196 pass out on dc0 inet proto tcp from $employeehosts to any port 80 \e
1198 pass out on dc0 inet proto tcp from any to any port 22 \e
1199 queue(ssh_bulk, ssh_interactive)
1200 pass out on dc0 inet proto tcp from any to any port 25 \e
1204 Translation rules modify either the source or destination address of the
1205 packets associated with a stateful connection.
1206 A stateful connection is automatically created to track packets matching
1207 such a rule as long as they are not blocked by the filtering section of
1209 The translation engine modifies the specified address and/or port in the
1210 packet, recalculates IP, TCP and UDP checksums as necessary, and passes it to
1211 the packet filter for evaluation.
1213 Since translation occurs before filtering the filter
1214 engine will see packets as they look after any
1215 addresses and ports have been translated.
1216 Filter rules will therefore have to filter based on the translated
1217 address and port number.
1218 Packets that match a translation rule are only automatically passed if
1221 modifier is given, otherwise they are
1228 The state entry created permits
1230 to keep track of the original address for traffic associated with that state
1231 and correctly direct return traffic for that connection.
1233 Various types of translation are possible with pf:
1234 .Bl -tag -width xxxx
1238 rule specifies a bidirectional mapping between an external IP netblock
1239 and an internal IP netblock.
1243 rule specifies that IP addresses are to be changed as the packet
1244 traverses the given interface.
1245 This technique allows one or more IP addresses
1246 on the translating host to support network traffic for a larger range of
1247 machines on an "inside" network.
1248 Although in theory any IP address can be used on the inside, it is strongly
1249 recommended that one of the address ranges defined by RFC 1918 be used.
1250 These netblocks are:
1252 10.0.0.0 - 10.255.255.255 (all of net 10, i.e., 10/8)
1253 172.16.0.0 - 172.31.255.255 (i.e., 172.16/12)
1254 192.168.0.0 - 192.168.255.255 (i.e., 192.168/16)
1257 The packet is redirected to another destination and possibly a
1260 rules can optionally specify port ranges instead of single ports.
1261 rdr ... port 2000:2999 -\*(Gt ... port 4000
1262 redirects ports 2000 to 2999 (inclusive) to port 4000.
1263 rdr ... port 2000:2999 -\*(Gt ... port 4000:*
1264 redirects port 2000 to 4000, 2001 to 4001, ..., 2999 to 4999.
1267 In addition to modifying the address, some translation rules may modify
1268 source or destination ports for
1272 connections; implicitly in the case of
1274 rules and explicitly in the case of
1277 Port numbers are never translated with a
1281 Evaluation order of the translation rules is dependent on the type
1282 of the translation rules and of the direction of a packet.
1284 rules are always evaluated first.
1287 rules are evaluated on an inbound packet or the
1289 rules on an outbound packet.
1290 Rules of the same type are evaluated in the same order in which they
1291 appear in the ruleset.
1292 The first matching rule decides what action is taken.
1296 option prefixed to a translation rule causes packets to remain untranslated,
1297 much in the same way as
1299 works in the packet filter (see below).
1300 If no rule matches the packet it is passed to the filter engine unmodified.
1302 Translation rules apply only to packets that pass through
1303 the specified interface, and if no interface is specified,
1304 translation is applied to packets on all interfaces.
1305 For instance, redirecting port 80 on an external interface to an internal
1306 web server will only work for connections originating from the outside.
1307 Connections to the address of the external interface from local hosts will
1308 not be redirected, since such packets do not actually pass through the
1310 Redirections cannot reflect packets back through the interface they arrive
1311 on, they can only be redirected to hosts connected to different interfaces
1312 or to the firewall itself.
1314 Note that redirecting external incoming connections to the loopback
1316 .Bd -literal -offset indent
1317 rdr on ne3 inet proto tcp to port smtp -\*(Gt 127.0.0.1 port spamd
1320 will effectively allow an external host to connect to daemons
1321 bound solely to the loopback address, circumventing the traditional
1322 blocking of such connections on a real interface.
1323 Unless this effect is desired, any of the local non-loopback addresses
1324 should be used as redirection target instead, which allows external
1325 connections only to daemons bound to this address or not bound to
1329 .Sx TRANSLATION EXAMPLES
1331 .Sh PACKET FILTERING
1337 packets based on attributes of their layer 3 (see
1347 In addition, packets may also be
1348 assigned to queues for the purpose of bandwidth control.
1350 For each packet processed by the packet filter, the filter rules are
1351 evaluated in sequential order, from first to last.
1352 The last matching rule decides what action is taken.
1353 If no rule matches the packet, the default action is to pass
1356 The following actions can be used in the filter:
1357 .Bl -tag -width xxxx
1359 The packet is blocked.
1360 There are a number of ways in which a
1362 rule can behave when blocking a packet.
1363 The default behaviour is to
1365 packets silently, however this can be overridden or made
1366 explicit either globally, by setting the
1368 option, or on a per-rule basis with one of the following options:
1370 .Bl -tag -width xxxx -compact
1372 The packet is silently dropped.
1374 This applies only to
1376 packets, and issues a TCP RST which closes the
1380 This causes ICMP messages to be returned for packets which match the rule.
1381 By default this is an ICMP UNREACHABLE message, however this
1382 can be overridden by specifying a message as a code or number.
1384 This causes a TCP RST to be returned for
1386 packets and an ICMP UNREACHABLE for UDP and other packets.
1389 Options returning ICMP packets currently have no effect if
1393 as the code to support this feature has not yet been implemented.
1395 The simplest mechanism to block everything by default and only pass
1396 packets that match explicit rules is specify a first filter rule of:
1397 .Bd -literal -offset indent
1401 The packet is passed;
1402 state is created unless the
1404 option is specified.
1409 filters packets statefully; the first time a packet matches a
1411 rule, a state entry is created; for subsequent packets the filter checks
1412 whether the packet matches any state.
1413 If it does, the packet is passed without evaluation of any rules.
1414 After the connection is closed or times out, the state entry is automatically
1417 This has several advantages.
1418 For TCP connections, comparing a packet to a state involves checking
1419 its sequence numbers, as well as TCP timestamps if a
1420 .Ar scrub reassemble tcp
1421 rule applies to the connection.
1422 If these values are outside the narrow windows of expected
1423 values, the packet is dropped.
1424 This prevents spoofing attacks, such as when an attacker sends packets with
1425 a fake source address/port but does not know the connection's sequence
1429 knows how to match ICMP replies to states.
1431 .Bd -literal -offset indent
1432 pass out inet proto icmp all icmp-type echoreq
1435 allows echo requests (such as those created by
1437 out statefully, and matches incoming echo replies correctly to states.
1439 Also, looking up states is usually faster than evaluating rules.
1440 If there are 50 rules, all of them are evaluated sequentially in O(n).
1441 Even with 50000 states, only 16 comparisons are needed to match a
1442 state, since states are stored in a binary search tree that allows
1443 searches in O(log2 n).
1445 Furthermore, correct handling of ICMP error messages is critical to
1446 many protocols, particularly TCP.
1448 matches ICMP error messages to the correct connection, checks them against
1449 connection parameters, and passes them if appropriate.
1450 For example if an ICMP source quench message referring to a stateful TCP
1451 connection arrives, it will be matched to the state and get passed.
1453 Finally, state tracking is required for
1454 .Ar nat , binat No and Ar rdr
1455 rules, in order to track address and port translations and reverse the
1456 translation on returning packets.
1459 will also create state for other protocols which are effectively stateless by
1461 UDP packets are matched to states using only host addresses and ports,
1462 and other protocols are matched to states using only the host addresses.
1464 If stateless filtering of individual packets is desired,
1467 keyword can be used to specify that state will not be created
1468 if this is the last matching rule.
1469 A number of parameters can also be set to affect how
1471 handles state tracking.
1473 .Sx STATEFUL TRACKING OPTIONS
1474 below for further details.
1476 The rule parameters specify the packets to which a rule applies.
1477 A packet always comes in on, or goes out through, one interface.
1478 Most parameters are optional.
1479 If a parameter is specified, the rule only applies to packets with
1480 matching attributes.
1481 Certain parameters can be expressed as lists, in which case
1483 generates all needed rule combinations.
1484 .Bl -tag -width xxxx
1485 .It Ar in No or Ar out
1486 This rule applies to incoming or outgoing packets.
1491 are specified, the rule will match packets in both directions.
1493 In addition to the action specified, a log message is generated.
1494 Only the packet that establishes the state is logged,
1497 option is specified.
1498 The logged packets are sent to a
1500 interface, by default
1502 This interface is monitored by the
1504 logging daemon, which dumps the logged packets to the file
1510 Used to force logging of all packets for a connection.
1511 This is not necessary when
1513 is explicitly specified.
1516 packets are logged to
1521 user ID of the user that owns the socket and the PID of the process that
1522 has the socket open where the packet is sourced from or destined to
1523 (depending on which socket is local).
1524 This is in addition to the normal information logged.
1525 .It Ar log (to Aq Ar interface )
1526 Send logs to the specified
1528 interface instead of
1531 If a packet matches a rule which has the
1533 option set, this rule
1534 is considered the last matching rule, and evaluation of subsequent rules
1536 .It Ar on Aq Ar interface
1537 This rule applies only to packets coming in on, or going out through, this
1538 particular interface.
1540 This rule applies only to packets of this address family.
1541 Supported values are
1545 .It Ar proto Aq Ar protocol
1546 This rule applies only to packets of this protocol.
1547 Common protocols are
1553 For a list of all the protocol name to number mappings used by
1556 .Pa /etc/protocols .
1558 .Ar from Aq Ar source
1559 .Ar port Aq Ar source
1564 This rule applies only to packets with the specified source and destination
1565 addresses and ports.
1567 Addresses can be specified in CIDR notation (matching netblocks), as
1568 symbolic host names or interface names, or as any of the following keywords:
1570 .Bl -tag -width xxxxxxxxxxxxxx -compact
1573 .It Ar route Aq Ar label
1574 Any address whose associated route has label
1581 Any address which is not currently routable.
1583 Any source address that fails a unicast reverse path forwarding (URPF)
1584 check, i.e. packets coming in on an interface other than that which holds
1585 the route back to the packet's source address.
1587 Any address that matches the given table.
1590 Ranges of addresses are specified by using the
1594 .Dq 10.1.1.10 - 10.1.1.12
1595 means all addresses from 10.1.1.10 to 10.1.1.12,
1596 hence addresses 10.1.1.10, 10.1.1.11, and 10.1.1.12.
1598 Interface names can have modifiers appended:
1600 .Bl -tag -width xxxxxxxxxxxx -compact
1602 Translates to the network(s) attached to the interface.
1604 Translates to the interface's broadcast address(es).
1606 Translates to the point to point interface's peer address(es).
1608 Do not include interface aliases.
1611 Host names may also have the
1613 option appended to restrict the name resolution to the first of each
1614 v4 and v6 address found.
1616 Host name resolution and interface to address translation are done at
1618 When the address of an interface (or host name) changes (under DHCP or PPP,
1619 for instance), the ruleset must be reloaded for the change to be reflected
1621 Surrounding the interface name (and optional modifiers) in parentheses
1622 changes this behaviour.
1623 When the interface name is surrounded by parentheses, the rule is
1624 automatically updated whenever the interface changes its address.
1625 The ruleset does not need to be reloaded.
1626 This is especially useful with
1629 Ports can be specified either by number or by name.
1630 For example, port 80 can be specified as
1632 For a list of all port name to number mappings used by
1637 Ports and ranges of ports are specified by using these operators:
1638 .Bd -literal -offset indent
1642 \*(Le (less than or equal)
1643 \*(Gt (greater than)
1644 \*(Ge (greater than or equal)
1645 : (range including boundaries)
1646 \*(Gt\*(Lt (range excluding boundaries)
1647 \*(Lt\*(Gt (except range)
1654 are binary operators (they take two arguments).
1657 .It Ar port 2000:2004
1659 .Sq all ports \*(Ge 2000 and \*(Le 2004 ,
1660 hence ports 2000, 2001, 2002, 2003 and 2004.
1661 .It Ar port 2000 \*(Gt\*(Lt 2004
1663 .Sq all ports \*(Gt 2000 and \*(Lt 2004 ,
1664 hence ports 2001, 2002 and 2003.
1665 .It Ar port 2000 \*(Lt\*(Gt 2004
1667 .Sq all ports \*(Lt 2000 or \*(Gt 2004 ,
1668 hence ports 1-1999 and 2005-65535.
1671 The operating system of the source host can be specified in the case of TCP
1676 .Sx OPERATING SYSTEM FINGERPRINTING
1677 section for more information.
1679 The host, port and OS specifications are optional, as in the following examples:
1680 .Bd -literal -offset indent
1682 pass in from any to any
1683 pass in proto tcp from any port \*(Le 1024 to any
1684 pass in proto tcp from any to any port 25
1685 pass in proto tcp from 10.0.0.0/8 port \*(Gt 1024 \e
1686 to ! 10.1.2.3 port != ssh
1687 pass in proto tcp from any os "OpenBSD"
1688 pass in proto tcp from route "DTAG"
1691 This is equivalent to "from any to any".
1692 .It Ar group Aq Ar group
1695 this rule only applies to packets of sockets owned by the specified group.
1696 .It Ar user Aq Ar user
1697 This rule only applies to packets of sockets owned by the specified user.
1698 For outgoing connections initiated from the firewall, this is the user
1699 that opened the connection.
1700 For incoming connections to the firewall itself, this is the user that
1701 listens on the destination port.
1702 For forwarded connections, where the firewall is not a connection endpoint,
1703 the user and group are
1706 All packets, both outgoing and incoming, of one connection are associated
1707 with the same user and group.
1708 Only TCP and UDP packets can be associated with users; for other protocols
1709 these parameters are ignored.
1711 User and group refer to the effective (as opposed to the real) IDs, in
1712 case the socket is created by a setuid/setgid process.
1713 User and group IDs are stored when a socket is created;
1714 when a process creates a listening socket as root (for instance, by
1715 binding to a privileged port) and subsequently changes to another
1716 user ID (to drop privileges), the credentials will remain root.
1718 User and group IDs can be specified as either numbers or names.
1719 The syntax is similar to the one for ports.
1722 matches packets of forwarded connections.
1724 can only be used with the operators
1728 Other constructs like
1729 .Cm user \*(Ge unknown
1731 Forwarded packets with unknown user and group ID match only rules
1732 that explicitly compare against
1740 does not match forwarded packets.
1741 The following example allows only selected users to open outgoing
1743 .Bd -literal -offset indent
1744 block out proto { tcp, udp } all
1745 pass out proto { tcp, udp } all user { \*(Lt 1000, dhartmei }
1747 .It Xo Ar flags Aq Ar a
1749 .No \*(Ba / Ns Aq Ar b
1752 This rule only applies to TCP packets that have the flags
1756 Flags not specified in
1759 For stateful connections, the default is
1761 To indicate that flags should not be checked at all, specify
1763 The flags are: (F)IN, (S)YN, (R)ST, (P)USH, (A)CK, (U)RG, (E)CE, and C(W)R.
1767 The other flags are ignored.
1769 This is the default setting for stateful connections.
1770 Out of SYN and ACK, exactly SYN may be set.
1771 SYN, SYN+PSH and SYN+RST match, but SYN+ACK, ACK and ACK+RST do not.
1772 This is more restrictive than the previous example.
1774 If the first set is not specified, it defaults to none.
1775 All of SYN, FIN, RST and ACK must be unset.
1780 is applied by default (unless
1782 is specified), only the initial SYN packet of a TCP handshake will create
1783 a state for a TCP connection.
1784 It is possible to be less restrictive, and allow state creation from
1787 packets, by specifying
1791 to synchronize to existing connections, for instance
1792 if one flushes the state table.
1793 However, states created from such intermediate packets may be missing
1794 connection details such as the TCP window scaling factor.
1795 States which modify the packet flow, such as those affected by
1796 .Ar nat , binat No or Ar rdr
1798 .Ar modulate No or Ar synproxy state
1799 options, or scrubbed with
1801 will also not be recoverable from intermediate packets.
1802 Such connections will stall and time out.
1803 .It Xo Ar icmp-type Aq Ar type
1806 .It Xo Ar icmp6-type Aq Ar type
1809 This rule only applies to ICMP or ICMPv6 packets with the specified type
1811 Text names for ICMP types and codes are listed in
1815 This parameter is only valid for rules that cover protocols ICMP or
1817 The protocol and the ICMP type indicator
1824 .It Xo Ar tos Aq Ar string
1825 .No \*(Ba Aq Ar number
1827 This rule applies to packets with the specified
1836 or as either hex or decimal.
1838 For example, the following rules are identical:
1839 .Bd -literal -offset indent
1840 pass all tos lowdelay
1845 By default, IPv4 packets with IP options or IPv6 packets with routing
1846 extension headers are blocked.
1851 rule, packets that pass the filter based on that rule (last matching)
1852 do so even if they contain IP options or routing extension headers.
1853 For packets that match state, the rule that initially created the
1857 rule that is used when a packet does not match any rules does not
1859 .It Ar label Aq Ar string
1860 Adds a label (name) to the rule, which can be used to identify the rule.
1863 shows per-rule statistics for rules that have labels.
1865 The following macros can be used in labels:
1867 .Bl -tag -width $srcaddr -compact -offset indent
1871 The source IP address.
1873 The destination IP address.
1875 The source port specification.
1877 The destination port specification.
1885 .Bd -literal -offset indent
1886 ips = \&"{ 1.2.3.4, 1.2.3.5 }\&"
1887 pass in proto tcp from any to $ips \e
1888 port \*(Gt 1023 label \&"$dstaddr:$dstport\&"
1892 .Bd -literal -offset indent
1893 pass in inet proto tcp from any to 1.2.3.4 \e
1894 port \*(Gt 1023 label \&"1.2.3.4:\*(Gt1023\&"
1895 pass in inet proto tcp from any to 1.2.3.5 \e
1896 port \*(Gt 1023 label \&"1.2.3.5:\*(Gt1023\&"
1899 The macro expansion for the
1901 directive occurs only at configuration file parse time, not during runtime.
1902 .It Xo Ar queue Aq Ar queue
1903 .No \*(Ba ( Aq Ar queue ,
1906 Packets matching this rule will be assigned to the specified queue.
1907 If two queues are given, packets which have a
1911 and TCP ACKs with no data payload will be assigned to the second one.
1917 .Bd -literal -offset indent
1918 pass in proto tcp to port 25 queue mail
1919 pass in proto tcp to port 22 queue(ssh_bulk, ssh_prio)
1921 .It Ar tag Aq Ar string
1922 Packets matching this rule will be tagged with the
1924 The tag acts as an internal marker that can be used to
1925 identify these packets later on.
1926 This can be used, for example, to provide trust between
1927 interfaces and to determine if packets have been
1928 processed by translation rules.
1931 meaning that the packet will be tagged even if the rule
1932 is not the last matching rule.
1933 Further matching rules can replace the tag with a
1934 new one but will not remove a previously applied tag.
1935 A packet is only ever assigned one tag at a time.
1936 Packet tagging can be done during
1941 rules in addition to filter rules.
1942 Tags take the same macros as labels (see above).
1943 .It Ar tagged Aq Ar string
1944 Used with filter, translation or scrub rules
1945 to specify that packets must already
1946 be tagged with the given tag in order to match the rule.
1947 Inverse tag matching can also be done
1953 .It Ar rtable Aq Ar number
1954 Used to select an alternate routing table for the routing lookup.
1955 Only effective before the route lookup happened, i.e. when filtering inbound.
1956 .It Xo Ar divert-to Aq Ar host
1959 Used to redirect packets to a local socket bound to
1963 The packets will not be modified, so
1965 on the socket will return the original destination address of the packet.
1967 Used to receive replies for sockets that are bound to addresses
1968 which are not local to the machine.
1971 for information on how to bind these sockets.
1972 .It Ar probability Aq Ar number
1973 A probability attribute can be attached to a rule, with a value set between
1974 0 and 1, bounds not included.
1975 In that case, the rule will be honoured using the given probability value
1977 For example, the following rule will drop 20% of incoming ICMP packets:
1978 .Bd -literal -offset indent
1979 block in proto icmp probability 20%
1983 If a packet matches a rule with a route option set, the packet filter will
1984 route the packet according to the type of route option.
1985 When such a rule creates state, the route option is also applied to all
1986 packets matching the same connection.
1987 .Bl -tag -width xxxx
1991 option does a normal route lookup to find the next hop for the packet.
1995 option routes the packet to the specified interface with an optional address
1999 rule creates state, only packets that pass in the same direction as the
2000 filter rule specifies will be routed in this way.
2001 Packets passing in the opposite direction (replies) are not affected
2002 and are routed normally.
2006 option is similar to
2008 but routes packets that pass in the opposite direction (replies) to the
2009 specified interface.
2010 Opposite direction is only defined in the context of a state entry, and
2012 is useful only in rules that create state.
2013 It can be used on systems with multiple external connections to
2014 route all outgoing packets of a connection through the interface
2015 the incoming connection arrived through (symmetric routing enforcement).
2019 option creates a duplicate of the packet and routes it like
2021 The original packet gets routed as it normally would.
2028 rules, (as well as for the
2033 rule options) for which there is a single redirection address which has a
2034 subnet mask smaller than 32 for IPv4 or 128 for IPv6 (more than one IP
2035 address), a variety of different methods for assigning this address can be
2037 .Bl -tag -width xxxx
2041 option applies the network portion of the redirection address to the address
2042 to be modified (source with
2049 option selects an address at random within the defined block of addresses.
2053 option uses a hash of the source address to determine the redirection address,
2054 ensuring that the redirection address is always the same for a given source.
2055 An optional key can be specified after this keyword either in hex or as a
2058 randomly generates a key for source-hash every time the
2059 ruleset is reloaded.
2063 option loops through the redirection address(es).
2065 When more than one redirection address is specified,
2067 is the only permitted pool type.
2075 from modifying the source port on TCP and UDP packets.
2080 option can be specified to help ensure that multiple connections from the
2081 same source are mapped to the same redirection address.
2082 This option can be used with the
2087 Note that by default these associations are destroyed as soon as there are
2088 no longer states which refer to them; in order to make the mappings last
2089 beyond the lifetime of the states, increase the global options with
2090 .Ar set timeout src.track .
2092 .Sx STATEFUL TRACKING OPTIONS
2093 for more ways to control the source tracking.
2094 .Sh STATE MODULATION
2095 Much of the security derived from TCP is attributable to how well the
2096 initial sequence numbers (ISNs) are chosen.
2097 Some popular stack implementations choose
2099 poor ISNs and thus are normally susceptible to ISN prediction exploits.
2102 rule to a TCP connection,
2104 will create a high quality random sequence number for each connection
2109 directive implicitly keeps state on the rule and is
2110 only applicable to TCP connections.
2113 .Bd -literal -offset indent
2115 pass out proto tcp from any to any modulate state
2116 pass in proto tcp from any to any port 25 flags S/SFRA modulate state
2119 Note that modulated connections will not recover when the state table
2120 is lost (firewall reboot, flushing the state table, etc...).
2122 will not be able to infer a connection again after the state table flushes
2123 the connection's modulator.
2124 When the state is lost, the connection may be left dangling until the
2125 respective endpoints time out the connection.
2126 It is possible on a fast local network for the endpoints to start an ACK
2127 storm while trying to resynchronize after the loss of the modulator.
2130 settings (or a more strict equivalent) should be used on
2132 rules to prevent ACK storms.
2134 Note that alternative methods are available
2135 to prevent loss of the state table
2136 and allow for firewall failover.
2141 for further information.
2145 passes packets that are part of a
2147 handshake between the endpoints.
2150 option can be used to cause
2152 itself to complete the handshake with the active endpoint, perform a handshake
2153 with the passive endpoint, and then forward packets between the endpoints.
2155 No packets are sent to the passive endpoint before the active endpoint has
2156 completed the handshake, hence so-called SYN floods with spoofed source
2157 addresses will not reach the passive endpoint, as the sender can't complete the
2160 The proxy is transparent to both endpoints, they each see a single
2161 connection from/to the other endpoint.
2163 chooses random initial sequence numbers for both handshakes.
2164 Once the handshakes are completed, the sequence number modulators
2165 (see previous section) are used to translate further packets of the
2169 .Ar modulate state .
2179 .Bd -literal -offset indent
2180 pass in proto tcp from any to any port www synproxy state
2182 .Sh STATEFUL TRACKING OPTIONS
2183 A number of options related to stateful tracking can be applied on a
2189 support these options, and
2191 must be specified explicitly to apply options to a rule.
2193 .Bl -tag -width xxxx -compact
2194 .It Ar max Aq Ar number
2195 Limits the number of concurrent states the rule may create.
2196 When this limit is reached, further packets that would create
2197 state will not match this rule until existing states time out.
2199 Prevent state changes for states created by this rule from appearing on the
2202 .It Xo Aq Ar timeout
2205 Changes the timeout values used for states created by this rule.
2206 For a list of all valid timeout names, see
2210 Uses a sloppy TCP connection tracker that does not check sequence
2211 numbers at all, which makes insertion and ICMP teardown attacks way
2213 This is intended to be used in situations where one does not see all
2214 packets of a connection, e.g. in asymmetric routing situations.
2215 Cannot be used with modulate or synproxy state.
2218 Multiple options can be specified, separated by commas:
2219 .Bd -literal -offset indent
2220 pass in proto tcp from any to any \e
2221 port www keep state \e
2222 (max 100, source-track rule, max-src-nodes 75, \e
2223 max-src-states 3, tcp.established 60, tcp.closing 5)
2228 keyword is specified, the number of states per source IP is tracked.
2230 .Bl -tag -width xxxx -compact
2231 .It Ar source-track rule
2232 The maximum number of states created by this rule is limited by the rule's
2237 Only state entries created by this particular rule count toward the rule's
2239 .It Ar source-track global
2240 The number of states created by all rules that use this option is limited.
2241 Each rule can specify different
2245 options, however state entries created by any participating rule count towards
2246 each individual rule's limits.
2249 The following limits can be set:
2251 .Bl -tag -width xxxx -compact
2252 .It Ar max-src-nodes Aq Ar number
2253 Limits the maximum number of source addresses which can simultaneously
2254 have state table entries.
2255 .It Ar max-src-states Aq Ar number
2256 Limits the maximum number of simultaneous state entries that a single
2257 source address can create with this rule.
2259 Specify that mid-stream pickups are to be allowed.
2260 The default is to NOT allow mid-stream pickups and implies flags
2261 S/SA for TCP connections.
2262 If pickups are enabled, flags S/SA are not implied
2263 for TCP connections and state can be created for any packet.
2265 The implied flags parameters need not be specified in either case
2266 unless you explicitly wish to override them, which also allows
2267 you to roll-up several protocols into a single rule.
2269 Certain validations are disabled when mid-stream pickups occur.
2270 For example, the window scaling options are not known for
2271 TCP pickups and sequence space comparisons must be disabled.
2273 This does not effect state representing fully quantified
2274 connections (for which the SYN/SYN-ACK passed through the routing
2276 Those connections continue to be fully validated.
2278 Specify that mid-stream pickups are to be allowed, but unconditionally
2279 disables sequence space checks even if full state is available.
2281 Specify that mid-stream pickups are not to be allowed.
2283 default and this keyword does not normally need to be specified.
2284 However, if you are concerned about rule set portability then
2285 specifying this keyword will at least result in an error from
2287 if it doesn't understand the feature.
2288 TCP flags of S/SA are implied
2289 and do not need to explicitly specified.
2292 For stateful TCP connections, limits on established connections (connections
2293 which have completed the TCP 3-way handshake) can also be enforced
2296 .Bl -tag -width xxxx -compact
2297 .It Ar max-src-conn Aq Ar number
2298 Limits the maximum number of simultaneous TCP connections which have
2299 completed the 3-way handshake that a single host can make.
2300 .It Xo Ar max-src-conn-rate Aq Ar number
2303 Limit the rate of new connections over a time interval.
2304 The connection rate is an approximation calculated as a moving average.
2307 Because the 3-way handshake ensures that the source address is not being
2308 spoofed, more aggressive action can be taken based on these limits.
2310 .Ar overload Aq Ar table
2311 state option, source IP addresses which hit either of the limits on
2312 established connections will be added to the named table.
2313 This table can be used in the ruleset to block further activity from
2314 the offending host, redirect it to a tarpit process, or restrict its
2319 keyword kills all states created by the matching rule which originate
2320 from the host which exceeds these limits.
2323 modifier to the flush command kills all states originating from the
2324 offending host, regardless of which rule created the state.
2326 For example, the following rules will protect the webserver against
2327 hosts making more than 100 connections in 10 seconds.
2328 Any host which connects faster than this rate will have its address added
2331 table and have all states originating from it flushed.
2332 Any new packets arriving from this host will be dropped unconditionally
2334 .Bd -literal -offset indent
2335 block quick from \*(Ltbad_hosts\*(Gt
2336 pass in on $ext_if proto tcp to $webserver port www keep state \e
2337 (max-src-conn-rate 100/10, overload \*(Ltbad_hosts\*(Gt flush global)
2339 .Sh OPERATING SYSTEM FINGERPRINTING
2340 Passive OS Fingerprinting is a mechanism to inspect nuances of a TCP
2341 connection's initial SYN packet and guess at the host's operating system.
2342 Unfortunately these nuances are easily spoofed by an attacker so the
2343 fingerprint is not useful in making security decisions.
2344 But the fingerprint is typically accurate enough to make policy decisions
2347 The fingerprints may be specified by operating system class, by
2348 version, or by subtype/patchlevel.
2349 The class of an operating system is typically the vendor or genre
2355 The version of the oldest available
2357 release on the main FTP site
2358 would be 2.6 and the fingerprint would be written
2360 .Dl \&"OpenBSD 2.6\&"
2362 The subtype of an operating system is typically used to describe the
2363 patchlevel if that patch led to changes in the TCP stack behavior.
2366 the only subtype is for a fingerprint that was
2369 scrub option and would be specified as
2371 .Dl \&"OpenBSD 3.3 no-df\&"
2373 Fingerprints for most popular operating systems are provided by
2377 is running, a complete list of known operating system fingerprints may
2378 be listed by running:
2382 Filter rules can enforce policy at any level of operating system specification
2383 assuming a fingerprint is present.
2384 Policy could limit traffic to approved operating systems or even ban traffic
2385 from hosts that aren't at the latest service pack.
2389 class can also be used as the fingerprint which will match packets for
2390 which no operating system fingerprint is known.
2393 .Bd -literal -offset indent
2394 pass out proto tcp from any os OpenBSD
2395 block out proto tcp from any os Doors
2396 block out proto tcp from any os "Doors PT"
2397 block out proto tcp from any os "Doors PT SP3"
2398 block out from any os "unknown"
2399 pass on lo0 proto tcp from any os "OpenBSD 3.3 lo0"
2402 Operating system fingerprinting is limited only to the TCP SYN packet.
2403 This means that it will not work on other protocols and will not match
2404 a currently established connection.
2406 Caveat: operating system fingerprints are occasionally wrong.
2407 There are three problems: an attacker can trivially craft his packets to
2408 appear as any operating system he chooses;
2409 an operating system patch could change the stack behavior and no fingerprints
2410 will match it until the database is updated;
2411 and multiple operating systems may have the same fingerprint.
2412 .Sh BLOCKING SPOOFED TRAFFIC
2413 "Spoofing" is the faking of IP addresses, typically for malicious
2417 directive expands to a set of filter rules which will block all
2418 traffic with a source IP from the network(s) directly connected
2419 to the specified interface(s) from entering the system through
2420 any other interface.
2422 For example, the line
2423 .Bd -literal -offset indent
2428 .Bd -literal -offset indent
2429 block drop in on ! lo0 inet from 127.0.0.1/8 to any
2430 block drop in on ! lo0 inet6 from ::1 to any
2433 For non-loopback interfaces, there are additional rules to block incoming
2434 packets with a source IP address identical to the interface's IP(s).
2435 For example, assuming the interface wi0 had an IP address of 10.0.0.1 and a
2436 netmask of 255.255.255.0,
2438 .Bd -literal -offset indent
2439 antispoof for wi0 inet
2443 .Bd -literal -offset indent
2444 block drop in on ! wi0 inet from 10.0.0.0/24 to any
2445 block drop in inet from 10.0.0.1 to any
2448 Caveat: Rules created by the
2450 directive interfere with packets sent over loopback interfaces
2452 One should pass these explicitly.
2453 .Sh FRAGMENT HANDLING
2454 The size of IP datagrams (packets) can be significantly larger than the
2455 maximum transmission unit (MTU) of the network.
2456 In cases when it is necessary or more efficient to send such large packets,
2457 the large packet will be fragmented into many smaller packets that will each
2459 Unfortunately for a firewalling device, only the first logical fragment will
2460 contain the necessary header information for the subprotocol that allows
2462 to filter on things such as TCP ports or to perform NAT.
2466 rules as described in
2467 .Sx TRAFFIC NORMALIZATION
2468 above, there are three options for handling fragments in the packet filter.
2470 One alternative is to filter individual fragments with filter rules.
2473 rule applies to a fragment, it is passed to the filter.
2474 Filter rules with matching IP header parameters decide whether the
2475 fragment is passed or blocked, in the same way as complete packets
2477 Without reassembly, fragments can only be filtered based on IP header
2478 fields (source/destination address, protocol), since subprotocol header
2479 fields are not available (TCP/UDP port numbers, ICMP code/type).
2482 option can be used to restrict filter rules to apply only to
2483 fragments, but not complete packets.
2484 Filter rules without the
2486 option still apply to fragments, if they only specify IP header fields.
2487 For instance, the rule
2488 .Bd -literal -offset indent
2489 pass in proto tcp from any to any port 80
2492 never applies to a fragment, even if the fragment is part of a TCP
2493 packet with destination port 80, because without reassembly this information
2494 is not available for each fragment.
2495 This also means that fragments cannot create new or match existing
2496 state table entries, which makes stateful filtering and address
2497 translation (NAT, redirection) for fragments impossible.
2499 It's also possible to reassemble only certain fragments by specifying
2500 source or destination addresses or protocols as parameters in
2504 In most cases, the benefits of reassembly outweigh the additional
2505 memory cost, and it's recommended to use
2508 all fragments via the
2509 .Ar fragment reassemble
2512 The memory allocated for fragment caching can be limited using
2514 Once this limit is reached, fragments that would have to be cached
2515 are dropped until other entries time out.
2516 The timeout value can also be adjusted.
2518 Currently, only IPv4 fragments are supported and IPv6 fragments
2519 are blocked unconditionally.
2521 Besides the main ruleset,
2523 can load rulesets into
2528 is a container that can hold rules, address tables, and other anchors.
2532 has a name which specifies the path where
2534 can be used to access the anchor to perform operations on it, such as
2535 attaching child anchors to it or loading rules into it.
2536 Anchors may be nested, with components separated by
2538 characters, similar to how file system hierarchies are laid out.
2539 The main ruleset is actually the default anchor, so filter and
2540 translation rules, for example, may also be contained in any anchor.
2542 An anchor can reference another
2545 using the following kinds
2547 .Bl -tag -width xxxx
2548 .It Ar nat-anchor Aq Ar name
2551 rules in the specified
2553 .It Ar rdr-anchor Aq Ar name
2556 rules in the specified
2558 .It Ar binat-anchor Aq Ar name
2561 rules in the specified
2563 .It Ar anchor Aq Ar name
2564 Evaluates the filter rules in the specified
2566 .It Xo Ar load anchor
2570 Loads the rules from the specified file into the
2575 When evaluation of the main ruleset reaches an
2579 will proceed to evaluate all rules specified in that anchor.
2581 Matching filter and translation rules marked with the
2583 option are final and abort the evaluation of the rules in other
2584 anchors and the main ruleset.
2587 itself is marked with the
2590 ruleset evaluation will terminate when the anchor is exited if the packet is
2591 matched by any rule within the anchor.
2594 rules are evaluated relative to the anchor in which they are contained.
2597 rules specified in the main ruleset will reference anchor
2598 attachment points underneath the main ruleset, and
2600 rules specified in a file loaded from a
2602 rule will be attached under that anchor point.
2604 Rules may be contained in
2606 attachment points which do not contain any rules when the main ruleset
2607 is loaded, and later such anchors can be manipulated through
2609 without reloading the main ruleset or other anchors.
2611 .Bd -literal -offset indent
2613 block on $ext_if all
2615 pass out on $ext_if all
2616 pass in on $ext_if proto tcp from any \e
2617 to $ext_if port smtp
2620 blocks all packets on the external interface by default, then evaluates
2623 named "spam", and finally passes all outgoing connections and
2624 incoming connections to port 25.
2625 .Bd -literal -offset indent
2626 # echo \&"block in quick from 1.2.3.4 to any\&" \&| \e
2630 This loads a single rule into the
2632 which blocks all packets from a specific address.
2634 The anchor can also be populated by adding a
2639 .Bd -literal -offset indent
2641 load anchor spam from "/etc/pf-spam.conf"
2648 it will also load all the rules from the file
2649 .Pa /etc/pf-spam.conf
2654 rules can specify packet filtering parameters using the same syntax as
2656 When parameters are used, the
2658 rule is only evaluated for matching packets.
2659 This allows conditional evaluation of anchors, like:
2660 .Bd -literal -offset indent
2661 block on $ext_if all
2662 anchor spam proto tcp from any to any port smtp
2663 pass out on $ext_if all
2664 pass in on $ext_if proto tcp from any to $ext_if port smtp
2669 spam are only evaluated for
2671 packets with destination port 25.
2673 .Bd -literal -offset indent
2674 # echo \&"block in quick from 1.2.3.4 to any" \&| \e
2678 will only block connections from 1.2.3.4 to port 25.
2680 Anchors may end with the asterisk
2682 character, which signifies that all anchors attached at that point
2683 should be evaluated in the alphabetical ordering of their anchor name.
2685 .Bd -literal -offset indent
2689 will evaluate each rule in each anchor attached to the
2692 Note that it will only evaluate anchors that are directly attached to the
2694 anchor, and will not descend to evaluate anchors recursively.
2696 Since anchors are evaluated relative to the anchor in which they are
2697 contained, there is a mechanism for accessing the parent and ancestor
2698 anchors of a given anchor.
2699 Similar to file system path name resolution, if the sequence
2701 appears as an anchor path component, the parent anchor of the current
2702 anchor in the path evaluation at that point will become the new current
2704 As an example, consider the following:
2705 .Bd -literal -offset indent
2706 # echo ' anchor "spam/allowed" ' | pfctl -f -
2707 # echo -e ' anchor "../banned" \en pass' | \e
2708 pfctl -a spam/allowed -f -
2711 Evaluation of the main ruleset will lead into the
2713 anchor, which will evaluate the rules in the
2715 anchor, if any, before finally evaluating the
2721 can also be loaded inline in the ruleset within a brace ('{' '}') delimited
2723 Brace delimited blocks may contain rules or other brace-delimited blocks.
2724 When anchors are loaded this way the anchor name becomes optional.
2725 .Bd -literal -offset indent
2726 anchor "external" on egress {
2729 pass proto tcp from any to port { 25, 80, 443 }
2731 pass in proto tcp to any port 22
2735 Since the parser specification for anchor names is a string, any
2736 reference to an anchor name containing
2738 characters will require double quote
2740 characters around the anchor name.
2741 .Sh TRANSLATION EXAMPLES
2742 This example maps incoming requests on port 80 to port 8080, on
2743 which a daemon is running (because, for example, it is not run as root,
2744 and therefore lacks permission to bind to port 80).
2746 # use a macro for the interface name, so it can be changed easily
2749 # map daemon on 8080 to appear to be on 80
2750 rdr on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 port 8080
2755 modifier is given, packets matching the translation rule are passed without
2756 inspecting the filter rules:
2758 rdr pass on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 \e
2762 In the example below, vlan12 is configured as 192.168.168.1;
2763 the machine translates all packets coming from 192.168.168.0/24 to 204.92.77.111
2764 when they are going out any interface except vlan12.
2765 This has the net effect of making traffic from the 192.168.168.0/24
2766 network appear as though it is the Internet routable address
2767 204.92.77.111 to nodes behind any interface on the router except
2768 for the nodes on vlan12.
2769 (Thus, 192.168.168.1 can talk to the 192.168.168.0/24 nodes.)
2771 nat on ! vlan12 from 192.168.168.0/24 to any -\*(Gt 204.92.77.111
2774 In the example below, the machine sits between a fake internal 144.19.74.*
2775 network, and a routable external IP of 204.92.77.100.
2778 rule excludes protocol AH from being translated.
2781 no nat on $ext_if proto ah from 144.19.74.0/24 to any
2782 nat on $ext_if from 144.19.74.0/24 to any -\*(Gt 204.92.77.100
2785 In the example below, packets bound for one specific server, as well as those
2786 generated by the sysadmins are not proxied; all other connections are.
2789 no rdr on $int_if proto { tcp, udp } from any to $server port 80
2790 no rdr on $int_if proto { tcp, udp } from $sysadmins to any port 80
2791 rdr on $int_if proto { tcp, udp } from any to any port 80 -\*(Gt 127.0.0.1 \e
2795 This longer example uses both a NAT and a redirection.
2796 The external interface has the address 157.161.48.183.
2797 On localhost, we are running
2799 waiting for FTP sessions to be redirected to it.
2800 The three mandatory anchors for
2802 are omitted from this example; see the
2807 # Translate outgoing packets' source addresses (any protocol).
2808 # In this case, any address but the gateway's external address is mapped.
2809 nat on $ext_if inet from ! ($ext_if) to any -\*(Gt ($ext_if)
2812 # Map outgoing packets' source port to an assigned proxy port instead of
2813 # an arbitrary port.
2814 # In this case, proxy outgoing isakmp with port 500 on the gateway.
2815 nat on $ext_if inet proto udp from any port = isakmp to any -\*(Gt ($ext_if) \e
2819 # Translate outgoing packets' source address (any protocol).
2820 # Translate incoming packets' destination address to an internal machine
2822 binat on $ext_if from 10.1.2.150 to any -\*(Gt $ext_if
2825 # Translate incoming packets' destination addresses.
2826 # As an example, redirect a TCP and UDP port to an internal machine.
2827 rdr on $ext_if inet proto tcp from any to ($ext_if) port 8080 \e
2828 -\*(Gt 10.1.2.151 port 22
2829 rdr on $ext_if inet proto udp from any to ($ext_if) port 8080 \e
2830 -\*(Gt 10.1.2.151 port 53
2833 # Translate outgoing ftp control connections to send them to localhost
2834 # for proxying with ftp-proxy(8) running on port 8021.
2835 rdr on $int_if proto tcp from any to any port 21 -\*(Gt 127.0.0.1 port 8021
2838 In this example, a NAT gateway is set up to translate internal addresses
2839 using a pool of public addresses (192.0.2.16/28) and to redirect
2840 incoming web server connections to a group of web servers on the internal
2844 # Translate outgoing packets' source addresses using an address pool.
2845 # A given source address is always translated to the same pool address by
2846 # using the source-hash keyword.
2847 nat on $ext_if inet from any to any -\*(Gt 192.0.2.16/28 source-hash
2850 # Translate incoming web server connections to a group of web servers on
2851 # the internal network.
2852 rdr on $ext_if proto tcp from any to any port 80 \e
2853 -\*(Gt { 10.1.2.155, 10.1.2.160, 10.1.2.161 } round-robin
2857 # The external interface is kue0
2858 # (157.161.48.183, the only routable address)
2859 # and the private network is 10.0.0.0/8, for which we are doing NAT.
2861 # use a macro for the interface name, so it can be changed easily
2864 # normalize all incoming traffic
2865 scrub in on $ext_if all fragment reassemble
2867 # block and log everything by default
2868 block return log on $ext_if all
2870 # block anything coming from source we have no back routes for
2871 block in from no-route to any
2873 # block packets whose ingress interface does not match the one in
2874 # the route back to their source address
2875 block in from urpf-failed to any
2877 # block and log outgoing packets that do not have our address as source,
2878 # they are either spoofed or something is misconfigured (NAT disabled,
2879 # for instance), we want to be nice and do not send out garbage.
2880 block out log quick on $ext_if from ! 157.161.48.183 to any
2882 # silently drop broadcasts (cable modem noise)
2883 block in quick on $ext_if from any to 255.255.255.255
2885 # block and log incoming packets from reserved address space and invalid
2886 # addresses, they are either spoofed or misconfigured, we cannot reply to
2887 # them anyway (hence, no return-rst).
2888 block in log quick on $ext_if from { 10.0.0.0/8, 172.16.0.0/12, \e
2889 192.168.0.0/16, 255.255.255.255/32 } to any
2893 # pass out/in certain ICMP queries and keep state (ping)
2894 # state matching is done on host addresses and ICMP id (not type/code),
2895 # so replies (like 0/0 for 8/0) will match queries
2896 # ICMP error messages (which always refer to a TCP/UDP packet) are
2897 # handled by the TCP/UDP states
2898 pass on $ext_if inet proto icmp all icmp-type 8 code 0
2902 # pass out all UDP connections and keep state
2903 pass out on $ext_if proto udp all
2905 # pass in certain UDP connections and keep state (DNS)
2906 pass in on $ext_if proto udp from any to any port domain
2910 # pass out all TCP connections and modulate state
2911 pass out on $ext_if proto tcp all modulate state
2913 # pass in certain TCP connections and keep state (SSH, SMTP, DNS, IDENT)
2914 pass in on $ext_if proto tcp from any to any port { ssh, smtp, domain, \e
2917 # Do not allow Windows 9x SMTP connections since they are typically
2918 # a viral worm. Alternately we could limit these OSes to 1 connection each.
2919 block in on $ext_if proto tcp from any os {"Windows 95", "Windows 98"} \e
2923 # pass in/out all IPv6 traffic: note that we have to enable this in two
2924 # different ways, on both our physical interface and our tunnel
2925 pass quick on gif0 inet6
2926 pass quick on $ext_if proto ipv6
2928 # Using the pickup options to keep/modulate/synproxy state
2930 # no-pickups (default) Do not allow connections to be picked up in the
2931 # middle. Implies flags S/SA (the 'no-pickups' option need
2932 # not be specified, it is the default).
2934 # pickups Allow connections to be picked up in the middle, even if
2935 # no window scaling information is known. Such connections
2936 # will disable sequence space checks. Implies no flag
2939 # hash-only Do not fail packets on sequence space checks. Implies no
2940 # flag restrictions.
2942 pass in on $ext_if proto tcp ... keep state (no-pickups)
2943 pass in on $ext_if proto tcp ... keep state (pickups)
2944 pass in on $ext_if proto tcp ... keep state (hash-only)
2948 # three interfaces: $int_if, $ext_if, and $wifi_if (wireless). NAT is
2949 # being done on $ext_if for all outgoing packets. tag packets in on
2950 # $int_if and pass those tagged packets out on $ext_if. all other
2951 # outgoing packets (i.e., packets from the wireless network) are only
2952 # permitted to access port 80.
2954 pass in on $int_if from any to any tag INTNET
2955 pass in on $wifi_if from any to any
2957 block out on $ext_if from any to any
2958 pass out quick on $ext_if tagged INTNET
2959 pass out on $ext_if proto tcp from any to any port 80
2961 # tag incoming packets as they are redirected to spamd(8). use the tag
2962 # to pass those packets through the packet filter.
2964 rdr on $ext_if inet proto tcp from \*(Ltspammers\*(Gt to port smtp \e
2965 tag SPAMD -\*(Gt 127.0.0.1 port spamd
2968 pass in on $ext_if inet proto tcp tagged SPAMD
2975 line = option | pf-rule | nat-rule | binat-rule | rdr-rule |
2976 antispoof-rule | altq-rule | queue-rule | trans-anchors |
2977 anchor-rule | anchor-close | load-anchor | table-rule | include
2979 option = "set" ( [ "timeout" ( timeout | "{" timeout-list "}" ) ] |
2980 [ "ruleset-optimization" [ "none" | "basic" | "profile" ] ] |
2981 [ "optimization" [ "default" | "normal" |
2982 "high-latency" | "satellite" |
2983 "aggressive" | "conservative" ] ]
2984 [ "limit" ( limit-item | "{" limit-list "}" ) ] |
2985 [ "loginterface" ( interface-name | "none" ) ] |
2986 [ "block-policy" ( "drop" | "return" ) ] |
2987 [ "keep-policy" keep ] |
2988 [ "state-policy" ( "if-bound" | "floating" ) ]
2989 [ "require-order" ( "yes" | "no" ) ]
2990 [ "fingerprints" filename ] |
2991 [ "skip on" ( interface-name | "{" interface-list "}" ) ] |
2992 [ "debug" ( "none" | "urgent" | "misc" | "loud" ) ] )
2994 pf-rule = action [ "in" | "out" ]
2995 [ "log" [ "(" logopts ")"] ] [ "quick" ]
2996 [ "on" ifspec ] [ "fastroute" | route ] [ af ] [ protospec ]
2997 hosts [ filteropt-list ]
2999 logopts = logopt [ "," logopts ]
3000 logopt = "all" | "user" | "to" interface-name
3002 filteropt-list = filteropt-list filteropt | filteropt
3003 filteropt = user | group | flags | icmp-type | icmp6-type | tos |
3004 keep | "fragment" | "no-df" | "min-ttl" number |
3005 "max-mss" number | "random-id" | "reassemble tcp" |
3006 fragmentation | "allow-opts" |
3007 "label" string | "tag" string | [ ! ] "tagged" string |
3008 "queue" ( string | "(" string [ [ "," ] string ] ")" ) |
3009 "probability" number"%"
3011 keep = "no" "state" |
3012 ( "keep" | "modulate" | "synproxy" ) "state"
3013 [ "(" state-opts ")" ]
3015 nat-rule = [ "no" ] "nat" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
3016 [ "on" ifspec ] [ af ]
3017 [ protospec ] hosts [ "tag" string ] [ "tagged" string ]
3018 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" )
3019 [ portspec ] [ pooltype ] [ "static-port" ] ]
3021 binat-rule = [ "no" ] "binat" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
3022 [ "on" interface-name ] [ af ]
3023 [ "proto" ( proto-name | proto-number ) ]
3024 "from" address [ "/" mask-bits ] "to" ipspec
3025 [ "tag" string ] [ "tagged" string ]
3026 [ "-\*(Gt" address [ "/" mask-bits ] ]
3028 rdr-rule = [ "no" ] "rdr" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
3029 [ "on" ifspec ] [ af ]
3030 [ protospec ] hosts [ "tag" string ] [ "tagged" string ]
3031 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" )
3032 [ portspec ] [ pooltype ] ]
3034 antispoof-rule = "antispoof" [ "log" ] [ "quick" ]
3035 "for" ( interface-name | "{" interface-list "}" )
3036 [ af ] [ "label" string ]
3038 table-rule = "table" "\*(Lt" string "\*(Gt" [ tableopts-list ]
3039 tableopts-list = tableopts-list tableopts | tableopts
3040 tableopts = "persist" | "const" | "counters" | "file" string |
3041 "{" [ tableaddr-list ] "}"
3042 tableaddr-list = tableaddr-list [ "," ] tableaddr-spec | tableaddr-spec
3043 tableaddr-spec = [ "!" ] tableaddr [ "/" mask-bits ]
3044 tableaddr = hostname | ipv4-dotted-quad | ipv6-coloned-hex |
3045 interface-name | "self"
3047 altq-rule = "altq on" interface-name queueopts-list
3049 queue-rule = "queue" string [ "on" interface-name ] queueopts-list
3052 anchor-rule = "anchor" string [ "in" | "out" ] [ "on" ifspec ]
3053 [ af ] [ "proto" ] [ protospec ] [ hosts ]
3055 trans-anchors = ( "nat-anchor" | "rdr-anchor" | "binat-anchor" ) string
3056 [ "on" ifspec ] [ af ] [ "proto" ] [ protospec ] [ hosts ]
3058 load-anchor = "load anchor" string "from" filename
3060 queueopts-list = queueopts-list queueopts | queueopts
3061 queueopts = "bandwidth" bandwidth-spec |
3062 "qlimit" number | "tbrsize" number |
3063 "priority" number | schedulers
3064 schedulers = cbq-def | hfsc-def | priq-def | fairq-def
3065 bandwidth-spec = "number" ( "b" | "Kb" | "Mb" | "Gb" | "%" )
3067 action = "pass" | "block" [ return ] | [ "no" ] "scrub"
3068 return = "drop" | "return" | "return-rst" [ "( ttl" number ")" ] |
3069 "return-icmp" [ "(" icmpcode [ [ "," ] icmp6code ] ")" ] |
3070 "return-icmp6" [ "(" icmp6code ")" ]
3071 icmpcode = icmp-code-name | icmp-code-number
3072 icmp6code = icmp6-code-name | icmp6-code-number
3074 ifspec = ( [ "!" ] interface-name ) | "{" interface-list "}"
3075 interface-list = [ "!" ] interface-name [ [ "," ] interface-list ]
3076 route = ( "route-to" | "reply-to" | "dup-to" )
3077 ( routehost | "{" routehost-list "}" )
3079 af = "inet" | "inet6"
3081 protospec = "proto" ( proto-name | proto-number |
3082 "{" proto-list "}" )
3083 proto-list = ( proto-name | proto-number ) [ [ "," ] proto-list ]
3086 "from" ( "any" | "no-route" | "urpf-failed" | "self" | host |
3087 "{" host-list "}" | "route" string ) [ port ] [ os ]
3088 "to" ( "any" | "no-route" | "self" | host |
3089 "{" host-list "}" | "route" string ) [ port ]
3091 ipspec = "any" | host | "{" host-list "}"
3092 host = [ "!" ] ( address [ "/" mask-bits ] | "\*(Lt" string "\*(Gt" )
3093 redirhost = address [ "/" mask-bits ]
3094 routehost = "(" interface-name [ address [ "/" mask-bits ] ] ")"
3095 address = interface-name | "(" interface-name ")" | hostname |
3096 ipv4-dotted-quad | ipv6-coloned-hex
3097 host-list = host [ [ "," ] host-list ]
3098 redirhost-list = redirhost [ [ "," ] redirhost-list ]
3099 routehost-list = routehost [ [ "," ] routehost-list ]
3101 port = "port" ( unary-op | binary-op | "{" op-list "}" )
3102 portspec = "port" ( number | name ) [ ":" ( "*" | number | name ) ]
3103 os = "os" ( os-name | "{" os-list "}" )
3104 user = "user" ( unary-op | binary-op | "{" op-list "}" )
3105 group = "group" ( unary-op | binary-op | "{" op-list "}" )
3107 unary-op = [ "=" | "!=" | "\*(Lt" | "\*(Le" | "\*(Gt" | "\*(Ge" ]
3109 binary-op = number ( "\*(Lt\*(Gt" | "\*(Gt\*(Lt" | ":" ) number
3110 op-list = ( unary-op | binary-op ) [ [ "," ] op-list ]
3112 os-name = operating-system-name
3113 os-list = os-name [ [ "," ] os-list ]
3115 flags = "flags" ( [ flag-set ] "/" flag-set | "any" )
3116 flag-set = [ "F" ] [ "S" ] [ "R" ] [ "P" ] [ "A" ] [ "U" ] [ "E" ]
3119 icmp-type = "icmp-type" ( icmp-type-code | "{" icmp-list "}" )
3120 icmp6-type = "icmp6-type" ( icmp-type-code | "{" icmp-list "}" )
3121 icmp-type-code = ( icmp-type-name | icmp-type-number )
3122 [ "code" ( icmp-code-name | icmp-code-number ) ]
3123 icmp-list = icmp-type-code [ [ "," ] icmp-list ]
3125 tos = ( "lowdelay" | "throughput" | "reliability" |
3128 state-opts = state-opt [ [ "," ] state-opts ]
3129 state-opt = "max" number | "no-sync" | timeout |
3130 "source-track" [ "rule" | "global" ] |
3131 "max-src-nodes" number | "max-src-states" number |
3132 "max-src-conn" number |
3133 "max-src-conn-rate" number "/" number |
3134 "overload" "\*(Lt" string "\*(Gt" [ "flush" ] |
3135 "if-bound" | "floating" |
3136 "pickups" | "no-pickups" | "hash-only"
3138 fragmentation = [ "fragment reassemble" | "fragment crop" |
3139 "fragment drop-ovl" ]
3141 timeout-list = timeout [ [ "," ] timeout-list ]
3142 timeout = ( "tcp.first" | "tcp.opening" | "tcp.established" |
3143 "tcp.closing" | "tcp.finwait" | "tcp.closed" |
3144 "udp.first" | "udp.single" | "udp.multiple" |
3145 "icmp.first" | "icmp.error" |
3146 "other.first" | "other.single" | "other.multiple" |
3147 "frag" | "interval" | "src.track" |
3148 "adaptive.start" | "adaptive.end" ) number
3150 limit-list = limit-item [ [ "," ] limit-list ]
3151 limit-item = ( "states" | "frags" | "src-nodes" ) number
3153 pooltype = ( "bitmask" | "random" |
3154 "source-hash" [ hex-key | string-key ] |
3155 "round-robin" ) [ sticky-address ]
3157 subqueue = string | "{" queue-list "}"
3158 queue-list = string [ [ "," ] string ]
3160 cbq-def = "cbq" [ "(" cbq-opts ")" ]
3161 priq-def = "priq" [ "(" priq-opts ")" ]
3162 hfsc-def = "hfsc" [ "(" hfsc-opts ")" ]
3163 fairq-def = "fairq" [ "(" fairq-opts ")" ]
3165 cbq-opts = cbq-opt [ [ "," ] cbq-opts ]
3166 priq-opts = priq-opt [ [ "," ] priq-opts ]
3167 hfsc-opts = hfsc-opt [ [ "," ] hfsc-opts ]
3168 fairq-opts = fairq-opt [ [ "," ] fairq-opts ]
3170 cbq-opt = "default" | "borrow" | "red" | "ecn" | "rio"
3171 priq-opt = "default" | "red" | "ecn" | "rio"
3172 hfsc-opt = "default" | "red" | "ecn" | "rio" |
3173 linkshare-sc | realtime-sc | upperlimit-sc
3174 fairq-opt = "default" | "red" | "ecn" | "rio" |
3175 "buckets" number | "hogs" number | linkshare-sc
3177 linkshare-sc = "linkshare" sc-spec
3178 realtime-sc = "realtime" sc-spec
3179 upperlimit-sc = "upperlimit" sc-spec
3180 sc-spec = ( bandwidth-spec |
3181 "(" bandwidth-spec number bandwidth-spec ")" )
3182 include = "include" filename
3185 .Bl -tag -width ".Pa /usr/share/examples/pf" -compact
3189 Default location of the ruleset file.
3191 Default location of OS fingerprints.
3192 .It Pa /etc/protocols
3193 Protocol name database.
3194 .It Pa /etc/services
3195 Service name database.
3196 .It Pa /usr/share/examples/pf
3221 file format first appeared in