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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
231 name, a valid interface group or the
233 keyword, in which case all addresses assigned to the interface(s) 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).
344 .It Ar set loginterface
345 Enable collection of packet and byte count statistics for the given
346 interface or interface group.
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
364 Sets hard limits on the memory pools used by the packet filter.
367 for an explanation of memory pools.
370 .Bd -literal -offset indent
371 set limit states 20000
374 sets the maximum number of entries in the memory pool used by state table
375 entries (generated by
377 rules which do not specify
381 .Bd -literal -offset indent
382 set limit frags 20000
385 sets the maximum number of entries in the memory pool used for fragment
386 reassembly (generated by
390 .Bd -literal -offset indent
391 set limit src-nodes 2000
394 sets the maximum number of entries in the memory pool used for tracking
395 source IP addresses (generated by the
401 .Bd -literal -offset indent
402 set limit tables 1000
403 set limit table-entries 100000
406 sets limits on the memory pools used by tables.
407 The first limits the number of tables that can exist to 1000.
408 The second limits the overall number of addresses that can be stored
411 Various limits can be combined on a single line:
412 .Bd -literal -offset indent
413 set limit { states 20000, frags 20000, src-nodes 2000 }
415 .It Ar set ruleset-optimization
416 .Bl -tag -width xxxxxxxx -compact
418 Disable the ruleset optimizer.
421 Enable basic ruleset optimization.
422 This is the default behaviour.
423 Basic ruleset optimization does four things to improve the
424 performance of ruleset evaluations:
428 remove duplicate rules
430 remove rules that are a subset of another rule
432 combine multiple rules into a table when advantageous
434 re-order the rules to improve evaluation performance
438 Uses the currently loaded ruleset as a feedback profile to tailor the
439 ordering of quick rules to actual network traffic.
442 It is important to note that the ruleset optimizer will modify the ruleset
443 to improve performance.
444 A side effect of the ruleset modification is that per-rule accounting
445 statistics will have different meanings than before.
446 If per-rule accounting is important for billing purposes or whatnot,
447 either the ruleset optimizer should not be used or a label field should
448 be added to all of the accounting rules to act as optimization barriers.
450 Optimization can also be set as a command-line argument to
452 overriding the settings in
454 .It Ar set optimization
455 Optimize state timeouts for one of the following network environments:
457 .Bl -tag -width xxxx -compact
459 A normal network environment.
460 Suitable for almost all networks.
462 A high-latency environment (such as a satellite connection).
467 Aggressively expire connections.
468 This can greatly reduce the memory usage of the firewall at the cost of
469 dropping idle connections early.
471 Extremely conservative settings.
472 Avoid dropping legitimate connections at the
473 expense of greater memory utilization (possibly much greater on a busy
474 network) and slightly increased processor utilization.
478 .Bd -literal -offset indent
479 set optimization aggressive
481 .It Ar set keep-policy keep_rule
484 option sets the default state retention policy for all
488 .Sx STATEFUL TRACKING OPTIONS
494 .Ar no Ns / Ns Ar keep Ns / Ns Ar modulate Ns / Ns Ar synproxy state
497 rule will override the default.
499 .Bd -literal -offset indent
500 set keep-policy keep state (pickups)
502 .It Ar set block-policy
505 option sets the default behaviour for the packet
509 .Bl -tag -width xxxxxxxx -compact
511 Packet is silently dropped.
513 A TCP RST is returned for blocked TCP packets,
514 an ICMP UNREACHABLE is returned for blocked UDP packets,
515 and all other packets are silently dropped.
519 .Bd -literal -offset indent
520 set block-policy return
522 .It Ar set state-policy
525 option sets the default behaviour for states:
527 .Bl -tag -width if-bound -compact
529 States are bound to interface.
531 States can match packets on any interfaces (the default).
535 .Bd -literal -offset indent
536 set state-policy if-bound
541 identifies this firewall's state table entries to other firewalls
545 By default the hostid is set to a pseudo-random value, however it may be
546 desirable to manually configure it, for example to more easily identify the
547 source of state table entries.
548 .Bd -literal -offset indent
552 The hostid may be specified in either decimal or hexadecimal.
553 .It Ar set require-order
556 enforces an ordering of the statement types in the ruleset to:
562 Setting this option to
564 disables this enforcement.
565 There may be non-trivial and non-obvious implications to an out of
567 Consider carefully before disabling the order enforcement.
568 .It Ar set fingerprints
569 Load fingerprints of known operating systems from the given filename.
570 By default fingerprints of known operating systems are automatically
575 but can be overridden via this option.
576 Setting this option may leave a small period of time where the fingerprints
577 referenced by the currently active ruleset are inconsistent until the new
578 ruleset finishes loading.
582 .Dl set fingerprints \&"/etc/pf.os.devel\&"
583 .It Ar set skip on Aq Ar ifspec
584 List interfaces for which packets should not be filtered.
585 Packets passing in or out on such interfaces are passed as if pf was
586 disabled, i.e. pf does not process them in any way.
587 This can be useful on loopback and other virtual interfaces, when
588 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.
701 .It Ar fragment drop-ovl
702 This option is similar to the
704 modifier except that all overlapping or duplicate fragments will be
705 dropped, and all further corresponding fragments will be
707 .It Ar reassemble tcp
708 Statefully normalizes TCP connections.
709 .Ar scrub reassemble tcp
710 rules may not have the direction (in/out) specified.
712 performs the following normalizations:
714 .Bl -tag -width timeout -compact
716 Neither side of the connection is allowed to reduce their IP TTL.
717 An attacker may send a packet such that it reaches the firewall, affects
718 the firewall state, and expires before reaching the destination host.
720 will raise the TTL of all packets back up to the highest value seen on
722 .It timestamp modulation
723 Modern TCP stacks will send a timestamp on every TCP packet and echo
724 the other endpoint's timestamp back to them.
725 Many operating systems will merely start the timestamp at zero when
726 first booted, and increment it several times a second.
727 The uptime of the host can be deduced by reading the timestamp and multiplying
729 Also observing several different timestamps can be used to count hosts
731 And spoofing TCP packets into a connection requires knowing or guessing
733 Timestamps merely need to be monotonically increasing and not derived off a
738 to modulate the TCP timestamps with a random number.
739 .It extended PAWS checks
740 There is a problem with TCP on long fat pipes, in that a packet might get
741 delayed for longer than it takes the connection to wrap its 32-bit sequence
743 In such an occurrence, the old packet would be indistinguishable from a
744 new packet and would be accepted as such.
745 The solution to this is called PAWS: Protection Against Wrapped Sequence
747 It protects against it by making sure the timestamp on each packet does
750 also makes sure the timestamp on the packet does not go forward more
754 artificially extends the security of TCP sequence numbers by 10 to 18
755 bits when the host uses appropriately randomized timestamps, since a
756 blind attacker would have to guess the timestamp as well.
761 .Bd -literal -offset indent
762 scrub in on $ext_if all fragment reassemble
767 option prefixed to a scrub rule causes matching packets to remain unscrubbed,
768 much in the same way as
770 works in the packet filter (see below).
771 This mechanism should be used when it is necessary to exclude specific packets
772 from broader scrub rules.
774 Packets can be assigned to queues for the purpose of bandwidth
776 At least two declarations are required to configure queues, and later
777 any packet filtering rule can reference the defined queues by name.
778 During the filtering component of
782 name is where any packets from
784 rules will be queued, while for
786 rules it specifies where any resulting ICMP or TCP RST
787 packets should be queued.
790 defines the algorithm used to decide which packets get delayed, dropped, or
791 sent out immediately.
795 .Bl -tag -width ".Ar fairq"
797 Class Based Queueing.
799 attached to an interface build a tree, thus each
801 can have further child
803 Each queue can have a
809 mainly controls the time packets take to get sent out, while
811 has primarily effects on throughput.
813 achieves both partitioning and sharing of link bandwidth
814 by hierarchically structured classes.
815 Each class has its own
817 and is assigned its share of
819 A child class can borrow bandwidth from its parent class
820 as long as excess bandwidth is available
827 are flat attached to the interface, thus,
829 cannot have further child
835 assigned, ranging from 0 to 15.
842 Hierarchical Fair Service Curve.
844 attached to an interface build a tree, thus each
846 can have further child
848 Each queue can have a
854 mainly controls the time packets take to get sent out, while
856 primarily affects throughput.
858 supports both link-sharing and guaranteed real-time services.
859 It employs a service curve based QoS model,
860 and its unique feature is an ability to decouple
868 are flat attached to the interface, thus,
870 cannot have further child
872 Each queue must be given a unique
874 and one must be marked
875 as the default queue.
876 Each queue implements a number of
878 (default 256) which sorts the
879 traffic based on a hash key generated by the
884 Each bucket contains a list of packets controlled by
888 to function properly,
890 must be enabled on most of the rule sets that route packets to the queue.
891 Any rules for which keep state is not enabled are added to the end of the
893 If you do not wish keep state to do TCP sequence space checks use
894 .Ar "keep state (no-pickups)"
896 .Ar "keep state (hash-only)" .
898 Packet selection operates as follows:
899 The queues are scanned from highest priority to lowest priority.
900 If a queue has pending packets and is under its bandwidth minimum the
901 scan stops and a packet is selected from that queue.
902 If all queues have reached their bandwidth minimum a scale factor based
903 on each queue's bandwidth minimum versus that queue's current bandwidth
904 usage is calculated and the queue with the lowest scale factor is selected.
905 This effectively uses the minimum bandwidth specification as a relative
906 weighting for apportioning any remaining bandwidth on the link.
908 The priority mechanic is only applicable in cases where the aggregate
909 minimum bandwidth guarantees exceed the link bandwidth, and also has
910 a small effect on queue selection when prioritizing between equal scale
915 round robins between its
917 extracting one packet from each bucket.
918 This essentially prevents large backlogs of packets from high volume
919 connections from destroying the interactive response of other connections.
925 is guaranteed minimum and more will be used if no higher priority traffic is
927 Creating a queue with one bucket as a catch-all for
929 rules not characterized by
932 Such a queue serves as a basic priority queue with a bandwidth specification.
934 Also note that when specifying rules it is always a good idea to specify
935 a secondary queue for any tcp rules.
936 The secondary queue is selected for pure ACKs without payloads and should
937 generally be dedicated to that purpose with a minimum bandwidth specification
938 sufficient to max-out the bandwidth for your incoming traffic.
941 The interfaces on which queueing should be activated are declared using
946 has the following keywords:
949 Queueing is enabled on the named interface.
951 Specifies which queueing scheduler to use.
952 Currently supported values
955 for Class Based Queueing,
957 for Priority Queueing,
959 for the Hierarchical Fair Service Curve scheduler, and
961 for the Fair Queueing.
962 .It Ar bandwidth Aq Ar bw
963 The maximum bitrate for all queues on an
964 interface may be specified using the
967 The value can be specified as an absolute value or as a
968 percentage of the interface bandwidth.
969 When using an absolute value, the suffixes
975 are used to represent bits, kilobits, megabits, and
976 gigabits per second, respectively.
977 The value must not exceed the interface bandwidth.
980 is not specified, the interface bandwidth is used
981 (but take note that some interfaces do not know their bandwidth,
982 or can adapt their bandwidth rates).
987 specifies a guaranteed minimum but the fairq is allowed to exceed it.
988 .It Ar qlimit Aq Ar limit
989 The maximum number of packets held in the queue.
991 .It Ar tbrsize Aq Ar size
992 Adjusts the size, in bytes, of the token bucket regulator.
993 If not specified, heuristics based on the
994 interface bandwidth are used to determine the size.
995 .It Ar queue Aq Ar list
996 Defines a list of subqueues to create on an interface.
999 In the following example, the interface dc0
1000 should queue up to 5 Mbit/s in four second-level queues using
1001 Class Based Queueing.
1002 Those four queues will be shown in a later example.
1003 .Bd -literal -offset indent
1004 altq on dc0 cbq bandwidth 5Mb queue { std, http, mail, ssh }
1007 Once interfaces are activated for queueing using the
1009 directive, a sequence of
1011 directives may be defined.
1012 The name associated with a
1014 must match a queue defined in the
1016 directive (e.g.\& mail), or, except for the
1024 The following keywords can be used:
1025 .Bl -tag -width xxxx
1026 .It Ar on Aq Ar interface
1027 Specifies the interface the queue operates on.
1028 If not given, it operates on all matching interfaces.
1029 .It Ar bandwidth Aq Ar bw
1030 Specifies the maximum bitrate to be processed by the queue.
1031 This value must not exceed the value of the parent
1033 and can be specified as an absolute value or a percentage of the parent
1035 If not specified, defaults to 100% of the parent queue's bandwidth.
1038 scheduler does not support bandwidth specification.
1041 scheduler uses the bandwidth specification as a guaranteed minimum and
1043 .It Ar priority Aq Ar level
1044 Between queues a priority level can be set.
1050 the range is 0 to 7 and for
1052 the range is 0 to 15.
1053 The default for all is 1.
1055 queues with a higher priority are always served first.
1057 queues with a higher priority are served first unless they exceed their
1058 bandwidth specification.
1062 queues with a higher priority are preferred in the case of overload.
1063 .It Ar qlimit Aq Ar limit
1064 The maximum number of packets held in the queue.
1068 this specified the maximum number of packets held per bucket.
1073 can get additional parameters with
1075 .Pf ( Aq Ar parameters ) .
1077 Parameters are as follows:
1080 Packets not matched by another queue are assigned to this one.
1081 Exactly one default queue is required.
1083 Enable RED (Random Early Detection) on this queue.
1084 RED drops packets with a probability proportional to the average
1087 Enables RIO on this queue.
1088 RIO is RED with IN/OUT, thus running
1089 RED two times more than RIO would achieve the same effect.
1091 Enables ECN (Explicit Congestion Notification) on this queue.
1098 supports the following additional options:
1100 .It Ar buckets Aq Ar number
1101 Specify the number of buckets, from 1 to 2048 in powers of 2.
1102 A bucket size of 1 causes a
1104 to essentially degenerate into a priority queue.
1105 .It Ar linkshare Aq Ar sc
1106 The bandwidth share of a backlogged queue.
1107 This option is parsed but not yet supported.
1108 .It Ar hogs Aq Ar bandwidth
1109 This option allows low bandwidth connections to burst up to the specified
1110 bandwidth by not advancing the round robin when taking packets out of
1112 When using this option a small value no greater than 1/20 available interface
1113 bandwidth is recommended.
1119 supports an additional option:
1122 The queue can borrow bandwidth from the parent.
1128 supports some additional options:
1130 .It Ar realtime Aq Ar sc
1131 The minimum required bandwidth for the queue.
1132 .It Ar upperlimit Aq Ar sc
1133 The maximum allowed bandwidth for the queue.
1134 .It Ar linkshare Aq Ar sc
1135 The bandwidth share of a backlogged queue.
1142 The format for service curve specifications is
1147 controls the bandwidth assigned to the queue.
1151 are optional and can be used to control the initial bandwidth assignment.
1154 milliseconds the queue gets the bandwidth given as
1156 afterwards the value given in
1163 child queues can be specified as in an
1165 declaration, thus building a tree of queues using a part of
1166 their parent's bandwidth.
1168 Packets can be assigned to queues based on filter rules by using the
1173 is specified; when a second one is specified it will instead be used for
1174 packets which have a
1178 and for TCP ACKs with no data payload.
1180 To continue the previous example, the examples below would specify the
1182 queues, plus a few child queues.
1185 sessions get priority over bulk transfers like
1189 The queues may then be referenced by filtering rules (see
1190 .Sx PACKET FILTERING
1193 queue std bandwidth 10% cbq(default)
1194 queue http bandwidth 60% priority 2 cbq(borrow red) \e
1195 { employees, developers }
1196 queue developers bandwidth 75% cbq(borrow)
1197 queue employees bandwidth 15%
1198 queue mail bandwidth 10% priority 0 cbq(borrow ecn)
1199 queue ssh bandwidth 20% cbq(borrow) { ssh_interactive, ssh_bulk }
1200 queue ssh_interactive bandwidth 50% priority 7 cbq(borrow)
1201 queue ssh_bulk bandwidth 50% priority 0 cbq(borrow)
1203 block return out on dc0 inet all queue std
1204 pass out on dc0 inet proto tcp from $developerhosts to any port 80 \e
1206 pass out on dc0 inet proto tcp from $employeehosts to any port 80 \e
1208 pass out on dc0 inet proto tcp from any to any port 22 \e
1209 queue(ssh_bulk, ssh_interactive)
1210 pass out on dc0 inet proto tcp from any to any port 25 \e
1214 Translation rules modify either the source or destination address of the
1215 packets associated with a stateful connection.
1216 A stateful connection is automatically created to track packets matching
1217 such a rule as long as they are not blocked by the filtering section of
1219 The translation engine modifies the specified address and/or port in the
1220 packet, recalculates IP, TCP and UDP checksums as necessary, and passes it to
1221 the packet filter for evaluation.
1223 Since translation occurs before filtering the filter
1224 engine will see packets as they look after any
1225 addresses and ports have been translated.
1226 Filter rules will therefore have to filter based on the translated
1227 address and port number.
1228 Packets that match a translation rule are only automatically passed if
1231 modifier is given, otherwise they are
1238 The state entry created permits
1240 to keep track of the original address for traffic associated with that state
1241 and correctly direct return traffic for that connection.
1243 Various types of translation are possible with pf:
1244 .Bl -tag -width xxxx
1248 rule specifies a bidirectional mapping between an external IP netblock
1249 and an internal IP netblock.
1253 rule specifies that IP addresses are to be changed as the packet
1254 traverses the given interface.
1255 This technique allows one or more IP addresses
1256 on the translating host to support network traffic for a larger range of
1257 machines on an "inside" network.
1258 Although in theory any IP address can be used on the inside, it is strongly
1259 recommended that one of the address ranges defined by RFC 1918 be used.
1260 These netblocks are:
1262 10.0.0.0 - 10.255.255.255 (all of net 10, i.e., 10/8)
1263 172.16.0.0 - 172.31.255.255 (i.e., 172.16/12)
1264 192.168.0.0 - 192.168.255.255 (i.e., 192.168/16)
1267 The packet is redirected to another destination and possibly a
1270 rules can optionally specify port ranges instead of single ports.
1271 rdr ... port 2000:2999 -\*(Gt ... port 4000
1272 redirects ports 2000 to 2999 (inclusive) to port 4000.
1273 rdr ... port 2000:2999 -\*(Gt ... port 4000:*
1274 redirects port 2000 to 4000, 2001 to 4001, ..., 2999 to 4999.
1277 In addition to modifying the address, some translation rules may modify
1278 source or destination ports for
1282 connections; implicitly in the case of
1284 rules and explicitly in the case of
1287 Port numbers are never translated with a
1291 Evaluation order of the translation rules is dependent on the type
1292 of the translation rules and of the direction of a packet.
1294 rules are always evaluated first.
1297 rules are evaluated on an inbound packet or the
1299 rules on an outbound packet.
1300 Rules of the same type are evaluated in the same order in which they
1301 appear in the ruleset.
1302 The first matching rule decides what action is taken.
1306 option prefixed to a translation rule causes packets to remain untranslated,
1307 much in the same way as
1309 works in the packet filter (see below).
1310 If no rule matches the packet it is passed to the filter engine unmodified.
1312 Translation rules apply only to packets that pass through
1313 the specified interface, and if no interface is specified,
1314 translation is applied to packets on all interfaces.
1315 For instance, redirecting port 80 on an external interface to an internal
1316 web server will only work for connections originating from the outside.
1317 Connections to the address of the external interface from local hosts will
1318 not be redirected, since such packets do not actually pass through the
1320 Redirections cannot reflect packets back through the interface they arrive
1321 on, they can only be redirected to hosts connected to different interfaces
1322 or to the firewall itself.
1324 Note that redirecting external incoming connections to the loopback
1326 .Bd -literal -offset indent
1327 rdr on ne3 inet proto tcp to port smtp -\*(Gt 127.0.0.1 port spamd
1330 will effectively allow an external host to connect to daemons
1331 bound solely to the loopback address, circumventing the traditional
1332 blocking of such connections on a real interface.
1333 Unless this effect is desired, any of the local non-loopback addresses
1334 should be used as redirection target instead, which allows external
1335 connections only to daemons bound to this address or not bound to
1339 .Sx TRANSLATION EXAMPLES
1341 .Sh PACKET FILTERING
1347 packets based on attributes of their layer 3 (see
1357 In addition, packets may also be
1358 assigned to queues for the purpose of bandwidth control.
1360 For each packet processed by the packet filter, the filter rules are
1361 evaluated in sequential order, from first to last.
1362 The last matching rule decides what action is taken.
1363 If no rule matches the packet, the default action is to pass
1366 The following actions can be used in the filter:
1367 .Bl -tag -width xxxx
1369 The packet is blocked.
1370 There are a number of ways in which a
1372 rule can behave when blocking a packet.
1373 The default behaviour is to
1375 packets silently, however this can be overridden or made
1376 explicit either globally, by setting the
1378 option, or on a per-rule basis with one of the following options:
1380 .Bl -tag -width xxxx -compact
1382 The packet is silently dropped.
1384 This applies only to
1386 packets, and issues a TCP RST which closes the
1390 This causes ICMP messages to be returned for packets which match the rule.
1391 By default this is an ICMP UNREACHABLE message, however this
1392 can be overridden by specifying a message as a code or number.
1394 This causes a TCP RST to be returned for
1396 packets and an ICMP UNREACHABLE for UDP and other packets.
1399 Options returning ICMP packets currently have no effect if
1403 as the code to support this feature has not yet been implemented.
1405 The simplest mechanism to block everything by default and only pass
1406 packets that match explicit rules is specify a first filter rule of:
1407 .Bd -literal -offset indent
1411 The packet is passed;
1412 state is created unless the
1414 option is specified.
1419 filters packets statefully; the first time a packet matches a
1421 rule, a state entry is created; for subsequent packets the filter checks
1422 whether the packet matches any state.
1423 If it does, the packet is passed without evaluation of any rules.
1424 After the connection is closed or times out, the state entry is automatically
1427 This has several advantages.
1428 For TCP connections, comparing a packet to a state involves checking
1429 its sequence numbers, as well as TCP timestamps if a
1430 .Ar scrub reassemble tcp
1431 rule applies to the connection.
1432 If these values are outside the narrow windows of expected
1433 values, the packet is dropped.
1434 This prevents spoofing attacks, such as when an attacker sends packets with
1435 a fake source address/port but does not know the connection's sequence
1439 knows how to match ICMP replies to states.
1441 .Bd -literal -offset indent
1442 pass out inet proto icmp all icmp-type echoreq
1445 allows echo requests (such as those created by
1447 out statefully, and matches incoming echo replies correctly to states.
1449 Also, looking up states is usually faster than evaluating rules.
1450 If there are 50 rules, all of them are evaluated sequentially in O(n).
1451 Even with 50000 states, only 16 comparisons are needed to match a
1452 state, since states are stored in a binary search tree that allows
1453 searches in O(log2 n).
1455 Furthermore, correct handling of ICMP error messages is critical to
1456 many protocols, particularly TCP.
1458 matches ICMP error messages to the correct connection, checks them against
1459 connection parameters, and passes them if appropriate.
1460 For example if an ICMP source quench message referring to a stateful TCP
1461 connection arrives, it will be matched to the state and get passed.
1463 Finally, state tracking is required for
1464 .Ar nat , binat No and Ar rdr
1465 rules, in order to track address and port translations and reverse the
1466 translation on returning packets.
1469 will also create state for other protocols which are effectively stateless by
1471 UDP packets are matched to states using only host addresses and ports,
1472 and other protocols are matched to states using only the host addresses.
1474 If stateless filtering of individual packets is desired,
1477 keyword can be used to specify that state will not be created
1478 if this is the last matching rule.
1479 A number of parameters can also be set to affect how
1481 handles state tracking.
1483 .Sx STATEFUL TRACKING OPTIONS
1484 below for further details.
1486 The rule parameters specify the packets to which a rule applies.
1487 A packet always comes in on, or goes out through, one interface.
1488 Most parameters are optional.
1489 If a parameter is specified, the rule only applies to packets with
1490 matching attributes.
1491 Certain parameters can be expressed as lists, in which case
1493 generates all needed rule combinations.
1494 .Bl -tag -width xxxx
1495 .It Ar in No or Ar out
1496 This rule applies to incoming or outgoing packets.
1501 are specified, the rule will match packets in both directions.
1503 In addition to the action specified, a log message is generated.
1504 Only the packet that establishes the state is logged,
1507 option is specified.
1508 The logged packets are sent to a
1510 interface, by default
1512 This interface is monitored by the
1514 logging daemon, which dumps the logged packets to the file
1520 Used to force logging of all packets for a connection.
1521 This is not necessary when
1523 is explicitly specified.
1526 packets are logged to
1531 user ID of the user that owns the socket and the PID of the process that
1532 has the socket open where the packet is sourced from or destined to
1533 (depending on which socket is local).
1534 This is in addition to the normal information logged.
1535 .It Ar log (to Aq Ar interface )
1536 Send logs to the specified
1538 interface instead of
1541 If a packet matches a rule which has the
1543 option set, this rule
1544 is considered the last matching rule, and evaluation of subsequent rules
1546 .It Ar on Aq Ar interface
1547 This rule applies only to packets coming in on, or going out through, this
1548 particular interface or interface group.
1549 For more information on interface groups,
1555 This rule applies only to packets of this address family.
1556 Supported values are
1560 .It Ar proto Aq Ar protocol
1561 This rule applies only to packets of this protocol.
1562 Common protocols are
1568 For a list of all the protocol name to number mappings used by
1571 .Pa /etc/protocols .
1573 .Ar from Aq Ar source
1574 .Ar port Aq Ar source
1579 This rule applies only to packets with the specified source and destination
1580 addresses and ports.
1582 Addresses can be specified in CIDR notation (matching netblocks), as
1583 symbolic host names, interface names or interface group names, or as any
1584 of the following keywords:
1586 .Bl -tag -width xxxxxxxxxxxxxx -compact
1589 .It Ar route Aq Ar label
1590 Any address whose associated route has label
1597 Any address which is not currently routable.
1599 Any source address that fails a unicast reverse path forwarding (URPF)
1600 check, i.e. packets coming in on an interface other than that which holds
1601 the route back to the packet's source address.
1603 Any address that matches the given table.
1606 Ranges of addresses are specified by using the
1610 .Dq 10.1.1.10 - 10.1.1.12
1611 means all addresses from 10.1.1.10 to 10.1.1.12,
1612 hence addresses 10.1.1.10, 10.1.1.11, and 10.1.1.12.
1614 Interface names and interface group names can have modifiers appended:
1616 .Bl -tag -width xxxxxxxxxxxx -compact
1618 Translates to the network(s) attached to the interface.
1620 Translates to the interface's broadcast address(es).
1622 Translates to the point-to-point interface's peer address(es).
1624 Do not include interface aliases.
1627 Host names may also have the
1629 option appended to restrict the name resolution to the first of each
1630 v4 and v6 address found.
1632 Host name resolution and interface to address translation are done at
1634 When the address of an interface (or host name) changes (under DHCP or PPP,
1635 for instance), the ruleset must be reloaded for the change to be reflected
1637 Surrounding the interface name (and optional modifiers) in parentheses
1638 changes this behaviour.
1639 When the interface name is surrounded by parentheses, the rule is
1640 automatically updated whenever the interface changes its address.
1641 The ruleset does not need to be reloaded.
1642 This is especially useful with
1645 Ports can be specified either by number or by name.
1646 For example, port 80 can be specified as
1648 For a list of all port name to number mappings used by
1653 Ports and ranges of ports are specified by using these operators:
1654 .Bd -literal -offset indent
1658 \*(Le (less than or equal)
1659 \*(Gt (greater than)
1660 \*(Ge (greater than or equal)
1661 : (range including boundaries)
1662 \*(Gt\*(Lt (range excluding boundaries)
1663 \*(Lt\*(Gt (except range)
1670 are binary operators (they take two arguments).
1673 .It Ar port 2000:2004
1675 .Sq all ports \*(Ge 2000 and \*(Le 2004 ,
1676 hence ports 2000, 2001, 2002, 2003 and 2004.
1677 .It Ar port 2000 \*(Gt\*(Lt 2004
1679 .Sq all ports \*(Gt 2000 and \*(Lt 2004 ,
1680 hence ports 2001, 2002 and 2003.
1681 .It Ar port 2000 \*(Lt\*(Gt 2004
1683 .Sq all ports \*(Lt 2000 or \*(Gt 2004 ,
1684 hence ports 1-1999 and 2005-65535.
1687 The operating system of the source host can be specified in the case of TCP
1692 .Sx OPERATING SYSTEM FINGERPRINTING
1693 section for more information.
1695 The host, port and OS specifications are optional, as in the following examples:
1696 .Bd -literal -offset indent
1698 pass in from any to any
1699 pass in proto tcp from any port \*(Le 1024 to any
1700 pass in proto tcp from any to any port 25
1701 pass in proto tcp from 10.0.0.0/8 port \*(Gt 1024 \e
1702 to ! 10.1.2.3 port != ssh
1703 pass in proto tcp from any os "OpenBSD"
1704 pass in proto tcp from route "DTAG"
1707 This is equivalent to "from any to any".
1708 .It Ar group Aq Ar group
1711 this rule only applies to packets of sockets owned by the specified group.
1712 .It Ar user Aq Ar user
1713 This rule only applies to packets of sockets owned by the specified user.
1714 For outgoing connections initiated from the firewall, this is the user
1715 that opened the connection.
1716 For incoming connections to the firewall itself, this is the user that
1717 listens on the destination port.
1718 For forwarded connections, where the firewall is not a connection endpoint,
1719 the user and group are
1722 All packets, both outgoing and incoming, of one connection are associated
1723 with the same user and group.
1724 Only TCP and UDP packets can be associated with users; for other protocols
1725 these parameters are ignored.
1727 User and group refer to the effective (as opposed to the real) IDs, in
1728 case the socket is created by a setuid/setgid process.
1729 User and group IDs are stored when a socket is created;
1730 when a process creates a listening socket as root (for instance, by
1731 binding to a privileged port) and subsequently changes to another
1732 user ID (to drop privileges), the credentials will remain root.
1734 User and group IDs can be specified as either numbers or names.
1735 The syntax is similar to the one for ports.
1738 matches packets of forwarded connections.
1740 can only be used with the operators
1744 Other constructs like
1745 .Cm user \*(Ge unknown
1747 Forwarded packets with unknown user and group ID match only rules
1748 that explicitly compare against
1756 does not match forwarded packets.
1757 The following example allows only selected users to open outgoing
1759 .Bd -literal -offset indent
1760 block out proto { tcp, udp } all
1761 pass out proto { tcp, udp } all user { \*(Lt 1000, dhartmei }
1763 .It Xo Ar flags Aq Ar a
1765 .No \*(Ba / Ns Aq Ar b
1768 This rule only applies to TCP packets that have the flags
1772 Flags not specified in
1775 For stateful connections, the default is
1777 To indicate that flags should not be checked at all, specify
1779 The flags are: (F)IN, (S)YN, (R)ST, (P)USH, (A)CK, (U)RG, (E)CE, and C(W)R.
1783 The other flags are ignored.
1785 This is the default setting for stateful connections.
1786 Out of SYN and ACK, exactly SYN may be set.
1787 SYN, SYN+PSH and SYN+RST match, but SYN+ACK, ACK and ACK+RST do not.
1788 This is more restrictive than the previous example.
1790 If the first set is not specified, it defaults to none.
1791 All of SYN, FIN, RST and ACK must be unset.
1796 is applied by default (unless
1798 is specified), only the initial SYN packet of a TCP handshake will create
1799 a state for a TCP connection.
1800 It is possible to be less restrictive, and allow state creation from
1803 packets, by specifying
1807 to synchronize to existing connections, for instance
1808 if one flushes the state table.
1809 However, states created from such intermediate packets may be missing
1810 connection details such as the TCP window scaling factor.
1811 States which modify the packet flow, such as those affected by
1812 .Ar nat , binat No or Ar rdr
1814 .Ar modulate No or Ar synproxy state
1815 options, or scrubbed with
1817 will also not be recoverable from intermediate packets.
1818 Such connections will stall and time out.
1819 .It Xo Ar icmp-type Aq Ar type
1822 .It Xo Ar icmp6-type Aq Ar type
1825 This rule only applies to ICMP or ICMPv6 packets with the specified type
1827 Text names for ICMP types and codes are listed in
1831 This parameter is only valid for rules that cover protocols ICMP or
1833 The protocol and the ICMP type indicator
1840 .It Xo Ar tos Aq Ar string
1841 .No \*(Ba Aq Ar number
1843 This rule applies to packets with the specified
1852 or as either hex or decimal.
1854 For example, the following rules are identical:
1855 .Bd -literal -offset indent
1856 pass all tos lowdelay
1861 By default, IPv4 packets with IP options or IPv6 packets with routing
1862 extension headers are blocked.
1867 rule, packets that pass the filter based on that rule (last matching)
1868 do so even if they contain IP options or routing extension headers.
1869 For packets that match state, the rule that initially created the
1873 rule that is used when a packet does not match any rules does not
1875 .It Ar label Aq Ar string
1876 Adds a label (name) to the rule, which can be used to identify the rule.
1879 shows per-rule statistics for rules that have labels.
1881 The following macros can be used in labels:
1883 .Bl -tag -width $srcaddr -compact -offset indent
1887 The source IP address.
1889 The destination IP address.
1891 The source port specification.
1893 The destination port specification.
1901 .Bd -literal -offset indent
1902 ips = \&"{ 1.2.3.4, 1.2.3.5 }\&"
1903 pass in proto tcp from any to $ips \e
1904 port \*(Gt 1023 label \&"$dstaddr:$dstport\&"
1908 .Bd -literal -offset indent
1909 pass in inet proto tcp from any to 1.2.3.4 \e
1910 port \*(Gt 1023 label \&"1.2.3.4:\*(Gt1023\&"
1911 pass in inet proto tcp from any to 1.2.3.5 \e
1912 port \*(Gt 1023 label \&"1.2.3.5:\*(Gt1023\&"
1915 The macro expansion for the
1917 directive occurs only at configuration file parse time, not during runtime.
1918 .It Xo Ar queue Aq Ar queue
1919 .No \*(Ba ( Aq Ar queue ,
1922 Packets matching this rule will be assigned to the specified queue.
1923 If two queues are given, packets which have a
1927 and TCP ACKs with no data payload will be assigned to the second one.
1933 .Bd -literal -offset indent
1934 pass in proto tcp to port 25 queue mail
1935 pass in proto tcp to port 22 queue(ssh_bulk, ssh_prio)
1937 .It Ar tag Aq Ar string
1938 Packets matching this rule will be tagged with the
1940 The tag acts as an internal marker that can be used to
1941 identify these packets later on.
1942 This can be used, for example, to provide trust between
1943 interfaces and to determine if packets have been
1944 processed by translation rules.
1947 meaning that the packet will be tagged even if the rule
1948 is not the last matching rule.
1949 Further matching rules can replace the tag with a
1950 new one but will not remove a previously applied tag.
1951 A packet is only ever assigned one tag at a time.
1952 Packet tagging can be done during
1957 rules in addition to filter rules.
1958 Tags take the same macros as labels (see above).
1959 .It Ar tagged Aq Ar string
1960 Used with filter, translation or scrub rules
1961 to specify that packets must already
1962 be tagged with the given tag in order to match the rule.
1963 Inverse tag matching can also be done
1969 .It Ar rtable Aq Ar number
1970 Used to select an alternate routing table for the routing lookup.
1971 Only effective before the route lookup happened, i.e. when filtering inbound.
1972 .It Xo Ar divert-to Aq Ar host
1975 Used to redirect packets to a local socket bound to
1979 The packets will not be modified, so
1981 on the socket will return the original destination address of the packet.
1983 Used to receive replies for sockets that are bound to addresses
1984 which are not local to the machine.
1987 for information on how to bind these sockets.
1988 .It Ar probability Aq Ar number
1989 A probability attribute can be attached to a rule, with a value set between
1990 0 and 1, bounds not included.
1991 In that case, the rule will be honoured using the given probability value
1993 For example, the following rule will drop 20% of incoming ICMP packets:
1994 .Bd -literal -offset indent
1995 block in proto icmp probability 20%
1999 If a packet matches a rule with a route option set, the packet filter will
2000 route the packet according to the type of route option.
2001 When such a rule creates state, the route option is also applied to all
2002 packets matching the same connection.
2003 .Bl -tag -width xxxx
2007 option does a normal route lookup to find the next hop for the packet.
2011 option routes the packet to the specified interface with an optional address
2015 rule creates state, only packets that pass in the same direction as the
2016 filter rule specifies will be routed in this way.
2017 Packets passing in the opposite direction (replies) are not affected
2018 and are routed normally.
2022 option is similar to
2024 but routes packets that pass in the opposite direction (replies) to the
2025 specified interface.
2026 Opposite direction is only defined in the context of a state entry, and
2028 is useful only in rules that create state.
2029 It can be used on systems with multiple external connections to
2030 route all outgoing packets of a connection through the interface
2031 the incoming connection arrived through (symmetric routing enforcement).
2035 option creates a duplicate of the packet and routes it like
2037 The original packet gets routed as it normally would.
2044 rules, (as well as for the
2049 rule options) for which there is a single redirection address which has a
2050 subnet mask smaller than 32 for IPv4 or 128 for IPv6 (more than one IP
2051 address), a variety of different methods for assigning this address can be
2053 .Bl -tag -width xxxx
2057 option applies the network portion of the redirection address to the address
2058 to be modified (source with
2065 option selects an address at random within the defined block of addresses.
2069 option uses a hash of the source address to determine the redirection address,
2070 ensuring that the redirection address is always the same for a given source.
2071 An optional key can be specified after this keyword either in hex or as a
2074 randomly generates a key for source-hash every time the
2075 ruleset is reloaded.
2079 option loops through the redirection address(es).
2081 When more than one redirection address is specified,
2083 is the only permitted pool type.
2091 from modifying the source port on TCP and UDP packets.
2096 option can be specified to help ensure that multiple connections from the
2097 same source are mapped to the same redirection address.
2098 This option can be used with the
2103 Note that by default these associations are destroyed as soon as there are
2104 no longer states which refer to them; in order to make the mappings last
2105 beyond the lifetime of the states, increase the global options with
2106 .Ar set timeout src.track .
2108 .Sx STATEFUL TRACKING OPTIONS
2109 for more ways to control the source tracking.
2110 .Sh STATE MODULATION
2111 Much of the security derived from TCP is attributable to how well the
2112 initial sequence numbers (ISNs) are chosen.
2113 Some popular stack implementations choose
2115 poor ISNs and thus are normally susceptible to ISN prediction exploits.
2118 rule to a TCP connection,
2120 will create a high quality random sequence number for each connection
2125 directive implicitly keeps state on the rule and is
2126 only applicable to TCP connections.
2129 .Bd -literal -offset indent
2131 pass out proto tcp from any to any modulate state
2132 pass in proto tcp from any to any port 25 flags S/SFRA modulate state
2135 Note that modulated connections will not recover when the state table
2136 is lost (firewall reboot, flushing the state table, etc...).
2138 will not be able to infer a connection again after the state table flushes
2139 the connection's modulator.
2140 When the state is lost, the connection may be left dangling until the
2141 respective endpoints time out the connection.
2142 It is possible on a fast local network for the endpoints to start an ACK
2143 storm while trying to resynchronize after the loss of the modulator.
2146 settings (or a more strict equivalent) should be used on
2148 rules to prevent ACK storms.
2150 Note that alternative methods are available
2151 to prevent loss of the state table
2152 and allow for firewall failover.
2157 for further information.
2161 passes packets that are part of a
2163 handshake between the endpoints.
2166 option can be used to cause
2168 itself to complete the handshake with the active endpoint, perform a handshake
2169 with the passive endpoint, and then forward packets between the endpoints.
2171 No packets are sent to the passive endpoint before the active endpoint has
2172 completed the handshake, hence so-called SYN floods with spoofed source
2173 addresses will not reach the passive endpoint, as the sender can't complete the
2176 The proxy is transparent to both endpoints, they each see a single
2177 connection from/to the other endpoint.
2179 chooses random initial sequence numbers for both handshakes.
2180 Once the handshakes are completed, the sequence number modulators
2181 (see previous section) are used to translate further packets of the
2185 .Ar modulate state .
2195 .Bd -literal -offset indent
2196 pass in proto tcp from any to any port www synproxy state
2198 .Sh STATEFUL TRACKING OPTIONS
2199 A number of options related to stateful tracking can be applied on a
2205 support these options, and
2207 must be specified explicitly to apply options to a rule.
2209 .Bl -tag -width xxxx -compact
2210 .It Ar max Aq Ar number
2211 Limits the number of concurrent states the rule may create.
2212 When this limit is reached, further packets that would create
2213 state will not match this rule until existing states time out.
2215 Prevent state changes for states created by this rule from appearing on the
2218 .It Xo Aq Ar timeout
2221 Changes the timeout values used for states created by this rule.
2222 For a list of all valid timeout names, see
2226 Uses a sloppy TCP connection tracker that does not check sequence
2227 numbers at all, which makes insertion and ICMP teardown attacks way
2229 This is intended to be used in situations where one does not see all
2230 packets of a connection, e.g. in asymmetric routing situations.
2231 Cannot be used with modulate or synproxy state.
2234 Multiple options can be specified, separated by commas:
2235 .Bd -literal -offset indent
2236 pass in proto tcp from any to any \e
2237 port www keep state \e
2238 (max 100, source-track rule, max-src-nodes 75, \e
2239 max-src-states 3, tcp.established 60, tcp.closing 5)
2244 keyword is specified, the number of states per source IP is tracked.
2246 .Bl -tag -width xxxx -compact
2247 .It Ar source-track rule
2248 The maximum number of states created by this rule is limited by the rule's
2253 Only state entries created by this particular rule count toward the rule's
2255 .It Ar source-track global
2256 The number of states created by all rules that use this option is limited.
2257 Each rule can specify different
2261 options, however state entries created by any participating rule count towards
2262 each individual rule's limits.
2265 The following limits can be set:
2267 .Bl -tag -width xxxx -compact
2268 .It Ar max-src-nodes Aq Ar number
2269 Limits the maximum number of source addresses which can simultaneously
2270 have state table entries.
2271 .It Ar max-src-states Aq Ar number
2272 Limits the maximum number of simultaneous state entries that a single
2273 source address can create with this rule.
2275 Specify that mid-stream pickups are to be allowed.
2276 The default is to NOT allow mid-stream pickups and implies flags
2277 S/SA for TCP connections.
2278 If pickups are enabled, flags S/SA are not implied
2279 for TCP connections and state can be created for any packet.
2281 The implied flags parameters need not be specified in either case
2282 unless you explicitly wish to override them, which also allows
2283 you to roll-up several protocols into a single rule.
2285 Certain validations are disabled when mid-stream pickups occur.
2286 For example, the window scaling options are not known for
2287 TCP pickups and sequence space comparisons must be disabled.
2289 This does not effect state representing fully quantified
2290 connections (for which the SYN/SYN-ACK passed through the routing
2292 Those connections continue to be fully validated.
2294 Specify that mid-stream pickups are to be allowed, but unconditionally
2295 disables sequence space checks even if full state is available.
2297 Specify that mid-stream pickups are not to be allowed.
2299 default and this keyword does not normally need to be specified.
2300 However, if you are concerned about rule set portability then
2301 specifying this keyword will at least result in an error from
2303 if it doesn't understand the feature.
2304 TCP flags of S/SA are implied
2305 and do not need to explicitly specified.
2308 For stateful TCP connections, limits on established connections (connections
2309 which have completed the TCP 3-way handshake) can also be enforced
2312 .Bl -tag -width xxxx -compact
2313 .It Ar max-src-conn Aq Ar number
2314 Limits the maximum number of simultaneous TCP connections which have
2315 completed the 3-way handshake that a single host can make.
2316 .It Xo Ar max-src-conn-rate Aq Ar number
2319 Limit the rate of new connections over a time interval.
2320 The connection rate is an approximation calculated as a moving average.
2323 Because the 3-way handshake ensures that the source address is not being
2324 spoofed, more aggressive action can be taken based on these limits.
2326 .Ar overload Aq Ar table
2327 state option, source IP addresses which hit either of the limits on
2328 established connections will be added to the named table.
2329 This table can be used in the ruleset to block further activity from
2330 the offending host, redirect it to a tarpit process, or restrict its
2335 keyword kills all states created by the matching rule which originate
2336 from the host which exceeds these limits.
2339 modifier to the flush command kills all states originating from the
2340 offending host, regardless of which rule created the state.
2342 For example, the following rules will protect the webserver against
2343 hosts making more than 100 connections in 10 seconds.
2344 Any host which connects faster than this rate will have its address added
2347 table and have all states originating from it flushed.
2348 Any new packets arriving from this host will be dropped unconditionally
2350 .Bd -literal -offset indent
2351 block quick from \*(Ltbad_hosts\*(Gt
2352 pass in on $ext_if proto tcp to $webserver port www keep state \e
2353 (max-src-conn-rate 100/10, overload \*(Ltbad_hosts\*(Gt flush global)
2355 .Sh OPERATING SYSTEM FINGERPRINTING
2356 Passive OS Fingerprinting is a mechanism to inspect nuances of a TCP
2357 connection's initial SYN packet and guess at the host's operating system.
2358 Unfortunately these nuances are easily spoofed by an attacker so the
2359 fingerprint is not useful in making security decisions.
2360 But the fingerprint is typically accurate enough to make policy decisions
2363 The fingerprints may be specified by operating system class, by
2364 version, or by subtype/patchlevel.
2365 The class of an operating system is typically the vendor or genre
2371 The version of the oldest available
2373 release on the main FTP site
2374 would be 2.6 and the fingerprint would be written
2376 .Dl \&"OpenBSD 2.6\&"
2378 The subtype of an operating system is typically used to describe the
2379 patchlevel if that patch led to changes in the TCP stack behavior.
2382 the only subtype is for a fingerprint that was
2385 scrub option and would be specified as
2387 .Dl \&"OpenBSD 3.3 no-df\&"
2389 Fingerprints for most popular operating systems are provided by
2393 is running, a complete list of known operating system fingerprints may
2394 be listed by running:
2398 Filter rules can enforce policy at any level of operating system specification
2399 assuming a fingerprint is present.
2400 Policy could limit traffic to approved operating systems or even ban traffic
2401 from hosts that aren't at the latest service pack.
2405 class can also be used as the fingerprint which will match packets for
2406 which no operating system fingerprint is known.
2409 .Bd -literal -offset indent
2410 pass out proto tcp from any os OpenBSD
2411 block out proto tcp from any os Doors
2412 block out proto tcp from any os "Doors PT"
2413 block out proto tcp from any os "Doors PT SP3"
2414 block out from any os "unknown"
2415 pass on lo0 proto tcp from any os "OpenBSD 3.3 lo0"
2418 Operating system fingerprinting is limited only to the TCP SYN packet.
2419 This means that it will not work on other protocols and will not match
2420 a currently established connection.
2422 Caveat: operating system fingerprints are occasionally wrong.
2423 There are three problems: an attacker can trivially craft his packets to
2424 appear as any operating system he chooses;
2425 an operating system patch could change the stack behavior and no fingerprints
2426 will match it until the database is updated;
2427 and multiple operating systems may have the same fingerprint.
2428 .Sh BLOCKING SPOOFED TRAFFIC
2429 "Spoofing" is the faking of IP addresses, typically for malicious
2433 directive expands to a set of filter rules which will block all
2434 traffic with a source IP from the network(s) directly connected
2435 to the specified interface(s) from entering the system through
2436 any other interface.
2438 For example, the line
2439 .Bd -literal -offset indent
2444 .Bd -literal -offset indent
2445 block drop in on ! lo0 inet from 127.0.0.1/8 to any
2446 block drop in on ! lo0 inet6 from ::1 to any
2449 For non-loopback interfaces, there are additional rules to block incoming
2450 packets with a source IP address identical to the interface's IP(s).
2451 For example, assuming the interface wi0 had an IP address of 10.0.0.1 and a
2452 netmask of 255.255.255.0,
2454 .Bd -literal -offset indent
2455 antispoof for wi0 inet
2459 .Bd -literal -offset indent
2460 block drop in on ! wi0 inet from 10.0.0.0/24 to any
2461 block drop in inet from 10.0.0.1 to any
2464 Caveat: Rules created by the
2466 directive interfere with packets sent over loopback interfaces
2468 One should pass these explicitly.
2469 .Sh FRAGMENT HANDLING
2470 The size of IP datagrams (packets) can be significantly larger than the
2471 maximum transmission unit (MTU) of the network.
2472 In cases when it is necessary or more efficient to send such large packets,
2473 the large packet will be fragmented into many smaller packets that will each
2475 Unfortunately for a firewalling device, only the first logical fragment will
2476 contain the necessary header information for the subprotocol that allows
2478 to filter on things such as TCP ports or to perform NAT.
2482 rules as described in
2483 .Sx TRAFFIC NORMALIZATION
2484 above, there are three options for handling fragments in the packet filter.
2486 One alternative is to filter individual fragments with filter rules.
2489 rule applies to a fragment, it is passed to the filter.
2490 Filter rules with matching IP header parameters decide whether the
2491 fragment is passed or blocked, in the same way as complete packets
2493 Without reassembly, fragments can only be filtered based on IP header
2494 fields (source/destination address, protocol), since subprotocol header
2495 fields are not available (TCP/UDP port numbers, ICMP code/type).
2498 option can be used to restrict filter rules to apply only to
2499 fragments, but not complete packets.
2500 Filter rules without the
2502 option still apply to fragments, if they only specify IP header fields.
2503 For instance, the rule
2504 .Bd -literal -offset indent
2505 pass in proto tcp from any to any port 80
2508 never applies to a fragment, even if the fragment is part of a TCP
2509 packet with destination port 80, because without reassembly this information
2510 is not available for each fragment.
2511 This also means that fragments cannot create new or match existing
2512 state table entries, which makes stateful filtering and address
2513 translation (NAT, redirection) for fragments impossible.
2515 It's also possible to reassemble only certain fragments by specifying
2516 source or destination addresses or protocols as parameters in
2520 In most cases, the benefits of reassembly outweigh the additional
2521 memory cost, and it's recommended to use
2524 all fragments via the
2525 .Ar fragment reassemble
2528 The memory allocated for fragment caching can be limited using
2530 Once this limit is reached, fragments that would have to be cached
2531 are dropped until other entries time out.
2532 The timeout value can also be adjusted.
2534 Currently, only IPv4 fragments are supported and IPv6 fragments
2535 are blocked unconditionally.
2537 Besides the main ruleset,
2539 can load rulesets into
2544 is a container that can hold rules, address tables, and other anchors.
2548 has a name which specifies the path where
2550 can be used to access the anchor to perform operations on it, such as
2551 attaching child anchors to it or loading rules into it.
2552 Anchors may be nested, with components separated by
2554 characters, similar to how file system hierarchies are laid out.
2555 The main ruleset is actually the default anchor, so filter and
2556 translation rules, for example, may also be contained in any anchor.
2558 An anchor can reference another
2561 using the following kinds
2563 .Bl -tag -width xxxx
2564 .It Ar nat-anchor Aq Ar name
2567 rules in the specified
2569 .It Ar rdr-anchor Aq Ar name
2572 rules in the specified
2574 .It Ar binat-anchor Aq Ar name
2577 rules in the specified
2579 .It Ar anchor Aq Ar name
2580 Evaluates the filter rules in the specified
2582 .It Xo Ar load anchor
2586 Loads the rules from the specified file into the
2591 When evaluation of the main ruleset reaches an
2595 will proceed to evaluate all rules specified in that anchor.
2597 Matching filter and translation rules marked with the
2599 option are final and abort the evaluation of the rules in other
2600 anchors and the main ruleset.
2603 itself is marked with the
2606 ruleset evaluation will terminate when the anchor is exited if the packet is
2607 matched by any rule within the anchor.
2610 rules are evaluated relative to the anchor in which they are contained.
2613 rules specified in the main ruleset will reference anchor
2614 attachment points underneath the main ruleset, and
2616 rules specified in a file loaded from a
2618 rule will be attached under that anchor point.
2620 Rules may be contained in
2622 attachment points which do not contain any rules when the main ruleset
2623 is loaded, and later such anchors can be manipulated through
2625 without reloading the main ruleset or other anchors.
2627 .Bd -literal -offset indent
2629 block on $ext_if all
2631 pass out on $ext_if all
2632 pass in on $ext_if proto tcp from any \e
2633 to $ext_if port smtp
2636 blocks all packets on the external interface by default, then evaluates
2639 named "spam", and finally passes all outgoing connections and
2640 incoming connections to port 25.
2641 .Bd -literal -offset indent
2642 # echo \&"block in quick from 1.2.3.4 to any\&" \&| \e
2646 This loads a single rule into the
2648 which blocks all packets from a specific address.
2650 The anchor can also be populated by adding a
2655 .Bd -literal -offset indent
2657 load anchor spam from "/etc/pf-spam.conf"
2664 it will also load all the rules from the file
2665 .Pa /etc/pf-spam.conf
2670 rules can specify packet filtering parameters using the same syntax as
2672 When parameters are used, the
2674 rule is only evaluated for matching packets.
2675 This allows conditional evaluation of anchors, like:
2676 .Bd -literal -offset indent
2677 block on $ext_if all
2678 anchor spam proto tcp from any to any port smtp
2679 pass out on $ext_if all
2680 pass in on $ext_if proto tcp from any to $ext_if port smtp
2685 spam are only evaluated for
2687 packets with destination port 25.
2689 .Bd -literal -offset indent
2690 # echo \&"block in quick from 1.2.3.4 to any" \&| \e
2694 will only block connections from 1.2.3.4 to port 25.
2696 Anchors may end with the asterisk
2698 character, which signifies that all anchors attached at that point
2699 should be evaluated in the alphabetical ordering of their anchor name.
2701 .Bd -literal -offset indent
2705 will evaluate each rule in each anchor attached to the
2708 Note that it will only evaluate anchors that are directly attached to the
2710 anchor, and will not descend to evaluate anchors recursively.
2712 Since anchors are evaluated relative to the anchor in which they are
2713 contained, there is a mechanism for accessing the parent and ancestor
2714 anchors of a given anchor.
2715 Similar to file system path name resolution, if the sequence
2717 appears as an anchor path component, the parent anchor of the current
2718 anchor in the path evaluation at that point will become the new current
2720 As an example, consider the following:
2721 .Bd -literal -offset indent
2722 # echo ' anchor "spam/allowed" ' | pfctl -f -
2723 # echo -e ' anchor "../banned" \en pass' | \e
2724 pfctl -a spam/allowed -f -
2727 Evaluation of the main ruleset will lead into the
2729 anchor, which will evaluate the rules in the
2731 anchor, if any, before finally evaluating the
2737 can also be loaded inline in the ruleset within a brace ('{' '}') delimited
2739 Brace delimited blocks may contain rules or other brace-delimited blocks.
2740 When anchors are loaded this way the anchor name becomes optional.
2741 .Bd -literal -offset indent
2742 anchor "external" on egress {
2745 pass proto tcp from any to port { 25, 80, 443 }
2747 pass in proto tcp to any port 22
2751 Since the parser specification for anchor names is a string, any
2752 reference to an anchor name containing
2754 characters will require double quote
2756 characters around the anchor name.
2757 .Sh TRANSLATION EXAMPLES
2758 This example maps incoming requests on port 80 to port 8080, on
2759 which a daemon is running (because, for example, it is not run as root,
2760 and therefore lacks permission to bind to port 80).
2762 # use a macro for the interface name, so it can be changed easily
2765 # map daemon on 8080 to appear to be on 80
2766 rdr on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 port 8080
2771 modifier is given, packets matching the translation rule are passed without
2772 inspecting the filter rules:
2774 rdr pass on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 \e
2778 In the example below, vlan12 is configured as 192.168.168.1;
2779 the machine translates all packets coming from 192.168.168.0/24 to 204.92.77.111
2780 when they are going out any interface except vlan12.
2781 This has the net effect of making traffic from the 192.168.168.0/24
2782 network appear as though it is the Internet routable address
2783 204.92.77.111 to nodes behind any interface on the router except
2784 for the nodes on vlan12.
2785 (Thus, 192.168.168.1 can talk to the 192.168.168.0/24 nodes.)
2787 nat on ! vlan12 from 192.168.168.0/24 to any -\*(Gt 204.92.77.111
2790 In the example below, the machine sits between a fake internal 144.19.74.*
2791 network, and a routable external IP of 204.92.77.100.
2794 rule excludes protocol AH from being translated.
2797 no nat on $ext_if proto ah from 144.19.74.0/24 to any
2798 nat on $ext_if from 144.19.74.0/24 to any -\*(Gt 204.92.77.100
2801 In the example below, packets bound for one specific server, as well as those
2802 generated by the sysadmins are not proxied; all other connections are.
2805 no rdr on $int_if proto { tcp, udp } from any to $server port 80
2806 no rdr on $int_if proto { tcp, udp } from $sysadmins to any port 80
2807 rdr on $int_if proto { tcp, udp } from any to any port 80 -\*(Gt 127.0.0.1 \e
2811 This longer example uses both a NAT and a redirection.
2812 The external interface has the address 157.161.48.183.
2813 On localhost, we are running
2815 waiting for FTP sessions to be redirected to it.
2816 The three mandatory anchors for
2818 are omitted from this example; see the
2823 # Translate outgoing packets' source addresses (any protocol).
2824 # In this case, any address but the gateway's external address is mapped.
2825 nat on $ext_if inet from ! ($ext_if) to any -\*(Gt ($ext_if)
2828 # Map outgoing packets' source port to an assigned proxy port instead of
2829 # an arbitrary port.
2830 # In this case, proxy outgoing isakmp with port 500 on the gateway.
2831 nat on $ext_if inet proto udp from any port = isakmp to any -\*(Gt ($ext_if) \e
2835 # Translate outgoing packets' source address (any protocol).
2836 # Translate incoming packets' destination address to an internal machine
2838 binat on $ext_if from 10.1.2.150 to any -\*(Gt $ext_if
2841 # Translate incoming packets' destination addresses.
2842 # As an example, redirect a TCP and UDP port to an internal machine.
2843 rdr on $ext_if inet proto tcp from any to ($ext_if) port 8080 \e
2844 -\*(Gt 10.1.2.151 port 22
2845 rdr on $ext_if inet proto udp from any to ($ext_if) port 8080 \e
2846 -\*(Gt 10.1.2.151 port 53
2849 # Translate outgoing ftp control connections to send them to localhost
2850 # for proxying with ftp-proxy(8) running on port 8021.
2851 rdr on $int_if proto tcp from any to any port 21 -\*(Gt 127.0.0.1 port 8021
2854 In this example, a NAT gateway is set up to translate internal addresses
2855 using a pool of public addresses (192.0.2.16/28) and to redirect
2856 incoming web server connections to a group of web servers on the internal
2860 # Translate outgoing packets' source addresses using an address pool.
2861 # A given source address is always translated to the same pool address by
2862 # using the source-hash keyword.
2863 nat on $ext_if inet from any to any -\*(Gt 192.0.2.16/28 source-hash
2866 # Translate incoming web server connections to a group of web servers on
2867 # the internal network.
2868 rdr on $ext_if proto tcp from any to any port 80 \e
2869 -\*(Gt { 10.1.2.155, 10.1.2.160, 10.1.2.161 } round-robin
2873 # The external interface is kue0
2874 # (157.161.48.183, the only routable address)
2875 # and the private network is 10.0.0.0/8, for which we are doing NAT.
2877 # use a macro for the interface name, so it can be changed easily
2880 # normalize all incoming traffic
2881 scrub in on $ext_if all fragment reassemble
2883 # block and log everything by default
2884 block return log on $ext_if all
2886 # block anything coming from source we have no back routes for
2887 block in from no-route to any
2889 # block packets whose ingress interface does not match the one in
2890 # the route back to their source address
2891 block in from urpf-failed to any
2893 # block and log outgoing packets that do not have our address as source,
2894 # they are either spoofed or something is misconfigured (NAT disabled,
2895 # for instance), we want to be nice and do not send out garbage.
2896 block out log quick on $ext_if from ! 157.161.48.183 to any
2898 # silently drop broadcasts (cable modem noise)
2899 block in quick on $ext_if from any to 255.255.255.255
2901 # block and log incoming packets from reserved address space and invalid
2902 # addresses, they are either spoofed or misconfigured, we cannot reply to
2903 # them anyway (hence, no return-rst).
2904 block in log quick on $ext_if from { 10.0.0.0/8, 172.16.0.0/12, \e
2905 192.168.0.0/16, 255.255.255.255/32 } to any
2909 # pass out/in certain ICMP queries and keep state (ping)
2910 # state matching is done on host addresses and ICMP id (not type/code),
2911 # so replies (like 0/0 for 8/0) will match queries
2912 # ICMP error messages (which always refer to a TCP/UDP packet) are
2913 # handled by the TCP/UDP states
2914 pass on $ext_if inet proto icmp all icmp-type 8 code 0
2918 # pass out all UDP connections and keep state
2919 pass out on $ext_if proto udp all
2921 # pass in certain UDP connections and keep state (DNS)
2922 pass in on $ext_if proto udp from any to any port domain
2926 # pass out all TCP connections and modulate state
2927 pass out on $ext_if proto tcp all modulate state
2929 # pass in certain TCP connections and keep state (SSH, SMTP, DNS, IDENT)
2930 pass in on $ext_if proto tcp from any to any port { ssh, smtp, domain, \e
2933 # Do not allow Windows 9x SMTP connections since they are typically
2934 # a viral worm. Alternately we could limit these OSes to 1 connection each.
2935 block in on $ext_if proto tcp from any os {"Windows 95", "Windows 98"} \e
2939 # pass in/out all IPv6 traffic: note that we have to enable this in two
2940 # different ways, on both our physical interface and our tunnel
2941 pass quick on gif0 inet6
2942 pass quick on $ext_if proto ipv6
2944 # Using the pickup options to keep/modulate/synproxy state
2946 # no-pickups (default) Do not allow connections to be picked up in the
2947 # middle. Implies flags S/SA (the 'no-pickups' option need
2948 # not be specified, it is the default).
2950 # pickups Allow connections to be picked up in the middle, even if
2951 # no window scaling information is known. Such connections
2952 # will disable sequence space checks. Implies no flag
2955 # hash-only Do not fail packets on sequence space checks. Implies no
2956 # flag restrictions.
2958 pass in on $ext_if proto tcp ... keep state (no-pickups)
2959 pass in on $ext_if proto tcp ... keep state (pickups)
2960 pass in on $ext_if proto tcp ... keep state (hash-only)
2964 # three interfaces: $int_if, $ext_if, and $wifi_if (wireless). NAT is
2965 # being done on $ext_if for all outgoing packets. tag packets in on
2966 # $int_if and pass those tagged packets out on $ext_if. all other
2967 # outgoing packets (i.e., packets from the wireless network) are only
2968 # permitted to access port 80.
2970 pass in on $int_if from any to any tag INTNET
2971 pass in on $wifi_if from any to any
2973 block out on $ext_if from any to any
2974 pass out quick on $ext_if tagged INTNET
2975 pass out on $ext_if proto tcp from any to any port 80
2977 # tag incoming packets as they are redirected to spamd(8). use the tag
2978 # to pass those packets through the packet filter.
2980 rdr on $ext_if inet proto tcp from \*(Ltspammers\*(Gt to port smtp \e
2981 tag SPAMD -\*(Gt 127.0.0.1 port spamd
2984 pass in on $ext_if inet proto tcp tagged SPAMD
2991 line = ( option | pf-rule | nat-rule | binat-rule | rdr-rule |
2992 antispoof-rule | altq-rule | queue-rule | trans-anchors |
2993 anchor-rule | anchor-close | load-anchor | table-rule |
2996 option = "set" ( [ "timeout" ( timeout | "{" timeout-list "}" ) ] |
2997 [ "ruleset-optimization" [ "none" | "basic" | "profile" ] ] |
2998 [ "optimization" [ "default" | "normal" |
2999 "high-latency" | "satellite" |
3000 "aggressive" | "conservative" ] ]
3001 [ "limit" ( limit-item | "{" limit-list "}" ) ] |
3002 [ "loginterface" ( interface-name | "none" ) ] |
3003 [ "block-policy" ( "drop" | "return" ) ] |
3004 [ "keep-policy" keep ] |
3005 [ "state-policy" ( "if-bound" | "floating" ) ]
3006 [ "require-order" ( "yes" | "no" ) ]
3007 [ "fingerprints" filename ] |
3008 [ "skip on" ifspec ] |
3009 [ "debug" ( "none" | "urgent" | "misc" | "loud" ) ] )
3011 pf-rule = action [ ( "in" | "out" ) ]
3012 [ "log" [ "(" logopts ")"] ] [ "quick" ]
3013 [ "on" ifspec ] [ "fastroute" | route ] [ af ] [ protospec ]
3014 hosts [ filteropt-list ]
3016 logopts = logopt [ "," logopts ]
3017 logopt = "all" | "user" | "to" interface-name
3019 filteropt-list = filteropt-list filteropt | filteropt
3020 filteropt = user | group | flags | icmp-type | icmp6-type | tos |
3021 keep | "fragment" | "no-df" | "min-ttl" number |
3022 "max-mss" number | "random-id" | "reassemble tcp" |
3023 fragmentation | "allow-opts" |
3024 "label" string | "tag" string | [ ! ] "tagged" string |
3025 "queue" ( string | "(" string [ [ "," ] string ] ")" ) |
3026 "probability" number"%"
3028 keep = "no" "state" |
3029 ( "keep" | "modulate" | "synproxy" ) "state"
3030 [ "(" state-opts ")" ]
3032 nat-rule = [ "no" ] "nat" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
3033 [ "on" ifspec ] [ af ]
3034 [ protospec ] hosts [ "tag" string ] [ "tagged" string ]
3035 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" )
3036 [ portspec ] [ pooltype ] [ "static-port" ] ]
3038 binat-rule = [ "no" ] "binat" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
3039 [ "on" interface-name ] [ af ]
3040 [ "proto" ( proto-name | proto-number ) ]
3041 "from" address [ "/" mask-bits ] "to" ipspec
3042 [ "tag" string ] [ "tagged" string ]
3043 [ "-\*(Gt" address [ "/" mask-bits ] ]
3045 rdr-rule = [ "no" ] "rdr" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
3046 [ "on" ifspec ] [ af ]
3047 [ protospec ] hosts [ "tag" string ] [ "tagged" string ]
3048 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" )
3049 [ portspec ] [ pooltype ] ]
3051 antispoof-rule = "antispoof" [ "log" ] [ "quick" ]
3052 "for" ifspec [ af ] [ "label" string ]
3054 table-rule = "table" "\*(Lt" string "\*(Gt" [ tableopts-list ]
3055 tableopts-list = tableopts-list tableopts | tableopts
3056 tableopts = "persist" | "const" | "counters" | "file" string |
3057 "{" [ tableaddr-list ] "}"
3058 tableaddr-list = tableaddr-list [ "," ] tableaddr-spec | tableaddr-spec
3059 tableaddr-spec = [ "!" ] tableaddr [ "/" mask-bits ]
3060 tableaddr = hostname | ifspec | "self" |
3061 ipv4-dotted-quad | ipv6-coloned-hex
3063 altq-rule = "altq on" interface-name queueopts-list
3065 queue-rule = "queue" string [ "on" interface-name ] queueopts-list
3068 anchor-rule = "anchor" [ string ] [ ( "in" | "out" ) ] [ "on" ifspec ]
3069 [ af ] [ "proto" ] [ protospec ] [ hosts ]
3071 trans-anchors = ( "nat-anchor" | "rdr-anchor" | "binat-anchor" ) string
3072 [ "on" ifspec ] [ af ] [ "proto" ] [ protospec ] [ hosts ]
3074 load-anchor = "load anchor" string "from" filename
3076 queueopts-list = queueopts-list queueopts | queueopts
3077 queueopts = [ "bandwidth" bandwidth-spec ] |
3078 [ "qlimit" number ] | [ "tbrsize" number ] |
3079 [ "priority" number ] | [ schedulers ]
3080 schedulers = ( cbq-def | hfsc-def | priq-def | fairq-def )
3081 bandwidth-spec = "number" ( "b" | "Kb" | "Mb" | "Gb" | "%" )
3083 action = "pass" | "block" [ return ] | [ "no" ] "scrub"
3084 return = "drop" | "return" | "return-rst" [ "( ttl" number ")" ] |
3085 "return-icmp" [ "(" icmpcode [ [ "," ] icmp6code ] ")" ] |
3086 "return-icmp6" [ "(" icmp6code ")" ]
3087 icmpcode = ( icmp-code-name | icmp-code-number )
3088 icmp6code = ( icmp6-code-name | icmp6-code-number )
3090 ifspec = ( [ "!" ] ( interface-name | interface-group ) ) |
3091 "{" interface-list "}"
3092 interface-list = [ "!" ] ( interface-name | interface-group )
3093 [ [ "," ] interface-list ]
3094 route = ( "route-to" | "reply-to" | "dup-to" )
3095 ( routehost | "{" routehost-list "}" )
3097 af = "inet" | "inet6"
3099 protospec = "proto" ( proto-name | proto-number |
3100 "{" proto-list "}" )
3101 proto-list = ( proto-name | proto-number ) [ [ "," ] proto-list ]
3104 "from" ( "any" | "no-route" | "urpf-failed" | "self" | host |
3105 "{" host-list "}" | "route" string ) [ port ] [ os ]
3106 "to" ( "any" | "no-route" | "self" | host |
3107 "{" host-list "}" | "route" string ) [ port ]
3109 ipspec = "any" | host | "{" host-list "}"
3110 host = [ "!" ] ( address [ "/" mask-bits ] | "\*(Lt" string "\*(Gt" )
3111 redirhost = address [ "/" mask-bits ]
3112 routehost = "(" interface-name [ address [ "/" mask-bits ] ] ")"
3113 address = ( interface-name | interface-group |
3114 "(" ( interface-name | interface-group ) ")" |
3115 hostname | ipv4-dotted-quad | ipv6-coloned-hex )
3116 host-list = host [ [ "," ] host-list ]
3117 redirhost-list = redirhost [ [ "," ] redirhost-list ]
3118 routehost-list = routehost [ [ "," ] routehost-list ]
3120 port = "port" ( unary-op | binary-op | "{" op-list "}" )
3121 portspec = "port" ( number | name ) [ ":" ( "*" | number | name ) ]
3122 os = "os" ( os-name | "{" os-list "}" )
3123 user = "user" ( unary-op | binary-op | "{" op-list "}" )
3124 group = "group" ( unary-op | binary-op | "{" op-list "}" )
3126 unary-op = [ "=" | "!=" | "\*(Lt" | "\*(Le" | "\*(Gt" | "\*(Ge" ]
3128 binary-op = number ( "\*(Lt\*(Gt" | "\*(Gt\*(Lt" | ":" ) number
3129 op-list = ( unary-op | binary-op ) [ [ "," ] op-list ]
3131 os-name = operating-system-name
3132 os-list = os-name [ [ "," ] os-list ]
3134 flags = "flags" ( [ flag-set ] "/" flag-set | "any" )
3135 flag-set = [ "F" ] [ "S" ] [ "R" ] [ "P" ] [ "A" ] [ "U" ] [ "E" ]
3138 icmp-type = "icmp-type" ( icmp-type-code | "{" icmp-list "}" )
3139 icmp6-type = "icmp6-type" ( icmp-type-code | "{" icmp-list "}" )
3140 icmp-type-code = ( icmp-type-name | icmp-type-number )
3141 [ "code" ( icmp-code-name | icmp-code-number ) ]
3142 icmp-list = icmp-type-code [ [ "," ] icmp-list ]
3144 tos = ( "lowdelay" | "throughput" | "reliability" |
3147 state-opts = state-opt [ [ "," ] state-opts ]
3148 state-opt = "max" number | "no-sync" | timeout |
3149 "source-track" [ "rule" | "global" ] |
3150 "max-src-nodes" number | "max-src-states" number |
3151 "max-src-conn" number |
3152 "max-src-conn-rate" number "/" number |
3153 "overload" "\*(Lt" string "\*(Gt" [ "flush" ] |
3154 "if-bound" | "floating" |
3155 "pickups" | "no-pickups" | "hash-only"
3157 fragmentation = [ "fragment reassemble" | "fragment crop" |
3158 "fragment drop-ovl" ]
3160 timeout-list = timeout [ [ "," ] timeout-list ]
3161 timeout = ( "tcp.first" | "tcp.opening" | "tcp.established" |
3162 "tcp.closing" | "tcp.finwait" | "tcp.closed" |
3163 "udp.first" | "udp.single" | "udp.multiple" |
3164 "icmp.first" | "icmp.error" |
3165 "other.first" | "other.single" | "other.multiple" |
3166 "frag" | "interval" | "src.track" |
3167 "adaptive.start" | "adaptive.end" ) number
3169 limit-list = limit-item [ [ "," ] limit-list ]
3170 limit-item = ( "states" | "frags" | "src-nodes" ) number
3172 pooltype = ( "bitmask" | "random" |
3173 "source-hash" [ hex-key | string-key ] |
3174 "round-robin" ) [ sticky-address ]
3176 subqueue = string | "{" queue-list "}"
3177 queue-list = string [ [ "," ] string ]
3179 cbq-def = "cbq" [ "(" cbq-opts ")" ]
3180 priq-def = "priq" [ "(" priq-opts ")" ]
3181 hfsc-def = "hfsc" [ "(" hfsc-opts ")" ]
3182 fairq-def = "fairq" [ "(" fairq-opts ")" ]
3184 cbq-opts = cbq-opt [ [ "," ] cbq-opts ]
3185 priq-opts = priq-opt [ [ "," ] priq-opts ]
3186 hfsc-opts = hfsc-opt [ [ "," ] hfsc-opts ]
3187 fairq-opts = fairq-opt [ [ "," ] fairq-opts ]
3189 cbq-opt = "default" | "borrow" | "red" | "ecn" | "rio"
3190 priq-opt = "default" | "red" | "ecn" | "rio"
3191 hfsc-opt = "default" | "red" | "ecn" | "rio" |
3192 linkshare-sc | realtime-sc | upperlimit-sc
3193 fairq-opt = "default" | "red" | "ecn" | "rio" |
3194 "buckets" number | "hogs" number | linkshare-sc
3196 linkshare-sc = "linkshare" sc-spec
3197 realtime-sc = "realtime" sc-spec
3198 upperlimit-sc = "upperlimit" sc-spec
3199 sc-spec = ( bandwidth-spec |
3200 "(" bandwidth-spec number bandwidth-spec ")" )
3201 include = "include" filename
3204 .Bl -tag -width ".Pa /usr/share/examples/pf" -compact
3208 Default location of the ruleset file.
3210 Default location of OS fingerprints.
3211 .It Pa /etc/protocols
3212 Protocol name database.
3213 .It Pa /etc/services
3214 Service name database.
3215 .It Pa /usr/share/examples/pf
3241 file format first appeared in
projects / dragonfly.git / blob