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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
195 .Bd -literal -offset indent
196 table \*(Ltprivate\*(Gt const { 10/8, 172.16/12, 192.168/16 }
197 table \*(Ltbadhosts\*(Gt persist
198 block on fxp0 from { \*(Ltprivate\*(Gt, \*(Ltbadhosts\*(Gt } to any
201 creates a table called private, to hold RFC 1918 private network
202 blocks, and a table called badhosts, which is initially empty.
203 A filter rule is set up to block all traffic coming from addresses listed in
205 The private table cannot have its contents changed and the badhosts table
206 will exist even when no active filter rules reference it.
207 Addresses may later be added to the badhosts table, so that traffic from
208 these hosts can be blocked by using
209 .Bd -literal -offset indent
210 # pfctl -t badhosts -Tadd 204.92.77.111
213 A table can also be initialized with an address list specified in one or more
214 external files, using the following syntax:
215 .Bd -literal -offset indent
216 table \*(Ltspam\*(Gt persist file \&"/etc/spammers\&" file \&"/etc/openrelays\&"
217 block on fxp0 from \*(Ltspam\*(Gt to any
224 list IP addresses, one per line.
225 Any lines beginning with a # are treated as comments and ignored.
226 In addition to being specified by IP address, hosts may also be
227 specified by their hostname.
228 When the resolver is called to add a hostname to a table,
230 resulting IPv4 and IPv6 addresses are placed into the table.
231 IP addresses can also be entered in a table by specifying a valid interface
232 name, a valid interface group or the
234 keyword, in which case all addresses assigned to the interface(s) will be
238 may be tuned for various situations using the
244 .Bl -tag -width "src.track" -compact
246 Interval between purging expired states and fragments.
248 Seconds before an unassembled fragment is expired.
250 Length of time to retain a source tracking entry after the last state
254 When a packet matches a stateful connection, the seconds to live for the
255 connection will be updated to that of the
257 which corresponds to the connection state.
258 Each packet which matches this state will reset the TTL.
259 Tuning these values may improve the performance of the
260 firewall at the risk of dropping valid idle connections.
262 .Bl -tag -width xxxx -compact
264 The state after the first packet.
266 The state before the destination host ever sends a packet.
267 .It Ar tcp.established
268 The fully established state.
270 The state after the first FIN has been sent.
272 The state after both FINs have been exchanged and the connection is closed.
273 Some hosts (notably web servers on Solaris) send TCP packets even after closing
279 can prevent blocking of such packets.
281 The state after one endpoint sends an RST.
284 ICMP and UDP are handled in a fashion similar to TCP, but with a much more
285 limited set of states:
287 .Bl -tag -width xxxx -compact
289 The state after the first packet.
291 The state if the source host sends more than one packet but the destination
292 host has never sent one back.
294 The state if both hosts have sent packets.
296 The state after the first packet.
298 The state after an ICMP error came back in response to an ICMP packet.
301 Other protocols are handled similarly to UDP:
303 .Bl -tag -width xxxx -compact
306 .It Ar other.multiple
309 Timeout values can be reduced adaptively as the number of state table
312 .Bl -tag -width xxxx -compact
313 .It Ar adaptive.start
314 When the number of state entries exceeds this value, adaptive scaling
316 All timeout values are scaled linearly with factor
317 (adaptive.end - number of states) / (adaptive.end - adaptive.start).
319 When reaching this number of state entries, all timeout values become
320 zero, effectively purging all state entries immediately.
321 This value is used to define the scale factor, it should not actually
322 be reached (set a lower state limit, see below).
325 Adaptive timeouts are enabled by default, with an adaptive.start value
326 equal to 60% of the state limit, and an adaptive.end value equal to
327 120% of the state limit.
328 They can be disabled by setting both adaptive.start and adaptive.end to 0.
330 The adaptive timeout values can be defined both globally and for each rule.
331 When used on a per-rule basis, the values relate to the number of
332 states created by the rule, otherwise to the total number of
336 .Bd -literal -offset indent
337 set timeout tcp.first 120
338 set timeout tcp.established 86400
339 set timeout { adaptive.start 6000, adaptive.end 12000 }
340 set limit states 10000
343 With 9000 state table entries, the timeout values are scaled to 50%
344 (tcp.first 60, tcp.established 43200).
345 .It Ar set loginterface
346 Enable collection of packet and byte count statistics for the given
347 interface or interface group.
348 These statistics can be viewed using
349 .Bd -literal -offset indent
355 collects statistics on the interface named dc0:
356 .Bd -literal -offset indent
360 One can disable the loginterface using:
361 .Bd -literal -offset indent
362 set loginterface none
365 Sets hard limits on the memory pools used by the packet filter.
368 for an explanation of memory pools.
371 .Bd -literal -offset indent
372 set limit states 20000
375 sets the maximum number of entries in the memory pool used by state table
376 entries (generated by
378 rules which do not specify
382 .Bd -literal -offset indent
383 set limit frags 20000
386 sets the maximum number of entries in the memory pool used for fragment
387 reassembly (generated by
391 .Bd -literal -offset indent
392 set limit src-nodes 2000
395 sets the maximum number of entries in the memory pool used for tracking
396 source IP addresses (generated by the
402 .Bd -literal -offset indent
403 set limit tables 1000
404 set limit table-entries 100000
407 sets limits on the memory pools used by tables.
408 The first limits the number of tables that can exist to 1000.
409 The second limits the overall number of addresses that can be stored
412 Various limits can be combined on a single line:
413 .Bd -literal -offset indent
414 set limit { states 20000, frags 20000, src-nodes 2000 }
416 .It Ar set ruleset-optimization
417 .Bl -tag -width xxxxxxxx -compact
419 Disable the ruleset optimizer.
421 Enable basic ruleset optimization.
422 This is the default behaviour.
423 Basic ruleset optimization does four things to improve the
424 performance of ruleset evaluations:
428 remove duplicate rules
430 remove rules that are a subset of another rule
432 combine multiple rules into a table when advantageous
434 re-order the rules to improve evaluation performance
438 Uses the currently loaded ruleset as a feedback profile to tailor the
439 ordering of quick rules to actual network traffic.
442 It is important to note that the ruleset optimizer will modify the ruleset
443 to improve performance.
444 A side effect of the ruleset modification is that per-rule accounting
445 statistics will have different meanings than before.
446 If per-rule accounting is important for billing purposes or whatnot,
447 either the ruleset optimizer should not be used or a label field should
448 be added to all of the accounting rules to act as optimization barriers.
450 Optimization can also be set as a command-line argument to
452 overriding the settings in
454 .It Ar set optimization
455 Optimize state timeouts for one of the following network environments:
457 .Bl -tag -width xxxx -compact
459 A normal network environment.
460 Suitable for almost all networks.
462 A high-latency environment (such as a satellite connection).
467 Aggressively expire connections.
468 This can greatly reduce the memory usage of the firewall at the cost of
469 dropping idle connections early.
471 Extremely conservative settings.
472 Avoid dropping legitimate connections at the
473 expense of greater memory utilization (possibly much greater on a busy
474 network) and slightly increased processor utilization.
478 .Bd -literal -offset indent
479 set optimization aggressive
481 .It Ar set block-policy
484 option sets the default behaviour for the packet
488 .Bl -tag -width xxxxxxxx -compact
490 Packet is silently dropped.
492 A TCP RST is returned for blocked TCP packets,
493 an ICMP UNREACHABLE is returned for blocked UDP packets,
494 and all other packets are silently dropped.
498 .Bd -literal -offset indent
499 set block-policy return
501 .It Ar set state-policy
504 option sets the default behaviour for states:
506 .Bl -tag -width group-bound -compact
508 States are bound to interface.
510 States can match packets on any interfaces (the default).
514 .Bd -literal -offset indent
515 set state-policy if-bound
517 .It Ar set state-defaults
520 option sets the state options for states created from rules
524 .Bd -literal -offset indent
525 set state-defaults pflow, no-sync
530 identifies this firewall's state table entries to other firewalls
534 By default the hostid is set to a pseudo-random value, however it may be
535 desirable to manually configure it, for example to more easily identify the
536 source of state table entries.
537 .Bd -literal -offset indent
541 The hostid may be specified in either decimal or hexadecimal.
542 .It Ar set require-order
545 enforces an ordering of the statement types in the ruleset to:
551 Setting this option to
553 disables this enforcement.
554 There may be non-trivial and non-obvious implications to an out of
556 Consider carefully before disabling the order enforcement.
557 .It Ar set fingerprints
558 Load fingerprints of known operating systems from the given filename.
559 By default fingerprints of known operating systems are automatically
564 but can be overridden via this option.
565 Setting this option may leave a small period of time where the fingerprints
566 referenced by the currently active ruleset are inconsistent until the new
567 ruleset finishes loading.
571 .Dl set fingerprints \&"/etc/pf.os.devel\&"
572 .It Ar set skip on Aq Ar ifspec
573 List interfaces for which packets should not be filtered.
574 Packets passing in or out on such interfaces are passed as if pf was
575 disabled, i.e. pf does not process them in any way.
576 This can be useful on loopback and other virtual interfaces, when
577 packet filtering is not desired and can have unexpected effects.
584 to one of the following:
586 .Bl -tag -width xxxxxxxxxxxx -compact
588 Don't generate debug messages.
590 Generate debug messages only for serious errors.
592 Generate debug messages for various errors.
594 Generate debug messages for common conditions.
597 .Sh TRAFFIC NORMALIZATION
598 Traffic normalization is used to sanitize packet content in such
599 a way that there are no ambiguities in packet interpretation on
601 The normalizer does IP fragment reassembly to prevent attacks
602 that confuse intrusion detection systems by sending overlapping
604 Packet normalization is invoked with the
609 has the following options:
614 bit from a matching IP packet.
615 Some operating systems are known to generate fragmented packets with the
618 This is particularly true with NFS.
620 will drop such fragmented
626 Unfortunately some operating systems also generate their
628 packets with a zero IP identification field.
631 bit on packets with a zero IP ID may cause deleterious results if an
632 upstream router later fragments the packet.
635 modifier (see below) is recommended in combination with the
637 modifier to ensure unique IP identifiers.
638 .It Ar min-ttl Aq Ar number
639 Enforces a minimum TTL for matching IP packets.
640 .It Ar max-mss Aq Ar number
641 Enforces a maximum MSS for matching TCP packets.
642 .It Xo Ar set-tos Aq Ar string
643 .No \*(Ba Aq Ar number
647 for matching IP packets.
654 or as either hex or decimal.
656 Replaces the IP identification field with random values to compensate
657 for predictable values generated by many hosts.
658 This option only applies to packets that are not fragmented
659 after the optional fragment reassembly.
660 .It Ar fragment reassemble
663 rules, fragments can be reassembled by normalization.
664 In this case, fragments are buffered until they form a complete
665 packet, and only the completed packet is passed on to the filter.
666 The advantage is that filter rules have to deal only with complete
667 packets, and can ignore fragments.
668 The drawback of caching fragments is the additional memory cost.
669 .It Ar reassemble tcp
670 Statefully normalizes TCP connections.
671 .Ar scrub reassemble tcp
672 rules may not have the direction (in/out) specified.
674 performs the following normalizations:
676 .Bl -tag -width timeout -compact
678 Neither side of the connection is allowed to reduce their IP TTL.
679 An attacker may send a packet such that it reaches the firewall, affects
680 the firewall state, and expires before reaching the destination host.
682 will raise the TTL of all packets back up to the highest value seen on
684 .It timestamp modulation
685 Modern TCP stacks will send a timestamp on every TCP packet and echo
686 the other endpoint's timestamp back to them.
687 Many operating systems will merely start the timestamp at zero when
688 first booted, and increment it several times a second.
689 The uptime of the host can be deduced by reading the timestamp and multiplying
691 Also observing several different timestamps can be used to count hosts
693 And spoofing TCP packets into a connection requires knowing or guessing
695 Timestamps merely need to be monotonically increasing and not derived off a
700 to modulate the TCP timestamps with a random number.
701 .It extended PAWS checks
702 There is a problem with TCP on long fat pipes, in that a packet might get
703 delayed for longer than it takes the connection to wrap its 32-bit sequence
705 In such an occurrence, the old packet would be indistinguishable from a
706 new packet and would be accepted as such.
707 The solution to this is called PAWS: Protection Against Wrapped Sequence
709 It protects against it by making sure the timestamp on each packet does
712 also makes sure the timestamp on the packet does not go forward more
716 artificially extends the security of TCP sequence numbers by 10 to 18
717 bits when the host uses appropriately randomized timestamps, since a
718 blind attacker would have to guess the timestamp as well.
723 .Bd -literal -offset indent
724 scrub in on $ext_if all fragment reassemble
729 option prefixed to a scrub rule causes matching packets to remain unscrubbed,
730 much in the same way as
732 works in the packet filter (see below).
733 This mechanism should be used when it is necessary to exclude specific packets
734 from broader scrub rules.
736 The ALTQ system is currently not available in the GENERIC kernel nor as
738 In order to use the herein after called queueing options one has to use a
742 to learn about the related kernel options.
744 Packets can be assigned to queues for the purpose of bandwidth
746 At least two declarations are required to configure queues, and later
747 any packet filtering rule can reference the defined queues by name.
748 During the filtering component of
752 name is where any packets from
754 rules will be queued, while for
756 rules it specifies where any resulting ICMP or TCP RST
757 packets should be queued.
760 defines the algorithm used to decide which packets get delayed, dropped, or
761 sent out immediately.
767 Class Based Queueing.
769 attached to an interface build a tree, thus each
771 can have further child
773 Each queue can have a
779 mainly controls the time packets take to get sent out, while
781 has primarily effects on throughput.
783 achieves both partitioning and sharing of link bandwidth
784 by hierarchically structured classes.
785 Each class has its own
787 and is assigned its share of
789 A child class can borrow bandwidth from its parent class
790 as long as excess bandwidth is available
797 are flat attached to the interface, thus,
799 cannot have further child
805 assigned, ranging from 0 to 15.
812 Hierarchical Fair Service Curve.
814 attached to an interface build a tree, thus each
816 can have further child
818 Each queue can have a
824 mainly controls the time packets take to get sent out, while
826 primarily affects throughput.
828 supports both link-sharing and guaranteed real-time services.
829 It employs a service curve based QoS model,
830 and its unique feature is an ability to decouple
837 The interfaces on which queueing should be activated are declared using
842 has the following keywords:
845 Queueing is enabled on the named interface.
847 Specifies which queueing scheduler to use.
848 Currently supported values
851 for Class Based Queueing,
853 for Priority Queueing and
855 for the Hierarchical Fair Service Curve scheduler.
856 .It Ar bandwidth Aq Ar bw
857 The maximum bitrate for all queues on an
858 interface may be specified using the
861 The value can be specified as an absolute value or as a
862 percentage of the interface bandwidth.
863 When using an absolute value, the suffixes
869 are used to represent bits, kilobits, megabits, and
870 gigabits per second, respectively.
871 The value must not exceed the interface bandwidth.
874 is not specified, the interface bandwidth is used
875 (but take note that some interfaces do not know their bandwidth,
876 or can adapt their bandwidth rates).
877 .It Ar qlimit Aq Ar limit
878 The maximum number of packets held in the queue.
880 .It Ar tbrsize Aq Ar size
881 Adjusts the size, in bytes, of the token bucket regulator.
882 If not specified, heuristics based on the
883 interface bandwidth are used to determine the size.
884 .It Ar queue Aq Ar list
885 Defines a list of subqueues to create on an interface.
888 In the following example, the interface dc0
889 should queue up to 5Mbps in four second-level queues using
890 Class Based Queueing.
891 Those four queues will be shown in a later example.
892 .Bd -literal -offset indent
893 altq on dc0 cbq bandwidth 5Mb queue { std, http, mail, ssh }
896 Once interfaces are activated for queueing using the
898 directive, a sequence of
900 directives may be defined.
901 The name associated with a
903 must match a queue defined in the
905 directive (e.g. mail), or, except for the
911 The following keywords can be used:
913 .It Ar on Aq Ar interface
914 Specifies the interface the queue operates on.
915 If not given, it operates on all matching interfaces.
916 .It Ar bandwidth Aq Ar bw
917 Specifies the maximum bitrate to be processed by the queue.
918 This value must not exceed the value of the parent
920 and can be specified as an absolute value or a percentage of the parent
922 If not specified, defaults to 100% of the parent queue's bandwidth.
925 scheduler does not support bandwidth specification.
926 .It Ar priority Aq Ar level
927 Between queues a priority level can be set.
932 the range is 0 to 7 and for
934 the range is 0 to 15.
935 The default for all is 1.
937 queues with a higher priority are always served first.
941 queues with a higher priority are preferred in the case of overload.
942 .It Ar qlimit Aq Ar limit
943 The maximum number of packets held in the queue.
949 can get additional parameters with
951 .Pf ( Aq Ar parameters ) .
953 Parameters are as follows:
956 Packets not matched by another queue are assigned to this one.
957 Exactly one default queue is required.
959 Enable RED (Random Early Detection) on this queue.
960 RED drops packets with a probability proportional to the average
963 Enables RIO on this queue.
964 RIO is RED with IN/OUT, thus running
965 RED two times more than RIO would achieve the same effect.
966 RIO is currently not supported in the GENERIC kernel.
968 Enables ECN (Explicit Congestion Notification) on this queue.
975 supports an additional option:
978 The queue can borrow bandwidth from the parent.
984 supports some additional options:
986 .It Ar realtime Aq Ar sc
987 The minimum required bandwidth for the queue.
988 .It Ar upperlimit Aq Ar sc
989 The maximum allowed bandwidth for the queue.
990 .It Ar linkshare Aq Ar sc
991 The bandwidth share of a backlogged queue.
998 The format for service curve specifications is
999 .Ar ( m1 , d , m2 ) .
1001 controls the bandwidth assigned to the queue.
1005 are optional and can be used to control the initial bandwidth assignment.
1008 milliseconds the queue gets the bandwidth given as
1010 afterwards the value given in
1017 child queues can be specified as in an
1019 declaration, thus building a tree of queues using a part of
1020 their parent's bandwidth.
1022 Packets can be assigned to queues based on filter rules by using the
1027 is specified; when a second one is specified it will instead be used for
1028 packets which have a
1032 and for TCP ACKs with no data payload.
1034 To continue the previous example, the examples below would specify the
1036 queues, plus a few child queues.
1039 sessions get priority over bulk transfers like
1043 The queues may then be referenced by filtering rules (see
1044 .Sx PACKET FILTERING
1047 queue std bandwidth 10% cbq(default)
1048 queue http bandwidth 60% priority 2 cbq(borrow red) \e
1049 { employees, developers }
1050 queue developers bandwidth 75% cbq(borrow)
1051 queue employees bandwidth 15%
1052 queue mail bandwidth 10% priority 0 cbq(borrow ecn)
1053 queue ssh bandwidth 20% cbq(borrow) { ssh_interactive, ssh_bulk }
1054 queue ssh_interactive bandwidth 50% priority 7 cbq(borrow)
1055 queue ssh_bulk bandwidth 50% priority 0 cbq(borrow)
1057 block return out on dc0 inet all queue std
1058 pass out on dc0 inet proto tcp from $developerhosts to any port 80 \e
1060 pass out on dc0 inet proto tcp from $employeehosts to any port 80 \e
1062 pass out on dc0 inet proto tcp from any to any port 22 \e
1063 queue(ssh_bulk, ssh_interactive)
1064 pass out on dc0 inet proto tcp from any to any port 25 \e
1068 Translation rules modify either the source or destination address of the
1069 packets associated with a stateful connection.
1070 A stateful connection is automatically created to track packets matching
1071 such a rule as long as they are not blocked by the filtering section of
1073 The translation engine modifies the specified address and/or port in the
1074 packet, recalculates IP, TCP and UDP checksums as necessary, and passes it to
1075 the packet filter for evaluation.
1077 Since translation occurs before filtering the filter
1078 engine will see packets as they look after any
1079 addresses and ports have been translated.
1080 Filter rules will therefore have to filter based on the translated
1081 address and port number.
1082 Packets that match a translation rule are only automatically passed if
1085 modifier is given, otherwise they are
1092 The state entry created permits
1094 to keep track of the original address for traffic associated with that state
1095 and correctly direct return traffic for that connection.
1097 Various types of translation are possible with pf:
1098 .Bl -tag -width xxxx
1102 rule specifies a bidirectional mapping between an external IP netblock
1103 and an internal IP netblock.
1107 rule specifies that IP addresses are to be changed as the packet
1108 traverses the given interface.
1109 This technique allows one or more IP addresses
1110 on the translating host to support network traffic for a larger range of
1111 machines on an "inside" network.
1112 Although in theory any IP address can be used on the inside, it is strongly
1113 recommended that one of the address ranges defined by RFC 1918 be used.
1114 These netblocks are:
1116 10.0.0.0 - 10.255.255.255 (all of net 10, i.e., 10/8)
1117 172.16.0.0 - 172.31.255.255 (i.e., 172.16/12)
1118 192.168.0.0 - 192.168.255.255 (i.e., 192.168/16)
1121 The packet is redirected to another destination and possibly a
1124 rules can optionally specify port ranges instead of single ports.
1125 rdr ... port 2000:2999 -\*(Gt ... port 4000
1126 redirects ports 2000 to 2999 (inclusive) to port 4000.
1127 rdr ... port 2000:2999 -\*(Gt ... port 4000:*
1128 redirects port 2000 to 4000, 2001 to 4001, ..., 2999 to 4999.
1131 In addition to modifying the address, some translation rules may modify
1132 source or destination ports for
1136 connections; implicitly in the case of
1138 rules and explicitly in the case of
1141 Port numbers are never translated with a
1145 Evaluation order of the translation rules is dependent on the type
1146 of the translation rules and of the direction of a packet.
1148 rules are always evaluated first.
1151 rules are evaluated on an inbound packet or the
1153 rules on an outbound packet.
1154 Rules of the same type are evaluated in the same order in which they
1155 appear in the ruleset.
1156 The first matching rule decides what action is taken.
1160 option prefixed to a translation rule causes packets to remain untranslated,
1161 much in the same way as
1163 works in the packet filter (see below).
1164 If no rule matches the packet it is passed to the filter engine unmodified.
1166 Translation rules apply only to packets that pass through
1167 the specified interface, and if no interface is specified,
1168 translation is applied to packets on all interfaces.
1169 For instance, redirecting port 80 on an external interface to an internal
1170 web server will only work for connections originating from the outside.
1171 Connections to the address of the external interface from local hosts will
1172 not be redirected, since such packets do not actually pass through the
1174 Redirections cannot reflect packets back through the interface they arrive
1175 on, they can only be redirected to hosts connected to different interfaces
1176 or to the firewall itself.
1178 Note that redirecting external incoming connections to the loopback
1180 .Bd -literal -offset indent
1181 rdr on ne3 inet proto tcp to port smtp -\*(Gt 127.0.0.1 port spamd
1184 will effectively allow an external host to connect to daemons
1185 bound solely to the loopback address, circumventing the traditional
1186 blocking of such connections on a real interface.
1187 Unless this effect is desired, any of the local non-loopback addresses
1188 should be used as redirection target instead, which allows external
1189 connections only to daemons bound to this address or not bound to
1193 .Sx TRANSLATION EXAMPLES
1195 .Sh PACKET FILTERING
1201 packets based on attributes of their layer 3 (see
1211 In addition, packets may also be
1212 assigned to queues for the purpose of bandwidth control.
1214 For each packet processed by the packet filter, the filter rules are
1215 evaluated in sequential order, from first to last.
1216 The last matching rule decides what action is taken.
1217 If no rule matches the packet, the default action is to pass
1220 The following actions can be used in the filter:
1221 .Bl -tag -width xxxx
1223 The packet is blocked.
1224 There are a number of ways in which a
1226 rule can behave when blocking a packet.
1227 The default behaviour is to
1229 packets silently, however this can be overridden or made
1230 explicit either globally, by setting the
1232 option, or on a per-rule basis with one of the following options:
1234 .Bl -tag -width xxxx -compact
1236 The packet is silently dropped.
1238 This applies only to
1240 packets, and issues a TCP RST which closes the
1244 This causes ICMP messages to be returned for packets which match the rule.
1245 By default this is an ICMP UNREACHABLE message, however this
1246 can be overridden by specifying a message as a code or number.
1248 This causes a TCP RST to be returned for
1250 packets and an ICMP UNREACHABLE for UDP and other packets.
1253 Options returning ICMP packets currently have no effect if
1257 as the code to support this feature has not yet been implemented.
1259 The simplest mechanism to block everything by default and only pass
1260 packets that match explicit rules is specify a first filter rule of:
1261 .Bd -literal -offset indent
1265 The packet is passed;
1266 state is created unless the
1268 option is specified.
1273 filters packets statefully; the first time a packet matches a
1275 rule, a state entry is created; for subsequent packets the filter checks
1276 whether the packet matches any state.
1277 If it does, the packet is passed without evaluation of any rules.
1278 After the connection is closed or times out, the state entry is automatically
1281 This has several advantages.
1282 For TCP connections, comparing a packet to a state involves checking
1283 its sequence numbers, as well as TCP timestamps if a
1284 .Ar scrub reassemble tcp
1285 rule applies to the connection.
1286 If these values are outside the narrow windows of expected
1287 values, the packet is dropped.
1288 This prevents spoofing attacks, such as when an attacker sends packets with
1289 a fake source address/port but does not know the connection's sequence
1293 knows how to match ICMP replies to states.
1295 .Bd -literal -offset indent
1296 pass out inet proto icmp all icmp-type echoreq
1299 allows echo requests (such as those created by
1301 out statefully, and matches incoming echo replies correctly to states.
1303 Also, looking up states is usually faster than evaluating rules.
1304 If there are 50 rules, all of them are evaluated sequentially in O(n).
1305 Even with 50000 states, only 16 comparisons are needed to match a
1306 state, since states are stored in a binary search tree that allows
1307 searches in O(log2 n).
1309 Furthermore, correct handling of ICMP error messages is critical to
1310 many protocols, particularly TCP.
1312 matches ICMP error messages to the correct connection, checks them against
1313 connection parameters, and passes them if appropriate.
1314 For example if an ICMP source quench message referring to a stateful TCP
1315 connection arrives, it will be matched to the state and get passed.
1317 Finally, state tracking is required for
1318 .Ar nat , binat No and Ar rdr
1319 rules, in order to track address and port translations and reverse the
1320 translation on returning packets.
1323 will also create state for other protocols which are effectively stateless by
1325 UDP packets are matched to states using only host addresses and ports,
1326 and other protocols are matched to states using only the host addresses.
1328 If stateless filtering of individual packets is desired,
1331 keyword can be used to specify that state will not be created
1332 if this is the last matching rule.
1333 A number of parameters can also be set to affect how
1335 handles state tracking.
1337 .Sx STATEFUL TRACKING OPTIONS
1338 below for further details.
1340 The rule parameters specify the packets to which a rule applies.
1341 A packet always comes in on, or goes out through, one interface.
1342 Most parameters are optional.
1343 If a parameter is specified, the rule only applies to packets with
1344 matching attributes.
1345 Certain parameters can be expressed as lists, in which case
1347 generates all needed rule combinations.
1348 .Bl -tag -width xxxx
1349 .It Ar in No or Ar out
1350 This rule applies to incoming or outgoing packets.
1355 are specified, the rule will match packets in both directions.
1357 In addition to the action specified, a log message is generated.
1358 Only the packet that establishes the state is logged,
1361 option is specified.
1362 The logged packets are sent to a
1364 interface, by default
1366 This interface is monitored by the
1368 logging daemon, which dumps the logged packets to the file
1374 Used to force logging of all packets for a connection.
1375 This is not necessary when
1377 is explicitly specified.
1380 packets are logged to
1385 user ID of the user that owns the socket and the PID of the process that
1386 has the socket open where the packet is sourced from or destined to
1387 (depending on which socket is local).
1388 This is in addition to the normal information logged.
1390 Only the first packet
1393 will have the user credentials logged when using stateful matching.
1394 .It Ar log (to Aq Ar interface )
1395 Send logs to the specified
1397 interface instead of
1400 If a packet matches a rule which has the
1402 option set, this rule
1403 is considered the last matching rule, and evaluation of subsequent rules
1405 .It Ar on Aq Ar interface
1406 This rule applies only to packets coming in on, or going out through, this
1407 particular interface or interface group.
1408 For more information on interface groups,
1414 This rule applies only to packets of this address family.
1415 Supported values are
1419 .It Ar proto Aq Ar protocol
1420 This rule applies only to packets of this protocol.
1421 Common protocols are
1427 For a list of all the protocol name to number mappings used by
1430 .Pa /etc/protocols .
1432 .Ar from Aq Ar source
1433 .Ar port Aq Ar source
1438 This rule applies only to packets with the specified source and destination
1439 addresses and ports.
1441 Addresses can be specified in CIDR notation (matching netblocks), as
1442 symbolic host names, interface names or interface group names, or as any
1443 of the following keywords:
1445 .Bl -tag -width xxxxxxxxxxxxxx -compact
1449 Any address which is not currently routable.
1451 Any source address that fails a unicast reverse path forwarding (URPF)
1452 check, i.e. packets coming in on an interface other than that which holds
1453 the route back to the packet's source address.
1455 Any address that matches the given table.
1458 Ranges of addresses are specified by using the
1462 .Dq 10.1.1.10 - 10.1.1.12
1463 means all addresses from 10.1.1.10 to 10.1.1.12,
1464 hence addresses 10.1.1.10, 10.1.1.11, and 10.1.1.12.
1466 Interface names and interface group names can have modifiers appended:
1468 .Bl -tag -width xxxxxxxxxxxx -compact
1470 Translates to the network(s) attached to the interface.
1472 Translates to the interface's broadcast address(es).
1474 Translates to the point-to-point interface's peer address(es).
1476 Do not include interface aliases.
1479 Host names may also have the
1481 option appended to restrict the name resolution to the first of each
1482 v4 and v6 address found.
1484 Host name resolution and interface to address translation are done at
1486 When the address of an interface (or host name) changes (under DHCP or PPP,
1487 for instance), the ruleset must be reloaded for the change to be reflected
1489 Surrounding the interface name (and optional modifiers) in parentheses
1490 changes this behaviour.
1491 When the interface name is surrounded by parentheses, the rule is
1492 automatically updated whenever the interface changes its address.
1493 The ruleset does not need to be reloaded.
1494 This is especially useful with
1497 Ports can be specified either by number or by name.
1498 For example, port 80 can be specified as
1500 For a list of all port name to number mappings used by
1505 Ports and ranges of ports are specified by using these operators:
1506 .Bd -literal -offset indent
1510 \*(Le (less than or equal)
1511 \*(Gt (greater than)
1512 \*(Ge (greater than or equal)
1513 : (range including boundaries)
1514 \*(Gt\*(Lt (range excluding boundaries)
1515 \*(Lt\*(Gt (except range)
1522 are binary operators (they take two arguments).
1525 .It Ar port 2000:2004
1527 .Sq all ports \*(Ge 2000 and \*(Le 2004 ,
1528 hence ports 2000, 2001, 2002, 2003 and 2004.
1529 .It Ar port 2000 \*(Gt\*(Lt 2004
1531 .Sq all ports \*(Gt 2000 and \*(Lt 2004 ,
1532 hence ports 2001, 2002 and 2003.
1533 .It Ar port 2000 \*(Lt\*(Gt 2004
1535 .Sq all ports \*(Lt 2000 or \*(Gt 2004 ,
1536 hence ports 1-1999 and 2005-65535.
1539 The operating system of the source host can be specified in the case of TCP
1544 .Sx OPERATING SYSTEM FINGERPRINTING
1545 section for more information.
1547 The host, port and OS specifications are optional, as in the following examples:
1548 .Bd -literal -offset indent
1550 pass in from any to any
1551 pass in proto tcp from any port \*(Le 1024 to any
1552 pass in proto tcp from any to any port 25
1553 pass in proto tcp from 10.0.0.0/8 port \*(Gt 1024 \e
1554 to ! 10.1.2.3 port != ssh
1555 pass in proto tcp from any os "OpenBSD"
1558 This is equivalent to "from any to any".
1559 .It Ar group Aq Ar group
1562 this rule only applies to packets of sockets owned by the specified group.
1563 .It Ar user Aq Ar user
1564 This rule only applies to packets of sockets owned by the specified user.
1565 For outgoing connections initiated from the firewall, this is the user
1566 that opened the connection.
1567 For incoming connections to the firewall itself, this is the user that
1568 listens on the destination port.
1569 For forwarded connections, where the firewall is not a connection endpoint,
1570 the user and group are
1573 All packets, both outgoing and incoming, of one connection are associated
1574 with the same user and group.
1575 Only TCP and UDP packets can be associated with users; for other protocols
1576 these parameters are ignored.
1578 User and group refer to the effective (as opposed to the real) IDs, in
1579 case the socket is created by a setuid/setgid process.
1580 User and group IDs are stored when a socket is created;
1581 when a process creates a listening socket as root (for instance, by
1582 binding to a privileged port) and subsequently changes to another
1583 user ID (to drop privileges), the credentials will remain root.
1585 User and group IDs can be specified as either numbers or names.
1586 The syntax is similar to the one for ports.
1589 matches packets of forwarded connections.
1591 can only be used with the operators
1595 Other constructs like
1596 .Cm user \*(Ge unknown
1598 Forwarded packets with unknown user and group ID match only rules
1599 that explicitly compare against
1607 does not match forwarded packets.
1608 The following example allows only selected users to open outgoing
1610 .Bd -literal -offset indent
1611 block out proto { tcp, udp } all
1612 pass out proto { tcp, udp } all user { \*(Lt 1000, dhartmei }
1614 .It Xo Ar flags Aq Ar a
1616 .No \*(Ba / Ns Aq Ar b
1619 This rule only applies to TCP packets that have the flags
1623 Flags not specified in
1626 For stateful connections, the default is
1628 To indicate that flags should not be checked at all, specify
1630 The flags are: (F)IN, (S)YN, (R)ST, (P)USH, (A)CK, (U)RG, (E)CE, and C(W)R.
1634 The other flags are ignored.
1636 This is the default setting for stateful connections.
1637 Out of SYN and ACK, exactly SYN may be set.
1638 SYN, SYN+PSH and SYN+RST match, but SYN+ACK, ACK and ACK+RST do not.
1639 This is more restrictive than the previous example.
1641 If the first set is not specified, it defaults to none.
1642 All of SYN, FIN, RST and ACK must be unset.
1647 is applied by default (unless
1649 is specified), only the initial SYN packet of a TCP handshake will create
1650 a state for a TCP connection.
1651 It is possible to be less restrictive, and allow state creation from
1654 packets, by specifying
1658 to synchronize to existing connections, for instance
1659 if one flushes the state table.
1660 However, states created from such intermediate packets may be missing
1661 connection details such as the TCP window scaling factor.
1662 States which modify the packet flow, such as those affected by
1663 .Ar nat , binat No or Ar rdr
1665 .Ar modulate No or Ar synproxy state
1666 options, or scrubbed with
1668 will also not be recoverable from intermediate packets.
1669 Such connections will stall and time out.
1670 .It Xo Ar icmp-type Aq Ar type
1673 .It Xo Ar icmp6-type Aq Ar type
1676 This rule only applies to ICMP or ICMPv6 packets with the specified type
1678 Text names for ICMP types and codes are listed in
1682 This parameter is only valid for rules that cover protocols ICMP or
1684 The protocol and the ICMP type indicator
1691 .It Xo Ar tos Aq Ar string
1692 .No \*(Ba Aq Ar number
1694 This rule applies to packets with the specified
1703 or as either hex or decimal.
1705 For example, the following rules are identical:
1706 .Bd -literal -offset indent
1707 pass all tos lowdelay
1712 By default, IPv4 packets with IP options or IPv6 packets with routing
1713 extension headers are blocked.
1718 rule, packets that pass the filter based on that rule (last matching)
1719 do so even if they contain IP options or routing extension headers.
1720 For packets that match state, the rule that initially created the
1724 rule that is used when a packet does not match any rules does not
1726 .It Ar label Aq Ar string
1727 Adds a label (name) to the rule, which can be used to identify the rule.
1730 shows per-rule statistics for rules that have labels.
1732 The following macros can be used in labels:
1734 .Bl -tag -width $srcaddr -compact -offset indent
1738 The source IP address.
1740 The destination IP address.
1742 The source port specification.
1744 The destination port specification.
1752 .Bd -literal -offset indent
1753 ips = \&"{ 1.2.3.4, 1.2.3.5 }\&"
1754 pass in proto tcp from any to $ips \e
1755 port \*(Gt 1023 label \&"$dstaddr:$dstport\&"
1759 .Bd -literal -offset indent
1760 pass in inet proto tcp from any to 1.2.3.4 \e
1761 port \*(Gt 1023 label \&"1.2.3.4:\*(Gt1023\&"
1762 pass in inet proto tcp from any to 1.2.3.5 \e
1763 port \*(Gt 1023 label \&"1.2.3.5:\*(Gt1023\&"
1766 The macro expansion for the
1768 directive occurs only at configuration file parse time, not during runtime.
1769 .It Xo Ar queue Aq Ar queue
1770 .No \*(Ba ( Aq Ar queue ,
1773 Packets matching this rule will be assigned to the specified queue.
1774 If two queues are given, packets which have a
1778 and TCP ACKs with no data payload will be assigned to the second one.
1784 .Bd -literal -offset indent
1785 pass in proto tcp to port 25 queue mail
1786 pass in proto tcp to port 22 queue(ssh_bulk, ssh_prio)
1788 .It Ar tag Aq Ar string
1789 Packets matching this rule will be tagged with the
1791 The tag acts as an internal marker that can be used to
1792 identify these packets later on.
1793 This can be used, for example, to provide trust between
1794 interfaces and to determine if packets have been
1795 processed by translation rules.
1798 meaning that the packet will be tagged even if the rule
1799 is not the last matching rule.
1800 Further matching rules can replace the tag with a
1801 new one but will not remove a previously applied tag.
1802 A packet is only ever assigned one tag at a time.
1803 Packet tagging can be done during
1808 rules in addition to filter rules.
1809 Tags take the same macros as labels (see above).
1810 .It Ar tagged Aq Ar string
1811 Used with filter, translation or scrub rules
1812 to specify that packets must already
1813 be tagged with the given tag in order to match the rule.
1814 Inverse tag matching can also be done
1820 .It Ar rtable Aq Ar number
1821 Used to select an alternate routing table for the routing lookup.
1822 Only effective before the route lookup happened, i.e. when filtering inbound.
1823 .It Xo Ar divert-to Aq Ar host
1826 Used to redirect packets to a local socket bound to
1830 The packets will not be modified, so
1832 on the socket will return the original destination address of the packet.
1834 Used to receive replies for sockets that are bound to addresses
1835 which are not local to the machine.
1838 for information on how to bind these sockets.
1839 .It Ar probability Aq Ar number
1840 A probability attribute can be attached to a rule, with a value set between
1841 0 and 1, bounds not included.
1842 In that case, the rule will be honoured using the given probability value
1844 For example, the following rule will drop 20% of incoming ICMP packets:
1845 .Bd -literal -offset indent
1846 block in proto icmp probability 20%
1850 If a packet matches a rule with a route option set, the packet filter will
1851 route the packet according to the type of route option.
1852 When such a rule creates state, the route option is also applied to all
1853 packets matching the same connection.
1854 .Bl -tag -width xxxx
1858 option does a normal route lookup to find the next hop for the packet.
1862 option routes the packet to the specified interface with an optional address
1866 rule creates state, only packets that pass in the same direction as the
1867 filter rule specifies will be routed in this way.
1868 Packets passing in the opposite direction (replies) are not affected
1869 and are routed normally.
1873 option is similar to
1875 but routes packets that pass in the opposite direction (replies) to the
1876 specified interface.
1877 Opposite direction is only defined in the context of a state entry, and
1879 is useful only in rules that create state.
1880 It can be used on systems with multiple external connections to
1881 route all outgoing packets of a connection through the interface
1882 the incoming connection arrived through (symmetric routing enforcement).
1886 option creates a duplicate of the packet and routes it like
1888 The original packet gets routed as it normally would.
1895 rules, (as well as for the
1900 rule options) for which there is a single redirection address which has a
1901 subnet mask smaller than 32 for IPv4 or 128 for IPv6 (more than one IP
1902 address), a variety of different methods for assigning this address can be
1904 .Bl -tag -width xxxx
1908 option applies the network portion of the redirection address to the address
1909 to be modified (source with
1916 option selects an address at random within the defined block of addresses.
1920 option uses a hash of the source address to determine the redirection address,
1921 ensuring that the redirection address is always the same for a given source.
1922 An optional key can be specified after this keyword either in hex or as a
1925 randomly generates a key for source-hash every time the
1926 ruleset is reloaded.
1930 option loops through the redirection address(es).
1932 When more than one redirection address is specified,
1934 is the only permitted pool type.
1942 from modifying the source port on TCP and UDP packets.
1947 option can be specified to help ensure that multiple connections from the
1948 same source are mapped to the same redirection address.
1949 This option can be used with the
1954 Note that by default these associations are destroyed as soon as there are
1955 no longer states which refer to them; in order to make the mappings last
1956 beyond the lifetime of the states, increase the global options with
1957 .Ar set timeout src.track .
1959 .Sx STATEFUL TRACKING OPTIONS
1960 for more ways to control the source tracking.
1961 .Sh STATE MODULATION
1962 Much of the security derived from TCP is attributable to how well the
1963 initial sequence numbers (ISNs) are chosen.
1964 Some popular stack implementations choose
1966 poor ISNs and thus are normally susceptible to ISN prediction exploits.
1969 rule to a TCP connection,
1971 will create a high quality random sequence number for each connection
1976 directive implicitly keeps state on the rule and is
1977 only applicable to TCP connections.
1980 .Bd -literal -offset indent
1982 pass out proto tcp from any to any modulate state
1983 pass in proto tcp from any to any port 25 flags S/SFRA modulate state
1986 Note that modulated connections will not recover when the state table
1987 is lost (firewall reboot, flushing the state table, etc...).
1989 will not be able to infer a connection again after the state table flushes
1990 the connection's modulator.
1991 When the state is lost, the connection may be left dangling until the
1992 respective endpoints time out the connection.
1993 It is possible on a fast local network for the endpoints to start an ACK
1994 storm while trying to resynchronize after the loss of the modulator.
1997 settings (or a more strict equivalent) should be used on
1999 rules to prevent ACK storms.
2001 Note that alternative methods are available
2002 to prevent loss of the state table
2003 and allow for firewall failover.
2008 for further information.
2012 passes packets that are part of a
2014 handshake between the endpoints.
2017 option can be used to cause
2019 itself to complete the handshake with the active endpoint, perform a handshake
2020 with the passive endpoint, and then forward packets between the endpoints.
2022 No packets are sent to the passive endpoint before the active endpoint has
2023 completed the handshake, hence so-called SYN floods with spoofed source
2024 addresses will not reach the passive endpoint, as the sender can't complete the
2027 The proxy is transparent to both endpoints, they each see a single
2028 connection from/to the other endpoint.
2030 chooses random initial sequence numbers for both handshakes.
2031 Once the handshakes are completed, the sequence number modulators
2032 (see previous section) are used to translate further packets of the
2036 .Ar modulate state .
2046 .Bd -literal -offset indent
2047 pass in proto tcp from any to any port www synproxy state
2049 .Sh STATEFUL TRACKING OPTIONS
2050 A number of options related to stateful tracking can be applied on a
2056 support these options, and
2058 must be specified explicitly to apply options to a rule.
2060 .Bl -tag -width xxxx -compact
2061 .It Ar max Aq Ar number
2062 Limits the number of concurrent states the rule may create.
2063 When this limit is reached, further packets that would create
2064 state will not match this rule until existing states time out.
2066 Prevent state changes for states created by this rule from appearing on the
2069 .It Xo Aq Ar timeout
2072 Changes the timeout values used for states created by this rule.
2073 For a list of all valid timeout names, see
2077 Uses a sloppy TCP connection tracker that does not check sequence
2078 numbers at all, which makes insertion and ICMP teardown attacks way
2080 This is intended to be used in situations where one does not see all
2081 packets of a connection, e.g. in asymmetric routing situations.
2082 Cannot be used with modulate or synproxy state.
2084 States created by this rule are exported on the
2089 Multiple options can be specified, separated by commas:
2090 .Bd -literal -offset indent
2091 pass in proto tcp from any to any \e
2092 port www keep state \e
2093 (max 100, source-track rule, max-src-nodes 75, \e
2094 max-src-states 3, tcp.established 60, tcp.closing 5)
2099 keyword is specified, the number of states per source IP is tracked.
2101 .Bl -tag -width xxxx -compact
2102 .It Ar source-track rule
2103 The maximum number of states created by this rule is limited by the rule's
2108 Only state entries created by this particular rule count toward the rule's
2110 .It Ar source-track global
2111 The number of states created by all rules that use this option is limited.
2112 Each rule can specify different
2116 options, however state entries created by any participating rule count towards
2117 each individual rule's limits.
2120 The following limits can be set:
2122 .Bl -tag -width xxxx -compact
2123 .It Ar max-src-nodes Aq Ar number
2124 Limits the maximum number of source addresses which can simultaneously
2125 have state table entries.
2126 .It Ar max-src-states Aq Ar number
2127 Limits the maximum number of simultaneous state entries that a single
2128 source address can create with this rule.
2131 For stateful TCP connections, limits on established connections (connections
2132 which have completed the TCP 3-way handshake) can also be enforced
2135 .Bl -tag -width xxxx -compact
2136 .It Ar max-src-conn Aq Ar number
2137 Limits the maximum number of simultaneous TCP connections which have
2138 completed the 3-way handshake that a single host can make.
2139 .It Xo Ar max-src-conn-rate Aq Ar number
2142 Limit the rate of new connections over a time interval.
2143 The connection rate is an approximation calculated as a moving average.
2146 Because the 3-way handshake ensures that the source address is not being
2147 spoofed, more aggressive action can be taken based on these limits.
2149 .Ar overload Aq Ar table
2150 state option, source IP addresses which hit either of the limits on
2151 established connections will be added to the named table.
2152 This table can be used in the ruleset to block further activity from
2153 the offending host, redirect it to a tarpit process, or restrict its
2158 keyword kills all states created by the matching rule which originate
2159 from the host which exceeds these limits.
2162 modifier to the flush command kills all states originating from the
2163 offending host, regardless of which rule created the state.
2165 For example, the following rules will protect the webserver against
2166 hosts making more than 100 connections in 10 seconds.
2167 Any host which connects faster than this rate will have its address added
2170 table and have all states originating from it flushed.
2171 Any new packets arriving from this host will be dropped unconditionally
2173 .Bd -literal -offset indent
2174 block quick from \*(Ltbad_hosts\*(Gt
2175 pass in on $ext_if proto tcp to $webserver port www keep state \e
2176 (max-src-conn-rate 100/10, overload \*(Ltbad_hosts\*(Gt flush global)
2178 .Sh OPERATING SYSTEM FINGERPRINTING
2179 Passive OS Fingerprinting is a mechanism to inspect nuances of a TCP
2180 connection's initial SYN packet and guess at the host's operating system.
2181 Unfortunately these nuances are easily spoofed by an attacker so the
2182 fingerprint is not useful in making security decisions.
2183 But the fingerprint is typically accurate enough to make policy decisions
2186 The fingerprints may be specified by operating system class, by
2187 version, or by subtype/patchlevel.
2188 The class of an operating system is typically the vendor or genre
2194 The version of the oldest available
2196 release on the main FTP site
2197 would be 2.6 and the fingerprint would be written
2199 .Dl \&"OpenBSD 2.6\&"
2201 The subtype of an operating system is typically used to describe the
2202 patchlevel if that patch led to changes in the TCP stack behavior.
2205 the only subtype is for a fingerprint that was
2208 scrub option and would be specified as
2210 .Dl \&"OpenBSD 3.3 no-df\&"
2212 Fingerprints for most popular operating systems are provided by
2216 is running, a complete list of known operating system fingerprints may
2217 be listed by running:
2221 Filter rules can enforce policy at any level of operating system specification
2222 assuming a fingerprint is present.
2223 Policy could limit traffic to approved operating systems or even ban traffic
2224 from hosts that aren't at the latest service pack.
2228 class can also be used as the fingerprint which will match packets for
2229 which no operating system fingerprint is known.
2232 .Bd -literal -offset indent
2233 pass out proto tcp from any os OpenBSD
2234 block out proto tcp from any os Doors
2235 block out proto tcp from any os "Doors PT"
2236 block out proto tcp from any os "Doors PT SP3"
2237 block out from any os "unknown"
2238 pass on lo0 proto tcp from any os "OpenBSD 3.3 lo0"
2241 Operating system fingerprinting is limited only to the TCP SYN packet.
2242 This means that it will not work on other protocols and will not match
2243 a currently established connection.
2245 Caveat: operating system fingerprints are occasionally wrong.
2246 There are three problems: an attacker can trivially craft his packets to
2247 appear as any operating system he chooses;
2248 an operating system patch could change the stack behavior and no fingerprints
2249 will match it until the database is updated;
2250 and multiple operating systems may have the same fingerprint.
2251 .Sh BLOCKING SPOOFED TRAFFIC
2252 "Spoofing" is the faking of IP addresses, typically for malicious
2256 directive expands to a set of filter rules which will block all
2257 traffic with a source IP from the network(s) directly connected
2258 to the specified interface(s) from entering the system through
2259 any other interface.
2261 For example, the line
2262 .Bd -literal -offset indent
2267 .Bd -literal -offset indent
2268 block drop in on ! lo0 inet from 127.0.0.1/8 to any
2269 block drop in on ! lo0 inet6 from ::1 to any
2272 For non-loopback interfaces, there are additional rules to block incoming
2273 packets with a source IP address identical to the interface's IP(s).
2274 For example, assuming the interface wi0 had an IP address of 10.0.0.1 and a
2275 netmask of 255.255.255.0,
2277 .Bd -literal -offset indent
2278 antispoof for wi0 inet
2282 .Bd -literal -offset indent
2283 block drop in on ! wi0 inet from 10.0.0.0/24 to any
2284 block drop in inet from 10.0.0.1 to any
2287 Caveat: Rules created by the
2289 directive interfere with packets sent over loopback interfaces
2291 One should pass these explicitly.
2292 .Sh FRAGMENT HANDLING
2293 The size of IP datagrams (packets) can be significantly larger than the
2294 maximum transmission unit (MTU) of the network.
2295 In cases when it is necessary or more efficient to send such large packets,
2296 the large packet will be fragmented into many smaller packets that will each
2298 Unfortunately for a firewalling device, only the first logical fragment will
2299 contain the necessary header information for the subprotocol that allows
2301 to filter on things such as TCP ports or to perform NAT.
2305 rules as described in
2306 .Sx TRAFFIC NORMALIZATION
2307 above, there are three options for handling fragments in the packet filter.
2309 One alternative is to filter individual fragments with filter rules.
2312 rule applies to a fragment, it is passed to the filter.
2313 Filter rules with matching IP header parameters decide whether the
2314 fragment is passed or blocked, in the same way as complete packets
2316 Without reassembly, fragments can only be filtered based on IP header
2317 fields (source/destination address, protocol), since subprotocol header
2318 fields are not available (TCP/UDP port numbers, ICMP code/type).
2321 option can be used to restrict filter rules to apply only to
2322 fragments, but not complete packets.
2323 Filter rules without the
2325 option still apply to fragments, if they only specify IP header fields.
2326 For instance, the rule
2327 .Bd -literal -offset indent
2328 pass in proto tcp from any to any port 80
2331 never applies to a fragment, even if the fragment is part of a TCP
2332 packet with destination port 80, because without reassembly this information
2333 is not available for each fragment.
2334 This also means that fragments cannot create new or match existing
2335 state table entries, which makes stateful filtering and address
2336 translation (NAT, redirection) for fragments impossible.
2338 It's also possible to reassemble only certain fragments by specifying
2339 source or destination addresses or protocols as parameters in
2343 In most cases, the benefits of reassembly outweigh the additional
2344 memory cost, and it's recommended to use
2347 all fragments via the
2348 .Ar fragment reassemble
2351 The memory allocated for fragment caching can be limited using
2353 Once this limit is reached, fragments that would have to be cached
2354 are dropped until other entries time out.
2355 The timeout value can also be adjusted.
2357 When forwarding reassembled IPv6 packets, pf refragments them with
2358 the original maximum fragment size.
2359 This allows the sender to determine the optimal fragment size by
2362 Besides the main ruleset,
2364 can load rulesets into
2369 is a container that can hold rules, address tables, and other anchors.
2373 has a name which specifies the path where
2375 can be used to access the anchor to perform operations on it, such as
2376 attaching child anchors to it or loading rules into it.
2377 Anchors may be nested, with components separated by
2379 characters, similar to how file system hierarchies are laid out.
2380 The main ruleset is actually the default anchor, so filter and
2381 translation rules, for example, may also be contained in any anchor.
2383 An anchor can reference another
2386 using the following kinds
2388 .Bl -tag -width xxxx
2389 .It Ar nat-anchor Aq Ar name
2392 rules in the specified
2394 .It Ar rdr-anchor Aq Ar name
2397 rules in the specified
2399 .It Ar binat-anchor Aq Ar name
2402 rules in the specified
2404 .It Ar anchor Aq Ar name
2405 Evaluates the filter rules in the specified
2407 .It Xo Ar load anchor
2411 Loads the rules from the specified file into the
2416 When evaluation of the main ruleset reaches an
2420 will proceed to evaluate all rules specified in that anchor.
2422 Matching filter and translation rules marked with the
2424 option are final and abort the evaluation of the rules in other
2425 anchors and the main ruleset.
2428 itself is marked with the
2431 ruleset evaluation will terminate when the anchor is exited if the packet is
2432 matched by any rule within the anchor.
2435 rules are evaluated relative to the anchor in which they are contained.
2438 rules specified in the main ruleset will reference anchor
2439 attachment points underneath the main ruleset, and
2441 rules specified in a file loaded from a
2443 rule will be attached under that anchor point.
2445 Rules may be contained in
2447 attachment points which do not contain any rules when the main ruleset
2448 is loaded, and later such anchors can be manipulated through
2450 without reloading the main ruleset or other anchors.
2452 .Bd -literal -offset indent
2454 block on $ext_if all
2456 pass out on $ext_if all
2457 pass in on $ext_if proto tcp from any \e
2458 to $ext_if port smtp
2461 blocks all packets on the external interface by default, then evaluates
2464 named "spam", and finally passes all outgoing connections and
2465 incoming connections to port 25.
2466 .Bd -literal -offset indent
2467 # echo \&"block in quick from 1.2.3.4 to any\&" \&| \e
2471 This loads a single rule into the
2473 which blocks all packets from a specific address.
2475 The anchor can also be populated by adding a
2480 .Bd -literal -offset indent
2482 load anchor spam from "/etc/pf-spam.conf"
2489 it will also load all the rules from the file
2490 .Pa /etc/pf-spam.conf
2495 rules can specify packet filtering parameters using the same syntax as
2497 When parameters are used, the
2499 rule is only evaluated for matching packets.
2500 This allows conditional evaluation of anchors, like:
2501 .Bd -literal -offset indent
2502 block on $ext_if all
2503 anchor spam proto tcp from any to any port smtp
2504 pass out on $ext_if all
2505 pass in on $ext_if proto tcp from any to $ext_if port smtp
2510 spam are only evaluated for
2512 packets with destination port 25.
2514 .Bd -literal -offset indent
2515 # echo \&"block in quick from 1.2.3.4 to any" \&| \e
2519 will only block connections from 1.2.3.4 to port 25.
2521 Anchors may end with the asterisk
2523 character, which signifies that all anchors attached at that point
2524 should be evaluated in the alphabetical ordering of their anchor name.
2526 .Bd -literal -offset indent
2530 will evaluate each rule in each anchor attached to the
2533 Note that it will only evaluate anchors that are directly attached to the
2535 anchor, and will not descend to evaluate anchors recursively.
2537 Since anchors are evaluated relative to the anchor in which they are
2538 contained, there is a mechanism for accessing the parent and ancestor
2539 anchors of a given anchor.
2540 Similar to file system path name resolution, if the sequence
2542 appears as an anchor path component, the parent anchor of the current
2543 anchor in the path evaluation at that point will become the new current
2545 As an example, consider the following:
2546 .Bd -literal -offset indent
2547 # echo ' anchor "spam/allowed" ' | pfctl -f -
2548 # echo -e ' anchor "../banned" \en pass' | \e
2549 pfctl -a spam/allowed -f -
2552 Evaluation of the main ruleset will lead into the
2554 anchor, which will evaluate the rules in the
2556 anchor, if any, before finally evaluating the
2562 can also be loaded inline in the ruleset within a brace ('{' '}') delimited
2564 Brace delimited blocks may contain rules or other brace-delimited blocks.
2565 When anchors are loaded this way the anchor name becomes optional.
2566 .Bd -literal -offset indent
2567 anchor "external" on egress {
2570 pass proto tcp from any to port { 25, 80, 443 }
2572 pass in proto tcp to any port 22
2576 Since the parser specification for anchor names is a string, any
2577 reference to an anchor name containing
2579 characters will require double quote
2581 characters around the anchor name.
2582 .Sh TRANSLATION EXAMPLES
2583 This example maps incoming requests on port 80 to port 8080, on
2584 which a daemon is running (because, for example, it is not run as root,
2585 and therefore lacks permission to bind to port 80).
2587 # use a macro for the interface name, so it can be changed easily
2590 # map daemon on 8080 to appear to be on 80
2591 rdr on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 port 8080
2596 modifier is given, packets matching the translation rule are passed without
2597 inspecting the filter rules:
2599 rdr pass on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 \e
2603 In the example below, vlan12 is configured as 192.168.168.1;
2604 the machine translates all packets coming from 192.168.168.0/24 to 204.92.77.111
2605 when they are going out any interface except vlan12.
2606 This has the net effect of making traffic from the 192.168.168.0/24
2607 network appear as though it is the Internet routable address
2608 204.92.77.111 to nodes behind any interface on the router except
2609 for the nodes on vlan12.
2610 (Thus, 192.168.168.1 can talk to the 192.168.168.0/24 nodes.)
2612 nat on ! vlan12 from 192.168.168.0/24 to any -\*(Gt 204.92.77.111
2615 In the example below, the machine sits between a fake internal 144.19.74.*
2616 network, and a routable external IP of 204.92.77.100.
2619 rule excludes protocol AH from being translated.
2622 no nat on $ext_if proto ah from 144.19.74.0/24 to any
2623 nat on $ext_if from 144.19.74.0/24 to any -\*(Gt 204.92.77.100
2626 In the example below, packets bound for one specific server, as well as those
2627 generated by the sysadmins are not proxied; all other connections are.
2630 no rdr on $int_if proto { tcp, udp } from any to $server port 80
2631 no rdr on $int_if proto { tcp, udp } from $sysadmins to any port 80
2632 rdr on $int_if proto { tcp, udp } from any to any port 80 -\*(Gt 127.0.0.1 \e
2636 This longer example uses both a NAT and a redirection.
2637 The external interface has the address 157.161.48.183.
2638 On localhost, we are running
2640 waiting for FTP sessions to be redirected to it.
2641 The three mandatory anchors for
2643 are omitted from this example; see the
2648 # Translate outgoing packets' source addresses (any protocol).
2649 # In this case, any address but the gateway's external address is mapped.
2650 nat on $ext_if inet from ! ($ext_if) to any -\*(Gt ($ext_if)
2653 # Map outgoing packets' source port to an assigned proxy port instead of
2654 # an arbitrary port.
2655 # In this case, proxy outgoing isakmp with port 500 on the gateway.
2656 nat on $ext_if inet proto udp from any port = isakmp to any -\*(Gt ($ext_if) \e
2660 # Translate outgoing packets' source address (any protocol).
2661 # Translate incoming packets' destination address to an internal machine
2663 binat on $ext_if from 10.1.2.150 to any -\*(Gt $ext_if
2666 # Translate incoming packets' destination addresses.
2667 # As an example, redirect a TCP and UDP port to an internal machine.
2668 rdr on $ext_if inet proto tcp from any to ($ext_if) port 8080 \e
2669 -\*(Gt 10.1.2.151 port 22
2670 rdr on $ext_if inet proto udp from any to ($ext_if) port 8080 \e
2671 -\*(Gt 10.1.2.151 port 53
2674 # Translate outgoing ftp control connections to send them to localhost
2675 # for proxying with ftp-proxy(8) running on port 8021.
2676 rdr on $int_if proto tcp from any to any port 21 -\*(Gt 127.0.0.1 port 8021
2679 In this example, a NAT gateway is set up to translate internal addresses
2680 using a pool of public addresses (192.0.2.16/28) and to redirect
2681 incoming web server connections to a group of web servers on the internal
2685 # Translate outgoing packets' source addresses using an address pool.
2686 # A given source address is always translated to the same pool address by
2687 # using the source-hash keyword.
2688 nat on $ext_if inet from any to any -\*(Gt 192.0.2.16/28 source-hash
2691 # Translate incoming web server connections to a group of web servers on
2692 # the internal network.
2693 rdr on $ext_if proto tcp from any to any port 80 \e
2694 -\*(Gt { 10.1.2.155, 10.1.2.160, 10.1.2.161 } round-robin
2698 # The external interface is kue0
2699 # (157.161.48.183, the only routable address)
2700 # and the private network is 10.0.0.0/8, for which we are doing NAT.
2702 # use a macro for the interface name, so it can be changed easily
2705 # normalize all incoming traffic
2706 scrub in on $ext_if all fragment reassemble
2708 # block and log everything by default
2709 block return log on $ext_if all
2711 # block anything coming from source we have no back routes for
2712 block in from no-route to any
2714 # block packets whose ingress interface does not match the one in
2715 # the route back to their source address
2716 block in from urpf-failed to any
2718 # block and log outgoing packets that do not have our address as source,
2719 # they are either spoofed or something is misconfigured (NAT disabled,
2720 # for instance), we want to be nice and do not send out garbage.
2721 block out log quick on $ext_if from ! 157.161.48.183 to any
2723 # silently drop broadcasts (cable modem noise)
2724 block in quick on $ext_if from any to 255.255.255.255
2726 # block and log incoming packets from reserved address space and invalid
2727 # addresses, they are either spoofed or misconfigured, we cannot reply to
2728 # them anyway (hence, no return-rst).
2729 block in log quick on $ext_if from { 10.0.0.0/8, 172.16.0.0/12, \e
2730 192.168.0.0/16, 255.255.255.255/32 } to any
2734 # pass out/in certain ICMP queries and keep state (ping)
2735 # state matching is done on host addresses and ICMP id (not type/code),
2736 # so replies (like 0/0 for 8/0) will match queries
2737 # ICMP error messages (which always refer to a TCP/UDP packet) are
2738 # handled by the TCP/UDP states
2739 pass on $ext_if inet proto icmp all icmp-type 8 code 0
2743 # pass out all UDP connections and keep state
2744 pass out on $ext_if proto udp all
2746 # pass in certain UDP connections and keep state (DNS)
2747 pass in on $ext_if proto udp from any to any port domain
2751 # pass out all TCP connections and modulate state
2752 pass out on $ext_if proto tcp all modulate state
2754 # pass in certain TCP connections and keep state (SSH, SMTP, DNS, IDENT)
2755 pass in on $ext_if proto tcp from any to any port { ssh, smtp, domain, \e
2758 # Do not allow Windows 9x SMTP connections since they are typically
2759 # a viral worm. Alternately we could limit these OSes to 1 connection each.
2760 block in on $ext_if proto tcp from any os {"Windows 95", "Windows 98"} \e
2764 # pass in/out all IPv6 traffic: note that we have to enable this in two
2765 # different ways, on both our physical interface and our tunnel
2766 pass quick on gif0 inet6
2767 pass quick on $ext_if proto ipv6
2771 # three interfaces: $int_if, $ext_if, and $wifi_if (wireless). NAT is
2772 # being done on $ext_if for all outgoing packets. tag packets in on
2773 # $int_if and pass those tagged packets out on $ext_if. all other
2774 # outgoing packets (i.e., packets from the wireless network) are only
2775 # permitted to access port 80.
2777 pass in on $int_if from any to any tag INTNET
2778 pass in on $wifi_if from any to any
2780 block out on $ext_if from any to any
2781 pass out quick on $ext_if tagged INTNET
2782 pass out on $ext_if proto tcp from any to any port 80
2784 # tag incoming packets as they are redirected to spamd(8). use the tag
2785 # to pass those packets through the packet filter.
2787 rdr on $ext_if inet proto tcp from \*(Ltspammers\*(Gt to port smtp \e
2788 tag SPAMD -\*(Gt 127.0.0.1 port spamd
2791 pass in on $ext_if inet proto tcp tagged SPAMD
2798 line = ( option | pf-rule | nat-rule | binat-rule | rdr-rule |
2799 antispoof-rule | altq-rule | queue-rule | trans-anchors |
2800 anchor-rule | anchor-close | load-anchor | table-rule |
2803 option = "set" ( [ "timeout" ( timeout | "{" timeout-list "}" ) ] |
2804 [ "ruleset-optimization" [ "none" | "basic" | "profile" ]] |
2805 [ "optimization" [ "default" | "normal" |
2806 "high-latency" | "satellite" |
2807 "aggressive" | "conservative" ] ]
2808 [ "limit" ( limit-item | "{" limit-list "}" ) ] |
2809 [ "loginterface" ( interface-name | "none" ) ] |
2810 [ "block-policy" ( "drop" | "return" ) ] |
2811 [ "state-policy" ( "if-bound" | "floating" ) ]
2812 [ "state-defaults" state-opts ]
2813 [ "require-order" ( "yes" | "no" ) ]
2814 [ "fingerprints" filename ] |
2815 [ "skip on" ifspec ] |
2816 [ "debug" ( "none" | "urgent" | "misc" | "loud" ) ] )
2818 pf-rule = action [ ( "in" | "out" ) ]
2819 [ "log" [ "(" logopts ")"] ] [ "quick" ]
2820 [ "on" ifspec ] [ "fastroute" | route ] [ af ] [ protospec ]
2821 hosts [ filteropt-list ]
2823 logopts = logopt [ "," logopts ]
2824 logopt = "all" | "user" | "to" interface-name
2826 filteropt-list = filteropt-list filteropt | filteropt
2827 filteropt = user | group | flags | icmp-type | icmp6-type | "tos" tos |
2828 ( "no" | "keep" | "modulate" | "synproxy" ) "state"
2829 [ "(" state-opts ")" ] |
2830 "fragment" | "no-df" | "min-ttl" number | "set-tos" tos |
2831 "max-mss" number | "random-id" | "reassemble tcp" |
2832 fragmentation | "allow-opts" |
2833 "label" string | "tag" string | [ ! ] "tagged" string |
2834 "queue" ( string | "(" string [ [ "," ] string ] ")" ) |
2835 "rtable" number | "probability" number"%"
2837 nat-rule = [ "no" ] "nat" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
2838 [ "on" ifspec ] [ af ]
2839 [ protospec ] hosts [ "tag" string ] [ "tagged" string ]
2840 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" )
2841 [ portspec ] [ pooltype ] [ "static-port" ] ]
2843 binat-rule = [ "no" ] "binat" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
2844 [ "on" interface-name ] [ af ]
2845 [ "proto" ( proto-name | proto-number ) ]
2846 "from" address [ "/" mask-bits ] "to" ipspec
2847 [ "tag" string ] [ "tagged" string ]
2848 [ "-\*(Gt" address [ "/" mask-bits ] ]
2850 rdr-rule = [ "no" ] "rdr" [ "pass" [ "log" [ "(" logopts ")" ] ] ]
2851 [ "on" ifspec ] [ af ]
2852 [ protospec ] hosts [ "tag" string ] [ "tagged" string ]
2853 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" )
2854 [ portspec ] [ pooltype ] ]
2856 antispoof-rule = "antispoof" [ "log" ] [ "quick" ]
2857 "for" ifspec [ af ] [ "label" string ]
2859 table-rule = "table" "\*(Lt" string "\*(Gt" [ tableopts-list ]
2860 tableopts-list = tableopts-list tableopts | tableopts
2861 tableopts = "persist" | "const" | "counters" | "file" string |
2862 "{" [ tableaddr-list ] "}"
2863 tableaddr-list = tableaddr-list [ "," ] tableaddr-spec | tableaddr-spec
2864 tableaddr-spec = [ "!" ] tableaddr [ "/" mask-bits ]
2865 tableaddr = hostname | ifspec | "self" |
2866 ipv4-dotted-quad | ipv6-coloned-hex
2868 altq-rule = "altq on" interface-name queueopts-list
2870 queue-rule = "queue" string [ "on" interface-name ] queueopts-list
2873 anchor-rule = "anchor" [ string ] [ ( "in" | "out" ) ] [ "on" ifspec ]
2874 [ af ] [ protospec ] [ hosts ] [ filteropt-list ] [ "{" ]
2878 trans-anchors = ( "nat-anchor" | "rdr-anchor" | "binat-anchor" ) string
2879 [ "on" ifspec ] [ af ] [ "proto" ] [ protospec ] [ hosts ]
2881 load-anchor = "load anchor" string "from" filename
2883 queueopts-list = queueopts-list queueopts | queueopts
2884 queueopts = [ "bandwidth" bandwidth-spec ] |
2885 [ "qlimit" number ] | [ "tbrsize" number ] |
2886 [ "priority" number ] | [ schedulers ]
2887 schedulers = ( cbq-def | priq-def | hfsc-def )
2888 bandwidth-spec = "number" ( "b" | "Kb" | "Mb" | "Gb" | "%" )
2890 action = "pass" | "block" [ return ] | [ "no" ] "scrub"
2891 return = "drop" | "return" | "return-rst" [ "( ttl" number ")" ] |
2892 "return-icmp" [ "(" icmpcode [ [ "," ] icmp6code ] ")" ] |
2893 "return-icmp6" [ "(" icmp6code ")" ]
2894 icmpcode = ( icmp-code-name | icmp-code-number )
2895 icmp6code = ( icmp6-code-name | icmp6-code-number )
2897 ifspec = ( [ "!" ] ( interface-name | interface-group ) ) |
2898 "{" interface-list "}"
2899 interface-list = [ "!" ] ( interface-name | interface-group )
2900 [ [ "," ] interface-list ]
2901 route = ( "route-to" | "reply-to" | "dup-to" )
2902 ( routehost | "{" routehost-list "}" )
2904 af = "inet" | "inet6"
2906 protospec = "proto" ( proto-name | proto-number |
2907 "{" proto-list "}" )
2908 proto-list = ( proto-name | proto-number ) [ [ "," ] proto-list ]
2911 "from" ( "any" | "no-route" | "urpf-failed" | "self" | host |
2912 "{" host-list "}" ) [ port ] [ os ]
2913 "to" ( "any" | "no-route" | "self" | host |
2914 "{" host-list "}" ) [ port ]
2916 ipspec = "any" | host | "{" host-list "}"
2917 host = [ "!" ] ( address [ "/" mask-bits ] | "\*(Lt" string "\*(Gt" )
2918 redirhost = address [ "/" mask-bits ]
2919 routehost = "(" interface-name [ address [ "/" mask-bits ] ] ")"
2920 address = ( interface-name | interface-group |
2921 "(" ( interface-name | interface-group ) ")" |
2922 hostname | ipv4-dotted-quad | ipv6-coloned-hex )
2923 host-list = host [ [ "," ] host-list ]
2924 redirhost-list = redirhost [ [ "," ] redirhost-list ]
2925 routehost-list = routehost [ [ "," ] routehost-list ]
2927 port = "port" ( unary-op | binary-op | "{" op-list "}" )
2928 portspec = "port" ( number | name ) [ ":" ( "*" | number | name ) ]
2929 os = "os" ( os-name | "{" os-list "}" )
2930 user = "user" ( unary-op | binary-op | "{" op-list "}" )
2931 group = "group" ( unary-op | binary-op | "{" op-list "}" )
2933 unary-op = [ "=" | "!=" | "\*(Lt" | "\*(Le" | "\*(Gt" | "\*(Ge" ]
2935 binary-op = number ( "\*(Lt\*(Gt" | "\*(Gt\*(Lt" | ":" ) number
2936 op-list = ( unary-op | binary-op ) [ [ "," ] op-list ]
2938 os-name = operating-system-name
2939 os-list = os-name [ [ "," ] os-list ]
2941 flags = "flags" ( [ flag-set ] "/" flag-set | "any" )
2942 flag-set = [ "F" ] [ "S" ] [ "R" ] [ "P" ] [ "A" ] [ "U" ] [ "E" ]
2945 icmp-type = "icmp-type" ( icmp-type-code | "{" icmp-list "}" )
2946 icmp6-type = "icmp6-type" ( icmp-type-code | "{" icmp-list "}" )
2947 icmp-type-code = ( icmp-type-name | icmp-type-number )
2948 [ "code" ( icmp-code-name | icmp-code-number ) ]
2949 icmp-list = icmp-type-code [ [ "," ] icmp-list ]
2951 tos = ( "lowdelay" | "throughput" | "reliability" |
2954 state-opts = state-opt [ [ "," ] state-opts ]
2955 state-opt = ( "max" number | "no-sync" | timeout | "sloppy" | "pflow" |
2956 "source-track" [ ( "rule" | "global" ) ] |
2957 "max-src-nodes" number | "max-src-states" number |
2958 "max-src-conn" number |
2959 "max-src-conn-rate" number "/" number |
2960 "overload" "\*(Lt" string "\*(Gt" [ "flush" ] |
2961 "if-bound" | "floating" )
2963 fragmentation = [ "fragment reassemble" ]
2965 timeout-list = timeout [ [ "," ] timeout-list ]
2966 timeout = ( "tcp.first" | "tcp.opening" | "tcp.established" |
2967 "tcp.closing" | "tcp.finwait" | "tcp.closed" |
2968 "udp.first" | "udp.single" | "udp.multiple" |
2969 "icmp.first" | "icmp.error" |
2970 "other.first" | "other.single" | "other.multiple" |
2971 "frag" | "interval" | "src.track" |
2972 "adaptive.start" | "adaptive.end" ) number
2974 limit-list = limit-item [ [ "," ] limit-list ]
2975 limit-item = ( "states" | "frags" | "src-nodes" ) number
2977 pooltype = ( "bitmask" | "random" |
2978 "source-hash" [ ( hex-key | string-key ) ] |
2979 "round-robin" ) [ sticky-address ]
2981 subqueue = string | "{" queue-list "}"
2982 queue-list = string [ [ "," ] string ]
2983 cbq-def = "cbq" [ "(" cbq-opt [ [ "," ] cbq-opt ] ")" ]
2984 priq-def = "priq" [ "(" priq-opt [ [ "," ] priq-opt ] ")" ]
2985 hfsc-def = "hfsc" [ "(" hfsc-opt [ [ "," ] hfsc-opt ] ")" ]
2986 cbq-opt = ( "default" | "borrow" | "red" | "ecn" | "rio" )
2987 priq-opt = ( "default" | "red" | "ecn" | "rio" )
2988 hfsc-opt = ( "default" | "red" | "ecn" | "rio" |
2989 linkshare-sc | realtime-sc | upperlimit-sc )
2990 linkshare-sc = "linkshare" sc-spec
2991 realtime-sc = "realtime" sc-spec
2992 upperlimit-sc = "upperlimit" sc-spec
2993 sc-spec = ( bandwidth-spec |
2994 "(" bandwidth-spec number bandwidth-spec ")" )
2995 include = "include" filename
2998 .Bl -tag -width "/etc/protocols" -compact
3002 Default location of the ruleset file.
3004 Default location of OS fingerprints.
3005 .It Pa /etc/protocols
3006 Protocol name database.
3007 .It Pa /etc/services
3008 Service name database.
3032 file format first appeared in