1.\" $OpenBSD: pf.conf.5,v 1.406 2009/01/31 19:37:12 sobrado Exp $ 2.\" 3.\" Copyright (c) 2002, Daniel Hartmeier 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 10.\" - Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" - Redistributions in binary form must reproduce the above 13.\" copyright notice, this list of conditions and the following 14.\" disclaimer in the documentation and/or other materials provided 15.\" with the distribution. 16.\" 17.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 18.\" "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 19.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 20.\" FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 21.\" COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 22.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 23.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 24.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 25.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 27.\" ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd April 22, 2025 31.Dt PF.CONF 5 32.Os 33.Sh NAME 34.Nm pf.conf 35.Nd packet filter configuration file 36.Sh DESCRIPTION 37The 38.Xr pf 4 39packet filter modifies, drops or passes packets according to rules or 40definitions specified in 41.Nm pf.conf . 42.Sh STATEMENT ORDER 43There are eight types of statements in 44.Nm pf.conf : 45.Bl -tag -width xxxx 46.It Cm Macros 47User-defined variables may be defined and used later, simplifying 48the configuration file. 49Macros must be defined before they are referenced in 50.Nm pf.conf . 51.It Cm Tables 52Tables provide a mechanism for increasing the performance and flexibility of 53rules with large numbers of source or destination addresses. 54.It Cm Options 55Options tune the behaviour of the packet filtering engine. 56.It Cm Ethernet Filtering 57Ethernet filtering provides rule-based blocking or passing of Ethernet packets. 58.It Cm Traffic Normalization Li (e.g. Em scrub ) 59Traffic normalization protects internal machines against inconsistencies 60in Internet protocols and implementations. 61.It Cm Queueing 62Queueing provides rule-based bandwidth control. 63.It Cm Translation Li (Various forms of NAT) 64Translation rules specify how addresses are to be mapped or redirected to 65other addresses. 66.It Cm Packet Filtering 67Packet filtering provides rule-based blocking or passing of packets. 68.El 69.Pp 70With the exception of 71.Cm macros 72and 73.Cm tables , 74the types of statements should be grouped and appear in 75.Nm pf.conf 76in the order shown above, as this matches the operation of the underlying 77packet filtering engine. 78By default 79.Xr pfctl 8 80enforces this order (see 81.Ar set require-order 82below). 83.Pp 84Comments can be put anywhere in the file using a hash mark 85.Pq Sq # , 86and extend to the end of the current line. 87.Pp 88Additional configuration files can be included with the 89.Ic include 90keyword, for example: 91.Bd -literal -offset indent 92include "/etc/pf/sub.filter.conf" 93.Ed 94.Sh MACROS 95Macros can be defined that will later be expanded in context. 96Macro names must start with a letter, and may contain letters, digits 97and underscores. 98Macro names may not be reserved words (for example 99.Ar pass , 100.Ar in , 101.Ar out ) . 102Macros are not expanded inside quotes. 103.Pp 104For example, 105.Bd -literal -offset indent 106ext_if = \&"kue0\&" 107all_ifs = \&"{\&" $ext_if lo0 \&"}\&" 108pass out on $ext_if from any to any 109pass in on $ext_if proto tcp from any to any port 25 110.Ed 111.Sh TABLES 112Tables are named structures which can hold a collection of addresses and 113networks. 114Lookups against tables in 115.Xr pf 4 116are relatively fast, making a single rule with tables much more efficient, 117in terms of 118processor usage and memory consumption, than a large number of rules which 119differ only in IP address (either created explicitly or automatically by rule 120expansion). 121.Pp 122Tables can be used as the source or destination of filter rules, 123.Ar scrub 124rules 125or 126translation rules such as 127.Ar nat 128or 129.Ar rdr 130(see below for details on the various rule types). 131Tables can also be used for the redirect address of 132.Ar nat 133and 134.Ar rdr 135and in the routing options of filter rules, but not for 136.Ar bitmask 137pools. 138.Pp 139Tables can be defined with any of the following 140.Xr pfctl 8 141mechanisms. 142As with macros, reserved words may not be used as table names. 143.Bl -tag -width "manually" 144.It Ar manually 145Persistent tables can be manually created with the 146.Ar add 147or 148.Ar replace 149option of 150.Xr pfctl 8 , 151before or after the ruleset has been loaded. 152.It Pa pf.conf 153Table definitions can be placed directly in this file, and loaded at the 154same time as other rules are loaded, atomically. 155Table definitions inside 156.Nm pf.conf 157use the 158.Ar table 159statement, and are especially useful to define non-persistent tables. 160The contents of a pre-existing table defined without a list of addresses 161to initialize it is not altered when 162.Nm pf.conf 163is loaded. 164A table initialized with the empty list, 165.Li { } , 166will be cleared on load. 167.El 168.Pp 169Tables may be defined with the following attributes: 170.Bl -tag -width counters 171.It Ar persist 172The 173.Ar persist 174flag forces the kernel to keep the table even when no rules refer to it. 175If the flag is not set, the kernel will automatically remove the table 176when the last rule referring to it is flushed. 177.It Ar const 178The 179.Ar const 180flag prevents the user from altering the contents of the table once it 181has been created. 182Without that flag, 183.Xr pfctl 8 184can be used to add or remove addresses from the table at any time, even 185when running with 186.Xr securelevel 7 187= 2. 188.It Ar counters 189The 190.Ar counters 191flag enables per-address packet and byte counters which can be displayed with 192.Xr pfctl 8 . 193Note that this feature carries significant memory overhead for large tables. 194.El 195.Pp 196For example, 197.Bd -literal -offset indent 198table <private> const { 10/8, 172.16/12, 192.168/16 } 199table <badhosts> persist 200block on fxp0 from { <private>, <badhosts> } to any 201.Ed 202.Pp 203creates a table called private, to hold RFC 1918 private network 204blocks, and a table called badhosts, which is initially empty. 205A filter rule is set up to block all traffic coming from addresses listed in 206either table. 207The private table cannot have its contents changed and the badhosts table 208will exist even when no active filter rules reference it. 209Addresses may later be added to the badhosts table, so that traffic from 210these hosts can be blocked by using 211.Bd -literal -offset indent 212# pfctl -t badhosts -Tadd 204.92.77.111 213.Ed 214.Pp 215A table can also be initialized with an address list specified in one or more 216external files, using the following syntax: 217.Bd -literal -offset indent 218table <spam> persist file \&"/etc/spammers\&" file \&"/etc/openrelays\&" 219block on fxp0 from <spam> to any 220.Ed 221.Pp 222The files 223.Pa /etc/spammers 224and 225.Pa /etc/openrelays 226list IP addresses, one per line. 227Any lines beginning with a # are treated as comments and ignored. 228In addition to being specified by IP address, hosts may also be 229specified by their hostname. 230When the resolver is called to add a hostname to a table, 231.Em all 232resulting IPv4 and IPv6 addresses are placed into the table. 233IP addresses can also be entered in a table by specifying a valid interface 234name, a valid interface group or the 235.Em self 236keyword, in which case all addresses assigned to the interface(s) will be 237added to the table. 238.Sh OPTIONS 239.Xr pf 4 240may be tuned for various situations using the 241.Ar set 242command. 243.Bl -tag -width xxxx 244.It Ar set timeout 245.Pp 246.Bl -tag -width "src.track" -compact 247.It Ar interval 248Interval between purging expired states and fragments. 249.It Ar frag 250Seconds before an unassembled fragment is expired. 251.It Ar src.track 252Length of time to retain a source tracking entry after the last state 253expires. 254.El 255.Pp 256When a packet matches a stateful connection, the seconds to live for the 257connection will be updated to that of the 258.Ar proto.modifier 259which corresponds to the connection state. 260Each packet which matches this state will reset the TTL. 261Tuning these values may improve the performance of the 262firewall at the risk of dropping valid idle connections. 263.Pp 264.Bl -tag -width xxxx -compact 265.It Ar tcp.first 266The state after the first packet. 267.It Ar tcp.opening 268The state after the second packet but before both endpoints have 269acknowledged the connection. 270.It Ar tcp.established 271The fully established state. 272.It Ar tcp.closing 273The state after the first FIN has been sent. 274.It Ar tcp.finwait 275The state after both FINs have been exchanged and the connection is closed. 276Some hosts (notably web servers on Solaris) send TCP packets even after closing 277the connection. 278Increasing 279.Ar tcp.finwait 280(and possibly 281.Ar tcp.closing ) 282can prevent blocking of such packets. 283.It Ar tcp.closed 284The state after one endpoint sends an RST. 285.El 286.Pp 287SCTP timeout are handled similar to TCP, but with its own set of states: 288.Pp 289.Bl -tag -width xxxx -compact 290.It Ar sctp.first 291The state after the first packet. 292.It Ar sctp.opening 293The state before the destination host ever sends a packet. 294.It Ar sctp.established 295The fully established state. 296.It Ar sctp.closing 297The state after the first SHUTDOWN chunk has been sent. 298.It Ar sctp.closed 299The state after SHUTDOWN_ACK has been exchanged and the connection is closed. 300.El 301.Pp 302ICMP and UDP are handled in a fashion similar to TCP, but with a much more 303limited set of states: 304.Pp 305.Bl -tag -width xxxx -compact 306.It Ar udp.first 307The state after the first packet. 308.It Ar udp.single 309The state if the source host sends more than one packet but the destination 310host has never sent one back. 311.It Ar udp.multiple 312The state if both hosts have sent packets. 313.It Ar icmp.first 314The state after the first packet. 315.It Ar icmp.error 316The state after an ICMP error came back in response to an ICMP packet. 317.El 318.Pp 319Other protocols are handled similarly to UDP: 320.Pp 321.Bl -tag -width xxxx -compact 322.It Ar other.first 323.It Ar other.single 324.It Ar other.multiple 325.El 326.Pp 327Timeout values can be reduced adaptively as the number of state table 328entries grows. 329.Pp 330.Bl -tag -width xxxx -compact 331.It Ar adaptive.start 332When the number of state entries exceeds this value, adaptive scaling 333begins. 334All timeout values are scaled linearly with factor 335(adaptive.end - number of states) / (adaptive.end - adaptive.start). 336.It Ar adaptive.end 337When reaching this number of state entries, all timeout values become 338zero, effectively purging all state entries immediately. 339This value is used to define the scale factor, it should not actually 340be reached (set a lower state limit, see below). 341.El 342.Pp 343Adaptive timeouts are enabled by default, with an adaptive.start value 344equal to 60% of the state limit, and an adaptive.end value equal to 345120% of the state limit. 346They can be disabled by setting both adaptive.start and adaptive.end to 0. 347.Pp 348The adaptive timeout values can be defined both globally and for each rule. 349When used on a per-rule basis, the values relate to the number of 350states created by the rule, otherwise to the total number of 351states. 352.Pp 353For example: 354.Bd -literal -offset indent 355set timeout tcp.first 120 356set timeout tcp.established 86400 357set timeout { adaptive.start 6000, adaptive.end 12000 } 358set limit states 10000 359.Ed 360.Pp 361With 9000 state table entries, the timeout values are scaled to 50% 362(tcp.first 60, tcp.established 43200). 363.It Ar set loginterface 364Enable collection of packet and byte count statistics for the given 365interface or interface group. 366These statistics can be viewed using 367.Bd -literal -offset indent 368# pfctl -s info 369.Ed 370.Pp 371In this example 372.Xr pf 4 373collects statistics on the interface named dc0: 374.Bd -literal -offset indent 375set loginterface dc0 376.Ed 377.Pp 378One can disable the loginterface using: 379.Bd -literal -offset indent 380set loginterface none 381.Ed 382.It Ar set limit 383Sets hard limits on the memory pools used by the packet filter. 384See 385.Xr zone 9 386for an explanation of memory pools. 387.Pp 388For example, 389.Bd -literal -offset indent 390set limit states 20000 391.Ed 392.Pp 393sets the maximum number of entries in the memory pool used by state table 394entries (generated by 395.Ar pass 396rules which do not specify 397.Ar no state ) 398to 20000. 399Using 400.Bd -literal -offset indent 401set limit frags 20000 402.Ed 403.Pp 404sets the maximum number of entries in the memory pool used for fragment 405reassembly (generated by the 406.Ar set reassemble 407option or 408.Ar scrub 409rules) to 20000. 410Using 411.Bd -literal -offset indent 412set limit src-nodes 2000 413.Ed 414.Pp 415sets the maximum number of entries in the memory pool used for tracking 416source IP addresses (generated by the 417.Ar sticky-address 418and 419.Ar src.track 420options) to 2000. 421Using 422.Bd -literal -offset indent 423set limit table-entries 100000 424.Ed 425.Pp 426sets the limit on the overall number of addresses that can be stored 427in tables to 100000. 428.Pp 429Various limits can be combined on a single line: 430.Bd -literal -offset indent 431set limit { states 20000, frags 20000, src-nodes 2000 } 432.Ed 433.It Ar set ruleset-optimization 434.Bl -tag -width xxxxxxxx -compact 435.It Ar none 436Disable the ruleset optimizer. 437.It Ar basic 438Enable basic ruleset optimization. 439This is the default behaviour. 440Basic ruleset optimization does four things to improve the 441performance of ruleset evaluations: 442.Pp 443.Bl -enum -compact 444.It 445remove duplicate rules 446.It 447remove rules that are a subset of another rule 448.It 449combine multiple rules into a table when advantageous 450.It 451re-order the rules to improve evaluation performance 452.El 453.Pp 454.It Ar profile 455Uses the currently loaded ruleset as a feedback profile to tailor the 456ordering of quick rules to actual network traffic. 457.El 458.Pp 459It is important to note that the ruleset optimizer will modify the ruleset 460to improve performance. 461A side effect of the ruleset modification is that per-rule accounting 462statistics will have different meanings than before. 463If per-rule accounting is important for billing purposes or whatnot, 464either the ruleset optimizer should not be used or a label field should 465be added to all of the accounting rules to act as optimization barriers. 466.Pp 467Optimization can also be set as a command-line argument to 468.Xr pfctl 8 , 469overriding the settings in 470.Nm . 471.It Ar set optimization 472Optimize state timeouts for one of the following network environments: 473.Pp 474.Bl -tag -width xxxx -compact 475.It Ar normal 476A normal network environment. 477Suitable for almost all networks. 478.It Ar high-latency 479A high-latency environment (such as a satellite connection). 480.It Ar satellite 481Alias for 482.Ar high-latency . 483.It Ar aggressive 484Aggressively expire connections. 485This can greatly reduce the memory usage of the firewall at the cost of 486dropping idle connections early. 487.It Ar conservative 488Extremely conservative settings. 489Avoid dropping legitimate connections at the 490expense of greater memory utilization (possibly much greater on a busy 491network) and slightly increased processor utilization. 492.El 493.Pp 494For example: 495.Bd -literal -offset indent 496set optimization aggressive 497.Ed 498.It Ar set reassemble yes | no Op Cm no-df 499The 500.Cm reassemble 501option is used to enable or disable the reassembly of fragmented packets, 502and can be set to 503.Cm yes 504or 505.Cm no . 506If 507.Cm no-df 508is also specified, fragments with the 509.Dq dont-fragment 510bit set are reassembled too, 511instead of being dropped; 512the reassembled packet will have the 513.Dq dont-fragment 514bit cleared. 515The default value is 516.Cm no . 517.Pp 518This option is ignored if there are pre-FreeBSD 14 519.Cm scrub 520rules present. 521.It Ar set block-policy 522The 523.Ar block-policy 524option sets the default behaviour for the packet 525.Ar block 526action: 527.Pp 528.Bl -tag -width xxxxxxxx -compact 529.It Ar drop 530Packet is silently dropped. 531.It Ar return 532A TCP RST is returned for blocked TCP packets, 533an SCTP ABORT chunk is returned for blocked SCTP packets, 534an ICMP UNREACHABLE is returned for blocked UDP packets, 535and all other packets are silently dropped. 536.El 537.Pp 538For example: 539.Bd -literal -offset indent 540set block-policy return 541.Ed 542.It Ar set fail-policy 543The 544.Ar fail-policy 545option sets the behaviour of rules which should pass a packet but were 546unable to do so. 547This might happen when a nat or route-to rule uses an empty table as list 548of targets or if a rule fails to create state or source node. 549The following 550.Ar block 551actions are possible: 552.Pp 553.Bl -tag -width xxxxxxxx -compact 554.It Ar drop 555Incoming packet is silently dropped. 556.It Ar return 557Incoming packet is dropped and TCP RST is returned for TCP packets, 558an SCTP ABORT chunk is returned for blocked SCTP packets, 559an ICMP UNREACHABLE is returned for UDP packets, 560and no response is sent for other packets. 561.El 562.Pp 563For example: 564.Bd -literal -offset indent 565set fail-policy return 566.Ed 567.It Ar set state-policy 568The 569.Ar state-policy 570option sets the default behaviour for states: 571.Pp 572.Bl -tag -width group-bound -compact 573.It Ar if-bound 574States are bound to interface. 575.It Ar floating 576States can match packets on any interfaces (the default). 577.El 578.Pp 579For example: 580.Bd -literal -offset indent 581set state-policy if-bound 582.Ed 583.It Ar set syncookies never | always | adaptive 584When 585.Cm syncookies 586are active, pf will answer each incoming TCP SYN with a syncookie SYNACK, 587without allocating any resources. 588Upon reception of the client's ACK in response to the syncookie 589SYNACK, pf will evaluate the ruleset and create state if the ruleset 590permits it, complete the three way handshake with the target host and 591continue the connection with synproxy in place. 592This allows pf to be resilient against large synflood attacks which would 593run the state table against its limits otherwise. 594Due to the blind answers to every incoming SYN syncookies share the caveats of 595synproxy, namely seemingly accepting connections that will be dropped later on. 596.Pp 597.Bl -tag -width adaptive -compact 598.It Cm never 599pf will never send syncookie SYNACKs (the default). 600.It Cm always 601pf will always send syncookie SYNACKs. 602.It Cm adaptive 603pf will enable syncookie mode when a given percentage of the state table 604is used up by half-open TCP connections, as in, those that saw the initial 605SYN but didn't finish the three way handshake. 606The thresholds for entering and leaving syncookie mode can be specified using 607.Bd -literal -offset indent 608set syncookies adaptive (start 25%, end 12%) 609.Ed 610.El 611.It Ar set state-defaults 612The 613.Ar state-defaults 614option sets the state options for states created from rules 615without an explicit 616.Ar keep state . 617For example: 618.Bd -literal -offset indent 619set state-defaults no-sync 620.Ed 621.It Ar set hostid 622The 32-bit 623.Ar hostid 624identifies this firewall's state table entries to other firewalls 625in a 626.Xr pfsync 4 627failover cluster. 628By default the hostid is set to a pseudo-random value, however it may be 629desirable to manually configure it, for example to more easily identify the 630source of state table entries. 631.Bd -literal -offset indent 632set hostid 1 633.Ed 634.Pp 635The hostid may be specified in either decimal or hexadecimal. 636.It Ar set require-order 637By default 638.Xr pfctl 8 639enforces an ordering of the statement types in the ruleset to: 640.Em options , 641.Em normalization , 642.Em queueing , 643.Em translation , 644.Em filtering . 645Setting this option to 646.Ar no 647disables this enforcement. 648There may be non-trivial and non-obvious implications to an out of 649order ruleset. 650Consider carefully before disabling the order enforcement. 651.It Ar set fingerprints 652Load fingerprints of known operating systems from the given filename. 653By default fingerprints of known operating systems are automatically 654loaded from 655.Xr pf.os 5 656in 657.Pa /etc 658but can be overridden via this option. 659Setting this option may leave a small period of time where the fingerprints 660referenced by the currently active ruleset are inconsistent until the new 661ruleset finishes loading. 662.Pp 663For example: 664.Pp 665.Dl set fingerprints \&"/etc/pf.os.devel\&" 666.It Ar set skip on Aq Ar ifspec 667List interfaces for which packets should not be filtered. 668Packets passing in or out on such interfaces are passed as if pf was 669disabled, i.e. pf does not process them in any way. 670This can be useful on loopback and other virtual interfaces, when 671packet filtering is not desired and can have unexpected effects. 672For example: 673.Pp 674.Dl set skip on lo0 675.It Ar set debug 676Set the debug 677.Ar level 678to one of the following: 679.Pp 680.Bl -tag -width xxxxxxxxxxxx -compact 681.It Ar none 682Don't generate debug messages. 683.It Ar urgent 684Generate debug messages only for serious errors. 685.It Ar misc 686Generate debug messages for various errors. 687.It Ar loud 688Generate debug messages for common conditions. 689.El 690.It Ar set keepcounters 691Preserve rule counters across rule updates. 692Usually rule counters are reset to zero on every update of the ruleset. 693With 694.Ar keepcounters 695set pf will attempt to find matching rules between old and new rulesets 696and preserve the rule counters. 697.El 698.Sh ETHERNET FILTERING 699.Xr pf 4 700has the ability to 701.Ar block 702and 703.Ar pass 704packets based on attributes of their Ethernet (layer 2) header. 705.Pp 706For each packet processed by the packet filter, the filter rules are 707evaluated in sequential order, from first to last. 708The last matching rule decides what action is taken. 709If no rule matches the packet, the default action is to pass 710the packet without creating a state. 711.Pp 712The following actions can be used in the filter: 713.Bl -tag -width xxxx 714.It Ar block 715The packet is blocked. 716Unlike for layer 3 traffic the packet is always silently dropped. 717.It Ar pass 718The packet is passed; 719no state is created for layer 2 traffic. 720.El 721.Sh PARAMETERS 722The rule parameters specify the packets to which a rule applies. 723A packet always comes in on, or goes out through, one interface. 724Most parameters are optional. 725If a parameter is specified, the rule only applies to packets with 726matching attributes. 727Certain parameters can be expressed as lists, in which case 728.Xr pfctl 8 729generates all needed rule combinations. 730.Bl -tag -width xxxx 731.It Ar in No or Ar out 732This rule applies to incoming or outgoing packets. 733If neither 734.Ar in 735nor 736.Ar out 737are specified, the rule will match packets in both directions. 738.It Ar quick 739If a packet matches a rule which has the 740.Ar quick 741option set, this rule 742is considered the last matching rule, and evaluation of subsequent rules 743is skipped. 744.It Ar on Aq Ar ifspec 745This rule applies only to packets coming in on, or going out through, this 746particular interface or interface group. 747For more information on interface groups, 748see the 749.Ic group 750keyword in 751.Xr ifconfig 8 . 752.Ar any 753will match any existing interface except loopback ones. 754.It Ar bridge-to Aq interface 755Packets matching this rule will be sent out of the specified interface without 756further processing. 757.It Ar proto Aq Ar protocol 758This rule applies only to packets of this protocol. 759Note that Ethernet protocol numbers are different from those used in 760.Xr ip 4 761and 762.Xr ip6 4 . 763.It Xo 764.Ar from Aq Ar source 765.Ar to Aq Ar dest 766.Xc 767This rule applies only to packets with the specified source and destination 768MAC addresses. 769.It Xo Ar queue Aq Ar queue 770.Xc 771Packets matching this rule will be assigned to the specified queue. 772See 773.Sx QUEUEING 774for setup details. 775.Pp 776.It Ar tag Aq Ar string 777Packets matching this rule will be tagged with the 778specified string. 779The tag acts as an internal marker that can be used to 780identify these packets later on. 781This can be used, for example, to provide trust between 782interfaces and to determine if packets have been 783processed by translation rules. 784Tags are 785.Qq sticky , 786meaning that the packet will be tagged even if the rule 787is not the last matching rule. 788Further matching rules can replace the tag with a 789new one but will not remove a previously applied tag. 790A packet is only ever assigned one tag at a time. 791.It Ar tagged Aq Ar string 792Used to specify that packets must already be tagged with the given tag in order 793to match the rule. 794Inverse tag matching can also be done by specifying the ! operator before the 795tagged keyword. 796.El 797.Sh TRAFFIC NORMALIZATION 798Traffic normalization is a broad umbrella term 799for aspects of the packet filter which deal with 800verifying packets, packet fragments, spoofed traffic, 801and other irregularities. 802.Ss Scrub 803Scrub involves sanitising packet content in such a way 804that there are no ambiguities in packet interpretation on the receiving side. 805It is invoked with the 806.Cm scrub 807option, added to filter rules. 808.Pp 809Parameters are specified enclosed in parentheses. 810At least one of the following parameters must be specified: 811.Bl -tag -width xxxx 812.It Ar no-df 813Clears the 814.Ar dont-fragment 815bit from a matching IP packet. 816Some operating systems are known to generate fragmented packets with the 817.Ar dont-fragment 818bit set. 819This is particularly true with NFS. 820.Ar Scrub 821will drop such fragmented 822.Ar dont-fragment 823packets unless 824.Ar no-df 825is specified. 826.Pp 827Unfortunately some operating systems also generate their 828.Ar dont-fragment 829packets with a zero IP identification field. 830Clearing the 831.Ar dont-fragment 832bit on packets with a zero IP ID may cause deleterious results if an 833upstream router later fragments the packet. 834Using the 835.Ar random-id 836modifier (see below) is recommended in combination with the 837.Ar no-df 838modifier to ensure unique IP identifiers. 839.It Ar min-ttl Aq Ar number 840Enforces a minimum TTL for matching IP packets. 841.It Ar max-mss Aq Ar number 842Enforces a maximum MSS for matching TCP packets. 843.It Xo Ar set-tos Aq Ar string 844.No \*(Ba Aq Ar number 845.Xc 846Enforces a 847.Em TOS 848for matching IP packets. 849.Em TOS 850may be 851given as one of 852.Ar critical , 853.Ar inetcontrol , 854.Ar lowdelay , 855.Ar netcontrol , 856.Ar throughput , 857.Ar reliability , 858or one of the DiffServ Code Points: 859.Ar ef , 860.Ar va , 861.Ar af11 No ... Ar af43 , 862.Ar cs0 No ... Ar cs7 ; 863or as either hex or decimal. 864.It Ar random-id 865Replaces the IP identification field with random values to compensate 866for predictable values generated by many hosts. 867This option only applies to packets that are not fragmented 868after the optional fragment reassembly. 869.It Ar reassemble tcp 870Statefully normalizes TCP connections. 871.Ar reassemble tcp 872performs the following normalizations: 873.Pp 874.Bl -tag -width timeout -compact 875.It ttl 876Neither side of the connection is allowed to reduce their IP TTL. 877An attacker may send a packet such that it reaches the firewall, affects 878the firewall state, and expires before reaching the destination host. 879.Ar reassemble tcp 880will raise the TTL of all packets back up to the highest value seen on 881the connection. 882.It timestamp modulation 883Modern TCP stacks will send a timestamp on every TCP packet and echo 884the other endpoint's timestamp back to them. 885Many operating systems will merely start the timestamp at zero when 886first booted, and increment it several times a second. 887The uptime of the host can be deduced by reading the timestamp and multiplying 888by a constant. 889Also observing several different timestamps can be used to count hosts 890behind a NAT device. 891And spoofing TCP packets into a connection requires knowing or guessing 892valid timestamps. 893Timestamps merely need to be monotonically increasing and not derived off a 894guessable base time. 895.Ar reassemble tcp 896will cause 897.Ar scrub 898to modulate the TCP timestamps with a random number. 899.It extended PAWS checks 900There is a problem with TCP on long fat pipes, in that a packet might get 901delayed for longer than it takes the connection to wrap its 32-bit sequence 902space. 903In such an occurrence, the old packet would be indistinguishable from a 904new packet and would be accepted as such. 905The solution to this is called PAWS: Protection Against Wrapped Sequence 906numbers. 907It protects against it by making sure the timestamp on each packet does 908not go backwards. 909.Ar reassemble tcp 910also makes sure the timestamp on the packet does not go forward more 911than the RFC allows. 912By doing this, 913.Xr pf 4 914artificially extends the security of TCP sequence numbers by 10 to 18 915bits when the host uses appropriately randomized timestamps, since a 916blind attacker would have to guess the timestamp as well. 917.El 918.El 919.Pp 920For example, 921.Bd -literal -offset indent 922match in all scrub (no-df random-id max-mss 1440) 923.Ed 924.Ss Scrub ruleset (pre-FreeBSD 14) 925In order to maintain compatibility with older releases of FreeBSD 926.Ar scrub 927rules can also be specified in their own ruleset. 928In such case they are invoked with the 929.Ar scrub 930directive. 931If there are such rules present they determine packet reassembly behaviour. 932When no such rules are present the option 933.Ar set reassembly 934takes precedence. 935The 936.Ar scrub 937rules can take all parameters specified above for a 938.Ar scrub 939option of filter rules and 2 more parameters controlling fragment reassembly: 940.Bl -tag -width xxxx 941.It Ar fragment reassemble 942Using 943.Ar scrub 944rules, fragments can be reassembled by normalization. 945In this case, fragments are buffered until they form a complete 946packet, and only the completed packet is passed on to the filter. 947The advantage is that filter rules have to deal only with complete 948packets, and can ignore fragments. 949The drawback of caching fragments is the additional memory cost. 950This is the default behaviour unless no fragment reassemble is specified. 951.It Ar no fragment reassemble 952Do not reassemble fragments. 953.El 954.Pp 955For example, 956.Bd -literal -offset indent 957scrub in on $ext_if all fragment reassemble 958.Ed 959.Pp 960The 961.Ar no 962option prefixed to a scrub rule causes matching packets to remain unscrubbed, 963much in the same way as 964.Ar drop quick 965works in the packet filter (see below). 966This mechanism should be used when it is necessary to exclude specific packets 967from broader scrub rules. 968.Pp 969.Ar scrub 970rules in the 971.Ar scrub 972ruleset are evaluated for every packet before stateful filtering. 973This means excessive usage of them will cause performance penalty. 974.Ar scrub reassemble tcp 975rules must not have the direction (in/out) specified. 976.Sh QUEUEING with ALTQ 977The ALTQ system is currently not available in the GENERIC kernel nor as 978loadable modules. 979In order to use the herein after called queueing options one has to use a 980custom built kernel. 981Please refer to 982.Xr altq 4 983to learn about the related kernel options. 984.Pp 985Packets can be assigned to queues for the purpose of bandwidth 986control. 987At least two declarations are required to configure queues, and later 988any packet filtering rule can reference the defined queues by name. 989During the filtering component of 990.Nm pf.conf , 991the last referenced 992.Ar queue 993name is where any packets from 994.Ar pass 995rules will be queued, while for 996.Ar block 997rules it specifies where any resulting ICMP or TCP RST 998packets should be queued. 999The 1000.Ar scheduler 1001defines the algorithm used to decide which packets get delayed, dropped, or 1002sent out immediately. 1003There are three 1004.Ar schedulers 1005currently supported. 1006.Bl -tag -width xxxx 1007.It Ar cbq 1008Class Based Queueing. 1009.Ar Queues 1010attached to an interface build a tree, thus each 1011.Ar queue 1012can have further child 1013.Ar queues . 1014Each queue can have a 1015.Ar priority 1016and a 1017.Ar bandwidth 1018assigned. 1019.Ar Priority 1020mainly controls the time packets take to get sent out, while 1021.Ar bandwidth 1022has primarily effects on throughput. 1023.Ar cbq 1024achieves both partitioning and sharing of link bandwidth 1025by hierarchically structured classes. 1026Each class has its own 1027.Ar queue 1028and is assigned its share of 1029.Ar bandwidth . 1030A child class can borrow bandwidth from its parent class 1031as long as excess bandwidth is available 1032(see the option 1033.Ar borrow , 1034below). 1035.It Ar priq 1036Priority Queueing. 1037.Ar Queues 1038are flat attached to the interface, thus, 1039.Ar queues 1040cannot have further child 1041.Ar queues . 1042Each 1043.Ar queue 1044has a unique 1045.Ar priority 1046assigned, ranging from 0 to 15. 1047Packets in the 1048.Ar queue 1049with the highest 1050.Ar priority 1051are processed first. 1052.It Ar hfsc 1053Hierarchical Fair Service Curve. 1054.Ar Queues 1055attached to an interface build a tree, thus each 1056.Ar queue 1057can have further child 1058.Ar queues . 1059Each queue can have a 1060.Ar priority 1061and a 1062.Ar bandwidth 1063assigned. 1064.Ar Priority 1065mainly controls the time packets take to get sent out, while 1066.Ar bandwidth 1067primarily affects throughput. 1068.Ar hfsc 1069supports both link-sharing and guaranteed real-time services. 1070It employs a service curve based QoS model, 1071and its unique feature is an ability to decouple 1072.Ar delay 1073and 1074.Ar bandwidth 1075allocation. 1076.El 1077.Pp 1078The interfaces on which queueing should be activated are declared using 1079the 1080.Ar altq on 1081declaration. 1082.Ar altq on 1083has the following keywords: 1084.Bl -tag -width xxxx 1085.It Aq Ar interface 1086Queueing is enabled on the named interface. 1087.It Aq Ar scheduler 1088Specifies which queueing scheduler to use. 1089Currently supported values 1090are 1091.Ar cbq 1092for Class Based Queueing, 1093.Ar priq 1094for Priority Queueing and 1095.Ar hfsc 1096for the Hierarchical Fair Service Curve scheduler. 1097.It Ar bandwidth Aq Ar bw 1098The maximum bitrate for all queues on an 1099interface may be specified using the 1100.Ar bandwidth 1101keyword. 1102The value can be specified as an absolute value or as a 1103percentage of the interface bandwidth. 1104When using an absolute value, the suffixes 1105.Ar b , 1106.Ar Kb , 1107.Ar Mb , 1108and 1109.Ar Gb 1110are used to represent bits, kilobits, megabits, and 1111gigabits per second, respectively. 1112The value must not exceed the interface bandwidth. 1113If 1114.Ar bandwidth 1115is not specified, the interface bandwidth is used 1116(but take note that some interfaces do not know their bandwidth, 1117or can adapt their bandwidth rates). 1118.It Ar qlimit Aq Ar limit 1119The maximum number of packets held in the queue. 1120The default is 50. 1121.It Ar tbrsize Aq Ar size 1122Adjusts the size, in bytes, of the token bucket regulator. 1123If not specified, heuristics based on the 1124interface bandwidth are used to determine the size. 1125.It Ar queue Aq Ar list 1126Defines a list of subqueues to create on an interface. 1127.El 1128.Pp 1129In the following example, the interface dc0 1130should queue up to 5Mbps in four second-level queues using 1131Class Based Queueing. 1132Those four queues will be shown in a later example. 1133.Bd -literal -offset indent 1134altq on dc0 cbq bandwidth 5Mb queue { std, http, mail, ssh } 1135.Ed 1136.Pp 1137Once interfaces are activated for queueing using the 1138.Ar altq 1139directive, a sequence of 1140.Ar queue 1141directives may be defined. 1142The name associated with a 1143.Ar queue 1144must match a queue defined in the 1145.Ar altq 1146directive (e.g. mail), or, except for the 1147.Ar priq 1148.Ar scheduler , 1149in a parent 1150.Ar queue 1151declaration. 1152The following keywords can be used: 1153.Bl -tag -width xxxx 1154.It Ar on Aq Ar interface 1155Specifies the interface the queue operates on. 1156If not given, it operates on all matching interfaces. 1157.It Ar bandwidth Aq Ar bw 1158Specifies the maximum bitrate to be processed by the queue. 1159This value must not exceed the value of the parent 1160.Ar queue 1161and can be specified as an absolute value or a percentage of the parent 1162queue's bandwidth. 1163If not specified, defaults to 100% of the parent queue's bandwidth. 1164The 1165.Ar priq 1166scheduler does not support bandwidth specification. 1167.It Ar priority Aq Ar level 1168Between queues a priority level can be set. 1169For 1170.Ar cbq 1171and 1172.Ar hfsc , 1173the range is 0 to 7 and for 1174.Ar priq , 1175the range is 0 to 15. 1176The default for all is 1. 1177.Ar Priq 1178queues with a higher priority are always served first. 1179.Ar Cbq 1180and 1181.Ar Hfsc 1182queues with a higher priority are preferred in the case of overload. 1183.It Ar qlimit Aq Ar limit 1184The maximum number of packets held in the queue. 1185The default is 50. 1186.El 1187.Pp 1188The 1189.Ar scheduler 1190can get additional parameters with 1191.Xo Aq Ar scheduler 1192.Pf ( Aq Ar parameters ) . 1193.Xc 1194Parameters are as follows: 1195.Bl -tag -width Fl 1196.It Ar default 1197Packets not matched by another queue are assigned to this one. 1198Exactly one default queue is required. 1199.It Ar red 1200Enable RED (Random Early Detection) on this queue. 1201RED drops packets with a probability proportional to the average 1202queue length. 1203.It Ar rio 1204Enables RIO on this queue. 1205RIO is RED with IN/OUT, thus running 1206RED two times more than RIO would achieve the same effect. 1207RIO is currently not supported in the GENERIC kernel. 1208.It Ar ecn 1209Enables ECN (Explicit Congestion Notification) on this queue. 1210ECN implies RED. 1211.El 1212.Pp 1213The 1214.Ar cbq 1215.Ar scheduler 1216supports an additional option: 1217.Bl -tag -width Fl 1218.It Ar borrow 1219The queue can borrow bandwidth from the parent. 1220.El 1221.Pp 1222The 1223.Ar hfsc 1224.Ar scheduler 1225supports some additional options: 1226.Bl -tag -width Fl 1227.It Ar realtime Aq Ar sc 1228The minimum required bandwidth for the queue. 1229.It Ar upperlimit Aq Ar sc 1230The maximum allowed bandwidth for the queue. 1231.It Ar linkshare Aq Ar sc 1232The bandwidth share of a backlogged queue. 1233.El 1234.Pp 1235.Aq Ar sc 1236is an acronym for 1237.Ar service curve . 1238.Pp 1239The format for service curve specifications is 1240.Ar ( m1 , d , m2 ) . 1241.Ar m2 1242controls the bandwidth assigned to the queue. 1243.Ar m1 1244and 1245.Ar d 1246are optional and can be used to control the initial bandwidth assignment. 1247For the first 1248.Ar d 1249milliseconds the queue gets the bandwidth given as 1250.Ar m1 , 1251afterwards the value given in 1252.Ar m2 . 1253.Pp 1254Furthermore, with 1255.Ar cbq 1256and 1257.Ar hfsc , 1258child queues can be specified as in an 1259.Ar altq 1260declaration, thus building a tree of queues using a part of 1261their parent's bandwidth. 1262.Pp 1263Packets can be assigned to queues based on filter rules by using the 1264.Ar queue 1265keyword. 1266Normally only one 1267.Ar queue 1268is specified; when a second one is specified it will instead be used for 1269packets which have a 1270.Em TOS 1271of 1272.Em lowdelay 1273and for TCP ACKs with no data payload. 1274.Pp 1275To continue the previous example, the examples below would specify the 1276four referenced 1277queues, plus a few child queues. 1278Interactive 1279.Xr ssh 1 1280sessions get priority over bulk transfers like 1281.Xr scp 1 1282and 1283.Xr sftp 1 . 1284The queues may then be referenced by filtering rules (see 1285.Sx PACKET FILTERING 1286below). 1287.Bd -literal 1288queue std bandwidth 10% cbq(default) 1289queue http bandwidth 60% priority 2 cbq(borrow red) \e 1290 { employees, developers } 1291queue developers bandwidth 75% cbq(borrow) 1292queue employees bandwidth 15% 1293queue mail bandwidth 10% priority 0 cbq(borrow ecn) 1294queue ssh bandwidth 20% cbq(borrow) { ssh_interactive, ssh_bulk } 1295queue ssh_interactive bandwidth 50% priority 7 cbq(borrow) 1296queue ssh_bulk bandwidth 50% priority 0 cbq(borrow) 1297 1298block return out on dc0 inet all queue std 1299pass out on dc0 inet proto tcp from $developerhosts to any port 80 \e 1300 queue developers 1301pass out on dc0 inet proto tcp from $employeehosts to any port 80 \e 1302 queue employees 1303pass out on dc0 inet proto tcp from any to any port 22 \e 1304 queue(ssh_bulk, ssh_interactive) 1305pass out on dc0 inet proto tcp from any to any port 25 \e 1306 queue mail 1307.Ed 1308.Sh QUEUEING with dummynet 1309Queueing can also be done with 1310.Xr dummynet 4 . 1311Queues and pipes can be created with 1312.Xr dnctl 8 . 1313.Pp 1314Packets can be assigned to queues and pipes using 1315.Ar dnqueue 1316and 1317.Ar dnpipe 1318respectively. 1319.Pp 1320Both 1321.Ar dnqueue 1322and 1323.Ar dnpipe 1324take either a single pipe or queue number or two numbers as arguments. 1325The first pipe or queue number will be used to shape the traffic in the rule 1326direction, the second will be used to shape the traffic in the reverse 1327direction. 1328If the rule does not specify a direction the first packet to create state will 1329be shaped according to the first number, and the response traffic according to 1330the second. 1331.Pp 1332If the 1333.Xr dummynet 4 1334module is not loaded any traffic sent into a queue or pipe will be dropped. 1335.Sh TRANSLATION 1336Translation rules modify either the source or destination address of the 1337packets associated with a stateful connection. 1338A stateful connection is automatically created to track packets matching 1339such a rule as long as they are not blocked by the filtering section of 1340.Nm pf.conf . 1341The translation engine modifies the specified address and/or port in the 1342packet, recalculates IP, TCP and UDP checksums as necessary, and passes 1343it to the packet filter for evaluation. 1344.Pp 1345Since translation occurs before filtering the filter 1346engine will see packets as they look after any 1347addresses and ports have been translated. 1348Filter rules will therefore have to filter based on the translated 1349address and port number. 1350Packets that match a translation rule are only automatically passed if 1351the 1352.Ar pass 1353modifier is given, otherwise they are 1354still subject to 1355.Ar block 1356and 1357.Ar pass 1358rules. 1359.Pp 1360The state entry created permits 1361.Xr pf 4 1362to keep track of the original address for traffic associated with that state 1363and correctly direct return traffic for that connection. 1364.Pp 1365Various types of translation are possible with pf: 1366.Bl -tag -width xxxx 1367.It Ar af-to 1368Translation between different address families (NAT64) is handled 1369using 1370.Ar af-to 1371rules. 1372Because address family translation overrides the routing table, it's 1373only possible to use 1374.Ar af-to 1375on inbound rules, and a source address of the resulting translation 1376must always be specified. 1377.Pp 1378The optional second argument is the host or subnet the original 1379addresses are translated into for the destination. 1380The lowest bits of the original destination address form the host 1381part of the new destination address according to the specified subnet. 1382It is possible to embed a complete IPv4 address into an IPv6 address 1383using a network prefix of /96 or smaller. 1384.Pp 1385When a destination address is not specified it is assumed that the host 1386part is 32-bit long. 1387For IPv6 to IPv4 translation this would mean using only the lower 32 1388bits of the original IPv6 destination address. 1389For IPv4 to IPv6 translation the destination subnet defaults to the 1390subnet of the new IPv6 source address with a prefix length of /96. 1391See RFC 6052 Section 2.2 for details on how the prefix determines the 1392destination address encoding. 1393.Pp 1394For example, the following rules are identical: 1395.Bd -literal -offset indent 1396pass in inet af-to inet6 from 2001:db8::1 to 2001:db8::/96 1397pass in inet af-to inet6 from 2001:db8::1 1398.Ed 1399.Pp 1400In the above example the matching IPv4 packets will be modified to 1401have a source address of 2001:db8::1 and a destination address will 1402get prefixed with 2001:db8::/96, e.g. 198.51.100.100 will be 1403translated to 2001:db8::c633:6464. 1404.Pp 1405In the reverse case the following rules are identical: 1406.Bd -literal -offset indent 1407pass in inet6 from any to 64:ff9b::/96 af-to inet \e 1408 from 198.51.100.1 to 0.0.0.0/0 1409pass in inet6 from any to 64:ff9b::/96 af-to inet \e 1410 from 198.51.100.1 1411.Ed 1412.Pp 1413The destination IPv4 address is assumed to be embedded inside the 1414original IPv6 destination address, e.g. 64:ff9b::c633:6464 will be 1415translated to 198.51.100.100. 1416.Pp 1417The current implementation will only extract IPv4 addresses from the 1418IPv6 addresses with a prefix length of /96 and greater. 1419.It Ar binat 1420A 1421.Ar binat 1422rule specifies a bidirectional mapping between an external IP netblock 1423and an internal IP netblock. 1424.It Ar nat 1425A 1426.Ar nat 1427rule specifies that IP addresses are to be changed as the packet 1428traverses the given interface. 1429This technique allows one or more IP addresses 1430on the translating host to support network traffic for a larger range of 1431machines on an "inside" network. 1432Although in theory any IP address can be used on the inside, it is strongly 1433recommended that one of the address ranges defined by RFC 1918 be used. 1434These netblocks are: 1435.Bd -literal 143610.0.0.0 - 10.255.255.255 (all of net 10, i.e., 10/8) 1437172.16.0.0 - 172.31.255.255 (i.e., 172.16/12) 1438192.168.0.0 - 192.168.255.255 (i.e., 192.168/16) 1439.Ed 1440.It Pa rdr 1441The packet is redirected to another destination and possibly a 1442different port. 1443.Ar rdr 1444rules can optionally specify port ranges instead of single ports. 1445rdr ... port 2000:2999 -> ... port 4000 1446redirects ports 2000 to 2999 (inclusive) to port 4000. 1447rdr ... port 2000:2999 -> ... port 4000:* 1448redirects port 2000 to 4000, 2001 to 4001, ..., 2999 to 4999. 1449.El 1450.Pp 1451In addition to modifying the address, some translation rules may modify 1452source or destination ports for 1453.Xr tcp 4 1454or 1455.Xr udp 4 1456connections; implicitly in the case of 1457.Ar nat 1458rules and both implicitly and explicitly in the case of 1459.Ar rdr 1460rules. 1461A 1462.Ar rdr 1463rule may cause the source port to be modified if doing so avoids a conflict 1464with an existing connection. 1465A random source port in the range 50001-65535 is chosen in this case; to 1466avoid excessive CPU consumption, the number of searches for a free port is 1467limited by the 1468.Va net.pf.rdr_srcport_rewrite_tries 1469sysctl. 1470Port numbers are never translated with a 1471.Ar binat 1472rule. 1473.Pp 1474Evaluation order of the translation rules is dependent on the type 1475of the translation rules and of the direction of a packet. 1476.Ar binat 1477rules are always evaluated first. 1478Then either the 1479.Ar rdr 1480rules are evaluated on an inbound packet or the 1481.Ar nat 1482rules on an outbound packet. 1483Rules of the same type are evaluated in the same order in which they 1484appear in the ruleset. 1485The first matching rule decides what action is taken. 1486.Pp 1487The 1488.Ar no 1489option prefixed to a translation rule causes packets to remain untranslated, 1490much in the same way as 1491.Ar drop quick 1492works in the packet filter (see below). 1493If no rule matches the packet it is passed to the filter engine unmodified. 1494.Pp 1495Translation rules apply only to packets that pass through 1496the specified interface, and if no interface is specified, 1497translation is applied to packets on all interfaces. 1498For instance, redirecting port 80 on an external interface to an internal 1499web server will only work for connections originating from the outside. 1500Connections to the address of the external interface from local hosts will 1501not be redirected, since such packets do not actually pass through the 1502external interface. 1503Redirections cannot reflect packets back through the interface they arrive 1504on, they can only be redirected to hosts connected to different interfaces 1505or to the firewall itself. 1506.Pp 1507Note that redirecting external incoming connections to the loopback 1508address, as in 1509.Bd -literal -offset indent 1510rdr on ne3 inet proto tcp to port smtp -> 127.0.0.1 port spamd 1511.Ed 1512.Pp 1513will effectively allow an external host to connect to daemons 1514bound solely to the loopback address, circumventing the traditional 1515blocking of such connections on a real interface. 1516Unless this effect is desired, any of the local non-loopback addresses 1517should be used as redirection target instead, which allows external 1518connections only to daemons bound to this address or not bound to 1519any address. 1520.Pp 1521See 1522.Sx TRANSLATION EXAMPLES 1523below. 1524.Sh PACKET FILTERING 1525.Xr pf 4 1526has the ability to 1527.Ar block 1528, 1529.Ar pass 1530and 1531.Ar match 1532packets based on attributes of their layer 3 (see 1533.Xr ip 4 1534and 1535.Xr ip6 4 ) 1536and layer 4 (see 1537.Xr icmp 4 , 1538.Xr icmp6 4 , 1539.Xr tcp 4 , 1540.Xr sctp 4 , 1541.Xr udp 4 ) 1542headers. 1543In addition, packets may also be 1544assigned to queues for the purpose of bandwidth control. 1545.Pp 1546For each packet processed by the packet filter, the filter rules are 1547evaluated in sequential order, from first to last. 1548For 1549.Ar block 1550and 1551.Ar pass 1552, the last matching rule decides what action is taken. 1553For 1554.Ar match 1555, rules are evaluated every time they match; the pass/block state of a packet 1556remains unchanged. 1557If no rule matches the packet, the default action is to pass 1558the packet. 1559.Pp 1560The following actions can be used in the filter: 1561.Bl -tag -width xxxx 1562.It Ar block 1563The packet is blocked. 1564There are a number of ways in which a 1565.Ar block 1566rule can behave when blocking a packet. 1567The default behaviour is to 1568.Ar drop 1569packets silently, however this can be overridden or made 1570explicit either globally, by setting the 1571.Ar block-policy 1572option, or on a per-rule basis with one of the following options: 1573.Pp 1574.Bl -tag -width xxxx -compact 1575.It Ar drop 1576The packet is silently dropped. 1577.It Ar return-rst 1578This applies only to 1579.Xr tcp 4 1580packets, and issues a TCP RST which closes the 1581connection. 1582.It Ar return-icmp 1583.It Ar return-icmp6 1584This causes ICMP messages to be returned for packets which match the rule. 1585By default this is an ICMP UNREACHABLE message, however this 1586can be overridden by specifying a message as a code or number. 1587.It Ar return 1588This causes a TCP RST to be returned for 1589.Xr tcp 4 1590packets, an SCTP ABORT for SCTP 1591and an ICMP UNREACHABLE for UDP and other packets. 1592.El 1593.Pp 1594Options returning ICMP packets currently have no effect if 1595.Xr pf 4 1596operates on a 1597.Xr if_bridge 4 , 1598as the code to support this feature has not yet been implemented. 1599.Pp 1600The simplest mechanism to block everything by default and only pass 1601packets that match explicit rules is specify a first filter rule of: 1602.Bd -literal -offset indent 1603block all 1604.Ed 1605.It Ar match 1606The packet is matched. 1607This mechanism is used to provide fine grained filtering without altering the 1608block/pass state of a packet. 1609.Ar match 1610rules differ from 1611.Ar block 1612and 1613.Ar pass 1614rules in that parameters are set for every rule a packet matches, not only 1615on the last matching rule. 1616For the following parameters, this means that the parameter effectively becomes 1617"sticky" until explicitly overridden: 1618.Ar queue , 1619.Ar dnpipe , 1620.Ar dnqueue , 1621.Ar rtable , 1622.Ar scrub 1623. 1624.It Ar pass 1625The packet is passed; 1626state is created unless the 1627.Ar no state 1628option is specified. 1629.El 1630.Pp 1631By default 1632.Xr pf 4 1633filters packets statefully; the first time a packet matches a 1634.Ar pass 1635rule, a state entry is created; for subsequent packets the filter checks 1636whether the packet matches any state. 1637If it does, the packet is passed without evaluation of any rules. 1638After the connection is closed or times out, the state entry is automatically 1639removed. 1640.Pp 1641This has several advantages. 1642For TCP connections, comparing a packet to a state involves checking 1643its sequence numbers, as well as TCP timestamps if a 1644.Ar scrub reassemble tcp 1645rule applies to the connection. 1646If these values are outside the narrow windows of expected 1647values, the packet is dropped. 1648This prevents spoofing attacks, such as when an attacker sends packets with 1649a fake source address/port but does not know the connection's sequence 1650numbers. 1651Similarly, 1652.Xr pf 4 1653knows how to match ICMP replies to states. 1654For example, 1655.Bd -literal -offset indent 1656pass out inet proto icmp all icmp-type echoreq 1657.Ed 1658.Pp 1659allows echo requests (such as those created by 1660.Xr ping 8 ) 1661out statefully, and matches incoming echo replies correctly to states. 1662.Pp 1663Also, looking up states is usually faster than evaluating rules. 1664.Pp 1665Furthermore, correct handling of ICMP error messages is critical to 1666many protocols, particularly TCP. 1667.Xr pf 4 1668matches ICMP error messages to the correct connection, checks them against 1669connection parameters, and passes them if appropriate. 1670For example if an ICMP source quench message referring to a stateful TCP 1671connection arrives, it will be matched to the state and get passed. 1672.Pp 1673Finally, state tracking is required for 1674.Ar nat , binat No and Ar rdr 1675rules, in order to track address and port translations and reverse the 1676translation on returning packets. 1677.Pp 1678.Xr pf 4 1679will also create state for other protocols which are effectively stateless by 1680nature. 1681UDP packets are matched to states using only host addresses and ports, 1682and other protocols are matched to states using only the host addresses. 1683.Pp 1684If stateless filtering of individual packets is desired, 1685the 1686.Ar no state 1687keyword can be used to specify that state will not be created 1688if this is the last matching rule. 1689A number of parameters can also be set to affect how 1690.Xr pf 4 1691handles state tracking. 1692See 1693.Sx STATEFUL TRACKING OPTIONS 1694below for further details. 1695.Sh PARAMETERS 1696The rule parameters specify the packets to which a rule applies. 1697A packet always comes in on, or goes out through, one interface. 1698Most parameters are optional. 1699If a parameter is specified, the rule only applies to packets with 1700matching attributes. 1701Certain parameters can be expressed as lists, in which case 1702.Xr pfctl 8 1703generates all needed rule combinations. 1704.Bl -tag -width xxxx 1705.It Ar in No or Ar out 1706This rule applies to incoming or outgoing packets. 1707If neither 1708.Ar in 1709nor 1710.Ar out 1711are specified, the rule will match packets in both directions. 1712.It Ar log Pq Cm all | matches | to Ao Ar interface Ac | Cm user 1713In addition to any action specified, 1714log the packet. 1715Only the packet that establishes the state is logged, 1716unless the 1717.Ar no state 1718option is specified. 1719The logged packets are sent to a 1720.Xr pflog 4 1721interface, by default pflog0; 1722pflog0 is monitored by the 1723.Xr pflogd 8 1724logging daemon which logs to the file 1725.Pa /var/log/pflog 1726in 1727.Xr pcap 3 1728binary format. 1729.Pp 1730The keywords 1731.Cm all , matches , to , 1732and 1733.Cm user 1734are optional and can be combined using commas, 1735but must be enclosed in parentheses if given. 1736.Pp 1737Use 1738.Cm all 1739to force logging of all packets for a connection. 1740This is not necessary when 1741.Ar no state 1742is explicitly specified. 1743.Pp 1744If 1745.Cm matches 1746is specified, 1747it logs the packet on all subsequent matching rules. 1748It is often combined with 1749.Cm to Aq Ar interface 1750to avoid adding noise to the default log file. 1751.Pp 1752The keyword 1753.Cm user 1754logs the 1755.Ux 1756user ID of the user that owns the socket and the PID of the process that 1757has the socket open where the packet is sourced from or destined to 1758(depending on which socket is local). 1759This is in addition to the normal information logged. 1760.Pp 1761Only the first packet 1762logged via 1763.Ar log (all, user) 1764will have the user credentials logged when using stateful matching. 1765.Pp 1766To specify a logging interface other than pflog0, 1767use the syntax 1768.Cm to Aq Ar interface . 1769.It Ar quick 1770If a packet matches a rule which has the 1771.Ar quick 1772option set, this rule 1773is considered the last matching rule, and evaluation of subsequent rules 1774is skipped. 1775.It Ar on Aq Ar interface 1776This rule applies only to packets coming in on, or going out through, this 1777particular interface or interface group. 1778For more information on interface groups, 1779see the 1780.Ic group 1781keyword in 1782.Xr ifconfig 8 . 1783.Ar any 1784will match any existing interface except loopback ones. 1785.It Aq Ar af 1786This rule applies only to packets of this address family. 1787Supported values are 1788.Ar inet 1789and 1790.Ar inet6 . 1791.It Ar proto Aq Ar protocol 1792This rule applies only to packets of this protocol. 1793Common protocols are 1794.Xr icmp 4 , 1795.Xr icmp6 4 , 1796.Xr tcp 4 , 1797.Xr sctp 4 , 1798and 1799.Xr udp 4 . 1800For a list of all the protocol name to number mappings used by 1801.Xr pfctl 8 , 1802see the file 1803.Pa /etc/protocols . 1804.It Xo 1805.Ar from Aq Ar source 1806.Ar port Aq Ar source 1807.Ar os Aq Ar source 1808.Ar to Aq Ar dest 1809.Ar port Aq Ar dest 1810.Xc 1811This rule applies only to packets with the specified source and destination 1812addresses and ports. 1813.Pp 1814Addresses can be specified in CIDR notation (matching netblocks), as 1815symbolic host names, interface names or interface group names, or as any 1816of the following keywords: 1817.Pp 1818.Bl -tag -width xxxxxxxxxxxxxx -compact 1819.It Ar any 1820Any address. 1821.It Ar no-route 1822Any address which is not currently routable. 1823.It Ar urpf-failed 1824Any source address that fails a unicast reverse path forwarding (URPF) 1825check, i.e. packets coming in on an interface other than that which holds 1826the route back to the packet's source address. 1827.It Ar self 1828Expands to all addresses assigned to all interfaces. 1829.It Aq Ar table 1830Any address that matches the given table. 1831.El 1832.Pp 1833Ranges of addresses are specified by using the 1834.Sq - 1835operator. 1836For instance: 1837.Dq 10.1.1.10 - 10.1.1.12 1838means all addresses from 10.1.1.10 to 10.1.1.12, 1839hence addresses 10.1.1.10, 10.1.1.11, and 10.1.1.12. 1840.Pp 1841Interface names and interface group names, and 1842.Ar self 1843can have modifiers appended: 1844.Pp 1845.Bl -tag -width xxxxxxxxxxxx -compact 1846.It Ar :network 1847Translates to the network(s) attached to the interface. 1848.It Ar :broadcast 1849Translates to the interface's broadcast address(es). 1850.It Ar :peer 1851Translates to the point-to-point interface's peer address(es). 1852.It Ar :0 1853Do not include interface aliases. 1854.El 1855.Pp 1856Host names may also have the 1857.Ar :0 1858option appended to restrict the name resolution to the first of each 1859v4 and non-link-local v6 address found. 1860.Pp 1861Host name resolution and interface to address translation are done at 1862ruleset load-time. 1863When the address of an interface (or host name) changes (under DHCP or PPP, 1864for instance), the ruleset must be reloaded for the change to be reflected 1865in the kernel. 1866Surrounding the interface name (and optional modifiers) in parentheses 1867changes this behaviour. 1868When the interface name is surrounded by parentheses, the rule is 1869automatically updated whenever the interface changes its address. 1870The ruleset does not need to be reloaded. 1871This is especially useful with 1872.Ar nat . 1873.Pp 1874Ports can be specified either by number or by name. 1875For example, port 80 can be specified as 1876.Em www . 1877For a list of all port name to number mappings used by 1878.Xr pfctl 8 , 1879see the file 1880.Pa /etc/services . 1881.Pp 1882Ports and ranges of ports are specified by using these operators: 1883.Bd -literal -offset indent 1884= (equal) 1885!= (unequal) 1886< (less than) 1887<= (less than or equal) 1888> (greater than) 1889>= (greater than or equal) 1890: (range including boundaries) 1891>< (range excluding boundaries) 1892<> (except range) 1893.Ed 1894.Pp 1895.Sq >< , 1896.Sq <> 1897and 1898.Sq \&: 1899are binary operators (they take two arguments). 1900For instance: 1901.Bl -tag -width Fl 1902.It Ar port 2000:2004 1903means 1904.Sq all ports >= 2000 and <= 2004 , 1905hence ports 2000, 2001, 2002, 2003 and 2004. 1906.It Ar port 2000 >< 2004 1907means 1908.Sq all ports > 2000 and < 2004 , 1909hence ports 2001, 2002 and 2003. 1910.It Ar port 2000 <> 2004 1911means 1912.Sq all ports < 2000 or > 2004 , 1913hence ports 1-1999 and 2005-65535. 1914.El 1915.Pp 1916The operating system of the source host can be specified in the case of TCP 1917rules with the 1918.Ar OS 1919modifier. 1920See the 1921.Sx OPERATING SYSTEM FINGERPRINTING 1922section for more information. 1923.Pp 1924The host, port and OS specifications are optional, as in the following examples: 1925.Bd -literal -offset indent 1926pass in all 1927pass in from any to any 1928pass in proto tcp from any port < 1024 to any 1929pass in proto tcp from any to any port 25 1930pass in proto tcp from 10.0.0.0/8 port >= 1024 \e 1931 to ! 10.1.2.3 port != ssh 1932pass in proto tcp from any os "OpenBSD" 1933.Ed 1934.It Ar all 1935This is equivalent to "from any to any". 1936.It Ar group Aq Ar group 1937Similar to 1938.Ar user , 1939this rule only applies to packets of sockets owned by the specified group. 1940.It Ar user Aq Ar user 1941This rule only applies to packets of sockets owned by the specified user. 1942For outgoing connections initiated from the firewall, this is the user 1943that opened the connection. 1944For incoming connections to the firewall itself, this is the user that 1945listens on the destination port. 1946For forwarded connections, where the firewall is not a connection endpoint, 1947the user and group are 1948.Em unknown . 1949.Pp 1950All packets, both outgoing and incoming, of one connection are associated 1951with the same user and group. 1952Only TCP and UDP packets can be associated with users; for other protocols 1953these parameters are ignored. 1954.Pp 1955User and group refer to the effective (as opposed to the real) IDs, in 1956case the socket is created by a setuid/setgid process. 1957User and group IDs are stored when a socket is created; 1958when a process creates a listening socket as root (for instance, by 1959binding to a privileged port) and subsequently changes to another 1960user ID (to drop privileges), the credentials will remain root. 1961.Pp 1962User and group IDs can be specified as either numbers or names. 1963The syntax is similar to the one for ports. 1964The value 1965.Em unknown 1966matches packets of forwarded connections. 1967.Em unknown 1968can only be used with the operators 1969.Cm = 1970and 1971.Cm != . 1972Other constructs like 1973.Cm user \*(Ge unknown 1974are invalid. 1975Forwarded packets with unknown user and group ID match only rules 1976that explicitly compare against 1977.Em unknown 1978with the operators 1979.Cm = 1980or 1981.Cm != . 1982For instance 1983.Cm user \*(Ge 0 1984does not match forwarded packets. 1985The following example allows only selected users to open outgoing 1986connections: 1987.Bd -literal -offset indent 1988block out proto { tcp, udp } all 1989pass out proto { tcp, udp } all user { < 1000, dhartmei } 1990.Ed 1991.It Xo Ar flags Aq Ar a 1992.Pf / Ns Aq Ar b 1993.No \*(Ba / Ns Aq Ar b 1994.No \*(Ba any 1995.Xc 1996This rule only applies to TCP packets that have the flags 1997.Aq Ar a 1998set out of set 1999.Aq Ar b . 2000Flags not specified in 2001.Aq Ar b 2002are ignored. 2003For stateful connections, the default is 2004.Ar flags S/SA . 2005To indicate that flags should not be checked at all, specify 2006.Ar flags any . 2007The flags are: (F)IN, (S)YN, (R)ST, (P)USH, (A)CK, (U)RG, (E)CE, and C(W)R. 2008.Bl -tag -width Fl 2009.It Ar flags S/S 2010Flag SYN is set. 2011The other flags are ignored. 2012.It Ar flags S/SA 2013This is the default setting for stateful connections. 2014Out of SYN and ACK, exactly SYN may be set. 2015SYN, SYN+PSH and SYN+RST match, but SYN+ACK, ACK and ACK+RST do not. 2016This is more restrictive than the previous example. 2017.It Ar flags /SFRA 2018If the first set is not specified, it defaults to none. 2019All of SYN, FIN, RST and ACK must be unset. 2020.El 2021.Pp 2022Because 2023.Ar flags S/SA 2024is applied by default (unless 2025.Ar no state 2026is specified), only the initial SYN packet of a TCP handshake will create 2027a state for a TCP connection. 2028It is possible to be less restrictive, and allow state creation from 2029intermediate 2030.Pq non-SYN 2031packets, by specifying 2032.Ar flags any . 2033This will cause 2034.Xr pf 4 2035to synchronize to existing connections, for instance 2036if one flushes the state table. 2037However, states created from such intermediate packets may be missing 2038connection details such as the TCP window scaling factor. 2039States which modify the packet flow, such as those affected by 2040.Ar af-to, 2041.Ar nat, 2042.Ar binat or 2043.Ar rdr 2044rules, 2045.Ar modulate No or Ar synproxy state 2046options, or scrubbed with 2047.Ar reassemble tcp 2048will also not be recoverable from intermediate packets. 2049Such connections will stall and time out. 2050.It Xo Ar icmp-type Aq Ar type 2051.Ar code Aq Ar code 2052.Xc 2053.It Xo Ar icmp6-type Aq Ar type 2054.Ar code Aq Ar code 2055.Xc 2056This rule only applies to ICMP or ICMPv6 packets with the specified type 2057and code. 2058Text names for ICMP types and codes are listed in 2059.Xr icmp 4 2060and 2061.Xr icmp6 4 . 2062This parameter is only valid for rules that cover protocols ICMP or 2063ICMP6. 2064The protocol and the ICMP type indicator 2065.Po 2066.Ar icmp-type 2067or 2068.Ar icmp6-type 2069.Pc 2070must match. 2071.It Xo Ar tos Aq Ar string 2072.No \*(Ba Aq Ar number 2073.Xc 2074This rule applies to packets with the specified 2075.Em TOS 2076bits set. 2077.Em TOS 2078may be 2079given as one of 2080.Ar critical , 2081.Ar inetcontrol , 2082.Ar lowdelay , 2083.Ar netcontrol , 2084.Ar throughput , 2085.Ar reliability , 2086or one of the DiffServ Code Points: 2087.Ar ef , 2088.Ar va , 2089.Ar af11 No ... Ar af43 , 2090.Ar cs0 No ... Ar cs7 ; 2091or as either hex or decimal. 2092.Pp 2093For example, the following rules are identical: 2094.Bd -literal -offset indent 2095pass all tos lowdelay 2096pass all tos 0x10 2097pass all tos 16 2098.Ed 2099.It Ar allow-opts 2100By default, IPv4 packets with IP options or IPv6 packets with routing 2101extension headers are blocked. 2102When 2103.Ar allow-opts 2104is specified for a 2105.Ar pass 2106rule, packets that pass the filter based on that rule (last matching) 2107do so even if they contain IP options or routing extension headers. 2108For packets that match state, the rule that initially created the 2109state is used. 2110The implicit 2111.Ar pass 2112rule that is used when a packet does not match any rules does not 2113allow IP options. 2114.It Ar label Aq Ar string 2115Adds a label (name) to the rule, which can be used to identify the rule. 2116For instance, 2117pfctl -s labels 2118shows per-rule statistics for rules that have labels. 2119.Pp 2120The following macros can be used in labels: 2121.Pp 2122.Bl -tag -width $srcaddr -compact -offset indent 2123.It Ar $if 2124The interface. 2125.It Ar $srcaddr 2126The source IP address. 2127.It Ar $dstaddr 2128The destination IP address. 2129.It Ar $srcport 2130The source port specification. 2131.It Ar $dstport 2132The destination port specification. 2133.It Ar $proto 2134The protocol name. 2135.It Ar $nr 2136The rule number. 2137.El 2138.Pp 2139For example: 2140.Bd -literal -offset indent 2141ips = \&"{ 1.2.3.4, 1.2.3.5 }\&" 2142pass in proto tcp from any to $ips \e 2143 port > 1023 label \&"$dstaddr:$dstport\&" 2144.Ed 2145.Pp 2146expands to 2147.Bd -literal -offset indent 2148pass in inet proto tcp from any to 1.2.3.4 \e 2149 port > 1023 label \&"1.2.3.4:>1023\&" 2150pass in inet proto tcp from any to 1.2.3.5 \e 2151 port > 1023 label \&"1.2.3.5:>1023\&" 2152.Ed 2153.Pp 2154The macro expansion for the 2155.Ar label 2156directive occurs only at configuration file parse time, not during runtime. 2157.It Ar ridentifier Aq Ar number 2158Add an identifier (number) to the rule, which can be used to correlate the rule 2159to pflog entries, even after ruleset updates. 2160.It Xo Ar queue Aq Ar queue 2161.No \*(Ba ( Aq Ar queue , 2162.Aq Ar queue ) 2163.Xc 2164Packets matching this rule will be assigned to the specified queue. 2165If two queues are given, packets which have a 2166.Em TOS 2167of 2168.Em lowdelay 2169and TCP ACKs with no data payload will be assigned to the second one. 2170See 2171.Sx QUEUEING 2172for setup details. 2173.Pp 2174For example: 2175.Bd -literal -offset indent 2176pass in proto tcp to port 25 queue mail 2177pass in proto tcp to port 22 queue(ssh_bulk, ssh_prio) 2178.Ed 2179.It Cm set prio Ar priority | Pq Ar priority , priority 2180Packets matching this rule will be assigned a specific queueing priority. 2181Priorities are assigned as integers 0 through 7. 2182If the packet is transmitted on a 2183.Xr vlan 4 2184interface, the queueing priority will be written as the priority 2185code point in the 802.1Q VLAN header. 2186If two priorities are given, packets which have a TOS of 2187.Cm lowdelay 2188and TCP ACKs with no data payload will be assigned to the second one. 2189.Pp 2190For example: 2191.Bd -literal -offset indent 2192pass in proto tcp to port 25 set prio 2 2193pass in proto tcp to port 22 set prio (2, 5) 2194.Ed 2195.It Ar received-on Aq Ar interface 2196Only match packets which were received on the specified 2197.Ar interface 2198(or interface group). 2199.Ar any 2200will match any existing interface except loopback ones. 2201.It Ar tag Aq Ar string 2202Packets matching this rule will be tagged with the 2203specified string. 2204The tag acts as an internal marker that can be used to 2205identify these packets later on. 2206This can be used, for example, to provide trust between 2207interfaces and to determine if packets have been 2208processed by translation rules. 2209Tags are 2210.Qq sticky , 2211meaning that the packet will be tagged even if the rule 2212is not the last matching rule. 2213Further matching rules can replace the tag with a 2214new one but will not remove a previously applied tag. 2215A packet is only ever assigned one tag at a time. 2216Packet tagging can be done during 2217.Ar nat , 2218.Ar rdr , 2219.Ar binat 2220or 2221.Ar ether 2222rules in addition to filter rules. 2223Tags take the same macros as labels (see above). 2224.It Ar tagged Aq Ar string 2225Used with filter, translation or scrub rules 2226to specify that packets must already 2227be tagged with the given tag in order to match the rule. 2228Inverse tag matching can also be done 2229by specifying the 2230.Cm !\& 2231operator before the 2232.Ar tagged 2233keyword. 2234.It Ar rtable Aq Ar number 2235Used to select an alternate routing table for the routing lookup. 2236Only effective before the route lookup happened, i.e. when filtering inbound. 2237.It Xo Ar divert-to Aq Ar host 2238.Ar port Aq Ar port 2239.Xc 2240Used to 2241.Xr divert 4 2242packets to the given divert 2243.Ar port . 2244Historically 2245.Ox pf has another meaning for this, and 2246.Fx pf uses 2247this syntax to support 2248.Xr divert 4 instead. Hence, 2249.Ar host 2250has no meaning and can be set to anything like 127.0.0.1. 2251If a packet is re-injected and does not change direction then it will not be 2252re-diverted. 2253.It Ar divert-reply 2254It has no meaning in 2255.Fx pf . 2256.It Ar probability Aq Ar number 2257A probability attribute can be attached to a rule, with a value set between 22580 and 1, bounds not included. 2259In that case, the rule will be honoured using the given probability value 2260only. 2261For example, the following rule will drop 20% of incoming ICMP packets: 2262.Bd -literal -offset indent 2263block in proto icmp probability 20% 2264.Ed 2265.It Ar prio Aq Ar number 2266Only match packets which have the given queueing priority assigned. 2267.El 2268.Sh ROUTING 2269If a packet matches a rule with a route option set, the packet filter will 2270route the packet according to the type of route option. 2271When such a rule creates state, the route option is also applied to all 2272packets matching the same connection. 2273.Bl -tag -width xxxx 2274.It Ar route-to 2275The 2276.Ar route-to 2277option routes the packet to the specified interface with an optional address 2278for the next hop. 2279When a 2280.Ar route-to 2281rule creates state, only packets that pass in the same direction as the 2282filter rule specifies will be routed in this way. 2283Packets passing in the opposite direction (replies) are not affected 2284and are routed normally. 2285.It Ar reply-to 2286The 2287.Ar reply-to 2288option is similar to 2289.Ar route-to , 2290but routes packets that pass in the opposite direction (replies) to the 2291specified interface. 2292Opposite direction is only defined in the context of a state entry, and 2293.Ar reply-to 2294is useful only in rules that create state. 2295It can be used on systems with multiple external connections to 2296route all outgoing packets of a connection through the interface 2297the incoming connection arrived through (symmetric routing enforcement). 2298.It Ar dup-to 2299The 2300.Ar dup-to 2301option creates a duplicate of the packet and routes it like 2302.Ar route-to . 2303The original packet gets routed as it normally would. 2304.El 2305.Sh POOL OPTIONS 2306For 2307.Ar nat 2308and 2309.Ar rdr 2310rules, (as well as for the 2311.Ar route-to , 2312.Ar reply-to 2313and 2314.Ar dup-to 2315rule options) for which there is a single redirection address which has a 2316subnet mask smaller than 32 for IPv4 or 128 for IPv6 (more than one IP 2317address), a variety of different methods for assigning this address can be 2318used: 2319.Bl -tag -width xxxx 2320.It Ar bitmask 2321The 2322.Ar bitmask 2323option applies the network portion of the redirection address to the address 2324to be modified (source with 2325.Ar nat , 2326destination with 2327.Ar rdr ) . 2328.It Ar random 2329The 2330.Ar random 2331option selects an address at random within the defined block of addresses. 2332.It Ar source-hash 2333The 2334.Ar source-hash 2335option uses a hash of the source address to determine the redirection address, 2336ensuring that the redirection address is always the same for a given source. 2337An optional key can be specified after this keyword either in hex or as a 2338string; by default 2339.Xr pfctl 8 2340randomly generates a key for source-hash every time the 2341ruleset is reloaded. 2342.It Ar round-robin 2343The 2344.Ar round-robin 2345option loops through the redirection address(es). 2346.Pp 2347When more than one redirection address is specified, 2348.Ar bitmask 2349is not permitted as a pool type. 2350.It Ar static-port 2351With 2352.Ar nat 2353rules, the 2354.Ar static-port 2355option prevents 2356.Xr pf 4 2357from modifying the source port on TCP and UDP packets. 2358.It Xo Ar map-e-portset Aq Ar psid-offset 2359.No / Aq Ar psid-len 2360.No / Aq Ar psid 2361.Xc 2362With 2363.Ar nat 2364rules, the 2365.Ar map-e-portset 2366option enables the source port translation of MAP-E (RFC 7597) Customer Edge. 2367In order to make the host act as a MAP-E Customer Edge, setting up a tunneling 2368interface and pass rules for encapsulated packets are required in addition 2369to the map-e-portset nat rule. 2370.Pp 2371For example: 2372.Bd -literal -offset indent 2373nat on $gif_mape_if from $int_if:network to any \e 2374 -> $ipv4_mape_src map-e-portset 6/8/0x34 2375.Ed 2376.Pp 2377sets PSID offset 6, PSID length 8, PSID 0x34. 2378.It Ar endpoint-independent 2379With 2380.Ar nat 2381rules, the 2382.Ar endpoint-independent 2383option caues 2384.Xr pf 4 2385to always map connections from a UDP source address and port to the same 2386NAT address and port. 2387This feature implements "full-cone" NAT behavior. 2388.El 2389.Pp 2390Additionally, the 2391.Ar sticky-address 2392option can be specified to help ensure that multiple connections from the 2393same source are mapped to the same redirection address. 2394This option can be used with the 2395.Ar random 2396and 2397.Ar round-robin 2398pool options. 2399Note that by default these associations are destroyed as soon as there are 2400no longer states which refer to them; in order to make the mappings last 2401beyond the lifetime of the states, increase the global options with 2402.Ar set timeout src.track . 2403See 2404.Sx STATEFUL TRACKING OPTIONS 2405for more ways to control the source tracking. 2406.Sh STATE MODULATION 2407Much of the security derived from TCP is attributable to how well the 2408initial sequence numbers (ISNs) are chosen. 2409Some popular stack implementations choose 2410.Em very 2411poor ISNs and thus are normally susceptible to ISN prediction exploits. 2412By applying a 2413.Ar modulate state 2414rule to a TCP connection, 2415.Xr pf 4 2416will create a high quality random sequence number for each connection 2417endpoint. 2418.Pp 2419The 2420.Ar modulate state 2421directive implicitly keeps state on the rule and is 2422only applicable to TCP connections. 2423.Pp 2424For instance: 2425.Bd -literal -offset indent 2426block all 2427pass out proto tcp from any to any modulate state 2428pass in proto tcp from any to any port 25 flags S/SFRA modulate state 2429.Ed 2430.Pp 2431Note that modulated connections will not recover when the state table 2432is lost (firewall reboot, flushing the state table, etc...). 2433.Xr pf 4 2434will not be able to infer a connection again after the state table flushes 2435the connection's modulator. 2436When the state is lost, the connection may be left dangling until the 2437respective endpoints time out the connection. 2438It is possible on a fast local network for the endpoints to start an ACK 2439storm while trying to resynchronize after the loss of the modulator. 2440The default 2441.Ar flags 2442settings (or a more strict equivalent) should be used on 2443.Ar modulate state 2444rules to prevent ACK storms. 2445.Pp 2446Note that alternative methods are available 2447to prevent loss of the state table 2448and allow for firewall failover. 2449See 2450.Xr carp 4 2451and 2452.Xr pfsync 4 2453for further information. 2454.Sh SYN PROXY 2455By default, 2456.Xr pf 4 2457passes packets that are part of a 2458.Xr tcp 4 2459handshake between the endpoints. 2460The 2461.Ar synproxy state 2462option can be used to cause 2463.Xr pf 4 2464itself to complete the handshake with the active endpoint, perform a handshake 2465with the passive endpoint, and then forward packets between the endpoints. 2466.Pp 2467No packets are sent to the passive endpoint before the active endpoint has 2468completed the handshake, hence so-called SYN floods with spoofed source 2469addresses will not reach the passive endpoint, as the sender can't complete the 2470handshake. 2471.Pp 2472The proxy is transparent to both endpoints, they each see a single 2473connection from/to the other endpoint. 2474.Xr pf 4 2475chooses random initial sequence numbers for both handshakes. 2476Once the handshakes are completed, the sequence number modulators 2477(see previous section) are used to translate further packets of the 2478connection. 2479.Ar synproxy state 2480includes 2481.Ar modulate state . 2482.Pp 2483Rules with 2484.Ar synproxy 2485will not work if 2486.Xr pf 4 2487operates on a 2488.Xr bridge 4 . 2489.Pp 2490Example: 2491.Bd -literal -offset indent 2492pass in proto tcp from any to any port www synproxy state 2493.Ed 2494.Sh STATEFUL TRACKING OPTIONS 2495A number of options related to stateful tracking can be applied on a 2496per-rule basis. 2497.Ar keep state , 2498.Ar modulate state 2499and 2500.Ar synproxy state 2501support these options, and 2502.Ar keep state 2503must be specified explicitly to apply options to a rule. 2504.Pp 2505.Bl -tag -width xxxx -compact 2506.It Ar max Aq Ar number 2507Limits the number of concurrent states the rule may create. 2508When this limit is reached, further packets that would create 2509state are dropped until existing states time out. 2510.It Ar no-sync 2511Prevent state changes for states created by this rule from appearing on the 2512.Xr pfsync 4 2513interface. 2514.It Xo Aq Ar timeout 2515.Aq Ar seconds 2516.Xc 2517Changes the timeout values used for states created by this rule. 2518For a list of all valid timeout names, see 2519.Sx OPTIONS 2520above. 2521.It Ar sloppy 2522Uses a sloppy TCP connection tracker that does not check sequence 2523numbers at all, which makes insertion and ICMP teardown attacks way 2524easier. 2525This is intended to be used in situations where one does not see all 2526packets of a connection, e.g. in asymmetric routing situations. 2527Cannot be used with modulate or synproxy state. 2528.It Ar pflow 2529States created by this rule are exported on the 2530.Xr pflow 4 2531interface. 2532.It Ar allow-related 2533Automatically allow connections related to this one, regardless of rules that 2534might otherwise affect them. 2535This currently only applies to SCTP multihomed connection. 2536.El 2537.Pp 2538Multiple options can be specified, separated by commas: 2539.Bd -literal -offset indent 2540pass in proto tcp from any to any \e 2541 port www keep state \e 2542 (max 100, source-track rule, max-src-nodes 75, \e 2543 max-src-states 3, tcp.established 60, tcp.closing 5) 2544.Ed 2545.Pp 2546When the 2547.Ar source-track 2548keyword is specified, the number of states per source IP is tracked. 2549.Pp 2550.Bl -tag -width xxxx -compact 2551.It Ar source-track rule 2552The maximum number of states created by this rule is limited by the rule's 2553.Ar max-src-nodes 2554and 2555.Ar max-src-states 2556options. 2557Only state entries created by this particular rule count toward the rule's 2558limits. 2559.It Ar source-track global 2560The number of states created by all rules that use this option is limited. 2561Each rule can specify different 2562.Ar max-src-nodes 2563and 2564.Ar max-src-states 2565options, however state entries created by any participating rule count towards 2566each individual rule's limits. 2567.El 2568.Pp 2569The following limits can be set: 2570.Pp 2571.Bl -tag -width xxxx -compact 2572.It Ar max-src-nodes Aq Ar number 2573Limits the maximum number of source addresses which can simultaneously 2574have state table entries. 2575.It Ar max-src-states Aq Ar number 2576Limits the maximum number of simultaneous state entries that a single 2577source address can create with this rule. 2578.El 2579.Pp 2580For stateful TCP connections, limits on established connections (connections 2581which have completed the TCP 3-way handshake) can also be enforced 2582per source IP. 2583.Pp 2584.Bl -tag -width xxxx -compact 2585.It Ar max-src-conn Aq Ar number 2586Limits the maximum number of simultaneous TCP connections which have 2587completed the 3-way handshake that a single host can make. 2588.It Xo Ar max-src-conn-rate Aq Ar number 2589.No / Aq Ar seconds 2590.Xc 2591Limit the rate of new connections over a time interval. 2592The connection rate is an approximation calculated as a moving average. 2593.El 2594.Pp 2595When one of these limits is reached, further packets that would create 2596state are dropped until existing states time out. 2597.Pp 2598Because the 3-way handshake ensures that the source address is not being 2599spoofed, more aggressive action can be taken based on these limits. 2600With the 2601.Ar overload Aq Ar table 2602state option, source IP addresses which hit either of the limits on 2603established connections will be added to the named table. 2604This table can be used in the ruleset to block further activity from 2605the offending host, redirect it to a tarpit process, or restrict its 2606bandwidth. 2607.Pp 2608The optional 2609.Ar flush 2610keyword kills all states created by the matching rule which originate 2611from the host which exceeds these limits. 2612The 2613.Ar global 2614modifier to the flush command kills all states originating from the 2615offending host, regardless of which rule created the state. 2616.Pp 2617For example, the following rules will protect the webserver against 2618hosts making more than 100 connections in 10 seconds. 2619Any host which connects faster than this rate will have its address added 2620to the 2621.Aq bad_hosts 2622table and have all states originating from it flushed. 2623Any new packets arriving from this host will be dropped unconditionally 2624by the block rule. 2625.Bd -literal -offset indent 2626block quick from <bad_hosts> 2627pass in on $ext_if proto tcp to $webserver port www keep state \e 2628 (max-src-conn-rate 100/10, overload <bad_hosts> flush global) 2629.Ed 2630.Sh OPERATING SYSTEM FINGERPRINTING 2631Passive OS Fingerprinting is a mechanism to inspect nuances of a TCP 2632connection's initial SYN packet and guess at the host's operating system. 2633Unfortunately these nuances are easily spoofed by an attacker so the 2634fingerprint is not useful in making security decisions. 2635But the fingerprint is typically accurate enough to make policy decisions 2636upon. 2637.Pp 2638The fingerprints may be specified by operating system class, by 2639version, or by subtype/patchlevel. 2640The class of an operating system is typically the vendor or genre 2641and would be 2642.Ox 2643for the 2644.Xr pf 4 2645firewall itself. 2646The version of the oldest available 2647.Ox 2648release on the main FTP site 2649would be 2.6 and the fingerprint would be written 2650.Pp 2651.Dl \&"OpenBSD 2.6\&" 2652.Pp 2653The subtype of an operating system is typically used to describe the 2654patchlevel if that patch led to changes in the TCP stack behavior. 2655In the case of 2656.Ox , 2657the only subtype is for a fingerprint that was 2658normalized by the 2659.Ar no-df 2660scrub option and would be specified as 2661.Pp 2662.Dl \&"OpenBSD 3.3 no-df\&" 2663.Pp 2664Fingerprints for most popular operating systems are provided by 2665.Xr pf.os 5 . 2666Once 2667.Xr pf 4 2668is running, a complete list of known operating system fingerprints may 2669be listed by running: 2670.Pp 2671.Dl # pfctl -so 2672.Pp 2673Filter rules can enforce policy at any level of operating system specification 2674assuming a fingerprint is present. 2675Policy could limit traffic to approved operating systems or even ban traffic 2676from hosts that aren't at the latest service pack. 2677.Pp 2678The 2679.Ar unknown 2680class can also be used as the fingerprint which will match packets for 2681which no operating system fingerprint is known. 2682.Pp 2683Examples: 2684.Bd -literal -offset indent 2685pass out proto tcp from any os OpenBSD 2686block out proto tcp from any os Doors 2687block out proto tcp from any os "Doors PT" 2688block out proto tcp from any os "Doors PT SP3" 2689block out from any os "unknown" 2690pass on lo0 proto tcp from any os "OpenBSD 3.3 lo0" 2691.Ed 2692.Pp 2693Operating system fingerprinting is limited only to the TCP SYN packet. 2694This means that it will not work on other protocols and will not match 2695a currently established connection. 2696.Pp 2697Caveat: operating system fingerprints are occasionally wrong. 2698There are three problems: an attacker can trivially craft his packets to 2699appear as any operating system he chooses; 2700an operating system patch could change the stack behavior and no fingerprints 2701will match it until the database is updated; 2702and multiple operating systems may have the same fingerprint. 2703.Sh BLOCKING SPOOFED TRAFFIC 2704"Spoofing" is the faking of IP addresses, typically for malicious 2705purposes. 2706The 2707.Ar antispoof 2708directive expands to a set of filter rules which will block all 2709traffic with a source IP from the network(s) directly connected 2710to the specified interface(s) from entering the system through 2711any other interface. 2712.Pp 2713For example, the line 2714.Bd -literal -offset indent 2715antispoof for lo0 2716.Ed 2717.Pp 2718expands to 2719.Bd -literal -offset indent 2720block drop in on ! lo0 inet from 127.0.0.1/8 to any 2721block drop in on ! lo0 inet6 from ::1 to any 2722.Ed 2723.Pp 2724For non-loopback interfaces, there are additional rules to block incoming 2725packets with a source IP address identical to the interface's IP(s). 2726For example, assuming the interface wi0 had an IP address of 10.0.0.1 and a 2727netmask of 255.255.255.0, 2728the line 2729.Bd -literal -offset indent 2730antispoof for wi0 inet 2731.Ed 2732.Pp 2733expands to 2734.Bd -literal -offset indent 2735block drop in on ! wi0 inet from 10.0.0.0/24 to any 2736block drop in inet from 10.0.0.1 to any 2737.Ed 2738.Pp 2739Caveat: Rules created by the 2740.Ar antispoof 2741directive interfere with packets sent over loopback interfaces 2742to local addresses. 2743One should pass these explicitly. 2744.Sh FRAGMENT HANDLING 2745The size of IP datagrams (packets) can be significantly larger than the 2746maximum transmission unit (MTU) of the network. 2747In cases when it is necessary or more efficient to send such large packets, 2748the large packet will be fragmented into many smaller packets that will each 2749fit onto the wire. 2750Unfortunately for a firewalling device, only the first logical fragment will 2751contain the necessary header information for the subprotocol that allows 2752.Xr pf 4 2753to filter on things such as TCP ports or to perform NAT. 2754.Pp 2755Besides the use of 2756.Ar set reassemble 2757option or 2758.Ar scrub 2759rules as described in 2760.Sx TRAFFIC NORMALIZATION 2761above, there are three options for handling fragments in the packet filter. 2762.Pp 2763One alternative is to filter individual fragments with filter rules. 2764If no 2765.Ar scrub 2766rule applies to a fragment or 2767.Ar set reassemble 2768is set to 2769.Cm no 2770, it is passed to the filter. 2771Filter rules with matching IP header parameters decide whether the 2772fragment is passed or blocked, in the same way as complete packets 2773are filtered. 2774Without reassembly, fragments can only be filtered based on IP header 2775fields (source/destination address, protocol), since subprotocol header 2776fields are not available (TCP/UDP port numbers, ICMP code/type). 2777The 2778.Ar fragment 2779option can be used to restrict filter rules to apply only to 2780fragments, but not complete packets. 2781Filter rules without the 2782.Ar fragment 2783option still apply to fragments, if they only specify IP header fields. 2784For instance, the rule 2785.Bd -literal -offset indent 2786pass in proto tcp from any to any port 80 2787.Ed 2788.Pp 2789never applies to a fragment, even if the fragment is part of a TCP 2790packet with destination port 80, because without reassembly this information 2791is not available for each fragment. 2792This also means that fragments cannot create new or match existing 2793state table entries, which makes stateful filtering and address 2794translation (NAT, redirection) for fragments impossible. 2795.Pp 2796It's also possible to reassemble only certain fragments by specifying 2797source or destination addresses or protocols as parameters in 2798.Ar scrub 2799rules. 2800.Pp 2801In most cases, the benefits of reassembly outweigh the additional 2802memory cost, and it's recommended to use 2803.Ar set reassemble 2804option or 2805.Ar scrub 2806rules with the 2807.Ar fragment reassemble 2808modifier to reassemble 2809all fragments. 2810.Pp 2811The memory allocated for fragment caching can be limited using 2812.Xr pfctl 8 . 2813Once this limit is reached, fragments that would have to be cached 2814are dropped until other entries time out. 2815The timeout value can also be adjusted. 2816.Pp 2817When forwarding reassembled IPv6 packets, pf refragments them with 2818the original maximum fragment size. 2819This allows the sender to determine the optimal fragment size by 2820path MTU discovery. 2821.Sh ANCHORS 2822Besides the main ruleset, 2823.Xr pfctl 8 2824can load rulesets into 2825.Ar anchor 2826attachment points. 2827An 2828.Ar anchor 2829is a container that can hold rules, address tables, and other anchors. 2830.Pp 2831An 2832.Ar anchor 2833has a name which specifies the path where 2834.Xr pfctl 8 2835can be used to access the anchor to perform operations on it, such as 2836attaching child anchors to it or loading rules into it. 2837Anchors may be nested, with components separated by 2838.Sq / 2839characters, similar to how file system hierarchies are laid out. 2840The main ruleset is actually the default anchor, so filter and 2841translation rules, for example, may also be contained in any anchor. 2842.Pp 2843An anchor can reference another 2844.Ar anchor 2845attachment point 2846using the following kinds 2847of rules: 2848.Bl -tag -width xxxx 2849.It Ar nat-anchor Aq Ar name 2850Evaluates the 2851.Ar nat 2852rules in the specified 2853.Ar anchor . 2854.It Ar rdr-anchor Aq Ar name 2855Evaluates the 2856.Ar rdr 2857rules in the specified 2858.Ar anchor . 2859.It Ar binat-anchor Aq Ar name 2860Evaluates the 2861.Ar binat 2862rules in the specified 2863.Ar anchor . 2864.It Ar anchor Aq Ar name 2865Evaluates the filter rules in the specified 2866.Ar anchor . 2867.It Xo Ar load anchor 2868.Aq Ar name 2869.Ar from Aq Ar file 2870.Xc 2871Loads the rules from the specified file into the 2872anchor 2873.Ar name . 2874.El 2875.Pp 2876When evaluation of the main ruleset reaches an 2877.Ar anchor 2878rule, 2879.Xr pf 4 2880will proceed to evaluate all rules specified in that anchor. 2881.Pp 2882Matching filter and translation rules marked with the 2883.Ar quick 2884option are final and abort the evaluation of the rules in other 2885anchors and the main ruleset. 2886If the 2887.Ar anchor 2888itself is marked with the 2889.Ar quick 2890option, 2891ruleset evaluation will terminate when the anchor is exited if the packet is 2892matched by any rule within the anchor. 2893.Pp 2894.Ar anchor 2895rules are evaluated relative to the anchor in which they are contained. 2896For example, all 2897.Ar anchor 2898rules specified in the main ruleset will reference anchor 2899attachment points underneath the main ruleset, and 2900.Ar anchor 2901rules specified in a file loaded from a 2902.Ar load anchor 2903rule will be attached under that anchor point. 2904.Pp 2905Rules may be contained in 2906.Ar anchor 2907attachment points which do not contain any rules when the main ruleset 2908is loaded, and later such anchors can be manipulated through 2909.Xr pfctl 8 2910without reloading the main ruleset or other anchors. 2911For example, 2912.Bd -literal -offset indent 2913ext_if = \&"kue0\&" 2914block on $ext_if all 2915anchor spam 2916pass out on $ext_if all 2917pass in on $ext_if proto tcp from any \e 2918 to $ext_if port smtp 2919.Ed 2920.Pp 2921blocks all packets on the external interface by default, then evaluates 2922all rules in the 2923.Ar anchor 2924named "spam", and finally passes all outgoing connections and 2925incoming connections to port 25. 2926.Bd -literal -offset indent 2927# echo \&"block in quick from 1.2.3.4 to any\&" \&| \e 2928 pfctl -a spam -f - 2929.Ed 2930.Pp 2931This loads a single rule into the 2932.Ar anchor , 2933which blocks all packets from a specific address. 2934.Pp 2935The anchor can also be populated by adding a 2936.Ar load anchor 2937rule after the 2938.Ar anchor 2939rule: 2940.Bd -literal -offset indent 2941anchor spam 2942load anchor spam from "/etc/pf-spam.conf" 2943.Ed 2944.Pp 2945When 2946.Xr pfctl 8 2947loads 2948.Nm pf.conf , 2949it will also load all the rules from the file 2950.Pa /etc/pf-spam.conf 2951into the anchor. 2952.Pp 2953Optionally, 2954.Ar anchor 2955rules can specify packet filtering parameters using the same syntax as 2956filter rules. 2957When parameters are used, the 2958.Ar anchor 2959rule is only evaluated for matching packets. 2960This allows conditional evaluation of anchors, like: 2961.Bd -literal -offset indent 2962block on $ext_if all 2963anchor spam proto tcp from any to any port smtp 2964pass out on $ext_if all 2965pass in on $ext_if proto tcp from any to $ext_if port smtp 2966.Ed 2967.Pp 2968The rules inside 2969.Ar anchor 2970spam are only evaluated for 2971.Ar tcp 2972packets with destination port 25. 2973Hence, 2974.Bd -literal -offset indent 2975# echo \&"block in quick from 1.2.3.4 to any" \&| \e 2976 pfctl -a spam -f - 2977.Ed 2978.Pp 2979will only block connections from 1.2.3.4 to port 25. 2980.Pp 2981Anchors may end with the asterisk 2982.Pq Sq * 2983character, which signifies that all anchors attached at that point 2984should be evaluated in the alphabetical ordering of their anchor name. 2985For example, 2986.Bd -literal -offset indent 2987anchor "spam/*" 2988.Ed 2989.Pp 2990will evaluate each rule in each anchor attached to the 2991.Li spam 2992anchor. 2993Note that it will only evaluate anchors that are directly attached to the 2994.Li spam 2995anchor, and will not descend to evaluate anchors recursively. 2996.Pp 2997Since anchors are evaluated relative to the anchor in which they are 2998contained, there is a mechanism for accessing the parent and ancestor 2999anchors of a given anchor. 3000Similar to file system path name resolution, if the sequence 3001.Dq .. 3002appears as an anchor path component, the parent anchor of the current 3003anchor in the path evaluation at that point will become the new current 3004anchor. 3005As an example, consider the following: 3006.Bd -literal -offset indent 3007# echo ' anchor "spam/allowed" ' | pfctl -f - 3008# echo -e ' anchor "../banned" \en pass' | \e 3009 pfctl -a spam/allowed -f - 3010.Ed 3011.Pp 3012Evaluation of the main ruleset will lead into the 3013.Li spam/allowed 3014anchor, which will evaluate the rules in the 3015.Li spam/banned 3016anchor, if any, before finally evaluating the 3017.Ar pass 3018rule. 3019.Pp 3020Filter rule 3021.Ar anchors 3022can also be loaded inline in the ruleset within a brace ('{' '}') delimited 3023block. 3024Brace delimited blocks may contain rules or other brace-delimited blocks. 3025When anchors are loaded this way the anchor name becomes optional. 3026.Bd -literal -offset indent 3027anchor "external" on $ext_if { 3028 block 3029 anchor out { 3030 pass proto tcp from any to port { 25, 80, 443 } 3031 } 3032 pass in proto tcp to any port 22 3033} 3034.Ed 3035.Pp 3036Since the parser specification for anchor names is a string, any 3037reference to an anchor name containing 3038.Sq / 3039characters will require double quote 3040.Pq Sq \&" 3041characters around the anchor name. 3042.Sh SCTP CONSIDERATIONS 3043.Xr pf 4 3044supports 3045.Xr sctp 4 3046connections. 3047It can match ports, track state and NAT SCTP traffic. 3048However, it will not alter port numbers during nat or rdr translations. 3049Doing so would break SCTP multihoming. 3050.Sh TRANSLATION EXAMPLES 3051This example maps incoming requests on port 80 to port 8080, on 3052which a daemon is running (because, for example, it is not run as root, 3053and therefore lacks permission to bind to port 80). 3054.Bd -literal 3055# use a macro for the interface name, so it can be changed easily 3056ext_if = \&"ne3\&" 3057 3058# map daemon on 8080 to appear to be on 80 3059rdr on $ext_if proto tcp from any to any port 80 -> 127.0.0.1 port 8080 3060.Ed 3061.Pp 3062If the 3063.Ar pass 3064modifier is given, packets matching the translation rule are passed without 3065inspecting the filter rules: 3066.Bd -literal 3067rdr pass on $ext_if proto tcp from any to any port 80 -> 127.0.0.1 \e 3068 port 8080 3069.Ed 3070.Pp 3071In the example below, vlan12 is configured as 192.168.168.1; 3072the machine translates all packets coming from 192.168.168.0/24 to 204.92.77.111 3073when they are going out any interface except vlan12. 3074This has the net effect of making traffic from the 192.168.168.0/24 3075network appear as though it is the Internet routable address 3076204.92.77.111 to nodes behind any interface on the router except 3077for the nodes on vlan12. 3078(Thus, 192.168.168.1 can talk to the 192.168.168.0/24 nodes.) 3079.Bd -literal 3080nat on ! vlan12 from 192.168.168.0/24 to any -> 204.92.77.111 3081.Ed 3082.Pp 3083In the example below, the machine sits between a fake internal 144.19.74.* 3084network, and a routable external IP of 204.92.77.100. 3085The 3086.Ar no nat 3087rule excludes protocol AH from being translated. 3088.Bd -literal 3089# NO NAT 3090no nat on $ext_if proto ah from 144.19.74.0/24 to any 3091nat on $ext_if from 144.19.74.0/24 to any -> 204.92.77.100 3092.Ed 3093.Pp 3094In the example below, packets bound for one specific server, as well as those 3095generated by the sysadmins are not proxied; all other connections are. 3096.Bd -literal 3097# NO RDR 3098no rdr on $int_if proto { tcp, udp } from any to $server port 80 3099no rdr on $int_if proto { tcp, udp } from $sysadmins to any port 80 3100rdr on $int_if proto { tcp, udp } from any to any port 80 -> 127.0.0.1 \e 3101 port 80 3102.Ed 3103.Pp 3104This longer example uses both a NAT and a redirection. 3105The external interface has the address 157.161.48.183. 3106On localhost, we are running 3107.Xr ftp-proxy 8 , 3108waiting for FTP sessions to be redirected to it. 3109The three mandatory anchors for 3110.Xr ftp-proxy 8 3111are omitted from this example; see the 3112.Xr ftp-proxy 8 3113manpage. 3114.Bd -literal 3115# NAT 3116# Translate outgoing packets' source addresses (any protocol). 3117# In this case, any address but the gateway's external address is mapped. 3118nat on $ext_if inet from ! ($ext_if) to any -> ($ext_if) 3119 3120# NAT PROXYING 3121# Map outgoing packets' source port to an assigned proxy port instead of 3122# an arbitrary port. 3123# In this case, proxy outgoing isakmp with port 500 on the gateway. 3124nat on $ext_if inet proto udp from any port = isakmp to any -> ($ext_if) \e 3125 port 500 3126 3127# BINAT 3128# Translate outgoing packets' source address (any protocol). 3129# Translate incoming packets' destination address to an internal machine 3130# (bidirectional). 3131binat on $ext_if from 10.1.2.150 to any -> $ext_if 3132 3133# Translate packets arriving on $peer_if addressed to 172.22.16.0/20 3134# to the corresponding address in 172.21.16.0/20 (bidirectional). 3135binat on $peer_if from 172.21.16.0/20 to any -> 172.22.16.0/20 3136 3137# RDR 3138# Translate incoming packets' destination addresses. 3139# As an example, redirect a TCP and UDP port to an internal machine. 3140rdr on $ext_if inet proto tcp from any to ($ext_if) port 8080 \e 3141 -> 10.1.2.151 port 22 3142rdr on $ext_if inet proto udp from any to ($ext_if) port 8080 \e 3143 -> 10.1.2.151 port 53 3144 3145# RDR 3146# Translate outgoing ftp control connections to send them to localhost 3147# for proxying with ftp-proxy(8) running on port 8021. 3148rdr on $int_if proto tcp from any to any port 21 -> 127.0.0.1 port 8021 3149.Ed 3150.Pp 3151In this example, a NAT gateway is set up to translate internal addresses 3152using a pool of public addresses (192.0.2.16/28) and to redirect 3153incoming web server connections to a group of web servers on the internal 3154network. 3155.Bd -literal 3156# NAT LOAD BALANCE 3157# Translate outgoing packets' source addresses using an address pool. 3158# A given source address is always translated to the same pool address by 3159# using the source-hash keyword. 3160nat on $ext_if inet from any to any -> 192.0.2.16/28 source-hash 3161 3162# RDR ROUND ROBIN 3163# Translate incoming web server connections to a group of web servers on 3164# the internal network. 3165rdr on $ext_if proto tcp from any to any port 80 \e 3166 -> { 10.1.2.155, 10.1.2.160, 10.1.2.161 } round-robin 3167.Ed 3168.Sh FILTER EXAMPLES 3169.Bd -literal 3170# The external interface is kue0 3171# (157.161.48.183, the only routable address) 3172# and the private network is 10.0.0.0/8, for which we are doing NAT. 3173 3174# Reassemble incoming traffic 3175set reassemble yes 3176 3177# use a macro for the interface name, so it can be changed easily 3178ext_if = \&"kue0\&" 3179 3180# block and log everything by default 3181block return log on $ext_if all 3182 3183# block anything coming from source we have no back routes for 3184block in from no-route to any 3185 3186# block packets whose ingress interface does not match the one in 3187# the route back to their source address 3188block in from urpf-failed to any 3189 3190# block and log outgoing packets that do not have our address as source, 3191# they are either spoofed or something is misconfigured (NAT disabled, 3192# for instance), we want to be nice and do not send out garbage. 3193block out log quick on $ext_if from ! 157.161.48.183 to any 3194 3195# silently drop broadcasts (cable modem noise) 3196block in quick on $ext_if from any to 255.255.255.255 3197 3198# block and log incoming packets from reserved address space and invalid 3199# addresses, they are either spoofed or misconfigured, we cannot reply to 3200# them anyway (hence, no return-rst). 3201block in log quick on $ext_if from { 10.0.0.0/8, 172.16.0.0/12, \e 3202 192.168.0.0/16, 255.255.255.255/32 } to any 3203 3204# ICMP 3205 3206# pass out/in certain ICMP queries and keep state (ping) 3207# state matching is done on host addresses and ICMP id (not type/code), 3208# so replies (like 0/0 for 8/0) will match queries 3209# ICMP error messages (which always refer to a TCP/UDP packet) are 3210# handled by the TCP/UDP states 3211pass on $ext_if inet proto icmp all icmp-type 8 code 0 3212 3213# UDP 3214 3215# pass out all UDP connections and keep state 3216pass out on $ext_if proto udp all 3217 3218# pass in certain UDP connections and keep state (DNS) 3219pass in on $ext_if proto udp from any to any port domain 3220 3221# TCP 3222 3223# pass out all TCP connections and modulate state 3224pass out on $ext_if proto tcp all modulate state 3225 3226# pass in certain TCP connections and keep state (SSH, SMTP, DNS, IDENT) 3227pass in on $ext_if proto tcp from any to any port { ssh, smtp, domain, \e 3228 auth } 3229 3230# Do not allow Windows 9x SMTP connections since they are typically 3231# a viral worm. Alternately we could limit these OSes to 1 connection each. 3232block in on $ext_if proto tcp from any os {"Windows 95", "Windows 98"} \e 3233 to any port smtp 3234 3235# IPv6 3236# pass in/out all IPv6 traffic: note that we have to enable this in two 3237# different ways, on both our physical interface and our tunnel 3238pass quick on gif0 inet6 3239pass quick on $ext_if proto ipv6 3240 3241# Packet Tagging 3242 3243# three interfaces: $int_if, $ext_if, and $wifi_if (wireless). NAT is 3244# being done on $ext_if for all outgoing packets. tag packets in on 3245# $int_if and pass those tagged packets out on $ext_if. all other 3246# outgoing packets (i.e., packets from the wireless network) are only 3247# permitted to access port 80. 3248 3249pass in on $int_if from any to any tag INTNET 3250pass in on $wifi_if from any to any 3251 3252block out on $ext_if from any to any 3253pass out quick on $ext_if tagged INTNET 3254pass out on $ext_if proto tcp from any to any port 80 3255 3256# tag incoming packets as they are redirected to spamd(8). use the tag 3257# to pass those packets through the packet filter. 3258 3259rdr on $ext_if inet proto tcp from <spammers> to port smtp \e 3260 tag SPAMD -> 127.0.0.1 port spamd 3261 3262block in on $ext_if 3263pass in on $ext_if inet proto tcp tagged SPAMD 3264.Ed 3265.Pp 3266In the example below, a router handling both address families 3267translates an internal IPv4 subnet to IPv6 using the well-known 326864:ff9b::/96 prefix: 3269.Bd -literal -offset 4n 3270pass in on $v4_if inet af-to inet6 from ($v6_if) to 64:ff9b::/96 3271.Ed 3272.Pp 3273Paired with the example above, the example below can be used on 3274another router handling both address families to translate back 3275to IPv4: 3276.Bd -literal -offset 4n 3277pass in on $v6_if inet6 to 64:ff9b::/96 af-to inet from ($v4_if) 3278.Ed 3279.Sh GRAMMAR 3280Syntax for 3281.Nm 3282in BNF: 3283.Bd -literal 3284line = ( option | ether-rule | pf-rule | nat-rule | binat-rule | 3285 rdr-rule | antispoof-rule | altq-rule | queue-rule | 3286 trans-anchors | anchor-rule | anchor-close | load-anchor | 3287 table-rule | include ) 3288 3289option = "set" ( [ "timeout" ( timeout | "{" timeout-list "}" ) ] | 3290 [ "ruleset-optimization" [ "none" | "basic" | "profile" ]] | 3291 [ "optimization" [ "default" | "normal" | 3292 "high-latency" | "satellite" | 3293 "aggressive" | "conservative" ] ] 3294 [ "limit" ( limit-item | "{" limit-list "}" ) ] | 3295 [ "loginterface" ( interface-name | "none" ) ] | 3296 [ "block-policy" ( "drop" | "return" ) ] | 3297 [ "state-policy" ( "if-bound" | "floating" ) ] 3298 [ "state-defaults" state-opts ] 3299 [ "require-order" ( "yes" | "no" ) ] 3300 [ "fingerprints" filename ] | 3301 [ "skip on" ifspec ] | 3302 [ "debug" ( "none" | "urgent" | "misc" | "loud" ) ] 3303 [ "keepcounters" ] ) 3304 3305ether-rule = "ether" etheraction [ ( "in" | "out" ) ] 3306 [ "quick" ] [ "on" ifspec ] [ "bridge-to" interface-name ] 3307 [ etherprotospec ] etherhosts [ "l3" hosts ] 3308 [ etherfilteropt-list ] 3309 3310pf-rule = action [ ( "in" | "out" ) ] 3311 [ "log" [ "(" logopts ")"] ] [ "quick" ] 3312 [ "on" ifspec ] [ route ] [ af ] [ protospec ] 3313 hosts [ filteropt-list ] 3314 3315logopts = logopt [ "," logopts ] 3316logopt = "all" | "matches" | "user" | "to" interface-name 3317 3318etherfilteropt-list = etherfilteropt-list etherfilteropt | etherfilteropt 3319etherfilteropt = "tag" string | "tagged" string | "queue" ( string ) | 3320 "ridentifier" number | "label" string 3321 3322filteropt-list = filteropt-list filteropt | filteropt 3323filteropt = user | group | flags | icmp-type | icmp6-type | "tos" tos | 3324 "af-to" af "from" ( redirhost | "{" redirhost-list "}" ) 3325 [ "to" ( redirhost | "{" redirhost-list "}" ) ] | 3326 ( "no" | "keep" | "modulate" | "synproxy" ) "state" 3327 [ "(" state-opts ")" ] | 3328 "fragment" | "no-df" | "min-ttl" number | "set-tos" tos | 3329 "max-mss" number | "random-id" | "reassemble tcp" | 3330 fragmentation | "allow-opts" | 3331 "label" string | "tag" string | [ ! ] "tagged" string | 3332 "set prio" ( number | "(" number [ [ "," ] number ] ")" ) | 3333 "queue" ( string | "(" string [ [ "," ] string ] ")" ) | 3334 "rtable" number | "probability" number"%" | "prio" number | 3335 "dnpipe" ( number | "(" number "," number ")" ) | 3336 "dnqueue" ( number | "(" number "," number ")" ) | 3337 "ridentifier" number | 3338 [ ! ] "received-on" ( interface-name | interface-group ) 3339 3340nat-rule = [ "no" ] "nat" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 3341 [ "on" ifspec ] [ af ] 3342 [ protospec ] hosts [ "tag" string ] [ "tagged" string ] 3343 [ "->" ( redirhost | "{" redirhost-list "}" ) 3344 [ portspec ] [ pooltype ] [ "static-port" ] 3345 [ "map-e-portset" number "/" number "/" number ] ] 3346 3347binat-rule = [ "no" ] "binat" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 3348 [ "on" interface-name ] [ af ] 3349 [ "proto" ( proto-name | proto-number ) ] 3350 "from" address [ "/" mask-bits ] "to" ipspec 3351 [ "tag" string ] [ "tagged" string ] 3352 [ "->" address [ "/" mask-bits ] ] 3353 3354rdr-rule = [ "no" ] "rdr" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 3355 [ "on" ifspec ] [ af ] 3356 [ protospec ] hosts [ "tag" string ] [ "tagged" string ] 3357 [ "->" ( redirhost | "{" redirhost-list "}" ) 3358 [ portspec ] [ pooltype ] ] 3359 3360antispoof-rule = "antispoof" [ "log" ] [ "quick" ] 3361 "for" ifspec [ af ] [ "label" string ] 3362 [ "ridentifier" number ] 3363 3364table-rule = "table" "<" string ">" [ tableopts-list ] 3365tableopts-list = tableopts-list tableopts | tableopts 3366tableopts = "persist" | "const" | "counters" | "file" string | 3367 "{" [ tableaddr-list ] "}" 3368tableaddr-list = tableaddr-list [ "," ] tableaddr-spec | tableaddr-spec 3369tableaddr-spec = [ "!" ] tableaddr [ "/" mask-bits ] 3370tableaddr = hostname | ifspec | "self" | 3371 ipv4-dotted-quad | ipv6-coloned-hex 3372 3373altq-rule = "altq on" interface-name queueopts-list 3374 "queue" subqueue 3375queue-rule = "queue" string [ "on" interface-name ] queueopts-list 3376 subqueue 3377 3378anchor-rule = "anchor" [ string ] [ ( "in" | "out" ) ] [ "on" ifspec ] 3379 [ af ] [ protospec ] [ hosts ] [ filteropt-list ] [ "{" ] 3380 3381anchor-close = "}" 3382 3383trans-anchors = ( "nat-anchor" | "rdr-anchor" | "binat-anchor" ) string 3384 [ "on" ifspec ] [ af ] [ "proto" ] [ protospec ] [ hosts ] 3385 3386load-anchor = "load anchor" string "from" filename 3387 3388queueopts-list = queueopts-list queueopts | queueopts 3389queueopts = [ "bandwidth" bandwidth-spec ] | 3390 [ "qlimit" number ] | [ "tbrsize" number ] | 3391 [ "priority" number ] | [ schedulers ] 3392schedulers = ( cbq-def | priq-def | hfsc-def ) 3393bandwidth-spec = "number" ( "b" | "Kb" | "Mb" | "Gb" | "%" ) 3394 3395etheraction = "pass" | "block" 3396action = "pass" | "match" | "block" [ return ] | [ "no" ] "scrub" 3397return = "drop" | "return" | "return-rst" [ "( ttl" number ")" ] | 3398 "return-icmp" [ "(" icmpcode [ [ "," ] icmp6code ] ")" ] | 3399 "return-icmp6" [ "(" icmp6code ")" ] 3400icmpcode = ( icmp-code-name | icmp-code-number ) 3401icmp6code = ( icmp6-code-name | icmp6-code-number ) 3402 3403ifspec = ( [ "!" ] ( interface-name | interface-group ) ) | 3404 "{" interface-list "}" 3405interface-list = [ "!" ] ( interface-name | interface-group ) 3406 [ [ "," ] interface-list ] 3407route = ( "route-to" | "reply-to" | "dup-to" ) 3408 ( routehost | "{" routehost-list "}" ) 3409 [ pooltype ] 3410af = "inet" | "inet6" 3411 3412etherprotospec = "proto" ( proto-number | "{" etherproto-list "}" ) 3413etherproto-list = proto-number [ [ "," ] etherproto-list ] 3414protospec = "proto" ( proto-name | proto-number | 3415 "{" proto-list "}" ) 3416proto-list = ( proto-name | proto-number ) [ [ "," ] proto-list ] 3417 3418etherhosts = "from" macaddress "to" macaddress 3419macaddress = mac | mac "/" masklen | mac "&" mask 3420 3421hosts = "all" | 3422 "from" ( "any" | "no-route" | "urpf-failed" | "self" | host | 3423 "{" host-list "}" ) [ port ] [ os ] 3424 "to" ( "any" | "no-route" | "self" | host | 3425 "{" host-list "}" ) [ port ] 3426 3427ipspec = "any" | host | "{" host-list "}" 3428host = [ "!" ] ( address [ "/" mask-bits ] | "<" string ">" ) 3429redirhost = address [ "/" mask-bits ] 3430routehost = "(" interface-name [ address [ "/" mask-bits ] ] ")" 3431address = ( interface-name | interface-group | 3432 "(" ( interface-name | interface-group ) ")" | 3433 hostname | ipv4-dotted-quad | ipv6-coloned-hex ) 3434host-list = host [ [ "," ] host-list ] 3435redirhost-list = redirhost [ [ "," ] redirhost-list ] 3436routehost-list = routehost [ [ "," ] routehost-list ] 3437 3438port = "port" ( unary-op | binary-op | "{" op-list "}" ) 3439portspec = "port" ( number | name ) [ ":" ( "*" | number | name ) ] 3440os = "os" ( os-name | "{" os-list "}" ) 3441user = "user" ( unary-op | binary-op | "{" op-list "}" ) 3442group = "group" ( unary-op | binary-op | "{" op-list "}" ) 3443 3444unary-op = [ "=" | "!=" | "<" | "<=" | ">" | ">=" ] 3445 ( name | number ) 3446binary-op = number ( "<>" | "><" | ":" ) number 3447op-list = ( unary-op | binary-op ) [ [ "," ] op-list ] 3448 3449os-name = operating-system-name 3450os-list = os-name [ [ "," ] os-list ] 3451 3452flags = "flags" ( [ flag-set ] "/" flag-set | "any" ) 3453flag-set = [ "F" ] [ "S" ] [ "R" ] [ "P" ] [ "A" ] [ "U" ] [ "E" ] 3454 [ "W" ] 3455 3456icmp-type = "icmp-type" ( icmp-type-code | "{" icmp-list "}" ) 3457icmp6-type = "icmp6-type" ( icmp-type-code | "{" icmp-list "}" ) 3458icmp-type-code = ( icmp-type-name | icmp-type-number ) 3459 [ "code" ( icmp-code-name | icmp-code-number ) ] 3460icmp-list = icmp-type-code [ [ "," ] icmp-list ] 3461 3462tos = ( "lowdelay" | "throughput" | "reliability" | 3463 [ "0x" ] number ) 3464 3465state-opts = state-opt [ [ "," ] state-opts ] 3466state-opt = ( "max" number | "no-sync" | timeout | "sloppy" | 3467 "source-track" [ ( "rule" | "global" ) ] | 3468 "max-src-nodes" number | "max-src-states" number | 3469 "max-src-conn" number | 3470 "max-src-conn-rate" number "/" number | 3471 "overload" "<" string ">" [ "flush" ] | 3472 "if-bound" | "floating" | "pflow" ) 3473 3474fragmentation = [ "fragment reassemble" ] 3475 3476timeout-list = timeout [ [ "," ] timeout-list ] 3477timeout = ( "tcp.first" | "tcp.opening" | "tcp.established" | 3478 "tcp.closing" | "tcp.finwait" | "tcp.closed" | 3479 "sctp.first" | "sctp.opening" | "sctp.established" | 3480 "sctp.closing" | "sctp.closed" | 3481 "udp.first" | "udp.single" | "udp.multiple" | 3482 "icmp.first" | "icmp.error" | 3483 "other.first" | "other.single" | "other.multiple" | 3484 "frag" | "interval" | "src.track" | 3485 "adaptive.start" | "adaptive.end" ) number 3486 3487limit-list = limit-item [ [ "," ] limit-list ] 3488limit-item = ( "states" | "frags" | "src-nodes" ) number 3489 3490pooltype = ( "bitmask" | "random" | 3491 "source-hash" [ ( hex-key | string-key ) ] | 3492 "round-robin" ) [ sticky-address ] 3493 3494subqueue = string | "{" queue-list "}" 3495queue-list = string [ [ "," ] string ] 3496cbq-def = "cbq" [ "(" cbq-opt [ [ "," ] cbq-opt ] ")" ] 3497priq-def = "priq" [ "(" priq-opt [ [ "," ] priq-opt ] ")" ] 3498hfsc-def = "hfsc" [ "(" hfsc-opt [ [ "," ] hfsc-opt ] ")" ] 3499cbq-opt = ( "default" | "borrow" | "red" | "ecn" | "rio" ) 3500priq-opt = ( "default" | "red" | "ecn" | "rio" ) 3501hfsc-opt = ( "default" | "red" | "ecn" | "rio" | 3502 linkshare-sc | realtime-sc | upperlimit-sc ) 3503linkshare-sc = "linkshare" sc-spec 3504realtime-sc = "realtime" sc-spec 3505upperlimit-sc = "upperlimit" sc-spec 3506sc-spec = ( bandwidth-spec | 3507 "(" bandwidth-spec number bandwidth-spec ")" ) 3508include = "include" filename 3509.Ed 3510.Sh FILES 3511.Bl -tag -width "/etc/protocols" -compact 3512.It Pa /etc/hosts 3513Host name database. 3514.It Pa /etc/pf.conf 3515Default location of the ruleset file. 3516The file has to be created manually as it is not installed with a 3517standard installation. 3518.It Pa /etc/pf.os 3519Default location of OS fingerprints. 3520.It Pa /etc/protocols 3521Protocol name database. 3522.It Pa /etc/services 3523Service name database. 3524.El 3525.Sh SEE ALSO 3526.Xr altq 4 , 3527.Xr carp 4 , 3528.Xr icmp 4 , 3529.Xr icmp6 4 , 3530.Xr ip 4 , 3531.Xr ip6 4 , 3532.Xr pf 4 , 3533.Xr pflow 4 , 3534.Xr pfsync 4 , 3535.Xr sctp 4 , 3536.Xr tcp 4 , 3537.Xr udp 4 , 3538.Xr hosts 5 , 3539.Xr pf.os 5 , 3540.Xr protocols 5 , 3541.Xr services 5 , 3542.Xr ftp-proxy 8 , 3543.Xr pfctl 8 , 3544.Xr pflogd 8 3545.Sh HISTORY 3546The 3547.Nm 3548file format first appeared in 3549.Ox 3.0 . 3550