7 .Nd User interface for firewall, traffic shaper, packet scheduler,
10 .Ss FIREWALL CONFIGURATION
19 .Op Ar rule | first-last ...
27 .Brq Cm delete | zero | resetlog
31 .Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ...
35 .Ar number Cm to Ar number
37 .Cm set swap Ar number number
43 .Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive
46 .Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive
49 .Oo Cm set Ar N Oc Cm table Ar name Cm create Ar create-options
51 .Oo Cm set Ar N Oc Cm table
55 .Oo Cm set Ar N Oc Cm table Ar name Cm modify Ar modify-options
57 .Oo Cm set Ar N Oc Cm table Ar name Cm swap Ar name
59 .Oo Cm set Ar N Oc Cm table Ar name Cm add Ar table-key Op Ar value
61 .Oo Cm set Ar N Oc Cm table Ar name Cm add Op Ar table-key Ar value ...
63 .Oo Cm set Ar N Oc Cm table Ar name Cm atomic add Op Ar table-key Ar value ...
65 .Oo Cm set Ar N Oc Cm table Ar name Cm delete Op Ar table-key ...
67 .Oo Cm set Ar N Oc Cm table Ar name Cm lookup Ar addr
69 .Oo Cm set Ar N Oc Cm table Ar name Cm lock
71 .Oo Cm set Ar N Oc Cm table Ar name Cm unlock
73 .Oo Cm set Ar N Oc Cm table
77 .Oo Cm set Ar N Oc Cm table
81 .Oo Cm set Ar N Oc Cm table
85 .Oo Cm set Ar N Oc Cm table
88 .Ss DUMMYNET CONFIGURATION (TRAFFIC SHAPER AND PACKET SCHEDULER)
90 .Brq Cm pipe | queue | sched
96 .Brq Cm pipe | queue | sched
97 .Brq Cm delete | list | show
111 .Ss STATEFUL IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
113 .Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm create Ar create-options
115 .Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm config Ar config-options
117 .Oo Cm set Ar N Oc Cm nat64lsn
122 .Oo Cm set Ar N Oc Cm nat64lsn
126 .Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm stats Op Cm reset
127 .Ss STATELESS IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
129 .Oo Cm set Ar N Oc Cm nat64stl Ar name Cm create Ar create-options
131 .Oo Cm set Ar N Oc Cm nat64stl Ar name Cm config Ar config-options
133 .Oo Cm set Ar N Oc Cm nat64stl
137 .Oo Cm set Ar N Oc Cm nat64stl
141 .Oo Cm set Ar N Oc Cm nat64stl Ar name Cm stats Op Cm reset
142 .Ss XLAT464 CLAT IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
144 .Oo Cm set Ar N Oc Cm nat64clat Ar name Cm create Ar create-options
146 .Oo Cm set Ar N Oc Cm nat64clat Ar name Cm config Ar config-options
148 .Oo Cm set Ar N Oc Cm nat64clat
152 .Oo Cm set Ar N Oc Cm nat64clat
156 .Oo Cm set Ar N Oc Cm nat64clat Ar name Cm stats Op Cm reset
157 .Ss IPv6-to-IPv6 NETWORK PREFIX TRANSLATION
159 .Oo Cm set Ar N Oc Cm nptv6 Ar name Cm create Ar create-options
161 .Oo Cm set Ar N Oc Cm nptv6
165 .Oo Cm set Ar N Oc Cm nptv6
169 .Oo Cm set Ar N Oc Cm nptv6 Ar name Cm stats Op Cm reset
170 .Ss INTERNAL DIAGNOSTICS
177 .Ss LIST OF RULES AND PREPROCESSING
190 utility is the user interface for controlling the
194 traffic shaper/packet scheduler, and the
195 in-kernel NAT services.
197 A firewall configuration, or
201 numbered from 1 to 65535.
202 Packets are passed to the firewall
203 from a number of different places in the protocol stack
204 (depending on the source and destination of the packet,
205 it is possible for the firewall to be
206 invoked multiple times on the same packet).
207 The packet passed to the firewall is compared
208 against each of the rules in the
211 (multiple rules with the same number are permitted, in which case
212 they are processed in order of insertion).
213 When a match is found, the action corresponding to the
214 matching rule is performed.
216 Depending on the action and certain system settings, packets
217 can be reinjected into the firewall at some rule after the
218 matching one for further processing.
220 A ruleset always includes a
222 rule (numbered 65535) which cannot be modified or deleted,
223 and matches all packets.
224 The action associated with the
230 depending on how the kernel is configured.
232 If the ruleset includes one or more rules with the
239 the firewall will have a
241 behaviour, i.e., upon a match it will create
243 i.e., rules that match packets with the same 5-tuple
244 (protocol, source and destination addresses and ports)
245 as the packet which caused their creation.
246 Dynamic rules, which have a limited lifetime, are checked
247 at the first occurrence of a
252 rule, and are typically used to open the firewall on-demand to
253 legitimate traffic only.
260 for all packets (not only these matched by the rule) but
267 .Sx STATEFUL FIREWALL
270 Sections below for more information on the stateful behaviour of
273 All rules (including dynamic ones) have a few associated counters:
274 a packet count, a byte count, a log count and a timestamp
275 indicating the time of the last match.
276 Counters can be displayed or reset with
280 Each rule belongs to one of 32 different
284 commands to atomically manipulate sets, such as enable,
285 disable, swap sets, move all rules in a set to another
286 one, delete all rules in a set.
287 These can be useful to
288 install temporary configurations, or to test them.
291 for more information on
294 Rules can be added with the
296 command; deleted individually or in groups with the
298 command, and globally (except those in set 31) with the
300 command; displayed, optionally with the content of the
306 Finally, counters can be reset with the
312 The following general options are available when invoking
314 .Bl -tag -width indent
316 Show counter values when listing rules.
319 command implies this option.
321 Only show the action and the comment, not the body of a rule.
325 When entering or showing rules, print them in compact form,
326 i.e., omitting the "ip from any to any" string
327 when this does not carry any additional information.
329 When listing, show dynamic rules in addition to static ones.
331 When listing, show only dynamic states.
332 When deleting, delete only dynamic states.
334 Run without prompting for confirmation for commands that can cause problems if misused,
337 If there is no tty associated with the process, this is implied.
340 command with this flag ignores possible errors,
341 i.e., nonexistent rule number.
342 And for batched commands execution continues with the next command.
344 When listing a table (see the
346 section below for more information on lookup tables), format values
348 By default, values are shown as integers.
350 Only check syntax of the command strings, without actually passing
353 Try to resolve addresses and service names in output.
355 Be quiet when executing the
365 This is useful when updating rulesets by executing multiple
369 .Ql sh\ /etc/rc.firewall ) ,
370 or by processing a file with many
372 rules across a remote login session.
373 It also stops a table add or delete
374 from failing if the entry already exists or is not present.
376 The reason why this option may be important is that
377 for some of these actions,
379 may print a message; if the action results in blocking the
380 traffic to the remote client,
381 the remote login session will be closed
382 and the rest of the ruleset will not be processed.
383 Access to the console would then be required to recover.
385 When listing rules, show the
387 each rule belongs to.
388 If this flag is not specified, disabled rules will not be
391 When listing pipes, sort according to one of the four
392 counters (total or current packets or bytes).
394 When listing, show last match timestamp converted with
397 When listing, show last match timestamp as seconds from the epoch.
398 This form can be more convenient for postprocessing by scripts.
400 .Ss LIST OF RULES AND PREPROCESSING
401 To ease configuration, rules can be put into a file which is
404 as shown in the last synopsis line.
408 The file will be read line by line and applied as arguments to the
412 Optionally, a preprocessor can be specified using
416 is to be piped through.
417 Useful preprocessors include
423 does not start with a slash
425 as its first character, the usual
427 name search is performed.
428 Care should be taken with this in environments where not all
429 file systems are mounted (yet) by the time
431 is being run (e.g.\& when they are mounted over NFS).
434 has been specified, any additional arguments are passed on to the preprocessor
436 This allows for flexible configuration files (like conditionalizing
437 them on the local hostname) and the use of macros to centralize
438 frequently required arguments like IP addresses.
439 .Ss TRAFFIC SHAPER CONFIGURATION
445 commands are used to configure the traffic shaper and packet scheduler.
447 .Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
448 Section below for details.
450 If the world and the kernel get out of sync the
452 ABI may break, preventing you from being able to add any rules.
453 This can adversely affect the booting process.
458 to temporarily disable the firewall to regain access to the network,
459 allowing you to fix the problem.
461 A packet is checked against the active ruleset in multiple places
462 in the protocol stack, under control of several sysctl variables.
463 These places and variables are shown below, and it is important to
464 have this picture in mind in order to design a correct ruleset.
465 .Bd -literal -offset indent
468 +----------->-----------+
470 [ip(6)_input] [ip(6)_output] net.inet(6).ip(6).fw.enable=1
473 [ether_demux] [ether_output_frame] net.link.ether.ipfw=1
475 +-->--[bdg_forward]-->--+ net.link.bridge.ipfw=1
481 times the same packet goes through the firewall can
482 vary between 0 and 4 depending on packet source and
483 destination, and system configuration.
485 Note that as packets flow through the stack, headers can be
486 stripped or added to it, and so they may or may not be available
488 E.g., incoming packets will include the MAC header when
492 but the same packets will have the MAC header stripped off when
499 Also note that each packet is always checked against the complete ruleset,
500 irrespective of the place where the check occurs, or the source of the packet.
501 If a rule contains some match patterns or actions which are not valid
502 for the place of invocation (e.g.\& trying to match a MAC header within
506 the match pattern will not match, but a
508 operator in front of such patterns
512 match on those packets.
513 It is thus the responsibility of
514 the programmer, if necessary, to write a suitable ruleset to
515 differentiate among the possible places.
517 rules can be useful here, as an example:
518 .Bd -literal -offset indent
519 # packets from ether_demux or bdg_forward
520 ipfw add 10 skipto 1000 all from any to any layer2 in
521 # packets from ip_input
522 ipfw add 10 skipto 2000 all from any to any not layer2 in
523 # packets from ip_output
524 ipfw add 10 skipto 3000 all from any to any not layer2 out
525 # packets from ether_output_frame
526 ipfw add 10 skipto 4000 all from any to any layer2 out
529 (yes, at the moment there is no way to differentiate between
530 ether_demux and bdg_forward).
532 Also note that only actions
541 frames and all other actions act as if they were
544 Full set of actions is supported for IP packets without
549 action does not divert
553 In general, each keyword or argument must be provided as
554 a separate command line argument, with no leading or trailing
556 Keywords are case-sensitive, whereas arguments may
557 or may not be case-sensitive depending on their nature
558 (e.g.\& uid's are, hostnames are not).
560 Some arguments (e.g., port or address lists) are comma-separated
562 In this case, spaces after commas ',' are allowed to make
563 the line more readable.
564 You can also put the entire
565 command (including flags) into a single argument.
566 E.g., the following forms are equivalent:
567 .Bd -literal -offset indent
568 ipfw -q add deny src-ip 10.0.0.0/24,127.0.0.1/8
569 ipfw -q add deny src-ip 10.0.0.0/24, 127.0.0.1/8
570 ipfw "-q add deny src-ip 10.0.0.0/24, 127.0.0.1/8"
573 The format of firewall rules is the following:
574 .Bd -ragged -offset indent
577 .Op Cm set Ar set_number
578 .Op Cm prob Ar match_probability
580 .Op Cm log Op Cm logamount Ar number
590 where the body of the rule specifies which information is used
591 for filtering packets, among the following:
593 .Bl -tag -width "Source and dest. addresses and ports" -offset XXX -compact
594 .It Layer2 header fields
596 .It IPv4 and IPv6 Protocol
597 SCTP, TCP, UDP, ICMP, etc.
598 .It Source and dest. addresses and ports
602 .It Transmit and receive interface
604 .It Misc. IP header fields
605 Version, type of service, datagram length, identification,
609 .It IPv6 Extension headers
610 Fragmentation, Hop-by-Hop options,
611 Routing Headers, Source routing rthdr0, Mobile IPv6 rthdr2, IPSec options.
613 .It Misc. TCP header fields
614 TCP flags (SYN, FIN, ACK, RST, etc.),
615 sequence number, acknowledgment number,
623 When the packet can be associated with a local socket.
625 Whether a packet came from a divert socket (e.g.,
627 .It Fib annotation state
628 Whether a packet has been tagged for using a specific FIB (routing table)
629 in future forwarding decisions.
632 Note that some of the above information, e.g.\& source MAC or IP addresses and
633 TCP/UDP ports, can be easily spoofed, so filtering on those fields
634 alone might not guarantee the desired results.
635 .Bl -tag -width indent
637 Each rule is associated with a
639 in the range 1..65535, with the latter reserved for the
642 Rules are checked sequentially by rule number.
643 Multiple rules can have the same number, in which case they are
644 checked (and listed) according to the order in which they have
646 If a rule is entered without specifying a number, the kernel will
647 assign one in such a way that the rule becomes the last one
651 Automatic rule numbers are assigned by incrementing the last
652 non-default rule number by the value of the sysctl variable
653 .Ar net.inet.ip.fw.autoinc_step
654 which defaults to 100.
655 If this is not possible (e.g.\& because we would go beyond the
656 maximum allowed rule number), the number of the last
657 non-default value is used instead.
658 .It Cm set Ar set_number
659 Each rule is associated with a
662 Sets can be individually disabled and enabled, so this parameter
663 is of fundamental importance for atomic ruleset manipulation.
664 It can be also used to simplify deletion of groups of rules.
665 If a rule is entered without specifying a set number,
668 Set 31 is special in that it cannot be disabled,
669 and rules in set 31 are not deleted by the
671 command (but you can delete them with the
672 .Nm ipfw delete set 31
674 Set 31 is also used for the
677 .It Cm prob Ar match_probability
678 A match is only declared with the specified probability
679 (floating point number between 0 and 1).
680 This can be useful for a number of applications such as
681 random packet drop or
684 to simulate the effect of multiple paths leading to out-of-order
687 Note: this condition is checked before any other condition, including
694 .It Cm log Op Cm logamount Ar number
695 Packets matching a rule with the
697 keyword will be made available for logging in two ways:
698 if the sysctl variable
699 .Va net.inet.ip.fw.verbose
700 is set to 0 (default), one can use
705 This pseudo interface can be created manually after a system
706 boot by using the following command:
707 .Bd -literal -offset indent
708 # ifconfig ipfw0 create
711 Or, automatically at boot time by adding the following
715 .Bd -literal -offset indent
719 There is zero overhead when no
721 is attached to the pseudo interface.
724 .Va net.inet.ip.fw.verbose
725 is set to 1, packets will be logged to
729 facility up to a maximum of
734 is specified, the limit is taken from the sysctl variable
735 .Va net.inet.ip.fw.verbose_limit .
736 In both cases, a value of 0 means unlimited logging.
738 Once the limit is reached, logging can be re-enabled by
739 clearing the logging counter or the packet counter for that entry, see the
743 Note: logging is done after all other packet matching conditions
744 have been successfully verified, and before performing the final
745 action (accept, deny, etc.) on the packet.
747 When a packet matches a rule with the
749 keyword, the numeric tag for the given
751 in the range 1..65534 will be attached to the packet.
752 The tag acts as an internal marker (it is not sent out over
753 the wire) that can be used to identify these packets later on.
754 This can be used, for example, to provide trust between interfaces
755 and to start doing policy-based filtering.
756 A packet can have multiple tags at the same time.
757 Tags are "sticky", meaning once a tag is applied to a packet by a
758 matching rule it exists until explicit removal.
759 Tags are kept with the packet everywhere within the kernel, but are
760 lost when the packet leaves the kernel, for example, on transmitting
761 packet out to the network or sending packet to a
765 To check for previously applied tags, use the
768 To delete previously applied tag, use the
772 Note: since tags are kept with the packet everywhere in kernelspace,
773 they can be set and unset anywhere in the kernel network subsystem
776 facility), not only by means of the
782 For example, there can be a specialized
784 node doing traffic analyzing and tagging for later inspecting
786 .It Cm untag Ar number
787 When a packet matches a rule with the
789 keyword, the tag with the number
791 is searched among the tags attached to this packet and,
792 if found, removed from it.
793 Other tags bound to packet, if present, are left untouched.
794 .It Cm setmark Ar value | tablearg
795 When a packet matches a rule with the
797 keyword, a 32-bit numeric mark is assigned to the packet.
798 The mark is an extension to the tags.
799 As tags, mark is "sticky" so the value is kept the same within the kernel and
800 is lost when the packet leaves the kernel.
801 Unlike tags, mark can be matched as a lookup table key or compared with bitwise
802 mask applied against another value.
803 Each packet can have only one mark, so
805 always overwrites the previous mark value.
807 The initial mark value is 0.
808 To check the current mark value, use the
813 can be entered as decimal or hexadecimal (if prefixed by 0x), and they
814 are always printed as hexadecimal.
816 When a packet matches a rule with the
818 keyword, the ALTQ identifier for the given
823 Note that this ALTQ tag is only meaningful for packets going "out" of IPFW,
824 and not being rejected or going to divert sockets.
825 Note that if there is insufficient memory at the time the packet is
826 processed, it will not be tagged, so it is wise to make your ALTQ
827 "default" queue policy account for this.
830 rules match a single packet, only the first one adds the ALTQ classification
832 In doing so, traffic may be shaped by using
833 .Cm count Cm altq Ar queue
834 rules for classification early in the ruleset, then later applying
835 the filtering decision.
840 rules may come later and provide the actual filtering decisions in
841 addition to the fallback ALTQ tag.
845 to set up the queues before IPFW will be able to look them up by name,
846 and if the ALTQ disciplines are rearranged, the rules in containing the
847 queue identifiers in the kernel will likely have gone stale and need
849 Stale queue identifiers will probably result in misclassification.
851 All system ALTQ processing can be turned on or off via
856 .Cm disable Ar altq .
858 .Va net.inet.ip.fw.one_pass
859 is irrelevant to ALTQ traffic shaping, as the actual rule action is followed
860 always after adding an ALTQ tag.
863 A rule can be associated with one of the following actions, which
864 will be executed when the packet matches the body of the rule.
865 .Bl -tag -width indent
866 .It Cm allow | accept | pass | permit
867 Allow packets that match rule.
868 The search terminates.
869 .It Cm check-state Op Ar :flowname | Cm :any
870 Checks the packet against the dynamic ruleset.
871 If a match is found, execute the action associated with
872 the rule which generated this dynamic rule, otherwise
873 move to the next rule.
876 rules do not have a body.
879 rule is found, the dynamic ruleset is checked at the first
886 is symbolic name assigned to dynamic rule by
891 can be used to ignore states flowname when matching.
894 keyword is special name used for compatibility with old rulesets.
896 Update counters for all packets that match rule.
897 The search continues with the next rule.
899 Discard packets that match this rule.
900 The search terminates.
901 .It Cm divert Ar port
902 Divert packets that match this rule to the
906 The search terminates.
907 .It Cm fwd | forward Ar ipaddr | tablearg Ns Op , Ns Ar port
908 Change the next-hop on matching packets to
910 which can be an IP address or a host name.
911 The next hop can also be supplied by the last table
912 looked up for the packet by using the
914 keyword instead of an explicit address.
915 The search terminates if this rule matches.
919 is a local address, then matching packets will be forwarded to
921 (or the port number in the packet if one is not specified in the rule)
922 on the local machine.
926 is not a local address, then the port number
927 (if specified) is ignored, and the packet will be
928 forwarded to the remote address, using the route as found in
929 the local routing table for that IP.
933 rule will not match layer2 packets (those received
934 on ether_input, ether_output, or bridged).
938 action does not change the contents of the packet at all.
939 In particular, the destination address remains unmodified, so
940 packets forwarded to another system will usually be rejected by that system
941 unless there is a matching rule on that system to capture them.
942 For packets forwarded locally,
943 the local address of the socket will be
944 set to the original destination address of the packet.
947 entry look rather weird but is intended for
948 use with transparent proxy servers.
949 .It Cm nat Ar nat_nr | global | tablearg
952 (for network address translation, address redirect, etc.):
954 .Sx NETWORK ADDRESS TRANSLATION (NAT)
955 Section for further information.
956 .It Cm nat64lsn Ar name
957 Pass packet to a stateful NAT64 instance (for IPv6/IPv4 network address and
958 protocol translation): see the
959 .Sx IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
960 Section for further information.
961 .It Cm nat64stl Ar name
962 Pass packet to a stateless NAT64 instance (for IPv6/IPv4 network address and
963 protocol translation): see the
964 .Sx IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
965 Section for further information.
966 .It Cm nat64clat Ar name
967 Pass packet to a CLAT NAT64 instance (for client-side IPv6/IPv4 network address and
968 protocol translation): see the
969 .Sx IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
970 Section for further information.
972 Pass packet to a NPTv6 instance (for IPv6-to-IPv6 network prefix translation):
974 .Sx IPv6-to-IPv6 NETWORK PREFIX TRANSLATION (NPTv6)
975 Section for further information.
976 .It Cm pipe Ar pipe_nr
980 (for bandwidth limitation, delay, etc.).
982 .Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
983 Section for further information.
984 The search terminates; however, on exit from the pipe and if
988 .Va net.inet.ip.fw.one_pass
989 is not set, the packet is passed again to the firewall code
990 starting from the next rule.
991 .It Cm queue Ar queue_nr
995 (for bandwidth limitation using WF2Q+).
1001 Discard packets that match this rule, and if the
1002 packet is a TCP packet, try to send a TCP reset (RST) notice.
1003 The search terminates.
1005 Discard packets that match this rule, and if the
1006 packet is a TCP packet, try to send a TCP reset (RST) notice.
1007 The search terminates.
1008 .It Cm skipto Ar number | tablearg
1009 Skip all subsequent rules numbered less than
1011 The search continues with the first rule numbered
1014 It is possible to use the
1016 keyword with a skipto for a
1019 Skipto may work either in O(log(N)) or in O(1) depending
1020 on amount of memory and/or sysctl variables.
1022 .Sx SYSCTL VARIABLES
1023 section for more details.
1024 .It Cm call Ar number | tablearg
1025 The current rule number is saved in the internal stack and
1026 ruleset processing continues with the first rule numbered
1029 If later a rule with the
1031 action is encountered, the processing returns to the first rule
1034 rule plus one or higher
1035 (the same behaviour as with packets returning from
1040 This could be used to make somewhat like an assembly language
1042 calls to rules with common checks for different interfaces, etc.
1044 Rule with any number could be called, not just forward jumps as with
1046 So, to prevent endless loops in case of mistakes, both
1050 actions don't do any jumps and simply go to the next rule if memory
1051 cannot be allocated or stack overflowed/underflowed.
1053 Internally stack for rule numbers is implemented using
1055 facility and currently has size of 16 entries.
1056 As mbuf tags are lost when packet leaves the kernel,
1058 should not be used in subroutines to avoid endless loops
1059 and other undesired effects.
1061 Takes rule number saved to internal stack by the last
1063 action and returns ruleset processing to the first rule
1064 with number greater than number of corresponding
1067 See description of the
1069 action for more details.
1075 and thus are unconditional, but
1077 command-line utility currently requires every action except
1080 While it is sometimes useful to return only on some packets,
1081 usually you want to print just
1084 A workaround for this is to use new syntax and
1087 .Bd -literal -offset indent
1088 # Add a rule without actual body
1089 ipfw add 2999 return via any
1091 # List rules without "from any to any" part
1095 This cosmetic annoyance may be fixed in future releases.
1097 Send a copy of packets matching this rule to the
1099 socket bound to port
1101 The search continues with the next rule.
1102 .It Cm unreach Ar code Op mtu
1103 Discard packets that match this rule, and try to send an ICMP
1104 unreachable notice with code
1108 is a number from 0 to 255, or one of these aliases:
1109 .Cm net , host , protocol , port ,
1110 .Cm needfrag , srcfail , net-unknown , host-unknown ,
1111 .Cm isolated , net-prohib , host-prohib , tosnet ,
1112 .Cm toshost , filter-prohib , host-precedence
1114 .Cm precedence-cutoff .
1117 code may have an optional
1120 If specified, the MTU value will be put into generated ICMP packet.
1121 The search terminates.
1122 .It Cm unreach6 Ar code
1123 Discard packets that match this rule, and try to send an ICMPv6
1124 unreachable notice with code
1128 is a number from 0, 1, 3 or 4, or one of these aliases:
1129 .Cm no-route, admin-prohib, address
1132 The search terminates.
1133 .It Cm netgraph Ar cookie
1134 Divert packet into netgraph with given
1136 The search terminates.
1137 If packet is later returned from netgraph it is either
1138 accepted or continues with the next rule, depending on
1139 .Va net.inet.ip.fw.one_pass
1141 .It Cm ngtee Ar cookie
1142 A copy of packet is diverted into netgraph, original
1143 packet continues with the next rule.
1146 for more information on
1151 .It Cm setfib Ar fibnum | tablearg
1152 The packet is tagged so as to use the FIB (routing table)
1154 in any subsequent forwarding decisions.
1155 In the current implementation, this is limited to the values 0 through 15, see
1157 Processing continues at the next rule.
1158 It is possible to use the
1160 keyword with setfib.
1161 If the tablearg value is not within the compiled range of fibs,
1162 the packet's fib is set to 0.
1163 .It Cm setdscp Ar DSCP | number | tablearg
1164 Set specified DiffServ codepoint for an IPv4/IPv6 packet.
1165 Processing continues at the next rule.
1166 Supported values are:
1214 Additionally, DSCP value can be specified by number (0..63).
1215 It is also possible to use the
1217 keyword with setdscp.
1218 If the tablearg value is not within the 0..63 range, lower 6 bits of supplied
1220 .It Cm tcp-setmss Ar mss
1221 Set the Maximum Segment Size (MSS) in the TCP segment to value
1225 should be loaded or kernel should have
1226 .Cm options IPFIREWALL_PMOD
1227 to be able use this action.
1228 This command does not change a packet if original MSS value is lower than
1230 Both TCP over IPv4 and over IPv6 are supported.
1231 Regardless of matched a packet or not by the
1233 rule, the search continues with the next rule.
1235 Queue and reassemble IPv4 fragments.
1236 If the packet is not fragmented, counters are updated and
1237 processing continues with the next rule.
1238 If the packet is the last logical fragment, the packet is reassembled and, if
1239 .Va net.inet.ip.fw.one_pass
1240 is set to 0, processing continues with the next rule.
1241 Otherwise, the packet is allowed to pass and the search terminates.
1242 If the packet is a fragment in the middle of a logical group of fragments,
1244 processing stops immediately.
1246 Fragment handling can be tuned via
1247 .Va net.inet.ip.maxfragpackets
1249 .Va net.inet.ip.maxfragsperpacket
1250 which limit, respectively, the maximum number of processable
1251 fragments (default: 800) and
1252 the maximum number of fragments per packet (default: 16).
1254 NOTA BENE: since fragments do not contain port numbers,
1255 they should be avoided with the
1258 Alternatively, direction-based (like
1262 ) and source-based (like
1264 ) match patterns can be used to select fragments.
1266 Usually a simple rule like:
1267 .Bd -literal -offset indent
1268 # reassemble incoming fragments
1269 ipfw add reass all from any to any in
1272 is all you need at the beginning of your ruleset.
1274 Discard packets that match this rule, and if the packet is an SCTP packet,
1275 try to send an SCTP packet containing an ABORT chunk.
1276 The search terminates.
1278 Discard packets that match this rule, and if the packet is an SCTP packet,
1279 try to send an SCTP packet containing an ABORT chunk.
1280 The search terminates.
1283 The body of a rule contains zero or more patterns (such as
1284 specific source and destination addresses or ports,
1285 protocol options, incoming or outgoing interfaces, etc.)
1286 that the packet must match in order to be recognised.
1287 In general, the patterns are connected by (implicit)
1289 operators -- i.e., all must match in order for the
1291 Individual patterns can be prefixed by the
1293 operator to reverse the result of the match, as in
1295 .Dl "ipfw add 100 allow ip from not 1.2.3.4 to any"
1297 Additionally, sets of alternative match patterns
1299 can be constructed by putting the patterns in
1300 lists enclosed between parentheses ( ) or braces { }, and
1303 operator as follows:
1305 .Dl "ipfw add 100 allow ip from { x or not y or z } to any"
1307 Only one level of parentheses is allowed.
1308 Beware that most shells have special meanings for parentheses
1309 or braces, so it is advisable to put a backslash \\ in front of them
1310 to prevent such interpretations.
1312 The body of a rule must in general include a source and destination
1316 can be used in various places to specify that the content of
1317 a required field is irrelevant.
1319 The rule body has the following format:
1320 .Bd -ragged -offset indent
1321 .Op Ar proto Cm from Ar src Cm to Ar dst
1325 The first part (proto from src to dst) is for backward
1326 compatibility with earlier versions of
1330 any match pattern (including MAC headers, IP protocols,
1331 addresses and ports) can be specified in the
1335 Rule fields have the following meaning:
1336 .Bl -tag -width indent
1337 .It Ar proto : protocol | Cm { Ar protocol Cm or ... }
1338 .It Ar protocol : Oo Cm not Oc Ar protocol-name | protocol-number
1339 An IP protocol specified by number or name
1340 (for a complete list see
1341 .Pa /etc/protocols ) ,
1342 or one of the following keywords:
1343 .Bl -tag -width indent
1345 Matches IPv4 packets.
1347 Matches IPv6 packets.
1356 option will be treated as inner protocol.
1364 .Cm { Ar protocol Cm or ... }
1367 is provided for convenience only but its use is deprecated.
1368 .It Ar src No and Ar dst : Bro Cm addr | Cm { Ar addr Cm or ... } Brc Op Oo Cm not Oc Ar ports
1369 An address (or a list, see below)
1370 optionally followed by
1376 with multiple addresses) is provided for convenience only and
1377 its use is discouraged.
1378 .It Ar addr : Oo Cm not Oc Bro
1379 .Cm any | me | me6 |
1380 .Cm table Ns Pq Ar name Ns Op , Ns Ar value
1381 .Ar | addr-list | addr-set
1383 .Bl -tag -width indent
1385 Matches any IP address.
1387 Matches any IP address configured on an interface in the system.
1389 Matches any IPv6 address configured on an interface in the system.
1390 The address list is evaluated at the time the packet is
1392 .It Cm table Ns Pq Ar name Ns Op , Ns Ar value
1393 Matches any IPv4 or IPv6 address for which an entry exists in the lookup table
1395 If an optional 32-bit unsigned
1397 is also specified, an entry will match only if it has this value.
1400 section below for more information on lookup tables.
1402 .It Ar addr-list : ip-addr Ns Op Ns , Ns Ar addr-list
1404 A host or subnet address specified in one of the following ways:
1405 .Bl -tag -width indent
1406 .It Ar numeric-ip | hostname
1407 Matches a single IPv4 address, specified as dotted-quad or a hostname.
1408 Hostnames are resolved at the time the rule is added to the firewall list.
1409 .It Ar addr Ns / Ns Ar masklen
1410 Matches all addresses with base
1412 (specified as an IP address, a network number, or a hostname)
1416 As an example, 1.2.3.4/25 or 1.2.3.0/25 will match
1417 all IP numbers from 1.2.3.0 to 1.2.3.127 .
1418 .It Ar addr Ns : Ns Ar mask
1419 Matches all addresses with base
1421 (specified as an IP address, a network number, or a hostname)
1424 specified as a dotted quad.
1425 As an example, 1.2.3.4:255.0.255.0 or 1.0.3.0:255.0.255.0 will match
1427 This form is advised only for non-contiguous
1429 It is better to resort to the
1430 .Ar addr Ns / Ns Ar masklen
1431 format for contiguous masks, which is more compact and less
1434 .It Ar addr-set : addr Ns Oo Ns / Ns Ar masklen Oc Ns Cm { Ns Ar list Ns Cm }
1435 .It Ar list : Bro Ar num | num-num Brc Ns Op Ns , Ns Ar list
1436 Matches all addresses with base address
1438 (specified as an IP address, a network number, or a hostname)
1439 and whose last byte is in the list between braces { } .
1440 Note that there must be no spaces between braces and
1441 numbers (spaces after commas are allowed).
1442 Elements of the list can be specified as single entries
1446 field is used to limit the size of the set of addresses,
1447 and can have any value between 24 and 32.
1449 it will be assumed as 24.
1451 This format is particularly useful to handle sparse address sets
1452 within a single rule.
1453 Because the matching occurs using a
1454 bitmask, it takes constant time and dramatically reduces
1455 the complexity of rulesets.
1457 As an example, an address specified as 1.2.3.4/24{128,35-55,89}
1458 or 1.2.3.0/24{128,35-55,89}
1459 will match the following IP addresses:
1461 1.2.3.128, 1.2.3.35 to 1.2.3.55, 1.2.3.89 .
1462 .It Ar addr6-list : ip6-addr Ns Op Ns , Ns Ar addr6-list
1464 A host or subnet specified one of the following ways:
1465 .Bl -tag -width indent
1466 .It Ar numeric-ip | hostname
1467 Matches a single IPv6 address as allowed by
1470 Hostnames are resolved at the time the rule is added to the firewall
1472 .It Ar addr Ns / Ns Ar masklen
1473 Matches all IPv6 addresses with base
1475 (specified as allowed by
1481 .It Ar addr Ns / Ns Ar mask
1482 Matches all IPv6 addresses with base
1484 (specified as allowed by
1489 specified as allowed by
1491 As an example, fe::640:0:0/ffff::ffff:ffff:0:0 will match
1493 This form is advised only for non-contiguous
1495 It is better to resort to the
1496 .Ar addr Ns / Ns Ar masklen
1497 format for contiguous masks, which is more compact and less
1501 No support for sets of IPv6 addresses is provided because IPv6 addresses
1502 are typically random past the initial prefix.
1503 .It Ar ports : Bro Ar port | port Ns \&- Ns Ar port Ns Brc Ns Op , Ns Ar ports
1504 For protocols which support port numbers (such as SCTP, TCP and UDP), optional
1506 may be specified as one or more ports or port ranges, separated
1507 by commas but no spaces, and an optional
1512 notation specifies a range of ports (including boundaries).
1516 may be used instead of numeric port values.
1517 The length of the port list is limited to 30 ports or ranges,
1518 though one can specify larger ranges by using an
1522 section of the rule.
1526 can be used to escape the dash
1528 character in a service name (from a shell, the backslash must be
1529 typed twice to avoid the shell itself interpreting it as an escape
1532 .Dl "ipfw add count tcp from any ftp\e\e-data-ftp to any"
1534 Fragmented packets which have a non-zero offset (i.e., not the first
1535 fragment) will never match a rule which has one or more port
1539 option for details on matching fragmented packets.
1541 .Ss RULE OPTIONS (MATCH PATTERNS)
1542 Additional match patterns can be used within
1544 Zero or more of these so-called
1546 can be present in a rule, optionally prefixed by the
1548 operand, and possibly grouped into
1551 The following match patterns can be used (listed in alphabetical order):
1552 .Bl -tag -width indent
1553 .It Cm // this is a comment .
1554 Inserts the specified text as a comment in the rule.
1555 Everything following // is considered as a comment and stored in the rule.
1556 You can have comment-only rules, which are listed as having a
1558 action followed by the comment.
1562 .It Cm defer-immediate-action | defer-action
1563 A rule with this option will not perform normal action
1565 This option is intended to be used with
1569 as the dynamic rule, created but ignored on match, will work
1574 .Cm defer-immediate-action
1575 create a dynamic rule and continue with the next rule without actually
1576 performing the action part of this rule.
1577 When the rule is later activated via the state table, the action is
1580 Matches only packets generated by a divert socket.
1581 .It Cm diverted-loopback
1582 Matches only packets coming from a divert socket back into the IP stack
1584 .It Cm diverted-output
1585 Matches only packets going from a divert socket back outward to the IP
1586 stack output for delivery.
1587 .It Cm dst-ip Ar ip-address
1588 Matches IPv4 packets whose destination IP is one of the address(es)
1589 specified as argument.
1590 .It Bro Cm dst-ip6 | dst-ipv6 Brc Ar ip6-address
1591 Matches IPv6 packets whose destination IP is one of the address(es)
1592 specified as argument.
1593 .It Cm dst-port Ar ports
1594 Matches IP packets whose destination port is one of the port(s)
1595 specified as argument.
1597 Matches TCP packets that have the RST or ACK bits set.
1598 .It Cm ext6hdr Ar header
1599 Matches IPv6 packets containing the extended header given by
1601 Supported headers are:
1607 any type of Routing Header
1609 Source routing Routing Header Type 0
1611 Mobile IPv6 Routing Header Type 2
1615 IPSec authentication headers
1617 and IPsec encapsulated security payload headers
1619 .It Cm fib Ar fibnum
1620 Matches a packet that has been tagged to use
1621 the given FIB (routing table) number.
1622 .It Cm flow Ar table Ns Pq Ar name Ns Op , Ns Ar value
1623 Search for the flow entry in lookup table
1625 If not found, the match fails.
1626 Otherwise, the match succeeds and
1628 is set to the value extracted from the table.
1630 This option can be useful to quickly dispatch traffic based on
1631 certain packet fields.
1634 section below for more information on lookup tables.
1635 .It Cm flow-id Ar labels
1636 Matches IPv6 packets containing any of the flow labels given in
1639 is a comma separated list of numeric flow labels.
1640 .It Cm dst-mac Ar table Ns Pq Ar name Ns Op , Ns Ar value
1641 Search for the destination MAC address entry in lookup table
1643 If not found, the match fails.
1644 Otherwise, the match succeeds and
1646 is set to the value extracted from the table.
1647 .It Cm src-mac Ar table Ns Pq Ar name Ns Op , Ns Ar value
1648 Search for the source MAC address entry in lookup table
1650 If not found, the match fails.
1651 Otherwise, the match succeeds and
1653 is set to the value extracted from the table.
1655 Matches IPv4 packets whose
1657 field contains the comma separated list of IPv4 fragmentation
1658 options specified in
1660 The recognized options are:
1662 .Pq Dv don't fragment ,
1664 .Pq Dv more fragments ,
1666 .Pq Dv reserved fragment bit
1668 .Pq Dv non-zero fragment offset .
1669 The absence of a particular options may be denoted
1673 Empty list of options defaults to matching on non-zero fragment offset.
1674 Such rule would match all not the first fragment datagrams,
1676 This is a backward compatibility with older rulesets.
1678 Matches all TCP or UDP packets sent by or received for a
1682 may be specified by name or number.
1684 Matches all TCP or UDP packets sent by or received for the
1685 jail whose ID or name is
1687 .It Cm icmptypes Ar types
1688 Matches ICMP packets whose ICMP type is in the list
1690 The list may be specified as any combination of
1691 individual types (numeric) separated by commas.
1692 .Em Ranges are not allowed .
1693 The supported ICMP types are:
1697 destination unreachable
1705 router advertisement
1709 time-to-live exceeded
1721 address mask request
1723 and address mask reply
1725 .It Cm icmp6types Ar types
1726 Matches ICMP6 packets whose ICMP6 type is in the list of
1728 The list may be specified as any combination of
1729 individual types (numeric) separated by commas.
1730 .Em Ranges are not allowed .
1732 Matches incoming or outgoing packets, respectively.
1736 are mutually exclusive (in fact,
1740 .It Cm ipid Ar id-list
1741 Matches IPv4 packets whose
1743 field has value included in
1745 which is either a single value or a list of values or ranges
1746 specified in the same way as
1748 .It Cm iplen Ar len-list
1749 Matches IP packets whose total length, including header and data, is
1752 which is either a single value or a list of values or ranges
1753 specified in the same way as
1755 .It Cm ipoptions Ar spec
1756 Matches packets whose IPv4 header contains the comma separated list of
1757 options specified in
1759 The supported IP options are:
1762 (strict source route),
1764 (loose source route),
1766 (record packet route) and
1769 The absence of a particular option may be denoted
1772 .It Cm ipprecedence Ar precedence
1773 Matches IPv4 packets whose precedence field is equal to
1776 Matches packets that have IPSEC history associated with them
1777 (i.e., the packet comes encapsulated in IPSEC, the kernel
1778 has IPSEC support, and can correctly decapsulate it).
1780 Note that specifying
1782 is different from specifying
1784 as the latter will only look at the specific IP protocol field,
1785 irrespective of IPSEC kernel support and the validity of the IPSEC data.
1787 Further note that this flag is silently ignored in kernels without
1789 It does not affect rule processing when given and the
1790 rules are handled as if with no
1793 .It Cm iptos Ar spec
1794 Matches IPv4 packets whose
1796 field contains the comma separated list of
1797 service types specified in
1799 The supported IP types of service are:
1802 .Pq Dv IPTOS_LOWDELAY ,
1804 .Pq Dv IPTOS_THROUGHPUT ,
1806 .Pq Dv IPTOS_RELIABILITY ,
1808 .Pq Dv IPTOS_MINCOST ,
1810 .Pq Dv IPTOS_ECN_CE .
1811 The absence of a particular type may be denoted
1814 .It Cm dscp spec Ns Op , Ns Ar spec
1815 Matches IPv4/IPv6 packets whose
1817 field value is contained in
1820 Multiple values can be specified via
1821 the comma separated list.
1822 Value can be one of keywords used in
1824 action or exact number.
1825 .It Cm ipttl Ar ttl-list
1826 Matches IPv4 packets whose time to live is included in
1828 which is either a single value or a list of values or ranges
1829 specified in the same way as
1831 .It Cm ipversion Ar ver
1832 Matches IP packets whose IP version field is
1834 .It Cm keep-state Op Ar :flowname
1835 Upon a match, the firewall will create a dynamic rule, whose
1836 default behaviour is to match bidirectional traffic between
1837 source and destination IP/port using the same protocol.
1838 The rule has a limited lifetime (controlled by a set of
1840 variables), and the lifetime is refreshed every time a matching
1844 is used to assign additional to addresses, ports and protocol parameter
1846 It can be used for more accurate matching by
1851 keyword is special name used for compatibility with old rulesets.
1853 Matches only layer2 packets, i.e., those passed to
1858 .Fn ether_output_frame .
1859 .It Cm limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N Op Ar :flowname
1860 The firewall will only allow
1862 connections with the same
1863 set of parameters as specified in the rule.
1865 of source and destination addresses and ports can be
1867 .It Cm lookup Bro Cm dst-ip | dst-port | dst-mac | src-ip | src-port | src-mac | uid |
1868 .Cm jail | dscp | mark Brc Ar name
1869 Search an entry in lookup table
1871 that matches the field specified as argument.
1872 If not found, the match fails.
1873 Otherwise, the match succeeds and
1875 is set to the value extracted from the table.
1877 This option can be useful to quickly dispatch traffic based on
1878 certain packet fields.
1881 section below for more information on lookup tables.
1882 .It Cm { MAC | mac } Ar dst-mac src-mac
1883 Match packets with a given
1887 addresses, specified as the
1889 keyword (matching any MAC address), or six groups of hex digits
1890 separated by colons,
1891 and optionally followed by a mask indicating the significant bits.
1892 The mask may be specified using either of the following methods:
1893 .Bl -enum -width indent
1897 followed by the number of significant bits.
1898 For example, an address with 33 significant bits could be specified as:
1900 .Dl "MAC 10:20:30:40:50:60/33 any"
1904 followed by a bitmask specified as six groups of hex digits separated
1906 For example, an address in which the last 16 bits are significant could
1909 .Dl "MAC 10:20:30:40:50:60&00:00:00:00:ff:ff any"
1911 Note that the ampersand character has a special meaning in many shells
1912 and should generally be escaped.
1914 Note that the order of MAC addresses (destination first,
1916 the same as on the wire, but the opposite of the one used for
1918 .It Cm mac-type Ar mac-type
1919 Matches packets whose Ethernet Type field
1920 corresponds to one of those specified as argument.
1922 is specified in the same way as
1924 (i.e., one or more comma-separated single values or ranges).
1925 You can use symbolic names for known values such as
1926 .Em vlan , ipv4, ipv6 .
1927 Values can be entered as decimal or hexadecimal (if prefixed by 0x),
1928 and they are always printed as hexadecimal (unless the
1930 option is used, in which case symbolic resolution will be attempted).
1931 .It Cm proto Ar protocol
1932 Matches packets with the corresponding IP protocol.
1934 Upon a match, the firewall will create a dynamic rule as if
1937 However, this option doesn't imply an implicit
1941 .It Cm recv | xmit | via Brq Ar ifX | Ar ifmask | Ar table Ns Po Ar name Ns Oo , Ns Ar value Oc Pc | Ar ipno | Ar any
1942 Matches packets received, transmitted or going through,
1943 respectively, the interface specified by exact name
1947 by IP address, or through some interface.
1950 name may be matched against
1954 according to the rules used by the shell (f.e. tun*).
1961 may be used to match interface by its kernel ifindex.
1964 section below for more information on lookup tables.
1968 keyword causes the interface to always be checked.
1975 then only the receive or transmit interface (respectively)
1977 By specifying both, it is possible to match packets based on
1978 both receive and transmit interface, e.g.:
1980 .Dl "ipfw add deny ip from any to any out recv ed0 xmit ed1"
1984 interface can be tested on either incoming or outgoing packets,
1987 interface can only be tested on outgoing packets.
1992 is invalid) whenever
1996 A packet might not have a receive or transmit interface: packets
1997 originating from the local host have no receive interface,
1998 while packets destined for the local host have no transmit
2000 .It Cm set-limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N
2003 but does not have an implicit
2007 Matches TCP packets that have the SYN bit set but no ACK bit.
2008 This is the short form of
2009 .Dq Li tcpflags\ syn,!ack .
2011 Matches packets that are associated to a local socket and
2012 for which the SO_USER_COOKIE socket option has been set
2013 to a non-zero value.
2014 As a side effect, the value of the
2015 option is made available as
2017 value, which in turn can be used as
2022 .It Cm src-ip Ar ip-address
2023 Matches IPv4 packets whose source IP is one of the address(es)
2024 specified as an argument.
2025 .It Cm src-ip6 Ar ip6-address
2026 Matches IPv6 packets whose source IP is one of the address(es)
2027 specified as an argument.
2028 .It Cm src-port Ar ports
2029 Matches IP packets whose source port is one of the port(s)
2030 specified as argument.
2031 .It Cm tagged Ar tag-list
2032 Matches packets whose tags are included in
2034 which is either a single value or a list of values or ranges
2035 specified in the same way as
2037 Tags can be applied to the packet using
2039 rule action parameter (see it's description for details on tags).
2040 .It Cm mark Ar value[:bitmask] | tablearg[:bitmask]
2041 Matches packets whose mark is equal to
2047 can also be used instead of an explicit
2049 to match a value supplied by the last table lookup.
2055 can be entered as decimal or hexadecimal (if prefixed by 0x), and they
2056 are always printed as hexadecimal.
2057 .It Cm tcpack Ar ack
2059 Match if the TCP header acknowledgment number field is set to
2061 .It Cm tcpdatalen Ar tcpdatalen-list
2062 Matches TCP packets whose length of TCP data is
2063 .Ar tcpdatalen-list ,
2064 which is either a single value or a list of values or ranges
2065 specified in the same way as
2067 .It Cm tcpflags Ar spec
2069 Match if the TCP header contains the comma separated list of
2072 The supported TCP flags are:
2081 The absence of a particular flag may be denoted
2084 A rule which contains a
2086 specification can never match a fragmented packet which has
2090 option for details on matching fragmented packets.
2091 .It Cm tcpmss Ar tcpmss-list
2092 Matches TCP packets whose MSS (maximum segment size) value is set to
2094 which is either a single value or a list of values or ranges
2095 specified in the same way as
2097 .It Cm tcpseq Ar seq
2099 Match if the TCP header sequence number field is set to
2101 .It Cm tcpwin Ar tcpwin-list
2102 Matches TCP packets whose header window field is set to
2104 which is either a single value or a list of values or ranges
2105 specified in the same way as
2107 .It Cm tcpoptions Ar spec
2109 Match if the TCP header contains the comma separated list of
2110 options specified in
2112 The supported TCP options are:
2115 (maximum segment size),
2117 (tcp window advertisement),
2121 (rfc1323 timestamp) and
2123 (rfc1644 t/tcp connection count).
2124 The absence of a particular option may be denoted
2128 Match all TCP or UDP packets sent by or received for a
2132 may be matched by name or identification number.
2134 For incoming packets,
2135 a routing table lookup is done on the packet's source address.
2136 If the interface on which the packet entered the system matches the
2137 outgoing interface for the route,
2139 If the interfaces do not match up,
2140 the packet does not match.
2141 All outgoing packets or packets with no incoming interface match.
2143 The name and functionality of the option is intentionally similar to
2144 the Cisco IOS command:
2146 .Dl ip verify unicast reverse-path
2148 This option can be used to make anti-spoofing rules to reject all
2149 packets with source addresses not from this interface.
2153 For incoming packets,
2154 a routing table lookup is done on the packet's source address.
2155 If a route to the source address exists, but not the default route
2156 or a blackhole/reject route, the packet matches.
2157 Otherwise, the packet does not match.
2158 All outgoing packets match.
2160 The name and functionality of the option is intentionally similar to
2161 the Cisco IOS command:
2163 .Dl ip verify unicast source reachable-via any
2165 This option can be used to make anti-spoofing rules to reject all
2166 packets whose source address is unreachable.
2168 For incoming packets, the packet's source address is checked if it
2169 belongs to a directly connected network.
2170 If the network is directly connected, then the interface the packet
2171 came on in is compared to the interface the network is connected to.
2172 When incoming interface and directly connected interface are not the
2173 same, the packet does not match.
2174 Otherwise, the packet does match.
2175 All outgoing packets match.
2177 This option can be used to make anti-spoofing rules to reject all
2178 packets that pretend to be from a directly connected network but do
2179 not come in through that interface.
2180 This option is similar to but more restricted than
2182 because it engages only on packets with source addresses of directly
2183 connected networks instead of all source addresses.
2186 Lookup tables are useful to handle large sparse sets of
2187 addresses or other search keys (e.g., ports, jail IDs, interface names).
2188 In the rest of this section we will use the term ``key''.
2189 Table name needs to match the following spec:
2191 Tables with the same name can be created in different
2193 However, rule links to the tables in
2196 This behavior can be controlled by
2197 .Va net.inet.ip.fw.tables_sets
2201 section for more information.
2202 There may be up to 65535 different lookup tables.
2204 The following table types are supported:
2205 .Bl -tag -width indent
2206 .It Ar table-type : Ar addr | iface | number | flow | mac
2207 .It Ar table-key : Ar addr Ns Oo / Ns Ar masklen Oc | iface-name | number | flow-spec
2208 .It Ar flow-spec : Ar flow-field Ns Op , Ns Ar flow-spec
2209 .It Ar flow-field : src-ip | proto | src-port | dst-ip | dst-port
2211 Matches IPv4 or IPv6 address.
2212 Each entry is represented by an
2213 .Ar addr Ns Op / Ns Ar masklen
2214 and will match all addresses with base
2216 (specified as an IPv4/IPv6 address, or a hostname) and mask width of
2221 is not specified, it defaults to 32 for IPv4 and 128 for IPv6.
2222 When looking up an IP address in a table, the most specific
2225 Matches interface names.
2226 Each entry is represented by string treated as interface name.
2227 Wildcards are not supported.
2229 Matches protocol ports, uids/gids or jail IDs.
2230 Each entry is represented by 32-bit unsigned integer.
2231 Ranges are not supported.
2233 Matches packet fields specified by
2235 type suboptions with table entries.
2237 Matches MAC address.
2238 Each entry is represented by an
2239 .Ar addr Ns Op / Ns Ar masklen
2240 and will match all addresses with base
2247 is not specified, it defaults to 48.
2248 When looking up an MAC address in a table, the most specific
2252 Tables require explicit creation via
2256 The following creation options are supported:
2257 .Bl -tag -width indent
2258 .It Ar create-options : Ar create-option | create-options
2259 .It Ar create-option : Cm type Ar table-type | Cm valtype Ar value-mask | Cm algo Ar algo-desc |
2260 .Cm limit Ar number | Cm locked | Cm missing | Cm or-flush
2266 Table algorithm to use (see below).
2268 Maximum number of items that may be inserted into table.
2270 Restrict any table modifications.
2272 Do not fail if table already exists and has exactly same options as new one.
2274 Flush existing table with same name instead of returning error.
2277 so existing table must be compatible with new one.
2280 Some of these options may be modified later via
2283 The following options can be changed:
2284 .Bl -tag -width indent
2285 .It Ar modify-options : Ar modify-option | modify-options
2286 .It Ar modify-option : Cm limit Ar number
2288 Alter maximum number of items that may be inserted into table.
2291 Additionally, table can be locked or unlocked using
2299 can be swapped with each other using
2302 Swap may fail if tables limits are set and data exchange
2303 would result in limits hit.
2304 Operation is performed atomically.
2306 One or more entries can be added to a table at once using
2309 Addition of all items are performed atomically.
2310 By default, error in addition of one entry does not influence
2311 addition of other entries.
2312 However, non-zero error code is returned in that case.
2315 keyword may be specified before
2317 to indicate all-or-none add request.
2319 One or more entries can be removed from a table at once using
2322 By default, error in removal of one entry does not influence
2323 removing of other entries.
2324 However, non-zero error code is returned in that case.
2326 It may be possible to check what entry will be found on particular
2332 This functionality is optional and may be unsupported in some algorithms.
2334 The following operations can be performed on
2339 .Bl -tag -width indent
2343 Removes all entries.
2345 Shows generic table information.
2347 Shows generic table information and algo-specific data.
2350 The following lookup algorithms are supported:
2351 .Bl -tag -width indent
2352 .It Ar algo-desc : algo-name | "algo-name algo-data"
2353 .It Ar algo-name : Ar addr: radix | addr: hash | iface: array | number: array | flow: hash | mac: radix
2355 Separate Radix trees for IPv4 and IPv6, the same way as the routing table (see
2361 Separate auto-growing hashes for IPv4 and IPv6.
2362 Accepts entries with the same mask length specified initially via
2363 .Cm "addr:hash masks=/v4,/v6"
2364 algorithm creation options.
2365 Assume /32 and /128 masks by default.
2366 Search removes host bits (according to mask) from supplied address and checks
2367 resulting key in appropriate hash.
2368 Mostly optimized for /64 and byte-ranged IPv6 masks.
2370 Array storing sorted indexes for entries which are presented in the system.
2371 Optimized for very fast lookup.
2373 Array storing sorted u32 numbers.
2375 Auto-growing hash storing flow entries.
2376 Search calculates hash on required packet fields and searches for matching
2377 entries in selected bucket.
2379 Radix tree for MAC address
2384 feature provides the ability to use a value, looked up in the table, as
2385 the argument for a rule action, action parameter or rule option.
2386 This can significantly reduce number of rules in some configurations.
2387 If two tables are used in a rule, the result of the second (destination)
2390 Each record may hold one or more values according to
2392 This mask is set on table creation via
2395 The following value types are supported:
2396 .Bl -tag -width indent
2397 .It Ar value-mask : Ar value-type Ns Op , Ns Ar value-mask
2398 .It Ar value-type : Ar skipto | pipe | fib | nat | dscp | tag | divert |
2399 .Ar netgraph | limit | ipv4 | ipv6 | mark
2401 rule number to jump to.
2405 fib number to match/set.
2407 nat number to jump to.
2409 dscp value to match/set.
2411 tag number to match/set.
2413 port number to divert traffic to.
2415 hook number to move packet to.
2417 maximum number of connections.
2419 IPv4 nexthop to fwd packets to.
2421 IPv6 nexthop to fwd packets to.
2423 mark value to match/set.
2428 argument can be used with the following actions:
2429 .Cm nat, pipe, queue, divert, tee, netgraph, ngtee, fwd, skipto, setfib ,
2434 .Cm limit, tagged, mark .
2438 action, the user should be aware that the code will walk the ruleset
2439 up to a rule equal to, or past, the given number.
2443 Section for example usage of tables and the tablearg keyword.
2445 Each rule or table belongs to one of 32 different
2448 Set 31 is reserved for the default rule.
2450 By default, rules or tables are put in set 0, unless you use the
2452 attribute when adding a new rule or table.
2453 Sets can be individually and atomically enabled or disabled,
2454 so this mechanism permits an easy way to store multiple configurations
2455 of the firewall and quickly (and atomically) switch between them.
2457 By default, tables from set 0 are referenced when adding rule with
2458 table opcodes regardless of rule set.
2459 This behavior can be changed by setting
2460 .Va net.inet.ip.fw.tables_sets
2462 Rule's set will then be used for table references.
2464 The command to enable/disable sets is
2465 .Bd -ragged -offset indent
2467 .Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ...
2474 sections can be specified.
2475 Command execution is atomic on all the sets specified in the command.
2476 By default, all sets are enabled.
2478 When you disable a set, its rules behave as if they do not exist
2479 in the firewall configuration, with only one exception:
2480 .Bd -ragged -offset indent
2481 dynamic rules created from a rule before it had been disabled
2482 will still be active until they expire.
2484 dynamic rules you have to explicitly delete the parent rule
2485 which generated them.
2488 The set number of rules can be changed with the command
2489 .Bd -ragged -offset indent
2492 .Brq Cm rule Ar rule-number | old-set
2496 Also, you can atomically swap two rulesets with the command
2497 .Bd -ragged -offset indent
2499 .Cm set swap Ar first-set second-set
2504 Section on some possible uses of sets of rules.
2505 .Sh STATEFUL FIREWALL
2506 Stateful operation is a way for the firewall to dynamically
2507 create rules for specific flows when packets that
2508 match a given pattern are detected.
2509 Support for stateful
2510 operation comes through the
2511 .Cm check-state , keep-state , record-state , limit
2517 Dynamic rules are created when a packet matches a
2523 rule, causing the creation of a
2525 rule which will match all and only packets with
2529 .Em src-ip/src-port dst-ip/dst-port
2534 are used here only to denote the initial match addresses, but they
2535 are completely equivalent afterwards).
2541 This name is used in matching together with addresses, ports and protocol.
2542 Dynamic rules will be checked at the first
2543 .Cm check-state, keep-state
2546 occurrence, and the action performed upon a match will be the same
2547 as in the parent rule.
2549 Note that no additional attributes other than protocol and IP addresses
2550 and ports and :flowname are checked on dynamic rules.
2552 The typical use of dynamic rules is to keep a closed firewall configuration,
2553 but let the first TCP SYN packet from the inside network install a
2554 dynamic rule for the flow so that packets belonging to that session
2555 will be allowed through the firewall:
2557 .Dl "ipfw add check-state :OUTBOUND"
2558 .Dl "ipfw add allow tcp from my-subnet to any setup keep-state :OUTBOUND"
2559 .Dl "ipfw add deny tcp from any to any"
2561 A similar approach can be used for UDP, where an UDP packet coming
2562 from the inside will install a dynamic rule to let the response through
2565 .Dl "ipfw add check-state :OUTBOUND"
2566 .Dl "ipfw add allow udp from my-subnet to any keep-state :OUTBOUND"
2567 .Dl "ipfw add deny udp from any to any"
2569 Dynamic rules expire after some time, which depends on the status
2570 of the flow and the setting of some
2574 .Sx SYSCTL VARIABLES
2576 For TCP sessions, dynamic rules can be instructed to periodically
2577 send keepalive packets to refresh the state of the rule when it is
2582 for more examples on how to use dynamic rules.
2583 .Sh TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
2585 is also the user interface for the
2587 traffic shaper, packet scheduler and network emulator, a subsystem that
2588 can artificially queue, delay or drop packets
2589 emulating the behaviour of certain network links
2590 or queueing systems.
2593 operates by first using the firewall to select packets
2594 using any match pattern that can be used in
2597 Matching packets are then passed to either of two
2598 different objects, which implement the traffic regulation:
2599 .Bl -hang -offset XXXX
2605 with given bandwidth and propagation delay,
2606 driven by a FIFO scheduler and a single queue with programmable
2607 queue size and packet loss rate.
2608 Packets are appended to the queue as they come out from
2610 and then transferred in FIFO order to the link at the desired rate.
2614 is an abstraction used to implement packet scheduling
2615 using one of several packet scheduling algorithms.
2618 are first grouped into flows according to a mask on the 5-tuple.
2619 Flows are then passed to the scheduler associated to the
2621 and each flow uses scheduling parameters (weight and others)
2622 as configured in the
2625 A scheduler in turn is connected to an emulated link,
2626 and arbitrates the link's bandwidth among backlogged flows according to
2627 weights and to the features of the scheduling algorithm in use.
2632 can be used to set hard limits to the bandwidth that a flow can use, whereas
2634 can be used to determine how different flows share the available bandwidth.
2636 A graphical representation of the binding of queues,
2637 flows, schedulers and links is below.
2638 .Bd -literal -offset indent
2639 (flow_mask|sched_mask) sched_mask
2640 +---------+ weight Wx +-------------+
2641 | |->-[flow]-->--| |-+
2642 -->--| QUEUE x | ... | | |
2643 | |->-[flow]-->--| SCHEDuler N | |
2645 ... | +--[LINK N]-->--
2646 +---------+ weight Wy | | +--[LINK N]-->--
2647 | |->-[flow]-->--| | |
2648 -->--| QUEUE y | ... | | |
2649 | |->-[flow]-->--| | |
2650 +---------+ +-------------+ |
2653 It is important to understand the role of the SCHED_MASK
2654 and FLOW_MASK, which are configured through the commands
2655 .Dl "ipfw sched N config mask SCHED_MASK ..."
2657 .Dl "ipfw queue X config mask FLOW_MASK ..." .
2659 The SCHED_MASK is used to assign flows to one or more
2660 scheduler instances, one for each
2661 value of the packet's 5-tuple after applying SCHED_MASK.
2662 As an example, using ``src-ip 0xffffff00'' creates one instance
2663 for each /24 destination subnet.
2665 The FLOW_MASK, together with the SCHED_MASK, is used to split
2667 As an example, using
2668 ``src-ip 0x000000ff''
2669 together with the previous SCHED_MASK makes a flow for
2670 each individual source address.
2671 In turn, flows for each /24
2672 subnet will be sent to the same scheduler instance.
2674 The above diagram holds even for the
2676 case, with the only restriction that a
2678 only supports a SCHED_MASK, and forces the use of a FIFO
2679 scheduler (these are for backward compatibility reasons;
2680 in fact, internally, a
2682 pipe is implemented exactly as above).
2684 There are two modes of
2692 mode tries to emulate a real link: the
2694 scheduler ensures that the packet will not leave the pipe faster than it
2695 would on the real link with a given bandwidth.
2698 mode allows certain packets to bypass the
2700 scheduler (if packet flow does not exceed pipe's bandwidth).
2701 This is the reason why the
2703 mode requires less CPU cycles per packet (on average) and packet latency
2704 can be significantly lower in comparison to a real link with the same
2710 mode can be enabled by setting the
2711 .Va net.inet.ip.dummynet.io_fast
2713 variable to a non-zero value.
2714 .Ss PIPE, QUEUE AND SCHEDULER CONFIGURATION
2720 configuration commands are the following:
2721 .Bd -ragged -offset indent
2722 .Cm pipe Ar number Cm config Ar pipe-configuration
2724 .Cm queue Ar number Cm config Ar queue-configuration
2726 .Cm sched Ar number Cm config Ar sched-configuration
2729 The following parameters can be configured for a pipe:
2731 .Bl -tag -width indent -compact
2732 .It Cm bw Ar bandwidth | device
2733 Bandwidth, measured in
2736 .Brq Cm bit/s | Byte/s .
2739 A value of 0 (default) means unlimited bandwidth.
2740 The unit must immediately follow the number, as in
2742 .Dl "dnctl pipe 1 config bw 300Kbit/s"
2744 If a device name is specified instead of a numeric value, as in
2746 .Dl "dnctl pipe 1 config bw tun0"
2748 then the transmit clock is supplied by the specified device.
2749 At the moment only the
2751 device supports this
2752 functionality, for use in conjunction with
2755 .It Cm delay Ar ms-delay
2756 Propagation delay, measured in milliseconds.
2757 The value is rounded to the next multiple of the clock tick
2758 (typically 10ms, but it is a good practice to run kernels
2760 .Dq "options HZ=1000"
2762 the granularity to 1ms or less).
2763 The default value is 0, meaning no delay.
2765 .It Cm burst Ar size
2766 If the data to be sent exceeds the pipe's bandwidth limit
2767 (and the pipe was previously idle), up to
2769 bytes of data are allowed to bypass the
2771 scheduler, and will be sent as fast as the physical link allows.
2772 Any additional data will be transmitted at the rate specified
2776 The burst size depends on how long the pipe has been idle;
2777 the effective burst size is calculated as follows:
2784 .It Cm profile Ar filename
2785 A file specifying the additional overhead incurred in the transmission
2786 of a packet on the link.
2788 Some link types introduce extra delays in the transmission
2789 of a packet, e.g., because of MAC level framing, contention on
2790 the use of the channel, MAC level retransmissions and so on.
2791 From our point of view, the channel is effectively unavailable
2792 for this extra time, which is constant or variable depending
2794 Additionally, packets may be dropped after this
2795 time (e.g., on a wireless link after too many retransmissions).
2796 We can model the additional delay with an empirical curve
2797 that represents its distribution.
2798 .Bd -literal -offset indent
2799 cumulative probability
2809 +-------*------------------->
2812 The empirical curve may have both vertical and horizontal lines.
2813 Vertical lines represent constant delay for a range of
2815 Horizontal lines correspond to a discontinuity in the delay
2816 distribution: the pipe will use the largest delay for a
2819 The file format is the following, with whitespace acting as
2820 a separator and '#' indicating the beginning a comment:
2821 .Bl -tag -width indent
2822 .It Cm name Ar identifier
2823 optional name (listed by "dnctl pipe show")
2824 to identify the delay distribution;
2826 the bandwidth used for the pipe.
2827 If not specified here, it must be present
2828 explicitly as a configuration parameter for the pipe;
2829 .It Cm loss-level Ar L
2830 the probability above which packets are lost.
2831 (0.0 <= L <= 1.0, default 1.0 i.e., no loss);
2833 the number of samples used in the internal
2834 representation of the curve (2..1024; default 100);
2835 .It Cm "delay prob" | "prob delay"
2836 One of these two lines is mandatory and defines
2837 the format of the following lines with data points.
2839 2 or more lines representing points in the curve,
2840 with either delay or probability first, according
2841 to the chosen format.
2842 The unit for delay is milliseconds.
2843 Data points do not need to be sorted.
2844 Also, the number of actual lines can be different
2845 from the value of the "samples" parameter:
2847 utility will sort and interpolate
2848 the curve as needed.
2851 Example of a profile file:
2852 .Bd -literal -offset indent
2857 0 200 # minimum overhead is 200ms
2863 #configuration file end
2867 The following parameters can be configured for a queue:
2869 .Bl -tag -width indent -compact
2870 .It Cm pipe Ar pipe_nr
2871 Connects a queue to the specified pipe.
2872 Multiple queues (with the same or different weights) can be connected to
2873 the same pipe, which specifies the aggregate rate for the set of queues.
2875 .It Cm weight Ar weight
2876 Specifies the weight to be used for flows matching this queue.
2877 The weight must be in the range 1..100, and defaults to 1.
2880 The following case-insensitive parameters can be configured for a
2883 .Bl -tag -width indent -compact
2884 .It Cm type Ar {fifo | wf2q+ | rr | qfq | fq_codel | fq_pie}
2885 specifies the scheduling algorithm to use.
2886 .Bl -tag -width indent -compact
2888 is just a FIFO scheduler (which means that all packets
2889 are stored in the same queue as they arrive to the scheduler).
2890 FIFO has O(1) per-packet time complexity, with very low
2891 constants (estimate 60-80ns on a 2GHz desktop machine)
2892 but gives no service guarantees.
2894 implements the WF2Q+ algorithm, which is a Weighted Fair Queueing
2895 algorithm which permits flows to share bandwidth according to
2897 Note that weights are not priorities; even a flow
2898 with a minuscule weight will never starve.
2899 WF2Q+ has O(log N) per-packet processing cost, where N is the number
2900 of flows, and is the default algorithm used by previous versions
2903 implements the Deficit Round Robin algorithm, which has O(1) processing
2904 costs (roughly, 100-150ns per packet)
2905 and permits bandwidth allocation according to weights, but
2906 with poor service guarantees.
2908 implements the QFQ algorithm, which is a very fast variant of
2909 WF2Q+, with similar service guarantees and O(1) processing
2910 costs (roughly, 200-250ns per packet).
2912 implements the FQ-CoDel (FlowQueue-CoDel) scheduler/AQM algorithm, which
2913 uses a modified Deficit Round Robin scheduler to manage two lists of sub-queues
2914 (old sub-queues and new sub-queues) for providing brief periods of priority to
2915 lightweight or short burst flows.
2916 By default, the total number of sub-queues is 1024.
2917 FQ-CoDel's internal, dynamically
2918 created sub-queues are controlled by separate instances of CoDel AQM.
2920 implements the FQ-PIE (FlowQueue-PIE) scheduler/AQM algorithm, which similar to
2922 but uses per sub-queue PIE AQM instance to control the queue delay.
2926 inherits AQM parameters and options from
2930 inherits AQM parameters and options from
2933 Additionally, both of
2937 have shared scheduler parameters which are:
2938 .Bl -tag -width indent
2941 specifies the quantum (credit) of the scheduler.
2943 is the number of bytes a queue can serve before being moved to the tail
2945 The default is 1514 bytes, and the maximum acceptable value
2949 specifies the hard size limit (in unit of packets) of all queues managed by an
2950 instance of the scheduler.
2951 The default value of
2953 is 10240 packets, and the maximum acceptable value is 20480 packets.
2956 specifies the total number of flow queues (sub-queues) that fq_*
2957 creates and manages.
2958 By default, 1024 sub-queues are created when an instance
2959 of the fq_{codel/pie} scheduler is created.
2960 The maximum acceptable value is
2964 Note that any token after
2968 is considered a parameter for fq_{codel/pie}.
2969 So, ensure all scheduler
2970 configuration options not related to fq_{codel/pie} are written before
2975 In addition to the type, all parameters allowed for a pipe can also
2976 be specified for a scheduler.
2978 Finally, the following parameters can be configured for both
2981 .Bl -tag -width XXXX -compact
2982 .It Cm buckets Ar hash-table-size
2983 Specifies the size of the hash table used for storing the
2985 Default value is 64 controlled by the
2988 .Va net.inet.ip.dummynet.hash_size ,
2989 allowed range is 16 to 65536.
2991 .It Cm mask Ar mask-specifier
2992 Packets sent to a given pipe or queue by an
2994 rule can be further classified into multiple flows, each of which is then
2998 A flow identifier is constructed by masking the IP addresses,
2999 ports and protocol types as specified with the
3001 options in the configuration of the pipe or queue.
3002 For each different flow identifier, a new pipe or queue is created
3003 with the same parameters as the original object, and matching packets
3008 are used, each flow will get the same bandwidth as defined by the pipe,
3011 are used, each flow will share the parent's pipe bandwidth evenly
3012 with other flows generated by the same queue (note that other queues
3013 with different weights might be connected to the same pipe).
3015 Available mask specifiers are a combination of one or more of the following:
3017 .Cm dst-ip Ar mask ,
3018 .Cm dst-ip6 Ar mask ,
3019 .Cm src-ip Ar mask ,
3020 .Cm src-ip6 Ar mask ,
3021 .Cm dst-port Ar mask ,
3022 .Cm src-port Ar mask ,
3023 .Cm flow-id Ar mask ,
3028 where the latter means all bits in all fields are significant.
3031 When a packet is dropped by a
3033 queue or pipe, the error
3034 is normally reported to the caller routine in the kernel, in the
3035 same way as it happens when a device queue fills up.
3037 option reports the packet as successfully delivered, which can be
3038 needed for some experimental setups where you want to simulate
3039 loss or congestion at a remote router.
3041 .It Cm plr Ar packet-loss-rate
3042 .It Cm plr Ar K,p,H,r
3045 .Ar packet-loss-rate
3046 is a floating-point number between 0 and 1, with 0 meaning no
3047 loss, 1 meaning 100% loss.
3049 When invoked with four arguments, the simple Gilbert-Elliott
3050 channel model with two states (Good and Bad) is used.
3051 .Bd -literal -offset indent
3055 .------------. .------------.
3057 | drop (K) | | drop (H) |
3058 '------------' '------------'
3064 This has the associated probabilities
3068 for the loss probability. This is different from the literature,
3069 where this model is described with probabilities of successful
3070 transmission k and h. However, converting from literature is
3073 K = 1 - k ; H = 1 - h
3075 This is to retain consistency within the interface and allow the
3076 quick re-use of loss probability when giving only a single argument.
3077 In addition the state change probabilities
3082 All of the above probabilities are internally represented on 31 bits.
3084 .It Cm queue Brq Ar slots | size Ns Cm Kbytes
3089 Default value is 50 slots, which
3090 is the typical queue size for Ethernet devices.
3091 Note that for slow speed links you should keep the queue
3092 size short or your traffic might be affected by a significant
3094 E.g., 50 max-sized Ethernet packets (1500 bytes) mean 600Kbit
3095 or 20s of queue on a 30Kbit/s pipe.
3096 Even worse effects can result if you get packets from an
3097 interface with a much larger MTU, e.g.\& the loopback interface
3098 with its 16KB packets.
3102 .Em net.inet.ip.dummynet.pipe_byte_limit
3104 .Em net.inet.ip.dummynet.pipe_slot_limit
3105 control the maximum lengths that can be specified.
3107 .It Cm red | gred Ar w_q Ns / Ns Ar min_th Ns / Ns Ar max_th Ns / Ns Ar max_p
3109 Make use of the RED (Random Early Detection) queue management algorithm.
3114 point numbers between 0 and 1 (inclusive), while
3118 are integer numbers specifying thresholds for queue management
3119 (thresholds are computed in bytes if the queue has been defined
3120 in bytes, in slots otherwise).
3121 The two parameters can also be of the same value if needed.
3124 also supports the gentle RED variant (gred) and ECN (Explicit Congestion
3125 Notification) as optional.
3128 variables can be used to control the RED behaviour:
3129 .Bl -tag -width indent
3130 .It Va net.inet.ip.dummynet.red_lookup_depth
3131 specifies the accuracy in computing the average queue
3132 when the link is idle (defaults to 256, must be greater than zero)
3133 .It Va net.inet.ip.dummynet.red_avg_pkt_size
3134 specifies the expected average packet size (defaults to 512, must be
3136 .It Va net.inet.ip.dummynet.red_max_pkt_size
3137 specifies the expected maximum packet size, only used when queue
3138 thresholds are in bytes (defaults to 1500, must be greater than zero).
3141 .It Cm codel Oo Cm target Ar time Oc Oo Cm interval Ar time Oc Oo Cm ecn |
3143 Make use of the CoDel (Controlled-Delay) queue management algorithm.
3145 is interpreted as milliseconds by default but seconds (s), milliseconds (ms) or
3146 microseconds (us) can be specified instead.
3147 CoDel drops or marks (ECN) packets
3148 depending on packet sojourn time in the queue.
3151 (5ms by default) is the minimum acceptable persistent queue delay that CoDel
3153 CoDel does not drop packets directly after packets sojourn time becomes
3160 (100ms default) before dropping.
3163 should be set to maximum RTT for all expected connections.
3165 enables (disabled by default) packet marking (instead of dropping) for
3166 ECN-enabled TCP flows when queue delay becomes high.
3168 Note that any token after
3170 is considered a parameter for CoDel.
3171 So, ensure all pipe/queue
3172 configuration options are written before
3179 .Va net.inet.ip.dummynet.codel.target
3181 .Va net.inet.ip.dummynet.codel.interval
3182 can be used to set CoDel default parameters.
3184 .It Cm pie Oo Cm target Ar time Oc Oo Cm tupdate Ar time Oc Oo
3185 .Cm alpha Ar n Oc Oo Cm beta Ar n Oc Oo Cm max_burst Ar time Oc Oo
3186 .Cm max_ecnth Ar n Oc Oo Cm ecn | Cm noecn Oc Oo Cm capdrop |
3187 .Cm nocapdrop Oc Oo Cm drand | Cm nodrand Oc Oo Cm onoff
3188 .Oc Oo Cm dre | Cm ts Oc
3189 Make use of the PIE (Proportional Integral controller Enhanced) queue management
3191 PIE drops or marks packets depending on a calculated drop probability during
3192 en-queue process, with the aim of achieving high throughput while keeping queue
3194 At regular time intervals of
3197 (15ms by default) a background process (re)calculates the probability based on queue delay
3201 (15ms by default) and queue delay trends.
3202 PIE approximates current queue
3203 delay by using a departure rate estimation method, or (optionally) by using a
3204 packet timestamp method similar to CoDel.
3206 is interpreted as milliseconds by default but seconds (s), milliseconds (ms) or
3207 microseconds (us) can be specified instead.
3208 The other PIE parameters and options are as follows:
3209 .Bl -tag -width indent
3212 is a floating point number between 0 and 7 which specifies the weight of queue
3213 delay deviations that is used in drop probability calculation.
3214 0.125 is the default.
3217 is a floating point number between 0 and 7 which specifies is the weight of queue
3218 delay trend that is used in drop probability calculation.
3219 1.25 is the default.
3220 .It Cm max_burst Ar time
3221 The maximum period of time that PIE does not drop/mark packets.
3223 default and 10s is the maximum value.
3224 .It Cm max_ecnth Ar n
3225 Even when ECN is enabled, PIE drops packets instead of marking them when drop
3226 probability becomes higher than ECN probability threshold
3228 , the default is 0.1 (i.e 10%) and 1 is the maximum value.
3230 enable or disable ECN marking for ECN-enabled TCP flows.
3231 Disabled by default.
3232 .It Cm capdrop | nocapdrop
3233 enable or disable cap drop adjustment.
3234 Cap drop adjustment is enabled by default.
3235 .It Cm drand | nodrand
3236 enable or disable drop probability de-randomisation.
3237 De-randomisation eliminates
3238 the problem of dropping packets too close or too far.
3239 De-randomisation is enabled by default.
3241 enable turning PIE on and off depending on queue load.
3242 If this option is enabled,
3243 PIE turns on when over 1/3 of queue becomes full.
3244 This option is disabled by
3247 Calculate queue delay using departure rate estimation
3255 Note that any token after
3257 is considered a parameter for PIE.
3258 So ensure all pipe/queue
3259 the configuration options are written before
3263 variables can be used to control the
3267 .Sx SYSCTL VARIABLES
3268 section for more details.
3271 When used with IPv6 data,
3273 currently has several limitations.
3274 Information necessary to route link-local packets to an
3275 interface is not available after processing by
3277 so those packets are dropped in the output path.
3278 Care should be taken to ensure that link-local packets are not passed to
3281 Here are some important points to consider when designing your
3285 Remember that you filter both packets going
3289 Most connections need packets going in both directions.
3291 Remember to test very carefully.
3292 It is a good idea to be near the console when doing this.
3293 If you cannot be near the console,
3294 use an auto-recovery script such as the one in
3295 .Pa /usr/share/examples/ipfw/change_rules.sh .
3297 Do not forget the loopback interface.
3302 There are circumstances where fragmented datagrams are unconditionally
3304 TCP packets are dropped if they do not contain at least 20 bytes of
3305 TCP header, UDP packets are dropped if they do not contain a full 8
3306 byte UDP header, and ICMP packets are dropped if they do not contain
3307 4 bytes of ICMP header, enough to specify the ICMP type, code, and
3309 These packets are simply logged as
3311 since there may not be enough good data in the packet to produce a
3312 meaningful log entry.
3314 Another type of packet is unconditionally dropped, a TCP packet with a
3315 fragment offset of one.
3316 This is a valid packet, but it only has one use, to try
3317 to circumvent firewalls.
3318 When logging is enabled, these packets are
3319 reported as being dropped by rule -1.
3321 If you are logged in over a network, loading the
3325 is probably not as straightforward as you would think.
3326 The following command line is recommended:
3327 .Bd -literal -offset indent
3329 ipfw add 32000 allow ip from any to any
3332 Along the same lines, doing an
3333 .Bd -literal -offset indent
3337 in similar surroundings is also a bad idea.
3341 filter list may not be modified if the system security level
3342 is set to 3 or higher
3345 for information on system security levels).
3347 .Sh PACKET DIVERSION
3350 socket bound to the specified port will receive all packets
3351 diverted to that port.
3352 If no socket is bound to the destination port, or if the divert module is
3353 not loaded, or if the kernel was not compiled with divert socket support,
3354 the packets are dropped.
3355 .Sh NETWORK ADDRESS TRANSLATION (NAT)
3357 support in-kernel NAT using the kernel version of
3361 should be loaded or kernel should have
3362 .Cm options IPFIREWALL_NAT
3365 The nat configuration command is the following:
3366 .Bd -ragged -offset indent
3371 .Ar nat-configuration
3375 The following parameters can be configured:
3376 .Bl -tag -width indent
3377 .It Cm ip Ar ip_address
3378 Define an ip address to use for aliasing.
3380 Use ip address of NIC for aliasing, dynamically changing
3381 it if NIC's ip address changes.
3383 Enable logging on this nat instance.
3385 Deny any incoming connection from outside world.
3387 Try to leave the alias port numbers unchanged from
3388 the actual local port numbers.
3390 Traffic on the local network not originating from a RFC 1918
3391 unregistered address spaces will be ignored.
3393 Like unreg_only, but includes the RFC 6598 (Carrier Grade NAT)
3396 Reset table of the packet aliasing engine on address change.
3398 Reverse the way libalias handles aliasing.
3400 Obey transparent proxy rules only, packet aliasing is not performed.
3402 Skip instance in case of global state lookup (see below).
3403 .It Cm port_range Ar lower-upper
3404 Set the aliasing ports between the ranges given.
3405 Upper port has to be greater than lower.
3408 Some special values can be supplied instead of
3410 in nat rule actions:
3411 .Bl -tag -width indent
3413 Looks up translation state in all configured nat instances.
3414 If an entry is found, packet is aliased according to that entry.
3415 If no entry was found in any of the instances, packet is passed unchanged,
3416 and no new entry will be created.
3418 .Sx MULTIPLE INSTANCES
3421 for more information.
3423 Uses argument supplied in lookup table.
3426 section below for more information on lookup tables.
3429 To let the packet continue after being (de)aliased, set the sysctl variable
3430 .Va net.inet.ip.fw.one_pass
3432 For more information about aliasing modes, refer to
3436 for some examples of nat usage.
3437 .Ss REDIRECT AND LSNAT SUPPORT IN IPFW
3438 Redirect and LSNAT support follow closely the syntax used in
3442 for some examples on how to do redirect and lsnat.
3443 .Ss SCTP NAT SUPPORT
3444 SCTP nat can be configured in a similar manner to TCP through the
3447 The main difference is that
3449 does not do port translation.
3450 Since the local and global side ports will be the same,
3451 there is no need to specify both.
3452 Ports are redirected as follows:
3453 .Bd -ragged -offset indent
3459 .Cm redirect_port sctp
3460 .Ar ip_address [,addr_list] {[port | port-port] [,ports]}
3466 configuration can be done in real-time through the
3469 All may be changed dynamically, though the hash_table size will only
3474 .Sx SYSCTL VARIABLES
3476 .Sh IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION
3477 .Ss Stateful translation
3479 supports in-kernel IPv6/IPv4 network address and protocol translation.
3480 Stateful NAT64 translation allows IPv6-only clients to contact IPv4 servers
3481 using unicast TCP, UDP or ICMP protocols.
3482 One or more IPv4 addresses assigned to a stateful NAT64 translator are shared
3483 among several IPv6-only clients.
3484 When stateful NAT64 is used in conjunction with DNS64, no changes are usually
3485 required in the IPv6 client or the IPv4 server.
3488 should be loaded or kernel should have
3489 .Cm options IPFIREWALL_NAT64
3490 to be able use stateful NAT64 translator.
3492 Stateful NAT64 uses a bunch of memory for several types of objects.
3493 When IPv6 client initiates connection, NAT64 translator creates a host entry
3494 in the states table.
3495 Each host entry uses preallocated IPv4 alias entry.
3496 Each alias entry has a number of ports group entries allocated on demand.
3497 Ports group entries contains connection state entries.
3498 There are several options to control limits and lifetime for these objects.
3500 NAT64 translator follows RFC7915 when does ICMPv6/ICMP translation,
3501 unsupported message types will be silently dropped.
3502 IPv6 needs several ICMPv6 message types to be explicitly allowed for correct
3504 Make sure that ND6 neighbor solicitation (ICMPv6 type 135) and neighbor
3505 advertisement (ICMPv6 type 136) messages will not be handled by translation
3508 After translation NAT64 translator by default sends packets through
3509 corresponding netisr queue.
3510 Thus translator host should be configured as IPv4 and IPv6 router.
3511 Also this means, that a packet is handled by firewall twice.
3512 First time an original packet is handled and consumed by translator,
3513 and then it is handled again as translated packet.
3514 This behavior can be changed by sysctl variable
3515 .Va net.inet.ip.fw.nat64_direct_output .
3516 Also translated packet can be tagged using
3518 rule action, and then matched by
3520 opcode to avoid loops and extra overhead.
3522 The stateful NAT64 configuration command is the following:
3523 .Bd -ragged -offset indent
3532 The following parameters can be configured:
3533 .Bl -tag -width indent
3534 .It Cm prefix4 Ar ipv4_prefix/plen
3535 The IPv4 prefix with mask defines the pool of IPv4 addresses used as
3536 source address after translation.
3537 Stateful NAT64 module translates IPv6 source address of client to one
3538 IPv4 address from this pool.
3539 Note that incoming IPv4 packets that don't have corresponding state entry
3540 in the states table will be dropped by translator.
3541 Make sure that translation rules handle packets, destined to configured prefix.
3542 .It Cm prefix6 Ar ipv6_prefix/length
3543 The IPv6 prefix defines IPv4-embedded IPv6 addresses used by translator
3544 to represent IPv4 addresses.
3545 This IPv6 prefix should be configured in DNS64.
3546 The translator implementation follows RFC6052, that restricts the length of
3547 prefixes to one of following: 32, 40, 48, 56, 64, or 96.
3548 The Well-Known IPv6 Prefix 64:ff9b:: must be 96 bits long.
3551 prefix can be used to handle several IPv6 prefixes with one NAT64 instance.
3552 The NAT64 instance will determine a destination IPv4 address from prefix
3554 .It Cm states_chunks Ar number
3555 The number of states chunks in single ports group.
3556 Each ports group by default can keep 64 state entries in single chunk.
3557 The above value affects the maximum number of states that can be associated with single IPv4 alias address and port.
3558 The value must be power of 2, and up to 128.
3559 .It Cm host_del_age Ar seconds
3560 The number of seconds until the host entry for a IPv6 client will be deleted
3561 and all its resources will be released due to inactivity.
3564 .It Cm pg_del_age Ar seconds
3565 The number of seconds until a ports group with unused state entries will
3569 .It Cm tcp_syn_age Ar seconds
3570 The number of seconds while a state entry for TCP connection with only SYN
3572 If TCP connection establishing will not be finished,
3573 state entry will be deleted.
3576 .It Cm tcp_est_age Ar seconds
3577 The number of seconds while a state entry for established TCP connection
3581 .It Cm tcp_close_age Ar seconds
3582 The number of seconds while a state entry for closed TCP connection
3584 Keeping state entries for closed connections is needed, because IPv4 servers
3585 typically keep closed connections in a TIME_WAIT state for a several minutes.
3586 Since translator's IPv4 addresses are shared among all IPv6 clients,
3587 new connections from the same addresses and ports may be rejected by server,
3588 because these connections are still in a TIME_WAIT state.
3589 Keeping them in translator's state table protects from such rejects.
3592 .It Cm udp_age Ar seconds
3593 The number of seconds while translator keeps state entry in a waiting for
3594 reply to the sent UDP datagram.
3597 .It Cm icmp_age Ar seconds
3598 The number of seconds while translator keeps state entry in a waiting for
3599 reply to the sent ICMP message.
3603 Turn on logging of all handled packets via BPF through
3607 is a pseudo interface and can be created after a boot manually with
3610 Note that it has different purpose than
3613 Translators sends to BPF an additional information with each packet.
3616 you are able to see each handled packet before and after translation.
3618 Turn off logging of all handled packets via BPF.
3619 .It Cm allow_private
3620 Turn on processing private IPv4 addresses.
3621 By default IPv6 packets with destinations mapped to private address ranges
3622 defined by RFC1918 are not processed.
3623 .It Cm -allow_private
3624 Turn off private address handling in
3629 To inspect a states table of stateful NAT64 the following command can be used:
3630 .Bd -ragged -offset indent
3638 Stateless NAT64 translator doesn't use a states table for translation
3639 and converts IPv4 addresses to IPv6 and vice versa solely based on the
3640 mappings taken from configured lookup tables.
3641 Since a states table doesn't used by stateless translator,
3642 it can be configured to pass IPv4 clients to IPv6-only servers.
3644 The stateless NAT64 configuration command is the following:
3645 .Bd -ragged -offset indent
3654 The following parameters can be configured:
3655 .Bl -tag -width indent
3656 .It Cm prefix6 Ar ipv6_prefix/length
3657 The IPv6 prefix defines IPv4-embedded IPv6 addresses used by translator
3658 to represent IPv4 addresses.
3659 This IPv6 prefix should be configured in DNS64.
3660 .It Cm table4 Ar table46
3663 contains mapping how IPv4 addresses should be translated to IPv6 addresses.
3664 .It Cm table6 Ar table64
3667 contains mapping how IPv6 addresses should be translated to IPv4 addresses.
3669 Turn on logging of all handled packets via BPF through
3673 Turn off logging of all handled packets via BPF.
3674 .It Cm allow_private
3675 Turn on processing private IPv4 addresses.
3676 By default IPv6 packets with destinations mapped to private address ranges
3677 defined by RFC1918 are not processed.
3678 .It Cm -allow_private
3679 Turn off private address handling in
3684 Note that the behavior of stateless translator with respect to not matched
3685 packets differs from stateful translator.
3686 If corresponding addresses was not found in the lookup tables, the packet
3687 will not be dropped and the search continues.
3688 .Ss XLAT464 CLAT translation
3689 XLAT464 CLAT NAT64 translator implements client-side stateless translation as
3690 defined in RFC6877 and is very similar to statless NAT64 translator
3692 Instead of lookup tables it uses one-to-one mapping between IPv4 and IPv6
3693 addresses using configured prefixes.
3694 This mode can be used as a replacement of DNS64 service for applications
3695 that are not using it (e.g. VoIP) allowing them to access IPv4-only Internet
3696 over IPv6-only networks with help of remote NAT64 translator.
3698 The CLAT NAT64 configuration command is the following:
3699 .Bd -ragged -offset indent
3708 The following parameters can be configured:
3709 .Bl -tag -width indent
3710 .It Cm clat_prefix Ar ipv6_prefix/length
3711 The IPv6 prefix defines IPv4-embedded IPv6 addresses used by translator
3712 to represent source IPv4 addresses.
3713 .It Cm plat_prefix Ar ipv6_prefix/length
3714 The IPv6 prefix defines IPv4-embedded IPv6 addresses used by translator
3715 to represent destination IPv4 addresses.
3716 This IPv6 prefix should be configured on a remote NAT64 translator.
3718 Turn on logging of all handled packets via BPF through
3722 Turn off logging of all handled packets via BPF.
3723 .It Cm allow_private
3724 Turn on processing private IPv4 addresses.
3727 instance will not process IPv4 packets with destination address from private
3728 ranges as defined in RFC1918.
3729 .It Cm -allow_private
3730 Turn off private address handling in
3735 Note that the behavior of CLAT translator with respect to not matched
3736 packets differs from stateful translator.
3737 If corresponding addresses were not matched against prefixes configured,
3738 the packet will not be dropped and the search continues.
3739 .Sh IPv6-to-IPv6 NETWORK PREFIX TRANSLATION (NPTv6)
3741 supports in-kernel IPv6-to-IPv6 network prefix translation as described
3745 should be loaded or kernel should has
3746 .Cm options IPFIREWALL_NPTV6
3747 to be able use NPTv6 translator.
3749 The NPTv6 configuration command is the following:
3750 .Bd -ragged -offset indent
3759 The following parameters can be configured:
3760 .Bl -tag -width indent
3761 .It Cm int_prefix Ar ipv6_prefix
3762 IPv6 prefix used in internal network.
3763 NPTv6 module translates source address when it matches this prefix.
3764 .It Cm ext_prefix Ar ipv6_prefix
3765 IPv6 prefix used in external network.
3766 NPTv6 module translates destination address when it matches this prefix.
3767 .It Cm ext_if Ar nic
3768 The NPTv6 module will use first global IPv6 address from interface
3771 It can be useful when IPv6 prefix of external network is dynamically obtained.
3775 options are mutually exclusive.
3776 .It Cm prefixlen Ar length
3777 The length of specified IPv6 prefixes.
3778 It must be in range from 8 to 64.
3781 Note that the prefix translation rules are silently ignored when IPv6 packet
3782 forwarding is disabled.
3783 To enable the packet forwarding, set the sysctl variable
3784 .Va net.inet6.ip6.forwarding
3787 To let the packet continue after being translated, set the sysctl variable
3788 .Va net.inet.ip.fw.one_pass
3791 Tunables can be set in
3797 before ipfw module gets loaded.
3798 .Bl -tag -width indent
3799 .It Va net.inet.ip.fw.enable : No 1
3800 Enables the firewall.
3801 Setting this variable to 0 lets you run your machine without
3802 firewall even if compiled in.
3803 .It Va net.inet6.ip6.fw.enable : No 1
3804 provides the same functionality as above for the IPv6 case.
3805 .It Va net.link.ether.ipfw : No 0
3806 Controls whether layer2 packets are passed to
3809 .It Va net.inet.ip.fw.default_to_accept : No 0
3810 Defines ipfw last rule behavior.
3811 This value overrides
3812 .Cd "options IPFW_DEFAULT_TO_(ACCEPT|DENY)"
3813 from kernel configuration file.
3814 .It Va net.inet.ip.fw.tables_max : No 128
3815 Defines number of tables available in ipfw.
3816 Number cannot exceed 65534.
3818 .Sh SYSCTL VARIABLES
3821 variables controls the behaviour of the firewall and
3823 .Pq Nm dummynet , bridge , sctp nat .
3824 These are shown below together with their default value
3825 (but always check with the
3827 command what value is actually in use) and meaning:
3828 .Bl -tag -width indent
3829 .It Va net.inet.ip.alias.sctp.accept_global_ootb_addip : No 0
3832 responds to receipt of global OOTB ASCONF-AddIP:
3833 .Bl -tag -width indent
3835 No response (unless a partially matching association exists -
3836 ports and vtags match but global address does not)
3839 will accept and process all OOTB global AddIP messages.
3842 Option 1 should never be selected as this forms a security risk.
3844 establish multiple fake associations by sending AddIP messages.
3845 .It Va net.inet.ip.alias.sctp.chunk_proc_limit : No 5
3846 Defines the maximum number of chunks in an SCTP packet that will be
3848 packet that matches an existing association.
3849 This value is enforced to be greater or equal than
3850 .Cm net.inet.ip.alias.sctp.initialising_chunk_proc_limit .
3852 a DoS risk yet setting too low a value may result in
3853 important control chunks in
3854 the packet not being located and parsed.
3855 .It Va net.inet.ip.alias.sctp.error_on_ootb : No 1
3858 responds to any Out-of-the-Blue (OOTB) packets with ErrorM packets.
3859 An OOTB packet is a packet that arrives with no existing association
3862 and is not an INIT or ASCONF-AddIP packet:
3863 .Bl -tag -width indent
3865 ErrorM is never sent in response to OOTB packets.
3867 ErrorM is only sent to OOTB packets received on the local side.
3869 ErrorM is sent to the local side and on the global side ONLY if there is a
3870 partial match (ports and vtags match but the source global IP does not).
3871 This value is only useful if the
3873 is tracking global IP addresses.
3875 ErrorM is sent in response to all OOTB packets on both
3876 the local and global side
3880 At the moment the default is 0, since the ErrorM packet is not yet
3881 supported by most SCTP stacks.
3882 When it is supported, and if not tracking
3883 global addresses, we recommend setting this value to 1 to allow
3884 multi-homed local hosts to function with the
3886 To track global addresses, we recommend setting this value to 2 to
3887 allow global hosts to be informed when they need to (re)send an
3889 Value 3 should never be chosen (except for debugging) as the
3891 will respond to all OOTB global packets (a DoS risk).
3892 .It Va net.inet.ip.alias.sctp.hashtable_size : No 2003
3893 Size of hash tables used for
3895 lookups (100 < prime_number > 1000001).
3898 size for any future created
3900 instance and therefore must be set prior to creating a
3903 The table sizes may be changed to suit specific needs.
3904 If there will be few
3905 concurrent associations, and memory is scarce, you may make these smaller.
3906 If there will be many thousands (or millions) of concurrent associations, you
3907 should make these larger.
3908 A prime number is best for the table size.
3910 update function will adjust your input value to the next highest prime number.
3911 .It Va net.inet.ip.alias.sctp.holddown_time : No 0
3912 Hold association in table for this many seconds after receiving a
3914 This allows endpoints to correct shutdown gracefully if a
3915 shutdown_complete is lost and retransmissions are required.
3916 .It Va net.inet.ip.alias.sctp.init_timer : No 15
3917 Timeout value while waiting for (INIT-ACK|AddIP-ACK).
3918 This value cannot be 0.
3919 .It Va net.inet.ip.alias.sctp.initialising_chunk_proc_limit : No 2
3920 Defines the maximum number of chunks in an SCTP packet that will be parsed when
3921 no existing association exists that matches that packet.
3923 will only be an INIT or ASCONF-AddIP packet.
3924 A higher value may become a DoS
3925 risk as malformed packets can consume processing resources.
3926 .It Va net.inet.ip.alias.sctp.param_proc_limit : No 25
3927 Defines the maximum number of parameters within a chunk that will be
3930 As for other similar sysctl variables, larger values pose a DoS risk.
3931 .It Va net.inet.ip.alias.sctp.log_level : No 0
3932 Level of detail in the system log messages (0 \- minimal, 1 \- event,
3933 2 \- info, 3 \- detail, 4 \- debug, 5 \- max debug).
3935 option in high loss environments.
3936 .It Va net.inet.ip.alias.sctp.shutdown_time : No 15
3937 Timeout value while waiting for SHUTDOWN-COMPLETE.
3938 This value cannot be 0.
3939 .It Va net.inet.ip.alias.sctp.track_global_addresses : No 0
3940 Enables/disables global IP address tracking within the
3943 upper limit on the number of addresses tracked for each association:
3944 .Bl -tag -width indent
3946 Global tracking is disabled
3948 Enables tracking, the maximum number of addresses tracked for each
3949 association is limited to this value
3952 This variable is fully dynamic, the new value will be adopted for all newly
3953 arriving associations, existing associations are treated
3954 as they were previously.
3955 Global tracking will decrease the number of collisions within the
3958 of increased processing load, memory usage, complexity, and possible
3961 problems in complex networks with multiple
3963 We recommend not tracking
3964 global IP addresses, this will still result in a fully functional
3966 .It Va net.inet.ip.alias.sctp.up_timer : No 300
3967 Timeout value to keep an association up with no traffic.
3968 This value cannot be 0.
3969 .It Va net.inet.ip.dummynet.codel.interval : No 100000
3972 AQM interval in microseconds.
3973 The value must be in the range 1..5000000.
3974 .It Va net.inet.ip.dummynet.codel.target : No 5000
3977 AQM target delay time in microseconds (the minimum acceptable persistent queue
3979 The value must be in the range 1..5000000.
3980 .It Va net.inet.ip.dummynet.expire : No 1
3981 Lazily delete dynamic pipes/queue once they have no pending traffic.
3982 You can disable this by setting the variable to 0, in which case
3983 the pipes/queues will only be deleted when the threshold is reached.
3984 .It Va net.inet.ip.dummynet.fqcodel.flows : No 1024
3985 Defines the default total number of flow queues (sub-queues) that
3987 creates and manages.
3988 The value must be in the range 1..65536.
3989 .It Va net.inet.ip.dummynet.fqcodel.interval : No 100000
3992 scheduler/AQM interval in microseconds.
3993 The value must be in the range 1..5000000.
3994 .It Va net.inet.ip.dummynet.fqcodel.limit : No 10240
3995 The default hard size limit (in unit of packet) of all queues managed by an
3999 The value must be in the range 1..20480.
4000 .It Va net.inet.ip.dummynet.fqcodel.quantum : No 1514
4001 The default quantum (credit) of the
4004 The value must be in the range 1..9000.
4005 .It Va net.inet.ip.dummynet.fqcodel.target : No 5000
4008 scheduler/AQM target delay time in microseconds (the minimum acceptable
4009 persistent queue delay).
4010 The value must be in the range 1..5000000.
4011 .It Va net.inet.ip.dummynet.fqpie.alpha : No 125
4014 parameter (scaled by 1000) for
4017 The value must be in the range 1..7000.
4018 .It Va net.inet.ip.dummynet.fqpie.beta : No 1250
4021 parameter (scaled by 1000) for
4024 The value must be in the range 1..7000.
4025 .It Va net.inet.ip.dummynet.fqpie.flows : No 1024
4026 Defines the default total number of flow queues (sub-queues) that
4028 creates and manages.
4029 The value must be in the range 1..65536.
4030 .It Va net.inet.ip.dummynet.fqpie.limit : No 10240
4031 The default hard size limit (in unit of packet) of all queues managed by an
4035 The value must be in the range 1..20480.
4036 .It Va net.inet.ip.dummynet.fqpie.max_burst : No 150000
4037 The default maximum period of microseconds that
4039 scheduler/AQM does not drop/mark packets.
4040 The value must be in the range 1..10000000.
4041 .It Va net.inet.ip.dummynet.fqpie.max_ecnth : No 99
4042 The default maximum ECN probability threshold (scaled by 1000) for
4045 The value must be in the range 1..7000.
4046 .It Va net.inet.ip.dummynet.fqpie.quantum : No 1514
4047 The default quantum (credit) of the
4050 The value must be in the range 1..9000.
4051 .It Va net.inet.ip.dummynet.fqpie.target : No 15000
4056 in unit of microsecond.
4057 The value must be in the range 1..5000000.
4058 .It Va net.inet.ip.dummynet.fqpie.tupdate : No 15000
4063 in unit of microsecond.
4064 The value must be in the range 1..5000000.
4065 .It Va net.inet.ip.dummynet.hash_size : No 64
4066 Default size of the hash table used for dynamic pipes/queues.
4067 This value is used when no
4069 option is specified when configuring a pipe/queue.
4070 .It Va net.inet.ip.dummynet.io_fast : No 0
4071 If set to a non-zero value,
4076 operation (see above) is enabled.
4077 .It Va net.inet.ip.dummynet.io_pkt
4078 Number of packets passed to
4080 .It Va net.inet.ip.dummynet.io_pkt_drop
4081 Number of packets dropped by
4083 .It Va net.inet.ip.dummynet.io_pkt_fast
4084 Number of packets bypassed by the
4087 .It Va net.inet.ip.dummynet.max_chain_len : No 16
4088 Target value for the maximum number of pipes/queues in a hash bucket.
4090 .Cm max_chain_len*hash_size
4091 is used to determine the threshold over which empty pipes/queues
4092 will be expired even when
4093 .Cm net.inet.ip.dummynet.expire=0 .
4094 .It Va net.inet.ip.dummynet.red_lookup_depth : No 256
4095 .It Va net.inet.ip.dummynet.red_avg_pkt_size : No 512
4096 .It Va net.inet.ip.dummynet.red_max_pkt_size : No 1500
4097 Parameters used in the computations of the drop probability
4098 for the RED algorithm.
4099 .It Va net.inet.ip.dummynet.pie.alpha : No 125
4102 parameter (scaled by 1000) for
4105 The value must be in the range 1..7000.
4106 .It Va net.inet.ip.dummynet.pie.beta : No 1250
4109 parameter (scaled by 1000) for
4112 The value must be in the range 1..7000.
4113 .It Va net.inet.ip.dummynet.pie.max_burst : No 150000
4114 The default maximum period of microseconds that
4116 AQM does not drop/mark packets.
4117 The value must be in the range 1..10000000.
4118 .It Va net.inet.ip.dummynet.pie.max_ecnth : No 99
4119 The default maximum ECN probability threshold (scaled by 1000) for
4122 The value must be in the range 1..7000.
4123 .It Va net.inet.ip.dummynet.pie.target : No 15000
4128 AQM in unit of microsecond.
4129 The value must be in the range 1..5000000.
4130 .It Va net.inet.ip.dummynet.pie.tupdate : No 15000
4135 AQM in unit of microsecond.
4136 The value must be in the range 1..5000000.
4137 .It Va net.inet.ip.dummynet.pipe_byte_limit : No 1048576
4138 .It Va net.inet.ip.dummynet.pipe_slot_limit : No 100
4139 The maximum queue size that can be specified in bytes or packets.
4140 These limits prevent accidental exhaustion of resources such as mbufs.
4141 If you raise these limits,
4142 you should make sure the system is configured so that sufficient resources
4144 .It Va net.inet.ip.fw.autoinc_step : No 100
4145 Delta between rule numbers when auto-generating them.
4146 The value must be in the range 1..1000.
4147 .It Va net.inet.ip.fw.curr_dyn_buckets : Va net.inet.ip.fw.dyn_buckets
4148 The current number of buckets in the hash table for dynamic rules
4150 .It Va net.inet.ip.fw.debug : No 1
4151 Controls debugging messages produced by
4153 .It Va net.inet.ip.fw.default_rule : No 65535
4154 The default rule number (read-only).
4156 .Nm , the default rule is the last one, so its number
4157 can also serve as the highest number allowed for a rule.
4158 .It Va net.inet.ip.fw.dyn_buckets : No 256
4159 The number of buckets in the hash table for dynamic rules.
4160 Must be a power of 2, up to 65536.
4161 It only takes effect when all dynamic rules have expired, so you
4162 are advised to use a
4164 command to make sure that the hash table is resized.
4165 .It Va net.inet.ip.fw.dyn_count : No 3
4166 Current number of dynamic rules
4168 .It Va net.inet.ip.fw.dyn_keepalive : No 1
4169 Enables generation of keepalive packets for
4171 rules on TCP sessions.
4172 A keepalive is generated to both
4173 sides of the connection every 5 seconds for the last 20
4174 seconds of the lifetime of the rule.
4175 .It Va net.inet.ip.fw.dyn_max : No 8192
4176 Maximum number of dynamic rules.
4177 When you hit this limit, no more dynamic rules can be
4178 installed until old ones expire.
4179 .It Va net.inet.ip.fw.dyn_ack_lifetime : No 300
4180 .It Va net.inet.ip.fw.dyn_syn_lifetime : No 20
4181 .It Va net.inet.ip.fw.dyn_fin_lifetime : No 1
4182 .It Va net.inet.ip.fw.dyn_rst_lifetime : No 1
4183 .It Va net.inet.ip.fw.dyn_udp_lifetime : No 5
4184 .It Va net.inet.ip.fw.dyn_short_lifetime : No 30
4185 These variables control the lifetime, in seconds, of dynamic
4187 Upon the initial SYN exchange the lifetime is kept short,
4188 then increased after both SYN have been seen, then decreased
4189 again during the final FIN exchange or when a RST is received.
4191 .Em dyn_fin_lifetime
4193 .Em dyn_rst_lifetime
4194 must be strictly lower than 5 seconds, the period of
4195 repetition of keepalives.
4196 The firewall enforces that.
4197 .It Va net.inet.ip.fw.dyn_keep_states : No 0
4198 Keep dynamic states on rule/set deletion.
4199 States are relinked to default rule (65535).
4200 This can be handly for ruleset reload.
4201 Turned off by default.
4202 .It Va net.inet.ip.fw.one_pass : No 1
4203 When set, the packet exiting from the
4207 node is not passed though the firewall again.
4208 Otherwise, after an action, the packet is
4209 reinjected into the firewall at the next rule.
4210 .It Va net.inet.ip.fw.tables_max : No 128
4211 Maximum number of tables.
4212 .It Va net.inet.ip.fw.verbose : No 1
4213 Enables verbose messages.
4214 .It Va net.inet.ip.fw.verbose_limit : No 0
4215 Limits the number of messages produced by a verbose firewall.
4216 .It Va net.inet6.ip6.fw.deny_unknown_exthdrs : No 1
4217 If enabled packets with unknown IPv6 Extension Headers will be denied.
4218 .It Va net.link.bridge.ipfw : No 0
4219 Controls whether bridged packets are passed to
4222 .It Va net.inet.ip.fw.nat64_debug : No 0
4223 Controls debugging messages produced by
4226 .It Va net.inet.ip.fw.nat64_direct_output : No 0
4227 Controls the output method used by
4230 .Bl -tag -width indent
4232 A packet is handled by
4235 First time an original packet is handled by
4240 Then translated packet is queued via netisr to input processing again.
4242 A packet is handled by
4244 only once, and after translation it will be pushed directly to outgoing
4248 .Sh INTERNAL DIAGNOSTICS
4249 There are some commands that may be useful to understand current state
4250 of certain subsystems inside kernel module.
4251 These commands provide debugging output which may change without notice.
4253 Currently the following commands are available as
4256 .Bl -tag -width indent
4258 Lists all interface which are currently tracked by
4260 with their in-kernel status.
4262 List all table lookup algorithms currently available.
4265 There are far too many possible uses of
4267 so this Section will only give a small set of examples.
4268 .Ss BASIC PACKET FILTERING
4269 This command adds an entry which denies all tcp packets from
4270 .Em cracker.evil.org
4271 to the telnet port of
4273 from being forwarded by the host:
4275 .Dl "ipfw add deny tcp from cracker.evil.org to wolf.tambov.su telnet"
4277 This one disallows any connection from the entire cracker's
4280 .Dl "ipfw add deny ip from 123.45.67.0/24 to my.host.org"
4282 A first and efficient way to limit access (not using dynamic rules)
4283 is the use of the following rules:
4285 .Dl "ipfw add allow tcp from any to any established"
4286 .Dl "ipfw add allow tcp from net1 portlist1 to net2 portlist2 setup"
4287 .Dl "ipfw add allow tcp from net3 portlist3 to net3 portlist3 setup"
4289 .Dl "ipfw add deny tcp from any to any"
4291 The first rule will be a quick match for normal TCP packets,
4292 but it will not match the initial SYN packet, which will be
4295 rules only for selected source/destination pairs.
4296 All other SYN packets will be rejected by the final
4300 If you administer one or more subnets, you can take advantage
4301 of the address sets and or-blocks and write extremely
4302 compact rulesets which selectively enable services to blocks
4303 of clients, as below:
4305 .Dl "goodguys=\*q{ 10.1.2.0/24{20,35,66,18} or 10.2.3.0/28{6,3,11} }\*q"
4306 .Dl "badguys=\*q10.1.2.0/24{8,38,60}\*q"
4308 .Dl "ipfw add allow ip from ${goodguys} to any"
4309 .Dl "ipfw add deny ip from ${badguys} to any"
4310 .Dl "... normal policies ..."
4312 Allow any transit packets coming from single vlan 10 and
4313 going out to vlans 100-1000:
4315 .Dl "ipfw add 10 allow out recv vlan10 \e"
4316 .Dl "{ xmit vlan1000 or xmit \*qvlan[1-9]??\*q }"
4320 option could be used to do automated anti-spoofing by adding the
4321 following to the top of a ruleset:
4323 .Dl "ipfw add deny ip from any to any not verrevpath in"
4325 This rule drops all incoming packets that appear to be coming to the
4326 system on the wrong interface.
4327 For example, a packet with a source
4328 address belonging to a host on a protected internal network would be
4329 dropped if it tried to enter the system from an external interface.
4333 option could be used to do similar but more restricted anti-spoofing
4334 by adding the following to the top of a ruleset:
4336 .Dl "ipfw add deny ip from any to any not antispoof in"
4338 This rule drops all incoming packets that appear to be coming from another
4339 directly connected system but on the wrong interface.
4340 For example, a packet with a source address of
4341 .Li 192.168.0.0/24 ,
4350 option could be used to (re)mark user traffic,
4351 by adding the following to the appropriate place in ruleset:
4353 .Dl "ipfw add setdscp be ip from any to any dscp af11,af21"
4354 .Ss SELECTIVE MIRRORING
4355 If your network has network traffic analyzer
4356 connected to your host directly via dedicated interface
4357 or remotely via RSPAN vlan, you can selectively mirror
4358 some Ethernet layer2 frames to the analyzer.
4360 First, make sure your firewall is already configured and runs.
4361 Then, enable layer2 processing if not already enabled:
4363 .Dl "sysctl net.link.ether.ipfw=1"
4365 Next, load needed additional kernel modules:
4367 .Dl "kldload ng_ether ng_ipfw"
4369 Optionally, make system load these modules automatically
4372 .Dl sysrc kld_list+="ng_ether ng_ipfw"
4376 kernel module to transmit mirrored copies of layer2 frames
4377 out via vlan900 interface:
4379 .Dl "ngctl connect ipfw: vlan900: 1 lower"
4381 Think of "1" here as of "mirroring instance index" and vlan900 is its
4383 You can have arbitrary number of instances.
4388 At last, actually start mirroring of selected frames using "instance 1".
4389 For frames incoming from em0 interface:
4391 .Dl "ipfw add ngtee 1 ip from any to 192.168.0.1 layer2 in recv em0"
4393 For frames outgoing to em0 interface:
4395 .Dl "ipfw add ngtee 1 ip from any to 192.168.0.1 layer2 out xmit em0"
4397 For both incoming and outgoing frames while flowing through em0:
4399 .Dl "ipfw add ngtee 1 ip from any to 192.168.0.1 layer2 via em0"
4401 Make sure you do not perform mirroring for already duplicated frames
4402 or kernel may hang as there is no safety net.
4404 In order to protect a site from flood attacks involving fake
4405 TCP packets, it is safer to use dynamic rules:
4407 .Dl "ipfw add check-state"
4408 .Dl "ipfw add deny tcp from any to any established"
4409 .Dl "ipfw add allow tcp from my-net to any setup keep-state"
4411 This will let the firewall install dynamic rules only for
4412 those connection which start with a regular SYN packet coming
4413 from the inside of our network.
4414 Dynamic rules are checked when encountering the first
4423 rule should usually be placed near the beginning of the
4424 ruleset to minimize the amount of work scanning the ruleset.
4425 Your mileage may vary.
4427 For more complex scenarios with dynamic rules
4431 can be used to precisely control creation and checking of dynamic rules.
4432 Example of usage of these options are provided in
4433 .Sx NETWORK ADDRESS TRANSLATION (NAT)
4436 To limit the number of connections a user can open
4437 you can use the following type of rules:
4439 .Dl "ipfw add allow tcp from my-net/24 to any setup limit src-addr 10"
4440 .Dl "ipfw add allow tcp from any to me setup limit src-addr 4"
4442 The former (assuming it runs on a gateway) will allow each host
4443 on a /24 network to open at most 10 TCP connections.
4444 The latter can be placed on a server to make sure that a single
4445 client does not use more than 4 simultaneous connections.
4448 stateful rules can be subject to denial-of-service attacks
4449 by a SYN-flood which opens a huge number of dynamic rules.
4450 The effects of such attacks can be partially limited by
4453 variables which control the operation of the firewall.
4455 Here is a good usage of the
4457 command to see accounting records and timestamp information:
4461 or in short form without timestamps:
4465 which is equivalent to:
4469 Next rule diverts all incoming packets from 192.168.2.0/24
4470 to divert port 5000:
4472 .Dl ipfw divert 5000 ip from 192.168.2.0/24 to any in
4474 The following rules show some of the applications of
4478 for simulations and the like.
4480 This rule drops random incoming packets with a probability
4483 .Dl "ipfw add prob 0.05 deny ip from any to any in"
4485 A similar effect can be achieved making use of
4489 .Dl "dnctl add pipe 10 ip from any to any"
4490 .Dl "dnctl pipe 10 config plr 0.05"
4492 We can use pipes to artificially limit bandwidth, e.g.\& on a
4493 machine acting as a router, if we want to limit traffic from
4494 local clients on 192.168.2.0/24 we do:
4496 .Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out"
4497 .Dl "dnctl pipe 1 config bw 300Kbit/s queue 50KBytes"
4499 note that we use the
4501 modifier so that the rule is not used twice.
4502 Remember in fact that
4504 rules are checked both on incoming and outgoing packets.
4506 Should we want to simulate a bidirectional link with bandwidth
4507 limitations, the correct way is the following:
4509 .Dl "ipfw add pipe 1 ip from any to any out"
4510 .Dl "ipfw add pipe 2 ip from any to any in"
4511 .Dl "dnctl pipe 1 config bw 64Kbit/s queue 10Kbytes"
4512 .Dl "dnctl pipe 2 config bw 64Kbit/s queue 10Kbytes"
4514 The above can be very useful, e.g.\& if you want to see how
4515 your fancy Web page will look for a residential user who
4516 is connected only through a slow link.
4517 You should not use only one pipe for both directions, unless
4518 you want to simulate a half-duplex medium (e.g.\& AppleTalk,
4520 It is not necessary that both pipes have the same configuration,
4521 so we can also simulate asymmetric links.
4523 Should we want to verify network performance with the RED queue
4524 management algorithm:
4526 .Dl "ipfw add pipe 1 ip from any to any"
4527 .Dl "dnctl pipe 1 config bw 500Kbit/s queue 100 red 0.002/30/80/0.1"
4529 Another typical application of the traffic shaper is to
4530 introduce some delay in the communication.
4531 This can significantly affect applications which do a lot of Remote
4532 Procedure Calls, and where the round-trip-time of the
4533 connection often becomes a limiting factor much more than
4536 .Dl "ipfw add pipe 1 ip from any to any out"
4537 .Dl "ipfw add pipe 2 ip from any to any in"
4538 .Dl "dnctl pipe 1 config delay 250ms bw 1Mbit/s"
4539 .Dl "dnctl pipe 2 config delay 250ms bw 1Mbit/s"
4541 Per-flow queueing can be useful for a variety of purposes.
4542 A very simple one is counting traffic:
4544 .Dl "ipfw add pipe 1 tcp from any to any"
4545 .Dl "ipfw add pipe 1 udp from any to any"
4546 .Dl "ipfw add pipe 1 ip from any to any"
4547 .Dl "dnctl pipe 1 config mask all"
4549 The above set of rules will create queues (and collect
4550 statistics) for all traffic.
4551 Because the pipes have no limitations, the only effect is
4552 collecting statistics.
4553 Note that we need 3 rules, not just the last one, because
4556 tries to match IP packets it will not consider ports, so we
4557 would not see connections on separate ports as different
4560 A more sophisticated example is limiting the outbound traffic
4561 on a net with per-host limits, rather than per-network limits:
4563 .Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out"
4564 .Dl "ipfw add pipe 2 ip from any to 192.168.2.0/24 in"
4565 .Dl "dnctl pipe 1 config mask src-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
4566 .Dl "dnctl pipe 2 config mask dst-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
4568 In the following example, we need to create several traffic bandwidth
4569 classes and we need different hosts/networks to fall into different classes.
4570 We create one pipe for each class and configure them accordingly.
4571 Then we create a single table and fill it with IP subnets and addresses.
4572 For each subnet/host we set the argument equal to the number of the pipe
4574 Then we classify traffic using a single rule:
4576 .Dl "dnctl pipe 1 config bw 1000Kbyte/s"
4577 .Dl "dnctl pipe 4 config bw 4000Kbyte/s"
4579 .Dl "ipfw table T1 create type addr"
4580 .Dl "ipfw table T1 add 192.168.2.0/24 1"
4581 .Dl "ipfw table T1 add 192.168.0.0/27 4"
4582 .Dl "ipfw table T1 add 192.168.0.2 1"
4584 .Dl "ipfw add pipe tablearg ip from 'table(T1)' to any"
4588 action, the table entries may include hostnames and IP addresses.
4590 .Dl "ipfw table T2 create type addr valtype ipv4"
4591 .Dl "ipfw table T2 add 192.168.2.0/24 10.23.2.1"
4592 .Dl "ipfw table T2 add 192.168.0.0/27 router1.dmz"
4594 .Dl "ipfw add 100 fwd tablearg ip from any to 'table(T2)'"
4596 In the following example per-interface firewall is created:
4598 .Dl "ipfw table IN create type iface valtype skipto,fib"
4599 .Dl "ipfw table IN add vlan20 12000,12"
4600 .Dl "ipfw table IN add vlan30 13000,13"
4601 .Dl "ipfw table OUT create type iface valtype skipto"
4602 .Dl "ipfw table OUT add vlan20 22000"
4603 .Dl "ipfw table OUT add vlan30 23000"
4605 .Dl "ipfw add 100 setfib tablearg ip from any to any recv 'table(IN)' in"
4606 .Dl "ipfw add 200 skipto tablearg ip from any to any recv 'table(IN)' in"
4607 .Dl "ipfw add 300 skipto tablearg ip from any to any xmit 'table(OUT)' out"
4609 The following example illustrate usage of flow tables:
4611 .Dl "ipfw table fl create type flow:src-ip,proto,dst-ip,dst-port"
4612 .Dl "ipfw table fl add 2a02:6b8:77::88,tcp,2a02:6b8:77::99,80 11"
4613 .Dl "ipfw table fl add 10.0.0.1,udp,10.0.0.2,53 12"
4615 .Dl "ipfw add 100 allow ip from any to any flow 'table(fl,11)' recv ix0"
4617 To add a set of rules atomically, e.g.\& set 18:
4619 .Dl "ipfw set disable 18"
4620 .Dl "ipfw add NN set 18 ... # repeat as needed"
4621 .Dl "ipfw set enable 18"
4623 To delete a set of rules atomically the command is simply:
4625 .Dl "ipfw delete set 18"
4627 To test a ruleset and disable it and regain control if something goes wrong:
4629 .Dl "ipfw set disable 18"
4630 .Dl "ipfw add NN set 18 ... # repeat as needed"
4631 .Dl "ipfw set enable 18; echo done; sleep 30 && ipfw set disable 18"
4633 Here if everything goes well, you press control-C before the "sleep"
4634 terminates, and your ruleset will be left active.
4635 Otherwise, e.g.\& if
4636 you cannot access your box, the ruleset will be disabled after
4637 the sleep terminates thus restoring the previous situation.
4639 To show rules of the specific set:
4641 .Dl "ipfw set 18 show"
4643 To show rules of the disabled set:
4645 .Dl "ipfw -S set 18 show"
4647 To clear a specific rule counters of the specific set:
4649 .Dl "ipfw set 18 zero NN"
4651 To delete a specific rule of the specific set:
4653 .Dl "ipfw set 18 delete NN"
4654 .Ss NAT, REDIRECT AND LSNAT
4655 First redirect all the traffic to nat instance 123:
4657 .Dl "ipfw add nat 123 all from any to any"
4659 Then to configure nat instance 123 to alias all the outgoing traffic with ip
4660 192.168.0.123, blocking all incoming connections, trying to keep
4661 same ports on both sides, clearing aliasing table on address change
4662 and keeping a log of traffic/link statistics:
4664 .Dl "ipfw nat 123 config ip 192.168.0.123 log deny_in reset same_ports"
4666 Or to change address of instance 123, aliasing table will be cleared (see
4669 .Dl "ipfw nat 123 config ip 10.0.0.1"
4671 To see configuration of nat instance 123:
4673 .Dl "ipfw nat 123 show config"
4675 To show logs of all instances:
4677 .Dl "ipfw nat show log"
4679 To see configurations of all instances:
4681 .Dl "ipfw nat show config"
4683 Or a redirect rule with mixed modes could looks like:
4684 .Bd -literal -offset 2n
4685 ipfw nat 123 config redirect_addr 10.0.0.1 10.0.0.66
4686 redirect_port tcp 192.168.0.1:80 500
4687 redirect_proto udp 192.168.1.43 192.168.1.1
4688 redirect_addr 192.168.0.10,192.168.0.11
4690 redirect_port tcp 192.168.0.1:80,192.168.0.10:22
4694 or it could be split in:
4695 .Bd -literal -offset 2n
4696 ipfw nat 1 config redirect_addr 10.0.0.1 10.0.0.66
4697 ipfw nat 2 config redirect_port tcp 192.168.0.1:80 500
4698 ipfw nat 3 config redirect_proto udp 192.168.1.43 192.168.1.1
4699 ipfw nat 4 config redirect_addr 192.168.0.10,192.168.0.11,192.168.0.12
4701 ipfw nat 5 config redirect_port tcp
4702 192.168.0.1:80,192.168.0.10:22,192.168.0.20:25 500
4705 Sometimes you may want to mix NAT and dynamic rules.
4706 It could be achieved with
4711 Problem is, you need to create dynamic rule before NAT and check it
4712 after NAT actions (or vice versa) to have consistent addresses and ports.
4715 option will trigger activation of existing dynamic state, and action of such
4716 rule will be performed as soon as rule is matched.
4719 rule packet need to be passed to NAT, not allowed as soon is possible.
4721 There is example of set of rules to achieve this.
4722 Bear in mind that this is example only and it is not very useful by itself.
4724 On way out, after all checks place this rules:
4726 .Dl "ipfw add allow record-state defer-action"
4727 .Dl "ipfw add nat 1"
4729 And on way in there should be something like this:
4731 .Dl "ipfw add nat 1"
4732 .Dl "ipfw add check-state"
4734 Please note, that first rule on way out doesn't allow packet and doesn't
4735 execute existing dynamic rules.
4736 All it does, create new dynamic rule with
4738 action, if it is not created yet.
4739 Later, this dynamic rule is used on way in by
4742 .Ss CONFIGURING CODEL, PIE, FQ-CODEL and FQ-PIE AQM
4746 AQM can be configured for
4756 AQM using default configuration for traffic from 192.168.0.0/24 and 1Mbits/s
4759 .Dl "dnctl pipe 1 config bw 1mbits/s codel"
4760 .Dl "ipfw add 100 pipe 1 ip from 192.168.0.0/24 to any"
4766 AQM using different configurations parameters for traffic from
4767 192.168.0.0/24 and 1Mbits/s rate limit, we do:
4769 .Dl "dnctl pipe 1 config bw 1mbits/s"
4770 .Dl "dnctl queue 1 config pipe 1 codel target 8ms interval 160ms ecn"
4771 .Dl "ipfw add 100 queue 1 ip from 192.168.0.0/24 to any"
4777 AQM using default configuration for traffic from 192.168.0.0/24 and 1Mbits/s
4780 .Dl "dnctl pipe 1 config bw 1mbits/s pie"
4781 .Dl "ipfw add 100 pipe 1 ip from 192.168.0.0/24 to any"
4787 AQM using different configuration parameters for traffic from
4788 192.168.0.0/24 and 1Mbits/s rate limit, we do:
4790 .Dl "dnctl pipe 1 config bw 1mbits/s"
4791 .Dl "dnctl queue 1 config pipe 1 pie target 20ms tupdate 30ms ecn"
4792 .Dl "ipfw add 100 queue 1 ip from 192.168.0.0/24 to any"
4797 AQM can be configured for
4803 scheduler using different configurations parameters for traffic from
4804 192.168.0.0/24 and 1Mbits/s rate limit, we do:
4806 .Dl "dnctl pipe 1 config bw 1mbits/s"
4807 .Dl "dnctl sched 1 config pipe 1 type fq_codel"
4808 .Dl "dnctl queue 1 config sched 1"
4809 .Dl "ipfw add 100 queue 1 ip from 192.168.0.0/24 to any"
4813 default configuration for a
4815 such as disable ECN and change the
4819 .Dl "dnctl sched 1 config pipe 1 type fq_codel target 10ms noecn"
4825 scheduler using different configurations parameters for traffic from
4826 192.168.0.0/24 and 1Mbits/s rate limit, we do:
4828 .Dl "dnctl pipe 1 config bw 1mbits/s"
4829 .Dl "dnctl sched 1 config pipe 1 type fq_pie"
4830 .Dl "dnctl queue 1 config sched 1"
4831 .Dl "ipfw add 100 queue 1 ip from 192.168.0.0/24 to any"
4833 The configurations of
4836 can be changed in a similar way as for
4861 utility first appeared in
4866 Stateful extensions were introduced in
4869 was introduced in Summer 2002.
4871 .An Ugen J. S. Antsilevich ,
4872 .An Poul-Henning Kamp ,
4876 .An Rasool Al-Saadi .
4879 API based upon code written by
4883 Dummynet has been introduced by Luigi Rizzo in 1997-1998.
4885 Some early work (1999-2000) on the
4887 traffic shaper supported by Akamba Corp.
4889 The ipfw core (ipfw2) has been completely redesigned and
4890 reimplemented by Luigi Rizzo in summer 2002.
4893 options have been added by various developers over the years.
4896 In-kernel NAT support written by
4897 .An Paolo Pisati Aq Mt piso@FreeBSD.org
4898 as part of a Summer of Code 2005 project.
4902 support has been developed by
4903 .An The Centre for Advanced Internet Architectures (CAIA) Aq http://www.caia.swin.edu.au .
4904 The primary developers and maintainers are David Hayes and Jason But.
4905 For further information visit:
4906 .Aq http://www.caia.swin.edu.au/urp/SONATA
4908 Delay profiles have been developed by Alessandro Cerri and
4909 Luigi Rizzo, supported by the
4910 European Commission within Projects Onelab and Onelab2.
4912 CoDel, PIE, FQ-CoDel and FQ-PIE AQM for Dummynet have been implemented by
4913 .An The Centre for Advanced Internet Architectures (CAIA)
4914 in 2016, supported by The Comcast Innovation Fund.
4915 The primary developer is
4918 The syntax has grown over the years and sometimes it might be confusing.
4919 Unfortunately, backward compatibility prevents cleaning up mistakes
4920 made in the definition of the syntax.
4924 Misconfiguring the firewall can put your computer in an unusable state,
4925 possibly shutting down network services and requiring console access to
4926 regain control of it.
4928 Incoming packet fragments diverted by
4930 are reassembled before delivery to the socket.
4931 The action used on those packet is the one from the
4932 rule which matches the first fragment of the packet.
4934 Packets diverted to userland, and then reinserted by a userland process
4935 may lose various packet attributes.
4936 The packet source interface name
4937 will be preserved if it is shorter than 8 bytes and the userland process
4938 saves and reuses the sockaddr_in
4941 otherwise, it may be lost.
4942 If a packet is reinserted in this manner, later rules may be incorrectly
4943 applied, making the order of
4945 rules in the rule sequence very important.
4947 Dummynet drops all packets with IPv6 link-local addresses.
4953 may not behave as expected.
4954 In particular, incoming SYN packets may
4955 have no uid or gid associated with them since they do not yet belong
4956 to a TCP connection, and the uid/gid associated with a packet may not
4957 be as expected if the associated process calls
4959 or similar system calls.
4961 Rule syntax is subject to the command line environment and some patterns
4962 may need to be escaped with the backslash character
4963 or quoted appropriately.
4965 Due to the architecture of
4967 ipfw nat is not compatible with the TCP segmentation offloading (TSO).
4968 Thus, to reliably nat your network traffic, please disable TSO
4972 ICMP error messages are not implicitly matched by dynamic rules
4973 for the respective conversations.
4974 To avoid failures of network error detection and path MTU discovery,
4975 ICMP error messages may need to be allowed explicitly through static
4982 actions may lead to confusing behaviour if ruleset has mistakes,
4983 and/or interaction with other subsystems (netgraph, dummynet, etc.) is used.
4984 One possible case for this is packet leaving
4986 in subroutine on the input pass, while later on output encountering unpaired
4989 As the call stack is kept intact after input pass, packet will suddenly
4990 return to the rule number used on input pass, not on output one.
4991 Order of processing should be checked carefully to avoid such mistakes.
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