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36 .Nd packet filter configuration file
40 packet filter modifies, drops or passes packets according to rules or
41 definitions specified in
44 There are seven types of statements in
48 User-defined variables may be defined and used later, simplifying
49 the configuration file.
50 Macros must be defined before they are referenced in
53 Tables provide a mechanism for increasing the performance and flexibility of
54 rules with large numbers of source or destination addresses.
56 Options tune the behaviour of the packet filtering engine.
57 .It Cm Traffic Normalization Li (e.g. Em scrub )
58 Traffic normalization protects internal machines against inconsistencies
59 in Internet protocols and implementations.
61 Queueing provides rule-based bandwidth control.
62 .It Cm Translation Li (Various forms of NAT)
63 Translation rules specify how addresses are to be mapped or redirected to
65 .It Cm Packet Filtering
66 Packet filtering provides rule-based blocking or passing of packets.
73 the types of statements should be grouped and appear in
75 in the order shown above, as this matches the operation of the underlying
76 packet filtering engine.
79 enforces this order (see
83 Comments can be put anywhere in the file using a hash mark
85 and extend to the end of the current line.
87 Additional configuration files can be included with the
90 .Bd -literal -offset indent
91 include "/etc/pf/sub.filter.conf"
94 Macros can be defined that will later be expanded in context.
95 Macro names must start with a letter, and may contain letters, digits
97 Macro names may not be reserved words (for example
101 Macros are not expanded inside quotes.
104 .Bd -literal -offset indent
106 all_ifs = \&"{\&" $ext_if lo0 \&"}\&"
107 pass out on $ext_if from any to any
108 pass in on $ext_if proto tcp from any to any port 25
111 Tables are named structures which can hold a collection of addresses and
113 Lookups against tables in
115 are relatively fast, making a single rule with tables much more efficient,
117 processor usage and memory consumption, than a large number of rules which
118 differ only in IP address (either created explicitly or automatically by rule
121 Tables can be used as the source or destination of filter rules,
125 translation rules such as
129 (see below for details on the various rule types).
130 Tables can also be used for the redirect address of
134 rules and in the routing options of filter rules, but only for
138 Tables can be defined with any of the following
141 As with macros, reserved words may not be used as table names.
142 .Bl -tag -width "manually"
144 Persistent tables can be manually created with the
150 before or after the ruleset has been loaded.
152 Table definitions can be placed directly in this file, and loaded at the
153 same time as other rules are loaded, atomically.
154 Table definitions inside
158 statement, and are especially useful to define non-persistent tables.
159 The contents of a pre-existing table defined without a list of addresses
160 to initialize it is not altered when
163 A table initialized with the empty list,
165 will be cleared on load.
168 Tables may be defined with the following attributes:
169 .Bl -tag -width persist
173 flag forces the kernel to keep the table even when no rules refer to it.
174 If the flag is not set, the kernel will automatically remove the table
175 when the last rule referring to it is flushed.
179 flag prevents the user from altering the contents of the table once it
183 can be used to add or remove addresses from the table at any time, even
190 flag enables per-address packet and byte counters which can be displayed with
192 Note that this feature carries significant memory overhead for large tables.
196 .Bd -literal -offset indent
197 table \*(Ltprivate\*(Gt const { 10/8, 172.16/12, 192.168/16 }
198 table \*(Ltbadhosts\*(Gt persist
199 block on fxp0 from { \*(Ltprivate\*(Gt, \*(Ltbadhosts\*(Gt } to any
202 creates a table called private, to hold RFC 1918 private network
203 blocks, and a table called badhosts, which is initially empty.
204 A filter rule is set up to block all traffic coming from addresses listed in
206 The private table cannot have its contents changed and the badhosts table
207 will exist even when no active filter rules reference it.
208 Addresses may later be added to the badhosts table, so that traffic from
209 these hosts can be blocked by using
210 .Bd -literal -offset indent
211 # pfctl -t badhosts -Tadd 204.92.77.111
214 A table can also be initialized with an address list specified in one or more
215 external files, using the following syntax:
216 .Bd -literal -offset indent
217 table \*(Ltspam\*(Gt persist file \&"/etc/spammers\&" file \&"/etc/openrelays\&"
218 block on fxp0 from \*(Ltspam\*(Gt to any
225 list IP addresses, one per line.
226 Any lines beginning with a # are treated as comments and ignored.
227 In addition to being specified by IP address, hosts may also be
228 specified by their hostname.
229 When the resolver is called to add a hostname to a table,
231 resulting IPv4 and IPv6 addresses are placed into the table.
232 IP addresses can also be entered in a table by specifying a valid interface
233 name, a valid interface group or the
235 keyword, in which case all addresses assigned to the interface(s) will be
239 may be tuned for various situations using the
245 .Bl -tag -width "src.track" -compact
247 Interval between purging expired states and fragments.
249 Seconds before an unassembled fragment is expired.
251 Length of time to retain a source tracking entry after the last state
255 When a packet matches a stateful connection, the seconds to live for the
256 connection will be updated to that of the
258 which corresponds to the connection state.
259 Each packet which matches this state will reset the TTL.
260 Tuning these values may improve the performance of the
261 firewall at the risk of dropping valid idle connections.
263 .Bl -tag -width xxxx -compact
265 The state after the first packet.
267 The state before the destination host ever sends a packet.
268 .It Ar tcp.established
269 The fully established state.
271 The state after the first FIN has been sent.
273 The state after both FINs have been exchanged and the connection is closed.
274 Some hosts (notably web servers on Solaris) send TCP packets even after closing
280 can prevent blocking of such packets.
282 The state after one endpoint sends an RST.
285 ICMP and UDP are handled in a fashion similar to TCP, but with a much more
286 limited set of states:
288 .Bl -tag -width xxxx -compact
290 The state after the first packet.
292 The state if the source host sends more than one packet but the destination
293 host has never sent one back.
295 The state if both hosts have sent packets.
297 The state after the first packet.
299 The state after an ICMP error came back in response to an ICMP packet.
302 Other protocols are handled similarly to UDP:
304 .Bl -tag -width xxxx -compact
307 .It Ar other.multiple
310 Timeout values can be reduced adaptively as the number of state table
313 .Bl -tag -width xxxx -compact
314 .It Ar adaptive.start
315 When the number of state entries exceeds this value, adaptive scaling
317 All timeout values are scaled linearly with factor
318 (adaptive.end - number of states) / (adaptive.end - adaptive.start).
320 When reaching this number of state entries, all timeout values become
321 zero, effectively purging all state entries immediately.
322 This value is used to define the scale factor, it should not actually
323 be reached (set a lower state limit, see below).
326 Adaptive timeouts are enabled by default, with an adaptive.start value
327 equal to 60% of the state limit, and an adaptive.end value equal to
328 120% of the state limit.
329 They can be disabled by setting both adaptive.start and adaptive.end to 0.
331 The adaptive timeout values can be defined both globally and for each rule.
332 When used on a per-rule basis, the values relate to the number of
333 states created by the rule, otherwise to the total number of
337 .Bd -literal -offset indent
338 set timeout tcp.first 120
339 set timeout tcp.established 86400
340 set timeout { adaptive.start 6000, adaptive.end 12000 }
341 set limit states 10000
344 With 9000 state table entries, the timeout values are scaled to 50%
345 (tcp.first 60, tcp.established 43200).
346 .It Ar set loginterface
347 Enable collection of packet and byte count statistics for the given
348 interface or interface group.
349 These statistics can be viewed using
350 .Bd -literal -offset indent
356 collects statistics on the interface named dc0:
357 .Bd -literal -offset indent
361 One can disable the loginterface using:
362 .Bd -literal -offset indent
363 set loginterface none
366 Sets hard limits on the memory pools used by the packet filter.
369 for an explanation of memory pools.
372 .Bd -literal -offset indent
373 set limit states 20000
376 sets the maximum number of entries in the memory pool used by state table
377 entries (generated by
379 rules which do not specify
383 .Bd -literal -offset indent
384 set limit frags 20000
387 sets the maximum number of entries in the memory pool used for fragment
388 reassembly (generated by
392 .Bd -literal -offset indent
393 set limit src-nodes 2000
396 sets the maximum number of entries in the memory pool used for tracking
397 source IP addresses (generated by the
403 .Bd -literal -offset indent
404 set limit tables 1000
405 set limit table-entries 100000
408 sets limits on the memory pools used by tables.
409 The first limits the number of tables that can exist to 1000.
410 The second limits the overall number of addresses that can be stored
413 Various limits can be combined on a single line:
414 .Bd -literal -offset indent
415 set limit { states 20000, frags 20000, src-nodes 2000 }
417 .It Ar set ruleset-optimization
418 .Bl -tag -width xxxxxxxx -compact
420 Disable the ruleset optimizer.
422 Enable basic ruleset optimization.
423 This is the default behaviour.
424 Basic ruleset optimization does four things to improve the
425 performance of ruleset evaluations:
429 remove duplicate rules
431 remove rules that are a subset of another rule
433 combine multiple rules into a table when advantageous
435 re-order the rules to improve evaluation performance
439 Uses the currently loaded ruleset as a feedback profile to tailor the
440 ordering of quick rules to actual network traffic.
443 It is important to note that the ruleset optimizer will modify the ruleset
444 to improve performance.
445 A side effect of the ruleset modification is that per-rule accounting
446 statistics will have different meanings than before.
447 If per-rule accounting is important for billing purposes or whatnot,
448 either the ruleset optimizer should not be used or a label field should
449 be added to all of the accounting rules to act as optimization barriers.
451 Optimization can also be set as a command-line argument to
453 overriding the settings in
455 .It Ar set optimization
456 Optimize state timeouts for one of the following network environments:
458 .Bl -tag -width xxxx -compact
460 A normal network environment.
461 Suitable for almost all networks.
463 A high-latency environment (such as a satellite connection).
468 Aggressively expire connections.
469 This can greatly reduce the memory usage of the firewall at the cost of
470 dropping idle connections early.
472 Extremely conservative settings.
473 Avoid dropping legitimate connections at the
474 expense of greater memory utilization (possibly much greater on a busy
475 network) and slightly increased processor utilization.
479 .Bd -literal -offset indent
480 set optimization aggressive
482 .It Ar set block-policy
485 option sets the default behaviour for the packet
489 .Bl -tag -width xxxxxxxx -compact
491 Packet is silently dropped.
493 A TCP RST is returned for blocked TCP packets,
494 an ICMP UNREACHABLE is returned for blocked UDP packets,
495 and all other packets are silently dropped.
499 .Bd -literal -offset indent
500 set block-policy return
503 .It Ar set fail-policy
506 option sets the behaviour of rules which should pass a packet but were unable to
507 do so. This might happen when a nat or route-to rule uses an empty table as list
508 of targets or if a rule fails to create state or source node.
511 actions are possible:
513 .Bl -tag -width xxxxxxxx -compact
515 Incoming packet is silently dropped.
517 Incoming packet is dropped and TCP RST is returned for TCP packets,
518 an ICMP UNREACHABLE is returned for UDP packets,
519 and no response is sent for other packets.
523 .Bd -literal -offset indent
524 set fail-policy return
527 .It Ar set state-policy
530 option sets the default behaviour for states:
532 .Bl -tag -width group-bound -compact
534 States are bound to interface.
536 States can match packets on any interfaces (the default).
540 .Bd -literal -offset indent
541 set state-policy if-bound
543 .It Ar set state-defaults
546 option sets the state options for states created from rules
550 .Bd -literal -offset indent
551 set state-defaults no-sync
556 identifies this firewall's state table entries to other firewalls
560 By default the hostid is set to a pseudo-random value, however it may be
561 desirable to manually configure it, for example to more easily identify the
562 source of state table entries.
563 .Bd -literal -offset indent
567 The hostid may be specified in either decimal or hexadecimal.
568 .It Ar set require-order
571 enforces an ordering of the statement types in the ruleset to:
577 Setting this option to
579 disables this enforcement.
580 There may be non-trivial and non-obvious implications to an out of
582 Consider carefully before disabling the order enforcement.
583 .It Ar set fingerprints
584 Load fingerprints of known operating systems from the given filename.
585 By default fingerprints of known operating systems are automatically
590 but can be overridden via this option.
591 Setting this option may leave a small period of time where the fingerprints
592 referenced by the currently active ruleset are inconsistent until the new
593 ruleset finishes loading.
597 .Dl set fingerprints \&"/etc/pf.os.devel\&"
598 .It Ar set skip on Aq Ar ifspec
599 List interfaces for which packets should not be filtered.
600 Packets passing in or out on such interfaces are passed as if pf was
601 disabled, i.e. pf does not process them in any way.
602 This can be useful on loopback and other virtual interfaces, when
603 packet filtering is not desired and can have unexpected effects.
610 to one of the following:
612 .Bl -tag -width xxxxxxxxxxxx -compact
614 Don't generate debug messages.
616 Generate debug messages only for serious errors.
618 Generate debug messages for various errors.
620 Generate debug messages for common conditions.
622 .It Ar set keepcounters
623 Preserve rule counters across rule updates.
624 Usually rule counters are reset to zero on every update of the ruleset.
627 set pf will attempt to find matching rules between old and new rulesets
628 and preserve the rule counters.
630 .Sh TRAFFIC NORMALIZATION
631 Traffic normalization is used to sanitize packet content in such
632 a way that there are no ambiguities in packet interpretation on
634 The normalizer does IP fragment reassembly to prevent attacks
635 that confuse intrusion detection systems by sending overlapping
637 Packet normalization is invoked with the
642 has the following options:
647 bit from a matching IP packet.
648 Some operating systems are known to generate fragmented packets with the
651 This is particularly true with NFS.
653 will drop such fragmented
659 Unfortunately some operating systems also generate their
661 packets with a zero IP identification field.
664 bit on packets with a zero IP ID may cause deleterious results if an
665 upstream router later fragments the packet.
668 modifier (see below) is recommended in combination with the
670 modifier to ensure unique IP identifiers.
671 .It Ar min-ttl Aq Ar number
672 Enforces a minimum TTL for matching IP packets.
673 .It Ar max-mss Aq Ar number
674 Enforces a maximum MSS for matching TCP packets.
675 .It Xo Ar set-tos Aq Ar string
676 .No \*(Ba Aq Ar number
680 for matching IP packets.
690 or one of the DiffServ Code Points:
693 .Ar af11 No ... Ar af43 ,
694 .Ar cs0 No ... Ar cs7 ;
695 or as either hex or decimal.
697 Replaces the IP identification field with random values to compensate
698 for predictable values generated by many hosts.
699 This option only applies to packets that are not fragmented
700 after the optional fragment reassembly.
701 .It Ar fragment reassemble
704 rules, fragments can be reassembled by normalization.
705 In this case, fragments are buffered until they form a complete
706 packet, and only the completed packet is passed on to the filter.
707 The advantage is that filter rules have to deal only with complete
708 packets, and can ignore fragments.
709 The drawback of caching fragments is the additional memory cost.
710 .It Ar reassemble tcp
711 Statefully normalizes TCP connections.
712 .Ar scrub reassemble tcp
713 rules may not have the direction (in/out) specified.
715 performs the following normalizations:
717 .Bl -tag -width timeout -compact
719 Neither side of the connection is allowed to reduce their IP TTL.
720 An attacker may send a packet such that it reaches the firewall, affects
721 the firewall state, and expires before reaching the destination host.
723 will raise the TTL of all packets back up to the highest value seen on
725 .It timestamp modulation
726 Modern TCP stacks will send a timestamp on every TCP packet and echo
727 the other endpoint's timestamp back to them.
728 Many operating systems will merely start the timestamp at zero when
729 first booted, and increment it several times a second.
730 The uptime of the host can be deduced by reading the timestamp and multiplying
732 Also observing several different timestamps can be used to count hosts
734 And spoofing TCP packets into a connection requires knowing or guessing
736 Timestamps merely need to be monotonically increasing and not derived off a
741 to modulate the TCP timestamps with a random number.
742 .It extended PAWS checks
743 There is a problem with TCP on long fat pipes, in that a packet might get
744 delayed for longer than it takes the connection to wrap its 32-bit sequence
746 In such an occurrence, the old packet would be indistinguishable from a
747 new packet and would be accepted as such.
748 The solution to this is called PAWS: Protection Against Wrapped Sequence
750 It protects against it by making sure the timestamp on each packet does
753 also makes sure the timestamp on the packet does not go forward more
757 artificially extends the security of TCP sequence numbers by 10 to 18
758 bits when the host uses appropriately randomized timestamps, since a
759 blind attacker would have to guess the timestamp as well.
764 .Bd -literal -offset indent
765 scrub in on $ext_if all fragment reassemble
770 option prefixed to a scrub rule causes matching packets to remain unscrubbed,
771 much in the same way as
773 works in the packet filter (see below).
774 This mechanism should be used when it is necessary to exclude specific packets
775 from broader scrub rules.
777 The ALTQ system is currently not available in the GENERIC kernel nor as
779 In order to use the herein after called queueing options one has to use a
783 to learn about the related kernel options.
785 Packets can be assigned to queues for the purpose of bandwidth
787 At least two declarations are required to configure queues, and later
788 any packet filtering rule can reference the defined queues by name.
789 During the filtering component of
793 name is where any packets from
795 rules will be queued, while for
797 rules it specifies where any resulting ICMP or TCP RST
798 packets should be queued.
801 defines the algorithm used to decide which packets get delayed, dropped, or
802 sent out immediately.
808 Class Based Queueing.
810 attached to an interface build a tree, thus each
812 can have further child
814 Each queue can have a
820 mainly controls the time packets take to get sent out, while
822 has primarily effects on throughput.
824 achieves both partitioning and sharing of link bandwidth
825 by hierarchically structured classes.
826 Each class has its own
828 and is assigned its share of
830 A child class can borrow bandwidth from its parent class
831 as long as excess bandwidth is available
838 are flat attached to the interface, thus,
840 cannot have further child
846 assigned, ranging from 0 to 15.
853 Hierarchical Fair Service Curve.
855 attached to an interface build a tree, thus each
857 can have further child
859 Each queue can have a
865 mainly controls the time packets take to get sent out, while
867 primarily affects throughput.
869 supports both link-sharing and guaranteed real-time services.
870 It employs a service curve based QoS model,
871 and its unique feature is an ability to decouple
878 The interfaces on which queueing should be activated are declared using
883 has the following keywords:
886 Queueing is enabled on the named interface.
888 Specifies which queueing scheduler to use.
889 Currently supported values
892 for Class Based Queueing,
894 for Priority Queueing and
896 for the Hierarchical Fair Service Curve scheduler.
897 .It Ar bandwidth Aq Ar bw
898 The maximum bitrate for all queues on an
899 interface may be specified using the
902 The value can be specified as an absolute value or as a
903 percentage of the interface bandwidth.
904 When using an absolute value, the suffixes
910 are used to represent bits, kilobits, megabits, and
911 gigabits per second, respectively.
912 The value must not exceed the interface bandwidth.
915 is not specified, the interface bandwidth is used
916 (but take note that some interfaces do not know their bandwidth,
917 or can adapt their bandwidth rates).
918 .It Ar qlimit Aq Ar limit
919 The maximum number of packets held in the queue.
921 .It Ar tbrsize Aq Ar size
922 Adjusts the size, in bytes, of the token bucket regulator.
923 If not specified, heuristics based on the
924 interface bandwidth are used to determine the size.
925 .It Ar queue Aq Ar list
926 Defines a list of subqueues to create on an interface.
929 In the following example, the interface dc0
930 should queue up to 5Mbps in four second-level queues using
931 Class Based Queueing.
932 Those four queues will be shown in a later example.
933 .Bd -literal -offset indent
934 altq on dc0 cbq bandwidth 5Mb queue { std, http, mail, ssh }
937 Once interfaces are activated for queueing using the
939 directive, a sequence of
941 directives may be defined.
942 The name associated with a
944 must match a queue defined in the
946 directive (e.g. mail), or, except for the
952 The following keywords can be used:
954 .It Ar on Aq Ar interface
955 Specifies the interface the queue operates on.
956 If not given, it operates on all matching interfaces.
957 .It Ar bandwidth Aq Ar bw
958 Specifies the maximum bitrate to be processed by the queue.
959 This value must not exceed the value of the parent
961 and can be specified as an absolute value or a percentage of the parent
963 If not specified, defaults to 100% of the parent queue's bandwidth.
966 scheduler does not support bandwidth specification.
967 .It Ar priority Aq Ar level
968 Between queues a priority level can be set.
973 the range is 0 to 7 and for
975 the range is 0 to 15.
976 The default for all is 1.
978 queues with a higher priority are always served first.
982 queues with a higher priority are preferred in the case of overload.
983 .It Ar qlimit Aq Ar limit
984 The maximum number of packets held in the queue.
990 can get additional parameters with
992 .Pf ( Aq Ar parameters ) .
994 Parameters are as follows:
997 Packets not matched by another queue are assigned to this one.
998 Exactly one default queue is required.
1000 Enable RED (Random Early Detection) on this queue.
1001 RED drops packets with a probability proportional to the average
1004 Enables RIO on this queue.
1005 RIO is RED with IN/OUT, thus running
1006 RED two times more than RIO would achieve the same effect.
1007 RIO is currently not supported in the GENERIC kernel.
1009 Enables ECN (Explicit Congestion Notification) on this queue.
1016 supports an additional option:
1019 The queue can borrow bandwidth from the parent.
1025 supports some additional options:
1027 .It Ar realtime Aq Ar sc
1028 The minimum required bandwidth for the queue.
1029 .It Ar upperlimit Aq Ar sc
1030 The maximum allowed bandwidth for the queue.
1031 .It Ar linkshare Aq Ar sc
1032 The bandwidth share of a backlogged queue.
1039 The format for service curve specifications is
1040 .Ar ( m1 , d , m2 ) .
1042 controls the bandwidth assigned to the queue.
1046 are optional and can be used to control the initial bandwidth assignment.
1049 milliseconds the queue gets the bandwidth given as
1051 afterwards the value given in
1058 child queues can be specified as in an
1060 declaration, thus building a tree of queues using a part of
1061 their parent's bandwidth.
1063 Packets can be assigned to queues based on filter rules by using the
1068 is specified; when a second one is specified it will instead be used for
1069 packets which have a
1073 and for TCP ACKs with no data payload.
1075 To continue the previous example, the examples below would specify the
1077 queues, plus a few child queues.
1080 sessions get priority over bulk transfers like
1084 The queues may then be referenced by filtering rules (see
1085 .Sx PACKET FILTERING
1088 queue std bandwidth 10% cbq(default)
1089 queue http bandwidth 60% priority 2 cbq(borrow red) \e
1090 { employees, developers }
1091 queue developers bandwidth 75% cbq(borrow)
1092 queue employees bandwidth 15%
1093 queue mail bandwidth 10% priority 0 cbq(borrow ecn)
1094 queue ssh bandwidth 20% cbq(borrow) { ssh_interactive, ssh_bulk }
1095 queue ssh_interactive bandwidth 50% priority 7 cbq(borrow)
1096 queue ssh_bulk bandwidth 50% priority 0 cbq(borrow)
1098 block return out on dc0 inet all queue std
1099 pass out on dc0 inet proto tcp from $developerhosts to any port 80 \e
1101 pass out on dc0 inet proto tcp from $employeehosts to any port 80 \e
1103 pass out on dc0 inet proto tcp from any to any port 22 \e
1104 queue(ssh_bulk, ssh_interactive)
1105 pass out on dc0 inet proto tcp from any to any port 25 \e
1109 Translation rules modify either the source or destination address of the
1110 packets associated with a stateful connection.
1111 A stateful connection is automatically created to track packets matching
1112 such a rule as long as they are not blocked by the filtering section of
1114 The translation engine modifies the specified address and/or port in the
1115 packet, recalculates IP, TCP and UDP checksums as necessary, and passes it to
1116 the packet filter for evaluation.
1118 Since translation occurs before filtering the filter
1119 engine will see packets as they look after any
1120 addresses and ports have been translated.
1121 Filter rules will therefore have to filter based on the translated
1122 address and port number.
1123 Packets that match a translation rule are only automatically passed if
1126 modifier is given, otherwise they are
1133 The state entry created permits
1135 to keep track of the original address for traffic associated with that state
1136 and correctly direct return traffic for that connection.
1138 Various types of translation are possible with pf:
1139 .Bl -tag -width xxxx
1143 rule specifies a bidirectional mapping between an external IP netblock
1144 and an internal IP netblock.
1148 rule specifies that IP addresses are to be changed as the packet
1149 traverses the given interface.
1150 This technique allows one or more IP addresses
1151 on the translating host to support network traffic for a larger range of
1152 machines on an "inside" network.
1153 Although in theory any IP address can be used on the inside, it is strongly
1154 recommended that one of the address ranges defined by RFC 1918 be used.
1155 These netblocks are:
1157 10.0.0.0 - 10.255.255.255 (all of net 10, i.e., 10/8)
1158 172.16.0.0 - 172.31.255.255 (i.e., 172.16/12)
1159 192.168.0.0 - 192.168.255.255 (i.e., 192.168/16)
1162 The packet is redirected to another destination and possibly a
1165 rules can optionally specify port ranges instead of single ports.
1166 rdr ... port 2000:2999 -\*(Gt ... port 4000
1167 redirects ports 2000 to 2999 (inclusive) to port 4000.
1168 rdr ... port 2000:2999 -\*(Gt ... port 4000:*
1169 redirects port 2000 to 4000, 2001 to 4001, ..., 2999 to 4999.
1172 In addition to modifying the address, some translation rules may modify
1173 source or destination ports for
1177 connections; implicitly in the case of
1179 rules and explicitly in the case of
1182 Port numbers are never translated with a
1186 Evaluation order of the translation rules is dependent on the type
1187 of the translation rules and of the direction of a packet.
1189 rules are always evaluated first.
1192 rules are evaluated on an inbound packet or the
1194 rules on an outbound packet.
1195 Rules of the same type are evaluated in the same order in which they
1196 appear in the ruleset.
1197 The first matching rule decides what action is taken.
1201 option prefixed to a translation rule causes packets to remain untranslated,
1202 much in the same way as
1204 works in the packet filter (see below).
1205 If no rule matches the packet it is passed to the filter engine unmodified.
1207 Translation rules apply only to packets that pass through
1208 the specified interface, and if no interface is specified,
1209 translation is applied to packets on all interfaces.
1210 For instance, redirecting port 80 on an external interface to an internal
1211 web server will only work for connections originating from the outside.
1212 Connections to the address of the external interface from local hosts will
1213 not be redirected, since such packets do not actually pass through the
1215 Redirections cannot reflect packets back through the interface they arrive
1216 on, they can only be redirected to hosts connected to different interfaces
1217 or to the firewall itself.
1219 Note that redirecting external incoming connections to the loopback
1221 .Bd -literal -offset indent
1222 rdr on ne3 inet proto tcp to port smtp -\*(Gt 127.0.0.1 port spamd
1225 will effectively allow an external host to connect to daemons
1226 bound solely to the loopback address, circumventing the traditional
1227 blocking of such connections on a real interface.
1228 Unless this effect is desired, any of the local non-loopback addresses
1229 should be used as redirection target instead, which allows external
1230 connections only to daemons bound to this address or not bound to
1234 .Sx TRANSLATION EXAMPLES
1236 .Sh PACKET FILTERING
1242 packets based on attributes of their layer 3 (see
1252 In addition, packets may also be
1253 assigned to queues for the purpose of bandwidth control.
1255 For each packet processed by the packet filter, the filter rules are
1256 evaluated in sequential order, from first to last.
1257 The last matching rule decides what action is taken.
1258 If no rule matches the packet, the default action is to pass
1261 The following actions can be used in the filter:
1262 .Bl -tag -width xxxx
1264 The packet is blocked.
1265 There are a number of ways in which a
1267 rule can behave when blocking a packet.
1268 The default behaviour is to
1270 packets silently, however this can be overridden or made
1271 explicit either globally, by setting the
1273 option, or on a per-rule basis with one of the following options:
1275 .Bl -tag -width xxxx -compact
1277 The packet is silently dropped.
1279 This applies only to
1281 packets, and issues a TCP RST which closes the
1285 This causes ICMP messages to be returned for packets which match the rule.
1286 By default this is an ICMP UNREACHABLE message, however this
1287 can be overridden by specifying a message as a code or number.
1289 This causes a TCP RST to be returned for
1291 packets and an ICMP UNREACHABLE for UDP and other packets.
1294 Options returning ICMP packets currently have no effect if
1298 as the code to support this feature has not yet been implemented.
1300 The simplest mechanism to block everything by default and only pass
1301 packets that match explicit rules is specify a first filter rule of:
1302 .Bd -literal -offset indent
1306 The packet is passed;
1307 state is created unless the
1309 option is specified.
1314 filters packets statefully; the first time a packet matches a
1316 rule, a state entry is created; for subsequent packets the filter checks
1317 whether the packet matches any state.
1318 If it does, the packet is passed without evaluation of any rules.
1319 After the connection is closed or times out, the state entry is automatically
1322 This has several advantages.
1323 For TCP connections, comparing a packet to a state involves checking
1324 its sequence numbers, as well as TCP timestamps if a
1325 .Ar scrub reassemble tcp
1326 rule applies to the connection.
1327 If these values are outside the narrow windows of expected
1328 values, the packet is dropped.
1329 This prevents spoofing attacks, such as when an attacker sends packets with
1330 a fake source address/port but does not know the connection's sequence
1334 knows how to match ICMP replies to states.
1336 .Bd -literal -offset indent
1337 pass out inet proto icmp all icmp-type echoreq
1340 allows echo requests (such as those created by
1342 out statefully, and matches incoming echo replies correctly to states.
1344 Also, looking up states is usually faster than evaluating rules.
1345 If there are 50 rules, all of them are evaluated sequentially in O(n).
1346 Even with 50000 states, only 16 comparisons are needed to match a
1347 state, since states are stored in a binary search tree that allows
1348 searches in O(log2 n).
1350 Furthermore, correct handling of ICMP error messages is critical to
1351 many protocols, particularly TCP.
1353 matches ICMP error messages to the correct connection, checks them against
1354 connection parameters, and passes them if appropriate.
1355 For example if an ICMP source quench message referring to a stateful TCP
1356 connection arrives, it will be matched to the state and get passed.
1358 Finally, state tracking is required for
1359 .Ar nat , binat No and Ar rdr
1360 rules, in order to track address and port translations and reverse the
1361 translation on returning packets.
1364 will also create state for other protocols which are effectively stateless by
1366 UDP packets are matched to states using only host addresses and ports,
1367 and other protocols are matched to states using only the host addresses.
1369 If stateless filtering of individual packets is desired,
1372 keyword can be used to specify that state will not be created
1373 if this is the last matching rule.
1374 A number of parameters can also be set to affect how
1376 handles state tracking.
1378 .Sx STATEFUL TRACKING OPTIONS
1379 below for further details.
1381 The rule parameters specify the packets to which a rule applies.
1382 A packet always comes in on, or goes out through, one interface.
1383 Most parameters are optional.
1384 If a parameter is specified, the rule only applies to packets with
1385 matching attributes.
1386 Certain parameters can be expressed as lists, in which case
1388 generates all needed rule combinations.
1389 .Bl -tag -width xxxx
1390 .It Ar in No or Ar out
1391 This rule applies to incoming or outgoing packets.
1396 are specified, the rule will match packets in both directions.
1398 In addition to the action specified, a log message is generated.
1399 Only the packet that establishes the state is logged,
1402 option is specified.
1403 The logged packets are sent to a
1405 interface, by default
1407 This interface is monitored by the
1409 logging daemon, which dumps the logged packets to the file
1415 Used to force logging of all packets for a connection.
1416 This is not necessary when
1418 is explicitly specified.
1421 packets are logged to
1426 user ID of the user that owns the socket and the PID of the process that
1427 has the socket open where the packet is sourced from or destined to
1428 (depending on which socket is local).
1429 This is in addition to the normal information logged.
1431 Only the first packet
1434 will have the user credentials logged when using stateful matching.
1435 .It Ar log (to Aq Ar interface )
1436 Send logs to the specified
1438 interface instead of
1441 If a packet matches a rule which has the
1443 option set, this rule
1444 is considered the last matching rule, and evaluation of subsequent rules
1446 .It Ar on Aq Ar interface
1447 This rule applies only to packets coming in on, or going out through, this
1448 particular interface or interface group.
1449 For more information on interface groups,
1455 This rule applies only to packets of this address family.
1456 Supported values are
1460 .It Ar proto Aq Ar protocol
1461 This rule applies only to packets of this protocol.
1462 Common protocols are
1468 For a list of all the protocol name to number mappings used by
1471 .Pa /etc/protocols .
1473 .Ar from Aq Ar source
1474 .Ar port Aq Ar source
1479 This rule applies only to packets with the specified source and destination
1480 addresses and ports.
1482 Addresses can be specified in CIDR notation (matching netblocks), as
1483 symbolic host names, interface names or interface group names, or as any
1484 of the following keywords:
1486 .Bl -tag -width xxxxxxxxxxxxxx -compact
1490 Any address which is not currently routable.
1492 Any source address that fails a unicast reverse path forwarding (URPF)
1493 check, i.e. packets coming in on an interface other than that which holds
1494 the route back to the packet's source address.
1496 Any address that matches the given table.
1499 Ranges of addresses are specified by using the
1503 .Dq 10.1.1.10 - 10.1.1.12
1504 means all addresses from 10.1.1.10 to 10.1.1.12,
1505 hence addresses 10.1.1.10, 10.1.1.11, and 10.1.1.12.
1507 Interface names and interface group names can have modifiers appended:
1509 .Bl -tag -width xxxxxxxxxxxx -compact
1511 Translates to the network(s) attached to the interface.
1513 Translates to the interface's broadcast address(es).
1515 Translates to the point-to-point interface's peer address(es).
1517 Do not include interface aliases.
1520 Host names may also have the
1522 option appended to restrict the name resolution to the first of each
1523 v4 and v6 address found.
1525 Host name resolution and interface to address translation are done at
1527 When the address of an interface (or host name) changes (under DHCP or PPP,
1528 for instance), the ruleset must be reloaded for the change to be reflected
1530 Surrounding the interface name (and optional modifiers) in parentheses
1531 changes this behaviour.
1532 When the interface name is surrounded by parentheses, the rule is
1533 automatically updated whenever the interface changes its address.
1534 The ruleset does not need to be reloaded.
1535 This is especially useful with
1538 Ports can be specified either by number or by name.
1539 For example, port 80 can be specified as
1541 For a list of all port name to number mappings used by
1546 Ports and ranges of ports are specified by using these operators:
1547 .Bd -literal -offset indent
1551 \*(Le (less than or equal)
1552 \*(Gt (greater than)
1553 \*(Ge (greater than or equal)
1554 : (range including boundaries)
1555 \*(Gt\*(Lt (range excluding boundaries)
1556 \*(Lt\*(Gt (except range)
1563 are binary operators (they take two arguments).
1566 .It Ar port 2000:2004
1568 .Sq all ports \*(Ge 2000 and \*(Le 2004 ,
1569 hence ports 2000, 2001, 2002, 2003 and 2004.
1570 .It Ar port 2000 \*(Gt\*(Lt 2004
1572 .Sq all ports \*(Gt 2000 and \*(Lt 2004 ,
1573 hence ports 2001, 2002 and 2003.
1574 .It Ar port 2000 \*(Lt\*(Gt 2004
1576 .Sq all ports \*(Lt 2000 or \*(Gt 2004 ,
1577 hence ports 1-1999 and 2005-65535.
1580 The operating system of the source host can be specified in the case of TCP
1585 .Sx OPERATING SYSTEM FINGERPRINTING
1586 section for more information.
1588 The host, port and OS specifications are optional, as in the following examples:
1589 .Bd -literal -offset indent
1591 pass in from any to any
1592 pass in proto tcp from any port \*(Le 1024 to any
1593 pass in proto tcp from any to any port 25
1594 pass in proto tcp from 10.0.0.0/8 port \*(Gt 1024 \e
1595 to ! 10.1.2.3 port != ssh
1596 pass in proto tcp from any os "OpenBSD"
1599 This is equivalent to "from any to any".
1600 .It Ar group Aq Ar group
1603 this rule only applies to packets of sockets owned by the specified group.
1604 .It Ar user Aq Ar user
1605 This rule only applies to packets of sockets owned by the specified user.
1606 For outgoing connections initiated from the firewall, this is the user
1607 that opened the connection.
1608 For incoming connections to the firewall itself, this is the user that
1609 listens on the destination port.
1610 For forwarded connections, where the firewall is not a connection endpoint,
1611 the user and group are
1614 All packets, both outgoing and incoming, of one connection are associated
1615 with the same user and group.
1616 Only TCP and UDP packets can be associated with users; for other protocols
1617 these parameters are ignored.
1619 User and group refer to the effective (as opposed to the real) IDs, in
1620 case the socket is created by a setuid/setgid process.
1621 User and group IDs are stored when a socket is created;
1622 when a process creates a listening socket as root (for instance, by
1623 binding to a privileged port) and subsequently changes to another
1624 user ID (to drop privileges), the credentials will remain root.
1626 User and group IDs can be specified as either numbers or names.
1627 The syntax is similar to the one for ports.
1630 matches packets of forwarded connections.
1632 can only be used with the operators
1636 Other constructs like
1637 .Cm user \*(Ge unknown
1639 Forwarded packets with unknown user and group ID match only rules
1640 that explicitly compare against
1648 does not match forwarded packets.
1649 The following example allows only selected users to open outgoing
1651 .Bd -literal -offset indent
1652 block out proto { tcp, udp } all
1653 pass out proto { tcp, udp } all user { \*(Lt 1000, dhartmei }
1655 .It Xo Ar flags Aq Ar a
1657 .No \*(Ba / Ns Aq Ar b
1660 This rule only applies to TCP packets that have the flags
1664 Flags not specified in
1667 For stateful connections, the default is
1669 To indicate that flags should not be checked at all, specify
1671 The flags are: (F)IN, (S)YN, (R)ST, (P)USH, (A)CK, (U)RG, (E)CE, and C(W)R.
1675 The other flags are ignored.
1677 This is the default setting for stateful connections.
1678 Out of SYN and ACK, exactly SYN may be set.
1679 SYN, SYN+PSH and SYN+RST match, but SYN+ACK, ACK and ACK+RST do not.
1680 This is more restrictive than the previous example.
1682 If the first set is not specified, it defaults to none.
1683 All of SYN, FIN, RST and ACK must be unset.
1688 is applied by default (unless
1690 is specified), only the initial SYN packet of a TCP handshake will create
1691 a state for a TCP connection.
1692 It is possible to be less restrictive, and allow state creation from
1695 packets, by specifying
1699 to synchronize to existing connections, for instance
1700 if one flushes the state table.
1701 However, states created from such intermediate packets may be missing
1702 connection details such as the TCP window scaling factor.
1703 States which modify the packet flow, such as those affected by
1704 .Ar nat , binat No or Ar rdr
1706 .Ar modulate No or Ar synproxy state
1707 options, or scrubbed with
1709 will also not be recoverable from intermediate packets.
1710 Such connections will stall and time out.
1711 .It Xo Ar icmp-type Aq Ar type
1714 .It Xo Ar icmp6-type Aq Ar type
1717 This rule only applies to ICMP or ICMPv6 packets with the specified type
1719 Text names for ICMP types and codes are listed in
1723 This parameter is only valid for rules that cover protocols ICMP or
1725 The protocol and the ICMP type indicator
1732 .It Xo Ar tos Aq Ar string
1733 .No \*(Ba Aq Ar number
1735 This rule applies to packets with the specified
1747 or one of the DiffServ Code Points:
1750 .Ar af11 No ... Ar af43 ,
1751 .Ar cs0 No ... Ar cs7 ;
1752 or as either hex or decimal.
1754 For example, the following rules are identical:
1755 .Bd -literal -offset indent
1756 pass all tos lowdelay
1761 By default, IPv4 packets with IP options or IPv6 packets with routing
1762 extension headers are blocked.
1767 rule, packets that pass the filter based on that rule (last matching)
1768 do so even if they contain IP options or routing extension headers.
1769 For packets that match state, the rule that initially created the
1773 rule that is used when a packet does not match any rules does not
1775 .It Ar label Aq Ar string
1776 Adds a label (name) to the rule, which can be used to identify the rule.
1779 shows per-rule statistics for rules that have labels.
1781 The following macros can be used in labels:
1783 .Bl -tag -width $srcaddr -compact -offset indent
1787 The source IP address.
1789 The destination IP address.
1791 The source port specification.
1793 The destination port specification.
1801 .Bd -literal -offset indent
1802 ips = \&"{ 1.2.3.4, 1.2.3.5 }\&"
1803 pass in proto tcp from any to $ips \e
1804 port \*(Gt 1023 label \&"$dstaddr:$dstport\&"
1808 .Bd -literal -offset indent
1809 pass in inet proto tcp from any to 1.2.3.4 \e
1810 port \*(Gt 1023 label \&"1.2.3.4:\*(Gt1023\&"
1811 pass in inet proto tcp from any to 1.2.3.5 \e
1812 port \*(Gt 1023 label \&"1.2.3.5:\*(Gt1023\&"
1815 The macro expansion for the
1817 directive occurs only at configuration file parse time, not during runtime.
1818 .It Xo Ar queue Aq Ar queue
1819 .No \*(Ba ( Aq Ar queue ,
1822 Packets matching this rule will be assigned to the specified queue.
1823 If two queues are given, packets which have a
1827 and TCP ACKs with no data payload will be assigned to the second one.
1833 .Bd -literal -offset indent
1834 pass in proto tcp to port 25 queue mail
1835 pass in proto tcp to port 22 queue(ssh_bulk, ssh_prio)
1838 .It Cm set prio Ar priority | Pq Ar priority , priority
1839 Packets matching this rule will be assigned a specific queueing priority.
1840 Priorities are assigned as integers 0 through 7.
1841 If the packet is transmitted on a
1843 interface, the queueing priority will be written as the priority
1844 code point in the 802.1Q VLAN header.
1845 If two priorities are given, packets which have a TOS of
1847 and TCP ACKs with no data payload will be assigned to the second one.
1850 .Bd -literal -offset indent
1851 pass in proto tcp to port 25 set prio 2
1852 pass in proto tcp to port 22 set prio (2, 5)
1855 .It Ar tag Aq Ar string
1856 Packets matching this rule will be tagged with the
1858 The tag acts as an internal marker that can be used to
1859 identify these packets later on.
1860 This can be used, for example, to provide trust between
1861 interfaces and to determine if packets have been
1862 processed by translation rules.
1865 meaning that the packet will be tagged even if the rule
1866 is not the last matching rule.
1867 Further matching rules can replace the tag with a
1868 new one but will not remove a previously applied tag.
1869 A packet is only ever assigned one tag at a time.
1870 Packet tagging can be done during
1875 rules in addition to filter rules.
1876 Tags take the same macros as labels (see above).
1877 .It Ar tagged Aq Ar string
1878 Used with filter, translation or scrub rules
1879 to specify that packets must already
1880 be tagged with the given tag in order to match the rule.
1881 Inverse tag matching can also be done
1887 .It Ar rtable Aq Ar number
1888 Used to select an alternate routing table for the routing lookup.
1889 Only effective before the route lookup happened, i.e. when filtering inbound.
1890 .It Xo Ar divert-to Aq Ar host
1893 Used to redirect packets to a local socket bound to
1897 The packets will not be modified, so
1899 on the socket will return the original destination address of the packet.
1901 Used to receive replies for sockets that are bound to addresses
1902 which are not local to the machine.
1905 for information on how to bind these sockets.
1906 .It Ar probability Aq Ar number
1907 A probability attribute can be attached to a rule, with a value set between
1908 0 and 1, bounds not included.
1909 In that case, the rule will be honoured using the given probability value
1911 For example, the following rule will drop 20% of incoming ICMP packets:
1912 .Bd -literal -offset indent
1913 block in proto icmp probability 20%
1915 .It Ar prio Aq Ar number
1916 Only match packets which have the given queueing priority assigned.
1920 If a packet matches a rule with a route option set, the packet filter will
1921 route the packet according to the type of route option.
1922 When such a rule creates state, the route option is also applied to all
1923 packets matching the same connection.
1924 .Bl -tag -width xxxx
1928 option routes the packet to the specified interface with an optional address
1932 rule creates state, only packets that pass in the same direction as the
1933 filter rule specifies will be routed in this way.
1934 Packets passing in the opposite direction (replies) are not affected
1935 and are routed normally.
1939 option is similar to
1941 but routes packets that pass in the opposite direction (replies) to the
1942 specified interface.
1943 Opposite direction is only defined in the context of a state entry, and
1945 is useful only in rules that create state.
1946 It can be used on systems with multiple external connections to
1947 route all outgoing packets of a connection through the interface
1948 the incoming connection arrived through (symmetric routing enforcement).
1952 option creates a duplicate of the packet and routes it like
1954 The original packet gets routed as it normally would.
1961 rules, (as well as for the
1966 rule options) for which there is a single redirection address which has a
1967 subnet mask smaller than 32 for IPv4 or 128 for IPv6 (more than one IP
1968 address), a variety of different methods for assigning this address can be
1970 .Bl -tag -width xxxx
1974 option applies the network portion of the redirection address to the address
1975 to be modified (source with
1982 option selects an address at random within the defined block of addresses.
1986 option uses a hash of the source address to determine the redirection address,
1987 ensuring that the redirection address is always the same for a given source.
1988 An optional key can be specified after this keyword either in hex or as a
1991 randomly generates a key for source-hash every time the
1992 ruleset is reloaded.
1996 option loops through the redirection address(es).
1998 When more than one redirection address is specified,
2000 is the only permitted pool type.
2008 from modifying the source port on TCP and UDP packets.
2009 .It Xo Ar map-e-portset Aq Ar psid-offset
2010 .No / Aq Ar psid-len
2017 option enables the source port translation of MAP-E (RFC 7597) Customer Edge.
2018 In order to make the host act as a MAP-E Customer Edge, setting up a tunneling
2019 interface and pass rules for encapsulated packets are required in addition
2020 to the map-e-portset nat rule.
2023 .Bd -literal -offset indent
2024 nat on $gif_mape_if from $int_if:network to any \e
2025 -> $ipv4_mape_src map-e-portset 6/8/0x34
2028 sets PSID offset 6, PSID length 8, PSID 0x34.
2034 option can be specified to help ensure that multiple connections from the
2035 same source are mapped to the same redirection address.
2036 This option can be used with the
2041 Note that by default these associations are destroyed as soon as there are
2042 no longer states which refer to them; in order to make the mappings last
2043 beyond the lifetime of the states, increase the global options with
2044 .Ar set timeout src.track .
2046 .Sx STATEFUL TRACKING OPTIONS
2047 for more ways to control the source tracking.
2048 .Sh STATE MODULATION
2049 Much of the security derived from TCP is attributable to how well the
2050 initial sequence numbers (ISNs) are chosen.
2051 Some popular stack implementations choose
2053 poor ISNs and thus are normally susceptible to ISN prediction exploits.
2056 rule to a TCP connection,
2058 will create a high quality random sequence number for each connection
2063 directive implicitly keeps state on the rule and is
2064 only applicable to TCP connections.
2067 .Bd -literal -offset indent
2069 pass out proto tcp from any to any modulate state
2070 pass in proto tcp from any to any port 25 flags S/SFRA modulate state
2073 Note that modulated connections will not recover when the state table
2074 is lost (firewall reboot, flushing the state table, etc...).
2076 will not be able to infer a connection again after the state table flushes
2077 the connection's modulator.
2078 When the state is lost, the connection may be left dangling until the
2079 respective endpoints time out the connection.
2080 It is possible on a fast local network for the endpoints to start an ACK
2081 storm while trying to resynchronize after the loss of the modulator.
2084 settings (or a more strict equivalent) should be used on
2086 rules to prevent ACK storms.
2088 Note that alternative methods are available
2089 to prevent loss of the state table
2090 and allow for firewall failover.
2095 for further information.
2099 passes packets that are part of a
2101 handshake between the endpoints.
2104 option can be used to cause
2106 itself to complete the handshake with the active endpoint, perform a handshake
2107 with the passive endpoint, and then forward packets between the endpoints.
2109 No packets are sent to the passive endpoint before the active endpoint has
2110 completed the handshake, hence so-called SYN floods with spoofed source
2111 addresses will not reach the passive endpoint, as the sender can't complete the
2114 The proxy is transparent to both endpoints, they each see a single
2115 connection from/to the other endpoint.
2117 chooses random initial sequence numbers for both handshakes.
2118 Once the handshakes are completed, the sequence number modulators
2119 (see previous section) are used to translate further packets of the
2123 .Ar modulate state .
2133 .Bd -literal -offset indent
2134 pass in proto tcp from any to any port www synproxy state
2136 .Sh STATEFUL TRACKING OPTIONS
2137 A number of options related to stateful tracking can be applied on a
2143 support these options, and
2145 must be specified explicitly to apply options to a rule.
2147 .Bl -tag -width xxxx -compact
2148 .It Ar max Aq Ar number
2149 Limits the number of concurrent states the rule may create.
2150 When this limit is reached, further packets that would create
2151 state will not match this rule until existing states time out.
2153 Prevent state changes for states created by this rule from appearing on the
2156 .It Xo Aq Ar timeout
2159 Changes the timeout values used for states created by this rule.
2160 For a list of all valid timeout names, see
2164 Uses a sloppy TCP connection tracker that does not check sequence
2165 numbers at all, which makes insertion and ICMP teardown attacks way
2167 This is intended to be used in situations where one does not see all
2168 packets of a connection, e.g. in asymmetric routing situations.
2169 Cannot be used with modulate or synproxy state.
2172 Multiple options can be specified, separated by commas:
2173 .Bd -literal -offset indent
2174 pass in proto tcp from any to any \e
2175 port www keep state \e
2176 (max 100, source-track rule, max-src-nodes 75, \e
2177 max-src-states 3, tcp.established 60, tcp.closing 5)
2182 keyword is specified, the number of states per source IP is tracked.
2184 .Bl -tag -width xxxx -compact
2185 .It Ar source-track rule
2186 The maximum number of states created by this rule is limited by the rule's
2191 Only state entries created by this particular rule count toward the rule's
2193 .It Ar source-track global
2194 The number of states created by all rules that use this option is limited.
2195 Each rule can specify different
2199 options, however state entries created by any participating rule count towards
2200 each individual rule's limits.
2203 The following limits can be set:
2205 .Bl -tag -width xxxx -compact
2206 .It Ar max-src-nodes Aq Ar number
2207 Limits the maximum number of source addresses which can simultaneously
2208 have state table entries.
2209 .It Ar max-src-states Aq Ar number
2210 Limits the maximum number of simultaneous state entries that a single
2211 source address can create with this rule.
2214 For stateful TCP connections, limits on established connections (connections
2215 which have completed the TCP 3-way handshake) can also be enforced
2218 .Bl -tag -width xxxx -compact
2219 .It Ar max-src-conn Aq Ar number
2220 Limits the maximum number of simultaneous TCP connections which have
2221 completed the 3-way handshake that a single host can make.
2222 .It Xo Ar max-src-conn-rate Aq Ar number
2225 Limit the rate of new connections over a time interval.
2226 The connection rate is an approximation calculated as a moving average.
2229 Because the 3-way handshake ensures that the source address is not being
2230 spoofed, more aggressive action can be taken based on these limits.
2232 .Ar overload Aq Ar table
2233 state option, source IP addresses which hit either of the limits on
2234 established connections will be added to the named table.
2235 This table can be used in the ruleset to block further activity from
2236 the offending host, redirect it to a tarpit process, or restrict its
2241 keyword kills all states created by the matching rule which originate
2242 from the host which exceeds these limits.
2245 modifier to the flush command kills all states originating from the
2246 offending host, regardless of which rule created the state.
2248 For example, the following rules will protect the webserver against
2249 hosts making more than 100 connections in 10 seconds.
2250 Any host which connects faster than this rate will have its address added
2253 table and have all states originating from it flushed.
2254 Any new packets arriving from this host will be dropped unconditionally
2256 .Bd -literal -offset indent
2257 block quick from \*(Ltbad_hosts\*(Gt
2258 pass in on $ext_if proto tcp to $webserver port www keep state \e
2259 (max-src-conn-rate 100/10, overload \*(Ltbad_hosts\*(Gt flush global)
2261 .Sh OPERATING SYSTEM FINGERPRINTING
2262 Passive OS Fingerprinting is a mechanism to inspect nuances of a TCP
2263 connection's initial SYN packet and guess at the host's operating system.
2264 Unfortunately these nuances are easily spoofed by an attacker so the
2265 fingerprint is not useful in making security decisions.
2266 But the fingerprint is typically accurate enough to make policy decisions
2269 The fingerprints may be specified by operating system class, by
2270 version, or by subtype/patchlevel.
2271 The class of an operating system is typically the vendor or genre
2277 The version of the oldest available
2279 release on the main FTP site
2280 would be 2.6 and the fingerprint would be written
2282 .Dl \&"OpenBSD 2.6\&"
2284 The subtype of an operating system is typically used to describe the
2285 patchlevel if that patch led to changes in the TCP stack behavior.
2288 the only subtype is for a fingerprint that was
2291 scrub option and would be specified as
2293 .Dl \&"OpenBSD 3.3 no-df\&"
2295 Fingerprints for most popular operating systems are provided by
2299 is running, a complete list of known operating system fingerprints may
2300 be listed by running:
2304 Filter rules can enforce policy at any level of operating system specification
2305 assuming a fingerprint is present.
2306 Policy could limit traffic to approved operating systems or even ban traffic
2307 from hosts that aren't at the latest service pack.
2311 class can also be used as the fingerprint which will match packets for
2312 which no operating system fingerprint is known.
2315 .Bd -literal -offset indent
2316 pass out proto tcp from any os OpenBSD
2317 block out proto tcp from any os Doors
2318 block out proto tcp from any os "Doors PT"
2319 block out proto tcp from any os "Doors PT SP3"
2320 block out from any os "unknown"
2321 pass on lo0 proto tcp from any os "OpenBSD 3.3 lo0"
2324 Operating system fingerprinting is limited only to the TCP SYN packet.
2325 This means that it will not work on other protocols and will not match
2326 a currently established connection.
2328 Caveat: operating system fingerprints are occasionally wrong.
2329 There are three problems: an attacker can trivially craft his packets to
2330 appear as any operating system he chooses;
2331 an operating system patch could change the stack behavior and no fingerprints
2332 will match it until the database is updated;
2333 and multiple operating systems may have the same fingerprint.
2334 .Sh BLOCKING SPOOFED TRAFFIC
2335 "Spoofing" is the faking of IP addresses, typically for malicious
2339 directive expands to a set of filter rules which will block all
2340 traffic with a source IP from the network(s) directly connected
2341 to the specified interface(s) from entering the system through
2342 any other interface.
2344 For example, the line
2345 .Bd -literal -offset indent
2350 .Bd -literal -offset indent
2351 block drop in on ! lo0 inet from 127.0.0.1/8 to any
2352 block drop in on ! lo0 inet6 from ::1 to any
2355 For non-loopback interfaces, there are additional rules to block incoming
2356 packets with a source IP address identical to the interface's IP(s).
2357 For example, assuming the interface wi0 had an IP address of 10.0.0.1 and a
2358 netmask of 255.255.255.0,
2360 .Bd -literal -offset indent
2361 antispoof for wi0 inet
2365 .Bd -literal -offset indent
2366 block drop in on ! wi0 inet from 10.0.0.0/24 to any
2367 block drop in inet from 10.0.0.1 to any
2370 Caveat: Rules created by the
2372 directive interfere with packets sent over loopback interfaces
2374 One should pass these explicitly.
2375 .Sh FRAGMENT HANDLING
2376 The size of IP datagrams (packets) can be significantly larger than the
2377 maximum transmission unit (MTU) of the network.
2378 In cases when it is necessary or more efficient to send such large packets,
2379 the large packet will be fragmented into many smaller packets that will each
2381 Unfortunately for a firewalling device, only the first logical fragment will
2382 contain the necessary header information for the subprotocol that allows
2384 to filter on things such as TCP ports or to perform NAT.
2388 rules as described in
2389 .Sx TRAFFIC NORMALIZATION
2390 above, there are three options for handling fragments in the packet filter.
2392 One alternative is to filter individual fragments with filter rules.
2395 rule applies to a fragment, it is passed to the filter.
2396 Filter rules with matching IP header parameters decide whether the
2397 fragment is passed or blocked, in the same way as complete packets
2399 Without reassembly, fragments can only be filtered based on IP header
2400 fields (source/destination address, protocol), since subprotocol header
2401 fields are not available (TCP/UDP port numbers, ICMP code/type).
2404 option can be used to restrict filter rules to apply only to
2405 fragments, but not complete packets.
2406 Filter rules without the
2408 option still apply to fragments, if they only specify IP header fields.
2409 For instance, the rule
2410 .Bd -literal -offset indent
2411 pass in proto tcp from any to any port 80
2414 never applies to a fragment, even if the fragment is part of a TCP
2415 packet with destination port 80, because without reassembly this information
2416 is not available for each fragment.
2417 This also means that fragments cannot create new or match existing
2418 state table entries, which makes stateful filtering and address
2419 translation (NAT, redirection) for fragments impossible.
2421 It's also possible to reassemble only certain fragments by specifying
2422 source or destination addresses or protocols as parameters in
2426 In most cases, the benefits of reassembly outweigh the additional
2427 memory cost, and it's recommended to use
2430 all fragments via the
2431 .Ar fragment reassemble
2434 The memory allocated for fragment caching can be limited using
2436 Once this limit is reached, fragments that would have to be cached
2437 are dropped until other entries time out.
2438 The timeout value can also be adjusted.
2440 When forwarding reassembled IPv6 packets, pf refragments them with
2441 the original maximum fragment size.
2442 This allows the sender to determine the optimal fragment size by
2445 Besides the main ruleset,
2447 can load rulesets into
2452 is a container that can hold rules, address tables, and other anchors.
2456 has a name which specifies the path where
2458 can be used to access the anchor to perform operations on it, such as
2459 attaching child anchors to it or loading rules into it.
2460 Anchors may be nested, with components separated by
2462 characters, similar to how file system hierarchies are laid out.
2463 The main ruleset is actually the default anchor, so filter and
2464 translation rules, for example, may also be contained in any anchor.
2466 An anchor can reference another
2469 using the following kinds
2471 .Bl -tag -width xxxx
2472 .It Ar nat-anchor Aq Ar name
2475 rules in the specified
2477 .It Ar rdr-anchor Aq Ar name
2480 rules in the specified
2482 .It Ar binat-anchor Aq Ar name
2485 rules in the specified
2487 .It Ar anchor Aq Ar name
2488 Evaluates the filter rules in the specified
2490 .It Xo Ar load anchor
2494 Loads the rules from the specified file into the
2499 When evaluation of the main ruleset reaches an
2503 will proceed to evaluate all rules specified in that anchor.
2505 Matching filter and translation rules marked with the
2507 option are final and abort the evaluation of the rules in other
2508 anchors and the main ruleset.
2511 itself is marked with the
2514 ruleset evaluation will terminate when the anchor is exited if the packet is
2515 matched by any rule within the anchor.
2518 rules are evaluated relative to the anchor in which they are contained.
2521 rules specified in the main ruleset will reference anchor
2522 attachment points underneath the main ruleset, and
2524 rules specified in a file loaded from a
2526 rule will be attached under that anchor point.
2528 Rules may be contained in
2530 attachment points which do not contain any rules when the main ruleset
2531 is loaded, and later such anchors can be manipulated through
2533 without reloading the main ruleset or other anchors.
2535 .Bd -literal -offset indent
2537 block on $ext_if all
2539 pass out on $ext_if all
2540 pass in on $ext_if proto tcp from any \e
2541 to $ext_if port smtp
2544 blocks all packets on the external interface by default, then evaluates
2547 named "spam", and finally passes all outgoing connections and
2548 incoming connections to port 25.
2549 .Bd -literal -offset indent
2550 # echo \&"block in quick from 1.2.3.4 to any\&" \&| \e
2554 This loads a single rule into the
2556 which blocks all packets from a specific address.
2558 The anchor can also be populated by adding a
2563 .Bd -literal -offset indent
2565 load anchor spam from "/etc/pf-spam.conf"
2572 it will also load all the rules from the file
2573 .Pa /etc/pf-spam.conf
2578 rules can specify packet filtering parameters using the same syntax as
2580 When parameters are used, the
2582 rule is only evaluated for matching packets.
2583 This allows conditional evaluation of anchors, like:
2584 .Bd -literal -offset indent
2585 block on $ext_if all
2586 anchor spam proto tcp from any to any port smtp
2587 pass out on $ext_if all
2588 pass in on $ext_if proto tcp from any to $ext_if port smtp
2593 spam are only evaluated for
2595 packets with destination port 25.
2597 .Bd -literal -offset indent
2598 # echo \&"block in quick from 1.2.3.4 to any" \&| \e
2602 will only block connections from 1.2.3.4 to port 25.
2604 Anchors may end with the asterisk
2606 character, which signifies that all anchors attached at that point
2607 should be evaluated in the alphabetical ordering of their anchor name.
2609 .Bd -literal -offset indent
2613 will evaluate each rule in each anchor attached to the
2616 Note that it will only evaluate anchors that are directly attached to the
2618 anchor, and will not descend to evaluate anchors recursively.
2620 Since anchors are evaluated relative to the anchor in which they are
2621 contained, there is a mechanism for accessing the parent and ancestor
2622 anchors of a given anchor.
2623 Similar to file system path name resolution, if the sequence
2625 appears as an anchor path component, the parent anchor of the current
2626 anchor in the path evaluation at that point will become the new current
2628 As an example, consider the following:
2629 .Bd -literal -offset indent
2630 # echo ' anchor "spam/allowed" ' | pfctl -f -
2631 # echo -e ' anchor "../banned" \en pass' | \e
2632 pfctl -a spam/allowed -f -
2635 Evaluation of the main ruleset will lead into the
2637 anchor, which will evaluate the rules in the
2639 anchor, if any, before finally evaluating the
2645 can also be loaded inline in the ruleset within a brace ('{' '}') delimited
2647 Brace delimited blocks may contain rules or other brace-delimited blocks.
2648 When anchors are loaded this way the anchor name becomes optional.
2649 .Bd -literal -offset indent
2650 anchor "external" on egress {
2653 pass proto tcp from any to port { 25, 80, 443 }
2655 pass in proto tcp to any port 22
2659 Since the parser specification for anchor names is a string, any
2660 reference to an anchor name containing
2662 characters will require double quote
2664 characters around the anchor name.
2665 .Sh TRANSLATION EXAMPLES
2666 This example maps incoming requests on port 80 to port 8080, on
2667 which a daemon is running (because, for example, it is not run as root,
2668 and therefore lacks permission to bind to port 80).
2670 # use a macro for the interface name, so it can be changed easily
2673 # map daemon on 8080 to appear to be on 80
2674 rdr on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 port 8080
2679 modifier is given, packets matching the translation rule are passed without
2680 inspecting the filter rules:
2682 rdr pass on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 \e
2686 In the example below, vlan12 is configured as 192.168.168.1;
2687 the machine translates all packets coming from 192.168.168.0/24 to 204.92.77.111
2688 when they are going out any interface except vlan12.
2689 This has the net effect of making traffic from the 192.168.168.0/24
2690 network appear as though it is the Internet routable address
2691 204.92.77.111 to nodes behind any interface on the router except
2692 for the nodes on vlan12.
2693 (Thus, 192.168.168.1 can talk to the 192.168.168.0/24 nodes.)
2695 nat on ! vlan12 from 192.168.168.0/24 to any -\*(Gt 204.92.77.111
2698 In the example below, the machine sits between a fake internal 144.19.74.*
2699 network, and a routable external IP of 204.92.77.100.
2702 rule excludes protocol AH from being translated.
2705 no nat on $ext_if proto ah from 144.19.74.0/24 to any
2706 nat on $ext_if from 144.19.74.0/24 to any -\*(Gt 204.92.77.100
2709 In the example below, packets bound for one specific server, as well as those
2710 generated by the sysadmins are not proxied; all other connections are.
2713 no rdr on $int_if proto { tcp, udp } from any to $server port 80
2714 no rdr on $int_if proto { tcp, udp } from $sysadmins to any port 80
2715 rdr on $int_if proto { tcp, udp } from any to any port 80 -\*(Gt 127.0.0.1 \e
2719 This longer example uses both a NAT and a redirection.
2720 The external interface has the address 157.161.48.183.
2721 On localhost, we are running
2723 waiting for FTP sessions to be redirected to it.
2724 The three mandatory anchors for
2726 are omitted from this example; see the
2731 # Translate outgoing packets' source addresses (any protocol).
2732 # In this case, any address but the gateway's external address is mapped.
2733 nat on $ext_if inet from ! ($ext_if) to any -\*(Gt ($ext_if)
2736 # Map outgoing packets' source port to an assigned proxy port instead of
2737 # an arbitrary port.
2738 # In this case, proxy outgoing isakmp with port 500 on the gateway.
2739 nat on $ext_if inet proto udp from any port = isakmp to any -\*(Gt ($ext_if) \e
2743 # Translate outgoing packets' source address (any protocol).
2744 # Translate incoming packets' destination address to an internal machine
2746 binat on $ext_if from 10.1.2.150 to any -\*(Gt $ext_if
2749 # Translate incoming packets' destination addresses.
2750 # As an example, redirect a TCP and UDP port to an internal machine.
2751 rdr on $ext_if inet proto tcp from any to ($ext_if) port 8080 \e
2752 -\*(Gt 10.1.2.151 port 22
2753 rdr on $ext_if inet proto udp from any to ($ext_if) port 8080 \e
2754 -\*(Gt 10.1.2.151 port 53
2757 # Translate outgoing ftp control connections to send them to localhost
2758 # for proxying with ftp-proxy(8) running on port 8021.
2759 rdr on $int_if proto tcp from any to any port 21 -\*(Gt 127.0.0.1 port 8021
2762 In this example, a NAT gateway is set up to translate internal addresses
2763 using a pool of public addresses (192.0.2.16/28) and to redirect
2764 incoming web server connections to a group of web servers on the internal
2768 # Translate outgoing packets' source addresses using an address pool.
2769 # A given source address is always translated to the same pool address by
2770 # using the source-hash keyword.
2771 nat on $ext_if inet from any to any -\*(Gt 192.0.2.16/28 source-hash
2774 # Translate incoming web server connections to a group of web servers on
2775 # the internal network.
2776 rdr on $ext_if proto tcp from any to any port 80 \e
2777 -\*(Gt { 10.1.2.155, 10.1.2.160, 10.1.2.161 } round-robin
2781 # The external interface is kue0
2782 # (157.161.48.183, the only routable address)
2783 # and the private network is 10.0.0.0/8, for which we are doing NAT.
2785 # use a macro for the interface name, so it can be changed easily
2788 # normalize all incoming traffic
2789 scrub in on $ext_if all fragment reassemble
2791 # block and log everything by default
2792 block return log on $ext_if all
2794 # block anything coming from source we have no back routes for
2795 block in from no-route to any
2797 # block packets whose ingress interface does not match the one in
2798 # the route back to their source address
2799 block in from urpf-failed to any
2801 # block and log outgoing packets that do not have our address as source,
2802 # they are either spoofed or something is misconfigured (NAT disabled,
2803 # for instance), we want to be nice and do not send out garbage.
2804 block out log quick on $ext_if from ! 157.161.48.183 to any
2806 # silently drop broadcasts (cable modem noise)
2807 block in quick on $ext_if from any to 255.255.255.255
2809 # block and log incoming packets from reserved address space and invalid
2810 # addresses, they are either spoofed or misconfigured, we cannot reply to
2811 # them anyway (hence, no return-rst).
2812 block in log quick on $ext_if from { 10.0.0.0/8, 172.16.0.0/12, \e
2813 192.168.0.0/16, 255.255.255.255/32 } to any
2817 # pass out/in certain ICMP queries and keep state (ping)
2818 # state matching is done on host addresses and ICMP id (not type/code),
2819 # so replies (like 0/0 for 8/0) will match queries
2820 # ICMP error messages (which always refer to a TCP/UDP packet) are
2821 # handled by the TCP/UDP states
2822 pass on $ext_if inet proto icmp all icmp-type 8 code 0
2826 # pass out all UDP connections and keep state
2827 pass out on $ext_if proto udp all
2829 # pass in certain UDP connections and keep state (DNS)
2830 pass in on $ext_if proto udp from any to any port domain
2834 # pass out all TCP connections and modulate state
2835 pass out on $ext_if proto tcp all modulate state
2837 # pass in certain TCP connections and keep state (SSH, SMTP, DNS, IDENT)
2838 pass in on $ext_if proto tcp from any to any port { ssh, smtp, domain, \e
2841 # Do not allow Windows 9x SMTP connections since they are typically
2842 # a viral worm. Alternately we could limit these OSes to 1 connection each.
2843 block in on $ext_if proto tcp from any os {"Windows 95", "Windows 98"} \e
2847 # pass in/out all IPv6 traffic: note that we have to enable this in two
2848 # different ways, on both our physical interface and our tunnel
2849 pass quick on gif0 inet6
2850 pass quick on $ext_if proto ipv6
2854 # three interfaces: $int_if, $ext_if, and $wifi_if (wireless). NAT is
2855 # being done on $ext_if for all outgoing packets. tag packets in on
2856 # $int_if and pass those tagged packets out on $ext_if. all other
2857 # outgoing packets (i.e., packets from the wireless network) are only
2858 # permitted to access port 80.
2860 pass in on $int_if from any to any tag INTNET
2861 pass in on $wifi_if from any to any
2863 block out on $ext_if from any to any
2864 pass out quick on $ext_if tagged INTNET
2865 pass out on $ext_if proto tcp from any to any port 80
2867 # tag incoming packets as they are redirected to spamd(8). use the tag
2868 # to pass those packets through the packet filter.
2870 rdr on $ext_if inet proto tcp from \*(Ltspammers\*(Gt to port smtp \e
2871 tag SPAMD -\*(Gt 127.0.0.1 port spamd
2874 pass in on $ext_if inet proto tcp tagged SPAMD
2881 line = ( option | pf-rule | nat-rule | binat-rule | rdr-rule |
2882 antispoof-rule | altq-rule | queue-rule | trans-anchors |
2883 anchor-rule | anchor-close | load-anchor | table-rule |
2886 option = "set" ( [ "timeout" ( timeout | "{" timeout-list "}" ) ] |
2887 [ "ruleset-optimization" [ "none" | "basic" | "profile" ]] |
2888 [ "optimization" [ "default" | "normal" |
2889 "high-latency" | "satellite" |
2890 "aggressive" | "conservative" ] ]
2891 [ "limit" ( limit-item | "{" limit-list "}" ) ] |
2892 [ "loginterface" ( interface-name | "none" ) ] |
2893 [ "block-policy" ( "drop" | "return" ) ] |
2894 [ "state-policy" ( "if-bound" | "floating" ) ]
2895 [ "state-defaults" state-opts ]
2896 [ "require-order" ( "yes" | "no" ) ]
2897 [ "fingerprints" filename ] |
2898 [ "skip on" ifspec ] |
2899 [ "debug" ( "none" | "urgent" | "misc" | "loud" ) ]
2900 [ "keepcounters" ] )
2902 pf-rule = action [ ( "in" | "out" ) ]
2903 [ "log" [ "(" logopts ")"] ] [ "quick" ]
2904 [ "on" ifspec ] [ route ] [ af ] [ protospec ]
2905 hosts [ filteropt-list ]
2907 logopts = logopt [ "," logopts ]
2908 logopt = "all" | "user" | "to" interface-name
2910 filteropt-list = filteropt-list filteropt | filteropt
2911 filteropt = user | group | flags | icmp-type | icmp6-type | "tos" tos |
2912 ( "no" | "keep" | "modulate" | "synproxy" ) "state"
2913 [ "(" state-opts ")" ] |
2914 "fragment" | "no-df" | "min-ttl" number | "set-tos" tos |
2915 "max-mss" number | "random-id" | "reassemble tcp" |
2916 fragmentation | "allow-opts" |
2917 "label" string | "tag" string | [ ! ] "tagged" string |
2918 "set prio" ( number | "(" number [ [ "," ] number ] ")" ) |
2919 "queue" ( string | "(" string [ [ "," ] string ] ")" ) |
2920 "rtable" number | "probability" number"%" | "prio" number
2922 nat-rule = [ "no" ] "nat" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
2923 [ "on" ifspec ] [ af ]
2924 [ protospec ] hosts [ "tag" string ] [ "tagged" string ]
2925 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" )
2926 [ portspec ] [ pooltype ] [ "static-port" ]
2927 [ "map-e-portset" number "/" number "/" number ] ]
2929 binat-rule = [ "no" ] "binat" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
2930 [ "on" interface-name ] [ af ]
2931 [ "proto" ( proto-name | proto-number ) ]
2932 "from" address [ "/" mask-bits ] "to" ipspec
2933 [ "tag" string ] [ "tagged" string ]
2934 [ "-\*(Gt" address [ "/" mask-bits ] ]
2936 rdr-rule = [ "no" ] "rdr" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
2937 [ "on" ifspec ] [ af ]
2938 [ protospec ] hosts [ "tag" string ] [ "tagged" string ]
2939 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" )
2940 [ portspec ] [ pooltype ] ]
2942 antispoof-rule = "antispoof" [ "log" ] [ "quick" ]
2943 "for" ifspec [ af ] [ "label" string ]
2945 table-rule = "table" "\*(Lt" string "\*(Gt" [ tableopts-list ]
2946 tableopts-list = tableopts-list tableopts | tableopts
2947 tableopts = "persist" | "const" | "counters" | "file" string |
2948 "{" [ tableaddr-list ] "}"
2949 tableaddr-list = tableaddr-list [ "," ] tableaddr-spec | tableaddr-spec
2950 tableaddr-spec = [ "!" ] tableaddr [ "/" mask-bits ]
2951 tableaddr = hostname | ifspec | "self" |
2952 ipv4-dotted-quad | ipv6-coloned-hex
2954 altq-rule = "altq on" interface-name queueopts-list
2956 queue-rule = "queue" string [ "on" interface-name ] queueopts-list
2959 anchor-rule = "anchor" [ string ] [ ( "in" | "out" ) ] [ "on" ifspec ]
2960 [ af ] [ protospec ] [ hosts ] [ filteropt-list ] [ "{" ]
2964 trans-anchors = ( "nat-anchor" | "rdr-anchor" | "binat-anchor" ) string
2965 [ "on" ifspec ] [ af ] [ "proto" ] [ protospec ] [ hosts ]
2967 load-anchor = "load anchor" string "from" filename
2969 queueopts-list = queueopts-list queueopts | queueopts
2970 queueopts = [ "bandwidth" bandwidth-spec ] |
2971 [ "qlimit" number ] | [ "tbrsize" number ] |
2972 [ "priority" number ] | [ schedulers ]
2973 schedulers = ( cbq-def | priq-def | hfsc-def )
2974 bandwidth-spec = "number" ( "b" | "Kb" | "Mb" | "Gb" | "%" )
2976 action = "pass" | "block" [ return ] | [ "no" ] "scrub"
2977 return = "drop" | "return" | "return-rst" [ "( ttl" number ")" ] |
2978 "return-icmp" [ "(" icmpcode [ [ "," ] icmp6code ] ")" ] |
2979 "return-icmp6" [ "(" icmp6code ")" ]
2980 icmpcode = ( icmp-code-name | icmp-code-number )
2981 icmp6code = ( icmp6-code-name | icmp6-code-number )
2983 ifspec = ( [ "!" ] ( interface-name | interface-group ) ) |
2984 "{" interface-list "}"
2985 interface-list = [ "!" ] ( interface-name | interface-group )
2986 [ [ "," ] interface-list ]
2987 route = ( "route-to" | "reply-to" | "dup-to" )
2988 ( routehost | "{" routehost-list "}" )
2990 af = "inet" | "inet6"
2992 protospec = "proto" ( proto-name | proto-number |
2993 "{" proto-list "}" )
2994 proto-list = ( proto-name | proto-number ) [ [ "," ] proto-list ]
2997 "from" ( "any" | "no-route" | "urpf-failed" | "self" | host |
2998 "{" host-list "}" ) [ port ] [ os ]
2999 "to" ( "any" | "no-route" | "self" | host |
3000 "{" host-list "}" ) [ port ]
3002 ipspec = "any" | host | "{" host-list "}"
3003 host = [ "!" ] ( address [ "/" mask-bits ] | "\*(Lt" string "\*(Gt" )
3004 redirhost = address [ "/" mask-bits ]
3005 routehost = "(" interface-name [ address [ "/" mask-bits ] ] ")"
3006 address = ( interface-name | interface-group |
3007 "(" ( interface-name | interface-group ) ")" |
3008 hostname | ipv4-dotted-quad | ipv6-coloned-hex )
3009 host-list = host [ [ "," ] host-list ]
3010 redirhost-list = redirhost [ [ "," ] redirhost-list ]
3011 routehost-list = routehost [ [ "," ] routehost-list ]
3013 port = "port" ( unary-op | binary-op | "{" op-list "}" )
3014 portspec = "port" ( number | name ) [ ":" ( "*" | number | name ) ]
3015 os = "os" ( os-name | "{" os-list "}" )
3016 user = "user" ( unary-op | binary-op | "{" op-list "}" )
3017 group = "group" ( unary-op | binary-op | "{" op-list "}" )
3019 unary-op = [ "=" | "!=" | "\*(Lt" | "\*(Le" | "\*(Gt" | "\*(Ge" ]
3021 binary-op = number ( "\*(Lt\*(Gt" | "\*(Gt\*(Lt" | ":" ) number
3022 op-list = ( unary-op | binary-op ) [ [ "," ] op-list ]
3024 os-name = operating-system-name
3025 os-list = os-name [ [ "," ] os-list ]
3027 flags = "flags" ( [ flag-set ] "/" flag-set | "any" )
3028 flag-set = [ "F" ] [ "S" ] [ "R" ] [ "P" ] [ "A" ] [ "U" ] [ "E" ]
3031 icmp-type = "icmp-type" ( icmp-type-code | "{" icmp-list "}" )
3032 icmp6-type = "icmp6-type" ( icmp-type-code | "{" icmp-list "}" )
3033 icmp-type-code = ( icmp-type-name | icmp-type-number )
3034 [ "code" ( icmp-code-name | icmp-code-number ) ]
3035 icmp-list = icmp-type-code [ [ "," ] icmp-list ]
3037 tos = ( "lowdelay" | "throughput" | "reliability" |
3040 state-opts = state-opt [ [ "," ] state-opts ]
3041 state-opt = ( "max" number | "no-sync" | timeout | "sloppy" |
3042 "source-track" [ ( "rule" | "global" ) ] |
3043 "max-src-nodes" number | "max-src-states" number |
3044 "max-src-conn" number |
3045 "max-src-conn-rate" number "/" number |
3046 "overload" "\*(Lt" string "\*(Gt" [ "flush" ] |
3047 "if-bound" | "floating" )
3049 fragmentation = [ "fragment reassemble" ]
3051 timeout-list = timeout [ [ "," ] timeout-list ]
3052 timeout = ( "tcp.first" | "tcp.opening" | "tcp.established" |
3053 "tcp.closing" | "tcp.finwait" | "tcp.closed" |
3054 "udp.first" | "udp.single" | "udp.multiple" |
3055 "icmp.first" | "icmp.error" |
3056 "other.first" | "other.single" | "other.multiple" |
3057 "frag" | "interval" | "src.track" |
3058 "adaptive.start" | "adaptive.end" ) number
3060 limit-list = limit-item [ [ "," ] limit-list ]
3061 limit-item = ( "states" | "frags" | "src-nodes" ) number
3063 pooltype = ( "bitmask" | "random" |
3064 "source-hash" [ ( hex-key | string-key ) ] |
3065 "round-robin" ) [ sticky-address ]
3067 subqueue = string | "{" queue-list "}"
3068 queue-list = string [ [ "," ] string ]
3069 cbq-def = "cbq" [ "(" cbq-opt [ [ "," ] cbq-opt ] ")" ]
3070 priq-def = "priq" [ "(" priq-opt [ [ "," ] priq-opt ] ")" ]
3071 hfsc-def = "hfsc" [ "(" hfsc-opt [ [ "," ] hfsc-opt ] ")" ]
3072 cbq-opt = ( "default" | "borrow" | "red" | "ecn" | "rio" )
3073 priq-opt = ( "default" | "red" | "ecn" | "rio" )
3074 hfsc-opt = ( "default" | "red" | "ecn" | "rio" |
3075 linkshare-sc | realtime-sc | upperlimit-sc )
3076 linkshare-sc = "linkshare" sc-spec
3077 realtime-sc = "realtime" sc-spec
3078 upperlimit-sc = "upperlimit" sc-spec
3079 sc-spec = ( bandwidth-spec |
3080 "(" bandwidth-spec number bandwidth-spec ")" )
3081 include = "include" filename
3084 .Bl -tag -width "/etc/protocols" -compact
3088 Default location of the ruleset file.
3089 The file has to be created manually as it is not installed with a
3090 standard installation.
3092 Default location of OS fingerprints.
3093 .It Pa /etc/protocols
3094 Protocol name database.
3095 .It Pa /etc/services
3096 Service name database.
3119 file format first appeared in