1.\" 2.\" $FreeBSD$ 3.\" 4.Dd March 19, 2018 5.Dt IPFW 8 6.Os 7.Sh NAME 8.Nm ipfw 9.Nd User interface for firewall, traffic shaper, packet scheduler, 10in-kernel NAT. 11.Sh SYNOPSIS 12.Ss FIREWALL CONFIGURATION 13.Nm 14.Op Fl cq 15.Cm add 16.Ar rule 17.Nm 18.Op Fl acdefnNStT 19.Op Cm set Ar N 20.Brq Cm list | show 21.Op Ar rule | first-last ... 22.Nm 23.Op Fl f | q 24.Op Cm set Ar N 25.Cm flush 26.Nm 27.Op Fl q 28.Op Cm set Ar N 29.Brq Cm delete | zero | resetlog 30.Op Ar number ... 31.Pp 32.Nm 33.Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ... 34.Nm 35.Cm set move 36.Op Cm rule 37.Ar number Cm to Ar number 38.Nm 39.Cm set swap Ar number number 40.Nm 41.Cm set show 42.Ss SYSCTL SHORTCUTS 43.Nm 44.Cm enable 45.Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive 46.Nm 47.Cm disable 48.Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive 49.Ss LOOKUP TABLES 50.Nm 51.Oo Cm set Ar N Oc Cm table Ar name Cm create Ar create-options 52.Nm 53.Oo Cm set Ar N Oc Cm table 54.Brq Ar name | all 55.Cm destroy 56.Nm 57.Oo Cm set Ar N Oc Cm table Ar name Cm modify Ar modify-options 58.Nm 59.Oo Cm set Ar N Oc Cm table Ar name Cm swap Ar name 60.Nm 61.Oo Cm set Ar N Oc Cm table Ar name Cm add Ar table-key Op Ar value 62.Nm 63.Oo Cm set Ar N Oc Cm table Ar name Cm add Op Ar table-key Ar value ... 64.Nm 65.Oo Cm set Ar N Oc Cm table Ar name Cm atomic add Op Ar table-key Ar value ... 66.Nm 67.Oo Cm set Ar N Oc Cm table Ar name Cm delete Op Ar table-key ... 68.Nm 69.Oo Cm set Ar N Oc Cm table Ar name Cm lookup Ar addr 70.Nm 71.Oo Cm set Ar N Oc Cm table Ar name Cm lock 72.Nm 73.Oo Cm set Ar N Oc Cm table Ar name Cm unlock 74.Nm 75.Oo Cm set Ar N Oc Cm table 76.Brq Ar name | all 77.Cm list 78.Nm 79.Oo Cm set Ar N Oc Cm table 80.Brq Ar name | all 81.Cm info 82.Nm 83.Oo Cm set Ar N Oc Cm table 84.Brq Ar name | all 85.Cm detail 86.Nm 87.Oo Cm set Ar N Oc Cm table 88.Brq Ar name | all 89.Cm flush 90.Ss DUMMYNET CONFIGURATION (TRAFFIC SHAPER AND PACKET SCHEDULER) 91.Nm 92.Brq Cm pipe | queue | sched 93.Ar number 94.Cm config 95.Ar config-options 96.Nm 97.Op Fl s Op Ar field 98.Brq Cm pipe | queue | sched 99.Brq Cm delete | list | show 100.Op Ar number ... 101.Ss IN-KERNEL NAT 102.Nm 103.Op Fl q 104.Cm nat 105.Ar number 106.Cm config 107.Ar config-options 108.Pp 109.Nm 110.Op Fl cfnNqS 111.Oo 112.Fl p Ar preproc 113.Oo 114.Ar preproc-flags 115.Oc 116.Oc 117.Ar pathname 118.Ss STATEFUL IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION 119.Nm 120.Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm create Ar create-options 121.Nm 122.Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm config Ar config-options 123.Nm 124.Oo Cm set Ar N Oc Cm nat64lsn 125.Brq Ar name | all 126.Brq Cm list | show 127.Op Cm states 128.Nm 129.Oo Cm set Ar N Oc Cm nat64lsn 130.Brq Ar name | all 131.Cm destroy 132.Nm 133.Oo Cm set Ar N Oc Cm nat64lsn Ar name Cm stats Op Cm reset 134.Ss STATELESS IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION 135.Nm 136.Oo Cm set Ar N Oc Cm nat64stl Ar name Cm create Ar create-options 137.Nm 138.Oo Cm set Ar N Oc Cm nat64stl Ar name Cm config Ar config-options 139.Nm 140.Oo Cm set Ar N Oc Cm nat64stl 141.Brq Ar name | all 142.Brq Cm list | show 143.Nm 144.Oo Cm set Ar N Oc Cm nat64stl 145.Brq Ar name | all 146.Cm destroy 147.Nm 148.Oo Cm set Ar N Oc Cm nat64stl Ar name Cm stats Op Cm reset 149.Ss IPv6-to-IPv6 NETWORK PREFIX TRANSLATION 150.Nm 151.Oo Cm set Ar N Oc Cm nptv6 Ar name Cm create Ar create-options 152.Nm 153.Oo Cm set Ar N Oc Cm nptv6 154.Brq Ar name | all 155.Brq Cm list | show 156.Nm 157.Oo Cm set Ar N Oc Cm nptv6 158.Brq Ar name | all 159.Cm destroy 160.Nm 161.Oo Cm set Ar N Oc Cm nptv6 Ar name Cm stats Op Cm reset 162.Ss INTERNAL DIAGNOSTICS 163.Nm 164.Cm internal iflist 165.Nm 166.Cm internal talist 167.Nm 168.Cm internal vlist 169.Sh DESCRIPTION 170The 171.Nm 172utility is the user interface for controlling the 173.Xr ipfw 4 174firewall, the 175.Xr dummynet 4 176traffic shaper/packet scheduler, and the 177in-kernel NAT services. 178.Pp 179A firewall configuration, or 180.Em ruleset , 181is made of a list of 182.Em rules 183numbered from 1 to 65535. 184Packets are passed to the firewall 185from a number of different places in the protocol stack 186(depending on the source and destination of the packet, 187it is possible for the firewall to be 188invoked multiple times on the same packet). 189The packet passed to the firewall is compared 190against each of the rules in the 191.Em ruleset , 192in rule-number order 193(multiple rules with the same number are permitted, in which case 194they are processed in order of insertion). 195When a match is found, the action corresponding to the 196matching rule is performed. 197.Pp 198Depending on the action and certain system settings, packets 199can be reinjected into the firewall at some rule after the 200matching one for further processing. 201.Pp 202A ruleset always includes a 203.Em default 204rule (numbered 65535) which cannot be modified or deleted, 205and matches all packets. 206The action associated with the 207.Em default 208rule can be either 209.Cm deny 210or 211.Cm allow 212depending on how the kernel is configured. 213.Pp 214If the ruleset includes one or more rules with the 215.Cm keep-state 216or 217.Cm limit 218option, 219the firewall will have a 220.Em stateful 221behaviour, i.e., upon a match it will create 222.Em dynamic rules , 223i.e., rules that match packets with the same 5-tuple 224(protocol, source and destination addresses and ports) 225as the packet which caused their creation. 226Dynamic rules, which have a limited lifetime, are checked 227at the first occurrence of a 228.Cm check-state , 229.Cm keep-state 230or 231.Cm limit 232rule, and are typically used to open the firewall on-demand to 233legitimate traffic only. 234See the 235.Sx STATEFUL FIREWALL 236and 237.Sx EXAMPLES 238Sections below for more information on the stateful behaviour of 239.Nm . 240.Pp 241All rules (including dynamic ones) have a few associated counters: 242a packet count, a byte count, a log count and a timestamp 243indicating the time of the last match. 244Counters can be displayed or reset with 245.Nm 246commands. 247.Pp 248Each rule belongs to one of 32 different 249.Em sets 250, and there are 251.Nm 252commands to atomically manipulate sets, such as enable, 253disable, swap sets, move all rules in a set to another 254one, delete all rules in a set. 255These can be useful to 256install temporary configurations, or to test them. 257See Section 258.Sx SETS OF RULES 259for more information on 260.Em sets . 261.Pp 262Rules can be added with the 263.Cm add 264command; deleted individually or in groups with the 265.Cm delete 266command, and globally (except those in set 31) with the 267.Cm flush 268command; displayed, optionally with the content of the 269counters, using the 270.Cm show 271and 272.Cm list 273commands. 274Finally, counters can be reset with the 275.Cm zero 276and 277.Cm resetlog 278commands. 279.Pp 280.Ss COMMAND OPTIONS 281The following general options are available when invoking 282.Nm : 283.Bl -tag -width indent 284.It Fl a 285Show counter values when listing rules. 286The 287.Cm show 288command implies this option. 289.It Fl b 290Only show the action and the comment, not the body of a rule. 291Implies 292.Fl c . 293.It Fl c 294When entering or showing rules, print them in compact form, 295i.e., omitting the "ip from any to any" string 296when this does not carry any additional information. 297.It Fl d 298When listing, show dynamic rules in addition to static ones. 299.It Fl e 300When listing and 301.Fl d 302is specified, also show expired dynamic rules. 303.It Fl f 304Do not ask for confirmation for commands that can cause problems 305if misused, i.e., 306.Cm flush . 307If there is no tty associated with the process, this is implied. 308.It Fl i 309When listing a table (see the 310.Sx LOOKUP TABLES 311section below for more information on lookup tables), format values 312as IP addresses. 313By default, values are shown as integers. 314.It Fl n 315Only check syntax of the command strings, without actually passing 316them to the kernel. 317.It Fl N 318Try to resolve addresses and service names in output. 319.It Fl q 320Be quiet when executing the 321.Cm add , 322.Cm nat , 323.Cm zero , 324.Cm resetlog 325or 326.Cm flush 327commands; 328(implies 329.Fl f ) . 330This is useful when updating rulesets by executing multiple 331.Nm 332commands in a script 333(e.g., 334.Ql sh\ /etc/rc.firewall ) , 335or by processing a file with many 336.Nm 337rules across a remote login session. 338It also stops a table add or delete 339from failing if the entry already exists or is not present. 340.Pp 341The reason why this option may be important is that 342for some of these actions, 343.Nm 344may print a message; if the action results in blocking the 345traffic to the remote client, 346the remote login session will be closed 347and the rest of the ruleset will not be processed. 348Access to the console would then be required to recover. 349.It Fl S 350When listing rules, show the 351.Em set 352each rule belongs to. 353If this flag is not specified, disabled rules will not be 354listed. 355.It Fl s Op Ar field 356When listing pipes, sort according to one of the four 357counters (total or current packets or bytes). 358.It Fl t 359When listing, show last match timestamp converted with ctime(). 360.It Fl T 361When listing, show last match timestamp as seconds from the epoch. 362This form can be more convenient for postprocessing by scripts. 363.El 364.Ss LIST OF RULES AND PREPROCESSING 365To ease configuration, rules can be put into a file which is 366processed using 367.Nm 368as shown in the last synopsis line. 369An absolute 370.Ar pathname 371must be used. 372The file will be read line by line and applied as arguments to the 373.Nm 374utility. 375.Pp 376Optionally, a preprocessor can be specified using 377.Fl p Ar preproc 378where 379.Ar pathname 380is to be piped through. 381Useful preprocessors include 382.Xr cpp 1 383and 384.Xr m4 1 . 385If 386.Ar preproc 387does not start with a slash 388.Pq Ql / 389as its first character, the usual 390.Ev PATH 391name search is performed. 392Care should be taken with this in environments where not all 393file systems are mounted (yet) by the time 394.Nm 395is being run (e.g.\& when they are mounted over NFS). 396Once 397.Fl p 398has been specified, any additional arguments are passed on to the preprocessor 399for interpretation. 400This allows for flexible configuration files (like conditionalizing 401them on the local hostname) and the use of macros to centralize 402frequently required arguments like IP addresses. 403.Ss TRAFFIC SHAPER CONFIGURATION 404The 405.Nm 406.Cm pipe , queue 407and 408.Cm sched 409commands are used to configure the traffic shaper and packet scheduler. 410See the 411.Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION 412Section below for details. 413.Pp 414If the world and the kernel get out of sync the 415.Nm 416ABI may break, preventing you from being able to add any rules. 417This can adversely affect the booting process. 418You can use 419.Nm 420.Cm disable 421.Cm firewall 422to temporarily disable the firewall to regain access to the network, 423allowing you to fix the problem. 424.Sh PACKET FLOW 425A packet is checked against the active ruleset in multiple places 426in the protocol stack, under control of several sysctl variables. 427These places and variables are shown below, and it is important to 428have this picture in mind in order to design a correct ruleset. 429.Bd -literal -offset indent 430 ^ to upper layers V 431 | | 432 +----------->-----------+ 433 ^ V 434 [ip(6)_input] [ip(6)_output] net.inet(6).ip(6).fw.enable=1 435 | | 436 ^ V 437 [ether_demux] [ether_output_frame] net.link.ether.ipfw=1 438 | | 439 +-->--[bdg_forward]-->--+ net.link.bridge.ipfw=1 440 ^ V 441 | to devices | 442.Ed 443.Pp 444The number of 445times the same packet goes through the firewall can 446vary between 0 and 4 depending on packet source and 447destination, and system configuration. 448.Pp 449Note that as packets flow through the stack, headers can be 450stripped or added to it, and so they may or may not be available 451for inspection. 452E.g., incoming packets will include the MAC header when 453.Nm 454is invoked from 455.Cm ether_demux() , 456but the same packets will have the MAC header stripped off when 457.Nm 458is invoked from 459.Cm ip_input() 460or 461.Cm ip6_input() . 462.Pp 463Also note that each packet is always checked against the complete ruleset, 464irrespective of the place where the check occurs, or the source of the packet. 465If a rule contains some match patterns or actions which are not valid 466for the place of invocation (e.g.\& trying to match a MAC header within 467.Cm ip_input 468or 469.Cm ip6_input ), 470the match pattern will not match, but a 471.Cm not 472operator in front of such patterns 473.Em will 474cause the pattern to 475.Em always 476match on those packets. 477It is thus the responsibility of 478the programmer, if necessary, to write a suitable ruleset to 479differentiate among the possible places. 480.Cm skipto 481rules can be useful here, as an example: 482.Bd -literal -offset indent 483# packets from ether_demux or bdg_forward 484ipfw add 10 skipto 1000 all from any to any layer2 in 485# packets from ip_input 486ipfw add 10 skipto 2000 all from any to any not layer2 in 487# packets from ip_output 488ipfw add 10 skipto 3000 all from any to any not layer2 out 489# packets from ether_output_frame 490ipfw add 10 skipto 4000 all from any to any layer2 out 491.Ed 492.Pp 493(yes, at the moment there is no way to differentiate between 494ether_demux and bdg_forward). 495.Sh SYNTAX 496In general, each keyword or argument must be provided as 497a separate command line argument, with no leading or trailing 498spaces. 499Keywords are case-sensitive, whereas arguments may 500or may not be case-sensitive depending on their nature 501(e.g.\& uid's are, hostnames are not). 502.Pp 503Some arguments (e.g., port or address lists) are comma-separated 504lists of values. 505In this case, spaces after commas ',' are allowed to make 506the line more readable. 507You can also put the entire 508command (including flags) into a single argument. 509E.g., the following forms are equivalent: 510.Bd -literal -offset indent 511ipfw -q add deny src-ip 10.0.0.0/24,127.0.0.1/8 512ipfw -q add deny src-ip 10.0.0.0/24, 127.0.0.1/8 513ipfw "-q add deny src-ip 10.0.0.0/24, 127.0.0.1/8" 514.Ed 515.Sh RULE FORMAT 516The format of firewall rules is the following: 517.Bd -ragged -offset indent 518.Bk -words 519.Op Ar rule_number 520.Op Cm set Ar set_number 521.Op Cm prob Ar match_probability 522.Ar action 523.Op Cm log Op Cm logamount Ar number 524.Op Cm altq Ar queue 525.Oo 526.Bro Cm tag | untag 527.Brc Ar number 528.Oc 529.Ar body 530.Ek 531.Ed 532.Pp 533where the body of the rule specifies which information is used 534for filtering packets, among the following: 535.Pp 536.Bl -tag -width "Source and dest. addresses and ports" -offset XXX -compact 537.It Layer-2 header fields 538When available 539.It IPv4 and IPv6 Protocol 540SCTP, TCP, UDP, ICMP, etc. 541.It Source and dest. addresses and ports 542.It Direction 543See Section 544.Sx PACKET FLOW 545.It Transmit and receive interface 546By name or address 547.It Misc. IP header fields 548Version, type of service, datagram length, identification, 549fragment flag (non-zero IP offset), 550Time To Live 551.It IP options 552.It IPv6 Extension headers 553Fragmentation, Hop-by-Hop options, 554Routing Headers, Source routing rthdr0, Mobile IPv6 rthdr2, IPSec options. 555.It IPv6 Flow-ID 556.It Misc. TCP header fields 557TCP flags (SYN, FIN, ACK, RST, etc.), 558sequence number, acknowledgment number, 559window 560.It TCP options 561.It ICMP types 562for ICMP packets 563.It ICMP6 types 564for ICMP6 packets 565.It User/group ID 566When the packet can be associated with a local socket. 567.It Divert status 568Whether a packet came from a divert socket (e.g., 569.Xr natd 8 ) . 570.It Fib annotation state 571Whether a packet has been tagged for using a specific FIB (routing table) 572in future forwarding decisions. 573.El 574.Pp 575Note that some of the above information, e.g.\& source MAC or IP addresses and 576TCP/UDP ports, can be easily spoofed, so filtering on those fields 577alone might not guarantee the desired results. 578.Bl -tag -width indent 579.It Ar rule_number 580Each rule is associated with a 581.Ar rule_number 582in the range 1..65535, with the latter reserved for the 583.Em default 584rule. 585Rules are checked sequentially by rule number. 586Multiple rules can have the same number, in which case they are 587checked (and listed) according to the order in which they have 588been added. 589If a rule is entered without specifying a number, the kernel will 590assign one in such a way that the rule becomes the last one 591before the 592.Em default 593rule. 594Automatic rule numbers are assigned by incrementing the last 595non-default rule number by the value of the sysctl variable 596.Ar net.inet.ip.fw.autoinc_step 597which defaults to 100. 598If this is not possible (e.g.\& because we would go beyond the 599maximum allowed rule number), the number of the last 600non-default value is used instead. 601.It Cm set Ar set_number 602Each rule is associated with a 603.Ar set_number 604in the range 0..31. 605Sets can be individually disabled and enabled, so this parameter 606is of fundamental importance for atomic ruleset manipulation. 607It can be also used to simplify deletion of groups of rules. 608If a rule is entered without specifying a set number, 609set 0 will be used. 610.br 611Set 31 is special in that it cannot be disabled, 612and rules in set 31 are not deleted by the 613.Nm ipfw flush 614command (but you can delete them with the 615.Nm ipfw delete set 31 616command). 617Set 31 is also used for the 618.Em default 619rule. 620.It Cm prob Ar match_probability 621A match is only declared with the specified probability 622(floating point number between 0 and 1). 623This can be useful for a number of applications such as 624random packet drop or 625(in conjunction with 626.Nm dummynet ) 627to simulate the effect of multiple paths leading to out-of-order 628packet delivery. 629.Pp 630Note: this condition is checked before any other condition, including 631ones such as keep-state or check-state which might have side effects. 632.It Cm log Op Cm logamount Ar number 633Packets matching a rule with the 634.Cm log 635keyword will be made available for logging in two ways: 636if the sysctl variable 637.Va net.inet.ip.fw.verbose 638is set to 0 (default), one can use 639.Xr bpf 4 640attached to the 641.Li ipfw0 642pseudo interface. 643This pseudo interface can be created after a boot 644manually by using the following command: 645.Bd -literal -offset indent 646# ifconfig ipfw0 create 647.Ed 648.Pp 649Or, automatically at boot time by adding the following 650line to the 651.Xr rc.conf 5 652file: 653.Bd -literal -offset indent 654firewall_logif="YES" 655.Ed 656.Pp 657There is no overhead if no 658.Xr bpf 4 659is attached to the pseudo interface. 660.Pp 661If 662.Va net.inet.ip.fw.verbose 663is set to 1, packets will be logged to 664.Xr syslogd 8 665with a 666.Dv LOG_SECURITY 667facility up to a maximum of 668.Cm logamount 669packets. 670If no 671.Cm logamount 672is specified, the limit is taken from the sysctl variable 673.Va net.inet.ip.fw.verbose_limit . 674In both cases, a value of 0 means unlimited logging. 675.Pp 676Once the limit is reached, logging can be re-enabled by 677clearing the logging counter or the packet counter for that entry, see the 678.Cm resetlog 679command. 680.Pp 681Note: logging is done after all other packet matching conditions 682have been successfully verified, and before performing the final 683action (accept, deny, etc.) on the packet. 684.It Cm tag Ar number 685When a packet matches a rule with the 686.Cm tag 687keyword, the numeric tag for the given 688.Ar number 689in the range 1..65534 will be attached to the packet. 690The tag acts as an internal marker (it is not sent out over 691the wire) that can be used to identify these packets later on. 692This can be used, for example, to provide trust between interfaces 693and to start doing policy-based filtering. 694A packet can have multiple tags at the same time. 695Tags are "sticky", meaning once a tag is applied to a packet by a 696matching rule it exists until explicit removal. 697Tags are kept with the packet everywhere within the kernel, but are 698lost when packet leaves the kernel, for example, on transmitting 699packet out to the network or sending packet to a 700.Xr divert 4 701socket. 702.Pp 703To check for previously applied tags, use the 704.Cm tagged 705rule option. 706To delete previously applied tag, use the 707.Cm untag 708keyword. 709.Pp 710Note: since tags are kept with the packet everywhere in kernelspace, 711they can be set and unset anywhere in the kernel network subsystem 712(using the 713.Xr mbuf_tags 9 714facility), not only by means of the 715.Xr ipfw 4 716.Cm tag 717and 718.Cm untag 719keywords. 720For example, there can be a specialized 721.Xr netgraph 4 722node doing traffic analyzing and tagging for later inspecting 723in firewall. 724.It Cm untag Ar number 725When a packet matches a rule with the 726.Cm untag 727keyword, the tag with the number 728.Ar number 729is searched among the tags attached to this packet and, 730if found, removed from it. 731Other tags bound to packet, if present, are left untouched. 732.It Cm altq Ar queue 733When a packet matches a rule with the 734.Cm altq 735keyword, the ALTQ identifier for the given 736.Ar queue 737(see 738.Xr altq 4 ) 739will be attached. 740Note that this ALTQ tag is only meaningful for packets going "out" of IPFW, 741and not being rejected or going to divert sockets. 742Note that if there is insufficient memory at the time the packet is 743processed, it will not be tagged, so it is wise to make your ALTQ 744"default" queue policy account for this. 745If multiple 746.Cm altq 747rules match a single packet, only the first one adds the ALTQ classification 748tag. 749In doing so, traffic may be shaped by using 750.Cm count Cm altq Ar queue 751rules for classification early in the ruleset, then later applying 752the filtering decision. 753For example, 754.Cm check-state 755and 756.Cm keep-state 757rules may come later and provide the actual filtering decisions in 758addition to the fallback ALTQ tag. 759.Pp 760You must run 761.Xr pfctl 8 762to set up the queues before IPFW will be able to look them up by name, 763and if the ALTQ disciplines are rearranged, the rules in containing the 764queue identifiers in the kernel will likely have gone stale and need 765to be reloaded. 766Stale queue identifiers will probably result in misclassification. 767.Pp 768All system ALTQ processing can be turned on or off via 769.Nm 770.Cm enable Ar altq 771and 772.Nm 773.Cm disable Ar altq . 774The usage of 775.Va net.inet.ip.fw.one_pass 776is irrelevant to ALTQ traffic shaping, as the actual rule action is followed 777always after adding an ALTQ tag. 778.El 779.Ss RULE ACTIONS 780A rule can be associated with one of the following actions, which 781will be executed when the packet matches the body of the rule. 782.Bl -tag -width indent 783.It Cm allow | accept | pass | permit 784Allow packets that match rule. 785The search terminates. 786.It Cm check-state Op Ar :flowname | Cm :any 787Checks the packet against the dynamic ruleset. 788If a match is found, execute the action associated with 789the rule which generated this dynamic rule, otherwise 790move to the next rule. 791.br 792.Cm Check-state 793rules do not have a body. 794If no 795.Cm check-state 796rule is found, the dynamic ruleset is checked at the first 797.Cm keep-state 798or 799.Cm limit 800rule. 801The 802.Ar :flowname 803is symbolic name assigned to dynamic rule by 804.Cm keep-state 805opcode. 806The special flowname 807.Cm :any 808can be used to ignore states flowname when matching. 809The 810.Cm :default 811keyword is special name used for compatibility with old rulesets. 812.It Cm count 813Update counters for all packets that match rule. 814The search continues with the next rule. 815.It Cm deny | drop 816Discard packets that match this rule. 817The search terminates. 818.It Cm divert Ar port 819Divert packets that match this rule to the 820.Xr divert 4 821socket bound to port 822.Ar port . 823The search terminates. 824.It Cm fwd | forward Ar ipaddr | tablearg Ns Op , Ns Ar port 825Change the next-hop on matching packets to 826.Ar ipaddr , 827which can be an IP address or a host name. 828The next hop can also be supplied by the last table 829looked up for the packet by using the 830.Cm tablearg 831keyword instead of an explicit address. 832The search terminates if this rule matches. 833.Pp 834If 835.Ar ipaddr 836is a local address, then matching packets will be forwarded to 837.Ar port 838(or the port number in the packet if one is not specified in the rule) 839on the local machine. 840.br 841If 842.Ar ipaddr 843is not a local address, then the port number 844(if specified) is ignored, and the packet will be 845forwarded to the remote address, using the route as found in 846the local routing table for that IP. 847.br 848A 849.Ar fwd 850rule will not match layer-2 packets (those received 851on ether_input, ether_output, or bridged). 852.br 853The 854.Cm fwd 855action does not change the contents of the packet at all. 856In particular, the destination address remains unmodified, so 857packets forwarded to another system will usually be rejected by that system 858unless there is a matching rule on that system to capture them. 859For packets forwarded locally, 860the local address of the socket will be 861set to the original destination address of the packet. 862This makes the 863.Xr netstat 1 864entry look rather weird but is intended for 865use with transparent proxy servers. 866.It Cm nat Ar nat_nr | tablearg 867Pass packet to a 868nat instance 869(for network address translation, address redirect, etc.): 870see the 871.Sx NETWORK ADDRESS TRANSLATION (NAT) 872Section for further information. 873.It Cm nat64lsn Ar name 874Pass packet to a stateful NAT64 instance (for IPv6/IPv4 network address and 875protocol translation): see the 876.Sx IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION 877Section for further information. 878.It Cm nat64stl Ar name 879Pass packet to a stateless NAT64 instance (for IPv6/IPv4 network address and 880protocol translation): see the 881.Sx IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION 882Section for further information. 883.It Cm nptv6 Ar name 884Pass packet to a NPTv6 instance (for IPv6-to-IPv6 network prefix translation): 885see the 886.Sx IPv6-to-IPv6 NETWORK PREFIX TRANSLATION (NPTv6) 887Section for further information. 888.It Cm pipe Ar pipe_nr 889Pass packet to a 890.Nm dummynet 891.Dq pipe 892(for bandwidth limitation, delay, etc.). 893See the 894.Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION 895Section for further information. 896The search terminates; however, on exit from the pipe and if 897the 898.Xr sysctl 8 899variable 900.Va net.inet.ip.fw.one_pass 901is not set, the packet is passed again to the firewall code 902starting from the next rule. 903.It Cm queue Ar queue_nr 904Pass packet to a 905.Nm dummynet 906.Dq queue 907(for bandwidth limitation using WF2Q+). 908.It Cm reject 909(Deprecated). 910Synonym for 911.Cm unreach host . 912.It Cm reset 913Discard packets that match this rule, and if the 914packet is a TCP packet, try to send a TCP reset (RST) notice. 915The search terminates. 916.It Cm reset6 917Discard packets that match this rule, and if the 918packet is a TCP packet, try to send a TCP reset (RST) notice. 919The search terminates. 920.It Cm skipto Ar number | tablearg 921Skip all subsequent rules numbered less than 922.Ar number . 923The search continues with the first rule numbered 924.Ar number 925or higher. 926It is possible to use the 927.Cm tablearg 928keyword with a skipto for a 929.Em computed 930skipto. Skipto may work either in O(log(N)) or in O(1) depending 931on amount of memory and/or sysctl variables. 932See the 933.Sx SYSCTL VARIABLES 934section for more details. 935.It Cm call Ar number | tablearg 936The current rule number is saved in the internal stack and 937ruleset processing continues with the first rule numbered 938.Ar number 939or higher. 940If later a rule with the 941.Cm return 942action is encountered, the processing returns to the first rule 943with number of this 944.Cm call 945rule plus one or higher 946(the same behaviour as with packets returning from 947.Xr divert 4 948socket after a 949.Cm divert 950action). 951This could be used to make somewhat like an assembly language 952.Dq subroutine 953calls to rules with common checks for different interfaces, etc. 954.Pp 955Rule with any number could be called, not just forward jumps as with 956.Cm skipto . 957So, to prevent endless loops in case of mistakes, both 958.Cm call 959and 960.Cm return 961actions don't do any jumps and simply go to the next rule if memory 962cannot be allocated or stack overflowed/underflowed. 963.Pp 964Internally stack for rule numbers is implemented using 965.Xr mbuf_tags 9 966facility and currently has size of 16 entries. 967As mbuf tags are lost when packet leaves the kernel, 968.Cm divert 969should not be used in subroutines to avoid endless loops 970and other undesired effects. 971.It Cm return 972Takes rule number saved to internal stack by the last 973.Cm call 974action and returns ruleset processing to the first rule 975with number greater than number of corresponding 976.Cm call 977rule. 978See description of the 979.Cm call 980action for more details. 981.Pp 982Note that 983.Cm return 984rules usually end a 985.Dq subroutine 986and thus are unconditional, but 987.Nm 988command-line utility currently requires every action except 989.Cm check-state 990to have body. 991While it is sometimes useful to return only on some packets, 992usually you want to print just 993.Dq return 994for readability. 995A workaround for this is to use new syntax and 996.Fl c 997switch: 998.Bd -literal -offset indent 999# Add a rule without actual body 1000ipfw add 2999 return via any 1001 1002# List rules without "from any to any" part 1003ipfw -c list 1004.Ed 1005.Pp 1006This cosmetic annoyance may be fixed in future releases. 1007.It Cm tee Ar port 1008Send a copy of packets matching this rule to the 1009.Xr divert 4 1010socket bound to port 1011.Ar port . 1012The search continues with the next rule. 1013.It Cm unreach Ar code 1014Discard packets that match this rule, and try to send an ICMP 1015unreachable notice with code 1016.Ar code , 1017where 1018.Ar code 1019is a number from 0 to 255, or one of these aliases: 1020.Cm net , host , protocol , port , 1021.Cm needfrag , srcfail , net-unknown , host-unknown , 1022.Cm isolated , net-prohib , host-prohib , tosnet , 1023.Cm toshost , filter-prohib , host-precedence 1024or 1025.Cm precedence-cutoff . 1026The search terminates. 1027.It Cm unreach6 Ar code 1028Discard packets that match this rule, and try to send an ICMPv6 1029unreachable notice with code 1030.Ar code , 1031where 1032.Ar code 1033is a number from 0, 1, 3 or 4, or one of these aliases: 1034.Cm no-route, admin-prohib, address 1035or 1036.Cm port . 1037The search terminates. 1038.It Cm netgraph Ar cookie 1039Divert packet into netgraph with given 1040.Ar cookie . 1041The search terminates. 1042If packet is later returned from netgraph it is either 1043accepted or continues with the next rule, depending on 1044.Va net.inet.ip.fw.one_pass 1045sysctl variable. 1046.It Cm ngtee Ar cookie 1047A copy of packet is diverted into netgraph, original 1048packet continues with the next rule. 1049See 1050.Xr ng_ipfw 4 1051for more information on 1052.Cm netgraph 1053and 1054.Cm ngtee 1055actions. 1056.It Cm setfib Ar fibnum | tablearg 1057The packet is tagged so as to use the FIB (routing table) 1058.Ar fibnum 1059in any subsequent forwarding decisions. 1060In the current implementation, this is limited to the values 0 through 15, see 1061.Xr setfib 2 . 1062Processing continues at the next rule. 1063It is possible to use the 1064.Cm tablearg 1065keyword with setfib. 1066If the tablearg value is not within the compiled range of fibs, 1067the packet's fib is set to 0. 1068.It Cm setdscp Ar DSCP | number | tablearg 1069Set specified DiffServ codepoint for an IPv4/IPv6 packet. 1070Processing continues at the next rule. 1071Supported values are: 1072.Pp 1073.Cm cs0 1074.Pq Dv 000000 , 1075.Cm cs1 1076.Pq Dv 001000 , 1077.Cm cs2 1078.Pq Dv 010000 , 1079.Cm cs3 1080.Pq Dv 011000 , 1081.Cm cs4 1082.Pq Dv 100000 , 1083.Cm cs5 1084.Pq Dv 101000 , 1085.Cm cs6 1086.Pq Dv 110000 , 1087.Cm cs7 1088.Pq Dv 111000 , 1089.Cm af11 1090.Pq Dv 001010 , 1091.Cm af12 1092.Pq Dv 001100 , 1093.Cm af13 1094.Pq Dv 001110 , 1095.Cm af21 1096.Pq Dv 010010 , 1097.Cm af22 1098.Pq Dv 010100 , 1099.Cm af23 1100.Pq Dv 010110 , 1101.Cm af31 1102.Pq Dv 011010 , 1103.Cm af32 1104.Pq Dv 011100 , 1105.Cm af33 1106.Pq Dv 011110 , 1107.Cm af41 1108.Pq Dv 100010 , 1109.Cm af42 1110.Pq Dv 100100 , 1111.Cm af43 1112.Pq Dv 100110 , 1113.Cm ef 1114.Pq Dv 101110 , 1115.Cm be 1116.Pq Dv 000000 . 1117Additionally, DSCP value can be specified by number (0..64). 1118It is also possible to use the 1119.Cm tablearg 1120keyword with setdscp. 1121If the tablearg value is not within the 0..64 range, lower 6 bits of supplied 1122value are used. 1123.It Cm tcp-setmss Ar mss 1124Set the Maximum Segment Size (MSS) in the TCP segment to value 1125.Ar mss . 1126The kernel module 1127.Cm ipfw_pmod 1128should be loaded or kernel should have 1129.Cm options IPFIREWALL_PMOD 1130to be able use this action. 1131This command does not change a packet if original MSS value is lower than 1132specified value. 1133Both TCP over IPv4 and over IPv6 are supported. 1134Regardless of matched a packet or not by the 1135.Cm tcp-setmss 1136rule, the search continues with the next rule. 1137.It Cm reass 1138Queue and reassemble IPv4 fragments. 1139If the packet is not fragmented, counters are updated and 1140processing continues with the next rule. 1141If the packet is the last logical fragment, the packet is reassembled and, if 1142.Va net.inet.ip.fw.one_pass 1143is set to 0, processing continues with the next rule. 1144Otherwise, the packet is allowed to pass and the search terminates. 1145If the packet is a fragment in the middle of a logical group of fragments, 1146it is consumed and 1147processing stops immediately. 1148.Pp 1149Fragment handling can be tuned via 1150.Va net.inet.ip.maxfragpackets 1151and 1152.Va net.inet.ip.maxfragsperpacket 1153which limit, respectively, the maximum number of processable 1154fragments (default: 800) and 1155the maximum number of fragments per packet (default: 16). 1156.Pp 1157NOTA BENE: since fragments do not contain port numbers, 1158they should be avoided with the 1159.Nm reass 1160rule. 1161Alternatively, direction-based (like 1162.Nm in 1163/ 1164.Nm out 1165) and source-based (like 1166.Nm via 1167) match patterns can be used to select fragments. 1168.Pp 1169Usually a simple rule like: 1170.Bd -literal -offset indent 1171# reassemble incoming fragments 1172ipfw add reass all from any to any in 1173.Ed 1174.Pp 1175is all you need at the beginning of your ruleset. 1176.It Cm abort 1177Discard packets that match this rule, and if the packet is an SCTP packet, 1178try to send an SCTP packet containing an ABORT chunk. 1179The search terminates. 1180.It Cm abort6 1181Discard packets that match this rule, and if the packet is an SCTP packet, 1182try to send an SCTP packet containing an ABORT chunk. 1183The search terminates. 1184.El 1185.Ss RULE BODY 1186The body of a rule contains zero or more patterns (such as 1187specific source and destination addresses or ports, 1188protocol options, incoming or outgoing interfaces, etc.) 1189that the packet must match in order to be recognised. 1190In general, the patterns are connected by (implicit) 1191.Cm and 1192operators -- i.e., all must match in order for the 1193rule to match. 1194Individual patterns can be prefixed by the 1195.Cm not 1196operator to reverse the result of the match, as in 1197.Pp 1198.Dl "ipfw add 100 allow ip from not 1.2.3.4 to any" 1199.Pp 1200Additionally, sets of alternative match patterns 1201.Pq Em or-blocks 1202can be constructed by putting the patterns in 1203lists enclosed between parentheses ( ) or braces { }, and 1204using the 1205.Cm or 1206operator as follows: 1207.Pp 1208.Dl "ipfw add 100 allow ip from { x or not y or z } to any" 1209.Pp 1210Only one level of parentheses is allowed. 1211Beware that most shells have special meanings for parentheses 1212or braces, so it is advisable to put a backslash \\ in front of them 1213to prevent such interpretations. 1214.Pp 1215The body of a rule must in general include a source and destination 1216address specifier. 1217The keyword 1218.Ar any 1219can be used in various places to specify that the content of 1220a required field is irrelevant. 1221.Pp 1222The rule body has the following format: 1223.Bd -ragged -offset indent 1224.Op Ar proto Cm from Ar src Cm to Ar dst 1225.Op Ar options 1226.Ed 1227.Pp 1228The first part (proto from src to dst) is for backward 1229compatibility with earlier versions of 1230.Fx . 1231In modern 1232.Fx 1233any match pattern (including MAC headers, IP protocols, 1234addresses and ports) can be specified in the 1235.Ar options 1236section. 1237.Pp 1238Rule fields have the following meaning: 1239.Bl -tag -width indent 1240.It Ar proto : protocol | Cm { Ar protocol Cm or ... } 1241.It Ar protocol : Oo Cm not Oc Ar protocol-name | protocol-number 1242An IP protocol specified by number or name 1243(for a complete list see 1244.Pa /etc/protocols ) , 1245or one of the following keywords: 1246.Bl -tag -width indent 1247.It Cm ip4 | ipv4 1248Matches IPv4 packets. 1249.It Cm ip6 | ipv6 1250Matches IPv6 packets. 1251.It Cm ip | all 1252Matches any packet. 1253.El 1254.Pp 1255The 1256.Cm ipv6 1257in 1258.Cm proto 1259option will be treated as inner protocol. 1260And, the 1261.Cm ipv4 1262is not available in 1263.Cm proto 1264option. 1265.Pp 1266The 1267.Cm { Ar protocol Cm or ... } 1268format (an 1269.Em or-block ) 1270is provided for convenience only but its use is deprecated. 1271.It Ar src No and Ar dst : Bro Cm addr | Cm { Ar addr Cm or ... } Brc Op Oo Cm not Oc Ar ports 1272An address (or a list, see below) 1273optionally followed by 1274.Ar ports 1275specifiers. 1276.Pp 1277The second format 1278.Em ( or-block 1279with multiple addresses) is provided for convenience only and 1280its use is discouraged. 1281.It Ar addr : Oo Cm not Oc Bro 1282.Cm any | me | me6 | 1283.Cm table Ns Pq Ar name Ns Op , Ns Ar value 1284.Ar | addr-list | addr-set 1285.Brc 1286.Bl -tag -width indent 1287.It Cm any 1288matches any IP address. 1289.It Cm me 1290matches any IP address configured on an interface in the system. 1291.It Cm me6 1292matches any IPv6 address configured on an interface in the system. 1293The address list is evaluated at the time the packet is 1294analysed. 1295.It Cm table Ns Pq Ar name Ns Op , Ns Ar value 1296Matches any IPv4 or IPv6 address for which an entry exists in the lookup table 1297.Ar number . 1298If an optional 32-bit unsigned 1299.Ar value 1300is also specified, an entry will match only if it has this value. 1301See the 1302.Sx LOOKUP TABLES 1303section below for more information on lookup tables. 1304.El 1305.It Ar addr-list : ip-addr Ns Op Ns , Ns Ar addr-list 1306.It Ar ip-addr : 1307A host or subnet address specified in one of the following ways: 1308.Bl -tag -width indent 1309.It Ar numeric-ip | hostname 1310Matches a single IPv4 address, specified as dotted-quad or a hostname. 1311Hostnames are resolved at the time the rule is added to the firewall list. 1312.It Ar addr Ns / Ns Ar masklen 1313Matches all addresses with base 1314.Ar addr 1315(specified as an IP address, a network number, or a hostname) 1316and mask width of 1317.Cm masklen 1318bits. 1319As an example, 1.2.3.4/25 or 1.2.3.0/25 will match 1320all IP numbers from 1.2.3.0 to 1.2.3.127 . 1321.It Ar addr Ns : Ns Ar mask 1322Matches all addresses with base 1323.Ar addr 1324(specified as an IP address, a network number, or a hostname) 1325and the mask of 1326.Ar mask , 1327specified as a dotted quad. 1328As an example, 1.2.3.4:255.0.255.0 or 1.0.3.0:255.0.255.0 will match 13291.*.3.*. 1330This form is advised only for non-contiguous 1331masks. 1332It is better to resort to the 1333.Ar addr Ns / Ns Ar masklen 1334format for contiguous masks, which is more compact and less 1335error-prone. 1336.El 1337.It Ar addr-set : addr Ns Oo Ns / Ns Ar masklen Oc Ns Cm { Ns Ar list Ns Cm } 1338.It Ar list : Bro Ar num | num-num Brc Ns Op Ns , Ns Ar list 1339Matches all addresses with base address 1340.Ar addr 1341(specified as an IP address, a network number, or a hostname) 1342and whose last byte is in the list between braces { } . 1343Note that there must be no spaces between braces and 1344numbers (spaces after commas are allowed). 1345Elements of the list can be specified as single entries 1346or ranges. 1347The 1348.Ar masklen 1349field is used to limit the size of the set of addresses, 1350and can have any value between 24 and 32. 1351If not specified, 1352it will be assumed as 24. 1353.br 1354This format is particularly useful to handle sparse address sets 1355within a single rule. 1356Because the matching occurs using a 1357bitmask, it takes constant time and dramatically reduces 1358the complexity of rulesets. 1359.br 1360As an example, an address specified as 1.2.3.4/24{128,35-55,89} 1361or 1.2.3.0/24{128,35-55,89} 1362will match the following IP addresses: 1363.br 13641.2.3.128, 1.2.3.35 to 1.2.3.55, 1.2.3.89 . 1365.It Ar addr6-list : ip6-addr Ns Op Ns , Ns Ar addr6-list 1366.It Ar ip6-addr : 1367A host or subnet specified one of the following ways: 1368.Bl -tag -width indent 1369.It Ar numeric-ip | hostname 1370Matches a single IPv6 address as allowed by 1371.Xr inet_pton 3 1372or a hostname. 1373Hostnames are resolved at the time the rule is added to the firewall 1374list. 1375.It Ar addr Ns / Ns Ar masklen 1376Matches all IPv6 addresses with base 1377.Ar addr 1378(specified as allowed by 1379.Xr inet_pton 1380or a hostname) 1381and mask width of 1382.Cm masklen 1383bits. 1384.It Ar addr Ns / Ns Ar mask 1385Matches all IPv6 addresses with base 1386.Ar addr 1387(specified as allowed by 1388.Xr inet_pton 1389or a hostname) 1390and the mask of 1391.Ar mask , 1392specified as allowed by 1393.Xr inet_pton. 1394As an example, fe::640:0:0/ffff::ffff:ffff:0:0 will match 1395fe:*:*:*:0:640:*:*. 1396This form is advised only for non-contiguous 1397masks. 1398It is better to resort to the 1399.Ar addr Ns / Ns Ar masklen 1400format for contiguous masks, which is more compact and less 1401error-prone. 1402.El 1403.Pp 1404No support for sets of IPv6 addresses is provided because IPv6 addresses 1405are typically random past the initial prefix. 1406.It Ar ports : Bro Ar port | port Ns \&- Ns Ar port Ns Brc Ns Op , Ns Ar ports 1407For protocols which support port numbers (such as SCTP, TCP and UDP), optional 1408.Cm ports 1409may be specified as one or more ports or port ranges, separated 1410by commas but no spaces, and an optional 1411.Cm not 1412operator. 1413The 1414.Ql \&- 1415notation specifies a range of ports (including boundaries). 1416.Pp 1417Service names (from 1418.Pa /etc/services ) 1419may be used instead of numeric port values. 1420The length of the port list is limited to 30 ports or ranges, 1421though one can specify larger ranges by using an 1422.Em or-block 1423in the 1424.Cm options 1425section of the rule. 1426.Pp 1427A backslash 1428.Pq Ql \e 1429can be used to escape the dash 1430.Pq Ql - 1431character in a service name (from a shell, the backslash must be 1432typed twice to avoid the shell itself interpreting it as an escape 1433character). 1434.Pp 1435.Dl "ipfw add count tcp from any ftp\e\e-data-ftp to any" 1436.Pp 1437Fragmented packets which have a non-zero offset (i.e., not the first 1438fragment) will never match a rule which has one or more port 1439specifications. 1440See the 1441.Cm frag 1442option for details on matching fragmented packets. 1443.El 1444.Ss RULE OPTIONS (MATCH PATTERNS) 1445Additional match patterns can be used within 1446rules. 1447Zero or more of these so-called 1448.Em options 1449can be present in a rule, optionally prefixed by the 1450.Cm not 1451operand, and possibly grouped into 1452.Em or-blocks . 1453.Pp 1454The following match patterns can be used (listed in alphabetical order): 1455.Bl -tag -width indent 1456.It Cm // this is a comment. 1457Inserts the specified text as a comment in the rule. 1458Everything following // is considered as a comment and stored in the rule. 1459You can have comment-only rules, which are listed as having a 1460.Cm count 1461action followed by the comment. 1462.It Cm bridged 1463Alias for 1464.Cm layer2 . 1465.It Cm diverted 1466Matches only packets generated by a divert socket. 1467.It Cm diverted-loopback 1468Matches only packets coming from a divert socket back into the IP stack 1469input for delivery. 1470.It Cm diverted-output 1471Matches only packets going from a divert socket back outward to the IP 1472stack output for delivery. 1473.It Cm dst-ip Ar ip-address 1474Matches IPv4 packets whose destination IP is one of the address(es) 1475specified as argument. 1476.It Bro Cm dst-ip6 | dst-ipv6 Brc Ar ip6-address 1477Matches IPv6 packets whose destination IP is one of the address(es) 1478specified as argument. 1479.It Cm dst-port Ar ports 1480Matches IP packets whose destination port is one of the port(s) 1481specified as argument. 1482.It Cm established 1483Matches TCP packets that have the RST or ACK bits set. 1484.It Cm ext6hdr Ar header 1485Matches IPv6 packets containing the extended header given by 1486.Ar header . 1487Supported headers are: 1488.Pp 1489Fragment, 1490.Pq Cm frag , 1491Hop-to-hop options 1492.Pq Cm hopopt , 1493any type of Routing Header 1494.Pq Cm route , 1495Source routing Routing Header Type 0 1496.Pq Cm rthdr0 , 1497Mobile IPv6 Routing Header Type 2 1498.Pq Cm rthdr2 , 1499Destination options 1500.Pq Cm dstopt , 1501IPSec authentication headers 1502.Pq Cm ah , 1503and IPsec encapsulated security payload headers 1504.Pq Cm esp . 1505.It Cm fib Ar fibnum 1506Matches a packet that has been tagged to use 1507the given FIB (routing table) number. 1508.It Cm flow Ar table Ns Pq Ar name Ns Op , Ns Ar value 1509Search for the flow entry in lookup table 1510.Ar name . 1511If not found, the match fails. 1512Otherwise, the match succeeds and 1513.Cm tablearg 1514is set to the value extracted from the table. 1515.Pp 1516This option can be useful to quickly dispatch traffic based on 1517certain packet fields. 1518See the 1519.Sx LOOKUP TABLES 1520section below for more information on lookup tables. 1521.It Cm flow-id Ar labels 1522Matches IPv6 packets containing any of the flow labels given in 1523.Ar labels . 1524.Ar labels 1525is a comma separated list of numeric flow labels. 1526.It Cm frag 1527Matches packets that are fragments and not the first 1528fragment of an IP datagram. 1529Note that these packets will not have 1530the next protocol header (e.g.\& TCP, UDP) so options that look into 1531these headers cannot match. 1532.It Cm gid Ar group 1533Matches all TCP or UDP packets sent by or received for a 1534.Ar group . 1535A 1536.Ar group 1537may be specified by name or number. 1538.It Cm jail Ar prisonID 1539Matches all TCP or UDP packets sent by or received for the 1540jail whos prison ID is 1541.Ar prisonID . 1542.It Cm icmptypes Ar types 1543Matches ICMP packets whose ICMP type is in the list 1544.Ar types . 1545The list may be specified as any combination of 1546individual types (numeric) separated by commas. 1547.Em Ranges are not allowed . 1548The supported ICMP types are: 1549.Pp 1550echo reply 1551.Pq Cm 0 , 1552destination unreachable 1553.Pq Cm 3 , 1554source quench 1555.Pq Cm 4 , 1556redirect 1557.Pq Cm 5 , 1558echo request 1559.Pq Cm 8 , 1560router advertisement 1561.Pq Cm 9 , 1562router solicitation 1563.Pq Cm 10 , 1564time-to-live exceeded 1565.Pq Cm 11 , 1566IP header bad 1567.Pq Cm 12 , 1568timestamp request 1569.Pq Cm 13 , 1570timestamp reply 1571.Pq Cm 14 , 1572information request 1573.Pq Cm 15 , 1574information reply 1575.Pq Cm 16 , 1576address mask request 1577.Pq Cm 17 1578and address mask reply 1579.Pq Cm 18 . 1580.It Cm icmp6types Ar types 1581Matches ICMP6 packets whose ICMP6 type is in the list of 1582.Ar types . 1583The list may be specified as any combination of 1584individual types (numeric) separated by commas. 1585.Em Ranges are not allowed . 1586.It Cm in | out 1587Matches incoming or outgoing packets, respectively. 1588.Cm in 1589and 1590.Cm out 1591are mutually exclusive (in fact, 1592.Cm out 1593is implemented as 1594.Cm not in Ns No ). 1595.It Cm ipid Ar id-list 1596Matches IPv4 packets whose 1597.Cm ip_id 1598field has value included in 1599.Ar id-list , 1600which is either a single value or a list of values or ranges 1601specified in the same way as 1602.Ar ports . 1603.It Cm iplen Ar len-list 1604Matches IP packets whose total length, including header and data, is 1605in the set 1606.Ar len-list , 1607which is either a single value or a list of values or ranges 1608specified in the same way as 1609.Ar ports . 1610.It Cm ipoptions Ar spec 1611Matches packets whose IPv4 header contains the comma separated list of 1612options specified in 1613.Ar spec . 1614The supported IP options are: 1615.Pp 1616.Cm ssrr 1617(strict source route), 1618.Cm lsrr 1619(loose source route), 1620.Cm rr 1621(record packet route) and 1622.Cm ts 1623(timestamp). 1624The absence of a particular option may be denoted 1625with a 1626.Ql \&! . 1627.It Cm ipprecedence Ar precedence 1628Matches IPv4 packets whose precedence field is equal to 1629.Ar precedence . 1630.It Cm ipsec 1631Matches packets that have IPSEC history associated with them 1632(i.e., the packet comes encapsulated in IPSEC, the kernel 1633has IPSEC support, and can correctly decapsulate it). 1634.Pp 1635Note that specifying 1636.Cm ipsec 1637is different from specifying 1638.Cm proto Ar ipsec 1639as the latter will only look at the specific IP protocol field, 1640irrespective of IPSEC kernel support and the validity of the IPSEC data. 1641.Pp 1642Further note that this flag is silently ignored in kernels without 1643IPSEC support. 1644It does not affect rule processing when given and the 1645rules are handled as if with no 1646.Cm ipsec 1647flag. 1648.It Cm iptos Ar spec 1649Matches IPv4 packets whose 1650.Cm tos 1651field contains the comma separated list of 1652service types specified in 1653.Ar spec . 1654The supported IP types of service are: 1655.Pp 1656.Cm lowdelay 1657.Pq Dv IPTOS_LOWDELAY , 1658.Cm throughput 1659.Pq Dv IPTOS_THROUGHPUT , 1660.Cm reliability 1661.Pq Dv IPTOS_RELIABILITY , 1662.Cm mincost 1663.Pq Dv IPTOS_MINCOST , 1664.Cm congestion 1665.Pq Dv IPTOS_ECN_CE . 1666The absence of a particular type may be denoted 1667with a 1668.Ql \&! . 1669.It Cm dscp spec Ns Op , Ns Ar spec 1670Matches IPv4/IPv6 packets whose 1671.Cm DS 1672field value is contained in 1673.Ar spec 1674mask. 1675Multiple values can be specified via 1676the comma separated list. 1677Value can be one of keywords used in 1678.Cm setdscp 1679action or exact number. 1680.It Cm ipttl Ar ttl-list 1681Matches IPv4 packets whose time to live is included in 1682.Ar ttl-list , 1683which is either a single value or a list of values or ranges 1684specified in the same way as 1685.Ar ports . 1686.It Cm ipversion Ar ver 1687Matches IP packets whose IP version field is 1688.Ar ver . 1689.It Cm keep-state Op Ar :flowname 1690Upon a match, the firewall will create a dynamic rule, whose 1691default behaviour is to match bidirectional traffic between 1692source and destination IP/port using the same protocol. 1693The rule has a limited lifetime (controlled by a set of 1694.Xr sysctl 8 1695variables), and the lifetime is refreshed every time a matching 1696packet is found. 1697The 1698.Ar :flowname 1699is used to assign additional to addresses, ports and protocol parameter 1700to dynamic rule. It can be used for more accurate matching by 1701.Cm check-state 1702rule. 1703The 1704.Cm :default 1705keyword is special name used for compatibility with old rulesets. 1706.It Cm layer2 1707Matches only layer2 packets, i.e., those passed to 1708.Nm 1709from ether_demux() and ether_output_frame(). 1710.It Cm limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N Op Ar :flowname 1711The firewall will only allow 1712.Ar N 1713connections with the same 1714set of parameters as specified in the rule. 1715One or more 1716of source and destination addresses and ports can be 1717specified. 1718.It Cm lookup Bro Cm dst-ip | dst-port | src-ip | src-port | uid | jail Brc Ar name 1719Search an entry in lookup table 1720.Ar name 1721that matches the field specified as argument. 1722If not found, the match fails. 1723Otherwise, the match succeeds and 1724.Cm tablearg 1725is set to the value extracted from the table. 1726.Pp 1727This option can be useful to quickly dispatch traffic based on 1728certain packet fields. 1729See the 1730.Sx LOOKUP TABLES 1731section below for more information on lookup tables. 1732.It Cm { MAC | mac } Ar dst-mac src-mac 1733Match packets with a given 1734.Ar dst-mac 1735and 1736.Ar src-mac 1737addresses, specified as the 1738.Cm any 1739keyword (matching any MAC address), or six groups of hex digits 1740separated by colons, 1741and optionally followed by a mask indicating the significant bits. 1742The mask may be specified using either of the following methods: 1743.Bl -enum -width indent 1744.It 1745A slash 1746.Pq / 1747followed by the number of significant bits. 1748For example, an address with 33 significant bits could be specified as: 1749.Pp 1750.Dl "MAC 10:20:30:40:50:60/33 any" 1751.It 1752An ampersand 1753.Pq & 1754followed by a bitmask specified as six groups of hex digits separated 1755by colons. 1756For example, an address in which the last 16 bits are significant could 1757be specified as: 1758.Pp 1759.Dl "MAC 10:20:30:40:50:60&00:00:00:00:ff:ff any" 1760.Pp 1761Note that the ampersand character has a special meaning in many shells 1762and should generally be escaped. 1763.El 1764Note that the order of MAC addresses (destination first, 1765source second) is 1766the same as on the wire, but the opposite of the one used for 1767IP addresses. 1768.It Cm mac-type Ar mac-type 1769Matches packets whose Ethernet Type field 1770corresponds to one of those specified as argument. 1771.Ar mac-type 1772is specified in the same way as 1773.Cm port numbers 1774(i.e., one or more comma-separated single values or ranges). 1775You can use symbolic names for known values such as 1776.Em vlan , ipv4, ipv6 . 1777Values can be entered as decimal or hexadecimal (if prefixed by 0x), 1778and they are always printed as hexadecimal (unless the 1779.Cm -N 1780option is used, in which case symbolic resolution will be attempted). 1781.It Cm proto Ar protocol 1782Matches packets with the corresponding IP protocol. 1783.It Cm recv | xmit | via Brq Ar ifX | Ar if Ns Cm * | Ar table Ns Po Ar name Ns Oo , Ns Ar value Oc Pc | Ar ipno | Ar any 1784Matches packets received, transmitted or going through, 1785respectively, the interface specified by exact name 1786.Po Ar ifX Pc , 1787by device name 1788.Po Ar if* Pc , 1789by IP address, or through some interface. 1790Table 1791.Ar name 1792may be used to match interface by its kernel ifindex. 1793See the 1794.Sx LOOKUP TABLES 1795section below for more information on lookup tables. 1796.Pp 1797The 1798.Cm via 1799keyword causes the interface to always be checked. 1800If 1801.Cm recv 1802or 1803.Cm xmit 1804is used instead of 1805.Cm via , 1806then only the receive or transmit interface (respectively) 1807is checked. 1808By specifying both, it is possible to match packets based on 1809both receive and transmit interface, e.g.: 1810.Pp 1811.Dl "ipfw add deny ip from any to any out recv ed0 xmit ed1" 1812.Pp 1813The 1814.Cm recv 1815interface can be tested on either incoming or outgoing packets, 1816while the 1817.Cm xmit 1818interface can only be tested on outgoing packets. 1819So 1820.Cm out 1821is required (and 1822.Cm in 1823is invalid) whenever 1824.Cm xmit 1825is used. 1826.Pp 1827A packet might not have a receive or transmit interface: packets 1828originating from the local host have no receive interface, 1829while packets destined for the local host have no transmit 1830interface. 1831.It Cm setup 1832Matches TCP packets that have the SYN bit set but no ACK bit. 1833This is the short form of 1834.Dq Li tcpflags\ syn,!ack . 1835.It Cm sockarg 1836Matches packets that are associated to a local socket and 1837for which the SO_USER_COOKIE socket option has been set 1838to a non-zero value. 1839As a side effect, the value of the 1840option is made available as 1841.Cm tablearg 1842value, which in turn can be used as 1843.Cm skipto 1844or 1845.Cm pipe 1846number. 1847.It Cm src-ip Ar ip-address 1848Matches IPv4 packets whose source IP is one of the address(es) 1849specified as an argument. 1850.It Cm src-ip6 Ar ip6-address 1851Matches IPv6 packets whose source IP is one of the address(es) 1852specified as an argument. 1853.It Cm src-port Ar ports 1854Matches IP packets whose source port is one of the port(s) 1855specified as argument. 1856.It Cm tagged Ar tag-list 1857Matches packets whose tags are included in 1858.Ar tag-list , 1859which is either a single value or a list of values or ranges 1860specified in the same way as 1861.Ar ports . 1862Tags can be applied to the packet using 1863.Cm tag 1864rule action parameter (see it's description for details on tags). 1865.It Cm tcpack Ar ack 1866TCP packets only. 1867Match if the TCP header acknowledgment number field is set to 1868.Ar ack . 1869.It Cm tcpdatalen Ar tcpdatalen-list 1870Matches TCP packets whose length of TCP data is 1871.Ar tcpdatalen-list , 1872which is either a single value or a list of values or ranges 1873specified in the same way as 1874.Ar ports . 1875.It Cm tcpflags Ar spec 1876TCP packets only. 1877Match if the TCP header contains the comma separated list of 1878flags specified in 1879.Ar spec . 1880The supported TCP flags are: 1881.Pp 1882.Cm fin , 1883.Cm syn , 1884.Cm rst , 1885.Cm psh , 1886.Cm ack 1887and 1888.Cm urg . 1889The absence of a particular flag may be denoted 1890with a 1891.Ql \&! . 1892A rule which contains a 1893.Cm tcpflags 1894specification can never match a fragmented packet which has 1895a non-zero offset. 1896See the 1897.Cm frag 1898option for details on matching fragmented packets. 1899.It Cm tcpseq Ar seq 1900TCP packets only. 1901Match if the TCP header sequence number field is set to 1902.Ar seq . 1903.It Cm tcpwin Ar tcpwin-list 1904Matches TCP packets whose header window field is set to 1905.Ar tcpwin-list , 1906which is either a single value or a list of values or ranges 1907specified in the same way as 1908.Ar ports . 1909.It Cm tcpoptions Ar spec 1910TCP packets only. 1911Match if the TCP header contains the comma separated list of 1912options specified in 1913.Ar spec . 1914The supported TCP options are: 1915.Pp 1916.Cm mss 1917(maximum segment size), 1918.Cm window 1919(tcp window advertisement), 1920.Cm sack 1921(selective ack), 1922.Cm ts 1923(rfc1323 timestamp) and 1924.Cm cc 1925(rfc1644 t/tcp connection count). 1926The absence of a particular option may be denoted 1927with a 1928.Ql \&! . 1929.It Cm uid Ar user 1930Match all TCP or UDP packets sent by or received for a 1931.Ar user . 1932A 1933.Ar user 1934may be matched by name or identification number. 1935.It Cm verrevpath 1936For incoming packets, 1937a routing table lookup is done on the packet's source address. 1938If the interface on which the packet entered the system matches the 1939outgoing interface for the route, 1940the packet matches. 1941If the interfaces do not match up, 1942the packet does not match. 1943All outgoing packets or packets with no incoming interface match. 1944.Pp 1945The name and functionality of the option is intentionally similar to 1946the Cisco IOS command: 1947.Pp 1948.Dl ip verify unicast reverse-path 1949.Pp 1950This option can be used to make anti-spoofing rules to reject all 1951packets with source addresses not from this interface. 1952See also the option 1953.Cm antispoof . 1954.It Cm versrcreach 1955For incoming packets, 1956a routing table lookup is done on the packet's source address. 1957If a route to the source address exists, but not the default route 1958or a blackhole/reject route, the packet matches. 1959Otherwise, the packet does not match. 1960All outgoing packets match. 1961.Pp 1962The name and functionality of the option is intentionally similar to 1963the Cisco IOS command: 1964.Pp 1965.Dl ip verify unicast source reachable-via any 1966.Pp 1967This option can be used to make anti-spoofing rules to reject all 1968packets whose source address is unreachable. 1969.It Cm antispoof 1970For incoming packets, the packet's source address is checked if it 1971belongs to a directly connected network. 1972If the network is directly connected, then the interface the packet 1973came on in is compared to the interface the network is connected to. 1974When incoming interface and directly connected interface are not the 1975same, the packet does not match. 1976Otherwise, the packet does match. 1977All outgoing packets match. 1978.Pp 1979This option can be used to make anti-spoofing rules to reject all 1980packets that pretend to be from a directly connected network but do 1981not come in through that interface. 1982This option is similar to but more restricted than 1983.Cm verrevpath 1984because it engages only on packets with source addresses of directly 1985connected networks instead of all source addresses. 1986.El 1987.Sh LOOKUP TABLES 1988Lookup tables are useful to handle large sparse sets of 1989addresses or other search keys (e.g., ports, jail IDs, interface names). 1990In the rest of this section we will use the term ``key''. 1991Table name needs to match the following spec: 1992.Ar table-name . 1993Tables with the same name can be created in different 1994.Ar sets . 1995However, rule links to the tables in 1996.Ar set 0 1997by default. 1998This behavior can be controlled by 1999.Va net.inet.ip.fw.tables_sets 2000variable. 2001See the 2002.Sx SETS OF RULES 2003section for more information. 2004There may be up to 65535 different lookup tables. 2005.Pp 2006The following table types are supported: 2007.Bl -tag -width indent 2008.It Ar table-type : Ar addr | iface | number | flow 2009.It Ar table-key : Ar addr Ns Oo / Ns Ar masklen Oc | iface-name | number | flow-spec 2010.It Ar flow-spec : Ar flow-field Ns Op , Ns Ar flow-spec 2011.It Ar flow-field : src-ip | proto | src-port | dst-ip | dst-port 2012.It Cm addr 2013matches IPv4 or IPv6 address. 2014Each entry is represented by an 2015.Ar addr Ns Op / Ns Ar masklen 2016and will match all addresses with base 2017.Ar addr 2018(specified as an IPv4/IPv6 address, or a hostname) and mask width of 2019.Ar masklen 2020bits. 2021If 2022.Ar masklen 2023is not specified, it defaults to 32 for IPv4 and 128 for IPv6. 2024When looking up an IP address in a table, the most specific 2025entry will match. 2026.It Cm iface 2027matches interface names. 2028Each entry is represented by string treated as interface name. 2029Wildcards are not supported. 2030.It Cm number 2031maches protocol ports, uids/gids or jail IDs. 2032Each entry is represented by 32-bit unsigned integer. 2033Ranges are not supported. 2034.It Cm flow 2035Matches packet fields specified by 2036.Ar flow 2037type suboptions with table entries. 2038.El 2039.Pp 2040Tables require explicit creation via 2041.Cm create 2042before use. 2043.Pp 2044The following creation options are supported: 2045.Bl -tag -width indent 2046.It Ar create-options : Ar create-option | create-options 2047.It Ar create-option : Cm type Ar table-type | Cm valtype Ar value-mask | Cm algo Ar algo-desc | 2048.Cm limit Ar number | Cm locked 2049.It Cm type 2050Table key type. 2051.It Cm valtype 2052Table value mask. 2053.It Cm algo 2054Table algorithm to use (see below). 2055.It Cm limit 2056Maximum number of items that may be inserted into table. 2057.It Cm locked 2058Restrict any table modifications. 2059.El 2060.Pp 2061Some of these options may be modified later via 2062.Cm modify 2063keyword. 2064The following options can be changed: 2065.Bl -tag -width indent 2066.It Ar modify-options : Ar modify-option | modify-options 2067.It Ar modify-option : Cm limit Ar number 2068.It Cm limit 2069Alter maximum number of items that may be inserted into table. 2070.El 2071.Pp 2072Additionally, table can be locked or unlocked using 2073.Cm lock 2074or 2075.Cm unlock 2076commands. 2077.Pp 2078Tables of the same 2079.Ar type 2080can be swapped with each other using 2081.Cm swap Ar name 2082command. 2083Swap may fail if tables limits are set and data exchange 2084would result in limits hit. 2085Operation is performed atomically. 2086.Pp 2087One or more entries can be added to a table at once using 2088.Cm add 2089command. 2090Addition of all items are performed atomically. 2091By default, error in addition of one entry does not influence 2092addition of other entries. However, non-zero error code is returned 2093in that case. 2094Special 2095.Cm atomic 2096keyword may be specified before 2097.Cm add 2098to indicate all-or-none add request. 2099.Pp 2100One or more entries can be removed from a table at once using 2101.Cm delete 2102command. 2103By default, error in removal of one entry does not influence 2104removing of other entries. However, non-zero error code is returned 2105in that case. 2106.Pp 2107It may be possible to check what entry will be found on particular 2108.Ar table-key 2109using 2110.Cm lookup 2111.Ar table-key 2112command. 2113This functionality is optional and may be unsupported in some algorithms. 2114.Pp 2115The following operations can be performed on 2116.Ar one 2117or 2118.Cm all 2119tables: 2120.Bl -tag -width indent 2121.It Cm list 2122List all entries. 2123.It Cm flush 2124Removes all entries. 2125.It Cm info 2126Shows generic table information. 2127.It Cm detail 2128Shows generic table information and algo-specific data. 2129.El 2130.Pp 2131The following lookup algorithms are supported: 2132.Bl -tag -width indent 2133.It Ar algo-desc : algo-name | "algo-name algo-data" 2134.It Ar algo-name: Ar addr:radix | addr:hash | iface:array | number:array | flow:hash 2135.It Cm addr:radix 2136Separate Radix trees for IPv4 and IPv6, the same way as the routing table (see 2137.Xr route 4 ) . 2138Default choice for 2139.Ar addr 2140type. 2141.It Cm addr:hash 2142Separate auto-growing hashes for IPv4 and IPv6. 2143Accepts entries with the same mask length specified initially via 2144.Cm "addr:hash masks=/v4,/v6" 2145algorithm creation options. 2146Assume /32 and /128 masks by default. 2147Search removes host bits (according to mask) from supplied address and checks 2148resulting key in appropriate hash. 2149Mostly optimized for /64 and byte-ranged IPv6 masks. 2150.It Cm iface:array 2151Array storing sorted indexes for entries which are presented in the system. 2152Optimized for very fast lookup. 2153.It Cm number:array 2154Array storing sorted u32 numbers. 2155.It Cm flow:hash 2156Auto-growing hash storing flow entries. 2157Search calculates hash on required packet fields and searches for matching 2158entries in selected bucket. 2159.El 2160.Pp 2161The 2162.Cm tablearg 2163feature provides the ability to use a value, looked up in the table, as 2164the argument for a rule action, action parameter or rule option. 2165This can significantly reduce number of rules in some configurations. 2166If two tables are used in a rule, the result of the second (destination) 2167is used. 2168.Pp 2169Each record may hold one or more values according to 2170.Ar value-mask . 2171This mask is set on table creation via 2172.Cm valtype 2173option. 2174The following value types are supported: 2175.Bl -tag -width indent 2176.It Ar value-mask : Ar value-type Ns Op , Ns Ar value-mask 2177.It Ar value-type : Ar skipto | pipe | fib | nat | dscp | tag | divert | 2178.Ar netgraph | limit | ipv4 2179.It Cm skipto 2180rule number to jump to. 2181.It Cm pipe 2182Pipe number to use. 2183.It Cm fib 2184fib number to match/set. 2185.It Cm nat 2186nat number to jump to. 2187.It Cm dscp 2188dscp value to match/set. 2189.It Cm tag 2190tag number to match/set. 2191.It Cm divert 2192port number to divert traffic to. 2193.It Cm netgraph 2194hook number to move packet to. 2195.It Cm limit 2196maximum number of connections. 2197.It Cm ipv4 2198IPv4 nexthop to fwd packets to. 2199.It Cm ipv6 2200IPv6 nexthop to fwd packets to. 2201.El 2202.Pp 2203The 2204.Cm tablearg 2205argument can be used with the following actions: 2206.Cm nat, pipe , queue, divert, tee, netgraph, ngtee, fwd, skipto, setfib, 2207action parameters: 2208.Cm tag, untag, 2209rule options: 2210.Cm limit, tagged. 2211.Pp 2212When used with the 2213.Cm skipto 2214action, the user should be aware that the code will walk the ruleset 2215up to a rule equal to, or past, the given number. 2216.Pp 2217See the 2218.Sx EXAMPLES 2219Section for example usage of tables and the tablearg keyword. 2220.Sh SETS OF RULES 2221Each rule or table belongs to one of 32 different 2222.Em sets 2223, numbered 0 to 31. 2224Set 31 is reserved for the default rule. 2225.Pp 2226By default, rules or tables are put in set 0, unless you use the 2227.Cm set N 2228attribute when adding a new rule or table. 2229Sets can be individually and atomically enabled or disabled, 2230so this mechanism permits an easy way to store multiple configurations 2231of the firewall and quickly (and atomically) switch between them. 2232.Pp 2233By default, tables from set 0 are referenced when adding rule with 2234table opcodes regardless of rule set. 2235This behavior can be changed by setting 2236.Va net.inet.ip.fw.tables_set 2237variable to 1. 2238Rule's set will then be used for table references. 2239.Pp 2240The command to enable/disable sets is 2241.Bd -ragged -offset indent 2242.Nm 2243.Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ... 2244.Ed 2245.Pp 2246where multiple 2247.Cm enable 2248or 2249.Cm disable 2250sections can be specified. 2251Command execution is atomic on all the sets specified in the command. 2252By default, all sets are enabled. 2253.Pp 2254When you disable a set, its rules behave as if they do not exist 2255in the firewall configuration, with only one exception: 2256.Bd -ragged -offset indent 2257dynamic rules created from a rule before it had been disabled 2258will still be active until they expire. 2259In order to delete 2260dynamic rules you have to explicitly delete the parent rule 2261which generated them. 2262.Ed 2263.Pp 2264The set number of rules can be changed with the command 2265.Bd -ragged -offset indent 2266.Nm 2267.Cm set move 2268.Brq Cm rule Ar rule-number | old-set 2269.Cm to Ar new-set 2270.Ed 2271.Pp 2272Also, you can atomically swap two rulesets with the command 2273.Bd -ragged -offset indent 2274.Nm 2275.Cm set swap Ar first-set second-set 2276.Ed 2277.Pp 2278See the 2279.Sx EXAMPLES 2280Section on some possible uses of sets of rules. 2281.Sh STATEFUL FIREWALL 2282Stateful operation is a way for the firewall to dynamically 2283create rules for specific flows when packets that 2284match a given pattern are detected. 2285Support for stateful 2286operation comes through the 2287.Cm check-state , keep-state 2288and 2289.Cm limit 2290options of 2291.Nm rules . 2292.Pp 2293Dynamic rules are created when a packet matches a 2294.Cm keep-state 2295or 2296.Cm limit 2297rule, causing the creation of a 2298.Em dynamic 2299rule which will match all and only packets with 2300a given 2301.Em protocol 2302between a 2303.Em src-ip/src-port dst-ip/dst-port 2304pair of addresses 2305.Em ( src 2306and 2307.Em dst 2308are used here only to denote the initial match addresses, but they 2309are completely equivalent afterwards). 2310Rules created by 2311.Cm keep-state 2312option also have a 2313.Ar :flowname 2314taken from it. 2315This name is used in matching together with addresses, ports and protocol. 2316Dynamic rules will be checked at the first 2317.Cm check-state, keep-state 2318or 2319.Cm limit 2320occurrence, and the action performed upon a match will be the same 2321as in the parent rule. 2322.Pp 2323Note that no additional attributes other than protocol and IP addresses 2324and ports and :flowname are checked on dynamic rules. 2325.Pp 2326The typical use of dynamic rules is to keep a closed firewall configuration, 2327but let the first TCP SYN packet from the inside network install a 2328dynamic rule for the flow so that packets belonging to that session 2329will be allowed through the firewall: 2330.Pp 2331.Dl "ipfw add check-state :OUTBOUND" 2332.Dl "ipfw add allow tcp from my-subnet to any setup keep-state :OUTBOUND" 2333.Dl "ipfw add deny tcp from any to any" 2334.Pp 2335A similar approach can be used for UDP, where an UDP packet coming 2336from the inside will install a dynamic rule to let the response through 2337the firewall: 2338.Pp 2339.Dl "ipfw add check-state :OUTBOUND" 2340.Dl "ipfw add allow udp from my-subnet to any keep-state :OUTBOUND" 2341.Dl "ipfw add deny udp from any to any" 2342.Pp 2343Dynamic rules expire after some time, which depends on the status 2344of the flow and the setting of some 2345.Cm sysctl 2346variables. 2347See Section 2348.Sx SYSCTL VARIABLES 2349for more details. 2350For TCP sessions, dynamic rules can be instructed to periodically 2351send keepalive packets to refresh the state of the rule when it is 2352about to expire. 2353.Pp 2354See Section 2355.Sx EXAMPLES 2356for more examples on how to use dynamic rules. 2357.Sh TRAFFIC SHAPER (DUMMYNET) CONFIGURATION 2358.Nm 2359is also the user interface for the 2360.Nm dummynet 2361traffic shaper, packet scheduler and network emulator, a subsystem that 2362can artificially queue, delay or drop packets 2363emulating the behaviour of certain network links 2364or queueing systems. 2365.Pp 2366.Nm dummynet 2367operates by first using the firewall to select packets 2368using any match pattern that can be used in 2369.Nm 2370rules. 2371Matching packets are then passed to either of two 2372different objects, which implement the traffic regulation: 2373.Bl -hang -offset XXXX 2374.It Em pipe 2375A 2376.Em pipe 2377emulates a 2378.Em link 2379with given bandwidth and propagation delay, 2380driven by a FIFO scheduler and a single queue with programmable 2381queue size and packet loss rate. 2382Packets are appended to the queue as they come out from 2383.Nm ipfw , 2384and then transferred in FIFO order to the link at the desired rate. 2385.It Em queue 2386A 2387.Em queue 2388is an abstraction used to implement packet scheduling 2389using one of several packet scheduling algorithms. 2390Packets sent to a 2391.Em queue 2392are first grouped into flows according to a mask on the 5-tuple. 2393Flows are then passed to the scheduler associated to the 2394.Em queue , 2395and each flow uses scheduling parameters (weight and others) 2396as configured in the 2397.Em queue 2398itself. 2399A scheduler in turn is connected to an emulated link, 2400and arbitrates the link's bandwidth among backlogged flows according to 2401weights and to the features of the scheduling algorithm in use. 2402.El 2403.Pp 2404In practice, 2405.Em pipes 2406can be used to set hard limits to the bandwidth that a flow can use, whereas 2407.Em queues 2408can be used to determine how different flows share the available bandwidth. 2409.Pp 2410A graphical representation of the binding of queues, 2411flows, schedulers and links is below. 2412.Bd -literal -offset indent 2413 (flow_mask|sched_mask) sched_mask 2414 +---------+ weight Wx +-------------+ 2415 | |->-[flow]-->--| |-+ 2416 -->--| QUEUE x | ... | | | 2417 | |->-[flow]-->--| SCHEDuler N | | 2418 +---------+ | | | 2419 ... | +--[LINK N]-->-- 2420 +---------+ weight Wy | | +--[LINK N]-->-- 2421 | |->-[flow]-->--| | | 2422 -->--| QUEUE y | ... | | | 2423 | |->-[flow]-->--| | | 2424 +---------+ +-------------+ | 2425 +-------------+ 2426.Ed 2427It is important to understand the role of the SCHED_MASK 2428and FLOW_MASK, which are configured through the commands 2429.Dl "ipfw sched N config mask SCHED_MASK ..." 2430and 2431.Dl "ipfw queue X config mask FLOW_MASK ..." . 2432.Pp 2433The SCHED_MASK is used to assign flows to one or more 2434scheduler instances, one for each 2435value of the packet's 5-tuple after applying SCHED_MASK. 2436As an example, using ``src-ip 0xffffff00'' creates one instance 2437for each /24 destination subnet. 2438.Pp 2439The FLOW_MASK, together with the SCHED_MASK, is used to split 2440packets into flows. 2441As an example, using 2442``src-ip 0x000000ff'' 2443together with the previous SCHED_MASK makes a flow for 2444each individual source address. 2445In turn, flows for each /24 2446subnet will be sent to the same scheduler instance. 2447.Pp 2448The above diagram holds even for the 2449.Em pipe 2450case, with the only restriction that a 2451.Em pipe 2452only supports a SCHED_MASK, and forces the use of a FIFO 2453scheduler (these are for backward compatibility reasons; 2454in fact, internally, a 2455.Nm dummynet's 2456pipe is implemented exactly as above). 2457.Pp 2458There are two modes of 2459.Nm dummynet 2460operation: 2461.Dq normal 2462and 2463.Dq fast . 2464The 2465.Dq normal 2466mode tries to emulate a real link: the 2467.Nm dummynet 2468scheduler ensures that the packet will not leave the pipe faster than it 2469would on the real link with a given bandwidth. 2470The 2471.Dq fast 2472mode allows certain packets to bypass the 2473.Nm dummynet 2474scheduler (if packet flow does not exceed pipe's bandwidth). 2475This is the reason why the 2476.Dq fast 2477mode requires less CPU cycles per packet (on average) and packet latency 2478can be significantly lower in comparison to a real link with the same 2479bandwidth. 2480The default mode is 2481.Dq normal . 2482The 2483.Dq fast 2484mode can be enabled by setting the 2485.Va net.inet.ip.dummynet.io_fast 2486.Xr sysctl 8 2487variable to a non-zero value. 2488.Pp 2489.Ss PIPE, QUEUE AND SCHEDULER CONFIGURATION 2490The 2491.Em pipe , 2492.Em queue 2493and 2494.Em scheduler 2495configuration commands are the following: 2496.Bd -ragged -offset indent 2497.Cm pipe Ar number Cm config Ar pipe-configuration 2498.Pp 2499.Cm queue Ar number Cm config Ar queue-configuration 2500.Pp 2501.Cm sched Ar number Cm config Ar sched-configuration 2502.Ed 2503.Pp 2504The following parameters can be configured for a pipe: 2505.Pp 2506.Bl -tag -width indent -compact 2507.It Cm bw Ar bandwidth | device 2508Bandwidth, measured in 2509.Sm off 2510.Op Cm K | M | G 2511.Brq Cm bit/s | Byte/s . 2512.Sm on 2513.Pp 2514A value of 0 (default) means unlimited bandwidth. 2515The unit must immediately follow the number, as in 2516.Pp 2517.Dl "ipfw pipe 1 config bw 300Kbit/s" 2518.Pp 2519If a device name is specified instead of a numeric value, as in 2520.Pp 2521.Dl "ipfw pipe 1 config bw tun0" 2522.Pp 2523then the transmit clock is supplied by the specified device. 2524At the moment only the 2525.Xr tun 4 2526device supports this 2527functionality, for use in conjunction with 2528.Xr ppp 8 . 2529.Pp 2530.It Cm delay Ar ms-delay 2531Propagation delay, measured in milliseconds. 2532The value is rounded to the next multiple of the clock tick 2533(typically 10ms, but it is a good practice to run kernels 2534with 2535.Dq "options HZ=1000" 2536to reduce 2537the granularity to 1ms or less). 2538The default value is 0, meaning no delay. 2539.Pp 2540.It Cm burst Ar size 2541If the data to be sent exceeds the pipe's bandwidth limit 2542(and the pipe was previously idle), up to 2543.Ar size 2544bytes of data are allowed to bypass the 2545.Nm dummynet 2546scheduler, and will be sent as fast as the physical link allows. 2547Any additional data will be transmitted at the rate specified 2548by the 2549.Nm pipe 2550bandwidth. 2551The burst size depends on how long the pipe has been idle; 2552the effective burst size is calculated as follows: 2553MAX( 2554.Ar size 2555, 2556.Nm bw 2557* pipe_idle_time). 2558.Pp 2559.It Cm profile Ar filename 2560A file specifying the additional overhead incurred in the transmission 2561of a packet on the link. 2562.Pp 2563Some link types introduce extra delays in the transmission 2564of a packet, e.g., because of MAC level framing, contention on 2565the use of the channel, MAC level retransmissions and so on. 2566From our point of view, the channel is effectively unavailable 2567for this extra time, which is constant or variable depending 2568on the link type. 2569Additionally, packets may be dropped after this 2570time (e.g., on a wireless link after too many retransmissions). 2571We can model the additional delay with an empirical curve 2572that represents its distribution. 2573.Bd -literal -offset indent 2574 cumulative probability 2575 1.0 ^ 2576 | 2577 L +-- loss-level x 2578 | ****** 2579 | * 2580 | ***** 2581 | * 2582 | ** 2583 | * 2584 +-------*-------------------> 2585 delay 2586.Ed 2587The empirical curve may have both vertical and horizontal lines. 2588Vertical lines represent constant delay for a range of 2589probabilities. 2590Horizontal lines correspond to a discontinuity in the delay 2591distribution: the pipe will use the largest delay for a 2592given probability. 2593.Pp 2594The file format is the following, with whitespace acting as 2595a separator and '#' indicating the beginning a comment: 2596.Bl -tag -width indent 2597.It Cm name Ar identifier 2598optional name (listed by "ipfw pipe show") 2599to identify the delay distribution; 2600.It Cm bw Ar value 2601the bandwidth used for the pipe. 2602If not specified here, it must be present 2603explicitly as a configuration parameter for the pipe; 2604.It Cm loss-level Ar L 2605the probability above which packets are lost. 2606(0.0 <= L <= 1.0, default 1.0 i.e., no loss); 2607.It Cm samples Ar N 2608the number of samples used in the internal 2609representation of the curve (2..1024; default 100); 2610.It Cm "delay prob" | "prob delay" 2611One of these two lines is mandatory and defines 2612the format of the following lines with data points. 2613.It Ar XXX Ar YYY 26142 or more lines representing points in the curve, 2615with either delay or probability first, according 2616to the chosen format. 2617The unit for delay is milliseconds. 2618Data points do not need to be sorted. 2619Also, the number of actual lines can be different 2620from the value of the "samples" parameter: 2621.Nm 2622utility will sort and interpolate 2623the curve as needed. 2624.El 2625.Pp 2626Example of a profile file: 2627.Bd -literal -offset indent 2628name bla_bla_bla 2629samples 100 2630loss-level 0.86 2631prob delay 26320 200 # minimum overhead is 200ms 26330.5 200 26340.5 300 26350.8 1000 26360.9 1300 26371 1300 2638#configuration file end 2639.Ed 2640.El 2641.Pp 2642The following parameters can be configured for a queue: 2643.Pp 2644.Bl -tag -width indent -compact 2645.It Cm pipe Ar pipe_nr 2646Connects a queue to the specified pipe. 2647Multiple queues (with the same or different weights) can be connected to 2648the same pipe, which specifies the aggregate rate for the set of queues. 2649.Pp 2650.It Cm weight Ar weight 2651Specifies the weight to be used for flows matching this queue. 2652The weight must be in the range 1..100, and defaults to 1. 2653.El 2654.Pp 2655The following case-insensitive parameters can be configured for a 2656scheduler: 2657.Pp 2658.Bl -tag -width indent -compact 2659.It Cm type Ar {fifo | wf2q+ | rr | qfq} 2660specifies the scheduling algorithm to use. 2661.Bl -tag -width indent -compact 2662.It Cm fifo 2663is just a FIFO scheduler (which means that all packets 2664are stored in the same queue as they arrive to the scheduler). 2665FIFO has O(1) per-packet time complexity, with very low 2666constants (estimate 60-80ns on a 2GHz desktop machine) 2667but gives no service guarantees. 2668.It Cm wf2q+ 2669implements the WF2Q+ algorithm, which is a Weighted Fair Queueing 2670algorithm which permits flows to share bandwidth according to 2671their weights. 2672Note that weights are not priorities; even a flow 2673with a minuscule weight will never starve. 2674WF2Q+ has O(log N) per-packet processing cost, where N is the number 2675of flows, and is the default algorithm used by previous versions 2676dummynet's queues. 2677.It Cm rr 2678implements the Deficit Round Robin algorithm, which has O(1) processing 2679costs (roughly, 100-150ns per packet) 2680and permits bandwidth allocation according to weights, but 2681with poor service guarantees. 2682.It Cm qfq 2683implements the QFQ algorithm, which is a very fast variant of 2684WF2Q+, with similar service guarantees and O(1) processing 2685costs (roughly, 200-250ns per packet). 2686.El 2687.El 2688.Pp 2689In addition to the type, all parameters allowed for a pipe can also 2690be specified for a scheduler. 2691.Pp 2692Finally, the following parameters can be configured for both 2693pipes and queues: 2694.Pp 2695.Bl -tag -width XXXX -compact 2696.It Cm buckets Ar hash-table-size 2697Specifies the size of the hash table used for storing the 2698various queues. 2699Default value is 64 controlled by the 2700.Xr sysctl 8 2701variable 2702.Va net.inet.ip.dummynet.hash_size , 2703allowed range is 16 to 65536. 2704.Pp 2705.It Cm mask Ar mask-specifier 2706Packets sent to a given pipe or queue by an 2707.Nm 2708rule can be further classified into multiple flows, each of which is then 2709sent to a different 2710.Em dynamic 2711pipe or queue. 2712A flow identifier is constructed by masking the IP addresses, 2713ports and protocol types as specified with the 2714.Cm mask 2715options in the configuration of the pipe or queue. 2716For each different flow identifier, a new pipe or queue is created 2717with the same parameters as the original object, and matching packets 2718are sent to it. 2719.Pp 2720Thus, when 2721.Em dynamic pipes 2722are used, each flow will get the same bandwidth as defined by the pipe, 2723whereas when 2724.Em dynamic queues 2725are used, each flow will share the parent's pipe bandwidth evenly 2726with other flows generated by the same queue (note that other queues 2727with different weights might be connected to the same pipe). 2728.br 2729Available mask specifiers are a combination of one or more of the following: 2730.Pp 2731.Cm dst-ip Ar mask , 2732.Cm dst-ip6 Ar mask , 2733.Cm src-ip Ar mask , 2734.Cm src-ip6 Ar mask , 2735.Cm dst-port Ar mask , 2736.Cm src-port Ar mask , 2737.Cm flow-id Ar mask , 2738.Cm proto Ar mask 2739or 2740.Cm all , 2741.Pp 2742where the latter means all bits in all fields are significant. 2743.Pp 2744.It Cm noerror 2745When a packet is dropped by a 2746.Nm dummynet 2747queue or pipe, the error 2748is normally reported to the caller routine in the kernel, in the 2749same way as it happens when a device queue fills up. 2750Setting this 2751option reports the packet as successfully delivered, which can be 2752needed for some experimental setups where you want to simulate 2753loss or congestion at a remote router. 2754.Pp 2755.It Cm plr Ar packet-loss-rate 2756Packet loss rate. 2757Argument 2758.Ar packet-loss-rate 2759is a floating-point number between 0 and 1, with 0 meaning no 2760loss, 1 meaning 100% loss. 2761The loss rate is internally represented on 31 bits. 2762.Pp 2763.It Cm queue Brq Ar slots | size Ns Cm Kbytes 2764Queue size, in 2765.Ar slots 2766or 2767.Cm KBytes . 2768Default value is 50 slots, which 2769is the typical queue size for Ethernet devices. 2770Note that for slow speed links you should keep the queue 2771size short or your traffic might be affected by a significant 2772queueing delay. 2773E.g., 50 max-sized ethernet packets (1500 bytes) mean 600Kbit 2774or 20s of queue on a 30Kbit/s pipe. 2775Even worse effects can result if you get packets from an 2776interface with a much larger MTU, e.g.\& the loopback interface 2777with its 16KB packets. 2778The 2779.Xr sysctl 8 2780variables 2781.Em net.inet.ip.dummynet.pipe_byte_limit 2782and 2783.Em net.inet.ip.dummynet.pipe_slot_limit 2784control the maximum lengths that can be specified. 2785.Pp 2786.It Cm red | gred Ar w_q Ns / Ns Ar min_th Ns / Ns Ar max_th Ns / Ns Ar max_p 2787[ecn] 2788Make use of the RED (Random Early Detection) queue management algorithm. 2789.Ar w_q 2790and 2791.Ar max_p 2792are floating 2793point numbers between 0 and 1 (inclusive), while 2794.Ar min_th 2795and 2796.Ar max_th 2797are integer numbers specifying thresholds for queue management 2798(thresholds are computed in bytes if the queue has been defined 2799in bytes, in slots otherwise). 2800The two parameters can also be of the same value if needed. The 2801.Nm dummynet 2802also supports the gentle RED variant (gred) and ECN (Explicit Congestion 2803Notification) as optional. Three 2804.Xr sysctl 8 2805variables can be used to control the RED behaviour: 2806.Bl -tag -width indent 2807.It Va net.inet.ip.dummynet.red_lookup_depth 2808specifies the accuracy in computing the average queue 2809when the link is idle (defaults to 256, must be greater than zero) 2810.It Va net.inet.ip.dummynet.red_avg_pkt_size 2811specifies the expected average packet size (defaults to 512, must be 2812greater than zero) 2813.It Va net.inet.ip.dummynet.red_max_pkt_size 2814specifies the expected maximum packet size, only used when queue 2815thresholds are in bytes (defaults to 1500, must be greater than zero). 2816.El 2817.El 2818.Pp 2819When used with IPv6 data, 2820.Nm dummynet 2821currently has several limitations. 2822Information necessary to route link-local packets to an 2823interface is not available after processing by 2824.Nm dummynet 2825so those packets are dropped in the output path. 2826Care should be taken to ensure that link-local packets are not passed to 2827.Nm dummynet . 2828.Sh CHECKLIST 2829Here are some important points to consider when designing your 2830rules: 2831.Bl -bullet 2832.It 2833Remember that you filter both packets going 2834.Cm in 2835and 2836.Cm out . 2837Most connections need packets going in both directions. 2838.It 2839Remember to test very carefully. 2840It is a good idea to be near the console when doing this. 2841If you cannot be near the console, 2842use an auto-recovery script such as the one in 2843.Pa /usr/share/examples/ipfw/change_rules.sh . 2844.It 2845Do not forget the loopback interface. 2846.El 2847.Sh FINE POINTS 2848.Bl -bullet 2849.It 2850There are circumstances where fragmented datagrams are unconditionally 2851dropped. 2852TCP packets are dropped if they do not contain at least 20 bytes of 2853TCP header, UDP packets are dropped if they do not contain a full 8 2854byte UDP header, and ICMP packets are dropped if they do not contain 28554 bytes of ICMP header, enough to specify the ICMP type, code, and 2856checksum. 2857These packets are simply logged as 2858.Dq pullup failed 2859since there may not be enough good data in the packet to produce a 2860meaningful log entry. 2861.It 2862Another type of packet is unconditionally dropped, a TCP packet with a 2863fragment offset of one. 2864This is a valid packet, but it only has one use, to try 2865to circumvent firewalls. 2866When logging is enabled, these packets are 2867reported as being dropped by rule -1. 2868.It 2869If you are logged in over a network, loading the 2870.Xr kld 4 2871version of 2872.Nm 2873is probably not as straightforward as you would think. 2874The following command line is recommended: 2875.Bd -literal -offset indent 2876kldload ipfw && \e 2877ipfw add 32000 allow ip from any to any 2878.Ed 2879.Pp 2880Along the same lines, doing an 2881.Bd -literal -offset indent 2882ipfw flush 2883.Ed 2884.Pp 2885in similar surroundings is also a bad idea. 2886.It 2887The 2888.Nm 2889filter list may not be modified if the system security level 2890is set to 3 or higher 2891(see 2892.Xr init 8 2893for information on system security levels). 2894.El 2895.Sh PACKET DIVERSION 2896A 2897.Xr divert 4 2898socket bound to the specified port will receive all packets 2899diverted to that port. 2900If no socket is bound to the destination port, or if the divert module is 2901not loaded, or if the kernel was not compiled with divert socket support, 2902the packets are dropped. 2903.Sh NETWORK ADDRESS TRANSLATION (NAT) 2904.Nm 2905support in-kernel NAT using the kernel version of 2906.Xr libalias 3 . 2907The kernel module 2908.Cm ipfw_nat 2909should be loaded or kernel should have 2910.Cm options IPFIREWALL_NAT 2911to be able use NAT. 2912.Pp 2913The nat configuration command is the following: 2914.Bd -ragged -offset indent 2915.Bk -words 2916.Cm nat 2917.Ar nat_number 2918.Cm config 2919.Ar nat-configuration 2920.Ek 2921.Ed 2922.Pp 2923The following parameters can be configured: 2924.Bl -tag -width indent 2925.It Cm ip Ar ip_address 2926Define an ip address to use for aliasing. 2927.It Cm if Ar nic 2928Use ip address of NIC for aliasing, dynamically changing 2929it if NIC's ip address changes. 2930.It Cm log 2931Enable logging on this nat instance. 2932.It Cm deny_in 2933Deny any incoming connection from outside world. 2934.It Cm same_ports 2935Try to leave the alias port numbers unchanged from 2936the actual local port numbers. 2937.It Cm unreg_only 2938Traffic on the local network not originating from an 2939unregistered address spaces will be ignored. 2940.It Cm reset 2941Reset table of the packet aliasing engine on address change. 2942.It Cm reverse 2943Reverse the way libalias handles aliasing. 2944.It Cm proxy_only 2945Obey transparent proxy rules only, packet aliasing is not performed. 2946.It Cm skip_global 2947Skip instance in case of global state lookup (see below). 2948.El 2949.Pp 2950Some specials value can be supplied instead of 2951.Va nat_number: 2952.Bl -tag -width indent 2953.It Cm global 2954Looks up translation state in all configured nat instances. 2955If an entry is found, packet is aliased according to that entry. 2956If no entry was found in any of the instances, packet is passed unchanged, 2957and no new entry will be created. 2958See section 2959.Sx MULTIPLE INSTANCES 2960in 2961.Xr natd 8 2962for more information. 2963.It Cm tablearg 2964Uses argument supplied in lookup table. 2965See 2966.Sx LOOKUP TABLES 2967section below for more information on lookup tables. 2968.El 2969.Pp 2970To let the packet continue after being (de)aliased, set the sysctl variable 2971.Va net.inet.ip.fw.one_pass 2972to 0. 2973For more information about aliasing modes, refer to 2974.Xr libalias 3 . 2975See Section 2976.Sx EXAMPLES 2977for some examples about nat usage. 2978.Ss REDIRECT AND LSNAT SUPPORT IN IPFW 2979Redirect and LSNAT support follow closely the syntax used in 2980.Xr natd 8 . 2981See Section 2982.Sx EXAMPLES 2983for some examples on how to do redirect and lsnat. 2984.Ss SCTP NAT SUPPORT 2985SCTP nat can be configured in a similar manner to TCP through the 2986.Nm 2987command line tool. 2988The main difference is that 2989.Nm sctp nat 2990does not do port translation. 2991Since the local and global side ports will be the same, 2992there is no need to specify both. 2993Ports are redirected as follows: 2994.Bd -ragged -offset indent 2995.Bk -words 2996.Cm nat 2997.Ar nat_number 2998.Cm config if 2999.Ar nic 3000.Cm redirect_port sctp 3001.Ar ip_address [,addr_list] {[port | port-port] [,ports]} 3002.Ek 3003.Ed 3004.Pp 3005Most 3006.Nm sctp nat 3007configuration can be done in real-time through the 3008.Xr sysctl 8 3009interface. 3010All may be changed dynamically, though the hash_table size will only 3011change for new 3012.Nm nat 3013instances. 3014See 3015.Sx SYSCTL VARIABLES 3016for more info. 3017.Sh IPv6/IPv4 NETWORK ADDRESS AND PROTOCOL TRANSLATION 3018.Nm 3019supports in-kernel IPv6/IPv4 network address and protocol translation. 3020Stateful NAT64 translation allows IPv6-only clients to contact IPv4 servers 3021using unicast TCP, UDP or ICMP protocols. 3022One or more IPv4 addresses assigned to a stateful NAT64 translator are shared 3023among several IPv6-only clients. 3024When stateful NAT64 is used in conjunction with DNS64, no changes are usually 3025required in the IPv6 client or the IPv4 server. 3026The kernel module 3027.Cm ipfw_nat64 3028should be loaded or kernel should have 3029.Cm options IPFIREWALL_NAT64 3030to be able use stateful NAT64 translator. 3031.Pp 3032Stateful NAT64 uses a bunch of memory for several types of objects. 3033When IPv6 client initiates connection, NAT64 translator creates a host entry 3034in the states table. 3035Each host entry has a number of ports group entries allocated on demand. 3036Ports group entries contains connection state entries. 3037There are several options to control limits and lifetime for these objects. 3038.Pp 3039NAT64 translator follows RFC7915 when does ICMPv6/ICMP translation, 3040unsupported message types will be silently dropped. 3041IPv6 needs several ICMPv6 message types to be explicitly allowed for correct 3042operation. 3043Make sure that ND6 neighbor solicitation (ICMPv6 type 135) and neighbor 3044advertisement (ICMPv6 type 136) messages will not be handled by translation 3045rules. 3046.Pp 3047After translation NAT64 translator sends packets through corresponding netisr 3048queue. 3049Thus translator host should be configured as IPv4 and IPv6 router. 3050.Pp 3051Currently both stateful and stateless NAT64 translators use Well-Known IPv6 3052Prefix 3053.Ar 64:ff9b::/96 3054to represent IPv4 addresses in the IPv6 address. 3055Thus DNS64 service and routing should be configured to use Well-Known IPv6 3056Prefix. 3057.Pp 3058The stateful NAT64 configuration command is the following: 3059.Bd -ragged -offset indent 3060.Bk -words 3061.Cm nat64lsn 3062.Ar name 3063.Cm create 3064.Ar create-options 3065.Ek 3066.Ed 3067.Pp 3068The following parameters can be configured: 3069.Bl -tag -width indent 3070.It Cm prefix4 Ar ipv4_prefix/mask 3071The IPv4 prefix with mask defines the pool of IPv4 addresses used as 3072source address after translation. 3073Stateful NAT64 module translates IPv6 source address of client to one 3074IPv4 address from this pool. 3075Note that incoming IPv4 packets that don't have corresponding state entry 3076in the states table will be dropped by translator. 3077Make sure that translation rules handle packets, destined to configured prefix. 3078.It Cm max_ports Ar number 3079Maximum number of ports reserved for upper level protocols to one IPv6 client. 3080All reserved ports are divided into chunks between supported protocols. 3081The number of connections from one IPv6 client is limited by this option. 3082Note that closed TCP connections still remain in the list of connections until 3083.Cm tcp_close_age 3084interval will not expire. 3085Default value is 3086.Ar 2048 . 3087.It Cm host_del_age Ar seconds 3088The number of seconds until the host entry for a IPv6 client will be deleted 3089and all its resources will be released due to inactivity. 3090Default value is 3091.Ar 3600 . 3092.It Cm pg_del_age Ar seconds 3093The number of seconds until a ports group with unused state entries will 3094be released. 3095Default value is 3096.Ar 900 . 3097.It Cm tcp_syn_age Ar seconds 3098The number of seconds while a state entry for TCP connection with only SYN 3099sent will be kept. 3100If TCP connection establishing will not be finished, 3101state entry will be deleted. 3102Default value is 3103.Ar 10 . 3104.It Cm tcp_est_age Ar seconds 3105The number of seconds while a state entry for established TCP connection 3106will be kept. 3107Default value is 3108.Ar 7200 . 3109.It Cm tcp_close_age Ar seconds 3110The number of seconds while a state entry for closed TCP connection 3111will be kept. 3112Keeping state entries for closed connections is needed, because IPv4 servers 3113typically keep closed connections in a TIME_WAIT state for a several minutes. 3114Since translator's IPv4 addresses are shared among all IPv6 clients, 3115new connections from the same addresses and ports may be rejected by server, 3116because these connections are still in a TIME_WAIT state. 3117Keeping them in translator's state table protects from such rejects. 3118Default value is 3119.Ar 180 . 3120.It Cm udp_age Ar seconds 3121The number of seconds while translator keeps state entry in a waiting for 3122reply to the sent UDP datagram. 3123Default value is 3124.Ar 120 . 3125.It Cm icmp_age Ar seconds 3126The number of seconds while translator keeps state entry in a waiting for 3127reply to the sent ICMP message. 3128Default value is 3129.Ar 60 . 3130.It Cm log 3131Turn on logging of all handled packets via BPF through 3132.Ar ipfwlog0 3133interface. 3134.Ar ipfwlog0 3135is a pseudo interface and can be created after a boot manually with 3136.Cm ifconfig 3137command. 3138Note that it has different purpose than 3139.Ar ipfw0 3140interface. 3141Translators sends to BPF an additional information with each packet. 3142With 3143.Cm tcpdump 3144you are able to see each handled packet before and after translation. 3145.It Cm -log 3146Turn off logging of all handled packets via BPF. 3147.El 3148.Pp 3149To inspect a states table of stateful NAT64 the following command can be used: 3150.Bd -ragged -offset indent 3151.Bk -words 3152.Cm nat64lsn 3153.Ar name 3154.Cm show Cm states 3155.Ek 3156.Ed 3157.Pp 3158.Pp 3159Stateless NAT64 translator doesn't use a states table for translation 3160and converts IPv4 addresses to IPv6 and vice versa solely based on the 3161mappings taken from configured lookup tables. 3162Since a states table doesn't used by stateless translator, 3163it can be configured to pass IPv4 clients to IPv6-only servers. 3164.Pp 3165The stateless NAT64 configuration command is the following: 3166.Bd -ragged -offset indent 3167.Bk -words 3168.Cm nat64stl 3169.Ar name 3170.Cm create 3171.Ar create-options 3172.Ek 3173.Ed 3174.Pp 3175The following parameters can be configured: 3176.Bl -tag -width indent 3177.It Cm table4 Ar table46 3178The lookup table 3179.Ar table46 3180contains mapping how IPv4 addresses should be translated to IPv6 addresses. 3181.It Cm table6 Ar table64 3182The lookup table 3183.Ar table64 3184contains mapping how IPv6 addresses should be translated to IPv4 addresses. 3185.It Cm log 3186Turn on logging of all handled packets via BPF through 3187.Ar ipfwlog0 3188interface. 3189.It Cm -log 3190Turn off logging of all handled packets via BPF. 3191.El 3192.Pp 3193Note that the behavior of stateless translator with respect to not matched 3194packets differs from stateful translator. 3195If corresponding addresses was not found in the lookup tables, the packet 3196will not be dropped and the search continues. 3197.Sh IPv6-to-IPv6 NETWORK PREFIX TRANSLATION (NPTv6) 3198.Nm 3199supports in-kernel IPv6-to-IPv6 network prefix translation as described 3200in RFC6296. 3201The kernel module 3202.Cm ipfw_nptv6 3203should be loaded or kernel should has 3204.Cm options IPFIREWALL_NPTV6 3205to be able use NPTv6 translator. 3206.Pp 3207The NPTv6 configuration command is the following: 3208.Bd -ragged -offset indent 3209.Bk -words 3210.Cm nptv6 3211.Ar name 3212.Cm create 3213.Ar create-options 3214.Ek 3215.Ed 3216.Pp 3217The following parameters can be configured: 3218.Bl -tag -width indent 3219.It Cm int_prefix Ar ipv6_prefix 3220IPv6 prefix used in internal network. 3221NPTv6 module translates source address when it matches this prefix. 3222.It Cm ext_prefix Ar ipv6_prefix 3223IPv6 prefix used in external network. 3224NPTv6 module translates destination address when it matches this prefix. 3225.It Cm prefixlen Ar length 3226The length of specified IPv6 prefixes. It must be in range from 8 to 64. 3227.El 3228.Pp 3229Note that the prefix translation rules are silently ignored when IPv6 packet 3230forwarding is disabled. 3231To enable the packet forwarding, set the sysctl variable 3232.Va net.inet6.ip6.forwarding 3233to 1. 3234.Pp 3235To let the packet continue after being translated, set the sysctl variable 3236.Va net.inet.ip.fw.one_pass 3237to 0. 3238.Sh LOADER TUNABLES 3239Tunables can be set in 3240.Xr loader 8 3241prompt, 3242.Xr loader.conf 5 3243or 3244.Xr kenv 1 3245before ipfw module gets loaded. 3246.Bl -tag -width indent 3247.It Va net.inet.ip.fw.default_to_accept: No 0 3248Defines ipfw last rule behavior. 3249This value overrides 3250.Cd "options IPFW_DEFAULT_TO_(ACCEPT|DENY)" 3251from kernel configuration file. 3252.It Va net.inet.ip.fw.tables_max: No 128 3253Defines number of tables available in ipfw. 3254Number cannot exceed 65534. 3255.El 3256.Sh SYSCTL VARIABLES 3257A set of 3258.Xr sysctl 8 3259variables controls the behaviour of the firewall and 3260associated modules 3261.Pq Nm dummynet , bridge , sctp nat . 3262These are shown below together with their default value 3263(but always check with the 3264.Xr sysctl 8 3265command what value is actually in use) and meaning: 3266.Bl -tag -width indent 3267.It Va net.inet.ip.alias.sctp.accept_global_ootb_addip: No 0 3268Defines how the 3269.Nm nat 3270responds to receipt of global OOTB ASCONF-AddIP: 3271.Bl -tag -width indent 3272.It Cm 0 3273No response (unless a partially matching association exists - 3274ports and vtags match but global address does not) 3275.It Cm 1 3276.Nm nat 3277will accept and process all OOTB global AddIP messages. 3278.El 3279.Pp 3280Option 1 should never be selected as this forms a security risk. 3281An attacker can 3282establish multiple fake associations by sending AddIP messages. 3283.It Va net.inet.ip.alias.sctp.chunk_proc_limit: No 5 3284Defines the maximum number of chunks in an SCTP packet that will be 3285parsed for a 3286packet that matches an existing association. 3287This value is enforced to be greater or equal than 3288.Cm net.inet.ip.alias.sctp.initialising_chunk_proc_limit . 3289A high value is 3290a DoS risk yet setting too low a value may result in 3291important control chunks in 3292the packet not being located and parsed. 3293.It Va net.inet.ip.alias.sctp.error_on_ootb: No 1 3294Defines when the 3295.Nm nat 3296responds to any Out-of-the-Blue (OOTB) packets with ErrorM packets. 3297An OOTB packet is a packet that arrives with no existing association 3298registered in the 3299.Nm nat 3300and is not an INIT or ASCONF-AddIP packet: 3301.Bl -tag -width indent 3302.It Cm 0 3303ErrorM is never sent in response to OOTB packets. 3304.It Cm 1 3305ErrorM is only sent to OOTB packets received on the local side. 3306.It Cm 2 3307ErrorM is sent to the local side and on the global side ONLY if there is a 3308partial match (ports and vtags match but the source global IP does not). 3309This value is only useful if the 3310.Nm nat 3311is tracking global IP addresses. 3312.It Cm 3 3313ErrorM is sent in response to all OOTB packets on both 3314the local and global side 3315(DoS risk). 3316.El 3317.Pp 3318At the moment the default is 0, since the ErrorM packet is not yet 3319supported by most SCTP stacks. 3320When it is supported, and if not tracking 3321global addresses, we recommend setting this value to 1 to allow 3322multi-homed local hosts to function with the 3323.Nm nat . 3324To track global addresses, we recommend setting this value to 2 to 3325allow global hosts to be informed when they need to (re)send an 3326ASCONF-AddIP. 3327Value 3 should never be chosen (except for debugging) as the 3328.Nm nat 3329will respond to all OOTB global packets (a DoS risk). 3330.It Va net.inet.ip.alias.sctp.hashtable_size: No 2003 3331Size of hash tables used for 3332.Nm nat 3333lookups (100 < prime_number > 1000001). 3334This value sets the 3335.Nm hash table 3336size for any future created 3337.Nm nat 3338instance and therefore must be set prior to creating a 3339.Nm nat 3340instance. 3341The table sizes may be changed to suit specific needs. 3342If there will be few 3343concurrent associations, and memory is scarce, you may make these smaller. 3344If there will be many thousands (or millions) of concurrent associations, you 3345should make these larger. 3346A prime number is best for the table size. 3347The sysctl 3348update function will adjust your input value to the next highest prime number. 3349.It Va net.inet.ip.alias.sctp.holddown_time: No 0 3350Hold association in table for this many seconds after receiving a 3351SHUTDOWN-COMPLETE. 3352This allows endpoints to correct shutdown gracefully if a 3353shutdown_complete is lost and retransmissions are required. 3354.It Va net.inet.ip.alias.sctp.init_timer: No 15 3355Timeout value while waiting for (INIT-ACK|AddIP-ACK). 3356This value cannot be 0. 3357.It Va net.inet.ip.alias.sctp.initialising_chunk_proc_limit: No 2 3358Defines the maximum number of chunks in an SCTP packet that will be parsed when 3359no existing association exists that matches that packet. 3360Ideally this packet 3361will only be an INIT or ASCONF-AddIP packet. 3362A higher value may become a DoS 3363risk as malformed packets can consume processing resources. 3364.It Va net.inet.ip.alias.sctp.param_proc_limit: No 25 3365Defines the maximum number of parameters within a chunk that will be 3366parsed in a 3367packet. 3368As for other similar sysctl variables, larger values pose a DoS risk. 3369.It Va net.inet.ip.alias.sctp.log_level: No 0 3370Level of detail in the system log messages (0 \- minimal, 1 \- event, 33712 \- info, 3 \- detail, 4 \- debug, 5 \- max debug). 3372May be a good 3373option in high loss environments. 3374.It Va net.inet.ip.alias.sctp.shutdown_time: No 15 3375Timeout value while waiting for SHUTDOWN-COMPLETE. 3376This value cannot be 0. 3377.It Va net.inet.ip.alias.sctp.track_global_addresses: No 0 3378Enables/disables global IP address tracking within the 3379.Nm nat 3380and places an 3381upper limit on the number of addresses tracked for each association: 3382.Bl -tag -width indent 3383.It Cm 0 3384Global tracking is disabled 3385.It Cm >1 3386Enables tracking, the maximum number of addresses tracked for each 3387association is limited to this value 3388.El 3389.Pp 3390This variable is fully dynamic, the new value will be adopted for all newly 3391arriving associations, existing associations are treated 3392as they were previously. 3393Global tracking will decrease the number of collisions within the 3394.Nm nat 3395at a cost 3396of increased processing load, memory usage, complexity, and possible 3397.Nm nat 3398state 3399problems in complex networks with multiple 3400.Nm nats . 3401We recommend not tracking 3402global IP addresses, this will still result in a fully functional 3403.Nm nat . 3404.It Va net.inet.ip.alias.sctp.up_timer: No 300 3405Timeout value to keep an association up with no traffic. 3406This value cannot be 0. 3407.It Va net.inet.ip.dummynet.expire : No 1 3408Lazily delete dynamic pipes/queue once they have no pending traffic. 3409You can disable this by setting the variable to 0, in which case 3410the pipes/queues will only be deleted when the threshold is reached. 3411.It Va net.inet.ip.dummynet.hash_size : No 64 3412Default size of the hash table used for dynamic pipes/queues. 3413This value is used when no 3414.Cm buckets 3415option is specified when configuring a pipe/queue. 3416.It Va net.inet.ip.dummynet.io_fast : No 0 3417If set to a non-zero value, 3418the 3419.Dq fast 3420mode of 3421.Nm dummynet 3422operation (see above) is enabled. 3423.It Va net.inet.ip.dummynet.io_pkt 3424Number of packets passed to 3425.Nm dummynet . 3426.It Va net.inet.ip.dummynet.io_pkt_drop 3427Number of packets dropped by 3428.Nm dummynet . 3429.It Va net.inet.ip.dummynet.io_pkt_fast 3430Number of packets bypassed by the 3431.Nm dummynet 3432scheduler. 3433.It Va net.inet.ip.dummynet.max_chain_len : No 16 3434Target value for the maximum number of pipes/queues in a hash bucket. 3435The product 3436.Cm max_chain_len*hash_size 3437is used to determine the threshold over which empty pipes/queues 3438will be expired even when 3439.Cm net.inet.ip.dummynet.expire=0 . 3440.It Va net.inet.ip.dummynet.red_lookup_depth : No 256 3441.It Va net.inet.ip.dummynet.red_avg_pkt_size : No 512 3442.It Va net.inet.ip.dummynet.red_max_pkt_size : No 1500 3443Parameters used in the computations of the drop probability 3444for the RED algorithm. 3445.It Va net.inet.ip.dummynet.pipe_byte_limit : No 1048576 3446.It Va net.inet.ip.dummynet.pipe_slot_limit : No 100 3447The maximum queue size that can be specified in bytes or packets. 3448These limits prevent accidental exhaustion of resources such as mbufs. 3449If you raise these limits, 3450you should make sure the system is configured so that sufficient resources 3451are available. 3452.It Va net.inet.ip.fw.autoinc_step : No 100 3453Delta between rule numbers when auto-generating them. 3454The value must be in the range 1..1000. 3455.It Va net.inet.ip.fw.curr_dyn_buckets : Va net.inet.ip.fw.dyn_buckets 3456The current number of buckets in the hash table for dynamic rules 3457(readonly). 3458.It Va net.inet.ip.fw.debug : No 1 3459Controls debugging messages produced by 3460.Nm . 3461.It Va net.inet.ip.fw.default_rule : No 65535 3462The default rule number (read-only). 3463By the design of 3464.Nm , the default rule is the last one, so its number 3465can also serve as the highest number allowed for a rule. 3466.It Va net.inet.ip.fw.dyn_buckets : No 256 3467The number of buckets in the hash table for dynamic rules. 3468Must be a power of 2, up to 65536. 3469It only takes effect when all dynamic rules have expired, so you 3470are advised to use a 3471.Cm flush 3472command to make sure that the hash table is resized. 3473.It Va net.inet.ip.fw.dyn_count : No 3 3474Current number of dynamic rules 3475(read-only). 3476.It Va net.inet.ip.fw.dyn_keepalive : No 1 3477Enables generation of keepalive packets for 3478.Cm keep-state 3479rules on TCP sessions. 3480A keepalive is generated to both 3481sides of the connection every 5 seconds for the last 20 3482seconds of the lifetime of the rule. 3483.It Va net.inet.ip.fw.dyn_max : No 8192 3484Maximum number of dynamic rules. 3485When you hit this limit, no more dynamic rules can be 3486installed until old ones expire. 3487.It Va net.inet.ip.fw.dyn_ack_lifetime : No 300 3488.It Va net.inet.ip.fw.dyn_syn_lifetime : No 20 3489.It Va net.inet.ip.fw.dyn_fin_lifetime : No 1 3490.It Va net.inet.ip.fw.dyn_rst_lifetime : No 1 3491.It Va net.inet.ip.fw.dyn_udp_lifetime : No 5 3492.It Va net.inet.ip.fw.dyn_short_lifetime : No 30 3493These variables control the lifetime, in seconds, of dynamic 3494rules. 3495Upon the initial SYN exchange the lifetime is kept short, 3496then increased after both SYN have been seen, then decreased 3497again during the final FIN exchange or when a RST is received. 3498Both 3499.Em dyn_fin_lifetime 3500and 3501.Em dyn_rst_lifetime 3502must be strictly lower than 5 seconds, the period of 3503repetition of keepalives. 3504The firewall enforces that. 3505.It Va net.inet.ip.fw.dyn_keep_states: No 0 3506Keep dynamic states on rule/set deletion. 3507States are relinked to default rule (65535). 3508This can be handly for ruleset reload. 3509Turned off by default. 3510.It Va net.inet.ip.fw.enable : No 1 3511Enables the firewall. 3512Setting this variable to 0 lets you run your machine without 3513firewall even if compiled in. 3514.It Va net.inet6.ip6.fw.enable : No 1 3515provides the same functionality as above for the IPv6 case. 3516.It Va net.inet.ip.fw.one_pass : No 1 3517When set, the packet exiting from the 3518.Nm dummynet 3519pipe or from 3520.Xr ng_ipfw 4 3521node is not passed though the firewall again. 3522Otherwise, after an action, the packet is 3523reinjected into the firewall at the next rule. 3524.It Va net.inet.ip.fw.tables_max : No 128 3525Maximum number of tables. 3526.It Va net.inet.ip.fw.verbose : No 1 3527Enables verbose messages. 3528.It Va net.inet.ip.fw.verbose_limit : No 0 3529Limits the number of messages produced by a verbose firewall. 3530.It Va net.inet6.ip6.fw.deny_unknown_exthdrs : No 1 3531If enabled packets with unknown IPv6 Extension Headers will be denied. 3532.It Va net.link.ether.ipfw : No 0 3533Controls whether layer-2 packets are passed to 3534.Nm . 3535Default is no. 3536.It Va net.link.bridge.ipfw : No 0 3537Controls whether bridged packets are passed to 3538.Nm . 3539Default is no. 3540.El 3541.Sh INTERNAL DIAGNOSTICS 3542There are some commands that may be useful to understand current state 3543of certain subsystems inside kernel module. 3544These commands provide debugging output which may change without notice. 3545.Pp 3546Currently the following commands are available as 3547.Cm internal 3548sub-options: 3549.Bl -tag -width indent 3550.It Cm iflist 3551Lists all interface which are currently tracked by 3552.Nm 3553with their in-kernel status. 3554.It Cm talist 3555List all table lookup algorithms currently available. 3556.El 3557.Sh EXAMPLES 3558There are far too many possible uses of 3559.Nm 3560so this Section will only give a small set of examples. 3561.Pp 3562.Ss BASIC PACKET FILTERING 3563This command adds an entry which denies all tcp packets from 3564.Em cracker.evil.org 3565to the telnet port of 3566.Em wolf.tambov.su 3567from being forwarded by the host: 3568.Pp 3569.Dl "ipfw add deny tcp from cracker.evil.org to wolf.tambov.su telnet" 3570.Pp 3571This one disallows any connection from the entire cracker's 3572network to my host: 3573.Pp 3574.Dl "ipfw add deny ip from 123.45.67.0/24 to my.host.org" 3575.Pp 3576A first and efficient way to limit access (not using dynamic rules) 3577is the use of the following rules: 3578.Pp 3579.Dl "ipfw add allow tcp from any to any established" 3580.Dl "ipfw add allow tcp from net1 portlist1 to net2 portlist2 setup" 3581.Dl "ipfw add allow tcp from net3 portlist3 to net3 portlist3 setup" 3582.Dl "..." 3583.Dl "ipfw add deny tcp from any to any" 3584.Pp 3585The first rule will be a quick match for normal TCP packets, 3586but it will not match the initial SYN packet, which will be 3587matched by the 3588.Cm setup 3589rules only for selected source/destination pairs. 3590All other SYN packets will be rejected by the final 3591.Cm deny 3592rule. 3593.Pp 3594If you administer one or more subnets, you can take advantage 3595of the address sets and or-blocks and write extremely 3596compact rulesets which selectively enable services to blocks 3597of clients, as below: 3598.Pp 3599.Dl "goodguys=\*q{ 10.1.2.0/24{20,35,66,18} or 10.2.3.0/28{6,3,11} }\*q" 3600.Dl "badguys=\*q10.1.2.0/24{8,38,60}\*q" 3601.Dl "" 3602.Dl "ipfw add allow ip from ${goodguys} to any" 3603.Dl "ipfw add deny ip from ${badguys} to any" 3604.Dl "... normal policies ..." 3605.Pp 3606The 3607.Cm verrevpath 3608option could be used to do automated anti-spoofing by adding the 3609following to the top of a ruleset: 3610.Pp 3611.Dl "ipfw add deny ip from any to any not verrevpath in" 3612.Pp 3613This rule drops all incoming packets that appear to be coming to the 3614system on the wrong interface. 3615For example, a packet with a source 3616address belonging to a host on a protected internal network would be 3617dropped if it tried to enter the system from an external interface. 3618.Pp 3619The 3620.Cm antispoof 3621option could be used to do similar but more restricted anti-spoofing 3622by adding the following to the top of a ruleset: 3623.Pp 3624.Dl "ipfw add deny ip from any to any not antispoof in" 3625.Pp 3626This rule drops all incoming packets that appear to be coming from another 3627directly connected system but on the wrong interface. 3628For example, a packet with a source address of 3629.Li 192.168.0.0/24 , 3630configured on 3631.Li fxp0 , 3632but coming in on 3633.Li fxp1 3634would be dropped. 3635.Pp 3636The 3637.Cm setdscp 3638option could be used to (re)mark user traffic, 3639by adding the following to the appropriate place in ruleset: 3640.Pp 3641.Dl "ipfw add setdscp be ip from any to any dscp af11,af21" 3642.Ss DYNAMIC RULES 3643In order to protect a site from flood attacks involving fake 3644TCP packets, it is safer to use dynamic rules: 3645.Pp 3646.Dl "ipfw add check-state" 3647.Dl "ipfw add deny tcp from any to any established" 3648.Dl "ipfw add allow tcp from my-net to any setup keep-state" 3649.Pp 3650This will let the firewall install dynamic rules only for 3651those connection which start with a regular SYN packet coming 3652from the inside of our network. 3653Dynamic rules are checked when encountering the first 3654occurrence of a 3655.Cm check-state , 3656.Cm keep-state 3657or 3658.Cm limit 3659rule. 3660A 3661.Cm check-state 3662rule should usually be placed near the beginning of the 3663ruleset to minimize the amount of work scanning the ruleset. 3664Your mileage may vary. 3665.Pp 3666To limit the number of connections a user can open 3667you can use the following type of rules: 3668.Pp 3669.Dl "ipfw add allow tcp from my-net/24 to any setup limit src-addr 10" 3670.Dl "ipfw add allow tcp from any to me setup limit src-addr 4" 3671.Pp 3672The former (assuming it runs on a gateway) will allow each host 3673on a /24 network to open at most 10 TCP connections. 3674The latter can be placed on a server to make sure that a single 3675client does not use more than 4 simultaneous connections. 3676.Pp 3677.Em BEWARE : 3678stateful rules can be subject to denial-of-service attacks 3679by a SYN-flood which opens a huge number of dynamic rules. 3680The effects of such attacks can be partially limited by 3681acting on a set of 3682.Xr sysctl 8 3683variables which control the operation of the firewall. 3684.Pp 3685Here is a good usage of the 3686.Cm list 3687command to see accounting records and timestamp information: 3688.Pp 3689.Dl ipfw -at list 3690.Pp 3691or in short form without timestamps: 3692.Pp 3693.Dl ipfw -a list 3694.Pp 3695which is equivalent to: 3696.Pp 3697.Dl ipfw show 3698.Pp 3699Next rule diverts all incoming packets from 192.168.2.0/24 3700to divert port 5000: 3701.Pp 3702.Dl ipfw divert 5000 ip from 192.168.2.0/24 to any in 3703.Ss TRAFFIC SHAPING 3704The following rules show some of the applications of 3705.Nm 3706and 3707.Nm dummynet 3708for simulations and the like. 3709.Pp 3710This rule drops random incoming packets with a probability 3711of 5%: 3712.Pp 3713.Dl "ipfw add prob 0.05 deny ip from any to any in" 3714.Pp 3715A similar effect can be achieved making use of 3716.Nm dummynet 3717pipes: 3718.Pp 3719.Dl "ipfw add pipe 10 ip from any to any" 3720.Dl "ipfw pipe 10 config plr 0.05" 3721.Pp 3722We can use pipes to artificially limit bandwidth, e.g.\& on a 3723machine acting as a router, if we want to limit traffic from 3724local clients on 192.168.2.0/24 we do: 3725.Pp 3726.Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out" 3727.Dl "ipfw pipe 1 config bw 300Kbit/s queue 50KBytes" 3728.Pp 3729note that we use the 3730.Cm out 3731modifier so that the rule is not used twice. 3732Remember in fact that 3733.Nm 3734rules are checked both on incoming and outgoing packets. 3735.Pp 3736Should we want to simulate a bidirectional link with bandwidth 3737limitations, the correct way is the following: 3738.Pp 3739.Dl "ipfw add pipe 1 ip from any to any out" 3740.Dl "ipfw add pipe 2 ip from any to any in" 3741.Dl "ipfw pipe 1 config bw 64Kbit/s queue 10Kbytes" 3742.Dl "ipfw pipe 2 config bw 64Kbit/s queue 10Kbytes" 3743.Pp 3744The above can be very useful, e.g.\& if you want to see how 3745your fancy Web page will look for a residential user who 3746is connected only through a slow link. 3747You should not use only one pipe for both directions, unless 3748you want to simulate a half-duplex medium (e.g.\& AppleTalk, 3749Ethernet, IRDA). 3750It is not necessary that both pipes have the same configuration, 3751so we can also simulate asymmetric links. 3752.Pp 3753Should we want to verify network performance with the RED queue 3754management algorithm: 3755.Pp 3756.Dl "ipfw add pipe 1 ip from any to any" 3757.Dl "ipfw pipe 1 config bw 500Kbit/s queue 100 red 0.002/30/80/0.1" 3758.Pp 3759Another typical application of the traffic shaper is to 3760introduce some delay in the communication. 3761This can significantly affect applications which do a lot of Remote 3762Procedure Calls, and where the round-trip-time of the 3763connection often becomes a limiting factor much more than 3764bandwidth: 3765.Pp 3766.Dl "ipfw add pipe 1 ip from any to any out" 3767.Dl "ipfw add pipe 2 ip from any to any in" 3768.Dl "ipfw pipe 1 config delay 250ms bw 1Mbit/s" 3769.Dl "ipfw pipe 2 config delay 250ms bw 1Mbit/s" 3770.Pp 3771Per-flow queueing can be useful for a variety of purposes. 3772A very simple one is counting traffic: 3773.Pp 3774.Dl "ipfw add pipe 1 tcp from any to any" 3775.Dl "ipfw add pipe 1 udp from any to any" 3776.Dl "ipfw add pipe 1 ip from any to any" 3777.Dl "ipfw pipe 1 config mask all" 3778.Pp 3779The above set of rules will create queues (and collect 3780statistics) for all traffic. 3781Because the pipes have no limitations, the only effect is 3782collecting statistics. 3783Note that we need 3 rules, not just the last one, because 3784when 3785.Nm 3786tries to match IP packets it will not consider ports, so we 3787would not see connections on separate ports as different 3788ones. 3789.Pp 3790A more sophisticated example is limiting the outbound traffic 3791on a net with per-host limits, rather than per-network limits: 3792.Pp 3793.Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out" 3794.Dl "ipfw add pipe 2 ip from any to 192.168.2.0/24 in" 3795.Dl "ipfw pipe 1 config mask src-ip 0x000000ff bw 200Kbit/s queue 20Kbytes" 3796.Dl "ipfw pipe 2 config mask dst-ip 0x000000ff bw 200Kbit/s queue 20Kbytes" 3797.Ss LOOKUP TABLES 3798In the following example, we need to create several traffic bandwidth 3799classes and we need different hosts/networks to fall into different classes. 3800We create one pipe for each class and configure them accordingly. 3801Then we create a single table and fill it with IP subnets and addresses. 3802For each subnet/host we set the argument equal to the number of the pipe 3803that it should use. 3804Then we classify traffic using a single rule: 3805.Pp 3806.Dl "ipfw pipe 1 config bw 1000Kbyte/s" 3807.Dl "ipfw pipe 4 config bw 4000Kbyte/s" 3808.Dl "..." 3809.Dl "ipfw table T1 create type addr" 3810.Dl "ipfw table T1 add 192.168.2.0/24 1" 3811.Dl "ipfw table T1 add 192.168.0.0/27 4" 3812.Dl "ipfw table T1 add 192.168.0.2 1" 3813.Dl "..." 3814.Dl "ipfw add pipe tablearg ip from 'table(T1)' to any" 3815.Pp 3816Using the 3817.Cm fwd 3818action, the table entries may include hostnames and IP addresses. 3819.Pp 3820.Dl "ipfw table T2 create type addr ftype ip" 3821.Dl "ipfw table T2 add 192.168.2.0/24 10.23.2.1" 3822.Dl "ipfw table T21 add 192.168.0.0/27 router1.dmz" 3823.Dl "..." 3824.Dl "ipfw add 100 fwd tablearg ip from any to table(1)" 3825.Pp 3826In the following example per-interface firewall is created: 3827.Pp 3828.Dl "ipfw table IN create type iface valtype skipto,fib" 3829.Dl "ipfw table IN add vlan20 12000,12" 3830.Dl "ipfw table IN add vlan30 13000,13" 3831.Dl "ipfw table OUT create type iface valtype skipto" 3832.Dl "ipfw table OUT add vlan20 22000" 3833.Dl "ipfw table OUT add vlan30 23000" 3834.Dl ".." 3835.Dl "ipfw add 100 ipfw setfib tablearg ip from any to any recv 'table(IN)' in" 3836.Dl "ipfw add 200 ipfw skipto tablearg ip from any to any recv 'table(IN)' in" 3837.Dl "ipfw add 300 ipfw skipto tablearg ip from any to any xmit 'table(OUT)' out" 3838.Pp 3839The following example illustrate usage of flow tables: 3840.Pp 3841.Dl "ipfw table fl create type flow:flow:src-ip,proto,dst-ip,dst-port" 3842.Dl "ipfw table fl add 2a02:6b8:77::88,tcp,2a02:6b8:77::99,80 11" 3843.Dl "ipfw table fl add 10.0.0.1,udp,10.0.0.2,53 12" 3844.Dl ".." 3845.Dl "ipfw add 100 allow ip from any to any flow 'table(fl,11)' recv ix0" 3846.Ss SETS OF RULES 3847To add a set of rules atomically, e.g.\& set 18: 3848.Pp 3849.Dl "ipfw set disable 18" 3850.Dl "ipfw add NN set 18 ... # repeat as needed" 3851.Dl "ipfw set enable 18" 3852.Pp 3853To delete a set of rules atomically the command is simply: 3854.Pp 3855.Dl "ipfw delete set 18" 3856.Pp 3857To test a ruleset and disable it and regain control if something goes wrong: 3858.Pp 3859.Dl "ipfw set disable 18" 3860.Dl "ipfw add NN set 18 ... # repeat as needed" 3861.Dl "ipfw set enable 18; echo done; sleep 30 && ipfw set disable 18" 3862.Pp 3863Here if everything goes well, you press control-C before the "sleep" 3864terminates, and your ruleset will be left active. 3865Otherwise, e.g.\& if 3866you cannot access your box, the ruleset will be disabled after 3867the sleep terminates thus restoring the previous situation. 3868.Pp 3869To show rules of the specific set: 3870.Pp 3871.Dl "ipfw set 18 show" 3872.Pp 3873To show rules of the disabled set: 3874.Pp 3875.Dl "ipfw -S set 18 show" 3876.Pp 3877To clear a specific rule counters of the specific set: 3878.Pp 3879.Dl "ipfw set 18 zero NN" 3880.Pp 3881To delete a specific rule of the specific set: 3882.Pp 3883.Dl "ipfw set 18 delete NN" 3884.Ss NAT, REDIRECT AND LSNAT 3885First redirect all the traffic to nat instance 123: 3886.Pp 3887.Dl "ipfw add nat 123 all from any to any" 3888.Pp 3889Then to configure nat instance 123 to alias all the outgoing traffic with ip 3890192.168.0.123, blocking all incoming connections, trying to keep 3891same ports on both sides, clearing aliasing table on address change 3892and keeping a log of traffic/link statistics: 3893.Pp 3894.Dl "ipfw nat 123 config ip 192.168.0.123 log deny_in reset same_ports" 3895.Pp 3896Or to change address of instance 123, aliasing table will be cleared (see 3897reset option): 3898.Pp 3899.Dl "ipfw nat 123 config ip 10.0.0.1" 3900.Pp 3901To see configuration of nat instance 123: 3902.Pp 3903.Dl "ipfw nat 123 show config" 3904.Pp 3905To show logs of all the instances in range 111-999: 3906.Pp 3907.Dl "ipfw nat 111-999 show" 3908.Pp 3909To see configurations of all instances: 3910.Pp 3911.Dl "ipfw nat show config" 3912.Pp 3913Or a redirect rule with mixed modes could looks like: 3914.Pp 3915.Dl "ipfw nat 123 config redirect_addr 10.0.0.1 10.0.0.66" 3916.Dl " redirect_port tcp 192.168.0.1:80 500" 3917.Dl " redirect_proto udp 192.168.1.43 192.168.1.1" 3918.Dl " redirect_addr 192.168.0.10,192.168.0.11" 3919.Dl " 10.0.0.100 # LSNAT" 3920.Dl " redirect_port tcp 192.168.0.1:80,192.168.0.10:22" 3921.Dl " 500 # LSNAT" 3922.Pp 3923or it could be split in: 3924.Pp 3925.Dl "ipfw nat 1 config redirect_addr 10.0.0.1 10.0.0.66" 3926.Dl "ipfw nat 2 config redirect_port tcp 192.168.0.1:80 500" 3927.Dl "ipfw nat 3 config redirect_proto udp 192.168.1.43 192.168.1.1" 3928.Dl "ipfw nat 4 config redirect_addr 192.168.0.10,192.168.0.11,192.168.0.12" 3929.Dl " 10.0.0.100" 3930.Dl "ipfw nat 5 config redirect_port tcp" 3931.Dl " 192.168.0.1:80,192.168.0.10:22,192.168.0.20:25 500" 3932.Sh SEE ALSO 3933.Xr cpp 1 , 3934.Xr m4 1 , 3935.Xr altq 4 , 3936.Xr divert 4 , 3937.Xr dummynet 4 , 3938.Xr if_bridge 4 , 3939.Xr ip 4 , 3940.Xr ipfirewall 4 , 3941.Xr ng_ipfw 4 , 3942.Xr protocols 5 , 3943.Xr services 5 , 3944.Xr init 8 , 3945.Xr kldload 8 , 3946.Xr reboot 8 , 3947.Xr sysctl 8 , 3948.Xr syslogd 8 3949.Sh HISTORY 3950The 3951.Nm 3952utility first appeared in 3953.Fx 2.0 . 3954.Nm dummynet 3955was introduced in 3956.Fx 2.2.8 . 3957Stateful extensions were introduced in 3958.Fx 4.0 . 3959.Nm ipfw2 3960was introduced in Summer 2002. 3961.Sh AUTHORS 3962.An Ugen J. S. Antsilevich , 3963.An Poul-Henning Kamp , 3964.An Alex Nash , 3965.An Archie Cobbs , 3966.An Luigi Rizzo . 3967.Pp 3968.An -nosplit 3969API based upon code written by 3970.An Daniel Boulet 3971for BSDI. 3972.Pp 3973Dummynet has been introduced by Luigi Rizzo in 1997-1998. 3974.Pp 3975Some early work (1999-2000) on the 3976.Nm dummynet 3977traffic shaper supported by Akamba Corp. 3978.Pp 3979The ipfw core (ipfw2) has been completely redesigned and 3980reimplemented by Luigi Rizzo in summer 2002. 3981Further 3982actions and 3983options have been added by various developer over the years. 3984.Pp 3985.An -nosplit 3986In-kernel NAT support written by 3987.An Paolo Pisati Aq Mt piso@FreeBSD.org 3988as part of a Summer of Code 2005 project. 3989.Pp 3990SCTP 3991.Nm nat 3992support has been developed by 3993.An The Centre for Advanced Internet Architectures (CAIA) Aq http://www.caia.swin.edu.au . 3994The primary developers and maintainers are David Hayes and Jason But. 3995For further information visit: 3996.Aq http://www.caia.swin.edu.au/urp/SONATA 3997.Pp 3998Delay profiles have been developed by Alessandro Cerri and 3999Luigi Rizzo, supported by the 4000European Commission within Projects Onelab and Onelab2. 4001.Sh BUGS 4002The syntax has grown over the years and sometimes it might be confusing. 4003Unfortunately, backward compatibility prevents cleaning up mistakes 4004made in the definition of the syntax. 4005.Pp 4006.Em !!! WARNING !!! 4007.Pp 4008Misconfiguring the firewall can put your computer in an unusable state, 4009possibly shutting down network services and requiring console access to 4010regain control of it. 4011.Pp 4012Incoming packet fragments diverted by 4013.Cm divert 4014are reassembled before delivery to the socket. 4015The action used on those packet is the one from the 4016rule which matches the first fragment of the packet. 4017.Pp 4018Packets diverted to userland, and then reinserted by a userland process 4019may lose various packet attributes. 4020The packet source interface name 4021will be preserved if it is shorter than 8 bytes and the userland process 4022saves and reuses the sockaddr_in 4023(as does 4024.Xr natd 8 ) ; 4025otherwise, it may be lost. 4026If a packet is reinserted in this manner, later rules may be incorrectly 4027applied, making the order of 4028.Cm divert 4029rules in the rule sequence very important. 4030.Pp 4031Dummynet drops all packets with IPv6 link-local addresses. 4032.Pp 4033Rules using 4034.Cm uid 4035or 4036.Cm gid 4037may not behave as expected. 4038In particular, incoming SYN packets may 4039have no uid or gid associated with them since they do not yet belong 4040to a TCP connection, and the uid/gid associated with a packet may not 4041be as expected if the associated process calls 4042.Xr setuid 2 4043or similar system calls. 4044.Pp 4045Rule syntax is subject to the command line environment and some patterns 4046may need to be escaped with the backslash character 4047or quoted appropriately. 4048.Pp 4049Due to the architecture of 4050.Xr libalias 3 , 4051ipfw nat is not compatible with the TCP segmentation offloading (TSO). 4052Thus, to reliably nat your network traffic, please disable TSO 4053on your NICs using 4054.Xr ifconfig 8 . 4055.Pp 4056ICMP error messages are not implicitly matched by dynamic rules 4057for the respective conversations. 4058To avoid failures of network error detection and path MTU discovery, 4059ICMP error messages may need to be allowed explicitly through static 4060rules. 4061.Pp 4062Rules using 4063.Cm call 4064and 4065.Cm return 4066actions may lead to confusing behaviour if ruleset has mistakes, 4067and/or interaction with other subsystems (netgraph, dummynet, etc.) is used. 4068One possible case for this is packet leaving 4069.Nm 4070in subroutine on the input pass, while later on output encountering unpaired 4071.Cm return 4072first. 4073As the call stack is kept intact after input pass, packet will suddenly 4074return to the rule number used on input pass, not on output one. 4075Order of processing should be checked carefully to avoid such mistakes. 4076