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
57 .Oo Cm set Ar N Oc Cm table Ar name Cm modify Ar modify-options
59 .Oo Cm set Ar N Oc Cm table Ar name Cm swap Ar name
61 .Oo Cm set Ar N Oc Cm table Ar name Cm add Ar table-key Op Ar value
63 .Oo Cm set Ar N Oc Cm table Ar name Cm add Op Ar table-key Ar value ...
65 .Oo Cm set Ar N Oc Cm table Ar name Cm atomic add Op Ar table-key Ar value ...
67 .Oo Cm set Ar N Oc Cm table Ar name Cm delete Op Ar table-key ...
69 .Oo Cm set Ar N Oc Cm table Ar name Cm lookup Ar addr
71 .Oo Cm set Ar N Oc Cm table Ar name Cm lock
73 .Oo Cm set Ar N Oc Cm table Ar name Cm unlock
75 .Oo Cm set Ar N Oc Cm table
79 .Oo Cm set Ar N Oc Cm table
83 .Oo Cm set Ar N Oc Cm table
87 .Oo Cm set Ar N Oc Cm table
90 .Ss DUMMYNET CONFIGURATION (TRAFFIC SHAPER AND PACKET SCHEDULER)
92 .Brq Cm pipe | queue | sched
98 .Brq Cm pipe | queue | sched
99 .Brq Cm delete | list | show
118 .Ss STATEFUL IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
120 .Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm create Ar create-options
122 .Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm config Ar config-options
124 .Oo Cm set Ar N Oc Cm nat64lsn
129 .Oo Cm set Ar N Oc Cm nat64lsn
133 .Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm stats Op Cm reset
134 .Ss STATELESS IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
136 .Oo Cm set Ar N Oc Cm nat64stl Ar name Cm create Ar create-options
138 .Oo Cm set Ar N Oc Cm nat64stl Ar name Cm config Ar config-options
140 .Oo Cm set Ar N Oc Cm nat64stl
144 .Oo Cm set Ar N Oc Cm nat64stl
148 .Oo Cm set Ar N Oc Cm nat64stl Ar name Cm stats Op Cm reset
149 .Ss IPv6-to-IPv6 NETWORK PREFIX TRANSLATION
151 .Oo Cm set Ar N Oc Cm nptv6 Ar name Cm create Ar create-options
153 .Oo Cm set Ar N Oc Cm nptv6
157 .Oo Cm set Ar N Oc Cm nptv6
161 .Oo Cm set Ar N Oc Cm nptv6 Ar name Cm stats Op Cm reset
162 .Ss INTERNAL DIAGNOSTICS
172 utility is the user interface for controlling the
176 traffic shaper/packet scheduler, and the
177 in-kernel NAT services.
179 A firewall configuration, or
183 numbered from 1 to 65535.
184 Packets are passed to the firewall
185 from a number of different places in the protocol stack
186 (depending on the source and destination of the packet,
187 it is possible for the firewall to be
188 invoked multiple times on the same packet).
189 The packet passed to the firewall is compared
190 against each of the rules in the
193 (multiple rules with the same number are permitted, in which case
194 they are processed in order of insertion).
195 When a match is found, the action corresponding to the
196 matching rule is performed.
198 Depending on the action and certain system settings, packets
199 can be reinjected into the firewall at some rule after the
200 matching one for further processing.
202 A ruleset always includes a
204 rule (numbered 65535) which cannot be modified or deleted,
205 and matches all packets.
206 The action associated with the
212 depending on how the kernel is configured.
214 If the ruleset includes one or more rules with the
219 the firewall will have a
221 behaviour, i.e., upon a match it will create
223 i.e., rules that match packets with the same 5-tuple
224 (protocol, source and destination addresses and ports)
225 as the packet which caused their creation.
226 Dynamic rules, which have a limited lifetime, are checked
227 at the first occurrence of a
232 rule, and are typically used to open the firewall on-demand to
233 legitimate traffic only.
235 .Sx STATEFUL FIREWALL
238 Sections below for more information on the stateful behaviour of
241 All rules (including dynamic ones) have a few associated counters:
242 a packet count, a byte count, a log count and a timestamp
243 indicating the time of the last match.
244 Counters can be displayed or reset with
248 Each rule belongs to one of 32 different
252 commands to atomically manipulate sets, such as enable,
253 disable, swap sets, move all rules in a set to another
254 one, delete all rules in a set.
255 These can be useful to
256 install temporary configurations, or to test them.
259 for more information on
262 Rules can be added with the
264 command; deleted individually or in groups with the
266 command, and globally (except those in set 31) with the
268 command; displayed, optionally with the content of the
274 Finally, counters can be reset with the
281 The following general options are available when invoking
283 .Bl -tag -width indent
285 Show counter values when listing rules.
288 command implies this option.
290 Only show the action and the comment, not the body of a rule.
294 When entering or showing rules, print them in compact form,
295 i.e., omitting the "ip from any to any" string
296 when this does not carry any additional information.
298 When listing, show dynamic rules in addition to static ones.
302 is specified, also show expired dynamic rules.
304 Do not ask for confirmation for commands that can cause problems
307 If there is no tty associated with the process, this is implied.
309 When listing a table (see the
311 section below for more information on lookup tables), format values
313 By default, values are shown as integers.
315 Only check syntax of the command strings, without actually passing
318 Try to resolve addresses and service names in output.
320 Be quiet when executing the
330 This is useful when updating rulesets by executing multiple
334 .Ql sh\ /etc/rc.firewall ) ,
335 or by processing a file with many
337 rules across a remote login session.
338 It also stops a table add or delete
339 from failing if the entry already exists or is not present.
341 The reason why this option may be important is that
342 for some of these actions,
344 may print a message; if the action results in blocking the
345 traffic to the remote client,
346 the remote login session will be closed
347 and the rest of the ruleset will not be processed.
348 Access to the console would then be required to recover.
350 When listing rules, show the
352 each rule belongs to.
353 If this flag is not specified, disabled rules will not be
356 When listing pipes, sort according to one of the four
357 counters (total or current packets or bytes).
359 When listing, show last match timestamp converted with ctime().
361 When listing, show last match timestamp as seconds from the epoch.
362 This form can be more convenient for postprocessing by scripts.
364 .Ss LIST OF RULES AND PREPROCESSING
365 To ease configuration, rules can be put into a file which is
368 as shown in the last synopsis line.
372 The file will be read line by line and applied as arguments to the
376 Optionally, a preprocessor can be specified using
380 is to be piped through.
381 Useful preprocessors include
387 does not start with a slash
389 as its first character, the usual
391 name search is performed.
392 Care should be taken with this in environments where not all
393 file systems are mounted (yet) by the time
395 is being run (e.g.\& when they are mounted over NFS).
398 has been specified, any additional arguments are passed on to the preprocessor
400 This allows for flexible configuration files (like conditionalizing
401 them on the local hostname) and the use of macros to centralize
402 frequently required arguments like IP addresses.
403 .Ss TRAFFIC SHAPER CONFIGURATION
409 commands are used to configure the traffic shaper and packet scheduler.
411 .Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
412 Section below for details.
414 If the world and the kernel get out of sync the
416 ABI may break, preventing you from being able to add any rules.
417 This can adversely affect the booting process.
422 to temporarily disable the firewall to regain access to the network,
423 allowing you to fix the problem.
425 A packet is checked against the active ruleset in multiple places
426 in the protocol stack, under control of several sysctl variables.
427 These places and variables are shown below, and it is important to
428 have this picture in mind in order to design a correct ruleset.
429 .Bd -literal -offset indent
432 +----------->-----------+
434 [ip(6)_input] [ip(6)_output] net.inet(6).ip(6).fw.enable=1
437 [ether_demux] [ether_output_frame] net.link.ether.ipfw=1
439 +-->--[bdg_forward]-->--+ net.link.bridge.ipfw=1
445 times the same packet goes through the firewall can
446 vary between 0 and 4 depending on packet source and
447 destination, and system configuration.
449 Note that as packets flow through the stack, headers can be
450 stripped or added to it, and so they may or may not be available
452 E.g., incoming packets will include the MAC header when
456 but the same packets will have the MAC header stripped off when
463 Also note that each packet is always checked against the complete ruleset,
464 irrespective of the place where the check occurs, or the source of the packet.
465 If a rule contains some match patterns or actions which are not valid
466 for the place of invocation (e.g.\& trying to match a MAC header within
470 the match pattern will not match, but a
472 operator in front of such patterns
476 match on those packets.
477 It is thus the responsibility of
478 the programmer, if necessary, to write a suitable ruleset to
479 differentiate among the possible places.
481 rules can be useful here, as an example:
482 .Bd -literal -offset indent
483 # packets from ether_demux or bdg_forward
484 ipfw add 10 skipto 1000 all from any to any layer2 in
485 # packets from ip_input
486 ipfw add 10 skipto 2000 all from any to any not layer2 in
487 # packets from ip_output
488 ipfw add 10 skipto 3000 all from any to any not layer2 out
489 # packets from ether_output_frame
490 ipfw add 10 skipto 4000 all from any to any layer2 out
493 (yes, at the moment there is no way to differentiate between
494 ether_demux and bdg_forward).
496 In general, each keyword or argument must be provided as
497 a separate command line argument, with no leading or trailing
499 Keywords are case-sensitive, whereas arguments may
500 or may not be case-sensitive depending on their nature
501 (e.g.\& uid's are, hostnames are not).
503 Some arguments (e.g., port or address lists) are comma-separated
505 In this case, spaces after commas ',' are allowed to make
506 the line more readable.
507 You can also put the entire
508 command (including flags) into a single argument.
509 E.g., the following forms are equivalent:
510 .Bd -literal -offset indent
511 ipfw -q add deny src-ip 10.0.0.0/24,127.0.0.1/8
512 ipfw -q add deny src-ip 10.0.0.0/24, 127.0.0.1/8
513 ipfw "-q add deny src-ip 10.0.0.0/24, 127.0.0.1/8"
516 The format of firewall rules is the following:
517 .Bd -ragged -offset indent
520 .Op Cm set Ar set_number
521 .Op Cm prob Ar match_probability
523 .Op Cm log Op Cm logamount Ar number
533 where the body of the rule specifies which information is used
534 for filtering packets, among the following:
536 .Bl -tag -width "Source and dest. addresses and ports" -offset XXX -compact
537 .It Layer-2 header fields
539 .It IPv4 and IPv6 Protocol
541 .It Source and dest. addresses and ports
545 .It Transmit and receive interface
547 .It Misc. IP header fields
548 Version, type of service, datagram length, identification,
549 fragment flag (non-zero IP offset),
552 .It IPv6 Extension headers
553 Fragmentation, Hop-by-Hop options,
554 Routing Headers, Source routing rthdr0, Mobile IPv6 rthdr2, IPSec options.
556 .It Misc. TCP header fields
557 TCP flags (SYN, FIN, ACK, RST, etc.),
558 sequence number, acknowledgment number,
566 When the packet can be associated with a local socket.
568 Whether a packet came from a divert socket (e.g.,
570 .It Fib annotation state
571 Whether a packet has been tagged for using a specific FIB (routing table)
572 in future forwarding decisions.
575 Note that some of the above information, e.g.\& source MAC or IP addresses and
576 TCP/UDP ports, can be easily spoofed, so filtering on those fields
577 alone might not guarantee the desired results.
578 .Bl -tag -width indent
580 Each rule is associated with a
582 in the range 1..65535, with the latter reserved for the
585 Rules are checked sequentially by rule number.
586 Multiple rules can have the same number, in which case they are
587 checked (and listed) according to the order in which they have
589 If a rule is entered without specifying a number, the kernel will
590 assign one in such a way that the rule becomes the last one
594 Automatic rule numbers are assigned by incrementing the last
595 non-default rule number by the value of the sysctl variable
596 .Ar net.inet.ip.fw.autoinc_step
597 which defaults to 100.
598 If this is not possible (e.g.\& because we would go beyond the
599 maximum allowed rule number), the number of the last
600 non-default value is used instead.
601 .It Cm set Ar set_number
602 Each rule is associated with a
605 Sets can be individually disabled and enabled, so this parameter
606 is of fundamental importance for atomic ruleset manipulation.
607 It can be also used to simplify deletion of groups of rules.
608 If a rule is entered without specifying a set number,
611 Set 31 is special in that it cannot be disabled,
612 and rules in set 31 are not deleted by the
614 command (but you can delete them with the
615 .Nm ipfw delete set 31
617 Set 31 is also used for the
620 .It Cm prob Ar match_probability
621 A match is only declared with the specified probability
622 (floating point number between 0 and 1).
623 This can be useful for a number of applications such as
624 random packet drop or
627 to simulate the effect of multiple paths leading to out-of-order
630 Note: this condition is checked before any other condition, including
631 ones such as keep-state or check-state which might have side effects.
632 .It Cm log Op Cm logamount Ar number
633 Packets matching a rule with the
635 keyword will be made available for logging in two ways:
636 if the sysctl variable
637 .Va net.inet.ip.fw.verbose
638 is set to 0 (default), one can use
643 This pseudo interface can be created after a boot
644 manually by using the following command:
645 .Bd -literal -offset indent
646 # ifconfig ipfw0 create
649 Or, automatically at boot time by adding the following
653 .Bd -literal -offset indent
657 There is no overhead if no
659 is attached to the pseudo interface.
662 .Va net.inet.ip.fw.verbose
663 is set to 1, packets will be logged to
667 facility up to a maximum of
672 is specified, the limit is taken from the sysctl variable
673 .Va net.inet.ip.fw.verbose_limit .
674 In both cases, a value of 0 means unlimited logging.
676 Once the limit is reached, logging can be re-enabled by
677 clearing the logging counter or the packet counter for that entry, see the
681 Note: logging is done after all other packet matching conditions
682 have been successfully verified, and before performing the final
683 action (accept, deny, etc.) on the packet.
685 When a packet matches a rule with the
687 keyword, the numeric tag for the given
689 in the range 1..65534 will be attached to the packet.
690 The tag acts as an internal marker (it is not sent out over
691 the wire) that can be used to identify these packets later on.
692 This can be used, for example, to provide trust between interfaces
693 and to start doing policy-based filtering.
694 A packet can have multiple tags at the same time.
695 Tags are "sticky", meaning once a tag is applied to a packet by a
696 matching rule it exists until explicit removal.
697 Tags are kept with the packet everywhere within the kernel, but are
698 lost when packet leaves the kernel, for example, on transmitting
699 packet out to the network or sending packet to a
703 To check for previously applied tags, use the
706 To delete previously applied tag, use the
710 Note: since tags are kept with the packet everywhere in kernelspace,
711 they can be set and unset anywhere in the kernel network subsystem
714 facility), not only by means of the
720 For example, there can be a specialized
722 node doing traffic analyzing and tagging for later inspecting
724 .It Cm untag Ar number
725 When a packet matches a rule with the
727 keyword, the tag with the number
729 is searched among the tags attached to this packet and,
730 if found, removed from it.
731 Other tags bound to packet, if present, are left untouched.
733 When a packet matches a rule with the
735 keyword, the ALTQ identifier for the given
740 Note that this ALTQ tag is only meaningful for packets going "out" of IPFW,
741 and not being rejected or going to divert sockets.
742 Note that if there is insufficient memory at the time the packet is
743 processed, it will not be tagged, so it is wise to make your ALTQ
744 "default" queue policy account for this.
747 rules match a single packet, only the first one adds the ALTQ classification
749 In doing so, traffic may be shaped by using
750 .Cm count Cm altq Ar queue
751 rules for classification early in the ruleset, then later applying
752 the filtering decision.
757 rules may come later and provide the actual filtering decisions in
758 addition to the fallback ALTQ tag.
762 to set up the queues before IPFW will be able to look them up by name,
763 and if the ALTQ disciplines are rearranged, the rules in containing the
764 queue identifiers in the kernel will likely have gone stale and need
766 Stale queue identifiers will probably result in misclassification.
768 All system ALTQ processing can be turned on or off via
773 .Cm disable Ar altq .
775 .Va net.inet.ip.fw.one_pass
776 is irrelevant to ALTQ traffic shaping, as the actual rule action is followed
777 always after adding an ALTQ tag.
780 A rule can be associated with one of the following actions, which
781 will be executed when the packet matches the body of the rule.
782 .Bl -tag -width indent
783 .It Cm allow | accept | pass | permit
784 Allow packets that match rule.
785 The search terminates.
786 .It Cm check-state Op Ar :flowname | Cm :any
787 Checks the packet against the dynamic ruleset.
788 If a match is found, execute the action associated with
789 the rule which generated this dynamic rule, otherwise
790 move to the next rule.
793 rules do not have a body.
796 rule is found, the dynamic ruleset is checked at the first
803 is symbolic name assigned to dynamic rule by
808 can be used to ignore states flowname when matching.
811 keyword is special name used for compatibility with old rulesets.
813 Update counters for all packets that match rule.
814 The search continues with the next rule.
816 Discard packets that match this rule.
817 The search terminates.
818 .It Cm divert Ar port
819 Divert packets that match this rule to the
823 The search terminates.
824 .It Cm fwd | forward Ar ipaddr | tablearg Ns Op , Ns Ar port
825 Change the next-hop on matching packets to
827 which can be an IP address or a host name.
828 For IPv4, the next hop can also be supplied by the last table
829 looked up for the packet by using the
831 keyword instead of an explicit address.
832 The search terminates if this rule matches.
836 is a local address, then matching packets will be forwarded to
838 (or the port number in the packet if one is not specified in the rule)
839 on the local machine.
843 is not a local address, then the port number
844 (if specified) is ignored, and the packet will be
845 forwarded to the remote address, using the route as found in
846 the local routing table for that IP.
850 rule will not match layer-2 packets (those received
851 on ether_input, ether_output, or bridged).
855 action does not change the contents of the packet at all.
856 In particular, the destination address remains unmodified, so
857 packets forwarded to another system will usually be rejected by that system
858 unless there is a matching rule on that system to capture them.
859 For packets forwarded locally,
860 the local address of the socket will be
861 set to the original destination address of the packet.
864 entry look rather weird but is intended for
865 use with transparent proxy servers.
866 .It Cm nat Ar nat_nr | tablearg
869 (for network address translation, address redirect, etc.):
871 .Sx NETWORK ADDRESS TRANSLATION (NAT)
872 Section for further information.
873 .It Cm nat64lsn Ar name
874 Pass packet to a stateful NAT64 instance (for IPv6/IPv4 network address and
875 protocol translation): see the
876 .Sx IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
877 Section for further information.
878 .It Cm nat64stl Ar name
879 Pass packet to a stateless NAT64 instance (for IPv6/IPv4 network address and
880 protocol translation): see the
881 .Sx IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
882 Section for further information.
884 Pass packet to a NPTv6 instance (for IPv6-to-IPv6 network prefix translation):
886 .Sx IPv6-to-IPv6 NETWORK PREFIX TRANSLATION (NPTv6)
887 Section for further information.
888 .It Cm pipe Ar pipe_nr
892 (for bandwidth limitation, delay, etc.).
894 .Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
895 Section for further information.
896 The search terminates; however, on exit from the pipe and if
900 .Va net.inet.ip.fw.one_pass
901 is not set, the packet is passed again to the firewall code
902 starting from the next rule.
903 .It Cm queue Ar queue_nr
907 (for bandwidth limitation using WF2Q+).
913 Discard packets that match this rule, and if the
914 packet is a TCP packet, try to send a TCP reset (RST) notice.
915 The search terminates.
917 Discard packets that match this rule, and if the
918 packet is a TCP packet, try to send a TCP reset (RST) notice.
919 The search terminates.
920 .It Cm skipto Ar number | tablearg
921 Skip all subsequent rules numbered less than
923 The search continues with the first rule numbered
926 It is possible to use the
928 keyword with a skipto for a
930 skipto. Skipto may work either in O(log(N)) or in O(1) depending
931 on amount of memory and/or sysctl variables.
934 section for more details.
935 .It Cm call Ar number | tablearg
936 The current rule number is saved in the internal stack and
937 ruleset processing continues with the first rule numbered
940 If later a rule with the
942 action is encountered, the processing returns to the first rule
945 rule plus one or higher
946 (the same behaviour as with packets returning from
951 This could be used to make somewhat like an assembly language
953 calls to rules with common checks for different interfaces, etc.
955 Rule with any number could be called, not just forward jumps as with
957 So, to prevent endless loops in case of mistakes, both
961 actions don't do any jumps and simply go to the next rule if memory
962 cannot be allocated or stack overflowed/underflowed.
964 Internally stack for rule numbers is implemented using
966 facility and currently has size of 16 entries.
967 As mbuf tags are lost when packet leaves the kernel,
969 should not be used in subroutines to avoid endless loops
970 and other undesired effects.
972 Takes rule number saved to internal stack by the last
974 action and returns ruleset processing to the first rule
975 with number greater than number of corresponding
978 See description of the
980 action for more details.
986 and thus are unconditional, but
988 command-line utility currently requires every action except
991 While it is sometimes useful to return only on some packets,
992 usually you want to print just
995 A workaround for this is to use new syntax and
998 .Bd -literal -offset indent
999 # Add a rule without actual body
1000 ipfw add 2999 return via any
1002 # List rules without "from any to any" part
1006 This cosmetic annoyance may be fixed in future releases.
1008 Send a copy of packets matching this rule to the
1010 socket bound to port
1012 The search continues with the next rule.
1013 .It Cm unreach Ar code
1014 Discard packets that match this rule, and try to send an ICMP
1015 unreachable notice with code
1019 is a number from 0 to 255, or one of these aliases:
1020 .Cm net , host , protocol , port ,
1021 .Cm needfrag , srcfail , net-unknown , host-unknown ,
1022 .Cm isolated , net-prohib , host-prohib , tosnet ,
1023 .Cm toshost , filter-prohib , host-precedence
1025 .Cm precedence-cutoff .
1026 The search terminates.
1027 .It Cm unreach6 Ar code
1028 Discard packets that match this rule, and try to send an ICMPv6
1029 unreachable notice with code
1033 is a number from 0, 1, 3 or 4, or one of these aliases:
1034 .Cm no-route, admin-prohib, address
1037 The search terminates.
1038 .It Cm netgraph Ar cookie
1039 Divert packet into netgraph with given
1041 The search terminates.
1042 If packet is later returned from netgraph it is either
1043 accepted or continues with the next rule, depending on
1044 .Va net.inet.ip.fw.one_pass
1046 .It Cm ngtee Ar cookie
1047 A copy of packet is diverted into netgraph, original
1048 packet continues with the next rule.
1051 for more information on
1056 .It Cm setfib Ar fibnum | tablearg
1057 The packet is tagged so as to use the FIB (routing table)
1059 in any subsequent forwarding decisions.
1060 In the current implementation, this is limited to the values 0 through 15, see
1062 Processing continues at the next rule.
1063 It is possible to use the
1065 keyword with setfib.
1066 If the tablearg value is not within the compiled range of fibs,
1067 the packet's fib is set to 0.
1068 .It Cm setdscp Ar DSCP | number | tablearg
1069 Set specified DiffServ codepoint for an IPv4/IPv6 packet.
1070 Processing continues at the next rule.
1071 Supported values are:
1117 Additionally, DSCP value can be specified by number (0..64).
1118 It is also possible to use the
1120 keyword with setdscp.
1121 If the tablearg value is not within the 0..64 range, lower 6 bits of supplied
1123 .It Cm tcp-setmss Ar mss
1124 Set the Maximum Segment Size (MSS) in the TCP segment to value
1128 should be loaded or kernel should have
1129 .Cm options IPFIREWALL_PMOD
1130 to be able use this action.
1131 This command does not change a packet if original MSS value is lower than
1133 Both TCP over IPv4 and over IPv6 are supported.
1134 Regardless of matched a packet or not by the
1136 rule, the search continues with the next rule.
1138 Queue and reassemble IP fragments.
1139 If the packet is not fragmented, counters are updated and
1140 processing continues with the next rule.
1141 If the packet is the last logical fragment, the packet is reassembled and, if
1142 .Va net.inet.ip.fw.one_pass
1143 is set to 0, processing continues with the next rule.
1144 Otherwise, the packet is allowed to pass and the search terminates.
1145 If the packet is a fragment in the middle of a logical group of fragments,
1147 processing stops immediately.
1149 Fragment handling can be tuned via
1150 .Va net.inet.ip.maxfragpackets
1152 .Va net.inet.ip.maxfragsperpacket
1153 which limit, respectively, the maximum number of processable
1154 fragments (default: 800) and
1155 the maximum number of fragments per packet (default: 16).
1157 NOTA BENE: since fragments do not contain port numbers,
1158 they should be avoided with the
1161 Alternatively, direction-based (like
1165 ) and source-based (like
1167 ) match patterns can be used to select fragments.
1169 Usually a simple rule like:
1170 .Bd -literal -offset indent
1171 # reassemble incoming fragments
1172 ipfw add reass all from any to any in
1175 is all you need at the beginning of your ruleset.
1178 The body of a rule contains zero or more patterns (such as
1179 specific source and destination addresses or ports,
1180 protocol options, incoming or outgoing interfaces, etc.)
1181 that the packet must match in order to be recognised.
1182 In general, the patterns are connected by (implicit)
1184 operators -- i.e., all must match in order for the
1186 Individual patterns can be prefixed by the
1188 operator to reverse the result of the match, as in
1190 .Dl "ipfw add 100 allow ip from not 1.2.3.4 to any"
1192 Additionally, sets of alternative match patterns
1194 can be constructed by putting the patterns in
1195 lists enclosed between parentheses ( ) or braces { }, and
1198 operator as follows:
1200 .Dl "ipfw add 100 allow ip from { x or not y or z } to any"
1202 Only one level of parentheses is allowed.
1203 Beware that most shells have special meanings for parentheses
1204 or braces, so it is advisable to put a backslash \\ in front of them
1205 to prevent such interpretations.
1207 The body of a rule must in general include a source and destination
1211 can be used in various places to specify that the content of
1212 a required field is irrelevant.
1214 The rule body has the following format:
1215 .Bd -ragged -offset indent
1216 .Op Ar proto Cm from Ar src Cm to Ar dst
1220 The first part (proto from src to dst) is for backward
1221 compatibility with earlier versions of
1225 any match pattern (including MAC headers, IP protocols,
1226 addresses and ports) can be specified in the
1230 Rule fields have the following meaning:
1231 .Bl -tag -width indent
1232 .It Ar proto : protocol | Cm { Ar protocol Cm or ... }
1233 .It Ar protocol : Oo Cm not Oc Ar protocol-name | protocol-number
1234 An IP protocol specified by number or name
1235 (for a complete list see
1236 .Pa /etc/protocols ) ,
1237 or one of the following keywords:
1238 .Bl -tag -width indent
1240 Matches IPv4 packets.
1242 Matches IPv6 packets.
1251 option will be treated as inner protocol.
1259 .Cm { Ar protocol Cm or ... }
1262 is provided for convenience only but its use is deprecated.
1263 .It Ar src No and Ar dst : Bro Cm addr | Cm { Ar addr Cm or ... } Brc Op Oo Cm not Oc Ar ports
1264 An address (or a list, see below)
1265 optionally followed by
1271 with multiple addresses) is provided for convenience only and
1272 its use is discouraged.
1273 .It Ar addr : Oo Cm not Oc Bro
1274 .Cm any | me | me6 |
1275 .Cm table Ns Pq Ar name Ns Op , Ns Ar value
1276 .Ar | addr-list | addr-set
1278 .Bl -tag -width indent
1280 matches any IP address.
1282 matches any IP address configured on an interface in the system.
1284 matches any IPv6 address configured on an interface in the system.
1285 The address list is evaluated at the time the packet is
1287 .It Cm table Ns Pq Ar name Ns Op , Ns Ar value
1288 Matches any IPv4 or IPv6 address for which an entry exists in the lookup table
1290 If an optional 32-bit unsigned
1292 is also specified, an entry will match only if it has this value.
1295 section below for more information on lookup tables.
1297 .It Ar addr-list : ip-addr Ns Op Ns , Ns Ar addr-list
1299 A host or subnet address specified in one of the following ways:
1300 .Bl -tag -width indent
1301 .It Ar numeric-ip | hostname
1302 Matches a single IPv4 address, specified as dotted-quad or a hostname.
1303 Hostnames are resolved at the time the rule is added to the firewall list.
1304 .It Ar addr Ns / Ns Ar masklen
1305 Matches all addresses with base
1307 (specified as an IP address, a network number, or a hostname)
1311 As an example, 1.2.3.4/25 or 1.2.3.0/25 will match
1312 all IP numbers from 1.2.3.0 to 1.2.3.127 .
1313 .It Ar addr Ns : Ns Ar mask
1314 Matches all addresses with base
1316 (specified as an IP address, a network number, or a hostname)
1319 specified as a dotted quad.
1320 As an example, 1.2.3.4:255.0.255.0 or 1.0.3.0:255.0.255.0 will match
1322 This form is advised only for non-contiguous
1324 It is better to resort to the
1325 .Ar addr Ns / Ns Ar masklen
1326 format for contiguous masks, which is more compact and less
1329 .It Ar addr-set : addr Ns Oo Ns / Ns Ar masklen Oc Ns Cm { Ns Ar list Ns Cm }
1330 .It Ar list : Bro Ar num | num-num Brc Ns Op Ns , Ns Ar list
1331 Matches all addresses with base address
1333 (specified as an IP address, a network number, or a hostname)
1334 and whose last byte is in the list between braces { } .
1335 Note that there must be no spaces between braces and
1336 numbers (spaces after commas are allowed).
1337 Elements of the list can be specified as single entries
1341 field is used to limit the size of the set of addresses,
1342 and can have any value between 24 and 32.
1344 it will be assumed as 24.
1346 This format is particularly useful to handle sparse address sets
1347 within a single rule.
1348 Because the matching occurs using a
1349 bitmask, it takes constant time and dramatically reduces
1350 the complexity of rulesets.
1352 As an example, an address specified as 1.2.3.4/24{128,35-55,89}
1353 or 1.2.3.0/24{128,35-55,89}
1354 will match the following IP addresses:
1356 1.2.3.128, 1.2.3.35 to 1.2.3.55, 1.2.3.89 .
1357 .It Ar addr6-list : ip6-addr Ns Op Ns , Ns Ar addr6-list
1359 A host or subnet specified one of the following ways:
1360 .Bl -tag -width indent
1361 .It Ar numeric-ip | hostname
1362 Matches a single IPv6 address as allowed by
1365 Hostnames are resolved at the time the rule is added to the firewall
1367 .It Ar addr Ns / Ns Ar masklen
1368 Matches all IPv6 addresses with base
1370 (specified as allowed by
1376 .It Ar addr Ns / Ns Ar mask
1377 Matches all IPv6 addresses with base
1379 (specified as allowed by
1384 specified as allowed by
1386 As an example, fe::640:0:0/ffff::ffff:ffff:0:0 will match
1388 This form is advised only for non-contiguous
1390 It is better to resort to the
1391 .Ar addr Ns / Ns Ar masklen
1392 format for contiguous masks, which is more compact and less
1396 No support for sets of IPv6 addresses is provided because IPv6 addresses
1397 are typically random past the initial prefix.
1398 .It Ar ports : Bro Ar port | port Ns \&- Ns Ar port Ns Brc Ns Op , Ns Ar ports
1399 For protocols which support port numbers (such as TCP and UDP), optional
1401 may be specified as one or more ports or port ranges, separated
1402 by commas but no spaces, and an optional
1407 notation specifies a range of ports (including boundaries).
1411 may be used instead of numeric port values.
1412 The length of the port list is limited to 30 ports or ranges,
1413 though one can specify larger ranges by using an
1417 section of the rule.
1421 can be used to escape the dash
1423 character in a service name (from a shell, the backslash must be
1424 typed twice to avoid the shell itself interpreting it as an escape
1427 .Dl "ipfw add count tcp from any ftp\e\e-data-ftp to any"
1429 Fragmented packets which have a non-zero offset (i.e., not the first
1430 fragment) will never match a rule which has one or more port
1434 option for details on matching fragmented packets.
1436 .Ss RULE OPTIONS (MATCH PATTERNS)
1437 Additional match patterns can be used within
1439 Zero or more of these so-called
1441 can be present in a rule, optionally prefixed by the
1443 operand, and possibly grouped into
1446 The following match patterns can be used (listed in alphabetical order):
1447 .Bl -tag -width indent
1448 .It Cm // this is a comment.
1449 Inserts the specified text as a comment in the rule.
1450 Everything following // is considered as a comment and stored in the rule.
1451 You can have comment-only rules, which are listed as having a
1453 action followed by the comment.
1458 Matches only packets generated by a divert socket.
1459 .It Cm diverted-loopback
1460 Matches only packets coming from a divert socket back into the IP stack
1462 .It Cm diverted-output
1463 Matches only packets going from a divert socket back outward to the IP
1464 stack output for delivery.
1465 .It Cm dst-ip Ar ip-address
1466 Matches IPv4 packets whose destination IP is one of the address(es)
1467 specified as argument.
1468 .It Bro Cm dst-ip6 | dst-ipv6 Brc Ar ip6-address
1469 Matches IPv6 packets whose destination IP is one of the address(es)
1470 specified as argument.
1471 .It Cm dst-port Ar ports
1472 Matches IP packets whose destination port is one of the port(s)
1473 specified as argument.
1475 Matches TCP packets that have the RST or ACK bits set.
1476 .It Cm ext6hdr Ar header
1477 Matches IPv6 packets containing the extended header given by
1479 Supported headers are:
1485 any type of Routing Header
1487 Source routing Routing Header Type 0
1489 Mobile IPv6 Routing Header Type 2
1493 IPSec authentication headers
1495 and IPsec encapsulated security payload headers
1497 .It Cm fib Ar fibnum
1498 Matches a packet that has been tagged to use
1499 the given FIB (routing table) number.
1500 .It Cm flow Ar table Ns Pq Ar name Ns Op , Ns Ar value
1501 Search for the flow entry in lookup table
1503 If not found, the match fails.
1504 Otherwise, the match succeeds and
1506 is set to the value extracted from the table.
1508 This option can be useful to quickly dispatch traffic based on
1509 certain packet fields.
1512 section below for more information on lookup tables.
1513 .It Cm flow-id Ar labels
1514 Matches IPv6 packets containing any of the flow labels given in
1517 is a comma separated list of numeric flow labels.
1519 Matches packets that are fragments and not the first
1520 fragment of an IP datagram.
1521 Note that these packets will not have
1522 the next protocol header (e.g.\& TCP, UDP) so options that look into
1523 these headers cannot match.
1525 Matches all TCP or UDP packets sent by or received for a
1529 may be specified by name or number.
1530 .It Cm jail Ar prisonID
1531 Matches all TCP or UDP packets sent by or received for the
1532 jail whos prison ID is
1534 .It Cm icmptypes Ar types
1535 Matches ICMP packets whose ICMP type is in the list
1537 The list may be specified as any combination of
1538 individual types (numeric) separated by commas.
1539 .Em Ranges are not allowed .
1540 The supported ICMP types are:
1544 destination unreachable
1552 router advertisement
1556 time-to-live exceeded
1568 address mask request
1570 and address mask reply
1572 .It Cm icmp6types Ar types
1573 Matches ICMP6 packets whose ICMP6 type is in the list of
1575 The list may be specified as any combination of
1576 individual types (numeric) separated by commas.
1577 .Em Ranges are not allowed .
1579 Matches incoming or outgoing packets, respectively.
1583 are mutually exclusive (in fact,
1587 .It Cm ipid Ar id-list
1588 Matches IPv4 packets whose
1590 field has value included in
1592 which is either a single value or a list of values or ranges
1593 specified in the same way as
1595 .It Cm iplen Ar len-list
1596 Matches IP packets whose total length, including header and data, is
1599 which is either a single value or a list of values or ranges
1600 specified in the same way as
1602 .It Cm ipoptions Ar spec
1603 Matches packets whose IPv4 header contains the comma separated list of
1604 options specified in
1606 The supported IP options are:
1609 (strict source route),
1611 (loose source route),
1613 (record packet route) and
1616 The absence of a particular option may be denoted
1619 .It Cm ipprecedence Ar precedence
1620 Matches IPv4 packets whose precedence field is equal to
1623 Matches packets that have IPSEC history associated with them
1624 (i.e., the packet comes encapsulated in IPSEC, the kernel
1625 has IPSEC support, and can correctly decapsulate it).
1627 Note that specifying
1629 is different from specifying
1631 as the latter will only look at the specific IP protocol field,
1632 irrespective of IPSEC kernel support and the validity of the IPSEC data.
1634 Further note that this flag is silently ignored in kernels without
1636 It does not affect rule processing when given and the
1637 rules are handled as if with no
1640 .It Cm iptos Ar spec
1641 Matches IPv4 packets whose
1643 field contains the comma separated list of
1644 service types specified in
1646 The supported IP types of service are:
1649 .Pq Dv IPTOS_LOWDELAY ,
1651 .Pq Dv IPTOS_THROUGHPUT ,
1653 .Pq Dv IPTOS_RELIABILITY ,
1655 .Pq Dv IPTOS_MINCOST ,
1657 .Pq Dv IPTOS_ECN_CE .
1658 The absence of a particular type may be denoted
1661 .It Cm dscp spec Ns Op , Ns Ar spec
1662 Matches IPv4/IPv6 packets whose
1664 field value is contained in
1667 Multiple values can be specified via
1668 the comma separated list.
1669 Value can be one of keywords used in
1671 action or exact number.
1672 .It Cm ipttl Ar ttl-list
1673 Matches IPv4 packets whose time to live is included in
1675 which is either a single value or a list of values or ranges
1676 specified in the same way as
1678 .It Cm ipversion Ar ver
1679 Matches IP packets whose IP version field is
1681 .It Cm keep-state Op Ar :flowname
1682 Upon a match, the firewall will create a dynamic rule, whose
1683 default behaviour is to match bidirectional traffic between
1684 source and destination IP/port using the same protocol.
1685 The rule has a limited lifetime (controlled by a set of
1687 variables), and the lifetime is refreshed every time a matching
1691 is used to assign additional to addresses, ports and protocol parameter
1692 to dynamic rule. It can be used for more accurate matching by
1697 keyword is special name used for compatibility with old rulesets.
1699 Matches only layer2 packets, i.e., those passed to
1701 from ether_demux() and ether_output_frame().
1702 .It Cm limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N Op Ar :flowname
1703 The firewall will only allow
1705 connections with the same
1706 set of parameters as specified in the rule.
1708 of source and destination addresses and ports can be
1710 .It Cm lookup Bro Cm dst-ip | dst-port | src-ip | src-port | uid | jail Brc Ar name
1711 Search an entry in lookup table
1713 that matches the field specified as argument.
1714 If not found, the match fails.
1715 Otherwise, the match succeeds and
1717 is set to the value extracted from the table.
1719 This option can be useful to quickly dispatch traffic based on
1720 certain packet fields.
1723 section below for more information on lookup tables.
1724 .It Cm { MAC | mac } Ar dst-mac src-mac
1725 Match packets with a given
1729 addresses, specified as the
1731 keyword (matching any MAC address), or six groups of hex digits
1732 separated by colons,
1733 and optionally followed by a mask indicating the significant bits.
1734 The mask may be specified using either of the following methods:
1735 .Bl -enum -width indent
1739 followed by the number of significant bits.
1740 For example, an address with 33 significant bits could be specified as:
1742 .Dl "MAC 10:20:30:40:50:60/33 any"
1746 followed by a bitmask specified as six groups of hex digits separated
1748 For example, an address in which the last 16 bits are significant could
1751 .Dl "MAC 10:20:30:40:50:60&00:00:00:00:ff:ff any"
1753 Note that the ampersand character has a special meaning in many shells
1754 and should generally be escaped.
1756 Note that the order of MAC addresses (destination first,
1758 the same as on the wire, but the opposite of the one used for
1760 .It Cm mac-type Ar mac-type
1761 Matches packets whose Ethernet Type field
1762 corresponds to one of those specified as argument.
1764 is specified in the same way as
1766 (i.e., one or more comma-separated single values or ranges).
1767 You can use symbolic names for known values such as
1768 .Em vlan , ipv4, ipv6 .
1769 Values can be entered as decimal or hexadecimal (if prefixed by 0x),
1770 and they are always printed as hexadecimal (unless the
1772 option is used, in which case symbolic resolution will be attempted).
1773 .It Cm proto Ar protocol
1774 Matches packets with the corresponding IP protocol.
1775 .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
1776 Matches packets received, transmitted or going through,
1777 respectively, the interface specified by exact name
1781 by IP address, or through some interface.
1784 may be used to match interface by its kernel ifindex.
1787 section below for more information on lookup tables.
1791 keyword causes the interface to always be checked.
1798 then only the receive or transmit interface (respectively)
1800 By specifying both, it is possible to match packets based on
1801 both receive and transmit interface, e.g.:
1803 .Dl "ipfw add deny ip from any to any out recv ed0 xmit ed1"
1807 interface can be tested on either incoming or outgoing packets,
1810 interface can only be tested on outgoing packets.
1815 is invalid) whenever
1819 A packet might not have a receive or transmit interface: packets
1820 originating from the local host have no receive interface,
1821 while packets destined for the local host have no transmit
1824 Matches TCP packets that have the SYN bit set but no ACK bit.
1825 This is the short form of
1826 .Dq Li tcpflags\ syn,!ack .
1828 Matches packets that are associated to a local socket and
1829 for which the SO_USER_COOKIE socket option has been set
1830 to a non-zero value.
1831 As a side effect, the value of the
1832 option is made available as
1834 value, which in turn can be used as
1839 .It Cm src-ip Ar ip-address
1840 Matches IPv4 packets whose source IP is one of the address(es)
1841 specified as an argument.
1842 .It Cm src-ip6 Ar ip6-address
1843 Matches IPv6 packets whose source IP is one of the address(es)
1844 specified as an argument.
1845 .It Cm src-port Ar ports
1846 Matches IP packets whose source port is one of the port(s)
1847 specified as argument.
1848 .It Cm tagged Ar tag-list
1849 Matches packets whose tags are included in
1851 which is either a single value or a list of values or ranges
1852 specified in the same way as
1854 Tags can be applied to the packet using
1856 rule action parameter (see it's description for details on tags).
1857 .It Cm tcpack Ar ack
1859 Match if the TCP header acknowledgment number field is set to
1861 .It Cm tcpdatalen Ar tcpdatalen-list
1862 Matches TCP packets whose length of TCP data is
1863 .Ar tcpdatalen-list ,
1864 which is either a single value or a list of values or ranges
1865 specified in the same way as
1867 .It Cm tcpflags Ar spec
1869 Match if the TCP header contains the comma separated list of
1872 The supported TCP flags are:
1881 The absence of a particular flag may be denoted
1884 A rule which contains a
1886 specification can never match a fragmented packet which has
1890 option for details on matching fragmented packets.
1891 .It Cm tcpseq Ar seq
1893 Match if the TCP header sequence number field is set to
1895 .It Cm tcpwin Ar tcpwin-list
1896 Matches TCP packets whose header window field is set to
1898 which is either a single value or a list of values or ranges
1899 specified in the same way as
1901 .It Cm tcpoptions Ar spec
1903 Match if the TCP header contains the comma separated list of
1904 options specified in
1906 The supported TCP options are:
1909 (maximum segment size),
1911 (tcp window advertisement),
1915 (rfc1323 timestamp) and
1917 (rfc1644 t/tcp connection count).
1918 The absence of a particular option may be denoted
1922 Match all TCP or UDP packets sent by or received for a
1926 may be matched by name or identification number.
1928 For incoming packets,
1929 a routing table lookup is done on the packet's source address.
1930 If the interface on which the packet entered the system matches the
1931 outgoing interface for the route,
1933 If the interfaces do not match up,
1934 the packet does not match.
1935 All outgoing packets or packets with no incoming interface match.
1937 The name and functionality of the option is intentionally similar to
1938 the Cisco IOS command:
1940 .Dl ip verify unicast reverse-path
1942 This option can be used to make anti-spoofing rules to reject all
1943 packets with source addresses not from this interface.
1947 For incoming packets,
1948 a routing table lookup is done on the packet's source address.
1949 If a route to the source address exists, but not the default route
1950 or a blackhole/reject route, the packet matches.
1951 Otherwise, the packet does not match.
1952 All outgoing packets match.
1954 The name and functionality of the option is intentionally similar to
1955 the Cisco IOS command:
1957 .Dl ip verify unicast source reachable-via any
1959 This option can be used to make anti-spoofing rules to reject all
1960 packets whose source address is unreachable.
1962 For incoming packets, the packet's source address is checked if it
1963 belongs to a directly connected network.
1964 If the network is directly connected, then the interface the packet
1965 came on in is compared to the interface the network is connected to.
1966 When incoming interface and directly connected interface are not the
1967 same, the packet does not match.
1968 Otherwise, the packet does match.
1969 All outgoing packets match.
1971 This option can be used to make anti-spoofing rules to reject all
1972 packets that pretend to be from a directly connected network but do
1973 not come in through that interface.
1974 This option is similar to but more restricted than
1976 because it engages only on packets with source addresses of directly
1977 connected networks instead of all source addresses.
1980 Lookup tables are useful to handle large sparse sets of
1981 addresses or other search keys (e.g., ports, jail IDs, interface names).
1982 In the rest of this section we will use the term ``key''.
1983 Table name needs to match the following spec:
1985 Tables with the same name can be created in different
1987 However, rule links to the tables in
1990 This behavior can be controlled by
1991 .Va net.inet.ip.fw.tables_sets
1995 section for more information.
1996 There may be up to 65535 different lookup tables.
1998 The following table types are supported:
1999 .Bl -tag -width indent
2000 .It Ar table-type : Ar addr | iface | number | flow
2001 .It Ar table-key : Ar addr Ns Oo / Ns Ar masklen Oc | iface-name | number | flow-spec
2002 .It Ar flow-spec : Ar flow-field Ns Op , Ns Ar flow-spec
2003 .It Ar flow-field : src-ip | proto | src-port | dst-ip | dst-port
2005 matches IPv4 or IPv6 address.
2006 Each entry is represented by an
2007 .Ar addr Ns Op / Ns Ar masklen
2008 and will match all addresses with base
2010 (specified as an IPv4/IPv6 address, or a hostname) and mask width of
2015 is not specified, it defaults to 32 for IPv4 and 128 for IPv6.
2016 When looking up an IP address in a table, the most specific
2019 matches interface names.
2020 Each entry is represented by string treated as interface name.
2021 Wildcards are not supported.
2023 maches protocol ports, uids/gids or jail IDs.
2024 Each entry is represented by 32-bit unsigned integer.
2025 Ranges are not supported.
2027 Matches packet fields specified by
2029 type suboptions with table entries.
2032 Tables require explicit creation via
2036 The following creation options are supported:
2037 .Bl -tag -width indent
2038 .It Ar create-options : Ar create-option | create-options
2039 .It Ar create-option : Cm type Ar table-type | Cm valtype Ar value-mask | Cm algo Ar algo-desc |
2040 .Cm limit Ar number | Cm locked
2046 Table algorithm to use (see below).
2048 Maximum number of items that may be inserted into table.
2050 Restrict any table modifications.
2053 Some of these options may be modified later via
2056 The following options can be changed:
2057 .Bl -tag -width indent
2058 .It Ar modify-options : Ar modify-option | modify-options
2059 .It Ar modify-option : Cm limit Ar number
2061 Alter maximum number of items that may be inserted into table.
2064 Additionally, table can be locked or unlocked using
2072 can be swapped with each other using
2075 Swap may fail if tables limits are set and data exchange
2076 would result in limits hit.
2077 Operation is performed atomically.
2079 One or more entries can be added to a table at once using
2082 Addition of all items are performed atomically.
2083 By default, error in addition of one entry does not influence
2084 addition of other entries. However, non-zero error code is returned
2088 keyword may be specified before
2090 to indicate all-or-none add request.
2092 One or more entries can be removed from a table at once using
2095 By default, error in removal of one entry does not influence
2096 removing of other entries. However, non-zero error code is returned
2099 It may be possible to check what entry will be found on particular
2105 This functionality is optional and may be unsupported in some algorithms.
2107 The following operations can be performed on
2112 .Bl -tag -width indent
2116 Removes all entries.
2118 Shows generic table information.
2120 Shows generic table information and algo-specific data.
2123 The following lookup algorithms are supported:
2124 .Bl -tag -width indent
2125 .It Ar algo-desc : algo-name | "algo-name algo-data"
2126 .It Ar algo-name: Ar addr:radix | addr:hash | iface:array | number:array | flow:hash
2128 Separate Radix trees for IPv4 and IPv6, the same way as the routing table (see
2134 Separate auto-growing hashes for IPv4 and IPv6.
2135 Accepts entries with the same mask length specified initially via
2136 .Cm "addr:hash masks=/v4,/v6"
2137 algorithm creation options.
2138 Assume /32 and /128 masks by default.
2139 Search removes host bits (according to mask) from supplied address and checks
2140 resulting key in appropriate hash.
2141 Mostly optimized for /64 and byte-ranged IPv6 masks.
2143 Array storing sorted indexes for entries which are presented in the system.
2144 Optimized for very fast lookup.
2146 Array storing sorted u32 numbers.
2148 Auto-growing hash storing flow entries.
2149 Search calculates hash on required packet fields and searches for matching
2150 entries in selected bucket.
2155 feature provides the ability to use a value, looked up in the table, as
2156 the argument for a rule action, action parameter or rule option.
2157 This can significantly reduce number of rules in some configurations.
2158 If two tables are used in a rule, the result of the second (destination)
2161 Each record may hold one or more values according to
2163 This mask is set on table creation via
2166 The following value types are supported:
2167 .Bl -tag -width indent
2168 .It Ar value-mask : Ar value-type Ns Op , Ns Ar value-mask
2169 .It Ar value-type : Ar skipto | pipe | fib | nat | dscp | tag | divert |
2170 .Ar netgraph | limit | ipv4
2172 rule number to jump to.
2176 fib number to match/set.
2178 nat number to jump to.
2180 dscp value to match/set.
2182 tag number to match/set.
2184 port number to divert traffic to.
2186 hook number to move packet to.
2188 maximum number of connections.
2190 IPv4 nexthop to fwd packets to.
2192 IPv6 nexthop to fwd packets to.
2197 argument can be used with the following actions:
2198 .Cm nat, pipe , queue, divert, tee, netgraph, ngtee, fwd, skipto, setfib,
2206 action, the user should be aware that the code will walk the ruleset
2207 up to a rule equal to, or past, the given number.
2211 Section for example usage of tables and the tablearg keyword.
2213 Each rule or table belongs to one of 32 different
2216 Set 31 is reserved for the default rule.
2218 By default, rules or tables are put in set 0, unless you use the
2220 attribute when adding a new rule or table.
2221 Sets can be individually and atomically enabled or disabled,
2222 so this mechanism permits an easy way to store multiple configurations
2223 of the firewall and quickly (and atomically) switch between them.
2225 By default, tables from set 0 are referenced when adding rule with
2226 table opcodes regardless of rule set.
2227 This behavior can be changed by setting
2228 .Va net.inet.ip.fw.tables_set
2230 Rule's set will then be used for table references.
2232 The command to enable/disable sets is
2233 .Bd -ragged -offset indent
2235 .Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ...
2242 sections can be specified.
2243 Command execution is atomic on all the sets specified in the command.
2244 By default, all sets are enabled.
2246 When you disable a set, its rules behave as if they do not exist
2247 in the firewall configuration, with only one exception:
2248 .Bd -ragged -offset indent
2249 dynamic rules created from a rule before it had been disabled
2250 will still be active until they expire.
2252 dynamic rules you have to explicitly delete the parent rule
2253 which generated them.
2256 The set number of rules can be changed with the command
2257 .Bd -ragged -offset indent
2260 .Brq Cm rule Ar rule-number | old-set
2264 Also, you can atomically swap two rulesets with the command
2265 .Bd -ragged -offset indent
2267 .Cm set swap Ar first-set second-set
2272 Section on some possible uses of sets of rules.
2273 .Sh STATEFUL FIREWALL
2274 Stateful operation is a way for the firewall to dynamically
2275 create rules for specific flows when packets that
2276 match a given pattern are detected.
2277 Support for stateful
2278 operation comes through the
2279 .Cm check-state , keep-state
2285 Dynamic rules are created when a packet matches a
2289 rule, causing the creation of a
2291 rule which will match all and only packets with
2295 .Em src-ip/src-port dst-ip/dst-port
2300 are used here only to denote the initial match addresses, but they
2301 are completely equivalent afterwards).
2307 This name is used in matching together with addresses, ports and protocol.
2308 Dynamic rules will be checked at the first
2309 .Cm check-state, keep-state
2312 occurrence, and the action performed upon a match will be the same
2313 as in the parent rule.
2315 Note that no additional attributes other than protocol and IP addresses
2316 and ports and :flowname are checked on dynamic rules.
2318 The typical use of dynamic rules is to keep a closed firewall configuration,
2319 but let the first TCP SYN packet from the inside network install a
2320 dynamic rule for the flow so that packets belonging to that session
2321 will be allowed through the firewall:
2323 .Dl "ipfw add check-state :OUTBOUND"
2324 .Dl "ipfw add allow tcp from my-subnet to any setup keep-state :OUTBOUND"
2325 .Dl "ipfw add deny tcp from any to any"
2327 A similar approach can be used for UDP, where an UDP packet coming
2328 from the inside will install a dynamic rule to let the response through
2331 .Dl "ipfw add check-state :OUTBOUND"
2332 .Dl "ipfw add allow udp from my-subnet to any keep-state :OUTBOUND"
2333 .Dl "ipfw add deny udp from any to any"
2335 Dynamic rules expire after some time, which depends on the status
2336 of the flow and the setting of some
2340 .Sx SYSCTL VARIABLES
2342 For TCP sessions, dynamic rules can be instructed to periodically
2343 send keepalive packets to refresh the state of the rule when it is
2348 for more examples on how to use dynamic rules.
2349 .Sh TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
2351 is also the user interface for the
2353 traffic shaper, packet scheduler and network emulator, a subsystem that
2354 can artificially queue, delay or drop packets
2355 emulating the behaviour of certain network links
2356 or queueing systems.
2359 operates by first using the firewall to select packets
2360 using any match pattern that can be used in
2363 Matching packets are then passed to either of two
2364 different objects, which implement the traffic regulation:
2365 .Bl -hang -offset XXXX
2371 with given bandwidth and propagation delay,
2372 driven by a FIFO scheduler and a single queue with programmable
2373 queue size and packet loss rate.
2374 Packets are appended to the queue as they come out from
2376 and then transferred in FIFO order to the link at the desired rate.
2380 is an abstraction used to implement packet scheduling
2381 using one of several packet scheduling algorithms.
2384 are first grouped into flows according to a mask on the 5-tuple.
2385 Flows are then passed to the scheduler associated to the
2387 and each flow uses scheduling parameters (weight and others)
2388 as configured in the
2391 A scheduler in turn is connected to an emulated link,
2392 and arbitrates the link's bandwidth among backlogged flows according to
2393 weights and to the features of the scheduling algorithm in use.
2398 can be used to set hard limits to the bandwidth that a flow can use, whereas
2400 can be used to determine how different flows share the available bandwidth.
2402 A graphical representation of the binding of queues,
2403 flows, schedulers and links is below.
2404 .Bd -literal -offset indent
2405 (flow_mask|sched_mask) sched_mask
2406 +---------+ weight Wx +-------------+
2407 | |->-[flow]-->--| |-+
2408 -->--| QUEUE x | ... | | |
2409 | |->-[flow]-->--| SCHEDuler N | |
2411 ... | +--[LINK N]-->--
2412 +---------+ weight Wy | | +--[LINK N]-->--
2413 | |->-[flow]-->--| | |
2414 -->--| QUEUE y | ... | | |
2415 | |->-[flow]-->--| | |
2416 +---------+ +-------------+ |
2419 It is important to understand the role of the SCHED_MASK
2420 and FLOW_MASK, which are configured through the commands
2421 .Dl "ipfw sched N config mask SCHED_MASK ..."
2423 .Dl "ipfw queue X config mask FLOW_MASK ..." .
2425 The SCHED_MASK is used to assign flows to one or more
2426 scheduler instances, one for each
2427 value of the packet's 5-tuple after applying SCHED_MASK.
2428 As an example, using ``src-ip 0xffffff00'' creates one instance
2429 for each /24 destination subnet.
2431 The FLOW_MASK, together with the SCHED_MASK, is used to split
2433 As an example, using
2434 ``src-ip 0x000000ff''
2435 together with the previous SCHED_MASK makes a flow for
2436 each individual source address.
2437 In turn, flows for each /24
2438 subnet will be sent to the same scheduler instance.
2440 The above diagram holds even for the
2442 case, with the only restriction that a
2444 only supports a SCHED_MASK, and forces the use of a FIFO
2445 scheduler (these are for backward compatibility reasons;
2446 in fact, internally, a
2448 pipe is implemented exactly as above).
2450 There are two modes of
2458 mode tries to emulate a real link: the
2460 scheduler ensures that the packet will not leave the pipe faster than it
2461 would on the real link with a given bandwidth.
2464 mode allows certain packets to bypass the
2466 scheduler (if packet flow does not exceed pipe's bandwidth).
2467 This is the reason why the
2469 mode requires less CPU cycles per packet (on average) and packet latency
2470 can be significantly lower in comparison to a real link with the same
2476 mode can be enabled by setting the
2477 .Va net.inet.ip.dummynet.io_fast
2479 variable to a non-zero value.
2481 .Ss PIPE, QUEUE AND SCHEDULER CONFIGURATION
2487 configuration commands are the following:
2488 .Bd -ragged -offset indent
2489 .Cm pipe Ar number Cm config Ar pipe-configuration
2491 .Cm queue Ar number Cm config Ar queue-configuration
2493 .Cm sched Ar number Cm config Ar sched-configuration
2496 The following parameters can be configured for a pipe:
2498 .Bl -tag -width indent -compact
2499 .It Cm bw Ar bandwidth | device
2500 Bandwidth, measured in
2503 .Brq Cm bit/s | Byte/s .
2506 A value of 0 (default) means unlimited bandwidth.
2507 The unit must immediately follow the number, as in
2509 .Dl "ipfw pipe 1 config bw 300Kbit/s"
2511 If a device name is specified instead of a numeric value, as in
2513 .Dl "ipfw pipe 1 config bw tun0"
2515 then the transmit clock is supplied by the specified device.
2516 At the moment only the
2518 device supports this
2519 functionality, for use in conjunction with
2522 .It Cm delay Ar ms-delay
2523 Propagation delay, measured in milliseconds.
2524 The value is rounded to the next multiple of the clock tick
2525 (typically 10ms, but it is a good practice to run kernels
2527 .Dq "options HZ=1000"
2529 the granularity to 1ms or less).
2530 The default value is 0, meaning no delay.
2532 .It Cm burst Ar size
2533 If the data to be sent exceeds the pipe's bandwidth limit
2534 (and the pipe was previously idle), up to
2536 bytes of data are allowed to bypass the
2538 scheduler, and will be sent as fast as the physical link allows.
2539 Any additional data will be transmitted at the rate specified
2543 The burst size depends on how long the pipe has been idle;
2544 the effective burst size is calculated as follows:
2551 .It Cm profile Ar filename
2552 A file specifying the additional overhead incurred in the transmission
2553 of a packet on the link.
2555 Some link types introduce extra delays in the transmission
2556 of a packet, e.g., because of MAC level framing, contention on
2557 the use of the channel, MAC level retransmissions and so on.
2558 From our point of view, the channel is effectively unavailable
2559 for this extra time, which is constant or variable depending
2561 Additionally, packets may be dropped after this
2562 time (e.g., on a wireless link after too many retransmissions).
2563 We can model the additional delay with an empirical curve
2564 that represents its distribution.
2565 .Bd -literal -offset indent
2566 cumulative probability
2576 +-------*------------------->
2579 The empirical curve may have both vertical and horizontal lines.
2580 Vertical lines represent constant delay for a range of
2582 Horizontal lines correspond to a discontinuity in the delay
2583 distribution: the pipe will use the largest delay for a
2586 The file format is the following, with whitespace acting as
2587 a separator and '#' indicating the beginning a comment:
2588 .Bl -tag -width indent
2589 .It Cm name Ar identifier
2590 optional name (listed by "ipfw pipe show")
2591 to identify the delay distribution;
2593 the bandwidth used for the pipe.
2594 If not specified here, it must be present
2595 explicitly as a configuration parameter for the pipe;
2596 .It Cm loss-level Ar L
2597 the probability above which packets are lost.
2598 (0.0 <= L <= 1.0, default 1.0 i.e., no loss);
2600 the number of samples used in the internal
2601 representation of the curve (2..1024; default 100);
2602 .It Cm "delay prob" | "prob delay"
2603 One of these two lines is mandatory and defines
2604 the format of the following lines with data points.
2606 2 or more lines representing points in the curve,
2607 with either delay or probability first, according
2608 to the chosen format.
2609 The unit for delay is milliseconds.
2610 Data points do not need to be sorted.
2611 Also, the number of actual lines can be different
2612 from the value of the "samples" parameter:
2614 utility will sort and interpolate
2615 the curve as needed.
2618 Example of a profile file:
2619 .Bd -literal -offset indent
2624 0 200 # minimum overhead is 200ms
2630 #configuration file end
2634 The following parameters can be configured for a queue:
2636 .Bl -tag -width indent -compact
2637 .It Cm pipe Ar pipe_nr
2638 Connects a queue to the specified pipe.
2639 Multiple queues (with the same or different weights) can be connected to
2640 the same pipe, which specifies the aggregate rate for the set of queues.
2642 .It Cm weight Ar weight
2643 Specifies the weight to be used for flows matching this queue.
2644 The weight must be in the range 1..100, and defaults to 1.
2647 The following case-insensitive parameters can be configured for a
2650 .Bl -tag -width indent -compact
2651 .It Cm type Ar {fifo | wf2q+ | rr | qfq}
2652 specifies the scheduling algorithm to use.
2653 .Bl -tag -width indent -compact
2655 is just a FIFO scheduler (which means that all packets
2656 are stored in the same queue as they arrive to the scheduler).
2657 FIFO has O(1) per-packet time complexity, with very low
2658 constants (estimate 60-80ns on a 2GHz desktop machine)
2659 but gives no service guarantees.
2661 implements the WF2Q+ algorithm, which is a Weighted Fair Queueing
2662 algorithm which permits flows to share bandwidth according to
2664 Note that weights are not priorities; even a flow
2665 with a minuscule weight will never starve.
2666 WF2Q+ has O(log N) per-packet processing cost, where N is the number
2667 of flows, and is the default algorithm used by previous versions
2670 implements the Deficit Round Robin algorithm, which has O(1) processing
2671 costs (roughly, 100-150ns per packet)
2672 and permits bandwidth allocation according to weights, but
2673 with poor service guarantees.
2675 implements the QFQ algorithm, which is a very fast variant of
2676 WF2Q+, with similar service guarantees and O(1) processing
2677 costs (roughly, 200-250ns per packet).
2681 In addition to the type, all parameters allowed for a pipe can also
2682 be specified for a scheduler.
2684 Finally, the following parameters can be configured for both
2687 .Bl -tag -width XXXX -compact
2688 .It Cm buckets Ar hash-table-size
2689 Specifies the size of the hash table used for storing the
2691 Default value is 64 controlled by the
2694 .Va net.inet.ip.dummynet.hash_size ,
2695 allowed range is 16 to 65536.
2697 .It Cm mask Ar mask-specifier
2698 Packets sent to a given pipe or queue by an
2700 rule can be further classified into multiple flows, each of which is then
2704 A flow identifier is constructed by masking the IP addresses,
2705 ports and protocol types as specified with the
2707 options in the configuration of the pipe or queue.
2708 For each different flow identifier, a new pipe or queue is created
2709 with the same parameters as the original object, and matching packets
2714 are used, each flow will get the same bandwidth as defined by the pipe,
2717 are used, each flow will share the parent's pipe bandwidth evenly
2718 with other flows generated by the same queue (note that other queues
2719 with different weights might be connected to the same pipe).
2721 Available mask specifiers are a combination of one or more of the following:
2723 .Cm dst-ip Ar mask ,
2724 .Cm dst-ip6 Ar mask ,
2725 .Cm src-ip Ar mask ,
2726 .Cm src-ip6 Ar mask ,
2727 .Cm dst-port Ar mask ,
2728 .Cm src-port Ar mask ,
2729 .Cm flow-id Ar mask ,
2734 where the latter means all bits in all fields are significant.
2737 When a packet is dropped by a
2739 queue or pipe, the error
2740 is normally reported to the caller routine in the kernel, in the
2741 same way as it happens when a device queue fills up.
2743 option reports the packet as successfully delivered, which can be
2744 needed for some experimental setups where you want to simulate
2745 loss or congestion at a remote router.
2747 .It Cm plr Ar packet-loss-rate
2750 .Ar packet-loss-rate
2751 is a floating-point number between 0 and 1, with 0 meaning no
2752 loss, 1 meaning 100% loss.
2753 The loss rate is internally represented on 31 bits.
2755 .It Cm queue Brq Ar slots | size Ns Cm Kbytes
2760 Default value is 50 slots, which
2761 is the typical queue size for Ethernet devices.
2762 Note that for slow speed links you should keep the queue
2763 size short or your traffic might be affected by a significant
2765 E.g., 50 max-sized ethernet packets (1500 bytes) mean 600Kbit
2766 or 20s of queue on a 30Kbit/s pipe.
2767 Even worse effects can result if you get packets from an
2768 interface with a much larger MTU, e.g.\& the loopback interface
2769 with its 16KB packets.
2773 .Em net.inet.ip.dummynet.pipe_byte_limit
2775 .Em net.inet.ip.dummynet.pipe_slot_limit
2776 control the maximum lengths that can be specified.
2778 .It Cm red | gred Ar w_q Ns / Ns Ar min_th Ns / Ns Ar max_th Ns / Ns Ar max_p
2780 Make use of the RED (Random Early Detection) queue management algorithm.
2785 point numbers between 0 and 1 (inclusive), while
2789 are integer numbers specifying thresholds for queue management
2790 (thresholds are computed in bytes if the queue has been defined
2791 in bytes, in slots otherwise).
2792 The two parameters can also be of the same value if needed. The
2794 also supports the gentle RED variant (gred) and ECN (Explicit Congestion
2795 Notification) as optional. Three
2797 variables can be used to control the RED behaviour:
2798 .Bl -tag -width indent
2799 .It Va net.inet.ip.dummynet.red_lookup_depth
2800 specifies the accuracy in computing the average queue
2801 when the link is idle (defaults to 256, must be greater than zero)
2802 .It Va net.inet.ip.dummynet.red_avg_pkt_size
2803 specifies the expected average packet size (defaults to 512, must be
2805 .It Va net.inet.ip.dummynet.red_max_pkt_size
2806 specifies the expected maximum packet size, only used when queue
2807 thresholds are in bytes (defaults to 1500, must be greater than zero).
2811 When used with IPv6 data,
2813 currently has several limitations.
2814 Information necessary to route link-local packets to an
2815 interface is not available after processing by
2817 so those packets are dropped in the output path.
2818 Care should be taken to ensure that link-local packets are not passed to
2821 Here are some important points to consider when designing your
2825 Remember that you filter both packets going
2829 Most connections need packets going in both directions.
2831 Remember to test very carefully.
2832 It is a good idea to be near the console when doing this.
2833 If you cannot be near the console,
2834 use an auto-recovery script such as the one in
2835 .Pa /usr/share/examples/ipfw/change_rules.sh .
2837 Do not forget the loopback interface.
2842 There are circumstances where fragmented datagrams are unconditionally
2844 TCP packets are dropped if they do not contain at least 20 bytes of
2845 TCP header, UDP packets are dropped if they do not contain a full 8
2846 byte UDP header, and ICMP packets are dropped if they do not contain
2847 4 bytes of ICMP header, enough to specify the ICMP type, code, and
2849 These packets are simply logged as
2851 since there may not be enough good data in the packet to produce a
2852 meaningful log entry.
2854 Another type of packet is unconditionally dropped, a TCP packet with a
2855 fragment offset of one.
2856 This is a valid packet, but it only has one use, to try
2857 to circumvent firewalls.
2858 When logging is enabled, these packets are
2859 reported as being dropped by rule -1.
2861 If you are logged in over a network, loading the
2865 is probably not as straightforward as you would think.
2866 The following command line is recommended:
2867 .Bd -literal -offset indent
2869 ipfw add 32000 allow ip from any to any
2872 Along the same lines, doing an
2873 .Bd -literal -offset indent
2877 in similar surroundings is also a bad idea.
2881 filter list may not be modified if the system security level
2882 is set to 3 or higher
2885 for information on system security levels).
2887 .Sh PACKET DIVERSION
2890 socket bound to the specified port will receive all packets
2891 diverted to that port.
2892 If no socket is bound to the destination port, or if the divert module is
2893 not loaded, or if the kernel was not compiled with divert socket support,
2894 the packets are dropped.
2895 .Sh NETWORK ADDRESS TRANSLATION (NAT)
2897 support in-kernel NAT using the kernel version of
2901 should be loaded or kernel should have
2902 .Cm options IPFIREWALL_NAT
2905 The nat configuration command is the following:
2906 .Bd -ragged -offset indent
2911 .Ar nat-configuration
2915 The following parameters can be configured:
2916 .Bl -tag -width indent
2917 .It Cm ip Ar ip_address
2918 Define an ip address to use for aliasing.
2920 Use ip address of NIC for aliasing, dynamically changing
2921 it if NIC's ip address changes.
2923 Enable logging on this nat instance.
2925 Deny any incoming connection from outside world.
2927 Try to leave the alias port numbers unchanged from
2928 the actual local port numbers.
2930 Traffic on the local network not originating from an
2931 unregistered address spaces will be ignored.
2933 Reset table of the packet aliasing engine on address change.
2935 Reverse the way libalias handles aliasing.
2937 Obey transparent proxy rules only, packet aliasing is not performed.
2939 Skip instance in case of global state lookup (see below).
2942 Some specials value can be supplied instead of
2944 .Bl -tag -width indent
2946 Looks up translation state in all configured nat instances.
2947 If an entry is found, packet is aliased according to that entry.
2948 If no entry was found in any of the instances, packet is passed unchanged,
2949 and no new entry will be created.
2951 .Sx MULTIPLE INSTANCES
2954 for more information.
2956 Uses argument supplied in lookup table.
2959 section below for more information on lookup tables.
2962 To let the packet continue after being (de)aliased, set the sysctl variable
2963 .Va net.inet.ip.fw.one_pass
2965 For more information about aliasing modes, refer to
2969 for some examples about nat usage.
2970 .Ss REDIRECT AND LSNAT SUPPORT IN IPFW
2971 Redirect and LSNAT support follow closely the syntax used in
2975 for some examples on how to do redirect and lsnat.
2976 .Ss SCTP NAT SUPPORT
2977 SCTP nat can be configured in a similar manner to TCP through the
2980 The main difference is that
2982 does not do port translation.
2983 Since the local and global side ports will be the same,
2984 there is no need to specify both.
2985 Ports are redirected as follows:
2986 .Bd -ragged -offset indent
2992 .Cm redirect_port sctp
2993 .Ar ip_address [,addr_list] {[port | port-port] [,ports]}
2999 configuration can be done in real-time through the
3002 All may be changed dynamically, though the hash_table size will only
3007 .Sx SYSCTL VARIABLES
3009 .Sh IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
3011 supports in-kernel IPv6/IPv4 network address and protocol translation.
3012 Stateful NAT64 translation allows IPv6-only clients to contact IPv4 servers
3013 using unicast TCP, UDP or ICMP protocols.
3014 One or more IPv4 addresses assigned to a stateful NAT64 translator are shared
3015 among serveral IPv6-only clients.
3016 When stateful NAT64 is used in conjunction with DNS64, no changes are usually
3017 required in the IPv6 client or the IPv4 server.
3020 should be loaded or kernel should have
3021 .Cm options IPFIREWALL_NAT64
3022 to be able use stateful NAT64 translator.
3024 Stateful NAT64 uses a bunch of memory for several types of objects.
3025 When IPv6 client initiates connection, NAT64 translator creates a host entry
3026 in the states table.
3027 Each host entry has a number of ports group entries allocated on demand.
3028 Ports group entries contains connection state entries.
3029 There are several options to control limits and lifetime for these objects.
3031 NAT64 translator follows RFC7915 when does ICMPv6/ICMP translation,
3032 unsupported message types will be silently dropped.
3033 IPv6 needs several ICMPv6 message types to be explicitly allowed for correct
3035 Make sure that ND6 neighbor solicitation (ICMPv6 type 135) and neighbor
3036 advertisement (ICMPv6 type 136) messages will not be handled by translation
3039 After translation NAT64 translator sends packets through corresponding netisr
3041 Thus translator host should be configured as IPv4 and IPv6 router.
3043 Currently both stateful and stateless NAT64 translators use Well-Known IPv6
3046 to represent IPv4 addresses in the IPv6 address.
3047 Thus DNS64 service and routing should be configured to use Well-Known IPv6
3050 The stateful NAT64 configuration command is the following:
3051 .Bd -ragged -offset indent
3060 The following parameters can be configured:
3061 .Bl -tag -width indent
3062 .It Cm prefix4 Ar ipv4_prefix/mask
3063 The IPv4 prefix with mask defines the pool of IPv4 addresses used as
3064 source address after translation.
3065 Stateful NAT64 module translates IPv6 source address of client to one
3066 IPv4 address from this pool.
3067 Note that incoming IPv4 packets that don't have corresponding state entry
3068 in the states table will be dropped by translator.
3069 Make sure that translation rules handle packets, destined to configured prefix.
3070 .It Cm max_ports Ar number
3071 Maximum number of ports reserved for upper level protocols to one IPv6 client.
3072 All reserved ports are divided into chunks between supported protocols.
3073 The number of connections from one IPv6 client is limited by this option.
3074 Note that closed TCP connections still remain in the list of connections until
3076 interval will not expire.
3079 .It Cm host_del_age Ar seconds
3080 The number of seconds until the host entry for a IPv6 client will be deleted
3081 and all its resources will be released due to inactivity.
3084 .It Cm pg_del_age Ar seconds
3085 The number of seconds until a ports group with unused state entries will
3089 .It Cm tcp_syn_age Ar seconds
3090 The number of seconds while a state entry for TCP connection with only SYN
3092 If TCP connection establishing will not be finished,
3093 state entry will be deleted.
3096 .It Cm tcp_est_age Ar seconds
3097 The number of seconds while a state entry for established TCP connection
3101 .It Cm tcp_close_age Ar seconds
3102 The number of seconds while a state entry for closed TCP connection
3104 Keeping state entries for closed connections is needed, because IPv4 servers
3105 typically keep closed connections in a TIME_WAIT state for a several minutes.
3106 Since translator's IPv4 addresses are shared among all IPv6 clients,
3107 new connections from the same addresses and ports may be rejected by server,
3108 because these connections are still in a TIME_WAIT state.
3109 Keeping them in translator's state table protects from such rejects.
3112 .It Cm udp_age Ar seconds
3113 The number of seconds while translator keeps state entry in a waiting for
3114 reply to the sent UDP datagram.
3117 .It Cm icmp_age Ar seconds
3118 The number of seconds while translator keeps state entry in a waiting for
3119 reply to the sent ICMP message.
3123 Turn on logging of all handled packets via BPF through
3127 is a pseudo interface and can be created after a boot manually with
3130 Note that it has different purpose than
3133 Translators sends to BPF an additional information with each packet.
3136 you are able to see each handled packet before and after translation.
3138 Turn off logging of all handled packets via BPF.
3141 To inspect a states table of stateful NAT64 the following command can be used:
3142 .Bd -ragged -offset indent
3151 Stateless NAT64 translator doesn't use a states table for translation
3152 and converts IPv4 addresses to IPv6 and vice versa solely based on the
3153 mappings taken from configured lookup tables.
3154 Since a states table doesn't used by stateless translator,
3155 it can be configured to pass IPv4 clients to IPv6-only servers.
3157 The stateless NAT64 configuration command is the following:
3158 .Bd -ragged -offset indent
3167 The following parameters can be configured:
3168 .Bl -tag -width indent
3169 .It Cm table4 Ar table46
3172 contains mapping how IPv4 addresses should be translated to IPv6 addresses.
3173 .It Cm table6 Ar table64
3176 contains mapping how IPv6 addresses should be translated to IPv4 addresses.
3178 Turn on logging of all handled packets via BPF through
3182 Turn off logging of all handled packets via BPF.
3185 Note that the behavior of stateless translator with respect to not matched
3186 packets differs from stateful translator.
3187 If corresponding addresses was not found in the lookup tables, the packet
3188 will not be dropped and the search continues.
3189 .Sh IPv6-to-IPv6 NETWORK PREFIX TRANSLATION (NPTv6)
3191 supports in-kernel IPv6-to-IPv6 network prefix translation as described
3195 should be loaded or kernel should has
3196 .Cm options IPFIREWALL_NPTV6
3197 to be able use NPTv6 translator.
3199 The NPTv6 configuration command is the following:
3200 .Bd -ragged -offset indent
3209 The following parameters can be configured:
3210 .Bl -tag -width indent
3211 .It Cm int_prefix Ar ipv6_prefix
3212 IPv6 prefix used in internal network.
3213 NPTv6 module translates source address when it matches this prefix.
3214 .It Cm ext_prefix Ar ipv6_prefix
3215 IPv6 prefix used in external network.
3216 NPTv6 module translates destination address when it matches this prefix.
3217 .It Cm prefixlen Ar length
3218 The length of specified IPv6 prefixes. It must be in range from 8 to 64.
3221 Note that the prefix translation rules are silently ignored when IPv6 packet
3222 forwarding is disabled.
3223 To enable the packet forwarding, set the sysctl variable
3224 .Va net.inet6.ip6.forwarding
3227 To let the packet continue after being translated, set the sysctl variable
3228 .Va net.inet.ip.fw.one_pass
3231 Tunables can be set in
3237 before ipfw module gets loaded.
3238 .Bl -tag -width indent
3239 .It Va net.inet.ip.fw.default_to_accept: No 0
3240 Defines ipfw last rule behavior.
3241 This value overrides
3242 .Cd "options IPFW_DEFAULT_TO_(ACCEPT|DENY)"
3243 from kernel configuration file.
3244 .It Va net.inet.ip.fw.tables_max: No 128
3245 Defines number of tables available in ipfw.
3246 Number cannot exceed 65534.
3248 .Sh SYSCTL VARIABLES
3251 variables controls the behaviour of the firewall and
3253 .Pq Nm dummynet , bridge , sctp nat .
3254 These are shown below together with their default value
3255 (but always check with the
3257 command what value is actually in use) and meaning:
3258 .Bl -tag -width indent
3259 .It Va net.inet.ip.alias.sctp.accept_global_ootb_addip: No 0
3262 responds to receipt of global OOTB ASCONF-AddIP:
3263 .Bl -tag -width indent
3265 No response (unless a partially matching association exists -
3266 ports and vtags match but global address does not)
3269 will accept and process all OOTB global AddIP messages.
3272 Option 1 should never be selected as this forms a security risk.
3274 establish multiple fake associations by sending AddIP messages.
3275 .It Va net.inet.ip.alias.sctp.chunk_proc_limit: No 5
3276 Defines the maximum number of chunks in an SCTP packet that will be
3278 packet that matches an existing association.
3279 This value is enforced to be greater or equal than
3280 .Cm net.inet.ip.alias.sctp.initialising_chunk_proc_limit .
3282 a DoS risk yet setting too low a value may result in
3283 important control chunks in
3284 the packet not being located and parsed.
3285 .It Va net.inet.ip.alias.sctp.error_on_ootb: No 1
3288 responds to any Out-of-the-Blue (OOTB) packets with ErrorM packets.
3289 An OOTB packet is a packet that arrives with no existing association
3292 and is not an INIT or ASCONF-AddIP packet:
3293 .Bl -tag -width indent
3295 ErrorM is never sent in response to OOTB packets.
3297 ErrorM is only sent to OOTB packets received on the local side.
3299 ErrorM is sent to the local side and on the global side ONLY if there is a
3300 partial match (ports and vtags match but the source global IP does not).
3301 This value is only useful if the
3303 is tracking global IP addresses.
3305 ErrorM is sent in response to all OOTB packets on both
3306 the local and global side
3310 At the moment the default is 0, since the ErrorM packet is not yet
3311 supported by most SCTP stacks.
3312 When it is supported, and if not tracking
3313 global addresses, we recommend setting this value to 1 to allow
3314 multi-homed local hosts to function with the
3316 To track global addresses, we recommend setting this value to 2 to
3317 allow global hosts to be informed when they need to (re)send an
3319 Value 3 should never be chosen (except for debugging) as the
3321 will respond to all OOTB global packets (a DoS risk).
3322 .It Va net.inet.ip.alias.sctp.hashtable_size: No 2003
3323 Size of hash tables used for
3325 lookups (100 < prime_number > 1000001).
3328 size for any future created
3330 instance and therefore must be set prior to creating a
3333 The table sizes may be changed to suit specific needs.
3334 If there will be few
3335 concurrent associations, and memory is scarce, you may make these smaller.
3336 If there will be many thousands (or millions) of concurrent associations, you
3337 should make these larger.
3338 A prime number is best for the table size.
3340 update function will adjust your input value to the next highest prime number.
3341 .It Va net.inet.ip.alias.sctp.holddown_time: No 0
3342 Hold association in table for this many seconds after receiving a
3344 This allows endpoints to correct shutdown gracefully if a
3345 shutdown_complete is lost and retransmissions are required.
3346 .It Va net.inet.ip.alias.sctp.init_timer: No 15
3347 Timeout value while waiting for (INIT-ACK|AddIP-ACK).
3348 This value cannot be 0.
3349 .It Va net.inet.ip.alias.sctp.initialising_chunk_proc_limit: No 2
3350 Defines the maximum number of chunks in an SCTP packet that will be parsed when
3351 no existing association exists that matches that packet.
3353 will only be an INIT or ASCONF-AddIP packet.
3354 A higher value may become a DoS
3355 risk as malformed packets can consume processing resources.
3356 .It Va net.inet.ip.alias.sctp.param_proc_limit: No 25
3357 Defines the maximum number of parameters within a chunk that will be
3360 As for other similar sysctl variables, larger values pose a DoS risk.
3361 .It Va net.inet.ip.alias.sctp.log_level: No 0
3362 Level of detail in the system log messages (0 \- minimal, 1 \- event,
3363 2 \- info, 3 \- detail, 4 \- debug, 5 \- max debug).
3365 option in high loss environments.
3366 .It Va net.inet.ip.alias.sctp.shutdown_time: No 15
3367 Timeout value while waiting for SHUTDOWN-COMPLETE.
3368 This value cannot be 0.
3369 .It Va net.inet.ip.alias.sctp.track_global_addresses: No 0
3370 Enables/disables global IP address tracking within the
3373 upper limit on the number of addresses tracked for each association:
3374 .Bl -tag -width indent
3376 Global tracking is disabled
3378 Enables tracking, the maximum number of addresses tracked for each
3379 association is limited to this value
3382 This variable is fully dynamic, the new value will be adopted for all newly
3383 arriving associations, existing associations are treated
3384 as they were previously.
3385 Global tracking will decrease the number of collisions within the
3388 of increased processing load, memory usage, complexity, and possible
3391 problems in complex networks with multiple
3393 We recommend not tracking
3394 global IP addresses, this will still result in a fully functional
3396 .It Va net.inet.ip.alias.sctp.up_timer: No 300
3397 Timeout value to keep an association up with no traffic.
3398 This value cannot be 0.
3399 .It Va net.inet.ip.dummynet.expire : No 1
3400 Lazily delete dynamic pipes/queue once they have no pending traffic.
3401 You can disable this by setting the variable to 0, in which case
3402 the pipes/queues will only be deleted when the threshold is reached.
3403 .It Va net.inet.ip.dummynet.hash_size : No 64
3404 Default size of the hash table used for dynamic pipes/queues.
3405 This value is used when no
3407 option is specified when configuring a pipe/queue.
3408 .It Va net.inet.ip.dummynet.io_fast : No 0
3409 If set to a non-zero value,
3414 operation (see above) is enabled.
3415 .It Va net.inet.ip.dummynet.io_pkt
3416 Number of packets passed to
3418 .It Va net.inet.ip.dummynet.io_pkt_drop
3419 Number of packets dropped by
3421 .It Va net.inet.ip.dummynet.io_pkt_fast
3422 Number of packets bypassed by the
3425 .It Va net.inet.ip.dummynet.max_chain_len : No 16
3426 Target value for the maximum number of pipes/queues in a hash bucket.
3428 .Cm max_chain_len*hash_size
3429 is used to determine the threshold over which empty pipes/queues
3430 will be expired even when
3431 .Cm net.inet.ip.dummynet.expire=0 .
3432 .It Va net.inet.ip.dummynet.red_lookup_depth : No 256
3433 .It Va net.inet.ip.dummynet.red_avg_pkt_size : No 512
3434 .It Va net.inet.ip.dummynet.red_max_pkt_size : No 1500
3435 Parameters used in the computations of the drop probability
3436 for the RED algorithm.
3437 .It Va net.inet.ip.dummynet.pipe_byte_limit : No 1048576
3438 .It Va net.inet.ip.dummynet.pipe_slot_limit : No 100
3439 The maximum queue size that can be specified in bytes or packets.
3440 These limits prevent accidental exhaustion of resources such as mbufs.
3441 If you raise these limits,
3442 you should make sure the system is configured so that sufficient resources
3444 .It Va net.inet.ip.fw.autoinc_step : No 100
3445 Delta between rule numbers when auto-generating them.
3446 The value must be in the range 1..1000.
3447 .It Va net.inet.ip.fw.curr_dyn_buckets : Va net.inet.ip.fw.dyn_buckets
3448 The current number of buckets in the hash table for dynamic rules
3450 .It Va net.inet.ip.fw.debug : No 1
3451 Controls debugging messages produced by
3453 .It Va net.inet.ip.fw.default_rule : No 65535
3454 The default rule number (read-only).
3456 .Nm , the default rule is the last one, so its number
3457 can also serve as the highest number allowed for a rule.
3458 .It Va net.inet.ip.fw.dyn_buckets : No 256
3459 The number of buckets in the hash table for dynamic rules.
3460 Must be a power of 2, up to 65536.
3461 It only takes effect when all dynamic rules have expired, so you
3462 are advised to use a
3464 command to make sure that the hash table is resized.
3465 .It Va net.inet.ip.fw.dyn_count : No 3
3466 Current number of dynamic rules
3468 .It Va net.inet.ip.fw.dyn_keepalive : No 1
3469 Enables generation of keepalive packets for
3471 rules on TCP sessions.
3472 A keepalive is generated to both
3473 sides of the connection every 5 seconds for the last 20
3474 seconds of the lifetime of the rule.
3475 .It Va net.inet.ip.fw.dyn_max : No 8192
3476 Maximum number of dynamic rules.
3477 When you hit this limit, no more dynamic rules can be
3478 installed until old ones expire.
3479 .It Va net.inet.ip.fw.dyn_ack_lifetime : No 300
3480 .It Va net.inet.ip.fw.dyn_syn_lifetime : No 20
3481 .It Va net.inet.ip.fw.dyn_fin_lifetime : No 1
3482 .It Va net.inet.ip.fw.dyn_rst_lifetime : No 1
3483 .It Va net.inet.ip.fw.dyn_udp_lifetime : No 5
3484 .It Va net.inet.ip.fw.dyn_short_lifetime : No 30
3485 These variables control the lifetime, in seconds, of dynamic
3487 Upon the initial SYN exchange the lifetime is kept short,
3488 then increased after both SYN have been seen, then decreased
3489 again during the final FIN exchange or when a RST is received.
3491 .Em dyn_fin_lifetime
3493 .Em dyn_rst_lifetime
3494 must be strictly lower than 5 seconds, the period of
3495 repetition of keepalives.
3496 The firewall enforces that.
3497 .It Va net.inet.ip.fw.dyn_keep_states: No 0
3498 Keep dynamic states on rule/set deletion.
3499 States are relinked to default rule (65535).
3500 This can be handly for ruleset reload.
3501 Turned off by default.
3502 .It Va net.inet.ip.fw.enable : No 1
3503 Enables the firewall.
3504 Setting this variable to 0 lets you run your machine without
3505 firewall even if compiled in.
3506 .It Va net.inet6.ip6.fw.enable : No 1
3507 provides the same functionality as above for the IPv6 case.
3508 .It Va net.inet.ip.fw.one_pass : No 1
3509 When set, the packet exiting from the
3513 node is not passed though the firewall again.
3514 Otherwise, after an action, the packet is
3515 reinjected into the firewall at the next rule.
3516 .It Va net.inet.ip.fw.tables_max : No 128
3517 Maximum number of tables.
3518 .It Va net.inet.ip.fw.verbose : No 1
3519 Enables verbose messages.
3520 .It Va net.inet.ip.fw.verbose_limit : No 0
3521 Limits the number of messages produced by a verbose firewall.
3522 .It Va net.inet6.ip6.fw.deny_unknown_exthdrs : No 1
3523 If enabled packets with unknown IPv6 Extension Headers will be denied.
3524 .It Va net.link.ether.ipfw : No 0
3525 Controls whether layer-2 packets are passed to
3528 .It Va net.link.bridge.ipfw : No 0
3529 Controls whether bridged packets are passed to
3533 .Sh INTERNAL DIAGNOSTICS
3534 There are some commands that may be useful to understand current state
3535 of certain subsystems inside kernel module.
3536 These commands provide debugging output which may change without notice.
3538 Currently the following commands are available as
3541 .Bl -tag -width indent
3543 Lists all interface which are currently tracked by
3545 with their in-kernel status.
3547 List all table lookup algorithms currently available.
3550 There are far too many possible uses of
3552 so this Section will only give a small set of examples.
3554 .Ss BASIC PACKET FILTERING
3555 This command adds an entry which denies all tcp packets from
3556 .Em cracker.evil.org
3557 to the telnet port of
3559 from being forwarded by the host:
3561 .Dl "ipfw add deny tcp from cracker.evil.org to wolf.tambov.su telnet"
3563 This one disallows any connection from the entire cracker's
3566 .Dl "ipfw add deny ip from 123.45.67.0/24 to my.host.org"
3568 A first and efficient way to limit access (not using dynamic rules)
3569 is the use of the following rules:
3571 .Dl "ipfw add allow tcp from any to any established"
3572 .Dl "ipfw add allow tcp from net1 portlist1 to net2 portlist2 setup"
3573 .Dl "ipfw add allow tcp from net3 portlist3 to net3 portlist3 setup"
3575 .Dl "ipfw add deny tcp from any to any"
3577 The first rule will be a quick match for normal TCP packets,
3578 but it will not match the initial SYN packet, which will be
3581 rules only for selected source/destination pairs.
3582 All other SYN packets will be rejected by the final
3586 If you administer one or more subnets, you can take advantage
3587 of the address sets and or-blocks and write extremely
3588 compact rulesets which selectively enable services to blocks
3589 of clients, as below:
3591 .Dl "goodguys=\*q{ 10.1.2.0/24{20,35,66,18} or 10.2.3.0/28{6,3,11} }\*q"
3592 .Dl "badguys=\*q10.1.2.0/24{8,38,60}\*q"
3594 .Dl "ipfw add allow ip from ${goodguys} to any"
3595 .Dl "ipfw add deny ip from ${badguys} to any"
3596 .Dl "... normal policies ..."
3600 option could be used to do automated anti-spoofing by adding the
3601 following to the top of a ruleset:
3603 .Dl "ipfw add deny ip from any to any not verrevpath in"
3605 This rule drops all incoming packets that appear to be coming to the
3606 system on the wrong interface.
3607 For example, a packet with a source
3608 address belonging to a host on a protected internal network would be
3609 dropped if it tried to enter the system from an external interface.
3613 option could be used to do similar but more restricted anti-spoofing
3614 by adding the following to the top of a ruleset:
3616 .Dl "ipfw add deny ip from any to any not antispoof in"
3618 This rule drops all incoming packets that appear to be coming from another
3619 directly connected system but on the wrong interface.
3620 For example, a packet with a source address of
3621 .Li 192.168.0.0/24 ,
3630 option could be used to (re)mark user traffic,
3631 by adding the following to the appropriate place in ruleset:
3633 .Dl "ipfw add setdscp be ip from any to any dscp af11,af21"
3635 In order to protect a site from flood attacks involving fake
3636 TCP packets, it is safer to use dynamic rules:
3638 .Dl "ipfw add check-state"
3639 .Dl "ipfw add deny tcp from any to any established"
3640 .Dl "ipfw add allow tcp from my-net to any setup keep-state"
3642 This will let the firewall install dynamic rules only for
3643 those connection which start with a regular SYN packet coming
3644 from the inside of our network.
3645 Dynamic rules are checked when encountering the first
3654 rule should usually be placed near the beginning of the
3655 ruleset to minimize the amount of work scanning the ruleset.
3656 Your mileage may vary.
3658 To limit the number of connections a user can open
3659 you can use the following type of rules:
3661 .Dl "ipfw add allow tcp from my-net/24 to any setup limit src-addr 10"
3662 .Dl "ipfw add allow tcp from any to me setup limit src-addr 4"
3664 The former (assuming it runs on a gateway) will allow each host
3665 on a /24 network to open at most 10 TCP connections.
3666 The latter can be placed on a server to make sure that a single
3667 client does not use more than 4 simultaneous connections.
3670 stateful rules can be subject to denial-of-service attacks
3671 by a SYN-flood which opens a huge number of dynamic rules.
3672 The effects of such attacks can be partially limited by
3675 variables which control the operation of the firewall.
3677 Here is a good usage of the
3679 command to see accounting records and timestamp information:
3683 or in short form without timestamps:
3687 which is equivalent to:
3691 Next rule diverts all incoming packets from 192.168.2.0/24
3692 to divert port 5000:
3694 .Dl ipfw divert 5000 ip from 192.168.2.0/24 to any in
3696 The following rules show some of the applications of
3700 for simulations and the like.
3702 This rule drops random incoming packets with a probability
3705 .Dl "ipfw add prob 0.05 deny ip from any to any in"
3707 A similar effect can be achieved making use of
3711 .Dl "ipfw add pipe 10 ip from any to any"
3712 .Dl "ipfw pipe 10 config plr 0.05"
3714 We can use pipes to artificially limit bandwidth, e.g.\& on a
3715 machine acting as a router, if we want to limit traffic from
3716 local clients on 192.168.2.0/24 we do:
3718 .Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out"
3719 .Dl "ipfw pipe 1 config bw 300Kbit/s queue 50KBytes"
3721 note that we use the
3723 modifier so that the rule is not used twice.
3724 Remember in fact that
3726 rules are checked both on incoming and outgoing packets.
3728 Should we want to simulate a bidirectional link with bandwidth
3729 limitations, the correct way is the following:
3731 .Dl "ipfw add pipe 1 ip from any to any out"
3732 .Dl "ipfw add pipe 2 ip from any to any in"
3733 .Dl "ipfw pipe 1 config bw 64Kbit/s queue 10Kbytes"
3734 .Dl "ipfw pipe 2 config bw 64Kbit/s queue 10Kbytes"
3736 The above can be very useful, e.g.\& if you want to see how
3737 your fancy Web page will look for a residential user who
3738 is connected only through a slow link.
3739 You should not use only one pipe for both directions, unless
3740 you want to simulate a half-duplex medium (e.g.\& AppleTalk,
3742 It is not necessary that both pipes have the same configuration,
3743 so we can also simulate asymmetric links.
3745 Should we want to verify network performance with the RED queue
3746 management algorithm:
3748 .Dl "ipfw add pipe 1 ip from any to any"
3749 .Dl "ipfw pipe 1 config bw 500Kbit/s queue 100 red 0.002/30/80/0.1"
3751 Another typical application of the traffic shaper is to
3752 introduce some delay in the communication.
3753 This can significantly affect applications which do a lot of Remote
3754 Procedure Calls, and where the round-trip-time of the
3755 connection often becomes a limiting factor much more than
3758 .Dl "ipfw add pipe 1 ip from any to any out"
3759 .Dl "ipfw add pipe 2 ip from any to any in"
3760 .Dl "ipfw pipe 1 config delay 250ms bw 1Mbit/s"
3761 .Dl "ipfw pipe 2 config delay 250ms bw 1Mbit/s"
3763 Per-flow queueing can be useful for a variety of purposes.
3764 A very simple one is counting traffic:
3766 .Dl "ipfw add pipe 1 tcp from any to any"
3767 .Dl "ipfw add pipe 1 udp from any to any"
3768 .Dl "ipfw add pipe 1 ip from any to any"
3769 .Dl "ipfw pipe 1 config mask all"
3771 The above set of rules will create queues (and collect
3772 statistics) for all traffic.
3773 Because the pipes have no limitations, the only effect is
3774 collecting statistics.
3775 Note that we need 3 rules, not just the last one, because
3778 tries to match IP packets it will not consider ports, so we
3779 would not see connections on separate ports as different
3782 A more sophisticated example is limiting the outbound traffic
3783 on a net with per-host limits, rather than per-network limits:
3785 .Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out"
3786 .Dl "ipfw add pipe 2 ip from any to 192.168.2.0/24 in"
3787 .Dl "ipfw pipe 1 config mask src-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
3788 .Dl "ipfw pipe 2 config mask dst-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
3790 In the following example, we need to create several traffic bandwidth
3791 classes and we need different hosts/networks to fall into different classes.
3792 We create one pipe for each class and configure them accordingly.
3793 Then we create a single table and fill it with IP subnets and addresses.
3794 For each subnet/host we set the argument equal to the number of the pipe
3796 Then we classify traffic using a single rule:
3798 .Dl "ipfw pipe 1 config bw 1000Kbyte/s"
3799 .Dl "ipfw pipe 4 config bw 4000Kbyte/s"
3801 .Dl "ipfw table T1 create type addr"
3802 .Dl "ipfw table T1 add 192.168.2.0/24 1"
3803 .Dl "ipfw table T1 add 192.168.0.0/27 4"
3804 .Dl "ipfw table T1 add 192.168.0.2 1"
3806 .Dl "ipfw add pipe tablearg ip from 'table(T1)' to any"
3810 action, the table entries may include hostnames and IP addresses.
3812 .Dl "ipfw table T2 create type addr ftype ip"
3813 .Dl "ipfw table T2 add 192.168.2.0/24 10.23.2.1"
3814 .Dl "ipfw table T21 add 192.168.0.0/27 router1.dmz"
3816 .Dl "ipfw add 100 fwd tablearg ip from any to table(1)"
3818 In the following example per-interface firewall is created:
3820 .Dl "ipfw table IN create type iface valtype skipto,fib"
3821 .Dl "ipfw table IN add vlan20 12000,12"
3822 .Dl "ipfw table IN add vlan30 13000,13"
3823 .Dl "ipfw table OUT create type iface valtype skipto"
3824 .Dl "ipfw table OUT add vlan20 22000"
3825 .Dl "ipfw table OUT add vlan30 23000"
3827 .Dl "ipfw add 100 ipfw setfib tablearg ip from any to any recv 'table(IN)' in"
3828 .Dl "ipfw add 200 ipfw skipto tablearg ip from any to any recv 'table(IN)' in"
3829 .Dl "ipfw add 300 ipfw skipto tablearg ip from any to any xmit 'table(OUT)' out"
3831 The following example illustrate usage of flow tables:
3833 .Dl "ipfw table fl create type flow:flow:src-ip,proto,dst-ip,dst-port"
3834 .Dl "ipfw table fl add 2a02:6b8:77::88,tcp,2a02:6b8:77::99,80 11"
3835 .Dl "ipfw table fl add 10.0.0.1,udp,10.0.0.2,53 12"
3837 .Dl "ipfw add 100 allow ip from any to any flow 'table(fl,11)' recv ix0"
3839 To add a set of rules atomically, e.g.\& set 18:
3841 .Dl "ipfw set disable 18"
3842 .Dl "ipfw add NN set 18 ... # repeat as needed"
3843 .Dl "ipfw set enable 18"
3845 To delete a set of rules atomically the command is simply:
3847 .Dl "ipfw delete set 18"
3849 To test a ruleset and disable it and regain control if something goes wrong:
3851 .Dl "ipfw set disable 18"
3852 .Dl "ipfw add NN set 18 ... # repeat as needed"
3853 .Dl "ipfw set enable 18; echo done; sleep 30 && ipfw set disable 18"
3855 Here if everything goes well, you press control-C before the "sleep"
3856 terminates, and your ruleset will be left active.
3857 Otherwise, e.g.\& if
3858 you cannot access your box, the ruleset will be disabled after
3859 the sleep terminates thus restoring the previous situation.
3861 To show rules of the specific set:
3863 .Dl "ipfw set 18 show"
3865 To show rules of the disabled set:
3867 .Dl "ipfw -S set 18 show"
3869 To clear a specific rule counters of the specific set:
3871 .Dl "ipfw set 18 zero NN"
3873 To delete a specific rule of the specific set:
3875 .Dl "ipfw set 18 delete NN"
3876 .Ss NAT, REDIRECT AND LSNAT
3877 First redirect all the traffic to nat instance 123:
3879 .Dl "ipfw add nat 123 all from any to any"
3881 Then to configure nat instance 123 to alias all the outgoing traffic with ip
3882 192.168.0.123, blocking all incoming connections, trying to keep
3883 same ports on both sides, clearing aliasing table on address change
3884 and keeping a log of traffic/link statistics:
3886 .Dl "ipfw nat 123 config ip 192.168.0.123 log deny_in reset same_ports"
3888 Or to change address of instance 123, aliasing table will be cleared (see
3891 .Dl "ipfw nat 123 config ip 10.0.0.1"
3893 To see configuration of nat instance 123:
3895 .Dl "ipfw nat 123 show config"
3897 To show logs of all the instances in range 111-999:
3899 .Dl "ipfw nat 111-999 show"
3901 To see configurations of all instances:
3903 .Dl "ipfw nat show config"
3905 Or a redirect rule with mixed modes could looks like:
3907 .Dl "ipfw nat 123 config redirect_addr 10.0.0.1 10.0.0.66"
3908 .Dl " redirect_port tcp 192.168.0.1:80 500"
3909 .Dl " redirect_proto udp 192.168.1.43 192.168.1.1"
3910 .Dl " redirect_addr 192.168.0.10,192.168.0.11"
3911 .Dl " 10.0.0.100 # LSNAT"
3912 .Dl " redirect_port tcp 192.168.0.1:80,192.168.0.10:22"
3915 or it could be split in:
3917 .Dl "ipfw nat 1 config redirect_addr 10.0.0.1 10.0.0.66"
3918 .Dl "ipfw nat 2 config redirect_port tcp 192.168.0.1:80 500"
3919 .Dl "ipfw nat 3 config redirect_proto udp 192.168.1.43 192.168.1.1"
3920 .Dl "ipfw nat 4 config redirect_addr 192.168.0.10,192.168.0.11,192.168.0.12"
3922 .Dl "ipfw nat 5 config redirect_port tcp"
3923 .Dl " 192.168.0.1:80,192.168.0.10:22,192.168.0.20:25 500"
3944 utility first appeared in
3949 Stateful extensions were introduced in
3952 was introduced in Summer 2002.
3954 .An Ugen J. S. Antsilevich ,
3955 .An Poul-Henning Kamp ,
3961 API based upon code written by
3965 Dummynet has been introduced by Luigi Rizzo in 1997-1998.
3967 Some early work (1999-2000) on the
3969 traffic shaper supported by Akamba Corp.
3971 The ipfw core (ipfw2) has been completely redesigned and
3972 reimplemented by Luigi Rizzo in summer 2002.
3975 options have been added by various developer over the years.
3978 In-kernel NAT support written by
3979 .An Paolo Pisati Aq Mt piso@FreeBSD.org
3980 as part of a Summer of Code 2005 project.
3984 support has been developed by
3985 .An The Centre for Advanced Internet Architectures (CAIA) Aq http://www.caia.swin.edu.au .
3986 The primary developers and maintainers are David Hayes and Jason But.
3987 For further information visit:
3988 .Aq http://www.caia.swin.edu.au/urp/SONATA
3990 Delay profiles have been developed by Alessandro Cerri and
3991 Luigi Rizzo, supported by the
3992 European Commission within Projects Onelab and Onelab2.
3994 The syntax has grown over the years and sometimes it might be confusing.
3995 Unfortunately, backward compatibility prevents cleaning up mistakes
3996 made in the definition of the syntax.
4000 Misconfiguring the firewall can put your computer in an unusable state,
4001 possibly shutting down network services and requiring console access to
4002 regain control of it.
4004 Incoming packet fragments diverted by
4006 are reassembled before delivery to the socket.
4007 The action used on those packet is the one from the
4008 rule which matches the first fragment of the packet.
4010 Packets diverted to userland, and then reinserted by a userland process
4011 may lose various packet attributes.
4012 The packet source interface name
4013 will be preserved if it is shorter than 8 bytes and the userland process
4014 saves and reuses the sockaddr_in
4017 otherwise, it may be lost.
4018 If a packet is reinserted in this manner, later rules may be incorrectly
4019 applied, making the order of
4021 rules in the rule sequence very important.
4023 Dummynet drops all packets with IPv6 link-local addresses.
4029 may not behave as expected.
4030 In particular, incoming SYN packets may
4031 have no uid or gid associated with them since they do not yet belong
4032 to a TCP connection, and the uid/gid associated with a packet may not
4033 be as expected if the associated process calls
4035 or similar system calls.
4037 Rule syntax is subject to the command line environment and some patterns
4038 may need to be escaped with the backslash character
4039 or quoted appropriately.
4041 Due to the architecture of
4043 ipfw nat is not compatible with the TCP segmentation offloading (TSO).
4044 Thus, to reliably nat your network traffic, please disable TSO
4048 ICMP error messages are not implicitly matched by dynamic rules
4049 for the respective conversations.
4050 To avoid failures of network error detection and path MTU discovery,
4051 ICMP error messages may need to be allowed explicitly through static
4058 actions may lead to confusing behaviour if ruleset has mistakes,
4059 and/or interaction with other subsystems (netgraph, dummynet, etc.) is used.
4060 One possible case for this is packet leaving
4062 in subroutine on the input pass, while later on output encountering unpaired
4065 As the call stack is kept intact after input pass, packet will suddenly
4066 return to the rule number used on input pass, not on output one.
4067 Order of processing should be checked carefully to avoid such mistakes.
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