9 .Nd User interface for firewall, traffic shaper, packet scheduler,
12 .Ss FIREWALL CONFIGURATION
21 .Op Ar rule | first-last ...
29 .Brq Cm delete | zero | resetlog
33 .Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ...
37 .Ar number Cm to Ar number
39 .Cm set swap Ar number number
45 .Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive
48 .Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive
51 .Oo Cm set Ar N Oc Cm table Ar name Cm create Ar create-options
53 .Oo Cm set Ar N Oc Cm table Ar name Cm destroy
55 .Oo Cm set Ar N Oc Cm table Ar name Cm modify Ar modify-options
57 .Oo Cm set Ar N Oc Cm table Ar name Cm swap Ar name
59 .Oo Cm set Ar N Oc Cm table Ar name Cm add Ar table-key Op Ar value
61 .Oo Cm set Ar N Oc Cm table Ar name Cm add Op Ar table-key Ar value ...
63 .Oo Cm set Ar N Oc Cm table Ar name Cm atomic add Op Ar table-key Ar value ...
65 .Oo Cm set Ar N Oc Cm table Ar name Cm delete Op Ar table-key ...
67 .Oo Cm set Ar N Oc Cm table Ar name Cm lookup Ar addr
69 .Oo Cm set Ar N Oc Cm table Ar name Cm lock
71 .Oo Cm set Ar N Oc Cm table Ar name Cm unlock
73 .Oo Cm set Ar N Oc Cm table
77 .Oo Cm set Ar N Oc Cm table
81 .Oo Cm set Ar N Oc Cm table
85 .Oo Cm set Ar N Oc Cm table
88 .Ss DUMMYNET CONFIGURATION (TRAFFIC SHAPER AND PACKET SCHEDULER)
90 .Brq Cm pipe | queue | sched
96 .Brq Cm pipe | queue | sched
97 .Brq Cm delete | list | show
116 .Ss STATEFUL IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
118 .Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm create Ar create-options
120 .Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm config Ar config-options
122 .Oo Cm set Ar N Oc Cm nat64lsn
127 .Oo Cm set Ar N Oc Cm nat64lsn
131 .Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm stats Op Cm reset
132 .Ss STATELESS IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
134 .Oo Cm set Ar N Oc Cm nat64stl Ar name Cm create Ar create-options
136 .Oo Cm set Ar N Oc Cm nat64stl Ar name Cm config Ar config-options
138 .Oo Cm set Ar N Oc Cm nat64stl
142 .Oo Cm set Ar N Oc Cm nat64stl
146 .Oo Cm set Ar N Oc Cm nat64stl Ar name Cm stats Op Cm reset
147 .Ss IPv6-to-IPv6 NETWORK PREFIX TRANSLATION
149 .Oo Cm set Ar N Oc Cm nptv6 Ar name Cm create Ar create-options
151 .Oo Cm set Ar N Oc Cm nptv6
155 .Oo Cm set Ar N Oc Cm nptv6
159 .Oo Cm set Ar N Oc Cm nptv6 Ar name Cm stats Op Cm reset
160 .Ss INTERNAL DIAGNOSTICS
170 utility is the user interface for controlling the
174 traffic shaper/packet scheduler, and the
175 in-kernel NAT services.
177 A firewall configuration, or
181 numbered from 1 to 65535.
182 Packets are passed to the firewall
183 from a number of different places in the protocol stack
184 (depending on the source and destination of the packet,
185 it is possible for the firewall to be
186 invoked multiple times on the same packet).
187 The packet passed to the firewall is compared
188 against each of the rules in the
191 (multiple rules with the same number are permitted, in which case
192 they are processed in order of insertion).
193 When a match is found, the action corresponding to the
194 matching rule is performed.
196 Depending on the action and certain system settings, packets
197 can be reinjected into the firewall at some rule after the
198 matching one for further processing.
200 A ruleset always includes a
202 rule (numbered 65535) which cannot be modified or deleted,
203 and matches all packets.
204 The action associated with the
210 depending on how the kernel is configured.
212 If the ruleset includes one or more rules with the
217 the firewall will have a
219 behaviour, i.e., upon a match it will create
221 i.e., rules that match packets with the same 5-tuple
222 (protocol, source and destination addresses and ports)
223 as the packet which caused their creation.
224 Dynamic rules, which have a limited lifetime, are checked
225 at the first occurrence of a
230 rule, and are typically used to open the firewall on-demand to
231 legitimate traffic only.
233 .Sx STATEFUL FIREWALL
236 Sections below for more information on the stateful behaviour of
239 All rules (including dynamic ones) have a few associated counters:
240 a packet count, a byte count, a log count and a timestamp
241 indicating the time of the last match.
242 Counters can be displayed or reset with
246 Each rule belongs to one of 32 different
250 commands to atomically manipulate sets, such as enable,
251 disable, swap sets, move all rules in a set to another
252 one, delete all rules in a set.
253 These can be useful to
254 install temporary configurations, or to test them.
257 for more information on
260 Rules can be added with the
262 command; deleted individually or in groups with the
264 command, and globally (except those in set 31) with the
266 command; displayed, optionally with the content of the
272 Finally, counters can be reset with the
279 The following general options are available when invoking
281 .Bl -tag -width indent
283 Show counter values when listing rules.
286 command implies this option.
288 Only show the action and the comment, not the body of a rule.
292 When entering or showing rules, print them in compact form,
293 i.e., omitting the "ip from any to any" string
294 when this does not carry any additional information.
296 When listing, show dynamic rules in addition to static ones.
300 is specified, also show expired dynamic rules.
302 Do not ask for confirmation for commands that can cause problems
305 If there is no tty associated with the process, this is implied.
307 When listing a table (see the
309 section below for more information on lookup tables), format values
311 By default, values are shown as integers.
313 Only check syntax of the command strings, without actually passing
316 Try to resolve addresses and service names in output.
318 Be quiet when executing the
328 This is useful when updating rulesets by executing multiple
332 .Ql sh\ /etc/rc.firewall ) ,
333 or by processing a file with many
335 rules across a remote login session.
336 It also stops a table add or delete
337 from failing if the entry already exists or is not present.
339 The reason why this option may be important is that
340 for some of these actions,
342 may print a message; if the action results in blocking the
343 traffic to the remote client,
344 the remote login session will be closed
345 and the rest of the ruleset will not be processed.
346 Access to the console would then be required to recover.
348 When listing rules, show the
350 each rule belongs to.
351 If this flag is not specified, disabled rules will not be
354 When listing pipes, sort according to one of the four
355 counters (total or current packets or bytes).
357 When listing, show last match timestamp converted with ctime().
359 When listing, show last match timestamp as seconds from the epoch.
360 This form can be more convenient for postprocessing by scripts.
362 .Ss LIST OF RULES AND PREPROCESSING
363 To ease configuration, rules can be put into a file which is
366 as shown in the last synopsis line.
370 The file will be read line by line and applied as arguments to the
374 Optionally, a preprocessor can be specified using
378 is to be piped through.
379 Useful preprocessors include
385 does not start with a slash
387 as its first character, the usual
389 name search is performed.
390 Care should be taken with this in environments where not all
391 file systems are mounted (yet) by the time
393 is being run (e.g.\& when they are mounted over NFS).
396 has been specified, any additional arguments are passed on to the preprocessor
398 This allows for flexible configuration files (like conditionalizing
399 them on the local hostname) and the use of macros to centralize
400 frequently required arguments like IP addresses.
401 .Ss TRAFFIC SHAPER CONFIGURATION
407 commands are used to configure the traffic shaper and packet scheduler.
409 .Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
410 Section below for details.
412 If the world and the kernel get out of sync the
414 ABI may break, preventing you from being able to add any rules.
415 This can adversely affect the booting process.
420 to temporarily disable the firewall to regain access to the network,
421 allowing you to fix the problem.
423 A packet is checked against the active ruleset in multiple places
424 in the protocol stack, under control of several sysctl variables.
425 These places and variables are shown below, and it is important to
426 have this picture in mind in order to design a correct ruleset.
427 .Bd -literal -offset indent
430 +----------->-----------+
432 [ip(6)_input] [ip(6)_output] net.inet(6).ip(6).fw.enable=1
435 [ether_demux] [ether_output_frame] net.link.ether.ipfw=1
437 +-->--[bdg_forward]-->--+ net.link.bridge.ipfw=1
443 times the same packet goes through the firewall can
444 vary between 0 and 4 depending on packet source and
445 destination, and system configuration.
447 Note that as packets flow through the stack, headers can be
448 stripped or added to it, and so they may or may not be available
450 E.g., incoming packets will include the MAC header when
454 but the same packets will have the MAC header stripped off when
461 Also note that each packet is always checked against the complete ruleset,
462 irrespective of the place where the check occurs, or the source of the packet.
463 If a rule contains some match patterns or actions which are not valid
464 for the place of invocation (e.g.\& trying to match a MAC header within
468 the match pattern will not match, but a
470 operator in front of such patterns
474 match on those packets.
475 It is thus the responsibility of
476 the programmer, if necessary, to write a suitable ruleset to
477 differentiate among the possible places.
479 rules can be useful here, as an example:
480 .Bd -literal -offset indent
481 # packets from ether_demux or bdg_forward
482 ipfw add 10 skipto 1000 all from any to any layer2 in
483 # packets from ip_input
484 ipfw add 10 skipto 2000 all from any to any not layer2 in
485 # packets from ip_output
486 ipfw add 10 skipto 3000 all from any to any not layer2 out
487 # packets from ether_output_frame
488 ipfw add 10 skipto 4000 all from any to any layer2 out
491 (yes, at the moment there is no way to differentiate between
492 ether_demux and bdg_forward).
494 In general, each keyword or argument must be provided as
495 a separate command line argument, with no leading or trailing
497 Keywords are case-sensitive, whereas arguments may
498 or may not be case-sensitive depending on their nature
499 (e.g.\& uid's are, hostnames are not).
501 Some arguments (e.g., port or address lists) are comma-separated
503 In this case, spaces after commas ',' are allowed to make
504 the line more readable.
505 You can also put the entire
506 command (including flags) into a single argument.
507 E.g., the following forms are equivalent:
508 .Bd -literal -offset indent
509 ipfw -q add deny src-ip 10.0.0.0/24,127.0.0.1/8
510 ipfw -q add deny src-ip 10.0.0.0/24, 127.0.0.1/8
511 ipfw "-q add deny src-ip 10.0.0.0/24, 127.0.0.1/8"
514 The format of firewall rules is the following:
515 .Bd -ragged -offset indent
518 .Op Cm set Ar set_number
519 .Op Cm prob Ar match_probability
521 .Op Cm log Op Cm logamount Ar number
531 where the body of the rule specifies which information is used
532 for filtering packets, among the following:
534 .Bl -tag -width "Source and dest. addresses and ports" -offset XXX -compact
535 .It Layer-2 header fields
537 .It IPv4 and IPv6 Protocol
539 .It Source and dest. addresses and ports
543 .It Transmit and receive interface
545 .It Misc. IP header fields
546 Version, type of service, datagram length, identification,
547 fragment flag (non-zero IP offset),
550 .It IPv6 Extension headers
551 Fragmentation, Hop-by-Hop options,
552 Routing Headers, Source routing rthdr0, Mobile IPv6 rthdr2, IPSec options.
554 .It Misc. TCP header fields
555 TCP flags (SYN, FIN, ACK, RST, etc.),
556 sequence number, acknowledgment number,
564 When the packet can be associated with a local socket.
566 Whether a packet came from a divert socket (e.g.,
568 .It Fib annotation state
569 Whether a packet has been tagged for using a specific FIB (routing table)
570 in future forwarding decisions.
573 Note that some of the above information, e.g.\& source MAC or IP addresses and
574 TCP/UDP ports, can be easily spoofed, so filtering on those fields
575 alone might not guarantee the desired results.
576 .Bl -tag -width indent
578 Each rule is associated with a
580 in the range 1..65535, with the latter reserved for the
583 Rules are checked sequentially by rule number.
584 Multiple rules can have the same number, in which case they are
585 checked (and listed) according to the order in which they have
587 If a rule is entered without specifying a number, the kernel will
588 assign one in such a way that the rule becomes the last one
592 Automatic rule numbers are assigned by incrementing the last
593 non-default rule number by the value of the sysctl variable
594 .Ar net.inet.ip.fw.autoinc_step
595 which defaults to 100.
596 If this is not possible (e.g.\& because we would go beyond the
597 maximum allowed rule number), the number of the last
598 non-default value is used instead.
599 .It Cm set Ar set_number
600 Each rule is associated with a
603 Sets can be individually disabled and enabled, so this parameter
604 is of fundamental importance for atomic ruleset manipulation.
605 It can be also used to simplify deletion of groups of rules.
606 If a rule is entered without specifying a set number,
609 Set 31 is special in that it cannot be disabled,
610 and rules in set 31 are not deleted by the
612 command (but you can delete them with the
613 .Nm ipfw delete set 31
615 Set 31 is also used for the
618 .It Cm prob Ar match_probability
619 A match is only declared with the specified probability
620 (floating point number between 0 and 1).
621 This can be useful for a number of applications such as
622 random packet drop or
625 to simulate the effect of multiple paths leading to out-of-order
628 Note: this condition is checked before any other condition, including
629 ones such as keep-state or check-state which might have side effects.
630 .It Cm log Op Cm logamount Ar number
631 Packets matching a rule with the
633 keyword will be made available for logging in two ways:
634 if the sysctl variable
635 .Va net.inet.ip.fw.verbose
636 is set to 0 (default), one can use
641 This pseudo interface can be created after a boot
642 manually by using the following command:
643 .Bd -literal -offset indent
644 # ifconfig ipfw0 create
647 Or, automatically at boot time by adding the following
651 .Bd -literal -offset indent
655 There is no overhead if no
657 is attached to the pseudo interface.
660 .Va net.inet.ip.fw.verbose
661 is set to 1, packets will be logged to
665 facility up to a maximum of
670 is specified, the limit is taken from the sysctl variable
671 .Va net.inet.ip.fw.verbose_limit .
672 In both cases, a value of 0 means unlimited logging.
674 Once the limit is reached, logging can be re-enabled by
675 clearing the logging counter or the packet counter for that entry, see the
679 Note: logging is done after all other packet matching conditions
680 have been successfully verified, and before performing the final
681 action (accept, deny, etc.) on the packet.
683 When a packet matches a rule with the
685 keyword, the numeric tag for the given
687 in the range 1..65534 will be attached to the packet.
688 The tag acts as an internal marker (it is not sent out over
689 the wire) that can be used to identify these packets later on.
690 This can be used, for example, to provide trust between interfaces
691 and to start doing policy-based filtering.
692 A packet can have multiple tags at the same time.
693 Tags are "sticky", meaning once a tag is applied to a packet by a
694 matching rule it exists until explicit removal.
695 Tags are kept with the packet everywhere within the kernel, but are
696 lost when packet leaves the kernel, for example, on transmitting
697 packet out to the network or sending packet to a
701 To check for previously applied tags, use the
704 To delete previously applied tag, use the
708 Note: since tags are kept with the packet everywhere in kernelspace,
709 they can be set and unset anywhere in the kernel network subsystem
712 facility), not only by means of the
718 For example, there can be a specialized
720 node doing traffic analyzing and tagging for later inspecting
722 .It Cm untag Ar number
723 When a packet matches a rule with the
725 keyword, the tag with the number
727 is searched among the tags attached to this packet and,
728 if found, removed from it.
729 Other tags bound to packet, if present, are left untouched.
731 When a packet matches a rule with the
733 keyword, the ALTQ identifier for the given
738 Note that this ALTQ tag is only meaningful for packets going "out" of IPFW,
739 and not being rejected or going to divert sockets.
740 Note that if there is insufficient memory at the time the packet is
741 processed, it will not be tagged, so it is wise to make your ALTQ
742 "default" queue policy account for this.
745 rules match a single packet, only the first one adds the ALTQ classification
747 In doing so, traffic may be shaped by using
748 .Cm count Cm altq Ar queue
749 rules for classification early in the ruleset, then later applying
750 the filtering decision.
755 rules may come later and provide the actual filtering decisions in
756 addition to the fallback ALTQ tag.
760 to set up the queues before IPFW will be able to look them up by name,
761 and if the ALTQ disciplines are rearranged, the rules in containing the
762 queue identifiers in the kernel will likely have gone stale and need
764 Stale queue identifiers will probably result in misclassification.
766 All system ALTQ processing can be turned on or off via
771 .Cm disable Ar altq .
773 .Va net.inet.ip.fw.one_pass
774 is irrelevant to ALTQ traffic shaping, as the actual rule action is followed
775 always after adding an ALTQ tag.
778 A rule can be associated with one of the following actions, which
779 will be executed when the packet matches the body of the rule.
780 .Bl -tag -width indent
781 .It Cm allow | accept | pass | permit
782 Allow packets that match rule.
783 The search terminates.
784 .It Cm check-state Op Ar flowname | Cm any
785 Checks the packet against the dynamic ruleset.
786 If a match is found, execute the action associated with
787 the rule which generated this dynamic rule, otherwise
788 move to the next rule.
791 rules do not have a body.
794 rule is found, the dynamic ruleset is checked at the first
801 is symbolic name assigned to dynamic rule by
806 can be used to ignore states flowname when matching.
809 keyword is special name used for compatibility with old rulesets.
811 Update counters for all packets that match rule.
812 The search continues with the next rule.
814 Discard packets that match this rule.
815 The search terminates.
816 .It Cm divert Ar port
817 Divert packets that match this rule to the
821 The search terminates.
822 .It Cm fwd | forward Ar ipaddr | tablearg Ns Op , Ns Ar port
823 Change the next-hop on matching packets to
825 which can be an IP address or a host name.
826 For IPv4, the next hop can also be supplied by the last table
827 looked up for the packet by using the
829 keyword instead of an explicit address.
830 The search terminates if this rule matches.
834 is a local address, then matching packets will be forwarded to
836 (or the port number in the packet if one is not specified in the rule)
837 on the local machine.
841 is not a local address, then the port number
842 (if specified) is ignored, and the packet will be
843 forwarded to the remote address, using the route as found in
844 the local routing table for that IP.
848 rule will not match layer-2 packets (those received
849 on ether_input, ether_output, or bridged).
853 action does not change the contents of the packet at all.
854 In particular, the destination address remains unmodified, so
855 packets forwarded to another system will usually be rejected by that system
856 unless there is a matching rule on that system to capture them.
857 For packets forwarded locally,
858 the local address of the socket will be
859 set to the original destination address of the packet.
862 entry look rather weird but is intended for
863 use with transparent proxy servers.
864 .It Cm nat Ar nat_nr | tablearg
867 (for network address translation, address redirect, etc.):
869 .Sx NETWORK ADDRESS TRANSLATION (NAT)
870 Section for further information.
871 .It Cm nat64lsn Ar name
872 Pass packet to a stateful NAT64 instance (for IPv6/IPv4 network address and
873 protocol translation): see the
874 .Sx IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
875 Section for further information.
876 .It Cm nat64stl Ar name
877 Pass packet to a stateless NAT64 instance (for IPv6/IPv4 network address and
878 protocol translation): see the
879 .Sx IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
880 Section for further information.
882 Pass packet to a NPTv6 instance (for IPv6-to-IPv6 network prefix translation):
884 .Sx IPv6-to-IPv6 NETWORK PREFIX TRANSLATION (NPTv6)
885 Section for further information.
886 .It Cm pipe Ar pipe_nr
890 (for bandwidth limitation, delay, etc.).
892 .Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
893 Section for further information.
894 The search terminates; however, on exit from the pipe and if
898 .Va net.inet.ip.fw.one_pass
899 is not set, the packet is passed again to the firewall code
900 starting from the next rule.
901 .It Cm queue Ar queue_nr
905 (for bandwidth limitation using WF2Q+).
911 Discard packets that match this rule, and if the
912 packet is a TCP packet, try to send a TCP reset (RST) notice.
913 The search terminates.
915 Discard packets that match this rule, and if the
916 packet is a TCP packet, try to send a TCP reset (RST) notice.
917 The search terminates.
918 .It Cm skipto Ar number | tablearg
919 Skip all subsequent rules numbered less than
921 The search continues with the first rule numbered
924 It is possible to use the
926 keyword with a skipto for a
928 skipto. Skipto may work either in O(log(N)) or in O(1) depending
929 on amount of memory and/or sysctl variables.
932 section for more details.
933 .It Cm call Ar number | tablearg
934 The current rule number is saved in the internal stack and
935 ruleset processing continues with the first rule numbered
938 If later a rule with the
940 action is encountered, the processing returns to the first rule
943 rule plus one or higher
944 (the same behaviour as with packets returning from
949 This could be used to make somewhat like an assembly language
951 calls to rules with common checks for different interfaces, etc.
953 Rule with any number could be called, not just forward jumps as with
955 So, to prevent endless loops in case of mistakes, both
959 actions don't do any jumps and simply go to the next rule if memory
960 cannot be allocated or stack overflowed/underflowed.
962 Internally stack for rule numbers is implemented using
964 facility and currently has size of 16 entries.
965 As mbuf tags are lost when packet leaves the kernel,
967 should not be used in subroutines to avoid endless loops
968 and other undesired effects.
970 Takes rule number saved to internal stack by the last
972 action and returns ruleset processing to the first rule
973 with number greater than number of corresponding
976 See description of the
978 action for more details.
984 and thus are unconditional, but
986 command-line utility currently requires every action except
989 While it is sometimes useful to return only on some packets,
990 usually you want to print just
993 A workaround for this is to use new syntax and
996 .Bd -literal -offset indent
997 # Add a rule without actual body
998 ipfw add 2999 return via any
1000 # List rules without "from any to any" part
1004 This cosmetic annoyance may be fixed in future releases.
1006 Send a copy of packets matching this rule to the
1008 socket bound to port
1010 The search continues with the next rule.
1011 .It Cm unreach Ar code
1012 Discard packets that match this rule, and try to send an ICMP
1013 unreachable notice with code
1017 is a number from 0 to 255, or one of these aliases:
1018 .Cm net , host , protocol , port ,
1019 .Cm needfrag , srcfail , net-unknown , host-unknown ,
1020 .Cm isolated , net-prohib , host-prohib , tosnet ,
1021 .Cm toshost , filter-prohib , host-precedence
1023 .Cm precedence-cutoff .
1024 The search terminates.
1025 .It Cm unreach6 Ar code
1026 Discard packets that match this rule, and try to send an ICMPv6
1027 unreachable notice with code
1031 is a number from 0, 1, 3 or 4, or one of these aliases:
1032 .Cm no-route, admin-prohib, address
1035 The search terminates.
1036 .It Cm netgraph Ar cookie
1037 Divert packet into netgraph with given
1039 The search terminates.
1040 If packet is later returned from netgraph it is either
1041 accepted or continues with the next rule, depending on
1042 .Va net.inet.ip.fw.one_pass
1044 .It Cm ngtee Ar cookie
1045 A copy of packet is diverted into netgraph, original
1046 packet continues with the next rule.
1049 for more information on
1054 .It Cm setfib Ar fibnum | tablearg
1055 The packet is tagged so as to use the FIB (routing table)
1057 in any subsequent forwarding decisions.
1058 In the current implementation, this is limited to the values 0 through 15, see
1060 Processing continues at the next rule.
1061 It is possible to use the
1063 keyword with setfib.
1064 If the tablearg value is not within the compiled range of fibs,
1065 the packet's fib is set to 0.
1066 .It Cm setdscp Ar DSCP | number | tablearg
1067 Set specified DiffServ codepoint for an IPv4/IPv6 packet.
1068 Processing continues at the next rule.
1069 Supported values are:
1115 Additionally, DSCP value can be specified by number (0..64).
1116 It is also possible to use the
1118 keyword with setdscp.
1119 If the tablearg value is not within the 0..64 range, lower 6 bits of supplied
1122 Queue and reassemble IP fragments.
1123 If the packet is not fragmented, counters are updated and
1124 processing continues with the next rule.
1125 If the packet is the last logical fragment, the packet is reassembled and, if
1126 .Va net.inet.ip.fw.one_pass
1127 is set to 0, processing continues with the next rule.
1128 Otherwise, the packet is allowed to pass and the search terminates.
1129 If the packet is a fragment in the middle of a logical group of fragments,
1131 processing stops immediately.
1133 Fragment handling can be tuned via
1134 .Va net.inet.ip.maxfragpackets
1136 .Va net.inet.ip.maxfragsperpacket
1137 which limit, respectively, the maximum number of processable
1138 fragments (default: 800) and
1139 the maximum number of fragments per packet (default: 16).
1141 NOTA BENE: since fragments do not contain port numbers,
1142 they should be avoided with the
1145 Alternatively, direction-based (like
1149 ) and source-based (like
1151 ) match patterns can be used to select fragments.
1153 Usually a simple rule like:
1154 .Bd -literal -offset indent
1155 # reassemble incoming fragments
1156 ipfw add reass all from any to any in
1159 is all you need at the beginning of your ruleset.
1162 The body of a rule contains zero or more patterns (such as
1163 specific source and destination addresses or ports,
1164 protocol options, incoming or outgoing interfaces, etc.)
1165 that the packet must match in order to be recognised.
1166 In general, the patterns are connected by (implicit)
1168 operators -- i.e., all must match in order for the
1170 Individual patterns can be prefixed by the
1172 operator to reverse the result of the match, as in
1174 .Dl "ipfw add 100 allow ip from not 1.2.3.4 to any"
1176 Additionally, sets of alternative match patterns
1178 can be constructed by putting the patterns in
1179 lists enclosed between parentheses ( ) or braces { }, and
1182 operator as follows:
1184 .Dl "ipfw add 100 allow ip from { x or not y or z } to any"
1186 Only one level of parentheses is allowed.
1187 Beware that most shells have special meanings for parentheses
1188 or braces, so it is advisable to put a backslash \\ in front of them
1189 to prevent such interpretations.
1191 The body of a rule must in general include a source and destination
1195 can be used in various places to specify that the content of
1196 a required field is irrelevant.
1198 The rule body has the following format:
1199 .Bd -ragged -offset indent
1200 .Op Ar proto Cm from Ar src Cm to Ar dst
1204 The first part (proto from src to dst) is for backward
1205 compatibility with earlier versions of
1209 any match pattern (including MAC headers, IP protocols,
1210 addresses and ports) can be specified in the
1214 Rule fields have the following meaning:
1215 .Bl -tag -width indent
1216 .It Ar proto : protocol | Cm { Ar protocol Cm or ... }
1217 .It Ar protocol : Oo Cm not Oc Ar protocol-name | protocol-number
1218 An IP protocol specified by number or name
1219 (for a complete list see
1220 .Pa /etc/protocols ) ,
1221 or one of the following keywords:
1222 .Bl -tag -width indent
1224 Matches IPv4 packets.
1226 Matches IPv6 packets.
1235 option will be treated as inner protocol.
1243 .Cm { Ar protocol Cm or ... }
1246 is provided for convenience only but its use is deprecated.
1247 .It Ar src No and Ar dst : Bro Cm addr | Cm { Ar addr Cm or ... } Brc Op Oo Cm not Oc Ar ports
1248 An address (or a list, see below)
1249 optionally followed by
1255 with multiple addresses) is provided for convenience only and
1256 its use is discouraged.
1257 .It Ar addr : Oo Cm not Oc Bro
1258 .Cm any | me | me6 |
1259 .Cm table Ns Pq Ar name Ns Op , Ns Ar value
1260 .Ar | addr-list | addr-set
1262 .Bl -tag -width indent
1264 matches any IP address.
1266 matches any IP address configured on an interface in the system.
1268 matches any IPv6 address configured on an interface in the system.
1269 The address list is evaluated at the time the packet is
1271 .It Cm table Ns Pq Ar name Ns Op , Ns Ar value
1272 Matches any IPv4 or IPv6 address for which an entry exists in the lookup table
1274 If an optional 32-bit unsigned
1276 is also specified, an entry will match only if it has this value.
1279 section below for more information on lookup tables.
1281 .It Ar addr-list : ip-addr Ns Op Ns , Ns Ar addr-list
1283 A host or subnet address specified in one of the following ways:
1284 .Bl -tag -width indent
1285 .It Ar numeric-ip | hostname
1286 Matches a single IPv4 address, specified as dotted-quad or a hostname.
1287 Hostnames are resolved at the time the rule is added to the firewall list.
1288 .It Ar addr Ns / Ns Ar masklen
1289 Matches all addresses with base
1291 (specified as an IP address, a network number, or a hostname)
1295 As an example, 1.2.3.4/25 or 1.2.3.0/25 will match
1296 all IP numbers from 1.2.3.0 to 1.2.3.127 .
1297 .It Ar addr Ns : Ns Ar mask
1298 Matches all addresses with base
1300 (specified as an IP address, a network number, or a hostname)
1303 specified as a dotted quad.
1304 As an example, 1.2.3.4:255.0.255.0 or 1.0.3.0:255.0.255.0 will match
1306 This form is advised only for non-contiguous
1308 It is better to resort to the
1309 .Ar addr Ns / Ns Ar masklen
1310 format for contiguous masks, which is more compact and less
1313 .It Ar addr-set : addr Ns Oo Ns / Ns Ar masklen Oc Ns Cm { Ns Ar list Ns Cm }
1314 .It Ar list : Bro Ar num | num-num Brc Ns Op Ns , Ns Ar list
1315 Matches all addresses with base address
1317 (specified as an IP address, a network number, or a hostname)
1318 and whose last byte is in the list between braces { } .
1319 Note that there must be no spaces between braces and
1320 numbers (spaces after commas are allowed).
1321 Elements of the list can be specified as single entries
1325 field is used to limit the size of the set of addresses,
1326 and can have any value between 24 and 32.
1328 it will be assumed as 24.
1330 This format is particularly useful to handle sparse address sets
1331 within a single rule.
1332 Because the matching occurs using a
1333 bitmask, it takes constant time and dramatically reduces
1334 the complexity of rulesets.
1336 As an example, an address specified as 1.2.3.4/24{128,35-55,89}
1337 or 1.2.3.0/24{128,35-55,89}
1338 will match the following IP addresses:
1340 1.2.3.128, 1.2.3.35 to 1.2.3.55, 1.2.3.89 .
1341 .It Ar addr6-list : ip6-addr Ns Op Ns , Ns Ar addr6-list
1343 A host or subnet specified one of the following ways:
1344 .Bl -tag -width indent
1345 .It Ar numeric-ip | hostname
1346 Matches a single IPv6 address as allowed by
1349 Hostnames are resolved at the time the rule is added to the firewall
1351 .It Ar addr Ns / Ns Ar masklen
1352 Matches all IPv6 addresses with base
1354 (specified as allowed by
1362 No support for sets of IPv6 addresses is provided because IPv6 addresses
1363 are typically random past the initial prefix.
1364 .It Ar ports : Bro Ar port | port Ns \&- Ns Ar port Ns Brc Ns Op , Ns Ar ports
1365 For protocols which support port numbers (such as TCP and UDP), optional
1367 may be specified as one or more ports or port ranges, separated
1368 by commas but no spaces, and an optional
1373 notation specifies a range of ports (including boundaries).
1377 may be used instead of numeric port values.
1378 The length of the port list is limited to 30 ports or ranges,
1379 though one can specify larger ranges by using an
1383 section of the rule.
1387 can be used to escape the dash
1389 character in a service name (from a shell, the backslash must be
1390 typed twice to avoid the shell itself interpreting it as an escape
1393 .Dl "ipfw add count tcp from any ftp\e\e-data-ftp to any"
1395 Fragmented packets which have a non-zero offset (i.e., not the first
1396 fragment) will never match a rule which has one or more port
1400 option for details on matching fragmented packets.
1402 .Ss RULE OPTIONS (MATCH PATTERNS)
1403 Additional match patterns can be used within
1405 Zero or more of these so-called
1407 can be present in a rule, optionally prefixed by the
1409 operand, and possibly grouped into
1412 The following match patterns can be used (listed in alphabetical order):
1413 .Bl -tag -width indent
1414 .It Cm // this is a comment.
1415 Inserts the specified text as a comment in the rule.
1416 Everything following // is considered as a comment and stored in the rule.
1417 You can have comment-only rules, which are listed as having a
1419 action followed by the comment.
1424 Matches only packets generated by a divert socket.
1425 .It Cm diverted-loopback
1426 Matches only packets coming from a divert socket back into the IP stack
1428 .It Cm diverted-output
1429 Matches only packets going from a divert socket back outward to the IP
1430 stack output for delivery.
1431 .It Cm dst-ip Ar ip-address
1432 Matches IPv4 packets whose destination IP is one of the address(es)
1433 specified as argument.
1434 .It Bro Cm dst-ip6 | dst-ipv6 Brc Ar ip6-address
1435 Matches IPv6 packets whose destination IP is one of the address(es)
1436 specified as argument.
1437 .It Cm dst-port Ar ports
1438 Matches IP packets whose destination port is one of the port(s)
1439 specified as argument.
1441 Matches TCP packets that have the RST or ACK bits set.
1442 .It Cm ext6hdr Ar header
1443 Matches IPv6 packets containing the extended header given by
1445 Supported headers are:
1451 any type of Routing Header
1453 Source routing Routing Header Type 0
1455 Mobile IPv6 Routing Header Type 2
1459 IPSec authentication headers
1461 and IPsec encapsulated security payload headers
1463 .It Cm fib Ar fibnum
1464 Matches a packet that has been tagged to use
1465 the given FIB (routing table) number.
1466 .It Cm flow Ar table Ns Pq Ar name Ns Op , Ns Ar value
1467 Search for the flow entry in lookup table
1469 If not found, the match fails.
1470 Otherwise, the match succeeds and
1472 is set to the value extracted from the table.
1474 This option can be useful to quickly dispatch traffic based on
1475 certain packet fields.
1478 section below for more information on lookup tables.
1479 .It Cm flow-id Ar labels
1480 Matches IPv6 packets containing any of the flow labels given in
1483 is a comma separated list of numeric flow labels.
1485 Matches packets that are fragments and not the first
1486 fragment of an IP datagram.
1487 Note that these packets will not have
1488 the next protocol header (e.g.\& TCP, UDP) so options that look into
1489 these headers cannot match.
1491 Matches all TCP or UDP packets sent by or received for a
1495 may be specified by name or number.
1496 .It Cm jail Ar prisonID
1497 Matches all TCP or UDP packets sent by or received for the
1498 jail whos prison ID is
1500 .It Cm icmptypes Ar types
1501 Matches ICMP packets whose ICMP type is in the list
1503 The list may be specified as any combination of
1504 individual types (numeric) separated by commas.
1505 .Em Ranges are not allowed .
1506 The supported ICMP types are:
1510 destination unreachable
1518 router advertisement
1522 time-to-live exceeded
1534 address mask request
1536 and address mask reply
1538 .It Cm icmp6types Ar types
1539 Matches ICMP6 packets whose ICMP6 type is in the list of
1541 The list may be specified as any combination of
1542 individual types (numeric) separated by commas.
1543 .Em Ranges are not allowed .
1545 Matches incoming or outgoing packets, respectively.
1549 are mutually exclusive (in fact,
1553 .It Cm ipid Ar id-list
1554 Matches IPv4 packets whose
1556 field has value included in
1558 which is either a single value or a list of values or ranges
1559 specified in the same way as
1561 .It Cm iplen Ar len-list
1562 Matches IP packets whose total length, including header and data, is
1565 which is either a single value or a list of values or ranges
1566 specified in the same way as
1568 .It Cm ipoptions Ar spec
1569 Matches packets whose IPv4 header contains the comma separated list of
1570 options specified in
1572 The supported IP options are:
1575 (strict source route),
1577 (loose source route),
1579 (record packet route) and
1582 The absence of a particular option may be denoted
1585 .It Cm ipprecedence Ar precedence
1586 Matches IPv4 packets whose precedence field is equal to
1589 Matches packets that have IPSEC history associated with them
1590 (i.e., the packet comes encapsulated in IPSEC, the kernel
1591 has IPSEC support, and can correctly decapsulate it).
1593 Note that specifying
1595 is different from specifying
1597 as the latter will only look at the specific IP protocol field,
1598 irrespective of IPSEC kernel support and the validity of the IPSEC data.
1600 Further note that this flag is silently ignored in kernels without
1602 It does not affect rule processing when given and the
1603 rules are handled as if with no
1606 .It Cm iptos Ar spec
1607 Matches IPv4 packets whose
1609 field contains the comma separated list of
1610 service types specified in
1612 The supported IP types of service are:
1615 .Pq Dv IPTOS_LOWDELAY ,
1617 .Pq Dv IPTOS_THROUGHPUT ,
1619 .Pq Dv IPTOS_RELIABILITY ,
1621 .Pq Dv IPTOS_MINCOST ,
1623 .Pq Dv IPTOS_ECN_CE .
1624 The absence of a particular type may be denoted
1627 .It Cm dscp spec Ns Op , Ns Ar spec
1628 Matches IPv4/IPv6 packets whose
1630 field value is contained in
1633 Multiple values can be specified via
1634 the comma separated list.
1635 Value can be one of keywords used in
1637 action or exact number.
1638 .It Cm ipttl Ar ttl-list
1639 Matches IPv4 packets whose time to live is included in
1641 which is either a single value or a list of values or ranges
1642 specified in the same way as
1644 .It Cm ipversion Ar ver
1645 Matches IP packets whose IP version field is
1647 .It Cm keep-state Op Ar flowname
1648 Upon a match, the firewall will create a dynamic rule, whose
1649 default behaviour is to match bidirectional traffic between
1650 source and destination IP/port using the same protocol.
1651 The rule has a limited lifetime (controlled by a set of
1653 variables), and the lifetime is refreshed every time a matching
1657 is used to assign additional to addresses, ports and protocol parameter
1658 to dynamic rule. It can be used for more accurate matching by
1663 keyword is special name used for compatibility with old rulesets.
1665 Matches only layer2 packets, i.e., those passed to
1667 from ether_demux() and ether_output_frame().
1668 .It Cm limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N Op Ar flowname
1669 The firewall will only allow
1671 connections with the same
1672 set of parameters as specified in the rule.
1674 of source and destination addresses and ports can be
1676 .It Cm lookup Bro Cm dst-ip | dst-port | src-ip | src-port | uid | jail Brc Ar name
1677 Search an entry in lookup table
1679 that matches the field specified as argument.
1680 If not found, the match fails.
1681 Otherwise, the match succeeds and
1683 is set to the value extracted from the table.
1685 This option can be useful to quickly dispatch traffic based on
1686 certain packet fields.
1689 section below for more information on lookup tables.
1690 .It Cm { MAC | mac } Ar dst-mac src-mac
1691 Match packets with a given
1695 addresses, specified as the
1697 keyword (matching any MAC address), or six groups of hex digits
1698 separated by colons,
1699 and optionally followed by a mask indicating the significant bits.
1700 The mask may be specified using either of the following methods:
1701 .Bl -enum -width indent
1705 followed by the number of significant bits.
1706 For example, an address with 33 significant bits could be specified as:
1708 .Dl "MAC 10:20:30:40:50:60/33 any"
1712 followed by a bitmask specified as six groups of hex digits separated
1714 For example, an address in which the last 16 bits are significant could
1717 .Dl "MAC 10:20:30:40:50:60&00:00:00:00:ff:ff any"
1719 Note that the ampersand character has a special meaning in many shells
1720 and should generally be escaped.
1722 Note that the order of MAC addresses (destination first,
1724 the same as on the wire, but the opposite of the one used for
1726 .It Cm mac-type Ar mac-type
1727 Matches packets whose Ethernet Type field
1728 corresponds to one of those specified as argument.
1730 is specified in the same way as
1732 (i.e., one or more comma-separated single values or ranges).
1733 You can use symbolic names for known values such as
1734 .Em vlan , ipv4, ipv6 .
1735 Values can be entered as decimal or hexadecimal (if prefixed by 0x),
1736 and they are always printed as hexadecimal (unless the
1738 option is used, in which case symbolic resolution will be attempted).
1739 .It Cm proto Ar protocol
1740 Matches packets with the corresponding IP protocol.
1741 .It Cm recv | xmit | via Brq Ar ifX | Ar if Ns Cm * | Ar table Ns Po Ar name Ns Oo , Ns Ar value Oc Pc | Ar ipno | Ar any
1742 Matches packets received, transmitted or going through,
1743 respectively, the interface specified by exact name
1747 by IP address, or through some interface.
1750 may be used to match interface by its kernel ifindex.
1753 section below for more information on lookup tables.
1757 keyword causes the interface to always be checked.
1764 then only the receive or transmit interface (respectively)
1766 By specifying both, it is possible to match packets based on
1767 both receive and transmit interface, e.g.:
1769 .Dl "ipfw add deny ip from any to any out recv ed0 xmit ed1"
1773 interface can be tested on either incoming or outgoing packets,
1776 interface can only be tested on outgoing packets.
1781 is invalid) whenever
1785 A packet might not have a receive or transmit interface: packets
1786 originating from the local host have no receive interface,
1787 while packets destined for the local host have no transmit
1790 Matches TCP packets that have the SYN bit set but no ACK bit.
1791 This is the short form of
1792 .Dq Li tcpflags\ syn,!ack .
1794 Matches packets that are associated to a local socket and
1795 for which the SO_USER_COOKIE socket option has been set
1796 to a non-zero value.
1797 As a side effect, the value of the
1798 option is made available as
1800 value, which in turn can be used as
1805 .It Cm src-ip Ar ip-address
1806 Matches IPv4 packets whose source IP is one of the address(es)
1807 specified as an argument.
1808 .It Cm src-ip6 Ar ip6-address
1809 Matches IPv6 packets whose source IP is one of the address(es)
1810 specified as an argument.
1811 .It Cm src-port Ar ports
1812 Matches IP packets whose source port is one of the port(s)
1813 specified as argument.
1814 .It Cm tagged Ar tag-list
1815 Matches packets whose tags are included in
1817 which is either a single value or a list of values or ranges
1818 specified in the same way as
1820 Tags can be applied to the packet using
1822 rule action parameter (see it's description for details on tags).
1823 .It Cm tcpack Ar ack
1825 Match if the TCP header acknowledgment number field is set to
1827 .It Cm tcpdatalen Ar tcpdatalen-list
1828 Matches TCP packets whose length of TCP data is
1829 .Ar tcpdatalen-list ,
1830 which is either a single value or a list of values or ranges
1831 specified in the same way as
1833 .It Cm tcpflags Ar spec
1835 Match if the TCP header contains the comma separated list of
1838 The supported TCP flags are:
1847 The absence of a particular flag may be denoted
1850 A rule which contains a
1852 specification can never match a fragmented packet which has
1856 option for details on matching fragmented packets.
1857 .It Cm tcpseq Ar seq
1859 Match if the TCP header sequence number field is set to
1861 .It Cm tcpwin Ar tcpwin-list
1862 Matches TCP packets whose header window field is set to
1864 which is either a single value or a list of values or ranges
1865 specified in the same way as
1867 .It Cm tcpoptions Ar spec
1869 Match if the TCP header contains the comma separated list of
1870 options specified in
1872 The supported TCP options are:
1875 (maximum segment size),
1877 (tcp window advertisement),
1881 (rfc1323 timestamp) and
1883 (rfc1644 t/tcp connection count).
1884 The absence of a particular option may be denoted
1888 Match all TCP or UDP packets sent by or received for a
1892 may be matched by name or identification number.
1894 For incoming packets,
1895 a routing table lookup is done on the packet's source address.
1896 If the interface on which the packet entered the system matches the
1897 outgoing interface for the route,
1899 If the interfaces do not match up,
1900 the packet does not match.
1901 All outgoing packets or packets with no incoming interface match.
1903 The name and functionality of the option is intentionally similar to
1904 the Cisco IOS command:
1906 .Dl ip verify unicast reverse-path
1908 This option can be used to make anti-spoofing rules to reject all
1909 packets with source addresses not from this interface.
1913 For incoming packets,
1914 a routing table lookup is done on the packet's source address.
1915 If a route to the source address exists, but not the default route
1916 or a blackhole/reject route, the packet matches.
1917 Otherwise, the packet does not match.
1918 All outgoing packets match.
1920 The name and functionality of the option is intentionally similar to
1921 the Cisco IOS command:
1923 .Dl ip verify unicast source reachable-via any
1925 This option can be used to make anti-spoofing rules to reject all
1926 packets whose source address is unreachable.
1928 For incoming packets, the packet's source address is checked if it
1929 belongs to a directly connected network.
1930 If the network is directly connected, then the interface the packet
1931 came on in is compared to the interface the network is connected to.
1932 When incoming interface and directly connected interface are not the
1933 same, the packet does not match.
1934 Otherwise, the packet does match.
1935 All outgoing packets match.
1937 This option can be used to make anti-spoofing rules to reject all
1938 packets that pretend to be from a directly connected network but do
1939 not come in through that interface.
1940 This option is similar to but more restricted than
1942 because it engages only on packets with source addresses of directly
1943 connected networks instead of all source addresses.
1946 Lookup tables are useful to handle large sparse sets of
1947 addresses or other search keys (e.g., ports, jail IDs, interface names).
1948 In the rest of this section we will use the term ``key''.
1949 Table name needs to match the following spec:
1951 Tables with the same name can be created in different
1953 However, rule links to the tables in
1956 This behavior can be controlled by
1957 .Va net.inet.ip.fw.tables_sets
1961 section for more information.
1962 There may be up to 65535 different lookup tables.
1964 The following table types are supported:
1965 .Bl -tag -width indent
1966 .It Ar table-type : Ar addr | iface | number | flow
1967 .It Ar table-key : Ar addr Ns Oo / Ns Ar masklen Oc | iface-name | number | flow-spec
1968 .It Ar flow-spec : Ar flow-field Ns Op , Ns Ar flow-spec
1969 .It Ar flow-field : src-ip | proto | src-port | dst-ip | dst-port
1971 matches IPv4 or IPv6 address.
1972 Each entry is represented by an
1973 .Ar addr Ns Op / Ns Ar masklen
1974 and will match all addresses with base
1976 (specified as an IPv4/IPv6 address, or a hostname) and mask width of
1981 is not specified, it defaults to 32 for IPv4 and 128 for IPv6.
1982 When looking up an IP address in a table, the most specific
1985 matches interface names.
1986 Each entry is represented by string treated as interface name.
1987 Wildcards are not supported.
1989 maches protocol ports, uids/gids or jail IDs.
1990 Each entry is represented by 32-bit unsigned integer.
1991 Ranges are not supported.
1993 Matches packet fields specified by
1995 type suboptions with table entries.
1998 Tables require explicit creation via
2002 The following creation options are supported:
2003 .Bl -tag -width indent
2004 .It Ar create-options : Ar create-option | create-options
2005 .It Ar create-option : Cm type Ar table-type | Cm valtype Ar value-mask | Cm algo Ar algo-desc |
2006 .Cm limit Ar number | Cm locked
2012 Table algorithm to use (see below).
2014 Maximum number of items that may be inserted into table.
2016 Restrict any table modifications.
2019 Some of these options may be modified later via
2022 The following options can be changed:
2023 .Bl -tag -width indent
2024 .It Ar modify-options : Ar modify-option | modify-options
2025 .It Ar modify-option : Cm limit Ar number
2027 Alter maximum number of items that may be inserted into table.
2030 Additionally, table can be locked or unlocked using
2038 can be swapped with each other using
2041 Swap may fail if tables limits are set and data exchange
2042 would result in limits hit.
2043 Operation is performed atomically.
2045 One or more entries can be added to a table at once using
2048 Addition of all items are performed atomically.
2049 By default, error in addition of one entry does not influence
2050 addition of other entries. However, non-zero error code is returned
2054 keyword may be specified before
2056 to indicate all-or-none add request.
2058 One or more entries can be removed from a table at once using
2061 By default, error in removal of one entry does not influence
2062 removing of other entries. However, non-zero error code is returned
2065 It may be possible to check what entry will be found on particular
2071 This functionality is optional and may be unsupported in some algorithms.
2073 The following operations can be performed on
2078 .Bl -tag -width indent
2082 Removes all entries.
2084 Shows generic table information.
2086 Shows generic table information and algo-specific data.
2089 The following lookup algorithms are supported:
2090 .Bl -tag -width indent
2091 .It Ar algo-desc : algo-name | "algo-name algo-data"
2092 .It Ar algo-name: Ar addr:radix | addr:hash | iface:array | number:array | flow:hash
2094 Separate Radix trees for IPv4 and IPv6, the same way as the routing table (see
2100 Separate auto-growing hashes for IPv4 and IPv6.
2101 Accepts entries with the same mask length specified initially via
2102 .Cm "addr:hash masks=/v4,/v6"
2103 algorithm creation options.
2104 Assume /32 and /128 masks by default.
2105 Search removes host bits (according to mask) from supplied address and checks
2106 resulting key in appropriate hash.
2107 Mostly optimized for /64 and byte-ranged IPv6 masks.
2109 Array storing sorted indexes for entries which are presented in the system.
2110 Optimized for very fast lookup.
2112 Array storing sorted u32 numbers.
2114 Auto-growing hash storing flow entries.
2115 Search calculates hash on required packet fields and searches for matching
2116 entries in selected bucket.
2121 feature provides the ability to use a value, looked up in the table, as
2122 the argument for a rule action, action parameter or rule option.
2123 This can significantly reduce number of rules in some configurations.
2124 If two tables are used in a rule, the result of the second (destination)
2127 Each record may hold one or more values according to
2129 This mask is set on table creation via
2132 The following value types are supported:
2133 .Bl -tag -width indent
2134 .It Ar value-mask : Ar value-type Ns Op , Ns Ar value-mask
2135 .It Ar value-type : Ar skipto | pipe | fib | nat | dscp | tag | divert |
2136 .Ar netgraph | limit | ipv4
2138 rule number to jump to.
2142 fib number to match/set.
2144 nat number to jump to.
2146 dscp value to match/set.
2148 tag number to match/set.
2150 port number to divert traffic to.
2152 hook number to move packet to.
2154 maximum number of connections.
2156 IPv4 nexthop to fwd packets to.
2158 IPv6 nexthop to fwd packets to.
2163 argument can be used with the following actions:
2164 .Cm nat, pipe , queue, divert, tee, netgraph, ngtee, fwd, skipto, setfib,
2172 action, the user should be aware that the code will walk the ruleset
2173 up to a rule equal to, or past, the given number.
2177 Section for example usage of tables and the tablearg keyword.
2179 Each rule or table belongs to one of 32 different
2182 Set 31 is reserved for the default rule.
2184 By default, rules or tables are put in set 0, unless you use the
2186 attribute when adding a new rule or table.
2187 Sets can be individually and atomically enabled or disabled,
2188 so this mechanism permits an easy way to store multiple configurations
2189 of the firewall and quickly (and atomically) switch between them.
2191 By default, tables from set 0 are referenced when adding rule with
2192 table opcodes regardless of rule set.
2193 This behavior can be changed by setting
2194 .Va net.inet.ip.fw.tables_set
2196 Rule's set will then be used for table references.
2198 The command to enable/disable sets is
2199 .Bd -ragged -offset indent
2201 .Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ...
2208 sections can be specified.
2209 Command execution is atomic on all the sets specified in the command.
2210 By default, all sets are enabled.
2212 When you disable a set, its rules behave as if they do not exist
2213 in the firewall configuration, with only one exception:
2214 .Bd -ragged -offset indent
2215 dynamic rules created from a rule before it had been disabled
2216 will still be active until they expire.
2218 dynamic rules you have to explicitly delete the parent rule
2219 which generated them.
2222 The set number of rules can be changed with the command
2223 .Bd -ragged -offset indent
2226 .Brq Cm rule Ar rule-number | old-set
2230 Also, you can atomically swap two rulesets with the command
2231 .Bd -ragged -offset indent
2233 .Cm set swap Ar first-set second-set
2238 Section on some possible uses of sets of rules.
2239 .Sh STATEFUL FIREWALL
2240 Stateful operation is a way for the firewall to dynamically
2241 create rules for specific flows when packets that
2242 match a given pattern are detected.
2243 Support for stateful
2244 operation comes through the
2245 .Cm check-state , keep-state
2251 Dynamic rules are created when a packet matches a
2255 rule, causing the creation of a
2257 rule which will match all and only packets with
2261 .Em src-ip/src-port dst-ip/dst-port
2266 are used here only to denote the initial match addresses, but they
2267 are completely equivalent afterwards).
2273 This name is used in matching together with addresses, ports and protocol.
2274 Dynamic rules will be checked at the first
2275 .Cm check-state, keep-state
2278 occurrence, and the action performed upon a match will be the same
2279 as in the parent rule.
2281 Note that no additional attributes other than protocol and IP addresses
2282 and ports and flowname are checked on dynamic rules.
2284 The typical use of dynamic rules is to keep a closed firewall configuration,
2285 but let the first TCP SYN packet from the inside network install a
2286 dynamic rule for the flow so that packets belonging to that session
2287 will be allowed through the firewall:
2289 .Dl "ipfw add check-state OUTBOUND"
2290 .Dl "ipfw add allow tcp from my-subnet to any setup keep-state OUTBOUND"
2291 .Dl "ipfw add deny tcp from any to any"
2293 A similar approach can be used for UDP, where an UDP packet coming
2294 from the inside will install a dynamic rule to let the response through
2297 .Dl "ipfw add check-state OUTBOUND"
2298 .Dl "ipfw add allow udp from my-subnet to any keep-state OUTBOUND"
2299 .Dl "ipfw add deny udp from any to any"
2301 Dynamic rules expire after some time, which depends on the status
2302 of the flow and the setting of some
2306 .Sx SYSCTL VARIABLES
2308 For TCP sessions, dynamic rules can be instructed to periodically
2309 send keepalive packets to refresh the state of the rule when it is
2314 for more examples on how to use dynamic rules.
2315 .Sh TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
2317 is also the user interface for the
2319 traffic shaper, packet scheduler and network emulator, a subsystem that
2320 can artificially queue, delay or drop packets
2321 emulating the behaviour of certain network links
2322 or queueing systems.
2325 operates by first using the firewall to select packets
2326 using any match pattern that can be used in
2329 Matching packets are then passed to either of two
2330 different objects, which implement the traffic regulation:
2331 .Bl -hang -offset XXXX
2337 with given bandwidth and propagation delay,
2338 driven by a FIFO scheduler and a single queue with programmable
2339 queue size and packet loss rate.
2340 Packets are appended to the queue as they come out from
2342 and then transferred in FIFO order to the link at the desired rate.
2346 is an abstraction used to implement packet scheduling
2347 using one of several packet scheduling algorithms.
2350 are first grouped into flows according to a mask on the 5-tuple.
2351 Flows are then passed to the scheduler associated to the
2353 and each flow uses scheduling parameters (weight and others)
2354 as configured in the
2357 A scheduler in turn is connected to an emulated link,
2358 and arbitrates the link's bandwidth among backlogged flows according to
2359 weights and to the features of the scheduling algorithm in use.
2364 can be used to set hard limits to the bandwidth that a flow can use, whereas
2366 can be used to determine how different flows share the available bandwidth.
2368 A graphical representation of the binding of queues,
2369 flows, schedulers and links is below.
2370 .Bd -literal -offset indent
2371 (flow_mask|sched_mask) sched_mask
2372 +---------+ weight Wx +-------------+
2373 | |->-[flow]-->--| |-+
2374 -->--| QUEUE x | ... | | |
2375 | |->-[flow]-->--| SCHEDuler N | |
2377 ... | +--[LINK N]-->--
2378 +---------+ weight Wy | | +--[LINK N]-->--
2379 | |->-[flow]-->--| | |
2380 -->--| QUEUE y | ... | | |
2381 | |->-[flow]-->--| | |
2382 +---------+ +-------------+ |
2385 It is important to understand the role of the SCHED_MASK
2386 and FLOW_MASK, which are configured through the commands
2387 .Dl "ipfw sched N config mask SCHED_MASK ..."
2389 .Dl "ipfw queue X config mask FLOW_MASK ..." .
2391 The SCHED_MASK is used to assign flows to one or more
2392 scheduler instances, one for each
2393 value of the packet's 5-tuple after applying SCHED_MASK.
2394 As an example, using ``src-ip 0xffffff00'' creates one instance
2395 for each /24 destination subnet.
2397 The FLOW_MASK, together with the SCHED_MASK, is used to split
2399 As an example, using
2400 ``src-ip 0x000000ff''
2401 together with the previous SCHED_MASK makes a flow for
2402 each individual source address.
2403 In turn, flows for each /24
2404 subnet will be sent to the same scheduler instance.
2406 The above diagram holds even for the
2408 case, with the only restriction that a
2410 only supports a SCHED_MASK, and forces the use of a FIFO
2411 scheduler (these are for backward compatibility reasons;
2412 in fact, internally, a
2414 pipe is implemented exactly as above).
2416 There are two modes of
2424 mode tries to emulate a real link: the
2426 scheduler ensures that the packet will not leave the pipe faster than it
2427 would on the real link with a given bandwidth.
2430 mode allows certain packets to bypass the
2432 scheduler (if packet flow does not exceed pipe's bandwidth).
2433 This is the reason why the
2435 mode requires less CPU cycles per packet (on average) and packet latency
2436 can be significantly lower in comparison to a real link with the same
2442 mode can be enabled by setting the
2443 .Va net.inet.ip.dummynet.io_fast
2445 variable to a non-zero value.
2447 .Ss PIPE, QUEUE AND SCHEDULER CONFIGURATION
2453 configuration commands are the following:
2454 .Bd -ragged -offset indent
2455 .Cm pipe Ar number Cm config Ar pipe-configuration
2457 .Cm queue Ar number Cm config Ar queue-configuration
2459 .Cm sched Ar number Cm config Ar sched-configuration
2462 The following parameters can be configured for a pipe:
2464 .Bl -tag -width indent -compact
2465 .It Cm bw Ar bandwidth | device
2466 Bandwidth, measured in
2469 .Brq Cm bit/s | Byte/s .
2472 A value of 0 (default) means unlimited bandwidth.
2473 The unit must immediately follow the number, as in
2475 .Dl "ipfw pipe 1 config bw 300Kbit/s"
2477 If a device name is specified instead of a numeric value, as in
2479 .Dl "ipfw pipe 1 config bw tun0"
2481 then the transmit clock is supplied by the specified device.
2482 At the moment only the
2484 device supports this
2485 functionality, for use in conjunction with
2488 .It Cm delay Ar ms-delay
2489 Propagation delay, measured in milliseconds.
2490 The value is rounded to the next multiple of the clock tick
2491 (typically 10ms, but it is a good practice to run kernels
2493 .Dq "options HZ=1000"
2495 the granularity to 1ms or less).
2496 The default value is 0, meaning no delay.
2498 .It Cm burst Ar size
2499 If the data to be sent exceeds the pipe's bandwidth limit
2500 (and the pipe was previously idle), up to
2502 bytes of data are allowed to bypass the
2504 scheduler, and will be sent as fast as the physical link allows.
2505 Any additional data will be transmitted at the rate specified
2509 The burst size depends on how long the pipe has been idle;
2510 the effective burst size is calculated as follows:
2517 .It Cm profile Ar filename
2518 A file specifying the additional overhead incurred in the transmission
2519 of a packet on the link.
2521 Some link types introduce extra delays in the transmission
2522 of a packet, e.g., because of MAC level framing, contention on
2523 the use of the channel, MAC level retransmissions and so on.
2524 From our point of view, the channel is effectively unavailable
2525 for this extra time, which is constant or variable depending
2527 Additionally, packets may be dropped after this
2528 time (e.g., on a wireless link after too many retransmissions).
2529 We can model the additional delay with an empirical curve
2530 that represents its distribution.
2531 .Bd -literal -offset indent
2532 cumulative probability
2542 +-------*------------------->
2545 The empirical curve may have both vertical and horizontal lines.
2546 Vertical lines represent constant delay for a range of
2548 Horizontal lines correspond to a discontinuity in the delay
2549 distribution: the pipe will use the largest delay for a
2552 The file format is the following, with whitespace acting as
2553 a separator and '#' indicating the beginning a comment:
2554 .Bl -tag -width indent
2555 .It Cm name Ar identifier
2556 optional name (listed by "ipfw pipe show")
2557 to identify the delay distribution;
2559 the bandwidth used for the pipe.
2560 If not specified here, it must be present
2561 explicitly as a configuration parameter for the pipe;
2562 .It Cm loss-level Ar L
2563 the probability above which packets are lost.
2564 (0.0 <= L <= 1.0, default 1.0 i.e., no loss);
2566 the number of samples used in the internal
2567 representation of the curve (2..1024; default 100);
2568 .It Cm "delay prob" | "prob delay"
2569 One of these two lines is mandatory and defines
2570 the format of the following lines with data points.
2572 2 or more lines representing points in the curve,
2573 with either delay or probability first, according
2574 to the chosen format.
2575 The unit for delay is milliseconds.
2576 Data points do not need to be sorted.
2577 Also, the number of actual lines can be different
2578 from the value of the "samples" parameter:
2580 utility will sort and interpolate
2581 the curve as needed.
2584 Example of a profile file:
2585 .Bd -literal -offset indent
2590 0 200 # minimum overhead is 200ms
2596 #configuration file end
2600 The following parameters can be configured for a queue:
2602 .Bl -tag -width indent -compact
2603 .It Cm pipe Ar pipe_nr
2604 Connects a queue to the specified pipe.
2605 Multiple queues (with the same or different weights) can be connected to
2606 the same pipe, which specifies the aggregate rate for the set of queues.
2608 .It Cm weight Ar weight
2609 Specifies the weight to be used for flows matching this queue.
2610 The weight must be in the range 1..100, and defaults to 1.
2613 The following case-insensitive parameters can be configured for a
2616 .Bl -tag -width indent -compact
2617 .It Cm type Ar {fifo | wf2q+ | rr | qfq}
2618 specifies the scheduling algorithm to use.
2619 .Bl -tag -width indent -compact
2621 is just a FIFO scheduler (which means that all packets
2622 are stored in the same queue as they arrive to the scheduler).
2623 FIFO has O(1) per-packet time complexity, with very low
2624 constants (estimate 60-80ns on a 2GHz desktop machine)
2625 but gives no service guarantees.
2627 implements the WF2Q+ algorithm, which is a Weighted Fair Queueing
2628 algorithm which permits flows to share bandwidth according to
2630 Note that weights are not priorities; even a flow
2631 with a minuscule weight will never starve.
2632 WF2Q+ has O(log N) per-packet processing cost, where N is the number
2633 of flows, and is the default algorithm used by previous versions
2636 implements the Deficit Round Robin algorithm, which has O(1) processing
2637 costs (roughly, 100-150ns per packet)
2638 and permits bandwidth allocation according to weights, but
2639 with poor service guarantees.
2641 implements the QFQ algorithm, which is a very fast variant of
2642 WF2Q+, with similar service guarantees and O(1) processing
2643 costs (roughly, 200-250ns per packet).
2647 In addition to the type, all parameters allowed for a pipe can also
2648 be specified for a scheduler.
2650 Finally, the following parameters can be configured for both
2653 .Bl -tag -width XXXX -compact
2654 .It Cm buckets Ar hash-table-size
2655 Specifies the size of the hash table used for storing the
2657 Default value is 64 controlled by the
2660 .Va net.inet.ip.dummynet.hash_size ,
2661 allowed range is 16 to 65536.
2663 .It Cm mask Ar mask-specifier
2664 Packets sent to a given pipe or queue by an
2666 rule can be further classified into multiple flows, each of which is then
2670 A flow identifier is constructed by masking the IP addresses,
2671 ports and protocol types as specified with the
2673 options in the configuration of the pipe or queue.
2674 For each different flow identifier, a new pipe or queue is created
2675 with the same parameters as the original object, and matching packets
2680 are used, each flow will get the same bandwidth as defined by the pipe,
2683 are used, each flow will share the parent's pipe bandwidth evenly
2684 with other flows generated by the same queue (note that other queues
2685 with different weights might be connected to the same pipe).
2687 Available mask specifiers are a combination of one or more of the following:
2689 .Cm dst-ip Ar mask ,
2690 .Cm dst-ip6 Ar mask ,
2691 .Cm src-ip Ar mask ,
2692 .Cm src-ip6 Ar mask ,
2693 .Cm dst-port Ar mask ,
2694 .Cm src-port Ar mask ,
2695 .Cm flow-id Ar mask ,
2700 where the latter means all bits in all fields are significant.
2703 When a packet is dropped by a
2705 queue or pipe, the error
2706 is normally reported to the caller routine in the kernel, in the
2707 same way as it happens when a device queue fills up.
2709 option reports the packet as successfully delivered, which can be
2710 needed for some experimental setups where you want to simulate
2711 loss or congestion at a remote router.
2713 .It Cm plr Ar packet-loss-rate
2716 .Ar packet-loss-rate
2717 is a floating-point number between 0 and 1, with 0 meaning no
2718 loss, 1 meaning 100% loss.
2719 The loss rate is internally represented on 31 bits.
2721 .It Cm queue Brq Ar slots | size Ns Cm Kbytes
2726 Default value is 50 slots, which
2727 is the typical queue size for Ethernet devices.
2728 Note that for slow speed links you should keep the queue
2729 size short or your traffic might be affected by a significant
2731 E.g., 50 max-sized ethernet packets (1500 bytes) mean 600Kbit
2732 or 20s of queue on a 30Kbit/s pipe.
2733 Even worse effects can result if you get packets from an
2734 interface with a much larger MTU, e.g.\& the loopback interface
2735 with its 16KB packets.
2739 .Em net.inet.ip.dummynet.pipe_byte_limit
2741 .Em net.inet.ip.dummynet.pipe_slot_limit
2742 control the maximum lengths that can be specified.
2744 .It Cm red | gred Ar w_q Ns / Ns Ar min_th Ns / Ns Ar max_th Ns / Ns Ar max_p
2746 Make use of the RED (Random Early Detection) queue management algorithm.
2751 point numbers between 0 and 1 (inclusive), while
2755 are integer numbers specifying thresholds for queue management
2756 (thresholds are computed in bytes if the queue has been defined
2757 in bytes, in slots otherwise).
2758 The two parameters can also be of the same value if needed. The
2760 also supports the gentle RED variant (gred) and ECN (Explicit Congestion
2761 Notification) as optional. Three
2763 variables can be used to control the RED behaviour:
2764 .Bl -tag -width indent
2765 .It Va net.inet.ip.dummynet.red_lookup_depth
2766 specifies the accuracy in computing the average queue
2767 when the link is idle (defaults to 256, must be greater than zero)
2768 .It Va net.inet.ip.dummynet.red_avg_pkt_size
2769 specifies the expected average packet size (defaults to 512, must be
2771 .It Va net.inet.ip.dummynet.red_max_pkt_size
2772 specifies the expected maximum packet size, only used when queue
2773 thresholds are in bytes (defaults to 1500, must be greater than zero).
2777 When used with IPv6 data,
2779 currently has several limitations.
2780 Information necessary to route link-local packets to an
2781 interface is not available after processing by
2783 so those packets are dropped in the output path.
2784 Care should be taken to ensure that link-local packets are not passed to
2787 Here are some important points to consider when designing your
2791 Remember that you filter both packets going
2795 Most connections need packets going in both directions.
2797 Remember to test very carefully.
2798 It is a good idea to be near the console when doing this.
2799 If you cannot be near the console,
2800 use an auto-recovery script such as the one in
2801 .Pa /usr/share/examples/ipfw/change_rules.sh .
2803 Do not forget the loopback interface.
2808 There are circumstances where fragmented datagrams are unconditionally
2810 TCP packets are dropped if they do not contain at least 20 bytes of
2811 TCP header, UDP packets are dropped if they do not contain a full 8
2812 byte UDP header, and ICMP packets are dropped if they do not contain
2813 4 bytes of ICMP header, enough to specify the ICMP type, code, and
2815 These packets are simply logged as
2817 since there may not be enough good data in the packet to produce a
2818 meaningful log entry.
2820 Another type of packet is unconditionally dropped, a TCP packet with a
2821 fragment offset of one.
2822 This is a valid packet, but it only has one use, to try
2823 to circumvent firewalls.
2824 When logging is enabled, these packets are
2825 reported as being dropped by rule -1.
2827 If you are logged in over a network, loading the
2831 is probably not as straightforward as you would think.
2832 The following command line is recommended:
2833 .Bd -literal -offset indent
2835 ipfw add 32000 allow ip from any to any
2838 Along the same lines, doing an
2839 .Bd -literal -offset indent
2843 in similar surroundings is also a bad idea.
2847 filter list may not be modified if the system security level
2848 is set to 3 or higher
2851 for information on system security levels).
2853 .Sh PACKET DIVERSION
2856 socket bound to the specified port will receive all packets
2857 diverted to that port.
2858 If no socket is bound to the destination port, or if the divert module is
2859 not loaded, or if the kernel was not compiled with divert socket support,
2860 the packets are dropped.
2861 .Sh NETWORK ADDRESS TRANSLATION (NAT)
2863 support in-kernel NAT using the kernel version of
2866 The nat configuration command is the following:
2867 .Bd -ragged -offset indent
2872 .Ar nat-configuration
2876 The following parameters can be configured:
2877 .Bl -tag -width indent
2878 .It Cm ip Ar ip_address
2879 Define an ip address to use for aliasing.
2881 Use ip address of NIC for aliasing, dynamically changing
2882 it if NIC's ip address changes.
2884 Enable logging on this nat instance.
2886 Deny any incoming connection from outside world.
2888 Try to leave the alias port numbers unchanged from
2889 the actual local port numbers.
2891 Traffic on the local network not originating from an
2892 unregistered address spaces will be ignored.
2894 Reset table of the packet aliasing engine on address change.
2896 Reverse the way libalias handles aliasing.
2898 Obey transparent proxy rules only, packet aliasing is not performed.
2900 Skip instance in case of global state lookup (see below).
2903 Some specials value can be supplied instead of
2905 .Bl -tag -width indent
2907 Looks up translation state in all configured nat instances.
2908 If an entry is found, packet is aliased according to that entry.
2909 If no entry was found in any of the instances, packet is passed unchanged,
2910 and no new entry will be created.
2912 .Sx MULTIPLE INSTANCES
2915 for more information.
2917 Uses argument supplied in lookup table.
2920 section below for more information on lookup tables.
2923 To let the packet continue after being (de)aliased, set the sysctl variable
2924 .Va net.inet.ip.fw.one_pass
2926 For more information about aliasing modes, refer to
2930 for some examples about nat usage.
2931 .Ss REDIRECT AND LSNAT SUPPORT IN IPFW
2932 Redirect and LSNAT support follow closely the syntax used in
2936 for some examples on how to do redirect and lsnat.
2937 .Ss SCTP NAT SUPPORT
2938 SCTP nat can be configured in a similar manner to TCP through the
2941 The main difference is that
2943 does not do port translation.
2944 Since the local and global side ports will be the same,
2945 there is no need to specify both.
2946 Ports are redirected as follows:
2947 .Bd -ragged -offset indent
2953 .Cm redirect_port sctp
2954 .Ar ip_address [,addr_list] {[port | port-port] [,ports]}
2960 configuration can be done in real-time through the
2963 All may be changed dynamically, though the hash_table size will only
2968 .Sx SYSCTL VARIABLES
2970 .Sh IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
2972 supports in-kernel IPv6/IPv4 network address and protocol translation.
2973 Stateful NAT64 translation allows IPv6-only clients to contact IPv4 servers
2974 using unicast TCP, UDP or ICMP protocols.
2975 One or more IPv4 addresses assigned to a stateful NAT64 translator are shared
2976 among serveral IPv6-only clients.
2977 When stateful NAT64 is used in conjunction with DNS64, no changes are usually
2978 required in the IPv6 client or the IPv4 server.
2981 should be loaded or kernel should have
2982 .Cm options IPFIREWALL_NAT64
2983 to be able use stateful NAT64 translator.
2985 Stateful NAT64 uses a bunch of memory for several types of objects.
2986 When IPv6 client initiates connection, NAT64 translator creates a host entry
2987 in the states table.
2988 Each host entry has a number of ports group entries allocated on demand.
2989 Ports group entries contains connection state entries.
2990 There are several options to control limits and lifetime for these objects.
2992 NAT64 translator follows RFC7915 when does ICMPv6/ICMP translation,
2993 unsupported message types will be silently dropped.
2994 IPv6 needs several ICMPv6 message types to be explicitly allowed for correct
2996 Make sure that ND6 neighbor solicitation (ICMPv6 type 135) and neighbor
2997 advertisement (ICMPv6 type 136) messages will not be handled by translation
3000 After translation NAT64 translator sends packets through corresponding netisr
3002 Thus translator host should be configured as IPv4 and IPv6 router.
3004 Currently both stateful and stateless NAT64 translators use Well-Known IPv6
3007 to represent IPv4 addresses in the IPv6 address.
3008 Thus DNS64 service and routing should be configured to use Well-Known IPv6
3011 The stateful NAT64 configuration command is the following:
3012 .Bd -ragged -offset indent
3021 The following parameters can be configured:
3022 .Bl -tag -width indent
3023 .It Cm prefix4 Ar ipv4_prefix/mask
3024 The IPv4 prefix with mask defines the pool of IPv4 addresses used as
3025 source address after translation.
3026 Stateful NAT64 module translates IPv6 source address of client to one
3027 IPv4 address from this pool.
3028 Note that incoming IPv4 packets that don't have corresponding state entry
3029 in the states table will be dropped by translator.
3030 Make sure that translation rules handle packets, destined to configured prefix.
3031 .It Cm max_ports Ar number
3032 Maximum number of ports reserved for upper level protocols to one IPv6 client.
3033 All reserved ports are divided into chunks between supported protocols.
3034 The number of connections from one IPv6 client is limited by this option.
3035 Note that closed TCP connections still remain in the list of connections until
3037 interval will not expire.
3040 .It Cm host_del_age Ar seconds
3041 The number of seconds until the host entry for a IPv6 client will be deleted
3042 and all its resources will be released due to inactivity.
3045 .It Cm pg_del_age Ar seconds
3046 The number of seconds until a ports group with unused state entries will
3050 .It Cm tcp_syn_age Ar seconds
3051 The number of seconds while a state entry for TCP connection with only SYN
3053 If TCP connection establishing will not be finished,
3054 state entry will be deleted.
3057 .It Cm tcp_est_age Ar seconds
3058 The number of seconds while a state entry for established TCP connection
3062 .It Cm tcp_close_age Ar seconds
3063 The number of seconds while a state entry for closed TCP connection
3065 Keeping state entries for closed connections is needed, because IPv4 servers
3066 typically keep closed connections in a TIME_WAIT state for a several minutes.
3067 Since translator's IPv4 addresses are shared among all IPv6 clients,
3068 new connections from the same addresses and ports may be rejected by server,
3069 because these connections are still in a TIME_WAIT state.
3070 Keeping them in translator's state table protects from such rejects.
3073 .It Cm udp_age Ar seconds
3074 The number of seconds while translator keeps state entry in a waiting for
3075 reply to the sent UDP datagram.
3078 .It Cm icmp_age Ar seconds
3079 The number of seconds while translator keeps state entry in a waiting for
3080 reply to the sent ICMP message.
3084 Turn on logging of all handled packets via BPF through
3088 is a pseudo interface and can be created after a boot manually with
3091 Note that it has different purpose than
3094 Translators sends to BPF an additional information with each packet.
3097 you are able to see each handled packet before and after translation.
3099 Turn off logging of all handled packets via BPF.
3102 To inspect a states table of stateful NAT64 the following command can be used:
3103 .Bd -ragged -offset indent
3112 Stateless NAT64 translator doesn't use a states table for translation
3113 and converts IPv4 addresses to IPv6 and vice versa solely based on the
3114 mappings taken from configured lookup tables.
3115 Since a states table doesn't used by stateless translator,
3116 it can be configured to pass IPv4 clients to IPv6-only servers.
3118 The stateless NAT64 configuration command is the following:
3119 .Bd -ragged -offset indent
3128 The following parameters can be configured:
3129 .Bl -tag -width indent
3130 .It Cm table4 Ar table46
3133 contains mapping how IPv4 addresses should be translated to IPv6 addresses.
3134 .It Cm table6 Ar table64
3137 contains mapping how IPv6 addresses should be translated to IPv4 addresses.
3139 Turn on logging of all handled packets via BPF through
3143 Turn off logging of all handled packets via BPF.
3146 Note that the behavior of stateless translator with respect to not matched
3147 packets differs from stateful translator.
3148 If corresponding addresses was not found in the lookup tables, the packet
3149 will not be dropped and the search continues.
3150 .Sh IPv6-to-IPv6 NETWORK PREFIX TRANSLATION (NPTv6)
3152 supports in-kernel IPv6-to-IPv6 network prefix translation as described
3156 should be loaded or kernel should has
3157 .Cm options IPFIREWALL_NPTV6
3158 to be able use NPTv6 translator.
3160 The NPTv6 configuration command is the following:
3161 .Bd -ragged -offset indent
3170 The following parameters can be configured:
3171 .Bl -tag -width indent
3172 .It Cm int_prefix Ar ipv6_prefix
3173 IPv6 prefix used in internal network.
3174 NPTv6 module translates source address when it matches this prefix.
3175 .It Cm ext_prefix Ar ipv6_prefix
3176 IPv6 prefix used in external network.
3177 NPTv6 module translates destination address when it matches this prefix.
3178 .It Cm prefixlen Ar length
3179 The length of specified IPv6 prefixes. It must be in range from 8 to 64.
3182 Note that the prefix translation rules are silently ignored when IPv6 packet
3183 forwarding is disabled.
3184 To enable the packet forwarding, set the sysctl variable
3185 .Va net.inet6.ip6.forwarding
3188 To let the packet continue after being translated, set the sysctl variable
3189 .Va net.inet.ip.fw.one_pass
3192 Tunables can be set in
3198 before ipfw module gets loaded.
3199 .Bl -tag -width indent
3200 .It Va net.inet.ip.fw.default_to_accept: No 0
3201 Defines ipfw last rule behavior.
3202 This value overrides
3203 .Cd "options IPFW_DEFAULT_TO_(ACCEPT|DENY)"
3204 from kernel configuration file.
3205 .It Va net.inet.ip.fw.tables_max: No 128
3206 Defines number of tables available in ipfw.
3207 Number cannot exceed 65534.
3209 .Sh SYSCTL VARIABLES
3212 variables controls the behaviour of the firewall and
3214 .Pq Nm dummynet , bridge , sctp nat .
3215 These are shown below together with their default value
3216 (but always check with the
3218 command what value is actually in use) and meaning:
3219 .Bl -tag -width indent
3220 .It Va net.inet.ip.alias.sctp.accept_global_ootb_addip: No 0
3223 responds to receipt of global OOTB ASCONF-AddIP:
3224 .Bl -tag -width indent
3226 No response (unless a partially matching association exists -
3227 ports and vtags match but global address does not)
3230 will accept and process all OOTB global AddIP messages.
3233 Option 1 should never be selected as this forms a security risk.
3235 establish multiple fake associations by sending AddIP messages.
3236 .It Va net.inet.ip.alias.sctp.chunk_proc_limit: No 5
3237 Defines the maximum number of chunks in an SCTP packet that will be
3239 packet that matches an existing association.
3240 This value is enforced to be greater or equal than
3241 .Cm net.inet.ip.alias.sctp.initialising_chunk_proc_limit .
3243 a DoS risk yet setting too low a value may result in
3244 important control chunks in
3245 the packet not being located and parsed.
3246 .It Va net.inet.ip.alias.sctp.error_on_ootb: No 1
3249 responds to any Out-of-the-Blue (OOTB) packets with ErrorM packets.
3250 An OOTB packet is a packet that arrives with no existing association
3253 and is not an INIT or ASCONF-AddIP packet:
3254 .Bl -tag -width indent
3256 ErrorM is never sent in response to OOTB packets.
3258 ErrorM is only sent to OOTB packets received on the local side.
3260 ErrorM is sent to the local side and on the global side ONLY if there is a
3261 partial match (ports and vtags match but the source global IP does not).
3262 This value is only useful if the
3264 is tracking global IP addresses.
3266 ErrorM is sent in response to all OOTB packets on both
3267 the local and global side
3271 At the moment the default is 0, since the ErrorM packet is not yet
3272 supported by most SCTP stacks.
3273 When it is supported, and if not tracking
3274 global addresses, we recommend setting this value to 1 to allow
3275 multi-homed local hosts to function with the
3277 To track global addresses, we recommend setting this value to 2 to
3278 allow global hosts to be informed when they need to (re)send an
3280 Value 3 should never be chosen (except for debugging) as the
3282 will respond to all OOTB global packets (a DoS risk).
3283 .It Va net.inet.ip.alias.sctp.hashtable_size: No 2003
3284 Size of hash tables used for
3286 lookups (100 < prime_number > 1000001).
3289 size for any future created
3291 instance and therefore must be set prior to creating a
3294 The table sizes may be changed to suit specific needs.
3295 If there will be few
3296 concurrent associations, and memory is scarce, you may make these smaller.
3297 If there will be many thousands (or millions) of concurrent associations, you
3298 should make these larger.
3299 A prime number is best for the table size.
3301 update function will adjust your input value to the next highest prime number.
3302 .It Va net.inet.ip.alias.sctp.holddown_time: No 0
3303 Hold association in table for this many seconds after receiving a
3305 This allows endpoints to correct shutdown gracefully if a
3306 shutdown_complete is lost and retransmissions are required.
3307 .It Va net.inet.ip.alias.sctp.init_timer: No 15
3308 Timeout value while waiting for (INIT-ACK|AddIP-ACK).
3309 This value cannot be 0.
3310 .It Va net.inet.ip.alias.sctp.initialising_chunk_proc_limit: No 2
3311 Defines the maximum number of chunks in an SCTP packet that will be parsed when
3312 no existing association exists that matches that packet.
3314 will only be an INIT or ASCONF-AddIP packet.
3315 A higher value may become a DoS
3316 risk as malformed packets can consume processing resources.
3317 .It Va net.inet.ip.alias.sctp.param_proc_limit: No 25
3318 Defines the maximum number of parameters within a chunk that will be
3321 As for other similar sysctl variables, larger values pose a DoS risk.
3322 .It Va net.inet.ip.alias.sctp.log_level: No 0
3323 Level of detail in the system log messages (0 \- minimal, 1 \- event,
3324 2 \- info, 3 \- detail, 4 \- debug, 5 \- max debug).
3326 option in high loss environments.
3327 .It Va net.inet.ip.alias.sctp.shutdown_time: No 15
3328 Timeout value while waiting for SHUTDOWN-COMPLETE.
3329 This value cannot be 0.
3330 .It Va net.inet.ip.alias.sctp.track_global_addresses: No 0
3331 Enables/disables global IP address tracking within the
3334 upper limit on the number of addresses tracked for each association:
3335 .Bl -tag -width indent
3337 Global tracking is disabled
3339 Enables tracking, the maximum number of addresses tracked for each
3340 association is limited to this value
3343 This variable is fully dynamic, the new value will be adopted for all newly
3344 arriving associations, existing associations are treated
3345 as they were previously.
3346 Global tracking will decrease the number of collisions within the
3349 of increased processing load, memory usage, complexity, and possible
3352 problems in complex networks with multiple
3354 We recommend not tracking
3355 global IP addresses, this will still result in a fully functional
3357 .It Va net.inet.ip.alias.sctp.up_timer: No 300
3358 Timeout value to keep an association up with no traffic.
3359 This value cannot be 0.
3360 .It Va net.inet.ip.dummynet.expire : No 1
3361 Lazily delete dynamic pipes/queue once they have no pending traffic.
3362 You can disable this by setting the variable to 0, in which case
3363 the pipes/queues will only be deleted when the threshold is reached.
3364 .It Va net.inet.ip.dummynet.hash_size : No 64
3365 Default size of the hash table used for dynamic pipes/queues.
3366 This value is used when no
3368 option is specified when configuring a pipe/queue.
3369 .It Va net.inet.ip.dummynet.io_fast : No 0
3370 If set to a non-zero value,
3375 operation (see above) is enabled.
3376 .It Va net.inet.ip.dummynet.io_pkt
3377 Number of packets passed to
3379 .It Va net.inet.ip.dummynet.io_pkt_drop
3380 Number of packets dropped by
3382 .It Va net.inet.ip.dummynet.io_pkt_fast
3383 Number of packets bypassed by the
3386 .It Va net.inet.ip.dummynet.max_chain_len : No 16
3387 Target value for the maximum number of pipes/queues in a hash bucket.
3389 .Cm max_chain_len*hash_size
3390 is used to determine the threshold over which empty pipes/queues
3391 will be expired even when
3392 .Cm net.inet.ip.dummynet.expire=0 .
3393 .It Va net.inet.ip.dummynet.red_lookup_depth : No 256
3394 .It Va net.inet.ip.dummynet.red_avg_pkt_size : No 512
3395 .It Va net.inet.ip.dummynet.red_max_pkt_size : No 1500
3396 Parameters used in the computations of the drop probability
3397 for the RED algorithm.
3398 .It Va net.inet.ip.dummynet.pipe_byte_limit : No 1048576
3399 .It Va net.inet.ip.dummynet.pipe_slot_limit : No 100
3400 The maximum queue size that can be specified in bytes or packets.
3401 These limits prevent accidental exhaustion of resources such as mbufs.
3402 If you raise these limits,
3403 you should make sure the system is configured so that sufficient resources
3405 .It Va net.inet.ip.fw.autoinc_step : No 100
3406 Delta between rule numbers when auto-generating them.
3407 The value must be in the range 1..1000.
3408 .It Va net.inet.ip.fw.curr_dyn_buckets : Va net.inet.ip.fw.dyn_buckets
3409 The current number of buckets in the hash table for dynamic rules
3411 .It Va net.inet.ip.fw.debug : No 1
3412 Controls debugging messages produced by
3414 .It Va net.inet.ip.fw.default_rule : No 65535
3415 The default rule number (read-only).
3417 .Nm , the default rule is the last one, so its number
3418 can also serve as the highest number allowed for a rule.
3419 .It Va net.inet.ip.fw.dyn_buckets : No 256
3420 The number of buckets in the hash table for dynamic rules.
3421 Must be a power of 2, up to 65536.
3422 It only takes effect when all dynamic rules have expired, so you
3423 are advised to use a
3425 command to make sure that the hash table is resized.
3426 .It Va net.inet.ip.fw.dyn_count : No 3
3427 Current number of dynamic rules
3429 .It Va net.inet.ip.fw.dyn_keepalive : No 1
3430 Enables generation of keepalive packets for
3432 rules on TCP sessions.
3433 A keepalive is generated to both
3434 sides of the connection every 5 seconds for the last 20
3435 seconds of the lifetime of the rule.
3436 .It Va net.inet.ip.fw.dyn_max : No 8192
3437 Maximum number of dynamic rules.
3438 When you hit this limit, no more dynamic rules can be
3439 installed until old ones expire.
3440 .It Va net.inet.ip.fw.dyn_ack_lifetime : No 300
3441 .It Va net.inet.ip.fw.dyn_syn_lifetime : No 20
3442 .It Va net.inet.ip.fw.dyn_fin_lifetime : No 1
3443 .It Va net.inet.ip.fw.dyn_rst_lifetime : No 1
3444 .It Va net.inet.ip.fw.dyn_udp_lifetime : No 5
3445 .It Va net.inet.ip.fw.dyn_short_lifetime : No 30
3446 These variables control the lifetime, in seconds, of dynamic
3448 Upon the initial SYN exchange the lifetime is kept short,
3449 then increased after both SYN have been seen, then decreased
3450 again during the final FIN exchange or when a RST is received.
3452 .Em dyn_fin_lifetime
3454 .Em dyn_rst_lifetime
3455 must be strictly lower than 5 seconds, the period of
3456 repetition of keepalives.
3457 The firewall enforces that.
3458 .It Va net.inet.ip.fw.dyn_keep_states: No 0
3459 Keep dynamic states on rule/set deletion.
3460 States are relinked to default rule (65535).
3461 This can be handly for ruleset reload.
3462 Turned off by default.
3463 .It Va net.inet.ip.fw.enable : No 1
3464 Enables the firewall.
3465 Setting this variable to 0 lets you run your machine without
3466 firewall even if compiled in.
3467 .It Va net.inet6.ip6.fw.enable : No 1
3468 provides the same functionality as above for the IPv6 case.
3469 .It Va net.inet.ip.fw.one_pass : No 1
3470 When set, the packet exiting from the
3474 node is not passed though the firewall again.
3475 Otherwise, after an action, the packet is
3476 reinjected into the firewall at the next rule.
3477 .It Va net.inet.ip.fw.tables_max : No 128
3478 Maximum number of tables.
3479 .It Va net.inet.ip.fw.verbose : No 1
3480 Enables verbose messages.
3481 .It Va net.inet.ip.fw.verbose_limit : No 0
3482 Limits the number of messages produced by a verbose firewall.
3483 .It Va net.inet6.ip6.fw.deny_unknown_exthdrs : No 1
3484 If enabled packets with unknown IPv6 Extension Headers will be denied.
3485 .It Va net.link.ether.ipfw : No 0
3486 Controls whether layer-2 packets are passed to
3489 .It Va net.link.bridge.ipfw : No 0
3490 Controls whether bridged packets are passed to
3494 .Sh INTERNAL DIAGNOSTICS
3495 There are some commands that may be useful to understand current state
3496 of certain subsystems inside kernel module.
3497 These commands provide debugging output which may change without notice.
3499 Currently the following commands are available as
3502 .Bl -tag -width indent
3504 Lists all interface which are currently tracked by
3506 with their in-kernel status.
3508 List all table lookup algorithms currently available.
3511 There are far too many possible uses of
3513 so this Section will only give a small set of examples.
3515 .Ss BASIC PACKET FILTERING
3516 This command adds an entry which denies all tcp packets from
3517 .Em cracker.evil.org
3518 to the telnet port of
3520 from being forwarded by the host:
3522 .Dl "ipfw add deny tcp from cracker.evil.org to wolf.tambov.su telnet"
3524 This one disallows any connection from the entire cracker's
3527 .Dl "ipfw add deny ip from 123.45.67.0/24 to my.host.org"
3529 A first and efficient way to limit access (not using dynamic rules)
3530 is the use of the following rules:
3532 .Dl "ipfw add allow tcp from any to any established"
3533 .Dl "ipfw add allow tcp from net1 portlist1 to net2 portlist2 setup"
3534 .Dl "ipfw add allow tcp from net3 portlist3 to net3 portlist3 setup"
3536 .Dl "ipfw add deny tcp from any to any"
3538 The first rule will be a quick match for normal TCP packets,
3539 but it will not match the initial SYN packet, which will be
3542 rules only for selected source/destination pairs.
3543 All other SYN packets will be rejected by the final
3547 If you administer one or more subnets, you can take advantage
3548 of the address sets and or-blocks and write extremely
3549 compact rulesets which selectively enable services to blocks
3550 of clients, as below:
3552 .Dl "goodguys=\*q{ 10.1.2.0/24{20,35,66,18} or 10.2.3.0/28{6,3,11} }\*q"
3553 .Dl "badguys=\*q10.1.2.0/24{8,38,60}\*q"
3555 .Dl "ipfw add allow ip from ${goodguys} to any"
3556 .Dl "ipfw add deny ip from ${badguys} to any"
3557 .Dl "... normal policies ..."
3561 option could be used to do automated anti-spoofing by adding the
3562 following to the top of a ruleset:
3564 .Dl "ipfw add deny ip from any to any not verrevpath in"
3566 This rule drops all incoming packets that appear to be coming to the
3567 system on the wrong interface.
3568 For example, a packet with a source
3569 address belonging to a host on a protected internal network would be
3570 dropped if it tried to enter the system from an external interface.
3574 option could be used to do similar but more restricted anti-spoofing
3575 by adding the following to the top of a ruleset:
3577 .Dl "ipfw add deny ip from any to any not antispoof in"
3579 This rule drops all incoming packets that appear to be coming from another
3580 directly connected system but on the wrong interface.
3581 For example, a packet with a source address of
3582 .Li 192.168.0.0/24 ,
3591 option could be used to (re)mark user traffic,
3592 by adding the following to the appropriate place in ruleset:
3594 .Dl "ipfw add setdscp be ip from any to any dscp af11,af21"
3596 In order to protect a site from flood attacks involving fake
3597 TCP packets, it is safer to use dynamic rules:
3599 .Dl "ipfw add check-state"
3600 .Dl "ipfw add deny tcp from any to any established"
3601 .Dl "ipfw add allow tcp from my-net to any setup keep-state"
3603 This will let the firewall install dynamic rules only for
3604 those connection which start with a regular SYN packet coming
3605 from the inside of our network.
3606 Dynamic rules are checked when encountering the first
3615 rule should usually be placed near the beginning of the
3616 ruleset to minimize the amount of work scanning the ruleset.
3617 Your mileage may vary.
3619 To limit the number of connections a user can open
3620 you can use the following type of rules:
3622 .Dl "ipfw add allow tcp from my-net/24 to any setup limit src-addr 10"
3623 .Dl "ipfw add allow tcp from any to me setup limit src-addr 4"
3625 The former (assuming it runs on a gateway) will allow each host
3626 on a /24 network to open at most 10 TCP connections.
3627 The latter can be placed on a server to make sure that a single
3628 client does not use more than 4 simultaneous connections.
3631 stateful rules can be subject to denial-of-service attacks
3632 by a SYN-flood which opens a huge number of dynamic rules.
3633 The effects of such attacks can be partially limited by
3636 variables which control the operation of the firewall.
3638 Here is a good usage of the
3640 command to see accounting records and timestamp information:
3644 or in short form without timestamps:
3648 which is equivalent to:
3652 Next rule diverts all incoming packets from 192.168.2.0/24
3653 to divert port 5000:
3655 .Dl ipfw divert 5000 ip from 192.168.2.0/24 to any in
3657 The following rules show some of the applications of
3661 for simulations and the like.
3663 This rule drops random incoming packets with a probability
3666 .Dl "ipfw add prob 0.05 deny ip from any to any in"
3668 A similar effect can be achieved making use of
3672 .Dl "ipfw add pipe 10 ip from any to any"
3673 .Dl "ipfw pipe 10 config plr 0.05"
3675 We can use pipes to artificially limit bandwidth, e.g.\& on a
3676 machine acting as a router, if we want to limit traffic from
3677 local clients on 192.168.2.0/24 we do:
3679 .Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out"
3680 .Dl "ipfw pipe 1 config bw 300Kbit/s queue 50KBytes"
3682 note that we use the
3684 modifier so that the rule is not used twice.
3685 Remember in fact that
3687 rules are checked both on incoming and outgoing packets.
3689 Should we want to simulate a bidirectional link with bandwidth
3690 limitations, the correct way is the following:
3692 .Dl "ipfw add pipe 1 ip from any to any out"
3693 .Dl "ipfw add pipe 2 ip from any to any in"
3694 .Dl "ipfw pipe 1 config bw 64Kbit/s queue 10Kbytes"
3695 .Dl "ipfw pipe 2 config bw 64Kbit/s queue 10Kbytes"
3697 The above can be very useful, e.g.\& if you want to see how
3698 your fancy Web page will look for a residential user who
3699 is connected only through a slow link.
3700 You should not use only one pipe for both directions, unless
3701 you want to simulate a half-duplex medium (e.g.\& AppleTalk,
3703 It is not necessary that both pipes have the same configuration,
3704 so we can also simulate asymmetric links.
3706 Should we want to verify network performance with the RED queue
3707 management algorithm:
3709 .Dl "ipfw add pipe 1 ip from any to any"
3710 .Dl "ipfw pipe 1 config bw 500Kbit/s queue 100 red 0.002/30/80/0.1"
3712 Another typical application of the traffic shaper is to
3713 introduce some delay in the communication.
3714 This can significantly affect applications which do a lot of Remote
3715 Procedure Calls, and where the round-trip-time of the
3716 connection often becomes a limiting factor much more than
3719 .Dl "ipfw add pipe 1 ip from any to any out"
3720 .Dl "ipfw add pipe 2 ip from any to any in"
3721 .Dl "ipfw pipe 1 config delay 250ms bw 1Mbit/s"
3722 .Dl "ipfw pipe 2 config delay 250ms bw 1Mbit/s"
3724 Per-flow queueing can be useful for a variety of purposes.
3725 A very simple one is counting traffic:
3727 .Dl "ipfw add pipe 1 tcp from any to any"
3728 .Dl "ipfw add pipe 1 udp from any to any"
3729 .Dl "ipfw add pipe 1 ip from any to any"
3730 .Dl "ipfw pipe 1 config mask all"
3732 The above set of rules will create queues (and collect
3733 statistics) for all traffic.
3734 Because the pipes have no limitations, the only effect is
3735 collecting statistics.
3736 Note that we need 3 rules, not just the last one, because
3739 tries to match IP packets it will not consider ports, so we
3740 would not see connections on separate ports as different
3743 A more sophisticated example is limiting the outbound traffic
3744 on a net with per-host limits, rather than per-network limits:
3746 .Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out"
3747 .Dl "ipfw add pipe 2 ip from any to 192.168.2.0/24 in"
3748 .Dl "ipfw pipe 1 config mask src-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
3749 .Dl "ipfw pipe 2 config mask dst-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
3751 In the following example, we need to create several traffic bandwidth
3752 classes and we need different hosts/networks to fall into different classes.
3753 We create one pipe for each class and configure them accordingly.
3754 Then we create a single table and fill it with IP subnets and addresses.
3755 For each subnet/host we set the argument equal to the number of the pipe
3757 Then we classify traffic using a single rule:
3759 .Dl "ipfw pipe 1 config bw 1000Kbyte/s"
3760 .Dl "ipfw pipe 4 config bw 4000Kbyte/s"
3762 .Dl "ipfw table T1 create type addr"
3763 .Dl "ipfw table T1 add 192.168.2.0/24 1"
3764 .Dl "ipfw table T1 add 192.168.0.0/27 4"
3765 .Dl "ipfw table T1 add 192.168.0.2 1"
3767 .Dl "ipfw add pipe tablearg ip from 'table(T1)' to any"
3771 action, the table entries may include hostnames and IP addresses.
3773 .Dl "ipfw table T2 create type addr ftype ip"
3774 .Dl "ipfw table T2 add 192.168.2.0/24 10.23.2.1"
3775 .Dl "ipfw table T21 add 192.168.0.0/27 router1.dmz"
3777 .Dl "ipfw add 100 fwd tablearg ip from any to table(1)"
3779 In the following example per-interface firewall is created:
3781 .Dl "ipfw table IN create type iface valtype skipto,fib"
3782 .Dl "ipfw table IN add vlan20 12000,12"
3783 .Dl "ipfw table IN add vlan30 13000,13"
3784 .Dl "ipfw table OUT create type iface valtype skipto"
3785 .Dl "ipfw table OUT add vlan20 22000"
3786 .Dl "ipfw table OUT add vlan30 23000"
3788 .Dl "ipfw add 100 ipfw setfib tablearg ip from any to any recv 'table(IN)' in"
3789 .Dl "ipfw add 200 ipfw skipto tablearg ip from any to any recv 'table(IN)' in"
3790 .Dl "ipfw add 300 ipfw skipto tablearg ip from any to any xmit 'table(OUT)' out"
3792 The following example illustrate usage of flow tables:
3794 .Dl "ipfw table fl create type flow:flow:src-ip,proto,dst-ip,dst-port"
3795 .Dl "ipfw table fl add 2a02:6b8:77::88,tcp,2a02:6b8:77::99,80 11"
3796 .Dl "ipfw table fl add 10.0.0.1,udp,10.0.0.2,53 12"
3798 .Dl "ipfw add 100 allow ip from any to any flow 'table(fl,11)' recv ix0"
3800 To add a set of rules atomically, e.g.\& set 18:
3802 .Dl "ipfw set disable 18"
3803 .Dl "ipfw add NN set 18 ... # repeat as needed"
3804 .Dl "ipfw set enable 18"
3806 To delete a set of rules atomically the command is simply:
3808 .Dl "ipfw delete set 18"
3810 To test a ruleset and disable it and regain control if something goes wrong:
3812 .Dl "ipfw set disable 18"
3813 .Dl "ipfw add NN set 18 ... # repeat as needed"
3814 .Dl "ipfw set enable 18; echo done; sleep 30 && ipfw set disable 18"
3816 Here if everything goes well, you press control-C before the "sleep"
3817 terminates, and your ruleset will be left active.
3818 Otherwise, e.g.\& if
3819 you cannot access your box, the ruleset will be disabled after
3820 the sleep terminates thus restoring the previous situation.
3822 To show rules of the specific set:
3824 .Dl "ipfw set 18 show"
3826 To show rules of the disabled set:
3828 .Dl "ipfw -S set 18 show"
3830 To clear a specific rule counters of the specific set:
3832 .Dl "ipfw set 18 zero NN"
3834 To delete a specific rule of the specific set:
3836 .Dl "ipfw set 18 delete NN"
3837 .Ss NAT, REDIRECT AND LSNAT
3838 First redirect all the traffic to nat instance 123:
3840 .Dl "ipfw add nat 123 all from any to any"
3842 Then to configure nat instance 123 to alias all the outgoing traffic with ip
3843 192.168.0.123, blocking all incoming connections, trying to keep
3844 same ports on both sides, clearing aliasing table on address change
3845 and keeping a log of traffic/link statistics:
3847 .Dl "ipfw nat 123 config ip 192.168.0.123 log deny_in reset same_ports"
3849 Or to change address of instance 123, aliasing table will be cleared (see
3852 .Dl "ipfw nat 123 config ip 10.0.0.1"
3854 To see configuration of nat instance 123:
3856 .Dl "ipfw nat 123 show config"
3858 To show logs of all the instances in range 111-999:
3860 .Dl "ipfw nat 111-999 show"
3862 To see configurations of all instances:
3864 .Dl "ipfw nat show config"
3866 Or a redirect rule with mixed modes could looks like:
3868 .Dl "ipfw nat 123 config redirect_addr 10.0.0.1 10.0.0.66"
3869 .Dl " redirect_port tcp 192.168.0.1:80 500"
3870 .Dl " redirect_proto udp 192.168.1.43 192.168.1.1"
3871 .Dl " redirect_addr 192.168.0.10,192.168.0.11"
3872 .Dl " 10.0.0.100 # LSNAT"
3873 .Dl " redirect_port tcp 192.168.0.1:80,192.168.0.10:22"
3876 or it could be split in:
3878 .Dl "ipfw nat 1 config redirect_addr 10.0.0.1 10.0.0.66"
3879 .Dl "ipfw nat 2 config redirect_port tcp 192.168.0.1:80 500"
3880 .Dl "ipfw nat 3 config redirect_proto udp 192.168.1.43 192.168.1.1"
3881 .Dl "ipfw nat 4 config redirect_addr 192.168.0.10,192.168.0.11,192.168.0.12"
3883 .Dl "ipfw nat 5 config redirect_port tcp"
3884 .Dl " 192.168.0.1:80,192.168.0.10:22,192.168.0.20:25 500"
3905 utility first appeared in
3910 Stateful extensions were introduced in
3913 was introduced in Summer 2002.
3915 .An Ugen J. S. Antsilevich ,
3916 .An Poul-Henning Kamp ,
3922 API based upon code written by
3926 Dummynet has been introduced by Luigi Rizzo in 1997-1998.
3928 Some early work (1999-2000) on the
3930 traffic shaper supported by Akamba Corp.
3932 The ipfw core (ipfw2) has been completely redesigned and
3933 reimplemented by Luigi Rizzo in summer 2002.
3936 options have been added by various developer over the years.
3939 In-kernel NAT support written by
3940 .An Paolo Pisati Aq Mt piso@FreeBSD.org
3941 as part of a Summer of Code 2005 project.
3945 support has been developed by
3946 .An The Centre for Advanced Internet Architectures (CAIA) Aq http://www.caia.swin.edu.au .
3947 The primary developers and maintainers are David Hayes and Jason But.
3948 For further information visit:
3949 .Aq http://www.caia.swin.edu.au/urp/SONATA
3951 Delay profiles have been developed by Alessandro Cerri and
3952 Luigi Rizzo, supported by the
3953 European Commission within Projects Onelab and Onelab2.
3955 The syntax has grown over the years and sometimes it might be confusing.
3956 Unfortunately, backward compatibility prevents cleaning up mistakes
3957 made in the definition of the syntax.
3961 Misconfiguring the firewall can put your computer in an unusable state,
3962 possibly shutting down network services and requiring console access to
3963 regain control of it.
3965 Incoming packet fragments diverted by
3967 are reassembled before delivery to the socket.
3968 The action used on those packet is the one from the
3969 rule which matches the first fragment of the packet.
3971 Packets diverted to userland, and then reinserted by a userland process
3972 may lose various packet attributes.
3973 The packet source interface name
3974 will be preserved if it is shorter than 8 bytes and the userland process
3975 saves and reuses the sockaddr_in
3978 otherwise, it may be lost.
3979 If a packet is reinserted in this manner, later rules may be incorrectly
3980 applied, making the order of
3982 rules in the rule sequence very important.
3984 Dummynet drops all packets with IPv6 link-local addresses.
3990 may not behave as expected.
3991 In particular, incoming SYN packets may
3992 have no uid or gid associated with them since they do not yet belong
3993 to a TCP connection, and the uid/gid associated with a packet may not
3994 be as expected if the associated process calls
3996 or similar system calls.
3998 Rule syntax is subject to the command line environment and some patterns
3999 may need to be escaped with the backslash character
4000 or quoted appropriately.
4002 Due to the architecture of
4004 ipfw nat is not compatible with the TCP segmentation offloading (TSO).
4005 Thus, to reliably nat your network traffic, please disable TSO
4009 ICMP error messages are not implicitly matched by dynamic rules
4010 for the respective conversations.
4011 To avoid failures of network error detection and path MTU discovery,
4012 ICMP error messages may need to be allowed explicitly through static
4019 actions may lead to confusing behaviour if ruleset has mistakes,
4020 and/or interaction with other subsystems (netgraph, dummynet, etc.) is used.
4021 One possible case for this is packet leaving
4023 in subroutine on the input pass, while later on output encountering unpaired
4026 As the call stack is kept intact after input pass, packet will suddenly
4027 return to the rule number used on input pass, not on output one.
4028 Order of processing should be checked carefully to avoid such mistakes.
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