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 December 6, 2024 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 135rules and in the routing options of filter rules, but only for 136.Ar round-robin 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 persist 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 \*(Ltprivate\*(Gt const { 10/8, 172.16/12, 192.168/16 } 199table \*(Ltbadhosts\*(Gt persist 200block on fxp0 from { \*(Ltprivate\*(Gt, \*(Ltbadhosts\*(Gt } 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 \*(Ltspam\*(Gt persist file \&"/etc/spammers\&" file \&"/etc/openrelays\&" 219block on fxp0 from \*(Ltspam\*(Gt 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 before the destination host ever sends a packet. 269.It Ar tcp.established 270The fully established state. 271.It Ar tcp.closing 272The state after the first FIN has been sent. 273.It Ar tcp.finwait 274The state after both FINs have been exchanged and the connection is closed. 275Some hosts (notably web servers on Solaris) send TCP packets even after closing 276the connection. 277Increasing 278.Ar tcp.finwait 279(and possibly 280.Ar tcp.closing ) 281can prevent blocking of such packets. 282.It Ar tcp.closed 283The state after one endpoint sends an RST. 284.El 285.Pp 286SCTP timeout are handled similar to TCP, but with its own set of states: 287.Pp 288.Bl -tag -width xxxx -compact 289.It Ar sctp.first 290The state after the first packet. 291.It Ar sctp.opening 292The state before the destination host ever sends a packet. 293.It Ar sctp.established 294The fully established state. 295.It Ar sctp.closing 296The state after the first SHUTDOWN chunk has been sent. 297.It Ar sctp.closed 298The state after SHUTDOWN_ACK has been exchanged and the connection is closed. 299.El 300.Pp 301ICMP and UDP are handled in a fashion similar to TCP, but with a much more 302limited set of states: 303.Pp 304.Bl -tag -width xxxx -compact 305.It Ar udp.first 306The state after the first packet. 307.It Ar udp.single 308The state if the source host sends more than one packet but the destination 309host has never sent one back. 310.It Ar udp.multiple 311The state if both hosts have sent packets. 312.It Ar icmp.first 313The state after the first packet. 314.It Ar icmp.error 315The state after an ICMP error came back in response to an ICMP packet. 316.El 317.Pp 318Other protocols are handled similarly to UDP: 319.Pp 320.Bl -tag -width xxxx -compact 321.It Ar other.first 322.It Ar other.single 323.It Ar other.multiple 324.El 325.Pp 326Timeout values can be reduced adaptively as the number of state table 327entries grows. 328.Pp 329.Bl -tag -width xxxx -compact 330.It Ar adaptive.start 331When the number of state entries exceeds this value, adaptive scaling 332begins. 333All timeout values are scaled linearly with factor 334(adaptive.end - number of states) / (adaptive.end - adaptive.start). 335.It Ar adaptive.end 336When reaching this number of state entries, all timeout values become 337zero, effectively purging all state entries immediately. 338This value is used to define the scale factor, it should not actually 339be reached (set a lower state limit, see below). 340.El 341.Pp 342Adaptive timeouts are enabled by default, with an adaptive.start value 343equal to 60% of the state limit, and an adaptive.end value equal to 344120% of the state limit. 345They can be disabled by setting both adaptive.start and adaptive.end to 0. 346.Pp 347The adaptive timeout values can be defined both globally and for each rule. 348When used on a per-rule basis, the values relate to the number of 349states created by the rule, otherwise to the total number of 350states. 351.Pp 352For example: 353.Bd -literal -offset indent 354set timeout tcp.first 120 355set timeout tcp.established 86400 356set timeout { adaptive.start 6000, adaptive.end 12000 } 357set limit states 10000 358.Ed 359.Pp 360With 9000 state table entries, the timeout values are scaled to 50% 361(tcp.first 60, tcp.established 43200). 362.It Ar set loginterface 363Enable collection of packet and byte count statistics for the given 364interface or interface group. 365These statistics can be viewed using 366.Bd -literal -offset indent 367# pfctl -s info 368.Ed 369.Pp 370In this example 371.Xr pf 4 372collects statistics on the interface named dc0: 373.Bd -literal -offset indent 374set loginterface dc0 375.Ed 376.Pp 377One can disable the loginterface using: 378.Bd -literal -offset indent 379set loginterface none 380.Ed 381.It Ar set limit 382Sets hard limits on the memory pools used by the packet filter. 383See 384.Xr zone 9 385for an explanation of memory pools. 386.Pp 387For example, 388.Bd -literal -offset indent 389set limit states 20000 390.Ed 391.Pp 392sets the maximum number of entries in the memory pool used by state table 393entries (generated by 394.Ar pass 395rules which do not specify 396.Ar no state ) 397to 20000. 398Using 399.Bd -literal -offset indent 400set limit frags 20000 401.Ed 402.Pp 403sets the maximum number of entries in the memory pool used for fragment 404reassembly (generated by the 405.Ar set reassemble 406option or 407.Ar scrub 408rules) to 20000. 409Using 410.Bd -literal -offset indent 411set limit src-nodes 2000 412.Ed 413.Pp 414sets the maximum number of entries in the memory pool used for tracking 415source IP addresses (generated by the 416.Ar sticky-address 417and 418.Ar src.track 419options) to 2000. 420Using 421.Bd -literal -offset indent 422set limit table-entries 100000 423.Ed 424.Pp 425sets the limit on the overall number of addresses that can be stored 426in tables to 100000. 427.Pp 428Various limits can be combined on a single line: 429.Bd -literal -offset indent 430set limit { states 20000, frags 20000, src-nodes 2000 } 431.Ed 432.It Ar set ruleset-optimization 433.Bl -tag -width xxxxxxxx -compact 434.It Ar none 435Disable the ruleset optimizer. 436.It Ar basic 437Enable basic ruleset optimization. 438This is the default behaviour. 439Basic ruleset optimization does four things to improve the 440performance of ruleset evaluations: 441.Pp 442.Bl -enum -compact 443.It 444remove duplicate rules 445.It 446remove rules that are a subset of another rule 447.It 448combine multiple rules into a table when advantageous 449.It 450re-order the rules to improve evaluation performance 451.El 452.Pp 453.It Ar profile 454Uses the currently loaded ruleset as a feedback profile to tailor the 455ordering of quick rules to actual network traffic. 456.El 457.Pp 458It is important to note that the ruleset optimizer will modify the ruleset 459to improve performance. 460A side effect of the ruleset modification is that per-rule accounting 461statistics will have different meanings than before. 462If per-rule accounting is important for billing purposes or whatnot, 463either the ruleset optimizer should not be used or a label field should 464be added to all of the accounting rules to act as optimization barriers. 465.Pp 466Optimization can also be set as a command-line argument to 467.Xr pfctl 8 , 468overriding the settings in 469.Nm . 470.It Ar set optimization 471Optimize state timeouts for one of the following network environments: 472.Pp 473.Bl -tag -width xxxx -compact 474.It Ar normal 475A normal network environment. 476Suitable for almost all networks. 477.It Ar high-latency 478A high-latency environment (such as a satellite connection). 479.It Ar satellite 480Alias for 481.Ar high-latency . 482.It Ar aggressive 483Aggressively expire connections. 484This can greatly reduce the memory usage of the firewall at the cost of 485dropping idle connections early. 486.It Ar conservative 487Extremely conservative settings. 488Avoid dropping legitimate connections at the 489expense of greater memory utilization (possibly much greater on a busy 490network) and slightly increased processor utilization. 491.El 492.Pp 493For example: 494.Bd -literal -offset indent 495set optimization aggressive 496.Ed 497.It Ar set reassemble yes | no Op Cm no-df 498The 499.Cm reassemble 500option is used to enable or disable the reassembly of fragmented packets, 501and can be set to 502.Cm yes 503or 504.Cm no . 505If 506.Cm no-df 507is also specified, fragments with the 508.Dq dont-fragment 509bit set are reassembled too, 510instead of being dropped; 511the reassembled packet will have the 512.Dq dont-fragment 513bit cleared. 514The default value is 515.Cm no . 516.Pp 517This option is ignored if there are pre-FreeBSD 14 518.Cm scrub 519rules present. 520.It Ar set block-policy 521The 522.Ar block-policy 523option sets the default behaviour for the packet 524.Ar block 525action: 526.Pp 527.Bl -tag -width xxxxxxxx -compact 528.It Ar drop 529Packet is silently dropped. 530.It Ar return 531A TCP RST is returned for blocked TCP packets, 532an SCTP ABORT chunk is returned for blocked SCTP packets, 533an ICMP UNREACHABLE is returned for blocked UDP packets, 534and all other packets are silently dropped. 535.El 536.Pp 537For example: 538.Bd -literal -offset indent 539set block-policy return 540.Ed 541.It Ar set fail-policy 542The 543.Ar fail-policy 544option sets the behaviour of rules which should pass a packet but were 545unable to do so. 546This might happen when a nat or route-to rule uses an empty table as list 547of targets or if a rule fails to create state or source node. 548The following 549.Ar block 550actions are possible: 551.Pp 552.Bl -tag -width xxxxxxxx -compact 553.It Ar drop 554Incoming packet is silently dropped. 555.It Ar return 556Incoming packet is dropped and TCP RST is returned for TCP packets, 557an SCTP ABORT chunk is returned for blocked SCTP packets, 558an ICMP UNREACHABLE is returned for UDP packets, 559and no response is sent for other packets. 560.El 561.Pp 562For example: 563.Bd -literal -offset indent 564set fail-policy return 565.Ed 566.It Ar set state-policy 567The 568.Ar state-policy 569option sets the default behaviour for states: 570.Pp 571.Bl -tag -width group-bound -compact 572.It Ar if-bound 573States are bound to interface. 574.It Ar floating 575States can match packets on any interfaces (the default). 576.El 577.Pp 578For example: 579.Bd -literal -offset indent 580set state-policy if-bound 581.Ed 582.It Ar set syncookies never | always | adaptive 583When 584.Cm syncookies 585are active, pf will answer each incoming TCP SYN with a syncookie SYNACK, 586without allocating any resources. 587Upon reception of the client's ACK in response to the syncookie 588SYNACK, pf will evaluate the ruleset and create state if the ruleset 589permits it, complete the three way handshake with the target host and 590continue the connection with synproxy in place. 591This allows pf to be resilient against large synflood attacks which would 592run the state table against its limits otherwise. 593Due to the blind answers to every incoming SYN syncookies share the caveats of 594synproxy, namely seemingly accepting connections that will be dropped later on. 595.Pp 596.Bl -tag -width adaptive -compact 597.It Cm never 598pf will never send syncookie SYNACKs (the default). 599.It Cm always 600pf will always send syncookie SYNACKs. 601.It Cm adaptive 602pf will enable syncookie mode when a given percentage of the state table 603is used up by half-open TCP connections, as in, those that saw the initial 604SYN but didn't finish the three way handshake. 605The thresholds for entering and leaving syncookie mode can be specified using 606.Bd -literal -offset indent 607set syncookies adaptive (start 25%, end 12%) 608.Ed 609.El 610.It Ar set state-defaults 611The 612.Ar state-defaults 613option sets the state options for states created from rules 614without an explicit 615.Ar keep state . 616For example: 617.Bd -literal -offset indent 618set state-defaults no-sync 619.Ed 620.It Ar set hostid 621The 32-bit 622.Ar hostid 623identifies this firewall's state table entries to other firewalls 624in a 625.Xr pfsync 4 626failover cluster. 627By default the hostid is set to a pseudo-random value, however it may be 628desirable to manually configure it, for example to more easily identify the 629source of state table entries. 630.Bd -literal -offset indent 631set hostid 1 632.Ed 633.Pp 634The hostid may be specified in either decimal or hexadecimal. 635.It Ar set require-order 636By default 637.Xr pfctl 8 638enforces an ordering of the statement types in the ruleset to: 639.Em options , 640.Em normalization , 641.Em queueing , 642.Em translation , 643.Em filtering . 644Setting this option to 645.Ar no 646disables this enforcement. 647There may be non-trivial and non-obvious implications to an out of 648order ruleset. 649Consider carefully before disabling the order enforcement. 650.It Ar set fingerprints 651Load fingerprints of known operating systems from the given filename. 652By default fingerprints of known operating systems are automatically 653loaded from 654.Xr pf.os 5 655in 656.Pa /etc 657but can be overridden via this option. 658Setting this option may leave a small period of time where the fingerprints 659referenced by the currently active ruleset are inconsistent until the new 660ruleset finishes loading. 661.Pp 662For example: 663.Pp 664.Dl set fingerprints \&"/etc/pf.os.devel\&" 665.It Ar set skip on Aq Ar ifspec 666List interfaces for which packets should not be filtered. 667Packets passing in or out on such interfaces are passed as if pf was 668disabled, i.e. pf does not process them in any way. 669This can be useful on loopback and other virtual interfaces, when 670packet filtering is not desired and can have unexpected effects. 671For example: 672.Pp 673.Dl set skip on lo0 674.It Ar set debug 675Set the debug 676.Ar level 677to one of the following: 678.Pp 679.Bl -tag -width xxxxxxxxxxxx -compact 680.It Ar none 681Don't generate debug messages. 682.It Ar urgent 683Generate debug messages only for serious errors. 684.It Ar misc 685Generate debug messages for various errors. 686.It Ar loud 687Generate debug messages for common conditions. 688.El 689.It Ar set keepcounters 690Preserve rule counters across rule updates. 691Usually rule counters are reset to zero on every update of the ruleset. 692With 693.Ar keepcounters 694set pf will attempt to find matching rules between old and new rulesets 695and preserve the rule counters. 696.El 697.Sh ETHERNET FILTERING 698.Xr pf 4 699has the ability to 700.Ar block 701and 702.Ar pass 703packets based on attributes of their Ethernet (layer 2) header. 704.Pp 705For each packet processed by the packet filter, the filter rules are 706evaluated in sequential order, from first to last. 707The last matching rule decides what action is taken. 708If no rule matches the packet, the default action is to pass 709the packet. 710.Pp 711The following actions can be used in the filter: 712.Bl -tag -width xxxx 713.It Ar block 714The packet is blocked. 715Unlike for layer 3 traffic the packet is always silently dropped. 716.It Ar pass 717The packet is passed; 718no state is created for layer 2 traffic. 719.El 720.Sh PARAMETERS 721The rule parameters specify the packets to which a rule applies. 722A packet always comes in on, or goes out through, one interface. 723Most parameters are optional. 724If a parameter is specified, the rule only applies to packets with 725matching attributes. 726Certain parameters can be expressed as lists, in which case 727.Xr pfctl 8 728generates all needed rule combinations. 729.Bl -tag -width xxxx 730.It Ar in No or Ar out 731This rule applies to incoming or outgoing packets. 732If neither 733.Ar in 734nor 735.Ar out 736are specified, the rule will match packets in both directions. 737.It Ar quick 738If a packet matches a rule which has the 739.Ar quick 740option set, this rule 741is considered the last matching rule, and evaluation of subsequent rules 742is skipped. 743.It Ar on Aq Ar ifspec 744This rule applies only to packets coming in on, or going out through, this 745particular interface or interface group. 746For more information on interface groups, 747see the 748.Ic group 749keyword in 750.Xr ifconfig 8 . 751.It Ar bridge-to Aq interface 752Packets matching this rule will be sent out of the specified interface without 753further processing. 754.It Ar proto Aq Ar protocol 755This rule applies only to packets of this protocol. 756Note that Ethernet protocol numbers are different from those used in 757.Xr ip 4 758and 759.Xr ip6 4 . 760.It Xo 761.Ar from Aq Ar source 762.Ar to Aq Ar dest 763.Xc 764This rule applies only to packets with the specified source and destination 765MAC addresses. 766.It Xo Ar queue Aq Ar queue 767.Xc 768Packets matching this rule will be assigned to the specified queue. 769See 770.Sx QUEUEING 771for setup details. 772.Pp 773.It Ar tag Aq Ar string 774Packets matching this rule will be tagged with the 775specified string. 776The tag acts as an internal marker that can be used to 777identify these packets later on. 778This can be used, for example, to provide trust between 779interfaces and to determine if packets have been 780processed by translation rules. 781Tags are 782.Qq sticky , 783meaning that the packet will be tagged even if the rule 784is not the last matching rule. 785Further matching rules can replace the tag with a 786new one but will not remove a previously applied tag. 787A packet is only ever assigned one tag at a time. 788.It Ar tagged Aq Ar string 789Used to specify that packets must already be tagged with the given tag in order 790to match the rule. 791Inverse tag matching can also be done by specifying the ! operator before the 792tagged keyword. 793.El 794.Sh TRAFFIC NORMALIZATION 795Traffic normalization is a broad umbrella term 796for aspects of the packet filter which deal with 797verifying packets, packet fragments, spoofed traffic, 798and other irregularities. 799.Ss Scrub 800Scrub involves sanitising packet content in such a way 801that there are no ambiguities in packet interpretation on the receiving side. 802It is invoked with the 803.Cm scrub 804option, added to filter rules. 805.Pp 806Parameters are specified enclosed in parentheses. 807At least one of the following parameters must be specified: 808.Bl -tag -width xxxx 809.It Ar no-df 810Clears the 811.Ar dont-fragment 812bit from a matching IP packet. 813Some operating systems are known to generate fragmented packets with the 814.Ar dont-fragment 815bit set. 816This is particularly true with NFS. 817.Ar Scrub 818will drop such fragmented 819.Ar dont-fragment 820packets unless 821.Ar no-df 822is specified. 823.Pp 824Unfortunately some operating systems also generate their 825.Ar dont-fragment 826packets with a zero IP identification field. 827Clearing the 828.Ar dont-fragment 829bit on packets with a zero IP ID may cause deleterious results if an 830upstream router later fragments the packet. 831Using the 832.Ar random-id 833modifier (see below) is recommended in combination with the 834.Ar no-df 835modifier to ensure unique IP identifiers. 836.It Ar min-ttl Aq Ar number 837Enforces a minimum TTL for matching IP packets. 838.It Ar max-mss Aq Ar number 839Enforces a maximum MSS for matching TCP packets. 840.It Xo Ar set-tos Aq Ar string 841.No \*(Ba Aq Ar number 842.Xc 843Enforces a 844.Em TOS 845for matching IP packets. 846.Em TOS 847may be 848given as one of 849.Ar critical , 850.Ar inetcontrol , 851.Ar lowdelay , 852.Ar netcontrol , 853.Ar throughput , 854.Ar reliability , 855or one of the DiffServ Code Points: 856.Ar ef , 857.Ar va , 858.Ar af11 No ... Ar af43 , 859.Ar cs0 No ... Ar cs7 ; 860or as either hex or decimal. 861.It Ar random-id 862Replaces the IP identification field with random values to compensate 863for predictable values generated by many hosts. 864This option only applies to packets that are not fragmented 865after the optional fragment reassembly. 866.It Ar reassemble tcp 867Statefully normalizes TCP connections. 868.Ar reassemble tcp 869performs the following normalizations: 870.Pp 871.Bl -tag -width timeout -compact 872.It ttl 873Neither side of the connection is allowed to reduce their IP TTL. 874An attacker may send a packet such that it reaches the firewall, affects 875the firewall state, and expires before reaching the destination host. 876.Ar reassemble tcp 877will raise the TTL of all packets back up to the highest value seen on 878the connection. 879.It timestamp modulation 880Modern TCP stacks will send a timestamp on every TCP packet and echo 881the other endpoint's timestamp back to them. 882Many operating systems will merely start the timestamp at zero when 883first booted, and increment it several times a second. 884The uptime of the host can be deduced by reading the timestamp and multiplying 885by a constant. 886Also observing several different timestamps can be used to count hosts 887behind a NAT device. 888And spoofing TCP packets into a connection requires knowing or guessing 889valid timestamps. 890Timestamps merely need to be monotonically increasing and not derived off a 891guessable base time. 892.Ar reassemble tcp 893will cause 894.Ar scrub 895to modulate the TCP timestamps with a random number. 896.It extended PAWS checks 897There is a problem with TCP on long fat pipes, in that a packet might get 898delayed for longer than it takes the connection to wrap its 32-bit sequence 899space. 900In such an occurrence, the old packet would be indistinguishable from a 901new packet and would be accepted as such. 902The solution to this is called PAWS: Protection Against Wrapped Sequence 903numbers. 904It protects against it by making sure the timestamp on each packet does 905not go backwards. 906.Ar reassemble tcp 907also makes sure the timestamp on the packet does not go forward more 908than the RFC allows. 909By doing this, 910.Xr pf 4 911artificially extends the security of TCP sequence numbers by 10 to 18 912bits when the host uses appropriately randomized timestamps, since a 913blind attacker would have to guess the timestamp as well. 914.El 915.El 916.Pp 917For example, 918.Bd -literal -offset indent 919match in all scrub (no-df random-id max-mss 1440) 920.Ed 921.Ss Scrub ruleset (pre-FreeBSD 14) 922In order to maintain compatibility with older releases of FreeBSD 923.Ar scrub 924rules can also be specified in their own ruleset. 925In such case they are invoked with the 926.Ar scrub 927directive. 928If there are such rules present they determine packet reassembly behaviour. 929When no such rules are present the option 930.Ar set reassembly 931takes precedence. 932The 933.Ar scrub 934rules can take all parameters specified above for a 935.Ar scrub 936option of filter rules and 2 more parameters controlling fragment reassembly: 937.Bl -tag -width xxxx 938.It Ar fragment reassemble 939Using 940.Ar scrub 941rules, fragments can be reassembled by normalization. 942In this case, fragments are buffered until they form a complete 943packet, and only the completed packet is passed on to the filter. 944The advantage is that filter rules have to deal only with complete 945packets, and can ignore fragments. 946The drawback of caching fragments is the additional memory cost. 947This is the default behaviour unless no fragment reassemble is specified. 948.It Ar no fragment reassemble 949Do not reassemble fragments. 950.El 951.Pp 952For example, 953.Bd -literal -offset indent 954scrub in on $ext_if all fragment reassemble 955.Ed 956.Pp 957The 958.Ar no 959option prefixed to a scrub rule causes matching packets to remain unscrubbed, 960much in the same way as 961.Ar drop quick 962works in the packet filter (see below). 963This mechanism should be used when it is necessary to exclude specific packets 964from broader scrub rules. 965.Pp 966.Ar scrub 967rules in the 968.Ar scrub 969ruleset are evaluated for every packet before stateful filtering. 970This means excessive usage of them will cause performance penalty. 971.Ar scrub reassemble tcp 972rules must not have the direction (in/out) specified. 973.Sh QUEUEING with ALTQ 974The ALTQ system is currently not available in the GENERIC kernel nor as 975loadable modules. 976In order to use the herein after called queueing options one has to use a 977custom built kernel. 978Please refer to 979.Xr altq 4 980to learn about the related kernel options. 981.Pp 982Packets can be assigned to queues for the purpose of bandwidth 983control. 984At least two declarations are required to configure queues, and later 985any packet filtering rule can reference the defined queues by name. 986During the filtering component of 987.Nm pf.conf , 988the last referenced 989.Ar queue 990name is where any packets from 991.Ar pass 992rules will be queued, while for 993.Ar block 994rules it specifies where any resulting ICMP or TCP RST 995packets should be queued. 996The 997.Ar scheduler 998defines the algorithm used to decide which packets get delayed, dropped, or 999sent out immediately. 1000There are three 1001.Ar schedulers 1002currently supported. 1003.Bl -tag -width xxxx 1004.It Ar cbq 1005Class Based Queueing. 1006.Ar Queues 1007attached to an interface build a tree, thus each 1008.Ar queue 1009can have further child 1010.Ar queues . 1011Each queue can have a 1012.Ar priority 1013and a 1014.Ar bandwidth 1015assigned. 1016.Ar Priority 1017mainly controls the time packets take to get sent out, while 1018.Ar bandwidth 1019has primarily effects on throughput. 1020.Ar cbq 1021achieves both partitioning and sharing of link bandwidth 1022by hierarchically structured classes. 1023Each class has its own 1024.Ar queue 1025and is assigned its share of 1026.Ar bandwidth . 1027A child class can borrow bandwidth from its parent class 1028as long as excess bandwidth is available 1029(see the option 1030.Ar borrow , 1031below). 1032.It Ar priq 1033Priority Queueing. 1034.Ar Queues 1035are flat attached to the interface, thus, 1036.Ar queues 1037cannot have further child 1038.Ar queues . 1039Each 1040.Ar queue 1041has a unique 1042.Ar priority 1043assigned, ranging from 0 to 15. 1044Packets in the 1045.Ar queue 1046with the highest 1047.Ar priority 1048are processed first. 1049.It Ar hfsc 1050Hierarchical Fair Service Curve. 1051.Ar Queues 1052attached to an interface build a tree, thus each 1053.Ar queue 1054can have further child 1055.Ar queues . 1056Each queue can have a 1057.Ar priority 1058and a 1059.Ar bandwidth 1060assigned. 1061.Ar Priority 1062mainly controls the time packets take to get sent out, while 1063.Ar bandwidth 1064primarily affects throughput. 1065.Ar hfsc 1066supports both link-sharing and guaranteed real-time services. 1067It employs a service curve based QoS model, 1068and its unique feature is an ability to decouple 1069.Ar delay 1070and 1071.Ar bandwidth 1072allocation. 1073.El 1074.Pp 1075The interfaces on which queueing should be activated are declared using 1076the 1077.Ar altq on 1078declaration. 1079.Ar altq on 1080has the following keywords: 1081.Bl -tag -width xxxx 1082.It Aq Ar interface 1083Queueing is enabled on the named interface. 1084.It Aq Ar scheduler 1085Specifies which queueing scheduler to use. 1086Currently supported values 1087are 1088.Ar cbq 1089for Class Based Queueing, 1090.Ar priq 1091for Priority Queueing and 1092.Ar hfsc 1093for the Hierarchical Fair Service Curve scheduler. 1094.It Ar bandwidth Aq Ar bw 1095The maximum bitrate for all queues on an 1096interface may be specified using the 1097.Ar bandwidth 1098keyword. 1099The value can be specified as an absolute value or as a 1100percentage of the interface bandwidth. 1101When using an absolute value, the suffixes 1102.Ar b , 1103.Ar Kb , 1104.Ar Mb , 1105and 1106.Ar Gb 1107are used to represent bits, kilobits, megabits, and 1108gigabits per second, respectively. 1109The value must not exceed the interface bandwidth. 1110If 1111.Ar bandwidth 1112is not specified, the interface bandwidth is used 1113(but take note that some interfaces do not know their bandwidth, 1114or can adapt their bandwidth rates). 1115.It Ar qlimit Aq Ar limit 1116The maximum number of packets held in the queue. 1117The default is 50. 1118.It Ar tbrsize Aq Ar size 1119Adjusts the size, in bytes, of the token bucket regulator. 1120If not specified, heuristics based on the 1121interface bandwidth are used to determine the size. 1122.It Ar queue Aq Ar list 1123Defines a list of subqueues to create on an interface. 1124.El 1125.Pp 1126In the following example, the interface dc0 1127should queue up to 5Mbps in four second-level queues using 1128Class Based Queueing. 1129Those four queues will be shown in a later example. 1130.Bd -literal -offset indent 1131altq on dc0 cbq bandwidth 5Mb queue { std, http, mail, ssh } 1132.Ed 1133.Pp 1134Once interfaces are activated for queueing using the 1135.Ar altq 1136directive, a sequence of 1137.Ar queue 1138directives may be defined. 1139The name associated with a 1140.Ar queue 1141must match a queue defined in the 1142.Ar altq 1143directive (e.g. mail), or, except for the 1144.Ar priq 1145.Ar scheduler , 1146in a parent 1147.Ar queue 1148declaration. 1149The following keywords can be used: 1150.Bl -tag -width xxxx 1151.It Ar on Aq Ar interface 1152Specifies the interface the queue operates on. 1153If not given, it operates on all matching interfaces. 1154.It Ar bandwidth Aq Ar bw 1155Specifies the maximum bitrate to be processed by the queue. 1156This value must not exceed the value of the parent 1157.Ar queue 1158and can be specified as an absolute value or a percentage of the parent 1159queue's bandwidth. 1160If not specified, defaults to 100% of the parent queue's bandwidth. 1161The 1162.Ar priq 1163scheduler does not support bandwidth specification. 1164.It Ar priority Aq Ar level 1165Between queues a priority level can be set. 1166For 1167.Ar cbq 1168and 1169.Ar hfsc , 1170the range is 0 to 7 and for 1171.Ar priq , 1172the range is 0 to 15. 1173The default for all is 1. 1174.Ar Priq 1175queues with a higher priority are always served first. 1176.Ar Cbq 1177and 1178.Ar Hfsc 1179queues with a higher priority are preferred in the case of overload. 1180.It Ar qlimit Aq Ar limit 1181The maximum number of packets held in the queue. 1182The default is 50. 1183.El 1184.Pp 1185The 1186.Ar scheduler 1187can get additional parameters with 1188.Xo Aq Ar scheduler 1189.Pf ( Aq Ar parameters ) . 1190.Xc 1191Parameters are as follows: 1192.Bl -tag -width Fl 1193.It Ar default 1194Packets not matched by another queue are assigned to this one. 1195Exactly one default queue is required. 1196.It Ar red 1197Enable RED (Random Early Detection) on this queue. 1198RED drops packets with a probability proportional to the average 1199queue length. 1200.It Ar rio 1201Enables RIO on this queue. 1202RIO is RED with IN/OUT, thus running 1203RED two times more than RIO would achieve the same effect. 1204RIO is currently not supported in the GENERIC kernel. 1205.It Ar ecn 1206Enables ECN (Explicit Congestion Notification) on this queue. 1207ECN implies RED. 1208.El 1209.Pp 1210The 1211.Ar cbq 1212.Ar scheduler 1213supports an additional option: 1214.Bl -tag -width Fl 1215.It Ar borrow 1216The queue can borrow bandwidth from the parent. 1217.El 1218.Pp 1219The 1220.Ar hfsc 1221.Ar scheduler 1222supports some additional options: 1223.Bl -tag -width Fl 1224.It Ar realtime Aq Ar sc 1225The minimum required bandwidth for the queue. 1226.It Ar upperlimit Aq Ar sc 1227The maximum allowed bandwidth for the queue. 1228.It Ar linkshare Aq Ar sc 1229The bandwidth share of a backlogged queue. 1230.El 1231.Pp 1232.Aq Ar sc 1233is an acronym for 1234.Ar service curve . 1235.Pp 1236The format for service curve specifications is 1237.Ar ( m1 , d , m2 ) . 1238.Ar m2 1239controls the bandwidth assigned to the queue. 1240.Ar m1 1241and 1242.Ar d 1243are optional and can be used to control the initial bandwidth assignment. 1244For the first 1245.Ar d 1246milliseconds the queue gets the bandwidth given as 1247.Ar m1 , 1248afterwards the value given in 1249.Ar m2 . 1250.Pp 1251Furthermore, with 1252.Ar cbq 1253and 1254.Ar hfsc , 1255child queues can be specified as in an 1256.Ar altq 1257declaration, thus building a tree of queues using a part of 1258their parent's bandwidth. 1259.Pp 1260Packets can be assigned to queues based on filter rules by using the 1261.Ar queue 1262keyword. 1263Normally only one 1264.Ar queue 1265is specified; when a second one is specified it will instead be used for 1266packets which have a 1267.Em TOS 1268of 1269.Em lowdelay 1270and for TCP ACKs with no data payload. 1271.Pp 1272To continue the previous example, the examples below would specify the 1273four referenced 1274queues, plus a few child queues. 1275Interactive 1276.Xr ssh 1 1277sessions get priority over bulk transfers like 1278.Xr scp 1 1279and 1280.Xr sftp 1 . 1281The queues may then be referenced by filtering rules (see 1282.Sx PACKET FILTERING 1283below). 1284.Bd -literal 1285queue std bandwidth 10% cbq(default) 1286queue http bandwidth 60% priority 2 cbq(borrow red) \e 1287 { employees, developers } 1288queue developers bandwidth 75% cbq(borrow) 1289queue employees bandwidth 15% 1290queue mail bandwidth 10% priority 0 cbq(borrow ecn) 1291queue ssh bandwidth 20% cbq(borrow) { ssh_interactive, ssh_bulk } 1292queue ssh_interactive bandwidth 50% priority 7 cbq(borrow) 1293queue ssh_bulk bandwidth 50% priority 0 cbq(borrow) 1294 1295block return out on dc0 inet all queue std 1296pass out on dc0 inet proto tcp from $developerhosts to any port 80 \e 1297 queue developers 1298pass out on dc0 inet proto tcp from $employeehosts to any port 80 \e 1299 queue employees 1300pass out on dc0 inet proto tcp from any to any port 22 \e 1301 queue(ssh_bulk, ssh_interactive) 1302pass out on dc0 inet proto tcp from any to any port 25 \e 1303 queue mail 1304.Ed 1305.Sh QUEUEING with dummynet 1306Queueing can also be done with 1307.Xr dummynet 4 . 1308Queues and pipes can be created with 1309.Xr dnctl 8 . 1310.Pp 1311Packets can be assigned to queues and pipes using 1312.Ar dnqueue 1313and 1314.Ar dnpipe 1315respectively. 1316.Pp 1317Both 1318.Ar dnqueue 1319and 1320.Ar dnpipe 1321take either a single pipe or queue number or two numbers as arguments. 1322The first pipe or queue number will be used to shape the traffic in the rule 1323direction, the second will be used to shape the traffic in the reverse 1324direction. 1325If the rule does not specify a direction the first packet to create state will 1326be shaped according to the first number, and the response traffic according to 1327the second. 1328.Pp 1329If the 1330.Xr dummynet 4 1331module is not loaded any traffic sent into a queue or pipe will be dropped. 1332.Sh TRANSLATION 1333Translation rules modify either the source or destination address of the 1334packets associated with a stateful connection. 1335A stateful connection is automatically created to track packets matching 1336such a rule as long as they are not blocked by the filtering section of 1337.Nm pf.conf . 1338The translation engine modifies the specified address and/or port in the 1339packet, recalculates IP, TCP and UDP checksums as necessary, and passes 1340it to the packet filter for evaluation. 1341.Pp 1342Since translation occurs before filtering the filter 1343engine will see packets as they look after any 1344addresses and ports have been translated. 1345Filter rules will therefore have to filter based on the translated 1346address and port number. 1347Packets that match a translation rule are only automatically passed if 1348the 1349.Ar pass 1350modifier is given, otherwise they are 1351still subject to 1352.Ar block 1353and 1354.Ar pass 1355rules. 1356.Pp 1357The state entry created permits 1358.Xr pf 4 1359to keep track of the original address for traffic associated with that state 1360and correctly direct return traffic for that connection. 1361.Pp 1362Various types of translation are possible with pf: 1363.Bl -tag -width xxxx 1364.It Ar af-to 1365Translation between different address families (NAT64) is handled 1366using 1367.Ar af-to 1368rules. 1369Because address family translation overrides the routing table, it's 1370only possible to use 1371.Ar af-to 1372on inbound rules, and a source address of the resulting translation 1373must always be specified. 1374.Pp 1375The optional second argument is the host or subnet the original 1376addresses are translated into for the destination. 1377The lowest bits of the original destination address form the host 1378part of the new destination address according to the specified subnet. 1379It is possible to embed a complete IPv4 address into an IPv6 address 1380using a network prefix of /96 or smaller. 1381.Pp 1382When a destination address is not specified it is assumed that the host 1383part is 32-bit long. 1384For IPv6 to IPv4 translation this would mean using only the lower 32 1385bits of the original IPv6 destination address. 1386For IPv4 to IPv6 translation the destination subnet defaults to the 1387subnet of the new IPv6 source address with a prefix length of /96. 1388See RFC 6052 Section 2.2 for details on how the prefix determines the 1389destination address encoding. 1390.Pp 1391For example, the following rules are identical: 1392.Bd -literal -offset indent 1393pass in inet af-to inet6 from 2001:db8::1 to 2001:db8::/96 1394pass in inet af-to inet6 from 2001:db8::1 1395.Ed 1396.Pp 1397In the above example the matching IPv4 packets will be modified to 1398have a source address of 2001:db8::1 and a destination address will 1399get prefixed with 2001:db8::/96, e.g. 198.51.100.100 will be 1400translated to 2001:db8::c633:6464. 1401.Pp 1402In the reverse case the following rules are identical: 1403.Bd -literal -offset indent 1404pass in inet6 af-to inet from 198.51.100.1 to 0.0.0.0/0 1405pass in inet6 af-to inet from 198.51.100.1 1406.Ed 1407.Pp 1408The destination IPv4 address is assumed to be embedded inside the 1409original IPv6 destination address, e.g. 64:ff9b::c633:6464 will be 1410translated to 198.51.100.100. 1411.Pp 1412The current implementation will only extract IPv4 addresses from the 1413IPv6 addresses with a prefix length of /96 and greater. 1414.It Ar binat 1415A 1416.Ar binat 1417rule specifies a bidirectional mapping between an external IP netblock 1418and an internal IP netblock. 1419.It Ar nat 1420A 1421.Ar nat 1422rule specifies that IP addresses are to be changed as the packet 1423traverses the given interface. 1424This technique allows one or more IP addresses 1425on the translating host to support network traffic for a larger range of 1426machines on an "inside" network. 1427Although in theory any IP address can be used on the inside, it is strongly 1428recommended that one of the address ranges defined by RFC 1918 be used. 1429These netblocks are: 1430.Bd -literal 143110.0.0.0 - 10.255.255.255 (all of net 10, i.e., 10/8) 1432172.16.0.0 - 172.31.255.255 (i.e., 172.16/12) 1433192.168.0.0 - 192.168.255.255 (i.e., 192.168/16) 1434.Ed 1435.It Pa rdr 1436The packet is redirected to another destination and possibly a 1437different port. 1438.Ar rdr 1439rules can optionally specify port ranges instead of single ports. 1440rdr ... port 2000:2999 -\*(Gt ... port 4000 1441redirects ports 2000 to 2999 (inclusive) to port 4000. 1442rdr ... port 2000:2999 -\*(Gt ... port 4000:* 1443redirects port 2000 to 4000, 2001 to 4001, ..., 2999 to 4999. 1444.El 1445.Pp 1446In addition to modifying the address, some translation rules may modify 1447source or destination ports for 1448.Xr tcp 4 1449or 1450.Xr udp 4 1451connections; implicitly in the case of 1452.Ar nat 1453rules and both implicitly and explicitly in the case of 1454.Ar rdr 1455rules. 1456A 1457.Ar rdr 1458rule may cause the source port to be modified if doing so avoids a conflict 1459with an existing connection. 1460A random source port in the range 50001-65535 is chosen in this case; to 1461avoid excessive CPU consumption, the number of searches for a free port is 1462limited by the 1463.Va net.pf.rdr_srcport_rewrite_tries 1464sysctl. 1465Port numbers are never translated with a 1466.Ar binat 1467rule. 1468.Pp 1469Evaluation order of the translation rules is dependent on the type 1470of the translation rules and of the direction of a packet. 1471.Ar binat 1472rules are always evaluated first. 1473Then either the 1474.Ar rdr 1475rules are evaluated on an inbound packet or the 1476.Ar nat 1477rules on an outbound packet. 1478Rules of the same type are evaluated in the same order in which they 1479appear in the ruleset. 1480The first matching rule decides what action is taken. 1481.Pp 1482The 1483.Ar no 1484option prefixed to a translation rule causes packets to remain untranslated, 1485much in the same way as 1486.Ar drop quick 1487works in the packet filter (see below). 1488If no rule matches the packet it is passed to the filter engine unmodified. 1489.Pp 1490Translation rules apply only to packets that pass through 1491the specified interface, and if no interface is specified, 1492translation is applied to packets on all interfaces. 1493For instance, redirecting port 80 on an external interface to an internal 1494web server will only work for connections originating from the outside. 1495Connections to the address of the external interface from local hosts will 1496not be redirected, since such packets do not actually pass through the 1497external interface. 1498Redirections cannot reflect packets back through the interface they arrive 1499on, they can only be redirected to hosts connected to different interfaces 1500or to the firewall itself. 1501.Pp 1502Note that redirecting external incoming connections to the loopback 1503address, as in 1504.Bd -literal -offset indent 1505rdr on ne3 inet proto tcp to port smtp -\*(Gt 127.0.0.1 port spamd 1506.Ed 1507.Pp 1508will effectively allow an external host to connect to daemons 1509bound solely to the loopback address, circumventing the traditional 1510blocking of such connections on a real interface. 1511Unless this effect is desired, any of the local non-loopback addresses 1512should be used as redirection target instead, which allows external 1513connections only to daemons bound to this address or not bound to 1514any address. 1515.Pp 1516See 1517.Sx TRANSLATION EXAMPLES 1518below. 1519.Sh PACKET FILTERING 1520.Xr pf 4 1521has the ability to 1522.Ar block 1523, 1524.Ar pass 1525and 1526.Ar match 1527packets based on attributes of their layer 3 (see 1528.Xr ip 4 1529and 1530.Xr ip6 4 ) 1531and layer 4 (see 1532.Xr icmp 4 , 1533.Xr icmp6 4 , 1534.Xr tcp 4 , 1535.Xr sctp 4 , 1536.Xr udp 4 ) 1537headers. 1538In addition, packets may also be 1539assigned to queues for the purpose of bandwidth control. 1540.Pp 1541For each packet processed by the packet filter, the filter rules are 1542evaluated in sequential order, from first to last. 1543For 1544.Ar block 1545and 1546.Ar pass 1547, the last matching rule decides what action is taken. 1548For 1549.Ar match 1550, rules are evaluated every time they match; the pass/block state of a packet 1551remains unchanged. 1552If no rule matches the packet, the default action is to pass 1553the packet. 1554.Pp 1555The following actions can be used in the filter: 1556.Bl -tag -width xxxx 1557.It Ar block 1558The packet is blocked. 1559There are a number of ways in which a 1560.Ar block 1561rule can behave when blocking a packet. 1562The default behaviour is to 1563.Ar drop 1564packets silently, however this can be overridden or made 1565explicit either globally, by setting the 1566.Ar block-policy 1567option, or on a per-rule basis with one of the following options: 1568.Pp 1569.Bl -tag -width xxxx -compact 1570.It Ar drop 1571The packet is silently dropped. 1572.It Ar return-rst 1573This applies only to 1574.Xr tcp 4 1575packets, and issues a TCP RST which closes the 1576connection. 1577.It Ar return-icmp 1578.It Ar return-icmp6 1579This causes ICMP messages to be returned for packets which match the rule. 1580By default this is an ICMP UNREACHABLE message, however this 1581can be overridden by specifying a message as a code or number. 1582.It Ar return 1583This causes a TCP RST to be returned for 1584.Xr tcp 4 1585packets, an SCTP ABORT for SCTP 1586and an ICMP UNREACHABLE for UDP and other packets. 1587.El 1588.Pp 1589Options returning ICMP packets currently have no effect if 1590.Xr pf 4 1591operates on a 1592.Xr if_bridge 4 , 1593as the code to support this feature has not yet been implemented. 1594.Pp 1595The simplest mechanism to block everything by default and only pass 1596packets that match explicit rules is specify a first filter rule of: 1597.Bd -literal -offset indent 1598block all 1599.Ed 1600.It Ar match 1601The packet is matched. 1602This mechanism is used to provide fine grained filtering without altering the 1603block/pass state of a packet. 1604.Ar match 1605rules differ from 1606.Ar block 1607and 1608.Ar pass 1609rules in that parameters are set for every rule a packet matches, not only 1610on the last matching rule. 1611For the following parameters, this means that the parameter effectively becomes 1612"sticky" until explicitly overridden: 1613.Ar queue , 1614.Ar dnpipe , 1615.Ar dnqueue , 1616.Ar rtable , 1617.Ar scrub 1618. 1619.It Ar pass 1620The packet is passed; 1621state is created unless the 1622.Ar no state 1623option is specified. 1624.El 1625.Pp 1626By default 1627.Xr pf 4 1628filters packets statefully; the first time a packet matches a 1629.Ar pass 1630rule, a state entry is created; for subsequent packets the filter checks 1631whether the packet matches any state. 1632If it does, the packet is passed without evaluation of any rules. 1633After the connection is closed or times out, the state entry is automatically 1634removed. 1635.Pp 1636This has several advantages. 1637For TCP connections, comparing a packet to a state involves checking 1638its sequence numbers, as well as TCP timestamps if a 1639.Ar scrub reassemble tcp 1640rule applies to the connection. 1641If these values are outside the narrow windows of expected 1642values, the packet is dropped. 1643This prevents spoofing attacks, such as when an attacker sends packets with 1644a fake source address/port but does not know the connection's sequence 1645numbers. 1646Similarly, 1647.Xr pf 4 1648knows how to match ICMP replies to states. 1649For example, 1650.Bd -literal -offset indent 1651pass out inet proto icmp all icmp-type echoreq 1652.Ed 1653.Pp 1654allows echo requests (such as those created by 1655.Xr ping 8 ) 1656out statefully, and matches incoming echo replies correctly to states. 1657.Pp 1658Also, looking up states is usually faster than evaluating rules. 1659If there are 50 rules, all of them are evaluated sequentially in O(n). 1660Even with 50000 states, only 16 comparisons are needed to match a 1661state, since states are stored in a binary search tree that allows 1662searches in O(log2 n). 1663.Pp 1664Furthermore, correct handling of ICMP error messages is critical to 1665many protocols, particularly TCP. 1666.Xr pf 4 1667matches ICMP error messages to the correct connection, checks them against 1668connection parameters, and passes them if appropriate. 1669For example if an ICMP source quench message referring to a stateful TCP 1670connection arrives, it will be matched to the state and get passed. 1671.Pp 1672Finally, state tracking is required for 1673.Ar nat , binat No and Ar rdr 1674rules, in order to track address and port translations and reverse the 1675translation on returning packets. 1676.Pp 1677.Xr pf 4 1678will also create state for other protocols which are effectively stateless by 1679nature. 1680UDP packets are matched to states using only host addresses and ports, 1681and other protocols are matched to states using only the host addresses. 1682.Pp 1683If stateless filtering of individual packets is desired, 1684the 1685.Ar no state 1686keyword can be used to specify that state will not be created 1687if this is the last matching rule. 1688A number of parameters can also be set to affect how 1689.Xr pf 4 1690handles state tracking. 1691See 1692.Sx STATEFUL TRACKING OPTIONS 1693below for further details. 1694.Sh PARAMETERS 1695The rule parameters specify the packets to which a rule applies. 1696A packet always comes in on, or goes out through, one interface. 1697Most parameters are optional. 1698If a parameter is specified, the rule only applies to packets with 1699matching attributes. 1700Certain parameters can be expressed as lists, in which case 1701.Xr pfctl 8 1702generates all needed rule combinations. 1703.Bl -tag -width xxxx 1704.It Ar in No or Ar out 1705This rule applies to incoming or outgoing packets. 1706If neither 1707.Ar in 1708nor 1709.Ar out 1710are specified, the rule will match packets in both directions. 1711.It Ar log 1712In addition to the action specified, a log message is generated. 1713Only the packet that establishes the state is logged, 1714unless the 1715.Ar no state 1716option is specified. 1717The logged packets are sent to a 1718.Xr pflog 4 1719interface, by default 1720.Ar pflog0 . 1721This interface is monitored by the 1722.Xr pflogd 8 1723logging daemon, which dumps the logged packets to the file 1724.Pa /var/log/pflog 1725in 1726.Xr pcap 3 1727binary format. 1728.It Ar log (all) 1729Used to force logging of all packets for a connection. 1730This is not necessary when 1731.Ar no state 1732is explicitly specified. 1733As with 1734.Ar log , 1735packets are logged to 1736.Xr pflog 4 . 1737.It Ar log (matches) 1738Used to force logging of this packet on all subsequent matching rules. 1739.It Ar log (user) 1740Logs the 1741.Ux 1742user ID of the user that owns the socket and the PID of the process that 1743has the socket open where the packet is sourced from or destined to 1744(depending on which socket is local). 1745This is in addition to the normal information logged. 1746.Pp 1747Only the first packet 1748logged via 1749.Ar log (all, user) 1750will have the user credentials logged when using stateful matching. 1751.It Ar log (to Aq Ar interface ) 1752Send logs to the specified 1753.Xr pflog 4 1754interface instead of 1755.Ar pflog0 . 1756.It Ar quick 1757If a packet matches a rule which has the 1758.Ar quick 1759option set, this rule 1760is considered the last matching rule, and evaluation of subsequent rules 1761is skipped. 1762.It Ar on Aq Ar interface 1763This rule applies only to packets coming in on, or going out through, this 1764particular interface or interface group. 1765For more information on interface groups, 1766see the 1767.Ic group 1768keyword in 1769.Xr ifconfig 8 . 1770.It Aq Ar af 1771This rule applies only to packets of this address family. 1772Supported values are 1773.Ar inet 1774and 1775.Ar inet6 . 1776.It Ar proto Aq Ar protocol 1777This rule applies only to packets of this protocol. 1778Common protocols are 1779.Xr icmp 4 , 1780.Xr icmp6 4 , 1781.Xr tcp 4 , 1782.Xr sctp 4 , 1783and 1784.Xr udp 4 . 1785For a list of all the protocol name to number mappings used by 1786.Xr pfctl 8 , 1787see the file 1788.Pa /etc/protocols . 1789.It Xo 1790.Ar from Aq Ar source 1791.Ar port Aq Ar source 1792.Ar os Aq Ar source 1793.Ar to Aq Ar dest 1794.Ar port Aq Ar dest 1795.Xc 1796This rule applies only to packets with the specified source and destination 1797addresses and ports. 1798.Pp 1799Addresses can be specified in CIDR notation (matching netblocks), as 1800symbolic host names, interface names or interface group names, or as any 1801of the following keywords: 1802.Pp 1803.Bl -tag -width xxxxxxxxxxxxxx -compact 1804.It Ar any 1805Any address. 1806.It Ar no-route 1807Any address which is not currently routable. 1808.It Ar urpf-failed 1809Any source address that fails a unicast reverse path forwarding (URPF) 1810check, i.e. packets coming in on an interface other than that which holds 1811the route back to the packet's source address. 1812.It Aq Ar table 1813Any address that matches the given table. 1814.El 1815.Pp 1816Ranges of addresses are specified by using the 1817.Sq - 1818operator. 1819For instance: 1820.Dq 10.1.1.10 - 10.1.1.12 1821means all addresses from 10.1.1.10 to 10.1.1.12, 1822hence addresses 10.1.1.10, 10.1.1.11, and 10.1.1.12. 1823.Pp 1824Interface names and interface group names can have modifiers appended: 1825.Pp 1826.Bl -tag -width xxxxxxxxxxxx -compact 1827.It Ar :network 1828Translates to the network(s) attached to the interface. 1829.It Ar :broadcast 1830Translates to the interface's broadcast address(es). 1831.It Ar :peer 1832Translates to the point-to-point interface's peer address(es). 1833.It Ar :0 1834Do not include interface aliases. 1835.El 1836.Pp 1837Host names may also have the 1838.Ar :0 1839option appended to restrict the name resolution to the first of each 1840v4 and non-link-local v6 address found. 1841.Pp 1842Host name resolution and interface to address translation are done at 1843ruleset load-time. 1844When the address of an interface (or host name) changes (under DHCP or PPP, 1845for instance), the ruleset must be reloaded for the change to be reflected 1846in the kernel. 1847Surrounding the interface name (and optional modifiers) in parentheses 1848changes this behaviour. 1849When the interface name is surrounded by parentheses, the rule is 1850automatically updated whenever the interface changes its address. 1851The ruleset does not need to be reloaded. 1852This is especially useful with 1853.Ar nat . 1854.Pp 1855Ports can be specified either by number or by name. 1856For example, port 80 can be specified as 1857.Em www . 1858For a list of all port name to number mappings used by 1859.Xr pfctl 8 , 1860see the file 1861.Pa /etc/services . 1862.Pp 1863Ports and ranges of ports are specified by using these operators: 1864.Bd -literal -offset indent 1865= (equal) 1866!= (unequal) 1867\*(Lt (less than) 1868\*(Le (less than or equal) 1869\*(Gt (greater than) 1870\*(Ge (greater than or equal) 1871: (range including boundaries) 1872\*(Gt\*(Lt (range excluding boundaries) 1873\*(Lt\*(Gt (except range) 1874.Ed 1875.Pp 1876.Sq \*(Gt\*(Lt , 1877.Sq \*(Lt\*(Gt 1878and 1879.Sq \&: 1880are binary operators (they take two arguments). 1881For instance: 1882.Bl -tag -width Fl 1883.It Ar port 2000:2004 1884means 1885.Sq all ports \*(Ge 2000 and \*(Le 2004 , 1886hence ports 2000, 2001, 2002, 2003 and 2004. 1887.It Ar port 2000 \*(Gt\*(Lt 2004 1888means 1889.Sq all ports \*(Gt 2000 and \*(Lt 2004 , 1890hence ports 2001, 2002 and 2003. 1891.It Ar port 2000 \*(Lt\*(Gt 2004 1892means 1893.Sq all ports \*(Lt 2000 or \*(Gt 2004 , 1894hence ports 1-1999 and 2005-65535. 1895.El 1896.Pp 1897The operating system of the source host can be specified in the case of TCP 1898rules with the 1899.Ar OS 1900modifier. 1901See the 1902.Sx OPERATING SYSTEM FINGERPRINTING 1903section for more information. 1904.Pp 1905The host, port and OS specifications are optional, as in the following examples: 1906.Bd -literal -offset indent 1907pass in all 1908pass in from any to any 1909pass in proto tcp from any port \*(Le 1024 to any 1910pass in proto tcp from any to any port 25 1911pass in proto tcp from 10.0.0.0/8 port \*(Gt 1024 \e 1912 to ! 10.1.2.3 port != ssh 1913pass in proto tcp from any os "OpenBSD" 1914.Ed 1915.It Ar all 1916This is equivalent to "from any to any". 1917.It Ar group Aq Ar group 1918Similar to 1919.Ar user , 1920this rule only applies to packets of sockets owned by the specified group. 1921.It Ar user Aq Ar user 1922This rule only applies to packets of sockets owned by the specified user. 1923For outgoing connections initiated from the firewall, this is the user 1924that opened the connection. 1925For incoming connections to the firewall itself, this is the user that 1926listens on the destination port. 1927For forwarded connections, where the firewall is not a connection endpoint, 1928the user and group are 1929.Em unknown . 1930.Pp 1931All packets, both outgoing and incoming, of one connection are associated 1932with the same user and group. 1933Only TCP and UDP packets can be associated with users; for other protocols 1934these parameters are ignored. 1935.Pp 1936User and group refer to the effective (as opposed to the real) IDs, in 1937case the socket is created by a setuid/setgid process. 1938User and group IDs are stored when a socket is created; 1939when a process creates a listening socket as root (for instance, by 1940binding to a privileged port) and subsequently changes to another 1941user ID (to drop privileges), the credentials will remain root. 1942.Pp 1943User and group IDs can be specified as either numbers or names. 1944The syntax is similar to the one for ports. 1945The value 1946.Em unknown 1947matches packets of forwarded connections. 1948.Em unknown 1949can only be used with the operators 1950.Cm = 1951and 1952.Cm != . 1953Other constructs like 1954.Cm user \*(Ge unknown 1955are invalid. 1956Forwarded packets with unknown user and group ID match only rules 1957that explicitly compare against 1958.Em unknown 1959with the operators 1960.Cm = 1961or 1962.Cm != . 1963For instance 1964.Cm user \*(Ge 0 1965does not match forwarded packets. 1966The following example allows only selected users to open outgoing 1967connections: 1968.Bd -literal -offset indent 1969block out proto { tcp, udp } all 1970pass out proto { tcp, udp } all user { \*(Lt 1000, dhartmei } 1971.Ed 1972.It Xo Ar flags Aq Ar a 1973.Pf / Ns Aq Ar b 1974.No \*(Ba / Ns Aq Ar b 1975.No \*(Ba any 1976.Xc 1977This rule only applies to TCP packets that have the flags 1978.Aq Ar a 1979set out of set 1980.Aq Ar b . 1981Flags not specified in 1982.Aq Ar b 1983are ignored. 1984For stateful connections, the default is 1985.Ar flags S/SA . 1986To indicate that flags should not be checked at all, specify 1987.Ar flags any . 1988The flags are: (F)IN, (S)YN, (R)ST, (P)USH, (A)CK, (U)RG, (E)CE, and C(W)R. 1989.Bl -tag -width Fl 1990.It Ar flags S/S 1991Flag SYN is set. 1992The other flags are ignored. 1993.It Ar flags S/SA 1994This is the default setting for stateful connections. 1995Out of SYN and ACK, exactly SYN may be set. 1996SYN, SYN+PSH and SYN+RST match, but SYN+ACK, ACK and ACK+RST do not. 1997This is more restrictive than the previous example. 1998.It Ar flags /SFRA 1999If the first set is not specified, it defaults to none. 2000All of SYN, FIN, RST and ACK must be unset. 2001.El 2002.Pp 2003Because 2004.Ar flags S/SA 2005is applied by default (unless 2006.Ar no state 2007is specified), only the initial SYN packet of a TCP handshake will create 2008a state for a TCP connection. 2009It is possible to be less restrictive, and allow state creation from 2010intermediate 2011.Pq non-SYN 2012packets, by specifying 2013.Ar flags any . 2014This will cause 2015.Xr pf 4 2016to synchronize to existing connections, for instance 2017if one flushes the state table. 2018However, states created from such intermediate packets may be missing 2019connection details such as the TCP window scaling factor. 2020States which modify the packet flow, such as those affected by 2021.Ar af-to, 2022.Ar nat, 2023.Ar binat or 2024.Ar rdr 2025rules, 2026.Ar modulate No or Ar synproxy state 2027options, or scrubbed with 2028.Ar reassemble tcp 2029will also not be recoverable from intermediate packets. 2030Such connections will stall and time out. 2031.It Xo Ar icmp-type Aq Ar type 2032.Ar code Aq Ar code 2033.Xc 2034.It Xo Ar icmp6-type Aq Ar type 2035.Ar code Aq Ar code 2036.Xc 2037This rule only applies to ICMP or ICMPv6 packets with the specified type 2038and code. 2039Text names for ICMP types and codes are listed in 2040.Xr icmp 4 2041and 2042.Xr icmp6 4 . 2043This parameter is only valid for rules that cover protocols ICMP or 2044ICMP6. 2045The protocol and the ICMP type indicator 2046.Po 2047.Ar icmp-type 2048or 2049.Ar icmp6-type 2050.Pc 2051must match. 2052.It Xo Ar tos Aq Ar string 2053.No \*(Ba Aq Ar number 2054.Xc 2055This rule applies to packets with the specified 2056.Em TOS 2057bits set. 2058.Em TOS 2059may be 2060given as one of 2061.Ar critical , 2062.Ar inetcontrol , 2063.Ar lowdelay , 2064.Ar netcontrol , 2065.Ar throughput , 2066.Ar reliability , 2067or one of the DiffServ Code Points: 2068.Ar ef , 2069.Ar va , 2070.Ar af11 No ... Ar af43 , 2071.Ar cs0 No ... Ar cs7 ; 2072or as either hex or decimal. 2073.Pp 2074For example, the following rules are identical: 2075.Bd -literal -offset indent 2076pass all tos lowdelay 2077pass all tos 0x10 2078pass all tos 16 2079.Ed 2080.It Ar allow-opts 2081By default, IPv4 packets with IP options or IPv6 packets with routing 2082extension headers are blocked. 2083When 2084.Ar allow-opts 2085is specified for a 2086.Ar pass 2087rule, packets that pass the filter based on that rule (last matching) 2088do so even if they contain IP options or routing extension headers. 2089For packets that match state, the rule that initially created the 2090state is used. 2091The implicit 2092.Ar pass 2093rule that is used when a packet does not match any rules does not 2094allow IP options. 2095.It Ar label Aq Ar string 2096Adds a label (name) to the rule, which can be used to identify the rule. 2097For instance, 2098pfctl -s labels 2099shows per-rule statistics for rules that have labels. 2100.Pp 2101The following macros can be used in labels: 2102.Pp 2103.Bl -tag -width $srcaddr -compact -offset indent 2104.It Ar $if 2105The interface. 2106.It Ar $srcaddr 2107The source IP address. 2108.It Ar $dstaddr 2109The destination IP address. 2110.It Ar $srcport 2111The source port specification. 2112.It Ar $dstport 2113The destination port specification. 2114.It Ar $proto 2115The protocol name. 2116.It Ar $nr 2117The rule number. 2118.El 2119.Pp 2120For example: 2121.Bd -literal -offset indent 2122ips = \&"{ 1.2.3.4, 1.2.3.5 }\&" 2123pass in proto tcp from any to $ips \e 2124 port \*(Gt 1023 label \&"$dstaddr:$dstport\&" 2125.Ed 2126.Pp 2127expands to 2128.Bd -literal -offset indent 2129pass in inet proto tcp from any to 1.2.3.4 \e 2130 port \*(Gt 1023 label \&"1.2.3.4:\*(Gt1023\&" 2131pass in inet proto tcp from any to 1.2.3.5 \e 2132 port \*(Gt 1023 label \&"1.2.3.5:\*(Gt1023\&" 2133.Ed 2134.Pp 2135The macro expansion for the 2136.Ar label 2137directive occurs only at configuration file parse time, not during runtime. 2138.It Ar ridentifier Aq Ar number 2139Add an identifier (number) to the rule, which can be used to correlate the rule 2140to pflog entries, even after ruleset updates. 2141.It Xo Ar queue Aq Ar queue 2142.No \*(Ba ( Aq Ar queue , 2143.Aq Ar queue ) 2144.Xc 2145Packets matching this rule will be assigned to the specified queue. 2146If two queues are given, packets which have a 2147.Em TOS 2148of 2149.Em lowdelay 2150and TCP ACKs with no data payload will be assigned to the second one. 2151See 2152.Sx QUEUEING 2153for setup details. 2154.Pp 2155For example: 2156.Bd -literal -offset indent 2157pass in proto tcp to port 25 queue mail 2158pass in proto tcp to port 22 queue(ssh_bulk, ssh_prio) 2159.Ed 2160.It Cm set prio Ar priority | Pq Ar priority , priority 2161Packets matching this rule will be assigned a specific queueing priority. 2162Priorities are assigned as integers 0 through 7. 2163If the packet is transmitted on a 2164.Xr vlan 4 2165interface, the queueing priority will be written as the priority 2166code point in the 802.1Q VLAN header. 2167If two priorities are given, packets which have a TOS of 2168.Cm lowdelay 2169and TCP ACKs with no data payload will be assigned to the second one. 2170.Pp 2171For example: 2172.Bd -literal -offset indent 2173pass in proto tcp to port 25 set prio 2 2174pass in proto tcp to port 22 set prio (2, 5) 2175.Ed 2176.It Ar received-on Aq Ar interface 2177Only match packets which were received on the specified 2178.Ar interface 2179(or interface group). 2180.It Ar tag Aq Ar string 2181Packets matching this rule will be tagged with the 2182specified string. 2183The tag acts as an internal marker that can be used to 2184identify these packets later on. 2185This can be used, for example, to provide trust between 2186interfaces and to determine if packets have been 2187processed by translation rules. 2188Tags are 2189.Qq sticky , 2190meaning that the packet will be tagged even if the rule 2191is not the last matching rule. 2192Further matching rules can replace the tag with a 2193new one but will not remove a previously applied tag. 2194A packet is only ever assigned one tag at a time. 2195Packet tagging can be done during 2196.Ar nat , 2197.Ar rdr , 2198.Ar binat 2199or 2200.Ar ether 2201rules in addition to filter rules. 2202Tags take the same macros as labels (see above). 2203.It Ar tagged Aq Ar string 2204Used with filter, translation or scrub rules 2205to specify that packets must already 2206be tagged with the given tag in order to match the rule. 2207Inverse tag matching can also be done 2208by specifying the 2209.Cm !\& 2210operator before the 2211.Ar tagged 2212keyword. 2213.It Ar rtable Aq Ar number 2214Used to select an alternate routing table for the routing lookup. 2215Only effective before the route lookup happened, i.e. when filtering inbound. 2216.It Xo Ar divert-to Aq Ar host 2217.Ar port Aq Ar port 2218.Xc 2219Used to 2220.Xr divert 4 2221packets to the given divert 2222.Ar port . 2223Historically 2224.Ox pf has another meaning for this, and 2225.Fx pf uses 2226this syntax to support 2227.Xr divert 4 instead. Hence, 2228.Ar host 2229has no meaning and can be set to anything like 127.0.0.1. 2230If a packet is re-injected and does not change direction then it will not be 2231re-diverted. 2232.It Ar divert-reply 2233It has no meaning in 2234.Fx pf . 2235.It Ar probability Aq Ar number 2236A probability attribute can be attached to a rule, with a value set between 22370 and 1, bounds not included. 2238In that case, the rule will be honoured using the given probability value 2239only. 2240For example, the following rule will drop 20% of incoming ICMP packets: 2241.Bd -literal -offset indent 2242block in proto icmp probability 20% 2243.Ed 2244.It Ar prio Aq Ar number 2245Only match packets which have the given queueing priority assigned. 2246.El 2247.Sh ROUTING 2248If a packet matches a rule with a route option set, the packet filter will 2249route the packet according to the type of route option. 2250When such a rule creates state, the route option is also applied to all 2251packets matching the same connection. 2252.Bl -tag -width xxxx 2253.It Ar route-to 2254The 2255.Ar route-to 2256option routes the packet to the specified interface with an optional address 2257for the next hop. 2258When a 2259.Ar route-to 2260rule creates state, only packets that pass in the same direction as the 2261filter rule specifies will be routed in this way. 2262Packets passing in the opposite direction (replies) are not affected 2263and are routed normally. 2264.It Ar reply-to 2265The 2266.Ar reply-to 2267option is similar to 2268.Ar route-to , 2269but routes packets that pass in the opposite direction (replies) to the 2270specified interface. 2271Opposite direction is only defined in the context of a state entry, and 2272.Ar reply-to 2273is useful only in rules that create state. 2274It can be used on systems with multiple external connections to 2275route all outgoing packets of a connection through the interface 2276the incoming connection arrived through (symmetric routing enforcement). 2277.It Ar dup-to 2278The 2279.Ar dup-to 2280option creates a duplicate of the packet and routes it like 2281.Ar route-to . 2282The original packet gets routed as it normally would. 2283.El 2284.Sh POOL OPTIONS 2285For 2286.Ar nat 2287and 2288.Ar rdr 2289rules, (as well as for the 2290.Ar route-to , 2291.Ar reply-to 2292and 2293.Ar dup-to 2294rule options) for which there is a single redirection address which has a 2295subnet mask smaller than 32 for IPv4 or 128 for IPv6 (more than one IP 2296address), a variety of different methods for assigning this address can be 2297used: 2298.Bl -tag -width xxxx 2299.It Ar bitmask 2300The 2301.Ar bitmask 2302option applies the network portion of the redirection address to the address 2303to be modified (source with 2304.Ar nat , 2305destination with 2306.Ar rdr ) . 2307.It Ar random 2308The 2309.Ar random 2310option selects an address at random within the defined block of addresses. 2311.It Ar source-hash 2312The 2313.Ar source-hash 2314option uses a hash of the source address to determine the redirection address, 2315ensuring that the redirection address is always the same for a given source. 2316An optional key can be specified after this keyword either in hex or as a 2317string; by default 2318.Xr pfctl 8 2319randomly generates a key for source-hash every time the 2320ruleset is reloaded. 2321.It Ar round-robin 2322The 2323.Ar round-robin 2324option loops through the redirection address(es). 2325.Pp 2326When more than one redirection address is specified, 2327.Ar round-robin 2328is the only permitted pool type. 2329.It Ar static-port 2330With 2331.Ar nat 2332rules, the 2333.Ar static-port 2334option prevents 2335.Xr pf 4 2336from modifying the source port on TCP and UDP packets. 2337.It Xo Ar map-e-portset Aq Ar psid-offset 2338.No / Aq Ar psid-len 2339.No / Aq Ar psid 2340.Xc 2341With 2342.Ar nat 2343rules, the 2344.It Ar endpoint-independent 2345With 2346.Ar nat 2347rules, the 2348.Ar endpoint-independent 2349option caues 2350.Xr pf 4 2351to always map connections from a UDP source address and port to the same 2352NAT address and port. 2353This feature implements "full-cone" NAT behavior. 2354.Ar map-e-portset 2355option enables the source port translation of MAP-E (RFC 7597) Customer Edge. 2356In order to make the host act as a MAP-E Customer Edge, setting up a tunneling 2357interface and pass rules for encapsulated packets are required in addition 2358to the map-e-portset nat rule. 2359.Pp 2360For example: 2361.Bd -literal -offset indent 2362nat on $gif_mape_if from $int_if:network to any \e 2363 -> $ipv4_mape_src map-e-portset 6/8/0x34 2364.Ed 2365.Pp 2366sets PSID offset 6, PSID length 8, PSID 0x34. 2367.El 2368.Pp 2369Additionally, the 2370.Ar sticky-address 2371option can be specified to help ensure that multiple connections from the 2372same source are mapped to the same redirection address. 2373This option can be used with the 2374.Ar random 2375and 2376.Ar round-robin 2377pool options. 2378Note that by default these associations are destroyed as soon as there are 2379no longer states which refer to them; in order to make the mappings last 2380beyond the lifetime of the states, increase the global options with 2381.Ar set timeout src.track . 2382See 2383.Sx STATEFUL TRACKING OPTIONS 2384for more ways to control the source tracking. 2385.Sh STATE MODULATION 2386Much of the security derived from TCP is attributable to how well the 2387initial sequence numbers (ISNs) are chosen. 2388Some popular stack implementations choose 2389.Em very 2390poor ISNs and thus are normally susceptible to ISN prediction exploits. 2391By applying a 2392.Ar modulate state 2393rule to a TCP connection, 2394.Xr pf 4 2395will create a high quality random sequence number for each connection 2396endpoint. 2397.Pp 2398The 2399.Ar modulate state 2400directive implicitly keeps state on the rule and is 2401only applicable to TCP connections. 2402.Pp 2403For instance: 2404.Bd -literal -offset indent 2405block all 2406pass out proto tcp from any to any modulate state 2407pass in proto tcp from any to any port 25 flags S/SFRA modulate state 2408.Ed 2409.Pp 2410Note that modulated connections will not recover when the state table 2411is lost (firewall reboot, flushing the state table, etc...). 2412.Xr pf 4 2413will not be able to infer a connection again after the state table flushes 2414the connection's modulator. 2415When the state is lost, the connection may be left dangling until the 2416respective endpoints time out the connection. 2417It is possible on a fast local network for the endpoints to start an ACK 2418storm while trying to resynchronize after the loss of the modulator. 2419The default 2420.Ar flags 2421settings (or a more strict equivalent) should be used on 2422.Ar modulate state 2423rules to prevent ACK storms. 2424.Pp 2425Note that alternative methods are available 2426to prevent loss of the state table 2427and allow for firewall failover. 2428See 2429.Xr carp 4 2430and 2431.Xr pfsync 4 2432for further information. 2433.Sh SYN PROXY 2434By default, 2435.Xr pf 4 2436passes packets that are part of a 2437.Xr tcp 4 2438handshake between the endpoints. 2439The 2440.Ar synproxy state 2441option can be used to cause 2442.Xr pf 4 2443itself to complete the handshake with the active endpoint, perform a handshake 2444with the passive endpoint, and then forward packets between the endpoints. 2445.Pp 2446No packets are sent to the passive endpoint before the active endpoint has 2447completed the handshake, hence so-called SYN floods with spoofed source 2448addresses will not reach the passive endpoint, as the sender can't complete the 2449handshake. 2450.Pp 2451The proxy is transparent to both endpoints, they each see a single 2452connection from/to the other endpoint. 2453.Xr pf 4 2454chooses random initial sequence numbers for both handshakes. 2455Once the handshakes are completed, the sequence number modulators 2456(see previous section) are used to translate further packets of the 2457connection. 2458.Ar synproxy state 2459includes 2460.Ar modulate state . 2461.Pp 2462Rules with 2463.Ar synproxy 2464will not work if 2465.Xr pf 4 2466operates on a 2467.Xr bridge 4 . 2468.Pp 2469Example: 2470.Bd -literal -offset indent 2471pass in proto tcp from any to any port www synproxy state 2472.Ed 2473.Sh STATEFUL TRACKING OPTIONS 2474A number of options related to stateful tracking can be applied on a 2475per-rule basis. 2476.Ar keep state , 2477.Ar modulate state 2478and 2479.Ar synproxy state 2480support these options, and 2481.Ar keep state 2482must be specified explicitly to apply options to a rule. 2483.Pp 2484.Bl -tag -width xxxx -compact 2485.It Ar max Aq Ar number 2486Limits the number of concurrent states the rule may create. 2487When this limit is reached, further packets that would create 2488state are dropped until existing states time out. 2489.It Ar no-sync 2490Prevent state changes for states created by this rule from appearing on the 2491.Xr pfsync 4 2492interface. 2493.It Xo Aq Ar timeout 2494.Aq Ar seconds 2495.Xc 2496Changes the timeout values used for states created by this rule. 2497For a list of all valid timeout names, see 2498.Sx OPTIONS 2499above. 2500.It Ar sloppy 2501Uses a sloppy TCP connection tracker that does not check sequence 2502numbers at all, which makes insertion and ICMP teardown attacks way 2503easier. 2504This is intended to be used in situations where one does not see all 2505packets of a connection, e.g. in asymmetric routing situations. 2506Cannot be used with modulate or synproxy state. 2507.It Ar pflow 2508States created by this rule are exported on the 2509.Xr pflow 4 2510interface. 2511.El 2512.Pp 2513Multiple options can be specified, separated by commas: 2514.Bd -literal -offset indent 2515pass in proto tcp from any to any \e 2516 port www keep state \e 2517 (max 100, source-track rule, max-src-nodes 75, \e 2518 max-src-states 3, tcp.established 60, tcp.closing 5) 2519.Ed 2520.Pp 2521When the 2522.Ar source-track 2523keyword is specified, the number of states per source IP is tracked. 2524.Pp 2525.Bl -tag -width xxxx -compact 2526.It Ar source-track rule 2527The maximum number of states created by this rule is limited by the rule's 2528.Ar max-src-nodes 2529and 2530.Ar max-src-states 2531options. 2532Only state entries created by this particular rule count toward the rule's 2533limits. 2534.It Ar source-track global 2535The number of states created by all rules that use this option is limited. 2536Each rule can specify different 2537.Ar max-src-nodes 2538and 2539.Ar max-src-states 2540options, however state entries created by any participating rule count towards 2541each individual rule's limits. 2542.El 2543.Pp 2544The following limits can be set: 2545.Pp 2546.Bl -tag -width xxxx -compact 2547.It Ar max-src-nodes Aq Ar number 2548Limits the maximum number of source addresses which can simultaneously 2549have state table entries. 2550.It Ar max-src-states Aq Ar number 2551Limits the maximum number of simultaneous state entries that a single 2552source address can create with this rule. 2553.El 2554.Pp 2555For stateful TCP connections, limits on established connections (connections 2556which have completed the TCP 3-way handshake) can also be enforced 2557per source IP. 2558.Pp 2559.Bl -tag -width xxxx -compact 2560.It Ar max-src-conn Aq Ar number 2561Limits the maximum number of simultaneous TCP connections which have 2562completed the 3-way handshake that a single host can make. 2563.It Xo Ar max-src-conn-rate Aq Ar number 2564.No / Aq Ar seconds 2565.Xc 2566Limit the rate of new connections over a time interval. 2567The connection rate is an approximation calculated as a moving average. 2568.El 2569.Pp 2570When one of these limits is reached, further packets that would create 2571state are dropped until existing states time out. 2572.Pp 2573Because the 3-way handshake ensures that the source address is not being 2574spoofed, more aggressive action can be taken based on these limits. 2575With the 2576.Ar overload Aq Ar table 2577state option, source IP addresses which hit either of the limits on 2578established connections will be added to the named table. 2579This table can be used in the ruleset to block further activity from 2580the offending host, redirect it to a tarpit process, or restrict its 2581bandwidth. 2582.Pp 2583The optional 2584.Ar flush 2585keyword kills all states created by the matching rule which originate 2586from the host which exceeds these limits. 2587The 2588.Ar global 2589modifier to the flush command kills all states originating from the 2590offending host, regardless of which rule created the state. 2591.Pp 2592For example, the following rules will protect the webserver against 2593hosts making more than 100 connections in 10 seconds. 2594Any host which connects faster than this rate will have its address added 2595to the 2596.Aq bad_hosts 2597table and have all states originating from it flushed. 2598Any new packets arriving from this host will be dropped unconditionally 2599by the block rule. 2600.Bd -literal -offset indent 2601block quick from \*(Ltbad_hosts\*(Gt 2602pass in on $ext_if proto tcp to $webserver port www keep state \e 2603 (max-src-conn-rate 100/10, overload \*(Ltbad_hosts\*(Gt flush global) 2604.Ed 2605.Sh OPERATING SYSTEM FINGERPRINTING 2606Passive OS Fingerprinting is a mechanism to inspect nuances of a TCP 2607connection's initial SYN packet and guess at the host's operating system. 2608Unfortunately these nuances are easily spoofed by an attacker so the 2609fingerprint is not useful in making security decisions. 2610But the fingerprint is typically accurate enough to make policy decisions 2611upon. 2612.Pp 2613The fingerprints may be specified by operating system class, by 2614version, or by subtype/patchlevel. 2615The class of an operating system is typically the vendor or genre 2616and would be 2617.Ox 2618for the 2619.Xr pf 4 2620firewall itself. 2621The version of the oldest available 2622.Ox 2623release on the main FTP site 2624would be 2.6 and the fingerprint would be written 2625.Pp 2626.Dl \&"OpenBSD 2.6\&" 2627.Pp 2628The subtype of an operating system is typically used to describe the 2629patchlevel if that patch led to changes in the TCP stack behavior. 2630In the case of 2631.Ox , 2632the only subtype is for a fingerprint that was 2633normalized by the 2634.Ar no-df 2635scrub option and would be specified as 2636.Pp 2637.Dl \&"OpenBSD 3.3 no-df\&" 2638.Pp 2639Fingerprints for most popular operating systems are provided by 2640.Xr pf.os 5 . 2641Once 2642.Xr pf 4 2643is running, a complete list of known operating system fingerprints may 2644be listed by running: 2645.Pp 2646.Dl # pfctl -so 2647.Pp 2648Filter rules can enforce policy at any level of operating system specification 2649assuming a fingerprint is present. 2650Policy could limit traffic to approved operating systems or even ban traffic 2651from hosts that aren't at the latest service pack. 2652.Pp 2653The 2654.Ar unknown 2655class can also be used as the fingerprint which will match packets for 2656which no operating system fingerprint is known. 2657.Pp 2658Examples: 2659.Bd -literal -offset indent 2660pass out proto tcp from any os OpenBSD 2661block out proto tcp from any os Doors 2662block out proto tcp from any os "Doors PT" 2663block out proto tcp from any os "Doors PT SP3" 2664block out from any os "unknown" 2665pass on lo0 proto tcp from any os "OpenBSD 3.3 lo0" 2666.Ed 2667.Pp 2668Operating system fingerprinting is limited only to the TCP SYN packet. 2669This means that it will not work on other protocols and will not match 2670a currently established connection. 2671.Pp 2672Caveat: operating system fingerprints are occasionally wrong. 2673There are three problems: an attacker can trivially craft his packets to 2674appear as any operating system he chooses; 2675an operating system patch could change the stack behavior and no fingerprints 2676will match it until the database is updated; 2677and multiple operating systems may have the same fingerprint. 2678.Sh BLOCKING SPOOFED TRAFFIC 2679"Spoofing" is the faking of IP addresses, typically for malicious 2680purposes. 2681The 2682.Ar antispoof 2683directive expands to a set of filter rules which will block all 2684traffic with a source IP from the network(s) directly connected 2685to the specified interface(s) from entering the system through 2686any other interface. 2687.Pp 2688For example, the line 2689.Bd -literal -offset indent 2690antispoof for lo0 2691.Ed 2692.Pp 2693expands to 2694.Bd -literal -offset indent 2695block drop in on ! lo0 inet from 127.0.0.1/8 to any 2696block drop in on ! lo0 inet6 from ::1 to any 2697.Ed 2698.Pp 2699For non-loopback interfaces, there are additional rules to block incoming 2700packets with a source IP address identical to the interface's IP(s). 2701For example, assuming the interface wi0 had an IP address of 10.0.0.1 and a 2702netmask of 255.255.255.0, 2703the line 2704.Bd -literal -offset indent 2705antispoof for wi0 inet 2706.Ed 2707.Pp 2708expands to 2709.Bd -literal -offset indent 2710block drop in on ! wi0 inet from 10.0.0.0/24 to any 2711block drop in inet from 10.0.0.1 to any 2712.Ed 2713.Pp 2714Caveat: Rules created by the 2715.Ar antispoof 2716directive interfere with packets sent over loopback interfaces 2717to local addresses. 2718One should pass these explicitly. 2719.Sh FRAGMENT HANDLING 2720The size of IP datagrams (packets) can be significantly larger than the 2721maximum transmission unit (MTU) of the network. 2722In cases when it is necessary or more efficient to send such large packets, 2723the large packet will be fragmented into many smaller packets that will each 2724fit onto the wire. 2725Unfortunately for a firewalling device, only the first logical fragment will 2726contain the necessary header information for the subprotocol that allows 2727.Xr pf 4 2728to filter on things such as TCP ports or to perform NAT. 2729.Pp 2730Besides the use of 2731.Ar set reassemble 2732option or 2733.Ar scrub 2734rules as described in 2735.Sx TRAFFIC NORMALIZATION 2736above, there are three options for handling fragments in the packet filter. 2737.Pp 2738One alternative is to filter individual fragments with filter rules. 2739If no 2740.Ar scrub 2741rule applies to a fragment or 2742.Ar set reassemble 2743is set to 2744.Cm no 2745, it is passed to the filter. 2746Filter rules with matching IP header parameters decide whether the 2747fragment is passed or blocked, in the same way as complete packets 2748are filtered. 2749Without reassembly, fragments can only be filtered based on IP header 2750fields (source/destination address, protocol), since subprotocol header 2751fields are not available (TCP/UDP port numbers, ICMP code/type). 2752The 2753.Ar fragment 2754option can be used to restrict filter rules to apply only to 2755fragments, but not complete packets. 2756Filter rules without the 2757.Ar fragment 2758option still apply to fragments, if they only specify IP header fields. 2759For instance, the rule 2760.Bd -literal -offset indent 2761pass in proto tcp from any to any port 80 2762.Ed 2763.Pp 2764never applies to a fragment, even if the fragment is part of a TCP 2765packet with destination port 80, because without reassembly this information 2766is not available for each fragment. 2767This also means that fragments cannot create new or match existing 2768state table entries, which makes stateful filtering and address 2769translation (NAT, redirection) for fragments impossible. 2770.Pp 2771It's also possible to reassemble only certain fragments by specifying 2772source or destination addresses or protocols as parameters in 2773.Ar scrub 2774rules. 2775.Pp 2776In most cases, the benefits of reassembly outweigh the additional 2777memory cost, and it's recommended to use 2778.Ar set reassemble 2779option or 2780.Ar scrub 2781rules with the 2782.Ar fragment reassemble 2783modifier to reassemble 2784all fragments. 2785.Pp 2786The memory allocated for fragment caching can be limited using 2787.Xr pfctl 8 . 2788Once this limit is reached, fragments that would have to be cached 2789are dropped until other entries time out. 2790The timeout value can also be adjusted. 2791.Pp 2792When forwarding reassembled IPv6 packets, pf refragments them with 2793the original maximum fragment size. 2794This allows the sender to determine the optimal fragment size by 2795path MTU discovery. 2796.Sh ANCHORS 2797Besides the main ruleset, 2798.Xr pfctl 8 2799can load rulesets into 2800.Ar anchor 2801attachment points. 2802An 2803.Ar anchor 2804is a container that can hold rules, address tables, and other anchors. 2805.Pp 2806An 2807.Ar anchor 2808has a name which specifies the path where 2809.Xr pfctl 8 2810can be used to access the anchor to perform operations on it, such as 2811attaching child anchors to it or loading rules into it. 2812Anchors may be nested, with components separated by 2813.Sq / 2814characters, similar to how file system hierarchies are laid out. 2815The main ruleset is actually the default anchor, so filter and 2816translation rules, for example, may also be contained in any anchor. 2817.Pp 2818An anchor can reference another 2819.Ar anchor 2820attachment point 2821using the following kinds 2822of rules: 2823.Bl -tag -width xxxx 2824.It Ar nat-anchor Aq Ar name 2825Evaluates the 2826.Ar nat 2827rules in the specified 2828.Ar anchor . 2829.It Ar rdr-anchor Aq Ar name 2830Evaluates the 2831.Ar rdr 2832rules in the specified 2833.Ar anchor . 2834.It Ar binat-anchor Aq Ar name 2835Evaluates the 2836.Ar binat 2837rules in the specified 2838.Ar anchor . 2839.It Ar anchor Aq Ar name 2840Evaluates the filter rules in the specified 2841.Ar anchor . 2842.It Xo Ar load anchor 2843.Aq Ar name 2844.Ar from Aq Ar file 2845.Xc 2846Loads the rules from the specified file into the 2847anchor 2848.Ar name . 2849.El 2850.Pp 2851When evaluation of the main ruleset reaches an 2852.Ar anchor 2853rule, 2854.Xr pf 4 2855will proceed to evaluate all rules specified in that anchor. 2856.Pp 2857Matching filter and translation rules marked with the 2858.Ar quick 2859option are final and abort the evaluation of the rules in other 2860anchors and the main ruleset. 2861If the 2862.Ar anchor 2863itself is marked with the 2864.Ar quick 2865option, 2866ruleset evaluation will terminate when the anchor is exited if the packet is 2867matched by any rule within the anchor. 2868.Pp 2869.Ar anchor 2870rules are evaluated relative to the anchor in which they are contained. 2871For example, all 2872.Ar anchor 2873rules specified in the main ruleset will reference anchor 2874attachment points underneath the main ruleset, and 2875.Ar anchor 2876rules specified in a file loaded from a 2877.Ar load anchor 2878rule will be attached under that anchor point. 2879.Pp 2880Rules may be contained in 2881.Ar anchor 2882attachment points which do not contain any rules when the main ruleset 2883is loaded, and later such anchors can be manipulated through 2884.Xr pfctl 8 2885without reloading the main ruleset or other anchors. 2886For example, 2887.Bd -literal -offset indent 2888ext_if = \&"kue0\&" 2889block on $ext_if all 2890anchor spam 2891pass out on $ext_if all 2892pass in on $ext_if proto tcp from any \e 2893 to $ext_if port smtp 2894.Ed 2895.Pp 2896blocks all packets on the external interface by default, then evaluates 2897all rules in the 2898.Ar anchor 2899named "spam", and finally passes all outgoing connections and 2900incoming connections to port 25. 2901.Bd -literal -offset indent 2902# echo \&"block in quick from 1.2.3.4 to any\&" \&| \e 2903 pfctl -a spam -f - 2904.Ed 2905.Pp 2906This loads a single rule into the 2907.Ar anchor , 2908which blocks all packets from a specific address. 2909.Pp 2910The anchor can also be populated by adding a 2911.Ar load anchor 2912rule after the 2913.Ar anchor 2914rule: 2915.Bd -literal -offset indent 2916anchor spam 2917load anchor spam from "/etc/pf-spam.conf" 2918.Ed 2919.Pp 2920When 2921.Xr pfctl 8 2922loads 2923.Nm pf.conf , 2924it will also load all the rules from the file 2925.Pa /etc/pf-spam.conf 2926into the anchor. 2927.Pp 2928Optionally, 2929.Ar anchor 2930rules can specify packet filtering parameters using the same syntax as 2931filter rules. 2932When parameters are used, the 2933.Ar anchor 2934rule is only evaluated for matching packets. 2935This allows conditional evaluation of anchors, like: 2936.Bd -literal -offset indent 2937block on $ext_if all 2938anchor spam proto tcp from any to any port smtp 2939pass out on $ext_if all 2940pass in on $ext_if proto tcp from any to $ext_if port smtp 2941.Ed 2942.Pp 2943The rules inside 2944.Ar anchor 2945spam are only evaluated for 2946.Ar tcp 2947packets with destination port 25. 2948Hence, 2949.Bd -literal -offset indent 2950# echo \&"block in quick from 1.2.3.4 to any" \&| \e 2951 pfctl -a spam -f - 2952.Ed 2953.Pp 2954will only block connections from 1.2.3.4 to port 25. 2955.Pp 2956Anchors may end with the asterisk 2957.Pq Sq * 2958character, which signifies that all anchors attached at that point 2959should be evaluated in the alphabetical ordering of their anchor name. 2960For example, 2961.Bd -literal -offset indent 2962anchor "spam/*" 2963.Ed 2964.Pp 2965will evaluate each rule in each anchor attached to the 2966.Li spam 2967anchor. 2968Note that it will only evaluate anchors that are directly attached to the 2969.Li spam 2970anchor, and will not descend to evaluate anchors recursively. 2971.Pp 2972Since anchors are evaluated relative to the anchor in which they are 2973contained, there is a mechanism for accessing the parent and ancestor 2974anchors of a given anchor. 2975Similar to file system path name resolution, if the sequence 2976.Dq .. 2977appears as an anchor path component, the parent anchor of the current 2978anchor in the path evaluation at that point will become the new current 2979anchor. 2980As an example, consider the following: 2981.Bd -literal -offset indent 2982# echo ' anchor "spam/allowed" ' | pfctl -f - 2983# echo -e ' anchor "../banned" \en pass' | \e 2984 pfctl -a spam/allowed -f - 2985.Ed 2986.Pp 2987Evaluation of the main ruleset will lead into the 2988.Li spam/allowed 2989anchor, which will evaluate the rules in the 2990.Li spam/banned 2991anchor, if any, before finally evaluating the 2992.Ar pass 2993rule. 2994.Pp 2995Filter rule 2996.Ar anchors 2997can also be loaded inline in the ruleset within a brace ('{' '}') delimited 2998block. 2999Brace delimited blocks may contain rules or other brace-delimited blocks. 3000When anchors are loaded this way the anchor name becomes optional. 3001.Bd -literal -offset indent 3002anchor "external" on $ext_if { 3003 block 3004 anchor out { 3005 pass proto tcp from any to port { 25, 80, 443 } 3006 } 3007 pass in proto tcp to any port 22 3008} 3009.Ed 3010.Pp 3011Since the parser specification for anchor names is a string, any 3012reference to an anchor name containing 3013.Sq / 3014characters will require double quote 3015.Pq Sq \&" 3016characters around the anchor name. 3017.Sh SCTP CONSIDERATIONS 3018.Xr pf 4 3019supports 3020.Xr sctp 4 3021connections. 3022It can match ports, track state and NAT SCTP traffic. 3023However, it will not alter port numbers during nat or rdr translations. 3024Doing so would break SCTP multihoming. 3025.Sh TRANSLATION EXAMPLES 3026This example maps incoming requests on port 80 to port 8080, on 3027which a daemon is running (because, for example, it is not run as root, 3028and therefore lacks permission to bind to port 80). 3029.Bd -literal 3030# use a macro for the interface name, so it can be changed easily 3031ext_if = \&"ne3\&" 3032 3033# map daemon on 8080 to appear to be on 80 3034rdr on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 port 8080 3035.Ed 3036.Pp 3037If the 3038.Ar pass 3039modifier is given, packets matching the translation rule are passed without 3040inspecting the filter rules: 3041.Bd -literal 3042rdr pass on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 \e 3043 port 8080 3044.Ed 3045.Pp 3046In the example below, vlan12 is configured as 192.168.168.1; 3047the machine translates all packets coming from 192.168.168.0/24 to 204.92.77.111 3048when they are going out any interface except vlan12. 3049This has the net effect of making traffic from the 192.168.168.0/24 3050network appear as though it is the Internet routable address 3051204.92.77.111 to nodes behind any interface on the router except 3052for the nodes on vlan12. 3053(Thus, 192.168.168.1 can talk to the 192.168.168.0/24 nodes.) 3054.Bd -literal 3055nat on ! vlan12 from 192.168.168.0/24 to any -\*(Gt 204.92.77.111 3056.Ed 3057.Pp 3058In the example below, the machine sits between a fake internal 144.19.74.* 3059network, and a routable external IP of 204.92.77.100. 3060The 3061.Ar no nat 3062rule excludes protocol AH from being translated. 3063.Bd -literal 3064# NO NAT 3065no nat on $ext_if proto ah from 144.19.74.0/24 to any 3066nat on $ext_if from 144.19.74.0/24 to any -\*(Gt 204.92.77.100 3067.Ed 3068.Pp 3069In the example below, packets bound for one specific server, as well as those 3070generated by the sysadmins are not proxied; all other connections are. 3071.Bd -literal 3072# NO RDR 3073no rdr on $int_if proto { tcp, udp } from any to $server port 80 3074no rdr on $int_if proto { tcp, udp } from $sysadmins to any port 80 3075rdr on $int_if proto { tcp, udp } from any to any port 80 -\*(Gt 127.0.0.1 \e 3076 port 80 3077.Ed 3078.Pp 3079This longer example uses both a NAT and a redirection. 3080The external interface has the address 157.161.48.183. 3081On localhost, we are running 3082.Xr ftp-proxy 8 , 3083waiting for FTP sessions to be redirected to it. 3084The three mandatory anchors for 3085.Xr ftp-proxy 8 3086are omitted from this example; see the 3087.Xr ftp-proxy 8 3088manpage. 3089.Bd -literal 3090# NAT 3091# Translate outgoing packets' source addresses (any protocol). 3092# In this case, any address but the gateway's external address is mapped. 3093nat on $ext_if inet from ! ($ext_if) to any -\*(Gt ($ext_if) 3094 3095# NAT PROXYING 3096# Map outgoing packets' source port to an assigned proxy port instead of 3097# an arbitrary port. 3098# In this case, proxy outgoing isakmp with port 500 on the gateway. 3099nat on $ext_if inet proto udp from any port = isakmp to any -\*(Gt ($ext_if) \e 3100 port 500 3101 3102# BINAT 3103# Translate outgoing packets' source address (any protocol). 3104# Translate incoming packets' destination address to an internal machine 3105# (bidirectional). 3106binat on $ext_if from 10.1.2.150 to any -\*(Gt $ext_if 3107 3108# Translate packets arriving on $peer_if addressed to 172.22.16.0/20 3109# to the corresponding address in 172.21.16.0/20 (bidirectional). 3110binat on $peer_if from 172.21.16.0/20 to any -> 172.22.16.0/20 3111 3112# RDR 3113# Translate incoming packets' destination addresses. 3114# As an example, redirect a TCP and UDP port to an internal machine. 3115rdr on $ext_if inet proto tcp from any to ($ext_if) port 8080 \e 3116 -\*(Gt 10.1.2.151 port 22 3117rdr on $ext_if inet proto udp from any to ($ext_if) port 8080 \e 3118 -\*(Gt 10.1.2.151 port 53 3119 3120# RDR 3121# Translate outgoing ftp control connections to send them to localhost 3122# for proxying with ftp-proxy(8) running on port 8021. 3123rdr on $int_if proto tcp from any to any port 21 -\*(Gt 127.0.0.1 port 8021 3124.Ed 3125.Pp 3126In this example, a NAT gateway is set up to translate internal addresses 3127using a pool of public addresses (192.0.2.16/28) and to redirect 3128incoming web server connections to a group of web servers on the internal 3129network. 3130.Bd -literal 3131# NAT LOAD BALANCE 3132# Translate outgoing packets' source addresses using an address pool. 3133# A given source address is always translated to the same pool address by 3134# using the source-hash keyword. 3135nat on $ext_if inet from any to any -\*(Gt 192.0.2.16/28 source-hash 3136 3137# RDR ROUND ROBIN 3138# Translate incoming web server connections to a group of web servers on 3139# the internal network. 3140rdr on $ext_if proto tcp from any to any port 80 \e 3141 -\*(Gt { 10.1.2.155, 10.1.2.160, 10.1.2.161 } round-robin 3142.Ed 3143.Sh FILTER EXAMPLES 3144.Bd -literal 3145# The external interface is kue0 3146# (157.161.48.183, the only routable address) 3147# and the private network is 10.0.0.0/8, for which we are doing NAT. 3148 3149# Reassemble incoming traffic 3150set reassemble yes 3151 3152# use a macro for the interface name, so it can be changed easily 3153ext_if = \&"kue0\&" 3154 3155# block and log everything by default 3156block return log on $ext_if all 3157 3158# block anything coming from source we have no back routes for 3159block in from no-route to any 3160 3161# block packets whose ingress interface does not match the one in 3162# the route back to their source address 3163block in from urpf-failed to any 3164 3165# block and log outgoing packets that do not have our address as source, 3166# they are either spoofed or something is misconfigured (NAT disabled, 3167# for instance), we want to be nice and do not send out garbage. 3168block out log quick on $ext_if from ! 157.161.48.183 to any 3169 3170# silently drop broadcasts (cable modem noise) 3171block in quick on $ext_if from any to 255.255.255.255 3172 3173# block and log incoming packets from reserved address space and invalid 3174# addresses, they are either spoofed or misconfigured, we cannot reply to 3175# them anyway (hence, no return-rst). 3176block in log quick on $ext_if from { 10.0.0.0/8, 172.16.0.0/12, \e 3177 192.168.0.0/16, 255.255.255.255/32 } to any 3178 3179# ICMP 3180 3181# pass out/in certain ICMP queries and keep state (ping) 3182# state matching is done on host addresses and ICMP id (not type/code), 3183# so replies (like 0/0 for 8/0) will match queries 3184# ICMP error messages (which always refer to a TCP/UDP packet) are 3185# handled by the TCP/UDP states 3186pass on $ext_if inet proto icmp all icmp-type 8 code 0 3187 3188# UDP 3189 3190# pass out all UDP connections and keep state 3191pass out on $ext_if proto udp all 3192 3193# pass in certain UDP connections and keep state (DNS) 3194pass in on $ext_if proto udp from any to any port domain 3195 3196# TCP 3197 3198# pass out all TCP connections and modulate state 3199pass out on $ext_if proto tcp all modulate state 3200 3201# pass in certain TCP connections and keep state (SSH, SMTP, DNS, IDENT) 3202pass in on $ext_if proto tcp from any to any port { ssh, smtp, domain, \e 3203 auth } 3204 3205# Do not allow Windows 9x SMTP connections since they are typically 3206# a viral worm. Alternately we could limit these OSes to 1 connection each. 3207block in on $ext_if proto tcp from any os {"Windows 95", "Windows 98"} \e 3208 to any port smtp 3209 3210# IPv6 3211# pass in/out all IPv6 traffic: note that we have to enable this in two 3212# different ways, on both our physical interface and our tunnel 3213pass quick on gif0 inet6 3214pass quick on $ext_if proto ipv6 3215 3216# Packet Tagging 3217 3218# three interfaces: $int_if, $ext_if, and $wifi_if (wireless). NAT is 3219# being done on $ext_if for all outgoing packets. tag packets in on 3220# $int_if and pass those tagged packets out on $ext_if. all other 3221# outgoing packets (i.e., packets from the wireless network) are only 3222# permitted to access port 80. 3223 3224pass in on $int_if from any to any tag INTNET 3225pass in on $wifi_if from any to any 3226 3227block out on $ext_if from any to any 3228pass out quick on $ext_if tagged INTNET 3229pass out on $ext_if proto tcp from any to any port 80 3230 3231# tag incoming packets as they are redirected to spamd(8). use the tag 3232# to pass those packets through the packet filter. 3233 3234rdr on $ext_if inet proto tcp from \*(Ltspammers\*(Gt to port smtp \e 3235 tag SPAMD -\*(Gt 127.0.0.1 port spamd 3236 3237block in on $ext_if 3238pass in on $ext_if inet proto tcp tagged SPAMD 3239.Ed 3240.Pp 3241In the example below, a router handling both address families 3242translates an internal IPv4 subnet to IPv6 using the well-known 324364:ff9b::/96 prefix: 3244.Bd -literal -offset 4n 3245pass in on $v4_if inet af-to inet6 from ($v6_if) to 64:ff9b::/96 3246.Ed 3247.Pp 3248Paired with the example above, the example below can be used on 3249another router handling both address families to translate back 3250to IPv4: 3251.Bd -literal -offset 4n 3252pass in on $v6_if inet6 to 64:ff9b::/96 af-to inet from ($v4_if) 3253.Ed 3254.Sh GRAMMAR 3255Syntax for 3256.Nm 3257in BNF: 3258.Bd -literal 3259line = ( option | ether-rule | pf-rule | nat-rule | binat-rule | 3260 rdr-rule | antispoof-rule | altq-rule | queue-rule | 3261 trans-anchors | anchor-rule | anchor-close | load-anchor | 3262 table-rule | include ) 3263 3264option = "set" ( [ "timeout" ( timeout | "{" timeout-list "}" ) ] | 3265 [ "ruleset-optimization" [ "none" | "basic" | "profile" ]] | 3266 [ "optimization" [ "default" | "normal" | 3267 "high-latency" | "satellite" | 3268 "aggressive" | "conservative" ] ] 3269 [ "limit" ( limit-item | "{" limit-list "}" ) ] | 3270 [ "loginterface" ( interface-name | "none" ) ] | 3271 [ "block-policy" ( "drop" | "return" ) ] | 3272 [ "state-policy" ( "if-bound" | "floating" ) ] 3273 [ "state-defaults" state-opts ] 3274 [ "require-order" ( "yes" | "no" ) ] 3275 [ "fingerprints" filename ] | 3276 [ "skip on" ifspec ] | 3277 [ "debug" ( "none" | "urgent" | "misc" | "loud" ) ] 3278 [ "keepcounters" ] ) 3279 3280ether-rule = "ether" etheraction [ ( "in" | "out" ) ] 3281 [ "quick" ] [ "on" ifspec ] [ "bridge-to" interface-name ] 3282 [ etherprotospec ] etherhosts [ "l3" hosts ] 3283 [ etherfilteropt-list ] 3284 3285pf-rule = action [ ( "in" | "out" ) ] 3286 [ "log" [ "(" logopts ")"] ] [ "quick" ] 3287 [ "on" ifspec ] [ route ] [ af ] [ protospec ] 3288 hosts [ filteropt-list ] 3289 3290logopts = logopt [ "," logopts ] 3291logopt = "all" | "matches" | "user" | "to" interface-name 3292 3293etherfilteropt-list = etherfilteropt-list etherfilteropt | etherfilteropt 3294etherfilteropt = "tag" string | "tagged" string | "queue" ( string ) | 3295 "ridentifier" number | "label" string 3296 3297filteropt-list = filteropt-list filteropt | filteropt 3298filteropt = user | group | flags | icmp-type | icmp6-type | "tos" tos | 3299 "af-to" af "from" ( redirhost | "{" redirhost-list "}" ) 3300 [ "to" ( redirhost | "{" redirhost-list "}" ) ] | 3301 ( "no" | "keep" | "modulate" | "synproxy" ) "state" 3302 [ "(" state-opts ")" ] | 3303 "fragment" | "no-df" | "min-ttl" number | "set-tos" tos | 3304 "max-mss" number | "random-id" | "reassemble tcp" | 3305 fragmentation | "allow-opts" | 3306 "label" string | "tag" string | [ ! ] "tagged" string | 3307 "set prio" ( number | "(" number [ [ "," ] number ] ")" ) | 3308 "queue" ( string | "(" string [ [ "," ] string ] ")" ) | 3309 "rtable" number | "probability" number"%" | "prio" number | 3310 "dnpipe" ( number | "(" number "," number ")" ) | 3311 "dnqueue" ( number | "(" number "," number ")" ) | 3312 "ridentifier" number | 3313 "received-on" ( interface-name | interface-group ) 3314 3315nat-rule = [ "no" ] "nat" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 3316 [ "on" ifspec ] [ af ] 3317 [ protospec ] hosts [ "tag" string ] [ "tagged" string ] 3318 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" ) 3319 [ portspec ] [ pooltype ] [ "static-port" ] 3320 [ "map-e-portset" number "/" number "/" number ] ] 3321 3322binat-rule = [ "no" ] "binat" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 3323 [ "on" interface-name ] [ af ] 3324 [ "proto" ( proto-name | proto-number ) ] 3325 "from" address [ "/" mask-bits ] "to" ipspec 3326 [ "tag" string ] [ "tagged" string ] 3327 [ "-\*(Gt" address [ "/" mask-bits ] ] 3328 3329rdr-rule = [ "no" ] "rdr" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 3330 [ "on" ifspec ] [ af ] 3331 [ protospec ] hosts [ "tag" string ] [ "tagged" string ] 3332 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" ) 3333 [ portspec ] [ pooltype ] ] 3334 3335antispoof-rule = "antispoof" [ "log" ] [ "quick" ] 3336 "for" ifspec [ af ] [ "label" string ] 3337 [ "ridentifier" number ] 3338 3339table-rule = "table" "\*(Lt" string "\*(Gt" [ tableopts-list ] 3340tableopts-list = tableopts-list tableopts | tableopts 3341tableopts = "persist" | "const" | "counters" | "file" string | 3342 "{" [ tableaddr-list ] "}" 3343tableaddr-list = tableaddr-list [ "," ] tableaddr-spec | tableaddr-spec 3344tableaddr-spec = [ "!" ] tableaddr [ "/" mask-bits ] 3345tableaddr = hostname | ifspec | "self" | 3346 ipv4-dotted-quad | ipv6-coloned-hex 3347 3348altq-rule = "altq on" interface-name queueopts-list 3349 "queue" subqueue 3350queue-rule = "queue" string [ "on" interface-name ] queueopts-list 3351 subqueue 3352 3353anchor-rule = "anchor" [ string ] [ ( "in" | "out" ) ] [ "on" ifspec ] 3354 [ af ] [ protospec ] [ hosts ] [ filteropt-list ] [ "{" ] 3355 3356anchor-close = "}" 3357 3358trans-anchors = ( "nat-anchor" | "rdr-anchor" | "binat-anchor" ) string 3359 [ "on" ifspec ] [ af ] [ "proto" ] [ protospec ] [ hosts ] 3360 3361load-anchor = "load anchor" string "from" filename 3362 3363queueopts-list = queueopts-list queueopts | queueopts 3364queueopts = [ "bandwidth" bandwidth-spec ] | 3365 [ "qlimit" number ] | [ "tbrsize" number ] | 3366 [ "priority" number ] | [ schedulers ] 3367schedulers = ( cbq-def | priq-def | hfsc-def ) 3368bandwidth-spec = "number" ( "b" | "Kb" | "Mb" | "Gb" | "%" ) 3369 3370etheraction = "pass" | "block" 3371action = "pass" | "match" | "block" [ return ] | [ "no" ] "scrub" 3372return = "drop" | "return" | "return-rst" [ "( ttl" number ")" ] | 3373 "return-icmp" [ "(" icmpcode [ [ "," ] icmp6code ] ")" ] | 3374 "return-icmp6" [ "(" icmp6code ")" ] 3375icmpcode = ( icmp-code-name | icmp-code-number ) 3376icmp6code = ( icmp6-code-name | icmp6-code-number ) 3377 3378ifspec = ( [ "!" ] ( interface-name | interface-group ) ) | 3379 "{" interface-list "}" 3380interface-list = [ "!" ] ( interface-name | interface-group ) 3381 [ [ "," ] interface-list ] 3382route = ( "route-to" | "reply-to" | "dup-to" ) 3383 ( routehost | "{" routehost-list "}" ) 3384 [ pooltype ] 3385af = "inet" | "inet6" 3386 3387etherprotospec = "proto" ( proto-number | "{" etherproto-list "}" ) 3388etherproto-list = proto-number [ [ "," ] etherproto-list ] 3389protospec = "proto" ( proto-name | proto-number | 3390 "{" proto-list "}" ) 3391proto-list = ( proto-name | proto-number ) [ [ "," ] proto-list ] 3392 3393etherhosts = "from" macaddress "to" macaddress 3394macaddress = mac | mac "/" masklen | mac "&" mask 3395 3396hosts = "all" | 3397 "from" ( "any" | "no-route" | "urpf-failed" | "self" | host | 3398 "{" host-list "}" ) [ port ] [ os ] 3399 "to" ( "any" | "no-route" | "self" | host | 3400 "{" host-list "}" ) [ port ] 3401 3402ipspec = "any" | host | "{" host-list "}" 3403host = [ "!" ] ( address [ "/" mask-bits ] | "\*(Lt" string "\*(Gt" ) 3404redirhost = address [ "/" mask-bits ] 3405routehost = "(" interface-name [ address [ "/" mask-bits ] ] ")" 3406address = ( interface-name | interface-group | 3407 "(" ( interface-name | interface-group ) ")" | 3408 hostname | ipv4-dotted-quad | ipv6-coloned-hex ) 3409host-list = host [ [ "," ] host-list ] 3410redirhost-list = redirhost [ [ "," ] redirhost-list ] 3411routehost-list = routehost [ [ "," ] routehost-list ] 3412 3413port = "port" ( unary-op | binary-op | "{" op-list "}" ) 3414portspec = "port" ( number | name ) [ ":" ( "*" | number | name ) ] 3415os = "os" ( os-name | "{" os-list "}" ) 3416user = "user" ( unary-op | binary-op | "{" op-list "}" ) 3417group = "group" ( unary-op | binary-op | "{" op-list "}" ) 3418 3419unary-op = [ "=" | "!=" | "\*(Lt" | "\*(Le" | "\*(Gt" | "\*(Ge" ] 3420 ( name | number ) 3421binary-op = number ( "\*(Lt\*(Gt" | "\*(Gt\*(Lt" | ":" ) number 3422op-list = ( unary-op | binary-op ) [ [ "," ] op-list ] 3423 3424os-name = operating-system-name 3425os-list = os-name [ [ "," ] os-list ] 3426 3427flags = "flags" ( [ flag-set ] "/" flag-set | "any" ) 3428flag-set = [ "F" ] [ "S" ] [ "R" ] [ "P" ] [ "A" ] [ "U" ] [ "E" ] 3429 [ "W" ] 3430 3431icmp-type = "icmp-type" ( icmp-type-code | "{" icmp-list "}" ) 3432icmp6-type = "icmp6-type" ( icmp-type-code | "{" icmp-list "}" ) 3433icmp-type-code = ( icmp-type-name | icmp-type-number ) 3434 [ "code" ( icmp-code-name | icmp-code-number ) ] 3435icmp-list = icmp-type-code [ [ "," ] icmp-list ] 3436 3437tos = ( "lowdelay" | "throughput" | "reliability" | 3438 [ "0x" ] number ) 3439 3440state-opts = state-opt [ [ "," ] state-opts ] 3441state-opt = ( "max" number | "no-sync" | timeout | "sloppy" | 3442 "source-track" [ ( "rule" | "global" ) ] | 3443 "max-src-nodes" number | "max-src-states" number | 3444 "max-src-conn" number | 3445 "max-src-conn-rate" number "/" number | 3446 "overload" "\*(Lt" string "\*(Gt" [ "flush" ] | 3447 "if-bound" | "floating" | "pflow" ) 3448 3449fragmentation = [ "fragment reassemble" ] 3450 3451timeout-list = timeout [ [ "," ] timeout-list ] 3452timeout = ( "tcp.first" | "tcp.opening" | "tcp.established" | 3453 "tcp.closing" | "tcp.finwait" | "tcp.closed" | 3454 "sctp.first" | "sctp.opening" | "sctp.established" | 3455 "sctp.closing" | "sctp.closed" | 3456 "udp.first" | "udp.single" | "udp.multiple" | 3457 "icmp.first" | "icmp.error" | 3458 "other.first" | "other.single" | "other.multiple" | 3459 "frag" | "interval" | "src.track" | 3460 "adaptive.start" | "adaptive.end" ) number 3461 3462limit-list = limit-item [ [ "," ] limit-list ] 3463limit-item = ( "states" | "frags" | "src-nodes" ) number 3464 3465pooltype = ( "bitmask" | "random" | 3466 "source-hash" [ ( hex-key | string-key ) ] | 3467 "round-robin" ) [ sticky-address ] 3468 3469subqueue = string | "{" queue-list "}" 3470queue-list = string [ [ "," ] string ] 3471cbq-def = "cbq" [ "(" cbq-opt [ [ "," ] cbq-opt ] ")" ] 3472priq-def = "priq" [ "(" priq-opt [ [ "," ] priq-opt ] ")" ] 3473hfsc-def = "hfsc" [ "(" hfsc-opt [ [ "," ] hfsc-opt ] ")" ] 3474cbq-opt = ( "default" | "borrow" | "red" | "ecn" | "rio" ) 3475priq-opt = ( "default" | "red" | "ecn" | "rio" ) 3476hfsc-opt = ( "default" | "red" | "ecn" | "rio" | 3477 linkshare-sc | realtime-sc | upperlimit-sc ) 3478linkshare-sc = "linkshare" sc-spec 3479realtime-sc = "realtime" sc-spec 3480upperlimit-sc = "upperlimit" sc-spec 3481sc-spec = ( bandwidth-spec | 3482 "(" bandwidth-spec number bandwidth-spec ")" ) 3483include = "include" filename 3484.Ed 3485.Sh FILES 3486.Bl -tag -width "/etc/protocols" -compact 3487.It Pa /etc/hosts 3488Host name database. 3489.It Pa /etc/pf.conf 3490Default location of the ruleset file. 3491The file has to be created manually as it is not installed with a 3492standard installation. 3493.It Pa /etc/pf.os 3494Default location of OS fingerprints. 3495.It Pa /etc/protocols 3496Protocol name database. 3497.It Pa /etc/services 3498Service name database. 3499.El 3500.Sh SEE ALSO 3501.Xr altq 4 , 3502.Xr carp 4 , 3503.Xr icmp 4 , 3504.Xr icmp6 4 , 3505.Xr ip 4 , 3506.Xr ip6 4 , 3507.Xr pf 4 , 3508.Xr pflow 4 , 3509.Xr pfsync 4 , 3510.Xr sctp 4 , 3511.Xr tcp 4 , 3512.Xr udp 4 , 3513.Xr hosts 5 , 3514.Xr pf.os 5 , 3515.Xr protocols 5 , 3516.Xr services 5 , 3517.Xr ftp-proxy 8 , 3518.Xr pfctl 8 , 3519.Xr pflogd 8 3520.Sh HISTORY 3521The 3522.Nm 3523file format first appeared in 3524.Ox 3.0 . 3525