9 .Nd User interface for firewall, traffic shaper, packet scheduler,
12 .Ss FIREWALL CONFIGURATION
21 .Op Ar rule | first-last ...
29 .Brq Cm delete | zero | resetlog
33 .Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ...
37 .Ar number Cm to Ar number
39 .Cm set swap Ar number number
46 .Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive
49 .Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive
53 .Cm table Ar number Cm add Ar addr Ns Oo / Ns Ar masklen Oc Op Ar value
55 .Cm table Ar number Cm delete Ar addr Ns Op / Ns Ar masklen
65 .Ss DUMMYNET CONFIGURATION (TRAFFIC SHAPER AND PACKET SCHEDULER)
67 .Brq Cm pipe | queue | sched
73 .Brq Cm pipe | queue | sched
74 .Brq Cm delete | list | show
97 utility is the user interface for controlling the
101 traffic shaper/packet scheduler, and the
102 in-kernel NAT services.
104 A firewall configuration, or
108 numbered from 1 to 65535.
109 Packets are passed to the firewall
110 from a number of different places in the protocol stack
111 (depending on the source and destination of the packet,
112 it is possible for the firewall to be
113 invoked multiple times on the same packet).
114 The packet passed to the firewall is compared
115 against each of the rules in the
118 (multiple rules with the same number are permitted, in which case
119 they are processed in order of insertion).
120 When a match is found, the action corresponding to the
121 matching rule is performed.
123 Depending on the action and certain system settings, packets
124 can be reinjected into the firewall at some rule after the
125 matching one for further processing.
127 A ruleset always includes a
129 rule (numbered 65535) which cannot be modified or deleted,
130 and matches all packets.
131 The action associated with the
137 depending on how the kernel is configured.
139 If the ruleset includes one or more rules with the
144 the firewall will have a
146 behaviour, i.e., upon a match it will create
148 i.e. rules that match packets with the same 5-tuple
149 (protocol, source and destination addresses and ports)
150 as the packet which caused their creation.
151 Dynamic rules, which have a limited lifetime, are checked
152 at the first occurrence of a
157 rule, and are typically used to open the firewall on-demand to
158 legitimate traffic only.
160 .Sx STATEFUL FIREWALL
163 Sections below for more information on the stateful behaviour of
166 All rules (including dynamic ones) have a few associated counters:
167 a packet count, a byte count, a log count and a timestamp
168 indicating the time of the last match.
169 Counters can be displayed or reset with
173 Each rule belongs to one of 32 different
177 commands to atomically manipulate sets, such as enable,
178 disable, swap sets, move all rules in a set to another
179 one, delete all rules in a set.
180 These can be useful to
181 install temporary configurations, or to test them.
184 for more information on
188 Rules can be added with the
190 command; deleted individually or in groups with the
192 command, and globally (except those in set 31) with the
194 command; displayed, optionally with the content of the
200 Finally, counters can be reset with the
207 The following general options are available when invoking
209 .Bl -tag -width indent
211 Show counter values when listing rules.
214 command implies this option.
216 Only show the action and the comment, not the body of a rule.
220 When entering or showing rules, print them in compact form,
221 i.e., omitting the "ip from any to any" string
222 when this does not carry any additional information.
224 When listing, show dynamic rules in addition to static ones.
228 is specified, also show expired dynamic rules.
230 Do not ask for confirmation for commands that can cause problems
233 If there is no tty associated with the process, this is implied.
235 When listing a table (see the
237 section below for more information on lookup tables), format values
238 as IP addresses. By default, values are shown as integers.
240 Only check syntax of the command strings, without actually passing
243 Try to resolve addresses and service names in output.
245 Be quiet when executing the
255 This is useful when updating rulesets by executing multiple
259 .Ql sh\ /etc/rc.firewall ) ,
260 or by processing a file with many
262 rules across a remote login session.
263 It also stops a table add or delete
264 from failing if the entry already exists or is not present.
266 The reason why this option may be important is that
267 for some of these actions,
269 may print a message; if the action results in blocking the
270 traffic to the remote client,
271 the remote login session will be closed
272 and the rest of the ruleset will not be processed.
273 Access to the console would then be required to recover.
275 When listing rules, show the
277 each rule belongs to.
278 If this flag is not specified, disabled rules will not be
281 When listing pipes, sort according to one of the four
282 counters (total or current packets or bytes).
284 When listing, show last match timestamp converted with ctime().
286 When listing, show last match timestamp as seconds from the epoch.
287 This form can be more convenient for postprocessing by scripts.
290 .Ss LIST OF RULES AND PREPROCESSING
291 To ease configuration, rules can be put into a file which is
294 as shown in the last synopsis line.
298 The file will be read line by line and applied as arguments to the
302 Optionally, a preprocessor can be specified using
306 is to be piped through.
307 Useful preprocessors include
313 does not start with a slash
315 as its first character, the usual
317 name search is performed.
318 Care should be taken with this in environments where not all
319 file systems are mounted (yet) by the time
321 is being run (e.g.\& when they are mounted over NFS).
324 has been specified, any additional arguments are passed on to the preprocessor
326 This allows for flexible configuration files (like conditionalizing
327 them on the local hostname) and the use of macros to centralize
328 frequently required arguments like IP addresses.
330 .Ss TRAFFIC SHAPER CONFIGURATION
336 commands are used to configure the traffic shaper and packet scheduler.
338 .Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
339 Section below for details.
341 If the world and the kernel get out of sync the
343 ABI may break, preventing you from being able to add any rules.
345 adversely effect the booting process.
350 to temporarily disable the firewall to regain access to the network,
351 allowing you to fix the problem.
353 A packet is checked against the active ruleset in multiple places
354 in the protocol stack, under control of several sysctl variables.
355 These places and variables are shown below, and it is important to
356 have this picture in mind in order to design a correct ruleset.
357 .Bd -literal -offset indent
360 +----------->-----------+
362 [ip(6)_input] [ip(6)_output] net.inet(6).ip(6).fw.enable=1
365 [ether_demux] [ether_output_frame] net.link.ether.ipfw=1
367 +-->--[bdg_forward]-->--+ net.link.bridge.ipfw=1
373 times the same packet goes through the firewall can
374 vary between 0 and 4 depending on packet source and
375 destination, and system configuration.
377 Note that as packets flow through the stack, headers can be
378 stripped or added to it, and so they may or may not be available
380 E.g., incoming packets will include the MAC header when
384 but the same packets will have the MAC header stripped off when
391 Also note that each packet is always checked against the complete ruleset,
392 irrespective of the place where the check occurs, or the source of the packet.
393 If a rule contains some match patterns or actions which are not valid
394 for the place of invocation (e.g.\& trying to match a MAC header within
398 the match pattern will not match, but a
400 operator in front of such patterns
404 match on those packets.
405 It is thus the responsibility of
406 the programmer, if necessary, to write a suitable ruleset to
407 differentiate among the possible places.
409 rules can be useful here, as an example:
410 .Bd -literal -offset indent
411 # packets from ether_demux or bdg_forward
412 ipfw add 10 skipto 1000 all from any to any layer2 in
413 # packets from ip_input
414 ipfw add 10 skipto 2000 all from any to any not layer2 in
415 # packets from ip_output
416 ipfw add 10 skipto 3000 all from any to any not layer2 out
417 # packets from ether_output_frame
418 ipfw add 10 skipto 4000 all from any to any layer2 out
421 (yes, at the moment there is no way to differentiate between
422 ether_demux and bdg_forward).
424 In general, each keyword or argument must be provided as
425 a separate command line argument, with no leading or trailing
427 Keywords are case-sensitive, whereas arguments may
428 or may not be case-sensitive depending on their nature
429 (e.g.\& uid's are, hostnames are not).
431 Some arguments (e.g. port or address lists) are comma-separated
433 In this case, spaces after commas ',' are allowed to make
434 the line more readable.
435 You can also put the entire
436 command (including flags) into a single argument.
437 E.g., the following forms are equivalent:
438 .Bd -literal -offset indent
439 ipfw -q add deny src-ip 10.0.0.0/24,127.0.0.1/8
440 ipfw -q add deny src-ip 10.0.0.0/24, 127.0.0.1/8
441 ipfw "-q add deny src-ip 10.0.0.0/24, 127.0.0.1/8"
444 The format of firewall rules is the following:
445 .Bd -ragged -offset indent
448 .Op Cm set Ar set_number
449 .Op Cm prob Ar match_probability
451 .Op Cm log Op Cm logamount Ar number
461 where the body of the rule specifies which information is used
462 for filtering packets, among the following:
464 .Bl -tag -width "Source and dest. addresses and ports" -offset XXX -compact
465 .It Layer-2 header fields
467 .It IPv4 and IPv6 Protocol
469 .It Source and dest. addresses and ports
473 .It Transmit and receive interface
475 .It Misc. IP header fields
476 Version, type of service, datagram length, identification,
477 fragment flag (non-zero IP offset),
480 .It IPv6 Extension headers
481 Fragmentation, Hop-by-Hop options,
482 Routing Headers, Source routing rthdr0, Mobile IPv6 rthdr2, IPSec options.
484 .It Misc. TCP header fields
485 TCP flags (SYN, FIN, ACK, RST, etc.),
486 sequence number, acknowledgment number,
494 When the packet can be associated with a local socket.
496 Whether a packet came from a divert socket (e.g.,
498 .It Fib annotation state
499 Whether a packet has been tagged for using a specific FIB (routing table)
500 in future forwarding decisions.
503 Note that some of the above information, e.g.\& source MAC or IP addresses and
504 TCP/UDP ports, can be easily spoofed, so filtering on those fields
505 alone might not guarantee the desired results.
506 .Bl -tag -width indent
508 Each rule is associated with a
510 in the range 1..65535, with the latter reserved for the
513 Rules are checked sequentially by rule number.
514 Multiple rules can have the same number, in which case they are
515 checked (and listed) according to the order in which they have
517 If a rule is entered without specifying a number, the kernel will
518 assign one in such a way that the rule becomes the last one
522 Automatic rule numbers are assigned by incrementing the last
523 non-default rule number by the value of the sysctl variable
524 .Ar net.inet.ip.fw.autoinc_step
525 which defaults to 100.
526 If this is not possible (e.g.\& because we would go beyond the
527 maximum allowed rule number), the number of the last
528 non-default value is used instead.
529 .It Cm set Ar set_number
530 Each rule is associated with a
533 Sets can be individually disabled and enabled, so this parameter
534 is of fundamental importance for atomic ruleset manipulation.
535 It can be also used to simplify deletion of groups of rules.
536 If a rule is entered without specifying a set number,
539 Set 31 is special in that it cannot be disabled,
540 and rules in set 31 are not deleted by the
542 command (but you can delete them with the
543 .Nm ipfw delete set 31
545 Set 31 is also used for the
548 .It Cm prob Ar match_probability
549 A match is only declared with the specified probability
550 (floating point number between 0 and 1).
551 This can be useful for a number of applications such as
552 random packet drop or
555 to simulate the effect of multiple paths leading to out-of-order
558 Note: this condition is checked before any other condition, including
559 ones such as keep-state or check-state which might have side effects.
560 .It Cm log Op Cm logamount Ar number
561 When a packet matches a rule with the
563 keyword, a message will be
569 The logging only occurs if the sysctl variable
570 .Va net.inet.ip.fw.verbose
572 (which is the default when the kernel is compiled with
573 .Dv IPFIREWALL_VERBOSE )
574 and the number of packets logged so far for that
575 particular rule does not exceed the
580 is specified, the limit is taken from the sysctl variable
581 .Va net.inet.ip.fw.verbose_limit .
582 In both cases, a value of 0 removes the logging limit.
584 Once the limit is reached, logging can be re-enabled by
585 clearing the logging counter or the packet counter for that entry, see the
589 Note: logging is done after all other packet matching conditions
590 have been successfully verified, and before performing the final
591 action (accept, deny, etc.) on the packet.
593 When a packet matches a rule with the
595 keyword, the numeric tag for the given
597 in the range 1..65534 will be attached to the packet.
598 The tag acts as an internal marker (it is not sent out over
599 the wire) that can be used to identify these packets later on.
600 This can be used, for example, to provide trust between interfaces
601 and to start doing policy-based filtering.
602 A packet can have multiple tags at the same time.
603 Tags are "sticky", meaning once a tag is applied to a packet by a
604 matching rule it exists until explicit removal.
605 Tags are kept with the packet everywhere within the kernel, but are
606 lost when packet leaves the kernel, for example, on transmitting
607 packet out to the network or sending packet to a
611 To check for previously applied tags, use the
614 To delete previously applied tag, use the
618 Note: since tags are kept with the packet everywhere in kernelspace,
619 they can be set and unset anywhere in the kernel network subsystem
622 facility), not only by means of the
628 For example, there can be a specialized
630 node doing traffic analyzing and tagging for later inspecting
632 .It Cm untag Ar number
633 When a packet matches a rule with the
635 keyword, the tag with the number
637 is searched among the tags attached to this packet and,
638 if found, removed from it.
639 Other tags bound to packet, if present, are left untouched.
641 When a packet matches a rule with the
643 keyword, the ALTQ identifier for the given
648 Note that this ALTQ tag is only meaningful for packets going "out" of IPFW,
649 and not being rejected or going to divert sockets.
650 Note that if there is insufficient memory at the time the packet is
651 processed, it will not be tagged, so it is wise to make your ALTQ
652 "default" queue policy account for this.
655 rules match a single packet, only the first one adds the ALTQ classification
657 In doing so, traffic may be shaped by using
658 .Cm count Cm altq Ar queue
659 rules for classification early in the ruleset, then later applying
660 the filtering decision.
665 rules may come later and provide the actual filtering decisions in
666 addition to the fallback ALTQ tag.
670 to set up the queues before IPFW will be able to look them up by name,
671 and if the ALTQ disciplines are rearranged, the rules in containing the
672 queue identifiers in the kernel will likely have gone stale and need
674 Stale queue identifiers will probably result in misclassification.
676 All system ALTQ processing can be turned on or off via
681 .Cm disable Ar altq .
683 .Va net.inet.ip.fw.one_pass
684 is irrelevant to ALTQ traffic shaping, as the actual rule action is followed
685 always after adding an ALTQ tag.
688 A rule can be associated with one of the following actions, which
689 will be executed when the packet matches the body of the rule.
690 .Bl -tag -width indent
691 .It Cm allow | accept | pass | permit
692 Allow packets that match rule.
693 The search terminates.
695 Checks the packet against the dynamic ruleset.
696 If a match is found, execute the action associated with
697 the rule which generated this dynamic rule, otherwise
698 move to the next rule.
701 rules do not have a body.
704 rule is found, the dynamic ruleset is checked at the first
710 Update counters for all packets that match rule.
711 The search continues with the next rule.
713 Discard packets that match this rule.
714 The search terminates.
715 .It Cm divert Ar port
716 Divert packets that match this rule to the
720 The search terminates.
721 .It Cm fwd | forward Ar ipaddr | tablearg Ns Op , Ns Ar port
722 Change the next-hop on matching packets to
724 which can be an IP address or a host name.
725 The next hop can also be supplied by the last table
726 looked up for the packet by using the
728 keyword instead of an explicit address.
729 The search terminates if this rule matches.
733 is a local address, then matching packets will be forwarded to
735 (or the port number in the packet if one is not specified in the rule)
736 on the local machine.
740 is not a local address, then the port number
741 (if specified) is ignored, and the packet will be
742 forwarded to the remote address, using the route as found in
743 the local routing table for that IP.
747 rule will not match layer-2 packets (those received
748 on ether_input, ether_output, or bridged).
752 action does not change the contents of the packet at all.
753 In particular, the destination address remains unmodified, so
754 packets forwarded to another system will usually be rejected by that system
755 unless there is a matching rule on that system to capture them.
756 For packets forwarded locally,
757 the local address of the socket will be
758 set to the original destination address of the packet.
761 entry look rather weird but is intended for
762 use with transparent proxy servers.
766 a custom kernel needs to be compiled with the option
767 .Cd "options IPFIREWALL_FORWARD" .
771 (for network address translation, address redirect, etc.):
773 .Sx NETWORK ADDRESS TRANSLATION (NAT)
774 Section for further information.
775 .It Cm pipe Ar pipe_nr
779 (for bandwidth limitation, delay, etc.).
781 .Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
782 Section for further information.
783 The search terminates; however, on exit from the pipe and if
787 .Va net.inet.ip.fw.one_pass
788 is not set, the packet is passed again to the firewall code
789 starting from the next rule.
790 .It Cm queue Ar queue_nr
794 (for bandwidth limitation using WF2Q+).
800 Discard packets that match this rule, and if the
801 packet is a TCP packet, try to send a TCP reset (RST) notice.
802 The search terminates.
804 Discard packets that match this rule, and if the
805 packet is a TCP packet, try to send a TCP reset (RST) notice.
806 The search terminates.
807 .It Cm skipto Ar number | tablearg
808 Skip all subsequent rules numbered less than
810 The search continues with the first rule numbered
813 It is possible to use the
815 keyword with a skipto for a
817 skipto, but care should be used, as no destination caching
818 is possible in this case so the rules are always walked to find it,
822 Send a copy of packets matching this rule to the
826 The search continues with the next rule.
827 .It Cm unreach Ar code
828 Discard packets that match this rule, and try to send an ICMP
829 unreachable notice with code
833 is a number from 0 to 255, or one of these aliases:
834 .Cm net , host , protocol , port ,
835 .Cm needfrag , srcfail , net-unknown , host-unknown ,
836 .Cm isolated , net-prohib , host-prohib , tosnet ,
837 .Cm toshost , filter-prohib , host-precedence
839 .Cm precedence-cutoff .
840 The search terminates.
841 .It Cm unreach6 Ar code
842 Discard packets that match this rule, and try to send an ICMPv6
843 unreachable notice with code
847 is a number from 0, 1, 3 or 4, or one of these aliases:
848 .Cm no-route, admin-prohib, address
851 The search terminates.
852 .It Cm netgraph Ar cookie
853 Divert packet into netgraph with given
855 The search terminates.
856 If packet is later returned from netgraph it is either
857 accepted or continues with the next rule, depending on
858 .Va net.inet.ip.fw.one_pass
860 .It Cm ngtee Ar cookie
861 A copy of packet is diverted into netgraph, original
862 packet continues with the next rule.
865 for more information on
870 .It Cm setfib Ar fibnum | tablearg
871 The packet is tagged so as to use the FIB (routing table)
873 in any subsequent forwarding decisions.
874 Initially this is limited to the values 0 through 15, see
876 Processing continues at the next rule.
877 It is possible to use the
879 keyword with a setfib. If tablearg value is not within compiled FIB range packet fib is set to 0.
881 Queue and reassemble ip fragments.
882 If the packet is not fragmented, counters are updated and processing continues with the next rule.
883 If the packet is the last logical fragment, the packet is reassembled and, if
884 .Va net.inet.ip.fw.one_pass
885 is set to 0, processing continues with the next rule, else packet is allowed to pass and search terminates.
886 If the packet is a fragment in the middle, it is consumed and processing stops immediately.
888 Fragments handling can be tuned via
889 .Va net.inet.ip.maxfragpackets
891 .Va net.inet.ip.maxfragsperpacket
892 which limit, respectively, the maximum number of processable fragments (default: 800) and
893 the maximum number of fragments per packet (default: 16).
895 NOTA BENE: since fragments do not contain port numbers, they should be avoided with the
898 Alternatively, direction-based (like
902 ) and source-based (like
904 ) match patterns can be used to select fragments.
906 Usually a simple rule like:
907 .Bd -literal -offset indent
908 # reassemble incoming fragments
909 ipfw add reass all from any to any in
912 is all you need at the beginning of your ruleset.
915 The body of a rule contains zero or more patterns (such as
916 specific source and destination addresses or ports,
917 protocol options, incoming or outgoing interfaces, etc.)
918 that the packet must match in order to be recognised.
919 In general, the patterns are connected by (implicit)
921 operators -- i.e., all must match in order for the
923 Individual patterns can be prefixed by the
925 operator to reverse the result of the match, as in
927 .Dl "ipfw add 100 allow ip from not 1.2.3.4 to any"
929 Additionally, sets of alternative match patterns
931 can be constructed by putting the patterns in
932 lists enclosed between parentheses ( ) or braces { }, and
937 .Dl "ipfw add 100 allow ip from { x or not y or z } to any"
939 Only one level of parentheses is allowed.
940 Beware that most shells have special meanings for parentheses
941 or braces, so it is advisable to put a backslash \\ in front of them
942 to prevent such interpretations.
944 The body of a rule must in general include a source and destination
948 can be used in various places to specify that the content of
949 a required field is irrelevant.
951 The rule body has the following format:
952 .Bd -ragged -offset indent
953 .Op Ar proto Cm from Ar src Cm to Ar dst
957 The first part (proto from src to dst) is for backward
958 compatibility with earlier versions of
962 any match pattern (including MAC headers, IP protocols,
963 addresses and ports) can be specified in the
967 Rule fields have the following meaning:
968 .Bl -tag -width indent
969 .It Ar proto : protocol | Cm { Ar protocol Cm or ... }
970 .It Ar protocol : Oo Cm not Oc Ar protocol-name | protocol-number
971 An IP protocol specified by number or name
972 (for a complete list see
973 .Pa /etc/protocols ) ,
974 or one of the following keywords:
975 .Bl -tag -width indent
977 Matches IPv4 packets.
979 Matches IPv6 packets.
988 option will be treated as inner protocol.
996 .Cm { Ar protocol Cm or ... }
999 is provided for convenience only but its use is deprecated.
1000 .It Ar src No and Ar dst : Bro Cm addr | Cm { Ar addr Cm or ... } Brc Op Oo Cm not Oc Ar ports
1001 An address (or a list, see below)
1002 optionally followed by
1008 with multiple addresses) is provided for convenience only and
1009 its use is discouraged.
1010 .It Ar addr : Oo Cm not Oc Bro
1011 .Bl -tag -width indent
1012 .Cm any | me | me6 |
1013 .Cm table Ns Pq Ar number Ns Op , Ns Ar value
1014 .Ar | addr-list | addr-set
1017 matches any IP address.
1019 matches any IP address configured on an interface in the system.
1021 matches any IPv6 address configured on an interface in the system.
1022 The address list is evaluated at the time the packet is
1024 .It Cm table Ns Pq Ar number Ns Op , Ns Ar value
1025 Matches any IPv4 address for which an entry exists in the lookup table
1027 If an optional 32-bit unsigned
1029 is also specified, an entry will match only if it has this value.
1032 section below for more information on lookup tables.
1034 .It Ar addr-list : ip-addr Ns Op Ns , Ns Ar addr-list
1036 A host or subnet address specified in one of the following ways:
1037 .Bl -tag -width indent
1038 .It Ar numeric-ip | hostname
1039 Matches a single IPv4 address, specified as dotted-quad or a hostname.
1040 Hostnames are resolved at the time the rule is added to the firewall list.
1041 .It Ar addr Ns / Ns Ar masklen
1042 Matches all addresses with base
1044 (specified as an IP address, a network number, or a hostname)
1048 As an example, 1.2.3.4/25 or 1.2.3.0/25 will match
1049 all IP numbers from 1.2.3.0 to 1.2.3.127 .
1050 .It Ar addr Ns : Ns Ar mask
1051 Matches all addresses with base
1053 (specified as an IP address, a network number, or a hostname)
1056 specified as a dotted quad.
1057 As an example, 1.2.3.4:255.0.255.0 or 1.0.3.0:255.0.255.0 will match
1059 This form is advised only for non-contiguous
1061 It is better to resort to the
1062 .Ar addr Ns / Ns Ar masklen
1063 format for contiguous masks, which is more compact and less
1066 .It Ar addr-set : addr Ns Oo Ns / Ns Ar masklen Oc Ns Cm { Ns Ar list Ns Cm }
1067 .It Ar list : Bro Ar num | num-num Brc Ns Op Ns , Ns Ar list
1068 Matches all addresses with base address
1070 (specified as an IP address, a network number, or a hostname)
1071 and whose last byte is in the list between braces { } .
1072 Note that there must be no spaces between braces and
1073 numbers (spaces after commas are allowed).
1074 Elements of the list can be specified as single entries
1078 field is used to limit the size of the set of addresses,
1079 and can have any value between 24 and 32.
1081 it will be assumed as 24.
1083 This format is particularly useful to handle sparse address sets
1084 within a single rule.
1085 Because the matching occurs using a
1086 bitmask, it takes constant time and dramatically reduces
1087 the complexity of rulesets.
1089 As an example, an address specified as 1.2.3.4/24{128,35-55,89}
1090 or 1.2.3.0/24{128,35-55,89}
1091 will match the following IP addresses:
1093 1.2.3.128, 1.2.3.35 to 1.2.3.55, 1.2.3.89 .
1094 .It Ar addr6-list : ip6-addr Ns Op Ns , Ns Ar addr6-list
1096 A host or subnet specified one of the following ways:
1098 .Bl -tag -width indent
1099 .It Ar numeric-ip | hostname
1100 Matches a single IPv6 address as allowed by
1103 Hostnames are resolved at the time the rule is added to the firewall
1105 .It Ar addr Ns / Ns Ar masklen
1106 Matches all IPv6 addresses with base
1108 (specified as allowed by
1116 No support for sets of IPv6 addresses is provided because IPv6 addresses
1117 are typically random past the initial prefix.
1118 .It Ar ports : Bro Ar port | port Ns \&- Ns Ar port Ns Brc Ns Op , Ns Ar ports
1119 For protocols which support port numbers (such as TCP and UDP), optional
1121 may be specified as one or more ports or port ranges, separated
1122 by commas but no spaces, and an optional
1127 notation specifies a range of ports (including boundaries).
1131 may be used instead of numeric port values.
1132 The length of the port list is limited to 30 ports or ranges,
1133 though one can specify larger ranges by using an
1137 section of the rule.
1141 can be used to escape the dash
1143 character in a service name (from a shell, the backslash must be
1144 typed twice to avoid the shell itself interpreting it as an escape
1147 .Dl "ipfw add count tcp from any ftp\e\e-data-ftp to any"
1149 Fragmented packets which have a non-zero offset (i.e., not the first
1150 fragment) will never match a rule which has one or more port
1154 option for details on matching fragmented packets.
1156 .Ss RULE OPTIONS (MATCH PATTERNS)
1157 Additional match patterns can be used within
1159 Zero or more of these so-called
1161 can be present in a rule, optionally prefixed by the
1163 operand, and possibly grouped into
1166 The following match patterns can be used (listed in alphabetical order):
1167 .Bl -tag -width indent
1168 .It Cm // this is a comment.
1169 Inserts the specified text as a comment in the rule.
1170 Everything following // is considered as a comment and stored in the rule.
1171 You can have comment-only rules, which are listed as having a
1173 action followed by the comment.
1178 Matches only packets generated by a divert socket.
1179 .It Cm diverted-loopback
1180 Matches only packets coming from a divert socket back into the IP stack
1182 .It Cm diverted-output
1183 Matches only packets going from a divert socket back outward to the IP
1184 stack output for delivery.
1185 .It Cm dst-ip Ar ip-address
1186 Matches IPv4 packets whose destination IP is one of the address(es)
1187 specified as argument.
1188 .It Bro Cm dst-ip6 | dst-ipv6 Brc Ar ip6-address
1189 Matches IPv6 packets whose destination IP is one of the address(es)
1190 specified as argument.
1191 .It Cm dst-port Ar ports
1192 Matches IP packets whose destination port is one of the port(s)
1193 specified as argument.
1195 Matches TCP packets that have the RST or ACK bits set.
1196 .It Cm ext6hdr Ar header
1197 Matches IPv6 packets containing the extended header given by
1199 Supported headers are:
1205 any type of Routing Header
1207 Source routing Routing Header Type 0
1209 Mobile IPv6 Routing Header Type 2
1213 IPSec authentication headers
1215 and IPsec encapsulated security payload headers
1217 .It Cm fib Ar fibnum
1218 Matches a packet that has been tagged to use
1219 the given FIB (routing table) number.
1220 .It Cm flow-id Ar labels
1221 Matches IPv6 packets containing any of the flow labels given in
1224 is a comma separated list of numeric flow labels.
1226 Matches packets that are fragments and not the first
1227 fragment of an IP datagram.
1228 Note that these packets will not have
1229 the next protocol header (e.g.\& TCP, UDP) so options that look into
1230 these headers cannot match.
1232 Matches all TCP or UDP packets sent by or received for a
1236 may be specified by name or number.
1237 .It Cm jail Ar prisonID
1238 Matches all TCP or UDP packets sent by or received for the
1239 jail whos prison ID is
1241 .It Cm icmptypes Ar types
1242 Matches ICMP packets whose ICMP type is in the list
1244 The list may be specified as any combination of
1245 individual types (numeric) separated by commas.
1246 .Em Ranges are not allowed .
1247 The supported ICMP types are:
1251 destination unreachable
1259 router advertisement
1263 time-to-live exceeded
1275 address mask request
1277 and address mask reply
1279 .It Cm icmp6types Ar types
1280 Matches ICMP6 packets whose ICMP6 type is in the list of
1282 The list may be specified as any combination of
1283 individual types (numeric) separated by commas.
1284 .Em Ranges are not allowed .
1286 Matches incoming or outgoing packets, respectively.
1290 are mutually exclusive (in fact,
1294 .It Cm ipid Ar id-list
1295 Matches IPv4 packets whose
1297 field has value included in
1299 which is either a single value or a list of values or ranges
1300 specified in the same way as
1302 .It Cm iplen Ar len-list
1303 Matches IP packets whose total length, including header and data, is
1306 which is either a single value or a list of values or ranges
1307 specified in the same way as
1309 .It Cm ipoptions Ar spec
1310 Matches packets whose IPv4 header contains the comma separated list of
1311 options specified in
1313 The supported IP options are:
1316 (strict source route),
1318 (loose source route),
1320 (record packet route) and
1323 The absence of a particular option may be denoted
1326 .It Cm ipprecedence Ar precedence
1327 Matches IPv4 packets whose precedence field is equal to
1330 Matches packets that have IPSEC history associated with them
1331 (i.e., the packet comes encapsulated in IPSEC, the kernel
1332 has IPSEC support and IPSEC_FILTERTUNNEL option, and can correctly
1335 Note that specifying
1337 is different from specifying
1339 as the latter will only look at the specific IP protocol field,
1340 irrespective of IPSEC kernel support and the validity of the IPSEC data.
1342 Further note that this flag is silently ignored in kernels without
1344 It does not affect rule processing when given and the
1345 rules are handled as if with no
1348 .It Cm iptos Ar spec
1349 Matches IPv4 packets whose
1351 field contains the comma separated list of
1352 service types specified in
1354 The supported IP types of service are:
1357 .Pq Dv IPTOS_LOWDELAY ,
1359 .Pq Dv IPTOS_THROUGHPUT ,
1361 .Pq Dv IPTOS_RELIABILITY ,
1363 .Pq Dv IPTOS_MINCOST ,
1365 .Pq Dv IPTOS_ECN_CE .
1366 The absence of a particular type may be denoted
1369 .It Cm ipttl Ar ttl-list
1370 Matches IPv4 packets whose time to live is included in
1372 which is either a single value or a list of values or ranges
1373 specified in the same way as
1375 .It Cm ipversion Ar ver
1376 Matches IP packets whose IP version field is
1379 Upon a match, the firewall will create a dynamic rule, whose
1380 default behaviour is to match bidirectional traffic between
1381 source and destination IP/port using the same protocol.
1382 The rule has a limited lifetime (controlled by a set of
1384 variables), and the lifetime is refreshed every time a matching
1387 Matches only layer2 packets, i.e., those passed to
1389 from ether_demux() and ether_output_frame().
1390 .It Cm limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N
1391 The firewall will only allow
1393 connections with the same
1394 set of parameters as specified in the rule.
1396 of source and destination addresses and ports can be
1399 only IPv4 flows are supported.
1400 .It Cm lookup Bro Cm dst-ip | dst-port | src-ip | src-port | uid | jail Brc Ar N
1401 Search an entry in lookup table
1403 that matches the field specified as argument.
1404 If not found, the match fails.
1405 Otherwise, the match succeeds and
1407 is set to the value extracted from the table.
1409 This option can be useful to quickly dispatch traffic based on
1410 certain packet fields.
1413 section below for more information on lookup tables.
1414 .It Cm { MAC | mac } Ar dst-mac src-mac
1415 Match packets with a given
1419 addresses, specified as the
1421 keyword (matching any MAC address), or six groups of hex digits
1422 separated by colons,
1423 and optionally followed by a mask indicating the significant bits.
1424 The mask may be specified using either of the following methods:
1425 .Bl -enum -width indent
1429 followed by the number of significant bits.
1430 For example, an address with 33 significant bits could be specified as:
1432 .Dl "MAC 10:20:30:40:50:60/33 any"
1437 followed by a bitmask specified as six groups of hex digits separated
1439 For example, an address in which the last 16 bits are significant could
1442 .Dl "MAC 10:20:30:40:50:60&00:00:00:00:ff:ff any"
1444 Note that the ampersand character has a special meaning in many shells
1445 and should generally be escaped.
1448 Note that the order of MAC addresses (destination first,
1450 the same as on the wire, but the opposite of the one used for
1452 .It Cm mac-type Ar mac-type
1453 Matches packets whose Ethernet Type field
1454 corresponds to one of those specified as argument.
1456 is specified in the same way as
1458 (i.e., one or more comma-separated single values or ranges).
1459 You can use symbolic names for known values such as
1460 .Em vlan , ipv4, ipv6 .
1461 Values can be entered as decimal or hexadecimal (if prefixed by 0x),
1462 and they are always printed as hexadecimal (unless the
1464 option is used, in which case symbolic resolution will be attempted).
1465 .It Cm proto Ar protocol
1466 Matches packets with the corresponding IP protocol.
1467 .It Cm recv | xmit | via Brq Ar ifX | Ar if Ns Cm * | Ar ipno | Ar any
1468 Matches packets received, transmitted or going through,
1469 respectively, the interface specified by exact name
1470 .Ns No ( Ar ifX Ns No ),
1472 .Ns No ( Ar if Ns Ar * Ns No ),
1473 by IP address, or through some interface.
1477 keyword causes the interface to always be checked.
1484 then only the receive or transmit interface (respectively)
1486 By specifying both, it is possible to match packets based on
1487 both receive and transmit interface, e.g.:
1489 .Dl "ipfw add deny ip from any to any out recv ed0 xmit ed1"
1493 interface can be tested on either incoming or outgoing packets,
1496 interface can only be tested on outgoing packets.
1501 is invalid) whenever
1505 A packet might not have a receive or transmit interface: packets
1506 originating from the local host have no receive interface,
1507 while packets destined for the local host have no transmit
1510 Matches TCP packets that have the SYN bit set but no ACK bit.
1511 This is the short form of
1512 .Dq Li tcpflags\ syn,!ack .
1513 .It Cm src-ip Ar ip-address
1514 Matches IPv4 packets whose source IP is one of the address(es)
1515 specified as an argument.
1516 .It Cm src-ip6 Ar ip6-address
1517 Matches IPv6 packets whose source IP is one of the address(es)
1518 specified as an argument.
1519 .It Cm src-port Ar ports
1520 Matches IP packets whose source port is one of the port(s)
1521 specified as argument.
1522 .It Cm tagged Ar tag-list
1523 Matches packets whose tags are included in
1525 which is either a single value or a list of values or ranges
1526 specified in the same way as
1528 Tags can be applied to the packet using
1530 rule action parameter (see it's description for details on tags).
1531 .It Cm tcpack Ar ack
1533 Match if the TCP header acknowledgment number field is set to
1535 .It Cm tcpdatalen Ar tcpdatalen-list
1536 Matches TCP packets whose length of TCP data is
1537 .Ar tcpdatalen-list ,
1538 which is either a single value or a list of values or ranges
1539 specified in the same way as
1541 .It Cm tcpflags Ar spec
1543 Match if the TCP header contains the comma separated list of
1546 The supported TCP flags are:
1555 The absence of a particular flag may be denoted
1558 A rule which contains a
1560 specification can never match a fragmented packet which has
1564 option for details on matching fragmented packets.
1565 .It Cm tcpseq Ar seq
1567 Match if the TCP header sequence number field is set to
1569 .It Cm tcpwin Ar win
1571 Match if the TCP header window field is set to
1573 .It Cm tcpoptions Ar spec
1575 Match if the TCP header contains the comma separated list of
1576 options specified in
1578 The supported TCP options are:
1581 (maximum segment size),
1583 (tcp window advertisement),
1587 (rfc1323 timestamp) and
1589 (rfc1644 t/tcp connection count).
1590 The absence of a particular option may be denoted
1594 Match all TCP or UDP packets sent by or received for a
1598 may be matched by name or identification number.
1600 For incoming packets,
1601 a routing table lookup is done on the packet's source address.
1602 If the interface on which the packet entered the system matches the
1603 outgoing interface for the route,
1605 If the interfaces do not match up,
1606 the packet does not match.
1607 All outgoing packets or packets with no incoming interface match.
1609 The name and functionality of the option is intentionally similar to
1610 the Cisco IOS command:
1612 .Dl ip verify unicast reverse-path
1614 This option can be used to make anti-spoofing rules to reject all
1615 packets with source addresses not from this interface.
1619 For incoming packets,
1620 a routing table lookup is done on the packet's source address.
1621 If a route to the source address exists, but not the default route
1622 or a blackhole/reject route, the packet matches.
1623 Otherwise, the packet does not match.
1624 All outgoing packets match.
1626 The name and functionality of the option is intentionally similar to
1627 the Cisco IOS command:
1629 .Dl ip verify unicast source reachable-via any
1631 This option can be used to make anti-spoofing rules to reject all
1632 packets whose source address is unreachable.
1634 For incoming packets, the packet's source address is checked if it
1635 belongs to a directly connected network.
1636 If the network is directly connected, then the interface the packet
1637 came on in is compared to the interface the network is connected to.
1638 When incoming interface and directly connected interface are not the
1639 same, the packet does not match.
1640 Otherwise, the packet does match.
1641 All outgoing packets match.
1643 This option can be used to make anti-spoofing rules to reject all
1644 packets that pretend to be from a directly connected network but do
1645 not come in through that interface.
1646 This option is similar to but more restricted than
1648 because it engages only on packets with source addresses of directly
1649 connected networks instead of all source addresses.
1652 Lookup tables are useful to handle large sparse sets of
1653 addresses or other search keys (e.g. ports, jail IDs).
1654 In the rest of this section we will use the term ``address''
1655 to mean any unsigned value of up to 32-bit.
1656 There may be up to 128 different lookup tables, numbered 0 to 127.
1658 Each entry is represented by an
1659 .Ar addr Ns Op / Ns Ar masklen
1660 and will match all addresses with base
1662 (specified as an IP address, a hostname or an unsigned integer)
1668 is not specified, it defaults to 32.
1669 When looking up an IP address in a table, the most specific
1671 Associated with each entry is a 32-bit unsigned
1673 which can optionally be checked by a rule matching code.
1674 When adding an entry, if
1676 is not specified, it defaults to 0.
1678 An entry can be added to a table
1680 or removed from a table
1682 A table can be examined
1687 Internally, each table is stored in a Radix tree, the same way as
1688 the routing table (see
1691 Lookup tables currently support only ports, jail IDs and IPv4 addresses.
1695 feature provides the ability to use a value, looked up in the table, as
1696 the argument for a rule action, action parameter or rule option.
1697 This can significantly reduce number of rules in some configurations.
1698 If two tables are used in a rule, the result of the second (destination)
1702 argument can be used with the following actions:
1703 .Cm nat, pipe , queue, divert, tee, netgraph, ngtee, fwd, skipto, setfib,
1711 it is possible to supply table entries with values
1712 that are in the form of IP addresses or hostnames.
1715 Section for example usage of tables and the tablearg keyword.
1719 action, the user should be aware that the code will walk the ruleset
1720 up to a rule equal to, or past, the given number, and should therefore try keep the
1721 ruleset compact between the skipto and the target rules.
1723 Each rule belongs to one of 32 different
1726 Set 31 is reserved for the default rule.
1728 By default, rules are put in set 0, unless you use the
1730 attribute when entering a new rule.
1731 Sets can be individually and atomically enabled or disabled,
1732 so this mechanism permits an easy way to store multiple configurations
1733 of the firewall and quickly (and atomically) switch between them.
1734 The command to enable/disable sets is
1735 .Bd -ragged -offset indent
1737 .Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ...
1744 sections can be specified.
1745 Command execution is atomic on all the sets specified in the command.
1746 By default, all sets are enabled.
1748 When you disable a set, its rules behave as if they do not exist
1749 in the firewall configuration, with only one exception:
1750 .Bd -ragged -offset indent
1751 dynamic rules created from a rule before it had been disabled
1752 will still be active until they expire.
1754 dynamic rules you have to explicitly delete the parent rule
1755 which generated them.
1758 The set number of rules can be changed with the command
1759 .Bd -ragged -offset indent
1762 .Brq Cm rule Ar rule-number | old-set
1766 Also, you can atomically swap two rulesets with the command
1767 .Bd -ragged -offset indent
1769 .Cm set swap Ar first-set second-set
1774 Section on some possible uses of sets of rules.
1775 .Sh STATEFUL FIREWALL
1776 Stateful operation is a way for the firewall to dynamically
1777 create rules for specific flows when packets that
1778 match a given pattern are detected.
1779 Support for stateful
1780 operation comes through the
1781 .Cm check-state , keep-state
1787 Dynamic rules are created when a packet matches a
1791 rule, causing the creation of a
1793 rule which will match all and only packets with
1797 .Em src-ip/src-port dst-ip/dst-port
1802 are used here only to denote the initial match addresses, but they
1803 are completely equivalent afterwards).
1804 Dynamic rules will be checked at the first
1805 .Cm check-state, keep-state
1808 occurrence, and the action performed upon a match will be the same
1809 as in the parent rule.
1811 Note that no additional attributes other than protocol and IP addresses
1812 and ports are checked on dynamic rules.
1814 The typical use of dynamic rules is to keep a closed firewall configuration,
1815 but let the first TCP SYN packet from the inside network install a
1816 dynamic rule for the flow so that packets belonging to that session
1817 will be allowed through the firewall:
1819 .Dl "ipfw add check-state"
1820 .Dl "ipfw add allow tcp from my-subnet to any setup keep-state"
1821 .Dl "ipfw add deny tcp from any to any"
1823 A similar approach can be used for UDP, where an UDP packet coming
1824 from the inside will install a dynamic rule to let the response through
1827 .Dl "ipfw add check-state"
1828 .Dl "ipfw add allow udp from my-subnet to any keep-state"
1829 .Dl "ipfw add deny udp from any to any"
1831 Dynamic rules expire after some time, which depends on the status
1832 of the flow and the setting of some
1836 .Sx SYSCTL VARIABLES
1838 For TCP sessions, dynamic rules can be instructed to periodically
1839 send keepalive packets to refresh the state of the rule when it is
1844 for more examples on how to use dynamic rules.
1845 .Sh TRAFFIC SHAPER (DUMMYNET) CONFIGURATION
1847 is also the user interface for the
1849 traffic shaper, packet scheduler and network emulator, a subsystem that
1850 can artificially queue, delay or drop packets
1851 emulating the behaviour of certain network links
1852 or queueing systems.
1855 operates by first using the firewall to select packets
1856 using any match pattern that can be used in
1859 Matching packets are then passed to either of two
1860 different objects, which implement the traffic regulation:
1861 .Bl -hang -offset XXXX
1867 with given bandwidth and propagation delay,
1868 driven by a FIFO scheduler and a single queue with programmable
1869 queue size and packet loss rate.
1870 Packets are appended to the queue as they come out from
1872 and then transferred in FIFO order to the link at the desired rate.
1876 is an abstraction used to implement packet scheduling
1877 using one of several packet scheduling algorithms.
1880 are first grouped into flows according to a mask on the 5-tuple.
1881 Flows are then passed to the scheduler associated to the
1883 and each flow uses scheduling parameters (weight and others)
1884 as configured in the
1887 A scheduler in turn is connected to an emulated link,
1888 and arbitrates the link's bandwidth among backlogged flows according to
1889 weights and to the features of the scheduling algorithm in use.
1894 can be used to set hard limits to the bandwidth that a flow can use, whereas
1896 can be used to determine how different flows share the available bandwidth.
1898 A graphical representation of the binding of queues,
1899 flows, schedulers and links is below.
1900 .Bd -literal -offset indent
1901 (flow_mask|sched_mask) sched_mask
1902 +---------+ weight Wx +-------------+
1903 | |->-[flow]-->--| |-+
1904 -->--| QUEUE x | ... | | |
1905 | |->-[flow]-->--| SCHEDuler N | |
1907 ... | +--[LINK N]-->--
1908 +---------+ weight Wy | | +--[LINK N]-->--
1909 | |->-[flow]-->--| | |
1910 -->--| QUEUE y | ... | | |
1911 | |->-[flow]-->--| | |
1912 +---------+ +-------------+ |
1915 It is important to understand the role of the SCHED_MASK
1916 and FLOW_MASK, which are configured through the commands
1917 .Dl "ipfw sched N config mask SCHED_MASK ..."
1919 .Dl "ipfw queue X config mask FLOW_MASK ..." .
1921 The SCHED_MASK is used to assign flows to one or more
1922 scheduler instances, one for each
1923 value of the packet's 5-fuple after applying SCHED_MASK.
1924 As an example, using ``src-ip 0xffffff00'' creates one instance
1925 for each /24 destination subnet.
1927 The FLOW_MASK, together with the SCHED_MASK, is used to split
1928 packets into flows. As an example, using
1929 ``src-ip 0x000000ff''
1930 together with the previous SCHED_MASK makes a flow for
1931 each individual source address. In turn, flows for each /24
1932 subnet will be sent to the same scheduler instance.
1934 The above diagram holds even for the
1936 case, with the only restriction that a
1938 only supports a SCHED_MASK, and forces the use of a FIFO
1939 scheduler (these are for backward compatibility reasons;
1940 in fact, internally, a
1942 pipe is implemented exactly as above).
1944 There are two modes of
1952 mode tries to emulate a real link: the
1954 scheduler ensures that the packet will not leave the pipe faster than it
1955 would on the real link with a given bandwidth.
1958 mode allows certain packets to bypass the
1960 scheduler (if packet flow does not exceed pipe's bandwidth).
1961 This is the reason why the
1963 mode requires less CPU cycles per packet (on average) and packet latency
1964 can be significantly lower in comparison to a real link with the same
1970 mode can be enabled by setting the
1971 .Va net.inet.ip.dummynet.io_fast
1973 variable to a non-zero value.
1975 .Ss PIPE, QUEUE AND SCHEDULER CONFIGURATION
1981 configuration commands are the following:
1982 .Bd -ragged -offset indent
1983 .Cm pipe Ar number Cm config Ar pipe-configuration
1985 .Cm queue Ar number Cm config Ar queue-configuration
1987 .Cm sched Ar number Cm config Ar sched-configuration
1990 The following parameters can be configured for a pipe:
1992 .Bl -tag -width indent -compact
1993 .It Cm bw Ar bandwidth | device
1994 Bandwidth, measured in
1997 .Brq Cm bit/s | Byte/s .
2000 A value of 0 (default) means unlimited bandwidth.
2001 The unit must immediately follow the number, as in
2003 .Dl "ipfw pipe 1 config bw 300Kbit/s"
2005 If a device name is specified instead of a numeric value, as in
2007 .Dl "ipfw pipe 1 config bw tun0"
2009 then the transmit clock is supplied by the specified device.
2010 At the moment only the
2012 device supports this
2013 functionality, for use in conjunction with
2016 .It Cm delay Ar ms-delay
2017 Propagation delay, measured in milliseconds.
2018 The value is rounded to the next multiple of the clock tick
2019 (typically 10ms, but it is a good practice to run kernels
2021 .Dq "options HZ=1000"
2023 the granularity to 1ms or less).
2024 The default value is 0, meaning no delay.
2026 .It Cm burst Ar size
2027 If the data to be sent exceeds the pipe's bandwidth limit
2028 (and the pipe was previously idle), up to
2030 bytes of data are allowed to bypass the
2032 scheduler, and will be sent as fast as the physical link allows.
2033 Any additional data will be transmitted at the rate specified
2037 The burst size depends on how long the pipe has been idle;
2038 the effective burst size is calculated as follows:
2045 .It Cm profile Ar filename
2046 A file specifying the additional overhead incurred in the transmission
2047 of a packet on the link.
2049 Some link types introduce extra delays in the transmission
2050 of a packet, e.g. because of MAC level framing, contention on
2051 the use of the channel, MAC level retransmissions and so on.
2052 From our point of view, the channel is effectively unavailable
2053 for this extra time, which is constant or variable depending
2054 on the link type. Additionally, packets may be dropped after this
2055 time (e.g. on a wireless link after too many retransmissions).
2056 We can model the additional delay with an empirical curve
2057 that represents its distribution.
2058 .Bd -literal -offset indent
2059 cumulative probability
2069 +-------*------------------->
2072 The empirical curve may have both vertical and horizontal lines.
2073 Vertical lines represent constant delay for a range of
2075 Horizontal lines correspond to a discontinuity in the delay
2076 distribution: the pipe will use the largest delay for a
2079 The file format is the following, with whitespace acting as
2080 a separator and '#' indicating the beginning a comment:
2081 .Bl -tag -width indent
2082 .It Cm name Ar identifier
2083 optional name (listed by "ipfw pipe show")
2084 to identify the delay distribution;
2086 the bandwidth used for the pipe.
2087 If not specified here, it must be present
2088 explicitly as a configuration parameter for the pipe;
2089 .It Cm loss-level Ar L
2090 the probability above which packets are lost.
2091 (0.0 <= L <= 1.0, default 1.0 i.e. no loss);
2093 the number of samples used in the internal
2094 representation of the curve (2..1024; default 100);
2095 .It Cm "delay prob" | "prob delay"
2096 One of these two lines is mandatory and defines
2097 the format of the following lines with data points.
2099 2 or more lines representing points in the curve,
2100 with either delay or probability first, according
2101 to the chosen format.
2102 The unit for delay is milliseconds.
2103 Data points do not need to be sorted.
2104 Also, tne number of actual lines can be different
2105 from the value of the "samples" parameter:
2107 utility will sort and interpolate
2108 the curve as needed.
2111 Example of a profile file:
2112 .Bd -literal -offset indent
2117 0 200 # minimum overhead is 200ms
2123 #configuration file end
2127 The following parameters can be configured for a queue:
2129 .Bl -tag -width indent -compact
2130 .It Cm pipe Ar pipe_nr
2131 Connects a queue to the specified pipe.
2132 Multiple queues (with the same or different weights) can be connected to
2133 the same pipe, which specifies the aggregate rate for the set of queues.
2135 .It Cm weight Ar weight
2136 Specifies the weight to be used for flows matching this queue.
2137 The weight must be in the range 1..100, and defaults to 1.
2140 The following parameters can be configured for a scheduler:
2142 .Bl -tag -width indent -compact
2143 .It Cm type Ar {fifo | wf2qp | rr | qfq}
2144 specifies the scheduling algorithm to use.
2145 .Bl -tag -width indent -compact
2147 is just a FIFO scheduler (which means that all packets
2148 are stored in the same queue as they arrive to the scheduler).
2149 FIFO has O(1) per-packet time complexity, with very low
2150 constants (estimate 60-80ns on a 2Ghz desktop machine)
2151 but gives no service guarantees.
2153 implements the WF2Q+ algorithm, which is a Weighted Fair Queueing
2154 algorithm which permits flows to share bandwidth according to
2155 their weights. Note that weights are not priorities; even a flow
2156 with a minuscule weight will never starve.
2157 WF2Q+ has O(log N) per-packet processing cost, where N is the number
2158 of flows, and is the default algorithm used by previous versions
2161 implements the Deficit Round Robin algorithm, which has O(1) processing
2162 costs (roughly, 100-150ns per packet)
2163 and permits bandwidth allocation according to weights, but
2164 with poor service guarantees.
2166 implements the QFQ algorithm, which is a very fast variant of
2167 WF2Q+, with similar service guarantees and O(1) processing
2168 costs (roughly, 200-250ns per packet).
2172 In addition to the type, all parameters allowed for a pipe can also
2173 be specified for a scheduler.
2175 Finally, the following parameters can be configured for both
2178 .Bl -tag -width XXXX -compact
2180 .It Cm buckets Ar hash-table-size
2181 Specifies the size of the hash table used for storing the
2183 Default value is 64 controlled by the
2186 .Va net.inet.ip.dummynet.hash_size ,
2187 allowed range is 16 to 65536.
2189 .It Cm mask Ar mask-specifier
2190 Packets sent to a given pipe or queue by an
2192 rule can be further classified into multiple flows, each of which is then
2196 A flow identifier is constructed by masking the IP addresses,
2197 ports and protocol types as specified with the
2199 options in the configuration of the pipe or queue.
2200 For each different flow identifier, a new pipe or queue is created
2201 with the same parameters as the original object, and matching packets
2206 are used, each flow will get the same bandwidth as defined by the pipe,
2209 are used, each flow will share the parent's pipe bandwidth evenly
2210 with other flows generated by the same queue (note that other queues
2211 with different weights might be connected to the same pipe).
2213 Available mask specifiers are a combination of one or more of the following:
2215 .Cm dst-ip Ar mask ,
2216 .Cm dst-ip6 Ar mask ,
2217 .Cm src-ip Ar mask ,
2218 .Cm src-ip6 Ar mask ,
2219 .Cm dst-port Ar mask ,
2220 .Cm src-port Ar mask ,
2221 .Cm flow-id Ar mask ,
2226 where the latter means all bits in all fields are significant.
2229 When a packet is dropped by a
2231 queue or pipe, the error
2232 is normally reported to the caller routine in the kernel, in the
2233 same way as it happens when a device queue fills up.
2235 option reports the packet as successfully delivered, which can be
2236 needed for some experimental setups where you want to simulate
2237 loss or congestion at a remote router.
2239 .It Cm plr Ar packet-loss-rate
2242 .Ar packet-loss-rate
2243 is a floating-point number between 0 and 1, with 0 meaning no
2244 loss, 1 meaning 100% loss.
2245 The loss rate is internally represented on 31 bits.
2247 .It Cm queue Brq Ar slots | size Ns Cm Kbytes
2252 Default value is 50 slots, which
2253 is the typical queue size for Ethernet devices.
2254 Note that for slow speed links you should keep the queue
2255 size short or your traffic might be affected by a significant
2257 E.g., 50 max-sized ethernet packets (1500 bytes) mean 600Kbit
2258 or 20s of queue on a 30Kbit/s pipe.
2259 Even worse effects can result if you get packets from an
2260 interface with a much larger MTU, e.g.\& the loopback interface
2261 with its 16KB packets.
2265 .Em net.inet.ip.dummynet.pipe_byte_limit
2267 .Em net.inet.ip.dummynet.pipe_slot_limit
2268 control the maximum lengths that can be specified.
2270 .It Cm red | gred Ar w_q Ns / Ns Ar min_th Ns / Ns Ar max_th Ns / Ns Ar max_p
2271 Make use of the RED (Random Early Detection) queue management algorithm.
2276 point numbers between 0 and 1 (0 not included), while
2280 are integer numbers specifying thresholds for queue management
2281 (thresholds are computed in bytes if the queue has been defined
2282 in bytes, in slots otherwise).
2285 also supports the gentle RED variant (gred).
2288 variables can be used to control the RED behaviour:
2289 .Bl -tag -width indent
2290 .It Va net.inet.ip.dummynet.red_lookup_depth
2291 specifies the accuracy in computing the average queue
2292 when the link is idle (defaults to 256, must be greater than zero)
2293 .It Va net.inet.ip.dummynet.red_avg_pkt_size
2294 specifies the expected average packet size (defaults to 512, must be
2296 .It Va net.inet.ip.dummynet.red_max_pkt_size
2297 specifies the expected maximum packet size, only used when queue
2298 thresholds are in bytes (defaults to 1500, must be greater than zero).
2302 When used with IPv6 data,
2304 currently has several limitations.
2305 Information necessary to route link-local packets to an
2306 interface is not available after processing by
2308 so those packets are dropped in the output path.
2309 Care should be taken to insure that link-local packets are not passed to
2312 Here are some important points to consider when designing your
2316 Remember that you filter both packets going
2320 Most connections need packets going in both directions.
2322 Remember to test very carefully.
2323 It is a good idea to be near the console when doing this.
2324 If you cannot be near the console,
2325 use an auto-recovery script such as the one in
2326 .Pa /usr/share/examples/ipfw/change_rules.sh .
2328 Do not forget the loopback interface.
2333 There are circumstances where fragmented datagrams are unconditionally
2335 TCP packets are dropped if they do not contain at least 20 bytes of
2336 TCP header, UDP packets are dropped if they do not contain a full 8
2337 byte UDP header, and ICMP packets are dropped if they do not contain
2338 4 bytes of ICMP header, enough to specify the ICMP type, code, and
2340 These packets are simply logged as
2342 since there may not be enough good data in the packet to produce a
2343 meaningful log entry.
2345 Another type of packet is unconditionally dropped, a TCP packet with a
2346 fragment offset of one.
2347 This is a valid packet, but it only has one use, to try
2348 to circumvent firewalls.
2349 When logging is enabled, these packets are
2350 reported as being dropped by rule -1.
2352 If you are logged in over a network, loading the
2356 is probably not as straightforward as you would think.
2357 The following command line is recommended:
2358 .Bd -literal -offset indent
2360 ipfw add 32000 allow ip from any to any
2363 Along the same lines, doing an
2364 .Bd -literal -offset indent
2368 in similar surroundings is also a bad idea.
2372 filter list may not be modified if the system security level
2373 is set to 3 or higher
2376 for information on system security levels).
2378 .Sh PACKET DIVERSION
2381 socket bound to the specified port will receive all packets
2382 diverted to that port.
2383 If no socket is bound to the destination port, or if the divert module is
2384 not loaded, or if the kernel was not compiled with divert socket support,
2385 the packets are dropped.
2386 .Sh NETWORK ADDRESS TRANSLATION (NAT)
2389 support in-kernel NAT using the kernel version of
2392 The nat configuration command is the following:
2393 .Bd -ragged -offset indent
2398 .Ar nat-configuration
2402 The following parameters can be configured:
2403 .Bl -tag -width indent
2404 .It Cm ip Ar ip_address
2405 Define an ip address to use for aliasing.
2407 Use ip address of NIC for aliasing, dynamically changing
2408 it if NIC's ip address changes.
2410 Enable logging on this nat instance.
2412 Deny any incoming connection from outside world.
2414 Try to leave the alias port numbers unchanged from
2415 the actual local port numbers.
2417 Traffic on the local network not originating from an
2418 unregistered address spaces will be ignored.
2420 Reset table of the packet aliasing engine on address change.
2422 Reverse the way libalias handles aliasing.
2424 Obey transparent proxy rules only, packet aliasing is not performed.
2427 To let the packet continue after being (de)aliased, set the sysctl variable
2428 .Va net.inet.ip.fw.one_pass
2430 For more information about aliasing modes, refer to
2434 for some examples about nat usage.
2435 .Ss REDIRECT AND LSNAT SUPPORT IN IPFW
2436 Redirect and LSNAT support follow closely the syntax used in
2440 for some examples on how to do redirect and lsnat.
2441 .Ss SCTP NAT SUPPORT
2442 SCTP nat can be configured in a similar manner to TCP through the
2445 The main difference is that
2447 does not do port translation.
2448 Since the local and global side ports will be the same,
2449 there is no need to specify both.
2450 Ports are redirected as follows:
2451 .Bd -ragged -offset indent
2457 .Cm redirect_port sctp
2458 .Ar ip_address [,addr_list] {[port | port-port] [,ports]}
2464 configuration can be done in real-time through the
2467 All may be changed dynamically, though the hash_table size will only
2472 .Sx SYSCTL VARIABLES
2474 .Sh SYSCTL VARIABLES
2477 variables controls the behaviour of the firewall and
2479 .Pq Nm dummynet , bridge , sctp nat .
2480 These are shown below together with their default value
2481 (but always check with the
2483 command what value is actually in use) and meaning:
2484 .Bl -tag -width indent
2485 .It Va net.inet.ip.alias.sctp.accept_global_ootb_addip: No 0
2488 responds to receipt of global OOTB ASCONF-AddIP:
2489 .Bl -tag -width indent
2491 No response (unless a partially matching association exists -
2492 ports and vtags match but global address does not)
2495 will accept and process all OOTB global AddIP messages.
2498 Option 1 should never be selected as this forms a security risk.
2500 establish multiple fake associations by sending AddIP messages.
2501 .It Va net.inet.ip.alias.sctp.chunk_proc_limit: No 5
2502 Defines the maximum number of chunks in an SCTP packet that will be parsed for a
2503 packet that matches an existing association.
2504 This value is enforced to be greater or equal than
2505 .Cm net.inet.ip.alias.sctp.initialising_chunk_proc_limit .
2507 a DoS risk yet setting too low a value may result in important control chunks in
2508 the packet not being located and parsed.
2509 .It Va net.inet.ip.alias.sctp.error_on_ootb: No 1
2512 responds to any Out-of-the-Blue (OOTB) packets with ErrorM packets.
2513 An OOTB packet is a packet that arrives with no existing association
2516 and is not an INIT or ASCONF-AddIP packet:
2517 .Bl -tag -width indent
2519 ErrorM is never sent in response to OOTB packets.
2521 ErrorM is only sent to OOTB packets received on the local side.
2523 ErrorM is sent to the local side and on the global side ONLY if there is a
2524 partial match (ports and vtags match but the source global IP does not).
2525 This value is only useful if the
2527 is tracking global IP addresses.
2529 ErrorM is sent in response to all OOTB packets on both the local and global side
2533 At the moment the default is 0, since the ErrorM packet is not yet
2534 supported by most SCTP stacks.
2535 When it is supported, and if not tracking
2536 global addresses, we recommend setting this value to 1 to allow
2537 multi-homed local hosts to function with the
2539 To track global addresses, we recommend setting this value to 2 to
2540 allow global hosts to be informed when they need to (re)send an
2542 Value 3 should never be chosen (except for debugging) as the
2544 will respond to all OOTB global packets (a DoS risk).
2545 .It Va net.inet.ip.alias.sctp.hashtable_size: No 2003
2546 Size of hash tables used for
2548 lookups (100 < prime_number > 1000001).
2551 size for any future created
2553 instance and therefore must be set prior to creating a
2556 The table sizes may be changed to suit specific needs.
2557 If there will be few
2558 concurrent associations, and memory is scarce, you may make these smaller.
2559 If there will be many thousands (or millions) of concurrent associations, you
2560 should make these larger.
2561 A prime number is best for the table size.
2563 update function will adjust your input value to the next highest prime number.
2564 .It Va net.inet.ip.alias.sctp.holddown_time: No 0
2565 Hold association in table for this many seconds after receiving a
2567 This allows endpoints to correct shutdown gracefully if a
2568 shutdown_complete is lost and retransmissions are required.
2569 .It Va net.inet.ip.alias.sctp.init_timer: No 15
2570 Timeout value while waiting for (INIT-ACK|AddIP-ACK).
2571 This value cannot be 0.
2572 .It Va net.inet.ip.alias.sctp.initialising_chunk_proc_limit: No 2
2573 Defines the maximum number of chunks in an SCTP packet that will be parsed when
2574 no existing association exists that matches that packet.
2576 will only be an INIT or ASCONF-AddIP packet.
2577 A higher value may become a DoS
2578 risk as malformed packets can consume processing resources.
2579 .It Va net.inet.ip.alias.sctp.param_proc_limit: No 25
2580 Defines the maximum number of parameters within a chunk that will be parsed in a
2582 As for other similar sysctl variables, larger values pose a DoS risk.
2583 .It Va net.inet.ip.alias.sctp.log_level: No 0
2584 Level of detail in the system log messages (0 \- minimal, 1 \- event,
2585 2 \- info, 3 \- detail, 4 \- debug, 5 \- max debug). May be a good
2586 option in high loss environments.
2587 .It Va net.inet.ip.alias.sctp.shutdown_time: No 15
2588 Timeout value while waiting for SHUTDOWN-COMPLETE.
2589 This value cannot be 0.
2590 .It Va net.inet.ip.alias.sctp.track_global_addresses: No 0
2591 Enables/disables global IP address tracking within the
2594 upper limit on the number of addresses tracked for each association:
2595 .Bl -tag -width indent
2597 Global tracking is disabled
2599 Enables tracking, the maximum number of addresses tracked for each
2600 association is limited to this value
2603 This variable is fully dynamic, the new value will be adopted for all newly
2604 arriving associations, existing associations are treated as they were previously.
2605 Global tracking will decrease the number of collisions within the
2608 of increased processing load, memory usage, complexity, and possible
2611 problems in complex networks with multiple
2613 We recommend not tracking
2614 global IP addresses, this will still result in a fully functional
2616 .It Va net.inet.ip.alias.sctp.up_timer: No 300
2617 Timeout value to keep an association up with no traffic.
2618 This value cannot be 0.
2619 .It Va net.inet.ip.dummynet.expire : No 1
2620 Lazily delete dynamic pipes/queue once they have no pending traffic.
2621 You can disable this by setting the variable to 0, in which case
2622 the pipes/queues will only be deleted when the threshold is reached.
2623 .It Va net.inet.ip.dummynet.hash_size : No 64
2624 Default size of the hash table used for dynamic pipes/queues.
2625 This value is used when no
2627 option is specified when configuring a pipe/queue.
2628 .It Va net.inet.ip.dummynet.io_fast : No 0
2629 If set to a non-zero value,
2634 operation (see above) is enabled.
2635 .It Va net.inet.ip.dummynet.io_pkt
2636 Number of packets passed to
2638 .It Va net.inet.ip.dummynet.io_pkt_drop
2639 Number of packets dropped by
2641 .It Va net.inet.ip.dummynet.io_pkt_fast
2642 Number of packets bypassed by the
2645 .It Va net.inet.ip.dummynet.max_chain_len : No 16
2646 Target value for the maximum number of pipes/queues in a hash bucket.
2648 .Cm max_chain_len*hash_size
2649 is used to determine the threshold over which empty pipes/queues
2650 will be expired even when
2651 .Cm net.inet.ip.dummynet.expire=0 .
2652 .It Va net.inet.ip.dummynet.red_lookup_depth : No 256
2653 .It Va net.inet.ip.dummynet.red_avg_pkt_size : No 512
2654 .It Va net.inet.ip.dummynet.red_max_pkt_size : No 1500
2655 Parameters used in the computations of the drop probability
2656 for the RED algorithm.
2657 .It Va net.inet.ip.dummynet.pipe_byte_limit : No 1048576
2658 .It Va net.inet.ip.dummynet.pipe_slot_limit : No 100
2659 The maximum queue size that can be specified in bytes or packets.
2660 These limits prevent accidental exhaustion of resources such as mbufs.
2661 If you raise these limits,
2662 you should make sure the system is configured so that sufficient resources
2664 .It Va net.inet.ip.fw.autoinc_step : No 100
2665 Delta between rule numbers when auto-generating them.
2666 The value must be in the range 1..1000.
2667 .It Va net.inet.ip.fw.curr_dyn_buckets : Va net.inet.ip.fw.dyn_buckets
2668 The current number of buckets in the hash table for dynamic rules
2670 .It Va net.inet.ip.fw.debug : No 1
2671 Controls debugging messages produced by
2673 .It Va net.inet.ip.fw.default_rule : No 65535
2674 The default rule number (read-only).
2676 .Nm , the default rule is the last one, so its number
2677 can also serve as the highest number allowed for a rule.
2678 .It Va net.inet.ip.fw.dyn_buckets : No 256
2679 The number of buckets in the hash table for dynamic rules.
2680 Must be a power of 2, up to 65536.
2681 It only takes effect when all dynamic rules have expired, so you
2682 are advised to use a
2684 command to make sure that the hash table is resized.
2685 .It Va net.inet.ip.fw.dyn_count : No 3
2686 Current number of dynamic rules
2688 .It Va net.inet.ip.fw.dyn_keepalive : No 1
2689 Enables generation of keepalive packets for
2691 rules on TCP sessions.
2692 A keepalive is generated to both
2693 sides of the connection every 5 seconds for the last 20
2694 seconds of the lifetime of the rule.
2695 .It Va net.inet.ip.fw.dyn_max : No 8192
2696 Maximum number of dynamic rules.
2697 When you hit this limit, no more dynamic rules can be
2698 installed until old ones expire.
2699 .It Va net.inet.ip.fw.dyn_ack_lifetime : No 300
2700 .It Va net.inet.ip.fw.dyn_syn_lifetime : No 20
2701 .It Va net.inet.ip.fw.dyn_fin_lifetime : No 1
2702 .It Va net.inet.ip.fw.dyn_rst_lifetime : No 1
2703 .It Va net.inet.ip.fw.dyn_udp_lifetime : No 5
2704 .It Va net.inet.ip.fw.dyn_short_lifetime : No 30
2705 These variables control the lifetime, in seconds, of dynamic
2707 Upon the initial SYN exchange the lifetime is kept short,
2708 then increased after both SYN have been seen, then decreased
2709 again during the final FIN exchange or when a RST is received.
2711 .Em dyn_fin_lifetime
2713 .Em dyn_rst_lifetime
2714 must be strictly lower than 5 seconds, the period of
2715 repetition of keepalives.
2716 The firewall enforces that.
2717 .It Va net.inet.ip.fw.enable : No 1
2718 Enables the firewall.
2719 Setting this variable to 0 lets you run your machine without
2720 firewall even if compiled in.
2721 .It Va net.inet6.ip6.fw.enable : No 1
2722 provides the same functionality as above for the IPv6 case.
2723 .It Va net.inet.ip.fw.one_pass : No 1
2724 When set, the packet exiting from the
2728 node is not passed though the firewall again.
2729 Otherwise, after an action, the packet is
2730 reinjected into the firewall at the next rule.
2731 .It Va net.inet.ip.fw.tables_max : No 128
2732 Maximum number of tables (read-only).
2733 .It Va net.inet.ip.fw.verbose : No 1
2734 Enables verbose messages.
2735 .It Va net.inet.ip.fw.verbose_limit : No 0
2736 Limits the number of messages produced by a verbose firewall.
2737 .It Va net.inet6.ip6.fw.deny_unknown_exthdrs : No 1
2738 If enabled packets with unknown IPv6 Extension Headers will be denied.
2739 .It Va net.link.ether.ipfw : No 0
2740 Controls whether layer-2 packets are passed to
2743 .It Va net.link.bridge.ipfw : No 0
2744 Controls whether bridged packets are passed to
2750 There are far too many possible uses of
2752 so this Section will only give a small set of examples.
2754 .Ss BASIC PACKET FILTERING
2755 This command adds an entry which denies all tcp packets from
2756 .Em cracker.evil.org
2757 to the telnet port of
2759 from being forwarded by the host:
2761 .Dl "ipfw add deny tcp from cracker.evil.org to wolf.tambov.su telnet"
2763 This one disallows any connection from the entire cracker's
2766 .Dl "ipfw add deny ip from 123.45.67.0/24 to my.host.org"
2768 A first and efficient way to limit access (not using dynamic rules)
2769 is the use of the following rules:
2771 .Dl "ipfw add allow tcp from any to any established"
2772 .Dl "ipfw add allow tcp from net1 portlist1 to net2 portlist2 setup"
2773 .Dl "ipfw add allow tcp from net3 portlist3 to net3 portlist3 setup"
2775 .Dl "ipfw add deny tcp from any to any"
2777 The first rule will be a quick match for normal TCP packets,
2778 but it will not match the initial SYN packet, which will be
2781 rules only for selected source/destination pairs.
2782 All other SYN packets will be rejected by the final
2786 If you administer one or more subnets, you can take advantage
2787 of the address sets and or-blocks and write extremely
2788 compact rulesets which selectively enable services to blocks
2789 of clients, as below:
2791 .Dl "goodguys=\*q{ 10.1.2.0/24{20,35,66,18} or 10.2.3.0/28{6,3,11} }\*q"
2792 .Dl "badguys=\*q10.1.2.0/24{8,38,60}\*q"
2794 .Dl "ipfw add allow ip from ${goodguys} to any"
2795 .Dl "ipfw add deny ip from ${badguys} to any"
2796 .Dl "... normal policies ..."
2800 option could be used to do automated anti-spoofing by adding the
2801 following to the top of a ruleset:
2803 .Dl "ipfw add deny ip from any to any not verrevpath in"
2805 This rule drops all incoming packets that appear to be coming to the
2806 system on the wrong interface.
2807 For example, a packet with a source
2808 address belonging to a host on a protected internal network would be
2809 dropped if it tried to enter the system from an external interface.
2813 option could be used to do similar but more restricted anti-spoofing
2814 by adding the following to the top of a ruleset:
2816 .Dl "ipfw add deny ip from any to any not antispoof in"
2818 This rule drops all incoming packets that appear to be coming from another
2819 directly connected system but on the wrong interface.
2820 For example, a packet with a source address of
2821 .Li 192.168.0.0/24 ,
2828 In order to protect a site from flood attacks involving fake
2829 TCP packets, it is safer to use dynamic rules:
2831 .Dl "ipfw add check-state"
2832 .Dl "ipfw add deny tcp from any to any established"
2833 .Dl "ipfw add allow tcp from my-net to any setup keep-state"
2835 This will let the firewall install dynamic rules only for
2836 those connection which start with a regular SYN packet coming
2837 from the inside of our network.
2838 Dynamic rules are checked when encountering the first
2845 rule should usually be placed near the beginning of the
2846 ruleset to minimize the amount of work scanning the ruleset.
2847 Your mileage may vary.
2849 To limit the number of connections a user can open
2850 you can use the following type of rules:
2852 .Dl "ipfw add allow tcp from my-net/24 to any setup limit src-addr 10"
2853 .Dl "ipfw add allow tcp from any to me setup limit src-addr 4"
2855 The former (assuming it runs on a gateway) will allow each host
2856 on a /24 network to open at most 10 TCP connections.
2857 The latter can be placed on a server to make sure that a single
2858 client does not use more than 4 simultaneous connections.
2861 stateful rules can be subject to denial-of-service attacks
2862 by a SYN-flood which opens a huge number of dynamic rules.
2863 The effects of such attacks can be partially limited by
2866 variables which control the operation of the firewall.
2868 Here is a good usage of the
2870 command to see accounting records and timestamp information:
2874 or in short form without timestamps:
2878 which is equivalent to:
2882 Next rule diverts all incoming packets from 192.168.2.0/24
2883 to divert port 5000:
2885 .Dl ipfw divert 5000 ip from 192.168.2.0/24 to any in
2888 The following rules show some of the applications of
2892 for simulations and the like.
2894 This rule drops random incoming packets with a probability
2897 .Dl "ipfw add prob 0.05 deny ip from any to any in"
2899 A similar effect can be achieved making use of
2903 .Dl "ipfw add pipe 10 ip from any to any"
2904 .Dl "ipfw pipe 10 config plr 0.05"
2906 We can use pipes to artificially limit bandwidth, e.g.\& on a
2907 machine acting as a router, if we want to limit traffic from
2908 local clients on 192.168.2.0/24 we do:
2910 .Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out"
2911 .Dl "ipfw pipe 1 config bw 300Kbit/s queue 50KBytes"
2913 note that we use the
2915 modifier so that the rule is not used twice.
2916 Remember in fact that
2918 rules are checked both on incoming and outgoing packets.
2920 Should we want to simulate a bidirectional link with bandwidth
2921 limitations, the correct way is the following:
2923 .Dl "ipfw add pipe 1 ip from any to any out"
2924 .Dl "ipfw add pipe 2 ip from any to any in"
2925 .Dl "ipfw pipe 1 config bw 64Kbit/s queue 10Kbytes"
2926 .Dl "ipfw pipe 2 config bw 64Kbit/s queue 10Kbytes"
2928 The above can be very useful, e.g.\& if you want to see how
2929 your fancy Web page will look for a residential user who
2930 is connected only through a slow link.
2931 You should not use only one pipe for both directions, unless
2932 you want to simulate a half-duplex medium (e.g.\& AppleTalk,
2934 It is not necessary that both pipes have the same configuration,
2935 so we can also simulate asymmetric links.
2937 Should we want to verify network performance with the RED queue
2938 management algorithm:
2940 .Dl "ipfw add pipe 1 ip from any to any"
2941 .Dl "ipfw pipe 1 config bw 500Kbit/s queue 100 red 0.002/30/80/0.1"
2943 Another typical application of the traffic shaper is to
2944 introduce some delay in the communication.
2945 This can significantly affect applications which do a lot of Remote
2946 Procedure Calls, and where the round-trip-time of the
2947 connection often becomes a limiting factor much more than
2950 .Dl "ipfw add pipe 1 ip from any to any out"
2951 .Dl "ipfw add pipe 2 ip from any to any in"
2952 .Dl "ipfw pipe 1 config delay 250ms bw 1Mbit/s"
2953 .Dl "ipfw pipe 2 config delay 250ms bw 1Mbit/s"
2955 Per-flow queueing can be useful for a variety of purposes.
2956 A very simple one is counting traffic:
2958 .Dl "ipfw add pipe 1 tcp from any to any"
2959 .Dl "ipfw add pipe 1 udp from any to any"
2960 .Dl "ipfw add pipe 1 ip from any to any"
2961 .Dl "ipfw pipe 1 config mask all"
2963 The above set of rules will create queues (and collect
2964 statistics) for all traffic.
2965 Because the pipes have no limitations, the only effect is
2966 collecting statistics.
2967 Note that we need 3 rules, not just the last one, because
2970 tries to match IP packets it will not consider ports, so we
2971 would not see connections on separate ports as different
2974 A more sophisticated example is limiting the outbound traffic
2975 on a net with per-host limits, rather than per-network limits:
2977 .Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out"
2978 .Dl "ipfw add pipe 2 ip from any to 192.168.2.0/24 in"
2979 .Dl "ipfw pipe 1 config mask src-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
2980 .Dl "ipfw pipe 2 config mask dst-ip 0x000000ff bw 200Kbit/s queue 20Kbytes"
2982 In the following example, we need to create several traffic bandwidth
2983 classes and we need different hosts/networks to fall into different classes.
2984 We create one pipe for each class and configure them accordingly.
2985 Then we create a single table and fill it with IP subnets and addresses.
2986 For each subnet/host we set the argument equal to the number of the pipe
2988 Then we classify traffic using a single rule:
2990 .Dl "ipfw pipe 1 config bw 1000Kbyte/s"
2991 .Dl "ipfw pipe 4 config bw 4000Kbyte/s"
2993 .Dl "ipfw table 1 add 192.168.2.0/24 1"
2994 .Dl "ipfw table 1 add 192.168.0.0/27 4"
2995 .Dl "ipfw table 1 add 192.168.0.2 1"
2997 .Dl "ipfw add pipe tablearg ip from table(1) to any"
3001 action, the table entries may include hostnames and IP addresses.
3003 .Dl "ipfw table 1 add 192.168.2.0/24 10.23.2.1"
3004 .Dl "ipfw table 1 add 192.168.0.0/27 router1.dmz"
3006 .Dl "ipfw add 100 fwd tablearg ip from any to table(1)"
3008 To add a set of rules atomically, e.g.\& set 18:
3010 .Dl "ipfw set disable 18"
3011 .Dl "ipfw add NN set 18 ... # repeat as needed"
3012 .Dl "ipfw set enable 18"
3014 To delete a set of rules atomically the command is simply:
3016 .Dl "ipfw delete set 18"
3018 To test a ruleset and disable it and regain control if something goes wrong:
3020 .Dl "ipfw set disable 18"
3021 .Dl "ipfw add NN set 18 ... # repeat as needed"
3022 .Dl "ipfw set enable 18; echo done; sleep 30 && ipfw set disable 18"
3024 Here if everything goes well, you press control-C before the "sleep"
3025 terminates, and your ruleset will be left active.
3026 Otherwise, e.g.\& if
3027 you cannot access your box, the ruleset will be disabled after
3028 the sleep terminates thus restoring the previous situation.
3030 To show rules of the specific set:
3032 .Dl "ipfw set 18 show"
3034 To show rules of the disabled set:
3036 .Dl "ipfw -S set 18 show"
3038 To clear a specific rule counters of the specific set:
3040 .Dl "ipfw set 18 zero NN"
3042 To delete a specific rule of the specific set:
3044 .Dl "ipfw set 18 delete NN"
3045 .Ss NAT, REDIRECT AND LSNAT
3046 First redirect all the traffic to nat instance 123:
3048 .Dl "ipfw add nat 123 all from any to any"
3050 Then to configure nat instance 123 to alias all the outgoing traffic with ip
3051 192.168.0.123, blocking all incoming connections, trying to keep
3052 same ports on both sides, clearing aliasing table on address change
3053 and keeping a log of traffic/link statistics:
3055 .Dl "ipfw nat 123 config ip 192.168.0.123 log deny_in reset same_ports"
3057 Or to change address of instance 123, aliasing table will be cleared (see
3060 .Dl "ipfw nat 123 config ip 10.0.0.1"
3062 To see configuration of nat instance 123:
3064 .Dl "ipfw nat 123 show config"
3066 To show logs of all the instances in range 111-999:
3068 .Dl "ipfw nat 111-999 show"
3070 To see configurations of all instances:
3072 .Dl "ipfw nat show config"
3074 Or a redirect rule with mixed modes could looks like:
3076 .Dl "ipfw nat 123 config redirect_addr 10.0.0.1 10.0.0.66"
3077 .Dl " redirect_port tcp 192.168.0.1:80 500"
3078 .Dl " redirect_proto udp 192.168.1.43 192.168.1.1"
3079 .Dl " redirect_addr 192.168.0.10,192.168.0.11"
3080 .Dl " 10.0.0.100 # LSNAT"
3081 .Dl " redirect_port tcp 192.168.0.1:80,192.168.0.10:22"
3084 or it could be split in:
3086 .Dl "ipfw nat 1 config redirect_addr 10.0.0.1 10.0.0.66"
3087 .Dl "ipfw nat 2 config redirect_port tcp 192.168.0.1:80 500"
3088 .Dl "ipfw nat 3 config redirect_proto udp 192.168.1.43 192.168.1.1"
3089 .Dl "ipfw nat 4 config redirect_addr 192.168.0.10,192.168.0.11,192.168.0.12"
3091 .Dl "ipfw nat 5 config redirect_port tcp"
3092 .Dl " 192.168.0.1:80,192.168.0.10:22,192.168.0.20:25 500"
3114 utility first appeared in
3119 Stateful extensions were introduced in
3122 was introduced in Summer 2002.
3124 .An Ugen J. S. Antsilevich ,
3125 .An Poul-Henning Kamp ,
3131 API based upon code written by
3135 Dummynet has been introduced by Luigi Rizzo in 1997-1998.
3137 Some early work (1999-2000) on the
3139 traffic shaper supported by Akamba Corp.
3141 The ipfw core (ipfw2) has been completely redesigned and
3142 reimplemented by Luigi Rizzo in summer 2002. Further
3144 options have been added by various developer over the years.
3147 In-kernel NAT support written by
3148 .An Paolo Pisati Aq piso@FreeBSD.org
3149 as part of a Summer of Code 2005 project.
3153 support has been developed by
3154 .An The Centre for Advanced Internet Architectures (CAIA) Aq http://www.caia.swin.edu.au .
3155 The primary developers and maintainers are David Hayes and Jason But.
3156 For further information visit:
3157 .Aq http://www.caia.swin.edu.au/urp/SONATA
3159 Delay profiles have been developed by Alessandro Cerri and
3160 Luigi Rizzo, supported by the
3161 European Commission within Projects Onelab and Onelab2.
3163 The syntax has grown over the years and sometimes it might be confusing.
3164 Unfortunately, backward compatibility prevents cleaning up mistakes
3165 made in the definition of the syntax.
3169 Misconfiguring the firewall can put your computer in an unusable state,
3170 possibly shutting down network services and requiring console access to
3171 regain control of it.
3173 Incoming packet fragments diverted by
3175 are reassembled before delivery to the socket.
3176 The action used on those packet is the one from the
3177 rule which matches the first fragment of the packet.
3179 Packets diverted to userland, and then reinserted by a userland process
3180 may lose various packet attributes.
3181 The packet source interface name
3182 will be preserved if it is shorter than 8 bytes and the userland process
3183 saves and reuses the sockaddr_in
3186 otherwise, it may be lost.
3187 If a packet is reinserted in this manner, later rules may be incorrectly
3188 applied, making the order of
3190 rules in the rule sequence very important.
3192 Dummynet drops all packets with IPv6 link-local addresses.
3198 may not behave as expected.
3199 In particular, incoming SYN packets may
3200 have no uid or gid associated with them since they do not yet belong
3201 to a TCP connection, and the uid/gid associated with a packet may not
3202 be as expected if the associated process calls
3204 or similar system calls.
3206 Rule syntax is subject to the command line environment and some patterns
3207 may need to be escaped with the backslash character
3208 or quoted appropriately.
3210 Due to the architecture of
3212 ipfw nat is not compatible with the TCP segmentation offloading (TSO).
3213 Thus, to reliably nat your network traffic, please disable TSO
3217 ICMP error messages are not implicitly matched by dynamic rules
3218 for the respective conversations.
3219 To avoid failures of network error detection and path MTU discovery,
3220 ICMP error messages may need to be allowed explicitly through static
projects / FreeBSD / stable / 8.git / blob