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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.
623 .Sh TRAFFIC NORMALIZATION
624 Traffic normalization is used to sanitize packet content in such
625 a way that there are no ambiguities in packet interpretation on
627 The normalizer does IP fragment reassembly to prevent attacks
628 that confuse intrusion detection systems by sending overlapping
630 Packet normalization is invoked with the
635 has the following options:
640 bit from a matching IP packet.
641 Some operating systems are known to generate fragmented packets with the
644 This is particularly true with NFS.
646 will drop such fragmented
652 Unfortunately some operating systems also generate their
654 packets with a zero IP identification field.
657 bit on packets with a zero IP ID may cause deleterious results if an
658 upstream router later fragments the packet.
661 modifier (see below) is recommended in combination with the
663 modifier to ensure unique IP identifiers.
664 .It Ar min-ttl Aq Ar number
665 Enforces a minimum TTL for matching IP packets.
666 .It Ar max-mss Aq Ar number
667 Enforces a maximum MSS for matching TCP packets.
668 .It Xo Ar set-tos Aq Ar string
669 .No \*(Ba Aq Ar number
673 for matching IP packets.
683 or one of the DiffServ Code Points:
686 .Ar af11 No ... Ar af43 ,
687 .Ar cs0 No ... Ar cs7 ;
688 or as either hex or decimal.
690 Replaces the IP identification field with random values to compensate
691 for predictable values generated by many hosts.
692 This option only applies to packets that are not fragmented
693 after the optional fragment reassembly.
694 .It Ar fragment reassemble
697 rules, fragments can be reassembled by normalization.
698 In this case, fragments are buffered until they form a complete
699 packet, and only the completed packet is passed on to the filter.
700 The advantage is that filter rules have to deal only with complete
701 packets, and can ignore fragments.
702 The drawback of caching fragments is the additional memory cost.
703 .It Ar reassemble tcp
704 Statefully normalizes TCP connections.
705 .Ar scrub reassemble tcp
706 rules may not have the direction (in/out) specified.
708 performs the following normalizations:
710 .Bl -tag -width timeout -compact
712 Neither side of the connection is allowed to reduce their IP TTL.
713 An attacker may send a packet such that it reaches the firewall, affects
714 the firewall state, and expires before reaching the destination host.
716 will raise the TTL of all packets back up to the highest value seen on
718 .It timestamp modulation
719 Modern TCP stacks will send a timestamp on every TCP packet and echo
720 the other endpoint's timestamp back to them.
721 Many operating systems will merely start the timestamp at zero when
722 first booted, and increment it several times a second.
723 The uptime of the host can be deduced by reading the timestamp and multiplying
725 Also observing several different timestamps can be used to count hosts
727 And spoofing TCP packets into a connection requires knowing or guessing
729 Timestamps merely need to be monotonically increasing and not derived off a
734 to modulate the TCP timestamps with a random number.
735 .It extended PAWS checks
736 There is a problem with TCP on long fat pipes, in that a packet might get
737 delayed for longer than it takes the connection to wrap its 32-bit sequence
739 In such an occurrence, the old packet would be indistinguishable from a
740 new packet and would be accepted as such.
741 The solution to this is called PAWS: Protection Against Wrapped Sequence
743 It protects against it by making sure the timestamp on each packet does
746 also makes sure the timestamp on the packet does not go forward more
750 artificially extends the security of TCP sequence numbers by 10 to 18
751 bits when the host uses appropriately randomized timestamps, since a
752 blind attacker would have to guess the timestamp as well.
757 .Bd -literal -offset indent
758 scrub in on $ext_if all fragment reassemble
763 option prefixed to a scrub rule causes matching packets to remain unscrubbed,
764 much in the same way as
766 works in the packet filter (see below).
767 This mechanism should be used when it is necessary to exclude specific packets
768 from broader scrub rules.
770 The ALTQ system is currently not available in the GENERIC kernel nor as
772 In order to use the herein after called queueing options one has to use a
776 to learn about the related kernel options.
778 Packets can be assigned to queues for the purpose of bandwidth
780 At least two declarations are required to configure queues, and later
781 any packet filtering rule can reference the defined queues by name.
782 During the filtering component of
786 name is where any packets from
788 rules will be queued, while for
790 rules it specifies where any resulting ICMP or TCP RST
791 packets should be queued.
794 defines the algorithm used to decide which packets get delayed, dropped, or
795 sent out immediately.
801 Class Based Queueing.
803 attached to an interface build a tree, thus each
805 can have further child
807 Each queue can have a
813 mainly controls the time packets take to get sent out, while
815 has primarily effects on throughput.
817 achieves both partitioning and sharing of link bandwidth
818 by hierarchically structured classes.
819 Each class has its own
821 and is assigned its share of
823 A child class can borrow bandwidth from its parent class
824 as long as excess bandwidth is available
831 are flat attached to the interface, thus,
833 cannot have further child
839 assigned, ranging from 0 to 15.
846 Hierarchical Fair Service Curve.
848 attached to an interface build a tree, thus each
850 can have further child
852 Each queue can have a
858 mainly controls the time packets take to get sent out, while
860 primarily affects throughput.
862 supports both link-sharing and guaranteed real-time services.
863 It employs a service curve based QoS model,
864 and its unique feature is an ability to decouple
871 The interfaces on which queueing should be activated are declared using
876 has the following keywords:
879 Queueing is enabled on the named interface.
881 Specifies which queueing scheduler to use.
882 Currently supported values
885 for Class Based Queueing,
887 for Priority Queueing and
889 for the Hierarchical Fair Service Curve scheduler.
890 .It Ar bandwidth Aq Ar bw
891 The maximum bitrate for all queues on an
892 interface may be specified using the
895 The value can be specified as an absolute value or as a
896 percentage of the interface bandwidth.
897 When using an absolute value, the suffixes
903 are used to represent bits, kilobits, megabits, and
904 gigabits per second, respectively.
905 The value must not exceed the interface bandwidth.
908 is not specified, the interface bandwidth is used
909 (but take note that some interfaces do not know their bandwidth,
910 or can adapt their bandwidth rates).
911 .It Ar qlimit Aq Ar limit
912 The maximum number of packets held in the queue.
914 .It Ar tbrsize Aq Ar size
915 Adjusts the size, in bytes, of the token bucket regulator.
916 If not specified, heuristics based on the
917 interface bandwidth are used to determine the size.
918 .It Ar queue Aq Ar list
919 Defines a list of subqueues to create on an interface.
922 In the following example, the interface dc0
923 should queue up to 5Mbps in four second-level queues using
924 Class Based Queueing.
925 Those four queues will be shown in a later example.
926 .Bd -literal -offset indent
927 altq on dc0 cbq bandwidth 5Mb queue { std, http, mail, ssh }
930 Once interfaces are activated for queueing using the
932 directive, a sequence of
934 directives may be defined.
935 The name associated with a
937 must match a queue defined in the
939 directive (e.g. mail), or, except for the
945 The following keywords can be used:
947 .It Ar on Aq Ar interface
948 Specifies the interface the queue operates on.
949 If not given, it operates on all matching interfaces.
950 .It Ar bandwidth Aq Ar bw
951 Specifies the maximum bitrate to be processed by the queue.
952 This value must not exceed the value of the parent
954 and can be specified as an absolute value or a percentage of the parent
956 If not specified, defaults to 100% of the parent queue's bandwidth.
959 scheduler does not support bandwidth specification.
960 .It Ar priority Aq Ar level
961 Between queues a priority level can be set.
966 the range is 0 to 7 and for
968 the range is 0 to 15.
969 The default for all is 1.
971 queues with a higher priority are always served first.
975 queues with a higher priority are preferred in the case of overload.
976 .It Ar qlimit Aq Ar limit
977 The maximum number of packets held in the queue.
983 can get additional parameters with
985 .Pf ( Aq Ar parameters ) .
987 Parameters are as follows:
990 Packets not matched by another queue are assigned to this one.
991 Exactly one default queue is required.
993 Enable RED (Random Early Detection) on this queue.
994 RED drops packets with a probability proportional to the average
997 Enables RIO on this queue.
998 RIO is RED with IN/OUT, thus running
999 RED two times more than RIO would achieve the same effect.
1000 RIO is currently not supported in the GENERIC kernel.
1002 Enables ECN (Explicit Congestion Notification) on this queue.
1009 supports an additional option:
1012 The queue can borrow bandwidth from the parent.
1018 supports some additional options:
1020 .It Ar realtime Aq Ar sc
1021 The minimum required bandwidth for the queue.
1022 .It Ar upperlimit Aq Ar sc
1023 The maximum allowed bandwidth for the queue.
1024 .It Ar linkshare Aq Ar sc
1025 The bandwidth share of a backlogged queue.
1032 The format for service curve specifications is
1033 .Ar ( m1 , d , m2 ) .
1035 controls the bandwidth assigned to the queue.
1039 are optional and can be used to control the initial bandwidth assignment.
1042 milliseconds the queue gets the bandwidth given as
1044 afterwards the value given in
1051 child queues can be specified as in an
1053 declaration, thus building a tree of queues using a part of
1054 their parent's bandwidth.
1056 Packets can be assigned to queues based on filter rules by using the
1061 is specified; when a second one is specified it will instead be used for
1062 packets which have a
1066 and for TCP ACKs with no data payload.
1068 To continue the previous example, the examples below would specify the
1070 queues, plus a few child queues.
1073 sessions get priority over bulk transfers like
1077 The queues may then be referenced by filtering rules (see
1078 .Sx PACKET FILTERING
1081 queue std bandwidth 10% cbq(default)
1082 queue http bandwidth 60% priority 2 cbq(borrow red) \e
1083 { employees, developers }
1084 queue developers bandwidth 75% cbq(borrow)
1085 queue employees bandwidth 15%
1086 queue mail bandwidth 10% priority 0 cbq(borrow ecn)
1087 queue ssh bandwidth 20% cbq(borrow) { ssh_interactive, ssh_bulk }
1088 queue ssh_interactive bandwidth 50% priority 7 cbq(borrow)
1089 queue ssh_bulk bandwidth 50% priority 0 cbq(borrow)
1091 block return out on dc0 inet all queue std
1092 pass out on dc0 inet proto tcp from $developerhosts to any port 80 \e
1094 pass out on dc0 inet proto tcp from $employeehosts to any port 80 \e
1096 pass out on dc0 inet proto tcp from any to any port 22 \e
1097 queue(ssh_bulk, ssh_interactive)
1098 pass out on dc0 inet proto tcp from any to any port 25 \e
1102 Translation rules modify either the source or destination address of the
1103 packets associated with a stateful connection.
1104 A stateful connection is automatically created to track packets matching
1105 such a rule as long as they are not blocked by the filtering section of
1107 The translation engine modifies the specified address and/or port in the
1108 packet, recalculates IP, TCP and UDP checksums as necessary, and passes it to
1109 the packet filter for evaluation.
1111 Since translation occurs before filtering the filter
1112 engine will see packets as they look after any
1113 addresses and ports have been translated.
1114 Filter rules will therefore have to filter based on the translated
1115 address and port number.
1116 Packets that match a translation rule are only automatically passed if
1119 modifier is given, otherwise they are
1126 The state entry created permits
1128 to keep track of the original address for traffic associated with that state
1129 and correctly direct return traffic for that connection.
1131 Various types of translation are possible with pf:
1132 .Bl -tag -width xxxx
1136 rule specifies a bidirectional mapping between an external IP netblock
1137 and an internal IP netblock.
1141 rule specifies that IP addresses are to be changed as the packet
1142 traverses the given interface.
1143 This technique allows one or more IP addresses
1144 on the translating host to support network traffic for a larger range of
1145 machines on an "inside" network.
1146 Although in theory any IP address can be used on the inside, it is strongly
1147 recommended that one of the address ranges defined by RFC 1918 be used.
1148 These netblocks are:
1150 10.0.0.0 - 10.255.255.255 (all of net 10, i.e., 10/8)
1151 172.16.0.0 - 172.31.255.255 (i.e., 172.16/12)
1152 192.168.0.0 - 192.168.255.255 (i.e., 192.168/16)
1155 The packet is redirected to another destination and possibly a
1158 rules can optionally specify port ranges instead of single ports.
1159 rdr ... port 2000:2999 -\*(Gt ... port 4000
1160 redirects ports 2000 to 2999 (inclusive) to port 4000.
1161 rdr ... port 2000:2999 -\*(Gt ... port 4000:*
1162 redirects port 2000 to 4000, 2001 to 4001, ..., 2999 to 4999.
1165 In addition to modifying the address, some translation rules may modify
1166 source or destination ports for
1170 connections; implicitly in the case of
1172 rules and explicitly in the case of
1175 Port numbers are never translated with a
1179 Evaluation order of the translation rules is dependent on the type
1180 of the translation rules and of the direction of a packet.
1182 rules are always evaluated first.
1185 rules are evaluated on an inbound packet or the
1187 rules on an outbound packet.
1188 Rules of the same type are evaluated in the same order in which they
1189 appear in the ruleset.
1190 The first matching rule decides what action is taken.
1194 option prefixed to a translation rule causes packets to remain untranslated,
1195 much in the same way as
1197 works in the packet filter (see below).
1198 If no rule matches the packet it is passed to the filter engine unmodified.
1200 Translation rules apply only to packets that pass through
1201 the specified interface, and if no interface is specified,
1202 translation is applied to packets on all interfaces.
1203 For instance, redirecting port 80 on an external interface to an internal
1204 web server will only work for connections originating from the outside.
1205 Connections to the address of the external interface from local hosts will
1206 not be redirected, since such packets do not actually pass through the
1208 Redirections cannot reflect packets back through the interface they arrive
1209 on, they can only be redirected to hosts connected to different interfaces
1210 or to the firewall itself.
1212 Note that redirecting external incoming connections to the loopback
1214 .Bd -literal -offset indent
1215 rdr on ne3 inet proto tcp to port smtp -\*(Gt 127.0.0.1 port spamd
1218 will effectively allow an external host to connect to daemons
1219 bound solely to the loopback address, circumventing the traditional
1220 blocking of such connections on a real interface.
1221 Unless this effect is desired, any of the local non-loopback addresses
1222 should be used as redirection target instead, which allows external
1223 connections only to daemons bound to this address or not bound to
1227 .Sx TRANSLATION EXAMPLES
1229 .Sh PACKET FILTERING
1235 packets based on attributes of their layer 3 (see
1245 In addition, packets may also be
1246 assigned to queues for the purpose of bandwidth control.
1248 For each packet processed by the packet filter, the filter rules are
1249 evaluated in sequential order, from first to last.
1250 The last matching rule decides what action is taken.
1251 If no rule matches the packet, the default action is to pass
1254 The following actions can be used in the filter:
1255 .Bl -tag -width xxxx
1257 The packet is blocked.
1258 There are a number of ways in which a
1260 rule can behave when blocking a packet.
1261 The default behaviour is to
1263 packets silently, however this can be overridden or made
1264 explicit either globally, by setting the
1266 option, or on a per-rule basis with one of the following options:
1268 .Bl -tag -width xxxx -compact
1270 The packet is silently dropped.
1272 This applies only to
1274 packets, and issues a TCP RST which closes the
1278 This causes ICMP messages to be returned for packets which match the rule.
1279 By default this is an ICMP UNREACHABLE message, however this
1280 can be overridden by specifying a message as a code or number.
1282 This causes a TCP RST to be returned for
1284 packets and an ICMP UNREACHABLE for UDP and other packets.
1287 Options returning ICMP packets currently have no effect if
1291 as the code to support this feature has not yet been implemented.
1293 The simplest mechanism to block everything by default and only pass
1294 packets that match explicit rules is specify a first filter rule of:
1295 .Bd -literal -offset indent
1299 The packet is passed;
1300 state is created unless the
1302 option is specified.
1307 filters packets statefully; the first time a packet matches a
1309 rule, a state entry is created; for subsequent packets the filter checks
1310 whether the packet matches any state.
1311 If it does, the packet is passed without evaluation of any rules.
1312 After the connection is closed or times out, the state entry is automatically
1315 This has several advantages.
1316 For TCP connections, comparing a packet to a state involves checking
1317 its sequence numbers, as well as TCP timestamps if a
1318 .Ar scrub reassemble tcp
1319 rule applies to the connection.
1320 If these values are outside the narrow windows of expected
1321 values, the packet is dropped.
1322 This prevents spoofing attacks, such as when an attacker sends packets with
1323 a fake source address/port but does not know the connection's sequence
1327 knows how to match ICMP replies to states.
1329 .Bd -literal -offset indent
1330 pass out inet proto icmp all icmp-type echoreq
1333 allows echo requests (such as those created by
1335 out statefully, and matches incoming echo replies correctly to states.
1337 Also, looking up states is usually faster than evaluating rules.
1338 If there are 50 rules, all of them are evaluated sequentially in O(n).
1339 Even with 50000 states, only 16 comparisons are needed to match a
1340 state, since states are stored in a binary search tree that allows
1341 searches in O(log2 n).
1343 Furthermore, correct handling of ICMP error messages is critical to
1344 many protocols, particularly TCP.
1346 matches ICMP error messages to the correct connection, checks them against
1347 connection parameters, and passes them if appropriate.
1348 For example if an ICMP source quench message referring to a stateful TCP
1349 connection arrives, it will be matched to the state and get passed.
1351 Finally, state tracking is required for
1352 .Ar nat , binat No and Ar rdr
1353 rules, in order to track address and port translations and reverse the
1354 translation on returning packets.
1357 will also create state for other protocols which are effectively stateless by
1359 UDP packets are matched to states using only host addresses and ports,
1360 and other protocols are matched to states using only the host addresses.
1362 If stateless filtering of individual packets is desired,
1365 keyword can be used to specify that state will not be created
1366 if this is the last matching rule.
1367 A number of parameters can also be set to affect how
1369 handles state tracking.
1371 .Sx STATEFUL TRACKING OPTIONS
1372 below for further details.
1374 The rule parameters specify the packets to which a rule applies.
1375 A packet always comes in on, or goes out through, one interface.
1376 Most parameters are optional.
1377 If a parameter is specified, the rule only applies to packets with
1378 matching attributes.
1379 Certain parameters can be expressed as lists, in which case
1381 generates all needed rule combinations.
1382 .Bl -tag -width xxxx
1383 .It Ar in No or Ar out
1384 This rule applies to incoming or outgoing packets.
1389 are specified, the rule will match packets in both directions.
1391 In addition to the action specified, a log message is generated.
1392 Only the packet that establishes the state is logged,
1395 option is specified.
1396 The logged packets are sent to a
1398 interface, by default
1400 This interface is monitored by the
1402 logging daemon, which dumps the logged packets to the file
1408 Used to force logging of all packets for a connection.
1409 This is not necessary when
1411 is explicitly specified.
1414 packets are logged to
1419 user ID of the user that owns the socket and the PID of the process that
1420 has the socket open where the packet is sourced from or destined to
1421 (depending on which socket is local).
1422 This is in addition to the normal information logged.
1424 Only the first packet
1427 will have the user credentials logged when using stateful matching.
1428 .It Ar log (to Aq Ar interface )
1429 Send logs to the specified
1431 interface instead of
1434 If a packet matches a rule which has the
1436 option set, this rule
1437 is considered the last matching rule, and evaluation of subsequent rules
1439 .It Ar on Aq Ar interface
1440 This rule applies only to packets coming in on, or going out through, this
1441 particular interface or interface group.
1442 For more information on interface groups,
1448 This rule applies only to packets of this address family.
1449 Supported values are
1453 .It Ar proto Aq Ar protocol
1454 This rule applies only to packets of this protocol.
1455 Common protocols are
1461 For a list of all the protocol name to number mappings used by
1464 .Pa /etc/protocols .
1466 .Ar from Aq Ar source
1467 .Ar port Aq Ar source
1472 This rule applies only to packets with the specified source and destination
1473 addresses and ports.
1475 Addresses can be specified in CIDR notation (matching netblocks), as
1476 symbolic host names, interface names or interface group names, or as any
1477 of the following keywords:
1479 .Bl -tag -width xxxxxxxxxxxxxx -compact
1483 Any address which is not currently routable.
1485 Any source address that fails a unicast reverse path forwarding (URPF)
1486 check, i.e. packets coming in on an interface other than that which holds
1487 the route back to the packet's source address.
1489 Any address that matches the given table.
1492 Ranges of addresses are specified by using the
1496 .Dq 10.1.1.10 - 10.1.1.12
1497 means all addresses from 10.1.1.10 to 10.1.1.12,
1498 hence addresses 10.1.1.10, 10.1.1.11, and 10.1.1.12.
1500 Interface names and interface group names can have modifiers appended:
1502 .Bl -tag -width xxxxxxxxxxxx -compact
1504 Translates to the network(s) attached to the interface.
1506 Translates to the interface's broadcast address(es).
1508 Translates to the point-to-point interface's peer address(es).
1510 Do not include interface aliases.
1513 Host names may also have the
1515 option appended to restrict the name resolution to the first of each
1516 v4 and v6 address found.
1518 Host name resolution and interface to address translation are done at
1520 When the address of an interface (or host name) changes (under DHCP or PPP,
1521 for instance), the ruleset must be reloaded for the change to be reflected
1523 Surrounding the interface name (and optional modifiers) in parentheses
1524 changes this behaviour.
1525 When the interface name is surrounded by parentheses, the rule is
1526 automatically updated whenever the interface changes its address.
1527 The ruleset does not need to be reloaded.
1528 This is especially useful with
1531 Ports can be specified either by number or by name.
1532 For example, port 80 can be specified as
1534 For a list of all port name to number mappings used by
1539 Ports and ranges of ports are specified by using these operators:
1540 .Bd -literal -offset indent
1544 \*(Le (less than or equal)
1545 \*(Gt (greater than)
1546 \*(Ge (greater than or equal)
1547 : (range including boundaries)
1548 \*(Gt\*(Lt (range excluding boundaries)
1549 \*(Lt\*(Gt (except range)
1556 are binary operators (they take two arguments).
1559 .It Ar port 2000:2004
1561 .Sq all ports \*(Ge 2000 and \*(Le 2004 ,
1562 hence ports 2000, 2001, 2002, 2003 and 2004.
1563 .It Ar port 2000 \*(Gt\*(Lt 2004
1565 .Sq all ports \*(Gt 2000 and \*(Lt 2004 ,
1566 hence ports 2001, 2002 and 2003.
1567 .It Ar port 2000 \*(Lt\*(Gt 2004
1569 .Sq all ports \*(Lt 2000 or \*(Gt 2004 ,
1570 hence ports 1-1999 and 2005-65535.
1573 The operating system of the source host can be specified in the case of TCP
1578 .Sx OPERATING SYSTEM FINGERPRINTING
1579 section for more information.
1581 The host, port and OS specifications are optional, as in the following examples:
1582 .Bd -literal -offset indent
1584 pass in from any to any
1585 pass in proto tcp from any port \*(Le 1024 to any
1586 pass in proto tcp from any to any port 25
1587 pass in proto tcp from 10.0.0.0/8 port \*(Gt 1024 \e
1588 to ! 10.1.2.3 port != ssh
1589 pass in proto tcp from any os "OpenBSD"
1592 This is equivalent to "from any to any".
1593 .It Ar group Aq Ar group
1596 this rule only applies to packets of sockets owned by the specified group.
1597 .It Ar user Aq Ar user
1598 This rule only applies to packets of sockets owned by the specified user.
1599 For outgoing connections initiated from the firewall, this is the user
1600 that opened the connection.
1601 For incoming connections to the firewall itself, this is the user that
1602 listens on the destination port.
1603 For forwarded connections, where the firewall is not a connection endpoint,
1604 the user and group are
1607 All packets, both outgoing and incoming, of one connection are associated
1608 with the same user and group.
1609 Only TCP and UDP packets can be associated with users; for other protocols
1610 these parameters are ignored.
1612 User and group refer to the effective (as opposed to the real) IDs, in
1613 case the socket is created by a setuid/setgid process.
1614 User and group IDs are stored when a socket is created;
1615 when a process creates a listening socket as root (for instance, by
1616 binding to a privileged port) and subsequently changes to another
1617 user ID (to drop privileges), the credentials will remain root.
1619 User and group IDs can be specified as either numbers or names.
1620 The syntax is similar to the one for ports.
1623 matches packets of forwarded connections.
1625 can only be used with the operators
1629 Other constructs like
1630 .Cm user \*(Ge unknown
1632 Forwarded packets with unknown user and group ID match only rules
1633 that explicitly compare against
1641 does not match forwarded packets.
1642 The following example allows only selected users to open outgoing
1644 .Bd -literal -offset indent
1645 block out proto { tcp, udp } all
1646 pass out proto { tcp, udp } all user { \*(Lt 1000, dhartmei }
1648 .It Xo Ar flags Aq Ar a
1650 .No \*(Ba / Ns Aq Ar b
1653 This rule only applies to TCP packets that have the flags
1657 Flags not specified in
1660 For stateful connections, the default is
1662 To indicate that flags should not be checked at all, specify
1664 The flags are: (F)IN, (S)YN, (R)ST, (P)USH, (A)CK, (U)RG, (E)CE, and C(W)R.
1668 The other flags are ignored.
1670 This is the default setting for stateful connections.
1671 Out of SYN and ACK, exactly SYN may be set.
1672 SYN, SYN+PSH and SYN+RST match, but SYN+ACK, ACK and ACK+RST do not.
1673 This is more restrictive than the previous example.
1675 If the first set is not specified, it defaults to none.
1676 All of SYN, FIN, RST and ACK must be unset.
1681 is applied by default (unless
1683 is specified), only the initial SYN packet of a TCP handshake will create
1684 a state for a TCP connection.
1685 It is possible to be less restrictive, and allow state creation from
1688 packets, by specifying
1692 to synchronize to existing connections, for instance
1693 if one flushes the state table.
1694 However, states created from such intermediate packets may be missing
1695 connection details such as the TCP window scaling factor.
1696 States which modify the packet flow, such as those affected by
1697 .Ar nat , binat No or Ar rdr
1699 .Ar modulate No or Ar synproxy state
1700 options, or scrubbed with
1702 will also not be recoverable from intermediate packets.
1703 Such connections will stall and time out.
1704 .It Xo Ar icmp-type Aq Ar type
1707 .It Xo Ar icmp6-type Aq Ar type
1710 This rule only applies to ICMP or ICMPv6 packets with the specified type
1712 Text names for ICMP types and codes are listed in
1716 This parameter is only valid for rules that cover protocols ICMP or
1718 The protocol and the ICMP type indicator
1725 .It Xo Ar tos Aq Ar string
1726 .No \*(Ba Aq Ar number
1728 This rule applies to packets with the specified
1740 or one of the DiffServ Code Points:
1743 .Ar af11 No ... Ar af43 ,
1744 .Ar cs0 No ... Ar cs7 ;
1745 or as either hex or decimal.
1747 For example, the following rules are identical:
1748 .Bd -literal -offset indent
1749 pass all tos lowdelay
1754 By default, IPv4 packets with IP options or IPv6 packets with routing
1755 extension headers are blocked.
1760 rule, packets that pass the filter based on that rule (last matching)
1761 do so even if they contain IP options or routing extension headers.
1762 For packets that match state, the rule that initially created the
1766 rule that is used when a packet does not match any rules does not
1768 .It Ar label Aq Ar string
1769 Adds a label (name) to the rule, which can be used to identify the rule.
1772 shows per-rule statistics for rules that have labels.
1774 The following macros can be used in labels:
1776 .Bl -tag -width $srcaddr -compact -offset indent
1780 The source IP address.
1782 The destination IP address.
1784 The source port specification.
1786 The destination port specification.
1794 .Bd -literal -offset indent
1795 ips = \&"{ 1.2.3.4, 1.2.3.5 }\&"
1796 pass in proto tcp from any to $ips \e
1797 port \*(Gt 1023 label \&"$dstaddr:$dstport\&"
1801 .Bd -literal -offset indent
1802 pass in inet proto tcp from any to 1.2.3.4 \e
1803 port \*(Gt 1023 label \&"1.2.3.4:\*(Gt1023\&"
1804 pass in inet proto tcp from any to 1.2.3.5 \e
1805 port \*(Gt 1023 label \&"1.2.3.5:\*(Gt1023\&"
1808 The macro expansion for the
1810 directive occurs only at configuration file parse time, not during runtime.
1811 .It Xo Ar queue Aq Ar queue
1812 .No \*(Ba ( Aq Ar queue ,
1815 Packets matching this rule will be assigned to the specified queue.
1816 If two queues are given, packets which have a
1820 and TCP ACKs with no data payload will be assigned to the second one.
1826 .Bd -literal -offset indent
1827 pass in proto tcp to port 25 queue mail
1828 pass in proto tcp to port 22 queue(ssh_bulk, ssh_prio)
1831 .It Cm set prio Ar priority | Pq Ar priority , priority
1832 Packets matching this rule will be assigned a specific queueing priority.
1833 Priorities are assigned as integers 0 through 7.
1834 If the packet is transmitted on a
1836 interface, the queueing priority will be written as the priority
1837 code point in the 802.1Q VLAN header.
1838 If two priorities are given, packets which have a TOS of
1840 and TCP ACKs with no data payload will be assigned to the second one.
1843 .Bd -literal -offset indent
1844 pass in proto tcp to port 25 set prio 2
1845 pass in proto tcp to port 22 set prio (2, 5)
1848 .It Ar tag Aq Ar string
1849 Packets matching this rule will be tagged with the
1851 The tag acts as an internal marker that can be used to
1852 identify these packets later on.
1853 This can be used, for example, to provide trust between
1854 interfaces and to determine if packets have been
1855 processed by translation rules.
1858 meaning that the packet will be tagged even if the rule
1859 is not the last matching rule.
1860 Further matching rules can replace the tag with a
1861 new one but will not remove a previously applied tag.
1862 A packet is only ever assigned one tag at a time.
1863 Packet tagging can be done during
1868 rules in addition to filter rules.
1869 Tags take the same macros as labels (see above).
1870 .It Ar tagged Aq Ar string
1871 Used with filter, translation or scrub rules
1872 to specify that packets must already
1873 be tagged with the given tag in order to match the rule.
1874 Inverse tag matching can also be done
1880 .It Ar rtable Aq Ar number
1881 Used to select an alternate routing table for the routing lookup.
1882 Only effective before the route lookup happened, i.e. when filtering inbound.
1883 .It Xo Ar divert-to Aq Ar host
1886 Used to redirect packets to a local socket bound to
1890 The packets will not be modified, so
1892 on the socket will return the original destination address of the packet.
1894 Used to receive replies for sockets that are bound to addresses
1895 which are not local to the machine.
1898 for information on how to bind these sockets.
1899 .It Ar probability Aq Ar number
1900 A probability attribute can be attached to a rule, with a value set between
1901 0 and 1, bounds not included.
1902 In that case, the rule will be honoured using the given probability value
1904 For example, the following rule will drop 20% of incoming ICMP packets:
1905 .Bd -literal -offset indent
1906 block in proto icmp probability 20%
1908 .It Ar prio Aq Ar number
1909 Only match packets which have the given queueing priority assigned.
1913 If a packet matches a rule with a route option set, the packet filter will
1914 route the packet according to the type of route option.
1915 When such a rule creates state, the route option is also applied to all
1916 packets matching the same connection.
1917 .Bl -tag -width xxxx
1921 option routes the packet to the specified interface with an optional address
1925 rule creates state, only packets that pass in the same direction as the
1926 filter rule specifies will be routed in this way.
1927 Packets passing in the opposite direction (replies) are not affected
1928 and are routed normally.
1932 option is similar to
1934 but routes packets that pass in the opposite direction (replies) to the
1935 specified interface.
1936 Opposite direction is only defined in the context of a state entry, and
1938 is useful only in rules that create state.
1939 It can be used on systems with multiple external connections to
1940 route all outgoing packets of a connection through the interface
1941 the incoming connection arrived through (symmetric routing enforcement).
1945 option creates a duplicate of the packet and routes it like
1947 The original packet gets routed as it normally would.
1954 rules, (as well as for the
1959 rule options) for which there is a single redirection address which has a
1960 subnet mask smaller than 32 for IPv4 or 128 for IPv6 (more than one IP
1961 address), a variety of different methods for assigning this address can be
1963 .Bl -tag -width xxxx
1967 option applies the network portion of the redirection address to the address
1968 to be modified (source with
1975 option selects an address at random within the defined block of addresses.
1979 option uses a hash of the source address to determine the redirection address,
1980 ensuring that the redirection address is always the same for a given source.
1981 An optional key can be specified after this keyword either in hex or as a
1984 randomly generates a key for source-hash every time the
1985 ruleset is reloaded.
1989 option loops through the redirection address(es).
1991 When more than one redirection address is specified,
1993 is the only permitted pool type.
2001 from modifying the source port on TCP and UDP packets.
2002 .It Xo Ar map-e-portset Aq Ar psid-offset
2003 .No / Aq Ar psid-len
2010 option enables the source port translation of MAP-E (RFC 7597) Customer Edge.
2011 In order to make the host act as a MAP-E Customer Edge, setting up a tunneling
2012 interface and pass rules for encapsulated packets are required in addition
2013 to the map-e-portset nat rule.
2016 .Bd -literal -offset indent
2017 nat on $gif_mape_if from $int_if:network to any \e
2018 -> $ipv4_mape_src map-e-portset 6/8/0x34
2021 sets PSID offset 6, PSID length 8, PSID 0x34.
2027 option can be specified to help ensure that multiple connections from the
2028 same source are mapped to the same redirection address.
2029 This option can be used with the
2034 Note that by default these associations are destroyed as soon as there are
2035 no longer states which refer to them; in order to make the mappings last
2036 beyond the lifetime of the states, increase the global options with
2037 .Ar set timeout src.track .
2039 .Sx STATEFUL TRACKING OPTIONS
2040 for more ways to control the source tracking.
2041 .Sh STATE MODULATION
2042 Much of the security derived from TCP is attributable to how well the
2043 initial sequence numbers (ISNs) are chosen.
2044 Some popular stack implementations choose
2046 poor ISNs and thus are normally susceptible to ISN prediction exploits.
2049 rule to a TCP connection,
2051 will create a high quality random sequence number for each connection
2056 directive implicitly keeps state on the rule and is
2057 only applicable to TCP connections.
2060 .Bd -literal -offset indent
2062 pass out proto tcp from any to any modulate state
2063 pass in proto tcp from any to any port 25 flags S/SFRA modulate state
2066 Note that modulated connections will not recover when the state table
2067 is lost (firewall reboot, flushing the state table, etc...).
2069 will not be able to infer a connection again after the state table flushes
2070 the connection's modulator.
2071 When the state is lost, the connection may be left dangling until the
2072 respective endpoints time out the connection.
2073 It is possible on a fast local network for the endpoints to start an ACK
2074 storm while trying to resynchronize after the loss of the modulator.
2077 settings (or a more strict equivalent) should be used on
2079 rules to prevent ACK storms.
2081 Note that alternative methods are available
2082 to prevent loss of the state table
2083 and allow for firewall failover.
2088 for further information.
2092 passes packets that are part of a
2094 handshake between the endpoints.
2097 option can be used to cause
2099 itself to complete the handshake with the active endpoint, perform a handshake
2100 with the passive endpoint, and then forward packets between the endpoints.
2102 No packets are sent to the passive endpoint before the active endpoint has
2103 completed the handshake, hence so-called SYN floods with spoofed source
2104 addresses will not reach the passive endpoint, as the sender can't complete the
2107 The proxy is transparent to both endpoints, they each see a single
2108 connection from/to the other endpoint.
2110 chooses random initial sequence numbers for both handshakes.
2111 Once the handshakes are completed, the sequence number modulators
2112 (see previous section) are used to translate further packets of the
2116 .Ar modulate state .
2126 .Bd -literal -offset indent
2127 pass in proto tcp from any to any port www synproxy state
2129 .Sh STATEFUL TRACKING OPTIONS
2130 A number of options related to stateful tracking can be applied on a
2136 support these options, and
2138 must be specified explicitly to apply options to a rule.
2140 .Bl -tag -width xxxx -compact
2141 .It Ar max Aq Ar number
2142 Limits the number of concurrent states the rule may create.
2143 When this limit is reached, further packets that would create
2144 state will not match this rule until existing states time out.
2146 Prevent state changes for states created by this rule from appearing on the
2149 .It Xo Aq Ar timeout
2152 Changes the timeout values used for states created by this rule.
2153 For a list of all valid timeout names, see
2157 Uses a sloppy TCP connection tracker that does not check sequence
2158 numbers at all, which makes insertion and ICMP teardown attacks way
2160 This is intended to be used in situations where one does not see all
2161 packets of a connection, e.g. in asymmetric routing situations.
2162 Cannot be used with modulate or synproxy state.
2165 Multiple options can be specified, separated by commas:
2166 .Bd -literal -offset indent
2167 pass in proto tcp from any to any \e
2168 port www keep state \e
2169 (max 100, source-track rule, max-src-nodes 75, \e
2170 max-src-states 3, tcp.established 60, tcp.closing 5)
2175 keyword is specified, the number of states per source IP is tracked.
2177 .Bl -tag -width xxxx -compact
2178 .It Ar source-track rule
2179 The maximum number of states created by this rule is limited by the rule's
2184 Only state entries created by this particular rule count toward the rule's
2186 .It Ar source-track global
2187 The number of states created by all rules that use this option is limited.
2188 Each rule can specify different
2192 options, however state entries created by any participating rule count towards
2193 each individual rule's limits.
2196 The following limits can be set:
2198 .Bl -tag -width xxxx -compact
2199 .It Ar max-src-nodes Aq Ar number
2200 Limits the maximum number of source addresses which can simultaneously
2201 have state table entries.
2202 .It Ar max-src-states Aq Ar number
2203 Limits the maximum number of simultaneous state entries that a single
2204 source address can create with this rule.
2207 For stateful TCP connections, limits on established connections (connections
2208 which have completed the TCP 3-way handshake) can also be enforced
2211 .Bl -tag -width xxxx -compact
2212 .It Ar max-src-conn Aq Ar number
2213 Limits the maximum number of simultaneous TCP connections which have
2214 completed the 3-way handshake that a single host can make.
2215 .It Xo Ar max-src-conn-rate Aq Ar number
2218 Limit the rate of new connections over a time interval.
2219 The connection rate is an approximation calculated as a moving average.
2222 Because the 3-way handshake ensures that the source address is not being
2223 spoofed, more aggressive action can be taken based on these limits.
2225 .Ar overload Aq Ar table
2226 state option, source IP addresses which hit either of the limits on
2227 established connections will be added to the named table.
2228 This table can be used in the ruleset to block further activity from
2229 the offending host, redirect it to a tarpit process, or restrict its
2234 keyword kills all states created by the matching rule which originate
2235 from the host which exceeds these limits.
2238 modifier to the flush command kills all states originating from the
2239 offending host, regardless of which rule created the state.
2241 For example, the following rules will protect the webserver against
2242 hosts making more than 100 connections in 10 seconds.
2243 Any host which connects faster than this rate will have its address added
2246 table and have all states originating from it flushed.
2247 Any new packets arriving from this host will be dropped unconditionally
2249 .Bd -literal -offset indent
2250 block quick from \*(Ltbad_hosts\*(Gt
2251 pass in on $ext_if proto tcp to $webserver port www keep state \e
2252 (max-src-conn-rate 100/10, overload \*(Ltbad_hosts\*(Gt flush global)
2254 .Sh OPERATING SYSTEM FINGERPRINTING
2255 Passive OS Fingerprinting is a mechanism to inspect nuances of a TCP
2256 connection's initial SYN packet and guess at the host's operating system.
2257 Unfortunately these nuances are easily spoofed by an attacker so the
2258 fingerprint is not useful in making security decisions.
2259 But the fingerprint is typically accurate enough to make policy decisions
2262 The fingerprints may be specified by operating system class, by
2263 version, or by subtype/patchlevel.
2264 The class of an operating system is typically the vendor or genre
2270 The version of the oldest available
2272 release on the main FTP site
2273 would be 2.6 and the fingerprint would be written
2275 .Dl \&"OpenBSD 2.6\&"
2277 The subtype of an operating system is typically used to describe the
2278 patchlevel if that patch led to changes in the TCP stack behavior.
2281 the only subtype is for a fingerprint that was
2284 scrub option and would be specified as
2286 .Dl \&"OpenBSD 3.3 no-df\&"
2288 Fingerprints for most popular operating systems are provided by
2292 is running, a complete list of known operating system fingerprints may
2293 be listed by running:
2297 Filter rules can enforce policy at any level of operating system specification
2298 assuming a fingerprint is present.
2299 Policy could limit traffic to approved operating systems or even ban traffic
2300 from hosts that aren't at the latest service pack.
2304 class can also be used as the fingerprint which will match packets for
2305 which no operating system fingerprint is known.
2308 .Bd -literal -offset indent
2309 pass out proto tcp from any os OpenBSD
2310 block out proto tcp from any os Doors
2311 block out proto tcp from any os "Doors PT"
2312 block out proto tcp from any os "Doors PT SP3"
2313 block out from any os "unknown"
2314 pass on lo0 proto tcp from any os "OpenBSD 3.3 lo0"
2317 Operating system fingerprinting is limited only to the TCP SYN packet.
2318 This means that it will not work on other protocols and will not match
2319 a currently established connection.
2321 Caveat: operating system fingerprints are occasionally wrong.
2322 There are three problems: an attacker can trivially craft his packets to
2323 appear as any operating system he chooses;
2324 an operating system patch could change the stack behavior and no fingerprints
2325 will match it until the database is updated;
2326 and multiple operating systems may have the same fingerprint.
2327 .Sh BLOCKING SPOOFED TRAFFIC
2328 "Spoofing" is the faking of IP addresses, typically for malicious
2332 directive expands to a set of filter rules which will block all
2333 traffic with a source IP from the network(s) directly connected
2334 to the specified interface(s) from entering the system through
2335 any other interface.
2337 For example, the line
2338 .Bd -literal -offset indent
2343 .Bd -literal -offset indent
2344 block drop in on ! lo0 inet from 127.0.0.1/8 to any
2345 block drop in on ! lo0 inet6 from ::1 to any
2348 For non-loopback interfaces, there are additional rules to block incoming
2349 packets with a source IP address identical to the interface's IP(s).
2350 For example, assuming the interface wi0 had an IP address of 10.0.0.1 and a
2351 netmask of 255.255.255.0,
2353 .Bd -literal -offset indent
2354 antispoof for wi0 inet
2358 .Bd -literal -offset indent
2359 block drop in on ! wi0 inet from 10.0.0.0/24 to any
2360 block drop in inet from 10.0.0.1 to any
2363 Caveat: Rules created by the
2365 directive interfere with packets sent over loopback interfaces
2367 One should pass these explicitly.
2368 .Sh FRAGMENT HANDLING
2369 The size of IP datagrams (packets) can be significantly larger than the
2370 maximum transmission unit (MTU) of the network.
2371 In cases when it is necessary or more efficient to send such large packets,
2372 the large packet will be fragmented into many smaller packets that will each
2374 Unfortunately for a firewalling device, only the first logical fragment will
2375 contain the necessary header information for the subprotocol that allows
2377 to filter on things such as TCP ports or to perform NAT.
2381 rules as described in
2382 .Sx TRAFFIC NORMALIZATION
2383 above, there are three options for handling fragments in the packet filter.
2385 One alternative is to filter individual fragments with filter rules.
2388 rule applies to a fragment, it is passed to the filter.
2389 Filter rules with matching IP header parameters decide whether the
2390 fragment is passed or blocked, in the same way as complete packets
2392 Without reassembly, fragments can only be filtered based on IP header
2393 fields (source/destination address, protocol), since subprotocol header
2394 fields are not available (TCP/UDP port numbers, ICMP code/type).
2397 option can be used to restrict filter rules to apply only to
2398 fragments, but not complete packets.
2399 Filter rules without the
2401 option still apply to fragments, if they only specify IP header fields.
2402 For instance, the rule
2403 .Bd -literal -offset indent
2404 pass in proto tcp from any to any port 80
2407 never applies to a fragment, even if the fragment is part of a TCP
2408 packet with destination port 80, because without reassembly this information
2409 is not available for each fragment.
2410 This also means that fragments cannot create new or match existing
2411 state table entries, which makes stateful filtering and address
2412 translation (NAT, redirection) for fragments impossible.
2414 It's also possible to reassemble only certain fragments by specifying
2415 source or destination addresses or protocols as parameters in
2419 In most cases, the benefits of reassembly outweigh the additional
2420 memory cost, and it's recommended to use
2423 all fragments via the
2424 .Ar fragment reassemble
2427 The memory allocated for fragment caching can be limited using
2429 Once this limit is reached, fragments that would have to be cached
2430 are dropped until other entries time out.
2431 The timeout value can also be adjusted.
2433 When forwarding reassembled IPv6 packets, pf refragments them with
2434 the original maximum fragment size.
2435 This allows the sender to determine the optimal fragment size by
2438 Besides the main ruleset,
2440 can load rulesets into
2445 is a container that can hold rules, address tables, and other anchors.
2449 has a name which specifies the path where
2451 can be used to access the anchor to perform operations on it, such as
2452 attaching child anchors to it or loading rules into it.
2453 Anchors may be nested, with components separated by
2455 characters, similar to how file system hierarchies are laid out.
2456 The main ruleset is actually the default anchor, so filter and
2457 translation rules, for example, may also be contained in any anchor.
2459 An anchor can reference another
2462 using the following kinds
2464 .Bl -tag -width xxxx
2465 .It Ar nat-anchor Aq Ar name
2468 rules in the specified
2470 .It Ar rdr-anchor Aq Ar name
2473 rules in the specified
2475 .It Ar binat-anchor Aq Ar name
2478 rules in the specified
2480 .It Ar anchor Aq Ar name
2481 Evaluates the filter rules in the specified
2483 .It Xo Ar load anchor
2487 Loads the rules from the specified file into the
2492 When evaluation of the main ruleset reaches an
2496 will proceed to evaluate all rules specified in that anchor.
2498 Matching filter and translation rules marked with the
2500 option are final and abort the evaluation of the rules in other
2501 anchors and the main ruleset.
2504 itself is marked with the
2507 ruleset evaluation will terminate when the anchor is exited if the packet is
2508 matched by any rule within the anchor.
2511 rules are evaluated relative to the anchor in which they are contained.
2514 rules specified in the main ruleset will reference anchor
2515 attachment points underneath the main ruleset, and
2517 rules specified in a file loaded from a
2519 rule will be attached under that anchor point.
2521 Rules may be contained in
2523 attachment points which do not contain any rules when the main ruleset
2524 is loaded, and later such anchors can be manipulated through
2526 without reloading the main ruleset or other anchors.
2528 .Bd -literal -offset indent
2530 block on $ext_if all
2532 pass out on $ext_if all
2533 pass in on $ext_if proto tcp from any \e
2534 to $ext_if port smtp
2537 blocks all packets on the external interface by default, then evaluates
2540 named "spam", and finally passes all outgoing connections and
2541 incoming connections to port 25.
2542 .Bd -literal -offset indent
2543 # echo \&"block in quick from 1.2.3.4 to any\&" \&| \e
2547 This loads a single rule into the
2549 which blocks all packets from a specific address.
2551 The anchor can also be populated by adding a
2556 .Bd -literal -offset indent
2558 load anchor spam from "/etc/pf-spam.conf"
2565 it will also load all the rules from the file
2566 .Pa /etc/pf-spam.conf
2571 rules can specify packet filtering parameters using the same syntax as
2573 When parameters are used, the
2575 rule is only evaluated for matching packets.
2576 This allows conditional evaluation of anchors, like:
2577 .Bd -literal -offset indent
2578 block on $ext_if all
2579 anchor spam proto tcp from any to any port smtp
2580 pass out on $ext_if all
2581 pass in on $ext_if proto tcp from any to $ext_if port smtp
2586 spam are only evaluated for
2588 packets with destination port 25.
2590 .Bd -literal -offset indent
2591 # echo \&"block in quick from 1.2.3.4 to any" \&| \e
2595 will only block connections from 1.2.3.4 to port 25.
2597 Anchors may end with the asterisk
2599 character, which signifies that all anchors attached at that point
2600 should be evaluated in the alphabetical ordering of their anchor name.
2602 .Bd -literal -offset indent
2606 will evaluate each rule in each anchor attached to the
2609 Note that it will only evaluate anchors that are directly attached to the
2611 anchor, and will not descend to evaluate anchors recursively.
2613 Since anchors are evaluated relative to the anchor in which they are
2614 contained, there is a mechanism for accessing the parent and ancestor
2615 anchors of a given anchor.
2616 Similar to file system path name resolution, if the sequence
2618 appears as an anchor path component, the parent anchor of the current
2619 anchor in the path evaluation at that point will become the new current
2621 As an example, consider the following:
2622 .Bd -literal -offset indent
2623 # echo ' anchor "spam/allowed" ' | pfctl -f -
2624 # echo -e ' anchor "../banned" \en pass' | \e
2625 pfctl -a spam/allowed -f -
2628 Evaluation of the main ruleset will lead into the
2630 anchor, which will evaluate the rules in the
2632 anchor, if any, before finally evaluating the
2638 can also be loaded inline in the ruleset within a brace ('{' '}') delimited
2640 Brace delimited blocks may contain rules or other brace-delimited blocks.
2641 When anchors are loaded this way the anchor name becomes optional.
2642 .Bd -literal -offset indent
2643 anchor "external" on egress {
2646 pass proto tcp from any to port { 25, 80, 443 }
2648 pass in proto tcp to any port 22
2652 Since the parser specification for anchor names is a string, any
2653 reference to an anchor name containing
2655 characters will require double quote
2657 characters around the anchor name.
2658 .Sh TRANSLATION EXAMPLES
2659 This example maps incoming requests on port 80 to port 8080, on
2660 which a daemon is running (because, for example, it is not run as root,
2661 and therefore lacks permission to bind to port 80).
2663 # use a macro for the interface name, so it can be changed easily
2666 # map daemon on 8080 to appear to be on 80
2667 rdr on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 port 8080
2672 modifier is given, packets matching the translation rule are passed without
2673 inspecting the filter rules:
2675 rdr pass on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 \e
2679 In the example below, vlan12 is configured as 192.168.168.1;
2680 the machine translates all packets coming from 192.168.168.0/24 to 204.92.77.111
2681 when they are going out any interface except vlan12.
2682 This has the net effect of making traffic from the 192.168.168.0/24
2683 network appear as though it is the Internet routable address
2684 204.92.77.111 to nodes behind any interface on the router except
2685 for the nodes on vlan12.
2686 (Thus, 192.168.168.1 can talk to the 192.168.168.0/24 nodes.)
2688 nat on ! vlan12 from 192.168.168.0/24 to any -\*(Gt 204.92.77.111
2691 In the example below, the machine sits between a fake internal 144.19.74.*
2692 network, and a routable external IP of 204.92.77.100.
2695 rule excludes protocol AH from being translated.
2698 no nat on $ext_if proto ah from 144.19.74.0/24 to any
2699 nat on $ext_if from 144.19.74.0/24 to any -\*(Gt 204.92.77.100
2702 In the example below, packets bound for one specific server, as well as those
2703 generated by the sysadmins are not proxied; all other connections are.
2706 no rdr on $int_if proto { tcp, udp } from any to $server port 80
2707 no rdr on $int_if proto { tcp, udp } from $sysadmins to any port 80
2708 rdr on $int_if proto { tcp, udp } from any to any port 80 -\*(Gt 127.0.0.1 \e
2712 This longer example uses both a NAT and a redirection.
2713 The external interface has the address 157.161.48.183.
2714 On localhost, we are running
2716 waiting for FTP sessions to be redirected to it.
2717 The three mandatory anchors for
2719 are omitted from this example; see the
2724 # Translate outgoing packets' source addresses (any protocol).
2725 # In this case, any address but the gateway's external address is mapped.
2726 nat on $ext_if inet from ! ($ext_if) to any -\*(Gt ($ext_if)
2729 # Map outgoing packets' source port to an assigned proxy port instead of
2730 # an arbitrary port.
2731 # In this case, proxy outgoing isakmp with port 500 on the gateway.
2732 nat on $ext_if inet proto udp from any port = isakmp to any -\*(Gt ($ext_if) \e
2736 # Translate outgoing packets' source address (any protocol).
2737 # Translate incoming packets' destination address to an internal machine
2739 binat on $ext_if from 10.1.2.150 to any -\*(Gt $ext_if
2742 # Translate incoming packets' destination addresses.
2743 # As an example, redirect a TCP and UDP port to an internal machine.
2744 rdr on $ext_if inet proto tcp from any to ($ext_if) port 8080 \e
2745 -\*(Gt 10.1.2.151 port 22
2746 rdr on $ext_if inet proto udp from any to ($ext_if) port 8080 \e
2747 -\*(Gt 10.1.2.151 port 53
2750 # Translate outgoing ftp control connections to send them to localhost
2751 # for proxying with ftp-proxy(8) running on port 8021.
2752 rdr on $int_if proto tcp from any to any port 21 -\*(Gt 127.0.0.1 port 8021
2755 In this example, a NAT gateway is set up to translate internal addresses
2756 using a pool of public addresses (192.0.2.16/28) and to redirect
2757 incoming web server connections to a group of web servers on the internal
2761 # Translate outgoing packets' source addresses using an address pool.
2762 # A given source address is always translated to the same pool address by
2763 # using the source-hash keyword.
2764 nat on $ext_if inet from any to any -\*(Gt 192.0.2.16/28 source-hash
2767 # Translate incoming web server connections to a group of web servers on
2768 # the internal network.
2769 rdr on $ext_if proto tcp from any to any port 80 \e
2770 -\*(Gt { 10.1.2.155, 10.1.2.160, 10.1.2.161 } round-robin
2774 # The external interface is kue0
2775 # (157.161.48.183, the only routable address)
2776 # and the private network is 10.0.0.0/8, for which we are doing NAT.
2778 # use a macro for the interface name, so it can be changed easily
2781 # normalize all incoming traffic
2782 scrub in on $ext_if all fragment reassemble
2784 # block and log everything by default
2785 block return log on $ext_if all
2787 # block anything coming from source we have no back routes for
2788 block in from no-route to any
2790 # block packets whose ingress interface does not match the one in
2791 # the route back to their source address
2792 block in from urpf-failed to any
2794 # block and log outgoing packets that do not have our address as source,
2795 # they are either spoofed or something is misconfigured (NAT disabled,
2796 # for instance), we want to be nice and do not send out garbage.
2797 block out log quick on $ext_if from ! 157.161.48.183 to any
2799 # silently drop broadcasts (cable modem noise)
2800 block in quick on $ext_if from any to 255.255.255.255
2802 # block and log incoming packets from reserved address space and invalid
2803 # addresses, they are either spoofed or misconfigured, we cannot reply to
2804 # them anyway (hence, no return-rst).
2805 block in log quick on $ext_if from { 10.0.0.0/8, 172.16.0.0/12, \e
2806 192.168.0.0/16, 255.255.255.255/32 } to any
2810 # pass out/in certain ICMP queries and keep state (ping)
2811 # state matching is done on host addresses and ICMP id (not type/code),
2812 # so replies (like 0/0 for 8/0) will match queries
2813 # ICMP error messages (which always refer to a TCP/UDP packet) are
2814 # handled by the TCP/UDP states
2815 pass on $ext_if inet proto icmp all icmp-type 8 code 0
2819 # pass out all UDP connections and keep state
2820 pass out on $ext_if proto udp all
2822 # pass in certain UDP connections and keep state (DNS)
2823 pass in on $ext_if proto udp from any to any port domain
2827 # pass out all TCP connections and modulate state
2828 pass out on $ext_if proto tcp all modulate state
2830 # pass in certain TCP connections and keep state (SSH, SMTP, DNS, IDENT)
2831 pass in on $ext_if proto tcp from any to any port { ssh, smtp, domain, \e
2834 # Do not allow Windows 9x SMTP connections since they are typically
2835 # a viral worm. Alternately we could limit these OSes to 1 connection each.
2836 block in on $ext_if proto tcp from any os {"Windows 95", "Windows 98"} \e
2840 # pass in/out all IPv6 traffic: note that we have to enable this in two
2841 # different ways, on both our physical interface and our tunnel
2842 pass quick on gif0 inet6
2843 pass quick on $ext_if proto ipv6
2847 # three interfaces: $int_if, $ext_if, and $wifi_if (wireless). NAT is
2848 # being done on $ext_if for all outgoing packets. tag packets in on
2849 # $int_if and pass those tagged packets out on $ext_if. all other
2850 # outgoing packets (i.e., packets from the wireless network) are only
2851 # permitted to access port 80.
2853 pass in on $int_if from any to any tag INTNET
2854 pass in on $wifi_if from any to any
2856 block out on $ext_if from any to any
2857 pass out quick on $ext_if tagged INTNET
2858 pass out on $ext_if proto tcp from any to any port 80
2860 # tag incoming packets as they are redirected to spamd(8). use the tag
2861 # to pass those packets through the packet filter.
2863 rdr on $ext_if inet proto tcp from \*(Ltspammers\*(Gt to port smtp \e
2864 tag SPAMD -\*(Gt 127.0.0.1 port spamd
2867 pass in on $ext_if inet proto tcp tagged SPAMD
2874 line = ( option | pf-rule | nat-rule | binat-rule | rdr-rule |
2875 antispoof-rule | altq-rule | queue-rule | trans-anchors |
2876 anchor-rule | anchor-close | load-anchor | table-rule |
2879 option = "set" ( [ "timeout" ( timeout | "{" timeout-list "}" ) ] |
2880 [ "ruleset-optimization" [ "none" | "basic" | "profile" ]] |
2881 [ "optimization" [ "default" | "normal" |
2882 "high-latency" | "satellite" |
2883 "aggressive" | "conservative" ] ]
2884 [ "limit" ( limit-item | "{" limit-list "}" ) ] |
2885 [ "loginterface" ( interface-name | "none" ) ] |
2886 [ "block-policy" ( "drop" | "return" ) ] |
2887 [ "state-policy" ( "if-bound" | "floating" ) ]
2888 [ "state-defaults" state-opts ]
2889 [ "require-order" ( "yes" | "no" ) ]
2890 [ "fingerprints" filename ] |
2891 [ "skip on" ifspec ] |
2892 [ "debug" ( "none" | "urgent" | "misc" | "loud" ) ] )
2894 pf-rule = action [ ( "in" | "out" ) ]
2895 [ "log" [ "(" logopts ")"] ] [ "quick" ]
2896 [ "on" ifspec ] [ route ] [ af ] [ protospec ]
2897 hosts [ filteropt-list ]
2899 logopts = logopt [ "," logopts ]
2900 logopt = "all" | "user" | "to" interface-name
2902 filteropt-list = filteropt-list filteropt | filteropt
2903 filteropt = user | group | flags | icmp-type | icmp6-type | "tos" tos |
2904 ( "no" | "keep" | "modulate" | "synproxy" ) "state"
2905 [ "(" state-opts ")" ] |
2906 "fragment" | "no-df" | "min-ttl" number | "set-tos" tos |
2907 "max-mss" number | "random-id" | "reassemble tcp" |
2908 fragmentation | "allow-opts" |
2909 "label" string | "tag" string | [ ! ] "tagged" string |
2910 "set prio" ( number | "(" number [ [ "," ] number ] ")" ) |
2911 "queue" ( string | "(" string [ [ "," ] string ] ")" ) |
2912 "rtable" number | "probability" number"%" | "prio" number
2914 nat-rule = [ "no" ] "nat" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
2915 [ "on" ifspec ] [ af ]
2916 [ protospec ] hosts [ "tag" string ] [ "tagged" string ]
2917 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" )
2918 [ portspec ] [ pooltype ] [ "static-port" ]
2919 [ "map-e-portset" number "/" number "/" number ] ]
2921 binat-rule = [ "no" ] "binat" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
2922 [ "on" interface-name ] [ af ]
2923 [ "proto" ( proto-name | proto-number ) ]
2924 "from" address [ "/" mask-bits ] "to" ipspec
2925 [ "tag" string ] [ "tagged" string ]
2926 [ "-\*(Gt" address [ "/" mask-bits ] ]
2928 rdr-rule = [ "no" ] "rdr" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
2929 [ "on" ifspec ] [ af ]
2930 [ protospec ] hosts [ "tag" string ] [ "tagged" string ]
2931 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" )
2932 [ portspec ] [ pooltype ] ]
2934 antispoof-rule = "antispoof" [ "log" ] [ "quick" ]
2935 "for" ifspec [ af ] [ "label" string ]
2937 table-rule = "table" "\*(Lt" string "\*(Gt" [ tableopts-list ]
2938 tableopts-list = tableopts-list tableopts | tableopts
2939 tableopts = "persist" | "const" | "counters" | "file" string |
2940 "{" [ tableaddr-list ] "}"
2941 tableaddr-list = tableaddr-list [ "," ] tableaddr-spec | tableaddr-spec
2942 tableaddr-spec = [ "!" ] tableaddr [ "/" mask-bits ]
2943 tableaddr = hostname | ifspec | "self" |
2944 ipv4-dotted-quad | ipv6-coloned-hex
2946 altq-rule = "altq on" interface-name queueopts-list
2948 queue-rule = "queue" string [ "on" interface-name ] queueopts-list
2951 anchor-rule = "anchor" [ string ] [ ( "in" | "out" ) ] [ "on" ifspec ]
2952 [ af ] [ protospec ] [ hosts ] [ filteropt-list ] [ "{" ]
2956 trans-anchors = ( "nat-anchor" | "rdr-anchor" | "binat-anchor" ) string
2957 [ "on" ifspec ] [ af ] [ "proto" ] [ protospec ] [ hosts ]
2959 load-anchor = "load anchor" string "from" filename
2961 queueopts-list = queueopts-list queueopts | queueopts
2962 queueopts = [ "bandwidth" bandwidth-spec ] |
2963 [ "qlimit" number ] | [ "tbrsize" number ] |
2964 [ "priority" number ] | [ schedulers ]
2965 schedulers = ( cbq-def | priq-def | hfsc-def )
2966 bandwidth-spec = "number" ( "b" | "Kb" | "Mb" | "Gb" | "%" )
2968 action = "pass" | "block" [ return ] | [ "no" ] "scrub"
2969 return = "drop" | "return" | "return-rst" [ "( ttl" number ")" ] |
2970 "return-icmp" [ "(" icmpcode [ [ "," ] icmp6code ] ")" ] |
2971 "return-icmp6" [ "(" icmp6code ")" ]
2972 icmpcode = ( icmp-code-name | icmp-code-number )
2973 icmp6code = ( icmp6-code-name | icmp6-code-number )
2975 ifspec = ( [ "!" ] ( interface-name | interface-group ) ) |
2976 "{" interface-list "}"
2977 interface-list = [ "!" ] ( interface-name | interface-group )
2978 [ [ "," ] interface-list ]
2979 route = ( "route-to" | "reply-to" | "dup-to" )
2980 ( routehost | "{" routehost-list "}" )
2982 af = "inet" | "inet6"
2984 protospec = "proto" ( proto-name | proto-number |
2985 "{" proto-list "}" )
2986 proto-list = ( proto-name | proto-number ) [ [ "," ] proto-list ]
2989 "from" ( "any" | "no-route" | "urpf-failed" | "self" | host |
2990 "{" host-list "}" ) [ port ] [ os ]
2991 "to" ( "any" | "no-route" | "self" | host |
2992 "{" host-list "}" ) [ port ]
2994 ipspec = "any" | host | "{" host-list "}"
2995 host = [ "!" ] ( address [ "/" mask-bits ] | "\*(Lt" string "\*(Gt" )
2996 redirhost = address [ "/" mask-bits ]
2997 routehost = "(" interface-name [ address [ "/" mask-bits ] ] ")"
2998 address = ( interface-name | interface-group |
2999 "(" ( interface-name | interface-group ) ")" |
3000 hostname | ipv4-dotted-quad | ipv6-coloned-hex )
3001 host-list = host [ [ "," ] host-list ]
3002 redirhost-list = redirhost [ [ "," ] redirhost-list ]
3003 routehost-list = routehost [ [ "," ] routehost-list ]
3005 port = "port" ( unary-op | binary-op | "{" op-list "}" )
3006 portspec = "port" ( number | name ) [ ":" ( "*" | number | name ) ]
3007 os = "os" ( os-name | "{" os-list "}" )
3008 user = "user" ( unary-op | binary-op | "{" op-list "}" )
3009 group = "group" ( unary-op | binary-op | "{" op-list "}" )
3011 unary-op = [ "=" | "!=" | "\*(Lt" | "\*(Le" | "\*(Gt" | "\*(Ge" ]
3013 binary-op = number ( "\*(Lt\*(Gt" | "\*(Gt\*(Lt" | ":" ) number
3014 op-list = ( unary-op | binary-op ) [ [ "," ] op-list ]
3016 os-name = operating-system-name
3017 os-list = os-name [ [ "," ] os-list ]
3019 flags = "flags" ( [ flag-set ] "/" flag-set | "any" )
3020 flag-set = [ "F" ] [ "S" ] [ "R" ] [ "P" ] [ "A" ] [ "U" ] [ "E" ]
3023 icmp-type = "icmp-type" ( icmp-type-code | "{" icmp-list "}" )
3024 icmp6-type = "icmp6-type" ( icmp-type-code | "{" icmp-list "}" )
3025 icmp-type-code = ( icmp-type-name | icmp-type-number )
3026 [ "code" ( icmp-code-name | icmp-code-number ) ]
3027 icmp-list = icmp-type-code [ [ "," ] icmp-list ]
3029 tos = ( "lowdelay" | "throughput" | "reliability" |
3032 state-opts = state-opt [ [ "," ] state-opts ]
3033 state-opt = ( "max" number | "no-sync" | timeout | "sloppy" |
3034 "source-track" [ ( "rule" | "global" ) ] |
3035 "max-src-nodes" number | "max-src-states" number |
3036 "max-src-conn" number |
3037 "max-src-conn-rate" number "/" number |
3038 "overload" "\*(Lt" string "\*(Gt" [ "flush" ] |
3039 "if-bound" | "floating" )
3041 fragmentation = [ "fragment reassemble" ]
3043 timeout-list = timeout [ [ "," ] timeout-list ]
3044 timeout = ( "tcp.first" | "tcp.opening" | "tcp.established" |
3045 "tcp.closing" | "tcp.finwait" | "tcp.closed" |
3046 "udp.first" | "udp.single" | "udp.multiple" |
3047 "icmp.first" | "icmp.error" |
3048 "other.first" | "other.single" | "other.multiple" |
3049 "frag" | "interval" | "src.track" |
3050 "adaptive.start" | "adaptive.end" ) number
3052 limit-list = limit-item [ [ "," ] limit-list ]
3053 limit-item = ( "states" | "frags" | "src-nodes" ) number
3055 pooltype = ( "bitmask" | "random" |
3056 "source-hash" [ ( hex-key | string-key ) ] |
3057 "round-robin" ) [ sticky-address ]
3059 subqueue = string | "{" queue-list "}"
3060 queue-list = string [ [ "," ] string ]
3061 cbq-def = "cbq" [ "(" cbq-opt [ [ "," ] cbq-opt ] ")" ]
3062 priq-def = "priq" [ "(" priq-opt [ [ "," ] priq-opt ] ")" ]
3063 hfsc-def = "hfsc" [ "(" hfsc-opt [ [ "," ] hfsc-opt ] ")" ]
3064 cbq-opt = ( "default" | "borrow" | "red" | "ecn" | "rio" )
3065 priq-opt = ( "default" | "red" | "ecn" | "rio" )
3066 hfsc-opt = ( "default" | "red" | "ecn" | "rio" |
3067 linkshare-sc | realtime-sc | upperlimit-sc )
3068 linkshare-sc = "linkshare" sc-spec
3069 realtime-sc = "realtime" sc-spec
3070 upperlimit-sc = "upperlimit" sc-spec
3071 sc-spec = ( bandwidth-spec |
3072 "(" bandwidth-spec number bandwidth-spec ")" )
3073 include = "include" filename
3076 .Bl -tag -width "/etc/protocols" -compact
3080 Default location of the ruleset file.
3081 The file has to be created manually as it is not installed with a
3082 standard installation.
3084 Default location of OS fingerprints.
3085 .It Pa /etc/protocols
3086 Protocol name database.
3087 .It Pa /etc/services
3088 Service name database.
3111 file format first appeared in